A magnet portion 27 of a magnetic encoder 26 includes a magnetic member and a resin, and a highly reliable magnetic encoder 26 having a high magnetic property and enabling to detect a rotational number with high accuracy, and a hub unit bearing 2a are provided. Further, the resin is preferably a thermoplastic resin and further preferably includes a thermoplastic resin including a soft segment in a molecule. Further, the magnetic encoder 26 further includes a fixed member 25 attached with the magnet portion 27 and comprising a magnetic material, and the magnet portion 27 and the fixed member 25 are bonded by an adhering agent including at least one of a phenolic resin based and an epoxy resin based.
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1. A bearing for a wheel comprising:
a fixed ring,
a rotating ring,
a plurality of rolling members rollably arranged in a circumferential direction between the fixed ring and the rotating ring, and
a magnetic encoder, wherein:
the magnetic encoder comprises a magnet portion substantially in a circular ring shape magnetized in multipoles in a circumferential direction and a fixed member,
the magnet portion is bonded to the fixed member and includes a magnetic member and a thermoplastic resin,
the magnet portion and the fixed member are bonded by at least one of a phenolic resin based adhering agent and an epoxy resin based adhering agent, and
the adhering agent is baked to the fixed member in a semicured state and further cured in a process of forming the magnet portion by insert molding, and
the magnetic member is strontium ferrite, and the thermoplastic resin is polyamide based resin.
0. 2. The bearing according to
3. The bearing according to claim 2 1, wherein the thermoplastic resin is polyamide 6, polyamide 12, polyamide 612 or polyamide 11.
4. The bearing according to
0. 5. The bearing according to
6. The bearing according to
7. The bearing according to
0. 8. The bearing according to
9. The bearing according to
the magnet portion includes at least ferrite as the magnetic member, and
the magnetic member magnet portion includes 60 through 80 volume % of a magnet portion powder.
10. The bearing according to
11. The bearing according to
12. The bearing according to
13. The bearing according to
14. The bearing according to
a number of poles of the magnet portion is about 70 through 130 poles, and
a single pitch error is equal to or smaller than ±2 %.
0. 15. The bearing according to
0. 16. The bearing according to
17. The bearing according to
18. The bearing according to
19. The bearing according to
0. 20. The bearing according to
21. The bearing according to
a notched portion is provided on an outer circumference of a flange portion of the fixed member, and
the magnet portion and the fixed member are mechanically bonded by the notched portion.
22. The bearing according to
0. 23. The bearing according to
24. The bearing according to
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(In the formula, R3 designates hydrocarbon group of n values having a carbon number of 2 through 10, and including one kind or more of nitrogen atom, oxygen atom and the like, R2 designates hydrocarbon group of one value hating a carbon number of 1 through 6 and which may include one kind or more of nitrogen atom, oxygen atom and the like, n designates integer of 1 through 6). And a specific example thereof is shown in formula 5.
##STR00005##
As other specific examples, there are pointed out a compound in which R3 designates phenyl group of 2 values and R2 designates propyl group, a compound in which R3 designates phenyl group of 3 values and R2 designates propyl group, a compound in which R3 designates phenyl group of 4 values and R2 designates propyl group. These may be used by themselves or may be used by combining 2 kinds or more thereof. Among them, a compound represented by chemical 1 is the most preferable in view of a balance between curing reactivity and storing stability.
Further, other than the above-described compounds, imidazole compounds of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-phnelimidazole or the like may be used as curing accelerators.
Further, as the curing accelerator, carboxylic acids of, for example, adipic acid or the like, which are compounds having active hydrogen for causing a ring opening reaction by being reacted with epoxy group may be used. By using adipic acid as the curing accelerator, epoxy group of epoxy resin and amino group of the curing agent are reacted and provided cured product includes flexibility as an amount of adding adipic acid increases. In order to manifest flexibility, the amount of adding adipic acid is 10 through 40 weight %, further preferably 20 through 30 weight % relative to a total amount of the adhering agent. When the adding amount is less than 10 weight %, sufficient flexibility is not manifested. In contrast thereto, when the adding amount exceeds 40 weight %, an amount of a total of epoxy resin in the adhering agent is reduced by that amount, an adhering force, mechanical strength are reduced, which is not preferable. Further, adipic acid is also a starting raw material of polyamide resin and therefore, when a binder of a magnetic powder is constituted by polyamide based resin of polyamide 12, polyamide 6 or the like, adipic acid is provided with also reactivity with monomer or oligomer component remaining in the binder material per se by an extremely small amount and further solid adherence can be carried out by constituting the adhering agent composition including adipic acid.
Further, as the curing accelerator, tertiary amine of dimethylbenzylamine or the like, quaternary ammonium salt of tetrabutylammoniumbromide or the like, alkyl urea of 3-(3′,4′-dichlorophenyl)-1,1-dimethyl urea or the like operated as a catalyst for accelerating a ring opening reaction of epoxy group may be added.
OH group formed by the ring opening reaction including the amines or the like, forms hydrogen bonding with hydroxyl group at a surface of a metal constituting a coated member, further, can maintain a solid adhered state by being operated with amide bonding of nylon constituting a binder material.
The inorganic filling member can be used without being particularly limited so far as the inorganic filling member is used in the background art. For example, melted silica powder, quartz glass powder, crystallized glass powder, glass fiber, alumina powder, talc, aluminum powder, titanium oxide or the like is pointed out.
As the bridged rubber small particle having a functional group capable of being reacted with epoxy group is preferable, specifically, vulkanized acrylonitrilebutadiene rubber having carboxyl group in a molecular chain is the most preferable. The smaller the particle diameter, the more preferable, an ultra small particle having about 30 through 200 nm by a mean particle diameter is the most preferable for manifesting a dispersing property and stable flexibility.
According to the one solution type epoxy adhering agent explained above, the curing reaction is hardly progressed at normal temperature, the adhering agent is brought into a semicured state at, for example, about 80 through 120° C. and a heat curing reaction is completely progressed by applying heat at high temperatures of 120 through 180° C. Further preferably, the adhering agent progressing the curing reaction by comparatively short time at 150 through 180° C. is preferable and the adhering agent capable of being adhered by high frequency heating at 180° C. is the most preferable.
According to a cured product after heat curing of the phenolic resin based adhering agent, epoxy resin based adhering agent explained above, as physical properties, it is preferable the bending elastic modulus or Young's modulus falls in a range of 0.02 through 5 GPa, further preferably, 0.03 through 4 GPa, or a hardness (duarometer D scale; HDD) falls in a range of 40 through 90, further preferably, 60 through 85. When the bending elastic modulus or Young's modulus is less than 0.02 GPa, or the hardness (HDD) is less than 40, the adhering agent per se is excessively soft and is easy to be deformed by vibration in running an automobile or the like, the magnet portion is easy to be moved thereby and therefore, there is a concern of deteriorating accuracy of detecting the rotational number, which is not preferable. On the other hand, when the bending elastic modulus or Young' modulus exceeds 5 GPa, or the hardness (HDD) exceeds 90, the adhering agent per se is excessively hard, it is difficult to be deformed to absorb the difference of thermal elongation and contraction between the magnet of the magnetic encoder and a fixed member (that is, a difference of elongation and contraction amount by a difference between linear expansion coefficients of the both members), in the worst case, there is a concern of producing a crack or the like in the magnet, which is not preferable. Heat shock resistance is requested for the one solution type epoxy based adhering agent of the invention when a premise is constituted by using the adhering agent in an automobile, and the adhering agent having flexibility in a cured state (deformed when a stress is applied) is further preferable.
A detailed explanation will be given of a method of fabricating a magnetic encoder according to the invention using the above-described material as follows. First, the roughening treatment accompanied by the chemical etching treatment is carried out on a surface of the slinger by the above-described steps, as shown by photographs of sections of
As shown by
As shown by
Further, in synchronism with injection of the melted plastic magnet material into the dies 89, 90 attached to the magnetic field injection molding machine 80, coil currents are applied to the coils 91, 92 at both ends of the dies 89, 90 to thereby magnetize the plastic magnet material by a generated magnetic field in one direction (same polarity) to orient the magnetic powder. Thereafter, demagnetization is carried out by at least one of steps of demagnetization for demagnetizing by a magnetic field in a direction reverse to a magnetizing direction and reversing demagnetization for demagnetizing by applying a plurality of pulse currents polarities of which are alternately reversed and amplitudes of which are gradually reduced to the coils 91, 92 at the both ends of the dies starting from an initial coil current higher than a coil current in magnetizing in cooling. Next, after removing the gate portion, the adhering agent is completely cured by being heated at constant temperature for constant time in a thermostat or the like. Further, depending on cases, the adhering agent may be completely cured by being heated at high temperature for short time by high frequency heating or the like. Thereafter, the material is further demagnetized to a magnetic flux density equal to or smaller than 2 mT, further preferably, 1 mT by using a demagnetizer of a well-known oil condenser type or the like. At a step thereafter, the material is overlapped on a well-known magnetizing yoke to magnetize the multipoles to thereby finish fabricating the magnet portion. A number of poles of the magnet portion is about 70 through 130 poles, preferably, 90 through 120 poles. When the number of poles is less than 70 poles, the number poles is excessively small and it is difficult to accurately detect a rotational number. In contrast thereto, when the number of poles exceeds 130 poles, respective pitches become excessively small, it is difficult to restrain a single pitch error to be small, and practical performance is low.
Further, in molding the encoder portion, as described above, injection molding (insert molding) in which the melted plastic magnet material flows from an inner diameter thick portion simultaneously into the dies, rapidly cooled in the dies to solidify is preferable. The melted resin is widened in a disk-like shape and flows to the dies of portions in correspondence with the inner diameter thick portion, thereby, the magnetic powder in a scale-like shape included therein is oriented in parallel with the face. Particularly, a portion between an inner diameter portion and an outer diameter portion at a vicinity of the inner diameter thickness portion detected by the rotation sensor is provided with higher orientation and is very near to axial anisotropy oriented in a thickness direction. When then magnetic field is applied in the thickness direction of the dies in molding, the anisotropy becomes further near to complete anisotropy.
Further, even when magnetic field molding is carried out, in a case in which the gate is constituted by other than the disk gate, for example, a side gate, in a procedure of gradually increasing a viscosity of the resin to solidification, it is difficult to completely make orientation at a weld portion anisotropic, thereby, there is a possibility of bringing about a crack or the like at the weld portion by which the magnetic property is deteriorated and the mechanical strength is deteriorated by a long period of use, which is not preferable. Therefore, according to the embodiment, insert molding by the disk gate is carried out in a state of applying the magnetic field in the thickness direction by constituting the core by the slinger.
Further, although a color of the molded magnetic pole forming ring 27 of the magnetic encoder 26 is black color since the ferrite powder is included, the color is more or less changed by an additive. Further, as shown by
According to the magnetic encoder of the embodiment, the magnet portion is constructed by the constitution of including the magnetic member and the resin and therefore, a comparatively large amount of the magnetic powder can be mixed to the rubber magnet, the magnetic encoder having an excellent magnetic property can be provided, further, injection molding (magnetic field molding) in a state of applying the magnetic field is facilitated and the anisotropic magnet indispensable for manifesting the excellent magnetic property can be provided.
Further, according to the magnetic encoder of the embodiment, the magnet portion comprises the plastic magnet material constituting the binder by the thermoplastic resin including 86 through 92 weight % of the magnetic powder, the magnet portion is chemically bonded to the slinger comprising the magnetic material by the adhering agent in which the curing reaction is progressed in insert molding and therefore, the magnet portion can carry out multipoles magnetization in a circumferential direction by a fine pitch having an excellent magnetic property and can ensure the strength of a total of the magnet.
Further, according to the magnetic encoder of the embodiment, the magnet portion comprises the magnet material including the ferritic magnetic powder and the thermoplastic resin, the magnet portion is integrally bonded to the slinger comprising the magnetic material, according to the magnet portion, the thickness is 3.0 mm and the bending amount at 23° C. falls in a range of 2 through 10 mm and therefore, crack resistance is promoted by increasing the bending amount. Therefore, even in the structure in which the magnet portion is mechanically bonded to the slinger by insert molding by constituting the core by the slinger, when the magnet portion is applied with a stress of heat shock or the like at high temperatures, low temperatures to which a downward portion of an automobile is exposed, in shifting between high temperatures and low temperatures, a crack can effectively be prevented from being brought about at the magnet portion and reliability can significantly be promoted. Further, the bending amount is provided by including denatured polyamide 12 resin as the binder.
Further, according to the magnetic encoder of the embodiment, the slinger comprises the iron based magnetic material roughened in accordance with the chemical etching treatment and therefore, adherence between the slinger and the magnet portion is promoted by the wedge effect of the adhering agent.
Further, by using the phenolic based adhering agent or the epoxy based adhering agent as the adhering agent, there is a low possibility of exfoliating the adhering portion by high temperatures, low temperatures, the heat shock in shifting between high temperatures and low temperatures to which the downward portion of the automobile is exposed, various chemicals of grease, oil or the like and the reliability is promoted. Further, by carrying out insert molding in the state of making the adhering agent in the semicured state by using the adhering agent capable of being cured in two stages, the slinger and the magnet portion can be bonded mechanically and chemically and productivity and reliability are also promoted.
Further, according to the method of fabricating the magnetic encoder according to the invention, there can be fabricated the highly reliable magnetic encoder which is not exfoliated to be detached from the slinger even under a severe condition of use. Further, the magnetic powder in the plastic magnet provided by the fabricating method of the embodiment is highly oriented in the thickness direction of the magnet in the ring-like shape and therefore, the magnetic property of the encoder provided by magnetizing the magnetic powder is extremely improved. Therefore, depending on the content of the magnetic powder in the magnet, the magnetic flux density which has been about 20 mT in the background art can be promoted to be equal to or higher than 26 mT. Therefore, when a gap between the magnetic encoder and the sensor is made to be 1 mm similar to that of the background art, the plastic magnet which has been magnetized in multipoles of 96 poles in the background art can be magnetized in multipoles to be equal to or larger than 120 poles while maintaining the magnetic flux per pole. At this occasion, the single pitch error can be made to be equal to or smaller than ±2%. That is, according to the magnetic encoder according to the embodiment, when an air gap equivalent to that of the background art is constituted, the accuracy of detecting the rotational speed of the wheel can be promoted by increasing a number of poles. Further, when the plastic magnet according to the embodiment is constituted by the number of poles the same as that of the background art, the air gap can be increased and a degree of freedom in arranging the sensor can be promoted.
Further, according a hub unit bearing of the embodiment, the magnetic pole forming ring 27 may be prevented from being exfoliated from the slinger 25, as shown by
Further, as shown by
Further, as shown by
Next, a detailed explanation will be given of a hub unit bearing constituting a bearing for a wheel for supporting a nondriven wheel supported by a suspension of an independent suspension type according to a second embodiment of the invention. Further, portions equivalent to those of the first embodiment are attached with the same notations and an explanation thereof will be omitted or simplified.
Although according to the first embodiment, the magnetic encoder 26 and the sensor 28 are of a type of being opposed to each other in an axial direction, according to hub unit bearing 30 of the embodiment, as shown by
According the magnetic encoder 31 of the embodiment, a slinger 33 in a circular ring shape constituting a fixed member is outwardly fitted to be fixed to an outer peripheral portion of an inner end portion of the inner ring 16a, and a magnetic pole forming ring 34 constituting a magnet portion is attached to an inner peripheral face of the slinger 33 extended from the inner ring 16a in an axial direction. Further, an outer peripheral face of the outer ring 5a is fixed with a cover member 35 constituting a stationary member to cover an end portion in the axial direction of the hub unit bearing 2a, and an opening portion formed at the cover member is attached with the sensor 32 to be opposed to the magnetic pole forming ring 34 in the radial direction.
Further, a composition, a molding method of the magnetic encoder 31 are similar to those of the first embodiment.
Therefore, according to the magnetic encoder 31 of the embodiment, in comparison with a magnetic encoder opposed thereto in an axial direction, a diameter of a detected face can be increased with regard to the same space and therefore, when the pitch number stays the same, respective pitch widths can be increased and the magnetic encoder 31 is easy to be fabricated.
Next, a detailed explanation will be given of a rolling bearing unit attached with a sealing apparatus attached with a magnetic encoder according to a third embodiment of the invention.
As shown by
The hermetically sealing apparatus 45 includes the sealing member 50 mounted to an inner peripheral face of the outer ring 41, and a slinger 60 arranged on an outer side of the bearing rather than a sealing member 50 and fixed to an outer peripheral face of the inner ring 42, an opening end portion of the ring-like gap is closed by the seal member 50 and the slinger 60, a foreign matter of dust or the like is prevented from invading inside of the bearing and a lubricant filled at inside of the bearing is prevented from being leaked. Further, the magnetic encoder 46 is constituted by the slinger 60 and the magnet portion 70 attached to the slinger 60, the magnet portion 70 is fixed to the inner ring 42 by constituting a fixed member by the slinger 60.
The sealing member 50 is constituted by reinforcing an elastic member 52 formed in a circular ring shape having a section substantially in an L-like shape by a core metal 51 similarly formed in a circular ring shape having a section substantially in an L-like shape and is mounted by being inwardly fitted to the outer ring 41. A front end portion of the elastic member 52 is branched to a plurality of sliding contact portions, the respective sliding contact portions are brought into sliding contact with an end face of a flange portion 62 of the slinger 60 facing inside of the bearing, or to an outer peripheral face of a fitting portion 61 over an entire periphery thereof. A high hermetically sealing force is provided thereby.
The slinger 60 is formed in a circular ring shape having a section in an L-like shape and includes the fitting portion 61 substantially in a cylindrical shape outwardly fitted to the outer peripheral face of the inner ring 42, the flange portion in a flange-like shape developed in a radius direction from one side end portion of the fitting portion 61, a projected portion 63 projected to an outer side in the axial direction from the flange portion 62 on an inner diameter side of the flange portion 62 by folding to bend the one side end portion of the fitting portion 61. Further, an outer peripheral face of the projected portion 63 is provided with notch portions 64 formed at a plurality of locations in a peripheral direction. An end face (hereinafter, referred to as bonding face) 62a facing an outer side of the bearing of the flange portion 62 is bonded with the magnet portion 70 for changing a magnetic field (for example, magnetic flux density) at a vicinity thereof in synchronism with rotation of the inner ring 42. Further, at the same time, the magnet portion 70 is also mechanically bonded to the notch portion 64 and the outer peripheral portion of the flange portion 62.
Further, a composition, a molding method of the magnetic encoder 46 are similar to those of the first embodiment.
Therefore, according to the magnetic encoder of the embodiment, the melted magnet material flows also to the notch portions 64 provided by a plurality thereof in the peripheral direction of the projected portion 63 provided on the inner diameter side in addition to the outer diameter portion of the flange portion 62 and is mechanically bonded thereto. Thereby, shrinkage of the magnet material is received not only by the outer diameter portion of the flange portion 62 but by the projected portion 630 on the inner diameter side, and a frequency of bringing about the crack of the magnet portion produced by heat shock or the like can further be reduced.
Further, the magnetic encoder 46 according to the embodiment can be integrated to be used by the hub unit bearing as shown by
Next, a detailed explanation will be given of a rolling bearing unit integrated with a magnetic encoders according to a fourth embodiment of the invention. Further, portions equivalent to those of the rolling bearing unit according to the third embodiment are attached with the same notations and an explanation thereof will be omitted or simplified.
As shown by
The hermetically sealing apparatus 45 includes the sealing member 50 fixed to the inner peripheral face of the outer ring 41 and having the core metal 51 and the elastic member 52, and a slinger 110 arranged on the outer side of the opening end portion more than the sealing member 50 and fixed to the outer peripheral face of the inner ring 42, the opening end portion of the ring-like gap is closed by the sealing member 50 and the slinger 110, a foreign matter of dust or the like is prevented from invading inside of the bearing and a lubricant filled at inside of the bearing is prevented from being leaked to outside of the bearing. Further, the magnetic encoder 120 is constituted by bonding the magnet portion 121 in the circular ring shape to the slinger 110 constituting the fixed member and is rotated along with the inner ring 42.
The slinger 110 is constituted by forming the magnet material in the circular ring shape having the section in the L-like shape and includes the fitting portion 112 substantially in the cylindrical shape outwardly fitted to the outer peripheral face of the inner ring 42, and the flange portion 111 substantially in a shape of a circular plate extended in the radius direction from one end on the side of the opening end portion of the fitting portion 112. Further, an outer peripheral edge portion of the flange portion 111 is provided with a plurality of locking portions 113 notched in a recessed shape at equal intervals in a circumferential direction, and the flange portion 111 is formed with through holes 114 at equal intervals in a peripheral direction. An end face on an outer side of an opening end portion of the flange portion 111 is bonded with the magnetic encoder 120 for changing a magnetic field (for example, magnetic flux density or the like) at a vicinity thereof in synchronism with rotation of the inner ring 42.
A magnet portion 121 is provided with a magnetizing portion 122 in a circular ring shape having a section substantially in a rectangular shape, a plurality of locking pieces engaged with the locking portions 113 of the slinger 110, and a connecting portion 123 for connecting the plurality of locking pieces. Therefore, by engaging the locking portion 113 and the locking piece and pinching the flange portion 111 by the magnetizing portion 122 of the encoder 120 and the connecting portion 123, the magnet portion 121 and the slinger 110 are mechanically bonded. Further, the melted magnet material is filled also to the through hole 114 of the flange portion 111 and the magnet portion 121 and the slinger 110 are mechanically bonded.
The magnet portion 121 is formed by subjecting the magnet material including the magnet powder pertinently in a range of 86 through 92 weight % and constituting the binder by the thermoplastic resin to injection molding and molded by insert molding by constituting the core by the slinger 110 in the dies. By carrying out insert molding, the melted magnet material is filled to the locking portion 113 of the slinger 110 to form the locking piece, and is filled also to a space in a circular ring shape in the dies provided to connect the locking pieces contiguously to the end face on the inner side of the opening end portion of the flange portion 111 to form the connecting portion 123. By engaging the locking portion 113 and the locking piece and pinching the flange portion 111 by the magnetizing portion 122 and the connecting portion 123 of the magnet portion 121, the magnet portion 121 and the slinger 110 are mechanically bonded.
The magnetizing portion 122 is magnetized with S poles and N poles alternately (that is, in multipoles) at equal intervals in the circumferential direction similar to the magnetic pole forming ring 27 shown in
In reference to
The gate 138 is a flow inlet by which the magnet material flows from the runner 137 to a cavity 139, and the cavity 139 is a space for molding a shape of the magnet portion 121. The cavity 139 is a space partitioned by a recessed portion in a circular ring shape, a peripheral face of the fixed side die plate 133 and the lower side face of the movable side die plate 131 in correspondence with the shape of the magnet portion 121 provided at the core 132 for holding the slinger, not illustrated. Further, a bottom face of the cavity 139 is provided with a plurality of the ejector pins 134b in the peripheral direction, after injection molding, the magnet portion 121 is separated from the core 132 by pushing up the magnet portion 121 from the lower side. The gate 138 is a space in a circular ring shape connecting the outer peripheral portion of the runner 137 and the inner peripheral portion of the cavity 139 over an entire periphery thereof to communicate the runner 137 and the cavity 139 and is a so-to-speak disk gate.
In the above-described injection molding machine, the magnet portion 121 is molded by making the melted magnet material flow to the runner 137 from the nozzle port 135 by way of the sprue 136, injecting the magnet material to the cavity 139 under high pressure from the disk gate 138 and rapidly cooling the magnet material to solidify. The magnet material injected from the disk gate 138 under high pressure is widened with a shape of a radial circle from the inner peripheral portion of the cavity 139 to be uniformly filled in the cavity 139 and therefore, the melted magnet materials do not collide with each other, the respective magnetic powders in the scale-like shape (plate-like crystal) included in the magnet material are oriented by aligning a normal line direction of a face (that is, axis of easy magnetization) in parallel with the thickness direction (in other words, axial direction) of the magnetic encoder 120. Particularly, an orientation degree of a vicinity of the inner peripheral portion (that is, magnetizing portion) scanned by the sensor is high and a magnetic property very near to axial anisotropy is shown. Further, by carrying out injection molding in a state of applying a magnetic field in the thickness direction, the magnetic powder in the magnet material can completely be oriented.
According to the rolling bearing unit 100 integrated to the magnetic encoder 120, the magnet material including the magnetic powder pertinently in a range of 86 through 92 weight % by constituting the binder by the thermoplastic resin is subjected to injection molding in the shape of the radial circle from the inner peripheral portion by the disk gate type to mold the magnet portion 121 in the circular ring shape and therefore, the orientation degree of the magnetic powder included in the magnet portion 121 can be promoted and the magnetic property of the magnetic encoder 120 can be promoted. Thereby, the gap between the magnetic encoder 120 and the sensor can be increased, further, the magnetizing portion 122 of the magnet portion 121 can be magnetized further in multipoles and therefore, the magnet portion can be facilitated to be integrated to the sensor and the rotational number of the inner ring 42 can highly accurately be detected. Further, the magnet portion 121 is not provided with the weld portion at which the magnet materials collide with each other to solidify, the mechanical strength is high and a crack or the like is difficult to be brought about. Further, the magnet portion 121 is subjected to insert molding by constituting the core by the slinger 110 and therefore, the encoder 120 at the magnet portion 121 can mechanically be bonded, the magnet portion 121 can firmly be prevented from being detached from the slinger 120 to thereby promote reliability.
Further, the composition explained in the first embodiment is applicable to the composition of the magnetic encoder 120 according to the embodiment.
Further, polyamide resin of polyamide 6, polyamide 12 or the like is used, by coating a silane coupling agent having epoxy group of γ-glycydoxypropyltriethoxy silane or the like to the face of bonding the slinger and the magnet portion and thereafter carrying high frequency heating, silanol group (Si—OH) formed by hydrolysis of methoxy group included in the silane coupling agent carries out a hydrating condensation reaction with hydroxyl group (OH) on the surface of the slinger to form a new bond, and epoxy group reacts with amide bond of the binder to form a new bond. Thereby, the magnet portion of the slinger is chemically bonded completely and reliability can be promoted by firmly preventing the magnet portion from being detached from the slinger.
Further, the structure of the flange portion 111 of the slinger 110 is not limited to the structure shown in
Further, also the magnetic encoder 120 according to the embodiment is applicable to a hub unit bearing, the magnet portion 121 may be bonded to the slinger constituting the hermetically sealing apparatus similar to the first embodiment, or may be arranged between two rows of inner ring track faces in parallel with each other and fixed to the rotating member by way of an attaching member as mentioned later. In this case, the sensor is arranged to be opposed to the outer peripheral face of the magnet portion 121 and is held by the outer ring. Further, the slinger and the attaching member may be constituted by a simple circular ring shape without a flange portion. Further, the magnet portion 121 may be formed separately from the slinger or the attaching member and bonded to the slinger or the attaching member by using an adhering agent. Further, the magnet portion 121 may be fixed by being press-fitted to the slinger or the attaching member, or the rotating member, or the magnet portion 121 may be fixed by using both of adhering by an adhering agent and fixing by press-fitting.
Next, a detailed explanation will be given of a rolling bearing unit integrated with a magnetic encoder according to a fifth embodiment of the invention. Further, portions equivalent to those of the rolling bearing unit according to the third embodiment are attached with the same notations and an explanation thereof will be omitted or simplified.
As shown by
The slinger 151 is constituted by forming the magnetic metal material in the circular ring shape having the section in the L-like shape and includes the fitting portion 153 substantially in the cylindrical shape outwardly fitted to the outer peripheral face of the inner ring 42 and the flange portion 152 substantially in the circular disk shape extended in the radius direction from one end on a side of the opening end portion of the fitting portion 153. The end face of the flange portion 152 facing outside of the bearing is adhered with the magnet portion 161 in the circular ring shape for changing a magnetic field (for example, magnetic flux density or the like) of a vicinity thereof in synchronism with rotation of the inner ring 42, and the magnetic encoder 160 is constituted by the slinger 151 and the magnet portion 161. Further, by forming the slinger 158 constituting the member of fixing the magnet portion 161 by the magnetic material, the magnetic property of the magnet portion 161 can be prevented from being deteriorated, thereby, the accuracy of detecting the rotational number of the inner ring 42 can be promoted.
Further in reference to
The grooves 163, 163 of the magnet portion 161 are respectively formed in a circular ring shape having a section substantially in a trapezoidal shape over entire peripheries thereof at peripheral edge portions on an outer diameter side and an inner diameter side of the adhering face 162. Further, the adhering face 162 is formed with recessed and projected portions over an entire face thereof to provide a pertinent surface roughness in a range of 0.8 through 5.0 μmRa. A middle portion of the grooves 163, 163 of the adhering face 162 (that is, a circumference at a center portion in a diameter direction of the adhering face 162) is coated with the adhering agent, and the adhering face 162 and the end face of the flange portion 152 are adhered to each other. Therefore, the magnet portion 161 is fixed to the slinger 151 in a state of directing the magnetizing face to outside of the bearing and is rotated along with the inner ring 162. During a time period of rotating the inner ring 162 by one rotation, a magnetic flux density at one point at a vicinity of the magnet portion 161 is periodically changed to provide a number of peaks in correspondence with a number of poles of the magnet portion 161. Further, the rotational number of the inner ring 42 is detected by detecting a change in the magnet flux density by the sensor 47 arranged opposedly the magnetizing face of the magnet portion 161.
Further, although in the above-described fifth embodiment, according to the magnet portion 161, the adhering face 162 is formed by a pertinent surface roughness in a range of 0.8 through 5.0 μmRa and the grooves 163, 163 are respectively formed at the peripheral edge portions on the inner diameter side and the outer diameter side of the adhering face 162, the embodiment is not limited thereto but, for example, the adhering face 162 may only be formed by the pertinent surface roughness in the range of 0.8 through 5.0 μmRa without providing the grooves 163, or, the grooves 163, 163 may be formed respectively at the peripheral edge portions of the inner diameter and the outer diameter of the adhering face 162 by constituting the adhering face 162 by a smooth face (about 0.4 μmRa achieved by normally finishing a die face). Further, as shown by
Further, also the magnetic encoder 160 of the embodiment is applicable to a hub unit bearing similar to the fourth embodiment, the magnet portion 161 may be bonded to the slinger constituting the hermetically sealing apparatus as in the first embodiment, or, as mentioned later, may be arranged between two rows of inner ring tracks in parallel with each other and fixed to a rotating member by way of a fixing member.
Further, according to the magnetic encoder 160 of the embodiment, the method of bonding the magnet portion 161 and the slinger 151 differs from those of the above-described embodiments and therefore, the adhering agent is not limited to that of the first embodiment but various adhering agents are applicable thereto, and also compositions of the magnet portion 161 and the slinger 151 can pertinently be changed in accordance therewith.
Next, an explanation will be given of a main shaft apparatus integrated with a magnetic encoder according to a sixth embodiment of the invention in reference to
The main shaft apparatus 200 contains a main shaft 215 constituting a rotating member at inside of a housing 216, the main shaft 215 is rotatably supported by rolling bearings 210, 210 arranged in parallel with each other in an axial direction at a gap between the housing 216 and the main shaft 215. The rolling bearing 210 is constituted by an outer ring 211, an inner ring 212, a plurality of balls 213 arranged rollably at a ring-like gap partitioned by the outer ring 211 and the inner ring 212, and sealing members 214, 214 for closing opening end portions on both sides in the axial direction of the ring-like gap respectively. A base end portion of the main shaft 215 is formed to project in the axial direction from the rolling bearing 210, a projected end thereof is provided with a fixed member 220 for fixing the magnet portion 221 to the main shaft 215, and the magnetic encoder 222 is constituted by the fixed member 222 and the magnet portion 221. The fixed member 220 may integrally be formed with the main shaft 215 substantially in a shape of a circular column, or, may be formed in a shape of a circular ring as a member separate from the main shaft 215 and outwardly fitted to the main shaft 215 to be fixed thereby. Further, an outer peripheral face of the fixed member 220 is outwardly fitted to be adhered with the magnet portion 221 formed in the shape of the circular ring for changing a magnetic field (for example, magnetic flux density or the like) of a vicinity thereof in synchronism with rotation of the main shaft 215.
Further, in reference to
Further, the composition of the magnetic encoder 222 is similar to that of the above-described fifth embodiment.
Further, a sensor 227 is held by a through hole 217 of the housing 216 provided on an extension to an outer side in the diameter direction of the magnetic encoder 222 by way of a holding member 218, and is arranged to make a Hall element 228 provided at a front end thereof opposed to the outer peripheral face of the magnetic encoder 222 by a small gap therebetween. The rotational number of the main shaft 215 is detected by detecting a change in the magnetic flux density by the sensor 227.
Further, in the above-described sixth embodiment, the fixed member 220 and the magnet portion 221 may be fixed to the main shaft 215 by being arranged between the rolling bearings 210, 210 arranged in parallel with each other. Further, the magnetic encoder 222 of the embodiment may be applied to the hub unit bearing.
Next, a detailed explanation will be given of a rolling bearing unit integrated with a magnetic encoder according to a seventh embodiment of the invention in reference to
As shown by
Further in reference to
The slinger 242 is constituted by forming the magnet material in a circular ring shape having a section in an L-like shape as a whole, and is constituted by a flange portion 244 in a flange-like shape developed in a radius direction from a side of the inner ring 42 to a side of the outer ring 41 at a gap in the circular ring shape, a cylindrical portion extended in the axial direction by being bent substantially by right angle from a peripheral edge portion on an inner diameter side of the flange portion 244, and a fitting portion 243 in a cylindrical shape extended in the axial direction by being bent substantially by 180 degrees from the end portion of the cylindrical portion to a side of the inner ring 42. Further, a peripheral edge portion on an outer diameter side of the flange portion 244 is provided with an outer frame 245 in a cylindrical shape extended in the axial direction by being bent substantially by right angle in a direction reverse to that of the cylindrical portion, further, an end portion of the outer frame 245 is provided with a plurality of notches at equal intervals in a circumferential direction, and a plurality of locking claws 247 are formed to be projected in the axial direction. Further, an end portion (hereinafter, referred to as inner frame) 246 of the fitting portion 243 opposed to the outer frame 245 in a radius direction are provided with a plurality of notches at equal intervals in a circumferential direction, and a plurality of locking claws 248 are formed to be projected in the axial direction. An inner diameter of the outer frame 245 is constituted by a diameter substantially equal to an outer diameter of the magnet portion 241 and an outer diameter of the inner frame 246 is constituted by a diameter substantially equal to an inner diameter of the magnet portion 241.
The magnet portion 241 is fitted to a recessed portion in a cylindrical shape partitioned by the flange portion 244, the outer frame 245 and the inner frame 246, and is tackedly supported in a state of bringing one magnetic pole face of the pair of magnetic pole faces into close contact with the flange portion 244 (that is, support portion). Further, the locking claw 247 of the outer frame 245 and the locking claw 248 of the inner frame 246 are folded to bend to be respectively engaged with peripheral edge portions of other magnetic pole face of the pair of magnetic pole faces, and fastened. Thereby, the magnet portion 241 is pinched by the flange portion 244 and the locking claws 247, 248 of the slinger 242 and the magnet portion 241 and the slinger 242 are mechanically bonded.
The slinger 242 integrated with the magnet portion 241 is fixed to an outer peripheral face of the inner ring 42 at the opening end portion of the gap in the ring-like shape to expose the magnetic pole face of the magnet portion 241 engaged with the locking claws 247, 248 to an outer side of the bearing, and is rotated along with the inner ring 42. Therefore, during a time period of rotating the inner ring 42 by one rotation, a magnetic flux density at one point of a vicinity of the magnet portion 241 is periodically changed by including a number of peaks in correspondence with a number of poles of the magnet portion 241. Further, a change in the magnetic flux density is detected by the sensor 47 arranged to be opposed to the magnetic pole face of the magnet portion 241 to thereby detect a rotational number of the inner ring 42.
According to the rolling bearing 240, the magnet portion 241 is fastened to be pinched by the flange portion 244 and the locking claws 247, 248 of the slinger 242 to be mechanically bonded to the slinger 242 and therefore, the magnet portion 241 can easily and firmly be prevented from being detached and reliability of the encoder 240 can be promoted. Further, by also using adherence between the magnet portion 241 and the flange portion 244, a degree of adhering the magnetic pole face of the magnet portion 241 and the flange portion 244 may be promoted and a strength of holding by the slinger 242 may be promoted. By constituting the fixed member of the magnet portion 241 by the slinger 242 constituting the hermetically sealing apparatus, a fixed member for rotating the magnet portion 241 along with the inner ring 42 is not separately needed, further, by forming the slinger 242 by the magnet material, the magnetic property of the magnet portion 241 can be prevented from being deteriorated, and the rotational number (rotational speed) of the inner ring 42 can highly accurately be detected.
Further, although according to the above-described rolling bearing 240, there is constructed a constitution of forming the pluralities of the locking claws 247, 248 at the outer frame 245 and the inner frame 246 in the cylindrical shape by respectively providing the notches at equal intervals in respective circumferential directions and folding to bend the locking claws 247, 248 to fasten, the embodiment is not limited thereto. For example, as a first modified example of the seventh embodiment, as shown by
Further, also according to the above-described rolling bearing 240, the slinger 242 constituting the fixed member is constituted as a single piece member, at a second modified example of a seventh embodiment, as shown by
Further, as a third modified example of the seventh embodiment, as shown by
Further, as a fourth modified example of the seventh embodiment, as shown by
Further, as a fifth modified example of the seventh embodiment, as shown by
Further, at the cylindrical portion of the first slinger member 242a, instead of constituting one end portion thereof in the axial direction connected to the flange portion 244 as described above by a thin wall by machining or the like, as a sixth modified example of the seventh embodiment, as shown by
Further, as a seventh modified example of the seventh embodiment, as shown by
According to the above-described embodiment, the magnetic encoder 240 is constituted by constituting the fixed member of the magnet portion 241 by the slinger 242 and therefore, a number of parts of the rolling bearing can be reduced by sharing the slinger 242 by the hermetically closing apparatus 45 and the magnetic encoder 240.
Further, the magnetic encoder 240 according to the embodiment can also be used by being integrated to the hub unit bearing as shown by
Next, a detailed explanation will be given of a hub unit bearing constituting a bearing for a wheel including a magnetic encoder according to an eighth embodiment of the invention in reference to
A hub unit 260 rotatably supports a wheel (not illustrated) fixed to the attaching flange 12 of the hub 7a. The inner peripheral face of the outer ring 5a is formed with two rows of outer ring tracks 10a, 10b in parallel with each other, further, the outer peripheral faces of the hub 7a and the inner ring member 16a constituting the rotating member are formed with inner ring tracks 14a, 14b respectively opposed to the outer ring tracks 10a, 10b. A gap between the outer ring track 10a and the inner ring track 14a, and a gap between the outer ring track 10b and the inner ring track 14b are respectively rollably arranged with a plurality of the ball rows 17a, 17a held at equal intervals in the circumferential direction by the retainers 18, 18. A magnetic encoder 270 is arranged at the outer peripheral face of the hub 7a between the ball rows 17a, 17a.
The magnetic encoder 270 is constituted by a magnet portion 271 and a fixed member 272, the magnet portion 271 is constituted by subjecting the magnet material including the magnetic powder and the thermoplastic resin as the binder of the magnetic powder and pertinently including the magnetic powder in the range of 86 through 92 weight % to injection molding in the cylindrical shape, and magnetized with N poles and S poles alternately (that is, in multipoles) in the circumferential direction as shown by
The fixed member 272 is constituted by forming the magnetic metal material in the cylindrical shape, a center portion thereof in the axial direction includes a fitting portion 273 fitted to the outer peripheral face of the hub 7a at an inner peripheral face thereof, and fitted to an inner peripheral face of the magnet portion 271 at an outer peripheral face thereof. Further, end portions on both sides in the axial direction of the fixed member 272 are provided with pluralities of notches at equal intervals in respective circumferential directions, and the pluralities of locking claws 274, 275 are formed to project in the axial direction.
The magnet portion 271 is inserted from one end portion in the axial direction of the fixed member 272 and is tackedly supported by the fixed member 272 in a state of bringing a magnetic pole face on an inner diameter side into close contact with an outer peripheral face of the fitting portion 273. Further, the locking claws 274, 275 are folded to bend to be respectively engaged with the peripheral edge portions of the magnetic pole face on the outer diameter side of the magnet portion 271 and are fastened further. Thereby, the magnet portion 271 is pinched by the fitting portion 273 and the locking claws 274, 275 of the fixed member 272, and the magnet portion 271 and the fixed member 272 are mechanically bonded.
The fixed member 272 integrated with the magnet portion 271 is rotated along with the hub 7a by fitting the fitting portion 273 to the outer peripheral face of the hub 7a. Therefore, during a time period of rotating the hub 7a by one rotation, a magnetic flux density at one point at a vicinity of the magnet portion 271 is periodically changed by including a number of peaks in correspondence with a number of poles of the magnet portion 271. Further, the rotational number of the hub 7a (or wheel) is detected by detecting a change in the magnetic flux density by the sensor 28 arranged to be opposed to the magnetic pole face on the outer peripheral side of the magnet portion 271 in a radius direction.
Further, although in the above-described hub unit bearing 260, there is constructed a constitution of respectively forming the pluralities of locking claws 274, 275 by providing notches at equal intervals in the circumferential direction at end portions on both sides in the axial direction of the fixed member 272 and folding to bend the locking claws 274, 275 to be fastened, the embodiment is not limited thereto. For example, there may be constructed a constitution in which one end portion in the axial direction of the fixed member 272 is formed in a circular ring shape having a section substantially in a U-like shape by previously bending the one end portion by 180 degrees to an outer side in the radius direction, the one end portion in the axial direction of the magnet portion 271 is fitted to a recessed portion in the circular ring shape to be tackedly supported thereby, thereafter, the locking claw formed on other end portion in the axial direction of the fixed member 272 may be folded to bend. Thereby, the magnet portion 271 which is tackedly supported can easily be positioned. Further, in this case, a notch may not be provided to one end portion in the axial direction formed in the circular ring shape having the section substantially in the U-like shape of the fixed member 272, further, as a modified example of the eighth embodiment, as shown by
Further, a composition of the magnetic encoder 270 according to the embodiment is similar to that of the seventh embodiment.
Further, the invention is not limited to the above-described embodiment but can pertinently be modified or improved.
Although according to the embodiment, the magnetic encoder is used by attaching the magnet portion to the fixed member of the slinger or the like, the invention is applicable also to a constitution in which the magnet portion is directly attached to a rotating member.
Although according to the embodiment, an explanation has been given of the hub unit bearing, the rolling bearing unit, the main shaft apparatus integrated with the magnetic encoder, the magnetic encoders of the respective embodiments are applicable also to any of the hub unit bearing, the rolling bearing unit and the main shaft apparatus. Further, the magnetic encoder of the invention can also be used by combining the magnetic encoders of the respective embodiments.
Although the invention will be explained further by showing examples as follows, the invention is not restricted at all thereby. First, an explanation will be given of a constitution of a rolling bearing of Examples 1 through 4 fabricated based on the invention. A magnetic encoder of the rolling bearing used in Examples 1 through 4 is constituted by subjecting a magnet material to insert molding in a state of holding a slinger in dies, provided with axial anisotropy by orienting the magnet material by a magnet field in a state of applying the magnetic field in an axial direction, thereafter, magnetized with N poles and S poles alternately in multipoles to a total of 96 poles.
In Example 1, the encoder is a PA (polyamide) 12 based axially anisotropic plastic magnet including 75 volume % of strontium ferrite and a maximum energy product thereof is 2.3 MGOe. Further, the slinger is formed by SUS430 and high frequency welding of the encoder and the slinger is not carried out. Further, a rubber material of a seal lip portion is constituted by NBR (acrylonitrile butadiene rubber) including carbon black, clay or the like.
In Example 2, the encoder is PPS based axially anisotropic bond magnet including 75 weight volume % of SmFeN (samarium-iron-nitrogen) and a maximum energy product thereof is 7.2 MGOe. Further, the slinger is formed by SUS430 and high frequency welding of the encoder and the slinger is not carried out. Further, the rubber material of the sealing portion is constituted by FKM (fluororubber) including carbon black, diatomite or the like.
In Example 3, the encoder is a PA 12 based axially anisotropic bond magnet including 75 weight volume % of NdFeB (neodymium-iron-boron), and a maximum energy product thereof is 11.9 MGOe. Further, the slinger is formed by SUS430 and high frequency welding of the encoder and the slinger is not carried out. Further, the rubber material of the sealing portion is constituted by NBR including carbon black, clay or the like.
In Example 4, an encoder is a PA 12 based axially anisotropic plastic magnet including 75 volume % of strontium ferrite and a maximum energy product thereof is 2.3 MGOe. Further, the slinger is formed by SUS430 and high frequency welding of the encoder and the slinger is carried out. Further, in high frequency welding, a silane coupling agent is constituted by γ-glycidoxypropyltrimethoxy silane, the slinger is dipped in methanol solution including 10 weight % of the silane coupling agent, insert molding of the encoder is carried out after having being dried, thereafter, welding is carried out by high frequency heating by being heated at 200° C. for 30 seconds. Further, the rubber material of the sealing portion is constituted by NBR including carbon black, clay or the like. Table 1 shows constitutions of Examples 1 through 4 mentioned above.
TABLE 1
Example 1
Example 2
Example 3
Example 4
magnet
PA 12 based axially
PPS based axial
PA 12 based axial
PA 12 based
portion
anisotropic plastic
anisotropic bond
anisotropic bond
axially
magnet (BHmax:
magnet (BHmax: 7.2
magnet (BHmax:
anisotropic
2.3 MGOe)
MGOe) including 75
11.9 GOe)
plastic magnet
including 75
volume % of SmFeN
including 75
(BHmax: 2.3
volume % of
96 (48 × 2) poles
volume % of
MGOe) including
strontium ferrite
Nd—Fe—B
75 volume % of
96 (48 × 2) poles
96 (48 × 2) poles
strontium ferrite
96 (48 × 2) poles
slinger
SUS430
SUS430
SUS430
SUS430
high
none
none
none
present
frequency
welding
seal lip
NBR including
FKM including
NBR including
NBR including
portion
carbon black, clay
carbon black,
carbon black, clay
carbon black,
rubber
etc
diatomite etc
etc
clay etc
material
According to the magnetic encoders of the rolling bearing according to Examples 1 through 4, when an air gap equivalent to that of the background art is constituted, a number of poles of the magnetic encoder can be increased and accuracy of detecting the rotational number of the wheel can be promoted. Further, when the magnetic encoder is constituted by the number of poles the same as that of that of the background art, the air gap can be enlarged and a degree of freedom in arranging the sensor can be promoted. Further, depending on a content of the magnetic powder, the magnetic flux density can be made to be equal to or larger than 26 mT, when an interval (air gap) between the magnetic encoder and the sensor is constituted by 1 mm similar to that of the background art, the magnetic encoder can be magnetized by multipoles equal to or larger than 120 poles. At this occasion, the single pitch error can be made to be equal to or smaller than ±2%.
Next, a difference of an adhering force based on a difference of a bonding method and an adhering agent is evaluated by the following method.
A phenolic resin based adhering agent (metalock N-15 made by Toyo Kagaku Kenkyusho) is coated on SUS430 plate member (width 40 mm, length 100 mm, thickness 1 mm) a surface of which is roughened by sand paper, dried by wind at room temperature for about 30 minutes, thereafter, a heating treatment is carried out at 120° C. for 30 minutes. The SUS430 plate member baked with the adhering agent is set to dies, and insert molding of a plastic magnet material (strontium ferrite including 12 nylon based anisotropic plastic magnet compound FEROTOP TP-A27N (content of strontium ferrite, 75 volume % made by Toda Kogyo)) is carried out by constituting a core thereby. Incidentally, a size of the molded plastic magnet is 20 mm in width, 30 mm in length, 3 mm in thickness, an area of a portion molded on SUS430 plate member by injection molding, that is, an area of bonding the plastic magnet and SUS430 plate is 200 mm2 (20 mm×10 mm). Thereafter, the bonded member is subjected to a heating (secondary curing) treatment at 130° C. for 2 hours to provide a test piece of Example 5.
A test piece of Example 6 is provided by a method similar to that of (Example 5) except that the phenolic resin based adhering agent used is metalock N-23 made by Toyo Kagaku Kenkyusho.
A phenolic resin based adhering agent (metalock N-15 made by Toyo Kagaku Kenkyusho) is coated on SUS430 plate member (width 40 mm, length 100 mm, thickness 1 mm) a surface of which is roughened by sand paper, dried by wind at room temperature for about 30 minutes, thereafter, subjected to a heating treatment at 120° C. for 30 minutes. A test piece (width 20 mm, length 30 mm, thickness 3 mm) of aplastic magnet (strontium ferrite including 12 nylon based anisotropic plastic magnet compound FEROTOP TP-A27N (content of strontium ferrite, 75 volume %) made by Toda Kogyo)) is fixed to SUS430 plate member by a fixing jig or the like baked with the adhering agent to constitute a bonding area to be 200 mm2, thereafter, the test piece is subjected to a heating treatment at 130° C. for 2 hours to provide a test piece of Example 7.
A test piece of Example 8 is provided by a method similar to that of (Example 7) except that the phenolic resin based adhering agent used is metalock N-23 made by Toyo Kagaku Kenkyusho.
A one solution type epoxy resin based adhering agent (LOCTITE Hysol 9432NA made by Henckel Japan) is coated on SUS430 plate member (width 40 mm, length 100 mm, thickness 1 mm) a surface of which is roughened by sandpaper, a test piece (width 20 mm, length 30 mm, thickness 3 mm) of a plastic magnet (strontium ferrite including 12 nylon based anisotropic plastic magnet compound EROTOP TP-A27N (content of strontium ferrite, 75 volume %) made by Toda Kogyo) is fixed onto the SUS430 plate member by a fixing jig or the like to constitute a bonding area to be 200 mm2, thereafter, the test piece is subjected to a heating treatment at 120° C. for 1 hour to completely cure the adherin member to provide a test piece of Example 9.
A test piece of Example 10 is provided by a method similar to that of (Example 9) except that the adhering agent used is a two solution type epoxy resin based adhering agent (LOCTITE E-20 HP made by Henckel Japan) and the heating treatment is not needed.
With regard to 6 kinds of adhering test pieces of Examples 5 through 10, a tensile test is carried out for respective 2 pieces thereof by a pulling speed of 5 mm/min and shear adhering strengths (average values) of respective adhering agents are evaluated. An experimental result is shown in Table as follows.
TABLE 2
Example 5
Example 6
Example 7
Example 8
Example 9
Example 10
composition
nylon 12 + strontium
nylon 12 + strontium
nylon 12 + strontium
nylon 12 + strontium
nylon 12 +
nylon 12 +
of plastic
ferrite magnetic
ferrite magnetic
ferrite
ferrite
strontium ferrite
strontium ferrite
magnet
powder (FEROTOP
powder (FEROTOP
magnetic powder
magnetic powder
magnetic powder
magnetic powder
TP-A27N made by
TP-A27N made by
(FEROTOP TP-A27N
(FEROTOP TP-A27N
(FEROTOP
(FEROTOP
Toda Kogyo)
Toda Kogyo)
made by Toda Kogyo)
made by Toda Kogyo)
TP-A27N made
TP-A27N made
by Toda
by Toda
Kogyo)
Kogyo)
route of
phenolic resin based
phenolic resin based
phenolic resin
phenolic resin
one solution type
Two solution type
adhering
adhering agent
adhering agent
based adhering
based adhering
epoxy resin based
epoxy resin based
agent
(metalock N-15 made
(metalock N-23 made
agent (metalock
agent (metalock
adhering agent
adhering agent
by Toyo kagaku
by Toyo Kagaku
N-15 made by Toyo
N-15 made by Toyo
(LOCTITE Hysol
(LOCTITE ∈-20HP
Kenkyusho)
Kenkyusho)
Kagaku Kenkyusho)
Kagaku Kenkyusho)
9432NA made by
made by Henckel
Henckel Japan)
Japan)
bonding
bonding + adhering by
bonding + adhering by
adhering
adhering
adhering
adhering
method
injection molding
injection molding
adhering
12.6 MPa or higher
13.1 MPa or higher
0.3 MPa
0.3 MPa
4.6 KPa
3.2 MPa
shear
(adhering portion is
(adhering portion is
strength
not exfoliated,
not exfoliated,
magnet material is
magnet material is
broken precedingly)
broken precedingly)
It is known from Table 2 that in Example 5 and Example 6 in which the bonding face of the plastic magnet test piece and the SUS430 material plate is molded to be adhered, in comparison with Example 7 and Example 8 in which the adhering force is going to be ensured by operation of only secondary curing of a phenolic resin based adhering agent, or Example 9 and Example 10 in which a test piece and the SUS material plate are simply adhered by using one solution type epoxy and two solution type epoxy adhering agents, a higher adhering strength is ensured.
Next, in the magnetic encoder fabricated by insert molding by constituting the core by the slinger according to the invention, a test is carried out with regard to an adhering state by a difference in a surface treatment.
Recesses and projections are formed by chemically etching an iron oxalate film formed on a surface of SUS430. An arithmetic mean height Ra of recesses and projections becomes 0.9 μm and a maximum height Rz thereof becomes 4.5 μm. Further, a phenolic resin based adhering agent (metalock N-15) made by Toyo Kagaku Kenkyusho) including 30% of a solid component whose major component is constituted by a resol type phenolic resin is further diluted by three times by methylethylketone and is coated on a surface of the slinger by a dipping treatment. The test piece is dried at room temperature for 30 minutes and left in a dehydrator at 120° C. for 30 minutes to thereby bring about a semicured state. SUS430 plate member baked with the adhering agent is set to dies, and insert molding of a plastic magnet material (strontium ferrite including 12 nylon based anisotropic plastic magnetic compound [FEROTOP TP-A27N] (content of strontium ferrite, 91 weight %) made by Toda Kogyo) is carried out from an inner peripheral portion by the disk gate by constituting a core thereby. After molding the gate is immediately cut, and a test piece in which the adhering agent is completely cured by secondary heating at 130° C. for 1 hour is made to constitute a SUS piece of Example 11.
A test piece of Example 12 is provided by a method similar to that of (Example 11) except that the surface of SUS430 is formed by recesses and projections by shot blast, an arithmetic mean height Ra of recesses and projections is made to be 0.8 μm a maximum height Rz thereof is made to be 5.0 μm.
Table 3 as follows shows a result of pulling a catch portion of an outer peripheral portion of the encoder after having been cured by pliers.
TABLE 3
Example 11
Example 12
recesses and
chemical etching by iron
shot blast
projections
oxalate
treatment
adhering state
By pulling by pliers,
sufficient
catch portion is
adhering force is
exfoliated to be broken,
maintained than in
magnet portion cannot be
not treating
exfoliated further.
surface
As is apparent from Table 3, although surface roughnesses hardly differ by the recesses and projections treatment, recesses and projections by the chemical etching treatment are constituted by a shape in which an inner portion of a recess portion is widened (
Next, as shown by Table 4 shown below, a heat shock test is carried out by using Examples 13 through 15 in which blending of the magnet material of the magnet portion is changed.
TABLE 4
Example 13
Example 14
Example 15
Sr ferrite (wt %)
91
89.5
91
PA12 (wt %)
6.5
7.6
8.7
denatured PA12
2.0
2.4
0
(wt %)
Plasticizer
0.2
0.2
0
silane coupling
0.3
0.3
0.3
agent
bending amount
2.8
6.2
1.6
(ASTM D790; t =
3.2, room
temperature)
BHmax [kJ/m3]
16.6 (2.0)
14.3 (1.8)
16.6 (2.0)
(MGOe)
heat shock test
no crack by
no crack by
crack by 50
result
1000 cycles
1000 cycles
through 100
(120° C. 30 min ⇔
cycles
−40° C.30 min)
Sr ferrite: anisotropic Sr ferrite for magnetic field orientation, FERO TOP FM-201 (made by Toda Kogyo)
PA12: PA 12 including copper based heat stabilizer (number average molecular weight 14000), UBE nylon P3014U (made by Ube Kosan)
denatured PA12: denatured PA12 (bending elastic modulus 147 MPa, melting point 154° C.), UBESTA XPA 9055X1 (made by Ube Kosan) plasticizer: p-hydroxy benzoic acid ethylhexyl (paraoxy benzoic acid ethylexyl), POBO (made by API corporation) silane coupling agent: y-aminopropyltriethoxy silane, A-1100 (made by Nippon Unicar)
Further, as a surface treatment of the slinger of Examples 13 through Example 15, similar to Example 11 mentioned above, a chemical blast treatment made by Nippon Parkerizing is carried out. Specifically, recesses and projections are formed by chemically etching an iron oxalate film formed on a surface of a plate member comprising SUS430 having a thickness of 0.6 mm. An arithmetic mean height Ra of recesses and projections is 0.2 through 0.3 μm, a maximum height Rz thereof is 1.8 through 3.1 μm.
Further, a phenolic resin based adhering agent (metalock N-15 made by Toyo Kagaku Kenkyusho) having 30% of a solid component whose major component is resol type phenolic resin is diluted further by three times by methylethylketone and is coated on the surface of the slinger by a dipping treatment. Thereafter, the adhering agent is brought into a semicured state by leaving the adhering agent in a dehydrator at 120° C. for 30 minutes after drying the adhering agent at room temperature for 30 minutes. A SUS430 plate member baked with the adhering agent is set to dies and insert molding of the magnet material is carried out from the inner peripheral portion by the disk gate by constituting the core thereby. After molding, the gate is immediately cut, further, the adhering agent is completely cured by subjecting the adhering agent to secondary heating at 150° C. for 1 hour.
Thereafter, a single member of the encoder portion (inner diameter 66 mm, outer diameter 76 mm, magnet portion thickness 0.9 mm) provided by integrating with the slinger by molding is subjected to a heat shock test repeating a cycle of 30 minutes at 120° C. and 30 minutes at −40° C. Respective 10 pieces of samples of Examples 13 through 15 are subjected to the test and cracks generated at the magnet portions are observed at respective 50 cycle.
As is apparent from Table 4, it is known that by including denatured PA12 resin as the binder, the bending amount of the material per se is increased and crack resistance is promoted.
Next, with regard to the magnet material of the composition of Example 14, magnetic property by presence or absence of a magnetic field is measured by using a magnetic field injection molding machine. Further, a shape of the magnetic encoder is constituted by that shown in
TABLE 5
magnetic field
generation
present
not present
magnetic flux density
37
27
(N pole average, mT)
single pitch error (%; maximum)
0.40
0.32
It is confirmed from a result of Table 5 that the magnetic property is promoted by carrying out molding under the magnetic field.
Next, a test is carried out with regard to a change in the magnetic property when the magnetic encoder is fabricated by different injection molding systems. Encoders of Examples 16 through 19 are magnetized in a circumferential direction after having been subjected to injection molding in the circular ring shape. Further, the magnet material of the magnet portion used in the magnetic encoder of Examples 16 through 19 is shown below.
magnet material for test:
strontium ferrite including 12 nylon based anisotropic plastic magnet compound [FEROTOP TP-A27N] (strontium ferrite: 75 volume %) made by Toda Kogyo
The encoder of Example 16 is molded by a disk gate type injection molding machine and is not oriented by the magnetic field in molding.
The encoder of Example 17 is molded by the disk gate type injection molding machine and is oriented by the magnetic field in molding.
The encoder of Example 18 is molded by 4 point pin gate type injection molding machine and is not oriented by the magnetic field in molding.
The encoder of Example 19 is molded by the 4 point pin gate type injection molding machine and is oriented by the magnetic field in molding.
Table 6 shows a result of measuring magnetic properties (maximum energy products BHmax) of the magnetic encoders of Examples 16 through 19 by using a BH tracer. Further, with regard to measured values of Examples 18 and 19, magnetic properties at the weld portions are measured.
TABLE 6
Example 16
Example 17
Example 18
Example 19
gate type
disk gate
disk gate
4 point pin
4 point pin
gate
gate
magnetic
none
present
none
present
field
orientation
BH max
1.8
2.1
0.8
1.6
(MGOe)
According to Table 6, it is known that an encoder subjected to injection molding by the disk gate type is provided with the magnetic property more excellent than that of the encoder subjected to injection molding by the 4 point pin gate type regardless of presence or absence of magnetic field orientation. That is, according to the disk gate type, a high orientation degree can be achieved by aligning an axis of easy magnetization of respective magnetic powders, thereby, an excellent magnetic property can be achieved. On the other hand, with regard to the 4 point pin gate type, at the weld portion, the magnetic powders in the melted magnet material collide with each other and the axis of easy magnetization becomes random (becomes isotropic) and therefore, the magnetic property is significantly deteriorated. Further, even when the magnetic field orientation is carried out in injection molding by the 4 point pin gate type, it is known that it is difficult to completely orient the magnetic powder at the weld and the magnetic property is inferior to the magnetic property of the encoder molded only by injection molding by the disk gate type without carrying out magnetic field orientation. Further, even when a plastic magnet material including a magnetic powder of rare earth based of SmFeN (samarium-iron-nitrogen) or the like is used, a similar result is provided.
Next, in order to confirm an effect when a groove is formed at an adhering face of the magnet portion, the following test is carried out. Magnet portions of Examples 20 and 21 include strontium ferrite as a magnetic powder and polyamide 12 as a binder, and an encoder having an inner diameter 60 mm, an outer diameter 70 mm, a thickness 0.9 mm is molded by injection molding from raw material pellet formed by agitating a magnet material having a content of the magnet powder of 70 volume % to be needed by a biaxial extruding machine. According to molding conditions, a temperature of heating the resin is 270° C., injection time is 1.5 seconds.
The encoder of Example 20 is formed with grooves in a circular ring shape having a section substantially in a trapezoidal shape at peripheral edge portions on an outer diameter side and an inner diameter side of one side end face in an axial direction thereof (that is, adhering face). Further, a surface roughness of the adhering face is made to be 0.8 μmRa by subjecting a die used in injection molding to crimping.
The encoder of Example 21 is formed by the dimension the same as that of the encoder of Example 20, and the adhering face is not formed with a groove. Further, a surface roughness of the adhering face is 0.4 μmRa achieved by normal die face finishing.
The encoder of Example 20 is coated with an adhering agent uniformly on a circumference of a center portion in a diameter direction of the adhering face (that is, a middle portion of two pieces of grooves) and is adhered to an attaching member by applying a predetermined pressure. Further, also the encoder of Example 21 is uniformly coated with the same amount of the adhering agent at a portion the same as that of Example 20 and is adhered to the attaching member by applying a predetermined pressure. According to the encoder of Example 21, at either of the inner diameter side and the outer diameter side, the extra adhering agent overflows from the adhering face to outside. On the other hand, according to the encoder of Example 20, the adhering agent overflowing from the adhering face to outside is not recognized, further, the adhering agent is permitted by a capillary phenomenon also to an adhering face riding over the groove (that is, at the peripheral edge portion on the outer diameter side, a plane portion provided contiguously to an outer side in a radius direction of the groove, in the peripheral edge portion on the inner diameter side, a plane portion provided contiguously to an inner side in the radius direction of the groove).
Next, with regard to magnetic encoders of Examples 22 through 25, an adhering strength between the encoder and the adhering agent owing to a surface roughness of the adhering face of the encoder is evaluated. Test pieces having a width 24 mm, length 100 mm, thickness 3 mm are molded by injection molding from raw material pellets from Examples 20 and 21. Surface roughnesses of a plane (that is, adhering face) rectified by a width direction and a length direction are changed for respective test pieces by subjecting a die used in injection molding to crimping. An acrylic based adhering agent (LOCTITE 648 made by Henckel corporation) is uniformly coated on the adhering face and the test piece is adhered to a flat plate of SUS430 constituting an attaching member by applying a predetermined pressure. Thereafter, a tensile load orthogonal to the adhering face is applied and a tensile strength is measured by a pulling speed of 5 mm/min. A result thereof is shown in Table 7. Further, Example 22 is a product finished by a normal die face and a surface roughness thereof is 0.4 μmRa.
Further, the tensile strengths of the respective test pieces are relative numerical values when the tensile strength of Example 22 is made to be 100.
TABLE 7
Example 22
Example 23
Example 24
Example 25
surface
0.4
0.8
2.4
3.6
roughness
[μmRa]
tensile
100
126
135
138
strength
According to Table 7 and
Next, a test is carried out with regard to holding strengths of magnetic encoders of Examples 26 through 29. Table 8 shows constitutions of the magnetic encoders of Examples 26 through 29. The magnet portions of the magnetic encoders of Examples 26 through 29 are subjected injection molding in a cylindrical shape in a state of applying a magnetic field in a thickness direction thereof, made to be axial anisotropy and magnetized with N poles and S poles in a circumferential direction alternately by a total of 96 poles. Further, the magnet portion and the fixed member are integrated by a constitution of the fixed member shown in the seventh embodiment.
TABLE 8
Example 26
Example 27
Example 28
Example 29
magnet
PA 12 based axially
PPS based axially
PA 12 based axially
PA 12 based axially
portion
anisotropic plastic
anisotropic bond
anisotropic bond
anisotropic plastic
magnet (BHmax:
magnet (BHmax:
magnet (BHmax:
magnet (BHmax:
2.3 MGOe)
7.2 MGOe)
11.9 GOe)
2.3 MGOe)
including 75
including 75
including 75
including 75
volume % of
volume % of
volume % of Nd—
volume % of
strontium ferrite
SmFeN
Fe—B
strontium ferrite
96 (48 × 2) poles
96 (48 × 2) poles
96 (48 × 2) poles
96 (48 × 2) poles
Slinger
SUS430
SUS430
SUS430
SUS430
high
none
none
none
present
frequency
welding
seal lip
NBR including
FKM including
NBR including
NBR including
portion
carbon black, clay
carbon black,
carbon black, clay
carbon black, clay
rubber
etc
diatomite etc
etc
etc
material
Holding
O
O
O
O
strength
Further, Table 9 shows constitutions of encoders of Example 30 and Example 31. Permanent magnets of the encoders of Example 30 and Example 31 are molded by injection molding in a cylindrical shape in a state of applying a magnetic field in a radius direction, made to be radial anisotropy and magnetized with N poles and S poles in a circumferential direction alternately by a total of 96 poles. Further, the magnet portion and the fixed member are integrated by a constitution of the fixed member shown in the seventh embodiment.
TABLE 9
Example 30
Example 31
magnet
PA 12 based radial
PPS based radial
portion
anisotropic plastic magnet
anisotropic bond magnet
(BHmax: 2.3 MGOe)
(BHmax 7.2 MGOe)
including 75 volume % of
including 75 volume %
strontium ferrite
of SmFeN
96 (48 × 2) poles
96 (48 × 2) poles
Slinger
SUS430
SUS430
Holding
O
O
Strength
In any of Example 26 through Example 31, the permanent magnet is not detached from the fixed member in a rotating test. Further, depending on the content of the magnetic powder, the magnetic flux density which has been about 20 mT in the background art can be increased to be equal to or larger than 26 mT. Therefore, when the air gap between the permanent magnet of the sensor is made to be 1 mm similar to that of the background art, the permanent magnet which has been magnetized in multipoles of 96 poles in the background art can be magnetized in multipoles equal to or larger than 120 poles while maintaining a magnetic flux per pole. At this occasion, the single pitch error can be made to be equal to or smaller than ±2%. That is, according to the encoder according to the invention, when an air gap equivalent to that of the background art is constituted, accuracy of detecting the rotational speed of the wheel can be promoted by increasing a number of poles of the permanent magnet. Further, when a pole number of the magnet is made to be equal to that of the background art, the air gap can be enlarged, and a degree of freedom in arranging a sensor can be promoted.
Although an explanation has been given of the invention in details and in reference to the specific embodiments, it is apparent for the skilled person that the invention can variously be changed or modified without deviating from the spirit and the range of the invention.
The application is based on Japanese Patent Application (Japanese Patent Application No. 2004-014033), filed on Jan. 22, 2004,
The invention provides the highly reliable magnetic encoder having a high magnetic property and enabling to detect a rotational number with high accuracy and is utilized for detecting a rotational number of a rotating member in a rolling bearing unit, a main shaft apparatus, a hub unit bearing or the like.
Murakami, Takeshi, Yabe, Toshikazu, Takajo, Toshimi, Aihara, Nariaki
| Patent | Priority | Assignee | Title |
| Patent | Priority | Assignee | Title |
| 4549157, | May 27 1982 | PHOENIX AMERICA, INC | Plastic bonded magnet with circumferentially spaced poles having substantially uniform magnetic properties |
| 6872325, | Sep 09 2002 | SABIC INNOVATIVE PLASTICS IP B V | Polymeric resin bonded magnets |
| 7207723, | Mar 11 2003 | NTN Corporation | Wheel support bearing assembly with magnetic encoder |
| 7229708, | Sep 12 2003 | NOK Corporation | Magnetic encoder |
| 7374343, | Feb 25 2003 | NTN Corporation | Magnetic encoder and wheel support bearing assembly using the same |
| 20020141673, | |||
| 20030059139, | |||
| 20040220316, | |||
| 20050275565, | |||
| JP10285895, | |||
| JP2000158476, | |||
| JP2000195714, | |||
| JP200060080, | |||
| JP2001255337, | |||
| JP2001272250, | |||
| JP2001323942, | |||
| JP2002228675, | |||
| JP2003035565, | |||
| JP2003130684, | |||
| JP2003183443, | |||
| JP2003222150, | |||
| JP2003280394, | |||
| JP2003297621, | |||
| JP200357070, | |||
| JP2004011827, | |||
| JP2004037441, | |||
| JP2004150859, | |||
| JP6055054, | |||
| JP61164215, | |||
| JP6331384, | |||
| JP6354712, | |||
| JP6425716, | |||
| JP7237266, | |||
| JP8227819, |
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