Rolling bearing and spindle apparatus for machine tool

Abstract

A rolling bearing includes an inner ring having an outer surface, an outer ring having an inner surface, a plurality of rolling elements rotatably disposed between the inner ring and the outer ring, and a retainer for retaining the rolling elements. The retainer is made of a resin material and is positioned with respect to the inner surface of the outer ring or the outer surface of the inner ring. The retainer includes a pair of annular portions axially arranged in parallel and a columnar portion coupling the annular portions. Then, the rolling bearing satisfies the following expression: AI=LH³/dm≥0.025 LH³/dm²≥0.025 mm² in which H is a radial length of a section of the annular portion, L is an axial length of the same, and dm is PCD of the rolling element.

Description

in which H is a radial length of a section of the annular portion, L is an axial length of the same, and dm is PCD of the rolling element.

According to this invention, the retainer is positioned with respect to the inner surface of the outer ring, that is, the guided surface of the retainer is provided in the retainer outer surface opposed to a raceway surface of the outer ring. Therefore, a clearance between the outer surface of the inner ring and the inner surface of the retainer, or a clearance between the inner surface of the outer ring and the outer surface of the retainer can be designed to be comparatively large. As a result, lubricating oil ejected from a nozzle for oil-air or oil-mist lubrication can be surely introduced into the bearing from the comparatively large clearance, and the lubricating oil is scattered to the outer ring side by centrifugal force, so that the guided surface of the retainer is lubricated smoothly.

The retainer is guided thus by the outer ring or the inner ring, whereby the whirling amount of the retainer at the time of the high-speed rotation can be controlled by the guide clearance. Further, as a material of the retainer, there is used a resin material in which the seizure is hardly caused even with a slight amount of lubrication, and the above expression (1) is satisfied, in which H is the radial length of the section of the annular portion, L is the axial length of the same, and dm is PCD of the rolling element, whereby higher rigidification becomes possible than in the conventional retainer, and the amount of deformation at the high-speed rotating time can be suppressed.

As the resin material of the retainer, phenol resin, polyamide 46, polyamide 66, polyphenylene sulfaid, thermoplastic polyimide, polyether etherketone, and the like can be used as base material. Further, it is preferable to add glass fiber by 10-40 wt %, carbon fiber by 10-30 wt %, or aramid fiber by 10-30 wt % in order to improve strength of the retainer. Further, in order to satisfy use in high-speed rotation, the carbon fiber or the aramid fiber is more preferable. However, according to the use, the glass fiber can be also selected. In case that the addition amount of the carbon fiber or the aramid fiber is 10 wt % or less, the strength cannot be sufficiently maintained. In case that it is 30 wt % or more, the molding property is deteriorated and the external appearance is also bad. Further, more preferably, the addition amount of the carbon fiber or the aramid fiber is 20-30 wt %, whereby both the strength and the molding property become improved. The addition amount of the glass fiber is preferably 10-40 wt %, and this reason is the same as the above reason.

However, in case of the cylindrical roller bearing, if the axial width of the retainer of the outer ring guide type is set so as to satisfy the above expression (1), there is a fear that a lead-in portion of the outer ring raceway surface, which is provided in order to smoothly perform the incorporation of the cylindrical rollers, interferes with the guided surface of the retainer by the axial movement of the inner ring due to an incorporation error and shaft expansion during running. Hereby, such a disadvantage is caused that the brake is applied on running of the retainer and the guided surface of the retainer wears. Against this, chamfering and tapering are applied to the peripheral portion of the guided surface of the retainer, and a clearance of 0.5 mm or more is provided axially up to an intersecting point of the raceway surface of the outer ring and the lead-in portion, whereby this disadvantage can be avoided.

Further, a notch is provided for at least one of four corners in each pocket of the retainer for retaining the rolling elements, whereby it is possible to speedily move the lubricating oil supplied to the raceway surface of the inner ring and the ribs, according to the rotational speed of the bearing, through the notch to the raceway surface of the outer ring.

Further, a roller or ball guide portion in circumferential direction of the pocket has a flat surface, which is parallel to the shaft which the bearing supports. Thus, a snap portion for retaining the roller or the ball, in view of the moving amount of the retainer and dimensional tolerance, can be formed so that it does not interfere with the roller or the ball at worst during running, and the high-speed rotation can be realized without obstructing the movement of the roller or the ball. In addition, in order to obtain high-speed stabilization of the retainer, the both-side guide effective for inclination of the retainer is preferable.

Further, in order to attain the above object, there is provided a rolling bearing comprising:

• • an inner ring having an outer surface;
  • an outer ring having an inner surface;
  • a plurality of rolling elements rotatably disposed between the inner ring and the outer ring; and,
  • a retainer for retaining the rolling elements, the retainer being made of a resin material, the retainer including a guided surface that is guided by the inner surface of the outer ring or the outer surface of the inner ring,
  • wherein the guided surface has two or more recesses.

The guided surface of the retainer is opposed to either the inner surface of the outer ring or the outer surface of the inner ring, and located on circumference of the retainer that comes into slide-contact with the outer ring or the inner ring.

According to this rolling bearing, even when it is used in such a high-speed rotation region that a Dmn value is over 1×10⁶, not only the grease can be held on the guided surface of the retainer made of synthetic resin but also an oil film by the grease is appropriately formed since a wedge effect is produced in the recess portion. Namely, the clearance between the guided surface of the retainer and the guide surface of the raceway ring is large in the point where the recess is provided and small in other points than it, and the grease held in the recess is pulled into the points where the clearance is small. As a result, it is prevented that the guided surface of the retainer is worn by the slide with the raceway surfaces of the outer ring and inner ring, and the rolling bearing that is superior in high-speed stability (low-torque, low-noise, low-vibration, seizure-resistance) can be provided. Further, since the rolling bearing of the invention can suppress the occurrence of the iron powder due to wear, the deterioration of the grease is prevented, so that a long use becomes possible.

In the above constitution, a depth of the recess portion in the radial direction of the retainer is preferably 0.3 mm or more. Hereby, on the guided surface of the retainer made of synthetic resin, the enough grease can be held.

Moreover, to attain the above object, there is provided a rolling bearing, comprising:

• • an inner ring;
  • an outer ring;
  • a plurality of rolling elements rotatably disposed between the inner ring and the outer ring; and
  • a retainer for retaining the rolling elements, the retainer being made of a resin material and formed by an injection-molding, the retainer having a recess axially extending on an outer periphery (an outermost surface) thereof,
  • wherein the recess has a parting line formed at the time of injection-molding.

Here, “outermost surface of the retainer” means an outer surface located outermost in the radial direction of the annular retainer, that is, an outer surface located outside in the radial direction of the retainer from a parting line formed on the outer surface except for at least the outermost surface.

Further, it is preferable that the recess formed on the outermost surface has such a depth that the parting line formed in the recess portion does not protrude outward of the retainer from the outermost surface.

According to the rolling bearing of the invention, since the parting line formed on the outer surface of the retainer does not protrude from the outermost surface of the retainer, the retainer can be incorporated into the bearing without having necessity to perform after-treatment after injection-molding of the retainer. Accordingly, the assembly process of the rolling bearing can be simplified, and yield of parts of the retainer can be also improved. Further, when the retainer is incorporated into the bearing, the parting line formed on the outer surface of the retainer does not come into slide-contact with the inner surface of the outer ring of the bearing. Namely, during running of the rolling bearing, the bad operation due to wear of the parting line and the torque change is not caused.

Further, in this case, a forming mold comprises a fixed mold for forming one end of the retainer, a columnar movable mold for forming the inner surface of the retainer and the other end, and a plurality of slide-cores that are arranged outside of the movable mold, formed convexly in a section, and form the outer surface of the retainer and the pocket portions. The slide cores have a circular-arc shaped base portion put side by side with the outer surface of the movable mold and a protrusion erectly provided on the surface on the movable mold side of the base portion nearly perpendicularly.

When a forming mold is tightened, the leading end surface of the protrusion of the slide core comes into contact with the outer surface of the movable mold, and side surfaces of the base portions of the slide cores adjacent to each other comes contact with each other, whereby a cavity space is formed at the periphery of the movable mold, and synthetic resin material is injected in the cavity space, so as to form a retainer. In a apparatus of manufacturing a rolling bearing retainer that forms thus the retainer, it is preferable that a projection member that protrudes to the movable mold side is provided on the inner surface of the contact portion of the base portion that becomes an outermost surface of the retainer when the side surfaces of the base portions adjacent to each other come into contact with each other, and that the parting line formed on the outermost surface of the retainer when the synthetic resin is injected is formed in the recess portion formed by the projection member.

According to this apparatus of manufacturing the rolling bearing retainer, since the parting line formed on the outer surface of the retainer does not protrude from the outermost surface of the retainer, it is necessary to perform after-treatment after injection-molding of the retainer. Accordingly, the assembly process of the rolling bearing can be simplified, and yield of parts of the retainer can be also improved.

In addition, there is provided a rolling bearing, including:

• • an inner ring having an outer surface;
  • an outer ring having an inner surface;
  • a plurality of rolling elements rotatably disposed between the inner ring and the outer ring; and
  • a retainer for retaining the rolling elements, the retainer being made of a resin material, the retainer including a guided surface that is guided by the inner surface of the outer ring or the outer surface of the inner ring and a pocket holding the rolling element,
  • wherein a guide clearance between the inner surface of the outer ring or the outer surface of the inner ring and the guided surface of the retainer is set to 0.05-0.4% of a diameter of the guided surface of the retainer, and
  • wherein a clearance between the pocket of the retainer- and the rolling element is set to 0.8-1.8% of the guide clearance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an axially sectional view showing a bearing apparatus according to a first embodiment of the invention;

FIG. 2 is an enlarged view showing only the bearing in this embodiment;

FIG. 3 is a diagram viewed from a direction of an arrow III in FIG. 1, in which an outer ring is removed from the bearing apparatus of FIG. 1;

FIG. 4 is a diagram showing a state in which an inner ring is removed from the bearing apparatus shown in FIG. 1, viewed axially;

FIGS. 5A to 5C are diagrams showing modified examples of a shape of a retainer;

FIG. 6 is a diagram showing a test result in the embodiment and a comparative example in a cylindrical roller bearing apparatus;

FIG. 7 is a sectional view of a cylindrical roller bearing apparatus according to a second embodiment of the invention, which is similar to the sectional view in FIG. 2;

FIG. 8 is a sectional view of a cylindrical roller bearing apparatus according to a third embodiment of the invention, which is similar to the sectional view in FIG. 2;

FIG. 9 is a sectional view of an angular ball bearing apparatus according to a fourth embodiment of the invention, which is similar to the sectional view in FIG. 2;

FIG. 10 is a sectional view of an angular ball bearing apparatus according to a fifth embodiment of the invention, which is similar to the sectional view in FIG. 2;

FIG. 11 is a sectional view of an angular ball bearing apparatus according to a sixth embodiment of the invention, which is similar to the sectional view in FIG. 2;

FIG. 12 is a sectional view of an angular ball bearing apparatus according to a seventh embodiment of the invention, which is similar to the sectional view in FIG. 2;

FIG. 13 is a diagram showing a test result in the embodiment and a comparative example in the angular ball bearing apparatus;

FIG. 14 is a diagram showing a modified example of the bearing apparatus in FIG. 1, which is similar to FIG. 3;

FIG. 15 is a diagram showing a modified example of the bearing apparatus in FIG. 1, which is similar to FIG. 4;

FIG. 16 is a whole side view of a cylindrical roller bearing according to an eighth embodiment of the invention;

FIG. 17 is a partially enlarged view of a retainer shown in FIG. 16;

FIGS. 18A to 18C are diagrams showing modified examples of the retainer in FIG. 16;

FIG. 19 is a whole side view of a cylindrical roller bearing according to a ninth embodiment of the invention;

FIG. 20 is a partially enlarged view of a retainer shown in FIG. 19;

FIG. 21 is a diagram showing a part of a side view of a retainer 110 of a rolling bearing according to a tenth embodiment of the invention;

FIG. 22 is a diagram showing a part of a plan view of the retainer 110 shown in FIG. 21;

FIG. 23 is a partially sectional view showing a part of a forming mold 120 for molding the retainer 110 shown in FIG. 21;

FIG. 24 is a diagram showing a part of a plan view of a retainer 130 of a rolling bearing according to an eleventh embodiment of the invention;

FIG. 25 is a diagram showing a part of a plan view of a retainer 140 of a rolling bearing according to a twelfth embodiment of the invention;

FIG. 26 is a diagram showing a part of a side view of a retainer 150 of a rolling bearing according to a thirteenth embodiment of the invention;

FIG. 27 is a diagram showing a part of a plan view of the retainer 150 shown in FIG. 26;

FIG. 28 is a diagram showing an analysis result of a retainer guide clearance and Fc run-out;

FIG. 29 is a diagram of a test machine into which a rolling bearing of the invention is incorporated;

FIG. 30 is a diagram showing the relation between a retainer guide clearance and Fc run-out;

FIG. 31 is a diagram showing the relation between a pocket clearance and Fc run-out;

FIG. 32 is a front view showing another embodiment of the retainer;

FIG. 33 is a side view of FIG. 32;

FIG. 34 is a whole side view showing a conventional cylindrical roller bearing;

FIG. 35 is a sectional view taken along a line XXXIV-XXXIV in FIG. 34;

FIG. 36 is a sectional view showing a forming mold 210 of a conventional radial draw type;

FIG. 37 is a diagram showing a part of a side view showing a retainer 220 of a conventional bearing;

FIG. 38 is a diagram showing a part of a plan view of the retainer 220 shown in FIG. 37; and

FIG. 39 is a schematic diagram of a general rolling bearing.

DETAILED DESCRIPTION OF THE PREFREED EMBODIMENTS

Description will be given of embodiments of the invention with reference to drawings.

FIG. 1 is an axially sectional view, showing a rolling bearing according to a first embodiment of the invention. FIG. 2 is an enlarged view showing only the rolling bearing in this embodiment. A rolling bearing 10 includes an outer ring 11 without rib, an inner ring 12 with ribs 12a at both ends, plural rollers (rolling elements) 13 rotatably provided between the both rings 11 and 12, and a retainer 14 for retaining the rollers 13. In FIG. 1, a lubricating oil supplying apparatus 20 for oil-air or oil-mist lubrication is provided adjacent to the rolling bearing 10. A supply passage 20a of the lubricating oil supplying apparatus 20 is directed to the inside of the rolling bearing 10 so as to eject the lubricating oil sent from the external with pressure, into the inside of the bearing 10.

The retainer 14 is positioned with respect to the inner periphery of the outer ring 11, and an outer surface 14a of the retainer 14 opposed to a raceway surface 11a of the outer ring 11 serves as a guided surface of the retainer 14. Therefore, it is possible to design a clearance between an outer surface 12b of the rib 12a of the inner ring 12 and an inner surface 14b of the retainer 14 relatively large. As a result, the lubricating oil ejected from the supply passage 20a of the lubricating oil supplying apparatus 20, as shown by an arrow in FIG. 1, is surely introduced from this relatively wide clearance into the inside of the rolling bearing 10, and the lubricating oil is scattered to the outer ring side by centrifugal force, so that the guided surface of the retainer 14 can be lubricated smoothly.

Further, the retainer 14 of the outer ring guide type can control the whirling amount of the retainer 14 at the time of high-speed rotation by the guide clearance. As a material of the retainer 14, phenol resin, polyamide 46, polyamide 66, polyphenylene sulfaid, thermoplastic polyimide, polyether etherketone, and the like can be used as base material. Further, in order to improve the strength of the retainer, it is preferable to add glass fiber by 10-40 wt %, carbon fiber by 10-30 wt % or aramid fiber by 10-30 wt %. Further, in order to satisfy use in the high-speed rotation, the carbon fiber or the aramid fiber is more preferable. However, according to the use, the glass fiber can be also selected. In case that the addition amount of the carbon fiber or the aramid fiber is 10 wt % or less, it is insufficient to keep the strength, and in case that it is 30 wt % or more, the molding property is deteriorated and the external appearance is also bad. Further, it is more preferable that the addition amount of the carbon fiber or the aramid fiber is 20-30 wt %, whereby both strength and the molding property are improved. The addition amount of the glass fiber is preferably 10-40 wt %, and this reason is the same as the above reason.

Further, as shown in FIG. 2, the retainer 14 has a pair of annular portions 14r juxtaposed axially and a columnar portion 14p coupling the annular portions 14r. And, the retainer 14 satisfies the following expression:


in which H is a radial length of a section of the annular portion 14r, L is an axial length of the same, and dm is PCD (pitch circle diameter) of the rolling element 13. The retainer 14 thus designed can obtain high rigidity compared with the conventional retainer, and suppress the amount of deformation at the high-speed rotating time.

However, in case that the annular portion 14r (i.e., pocket shape) of the outer ring guide type of the retainer 14 is designed so that the two expressions (1), (2) are satisfied, there is a fear that a lead-in portion 11b provided in order to incorporate the cylindrical roller 13 smoothly and formed inside the end portion of the raceway surface 11a of the outer ring 11 interferes with the guided surface 14a of the retainer 14 by the axial movement of the inner ring 12 due to the incorporation error and shaft expansion during running. Hereby, such a disadvantage causes that brake is applied on running of the retainer 14 or the guided surface 14a of the retainer 14 is worn. In case of this embodiment, chamfering (or tapering) 14c is provided at the outer peripheral end of the guided surface 14a of the retainer 14, and the inward end of the chamfering 14c is axially arranged apart from an intersecting point of the raceway surface 11a and the lead-in portion lib of the outer ring 11 by 0.5 mm or more, whereby avoiding the above disadvantage.

FIG. 3 is a diagram viewed from the direction of an arrow III in FIG. 1, in which the outer ring is removed from the bearing. FIG. 4 is a diagram viewed axially, in which the inner ring is removed from the bearing in FIG. 1. As shown in FIG. 3, a pocket 14d of the retainer 14 for retaining the roller 13 has notches 14g at its four-corners, whereby it is possible to speedily move the lubricating oil supplied to the raceway surface and ribs of the inner ring 12, according to the rotational speed of the bearing 10, through these notches 14g to the raceway surface 11a (FIG. 1) of the outer ring 11.

A roller guide surface 14e in circumferential direction of the pocket 14d is formed in a flat shape with an axial width a. Further, axial guide surfaces 14h of the retainer 14 come into contact with the both end surfaces of the roller 13 by a circumferential length b (refer to FIG. 4). The width a of the guide surface 14e is set to 20-80% of the roller length L2, the length b of the guide surface 14h to 40-80% of the roller diameter, and the height c (refer to FIG. 4) of the guide surface 14h from PCD of the roller 13 to 20-40% of the outer diameter D of the roller 13, so as to reduce the contact area of the roller 13 and the retainer 14, and suppress the interference between a chamfering portion 13a of the roller 13 and the guide surface 14h. A chamfering angle of a snap portion 14f is preferably is set to 25-60°. Further, the snap portion 14f is so designed that even if the retainer 14 moves radially by the guide clearance and the roller 13 moves in the circumferential direction by the pocket clearance, the snap portion does not interfere with the roller 13. In addition, this embodiment adopts the both-side guide effective for inclination of the retainer 14 in order to obtain high-speed stabilization of the retainer 14, but one-side guide may be adopted.

The axial guide surface 14h of the retainer 14 may be omitted like a modified example shown in FIGS. 14 and 15 as long as a space through which the lubricating oil can pass is provided. Further, the above is similar also in an inner ring guide type of the retainer serving as a retainer for under-race lubrication. Therefore, although the guide is performed by the outer ring, it may be guided by the inner ring. In the above embodiment, although the cylindrical roller bearing is described, the invention may be applied to ball bearings. Embodiments of these bearings will be described below with reference to drawings.

FIG. 7 is a sectional view of a cylindrical roller bearing according to a second embodiment of the invention, which is similar to the sectional view in FIG. 2. In FIG. 7, a bearing 30 has an outer ring 31 without rib, an inner ring 32 with ribs 32a at both ends, plural rollers (rolling elements) 33 rotatably provided between the both rings 31 and 32, and a retainer 34 for retaining the rollers 33. A lubricating oil supplying apparatus for oil-air or oil-mist lubrication (not shown in FIG. 7) is provided adjacent to the roller bearing 30.

Similarly to the embodiment shown in FIG. 2, the retainer 34 is also positioned with respect to the inner periphery of the outer ring 31. However, in this embodiment, a guided surface of the retainer 34 is provided on only an outer surface 34a of an annular portion 34r on the right side in FIG. 7, opposed to a raceway surface 31a of the outer ring 31. In this embodiment, H is a radial length of a section of the right annular portion 34r of the retainer 34, and L is an axial length of the same. Other constitution is the same as that in the above-described embodiment, and the working and the effect thereof can be obtained similarly.

FIG. 8 is a sectional view of a cylindrical roller bearing according to a third embodiment of the invention, which is similar to the sectional view in FIG. 2. In FIG. 8, a bearing 40 has an outer ring 41 with ribs, an inner ring 42, plural rollers (rolling elements) 43 rotatably provided between the both rings 41 and 42, and a retainer 44 for retaining the rollers 43. A lubricating oil supplying apparatus for oil-air or oil-mist lubrication (not shown in FIG. 8) is provided adjacent to the rolling bearing 40.

Similarly to the embodiment shown in FIG. 2, the retainer 44 is also positioned with respect to the inner periphery of the outer ring 41, and a guided surface of the retainer 44 is provided on a retainer outer surface 44a opposed to a raceway surface 41a of the outer ring 41. The basic constitution except that the inner ring 42 has no ribs is the same as that in the above-described embodiment, and the working and the effect can be obtained similarly.

FIG. 9 is a sectional view of an angular ball bearing according to a fourth embodiment of the invention, which is similar to the sectional view in FIG. 2. In FIG. 9, a bearing 50 has an outer ring 51, an inner ring 52, plural balls (rolling elements) 53 rotatably provided between the both rings 51 and 52, and a retainer 54 for retaining the balls 53. A lubricating oil supplying apparatus for oil-air or oil-mist lubrication (not shown in FIG. 9) is provided adjacent to the bearing 50.

Similarly to the embodiment shown in FIG. 2, the retainer 54 is also positioned with respect to the inner periphery of the outer ring 51. However, in this embodiment, a guided surface of the retainer 54 is provided on only an outer surface 54a of an annular portion 54r on the right side in FIG. 9, opposed to an inner surface 51a of the outer ring 51. In this embodiment, H is a radial length of a section of the right annular portion 54r of the retainer 54, and L is an axial length of the same. Other constitution than the above main different point is the same as that in the above-described embodiment, and the working and the effect can be obtained similarly.

FIG. 10 is a sectional view of an angular ball bearing according to a fifth embodiment of the invention, which is similar to the sectional view in FIG. 2. In FIG. 10, a bearing 60 has an outer ring 61, an inner ring 62, plural balls (rolling elements) 63 rotatably provided between the both rings 61 and 62, and a retainer 64 for retaining the balls 63. As shown in FIG. 10, oil supply ports 62b for under-race lubrication are provided for the inner ring 62, and lubricating oil is supplied to an inner surface 64a of the retainer 64.

The retainer 64 in this embodiment is positioned with respect to the outer periphery of the inner ring 62, so that a guided surface of the retainer 64 is provided on the retainer inner surface 64a opposed to an outer surface 62a of the inner ring 62. The basic constitution except for the above-described main different point is the same as that in the above-described embodiment, and the working and the effect can be also obtained similarly.

FIG. 11 is a sectional view of an angular ball bearing according to a sixth embodiment of the invention, which is similar to the sectional view in FIG. 2. In FIG. 11, a bearing 70 has an outer ring 71, an inner ring 72, plural balls (rolling elements) 73 rotatably provided between the both rings 71 and 72, and a retainer 74 for-retaining the balls 73. A lubricating oil supplying apparatus for oil-air or oil-mist lubrication (not shown in FIG. 11) is provided adjacent to the bearing 70.

Similarly to the embodiment shown in FIG. 2, the retainer 74 is also positioned with respect to the inner periphery of the outer ring 71. However, in this embodiment, a guided surface of the retainer 74 is provided on only an outer surface 74a of an annular portion 74r on the right side in FIG. 11, opposed to an inner surface 71a of the outer ring 71. And, step portions 74s faced inwardly are formed on the outer surfaces of a pair of the annular portions 74r of the retainer 74. In this embodiment, H is a radial length of a section of the right annular portion 74r of the retainer 74, and L is an axial length of the same. Other constitution than the above main different points is the same as that in the above-described embodiment, and the working and the effect can be obtained similarly.

FIG. 12 is a sectional view of an angular ball bearing according to a seventh embodiment of the invention, which is similar to the sectional view in FIG. 2. In FIG. 12, a bearing 80 has an outer ring 81, an inner ring 82, plural balls (rolling elements) 83 rotatably provided between the both rings 81 and 82, and a retainer 84 for retaining the balls 83. A lubricating oil supplying apparatus for oil-air or oil-mist lubrication (not shown in FIG. 12) is provided adjacent to the bearing 80.

Similarly to the embodiment shown in FIG. 2, the retainer 84 is also positioned with respect to the inner periphery of the outer ring 81, and a guide surfaced of the retainer 84 is provided on a retainer outer surface 84a opposed to an inner surface 81a of the outer ring 81. In this embodiment, H is a radial length of a section of an annular portion 84r of the retainer 84, and L is an axial length of the same. Other constitution than the above main different point is the same as that in the above-described embodiment, and the working and the effect can be obtained similarly.

Embodiments applied to the cylindrical roller bearing apparatus will be described below. A result of calculation in various sectional shapes in the embodiments will be shown.

• • (Calculating condition)
  • Dimension of retainer outer diameter: 99.5 mm.
  • Roller diameter: 9 mm
  • Roller length: 9 mm
  • Number of rollers: 20
  • Roller PCD (dm): 91 mm
  • Retainer material: PEEK resin
  • Rotation speed: 25000 rpm
  • Guide clearance: 0.4 mm
  • Retainer unbalance: 0.5 g·cm

A calculation result of the deformation amount of retainer under the above condition is shown in Table 1.

TABLE 1
			Retainer
	Retainer	Pocket	inner		[Al]	Amount of
	width	width	diameter	dm	LH3/dm2	deformation
1	17.1	9.3	90.51	91	0.043	0.13
2	17.1	9.3	91.5	91	0.030	0.18
3	17.1	9.3	92.5	91	0.020	0.25
4	13.5	9.3	90.51	91	0.023	0.21
5	13.5	9.3	91.5	91	0.016	0.29
6	13.5	9.3	92.5	91	0.011	0.42

From this calculation result, the condition 1 shown in Table 1 can obtain the smallest amount of deformation. Taking the deformation amount of the retainer at the high-speed running time into consideration,
Δc: guide clearance
dm: ball PCD
θi: layout angle (rad) of the i-th ball
Δθi: unequal layout angle (rad) generated in the i-th ball
(When the retainer whirls due to the guide clearance, the center portion of each pocket is geometrically shifted by a value of the expression (A). The expression (A) is assumed based on the thought that a center of the ball is, on an average, in a center of the pocket.)
{circle around (2)} In case that the angular unequal layout by the expression (A) is produced in each ball, and the inner ring of the bearing rotates upon reception of the axial load,

• • A) Power applied onto each ball from inner and outer rings
  • B) Centrifugal force of each ball
  • C) External force
  • D) Elastic proximity amount of each ball and inner and outer rings
  • E) Displacement of bearing center
    the bearing displacement in which the total of A), B), and C) is 0 and a contradiction is not produced in D) and E) is obtained by a convergent calculation. Twice the displacement of this radial displacement becomes FC run-out.

From the result of FIG. 28, it is known that by making the guide clearance small, the Fc run-out can be reduced.

Next, a test bearing is incorporated into a test machine shown in FIG. 29, and the relation between guide clearance and Fc run-out and the relation between pocket clearance and Fc run-out are respectively tested. Reference characters D and E shown in FIG. 29 are test bearings.

[Condition]

Test bearing: angular bearing (constant-position preload, back-to-back combination, inner ring guide type retainer)

• • Inner diameter: 85 mm
  • PCD: 107 mm
  • Ball diameter: 12.7 mm
  • Number of balls: 22
  • Ball: ceramic ball
  • Contact angle: 20°
  • Rotation speed: 5000-18000 rpm

Effectivity of the rolling bearing of the invention can be confirmed by measuring run-out of a point α shown in FIG. 29 during rotation.

In this test, only the retainer 4 is changed while using the entirely same outer ring 1, the inner ring 2, and the ball 3, and the influence by the guide clearance 5 of the retainer and the pocket clearance 6 was be confirmed.

FIGS. 30 and 31 are test results. FIG. 30 shows the relation between the guide clearance 5 and Fc run-out, and FIG. 31 shows the relation between the pocket clearance 6 and Fc run-out.

By making the guide clearance 5 of the retainer small, the FC run-out can be reduced (refer to FIG. 30). The Fc run-out becomes large in a high-speed rotation of more than 14000 rpm. On the contrary, in a low speed rotation, since there is little influence of whirling of the retainer 4, the Fc run-out is small and there is no correlation between the guide clearance 5 and the Fc run-out.

In case that the size of the pocket clearance 6 is changed, when the pocket clearance 6 is 0.8-1.8 times the size of the guide clearance 5, there is little influence on the Fc run-out (refer to FIG. 31). As the pocket clearance 6 becomes smaller than its size, the Fc run-out becomes larger.

As a retainer material, polyimide resin was used. Hereby, compared with the conventional copper alloy retainer, coefficient of friction on the guided surface can be reduced, and even if the guide clearance 5 is made small, the seizure of the guided surface can be prevented.

Further, the retainer material is not limited to the above material, but it can be appropriately selected and used within the range of the invention. For example, also in case that heat-resistant plastic that is high in rigidity such as PEEK (polyether etherketone) is used, the seizure of the guided surface can be improved.

The test result in FIG. 30 coincides with the analysis result in FIG. 28 in a tendency.

Since the analysis in FIG. 28 is analysis of only the bearing, it is different from the test result including the deformation of the shaft in FIG. 30 in an absolute value of the Fc displacement by about twice. However, their tendencies coincide with each other, so that the effectivity of the rolling bearing of the invention can be confirmed from both viewpoints of the analysis and the experiment.

FIGS. 32 and 33 show another embodiment of the invention.

In this embodiment, in order to prevent seizure in case that a guide clearance 5 of a retainer of an outer ring guide type is made small, oil exhausting grooves 7 as shown in FIGS. 32 and 33 are provided on a guided surface 4c of the retainers 4. Accordingly, heat generation due to oil on the guided surface 4c is reduced and the seizure can be prevented.

According to the invention, as described above, the guide clearance of the retainer is made smaller than that of the conventional retainer, whirling of the retainer is reduced, and the size of the pocket clearance is set to an appropriate value with respect to the guide clearance, whereby the unequal layout of the ball due to the whirling of the retainer is reduced and the rotational accuracy of the bearing can be improved. Namely, according to the invention, Fc run-out at the running time at a high speed can be reduced, and in case that this rolling bearing is used in the spindle apparatus for machine tool, the quality of the machined surface can be improved.

Particularly, a machine tool that performs finishing of a metal mold, requires high-speed machining and surface roughness of several μm. In case that the Fc run-out is about 20% or more with respect to this roughness, there are stripes on the external appearance, which may cause a problem in a finished surface. However, according to the invention, the guide clearance is 0.4% or less the size of the guide diameter, whereby the Fc can be made sufficiently small with respect to a target of the surface roughness and the machined surface can be improved. Further, since the guide clearance is 0.05 or more the size of the guide diameter, there is no fear of the seizure on the guided surface.

In case that the pocket clearance is made much smaller than the guide clearance, when the retainer whirls, there is increased a possibility that the ball cannot exist in the nearly uniform layout position. On the other, in case that the pocket clearance is made much larger than the guide clearance, there is increased a possibility that the ball exists in the position of the large unequal layout angle. In the invention, the pocket clearance is 0.8-1.8 times the size of the guide clearance, whereby the Fc run-out can be reduced.

Claims

1. A rolling bearing, comprising:

an inner ring having an outer surface;

an outer ring having an inner surface;

a plurality of rolling elements rotatably disposed between the inner ring and the outer ring, wherein each of the rolling elements is a cylindrical roller; and,

a retainer for retaining the rolling elements, the retainer being made of a resin material, the retainer being positioned with respect to the inner surface of the outer ring or the outer surface of the inner ring, the retainer including a pair of annular portions axially arranged in parallel and a columnar portion coupling the annular portions,

wherein the following expression is obtained:

line-formulae description="In-line Formulae" end="lead"?>AL=LH³/dm²≥0.025 mm² LH³/dm²≥0.025 mm²line-formulae description="In-line Formulae" end="tail"?>

in which H is a radial length of a section of the annular portion each of the annular portions, L is an axial length of the same each of the annular portions, and dm is PCD of the rolling element a pitch circle diameter of each of the rolling elements, and

further wherein the retainer is formed by an injection-molding and has a recess axially extending on an outer periphery thereof, and the recess has a parting line formed at the time of injection-molding.

2. The rolling bearing according to claim 1, wherein the retainer is positioned with respect to the inner surface of the outer ring.

3. The rolling bearing according to claim 2, wherein the inner ring has ribs at both ends thereof, and the rolling element is a cylindrical roller.

4. The rolling bearing according to claim 2, wherein the outer ring has ribs at both ends thereof, and the rolling element is a cylindrical roller.

5. The rolling bearing according to claim 2, wherein the rolling element is a ball.

6. The rolling bearing according to claim 1, wherein the retainer is positioned with respect to the outer surface of the inner ring.

7. The rolling bearing according to claim 6, wherein the rolling element is a ball.

8. A spindle apparatus for a machine tool including, wherein the spindle apparatus includes the rolling bearing according to claim 1.

9. The spindle apparatus according to claim 8, wherein the retainer further includes a guided surface that is guided by the inner surface of the outer ring or the outer surface of the inner ring, and the guided surface has two ten or more recesses.

10. The spindle apparatus according to claim 9, wherein the retainer further includes a pocket holding the rolling element,

wherein a guide clearance between the inner surface of the outer ring or the outer surface of the inner ring and the guided surface of the retainer is set to 0.05-0.4% of a diameter of the guided surface of the retainer, and

wherein a clearance between the pocket of the retainer and the rolling element is set to 0.8-1.8% of the guide clearance.

11. The rolling bearing according to claim 1, wherein the retainer further includes a guided surface that is guided by the inner surface of the outer ring or the outer surface of the inner ring, and the guided surface has two ten or more recesses.

12. The rolling bearing according to claim 11, wherein the retainer further includes a pocket holding the rolling element,

wherein a guide clearance between the inner surface of the outer ring or the outer surface of the inner ring and the guided surface of the retainer is set to 0.05-0.4% of a diameter of the guided surface of the retainer, and

wherein a clearance between the pocket of the retainer and the rolling element is set to 0.8-1.8% of the guide clearance.

13. A rolling bearing, comprising:

an inner ring;

an outer ring;

a plurality of rolling elements rotatably disposed between the inner ring and the outer ring; and

a retainer for retaining the rolling elements, the retainer being made of a resin material and formed by an injection-molding, the retainer having a recess axially extending on an outer periphery thereof, wherein said recess does not extend around an entire circumference of the retainer, and

wherein the recess has a parting line formed at the time of injection-molding.

14. The rolling bearing according to claim 13, wherein the retainer further includes a pocket holding the rolling element,

wherein a guide clearance between the inner surface of the outer ring or the outer surface of the inner ring and the guided surface of the retainer is set to 0.05-0.4% of a diameter of the guided surface of the retainer, and

wherein a clearance between the pocket of the retainer and the rolling element is set to 0.8-1.8% of the guide clearance.

15. A spindle apparatus for a machine tool including the rolling bearing according to claim 13.

16. A rolling bearing, comprising:

an inner ring having an outer surface;

an outer ring having an inner surface;

a plurality of rolling elements rotatably disposed between the inner ring and the outer ring; and

a retainer for retaining the rolling elements, the retainer being made of a resin material, the retainer including a guided surface that is guided by the inner surface of the outer ring or the outer surface of the inner ring and a pocket holding the rolling element,

wherein a guide clearance between the inner surface of the outer ring or the outer surface of the inner ring and the guided surface of the retainer is set to 0.05-0.4% of a diameter of the guided surface of the retainer, and

wherein a clearance between the pocket of the retainer and the rolling element is set to 0.8-1.8% of the guide clearance.

17. A spindle apparatus for a machine tool including the rolling bearing according to claim 16.

18. A rolling bearing comprising:

an inner ring having an outer surface;

an outer ring having an inner surface;

a plurality of rolling elements rotatably disposed between the inner ring and the outer ring; and,

a retainer for retaining the rolling elements, the retainer being made of a resin material, the retainer being positioned with respect to the inner surface of the outer ring or the outer surface of the inner ring, the retainer including a pair of annular portions axially arranged in parallel and a columnar portion coupling the annular portions,

wherein the following expression is obtained:

line-formulae description="In-line Formulae" end="lead"?>AI=LH³/dm²≥0.025 mm² line-formulae description="In-line Formulae" end="tail"?>

in which H is a radial length of a section of the annular portion, L is an axial length of the same, and dm is PCD of the rolling element, and

wherein the retainer further includes a guided surface that is guided by the inner surface of the outer ring or the outer surface of the inner ring, and a pocket holding the rolling element,

wherein a guide clearance between the inner surface of the outer ring or the outer surface of the inner ring and the guided surface of the retainer is set to 0.05-0.4% of a diameter of the guided surface of the retainer; and

wherein a clearance between the pocket of the retainer and the rolling element is set to 0.8-1.8% of the guide clearance.

19. A rolling bearing comprising:

an inner ring having an outer surface;

an outer ring having an inner surface;

a plurality of rolling elements rotatably disposed between the inner ring and the outer ring; and

a retainer for retaining the rolling elements, the retainer being made of a synthetic resin material, the retainer including a guided surface that is guided by the inner surface of the outer ring,

wherein the guided surface has two or more recesses and the number of the recesses is the same as the number of rolling elements, wherein a depth of the recesses is 0.3 mm or more,

wherein the synthetic resin material comprises glass fiber in the amount of 10-40 wt %, carbon fiber in the amount of 10-30 wt %, or aramid fiber in the amount of 10-30 wt %,

wherein the retainer further includes a pocket holding the rolling element,

wherein a guide clearance between the inner surface of the outer ring or the outer surface of the inner ring and the guided surface of the retainer is set to 0.05-0.4% of a diameter of the guided surface of the retainer; and

wherein a clearance between the pocket of the retainer and the rolling element is set to 0.8-1.8% of the guide clearance.

20. rolling bearing comprising:

an inner ring having an outer surface;

an outer ring having an inner surface;

a plurality of rolling elements rotatably disposed between the inner ring and the outer ring; and

a retainer for retaining the rolling elements, the retainer being made of a synthetic resin material, the retainer including a guided surface that is guided by the inner surface of the outer ring,

wherein the guided surface has two or more recesses and the number of the recesses is the same as the number of rolling elements, wherein a depth of the recesses is 0.3 mm or more,

wherein the synthetic resin material comprises glass fiber in the amount of 10-40 wt %, carbon fiber in the amount of 10-30 wt %, or aramid fiber in the amount of 10-30 wt %, and

further wherein the retainer is formed by an injection-molding, and the recess has a parting line formed at the time of injection-molding.

21. The rolling bearing according to claim 20, wherein the retainer further includes a pocket holding the rolling element,

wherein a guide clearance between the inner surface of the outer ring or the outer surface of the inner ring and the guided surface of the retainer is set to 0.05-0.4% of a diameter of the guided surface of the retainer, and

wherein a clearance between the pocket of the retainer and the rolling element is set to 0.8-1.8% of the guide clearance.