In order to reduce the cost of producing an in-hub a magnetic hard disk storage device having a motor, which consists of a hub and the motor which is located in this hub and which contains magnets, magnetic yokes, coils, and shieldings, the hub (2) made of magnetizable steel is coated at least on the outer surface (20) with a noncorrosive coating which is reduced by means of final machining in the completed state of the motor.
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0. 1. In-hub motor comprising:
a fixed shaft extending axially of the motor; a stator mounted on the fixed shaft; a pair of ball bearings mounted on the fixed shaft axially spaced apart from each other on either axial end of the stator; a rotor mounted over and at least foundationally supported by both said axially spaced apart ball bearings to rotate around the stator and be separated therefrom by a cylindrical air gap, the rotor including a yoke body of magnetic material having a cylindrical inner surface and a cylindrical outer surface and formed to axially span both said spaced apart ball bearings in support of the rotor and ring shaped permanent magnets mounted on the inner surface of the yoke body opposite the stator and defining an extent of the air gap; and a coating of machinable noncorrosive material applied to the outer surface of the yoke body, said coating being of a predetermined thickness to provide a surface capable of being machined to reduce radial eccentricity in a finished motor.
0. 3. In-hub motor comprising:
a fixed shaft extending axially of the motor; a stator mounted on the fixed shaft; a pair of ball bearings mounted on the fixed shaft axially spaced apart from each other on either axial end of the stator; a rotor mounted over and at least foundationally supported by both said axially spaced apart ball bearings to rotate around the stator and be separated therefrom by a cylindrical air gap, the rotor including a yoke body of magnetic material having a cylindrical inner surface and a cylindrical outer surface and formed to axially span both said spaced apart ball bearings in support of the rotor and ring shaped permanent magnets mounted on the inner surface of the yoke body opposite the stator and defining an extent of the air gap; and a casing of noncorrosive material of predetermined thickness having two axially opposing ends, one of which is for securing the casing to the yoke body of the rotor, the casing being made to conform to the outer surface of the yoke body and being nested over the outer surface of the yoke body providing a machinable surface for reducing radial eccentricity in a finished motor.
0. 10. A disk storage device, comprising:
a clean room having an internal mounting surface; at least one hard magnetic storage disk provided in said clean room for rotation about an axis, said at least one disk having a central opening; at least one read/write head mounted in said clean room for movement in operative relation to said at least one disk; a motor mounted on the internal mounting surface of said clean room for rotating said at least one disk about said axis, said motor including a stator and a bearing and shaft assembly, said assembly including a shaft extending axially of the motor and bearings surrounding said shaft, said motor further including a rotor which is rotatable via said bearings about said axis, said rotor including a cylindrical yoke body of magnetic material and a plurality of ring-shaped permanent magnets connected to said yoke body such that a cylindrical air gap is defined between adjacent surfaces of said permanent magnets and said stator, said motor further including a coating of a machinable noncorrosive material applied to a cylindrical outer surface of said rotor which extends through the central opening of and thereby supports said at least one disk, said coating being of a predetermined thickness to provide a surface capable of being machined to generally reduce radial eccentricity in a finished motor.
0. 18. A disk storage device, comprising:
a clean room having an internal mounting surface; at last one hard magnetic storage disk provided in said clean room for rotation about an axis, said at least one disk having a central opening; at least one read/write head mounted in said clean room for movement in operative relation to said at least one disk; a motor mounted on the internal mounting surface of said clean room for rotating said at least one disk about said axis, said motor including a stator and a bearing and shaft assembly, said assembly including a shaft extending axially of the motor and bearings surrounding said shaft, said motor further including a rotor which is rotatable via said bearings about said axis, said rotor including a cylindrical yoke body of magnetic material and a plurality of ring-shaped permanent magnets connected to said yoke body such that a cylindrical air gap is defined between adjacent surfaces of said permanent magnets and said stator, said motor further including a machinable noncorrosive casing of a predetermined thickness applied to a cylindrical outer surface of said rotor which extends through the central opening of and thereby mounts said at least one disk, said casing having two axially opposing ends, one of which is for securing said casing to the cylindrical outer surface of said rotor, said casing being made to conform to and be nested over the cylindrical outer surface of said rotor to provide a machinable surface for generally reducing radial eccentricity in a finished motor.
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This application is a continuation of application Ser. No. 200,654 filed May 31, 1988.
The invention concerns an in-hub motor.
In-hub motors, as found, for example, in Winchester mechanisms in data processing, have been developed to provide a particularly high degree of freedom with respect to radial and axial eccentricity. Among other things, this freedom is obtained by giving the aluminum vat, which forms the hub and in which the magnetic yokes and magnets are secured, its fine machining, i.e., grinding or stripping, on the finished motor.
In the case of motors with a large ratio of torque to volume, the magnetic yoke and the plate hub are constructed as one piece and consist of magnetizable steel, which must have a rustproof coating. This rustproof coating prevents any machining of the hub in the finished motor, thus requiring that the hub be manufactured with very high precision before installation.
It must be borne in mind that the eccentricity tolerance of the finished motor should be the result of the sum of the eccentricity tolerances of the constituent parts so that, for example, the ball bearings, the plate hub itself, and the joining accuracy required at the time of assembly must remain below 5 μ.
The rustproof coating must lie within these tolerance limits. On the other hand, it is not possible to avoid such a rustproof coating by the use of stainless steel because this steel would not exhibit those magnetic properties that are particularly necessary in this type of motor.
Thus, the expenditure of time and money in the production of this type of motor is very high due to grinding, honing, or polishing. This production expenditure cannot be reduced even if large quantities of the motor are produced.
The objective, therefore, should be to reduce this production expenditure as much as possible.
The solution to this problem is to coat the hub, which consists of magnetizable steel and which has the form of a yoke body, with a noncorrosive coating at least on the outer surface, which is reduced by final processing in the completed state.
In order to bond the noncorrosive coating to the hub, all currently known joining techniques, such as shrink coating, dipping, sputtering, or bonding of caps or casings on the hub, may be employed.
Particularly during the use of galvanically deposited aluminum, a considerable reduction in production expenditure results based on the high adhesive strength and excellent machinability.
Other materials, which adhere excellently to the iron core of the hub, are also appropriate. This suitability is even greater when the specific weights of the hub and the coating are identical.
An additional improvement can be obtained if the entire hub, both inside and outside, is covered with the noncorrosive coating. This results primarily in a long-term constancy of the minimum radial and axial eccentricity obtained after final forming. In addition, the temperature profile of shaft, ball bearing, and rotor is mutually adjusted so that eccentricity variations are minimized during operation.
The following are advantages of the process described above: the production expenditure is significantly reduced, instances of corrosion no longer occur, long- and short-term variations in eccentricity are minimized, and the mechanical stability of the rotor is improved.
The drawing which further illustrates the invention, shows
In
In order to reduce the volume, in the motor, as shown in
The conventionally employed noncorrosive coating 5, which is at least applied to the outer surface 20 of hub 1, however, is no longer only a few μ thick, but instead has a range in thickness of from 15 μ to approximately 200 μ. Thus, it is no longer just a protection against corrosion but a mechanically machinable component which can be primarily used to reduce radial eccentricity, particularly by means of final finishing of the built-in shaft.
The coating can consist of plastic or metal and should adhere very tightly to hub 1.
Conventional joining techniques, such as shrink coating of a cap or casing, bonding of such elements, or coating by dipping, sputtering, or galvanization, can be used to create the coating. On the one hand, the coating should be applied so as to be sufficiently thick to ensure satisfactory handling during assembly of the motor and, on the other hand, thin enough so that it can be reduced at minimum cost during the final machining procedure on the shaft.
A relatively modern shrink-coating process uses the dynamic effect of electromagnetic parts at high pulse-like currents. This so-called magnetic molding process is particularly suited for aluminum casing 35, which is to be tightly applied to the underlying steel core of the hub, thus forming a disk storage hub.
Thin coatings of aluminum up to a thickness of 0.2 mm can be applied most effectively by means of evaporation, thus giving a uniform thickness to the entire surface.
The invention can be used advantageously particularly in hard-disk storage devices with a disk diameter of 5.25 inches or less.
Magnetic yoke body 2 as well as casing 35, preferably made of aluminum, each have a Z-shaped cross section with parts of the casing 35 and yoke body 2, respectively, lying adjacent and parallel to each other. The radial outer ends of lower flanges 22 and 38 are designed in such a way as to form surrounding groove 23 into which metal ballast can be axially inserted (or removed).
Papst, Georg F., Cap, Heinrich
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Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Sep 07 1995 | Papst Licensing, GmbH | (assignment on the face of the patent) | / | |||
Nov 03 1998 | Papst Licensing GmbH | PAPST LICENSING GMBH & CO KG | LEGAL ORGANIZATION CHANGE | 009922 | /0250 |
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