JP5039491B2 - Bearing device and motor provided with the same - Google Patents

Description

  The present invention relates to a bearing device and a motor including the same, and more particularly to a bearing device having a sintered alloy bearing and a resin housing for holding the bearing, and a motor including the bearing device.

A sliding bearing using a sintered alloy bearing as a radial bearing is frequently used in a motor mounted on an ODD (Optical Disc Drive) or LBP (Laser Beam Printer) and rotating an optical disk or a polygon mirror.
In response to the demand for cost reduction from the market, the use of synthetic resin instead of metal is increasing for the material of the bearing holder in which the sintered alloy bearing is press-fitted and held.
An example of a bearing device employing a synthetic resin as a material for the bearing holder and a motor including the same is described in Patent Document 1.

JP 2004-28174 A

By the way, in the bearing device in which the sintered alloy bearing is press-fitted and held in the resin-made bearing holder and the motor including the same as described above, the following problems (1) and (2) may occur. Improvement is desired.
(1) Along with the rotational movement of the motor, the sintered alloy bearing is slightly displaced in the axial position with respect to the synthetic resin bearing holder, and the accuracy of each part dimension (verticality etc.) as the motor is sufficiently lowered. Will not be able to demonstrate the proper characteristics.
(2) Furthermore, a part of the sintered alloy bearing comes out (protrudes) from the synthetic resin bearing holder, and comes into contact with the rotating member of the motor to generate vibration and noise.

As a result of detailed investigation by the inventor on these problems, it has been found that the root cause is the draft provided in the bearing holder.
This draft angle is a taper provided to release the product well when the bearing holder is formed by injection molding. In the bearing holder, along the axial direction, the hole into which the bearing fits. It means that it is given a gradient so that the diameter increases.

Referring to FIG. 5, a synthetic resin bearing holder 103 formed by injection molding has a bottomed hole (so-called blind hole) 103a into which the bearing fits, and the bottomed hole 103a has an axis J Is provided with a gradient (draft gradient) having a small diameter on the bottom side and a large diameter on the opening side.
For example, when the hole diameter DPT is 6 mm, for example, when the hole diameter DPT is 6 mm, it is common to provide a draft so that the maximum difference is about 80 μm.

  A bearing device 110 in which the sintered alloy bearing 104 is press-fitted and held in such a bearing holder 103 and a motor 111 as an example of a motor provided with the bearing device 110 are shown in a half sectional view in FIG.

  In this motor 111, the bearing device 110 is fixed to the motor base 105 constituting the stator S, and the shaft 107 fixed to the hub 106 constituting the rotor R is a sintered alloy bearing 104 of the bearing device 110. The rotor R is rotatably supported with respect to the stator S.

  A motor 111 as shown in FIG. 6 is mounted on an ODD or LBP to rotate and drive an optical disk or a polygon mirror. However, the rotational speed of the motor 111 has been increasing in recent years. It is hot.

In such a structure in which the sintered alloy bearing is held by press fitting in the bearing holder, the inner diameter of the bearing holder made of synthetic resin is smaller than that of synthetic resin due to thermal expansion accompanying temperature rise. It becomes larger than the outer diameter of the sintered alloy bearing made of metal, and as a result, the press fit is loosened. That is, the press-fit holding force is reduced.
The degree of loosening becomes more prominent due to further increase in temperature during the operation of the device.

  For this reason, the sintered alloy bearing may be moved in the axial direction in which the diameter increases because the hole of the fitted bearing holder has a draft. This is the reason why the above problem (1) occurs.

Further, in the case of a usage pattern in which operation and non-operation are repeated, the temperature increase and the temperature decrease to room temperature are repeated.
That is, since the expansion and contraction of the hole diameter are repeated, the sintered alloy bearing repeatedly moves in the axial direction, and gradually moves toward the larger diameter side, and the bearing protrudes from the bearing holder. And the case where this protrusion part strikes the rotation member of a motor and a vibration and noise generate | occur | produce may arise. This is the reason why the above problem (2) occurs.

In order to prevent this problem from occurring, it is possible to take a measure of increasing the press-fitting margin, but if the press-fitting margin is increased, the roundness of the hole in the synthetic resin bearing holder into which the sintered alloy bearing fits. However, it is easy to be reflected on the inner peripheral surface of the bearing.
Since the bearing holder is made of synthetic resin, there is a limit to increasing the roundness, and usually only about 1/10 roundness can be obtained with respect to a metal bearing holder. Similarly, the roundness is likely to be about 1/10, and the characteristics required as a bearing cannot be stably maintained.
Therefore, the preventive measure of increasing the press-fit margin is difficult to adopt from the viewpoint of maintaining the motor characteristics.

  On the other hand, with regard to the draft angle that is the root cause, there may be a preventive measure of setting this to 0 (zero), that is, eliminating the gradient, but the releasability of the injection molding is extremely lowered, so that it can not be adopted. Absent.

Therefore, the problem to be solved by the present invention is that even if the bearing holder for press-fitting and holding the sintered alloy bearing is made of synthetic resin, its formability is not lowered, and the sintered alloy bearing held by the bearing holder is not deteriorated. It is an object of the present invention to provide a bearing device in which the axial position does not change and the characteristics of the bearing are stably maintained.
It is another object of the present invention to provide a motor that maintains its rotation characteristics for a long period of time and is unlikely to generate vibration or abnormal noise.

In order to solve the above problems, the present invention has the following configurations 1) to 5) as means.
1) A bearing holder (3, 23, 33) having a hole (3a, 23a, 33a) opened at least on one end side, and a bearing portion (10, 20,... Fixed by press-fitting into the hole (3a, 23a, 33a) 30) and bearing device (61, 62, 63) having
The bearing holders (3, 23, 33) are made of resin, and the holes (3a, 23a, 33a) have an inner diameter (φA) on one end side larger than an inner diameter (φB) on the other end side. The draft is
Movement for restricting movement of the hole (3a, 23a, 33a) in the axis (CL) direction of the bearing part (10, 20, 30) press-fitted to one end of the hole (3a, 23a, 33a) It is a bearing device (61, 62, 63) characterized by having a control part (4d1-4d4, 4d, 34).
2) The bearing device (61) according to 1), wherein the movement restricting portion is a caulking portion (4d1 to 4d4) formed by caulking the bearing holder (3).
3) The bearing device (62) according to 2), comprising at least one washer (11a) interposed between the bearing portion (20) and the caulking portion (4d).
4) The movement restricting portion intervenes in an annular recess (31a) provided in the shaft (31) supported by the bearing (30) to prevent the shaft (31) from coming off. It is a bearing device (63) as described in 1) characterized by the above.
5) a rotor part (R) having a disk-shaped hub (7, 27, 37) to which the shaft (1, 21, 31) is fixed;
A stator portion (S) having the bearing device (61 to 63) according to any one of 1) to 4) and a motor base (2, 32) to which the bearing device is fixed;
The shaft (1, 21, 31) is pivotally supported by the bearing portion (10, 20, 30) of the bearing device (61, 62, 63), and the rotor portion (R) is supported with respect to the stator portion (S). The motors (51, 52, 53) are configured to be freely rotatable.

According to the present invention, in the bearing device, even if the bearing holder is made of a synthetic resin, its formability is not lowered, and the axial position of the sintered alloy bearing held by the bearing holder is not changed. These characteristics are maintained stably.
In addition, the motor including the bearing device has an effect that the rotation characteristics are maintained for a long period of time, and vibration and abnormal noise are hardly generated.

  The preferred embodiments of the present invention will be described with reference to FIGS.

<First embodiment>
FIG. 1 shows the motor 51 of the first embodiment as a half sectional view.
The motor 51 is an ODD motor that rotationally drives the mounted disk D, and includes a rotor portion R including a hub 7 to which the shaft 1 is fixed and a stator portion S including a sintered alloy bearing 10 that supports the shaft 1. And the rotor portion R is rotatable with the shaft 1 integrally with the stator portion S.

  The stator portion S is press-fitted into the motor base 2, the bearing holder 3 fixed thereto, the shaft retaining ring 4 disposed at the bottom of the bottomed hole 3a provided in the bearing holder 3, and the bottomed hole 3a. And a core 6 around which the coil 5 is wound and fixed to the outer peripheral portion of the bearing holder 3.

The rotor portion R is fixed to a disk-shaped hub 7 having an outer peripheral wall 7a, a clamp portion 8 disposed on the upper surface side (upper side in FIG. 1) of the hub 7 for clamping the disk D, and the inner surface of the outer peripheral wall 7a. The ring-shaped magnet 9 is configured.
The shaft 1 is press-fitted and fixed in a center hole 7 b provided in the hub 7.
The shaft 1 is pivotally supported by the sintered alloy bearing 10 so that the rotor portion R is rotatable with respect to the stator portion S.
Further, the bearing device 61 includes the bearing holder 3 and the sintered alloy bearing 10.

  The shaft retaining ring 4 is elastically deformed and fitted into an annular recess 1a provided in the vicinity of the end opposite to the portion press-fitted into the hub 7 of the shaft 1 so that the shaft 1 is detached from the sintered alloy bearing 10. Is preventing.

  Here, the bearing holder 3 is formed by injection molding synthetic resin, and a draft angle is provided so that the inner diameter φA on the opening side of the bottomed hole 3a is larger than the inner diameter φB on the back side. Yes. An example of this synthetic resin is PBT (polybutylene terephthalate). This may contain glass filler. PBT has excellent oil resistance and high dimensional accuracy, and can also be caulked well as will be described later. Of course, the synthetic resin used is not limited to PBT.

The state before the motor 51 is assembled on the upper surface 3c side of the bearing holder 3 will be described with reference to FIG. 2A, which is a perspective view. The upper surface 3c has a direction along the axis CL. A projecting portion 3d that protrudes in an annular shape is formed.
Then, the sintered alloy bearing 10 is press-fitted into the bottomed hole 3a from the opening side in the direction of the arrow D2 to a predetermined position, and thereafter, the projecting parts 3d are caulked by four caulking punches to obtain a sintered alloy. The upper surface 10a (see also FIG. 1) of the bearing 10 is pressed to prevent it from coming off.

This state is shown in FIG. 2 (b) which is a perspective view.
That is, a part of the protrusion 3d is cut down and caulked so as to press the upper surface 10a of the press-fitted sintered alloy bearing 10. In this embodiment, the caulking is performed by four caulking portions 4d1 to 4d4. This caulking is performed using, for example, a punch having a cross-shaped convex portion (blade). FIG. 1 shows a cross section at the caulking portion 4d1.
The caulking portions 4d1 to 4d4 function as movement restricting portions that restrict the movement of the sintered alloy bearing 10 in the axis CL direction.

  The number of the caulking portions is not limited to four, and the width W (see FIG. 2) of each caulking portion can be appropriately set within a range in which a local excessive force is not applied to the sintered alloy bearing 10.

According to this embodiment, although the sintered alloy bearing 10 is press-fitted and fixed in the hole 3a provided with the draft angle in the bearing holder 3, the end face 10a of the sintered alloy bearing 10 is formed on the large diameter side of the hole 3a. Are pressed by the caulking portions 4d1 to 4d4 which are deformed by caulking a part of the bearing holder 3.
As a result, even if the motor 51 is heated by operation and the press-fitting is loosened due to the thermal expansion accompanying the temperature increase, the sintered alloy bearing 10 does not move in the axial direction, and also comes out of the bearing holder 3. It will not protrude.

  Therefore, the characteristics of the bearing device 61 are stably maintained without being affected by heat, and the motor 51 on which the bearing device 61 is mounted also maintains the characteristics for a long period of time, and vibrations and abnormal noise are hardly generated. The effect that can be obtained.

<Second embodiment>
FIG. 3 shows the motor 52 of the second embodiment as a half sectional view.
The motor 52 is obtained by caulking the metal 51 on the upper surface of the sintered alloy bearing with respect to the motor 51 of the first embodiment.
In this embodiment, the washer is made of stainless steel, has a thickness of 0.5 mm, and two washers 11a and 11b are placed thereon.
The motor 52 is a polygon mirror rotation driving motor mounted on the LBP and fixed to the hub 27 by a clamp spring 28 or the like to rotate the polygon mirror PM.

  In FIG. 3, the sintered alloy bearing 20 is press-fitted and fixed in the bottomed hole 23 a of the bearing holder 23. The bearing holder 23 is formed by injection molding synthetic resin, and a draft angle is provided in the bottomed hole 23a so that the diameter increases from the bottom side toward the opening side. Here, the bearing device 23 includes the bearing holder 23 and the sintered alloy bearing 20.

The sintered alloy bearing 20 supports a shaft 21 fixed to the hub 27.
On the opening side of the bearing holder 23, a projecting portion 23d protruding in a cylindrical shape is formed on the outer peripheral side of the upper surface 23c.
The position of the upper surface 23c in the direction of the axis CL is set to be the same as the upper surface 20a of the sintered alloy bearing 20 or slightly so that the sintered alloy bearing 20 protrudes.
The washer 11a is placed on the upper surface 23c, and the washer 11b is placed on the washer 11a.

In the protrusion 23d, as in the first embodiment, a caulking portion 24d is formed in which a plurality of protrusions 23d are caulked by caulking punches. For example, four caulking portions 23d are provided as in the first embodiment.
The caulking portion 24d presses the washer 11b, so that the sintered alloy bearing 20 is prevented from coming off from the bearing holder 23 via the two washers 11a and 11b. That is, the caulking portion 24d functions as a movement restricting portion that restricts the movement of the sintered alloy bearing 20 in the axis CL direction.

When caulking is performed partially, excessive force may be applied locally. Therefore, the roundness of the sintered alloy bearing may change due to caulking.
In the second embodiment, the washers 11a and 11b are sandwiched between the sintered alloy bearing 20 and the caulking portion 24d, so that the caulking force is dispersed and averaged.
Therefore, an excessive force is not locally applied to the sintered alloy bearing 20, and the roundness of the sintered alloy bearing 20 is extremely difficult to change.
Needless to say, this effect is exhibited as long as at least one washer is provided.

  On the other hand, when two or more washers are disposed, the following effects can be further obtained. At this time, the surfaces of the washers 11a and 11b are not mirror-finished and have a surface roughness having some unevenness.

That is, the lubricating oil that has overflowed upward from the inner surface side of the sintered alloy bearing 20 through the outer peripheral surface of the shaft 21 can enter the gap between the two washers 11a and 11b by capillary action.
The lubricating oil that has entered the gap moves from the inner circumference side to the outer circumference side, and again passes through the gap between the inner wall of the projection 23d of the bearing holder 23 and the outer circumference surface of the washer 11ba, and then the sintered alloy bearing 20 again. The lubrication path of returning to is formed.
By forming this lubrication path, leakage of the lubricating oil to the outside is prevented, and an effect that the sintered alloy bearing 20 has a long life can be obtained.

<Third embodiment>
FIG. 4 shows the motor 53 of the third embodiment as a half sectional view.
In this motor 53, the sintered alloy bearings are prevented from coming off with respect to the motors 51 and 52 of the first and second embodiments by a non-caulking method.

  The motor 53 is an ODD motor that rotationally drives the mounted disk D, and includes a rotor portion R to which the shaft 31 is fixed and a stator portion S that pivotally supports the shaft 31. The stator 31 is rotatable in unison with the shaft 31.

The stator portion S includes a motor base 32, a thrust plate 12 fixed to the motor base 32 with a male screw NJ and supporting the tip of the shaft 31 to function as a sliding bearing in the thrust direction, and a bearing holder fixed to the motor base with the screw NJ. 33, a shaft retaining ring 34 disposed in a lower opening of the through hole 33a provided in the bearing holder 33, a sintered alloy bearing 30 held by press fitting into the through hole 33a, and an outer periphery of the bearing holder 33 And a core 36 around which a coil 35 is wound.
The bearing holder 33 is formed by injection-molding synthetic resin, and a draft angle in a direction described later is provided in the through hole 33a.

The rotor portion R includes a disc-shaped hub 37 having an outer peripheral wall 37a, a clamp portion 38 disposed on the upper surface side of the hub 37 for clamping the disk D, and a ring-shaped magnet 39 fixed to the inner surface of the outer peripheral wall 37a. And is configured.
The shaft 31 is press-fitted and fixed in a center hole 37 b provided in the hub 37.
The shaft 31 is pivotally supported by the sintered alloy bearing 30 so that the rotor portion R is rotatable with respect to the stator portion S.
The bearing device 63 includes the belling holder 33, the sintered alloy bearing 30, the shaft retaining ring 34, and the thrust plate 12.

  The shaft retaining ring 34 is formed with high rigidity on the outer diameter side and elasticity on the inner diameter side. The inner diameter side is elastically deformed and fitted into an annular recess 31 a provided on the distal end side of the shaft 31, thereby preventing the shaft 31 from coming out of the sintered alloy bearing 30.

Here, the bearing holder 33 is provided with a draft angle in the through hole 33a so that the inner diameter φA on the lower opening side in FIG. 4 is larger than the upper inner diameter φB.
On the lower surface 33c of the bearing holder 33, a step portion 33d is formed at the opening edge of the through hole 33a.
The position of the stepped portion 33d in the direction of the axis CL is set to be the same as the lower surface 30a of the sintered alloy bearing 30 or slightly so that the sintered alloy bearing 30 protrudes downward.

The shaft retaining ring 34 comes into contact with the stepped portion 33d from the lower side in FIG. 4, and the lower surface of the ring 34 is pressed from below with the screw NJ fastened by the thrust plate 12, and the bearing holder 33 and the thrust plate 12 and is fixed between.
Therefore, the sintered alloy bearing 30 is prevented from coming off from the bearing holder 33 by the shaft retaining ring 34. In other words, the shaft retaining ring 34 functions as a movement restricting portion that restricts the movement of the sintered alloy bearing 30 in the axis CL direction.

The pressing member that presses the shaft retaining ring 34 is not limited to the thrust plate 12, and the method of fixing the pressing member to the motor base 32 is not limited to the fastening of screws.
According to the third embodiment, it is possible to prevent the sintered alloy bearing 30 from coming off from the bearing holder 33 without an additional member.

  In each of the embodiments described in detail above, the bearing holder is formed of a synthetic resin, and the bottomed hole or the through hole formed on the bearing holder to which the sintered alloy bearing is mounted has a good releasability at the time of molding. However, since a structure to prevent the sintered alloy bearing from slipping out is provided on the large diameter side of the bottomed hole or through-hole draft, a good separation during molding of the bearing holder is provided. Even when the press fit is loosened due to thermal expansion accompanying the temperature rise of the motor while maintaining the moldability, there is an effect that the axial position of the sintered alloy bearing does not shift or protrude from the bearing holder. can get.

The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.
In each embodiment, the radial bearing is described as a sintered alloy, but the material is not limited to this.

1 is a half sectional view showing a first embodiment of a motor of the present invention. It is a perspective view explaining the principal part in 1st Example of the motor of this invention. It is a half sectional view showing a 2nd example of a motor of the present invention. It is a half sectional view showing a 3rd example of a motor of the present invention. It is sectional drawing which shows the bearing holder used with the conventional motor. It is a half sectional view showing a conventional motor.

Explanation of symbols

1, 21, 31 Shaft 1a, 31a Recess 2, 32 Motor base 3, 23, 33 Bearing holder 3a, 23a Bottomed hole 3c, 23c Top surface 3d, 23d Projection 4, 34 Shaft retaining ring 4d1-4d4, 24d Caulking Portions 5, 35 Coils 6, 36 Cores 7, 27, 37 Hubs 7a, 37a Outer peripheral walls 7b, 37b Center holes 8, 38 Clamps 9, 39 Magnets 10, 20, 30 Sintered alloy bearings 10a, 20a Upper surfaces 11a, 11b Washer 12 Thrust plate 28 Clamp spring 30a Lower surface 33a Through hole 33c Lower surface 33d Step portion 51, 52, 53 Motor 61, 62, 63 Bearing device CL Axis D Disc NJ Male thread PM Polygon mirror R Rotor portion S Stator portion

Claims (10)

In the bearing device comprising a bearing holder, and a fixed to a bearing portion into the hole having a hole at least one end side is open,
The bearing holder is made of resin, and the hole has a draft angle in which the inner diameter on the one end side is larger than the inner diameter on the other end side,
At one end of the bore, a bearing apparatus characterized by having a movement restricting portion that restricts movement in the axial direction of the hole before Symbol shaft receiving portion.   The bearing device according to claim 1, wherein the movement restricting portion is a caulking portion formed by caulking the bearing holder. The bearing device according to claim 1, further comprising at least one washer interposed between the bearing portion and the movement restricting portion . The bearing device according to claim 1, wherein the movement restricting portion is a ring intervened in an annular recess provided in a shaft on which the bearing portion is pivotally supported. The said bearing part is formed from a sintered alloy, and the one end is press-fitted and fixed to the said hole so that the one end may contact | connect the said movement control part, The any one of Claims 1-4 characterized by the above-mentioned. The bearing device according to item. The bearing device according to any one of claims 1 to 5, wherein a bottom portion of the bearing holder is integrally formed by injection-molding polybutylene terephthalate containing a glass filler. A rotor unit having a hub shaft is fixed,
And a stator unit having a motor base of fixing the bearing device and the bearing device according to any one of claims 1 to 6,
The motor is characterized in that the shaft is supported by a bearing portion of the bearing device, and the rotor portion is rotatable with respect to the stator portion. The hub has a hanging part that hangs down in the axial direction toward the motor base,
  The motor according to claim 7, wherein the drooping portion is provided at a position surrounding the movement restricting portion and overlapping in the axial direction. The hanging portion forms a gap space between an inner peripheral surface thereof and an outer peripheral surface of the bearing holder, and the gap space is formed such that an axial dimension is longer than a radial gap dimension. The motor according to claim 8. The hub includes an outer peripheral portion provided in an axial direction on an outer periphery, and an overhang portion extending outward from the outer peripheral portion in a radial direction, and the overhang portion includes the movement restriction portion and the shaft. The motor according to any one of claims 7 to 9, wherein the motor is provided at a position overlapping in the direction.

Images