JP2003247557A - Bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device that can improve rotation accuracy by setting up fit-in length properly and reducing stress to an inner ring and a shaft in the combination of a shaft of various dimensions, and also a roller bearing. <P>SOLUTION: In this bearing device, the fit-in length between the shaft and the inner ring is made to be 1/3 or less of the shaft diameter. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to, for example, a VTR.
(Video tape recorder) Drum spindle motor, H
The present invention relates to a disk memory spindle motor such as a DD (hard disk drive) motor, an HDD swing arm, and a bearing device used for supporting a rotating shaft of other motors.

[0002]

2. Description of the Related Art As a bearing device used for the above applications,
There is a structure in which a rolling bearing is press-fitted onto a shaft.
The bearing device of this form has various sizes according to applications and models. The shaft diameter of the shaft and the dimensions of the rolling bearing (radial and axial dimensions) differ depending on their use and model.

When the rolling bearing is press-fitted onto the shaft, one or both of the shaft and the inner ring may be distorted. Therefore, in the bearing device disclosed in JP-A-9-53644, the press-fitting fitting length is set to 1/2 to 3/4 of the axial dimension of the rolling bearing in order to reduce distortion such as shaft bending.

[0004]

[Patent Document 1] Japanese Patent Application Laid-Open No. 9-53644
In the technique disclosed in the publication, for example, when a rolling bearing having an extremely large axial dimension (width) is selected, the press-fitting fitting length becomes unnecessarily large,
In some cases, it may be affected by the bending of the shaft. The present invention has been made in view of the above circumstances,
The purpose of the present invention is to provide a bearing device capable of appropriately setting the press-fitting fitting length for combinations of shafts and rolling bearings of various sizes and reducing the stress applied to the inner ring and the shaft to improve the rotation accuracy. To do.

[0005]

The above object of the present invention is to provide a bearing device having a shaft and an inner ring press-fitted to the shaft, in which a press-fitted fitting portion between the shaft and the inner ring is press-fitted. This is achieved by a bearing device characterized in that the length is 1/3 or less of the shaft diameter. Further, the above object of the present invention is to provide a bearing device having a shaft and a rolling bearing having an inner ring press-fitted to the shaft, in which a press-fitted fitting length of a press-fitted fitting portion between the shaft and the inner ring is provided. Is less than or equal to 1/3 of the shaft diameter. The thick-fitting fitting length of the thick-fitting fitting portion is preferably 1/3 or less of the shaft diameter and 1/10 or more. The thick fitting fitting length of the thick fitting fitting portion is set to 1/10 or more of the shaft diameter because it is difficult to secure the pulling force of the thick fitting fitting portion if it is smaller than 1/10.

The present inventors have found that by setting the press-fitting fitting length based on the shaft diameter of the shaft, an appropriate press-fitting state can be obtained for combinations of shafts and rolling bearings of various sizes. According to the bearing device having the above configuration, the stress applied to the inner ring and the shaft can be reduced to prevent these distortions regardless of the width of the rolling bearing to be assembled, and the runout at the time of rotation can be suppressed to improve the rotation accuracy. It is possible. here,
The press-fitting fitting portion means a portion where the shaft and the inner ring are press-fittingly fitted, and the press-fitting fitting length means an axial length of the press-fitting fitting portion.

Further, in the above bearing device, the press-fitting fitting portion intersects the radial plane perpendicular to the axial direction including the intersection of the contact angle extension line of the rolling bearing and the central axis of the shaft with the inner diameter surface of the inner ring. With the configuration provided at the location, since the press-fitting fitting portion is located near the point of action (intersection point of the contact angle extension line and the shaft center line), the runout due to the tilt of the rolling bearing can be reduced. it can. According to this configuration, it is not necessary to make the bearing abutting portion and the like highly accurate, and an inexpensive and highly accurate bearing device can be obtained. Here, the contact angle extension line means a line obtained by extending a straight line connecting two contact points of the rolling element of the rolling bearing and the bearing ring to the shaft side (the inner ring inner diameter surface side).

In the above bearing device, if the press-fitting fitting portion is provided at a position axially separated from the intersection of the contact angle extension line of the rolling bearing and the central axis of the shaft,
Since the press-fitting fitting portion is separated from the point of action, distortion is unlikely to occur in the inner ring and the shaft, so that NRRO can be lowered. Further, it is less likely to be affected by the roundness accuracy of the outer diameter surface of the shaft and the inner diameter surface of the inner ring.

Further, in the above-mentioned structure, it is preferable that the outer diameter surface of the shaft and / or the inner diameter surface of the inner ring is provided with a relief portion whose press-fitting fitting length is adjusted. By doing this, the clearance forms a radial gap between the shaft and the inner ring,
Even if the relative position of the shaft and the inner ring in the axial direction slightly changes, the length of the press-fitting fitting portion can be easily and accurately adjusted within the above range.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a first embodiment of the bearing device of the present invention. The bearing device 10 includes a shaft S that serves as a rotating shaft, and a pair of rolling bearings 11 that are fitted and mounted at two locations separated from each other in the axial direction of the shaft S. The rolling bearing 11 has an inner ring 13 that is press-fitted onto the outer periphery of the shaft S.
A ball bearing including an outer ring 14, a plurality of balls 15 as rolling elements mounted between these inner and outer rings, and a retainer 17 that regulates the interval between the balls. In the bearing device according to the present embodiment, the pair of rolling bearings 11 are the same rolling bearing. A compression coil spring (hereinafter referred to as a coil spring) 16 wound around the shaft S is mounted between the outer rings of the pair of rolling bearings 11, and the coil springs 16 are separated from each other by the outer rings 14. The preload is applied. A housing 12 as indicated by a chain double-dashed line in the figure may be fitted onto the pair of rolling bearings 11.

These rolling bearings 11 have a seal structure having seal members 14b at both ends of the outer ring 14 for preventing the lubricant filled between the inner and outer rings 13, 14 from leaking out. The seal member 14b has an outer ring 14 at the outer peripheral portion.
It is fixed to the end portion of the outer ring 14 by elastically fitting or caulking the axially stepped portion 14a formed in the counterbore. Further, each seal member 14b has a groove 14c as a step portion into which the wire rod at the end of the compression coil spring 16 is fitted.
Is formed in a circular shape along the outer peripheral portion. When the rolling bearings 11 are assembled to the shaft S, the outer rings 1 facing each other
The groove 14c of the seal member 14b located on the inner end side of 4 is
It is utilized as a spring seat for positioning and fixing the end of the compression coil spring 16 assembled in a compressed state between the pair of rolling bearings 11. In the bearing device 10 of the present embodiment, the preload applied to each outer ring 14 by the compression coil spring 16 prevents the inner and outer rings 13 and 14 of each rolling bearing 11 and the balls from rattling in the axial direction, thereby allowing the axial rotation. The noise of the time is reduced (that is, quietness).

A press-fitting fitting portion (hereinafter referred to as a fitting portion) 18 into which the inner diameter surface of the inner race 13 is press-fitted is provided on the outer diameter surface of the shaft S at intervals in the axial direction. The press-fitting fitting length W of the press-fitting fitting portion 18 is 1 with respect to the diameter of the shaft S (shaft diameter).
It is set to be / 3 or less. Further, in order to secure the pulling force of the thick-fitting fitting portion, the thick-fitting fitting length of the thick-fitting fitting portion is preferably 1/10 or more of the shaft diameter. In the present embodiment, the press-fitting fitting portion 18 is provided so that the press-fitting fitting length W is ¼ of the shaft diameter. On the outer diameter surface of the shaft, relief grooves 19 are provided as relief portions on both axial sides of each fitting portion 18. The clearance groove 19 is formed so that the shaft diameter is smaller than that of the fitting portion 18, and secures a radial gap between the inner ring inner diameter surface and the shaft outer diameter surface.
The press-fitting fitting length W of the fitting portion 18 is made uniform in the axial circumferential direction by the escape grooves 19 provided on both sides in the axial direction.

In the present embodiment, the fitting portion 18 has a radial plane R perpendicular to the axial direction including the intersection point P of the contact angle extension line of the ball bearing and the central axis of the shaft S and the inner diameter surface of the inner ring of the ball bearing. It is provided at the intersection. In the present embodiment, the shaft diameter is 2 mm, the ball bearing width is 3 mm, and the ball diameter is 1.
2 mm, the ball pitch circle diameter was about 3.9 mm, the press-fitting fitting length W was 0.5 mm, and the contact angle was 21 °. The contact angle is 11 ° to 25 ° in consideration of the variation in the internal radial clearance of the rolling bearing 11 and the dimension of the radius of curvature of the raceway surface.
It is preferably within the range of about. The fitting portion 18 is the inner ring 1
3 is preferably provided at a position centered on a position distant from the center of the raceway groove by about 0.4 to 0.9 mm in the axial direction. In the present embodiment, it is provided at a position distant from 0.8 mm by the center. Has been.

According to the configuration of this embodiment, the bearing device 10
With respect to shafts and rolling bearings of various sizes, it is possible to reliably prevent distortion such as shaft bending, suppress runout during rotation, and improve rotation accuracy. When this bearing device is used in the spindle motor of a recording device, the press-fitting fitting length is set to 1/3 or less of the shaft diameter, so shock such as dropping is applied during the spindle assembly or after the device is assembled into the device. Even in this case, it is possible to suppress the axis bending within a range where recording / reproduction is not hindered.
Further, since the fitting portion 18 is provided at a portion where the radial plane that passes through the intersection of the contact angle extension line of the rolling bearing 11 and the shaft center line and is orthogonal to the axial direction intersects the inner diameter surface of the inner ring 13, The rotation accuracy is maintained without being affected by the slight inclination of the press-fitted and fixed inner ring 13. Furthermore, the axis S
Since the length W of the press-fitting fitting portion can be adjusted by the relief groove 19 provided on the outer diameter surface of the standard rolling bearing, it is possible to incorporate a standard rolling bearing (having no relief portion or the like in the inner ring).

FIG. 2 is a vertical sectional view showing a bearing device 20 according to a second embodiment of the present invention. In the embodiments described below, members having the same configurations and operations as those already described will be given the same or corresponding symbols in the drawings to simplify or omit the description. In this embodiment, no concavity and convexity are formed on the outer diameter surface of the shaft S, and the outer diameter surface of the shaft is a cylindrical surface (straight shape). On the inner diameter surface of the inner ring 23, there is provided a fitting portion 28 having a tight margin with the outer diameter surface of the shaft S. Fitting part 28
Relief portions 29, which are set so that the diameter of the inner ring inner diameter surface is larger than that of the fitting portion 28, are provided on both sides in the axial direction of. A radial gap is formed between the position where the relief portion 29 is provided on the inner diameter surface of the inner ring and the outer diameter surface of the shaft S. In other words, the inner ring 23 is tightly fitted to the shaft S at the fitting portion 28 and fitted to the clearance S at the clearance portion 29.

The fitting portion 28 provided on the inner ring 23 has a first
Similar to the embodiment, a radial plane R perpendicular to the axial direction including the intersection point P of the contact angle extension line of the ball bearing and the shaft center of the shaft S is provided at a portion intersecting with the outer diameter surface of the shaft S. . The press-fitting fitting length W of the fitting portion 28 is set to 1/3 or less (here, 1/4) of the shaft diameter.

According to the configuration of this embodiment, the bearing device 20
Can achieve the same effect as the first embodiment. Further, since the fitting portion 28 and the escape portion 29 are provided on the inner ring 23, no special processing is required for the shaft S. Since the shaft diameters are uniform, the axial position of the rolling bearing 21 with respect to the shaft S is not limited. By manufacturing such one type of shaft, it can be applied to various bearing devices having different bearing positions, and bearing devices of various forms can be easily obtained. Also,
Since it is not necessary to machine the entire inner diameter surface of the inner ring with high accuracy, only the fitting portion 28 needs to be ground with high accuracy.
Processing of 3 becomes easy. Further, by finishing the outer diameter surface of the shaft S substantially uniformly, the pressure input of the rolling bearing 21 can be made substantially constant regardless of the position of the rolling bearing 21 on the shaft S, and the pressure input and the pulling force can be improved. Easy to manage.

FIG. 3 is a vertical sectional view showing a bearing device according to a third embodiment of the present invention. The bearing device 30 has the same configuration as the bearing device 10 of the first embodiment except that the position of the fitting portion 38 provided on the outer diameter surface of the shaft S with respect to the bearing is different. The press-fitting fitting length W is set to 1/3 or less (here, 1/4) of the shaft diameter, as in the first embodiment.

As shown in FIG. 3, the fitting portion 38 has a ball 35.
And the inner ring raceway surface are provided at an axial position apart from a certain axial position. Here, the fitting portion 38 is provided on the side opposite to the side where the contact point between the ball 35 and the inner ring 33 is located. Specifically, the fitting portion 38 of one of the rolling bearings 31 is centered at a position apart from the center in the width of the inner ring 33 by about 0.4 to 0.9 mm in the axial direction toward the other rolling bearing 31 side. It is preferable that they are provided at positions that are set to each other. In the present embodiment, they are provided at positions that are separated by 0.8 mm.

According to the structure of this embodiment, since the fitting portion 38 is provided at a position apart from the position where the contact point between the ball 35 and the inner ring raceway surface is located, the inner ring 33 and the shaft S are distorted. Hateful. Therefore, the NRRO of the bearing device 30 can be reduced. Further, when the bearing device 30 is in operation, the rotation drive section is less likely to be affected by the roundness accuracy of the outer diameter surface of the shaft and the inner diameter surface of the inner ring. Therefore, the shaft S and the inner ring 33 can be easily processed.

FIG. 4 is a vertical sectional view showing a bearing device according to a fourth embodiment of the present invention. The bearing device 40 includes the inner ring 4
The configuration is the same as that of the bearing device 20 of the second embodiment, except that the position of the fitting portion 48 provided on the inner diameter surface of No. 3 with respect to the bearing is different. As shown in FIG. 4, the fitting portion 48 is
The ball 45 and the inner ring raceway surface are provided at an axial position apart from a certain axial position. Here, the fitting portion 4
8 is provided on the side opposite to the side having the contact point between the ball 45 and the inner ring. Specifically, the fitting portion 48 of the one rolling bearing 41 is centered at a position separated from the center in the width of the inner ring 43 by about 0.4 to 0.9 mm in the axial direction toward the other rolling bearing 41 side. It is preferable that they are provided at positions that are set to each other. In the present embodiment, they are provided at positions that are separated by 0.8 mm. A housing 42 is fitted onto the outer rings 44 of the pair of rolling bearings 41.

According to the configuration of this embodiment, the same effect as that of the third embodiment can be obtained. Moreover, no special processing is required for the shaft S, and only the fitting portion of the inner ring may be processed.

FIG. 5 is a vertical sectional view showing a bearing device according to a fifth embodiment of the present invention. A rolling bearing 51A having the same specifications as those of the first embodiment and a rolling bearing 51B having an outer ring whose outer diameter is larger than that of the rolling bearing 51A are axially separated from each other and press-fitted to the shaft S. A pair of rolling bearings 51A,
The housing 52a is externally fitted to 51B. The side surface on the other rolling bearing 51A side of the outer ring of the rolling bearing 51B is
It is in contact with a step portion 52c formed on the inner peripheral surface of the housing 52a. In FIG. 5, 54c represents a step formed on the inner diameter surface of the inner ring, 54d represents a seal member, and 54e represents a groove of the seal member 54d. The step portion 54c, the seal member 54d, and the groove 54e have the same configurations as those already described in the above embodiment.

The shaft S is provided with two escape grooves 59 whose outer diameter surface is formed to have a small diameter and are separated from each other in the axial direction. A part 58 of the inner ring inner diameter surface of the bearing is press-fitted to only one of the positions of the shaft outer diameter surface adjacent to both sides in the axial direction of each clearance groove 59. The remaining portion of the inner ring inner diameter surface is the escape groove 5
A radial gap is formed between the clearance groove 9 and the clearance groove. A part 58 of the inner ring inner diameter surface of the pair of rolling bearings, which is press-fitted to the shaft S, is arranged on the side away from the other rolling bearing. Press-fitting fitting length W of the part 58 and the shaft S
Is set to 1/3 or less (for example, 1/4) of the shaft diameter.

The housing 52a may be formed integrally with a drum 52b that drives a magnetic recording tape such as a video tape.

FIG. 6 is a vertical sectional view showing a bearing device according to a sixth embodiment of the present invention. Bearing device 6 of the present embodiment
0 is not a configuration for applying a preload to the rolling bearing by a coil spring, but a configuration for applying a preload by bringing the outer ring 64 into contact with the step portion 62d formed in the cylindrical housing 62a (fixed position preload). There is. The axis S is the same as in the first embodiment. The bearing device 60 has a motor housing 62b arranged on the outer peripheral side of the housing 62a. On the inner peripheral surface of the cylindrical portion of the motor housing 62b, two fitting protrusions 62c that are axially separated are provided. Fitting protrusion 62c
Has a fitting margin having a uniform width in the circumferential direction of the inner peripheral surface of the cylindrical portion. Then, these fitting protrusions 62c are press-fitted to the outer peripheral surface of the housing 62a at positions corresponding to between the pair of rolling bearings 61.

The bearing device 60 is constructed so that the position where the housing 62a and the motor housing 62b are press-fitted and fitted is apart from the position where the rolling bearing 61 and the housing 62a are press-fitted and fitted. Therefore, the influence of press-fitting of the housing 62a and the motor housing 62b is not transmitted to the rolling bearing 61.

FIG. 7 is a vertical sectional view showing a bearing device according to a seventh embodiment of the present invention. The bearing device 70 is not configured to apply a preload to the rolling bearing with a coil spring, but is configured to apply a preload by abutting an outer ring 73 of the rolling bearing 71 in a cylindrical housing 72 (constant position preload). . The fitting portion 78 and the escape groove 79 of the shaft S are the same as in the third embodiment. The bearing device 70 is an example of a swing arm pivot.

Specifically, a step portion 72a is formed on the inner peripheral surface of the housing 72. On the inner peripheral surface of the housing 72, a surface 72b that is perpendicular to the inner peripheral surface is formed between both sides in the axial direction and the step portion 72a. The surface 72b is an abutting portion with which the side surface of the outer ring 74 abuts. Fitting margins 72c are formed on the surfaces located on both sides of the butting portion 72b and recessed toward the outer diameter side so as to be adjacent to each other in the axial direction of the butting portion 72b. The fitting margin 72c is press-fitted to the inner end portion (the end portion on the space side between the pair of rolling bearings) of the outer ring outer diameter surface of the rolling bearing 71. The portions of the inner peripheral surface of the housing that are recessed toward the outer diameter side, where the fitting margin 72c is not provided, are arranged in the outer ring outer diameter surface in the radial direction with an annular gap, and are tightened with the outer ring outer diameter surface. Has been done.

According to the above construction, since the shaft S does not bend due to impact after the bearing device is assembled, the inclination of the rotating shaft does not change.

FIG. 8 shows the axial runout when the shaft S is rotated in the initial stage and before and after a bending load is applied by fixing both outer rings 14 using the rolling bearing 11 described in the first embodiment. It shows how to measure. On the outer peripheral surface of the shaft S, the detection unit 80a of the displacement measuring instrument 80 (for example, an electric micrometer) is in contact with one end. Axis S
When the shaft is rotated, the displacement of the shaft S in the radial direction is detected by the detection unit 8.
The shaft runout is measured based on the displacement measured by the displacement measuring device 80. On the other hand, FIG. 9 shows a method in which one of the shafts S is fixed and a load is applied to the other of the shafts in a direction perpendicular to the shaft to evaluate whether the shaft runout changes.

Next, in order to confirm the effects of the present invention, the relationship between the press-fitting fitting length with respect to the shaft diameter and the shaft runout change before and after applying a load will be clarified by the following test. In this test, as the bearing device used in the test, the ratio of the press-fitting fitting length to the shaft diameter is 90%, 50%, 40%, 30
%, 20% bearing devices (A to E in FIG. 10) were prepared. Each bearing device had a shaft diameter of 2 mm, a rolling bearing width of 3 mm, a bearing ball pitch of 6.8 mm, and a shaft length of 19 mm. In addition, a bending load F of 30 N is applied to the bearing device used in the test. Then, before and after applying a bending load to the bearing device, as shown in FIG.
The shaft runout measurement shown in was performed. The press-fitting moving force was adjusted to the tightening margin, and was set in the range of 50N to 60N in all cases.
The results of this test are shown in the graph of FIG.

As shown in FIG. 10, before the load was applied, there was no great difference in the shaft runout of the bearing devices A to E. However, after the load is applied, in the bearing devices D and E in which the press-fitting fitting lengths are 30% and 20% of the shaft diameter, there is almost no change in shaft runout as compared with the other bearing devices A to C. There wasn't. In other words, press-fit the fitting length to the shaft diameter of 3
It was clarified that the bearing devices D and E with 0% and 20% were less affected by the load load than the other bearing devices A to C, and had good rotation control accuracy.

[0034]

As described above, according to the present invention,
For combinations of shafts and rolling bearings of various sizes,
It is possible to provide a bearing device in which the press-fitting fitting length can be appropriately set, and the stress applied to the inner ring and the shaft can be reduced to improve the rotation accuracy.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a bearing device according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a bearing device according to a second embodiment of the present invention.

FIG. 3 is a vertical sectional view showing a bearing device according to a third embodiment of the present invention.

FIG. 4 is a vertical sectional view showing a bearing device according to a fourth embodiment of the present invention.

FIG. 5 is a vertical sectional view showing a bearing device according to a fifth embodiment of the present invention.

FIG. 6 is a vertical sectional view showing a bearing device according to a sixth embodiment of the present invention.

FIG. 7 is a vertical sectional view showing a bearing device according to a seventh embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a method for measuring shaft runout of a rolling bearing.

FIG. 9 is an explanatory diagram showing another method for measuring the shaft runout of the rolling bearing.

FIG. 10 is a graph showing test results.

[Explanation of symbols]

10, 20, 30, 40, 50, 60, 70 Bearing device 11, 21, 31, 41, 51, 61, 71 Rolling bearing 12, 22, 32, 42 Housing 13, 23, 33, 43, 53a, 53b Inner ring 14, 24, 34, 44, 54a, 54b Outer ring 16, 26, 36, 46, 56 Coil spring 18, 28, 38, 48, 58, 68, 78 Fitting portion 19, 29, 39, 49, 59, 69 , 79 Relief part S axis

Claims (7)

[Claims] 1. A bearing device having a shaft and an inner ring press-fitted to the shaft, wherein a press-fitting length of a press-fitting fitting portion between the shaft and the inner ring is ⅓ or less of a shaft diameter. Bearing device characterized by the above. 2. A bearing device having a shaft and a rolling bearing provided with an inner ring press-fitted to the shaft, wherein a press-fitting fitting length of a press-fitting fitting portion between the shaft and the inner ring is a shaft diameter. A bearing device characterized by being set to 1/3 or less. 3. The press-fitting fitting portion is a portion where a radial plane orthogonal to the axial direction including an intersection of a contact angle extension line of the rolling bearing and a central axis line of the shaft intersects an inner diameter surface of the inner ring. The bearing device according to claim 2, wherein the bearing device is provided in. 4. The bearing according to claim 2, wherein the press-fitting fitting portion is provided at a position axially separated from an intersection of a contact angle extension line of the rolling bearing and a central axis line of the shaft. apparatus. 5. The housing according to claim 2, further comprising a housing that supports an outer diameter surface of an outer ring of the rolling bearing.
Bearing device. 6. The bearing device according to claim 1, wherein an escape portion is provided on the outer diameter surface of the shaft so as to adjust the press-fitting fitting length. 7. An escape portion is provided on an inner diameter surface of the inner ring for adjusting the press-fitting fitting length.
The bearing device according to any one of 1.