JP2001295837A - Bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold superior rotation accuracy, vibration characteristics, and sound characteristics even if using a ceramic material for a bearing body and being simple and inexpensive. SOLUTION: Roller bearings 1a and 1b are fixed to a shaft 5 with its inner ring 2a receiving preload by leaf springs 6a and 6b. A sleeve 8 is externally fitted and fixed around a first outer ring 3a, a top cover 11 is internally fitted and fixed into a housing 10, and the sleeve 8 and the housing 10 are connected to each other by a diaphragm 13 as a disc-shaped metal elastic member. A clearance 12 formed between the sleeve 8 and the internal circumferential face of the housing 10 is filled with lubricant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device, and more particularly, to a hard disk drive (hereinafter referred to as "HD").
D "), etc., and supports a rotating body (spindle) that rotates at high speed.

[0002]

2. Description of the Related Art Conventionally, in a bearing device, a preload is applied in order to increase the rigidity of a shaft by reducing the elastic deformation of the bearing against an external load. A bearing device employing a fixed position preloading system as shown in FIG. 9 is known.

The bearing device comprises two rolling bearings 101,
102 is fixed to the shaft 103 and the cylindrical portion 105 of the flange 104. That is, each rolling bearing 101, 102
Are inner rings 106 and 107 fixedly fitted to the shaft 103,
Outer rings 108 and 109 which are fixedly fitted in the cylindrical portion 105;
It has rolling elements 110 and 111 rotatably held between the inner rings 106 and 107 and the outer rings 108 and 109, and one of the inner ring 107 and the outer ring 109 is fixed to the shaft 103 and the cylindrical portion 105 by bonding. After that, the other inner ring 106 and outer ring 108 are fixed to the shaft 103 and the cylindrical portion 105, respectively, by pressing the inner ring 107 in the axial direction via an insertion jig or the like.

Further, in the bearing device, the two rolling bearings 101 and 102 are combined in a back-to-back (DB type) to increase rigidity against a moment load so that the overall height of the bearing device is reduced as much as possible. In the drawing, 112 is a stator, 113 is a rotor, and 114 is a rotor hub.

By the way, in this type of bearing device, in recent years,
From the viewpoint of improving bearing performance such as anti-fretting characteristics and vibration characteristics, those using a ceramic material as a bearing material have been proposed.

However, since the ceramic material has a smaller linear expansion coefficient and a lower thermal conductivity than a steel material and a large longitudinal elastic coefficient, a large temperature difference (normally 120 ° C. or more) between normal temperature and when the bearing is driven. As a result, the contact stress increases and the amount of preload decreases, which may cause so-called "preload loss", which may not be able to withstand use under severe conditions.

In view of the above, a method using a constant-pressure preload method instead of the fixed-position preload method as the preload method is considered.

By the way, as a conventional bearing device adopting a constant-pressure preload system, the devices shown in FIGS. 10 and 11 are known.

FIG. 10 shows a bearing device of a constant-pressure preload system showing a first prior art, which shows a case of a high-speed spindle for internal grinding of a built-in motor.

That is, the bearing device comprises two angular ball bearings (first and second angular ball bearings 126, 1).
27) are separated from each other so that
8, a rotor 129 is mounted on the shaft 128, and a stator 130 is fixed to the housing 131 in parallel with the rotor 129.

In this bearing device, the first angular ball bearing 126 on the side of the grindstone 132 is externally fitted and fixed by the bearing fixing member 133 and the stepped portion 128a of the shaft 128.
The angular contact ball bearing 127 is loaded with a constant pressure preload by the coil spring 134 and supported by a large number of guide balls 135.

More specifically, the second angular contact ball bearing 12
7 is externally fitted to the shaft 128, and the coil spring 134 is seated on the tip of the threaded portion 151 screwed to the intermediate member 136 to apply a thrust load between the bearings. A large number of guide balls 134 are arranged between the rear cover 2 and the rear holding cover 136 so as to support the entire balls. Further, the first rear-side pressing lid 137 and the second rear-side pressing lid 136 are connected via a pin 138 to prevent the second rear-side pressing lid 136 from rotating accompanying the guide ball 135. are doing.

FIG. 11 is a cross-sectional view of a constant-pressure preload type bearing device showing a second prior art, in which the first angular contact ball bearing 126 side is the same as the first prior art, but has the second constitution. The angular ball bearing 127 is supported by two disk-shaped diaphragms 141a and 141b while a constant-pressure preload is applied by a coil spring 134. That is, in the second prior art, two diaphragms 141a, 1
41b is fixed at its outer periphery to the intermediate member 143 by the holding lids 144a, 144b, 144c.
The inner peripheral portion is fixed to the lid 146 by 2b. Also,
A second angular ball bearing 127 is fixed to the lid 146.

[0014]

By the way, in recent years, HD
In the field of computer-related equipment such as D, the size of the device has been reduced more and more, for example, the shaft diameter of the HDD has been reduced to about 4 mm. Also, since the space for incorporating various components into the HDD is becoming narrower, it is required to reduce the number of components as much as possible. Furthermore, considering the recent price competition, it is necessary to reduce the cost of the bearing device. There is also a need to automate the assembly process so that it can be manufactured.

In addition, HDD spindles have strict requirements for rotational accuracy, vibration, sound, and the like. For example, non-repetitive rotational accuracy (NRRO) is required to be as high as about 20 to 30 nm.

However, when the above-mentioned conventional constant pressure preload type bearing device is applied to an HDD, in the first prior art (FIG. 10), many guide balls 135 are used in a small bearing device such as an HDD bearing device. There is a problem that there is no space for intervening and the radial rigidity tends to be unstable. Also, as described above, the NRRO (non-repetitive rotation accuracy) of the HDD spindle is 20 to 30 nm.
Although severe demands are made for sound and vibration, there is a problem that the above-mentioned ball guide may deform the groove of the raceway ring to deteriorate the acoustic and vibration characteristics. There is a point. Further, there is a problem that it is difficult to automate the assembling process due to the large number of parts.

In the second prior art (FIG. 11), since the diaphragms 141a and 141b cannot be expected to have a damping effect, vibration is likely to occur due to rotational runout and the like, and the two diaphragms 141a and 141b are incorporated. It is unavoidable to increase the size of the apparatus due to the need for securing a space for the same, and it is difficult to automate the assembling process due to the large number of parts as in the first prior art. There is a problem.

The present invention has been made in view of such circumstances, and even when a ceramic material is used for a bearing body, it is simple and inexpensive and has excellent rotational accuracy, vibration characteristics, and acoustic characteristics. An object of the present invention is to provide a bearing device capable of maintaining characteristics.

[0019]

In order to achieve the above object, a bearing device according to the present invention comprises: an inner ring fitted to a shaft; an outer ring fitted to a housing; and rolling between the inner ring and the outer ring. In a bearing device in which a plurality of bearing bodies composed of rolling elements that are freely held are disposed apart from each other in the axial direction, a specific bearing body among the plurality of bearing bodies applies a preload through an elastic member. While being loaded, the specific bearing body is mounted in the housing with at least one of a gap between the inner ring and the shaft, or between the outer ring and the housing, and the specific bearing body is axially mounted. It is connected and supported by a metal member having greater rigidity in the radial direction than in the direction.

According to the above configuration, the specific bearing main body is loaded with a constant pressure preload and at least one between the inner ring and the shaft or between the outer ring and the housing has no radial gap, and the specific bearing body is more radial than axial. The specific bearing body is supported in the radial direction without rattling because it is connected and supported by a metal member having high rigidity, and the axial direction is smaller than the thrust rigidity of the bearing body. And weak spring support.

In the bearing device, the specific bearing main body is fixed to a shaft while preload is applied to the specific bearing main body, and then the metal member is integrally connected to the housing and the bearing main body. The assembly can be performed, and thus the assembly process can be easily automated.

In the above bearing device, it is preferable that the bearing body and the metal member are arranged such that the intersection of the extension line of the contact angle of the rolling element and the center line of the shaft coincides with the horizontal plane of the metal member. In this way, by making the intersection of the extension line of the contact angle of the rolling element and the center line of the shaft coincide with the horizontal plane of the metal member, it is possible to avoid the moment rigidity of the bearing body from being reduced.

Further, in the above bearing device, it is preferable that the gap is filled with a lubricant. That is,
Although the metal member described above cannot be expected to have a damping effect in the axial direction, a damping effect can be generated by filling the gap with a lubricant, thereby reducing vibration and deteriorating acoustic characteristics. This can prevent the rotation accuracy from being lowered.

In the above bearing device, a specific bearing body to which a preload is applied is connected and supported by a metal member.
As another measure for supporting the specific bearing body, at least one between the inner ring and the shaft or between the outer ring and the housing is provided with a large number of elastic fine particles and filled with a lubricant, so that the elastic fine particles are used. "Rolling guide" is also preferable.

That is, a bearing device according to the present invention comprises a plurality of inner rings fitted to a shaft, outer rings fitted to a housing, and rolling elements rotatably held between the inner rings and the outer rings. In a bearing device in which the bearing bodies of the plurality of bearing bodies are disposed apart from each other in the axial direction, a specific bearing body of the plurality of bearing bodies is loaded with a preload via an elastic member,
It is also preferable that the specific bearing body is characterized in that at least one between the inner ring and the shaft or between the outer ring and the housing is provided with a large number of elastic fine particles and filled with a lubricant. .

According to the above configuration, since a large number of elastic fine particles are interposed between at least one of the inner ring and the shaft or between the outer ring and the housing, the bearings are averaged by the elastic fine particles. The radial rigidity of the bearing device can be increased without causing deformation of the outer ring or the inner ring in the device, and the lubricant is filled in the minute gap in which the elastic fine particles are interposed. The damping effect of the device can also be ensured, vibration can be prevented, and acoustic characteristics can be prevented from deteriorating, and rotation accuracy can be prevented from deteriorating.

In the bearing device, after the elastic fine particles are uniformly dispersed and dispersed, the elastic fine particles are supplied to the outer peripheral surface of the shaft on which the specific bearing body is mounted or the inner peripheral surface of the housing. The specific bearing main body can be assembled by fixing the specific bearing main body to the shaft in a state where a preload is applied to the shaft, so that the assembling process can be easily automated.

The material and particle size of the elastic fine particles are preferably selected based on the clearance value, the amount of elastic deformation, and the like of the minute gap in which the elastic fine particles are interposed. By selecting the material and the particle size of the fine particles, it is possible to secure desired rotational accuracy according to the type and use of the bearing device.

As another application of the guide method using the elastic fine particles, the present invention can also be applied to a machine tool such as a grinding machine equipped with a spindle for high-speed grinding or a turning machine.

That is, in a spindle for high-speed grinding having a first bearing main body constituting a fixed side and a second bearing main body to which a preload is applied, the first bearing main body is provided in each of a radial direction and an axial direction. The elastic rigidity of the bearing device can be ensured by using the elastic fine particle guide and the elastic fine particle guide only in the radial direction of the second bearing body.

In the grinding machine, by interposing elastic fine particles between the base and the swivel machine, it is possible to prevent the deterioration of positioning accuracy and the increase in driving force due to the main phenomenon of linking between planes. be able to.

[0032]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view of a main part showing an embodiment of a bearing device according to the present invention.

Referring to FIG. 1, first and second rolling bearings (angular ball bearings) 1a and 1b include first and second inner rings 2a and 2b, first and second outer rings 3a and 3b, first and second outer rings 3a and 3b. It has the second rolling elements 4a and 4b, and is mounted at regular intervals on the shaft 5 on which the female screw portion 5a is engraved. That is, the first and second inner races 2a, 2b are arranged such that the rolling bearings 1a, 1b are back-to-back (DB type).
b is pressed into the shaft 5 via an adhesive or an insertion jig (not shown), and is fixed to the shaft 5. Further, two disc springs 6a, 6b (elasticity) having a predetermined spring constant are provided between the first rolling bearing 1a and the second rolling bearing 1b so that a constant preload can be applied in the axial direction. Member) is seated on the step 7.

A sleeve 8 is externally fixed to the first outer ring 3a by bonding or press-fitting, and an upper lid 11 is bonded to a housing (rotor hub) 10 having an appropriate number of female screw portions 9 engraved thereon. Alternatively, the sleeve 8 and the housing 10 are connected by a disk-shaped diaphragm 13 (metal member) made of a metal material.

Then, a gap 12 formed between the sleeve 8 and the inner peripheral surface of the housing 10 is filled with a lubricant such as grease or lubricating oil, thereby forming the first rolling bearing 1.
a is provided with a damping effect, and the occurrence of vibration is prevented by matching two natural vibrations generated by the bearing elasticity and the diaphragm elasticity.

More specifically, the upper lid 11 is formed in a substantially cylindrical shape having a stepped portion 11a, and
3 has an outer diameter Do that is substantially the same as the inner peripheral surface 11b of the lid 11, and an inner diameter Di that is a diameter that can be joined to the sleeve 8. The diaphragm 13 is joined to the inner peripheral surface 11b of the upper lid 11 and the sleeve 8 by laser welding, and the first rolling bearing 1a is connected to and supported by the diaphragm 13 fixed to the upper lid 11.

In this embodiment, the first rolling elements 2
The intersection of the extension line of the contact angle α of a with the center line of the shaft 5 is defined as a virtual pivot P, and the position of the first bearing body 1a and the diaphragm 13 is adjusted so that the virtual pivot P and the horizontal plane of the diaphragm 13 coincide. This prevents the moment rigidity of the first bearing main body 1a from being reduced.

The radial rigidity is cos ² α (α: contact angle)
Therefore, even if the center position of the first rolling element 4a is displaced from the position of the horizontal plane of the diaphragm 13, the decrease in radial rigidity is small, and the spring constant of the bearing elasticity is reduced by the raceway ring (the inner ring 4a and the outer ring 3a). ) Groove shape and first rolling element 4a
The number of the first rolling elements 4a may be adjusted by adjusting the groove shape and the number of the first rolling elements 4a, which may be caused by a deviation between the horizontal plane of the diaphragm 13 and the center position of the first rolling elements 4a. A decrease in radial rigidity can be avoided as much as possible.

As for the outer diameter Do and the inner diameter Di of the diaphragm 13, it is preferable that the moment rigidity and the radial rigidity of the diaphragm 13 are large. For example, when the thickness of the diaphragm 13 is reduced, it is desirable to set the deviation (Do−Di) between the outer diameter Do and the inner diameter Di of the diaphragm 13 as small as possible.

The bearing device thus constructed is assembled as follows.

That is, first, the second inner ring 2b of the second rolling bearing 1b is bonded to the shaft 5 or press-fitted through an insertion jig to fix the second rolling bearing 1b at a predetermined position. The disc springs 6a, 6b are seated on the step 7, and then the first rolling bearing 1a is pressed into the shaft 5 via an insertion jig or the like, and the first outer ring 3a is preloaded with a preload. Inner ring 2a
To the shaft 5. As a result, even if the insertion jig is removed, the disc springs 6a and 6b are elastically deformed by an amount corresponding to the preload, and a constant pressure preload is applied to the first rolling bearing 1a.

Thereafter, the sleeve 8 is connected to the first outer race 3.
a, the upper lid 11 to which the outer peripheral portion of the diaphragm 13 is fixed is fixed to the housing 10, and then the inner periphery of the diaphragm 13 is fixed to the sleeve 8 by laser welding.

Thus, the present bearing device can be easily assembled, and the assembling process can be easily automated.

As described above, in the present embodiment, the disc spring 6
a, 6b, a constant-pressure preload is applied to the first rolling bearing 1a, and the first rolling bearing 1a is
Is supported in the radial direction by the diaphragm 13, so that the radial rigidity can be ensured, and "no backlash" occurs. In addition, in the present embodiment, since the gap 12 is filled with the lubricant, a damping effect can be ensured, and the deterioration of the vibration characteristics and the acoustic characteristics can be prevented.

FIG. 2 is a sectional view showing a second embodiment of the present invention. In this second embodiment, a coil spring 17 is used in place of the disc springs 6a and 6b as a form for applying a constant pressure preload. You are using

Even if the coil spring 17 is used as described above,
According to the same principle as described above, a constant-pressure preload can be applied, the radial rigidity of the first rolling bearing 1a can be ensured, and occurrence of "play" can be avoided.

The method of applying the constant-pressure preload is not limited to the above-mentioned disc springs 6a and 6b and the coil spring 17, but a rubber material such as chloroprene may be used.

FIG. 3 is a sectional view of a main part of a bearing device according to a third embodiment of the present invention. In the third embodiment, a portion between a first outer ring 3a and a housing 19 is shown. A large number of elastic fine particles 18 are interposed in the formed minute gap in an elastically deformed state, and the minute gap is filled with a lubricant such as grease or lubricating oil. Reference numeral 20 denotes an upper cover for sealing the first rolling bearing 1a.

That is, as described above, in the field of HDDs, there is a strong demand for miniaturization, so that the installation space of the bearing device is narrow and the cost is required to be reduced.
It is necessary to reduce the number of parts as much as possible. Therefore, it is conceivable that the rolling bearing itself to which a preload is applied is used as a ball guide.

However, in the HDD spindle, N
RRO has a strict requirement of about 20 to 30 nm, and also has strict requirements on sound and vibration.
Roundness of not only rolling elements but also raceway grooves of inner ring is 1-2 nm
Is required.

Therefore, in the ball guide described in the section of [Prior Art] (first prior art, FIG. 10), the number of balls that can be interposed is small, and there is a possibility that bearing components such as race rings are deformed. .

Therefore, in the third embodiment, for example, a well-known fine particle elastic body 18 (dispersed and dispersed between two glass substrates in order to make the thickness of a liquid crystal layer uniform in a liquid crystal display device or the like). (A particle diameter of 20 μm to 100 μm), a large number of fine particle elastic bodies 18 are interposed in a minute gap formed between the first outer ring 3 a and the housing 19 in an elastically deformed state. Are filled with lubricant.

In the third embodiment, as shown in FIG. 4, the inner peripheral surface of the housing 19 is perpendicular to the insertion direction of the first rolling bearing 1a (indicated by an arrow A in the figure). Are provided with a plurality of annular grooves 22, and similarly to the first and second embodiments, after the second rolling bearing 1b is fixed to the shaft 5, the elastic fine particles 18 are dispersed and dispersed, and 1
8 into the annular groove 22 and then the first rolling bearing 1a
Is inserted in the direction of arrow A to disperse a large number of the elastic fine particles 18 uniformly between the first outer ring 3a and the housing 19 by "rolling guide", and the first jig is loaded with a preload by an insertion jig. By automatically fixing the inner ring 2a to the shaft 5, automatic assembly can be easily performed.

As described above, in the third embodiment, the elastic fine particles 18 are elastically displaced in the minute gap formed between the inner peripheral surface of the housing 19 and the outer peripheral surface of the first outer ring 3a. The conventional ball guide (Fig. 1)
1), it is possible to interpose the elastic fine particles 18 in the minute gap much more, whereby a desired preload is applied to the first rolling bearing 1a via the disc springs 6a and 6b. In addition, the radial rigidity can be increased without causing deformation of the first outer ring 3a due to the averaging effect of the elastic fine particles 18.

The minute gap is filled with a lubricant, so that a constant pressure preload can be applied to the first rolling bearing 1a without deteriorating rotation accuracy, vibration characteristics, acoustic characteristics, and the like. Becomes

In addition, the compression load F of the elastic fine particles 18
(N) and the amount of elastic deformation S (mm) are approximately calculated by the following equation (1).
It is known that the optimum compressive load can be obtained by appropriately selecting various parameters such as the particle diameter, the particle material, and the number of particles in accordance with the amount of elastic deformation. The bearing device having the above radial rigidity can be obtained.

F = (9.8) (2 ^1/2/3 ) (S ^3/2 ) (E · R ^1/2 ) / (1−K ² ) (1) where E is compression elasticity. Rate (MPa), R is the radius (mm) of the elastic fine particles 18, and K is the Poisson's ratio of the elastic fine particles 18.

In FIG. 4, the smaller the angle θ, the easier it is to slide between the first outer ring 3a and the housing 19, and the elasticity between the inner peripheral surface of the housing 19 and the outer peripheral surface of the first outer ring 3a. In order to insert the body particles 18 reliably, it is necessary to set the angle θ to a friction angle of 15 ° or less.

FIG. 5 is a sectional view of a main part of a fourth embodiment of the bearing device according to the present invention. In the fourth embodiment, a coned disc spring 6a is provided above the first rolling bearing 1a. , 6b
And a preload is applied to the first rolling bearing 1a by elastically deforming the disc springs 6a and 6b by the holding lid 21.
A large number of elastic fine particles 18 are interposed between the outer peripheral surface of the shaft 5 and the inner peripheral surface of the first inner ring 2a together with a lubricant.

That is, in the fourth embodiment, after the elastic fine particles 18 are dispersed and supplied to the outer peripheral surface of the shaft 5, the first rolling bearing is provided by the upper lid 21 via the disc springs 6a and 6b. 1a is press-fitted, and the upper cover 21 applies a preload to the first rolling bearing 1a.

In the fourth embodiment, as in the third embodiment, the radial rigidity is increased without causing deformation of the first inner ring 2a due to the averaging effect of the elastic fine particles 18. And the first rolling bearing 1a is positioned by contacting a stepped portion 19a formed in the housing 19, and the disc springs 6a, 6b,
Since the preload is applied at 1, the spacer 7 (see FIG. 3) as in the third embodiment becomes unnecessary, the number of parts can be reduced, and the cost can be reduced. .

Next, an example of application of the above-described "rolling guide" by the elastic fine particles to a device other than the HDD will be described.

The fine particles of the elastic fine particles can be arbitrarily set by changing the particle size, the material and the like, and the fine gaps can be set arbitrarily. It is possible to exhibit a `` damping effect '', and it is possible to combine the rolling guide and the sliding guide, and therefore, in general, it can be applied to a bearing device using a conventional sliding guide. Conceivable.

Particularly, since the support rigidity and the damping constant are large, it is suitable for applications requiring dynamic characteristics such as a support bearing for a machine tool spindle.

FIG. 6 is a sectional view of a main part of a fifth embodiment of a bearing device according to the present invention, in which the bearing device is applied to a grinding spindle.

That is, the present bearing device is composed of two double row angular contact ball bearings (first type) in a parallel combination (DT type).
And the second double-row angular contact ball bearings 23, 24) are externally fitted to the shaft 25 so as to be separated from each other so as to be back-to-back, and a rotor 26 is mounted on the shaft 25. Fixed to the first housing 28.

Then, the first double-row angular contact ball bearing 23
Is positioned and fixed by the stepped portion 25 a of the shaft 25, the bearing fixing member 32, and the front holding lid 34. Further, a front sleeve 31 is externally fitted to the first double-row angular contact ball bearing 23, and a minute gap formed between the front sleeve 31, the second housing 29 and the front holding lid 34 has a cross section. A large number of elastic fine particles 35 are inserted in a U shape together with a lubricant.

A rear sleeve 36 is externally fitted to the second double row angular contact ball bearing 24, and a minute gap formed between the rear sleeve 36 and the third housing 30 is formed. Many elastic fine particles 39 are inserted in the axial direction together with the lubricant. Further, a coil spring 40 is seated in a recess provided in the third housing 30, and the coil spring 40 holds the second double-row angular ball bearing 24 with a preload applied thereto via a rear sleeve 36. It is fixed by a fixing member 37 and a rear holding lid 38.

The rear sleeve 36 is fixed to the diaphragm 42 via a screw 42 to prevent the rear sleeve 36 from rotating. In addition, 43 is a cooling groove, and 44 is a balance ring.

As described above, in the fourth embodiment,
The axial direction and the radial direction of the front sleeve 31 are guided by the elastic fine particles 35 and the first double row angular contact ball bearing 23 is fixed. The radial direction of the rear sleeve 36 is guided by the elastic fine particles 39 by the coil spring 40. The preload is applied to the double row angular contact ball bearings 24.

As described above, even in the high-speed spindle for grinding, the preload is reliably applied to the second double-row angular ball bearing 24, and the rotation shaft 25 is not rattled by the elastic fine particles 39, thereby preventing the rotation accuracy from deteriorating. It is possible,
Further, since the minute gap is filled with the lubricant, a desired damping effect can be ensured, and it is possible to prevent the vibration characteristics and the acoustic characteristics from being lowered.

FIG. 7 is a plan view showing another embodiment of guiding the elastic fine particles, and FIG. 8 is a sectional view taken along line XX of FIG.

That is, the other embodiment shows a case where the guide by the elastic fine particles is applied to the revolving plate.
Elastic fine particles 47 are inserted between the base 45 and the turning table 46. In the drawing, 48 is a shaft, 49 is a bearing unit, 50 is a sleeve, and 51 is an upper lid.

Conventionally, vibration characteristics have been generally considered to be good on a flat slide surface, but there has been a problem in that positioning accuracy is reduced and driving force is increased due to linking between flat surfaces as a main phenomenon.

Therefore, in the case of a revolving lathe having a small stroke and no opening surface, elastic fine particles are used for its guide surface, thereby avoiding the above-described reduction in positioning accuracy and increase in driving force. Here, it is known that the damping in the vertical direction of the guide surface is proportional to the cube of the gap, and the effect of the minute gap by the fine particles is effective. For example, for a gap of 200 μm, a gap of 20 μm
A 00-fold damping effect can be expected.

In this case, as the material of the elastic fine particles, it is preferable to use an inorganic material such as ceramics from the viewpoint of increasing the joining rigidity with the revolving plate 46.

In addition, as the guide by the elastic fine particles, application to a guide surface which can respond to set changeability and high accuracy using numerical control can be considered. For example, application to a sliding surface of a machining center can be considered.

[0079]

As described above in detail, the bearing device according to the present invention is rotatably held between the inner ring fitted to the shaft, the outer ring fitted to the housing, and the inner ring and the outer ring. In a bearing device in which a plurality of bearing bodies composed of rolling elements are disposed apart from each other in the axial direction, a specific bearing body among the plurality of bearing bodies is preloaded by an elastic member, and The specific bearing body is mounted in the housing with a gap between at least one of the inner ring and the shaft or between the outer ring and the housing, and the specific bearing body is arranged in a radial direction rather than an axial direction. Since it is connected and supported by a metal member having high rigidity, a constant pressure preload is applied to a specific bearing main body by an elastic member, and the specific bearing main body has a small spring constant in an axial direction and a radial bearing. Since the supports with large metal member spring constant, it without that is secured rigidity in the radial direction is "backlash" occurs, rotational accuracy is not deteriorated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing one embodiment (first embodiment) of a bearing device according to the present invention.

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

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

FIG. 4 is an explanatory view when a bearing main body is incorporated in a housing in a third embodiment.

FIG. 5 is a sectional view of a main part showing a fourth embodiment of the bearing device according to the present invention.

FIG. 6 is a sectional view showing a main part of a bearing device according to a fifth embodiment of the present invention.

FIG. 7 is a plan view of an essential part showing another embodiment of a guide method using elastic fine particles.

FIG. 8 is a sectional view taken along line XX of FIG. 7;

FIG. 9 is a cross-sectional view of a conventional bearing device employing a fixed-position preload system.

FIG. 10 is a cross-sectional view of a principal part showing a first related art of a bearing device employing a constant-pressure preload system.

FIG. 11 is a sectional view showing a second related art of a bearing device employing a constant-pressure preload system.

[Explanation of symbols]

 1a Bearing body 1b Bearing body 2a Inner ring 2b Inner ring 3a Outer ring 3b Outer ring 5 Shaft 6a Disc spring (elastic member) 6b Disc spring (elastic member) 10 Housing 12 Gap 13 Diaphragm (metal member) 17 Coil spring (elastic member)

Claims (1)

[Claims] A plurality of bearing bodies each including an inner ring fitted to a shaft, an outer ring fitted to a housing, and a rolling element rotatably held between the inner ring and the outer ring are provided in an axial direction. In the bearing device disposed apart, a specific bearing main body of the plurality of bearing main bodies is loaded with a preload via an elastic member, and the specific bearing main body is disposed between the inner ring and the shaft. Alternatively, at least one between the outer ring and the housing is mounted in the housing with a gap, and the outer ring of the specific bearing body is supported by a metal member having a greater rigidity in the radial direction than in the axial direction. A bearing device characterized in that: