JP2000352414A - Dynamic pressure type bearing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dynamic pressure type bearing unit which can be assembled precisely and efficiently with a simple facility. SOLUTION: This bearing unit comprises a housing 2, and a bearing body 3 housed in the housing 2 and having a bearing surface 3a opposite to an outer peripheral surface of a shaft member 1 with a bearing gap interposed therebetween and a dynamic pressure groove formed in the bearing surface 3a. Locking parts 13 and 17 are respectively provided at two positions in an axial direction in an inner peripheral surface of the housing 2, and the bearing body 3 is pressed to the first locking part 13 by elastic force of an elastic member 15 whereby the bearing body 13 is fixedly mounted between the locking parts 13 and 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure type bearing unit having excellent features such as high rotational accuracy, high speed stability and high durability. This bearing unit includes a magnetic disk device (HDD, FDD, etc.) and an optical disk device (CD-
ROM, DVD-ROM / RAM, etc.), information storage devices such as magneto-optical disk devices (MD, MO, etc.), and spindle motors for information processing devices (laser beam printers, etc.), and high rotational accuracy are required. It is suitable as a support device for equipment.

[0002]

2. Description of the Related Art Spindle motors for various information devices are required to have high rotational accuracy, high speed, low cost, low noise, and the like. One of the components that determine these required performances is a bearing that supports the spindle of the motor. In recent years, as this type of bearing, use of a hydrodynamic sintered oil-impregnated bearing having characteristics excellent in the required performance has been used. Have been considered or actually used.

[0003] This hydrodynamic sintered oil-impregnated bearing is housed in a cylindrical housing and fixed to the inner peripheral surface of the housing to form a unit. Pressing and bonding are considered as fixing methods at that time.

[0004] Press-fitting is the most common fixing method in ordinary sintered oil-impregnated bearings without dynamic pressure grooves. For example, as shown in Fig. 6, a press-fit pin 21 (correction pin) is inserted into a bearing body 23. At the same time, the pressing can be performed by pressing one end face of the bearing main body 23 with the press fitting jig 24. That is, the inner diameter surface of the bearing that contracts with pressurization is pierced by the press-fit pin 21, and the outer diameter surface of the bearing is pressed into the inner diameter surface of the housing 22 while correcting the inner diameter surface of the bearing. With this method, the press-in pin 21
The bearing inner diameter is finally finished by
Accuracy to be ensured, for example, the perpendicularity between the inner diameter surface of the bearing and the substrate mounting surface 22a of the housing 22, the coaxiality between the housing outer peripheral surface and the like can be ensured simultaneously with the completion of the press-fitting, and the cost is low. On the other hand, bonding is performed, for example, by using a jig shown in FIG.
By using the adhesive 26, an adhesive 27 can be supplied to the joint surface between the inner peripheral surface of the housing 22 and the outer peripheral surface of the bearing body 23.

[0005]

When the dynamic pressure groove is provided on the inner peripheral surface of the bearing body, the above-mentioned press-fitting is affected by the deviation of the coaxiality of the inner and outer diameters of the bearing (unevenness, uneven thickness) and the like. A part of the dynamic pressure groove may be crushed by the correction, and a predetermined groove shape and groove depth may not be obtained. This problem can be avoided by press-fitting without using the press-fit pin 21, but in this case, since the accuracy after press-fitting is equivalent to the accuracy of the joint surface between the housing inner peripheral surface and the bearing outer peripheral surface, this portion is not required. The unit accuracy must be higher than the required assembly accuracy, which makes mass production difficult and causes a cost increase.

After press-fitting, the inner diameter of the bearing is reduced due to the press-fit interference. However, the press-fit interference is dependent on the tolerance of the inner peripheral surface of the housing and the tolerance of the outer peripheral surface of the bearing. In such a case, the change in the bearing inner diameter size becomes large. In the case of a dynamic pressure bearing, it is necessary to strictly control the bearing clearance. If the bearing inner diameter is largely changed, the bearing clearance becomes excessively wide and the dynamic pressure effect is remarkably reduced. Therefore, it is necessary to set each tolerance of the inner peripheral surface of the housing and the outer peripheral surface of the bearing in a small range, which also causes an increase in cost. Further, in some cases, it is impossible to realize the tolerance.

[0007] On the other hand, in the case of bonding, it is possible to solve the above-mentioned problem in the case of press fitting. In other words, if the bonding jig is finished with high accuracy, a sufficiently practical assembly accuracy can be obtained even if the accuracy of each unit is equivalent to that of the current mass production equipment.

However, since the dynamic pressure type sintered oil-impregnated bearing is made of a sintered oil-impregnated material whose surface is wetted with oil, a variation in oil wetting is unavoidable, which appears as a variation in adhesive strength. It is conceivable to blow off the oil on the surface with a centrifuge, for example.However, the increase in the number of processes leads to an increase in cost, making it difficult to set the working conditions. It becomes difficult to align.

[0009] Naturally, a bonding facility is required. In the above information equipment applications, the inner diameter of the bearing is φ2
Around φ4 is mainstream and extremely small. If this kind of small bearing is to be bonded accurately, a special bonding equipment is required, resulting in an increase in cost.

[0010] Further, after the bonding, it is necessary to hold it for a while, so that the cycle time is poor and the mass productivity is poor.

Accordingly, an object of the present invention is to provide a dynamic pressure bearing unit that can be assembled accurately and efficiently with simple equipment.

[0012]

In order to achieve the above object, according to the present invention, a housing and a bearing surface which is housed in the housing and faces the outer peripheral surface of a shaft member to be supported via a bearing clearance, A bearing body provided with a dynamic pressure groove on the bearing surface, wherein the dynamic pressure action generated in the dynamic pressure groove at the time of relative rotation between the shaft member and the bearing body supports the shaft member in a non-contact manner; Are provided at two axial positions, and the bearing body is restrained by the two locking portions via an elastic body.

Accordingly, the bearing body is restrained from both sides in the axial direction of the housing, so that the bearing body can be positioned in the axial direction. In this case, since the fit between the outer peripheral surface of the bearing body and the inner peripheral surface of the housing may be loose,
There is no deformation of the inner peripheral surface of the bearing main body after assembling such as press fitting. Further, since the bearing body is fixed by the elastic force of the elastic body, problems such as variations in bonding strength, which may be a problem during bonding, are avoided.

If an axial ventilation path is provided between the outer peripheral surface of the bearing main body and the inner peripheral surface of the housing, which is open at both axial ends of the bearing main body, the shaft member can be inserted into the inner diameter of the bearing main body. In addition, the air trapped in the housing can be smoothly discharged out of the housing.

When the elastic body is used as described above, the axial ventilation path may be closed by the elastic body. In this case, the space between the elastic body and the end face of the bearing body facing the elastic body may be provided. It is preferable to provide a radial ventilation path that opens to the axial ventilation path, and to communicate the axial ventilation path with the outside of the housing via the radial ventilation path.

Any of the above-mentioned bearing bodies can be formed of a sintered metal having oil.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the bearing unit comprises a shaft member 1, a cylindrical housing 2 having a bottom, a cylindrical bearing body 3 fixed to the inner peripheral surface of the housing 2, and a shaft member 1. It has a radial bearing part 4 and a thrust bearing part 5 which support in the radial direction and the thrust direction, respectively.

A radial bearing surface 3a having a dynamic pressure groove is formed on the inner peripheral surface of the bearing body 3. As shown in FIG. 2A, this embodiment exemplifies a case in which radial bearing surfaces 3 a are provided at a plurality of locations (for example, two locations) on the inner peripheral surface of the bearing main body 3. However, the number of the radial bearing surfaces 3a is arbitrary, and may be one or three or more according to the use conditions of the bearing and the like. During relative rotation of the shaft member 1 and the bearing body 3 (at the time of rotation of the shaft member 1 in the present embodiment), dynamic pressure is generated in a bearing gap between the radial bearing surface 3a and the outer peripheral surface of the shaft member 1, A radial bearing portion 4 that supports the shaft member 1 in a non-contact manner is configured.

The shape of the dynamic pressure groove on the radial bearing surface 3a can be arbitrarily selected as long as each dynamic pressure groove is inclined with respect to the axial direction, and a well-known herringbone type or spiral type can be used. It is. FIG. 2A shows an example of a herringbone type radial bearing surface 3a.
Is a first groove region in which a dynamic pressure groove 6 inclined to one side is formed.
m1, a second groove region m2 in which the hydrodynamic grooves 6 are arranged axially separated from the first groove region m1 and inclined to the other, and a ring-shaped ring member located between the two groove regions m1 and m2. And a smoothing portion n.
The dynamic pressure grooves 6 of the two groove regions m1 and m2 are partitioned by the smooth portion n and are discontinuous. Back portion 7 between smooth portion n and dynamic pressure groove 6
Is at the same level. This type of discontinuous dynamic pressure groove 6
The oil is collected around the smooth portion n as compared with the continuous type, that is, compared with the case where the dynamic pressure groove 6 is formed in a V-shape continuous with each other between the two groove regions m1 and m2, in which the smooth portion n is omitted. In addition, since the oil film pressure is high and the smooth portion n having no groove is provided, there is an advantage that the bearing rigidity is high.

The bearing body 3 is made of a soft metal such as copper or brass,
Alternatively, the bearing body 3 formed of a sintered metal is illustrated in the present embodiment as an example.
When using a sintered metal, the dynamic pressure grooves on the radial bearing surface 3a
Compression molding, that is, forming an irregular groove shape corresponding to the dynamic pressure groove shape of the radial bearing surface 3a (see FIG. 2 (A)) on the outer peripheral surface of the core rod, supplying sintered metal to the outer periphery of the core rod and firing. By pressing the binding metal and transferring the dynamic pressure grooves corresponding to the groove shape to the inner peripheral portion of the sintered metal, it is possible to form the molding at low cost and with high precision. The release of the sintered metal can be easily performed using the springback of the material by releasing the pressing force. A hydrodynamic sintered oil-impregnated bearing is formed by impregnating the bearing body 3 after demolding with lubricating oil or lubricating grease to retain the oil.

As shown in FIGS. 2A and 2B, the outer peripheral surface of the bearing body 3 has one or more air vents for inserting the shaft member 1 into the inner diameter of the bearing body 3 (this embodiment). Then, two) groove-shaped axial ventilation paths 9 are formed along the axial direction. An annular groove 10 is provided on one end surface of the bearing body 3, specifically, an end surface 3b facing the bottom 2a of the housing 2. The annular groove 10 can function as, for example, an identification mark for determining an insertion direction when the bearing main body 3 is inserted into the housing 2. Annular groove 10 and axial ventilation path 9
A radial communication groove 11 is provided between the annular groove 10 and the annular groove 10 and the axial ventilation path 9 are connected through the communication groove 11. The axial ventilation path 9 may be formed on the inner peripheral surface of the housing 2.

As shown in FIG. 1, the housing 2 has a bottom
This is a so-called bag-shaped housing with a bottomed cylinder in which 2a is integrally formed. A plate-shaped thrust receiver 12 made of a low-friction material such as a resin is mounted on a bottom 2a of the housing 2 (a part facing the end surface of the bearing body 3). A thrust bearing portion 5 that pivotally supports the shaft member 1 in the thrust direction by bringing the shaft ends into contact with each other. A first locking portion 13 protruding in the radial direction is provided on the inner peripheral surface of the housing 2, for example, near the housing bottom 2a. The first locking portion 13 engages with the end surface 3b of the bearing body 3 on the housing bottom side to perform axial positioning thereof. The positioning is performed by the end surface 3b of the bearing body 3 and the bottom 2a of the housing 2 ( Specifically, it is performed such that an axial space 14 (bottom space) is formed between the thrust receiving plate 12). The first locking portion 13 may be formed integrally with the housing 2 as shown in FIG. The contact area of the end face 3b of the bearing body 3 with the first locking portion 13 is located on the outer diameter side of the annular groove 10, so that the bottom space 14 is ventilated in the axial direction through the annular groove 10 and the communication groove 11. It is in communication with Road 9.

An elastic body 15 is arranged in contact with the end face 3c of the bearing body 3 on the housing opening side. The elastic body 15 is formed in a ring shape, for example, a perforated disk shape, from an elastic material having appropriate elasticity (metal, fiber structure, rubber, resin material, or the like), and is fitted to the inner peripheral surface of the housing 2. . The inner peripheral surface of the elastic body 15 is in contact with or close to the outer peripheral surface of the shaft member 1 (refer to FIG. 1) (in the illustrated example, close to the outer peripheral surface), whereby the elastic body 15 seals the housing opening side of the bearing body 3. Functions as a sealing member. An oil refilling member having an oil replenishing function for the elastic body 15, for example, a material in which felt is impregnated with oil, a material in which oil is dispersed and held in a synthetic resin base material (this may be impregnated in felt and cured) In this case, oil can be successively replenished into the bearing gap, and stable formation of the dynamic pressure oil film becomes possible.

A groove-shaped radial ventilation path 16 is provided in the radial direction between the elastic body 15 and the end face 3c of the bearing body 3 (the end face on the housing opening side) facing the elastic body 15. This radial ventilation groove 16 is open on the inner peripheral surface and the outer peripheral surface of the elastic body 15,
As a result, the axial ventilation path 9 is composed of the radial ventilation path 16 and the elastic body 16.
The housing is connected to the outside of the housing through the gap between the inner peripheral surface of the shaft 15 and the outer peripheral surface of the shaft member 1. In FIG. 1, the radial ventilation path 16
Although a groove provided on the end face of the elastic body 15 is illustrated as an example, a similar groove may be provided on the end face of the bearing body 3. The outer diameter end of the radial ventilation path 16 is preferably opposed to the opening of the axial ventilation path 9, but an outer diameter chamfer section 3d is provided on the housing opening side end face 3c of the bearing body 3 as shown in the figure. In this case, the outer diameter chamfer portion 3d can be ventilated.
It is permissible for there to be a circumferential displacement between the 16 positions.

The elastic body 15 is supported from the housing opening side by a second locking portion 17 projecting in the radial direction. FIG. 1 illustrates a structure in which the opening side end of the housing 2 is caulked toward the inner diameter side as the second locking portion 17.

At the time of assembling the bearing unit, first, the housing 2 is held by an appropriate jig, and in this state, the bearing body 3 is inserted into the inner diameter portion of the housing 2 by a clearance fit, or
Alternatively, light press-fitting is performed with a slight interference fit (a fit that does not change the inner diameter of the bearing body 3).

At this time, if the pins 31 (refer to FIG. 5) positioned with respect to the jig 30 are inserted into the inner diameter of the bearing body 3, the bearing body 3 follows these pins and the inner diameter of the housing is adjusted. , The required assembly accuracy (particularly, accuracy in the radial direction) between the bearing body 3 and the housing 2 is ensured.

Next, the elastic body 15 is disposed on the end face 3c (housing opening side) of the bearing body 3, and the opening of the housing 2 is caulked to the inner diameter side while the elastic body 15 is compressed, so that the elastic body 15 is compressed. However, it is interposed in a compressed state between the caulking portion 17 constituting the second locking portion and the end face 3c of the bearing body 3.

With the above configuration, the bearing body 3 is provided with the two locking portions.
It is restrained from both sides in the axial direction by 13 and 17. At this time, the bearing main body 3 is pressed against the first locking portion 13 by the elastic force in the axial direction from the elastic body 15 in a compressed state. High assembling accuracy (particularly, assembling accuracy in the axial direction) can be secured between the bearing body 3 and the bearing body 3. Even when the accuracy between the inner diameter surface of the bearing body 3 and the housing opening side end surface 3c, for example, the perpendicularity, is insufficient, the run-out is absorbed by the deformation of the elastic body 15, so that the axial elasticity is reduced. As a result, the assembly accuracy is not impaired.

After the caulking, the shaft member 1 is inserted into the inner diameter portion of the bearing body 3 to complete the bearing unit. At this time, the air in the bottom space 14 also receives the air in the axial direction air passage 9 and the radial direction air passage. Since the shaft member 1 is discharged to the outside of the housing 2 through 16, the insertion operation of the shaft member 1 can be performed smoothly.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the second locking portion 17 supporting the elastic body 15 is configured by a leaf spring member 19 such as a disc spring, and the outer diameter end of the leaf spring member 19 is provided on the inner peripheral surface of the housing 2. Annular mounting groove 18
Is fitted. The first locking portion of the bearing body 3 by the composition and structure of the bearing body 3 and the elastic body 15 and the elastic force of the elastic body 15
The point of pressing the bottom space 13 and the point where the bottom space 14 is communicated with the outside of the housing by the axial ventilation path 9 and the radial ventilation path 16 are the same as those in FIG.

FIG. 4 shows another embodiment of the present invention, and illustrates a structure in which an elastic body 15 is disposed on the bottom side of the housing 2. In this case, the bottom 2a of the housing 2 is
The second locking portion 17 supports the second locking portion 17. Further, the swaging portion formed by caulking the opening of the housing 2 toward the inner diameter side becomes the first locking portion 13 projecting in the radial direction, and the bearing body 3 is made of an elastic body 15.
The elastic member is pressed against the first locking portion 13 and positioned in the axial direction. The other configuration, operation and effect are the same as those in FIG.

FIG. 5 illustrates an assembling apparatus used in the assembling process of the bearing unit shown in FIG. This device is a jig
30 and a pin 31 coaxially inserted into the inner peripheral portion of the jig 30. The jig 30 has an outer peripheral member 30a and an inner peripheral member elastically supported so as to be axially slidable with respect to the outer peripheral member 30a. 30b. By inserting the pin 31 into the inner peripheral portion of the bearing body 3, supporting the housing 2 with the outer peripheral member 30a, and pressing the upper end of the inner peripheral member 30b against the swaged portion of the opening of the housing 2, Assembly accuracy (particularly, assembly accuracy in the radial direction) with the bearing body 3 is ensured. By pressurizing the housing bottom 2a in this state, the opening of the housing 2 is swaged to the inner diameter side and the first locking portion 13a is pressed.
Is formed. The bearing unit shown in FIGS. 1 and 3 can be assembled basically in the same manner as in FIG.

[0035]

According to the present invention, the bearing body can be accurately fixed to the housing with a very simple structure.
In addition, the accuracy can be easily obtained, and a high-precision dynamic pressure bearing unit can be mass-produced at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a dynamic pressure bearing unit according to the present invention.

2A is a sectional view of a bearing main body of the dynamic pressure bearing unit, and FIG. 2B is a bottom view of the bearing main body.

FIG. 3 is a sectional view showing another embodiment of the dynamic pressure bearing unit.

FIG. 4 is a sectional view showing another embodiment of the dynamic pressure bearing unit.

FIG. 5 is a cross-sectional view showing an assembly process of the dynamic pressure bearing unit shown in FIG.

FIG. 6 is a cross-sectional view showing a conventional press-fitting step.

FIG. 7 is a cross-sectional view showing a conventional bonding step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaft member 2 Housing 3 Bearing body 3a Bearing surface 3b End surface (housing bottom side) 3c End surface (housing opening side) 9 Axial ventilation passage 13 First locking portion 15 Elastic body 16 Radial ventilation passage 17 Second locking portion

Claims (4)

[Claims] A housing, housed in the housing,
A bearing body having a bearing surface opposed to an outer peripheral surface of a shaft member to be supported via a bearing clearance, and a bearing body provided with a dynamic pressure groove on the bearing surface; In the one that supports the shaft member in a non-contact manner by the dynamic pressure action generated in the dynamic pressure groove, locking portions are provided at two locations in the axial direction of the housing, and the bearing body is restrained by the both locking portions via the elastic body. A dynamic pressure bearing unit characterized in that: 2. The dynamic pressure type bearing unit according to claim 1, further comprising an axial ventilation path opened at both axial ends of the bearing main body between the outer peripheral surface of the bearing main body and the inner peripheral surface of the housing. 3. The dynamic pressure bearing unit according to claim 2, wherein a radial ventilation path communicating with the axial ventilation path is provided between the elastic body and an end face of the bearing body facing the elastic body. 4. The dynamic pressure bearing unit according to claim 1, wherein the bearing body is formed of a sintered metal having oil.