JPH11190343A - Manufacture of dynamic pressure type porous oil retaining bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly separate a sintered metal material from a die without collapsing a dynamic pressure groove after the latter is formed. SOLUTION: A core rod 1 having a forming part 1b corresponding to a shape of a bearing surface is inserted in the inner peripheral surface of a cylindrical sintered metal material 2'. The material 2' is press-fitted in a die 3 while it is constrained at its axially opposite ends by punches 4, 5. With the use of a pressing force obtained at this time, the inner peripheral surface of the material 2' is pressed against the forming part 1b of the core rod 1, a bearing surface having, in its inner peripheral surface, a dynamic pressure groove whose shape corresponds to the forming part of the core rod 1, is formed. Thereafter, the sintered metal material 2' is taken out from the die 3 together with the core rod 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a bearing surface having a dynamic pressure groove on an inner peripheral surface of a bearing body made of a sintered metal.

[0002]

2. Description of the Related Art Recently, CD-ROM, DVD-ROM
For small spindle motors related to information devices such as (RAM), hard disk, and laser beam printers, there is a demand for further improvement in rotational performance and reduction in cost. Replacement with a sintered oil-impregnated bearing is being considered.

[0003] As this type of sintered oil-impregnated bearing, a perfect circular bearing (sintered oil-impregnated bearing having a flat cylindrical surface over its entire bearing surface) is generally used. After sintering the bearing body, secondary processing (sizing) for obtaining required dimensions is performed.

FIG. 6 shows an example of a sizing process in a perfect circular bearing. The sizing device has an axial core rod 21,
It comprises a die 23, upper and lower punches 24, 25, an upper ram 26 for pressing the upper punch 24, and a driving means (not shown) for driving the lower punch 25. The upper end of the core rod 21 is locked to the upper ram 26, so that the core rod 21 and the upper ram 26 can move integrally. First, the sintered material 22 is
The core rod 21 is inserted into the inner diameter part by the lowering of the upper ram 26 (step 2), and is pressed into the die 23 by being pressed by the upper punch 26 (step 2). (Steps 3 and 4). The sintered material 22 press-fitted into the die 23 is constrained on both sides in the axial direction by upper and lower punches 24 and 25,
The outer peripheral surface is formed by a die 23 and the inner peripheral surface is formed by a core rod 21.
Respectively (sizing). After sizing, the upper ram 26 is first lifted to remove the core rod 21 from the inner diameter of the sintered material 22 (steps 5 and 6), and then the sintered material 22 is pushed up by the lower punch 25 and fired from the die 23. The binder 22 (bearing body) is taken out (steps 7 and 8).

[0005]

In a perfect circular bearing, unstable vibration is likely to occur where the eccentricity of the shaft is small, and so-called whirling which swings at half the rotational speed is likely to occur. For this reason, a herringbone type or spiral type dynamic pressure groove is provided on the bearing surface on the inner peripheral surface of the bearing body, and a dynamic pressure oil film is formed in the bearing gap by the dynamic pressure effect accompanying the rotation of the shaft to support the shaft floating. Accordingly, attempts to solve the problem of unstable vibration such as whirl have been made conventionally (dynamic pressure type porous oil-impregnated bearings).

In this type of dynamic pressure type oil-impregnated bearing,
As a method of forming the bearing surface having the dynamic pressure groove, compression molding can be considered. That is, for example, in the sizing step, a molded portion having a concave and convex shape corresponding to the shape of the bearing surface having the dynamic pressure groove is formed on the outer peripheral surface of the core rod 21, and the sintered material 22 is placed on the inner diameter side of the core rod 21. 21 is pressed into a die 23 in a state in which the sintered material 22 is pressed in the die 23 to press the inner peripheral surface of the sintered material 22 against the molded portion of the core rod 21, and the inner peripheral surface of the molded portion is pressed. It transfers the shape.

However, in the conventional sizing process, the core rod 21 is first removed (at this time, the formed sintered material 22 remains in the die 23) when the sintered material is released from the die as described above. Since the sintered material is pushed out of the die 23 by the lower punch 24, there is a problem that the dynamic pressure groove formed in the inner diameter portion of the sintered material 22 collapses at the same time as the core rod 21 is removed when the mold is released.

In this case, if the lower punch 25 is raised at the same time when the core rod 21 is pulled (raised), the positional relationship between the sintered material and the core rod is maintained, and the collapse of the dynamic pressure groove can be prevented. It is necessary to completely match the rising timing of the core rod side and the lower punch side, and it is extremely difficult to achieve this, and even if it can be done, it becomes mechanically quite large and complicated.

Accordingly, the present invention provides a dynamic pressure type porous oil-impregnated body having a simple structure and capable of smoothly releasing a bearing body (sintered metal material) after forming a dynamic pressure groove without breaking the dynamic pressure groove. It is an object of the present invention to provide a bearing manufacturing method and a manufacturing apparatus.

[0010]

In order to achieve the above object, according to the present invention, a bearing surface having an inclined dynamic pressure groove is formed on the inner peripheral surface of a cylindrical bearing body made of sintered metal. A method of manufacturing a dynamic pressure type porous oil-impregnated bearing obtained by impregnating a lubricating oil or a lubricating grease into a bearing body, comprising: The sintered metal material is pressed into the die while pressing both sides in the axial direction with a pair of punches, while pressing the inner surface of the sintered metal material with a pair of punches. After forming a bearing surface having a dynamic pressure groove of a shape corresponding to the forming portion of the core rod on the inner peripheral surface by pressing the formed portion, the sintered metal material is pressed while maintaining the positional relationship with the core rod. The core rod was taken out of the die.

In this case, after forming the bearing surface on the inner peripheral surface of the sintered metal material, one of the punches is driven to pull out the die, the core rod and the other punch are driven synchronously, and the other punch is used for sintering. The sintered metal material is taken out from the die by pressing the metal material.

At this time, the sintered metal material is driven by synchronously driving the driving device and the other punch within the predetermined range while allowing the axial delay of the core rod with respect to the driving device for driving the core rod within a predetermined range. Should be taken out of the die.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
A description will be given based on FIGS.

FIG. 1 shows a molding apparatus (sizing apparatus) to which the present invention is applied. This device has a core rod 1 for forming the inner peripheral surface of the bearing main body 2 and a die 3 for forming the outer peripheral surface of the bearing main body 2, as in the conventional device shown in FIG.
And a pair of punches 4, 5 for restraining both sides of the bearing body 2 in the axial direction, and an upper ram 6 serving as a driving device for driving the core rod 1 and the upper punch 4.

Forming portions 1b for forming a bearing surface 2b on an inner peripheral surface 2a of a bearing body 2 (see FIG. 5) of a hydrodynamic porous oil-impregnated bearing are provided at two axial positions on an outer peripheral surface 1a of the core rod 1. They are formed spaced apart in the axial direction. As shown in FIG. 2, the forming portion 1b includes a first region 1b1 for forming a formation region of the dynamic pressure groove 2b1 on the bearing surface 2b, and a region other than the dynamic pressure groove 2b1 on the bearing surface 2b, that is, a dynamic pressure groove 2b1. And a second region 1b2 for forming an annular smooth portion 2b3 at the axially intermediate portion of the bearing surface 2b. The first region 1b1 is formed so as to correspond to the dynamic pressure groove pattern of the bearing surface 2b, and the drawing illustrates a case where the first region 1b1 corresponds to the so-called herringbone type dynamic pressure groove 2b1. The second region 1b2 is recessed by a predetermined amount with respect to the first region 1b1, and the amount of the recess is substantially equal to the depth of the dynamic pressure groove 2b1, for example, 2 to 4 μm. The shape of the dynamic pressure groove 2b1 is arbitrary as long as it is inclined with respect to the axial direction. In the case of another inclined groove such as a spiral type, the first region 1b1 is used.
Is formed in a shape corresponding to the groove shape. Core rod 1
Is not limited to two as shown in the figure, but may be one or three or more in accordance with the number of bearing surfaces 2b formed on the bearing body 2. In FIG. 2, the irregularities of the molded portion 1b are drawn in an exaggerated manner.

The upper ram 6 is formed with a space 6a (accommodating portion) whose axial length is longer than that of the bearing main body 2. A flange portion 1c formed at the upper end of the core rod 1 is slidably accommodated in the accommodation portion 6a in the axial direction, whereby relative displacement in the axial direction between the core rod 1 and the upper ram 6 is allowed. I have. An elastic member 7 such as a coil spring is interposed between the lower surface of the flange portion 1c and the lower surface of the housing portion 6a in a compressed state, and the core rod 1 is moved upward by the elastic member 7 in the drawing, that is, in a direction away from the die 3. It is constantly suppressed. At the time of standby before molding of the bearing body 2 (step 1 in FIG. 4), the flange portion 1c is moved by the elastic force of the elastic member 7 into the housing portion 6a.
, The core rod 1 is positioned.

Hereinafter, the step of forming the dynamic pressure grooves in the above-described forming apparatus will be described with reference to FIG.

First, a sintered material 2 '(see FIG. 3) previously formed into a thick cylindrical shape is arranged coaxially with the core rod 1 and the upper and lower punches 4, 5 on the die 3 (step 1). . At this time, the core rod 1, the upper punch 4, and the ram 6 are at the upper position (standby position). On the other hand, the lower punch 5 is slidably inserted into the die 3 and waits at the upper end of the forming hole of the die 3 to receive the lower surface of the sintered metal material 2 '.

At this time, the outer diameter of the sintered material 2 ′ is larger than the inner diameter of the die 23 by the press-fitting allowance, and the inner diameter is slightly larger than the inner diameter of the core rod 1. In the drawings, the sintered material 2 'having the inner peripheral surface 2a and the outer peripheral surface 2c as straight surfaces is illustrated, but the outer peripheral surface 2c may be a stepped surface having a large diameter portion in part. The sintered material 2 'is a sintered metal mainly composed of copper or iron, or both of them, and preferably contains 20 to 95% by weight of copper.
Formed using.

Next, a drive device such as a hydraulic mechanism is activated to move the upper ram 6 forward (down). As a result, the tip of the core rod 1 is first inserted into the inner diameter of the sintered material 2 '(step 2), and after that, the upper punch 4 pressed by the upper ram 6 descends, and the sintered material 2' (Step 3).
When the upper ram 6 is further lowered, the sintered material 2 'is pressed into the die 3 while being restrained from both sides in the axial direction by the upper and lower punches (step 4). At this time, the lower punch 5 descends in synchronization with the upper ram 6. With the press-fitting into the die 3, the sintered material 2 '
The upper and lower ends receive the compressive force from the upper and lower punches 4 and 5, and the upper and lower ends move toward the inner diameter side and are pressed against the opposing forming portions 1b. Thereby, the shape of the molded part 1b is changed to the sintered material 2 ′.
Is transferred to the upper and lower end portions of the inner peripheral surface of the first portion 1 of the molding portion 1b.
The dynamic pressure groove 2b1 is formed at b1, and the back portion 2b2 and the smooth portion 2b3 are formed at the same time in the second region 1b2.

Next, the upper ram 6 is retracted (raised) (step 5). At this time, the upper punch 4 is caused to follow the upward movement of the upper ram 6 by an appropriate following means. The core rod 1 is elastically supported by the ram 6 via the elastic member 7, and the elastic member 7 is compressed as the upper ram 6 rises. At the position of step 4), it is stopped and the positional relationship with the sintered material 2 'is maintained. At this time, if the elastic modulus of the elastic member 7 is too large, the elastic member 7 is not compressed, and the core rod 1 follows the upper ram 6 and breaks down the dynamic pressure groove. Since the positioning of the core rod 1 is inaccurate in the state (step 1), the elastic modulus of the elastic member 7 is determined in consideration of these.

In synchronization with the raising of the upper ram 6, the lower punch 5 is advanced (raised) by a drive device such as a cam mechanism or the like, and the sintered material 2 'is pushed out of the die 3 (step 6).
At this time, even if the ascent of the lower punch 5 is started with a delay with respect to the ascent of the upper ram 6, it may be performed while the delay of the core rod 1 with respect to the upper ram 6 is allowed, that is, before the elastic member 7 reaches the compression limit. For example, the time difference is absorbed by the elastic member 7, so that the dynamic pressure groove does not collapse. Even if there is a slight difference between the forward speed of the lower punch 5 and the retreat speed of the upper ram 6, the speed difference is absorbed by the elastic deformation of the elastic member 7, so that the dynamic pressure groove based on the speed difference is absorbed. Collapse can also be prevented.

After the sintered material 2 ′ is extruded from the die 3, the following relationship is cut off with respect to the upper ram 6 of the upper punch 4.
When the upper punch 4 is stopped while continuing to move upward, the upper end of the sintered material 2 'comes into contact with the lower end of the upper punch 4 (step 7). After that, if the upper ram 6 is further raised, the sintered material
2 'comes off the core rod 1 and the bearing body 2 shown in FIG.
Is taken out (step 8). The sintered material 2 ′ is spring-backed at the same time as being pushed out of the die 3, and its inner diameter is slightly enlarged. Therefore, when the sintered material 2 ′ is extracted from the core rod 1, the dynamic pressure groove is formed in the first region of the molded portion 1 b. It does not collide with 1b1. In the drawings, the case where the sintered material 2 ′ extruded from the die 3 rises together with the core rod 1 due to the frictional force with the core rod 1, but the amount of springback of the sintered material 2 ′ varies. If it is much larger than the depth of the press groove, the sintered material 2 ′ is pushed out of the die 3 and at the same time slides off the core rod 1 and falls off.

The bearing body 2 thus taken out
Is washed and dried, and then impregnated with lubricating oil or lubricating grease, whereby a hydrodynamic sintered oil-impregnated bearing having a hydrodynamic groove on the inner peripheral surface is manufactured.

[0025]

As described above, according to the method of the present invention, the sintered metal material is taken out of the die together with the core rod while maintaining the positional relationship with the core rod. Can be synchronized with each other to prevent the displacement between them, and the collapse of the dynamic pressure groove can be reliably avoided.

After the bearing surface is formed on the inner peripheral surface of the sintered metal material, one of the punches is driven to pull out the die, the core rod and the other punch are synchronously driven, and the other punch is used to drive the sintered metal. The material is pushed in to take out the sintered metal material from the die. Further, while allowing a delay in the axial direction of the core rod with respect to the drive device for driving the core rod within a predetermined range, the drive device and the other punch within the range. And the synchronous driving of the core rod and the other punch, even if there is a deviation (driving start timing, driving speed, etc.) in the synchronization between the core rod and the other punch, the sintered metal material is held together with the core rod while maintaining the positional relationship with the core rod. It can be taken out of the die, and the collapse of the dynamic pressure groove can be reliably avoided. Moreover, the structure can be simplified, and conversion from a conventional molding device (such as a sizing device) is easy.

[Brief description of the drawings]

FIG. 1 is a sectional view of a manufacturing apparatus according to the present invention.

FIG. 2 is a partially enlarged side view of a core rod.

FIG. 3 is a sectional view of a sintered body.

FIG. 4 is a sectional view showing a sizing step according to the present invention.

FIG. 5 is a cross-sectional view of the bearing main body after a dynamic pressure groove is formed.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core rod 1a Outer peripheral surface 1b Molding part 2 Bearing main body 2 'Sintered metal material (sintered material) 2a Inner peripheral surface 2b Bearing surface 2b1 Dynamic pressure groove 3 Die 4 One punch (upper punch) 5 The other punch (lower punch) 6) Drive (upper ram)

Claims (3)

[Claims] 1. A dynamic pressure type in which a bearing surface having an inclined dynamic pressure groove is formed on an inner peripheral surface of a cylindrical bearing body made of a sintered metal, and the bearing body is impregnated with lubricating oil or lubricating grease. A method for manufacturing a porous oil-impregnated bearing, comprising: inserting a core rod having a molded portion having a shape corresponding to the shape of the bearing surface into an inner peripheral surface of a cylindrical sintered metal material; While pressing both sides in a direction with a pair of punches and pressing into the die to press, the pressing force at this time presses the inner peripheral surface of the sintered metal material against the core rod forming part, forming the core rod on the inner peripheral surface. Manufacturing of a dynamic pressure-type porous oil-impregnated bearing in which after forming a bearing surface having a dynamic pressure groove having a shape corresponding to the portion, the sintered metal material is taken out of the die together with the core rod while maintaining the positional relationship with the core rod. Method. 2. After forming a bearing surface on the inner peripheral surface of the sintered metal material, one of the punches is driven to pull out the die, the core rod and the other punch are synchronously driven, and the other punch is used to drive the sintered metal. 2. The method for manufacturing a hydrodynamic porous oil-impregnated bearing according to claim 1, wherein the material is pushed in to take out the sintered metal material from the die. 3. While allowing a delay in the axial direction of the core rod with respect to a driving device for driving the core rod within a predetermined range,
3. The method according to claim 2, wherein the sintered metal material is taken out of the die by synchronously driving the driving device and the other punch within the range.