JPH11236604A - Oil-impregnated sintered bearing and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress or prevent the outflow of lubricating oil from a region between bearing faces which are distant in the shaft direction. SOLUTION: The bearing faces 31a of a bearing body 31 composed of an oil-impregnated sintered metal are formed distantly in the shaft direction, and the inside diameter dimension of the region (grinding undercut part 31b) between the bearing faces 31a is made larger then the inside diameter dimension of the bearing faces 31a. By subjecting both the inner circumferential faces of the bearing faces 31a and the grinding undercut part 31b to sizing, the surface opening ratio in the bearing faces is set to 5 to 15%, the surface opening ratio in the inner circumferential face of the grinding undercut part 31b is set to 10 to 20%, and the surface opening ratio in the bearing faces 31a is made smaller than the surface opening ratio in the inner circumferential face of the grinding undercut part 31b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a high rotational accuracy,
Precision small motors for information equipment requiring low torque (for example, drive motors for CD-ROM, DVD-ROM, DVD-RAM, laser beam printer, hard disk, floppy disk, high-density floppy disk, etc.) or axial fan motor TECHNICAL FIELD The present invention relates to a sintered oil-impregnated bearing suitable as a bearing for use and a method for producing the same.

[0002]

2. Description of the Related Art In a precision small motor related to information equipment, it has been studied to replace a bearing with a sintered oil-impregnated bearing in order to reduce the cost. This sintered oil-impregnated bearing is generally used as a single body. In addition, a structure is also known in which two sintered oil-impregnated bearings are pressed into a housing to support two portions of a shaft. ing.
This is effective in applications where a low torque is required or where temperature rise is reluctant, since the bearing surface of each bearing becomes smaller, and the accuracy of the bearing itself becomes better as the bearing width becomes smaller.

[0003] However, since it is difficult to ensure the coaxiality of the two bearings, there is a problem that the bearing gap has to be made large and the rotational accuracy is reduced.

To solve this problem, there is a method in which bearing surfaces are provided at both ends of one bearing, and a relief portion is formed by increasing the inner diameter of a region between the bearing surfaces. JP-B-63-43611 and JP-A-2-8302 are known.

[0005]

However, the above-mentioned 2)
Even in the two manufacturing methods, the relief is not sized (corrected), so the surface porosity at the relief (the surface porosity refers to the portion where the pores of the porous structure are open to the outer surface; The porosity means the area ratio of the surface aperture occupying in a unit area of the outer surface) is about 21 to 40%, which is much larger than the surface porosity of the bearing surface. For this reason, a large amount of oil impregnated in the bearing flows out from the surface opening of the escape portion, and the amount of oil supplied to the bearing surface (bearing gap) is reduced, so that a sufficient bearing function may not be obtained.

In Japanese Patent Publication No. 63-43611,
It is necessary to provide a ring-shaped groove on the outer peripheral surface at the central portion in the axial direction of the sintered metal material, which requires a special forming press or requires plastic working, which is costly. on the other hand,
In the thing of JP-A No. 2-8302, a sintered metal material having a large diameter portion and a small diameter portion on the inner peripheral surface is manufactured by compacting and sintering,
Since the sizing of the bearing surface is performed on the sintered metal material, the correction amount due to the sizing varies, and the inner diameter of the bearing surface and the surface opening ratio tend to vary.

Accordingly, the present invention is to improve the bearing function of a sintered oil-impregnated bearing of this type by supplying a suitable amount of oil from the inside of the bearing body to the bearing surface (bearing gap). It is another object of the present invention to provide a method capable of manufacturing such a bearing at low cost and with high accuracy.

[0008]

In order to achieve the above object, a sintered oil-impregnated bearing according to the present invention comprises two bearings made of sintered metal and opposed to an outer peripheral surface of a shaft to be supported via a bearing gap. Surfaces are formed in the axial direction, the inner diameter of the region between the bearing surfaces is larger than the inner diameter of the bearing surface, a porous bearing body, and having a lubricating oil or lubricating grease impregnated in the bearing body, Both the bearing surfaces and the region between the bearing surfaces are sized.

Specifically, the surface porosity of the bearing surface is set to 5 to 1
5%, and the surface porosity in the area between the bearing surfaces is 10 to 20%.
And the surface porosity of the inner peripheral surface in the region between the bearing surfaces is made larger than the surface porosity of the bearing surface.

In any case, it is desirable to set the outer diameter of the outer diameter portion corresponding to at least one bearing surface to be smaller than the outer diameter size of the outer diameter portion corresponding to the region between the bearing surfaces.

The sintered oil-impregnated bearing uses a stepped first core rod having a small-diameter portion and a large-diameter portion on the outer peripheral surface, and a stepped first die having a small-diameter portion and a large-diameter portion on the inner peripheral surface. A first sizing step of performing sizing, and a second sizing step of performing sizing using a second core rod having an outer peripheral surface having a uniform outer diameter and a second die having an inner peripheral surface having a uniform inner diameter.
In the first sizing step, the one end side region of the outer peripheral surface of the sintered metal material is compressed by the first core rod and the first die from the inner and outer diameter directions of the sintered metal material having a uniform thickness.
The large diameter portion of the die is pressed to form a large diameter, and the other area of the outer peripheral surface is pressed to the small diameter portion of the first die to form a small diameter, and at the same time, the other end of the inner peripheral surface of the sintered metal material. Side area first
While pressing to the small diameter part of the core rod to form a small diameter,
The other area of the inner peripheral surface is pressed to the large diameter portion of the first core rod to form a large diameter, and in the second sizing step, the sintered metal material that has undergone the first sizing step is combined with the second core rod and the second die. By pressing from the inner and outer radial directions, the entire area of the outer peripheral surface of the sintered metal material is pressed against the inner peripheral surface of the first die to form a uniform diameter, and at the same time, one end of the inner peripheral surface of the sintered metal material It can be manufactured by pressing the region and the other end region against the outer peripheral surface of the second core rod to form a bearing surface.

Further, a first sizing step of sizing using a stepped first core rod having a small diameter portion and a large diameter portion on the outer peripheral surface, a first die having an inner peripheral surface having a uniform inner diameter, A second sizing step of sizing using a second core rod having a uniform outer diameter and a stepped second die having a small-diameter portion and a large-diameter portion on an inner peripheral surface; The entire area of the outer peripheral surface of the sintered metal material is pressed against the inner peripheral surface of the first die by uniformly compressing the thick cylindrical sintered metal material from the inner and outer radial directions with the first core rod and the first die. At the same time, the other end of the inner peripheral surface of the sintered metal material is pressed to the small diameter portion of the first core rod to form a small diameter, and the other region of the inner peripheral surface is enlarged to the large diameter of the first core rod. Part to form a large diameter, and in the second sizing step, the first sizing By compressing the sintered metal material having passed through the sintering process from the inner and outer radial directions with the second core rod and the second die, one end side area of the outer peripheral surface of the sintered metal material is pressed against the small diameter portion of the second die to reduce the diameter. And the other region of the outer peripheral surface is pressed against the large diameter portion of the second die to form a large diameter, and at the same time, one end region and the other end region of the inner peripheral surface of the sintered metal material are formed in the second die. It can also be manufactured by pressing the outer peripheral surface of the core rod to form a bearing surface.

[0013]

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

The sintered oil-impregnated bearing according to the present invention is commercialized through steps such as compacting, sintering, sizing, washing, oil impregnation, and inspection.

The compacting is performed by a molding apparatus A shown in FIG. As shown in the drawing, the apparatus A includes a forming core rod 2 for pressing metal powder from the inner diameter side, a die 3 for pressing metal powder from the outer diameter side, and upper and lower punches 4a and 4b for pressing metal powder from both axial sides. Have. The outer peripheral surface of the forming core rod 2 and the inner peripheral surface of the die 3 are both cylindrical surfaces having a uniform diameter.

The metal powder is, for example, one containing copper or iron, or both as main components.
A blend of 95 wt% is used. Compacting is performed by using die
The cavity is filled with metal powder with the forming core rod 2 inserted therein, and the metal powder is compressed by upper and lower punches 4a and 4b. As shown in FIG. 2, the green compact 1 thus obtained has a cylindrical inner and outer peripheral surface having a uniform diameter. 11 is formed.

Next, the sintered metal material 11 is transferred to a first sizing step by a sizing apparatus B shown in FIG. The sizing device B includes a first core rod 12 for pressing the sintered metal material 11 from the inner diameter side, a first die 13 for pressing the sintered metal material 11 from the outer diameter side, and And upper and lower punches 14a and 14b for pressing from above. First
The core rod 12 has a stepped shaft shape having a small diameter portion 12b at the lower end and a large diameter portion 12a in the other region.
It can be moved up and down in conjunction with a. The forming hole 13a of the die 13 is
Has a large-diameter portion 13a1 at the upper end and a small-diameter portion
13a2, the axial width of the large diameter portion 13a1 is slightly larger than the axial width of the bearing surface (31a: see FIG. 6) described later, and the inner diameter of the small diameter portion 13a2 To ensure this, the outer diameter of the sintered metal material 11 is slightly smaller.

In the first sizing step, one end of the sintered metal material 11 is first inserted into the large diameter portion 13a1 of the forming hole 13a. Next, the first core rod 12 and the upper punch 14a descend in conjunction with each other, and after inserting the first core rod 12 into the inner diameter of the sintered metal material 11, the upper punch 14a inserts the sintered metal material 11 into the forming hole of the die 13. Press into 13a. By further lowering the upper punch 14a and the first core rod 12, the upper and lower punches 14a
a, 14b are pressed at a predetermined pressure, and the inner peripheral surface of the sintered metal material 11 is sintered on the outer peripheral surfaces of the large diameter portion 12a and the small diameter portion 12b of the first core rod 12. Metal material 11
Are pressed against the inner peripheral surfaces of the large diameter portion 13a1 and the small diameter portion 13a2 of the die 13, respectively. Therefore, as shown in FIG. 4, the sintered metal material 21 having passed through the first sizing step is
One end has a large-diameter outer peripheral surface 21a1 having a larger diameter than the outer peripheral surface (small-diameter outer peripheral surface 21a2) of the other region, and the other end has a smaller-diameter than the inner peripheral surface of the other region (large-diameter inner peripheral surface 21b2). It is formed into a stepped cylindrical shape having a small-diameter inner peripheral surface 21b1. In the sintered metal material 21, the entire inner peripheral surface (21b1, 21b2) is pressed and sized by the core rod 12, so that pores are crushed not only at both axial ends but also at the axial central portion, and the inner peripheral surface is deformed. The surface porosity is lower on the entire surface than before sizing.

As described above, the first core rod 12 is inserted into the inner diameter portion of the sintered metal material 11, and then the material 11 is pressed into the first die 13, and conversely, the sintered metal material 11 is The first core rod 12 may be press-fitted into the inner diameter of the material 11 after being press-fitted into one die 13.

The sintered metal material 21 having undergone the first sizing step
Is transferred to a second sizing step by the sizing device C shown in FIG. The sizing device C includes, similarly to the first sizing step, a second core rod 22 for pressing the inner peripheral surface of the sintered metal material 21, a second die 23 for pressing the outer peripheral surface of the sintered metal material 21, Upper and lower punches 24a and 24b for pressing the sintered metal material 21 from both sides in the axial direction are provided. The outer peripheral surface of the second core rod 22 and the inner peripheral surface of the forming hole 23a of the second die 23 are both cylindrical surfaces having a uniform diameter. The inner diameter of the forming hole 23a is the same as the outer diameter of the small-diameter outer peripheral surface 21a2 of the sintered metal material 21, and is smaller than the outer diameter of the large-diameter outer peripheral surface 21a1.

In the second sizing step, first, the sintered metal material 21 is inserted into the forming hole 23a with its small diameter side down. Next, the upper punch 24a and the second core rod 22 move down together and insert the second core rod 22 into the inner diameter portion of the sintered metal material 21.
Press into 23a. Along with this press-fitting, the large-diameter outer peripheral surface 21a1 of the sintered metal material 21 is pressed toward the inner diameter side due to a dimensional difference between its outer diameter and the inner diameter of the forming hole 23a.
Plastic flow to the inner diameter side occurs at the inner diameter side portion of 21a1. By further interlocking movement of the upper punch 24a and the second core rod 22, the sintered metal material sandwiched between the upper and lower punches 24a, 24b
21 is pressed with a predetermined pressure, and the inner peripheral surface of the upper end portion (the inner diameter side portion of the large-diameter outer peripheral surface 21a1) of the sintered metal material 21 and the small-diameter inner peripheral surface 21b1 of the lower end portion are formed on the outer peripheral surface of the second core rod 22. It is pressed and molded. On the other hand, since the region between the inner peripheral surfaces does not contact with the second core rod 22 or comes into contact with the second core rod 22 with a weak force, the inner diameter of the region is slightly larger than the inner diameter of the bearing surfaces at both ends (in the drawing, Although the dimensional difference is exaggerated, the actual dimensional difference is about several μm).

As described above, after inserting the second core rod 22 into the inner diameter of the sintered metal material 21, the material 21 is pressed into the second die 23, and conversely, the sintered metal material 21 is inserted into the second die 23. The second core rod 22 may be press-fitted into the inner diameter of the material 21 after being press-fitted into one die 23.

As shown in FIG. 6, the outer peripheral surface of the sintered metal material 31 having undergone the second sizing step is formed into a cylindrical surface having a uniform diameter, and the inner peripheral surface thereof is coaxial and of the same diameter at both ends in the axial direction. Bearing surface
31a and an inner diameter between the two bearing surfaces 31a.
It is formed into a stepped cylindrical surface having a larger relief portion 31b. In this case, since the surface of the relief portion 31b is hardly sized in the second sizing step, the surface porosity is larger than the surface porosity of the bearing surface 31a. The specific surface porosity is preferably about 10 to 20% at the escape portion 31b and 5 to 15% at the both bearing surfaces 31a. Further, the cross-sectional shape of the escape portion 31b is not particularly limited, and may be a straight line as shown in FIG. 6, a curved line, or a combination of a curved line and a straight line.

After the thus obtained sintered metal material 31 (bearing main body) is washed and then impregnated with lubricating oil or lubricating grease, the sintered oil-impregnated bearing of this embodiment is completed. FIG.
This is an example of a spindle motor for a disk drive such as a CD-ROM using the sintered oil-impregnated bearing. As shown in the drawing, the bearing body 31 is press-fitted or adhered and fixed to the inner diameter portion of the housing 32, and the two bearing surfaces 31a of the bearing body 31
The spindle 33 (shaft) inserted into the inner diameter portion is rotatably supported via a bearing gap. A rotating member such as a turntable 34 is mounted on the spindle 33. The turntable 34 is driven to rotate by an exciting force between a stator 35 and a rotor 36 opposed thereto. The spindle 33 is contacted and supported by a thrust plate 37 fitted into one opening of the housing 32.

Since the bearing body 31 has a small bearing surface 31a and a high precision for each bearing surface 31a, the bearing body 31 is excellent in low torque performance as compared with a bearing having the entire axial length as one bearing surface. Temperature rise can be reduced. In addition, in each process, since the sizing is performed with one core rod 12, 22, the coaxiality between the two bearing surfaces 31a is also good.

Also, sizing is applied to the escape portion 31b, and since the surface porosity of this portion is smaller than that of the conventional product, oil seepage from the escape portion 31b can be suppressed. In addition, the bearing performance can be maintained for a long time. Furthermore, as disclosed in JP-B-63-43611,
Since there is no need to apply a special forming press or plastic working at the time of forming 11, it is possible to work at low cost.
As described in Japanese Patent Application Laid-Open No. 2-8302, there is also an advantage that dimensional accuracy of the bearing surface 31a and variation in the distribution of the apertures are less likely to be caused due to deviation of the correction amount.

As shown in FIG. 12, by forming the uneven portions 52a at two locations in the axial direction (only one location is shown in the drawing) on the outer peripheral surface of the core rod 52, the two bearing surfaces 31 of the bearing body 31 can be formed.
A dynamic pressure groove may be formed in a. The forming portion 52a has a first region 52a1 for forming a dynamic pressure groove on the bearing surface 31a and a second region 52a2 for forming a portion other than the dynamic pressure groove. The first region 51a1 has a dynamic pressure groove pattern. Correspondingly formed (herringbone type is illustrated in the figure) and the second region
52a2 is recessed by a predetermined amount with respect to the first area. If this core rod 52 is used, for example, as the second core rod 22 in the second sizing step, the sizing and the bearing surface 31 are simultaneously performed.
The shape of a can be transfer-molded (the area of the dynamic pressure groove on the bearing surface 31a and the area other than the dynamic pressure groove can be simultaneously molded), and after the formation of the dynamic pressure groove, molding at the time of mold release. By utilizing the springback of the article, the molded article can be pulled out of the second core rod without breaking the dynamic pressure groove.

FIGS. 7 to 10 show another embodiment of the sizing step. This sizing step is composed of two steps as in the case of the sizing shown in FIGS. 3 to 6. As the sintered metal material 11, a cylinder having a uniform cylindrical shape is used as shown in FIG.

FIG. 7 shows a sizing apparatus B 'for performing a first sizing step. Similar to the sizing apparatus B shown in FIG. 3, a first core rod 12, a first die 13, and a pair of upper and lower punches 14a and 14b are provided. Is provided. 1st core rod 12
Is formed in a stepped shaft shape having a small-diameter portion 12b at the lower end and a large-diameter portion 12a above the same as in the apparatus B, but the forming hole 13a of the die 13 is formed into a cylindrical surface having a uniform diameter without irregularities. It is formed. The sintered metal material 11 is sized in the same process as that of the apparatus B, and the molded product 21 has a straight cylindrical outer peripheral surface and another inner peripheral surface (one end) as shown in FIG. It is formed into a cylindrical shape having a small-diameter inner peripheral surface 21b1 smaller in diameter than the large-diameter inner peripheral surface 21b2).

FIG. 9 shows a sizing device C 'for performing a second sizing step. Similar to the sizing device C shown in FIG. 5, a second core rod 22, a second die 23, and a pair of upper and lower punches 24a and 24b are formed. Have. The outer peripheral surface of the second core rod 22 is formed in a cylindrical shape having a uniform diameter similarly to the device C, but the forming hole 23a of the second die 23 is formed in a stepped circular shape having a diameter reduced downward, An upper portion has a large-diameter portion 23a1 and a lower portion has a smaller-diameter portion 23a2 having a smaller diameter.

The sintered metal material 21 having undergone the first sizing step
Is turned upside down in the second die 23 (small diameter inner peripheral surface 21b1).
Is placed upside down). When the sintered metal material 21 is pressurized in this state, the lower end is squeezed by the small diameter portion 23a2 to reduce the diameter, and the lower end of the large diameter inner peripheral surface 21b2 is pressed against the outer peripheral surface of the second core rod 22. At the same time, the small-diameter inner peripheral surface 21b1 at the upper end is pressed against the outer peripheral surface of the first core rod 22 to be molded. At this time, the large-diameter inner peripheral surface 21b2 between the two inner peripheral surfaces is
The second core rod 22 comes into non-contact or comes into contact with a weak force.

The sintered metal material 31 having undergone the second sizing step
As shown in FIG. 10, one end of the outer peripheral surface has a small diameter portion 31c whose diameter is smaller than that of the other portion, and two end surfaces of the inner peripheral surface are provided with two bearing surfaces 31a having the same diameter and the same diameter. It is formed into a substantially cylindrical shape having a relief portion 31b in a region between 31a. This sintered metal material 31 has the entire inner peripheral surface sized in the first sizing step, similarly to the sintered metal material 31 shown in FIG.
The surface opening ratio of the escape portion 31b is lower than that of the conventional product. Therefore, even when used as a bearing body, seepage of oil from the surface of the relief portion 31b can be suppressed, and bearing performance can be maintained for a long time.

As described above, the outer peripheral surface of the bearing body 31 shown in FIG.
c, the portion 31 corresponding to the region between the bearing surfaces (the relief portion 31b)
d2 and the portion 31d1 corresponding to the other bearing surface 31a are large diameter portions.
It is formed in a stepped cylindrical shape of 31d. This bearing body
When the bearing unit is constructed by press-fitting the inner part 31 of the housing 32 into the inner diameter part of the housing 32, as shown in FIG. 13, an outer diameter part 31d2 corresponding to the relief part 31b is formed on the small diameter part 32a1 of the housing inner peripheral surface 32a, and one of the bearing surfaces is formed. The outer diameter portion (small diameter portion 31c) corresponding to 31a is attached to the small diameter portion 32a1 of the inner peripheral surface 32a of the housing 32, and the other bearing surface 31a.
The outer diameter portion 31d1 corresponding to the large diameter portion 32a2 of the inner peripheral surface 32a of the housing 32 respectively faces. At this time, if a press-fitting allowance is formed between the outer diameter portion 31d2 corresponding to the relief portion 31b and the small diameter portion 32a1 of the housing inner peripheral surface 32a, the fixing force of the bearing main body 31 can be reduced by the close fitting of both. Can be secured. The inner peripheral surface of the relief portion 31b is formed to have a larger diameter than the bearing surface 31a, and is not directly involved in supporting the shaft. Has no effect on the accuracy of On the other hand, outer peripheral surfaces 31c and 31d1 corresponding to the two bearing surfaces 31a, and a housing inner peripheral surface 32 opposed thereto.
A clearance between the a1 and 32a2 is smaller than the press-fitting margin (a margin that does not affect bearing accuracy) or a radial gap is formed (in this embodiment, a radial gap is provided. The bearing surface 31 by press-in force.
a can be prevented or reduced, and a decrease in bearing accuracy can be prevented.

As shown in FIG. 14, even when the inner peripheral surface of the housing 32 is a cylindrical surface having a uniform diameter, the portion of the outer peripheral surface of the bearing body 31 corresponding to the two bearing surfaces 31a is reduced to the small diameter portion 31.
Similarly, if the portion corresponding to the relief portion 31b is set to the large diameter portion 31d, the deformation of the bearing surface 31a due to the press-fitting can be prevented or reduced.

In FIGS. 13 and 14, reference numeral 38 denotes a groove-shaped air passage provided in the large-diameter portion 31d on the outer peripheral surface of the bearing body 31.
Normally, the shaft 33 (see FIG. 11)
Is inserted into the inner diameter of the bearing body 31 with
Without the air passage 38, air is trapped in the space below the housing 32 without escaping from the bearing gap.
Insertion becomes difficult, and the trapped air expands due to the heat generated by the motor, which raises the shaft 33 and destabilizes the bearing performance.

[0036]

According to the present invention, the seepage of oil from the relief formed in the region between the bearing surfaces can be suppressed, and the desired bearing performance can be maintained for a long time. In addition, since there is no need to perform a special forming press or plastic working, the working can be carried out at low cost, and the dimensional accuracy of the bearing surface and the variation in the distribution of the apertures due to the uneven correction amount are less likely to occur.

If the outer diameter of the outer diameter portion corresponding to at least one bearing surface is set smaller than the outer diameter of the outer diameter portion corresponding to the region between the bearing surfaces, it is accompanied by press-fitting into the housing. The deformation of the bearing surface can be prevented or reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an apparatus for molding a green compact.

FIG. 2 is an axial sectional view of a sintered metal material having undergone a sintering step.

FIG. 3 is a sectional view showing a sizing device used in a first sizing step.

FIG. 4 is an axial sectional view of the sintered metal material having undergone a first sizing step.

FIG. 5 is a sectional view showing a sizing device used in a second sizing step.

FIG. 6 is an axial sectional view of a sintered metal material having undergone a second sizing step.

FIG. 7 is a sectional view showing a sizing device used in a first sizing step.

FIG. 8 is an axial sectional view of the sintered metal material having undergone a first sizing step.

FIG. 9 is a sectional view showing a sizing device used in a second sizing step.

FIG. 10 is an axial sectional view of the sintered metal material having undergone a second sizing step.

FIG. 11 is a sectional view of a disk drive unit.

FIG. 12 is an enlarged front view of a core rod provided with a mold for forming a dynamic pressure groove.

FIG. 13 is a sectional view of a bearing unit in which a bearing main body is incorporated in a housing.

FIG. 14 is a sectional view of a bearing unit in which a bearing main body is incorporated in a housing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Green compact 11 Sintered metal material 12 1st core rod 12a Large diameter portion 12b Small diameter portion 13 1st die 13a1 Large diameter portion 13a2 Small diameter portion 14a Upper punch 14b Lower punch 21 Sintered metal material 22 2nd core rod 23 2nd die 23a1 Large diameter part 23a2 Small diameter part 24a Upper punch 24b Lower punch 31 Sintered metal material (bearing body) 31a Bearing surface 31b Relief part

Claims (5)

[Claims] 1. A bearing made of sintered metal, and two bearing surfaces opposed to an outer peripheral surface of a shaft to be supported via a bearing gap are formed axially separated from each other, and an inner diameter of a region between the bearing surfaces is equal to that of the bearing surface. A sintered oil-impregnated product having a porous bearing body larger than the inner diameter and a lubricating oil or lubricating grease impregnated in the bearing body, wherein both the bearing surface and the region between the bearing surfaces are sized. bearing. 2. The surface porosity of the bearing surface is 5 to 15%, the surface porosity of the region between the bearing surfaces is 10 to 20%, and the surface of the inner peripheral surface in the region between the bearing surfaces. The sintered oil-impregnated bearing according to claim 1, wherein the porosity is larger than the surface porosity of the bearing surface. 3. An outer diameter of an outer diameter portion corresponding to at least one bearing surface is set smaller than an outer diameter of an outer diameter portion corresponding to a region between the bearing surfaces. Of sintered oil-impregnated bearing. 4. A bearing made of a sintered metal, and two bearing surfaces opposed to an outer peripheral surface of a shaft to be supported via a bearing gap are formed axially separated from each other, and an inner diameter of a region between the bearing surfaces is equal to that of the bearing surface. A method for producing a sintered oil-impregnated bearing having a porous bearing body larger than an inner diameter and a lubricating oil or lubricating grease impregnated in the bearing body, comprising a step having a small diameter portion and a large diameter portion on an outer peripheral surface. A first core rod, and a first sizing step of sizing using a stepped first die having a small diameter portion and a large diameter portion on the inner peripheral surface,
A second sizing step of performing sizing using a second core rod having an outer peripheral surface having a uniform outer diameter and a second die having an inner peripheral surface having a uniform inner diameter; By compressing the sintered metal material from the inner and outer radial directions with the first core rod and the first die, the one end side area of the outer peripheral surface of the sintered metal material is moved to the first side.
The large diameter portion of the die is pressed to form a large diameter, and the other area of the outer peripheral surface is pressed to the small diameter portion of the first die to form a small diameter, and at the same time, the other end of the inner peripheral surface of the sintered metal material. Side area first
While pressing to the small diameter part of the core rod to form a small diameter,
The other area of the inner peripheral surface is pressed to the large diameter portion of the first core rod to form a large diameter, and in the second sizing step, the sintered metal material that has undergone the first sizing step is subjected to the second core rod and the second die. By compressing from the inner and outer radial directions, the entire area of the outer peripheral surface of the sintered metal material is pressed to the inner peripheral surface of the first die to form a uniform diameter, and at the same time, one end of the inner peripheral surface of the sintered metal material A method for manufacturing a sintered oil-impregnated bearing, wherein a region and the other end region are pressed against an outer peripheral surface of a second core rod to form a bearing surface. 5. A bearing made of a sintered metal, and two bearing surfaces opposed to an outer peripheral surface of a shaft to be supported via a bearing gap are formed axially separated from each other, and an inner diameter of a region between the bearing surfaces is equal to that of the bearing surface. A method for producing a sintered oil-impregnated bearing having a porous bearing body larger than an inner diameter and a lubricating oil or lubricating grease impregnated in the bearing body, comprising a step having a small diameter portion and a large diameter portion on an outer peripheral surface. A first sizing step of sizing using a first core rod having a uniform inner diameter with a first die having an inner peripheral surface; a second core rod having an outer peripheral surface having a uniform outer diameter; A second sizing step of performing sizing using a stepped second die having a portion. In the first sizing step, a uniform cylindrical sintered metal material is formed by a first core rod and a first die. By compressing from the inside and outside radial direction, sintered metal material The entire area of the outer peripheral surface is pressed against the inner peripheral surface of the first die to form a uniform diameter, and at the same time, the other end of the inner peripheral surface of the sintered metal material is pressed against the small diameter portion of the first core rod to reduce the diameter. In the second sizing step, the sintered metal material that has passed through the first sizing step is combined with the second core rod. By compressing the outer peripheral surface of the sintered metal material with the second die in the inner and outer radial directions, the one end region of the outer peripheral surface of the sintered metal material is pressed to the small diameter portion of the second die to form a small diameter, and the other region of the outer peripheral surface is formed as the second A large diameter portion of the die is pressed to form a large diameter, and at the same time, one end region and the other end region of the inner peripheral surface of the sintered metal material are pressed against the outer peripheral surface of the second core rod to form a bearing surface. , Sintered oil-impregnated bearing manufacturing method.