JP4095215B2 - Manufacturing method of bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a sintered oil-impregnated bearing suitable for use in supporting a shaft rotating at a relatively high speed, such as a drive shaft of a spindle motor incorporated in a precision instrument, with high accuracy.
[0002]
[Prior art]
As a sintered oil-impregnated bearing used for the drive shaft of a spindle motor built in precision equipment, a clearance (hereinafter referred to as a center escape portion) that does not contact the rotating shaft is provided on the inner diameter of the axial central portion of the bearing. There is a sintered oil-impregnated bearing in which a shaft support surface is formed and two bearing functions are integrated with high precision. As a manufacturing method of this kind of sintered oil-impregnated bearing, the outer diameter of the end portion is pressed by press-fitting the outer diameter of one end portion or both end portions in the axial direction of the bearing material into a tapered drawing forming portion formed in the mold. There is a method of forming a throttle part by reducing the diameter of the throttle part and pressing the inner diameter surface of the throttle part against a core rod to form a shaft support surface.
[0003]
For example, in JP-A-3-240901, as a cylindrical molded product obtained by compacting, a tapered surface having an inner diameter on one end side as a bearing surface and an outer surface on the other end side having a smaller diameter toward the other end is provided. After sintering the formed product, with the core pin inserted into the inner diameter, it is pressed into a mold with a tapered surface at the end and compressed in the axial direction. An oil-impregnated bearing manufacturing technique is disclosed.
[0004]
Japanese Patent Laid-Open No. 6-233831 discloses that a sizing bar is disposed in the insertion hole of the bearing body, the end portion of the bearing body is subjected to pressure processing, and a small diameter portion equal to the outer diameter of the sizing bar is formed at the end portion of the insertion hole. Techniques for forming the are disclosed.
[0005]
[Problems to be solved by the invention]
When the bearing surface of the bearing formed by the above manufacturing method is observed closely, the bearing surface on the middle escape portion side (back side) becomes dense and the bearing surface on the end surface side tends to become rough. The reason is considered to be that the direction of the plastic deformation of the meat that occurs when the bearing material is press-fitted into the tapered diaphragm forming portion is an oblique direction toward the middle escape portion side (back side).
[0006]
Since the density of the end surface side of the shaft support portion is low and the shaft support surface is rough in this way, since the seepage of the lubricating oil becomes active near the end surface, the lubricating oil is likely to be wasted out of the bearing element. In addition, since the hydraulic pressure between the rotating shaft and the shaft support surface decreases on the end surface side, the support force for supporting the rotating shaft becomes unstable.
[0007]
The present invention provides a bearing manufacturing method that eliminates such problems, equalizes the amount of pores on the shaft support surface, stabilizes the support force of the rotating shaft, and reduces waste of lubricating oil. It is aimed.
[0008]
[Means for Solving the Problems]
The present invention has been made to achieve the above-mentioned object, and the technical means characterized by it are as follows:
A cylindrical bearing material is press-fitted into a mold with tapered throttles at one or both ends in the axial direction to reduce the outer diameter of the material end, and the inner diameter surface is pressed against the core rod to form a shaft support surface. In the manufacturing method of the bearing
After the material is press-fitted into the tapered drawing die, the end surface of the material whose outer diameter is reduced by the tapered drawing is pressed and compressed in the axial direction by pushing up the lower punch. It is a manufacturing method of a bearing.
[0009]
In the present invention, a core rod is inserted into a cylindrical bearing material, and the cylindrical material is press-fitted into a tapered diaphragm forming portion formed in one end or both ends in the axial direction of the cylindrical material. The outer diameter of the throttle portion is reduced to form a throttle portion, and the inner diameter surface of the throttle portion is pressed against the core rod to form a shaft support surface that supports the rotating shaft, while the axial center adjacent to the shaft support surface is formed. The present invention is applied to a method for manufacturing a bearing in which an inner clearance portion that does not contact the rotating shaft is formed on the inner diameter surface of the portion. Then, after press-fitting the material into the tapered diaphragm forming portion, the end surface of the material end portion whose outer diameter is reduced by the tapered diaphragm is pressed in the axial direction to compress the axial dimension of the material. Yes. This amount of compression equalizes the density and pore volume of the formed bearing surface, and can be set to an appropriate value according to the material, characteristics, dimensions, etc. of the bearing material, but is roughly 5% of the length of the bearing material. The following shrinkage is recommended. Further, the lower limit can be determined in the same manner, and it is preferable that the lower limit is 1% or more of the length of the bearing material.
[0010]
The taper of the tapered drawing forming portion formed in the molding die varies depending on the thickness of the bearing material, but is usually about 10 to 40 ° (inclination with respect to the axis is 5 to 20 °). When a cylindrical bearing material is pushed into such a drawing portion, the outer diameter of the bearing material shrinks along the surface of the mold, and the deformation reaches the inner diameter of the bearing material and comes into contact with the core rod. The inner diameter is reduced from the end face side toward the back side, but from the middle stage to the final stage of the push-in, it is plastically deformed from the taper face in a substantially perpendicular direction (back side). Furthermore, in a form in which the bearing material is pushed in with the core rod fixed, the bearing material moves in the axial direction of the core rod, and therefore the meat of the bearing material pressed against the core rod moves toward the back side. As a result, the amount of pores on the shaft support surface is small on the back side and large on the end surface side. In the present invention, the end face is compressed in such a state.
[0011]
Due to the compression of the end face, the deformation of the bearing material is active near the end face with a large amount of pores, reducing the amount of pores. As described above, the maximum compression amount is about 5% of the total length (axial length) of the bearing material. If the compression amount is larger than that, the deformation of the bearing material reaches the middle relief portion and the middle relief portion is reduced in diameter. Therefore, it is not preferable. In addition, if the amount of compression is less than 1% of the total length of the bearing material, the amount of shaft support surface pores near the end face cannot be clearly reduced. If the bearing material is a bronze-based material and has a normal density, 2-3% of the overall length is optimal.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 to FIG. 5 are longitudinal sectional views for explaining a molding apparatus and a compression process procedure for forming a shaft support portion and a center relief in a bearing. The molding apparatus includes a mold 20, a core rod 30, a lower punch 40, and an upper punch 50. The molding die 20 has a tapered drawing forming portion 21 below the inner hole, and a small diameter hole into which the lower punch 40 is fitted below the maximum drawing portion 21a shown in FIG.
[0013]
A cylindrical bearing material 10 shown in FIG. 1 has a uniform outer diameter, and has a small inner diameter portion 11 at the upper portion of the inner diameter, and an inner diameter large diameter portion 12 at the middle portion and the lower portion in the axial direction. The outer diameter of the bearing material 10 is set so as to fit or slightly larger than the inner hole diameter of the mold 20, the inner diameter small diameter portion 11 is smaller than the outer diameter of the core rod 30, and the inner diameter large diameter portion 12 is outside the core rod 30. The diameter is set larger than the diameter.
[0014]
The bearing material 10 shown in FIG. 2 includes an outer diameter large diameter portion 13 at the upper portion of the outer diameter, and the intermediate portion and the lower portion of the outer diameter in the axial direction have a uniform diameter. The outer diameter large diameter portion 13 is larger than the inner hole diameter of the mold 20. Further, the inner diameter is uniform and set larger than the outer diameter of the core rod 30. As these bearing materials 10, a sintered body or a sized member is used.
[0015]
FIG. 3 shows a state in which the bearing material of FIG. 1 or 2 is pushed into the mold 20. In the form in which the shape of the bearing material 10 is shown in FIG. 1, the inner diameter small diameter portion 11 of the bearing material 10 is expanded by the core rod 30 to form the shaft support surface 14 having a uniform pore state. On the other hand, the lower end of the bearing material 10 is pushed in along the tapered diaphragm forming portion 21 to reduce the diameter, and in accordance with this, presses against the core rod 30 from the bottom to the back. In addition, while the bearing material 10 is being pushed in, the shaft support surface 15 that is in pressure contact with the core rod 30 is squeezed by the core rod 30, and the shaft support surface is pushed toward the back (in the direction of the middle escape portion). In the form of the bearing material 10 shown in FIG. 2, the outer diameter large diameter portion 13 is press-fitted into the mold 20 to reduce the diameter, and accordingly, the inner diameter becomes the core rod 30 from the back toward the upper end face side. Press contact. Therefore, the amount of pores on the end surface side (upper side in FIG. 3) of the shaft support surface 14 is formed more densely than the back side. The diameter reduction by the tapered diaphragm forming portion 21 at the lower end of the material is the same as described above.
[0016]
FIG. 4 is an enlarged view of the vicinity of the aperture 17 in FIG. The bearing material 10 is pushed into the tapered diaphragm forming portion 21 to reduce the diameter, and the shaft support surface 15 is formed in pressure contact with the core rod 30. As described above, since the deformation direction of the shaft support surface 15 is the depth direction of the inner diameter, the inner diameter is reduced slightly to the back (in the middle escape portion direction) from the beginning of the tapered diaphragm forming portion 21. Is formed. The inner side of the shaft support surface 15 (in the direction of the middle relief portion) is relatively strongly pressed against the outer diameter of the core rod 30 to form a surface with few (small) pores. In the vicinity corresponding to 21a, a surface having relatively large (large) pores is formed. The lower end surface of the press-fitted bearing material 10 penetrates below the maximum throttle portion 21a.
[0017]
In the present invention, next, as shown in FIG. 5, the lower punch 40 is pushed up from the state shown in FIG. 4 to compress the lower end face of the bearing material 10. Due to this compression, the cylindrical portion on the lower punch 40 side disappears. The end shaft support surface 15a close to the lower punch 40 is densified by the compression, and forms a uniform pore state with the other part of the shaft support surface 15 (the back shaft support surface 15b). Naturally, when the amount of compression is small, densification is small. When the amount of compression is increased, the deformation of the bearing material 10 affects the middle escape portion 16 and finally comes into contact with the core rod 30 in order from the middle portion of the middle escape portion 16. If the middle relief portion 16 is remarkably narrow, the viscosity resistance of the lubricating oil increases when used, and this is not preferable because the frictional resistance increases or becomes unstable. The compression amount (shrinkage amount) is appropriately about 2 to 3% of the overall length of the bearing in a normal bearing.
[0018]
In the example of FIGS. 4 and 5, the lower end surface of the bearing material 10 press-fitted into the tapered throttle forming portion 21 penetrates below the maximum throttle portion 21a to form a cylindrical portion, and the end surface compression is performed on the cylindrical portion. However, even when the cylindrical portion is not formed when it is press-fitted, or when the cylindrical portion remains after compression of the end face, it can be adopted as long as the bearing shape is not affected.
[0019]
6 to 8 illustrate a procedure of a compression process for forming the shaft support portions 14 and 15 and the intermediate relief portion 16 in the cylindrical bearing material 10 by a molding apparatus having a tapered drawing forming portion 21 at the top and bottom. It is a longitudinal cross-sectional view. The molding apparatus includes a molding die 20, a lower punch 40, and a core rod 30 on the lower side, and a molding die 20 and an upper punch 50 on the upper side. It is the same as that shown in FIG. 1 that the tapered die forming portion 21 is provided in the upper and lower portions of the inner hole of the mold 20. Further, except for the lower mold 20, each can move up and down (advance and retreat).
[0020]
The cylindrical bearing material 10 shown in FIG. 6 has a uniform inner and outer diameter, and the inner diameter of the bearing material 10 is set larger than the outer diameter of the core rod 30. FIG. 6 shows a state where the upper mold 20 and the upper punch 50 are lowered after the core rod 30 is inserted into the bearing material 10.
[0021]
Next, in FIG. 7, the upper mold 20 and the upper punch 50 are further lowered, the bearing material 10 is pressed into the upper and lower tapered drawing portions 21 to reduce the diameter, and the shaft support surface is pressed against the core rod 30. 14 and 15 are formed. The upper and lower end surfaces of the press-fitted bearing material 10 penetrate into the upper and lower end portions of the upper and lower molds 20 as far as the punch, forming a cylindrical portion. Moreover, the intermediate part outer diameter of the bearing raw material 10 becomes thick. In this compression process, as described with reference to FIG. 4, since the upper and lower diameters of the bearing material 10 are in the depth direction of the inner diameter, the end shaft support surfaces 14 a and 14 b are compared to the back shaft support surfaces 14 b and 15 b. The surface has a large amount of pores of 15a.
[0022]
FIG. 8 shows a state in which the upper punch 50 and the lower punch 40 are respectively advanced toward the bearing material 10 and both end faces are compressed. Due to this compression, the cylindrical portion having the outer diameter of the end portion disappears on both the upper and lower sides of the bearing material 10, the amount of pores of the end shaft support surfaces 14a and 15a is reduced, and the entire shaft support surface forms a homogeneous pore state.
[0023]
The bearing material 10 is released from the state of FIG. 8 by raising the upper mold 20 and the upper punch 50, raising the lower punch 40, or lowering the core rod 30 and then raising the lower punch 40. The
[0024]
FIG. 9 shows an example of the shape of the bearing material 10 for explaining other embodiments. FIG. 9A shows a shape in which a flange is provided on the inner diameter small diameter portion side of the bearing material shown in FIG. In this case, it is the same as in the case of FIG. 1 except that the mold has an inner hole portion necessary for housing the flange portion. FIG. 9B shows a shape in which the outer diameter and large diameter portion of the bearing material shown in FIG. It can be manufactured in the same manner as in FIG. 1 except that the mold has an inner hole portion necessary for reducing the diameter of the flange portion to an appropriate amount.
[0025]
In the above description, the chamfering on the inside and outside of the end surface portion is omitted, but in practice, chamfering is provided from the viewpoint of insertion into the mold hole, assembling into the housing, and the like. Even if there is chamfering, there is no difference in the functions and effects of the present invention.
[0026]
【The invention's effect】
As described above, according to the present invention, when a bearing having a two-point support structure is formed by forming a shaft support surface together with the throttle portion, the end portion is compressed and densified after the throttle portion is formed. The density of the shaft support surface can be made uniform, and as a result, the support force of the rotating shaft can be stabilized and the waste of the lubricating oil can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a shape of a bearing and a molding apparatus according to an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view showing a shape of a bearing and a molding apparatus according to another embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing a state in which a bearing material according to an embodiment of the present invention is inserted into a molding apparatus.
4 is an enlarged vertical cross-sectional view of the aperture portion of FIG. 3 in the embodiment of the present invention.
FIG. 5 is a longitudinal sectional view showing an end face compressed state in the embodiment of the present invention.
FIG. 6 is a longitudinal sectional view showing a molding process according to another embodiment of the present invention.
FIG. 7 is a longitudinal sectional view showing a molding process according to another embodiment of the present invention.
FIG. 8 is a longitudinal sectional view showing a molding process according to another embodiment of the present invention.
FIG. 9 is a longitudinal sectional view showing another embodiment of the bearing material according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Bearing material 11 Inner diameter small diameter part 12 Inner diameter large diameter part 13 Outer diameter large diameter part 14, 15 Shaft support surface 14a, 15a End part shaft support surface 14b, 15b Back part shaft support surface 16 Middle relief part 17 Restriction part 20 Molding Mold 21 Taper-shaped drawing part 21a Maximum drawing part 30 Core rod 40 Lower punch 50 Upper punch

Claims (2)

A cylindrical bearing material is press-fitted into a mold with tapered throttles at one or both ends in the axial direction to reduce the outer diameter of the material end, and the inner diameter surface is pressed against the core rod to form a shaft support surface. In the manufacturing method of the bearing
After the material is press-fitted into the tapered drawing die, the end surface of the material whose outer diameter is reduced by the tapered drawing is pressed and compressed in the axial direction by pushing up the lower punch. Manufacturing method of bearing.   The bearing manufacturing method according to claim 1, wherein a compression amount for pressing and compressing the end face in the axial direction is 1 to 5% of an axial dimension of the bearing material.

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