JP4141280B2 - Method for producing sintered oil-impregnated bearing - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a sintered oil-impregnated bearing, and more particularly to a technique for producing a sintered oil-impregnated bearing that increases the amount of expansion of the inner diameter of the intermediate portion in the axial direction and is excellent in bearing performance and production cost.
[0002]
[Prior art]
Sintered oil-impregnated bearings used in spindle motors, fan motors, etc. reduce the frictional resistance between the bearings and the rotating shaft and increase the bearing rigidity by increasing the bearing span. A structure that is larger than the inner diameter of the portion is generally employed. In recent years, as the performance of the motor is improved and the structure of the motor is complicated, various oil-impregnated bearings are required for the sintered oil-impregnated bearing.
[0003]
In order to meet such demands, in the method of manufacturing a sintered oil-impregnated bearing, for example, a medium-bulged core is used, and a cylindrical sintered material is compressed in a mold so that the inner surface is in close contact with the core. A technique for releasing a sizing body from a core by releasing a mold and forming a gap with the core by utilizing an enlargement of an inner diameter by a springback is disclosed (for example, refer to Patent Document 1).
[0004]
[Patent Document 1]
Japanese Examined Patent Publication No. 7-116490 (second page, FIGS. 1 and 2)
[0005]
[Problems to be solved by the invention]
However, in the technique described in Patent Document 1, since the spring back is used in the mold release, the amount of expansion of the inner diameter of the axially intermediate portion of the sintered oil-impregnated bearing is not sufficient. There is a problem that the frictional resistance due to rotational friction with the rotating shaft cannot be sufficiently reduced during use of the. In recent years, in particular, there has been a demand for development of a technique for further improving the bearing performance of a sintered oil-impregnated bearing while manufacturing a sintered oil-impregnated bearing at a low cost.
[0006]
The present invention provides a method for producing a sintered oil-impregnated bearing capable of ensuring a sufficient amount of expansion of the inner diameter of the intermediate portion in the axial direction of the sintered oil-impregnated bearing, improving the bearing performance and inexpensively. The purpose is to do.
[0007]
[Means for Solving the Problems]
The method for producing a sintered oil-impregnated bearing according to the present invention is such that a lower punch is set on a die and a plurality of sintered members are combined on the lower punch in a state where an annular cavity is formed in an intermediate portion in the axial direction. The cylindrical core rod is fitted to the lower punch, the upper punch is set on the member, and the member is compressed in the axial direction in a die including the die, the core rod, and the upper and lower punches , The annular cavity is reduced or eliminated, and an intermediate portion of the inner peripheral surface of the sintered oil-impregnated bearing is formed as a relief shape portion having a larger diameter than the bearing surface .
[0008]
The manufacturing method of the sintered oil-impregnated bearing of the present invention is based on the following principle. That is, among the plurality of sintered members, the outer peripheral portion of the member positioned on the outside is brought into close contact with the inner wall of the die, and the inner peripheral portion of the member positioned on the inner side is brought into close contact with the core rod. Compress in the direction. At this time, due to the compression action from the upper and lower punches, the intermediate portion of the member located on the inner side is expanded and deformed toward the annular cavity. On the other hand, the thickness of the intermediate part of the member located outside increases in the direction (width direction) perpendicular to the axial direction as the axial dimension decreases due to the compression action. Combined with these diameter-expanding deformation action and thickness increasing action, the annular cavity shrinks and disappears in some cases. In this way, the intermediate portion of the inner peripheral surface of the sintered oil-impregnated bearing can be formed as a relief portion having a larger diameter than the bearing surface.
[0009]
Based on the above principle, according to the present invention, the amount of expansion of the inner diameter of the intermediate portion in the axial direction of the sintered oil-impregnated bearing is sufficient, and therefore the frictional resistance caused by rotational friction with the rotating shaft is sufficiently reduced. be able to. In addition, a material that is excellent in bearing performance is used for a portion that contacts the rotating shaft during use, that is, the above-mentioned inner member, and an inexpensive material is used for a portion that does not contact the rotating shaft, that is, the outer member. Thus, the bearing performance of the sintered oil-impregnated bearing can be improved while manufacturing the sintered oil-impregnated bearing at a low cost.
[0010]
In the sintered oil-impregnated bearing manufactured by the manufacturing method of the present invention, the opposing surfaces of the member located on the inner side and the member located on the outer side are bent in the length direction. For this reason, sufficient strength to withstand use as a sintered oil-impregnated bearing for a spindle motor or a fan motor is secured. Moreover, in the manufacturing method of this invention, the amount of expansion of the internal diameter of the axial direction intermediate part of a sintered oil-impregnated bearing can be adjusted freely by adjusting suitably the compression amount by both upper and lower punches. On the other hand, the volume of the annular cavity that originally existed is reduced so as to be inversely proportional to the diameter expansion amount, and may disappear depending on the case. However, this cavity does not have to be eliminated at any time, and it is effective to leave it in the opposite when obtaining a sintered oil-impregnated bearing having a relatively high oil content.
[0011]
In such a method for producing a sintered oil-impregnated bearing, it is desirable that sizing be performed in advance on the plurality of sintered members. When sizing is performed in advance as described above, not only the conformability when a member located on the inner side and a member located on the outer side are combined is improved, but in particular, the porosity of the member located on the inner side is reduced. It can be made suitable. In addition, a dynamic pressure groove can be formed in advance on the inner peripheral surface of the member located inside. In this case, if the density of the members located on the inside is high and the density of the members located on the outside is low, a bearing with high oil content can be obtained with less escape of dynamic pressure.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1A and 1B show a preferred embodiment of the present invention, in which FIG. 1A is a cross-sectional view showing a state before compressing a plurality of members in an axial direction, and FIG. 1B shows a state in which the plurality of members are compressed in an axial direction. It is sectional drawing which shows a back state.
[0013]
When producing a sintered oil-impregnated bearing according to the present invention, as shown in FIG. 1 (a), a lower punch 2 is set on a die 1 and a plurality of sintered members, in FIG. , 4 are set on the lower punch 2 in a combined state so as to form an annular cavity 5 in the middle in the axial direction. Next, the cylindrical core rod 6 is fitted to the lower punch 2 and the upper punch 7 is set on the members 3 and 4. At this time, the outer peripheral portion of the member 3 is in close contact with the inner wall of the die 1, and the inner peripheral portion of the member 4 is in close contact with the core rod 6.
[0014]
Under this state, as shown in FIG. 1B, the members 3 and 4 are compressed in the axial direction by the compression action of the upper and lower punches 7 and 2. At this time, the axially intermediate portion of the member 4 is expanded and deformed toward the annular cavity 5 side. On the other hand, about the axial direction intermediate part of the member 3, the thickness of the direction (width direction) perpendicular | vertical to an axial direction increases. The ring-shaped cavity 5 shown in FIG. 1A disappears due to a combination of the diameter expansion deformation action and the thickness increase action. In this way, as shown in FIG. 1 (b), the intermediate portion of the inner peripheral surface of the sintered oil-impregnated bearing can be made into a relief shape portion 8 having a larger diameter than the bearing surface.
[0015]
According to the method for manufacturing a sintered oil-impregnated bearing as described above, a sufficient amount of expansion of the inner diameter of the intermediate portion in the axial direction of the sintered oil-impregnated bearing is ensured, and the frictional resistance due to rotational friction with the rotating shaft is sufficient when in use. Can be reduced. Moreover, while using a material excellent in bearing performance for the member 4 shown in FIGS. 1A and 1B and using an inexpensive material for the member 3, a sintered oil-impregnated bearing can be manufactured at low cost. The bearing performance of the sintered oil-impregnated bearing can be improved.
[0016]
Further, according to the place shown in FIG. 1 (b), the opposing surfaces of the member 3 and the member 4 are bent in the length direction, so that it is difficult for the members 3 and 4 to come off during use. It is possible to ensure sufficient strength to withstand use as a sintered oil-impregnated bearing for a spindle motor or a fan motor. 1 (a) and 1 (b), the amount of expansion of the inner diameter of the intermediate portion in the axial direction of the sintered oil-impregnated bearing can be increased by appropriately adjusting the amount of compression by the upper and lower punches 7 and 2. It can be adjusted freely. On the other hand, in the example shown in FIG. 1B, the volume of the annular cavity 5 that originally existed disappears so as to be inversely proportional to the diameter expansion amount. However, this cavity 5 is preferably left when, for example, a sintered oil-impregnated bearing having a relatively high oil content is obtained.
[0017]
In addition, in the manufacturing method of the sintered oil impregnated bearing shown in FIGS. 1A and 1B, it is desirable to apply sizing to the members 3 and 4 in advance. Thus, when sizing is performed in advance, not only the conformability when the members 3 and 4 are combined is improved, but in particular, the pore amount of the member 4 can be made suitable.
[0018]
Next, FIGS. 2 (a) to 2 (d) are other preferred combinations of the members 3 and 4 shown in FIGS. 1 (a) and 1 (b). As shown in these examples, the members 3 and 4 can appropriately change the contact area with the upper and lower punches, the shape thereof, and the like, and the member 3 is divided as in the example shown in FIG. 3a may be arranged on the upper punch side, and 3b may be arranged on the lower punch side. However, the examples shown in FIGS. 2 (a) to 2 (d) are only a few examples of the combinations of the members 3 and 4, and the combinations of these members 3 and 4 are limited to these examples. is not. In addition, even if it employ | adopts any combination of Fig.2 (a)-FIG.2 (d), there exists an effect similar to the sintered oil-impregnated bearing shown in FIG.
[0019]
【The invention's effect】
As described above, according to the present invention, a sintered oil-impregnated bearing is manufactured by compressing a plurality of sintered members combined so as to form an annular cavity in an axially intermediate portion in the axial direction. A sufficient amount of expansion of the inner diameter of the intermediate portion in the axial direction of the oil-impregnated bearing can be secured, the bearing performance can be improved, and a sintered oil-impregnated bearing can be manufactured at low cost. Therefore, the present invention is promising in that a sintered oil-impregnated bearing suitable for a spindle motor, a fan motor or the like can be provided.
[Brief description of the drawings]
FIG. 1 shows a preferred embodiment of the present invention, in which (a) is a cross-sectional view showing a state before compressing a plurality of members in the axial direction, and (b) is compressing the plurality of members in the axial direction. It is sectional drawing which shows a back state.
FIGS. 2A to 2D are cross-sectional views showing other preferred combinations of members 3 and 4 shown in FIGS. 1A and 1B, respectively.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Die, 2 ... Lower punch, 3, 3a, 3b ... Member located outside, 4 ... Member located inside, 5 ... Circular cavity, 6 ... Core rod, 7 ... Upper punch, 8 ... Escape-shaped part

Claims (2)

Set the lower punch on the die,
A plurality of sintered members are set on the lower punch in a combined state so as to form an annular cavity in the axially intermediate portion,
While fitting a cylindrical core rod to the lower punch, set the upper punch on the member,
The member is compressed in the axial direction in a die having the die, the core rod, and the upper and lower punches so that the annular cavity is reduced or eliminated, and an intermediate portion of the inner peripheral surface of the sintered oil-impregnated bearing is formed. A method for producing a sintered oil-impregnated bearing, characterized in that a relief shape portion having a larger diameter than the bearing surface is formed .   The method for producing a sintered oil-impregnated bearing according to claim 1, wherein sizing is performed in advance on the plurality of sintered members.

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