JP2008240908A - Oil-impegnated sintered bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil-impregnated sintered bearing capable of alleviating concentrated stress occurring on a bearing face by avoiding local contact with a shaft and forming an excellent oil film regardless of the supported position of the shaft. <P>SOLUTION: On one side in the axial direction of the bearing face of the sintered oil retaining bearing, a first enlarged diameter face 5 is provided with the size of its inner diameter smoothly enlarging toward one end face of the sintered oil retaining bearing. On the other side in the axial direction, a second enlarged diameter face 6 is provided with the size of its inner diameter smoothly enlarging toward the other end face of the oil-impregnated sintered bearing. The bearing face is provided with a plurality of surface opening holes 8, and accompanying relative rotation of the shaft, lubricating oil retained in an inner air hole 3 oozes out from the surface opening holes 8 of the bearing face opposing an outer peripheral face of the shaft. In the first enlarged diameter face 5 positioned at one side in the axial direction of the bearing face, the percentage of the surface opening holes 8 on the surface (so called surface aperture rate) becomes gradually smaller from a cylindrical face (small diameter) toward an end face (large diameter) side. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sintered oil-impregnated bearing in which a porous body made of a sintered metal is impregnated with a lubricant (including lubricating oil and lubricating grease).

  Sintered oil-impregnated bearings are those in which the lubricating oil impregnated inside exudes to the sliding part with the shaft as a result of relative rotation with the shaft arranged on the inner periphery to form an oil film, and this oil film supports the shaft It is. Such sintered oil-impregnated bearings are widely used as bearing parts of various drive mechanisms or power transmission mechanisms because they have excellent quietness during use and can be used without lubrication for a long period of time. As one example, a sintered oil-impregnated bearing used in a power window power transmission mechanism for opening and closing a window glass provided on a door panel of a vehicle is known (see, for example, Patent Document 1).

  For example, when the power transmission mechanism for a power window is used, the lubricating oil impregnated in the sintered oil-impregnated bearing exudes into the sliding portion between the sintered oil-impregnated bearing and the shaft, and the oil film is formed by the exuded lubricating oil. It is formed. As a result, the shaft is supported on the sintered oil-impregnated bearing through the oil film, and a smooth sliding state is obtained between both members.

  In this type of sintered oil-impregnated bearing, the inner diameter of the bearing surface provided on the inner periphery thereof is usually constant over the entire length in the axial direction, and the shaft is slidably supported over the entire surface of the bearing surface. However, in the power transmission mechanism described above, due to its structure, the shaft receives a load (shear load) in a direction perpendicular to the axis, and causes deflection. Therefore, there is a possibility that the outer peripheral surface of the shaft slides locally at the axial end portion of the bearing surface and stress concentration occurs in this sliding region. This type of stress concentration may adversely affect the sintered oil-impregnated bearing, such as wear of the oil-impregnated sintered bearing on the bearing surface and generation of abnormal noise.

For example, Japanese Unexamined Patent Application Publication No. 2004-308684 (Patent Document 2) describes a sintered oil-impregnated bearing in which tapered inner wall portions that expand in the direction away from each other are formed at both axial ends of the inner periphery. . The tapered inner wall portion is formed so that the surface of the rotating shaft is in line contact with the tapered inner wall portion when the rotating shaft is subjected to a large shear load and tilted inside the bearing. The inclination angle is usually set to 3 ° or less. Further, there is disclosed a technique in which pores remaining on the surface of the tapered inner wall portion are smaller and smaller than pores remaining on the surface of the central inner wall portion.
JP 2003-247548 A JP 2004-308684 A

  However, in the case of the bearing disclosed in the cited document 2, it is difficult to substantially receive only the tapered surface unless the inclined surface (tapered surface) matches the inclination angle of the shaft. For example, the boundary between the cylindrical surface and the tapered surface Since it is received by the part (corner part), it is difficult to achieve sufficient stress relaxation.

  Further, as described above, when the bent shaft is received by the enlarged diameter portion, the shaft is supported in a partial region in the axial direction of the enlarged diameter portion. It is necessary to form an oil film.

  Patent Document 2 discloses a tapered inner wall portion in which the pores remaining on the surface thereof are smaller than the pores remaining on the surface of the inner wall portion on the center side and are made smaller to increase the sintered density from the center of the bearing. The structure having a difference in sintered density prevents the shaft from being misaligned (runout) with the lubricating oil pushed from the center side to the tapered inner wall side when the shaft is received at the center side of the bearing surface. Is aimed at. Therefore, when a shaft having a deflection is received by the tapered inner wall portion, the oil oozes out in the supporting region or in the vicinity thereof, and an oil film having a sufficient size cannot be formed between the shaft and the tapered inner wall portion. There is a fear.

  In view of the above circumstances, the present invention avoids local contact with the shaft, reduces stress concentration occurring on the bearing surface, and can form a good oil film regardless of the support position. Providing a bearing is a technical issue.

  In order to solve the above-mentioned problems, the present invention is a porous body made of sintered metal, in which internal pores are impregnated with a lubricating fluid, a bearing surface is provided on the inner periphery, and at least a part of the bearing surface is provided. A sintered oil-impregnated bearing configured with a diameter-enlarged surface that smoothly expands toward one end in the axial direction of the bearing surface, and configured such that the surface area ratio of the expanded-diameter surface decreases toward the larger diameter side. I will provide a.

  Thus, in the present invention, since at least a part of the bearing surface is configured with a surface that smoothly expands toward one end in the axial direction of the bearing surface, there is a region that is locally in sliding contact with the shaft. Excluded. Therefore, the shaft causing the deflection can be received on a smooth surface regardless of the deflection, and problems such as stress concentration and local wear can be eliminated as much as possible.

  In addition, according to the present invention, the surface area ratio of the diameter-expanded surface is reduced from the smaller diameter side toward the larger diameter side. According to this configuration, when the shaft in the bent state is supported by the diameter-expanded surface, the lubricating oil oozes better on the smaller diameter side (bearing center side) than the region that substantially supports the shaft. In particular, the lubricating oil that has oozed out on the center side of the bearing is supplied to the substantial support region by the centrifugal force generated as the shaft rotates. On the other hand, the oil film can be easily maintained because the action of the lubricating oil is suppressed outside the bearing area from the support region. Moreover, since there is little oozing-out of lubricating oil, the quantity of lubricating oil which does not participate in oil film formation can be reduced, and thereby leakage of lubricating oil can be suppressed. Due to the above-described action, abundant oil can be supplied to the substantial bearing portion regardless of the shaft support position, and a good oil film can be formed and maintained in the bearing portion. Further, it is possible to improve the utilization efficiency or the circulation efficiency of the lubricating oil and to exhibit excellent bearing performance.

  The enlarged surface having the above-described configuration can be formed by, for example, the following method. That is, as a means for solving the above-mentioned problems, the present invention is a porous body made of sintered metal, in which internal pores are impregnated with a lubricating fluid, a bearing surface is provided on the inner periphery, and the bearing surface Is a method for manufacturing a sintered oil-impregnated bearing including a diameter-enlarged surface that smoothly expands toward one end in the axial direction of the bearing surface, and inserting a pin into the inner periphery of the porous body , By inclining the pin axis with respect to the central axis of the porous body to press a part of the inner periphery of the porous body, and by moving the pin in the circumferential direction, Provided is a method for manufacturing a sintered oil-impregnated bearing that forms a diameter-expanded surface by moving along an inner periphery.

  As described above, the pin is tilted to pressurize the inner periphery of the sintered porous body, and the pressurizing region is moved along the inner periphery of the porous body by moving the pin in the circumferential direction. A pressure force due to the inclination of the pin and a frictional force due to the rotation of the pin are applied to the inner periphery of the porous body. Of these, the inner peripheral surface can be pressed and expanded by the pressure applied by the inclination of the pin, and the small opening can be crushed by the frictional force generated by the rotation of the pin, or the relatively large opening can be reduced, and the surface The hole area ratio can be reduced. In particular, by pressing and expanding the inner peripheral surface of the porous body with the rotation of the pin, the surface opening can be crushed more on the large diameter side where the amount of pressure expansion is larger. Moreover, it is preferable that the above-described operation is performed with the rotation of the pin, so that the effect of crushing the surface openings can be further enhanced.

  For example, a part or the whole of the diameter-enlarged surface can be configured by a curved surface having an arc-shaped cross section including a shaft and bulging on the axis side. Or the one part or the whole surface can be comprised by the surface which makes an axial cross section taper shape. Of these, the curved surface having an arcuate cross-section, for example, moves the pin along the inner periphery of the porous body while inclining the pin as described above, presses and expands the inner peripheral surface of the porous body, and the operation Can be formed by pulling out the pin. Moreover, if it is a surface which makes a cross-sectional taper shape, it can form by performing the above-mentioned operation | movement in the state which inserted the pin to the position which penetrates a porous body. In addition, when there are these enlarged diameter surfaces and a surface adjacent to the enlarged diameter surface on the bearing center side, these surfaces are smoothly connected, and the bearing surface has a smooth shape over its entire axial length. It is important to do.

  The bearing surface may have a second diameter-expanding surface that smoothly expands toward the other axial end of the bearing surface in addition to the above-described diameter-expanding surface. According to such a configuration, even when the shaft passing through the bearing is rotationally supported, it can always be supported by any one of the expanded surfaces regardless of the inclination direction (deflection direction). Become.

  As described above, according to the present invention, the sintered oil impregnation capable of avoiding local contact with the shaft, mitigating stress concentration generated on the bearing surface, and forming a good oil film regardless of the support position. A bearing can be provided.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a sintered oil-impregnated bearing 1 according to an embodiment of the present invention. The sintered oil-impregnated bearing 1 in the figure is a cylindrical porous body and is made of sintered metal. The sintered oil-impregnated bearing 1 has a large number of internal pores 3, and the internal pores 3 are impregnated with lubricating oil. On the inner periphery of the sintered oil-impregnated bearing 1, there is provided a bearing surface 4 for slidingly supporting the shaft 2 by sliding with the outer peripheral surface of the shaft 2 (one-dot chain line in the figure).

  On one side of the bearing surface 4 in the axial direction, there is provided a first diameter-expanded surface 5 that smoothly expands toward the one end surface 1a of the sintered oil-impregnated bearing 1, and on the other side in the axial direction, a sintered oil-impregnated oil. A second diameter-expanding surface 6 that smoothly increases the diameter toward the other end surface 1 b of the bearing 1 is provided. Each of the first and second diameter-expanded surfaces 5 and 6 has an arcuate cross-sectional arc shape, and is formed of an annular curved surface having a bulge on the axis side. In addition, a cylindrical surface 7 having a constant diameter is provided between both the enlarged diameter surfaces 5 and 6, with the central axis thereof coinciding with the central axis of the enlarged diameter surfaces 5 and 6. Therefore, in this embodiment, the bearing surface 4 is composed of the first diameter-expanded surface 5 and the second diameter-expanded surface 6 and the cylindrical surface 7 that connects these diameter-expanded surfaces 5 and 6. Therefore, the bearing surface 4 having the above-described configuration has a shape that is smoothly connected over the entire axial length thereof.

  FIG. 2 is an enlarged view of region A in FIG. As shown in the figure, the bearing surface 4 has a large number of surface apertures 8, and the internal pores through the surface apertures 8 of the bearing surface 4 facing the outer peripheral surface of the shaft 2 as the shaft 2 rotates relative to each other. The lubricating oil held in 3 oozes out. Further, as shown in FIG. 2, in the first diameter-expanded surface 5 located on one axial side of the bearing surface 4, the distribution of the surface openings 8 is different from the cylindrical surface 7 located in the center of the bearing. Yes. That is, as shown in FIG. 2, the ratio of the area occupied by the surface opening 8 to the diameter-expanded surface 5 (so-called surface opening ratio) decreases from the cylindrical surface 7 side toward the end surface 1 a side. Moreover, the number of the surface apertures 8 is decreasing toward the end surface 1a side. In particular, the ratio of the surface openings 8a having a relatively small opening diameter is reduced. The distribution mode of the surface apertures 8 on the second enlarged diameter surface 6 is also the same as that of the first enlarged diameter surface 5.

  In the sintered oil-impregnated bearing 1 having the above-described configuration, the lubricating oil retained in the internal pores 3 oozes out onto the bearing surface 4 through the surface openings 8 with the relative rotation of the shaft 2. As a result, a lubricating oil film is formed between the shaft 2 and the sintered oil-impregnated bearing 1, and the shaft 2 is rotatably supported via the lubricating oil film. In FIG. 1, when the rotation axis of the shaft 2 is parallel to the central axis of the sintered oil-impregnated bearing 1, the shaft 2 is a cylindrical surface 7 positioned at the center in the axial direction of the bearing surface 4. It is rotationally supported by a lubricating oil film that oozes out.

  Moreover, although illustration is abbreviate | omitted, when the rotating shaft of the axis | shaft 2 is in the state inclined with respect to the center axis | shaft of the sintered oil-impregnated bearing 1, the axis | shaft 2 goes to the axial direction edge part among the bearing surfaces 4. It is supported by the first expanded surface 5 and the second expanded surface 6 that expand smoothly. For this reason, regardless of the degree of inclination of the shaft 2, it is possible to avoid a situation in which the bearing surface 4 and the shaft 2 are in sliding contact with each other and to realize good and stable sliding support.

  Moreover, in this embodiment, it comprised so that the surface open area ratio of the enlarged diameter surfaces 5 and 6 might decrease as it goes to the large diameter side from each small diameter side. According to such a configuration, even when the shaft 2 having the deflection is supported by the enlarged diameter surfaces 5 and 6, the lubricating oil is substantially closer to the bearing center side (the cylindrical surface 7 side) than the region supporting the shaft 2. As a result, the lubricating oil that has oozed out can be positively supplied to the support region by the centrifugal force generated as the shaft 2 rotates. On the other hand, since there is little drawing of the lubricating oil on the outside of the bearing, the oil film can be favorably formed in the substantial support region. Further, since the lubricant does not ooze out on the bearing outer side (end surfaces 1a, 1b side) from the support region, the leakage of the lubricant can be suppressed as much as possible. Therefore, utilization or circulation of lubricating oil can be achieved very efficiently.

  Further, in this embodiment, the diameter-enlarged surfaces 5 and 6 are each formed of an annular curved surface having an axial cross-section arc shape and bulging on the axis side. Therefore, a constant sliding area (supporting area) can always be ensured regardless of the inclination angle of the shaft 2. In addition, the diameter-enlarged surface (for example, the second diameter-enlarged surface 6) disposed on one side of the bearing surface 4 can receive the shaft 2 following its deflection shape. As a result, it is possible to secure a support area, improve compatibility with the shaft, and reduce the surface pressure and sliding wear.

  The sintered oil-impregnated bearing 1 having the above-described configuration is manufactured through the following steps, for example.

  Specifically, the sintered oil-impregnated bearing 1 includes a step (a) of compacting metal powder as a raw material, a step (b) of sintering a compact, and a step of sizing the sintered body (c ), A step (d) of forming an enlarged surface, and a step (e) of impregnating the lubricating oil. Here, it demonstrates centering around a diameter-expansion surface formation process (d) especially.

  First, metal powder (for example, Cu-based powder, Fe-based powder, etc., including alloy powder and mixed powders of these different metals) is filled into the molding die, and this is compression molded into a finished product. A compact molded body having a close shape is obtained (compact molding step (a)). Next, the green compact obtained in the step (a) is sintered by heating to the sintering temperature of the metal powder as a raw material to obtain a sintered porous body (sintering step (b)). . Thereafter, by applying a pressing force to the sintered porous body obtained in the step (b) using an appropriate mold, the sintered porous body is shaped into a predetermined shape and its dimensions ( For example, the outer diameter dimension and the axial dimension) are finished within a predetermined range (sizing step (c)).

  A pin for molding is formed on the inner peripheral surface of the sintered porous body finished in the shape of the finished product (the shape shown in FIG. 1) except for the diameter-enlarged surfaces 5 and 6 through the steps (a) to (c). Are inserted, and by applying friction force and pressure to the sintered porous body using this pin, the enlarged diameter surfaces 5 and 6 are formed on the sintered porous body (expanded surface forming step (d)). ).

  FIG. 3 conceptually shows the same process, and the sintered porous body 11 is held by a jig 12 such as a die located on the outer periphery thereof. On one side of the sintered porous body 11 in the axial direction, a pin 13 for forming the first diameter-expanded surface 5 is disposed. The pin 13 is sized to be inserted into the inner periphery of the sintered porous body 11 and is configured to rotate (rotate) about its own central axis ax1 as a rotation axis. It is configured to be able to rotate (revolve) with the axis ax2 as a rotation axis. In this embodiment, since the outer diameter of the sintered porous body 11 is finished in the previous sizing step (c), the central axis of the jig 12 that holds the sintered porous body 11 on the inner periphery is used. By matching with the central axis ax1 of the pin 13, the pin 13 can be rotated (revolved) around the central axis ax2 of the sintered porous body 11 as a result.

  First, as shown in FIG. 3, the pin 13 is inserted into the inner periphery of the sintered porous body 11. When the sintered oil-impregnated bearing 1 illustrated in FIG. 1 is formed as in this embodiment, the bearing surface 4 has a constant diameter cylindrical surface 7 and a first expanded surface 5 (or a second expanded surface). 6) The pin 13 is inserted to a position that becomes a boundary with 6). Then, the pin 13 is gradually tilted in the direction of the arrow in FIG. 3, and the pin 13 is pressed (pressurized) against the inner peripheral surface of the sintered porous body 11.

  Then, as shown in FIG. 4, the pressure region generated by the above operation is moved along the inner periphery of the sintered porous body 11, in other words, the pin 13 is centered on the sintered porous body 11. By rotating (revolving) around the axis ax2, the inner peripheral surface of the sintered porous body 11 is pressed and expanded over the entire periphery, and the surface opening is crushed. In this embodiment, as shown in FIG. 3 and FIG. 4, the rotation of the pin 13 itself around the central axis ax1 (rotation) is performed, so that the inner periphery of the sintered porous body 11 is pressed and expanded. The surface openings are crushed by the rotation of the pins 13.

  Then, as shown in FIG. 5, the above-described processing is performed by increasing the inclination angle of the pin 13 (θ2> θ1) and pulling the pin 13 along its central axis ax1 direction. As shown in FIG. 1, a first diameter-expanding surface 5 having an axial cross-section arc shape is formed as the diameter gradually increases toward the end face of the porous body 11. In the above-described method, a larger rotational force (frictional force) is received on the larger diameter side of the first diameter-expanded surface 5, and more surface openings are crushed toward the larger diameter side. Therefore, the surface opening distribution shows a distribution mode as shown in FIG.

  By performing the above operation on the other side of the inner peripheral surface of the sintered porous body 11, as shown in FIG. A bearing surface 4 having an enlarged diameter surface 6 can be formed. This operation may be performed by inverting the sintered porous body 11 or the jig 12 holding the sintered porous body 11 upside down, or by inverting the pin 13 once pulled up and down. . Alternatively, the second enlarged diameter surface 6 may be formed by inserting a pin different from the pin 13 on which the first enlarged diameter surface 5 is formed from below the sintered porous body 11.

  Further, when the cylindrical surface 7 having a constant diameter is provided between each of the enlarged diameter surfaces 5 and 6 as in this embodiment, the pin 13 is placed at the center of the sintered porous body before and after the formation of the enlarged diameter surfaces 5 and 6. In a state of being arranged in parallel with the axis ax2, by rotating the central axis ax2 as the central axis, it is possible to form the cylindrical surface 7 in which the outer peripheral surface coincides with the central axis. Moreover, the chamfer part 1c shown in FIG. 1 can be previously molded in the compacting process (a) or the sizing process (c). In this case, in consideration of the formation of the enlarged diameter surfaces 5 and 6 by the pin 13, the chamfer portion 1c may be formed larger in advance and finally a part thereof may be left. If there is no particular problem in processing, the above-mentioned enlarged diameter surface forming step may be performed simultaneously with the sizing step (c).

  Finally, the sintered porous body 1 finished in the finished product shape through the step (d) is impregnated with lubricating oil (lubricating oil impregnation step (e)), whereby the sintered oil-impregnated bearing 1 is completed.

  As described above, the pin 13 inserted in the inner periphery of the sintered porous body 11 is rotated while being tilted, and the inner peripheral surface of the sintered porous body 11 is applied with a frictional force and a pressing force. In addition, the number of surface opening ratios can be reduced by crushing minute surface openings or reducing relatively large openings. Further, by pressing and expanding the inner peripheral surface of the sintered porous body 11 along with the rotation of the pin 13 and the revolution about the central axis ax2, the larger the diameter of the larger diameter side, the more the surface openings are crushed. be able to. In particular, as in this embodiment, by continuing the above-described operation while gradually pulling out the pin 13, the larger the diameter side, the more the rotational frictional force of the pin 13 is given to the inner peripheral surface. This is suitable when there is a significant difference in the surface area ratio between the large diameter side and the inner diameter side of the large diameter surface 5 (or the second large diameter surface 6).

  The first embodiment of the present invention has been described above, but the sintered oil-impregnated bearing and the manufacturing method thereof embodied by the present invention are not limited to these exemplary ranges. Examples thereof will be described below with reference to the drawings.

  FIG. 6 shows a cross-sectional view of the sintered oil-impregnated bearing 21 according to the second embodiment of the present invention. The sintered oil-impregnated bearing 21 shown in the figure has a first diameter-expanded surface 25 that smoothly expands the bearing surface 24 toward one end surface 21a of the sintered oil-impregnated bearing 21, and a smooth surface toward the other end surface 21b. A second diameter-expanding surface 26 that expands the diameter is used. In this respect, the structure of the sintered oil-impregnated bearing 21 according to the embodiment differs from that of the sintered oil-impregnated bearing 1 disclosed in the first embodiment.

  Specifically, the first diameter-expanded surface 25 and the second diameter-expanded surface 26 are both formed into an annular curved surface having an axial cross-section arc shape and bulging on the axis side. Further, the curvature radius and axial dimension are equal, and both surfaces 25 and 26 are smoothly connected so that the tangent at the center in the axial direction is parallel to the central axis of the sintered oil-impregnated bearing 21. Further, in each of the diameter-enlarged surfaces 25 and 26, as in the first embodiment, the surface open area ratio decreases from the center in the axial direction toward the end surfaces 21a and 21b.

  Therefore, in the case of the sintered oil-impregnated bearing 21 having the above-described configuration, the shaft 2 oozes from its internal pores 23 while always maintaining a constant contact state (sliding state) regardless of the degree of inclination (deflection) of the shaft 2. It can be rotationally supported by the lubricant film that comes out. In addition, the surface area of the bearing surface 24 (here, each of the enlarged diameter surfaces 25 and 26) decreases as it goes toward the larger diameter side, so that a good oil film can be formed while the lubricating oil is Leakage is prevented as much as possible, and it can be used as a bearing suitable for long-term use (durability).

  The bearing surface 24 (sintered oil-impregnated bearing 21) having the above-described configuration can be formed, for example, through the above-described steps (steps (a) to (e)). Specifically, in the diameter-enlarged surface forming step (d) shown in FIG. 3, the pin 13 is inserted up to the center in the axial direction of the sintered porous body 11, and from this state, as illustrated in the first embodiment, As the pin 13 rotates, the central axis ax1 is inclined with respect to the central axis ax2 of the sintered porous body 11, and the sintered porous body 11 is given a frictional force by rotation and an applied pressure by inclined pressing. By doing so, the bearing surface 24 having the above-described configuration can be formed.

  FIG. 7 shows a cross-sectional view of a sintered oil-impregnated bearing 31 according to the third embodiment of the present invention. The sintered oil-impregnated bearing 31 shown in the figure is disclosed in the first embodiment in that both the first diameter-expanded surface 35 and the second diameter-expanded surface 26 constituting the bearing surface 34 are tapered in section with shaft. The structure of the oil-impregnated sintered oil bearing 1 is different.

  In this case, the bearing surface 34 is located between the first enlarged surface 35 and the second enlarged surface 36, and both the enlarged surfaces 35, 36, each having a tapered cross section. It is comprised with the cylindrical surface 37 of constant diameter connected smoothly. Further, similarly to the first and second embodiments, the surface area ratio in each of the enlarged diameter surfaces 35 and 36 is configured to decrease from the axial center side (cylindrical surface 37) toward the end surfaces 31a and 31b. Yes.

  Therefore, in the case of the sintered oil-impregnated bearing 31 having the above-described configuration, the shaft 2 oozes from the internal pores 33 while always maintaining a constant contact state (sliding state) regardless of the degree of inclination (deflection) of the shaft 2. It can be rotationally supported by the lubricant film that comes out. Further, by forming the surface area ratio of the first diameter-expanded surface 35 and the second diameter-expanded surface 36 constituting the bearing surface 34 to decrease toward the larger diameter side, a good oil film can be formed. However, it is possible to prevent the lubricant from leaking out as much as possible and to use it as a bearing suitable for long-term use (durability).

  The bearing surface 34 (sintered oil-impregnated bearing 31) of the said structure can be formed by passing through the above-mentioned process (process (a)-(e)), for example. Specifically, in the diameter-enlarged surface forming step (d), as shown in FIG. 8, the pin 13 is inserted to a position penetrating the sintered porous body 11, and from this state, the first embodiment is exemplified. As described above, with the rotation of the pin 13, the central axis ax1 is inclined with respect to the central axis ax2 of the sintered porous body 11, the frictional force due to rotation and the applied pressure due to the inclined pressing are applied to the sintered porous body 11. Is provided, the bearing surface 34 having the above-described configuration is formed.

  Therefore, if the above-mentioned method is used, both of the enlarged diameter surfaces 35 and 36 can be formed simultaneously by a single process, so that an excellent concentricity between the enlarged diameter surfaces 35 and 36 can be formed. is there. Moreover, since it is not necessary to invert the arrangement of the sintered porous body 11 or the pins 13 or to process them separately using other pins, simple processing equipment is sufficient, and the process can be simplified. So it is economical. In the step (c), the inclination angle θ3 of the pin 13 in the final stage of processing (inclination angle of the central axis ax1 of the pin 13 with respect to the central axis ax2 of the sintered porous body 11) is tapered. Since this is the inclination angle of the enlarged diameter surfaces 35 and 36, it is preferable to set the inclination angle in consideration of this point. Further, if the above-described method is used, it is easy to form a shape in which the cylindrical surface 37 and each of the enlarged diameter surfaces 35 and 36 are smoothly connected.

  FIG. 9 shows a cross-sectional view of a sintered oil-impregnated bearing 41 according to the fourth embodiment of the present invention. The sintered oil-impregnated bearing 41 shown in the figure is the same as the sintered oil-impregnated bearings 1, 21, 31 disclosed in the first to third embodiments in that the diameter-expanded surface 45 constituting the bearing surface 44 is only one surface. The structure is different.

  Specifically, the bearing surface 44 is configured by a diameter-expanded surface 45 that smoothly increases in diameter toward one axial direction. The enlarged diameter surface 45 has an arc-shaped cross section including a shaft, and is formed of an annular curved surface having a bulge on the axis side. Further, the enlarged diameter surface 45 is formed so that the tangent at the other axial end (minimum diameter portion) of the enlarged diameter surface 45 is parallel to the central axis of the sintered oil-impregnated bearing 41. The surface open area ratio of the enlarged diameter surface 45 is configured to decrease toward the larger diameter side.

  Therefore, in the case of the sintered oil-impregnated bearing 41 having the above-described configuration, the shaft 2 is always maintained in a constant contact state (sliding state) regardless of the degree of inclination (deflection) of the shaft 2 inserted in the inner periphery thereof. It can be rotationally supported by a film of lubricating oil that has oozed out of the internal pores 43. In addition, since the surface area ratio of the enlarged diameter surface 45 constituting the bearing surface 44 is reduced toward the larger diameter side, the lubricating oil leaks out while forming a good oil film. It can be used as a bearing suitable for long-term use (durability) while preventing as much as possible.

  Moreover, if it is the bearing surface 44 (sintered oil-impregnated bearing 41) of the said structure, it can be formed by passing through the process (process (a)-(e)) similar to 1st Embodiment, for example.

  Of course, the sintered oil-impregnated bearing according to the above description is merely an example, and the bearing surface is a surface that smoothly expands in diameter toward one end in the axial direction, and the surface opening ratio is on the large diameter side. As long as it has the structure which decreases as it goes, it can take arbitrary structures. As for the manufacturing method, while the pin inserted into the inner periphery of the sintered porous body is tilted, the pin is rotated along the inner periphery of the sintered porous body (rotated about the central axis ax2). The method is not limited to the above as long as it includes a step of applying a frictional force and a pressing force to the sintered porous body.

  With the sintered oil-impregnated bearing according to the above description, stable support can be realized over a long period of time regardless of the tilting state of the shaft to be supported. Therefore, it can be suitably used as a bearing for supporting a power transmission shaft that rotates in response to a load in a shearing direction (a load perpendicular to the axis), for example, a drive shaft that forms a power transmission mechanism for a power window. it can. Alternatively, since a good oil film can be formed, it can be suitably used for applications requiring quietness, such as an electric motor for automobiles. Moreover, if it is a bearing which makes the form illustrated in FIG. 9, it is also possible to use it for the use which supports the drive shaft of the power transmission mechanism for power windows, for example in the edge part.

It is sectional drawing of the sintered oil-impregnated bearing which concerns on 1st Embodiment of this invention. It is an enlarged view of the area | region A in FIG. It is a figure which shows notionally an example of the process of forming the diameter expansion surface of the sintered oil-impregnated bearing shown in FIG. It is a figure which shows notionally an example of the process of forming the diameter expansion surface of the sintered oil-impregnated bearing shown in FIG. It is a figure which shows notionally an example of the process of forming the diameter expansion surface of the sintered oil-impregnated bearing shown in FIG. It is sectional drawing of the sintered oil-impregnated bearing which concerns on 2nd Embodiment of this invention. It is sectional drawing of the sintered oil-impregnated bearing which concerns on 3rd Embodiment of this invention. It is a figure which shows notionally an example of the process of forming the diameter expansion surface of the sintered oil-impregnated bearing shown in FIG. It is sectional drawing of the sintered oil-impregnated bearing which concerns on 4th Embodiment of this invention.

Explanation of symbols

1, 21, 31, 41 Sintered oil-impregnated bearing 2 Axes 3, 23, 33, 43 Internal pores 4, 24, 34, 44 Bearing surfaces 5, 6, 25, 26, 35, 36, 45 Expanded surface 7, 37 Cylindrical surface 8 Surface opening 11 Sintered porous body 13 Pin ax1 Center axis (pin)
ax2 Central axis (sintered porous body)

Claims (5)

A porous body made of sintered metal with its internal pores impregnated with a lubricating fluid,
A bearing surface is provided on the inner periphery, and at least a part of the bearing surface is constituted by a diameter-expanded surface that smoothly expands toward one axial end of the bearing surface,
A sintered oil-impregnated bearing configured such that the surface area ratio of the diameter-expanded surface decreases with increasing diameter.   2. The sintered oil-impregnated bearing according to claim 1, wherein a part or the entire surface of the diameter-enlarged surface is formed of a curved surface having a shaft-containing cross-sectional arc shape and bulging on the axis side.   The sintered oil-impregnated bearing according to claim 1, wherein a part or the whole of the diameter-expanded surface is configured by a surface having a tapered shaft-containing cross section.   The sintered oil-impregnated bearing according to claim 1, wherein the bearing surface further has a second diameter-expanding surface that smoothly expands toward the other axial end of the bearing surface. A porous body made of sintered metal, the internal pores of which are impregnated with a lubricating fluid. A bearing surface is provided on the inner periphery, and at least a part of the bearing surface is directed toward one axial end of the bearing surface. A method for producing a sintered oil-impregnated bearing composed of a diameter-enlarging surface that expands smoothly and smoothly,
Inserting a pin into the inner periphery of the porous body, inclining the axis of the pin with respect to the central axis of the porous body to press a part of the inner periphery of the porous body, and
The manufacturing method of the sintered oil impregnated bearing which forms the said enlarged diameter surface by moving the said pressurization area | region along the inner periphery of the said porous body by the movement to the circumferential direction of the said pin.

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