JP6449059B2 - Sintered oil-impregnated bearing and manufacturing method thereof - Google Patents

Description

  The present invention relates to a sintered oil-impregnated bearing and a method for manufacturing the same.

  In the sintered oil-impregnated bearing, along with the relative rotation with the shaft inserted in the inner periphery, the lubricating oil impregnated inside exudes to the sliding portion with the shaft to form an oil film, and the oil film supports the shaft. Is. Such a sintered oil-impregnated bearing is used by being incorporated into a power transmission mechanism for a power window for opening and closing a window glass of a vehicle, for example.

  For example, as shown in FIG. 12, the power transmission mechanism for the power window mainly includes a motor 61, a shaft 62 rotated by the motor 61, a worm gear 63 provided on the shaft 62, and a wheel gear 64 that meshes with the worm gear 63. Prepare for. The rotational power input from the motor 61 to the shaft 62 is transmitted to the wheel gear 64 through the worm gear 63 in a decelerated state, and further transmitted to a window glass opening / closing mechanism (not shown), so that the window glass opening / closing operation is performed. Done. The shaft 62 is rotatably supported with respect to the housing 66 via a plurality of bearings 65. A sintered oil-impregnated bearing is preferably used as the bearing 65 that supports the shaft 62.

  By the way, in the power transmission mechanism as shown in FIG. 12, since the load F in the direction perpendicular to the axis is applied to the intermediate portion of the shaft 62 due to the engagement between the worm gear 63 and the wheel gear 64, the shaft 62 is deflected. In this case, since the shaft 62 is inclined with respect to the central axis of the bearing 65, the outer peripheral surface of the shaft 62 locally slides on the axial end of the inner peripheral surface (bearing surface) of the bearing 65, and the bearing surface Problems such as wear and abnormal noise may occur.

  For example, in Patent Document 1 below, a cylindrical portion (axial support portion) is provided on the inner peripheral surface adjacent to one side in the axial direction of the cylindrical portion, and a tapered portion (expanded) toward one side in the axial direction. A sintered oil-impregnated bearing having a diameter) is shown. According to this sintered oil-impregnated bearing, when the shaft is deflected, the outer peripheral surface of the shaft is supported by the tapered portion of the inner peripheral surface of the sintered oil-impregnated bearing. Is alleviated.

  Moreover, in said patent document 1, by increasing the density of a taper part and making a surface opening ratio small, the penetration | invasion of the lubricating oil from a taper part to the internal hole of a bearing is suppressed, and the function which supports a shaft by this Is increasing. The density of the inner peripheral surface (cylindrical portion and tapered portion) of the sintered oil-impregnated bearing is adjusted by adjusting the compression in the correction step (sizing step) after the sintering step.

Japanese Patent Publication No. 8-19941

  However, the rotational accuracy of the shaft may not be sufficiently increased only by increasing the density of the tapered portion on the inner peripheral surface as described above.

  The above problems occur not only when the sintered oil-impregnated bearing is fixed and the shaft rotates, but also when the shaft is fixed and the sintered oil-impregnated bearing rotates.

  In view of the above circumstances, an object of the present invention is to sufficiently increase the relative rotational accuracy of a shaft inserted into the inner periphery of a sintered oil-impregnated bearing.

  In order to achieve the above object, the present invention is a sintered oil-impregnated bearing comprising a cylindrical sintered body, in which internal pores are impregnated with lubricating oil, the inner peripheral surface having a cylindrical portion, The cylindrical portion is provided adjacent to one side in the axial direction, gradually increases in diameter toward one side in the axial direction, and has a larger diameter portion having a higher density than the cylindrical portion. A sintered oil-impregnated bearing is provided in which a high-density portion having a higher density than other regions is provided in an axial region of a diameter portion.

  Thus, in the sintered oil-impregnated bearing according to the present invention, not only the diameter-expanded portion of the inner peripheral surface is densified to reduce the surface opening ratio, but also the axial region of the diameter-expanded portion of the sintered body is reduced. The density was increased from the outer peripheral side. As a result, the density of the sintered body in the axial region of the enlarged diameter portion is further increased, and the lubricating oil is less likely to enter the inside of the sintered body from the surface opening of the enlarged diameter portion. The pressure of the oil film interposed between the two is further increased.

  The sintered oil-impregnated bearing includes, for example, a forming step of compressing raw powder to obtain a green compact, a sintering step of sintering the green compact to obtain a sintered body, and the sintered body A method for producing a sintered oil-impregnated bearing comprising a sizing step for compression molding and an oil impregnation step for impregnating the internal pores of the sintered body with lubricating oil, wherein the inner peripheral surface of the sintered body in the sizing step And forming a cylindrical portion and a diameter-expanded portion which is provided adjacent to one side in the axial direction of the cylindrical portion and gradually increases in diameter toward one side in the axial direction and has a higher density than the cylindrical portion. The sintered oil-impregnated bearing can be manufactured by forming a high-density portion having a higher density than other regions in the axial region of the enlarged diameter portion of the outer peripheral surface of the sintered body.

  As described above, according to the present invention, even when the shaft is inclined with respect to the axis of the sintered oil-impregnated bearing, the oil film between the enlarged diameter portion of the inner peripheral surface of the sintered oil-impregnated bearing and the shaft has a high pressure. Therefore, the function of supporting the shaft by the enlarged diameter portion of the sintered oil-impregnated bearing is enhanced, and the relative rotational accuracy of the shaft can be enhanced.

It is sectional drawing of the sintered oil-impregnated bearing which concerns on one Embodiment of this invention. The upper part is a side view of the flat copper powder, and the lower part is a plan view. It is sectional drawing of the green compact which is a precursor of the said sintered oil-impregnated bearing. (A)-(c) is sectional drawing which shows a primary sizing process. (A)-(c) is sectional drawing which shows a secondary sizing process. It is sectional drawing of the sintered oil-impregnated bearing which concerns on other embodiment. It is sectional drawing which shows an example of the fixing method to the housing of a sintered oil-impregnated bearing. It is sectional drawing of the green compact which concerns on other embodiment. (A) And (b) is sectional drawing which shows the primary sizing process which concerns on other embodiment. (A) And (b) is sectional drawing which shows the secondary sizing process which concerns on other embodiment. It is sectional drawing of the sintered oil-impregnated bearing manufactured through the sizing process of FIG.9 and FIG.10. It is sectional drawing of the power transmission mechanism for power windows.

  FIG. 1 shows a sintered oil-impregnated bearing 1 according to an embodiment of the present invention. The sintered oil-impregnated bearing 1 is incorporated, for example, as a bearing 65 of a power transmission mechanism for a power window shown in FIG. In the present embodiment, a case where the sintered oil-impregnated bearing 1 is provided as a pair of bearings 65 that support the vicinity of both axial sides of the worm gear 63 in the shaft 62 will be described. In the description of the sintered oil-impregnated bearing 1 below, the worm gear 63 side in the axial direction is referred to as “one axial side”, and the opposite side is referred to as “the other axial direction”.

  The sintered oil-impregnated bearing 1 is made of a cylindrical sintered body, and the internal holes are impregnated with lubricating oil. The sintered oil-impregnated bearing 1 is composed of, for example, a copper-based, iron-based, or copper-iron-based sintered body, and in this embodiment is composed of a copper-iron-based sintered body mainly composed of copper and iron. .

  The sintered oil-impregnated bearing 1 has a substantially cylindrical shape, and is provided on the inner peripheral surface adjacent to the cylindrical portion 2 and one axial side (right side in the drawing) of the cylindrical portion 2, toward the one axial side. And a diameter-expanded portion that gradually increases in diameter. In the illustrated example, a first tapered portion 3 as a diameter-expanded portion is provided on one side in the axial direction of the cylindrical portion 2. On the other axial side of the cylindrical portion 2 (left side in the figure), a second tapered portion 4 is provided as another diameter-expanded portion that gradually increases in diameter toward the other axial direction. The 1st taper part 3 and the 2nd taper part 4 incline at the same angle with respect to an axial direction, The inclination angle shall be 1-3 degrees (preferably 1-2 degrees), for example. In FIG. 1, the inclination angles of the two taper portions 3 and 4 are exaggerated. In the illustrated example, both taper portions 3 and 4 have the same axial dimension.

  The cylindrical portion 2 functions as a bearing surface that supports the shaft 62. The first taper portion 3 functions as a bearing surface that supports the shaft 62 when the shaft 62 is bent by the force F (see FIG. 12) that the worm gear 63 receives from the worm wheel 64. The second taper portion 3 does not function as a bearing surface regardless of the state of the shaft 62 (that is, the second taper portion 3 and the shaft 62 do not slide). The inner peripheral surface of the sintered oil-impregnated bearing 1 has a higher density in the order of the first taper portion 3, the cylindrical portion 2, and the second taper portion 4, that is, the surface aperture ratio decreases in this order.

  The outer peripheral surface of the sintered oil-impregnated bearing 1 is provided with a low density portion and a high density portion having a higher density than the low density portion. In the present embodiment, the outer peripheral cylindrical portion 5 is provided as a low density portion on the outer peripheral surface of the sintered oil-impregnated bearing 1, and on the one side in the axial direction of the outer peripheral cylindrical portion 5 as a high density portion than the outer peripheral cylindrical portion 5. A small diameter portion is provided. In the illustrated example, an outer peripheral taper portion 6 that is gradually reduced in diameter toward one side in the axial direction is provided as a small diameter portion at the end on one side in the axial direction of the outer peripheral surface of the sintered oil-impregnated bearing 1.

  The outer periphery taper part 6 is provided in the axial direction area | region of the 1st taper part 4 of an internal peripheral surface. In the illustrated example, the outer peripheral taper portion 6 is provided over the entire region in the axial direction of the first taper portion 4. Specifically, the outer peripheral taper portion 6 is provided in the same axial region as the first taper portion 4. One end in the axial direction of the first taper portion 4 and the outer peripheral taper portion 6 both reaches the chamfered portion 7, and the other end in the axial direction of the first taper portion 4 and the outer peripheral taper portion 6 is arranged at the same axial position. . The inclination angle of the outer peripheral taper portion 6 with respect to the axial direction is larger than the inclination angle of the taper portions 3 and 4 on the inner peripheral surface, for example, 5 to 20 ° (preferably 10 to 15 °). The configuration of the outer peripheral taper portion 6 is not limited to the above, and for example, the other end in the axial direction of the outer peripheral taper portion 6 may be extended from the other end in the axial direction of the first taper portion 4 to the other end in the axial direction.

  Chamfered portions 7 are provided at both axial ends of the inner and outer peripheral surfaces of the sintered oil-impregnated bearing 1. Specifically, a chamfered portion 7 is provided between one end surface 8 in the axial direction and the first tapered portion 3 and the outer peripheral tapered portion 6. Further, chamfered portions 7 are provided between the other end surface 8 in the axial direction and the second tapered portion 4 and the outer peripheral cylindrical portion 5 of the outer peripheral surface. Each of the chamfered portions 7 is a tapered surface having a larger inclination angle with respect to the axial direction than the first tapered portion 3, the second tapered portion 4, and the outer peripheral tapered portion 6, and is inclined approximately 45 ° with respect to the axial direction in the illustrated example. It is a tapered surface. In the illustrated example, since the inclination angles of the first taper portion 3, the second taper portion 4, and the outer peripheral taper portion 6 are exaggerated, the radial direction dimensions of the chamfered portions 7 are the taper portions 3, 4, 4. 6, the radial dimension of each chamfered portion 7 is actually larger than the radial dimension of each tapered portion 3, 4, 6.

  The sintered oil-impregnated bearing 1 having the above-described configuration is manufactured through a mixing process, a forming process, a sintering process, a sizing process, and an oil-impregnating process. Hereinafter, each process will be described in detail.

[Mixing process]
In the mixing step, the raw material powder is prepared by mixing the main raw material powder, the low melting point metal powder, and the solid lubricant powder with a mixer. If necessary, various molding aids such as a lubricant (metal soap or the like) for improving mold release properties are added to the raw material powder.

The main raw material powder is a metal powder containing copper and iron. In this embodiment, a partial diffusion alloy powder containing copper and iron and a flat copper powder are used as the main raw material powder. As the partial diffusion alloy powder, for example, Fe—Cu partial diffusion alloy powder in which copper is diffused and adhered to the surface of iron powder (or iron alloy powder) is used. The flat copper powder is flattened by stamping raw material copper powder made of water atomized powder or the like. As the flat copper powder, those having a length L of 20 to 80 μm and a thickness t of 0.5 to 1.5 μm (aspect ratio L / t = 13.3 to 160) are mainly used. Here, “length” and “thickness” refer to the geometric maximum dimension of each particle 15 of the flat copper powder as shown in FIG. The apparent density of the flat copper powder is 1.0 g / cm ³ or less. It is preferable to apply a fluid lubricant to the flat copper powder in advance before mixing with the raw material powder. As the fluid lubricant, fatty acids, particularly linear saturated fatty acids, specifically stearic acid can be used. The main raw material powder is not limited to the above, and for example, copper powder (pure copper powder or copper alloy powder) and iron powder (pure iron powder or iron alloy powder) can also be used.

  The low melting point metal powder is a metal powder having a melting point lower than the sintering temperature, and for example, a powder of tin, zinc, phosphorus or the like is used. These low melting point metal powders have high wettability with respect to copper. At the time of sintering, a low melting point metal (for example, tin) is first melted to wet the surface of copper to form a copper-tin alloy layer. And the bonding strength of the partial diffusion alloy powders is strengthened by the diffusion bonding of the copper-tin alloy layers of the adjacent partial diffusion alloy powders.

  The solid lubricant powder is added to reduce friction with the shaft 62. For example, graphite powder is used. As graphite powder, artificial graphite powder or natural graphite powder can be used.

  The blending ratio of each powder in the raw material powder is, for example, 75 to 90 wt% for Fe-Cu partial diffusion alloy powder, 8 to 20 wt% for flat copper powder, 0.8 to 6.0 wt% for tin powder, and graphite powder. 0.5 to 2.0 wt%.

[Forming process]
In the forming step, the green compact shown in FIG. 3 is formed by filling the raw material powder into a forming mold (not shown) and compressing it. The inner peripheral surface 21 and the outer peripheral surface 22 of the green compact 20 are formed in a straight cylindrical surface over the entire axial direction. A chamfer 25 is formed between the inner peripheral surface 21 and both end surfaces 23 and 24 of the green compact 20 and between the outer peripheral surface 22 and both end surfaces 23 and 24.

  In this embodiment, since the raw material powder contains flat copper powder, when the raw material powder is filled into the forming mold or when the raw material powder is compressed by the forming mold, the forming surface of the forming mold is flattened. Copper powder adheres. For this reason, a lot of flat copper powder is exposed on the surface of the green compact 20. The flat copper powder is arranged so that the thickness orthogonal direction of each particle is along the surface of the green compact 20. As described above, since the copper is unevenly distributed on the surface of the green compact 20, the area ratio of copper can be maximized in the portion (bearing surface) that can slide with the shaft 62 of the sintered oil-impregnated bearing 1. The slidability with the shaft 62 can be improved.

[Sintering process]
In the sintering step, the sintered compact 30 is obtained by sintering the green compact 20 in a sintering furnace. The sintering temperature is lower than the melting point of the main raw material powder (the melting point of copper in this embodiment) and higher than the melting point of the low melting point metal powder (the melting point of tin in this embodiment), for example, 820 to 900 °. It is said.

[Sizing process]
In the sizing process, the sintered body 30 is compressed into a predetermined shape. In this embodiment, a primary sizing process and a secondary sizing process are performed as the sizing process. In addition, in the figure explaining a sizing process, only the left half of a sintered compact and a sizing metal mold | die is shown. Further, illustration of a chamfered portion provided in the sintered body is omitted.

  In the primary sizing step, the inner peripheral surface of the sintered body 30 is compressed to form the second tapered portion 4, and the outer peripheral surface of the sintered body 30 is compressed to form the outer peripheral tapered portion 6. As shown in FIG. 4, the primary sizing mold 40 used in this step has a die 41, a core 42, an upper punch 43, and a lower punch 44. The die 41 has an upper die 41a having a cylindrical surface 41a1 on the inner peripheral surface, and a lower die 41b having a tapered surface 41b1 having a diameter reduced downward on the inner peripheral surface. The core 42 includes a tapered portion 42a that has a diameter reduced downward, and a cylindrical portion 42b that is provided below the tapered portion 42a.

  Specifically, first, the cylindrical portion 42b of the core 42 is inserted into the inner periphery of the sintered body 30 {see FIG. 4 (a)}. The outer diameter of the cylindrical portion 42b is slightly smaller than the inner diameter of the sintered body 30, and both are fitted through a radial gap. In this state, the sintered body 30 is lowered and inserted into the inner periphery of the upper die 41a. At this time, the outer peripheral surface of the sintered body 30 and the cylindrical surface 41a1 of the upper die 41a are fitted via a radial clearance. The radial gap between the outer peripheral surface of the sintered body 30 and the cylindrical surface 41a1 of the upper die 41a is smaller than the radial gap between the inner peripheral surface of the sintered body 30 and the cylindrical portion 42b of the core 42.

  Thereafter, the sintered body 30 is further lowered, and the lower end of the sintered body 30 is pushed into the inner periphery of the lower die 41b {see FIG. 4B}. As a result, the shape of the lower die 41 b is transferred to the outer peripheral surface of the sintered body 30, and the outer peripheral taper portion 6 is formed at the lower end of the outer peripheral surface of the sintered body 30. When the outer peripheral tapered portion 6 is formed on the outer peripheral surface of the sintered body 30 in this way, the lowering of the sintered body 30 is stopped. Thereafter, the upper punch 43 is slightly lowered to compress the sintered body 30 in the axial direction, thereby expanding the outer peripheral surface of the sintered body 30, and the outer peripheral surface of the sintered body 30 is made the inner periphery of the upper die 41 a. The surface 41a1 is closely attached. At this time, the inner peripheral surface of the sintered body 30 is reduced in diameter, but the inner peripheral surface of the sintered body 30 is preferably not in contact with the cylindrical portion 42 a of the core 42.

  Thereafter, the core 42 is lowered and the taper portion 42a of the core 42 is pushed into the inner periphery of the sintered body 30 (see FIG. 4C). As a result, the shape of the tapered portion 42 a of the core 42 is transferred to the inner peripheral surface of the sintered body 30, and the second tapered portion 4 is formed on the upper end of the inner peripheral surface of the sintered body 30. In this way, while the sintered body 30 is being molded with the primary sizing mold 40, a radial gap is maintained between the inner peripheral surface of the sintered body 30 and the outer peripheral surface of the cylindrical portion 42 b of the core 42. That is, in the primary sizing process, the region excluding the second taper portion 4 in the inner peripheral surface of the sintered body 30 is not formed by the core 42.

  Thus, in the primary sizing process, the sintered body 30 is compressed by the die 41, the core 42, and the upper and lower punches 43 and 44, whereby the density of the sintered body 30 is increased. In particular, in the outer peripheral surface of the sintered body 30, the outer peripheral tapered portion 6 has a larger amount of compression in the radial direction than the other region (cylindrical region) of the outer peripheral surface, and therefore has a density higher than that of the other region of the outer peripheral surface. Get higher. Moreover, since the amount of compression in the radial direction of the second taper portion 4 in the inner peripheral surface of the sintered body 30 is larger than that in other regions, the density is higher than that in other regions (cylindrical regions) of the inner peripheral surface. Get higher. In addition, since the inclination angle with respect to the axial direction of the outer periphery taper part 6 is larger than the inclination angle with respect to the axial direction of the 2nd taper part 4, the outer periphery taper part 6 has a larger compression amount by primary sizing than the 2nd taper part 4. Therefore, the density is higher than that of the second taper portion 4.

  As described above, the density of the surface of the sintered body 30 that has undergone the primary sizing decreases in the order of the outer peripheral tapered portion 6, the second tapered portion 4, the outer peripheral surface, and the cylindrical region of the inner peripheral surface. Moreover, the surface aperture ratio of the sintered compact 30 becomes large in order of the outer peripheral taper part 6, the 2nd taper part 4, the outer peripheral surface, and the cylindrical area | region of an internal peripheral surface.

  In the secondary sizing step, the cylindrical portion 2 and the first tapered portion 3 are formed on the inner peripheral surface of the sintered body 30 that has undergone the primary sizing step, and the outer peripheral cylindrical portion 5 is formed on the outer peripheral surface of the sintered body 30. The secondary sizing die 50 used in this step has a die 51, a core 52, an upper punch 53, and a lower punch 54 as shown in FIG. The inner peripheral surface of the die 51 is a straight cylindrical surface. The core 52 has a tapered portion 52a having a diameter reduced downward and a cylindrical portion 52b provided below the tapered portion.

  Specifically, first, the sintered body 30 is placed on the lower punch 54 of the secondary sizing mold 50 {see FIG. 5A}. At this time, the sintered body 30 is disposed such that the second tapered portion 4 formed on the inner peripheral surface in the primary sizing step is downward. That is, the sintered body 30 is disposed in the secondary sizing mold in a state where the sintered body 30 is turned upside down from the state disposed in the primary sizing mold. Then, the cylindrical portion 52 b of the core 52 is press-fitted into the inner periphery of the sintered body 30. Thereby, the cylindrical area | region (including the area | region used as the 1st taper part 3 later) of the sintered compact 30 is compression-molded, and a density becomes high. At this time, the cylindrical region of the sintered body 30 slides while being in pressure contact with the outer peripheral surface of the cylindrical portion 52b of the core 52, so that the surface of the cylindrical region is crushed. A part of the cylindrical region on the inner peripheral surface of the sintered body 30 formed by the cylindrical portion 52 b of the core 52 in this manner becomes the cylindrical portion 2.

  Thereafter, the sintered body 30 is lowered and press-fitted into the inner periphery of the die 51 {see FIG. 5B}. Thereby, the cylindrical region excluding the outer peripheral taper portion 6 in the outer peripheral surface of the sintered body 30 is compression-molded on the inner peripheral surface of the die 51 to increase the density and press-contact with the inner peripheral surface of the die 51. The surface is crushed by sliding. At this time, the press-fitting allowance between the outer peripheral surface of the sintered body 30 and the inner peripheral surface of the die 51 (the difference in diameter between the outer diameter of the sintered body 30 subjected to primary sizing and the inner diameter of the die 51) is the sintered body 30. Is larger than the press-fitting allowance (the difference in diameter between the inner diameter of the sintered body 30 subjected to the primary sizing and the outer diameter of the cylindrical portion 52b of the core 52). In addition, after press-fitting the sintered body 30 into the inner periphery of the die 51, the sintered body 30 can be further compressed in the axial direction by the upper and lower punches 53 and 54, so that the sintered body 30 can be further densified. .

  Then, the taper part 52a of the core 52 is pushed into the inner periphery of the sintered body 30 {see FIG. 5C}. Thereby, the shape of the taper part 52a of the core 52 is transcribe | transferred to the internal peripheral surface of the sintered compact 30, and the 1st taper part 3 is shape | molded. Thus, the density of the first taper portion 3 is further increased by the compression molding of the first taper portion 3 by the taper portion 52 a of the core 52. Thus, the sintered body 30 is formed into a predetermined shape (the same shape as the sintered oil-impregnated bearing 1 in FIG. 1).

  Thus, in the sizing process, the sintered body 30 is compression-molded with the sizing mold. Specifically, of the inner peripheral surface of the sintered body 30, the second taper portion 4 is subjected only to compression molding by the taper portion 42 a of the core 42 in the primary sizing process. The cylindrical portion 2 on the inner peripheral surface of the sintered body 30 is subjected to compression molding and crushing by press-fitting the cylindrical portion 52b of the core 52 in the secondary sizing process. The first taper portion 3 on the inner peripheral surface of the sintered body 30 is subjected to compression molding and crushing by press-fitting the cylindrical portion 52b of the core 52 in the secondary sizing process, and compression molding by the taper portion 52a of the core 52. Accordingly, the surface opening ratio of the inner peripheral surface of the sintered body 30 decreases in the order of the second taper portion 4, the cylindrical portion 2, and the first taper portion 3. Further, the density of the first taper portion 3 is higher than the density of the cylindrical portion 2. In the present embodiment, the density increases in the order of the second tapered portion 4, the cylindrical portion 2, and the first tapered portion 3.

  Further, the outer peripheral tapered portion 6 of the sintered body 30 is subjected only to compression molding by the tapered surface 41b1 of the lower die 41b in the primary sizing process. The outer peripheral cylindrical portion 5 of the sintered body 30 is subjected to compression molding and crushing by press-fitting into the die 51 in the secondary sizing process. At this time, since the compression amount when the outer peripheral taper portion 6 is formed on the cylindrical outer peripheral surface of the sintered body 30 is larger than the compression amount when the sintered body 30 is press-fitted into the die 52, the outer peripheral taper portion 6. Is higher than the density of the outer cylindrical portion 5. Moreover, although the surface aperture ratio of the outer periphery taper part 6 and the outer periphery cylindrical part 5 changes with the compression molding amount of each area | region of the outer peripheral surface of the sintered compact 30, a press-fitting allowance, etc., in this embodiment, the surface of the outer periphery taper part 6 The aperture ratio is smaller than the surface aperture ratio of the outer cylindrical portion 5.

  Note that the chamfered portions 7 provided at both ends in the axial direction of the inner peripheral surface and the outer peripheral surface of the sintered body 30 are not compressed by sizing, and are formed by forming. Therefore, the chamfered portion 7 has the lowest density and the highest surface aperture ratio among the surfaces of the sintered body 30.

  Further, in the secondary sizing step, since there is a radial gap between the outer peripheral tapered portion 6 of the sintered body 30 and the inner peripheral surface of the die 51, the first tapered portion 3 is provided on the inner peripheral surface of the sintered body 30. By compression molding, the outer peripheral tapered portion 6 molded in the primary sizing process may be expanded in diameter. However, since the first taper portion 3 has a smaller inclination angle with respect to the axial direction than the outer peripheral taper portion 6 and the amount of compression by secondary sizing is small, the influence on the outer peripheral taper portion 6 due to the molding of the first taper portion 3 is small. Moreover, since the inclination angle of the outer periphery taper part 6 does not require so high accuracy, a slight fluctuation does not cause a problem.

[Oil impregnation process]
In the oil impregnation step, the sizing sintered body 30 is impregnated with a lubricating oil by a technique such as vacuum impregnation. As the lubricating oil to be impregnated into the sintered body, for example, an ester-based lubricating oil is used, and those having a kinematic viscosity of 30 mm ² / sec or more and 200 mm ² / sec or less are particularly preferable. Thus, the sintered oil-impregnated bearing 1 is completed.

  The sintered oil-impregnated bearing 1 is incorporated in a power transmission mechanism for a power window shown in FIG. Specifically, the shaft 62 is inserted into the inner periphery of the sintered oil-impregnated bearing 1 and the sintered oil-impregnated bearing 1 is press-fitted and fixed to a predetermined portion of the housing 66. The sintered oil-impregnated bearing 1 of the present embodiment is provided in the vicinity of both sides in the axial direction of the worm gear 63 and is fixed to the housing 66 so that the first tapered portion 3 is on the worm gear 63 side. When the sintered oil-impregnated bearing 1 of this embodiment is used as the other bearing (the rightmost bearing 65 in FIG. 12), the first tapered portion 3 is arranged on the motor 61 side. A part of the bearing 65 may be a bearing other than the sintered oil-impregnated bearing 1 described above. For example, a sintered oil-impregnated bearing in which the entire inner peripheral surface is a straight cylindrical surface may be used as the rightmost bearing in FIG.

  In the above power window power transmission mechanism, when the motor 61 is driven and the shaft 62 rotates, the lubricating oil that has oozed out from the inside of the sintered oil-impregnated bearing 1 or the lubricating oil supplied from the outside is sintered oil-impregnated. It is interposed between the inner peripheral surface of the bearing 1 and the outer peripheral surface of the shaft 62. When the deflection of the shaft 62 is small, an oil film is formed between the cylindrical portion 2 on the inner peripheral surface of the sintered oil-impregnated bearing 1 and the outer peripheral surface of the shaft 62, and the shaft 62 is rotated by the cylindrical portion 2 through this oil film. It is supported freely. When the deflection of the shaft 62 is increased, in addition to the support by the cylindrical portion 2 described above, the shaft 62 is interposed via an oil film between the first taper portion 3 on the inner peripheral surface of the sintered oil-impregnated bearing 1 and the outer peripheral surface of the shaft 62. 62 is rotatably supported by the first taper portion 3.

  Since the sintered oil-impregnated bearing 1 has the highest density of the first tapered portion 3 and the smallest surface opening ratio among the inner peripheral surfaces, the sintered tapered oil-impregnated bearing 1 has an inner hole from the first tapered portion 3. Lubrication oil is difficult to penetrate. Accordingly, the pressure of the lubricating oil interposed between the first tapered portion 3 and the shaft 62 is maintained, and the rotational accuracy of the shaft 62 is improved.

  Furthermore, the sintered oil-impregnated bearing 1 has the outer peripheral tapered portion 6 compression-molded on a part of the outer peripheral surface (the outer diameter side of the first tapered portion 3) by the primary sizing process. The density of the taper portion 6 is higher than that of other regions. As described above, in the sintered oil-impregnated bearing 1, the axial region of the first tapered portion 3 is densified from the outer peripheral side, so that the lubricating oil is supplied from the first tapered portion 3 to the internal holes of the sintered oil-impregnated bearing 1. Is further less likely to enter, so that the rotational accuracy of the shaft 62 is further enhanced.

  The present invention is not limited to the above embodiment. Hereinafter, although other embodiment of this invention is described, the same code | symbol is attached | subjected to the site | part which has the same function as said embodiment, and duplication description is abbreviate | omitted.

  The sintered oil-impregnated bearing 1 shown in FIG. 6 differs from the above-described embodiment in that the second tapered portion 4 is not provided on the inner peripheral surface. That is, in this sintered oil-impregnated bearing 1, the other axial end of the cylindrical portion 2 on the inner peripheral surface (the end opposite to the first taper portion 3) reaches the chamfered portion 7. In this case, after the outer peripheral tapered portion 6 is formed on the outer peripheral surface of the sintered body 30 by primary sizing, the cylindrical portion 2 and the first tapered portion 3 are formed on the inner peripheral surface of the sintered body by secondary sizing.

  Moreover, although the case where the outer periphery taper part 6 was shape | molded by primary sizing was shown in said embodiment, you may shape | mold not only this but the outer periphery taper part 6 by secondary sizing, for example. Specifically, for example, after the second tapered portion 4 is formed on the inner peripheral surface of the sintered body 30 by primary sizing, the cylindrical portion 2 and the first tapered portion are formed on the inner peripheral surface of the sintered body 30 by secondary sizing. 3 and the outer peripheral tapered portion 6 may be formed on the outer peripheral surface of the sintered body 30 (not shown).

  When the sintered oil-impregnated bearing 1 is assembled to the housing 66, as shown in FIG. 7, if the sintered oil-impregnated bearing 1 is inserted (for example, press-fitted) into the inner periphery of the housing 66 from the outer peripheral tapered portion 6 side, the outer peripheral tapered portion. Since the sintered oil-impregnated bearing 1 is guided with respect to the housing 66 by bringing the opening 6 and the housing 66 into contact with each other, the assembling work of the sintered oil-impregnated bearing 1 to the housing 66 can be performed smoothly.

  Moreover, although the case where the outer peripheral surface of the green compact 20 was a straight cylindrical surface was shown in the above embodiment, the present invention is not limited to this. For example, as shown in FIG. 8, a small diameter portion 22 a and a large diameter portion 22 b may be provided on the outer peripheral surface 22 of the green compact 20. The sintered body 30 obtained by sintering the green compact 20 is subjected to primary sizing using a primary sizing die 40 shown in FIG. This primary sizing mold 40 is different from the embodiment shown in FIG. 4 in that a die 41 is integrally formed and the entire axial direction of the molding surface is formed in a straight cylindrical surface.

  Specifically, the sintered body 30 is disposed in the primary sizing mold 40 so that the large diameter portion 32b is on the lower side {see FIG. 9A}. Thereafter, the sintered body 30 is press-fitted into the inner periphery of the die 41, so that the outer peripheral surface 32 of the sintered body 30 is formed into a straight cylindrical surface shape on the inner peripheral surface of the die 41 {FIG. reference}. After the sintered body 30 is press-fitted into the die 41, the second tapered portion 4 is formed at the upper end of the inner peripheral surface of the sintered body 30 by pressing the tapered portion 42 a of the core 42 into the inner periphery of the sintered body 30. The At this time, in the outer peripheral surface 32 of the sintered body 30, the region formed by compressing the small diameter portion 32a becomes the low density portion 5 ′, and the region formed by compressing the large diameter portion 32b is the high density portion 6 ′ (black coating). Area).

  Thereafter, secondary sizing is applied to the sintered body 30 by the secondary sizing mold 50 shown in FIG. Specifically, first, the sintered body 30 is disposed in the secondary sizing mold 50 so that the high-density portion 6 ′ is on the upper side, and the cylindrical portion 52 b of the core 52 is press-fitted into the inner periphery of the sintered body 30. {See FIG. 10 (a)}. Thereafter, the sintered body 30 is press-fitted into the inner periphery of the die 51, and the taper portion 52a of the core 52 is pushed into the inner periphery of the sintered body 30, {see FIG. 10B}. As described above, the cylindrical portion 2 and the first tapered portion 3 are formed on the inner peripheral surface of the sintered body 30.

  The sintered oil-impregnated bearing 1 shown in FIG. 11 is obtained by impregnating the sintered body 30 produced through the above steps with a lubricating oil. A cylindrical portion 2, a first taper portion 3, and a second taper portion 4 are provided on the inner peripheral surface of the sintered oil-impregnated bearing 1 as in the above embodiment. On the other hand, the outer peripheral surface of the sintered oil-impregnated bearing 1 is constituted by a straight cylindrical surface. A high density portion 6 ′ is provided in the axial direction region of the first taper portion 3 on the outer peripheral surface of the sintered oil-impregnated bearing 1. In the illustrated example, a high density portion 6 'is provided at one axial end of the outer peripheral surface of the sintered oil-impregnated bearing 1, and a low density portion 5' is provided adjacent to the other axial side of the high density portion 6 '. The low density portion 5 ′ and the high density portion 6 ′ are continuous cylindrical surfaces having the same diameter.

  In the above embodiment, the case where a gap is formed between the cylindrical portion 42b of the core 42 and the inner peripheral surface of the sintered body 30 in the primary sizing process has been described, but the present invention is not limited thereto. For example, in the primary sizing step, the cylindrical portion 42b of the core 42 has the same diameter as the inner diameter of the sintered body 30, and the gap between the cylindrical portion 42b and the inner peripheral surface of the sintered body 30 is substantially zero (for example, a light press-fit state). ). In this case, since the outer peripheral surface of the sintered body 30 is compressed by the tapered surface 41b1 of the lower die 41 with the cylindrical portion 42b supporting the inner peripheral surface of the sintered body 30 from the inner diameter side, The outer periphery taper part 6 can be shape | molded reliably.

  In the above embodiment, in the primary sizing process, the outer peripheral surface of the sintered body 30 and the cylindrical surface 41a1 of the upper die 41a are fitted via a radial gap. The inner diameter of 41a may be the same as the outer diameter of the sintered body 30, and the gap between the cylindrical surface 41a1 of the upper die 41a and the outer peripheral surface of the sintered body 30 may be substantially zero (for example, a light press-fit state).

  Moreover, in said embodiment, although the case where the sintered oil-impregnated bearing 1 was applied to the power transmission mechanism for power windows was shown, you may use not only this but for another use. For example, the sintered oil-impregnated bearing of the present invention can be applied to a vibration motor that functions as a vibrator for a mobile phone or the like.

  Moreover, in said embodiment, although the case where the axis | shaft 62 inserted in the inner periphery in the sintered oil-impregnated bearing 1 was rotated was shown, it is not restricted to this, When fixing a shaft and rotating a sintered oil-impregnated bearing Alternatively, the present invention may be applied when rotating both the shaft and the sintered oil-impregnated bearing.

  It goes without saying that the present invention is not limited to the above-described embodiments, and can be applied without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Sintered oil-impregnated bearing 2 Cylindrical part 3 1st taper part (expanded diameter part)
4 Second taper part 5 Outer cylindrical part (low density part)
6 Peripheral taper part (high density part)
7 Chamfered portion 20 Green compact 30 Sintered body 40 Primary sizing die 50 Secondary sizing die

Claims (8)

A sintered oil-impregnated bearing made of a cylindrical sintered body, in which internal pores are impregnated with lubricating oil,
A cylindrical portion is provided on the inner peripheral surface adjacent to one side in the axial direction of the cylindrical portion, and gradually increases in diameter toward one side in the axial direction, and a diameter-expanded portion having a higher density than the cylindrical portion. Have
A sintered oil-impregnated bearing in which a high-density portion having a higher density than other regions is provided in an axial region of the enlarged-diameter portion in the outer peripheral surface.   The sintered oil-impregnated bearing according to claim 1, wherein the high-density portion is a tapered surface having a diameter gradually reduced toward one side in the axial direction.   The sintered oil-impregnated bearing according to claim 1, wherein the outer peripheral surface is a straight cylindrical surface.   The sintered oil-impregnated bearing according to any one of claims 1 to 3, wherein the enlarged-diameter portion comprises a molding surface compressed by sizing. A forming step of compressing raw material powder to obtain a green compact, a sintering step of sintering the green compact to obtain a sintered body, a sizing step of compressing and molding the sintered body, and the sintering A method for producing a sintered oil-impregnated bearing comprising an oil impregnation step of impregnating a lubricating oil into an internal cavity of a body,
In the sizing step, a cylindrical portion is provided on the inner peripheral surface of the sintered body and adjacent to one side in the axial direction of the cylindrical portion, and the diameter gradually increases toward the one side in the axial direction. Sintering to form a higher-density portion having a higher density than the other regions in the axial region of the larger-diameter portion in the outer peripheral surface of the sintered body. Manufacturing method of oil-impregnated bearing. In the forming step, the outer peripheral surface of the green compact is a straight cylindrical surface,
The method for producing a sintered oil-impregnated bearing according to claim 5, wherein, in the sizing step, the high-density portion having a smaller diameter than other regions is formed by compressing an outer peripheral surface of the sintered body.   The sizing step includes a primary sizing step in which the high density portion is formed on the outer peripheral surface of the sintered body, and a secondary sizing step in which the cylindrical portion and the enlarged diameter portion are formed on the inner peripheral surface of the sintered body. A method for producing a sintered oil-impregnated bearing according to claim 6. In the forming step, a large diameter portion and a small diameter portion are provided on the outer peripheral surface of the green compact,
By sintering the green compact in the sintering step, the sintered body having a large diameter portion and a small diameter portion on the outer peripheral surface is obtained,
The method for producing a sintered oil-impregnated bearing according to claim 5, wherein the outer peripheral surface of the sintered body is formed into a straight cylindrical surface in the sizing step.

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