JP6625333B2 - Manufacturing method of sintered bearing and sintered bearing - Google Patents

Description

  The present invention relates to a method for manufacturing a sintered bearing and a sintered bearing.

  Sintered bearings are usually used with their internal pores impregnated with lubricating oil.In this case, the lubricating oil impregnated into the internal pores is filled with the shaft along with the relative rotation with the shaft inserted in the inner periphery. Oozes into the sliding part. Then, the oozed lubricating oil forms an oil film, and the shaft is rotatably supported by the oil film. Such a sintered bearing (sintered oil-impregnated bearing) is used, for example, by being incorporated in a power window power transmission mechanism for opening and closing a window glass of a vehicle.

  As shown in FIG. 13, for example, the power window power transmission mechanism 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 meshing with the worm gear 63. , The rotational power input to the shaft 62 from the motor 61 is transmitted to the wheel gear 64 via the worm gear 63 in a reduced state, and further transmitted to a window glass opening / closing mechanism (not shown). The shaft 62 is rotatably supported by a housing 66 by a plurality of bearings 65 spaced apart in the axial direction. As the bearing 65 that supports the shaft 62, a sintered bearing (sintered oil-impregnated bearing) is preferably used.

  In the power transmission mechanism shown in FIG. 13, a load F in a direction perpendicular to the shaft is applied to a part (a part in the longitudinal direction) of the shaft 62 due to the engagement of the worm gear 63 and the wheel gear 64, and thus the shaft 62 is bent. In this case, a part of the shaft 62 relatively rotates with respect to the bearing 65 while being inclined with respect to the axis, so that the outer peripheral surface of the shaft 62 locally slides on the inner peripheral surface (bearing surface) of the bearing 65. However, problems such as wear of the bearing surface and generation of abnormal noise may occur.

  Therefore, in the power transmission mechanism as described above, for example, a sintered bearing as disclosed in Patent Literature 1 below, specifically, a cylindrical portion and an axially one side of the cylindrical portion on the inner peripheral surface. The use of a sintered bearing having a radially enlarged portion (one-side radially enlarged portion) that is provided adjacent to and that gradually increases in diameter toward one side in the axial direction is being studied. In other words, if the above-described sintered bearing is incorporated in the power transmission mechanism with the enlarged diameter portion disposed on the side closer to the worm gear 63, the outer peripheral surface of the shaft 62 is sintered even if the shaft 62 is partially bent. It can be supported by the enlarged diameter portion of the coupling bearing. Therefore, stress concentration on the inner peripheral surface of the sintered bearing can be reduced, and occurrence of the above-mentioned various problems can be prevented as much as possible.

  The above-described sintered bearing having a cylindrical portion and an enlarged diameter portion on the inner peripheral surface is obtained by sizing the inner peripheral surface of a cylindrical sintered body, for example, as described in Patent Document 2 below. be able to. Specifically, first, a cylindrical portion forming surface corresponding to the shape of the cylindrical portion provided on the first core rod is pressed against the inner peripheral surface of the sintered body (a region of the inner peripheral surface where the cylindrical portion is to be formed). A cylindrical portion is formed, and then a large-diameter portion forming surface corresponding to the shape of the large-diameter portion provided on the second core rod is pressed against a region of the inner peripheral surface of the sintered body where the large-diameter portion is to be formed (gradually). Press in) to form the enlarged diameter part.

Japanese Utility Model Publication No. 3-73721 JP 2004-308683 A

  As described above, in order to accurately support the shaft 62 which may rotate relative to the axis (partly in the longitudinal direction) with respect to the axis, the sintered bearing is provided on the inner peripheral surface. It is necessary to form each of the cylindrical portion and the enlarged diameter portion with high accuracy, and also to form the boundary portion between the cylindrical portion and the enlarged diameter portion with high accuracy. In addition, since sintered bearings are mass-produced parts, it is desirable that they can be manufactured as inexpensively as possible.

  However, when the cylindrical portion and the enlarged diameter portion are individually molded as in Patent Literature 2, in particular, as the enlarged diameter molding surface of the second core rod is gradually pushed into the inner peripheral surface of the sintered body, The flesh of the sintered body moves toward the center in the axial direction of the sintered body (front side in the moving direction of the second core rod), and finally becomes convex near the boundary between the cylindrical portion and the enlarged diameter portion. A ridge is easily formed. In this case, there are inconveniences such as the position of the boundary between the two portions not being constant (variation between individuals), and the roundness (cylindricity) of the cylindrical portion being out of order. I do. Therefore, in order to be able to support the shaft 62 with high precision, additional processing for finishing the inner peripheral surface of the sintered body with high precision is required, and the manufacturing cost increases.

  In view of the above circumstances, an object of the present invention is to provide a low cost sintered bearing that can accurately support a shaft that may rotate relatively in an inclined state with respect to an axis for a long period of time. And

  The object described above is to provide a sintering apparatus having, on an inner peripheral surface thereof, a cylindrical portion having a constant diameter and an enlarged portion which is disposed adjacent to one side in the axial direction of the cylindrical portion and gradually increases in diameter toward one side in the axial direction. A method of manufacturing a coupling bearing, wherein, when sizing a cylindrical sintered body, a cylindrical part forming surface corresponding to a cylindrical part shape and an enlarged part forming surface corresponding to a shape of an enlarged part are axially oriented. The molding surface of the cylindrical portion of the sizing core provided in a row is pressed into the inner peripheral surface of the sintered body from one side in the axial direction, and then the outer peripheral surface of the sintered body is constrained by a cylindrical die. A method of manufacturing a sintered bearing, wherein a cylindrical portion and an enlarged diameter portion are formed on the inner peripheral surface of the sintered body by pressing the enlarged diameter portion forming surface against the inner peripheral surface of the sintered body. Can be achieved by:

  According to such a manufacturing method, the cylindrical portion and the enlarged diameter portion to be provided on the inner peripheral surface of the sintered bearing are provided with the cylindrical portion forming surface and the enlarged diameter portion forming surface corresponding to these shapes connected in the axial direction. The sizing core is molded using the sizing core, and the enlarged diameter portion is formed such that the outer peripheral surface of the sintered body is constrained by the die, and the inner peripheral surface of the sintered body (the forming region of the cylindrical portion of the inner peripheral surface). Is constrained by the cylindrical portion forming surface of the sizing core. In this case, even if the movement of the meat occurs in the peripheral portion of the sintered body along with the pressing (pressing) of the molding surface of the enlarged diameter portion of the sizing core, the meat is not moved on the front side in the moving direction of the sizing core (on the side of the cylindrical portion). Instead, it moves mainly toward the center in the radial direction (thickness direction) of the sintered body. For this reason, the cylindrical portion, the enlarged diameter portion, and the boundary portion between the two portions (in short, the entire region of the inner peripheral surface of the sintered bearing that is involved in supporting the shaft) can be finished to the target shape in one step. . Therefore, regardless of whether or not the shaft is inclined with respect to the axis, a sintered bearing that can accurately support the shaft over a long period of time can be obtained at low cost.

  In the above configuration, it is preferable to press the enlarged-diameter portion forming surface of the sizing core into a region where the cylindrical portion forming surface slides with the press-fit of the cylindrical portion forming surface of the sizing core, of the inner peripheral surface of the sintered body. . With this configuration, the enlarged diameter portion is pressure-formed (compression molded) in the inner peripheral surface of the sintered body that has been crushed by sliding with the sizing core. Can easily obtain a sintered bearing in which the surface porosity is smaller than the surface porosity of the cylindrical portion. In this case, since the pressure (rigidity) of the oil film formed between the enlarged diameter portion and the outer peripheral surface of the shaft to be supported can be increased, the shaft that relatively rotates while being inclined with respect to the axis can be accurately supported. It becomes possible.

  The constraint on the outer peripheral surface of the sintered body by the die is, for example, to press-fit the cylindrical part forming surface of the sizing core to the inner peripheral surface of the sintered body and then press-fit the (outer peripheral surface of) the sintered body to the die. Can be performed. This makes it possible to easily obtain a sintered bearing in which the surface porosity of the outer peripheral surface is reduced. In addition to this procedure, for example, by simultaneously pressing the cylindrical molding surface of the sizing core into the inner peripheral surface of the sintered body and pressing the sintered body into the die, The surface can be constrained by a die.

  Further, the above object, on the inner peripheral surface, a cylindrical portion having a constant diameter, disposed on one side in the axial direction of the cylindrical portion, a one-side enlarged portion gradually increases in diameter toward one side in the axial direction, A method for manufacturing a sintered bearing comprising: a cylindrical portion, which is disposed adjacent to the other side in the axial direction of the cylindrical portion, and gradually expands in diameter toward the other side in the axial direction. At the time of sizing, the other side of the first sizing core having the other-side enlarged-diameter portion forming surface corresponding to the shape of the other-side enlarged-diameter portion while the outer peripheral surface of the sintered body is constrained by the cylindrical first die. By pressing the molding surface of the side enlarged diameter portion against the inner peripheral surface of the sintered body, primary sizing for molding the other enlarged diameter portion on the inner peripheral surface of the sintered body is performed, and then the cylinder corresponding to the shape of the cylindrical portion is formed. Second sigmine provided with a portion forming surface and a one-side enlarged-diameter portion forming surface corresponding to the shape of the one-side enlarged portion in the axial direction. The cylindrical portion forming surface of the core is pressed into the inner peripheral surface of the sintered body from one side in the axial direction, and then, the outer peripheral surface of the sintered body is constrained by the cylindrical second die to one side of the second sizing core. A sintered bearing characterized in that a secondary sizing for forming a cylindrical portion and a one-side enlarged portion on the inner peripheral surface of the sintered body is performed by pressing the enlarged diameter forming surface against the inner peripheral surface of the sintered body. Can also be achieved by employing the manufacturing method described above.

  That is, if the secondary sizing is performed in the above aspect, the cylindrical portion and the one-side enlarged portion formed by the secondary sizing, and further, the boundary portion between both portions, can be finished to the target shape only by the secondary sizing. it can.

  In the secondary sizing, the inner peripheral surface of the sintered body slides along the cylindrical portion forming surface of the second sizing core along with the press-fitting of the cylindrical portion forming surface, and the one-side enlarged diameter portion of the second sizing core. The molding surface can be pressed. With this configuration, the one-side enlarged-diameter portion is press-molded in the inner peripheral surface of the sintered body, which is press-molded in a region crushed by sliding with the one-side molding surface of the second sizing core. A sintered bearing in which the surface porosity of the side enlarged diameter portion is smaller than the surface porosity of the cylindrical portion can be easily obtained.

  During the execution of the primary sizing, the area of the inner peripheral surface of the sintered body where the cylindrical portion and the one-side enlarged-diameter portion are to be formed and the first sizing core can be kept in a non-contact state. With this configuration, the surface porosity of the cylindrical portion and the one-side enlarged portion formed by the secondary sizing becomes extremely small, and the amount of the lubricating oil oozing from the surface opening of the cylindrical portion and the one-side enlarged portion is reduced. Can be prevented as much as possible.

  If the restraining force of the outer peripheral surface of the sintered body by the first die is relatively reduced and the restraining force of the outer peripheral surface of the sintered body by the second die is relatively increased, the one-side enlarged portion and the other-side enlarged portion are provided. It is possible to easily obtain a sintered bearing having a difference in surface porosity between the diameter and the diameter.

  On the inner peripheral surface, a cylindrical portion, as a sintered body subjected to sizing to obtain a sintered bearing having a one-side enlarged diameter portion and the other-side enlarged diameter portion, the cylindrical portion of the inner peripheral surface, one It is also possible to use a region in which the forming area of the side-side enlarged portion and the other-side enlarged portion is formed on a cylindrical surface having a constant diameter, or of the inner peripheral surface, the forming of the cylindrical portion and the one-side enlarged portion. A region in which the region is formed on a cylindrical surface having a constant diameter and a region in which the other-side enlarged-diameter portion is to be formed may be formed on a tapered surface whose diameter is gradually increased toward the other side in the axial direction may be used.

  In addition, in order to achieve the above object, in the present application, a cylindrical portion having a constant diameter is provided on the inner peripheral surface, and the cylindrical portion is arranged adjacent to one side in the axial direction of the cylindrical portion, and the diameter gradually increases toward one side in the axial direction. In the case of a sintered bearing formed by sizing a cylindrical sintered body with a cylindrical portion and an enlarged diameter portion having a diameter portion, the cylindrical portion is formed by squeezing with a sizing core to form a surface. The sintered bearing is characterized in that the part is a surface that is compression molded through ironing with a sizing core.

  Furthermore, in order to achieve the above object, in the present application, on the inner peripheral surface, a cylindrical portion having a constant diameter, and disposed adjacent to one side in the axial direction of the cylindrical portion, while gradually increasing in diameter toward one side in the axial direction. A side-side enlarged portion and a second-side enlarged portion that is disposed adjacent to the other side in the axial direction of the cylindrical portion and gradually increases in diameter toward the other side in the axial direction, and includes a cylindrical portion, one-side enlarged portion, and the other side. In a sintered bearing in which the enlarged diameter portion is formed by sizing a cylindrical sintered body, the enlarged diameter portion on the other side is compression-molded without passing through the sizing core, and the cylindrical portion is sized. A sintered bearing characterized in that the surface is formed by pressing with a core, and the one-side enlarged-diameter portion is a surface formed by compression through ironing with a sizing core.

  As described above, according to the present invention, regardless of whether the shaft relatively rotates in a state parallel to the axis or in a state where the shaft is inclined with respect to the axis, the shaft is elongated. A sintered bearing that can be accurately supported over a period can be obtained at low cost.

It is an outline sectional view of the sintered bearing concerning one embodiment of the present invention. It is a figure which shows a partial diffusion alloy powder typically. The upper part is a side view of the flat copper powder, and the lower part is the plan view. It is a schematic sectional drawing of a compact. FIG. 3 is a partially enlarged cross-sectional view of a molding die during molding of a green compact. FIG. 3 is a schematic sectional view of a primary sizing mold used in a primary sizing step. (A) is a schematic sectional view showing a stage immediately after the start of primary sizing, (b)-(d) is a schematic sectional view showing an intermediate stage of primary sizing, and (e) is a completion stage of primary sizing. FIG. It is a schematic sectional drawing of the secondary sizing die used in a secondary sizing process. (A) is a schematic sectional view showing a stage immediately after the start of secondary sizing, (b)-(d) is a schematic sectional view showing an intermediate stage of secondary sizing, and (e) is a secondary sizing. FIG. 9 is a schematic cross-sectional view showing a completion step of FIG. (A) is an enlarged view schematically showing a surface layer portion of the sintered body before sizing, (b) is an enlarged view schematically showing the surface of a cylindrical portion, and (c) is an enlarged view of one side enlarged diameter portion. An enlarged view schematically showing the surface, and FIG. 4D is an enlarged view schematically showing the surface of the other-side enlarged diameter portion. It is a schematic sectional drawing of the green compact which concerns on other embodiment. It is an outline sectional view of the sintered bearing concerning other embodiments. It is a schematic sectional drawing of the power transmission mechanism for power windows.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a sintered bearing 1 according to an embodiment of the present invention. The sintered bearing 1 is a bearing used to support the shaft 62 in a power window power transmission mechanism shown in FIG. 13, for example. Specifically, the sintered bearing 1 is provided on both sides of the worm gear 63 in the axial direction of the shaft 62. It is used as a pair of bearings 65 that support the parts. In the following description of the sintered bearing 1, the side relatively closer to the worm gear 63 in the axial direction is referred to as "one axial side", and the opposite side is referred to as "the other axial side".

The sintered bearing 1 is made of a cylindrical sintered body, and is used in a state where internal pores are impregnated with lubricating oil. As the lubricating oil, for example, an ester lubricating oil is used, and among them, those having a kinematic viscosity of 30 mm ² / sec or more and 200 mm ² / sec or less are preferably used. The sintered body constituting the sintered bearing 1 is, for example, a copper-based, iron-based, or copper-iron-based metal sintered body. In the present embodiment, a copper-iron-based metal sintered body containing copper and iron as main components is used. It is considered as union.

  The sintered bearing 1 is disposed on the inner peripheral surface adjacent to the cylindrical portion 2 and one side in the axial direction (the right side in FIG. 1) of the cylindrical portion 2, and the one side expanded gradually toward one side in the axial direction. It has a diameter portion 3 and an other-side enlarged portion 4 which is arranged adjacent to the other side in the axial direction of the cylindrical portion 2 (the left side in FIG. 1) and gradually increases in diameter toward the other side in the axial direction. When this sintered bearing 1 is used in the power window power transmission mechanism shown in FIG. 13, the cylindrical portion 2 has a shaft 62 (see a solid line in FIG. 1) that rotates without bending (a state parallel to the axis). The one-side enlarged-diameter portion 3 is bent (a state inclined with respect to the axis) when the worm gear 63 receives a force F (see FIG. 13) from the worm wheel 64. And functions as a bearing surface that supports the shaft 62 (see the two-dot chain line in FIG. 1) that rotates. On the other hand, the other-side enlarged diameter portion 4 does not function as a bearing surface regardless of whether or not the shaft 62 is bent. In short, the shaft 62 does not slide with respect to the other-side enlarged diameter portion 4 of the sintered bearing 1.

  In this embodiment, the one-side enlarged diameter portion 3 and the other-side enlarged diameter portion 4 are inclined at the same angle with respect to the axis, and the inclination angle is, for example, 0.5 ° to 3 ° (preferably 1 ° to 3 °). 2 °). In FIG. 1, the inclination angles of the enlarged diameter portions 3 and 4 are exaggerated for easy understanding.

  The cylindrical portion 2, the one-side enlarged diameter portion 3 and the other-side enlarged diameter portion 4 provided on the inner peripheral surface of the sintered bearing 1 have different surface porosity. Here, the surface porosity of the one-side enlarged portion 3 is smaller than the surface porosity of the cylindrical portion 2, and the surface porosity of the cylindrical portion 2 is smaller than the surface porosity of the other enlarged portion 4. . That is, the surface porosity of each of the portions 2 to 4 provided on the inner peripheral surface of the sintered bearing 1 is the smallest at the one-side enlarged portion 3 and the largest at the other-side enlarged portion 4. The outer peripheral surface of the sintered bearing 1 is formed as a cylindrical surface having a constant diameter, and the surface porosity of the outer peripheral surface is substantially the same as the surface porosity of the cylindrical portion 2. Although details will be described later, the cylindrical portion 2, the one-side enlarged diameter portion 3 and the other-side enlarged diameter portion 4, and the outer peripheral surface of the sintered bearing 1 provided on the inner peripheral surface of the sintered bearing 1 are all cylindrical. By sizing the sintered body, a predetermined shape and surface porosity are finished.

  In the above configuration, when the shaft 62 is rotated by driving the motor 61 (see FIG. 13), the lubricating oil impregnated into the internal pores of the sintered bearing 1 is condensed with the inner peripheral surface of the sintered bearing 1. Bleeds between (the bearing gap of) 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 of the sintered bearing 1 and the outer peripheral surface of the shaft 62, and the shaft 62 is rotatably supported via the oil film. On the other hand, when the deflection of the shaft 62 increases, the shaft 62 is rotatably supported via an oil film formed between the one-side enlarged diameter portion 3 of the sintered bearing 1 and the outer peripheral surface of the shaft 62.

  Further, a seal portion (taper seal portion) capable of holding a lubricating oil surface may be formed between the other-side enlarged diameter portion 4 of the sintered bearing 1 and the outer peripheral surface of the shaft 62 opposed thereto. it can. Therefore, it is possible to effectively prevent the lubricating oil interposed between the inner peripheral surface of the sintered bearing 1 and the outer peripheral surface of the shaft 62 from flowing out of the bearing through the opening on the other axial side of the sintered bearing 1. Can be prevented.

  Further, as described above, since the surface porosity of the other-side enlarged-diameter portion 4 is larger than the surface porosity of the cylindrical portion 2 and the one-side enlarged-diameter portion 3, when the shaft 62 rotates, the other-side enlarged portion is increased. The lubricating oil intervening in the area facing 4 can be drawn into the internal pores of sintered bearing 1 through the surface opening of other-diameter enlarged portion 4. When the shaft 62 rotates, the lubricating oil drawn into the internal pores again seeps into the sliding portion (bearing gap) with the shaft 62 via the surface openings of the cylindrical portion 2 and the one-side enlarged portion 3. As described above, in the sintered bearing 1 of the present embodiment, the lubricating oil can flow back and forth (flow and circulate) between the internal pores and the bearing gap, so that the characteristic change of the lubricating oil is prevented as much as possible. Thus, the shaft 62 can be stably supported over a long period of time.

  The sintered bearing 1 having the above configuration is manufactured through a mixing step, a compression molding step, a sintering step, a sizing step, and an oil impregnation step in this order. Hereinafter, each step will be described in detail.

[Mixing process]
The mixing step is a step of obtaining a compacting powder (raw material powder) by mixing a plurality of types of powders. In the present embodiment, the main raw material powder, the low melting point metal powder, and the solid lubricant powder are used. Are mixed to obtain a raw material powder. Various molding aids, for example, a lubricant for improving releasability are added to the raw material powder as needed. It should be noted that the raw material powder described below is merely an example, and the type and the mixing ratio of the powder included in the raw material powder are appropriately changed according to the required characteristics of the sintered bearing 1 and the like.

  The main raw material powder is a metal powder containing copper and iron. In this embodiment, a mixture of partially diffused alloy powder and flat copper powder is used as the main raw material powder. As shown in FIG. 2, as the partial diffusion alloy powder 11, for example, an Fe—Cu partial diffusion alloy powder in which a large number of copper powders 13 are partially diffused on the surface of an iron powder 12 is used. An Fe-Cu alloy is formed in the diffusion portion of the partially diffused alloy powder 11, and this alloy portion has a crystal structure in which iron atoms 12a and copper atoms 13a are mutually bonded and arranged (enlarged in FIG. 2). See figure).

  Known iron powders such as reduced iron powder and atomized iron powder can be used as the iron powder 12 constituting the partial diffusion alloy powder 11, and in this embodiment, a spongy (porous) having internal pores is used. And use reduced iron powder with excellent oil-impregnating properties. Further, as the copper powder 13, for example, electrolytic copper powder, atomized copper powder, or the like can be used. In the present embodiment, the surface has many irregularities and the whole particle has an irregular shape approximated to a sphere. Atomized copper powder with excellent moldability is used. As the copper powder 13, a powder having a smaller particle size than the iron powder 12 is used. The proportion of copper in the partial diffusion alloy powder 11 is, for example, 10 to 30 wt% (preferably 22 to 26 wt%).

The flat copper powder is obtained by milling (Stamping) raw copper powder made of water atomized powder or the like to flatten. As shown in FIG. 3, as the flat copper powder 14, each particle has 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). Things are mainly used. “Length” and “thickness” referred to herein mean the maximum geometric dimensions of each particle of the flat copper powder 14. The apparent density of the flat copper powder 14 is set to 1.0 g / cm ³ or less. It is preferable to apply a fluid lubricant to the flat copper powder 14 in advance in order to enhance the adhesion to the molding surface of the molding die (the surface defining the cavity). The fluid lubricant may be adhered to the flat copper powder 14 before filling the raw material powder into the mold, preferably before mixing the flat copper powder 14 with other powders, more preferably grinding the raw copper powder. At the stage of crushing, it is attached to the raw copper powder. Fatty acids, especially linear saturated fatty acids, specifically stearic acid, can be used as the fluid lubricant.

  As the low melting point metal powder 15 (see FIG. 5), for example, a powder of a metal having a lower melting point than copper, such as tin, zinc, and phosphorus, is used, and among these, tin that causes less evaporation during sintering is preferable. As the low melting point metal powder 15, a powder having a smaller particle diameter than the partial diffusion alloy powder 11 is used. Since these low-melting metal powders 15 have high wettability to copper, when a sintering step described later is performed, first, the low-melting metal (tin in this embodiment) melts to wet the surface of the copper powder, Diffuses the copper and melts the copper. Then, since liquid phase sintering proceeds due to alloying of the molten copper and the low melting point metal, the bonding strength between iron particles, between iron particles and copper particles, and between copper particles is enhanced.

  The solid lubricant powder is mainly added to reduce the frictional force between the shaft 62 and the sintered bearing 1, and for example, graphite powder is used. As the graphite powder, it is preferable to use flaky graphite powder having good adhesion to the flat copper powder 14. As the solid lubricant powder, for example, molybdenum disulfide powder can be used in addition to the graphite powder. If the solid lubricant powder is added, the frictional force between particles constituting the raw material powder and the frictional force between the raw material powder and the molding die are reduced, so that the compactability of the green compact is improved.

  The compounding ratio of each powder in the raw material powder is, for example, 75 to 90% by weight of Fe-Cu partial diffusion alloy powder 11, 8 to 20% by weight of flat copper powder 14, and 0.8% of tin powder as low melting point metal powder 15. To 6.0 wt%, and the graphite powder can be 0.5 to 2.0 wt%.

[Compression molding process]
In the compression molding step, the green compact 20 shown in FIG. 4 is formed by filling the raw material powder obtained in the above mixing step into a cavity of a molding die and compressing it. In the present embodiment, the inner peripheral surface of the green compact 20 is formed as a cylindrical surface with a constant diameter, and the outer peripheral surface of the green compact 20 is formed with chamfers formed at the outer peripheral edges at both ends of the green compact 20. Except for a cylindrical surface having a constant diameter.

  Here, among the metal powders contained in the raw material powder used in the present embodiment, the apparent density of the flat copper powder 14 is the smallest. The flat copper powder 14 has a thin plate shape as shown in FIG. 3 and has a large wide surface area per unit weight. Therefore, when the raw material powder is filled into the cavity of the molding die, the flat copper powder 14 is applied to the molding surface of the molding die under the influence of the adhesive force of the fluid lubricant adhered to the surface thereof and further the Coulomb force. Adhere to. More specifically, as shown in FIG. 5, the flat copper powder 14 has the wide surface 14 a facing the molding surface 24 of the molding die 23 and adheres over the entire area of the molding surface 24 in a state of layering. . On the other hand, in a region (region on the center side of the cavity) inside the layered structure of the flat copper powder 14, the partial diffusion alloy powder 11, the flat copper powder 14, the low melting point metal powder (tin powder) 15, and not shown. The dispersion state of the graphite powder is uniform throughout. Then, the compact 20 after molding keeps the distribution state of each powder as described above almost as it is.

[Sintering process]
In the sintering step, the green compact 20 is sintered to obtain a sintered body 30 (see FIG. 6) in which adjacent metal powders (particles) are combined. In the present embodiment, the inner peripheral surface of the sintered bearing 1 obtained by sizing the sintered body 30 can be formed as a copper-rich surface in which the copper structure is dominant (the maximum area ratio of copper). The sintering conditions are set so that the iron structure of the sintered body 30 has a two-phase structure of a ferrite phase and a pearlite phase. If the bearing surface is formed as a copper-rich surface as described above, it is possible to obtain a sintered bearing 1 excellent in slidability with the shaft 62, and to change the iron structure into a two-phase structure of a ferrite phase and a pearlite phase. If so, the hard pearlite phase contributes to the improvement of the wear resistance of the bearing surface of the sintered bearing 1, so that the durability life of the sintered bearing 1 can be improved. However, if the proportion of the pearlite phase in the iron structure becomes excessive, the aggressiveness of the pearlite phase on the shaft 62 increases, so that the shaft 62 is easily worn. Therefore, it is preferable to suppress the pearlite phase to such an extent that it is scattered at the grain boundaries of the ferrite phase.

  Here, if the sintering temperature (atmosphere temperature in the sintering furnace) is set to, for example, a temperature exceeding 900 ° C., the carbon in the graphite powder contained in the compact 20 reacts with iron, and a pearlite phase is required. It is formed as described above. Furthermore, if the sintering temperature is set to a high temperature (approximately 1100 ° C. or higher) which is generally adopted when obtaining a copper-iron-based sintered body, the sintering causes Since the existing flat copper powder 14 is melted and copper is drawn into the green compact 20 (sintered body 30), it is difficult to obtain a copper-rich bearing surface. On the other hand, as described above, in the present embodiment, the low-melting point metal powder 15 contained in the green compact 20 is melted and liquid phase sintering is advanced to secure the bonding strength between the particles. It is necessary to set the lower limit of the sintering temperature to a temperature higher than the melting point of the low melting point metal.

  In view of the above, in the present embodiment, the sintering temperature is set to about 820 ° C. to 900 ° C., and the green compact 20 is sintered in a gas atmosphere containing carbon (for example, natural gas or RX gas) as a furnace atmosphere. . If the green compact 20 is sintered under such sintering conditions, first, because the sintering temperature is sufficiently lower than the melting point of copper, the sintered body 30 having the copper-rich bearing surface ( A sintered bearing 1) can be obtained, and has an iron structure appropriately containing a pearlite phase due to carbon contained in a gas used during sintering being diffused into iron to form a pearlite phase. A sintered body 30 can be obtained.

[Sizing process]
In this sizing step, sizing is performed on the sintered body 30 to finish the inner and outer peripheral surfaces of the sintered body 30 into a predetermined shape (finished product shape). In the present embodiment, the sizing process is performed in two stages, a primary sizing process and a secondary sizing process. Hereinafter, each sizing step will be described in detail with reference to the drawings.

  In the primary sizing step, the other-side enlarged diameter portion 4 is compression-molded on the inner peripheral surface 30 a of the sintered body 30. As shown in FIG. 6, the primary sizing mold 40 used in this step has a die 41 as a first die, a core 42 as a first sizing core, an upper punch 43 and a lower punch 44 which are coaxially arranged. The core 42, the upper punch 43 and the lower punch 44 can be moved up and down by a drive mechanism (not shown).

The inner peripheral surface of the die 41 is formed as a cylindrical surface having a constant diameter. Inner diameter d ₄ of the die 41, while the sintered body 30 can be smoothly introduced into the inner periphery of the die 41, at the time of compression molding the other side enlarged diameter portion 4 [FIG 7 (d) Reference sintered 30 is set to a dimension capable of restraining the outer peripheral surface. To achieve this, the inner diameter d ₄ of the die 41 is equal to, or is slightly larger set the outer diameter d ₂ of the sintered body 30. Specifically, setting the dimensional difference between the outer diameter _{d 2} of the inner diameter _{d 4} and sintered 30 of the die 41, to the extent for example 10 [mu] m or less _{(0μm ≦ d 4 -d 2 ≦} 10μm).

The core 42 has a second-side enlarged-diameter portion forming surface 42 a (hereinafter, also simply referred to as “molding surface 42 a”) corresponding to the shape of the other-side enlarged-diameter portion 4, and a constant diameter provided continuously below the molding surface 42 a. Cylindrical surface 42b. Outer diameter d ₃ of the cylindrical surface 42b, even at the time of compression molding of the other side enlarged diameter portion 4 [FIG 7 (d) Reference is set to a dimension that is not in contact with the inner circumferential surface 30a of the sintered body 30 . In other words, the outer diameter d ₃ of the cylindrical surface 42b of the core 42 is set sufficiently smaller than the inner diameter d ₁ of the sintered body 30.

  In the primary sizing mold 40 having the above configuration, first, as shown in FIG. 6, the sintered body 30 is placed on the upper end surface of the lower punch 44 on the same plane as the upper end surface of the die 41, As shown in FIG. 7A, the core 42 and the upper punch 43 are moved downward to insert the cylindrical surface 42 b of the core 42 into the inner periphery of the sintered body 30. At this time, from the dimensional relationship described above, the inner peripheral surface 30a of the sintered body 30 and the cylindrical surface 42b of the core 42 face each other with a radial gap therebetween.

  Next, as shown in FIG. 7B, the upper punch 43 is moved downward, the sintered body 30 is sandwiched in the axial direction by the upper punch 43 and the lower punch 44 (in the axial direction of the sintered body 30). 7 (c), the core 42, the upper punch 43, and the lower punch 44 are moved downward integrally to form the sintered body 30 on the inner periphery of the die 41, as shown in FIG. Is introduced. After the sintered body 30 is introduced into the inner periphery of the die 41, the core 42 is further moved down as shown in FIG. 7D, and the molding surface 42a is gradually pushed into the inner periphery of the sintered body 30. Along with this, the sintered body 30 expands and deforms in the radial direction, the outer peripheral surface of the sintered body 30 is restrained by the inner peripheral surface of the die 41, and a part of the inner peripheral surface 30a of the sintered body 30 is cylindrical. Is pressed against the molding surface 42 a of the core 42. Thereby, a part of the cylindrical region of the inner peripheral surface 30a of the sintered body 30 is deformed following the forming surface 42a, and the other-side enlarged diameter portion 4 is formed. While the other-side enlarged-diameter portion 4 is being compression-molded on the inner peripheral surface 30a of the sintered body 30, the remaining cylindrical region (the cylindrical portion 2 and the one-side enlarged portion 3) of the inner peripheral surface 30a of the sintered body 30 is also formed. Of the core 42 and the cylindrical surface 42b of the core 42 are kept in a non-contact state. Therefore, in the primary sizing step, only the other-side enlarged diameter portion 4 is compression-molded on the inner peripheral surface 30 a of the sintered body 30.

  The sintered body 30 in which the other-side enlarged-diameter portion 4 is formed on the inner peripheral surface as described above is released from the primary sizing die 40 (see FIG. 7E). The release of the sintered body 30 is performed, for example, by discharging the sintered body 30 from the die 41 by integrally moving the core 42, the upper punch 43, and the lower punch 44, and then further moving the core 42 and the upper punch 43. This is done by moving up. Accordingly, the inner diameter and the outer diameter of the sintered body 30 are enlarged by springback, so that the core 42 is smoothly extracted.

  As described above, in the primary sizing step, only the other-side enlarged diameter portion 4 is formed on the inner peripheral surface 30 a of the sintered body 30. Therefore, the surface porosity of the inner peripheral surface of the sintered body subjected to the primary sizing (hereinafter, this sintered body is also referred to as “sintered body 30 ′”) depends on the area where the other-side enlarged-diameter portion 4 is formed. , And relatively large in the other cylindrical region (the region where the cylindrical portion 2 and the one-side enlarged portion 3 are to be formed). The other-side enlarged diameter portion 4 is formed by pressing the tapered other-side enlarged-diameter portion forming surface 42a against the inner peripheral surface 30a of the cylindrical sintered body 30. The surface porosity of the radial portion 4 in the axial range is smallest at the end on the other side in the axial direction (the side away from the cylindrical portion 2), and gradually increases toward one side in the axial direction. Further, from the above-described embodiment of the primary sizing, the other-side enlarged diameter portion 4 is a surface formed by compression molding without being squeezed by the core 42 (without sliding with the core 42).

  In the secondary sizing step, the cylindrical portion 2 and the one-side enlarged diameter portion 3 are formed on the inner peripheral surface of the sintered body 30 '. As shown in FIG. 8, the secondary sizing mold 50 used in this step has a die 51 as a second die coaxially arranged, a core 52 as a second sizing core, an upper punch 53 and a lower punch 54. The core 52, the upper punch 53 and the lower punch 54 can be moved up and down by a drive mechanism (not shown).

The inner peripheral surface of the die 51 is formed as a cylindrical surface having a constant diameter. Inner diameter _{d 14} of the die 51, the sintered body 30 is set sufficiently smaller than the outer diameter _{d 12} of ', both dimensional difference _(d 12 _{-d 14)} is, for example, about 50~60μm You.

The core 52 has a cylindrical portion forming surface 52a corresponding to the shape of the cylindrical portion 2 and a one-side enlarged-diameter portion forming surface 52b which is provided continuously above the cylindrical portion-formed surface 52a and corresponds to the shape of the one-side enlarged portion 3. And Outer diameter d ₁₃ of the cylindrical portion forming surface 52a is larger than the inner diameter d ₁₁ of 'cylindrical inner peripheral surface of the (shaped region where the cylindrical portion 2 and the one-side enlarged portion 3) 30a' sintered 30 The dimensional difference (d ₁₃ -d ₁₁ ) between the two is set to, for example, about 20 μm.

  In the secondary sizing mold 50 having the above configuration, first, as shown in FIG. 8, the sintered body 30 ′ is placed on the upper end surface of the lower punch 54 on the same plane as the upper end surface of the die 51. At this time, the sintered body 30 'is placed on the secondary sizing mold 50 in an upright posture with the other-side enlarged diameter portion 4 formed in the primary sizing step facing downward. That is, the sintered body 30 ′ is arranged on the secondary sizing mold 50 with the upside down of the sintered body 30 arranged on the primary sizing mold 40.

After arranging the sintered body 30 'in the secondary sizing mold 50, the core 52 and the upper punch 53 are moved downward as shown in FIG. Insert the cylindrical part forming surface 52a. At this time, 'the relationship between the inner diameter _{d 11} of the cylindrical portion forming surface 52a of the core 52, the sintered body 30' and the outer diameter _{d 13} of the cylindrical portion forming surface 52a as described above sintered body 30 cylinder It is inserted (press-fitted) into the inner periphery of the sintered body 30 'while sliding on the inner peripheral surface 30a'. Thereby, the cylindrical inner peripheral surface 30a 'of the sintered body 30' is slightly crushed.

Next, as shown in FIG. 9B, the upper punch 53 is moved downward, and the upper body 53 and the lower punch 54 sandwich the sintered body 30 ′ in the axial direction (the shaft of the sintered body 30 ′). 9C), the core 52, the upper punch 53, and the lower punch 54 are integrally moved downward to burn the inner periphery of the die 51, as shown in FIG. The aggregate 30 'is introduced. At this time, 'on the relationship that is set sufficiently smaller than the outer diameter d ₁₂ of the sintered body 30' inside diameter d ₁₄ of the die 51 is sintered 30, the inner periphery of the outer peripheral surface thereof a die 51 It is introduced (press-fitted) into the inner periphery of the die 51 while sliding on the surface. When the sintered body 30 ′ is introduced into the inner periphery of the die 51, the sintered body 30 ′ is restricted from being elongated in the axial direction, and the cylindrical inner peripheral surface 30 a ′ is formed by the outer peripheral surface of the core 52. Being restrained. Therefore, as the sintered body 30 ′ is introduced into the inner periphery of the die 51, the outer peripheral surface of the sintered body 30 ′ is squeezed by the inner peripheral surface of the die 51. Thereby, the outer peripheral surface of the sintered body 30 'is formed, and the surface porosity of the outer peripheral surface of the sintered body 30' is reduced. When the sintered body 30 ′ is introduced into the inner periphery of the die 51, the outer peripheral surface of the sintered body 30 ′ is restrained by the die 51.

  With the outer peripheral surface of the sintered body 30 'constrained by the die 51, the core 52 is further moved down as shown in FIG. At this time, since the core 52 is pressed into the cylindrical inner peripheral surface 30a 'of the sintered body 30', the cylindrical inner peripheral surface of the sintered body 30 ' The cylindrical portion 2 is formed by squeezing a part of the cylindrical region 30a 'on the cylindrical portion forming surface 52a of the core 52. Then, as the downward movement of the core 52 further progresses, the one-side enlarged-diameter portion forming surface 52b of the core 52 is pushed into the upper inner periphery of the sintered body 30 ', and the cylindrical inner peripheral surface 30a' The upper cylindrical region is deformed following the one-side enlarged-diameter portion forming surface 52b of the core 52, and the one-side enlarged-diameter portion 3 is formed. The one-side enlarged-diameter portion 3 has a cylindrical inner periphery in a state in which the outer peripheral surface of the sintered body 30 ′ is restrained by the die 51 (further, the state in which the axial expansion deformation of the sintered body 30 ′ is restricted). Since the upper cylindrical region of the surface 30a 'is formed by further compressing the upper cylindrical region toward the outer diameter side on the one-side enlarged-diameter portion forming surface 52b, the surface porosity of the one-side enlarged portion 3 is increased. It becomes smaller than the porosity.

In this embodiment, the dimensional relationship (see FIG. 6) between the inner diameter d ₄ of the die 41 to be used outside diameter d ₂ of the sintered body 30 in which the primary sizing is applied as a primary sizing, and a secondary sizing facilities dimensional relationship between the inner diameter d ₁₄ of the die 51 to be used in the outer diameter d ₁₂ and the secondary sizing of the sintered body 30 'that is considering (see FIG. 8), whereas during compression molding of the side enlarged diameter part 3 Is larger than the restraining force of the outer peripheral surface of the sintered body when the other-side enlarged-diameter portion 4 is compression-molded. Therefore, the amount of compression of the peripheral surface of the sintered body by the one-side enlarged-diameter portion forming surface 52b of the core 52 is relatively larger than the amount of compression of the peripheral surface of the sintered body by the other-side enlarged-diameter portion molding surface 42a of the core 42. growing. As a result, the surface porosity of the one-side enlarged portion 3 can be made significantly smaller than the surface porosity of the other-side enlarged portion 4. In short, after the execution of the secondary sizing, the surface porosity of the peripheral surface of the sintered body in the one-side enlarged-diameter portion 3 is the smallest and the other-side enlarged portion 4 is the largest.

  As described above, the sintered body 30 'in which the cylindrical portion 2 and the one-side enlarged-diameter portion 3 are formed on the inner peripheral surface is released from the secondary sizing mold 50 [see FIG. 9 (e)]. . When releasing the sintered body 30 ′ from the secondary sizing mold 50, for example, the core 42, the upper punch 43, and the lower punch 44 are integrally moved upward to move the sintered body 30 ′ from the die 41. After discharging, the core 42 and the upper punch 43 are further moved up.

  When releasing the sintered body 30 ′ from the secondary sizing mold 50, the core 52 is removed from the sintered body 30 ′ by integrally moving the core 52 and the upper punch 53 upward, and thereafter, A procedure may be performed in which the lower punch 54 is moved upward to discharge the sintered body 30 ′ from the die 51. When such a procedure is adopted, the removal of the core 52 is a so-called forced removal, so that the cylindrical portion 2 is additionally wrung. As a result, the surface porosity of the cylindrical portion 2 can be further reduced. Even when the sintered body 30 'is released from the mold in such a procedure, the magnitude relationship between the surface porosity of the cylindrical portion 2 and the one-side enlarged-diameter portion 3 does not change.

[Oil impregnation process]
Although not shown in detail, in the oil impregnation step, lubricating oil (for example, an ester-based lubricating oil) is impregnated into the internal pores of the sintered body 30 ′ finished in the sizing step by a technique such as vacuum impregnation. . Thus, the sintered bearing (sintered oil-impregnated bearing) 1 shown in FIG. 1 is completed.

  In the sintered bearing 1 of the present embodiment obtained as described above, the cylindrical portion 2 and the one-side enlarged-diameter portion 3 to be provided on the inner peripheral surface of the sintered bearing 1 form the molding surfaces 52a and 52b corresponding to these shapes in the axial direction. Is formed by applying sizing (secondary sizing) to the sintered body 30 ′ using the core 52 provided in series with the main body, and the outer peripheral surface of the sintered body 30 ′ is formed by the die 52. And the inner peripheral surface of the sintered body 30 ′ (the area of the inner peripheral surface where the cylindrical portion 2 is formed) is constrained by the cylindrical portion forming surface 52 a of the core 52. In this case, even if the flesh moves in the peripheral portion of the sintered body due to the pushing of the one-side enlarged-diameter portion forming surface 52b of the core 52, the flesh moves forward in the moving direction of the core 52 (the side of the cylindrical portion 2). Instead, it moves mainly toward the center of the sintered body 30 'in the radial direction (thickness direction). Thereby, not only the cylindrical portion 2 and the one-side enlarged-diameter portion 3 but also the boundary portion between the two portions 2 and 3 (in short, the entire region of the inner peripheral surface of the sintered bearing 1 that is involved in supporting the shaft 62). The desired shape can be formed in one step. Therefore, regardless of whether or not the shaft 62 is inclined with respect to the axis, the sintered bearing 1 that can accurately support the shaft 62 over a long period of time can be manufactured and provided at low cost.

  Further, in the secondary sizing step, one side of the core 52 is moved to a region of the inner peripheral surface of the sintered body 30 ′ where the cylindrical portion forming surface 52 a slides with the press-fitting of the cylindrical portion forming surface 52 a of the core 52. The one-side enlarged-diameter portion 3 is formed by pressing the enlarged-diameter portion forming surface 52b. In short, in the sintered bearing 1 according to the present embodiment, the cylindrical portion 2 becomes a surface formed by being squeezed by the cylindrical portion forming surface 52 a provided on the core 52, and the one-side enlarged diameter portion 3 becomes the core 52. After being ironed by the cylindrical portion forming surface 52a provided on the core 52, the one-side enlarged-diameter portion forming surface 52b provided on the core 52 becomes a surface formed by compression molding.

In this case, the cylindrical portion 2, as shown schematically in FIG. 10 (b), by extending the metal structure of the sintered body surface caused by the ironing, its surface opening diameter x _2, FIG. 10 (a ) to decrease compared to the surface opening diameter x ₁ in the sintered body before sizing shown schematically (x _{1> x 2).} In addition, in the one-side enlarged diameter portion 3, as shown schematically in FIG. 10 (c), the density of the metal structure of the surface layer of the sintered body is increased due to the compression molding process in which the compression amount is larger than that in the above-described ironing process. Accordingly, its surface opening diameter _{x 3,} is smaller than the surface opening diameter _{x 2} of the cylindrical portion _{2 (x 2> x 3)} . Therefore, after the secondary sizing step, in the sintered bearing 1 in which the surface porosity of the one-side enlarged-diameter portion 3 is smaller than the surface porosity of the cylindrical portion 2, that is, in a state inclined with respect to the axis. It is possible to easily obtain the sintered bearing 1 that can accurately support the relatively rotating shaft 62.

As described above, the other-side enlarged diameter portion 4 is a surface formed by compression molding without ironing in the primary sizing, and the amount of constraint on the outer peripheral surface is limited by the amount of constraint on the outer peripheral surface of the sintered body in the secondary sizing. Since the surface is compression-molded with a relatively smaller primary sizing, the width of reduction of the surface opening diameter due to compression molding is smaller than the width of reduction of the surface opening diameter due to ironing (sliding with the core 52). Is also smaller. Therefore, as schematically shown in FIG. 10 (d), the surface opening diameter x ₄ at the other side enlarged diameter portion 4, as compared with the surface opening diameter x ₁ in the sizing (primary sizing) before sintered body decreases although, larger than the surface pore diameter _{x 2} in the cylindrical section _{2 (x 1> x 4>} x 2). Therefore, the sintered bearing 1 in which the surface porosity of the other-side enlarged diameter portion 4 of the inner peripheral surface is larger than the surface porosity of the cylindrical portion 2 and the one-side enlarged diameter portion 3 can be obtained. . And, as described above, with such a sintered bearing 1, lubricating oil is mainly supplied between the internal pores of the sintered bearing 1 and the bearing gap through the surface opening of the other-side enlarged diameter portion 4 as described above. Since it is possible to move back and forth (flow and circulate), it is possible to prevent the characteristic change of the lubricating oil as much as possible and to stably support the shaft 62 for a long period of time.

  The sintered bearing 1 according to one embodiment of the present invention and the method of manufacturing the same have been described above, but the embodiment of the present invention is not limited to this.

  For example, in the compression molding process included in the manufacturing process of the sintered bearing 1, as schematically shown in FIG. 11, a part of the inner peripheral surface 21, more specifically, the formation of the other-side enlarged diameter portion 4 is scheduled. In the region, a green compact 20 ′ having an enlarged diameter portion 22 gradually increased in diameter toward the other side in the axial direction can be formed. In this case, as long as the primary sizing is performed on the sintered body obtained by sintering the green compact 20 ′ using the primary sizing mold 40 shown in FIG. Since the amount of compression becomes relatively small, it is possible to obtain a sintered bearing in which the surface porosity of the other-side enlarged-diameter portion 4 is larger than that of the sintered bearing 1 shown in FIG. With such a sintered bearing, the amount of lubricating oil drawn in through the surface opening of the other-side enlarged diameter portion 4 can be increased.

As shown in FIG. 12 , the method for manufacturing a sintered bearing according to the present invention has only the cylindrical portion 2 and the one-side enlarged portion 3 on the inner peripheral surface, and the other-side enlarged portion 4 on the inner peripheral surface. It can also be applied to the sintered bearing 1 having no. In this case, the one-side enlarged diameter portion 3 corresponds to the “increased diameter portion” defined in the first invention according to the sintered bearing (and the method of manufacturing the same) of the present application. That is, in the sizing process when manufacturing such a sintered bearing 1, the primary sizing process described with reference to FIGS. 6 and 7 is omitted, and the secondary sizing process described with reference to FIGS. Only the steps are performed. That is, in this case, each of the die 51 as the second die and the core 52 as the second sizing core used in the secondary sizing step is the “die” defined in the first invention according to the method of manufacturing a sintered bearing of the present application. "And" sizing core ". Also, the cylindrical portion forming surface 52a and the one-side enlarged diameter portion forming surface 52b provided on the core 52 respectively correspond to the “cylindrical portion forming surface” and the “diameter enlarged portion forming surface” defined in the first invention according to the manufacturing method. Corresponding.

  In the above, the case where the sintered bearing 1 according to the present invention is applied to a power transmission mechanism for a power window has been described. However, the sintered bearing 1 according to the present invention may be used for other applications. For example, the sintered bearing 1 according to the present invention can be applied to a vibration motor that functions as a vibrator for a mobile phone or the like.

  Further, the sintered bearing 1 according to the present invention is used not only for the application in which the other-side enlarged diameter portion 4 does not function as the bearing surface, but also for the use in which the other-side enlarged diameter portion 4 functions as the bearing surface, that is, when the shaft to be supported is not used. It can also be used for sliding (contact) with the other-side enlarged diameter portion 4.

  Further, in the above embodiment, the case where the sintered bearing 1 according to the present invention is used for supporting the rotating shaft 62 has been described. However, the present invention is not limited to this. It is also possible to use the sintered bearing 1 according to the present invention for an application in which both the shaft 62 and the sintered bearing 1 are rotated.

  The present invention is not limited to the above embodiments at all, and can be implemented in various other forms without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Sintered bearing 2 Cylindrical part 3 Large diameter part on one side (large diameter part)
4 Other-side enlarged diameter portion 20 Green compact 30 Sintered body 30 'Sintered body 40 Primary sizing mold 41 Die (first die)
42 cores (first sizing core)
42a Molding surface 50 on the other-side enlarged diameter part Secondary sizing mold 51 Die (second die)
52 cores (second sizing core)
52a Cylindrical part molding surface 52b One-side enlarged diameter part molding surface (increased diameter part molding surface)
61 Motor 62 Shaft 63 Worm gear 64 Wheel gear 65 Bearing

Claims (9)

On the inner peripheral surface, there is provided a cylindrical portion having a constant diameter, and a radially increasing portion which is disposed adjacent to one axial side of the cylindrical portion and gradually expands in diameter toward one axial side. A method for manufacturing a sintered bearing in which the end on one side in the direction and the end on the other side in the axial direction of the enlarged-diameter portion match , when sizing a cylindrical sintered body,
The cylindrical portion forming surface corresponding to the shape of the cylindrical portion and the enlarged portion forming surface corresponding to the shape of the enlarged portion are connected in the axial direction. The sintered body is pressed into the inner peripheral surface of the sintered body from the side to restrain the inner peripheral surface of the sintered body by the sizing core, and restrict the axial expansion deformation of the sintered body. the sizing are relatively moved in the axial direction of the outer peripheral surface is press-fitted into the inner periphery of a cylindrical die and restraining the outer peripheral surface of the sintered body by the die, the sizing core in this state with respect to the die A sintered bearing, wherein the cylindrical portion and the enlarged diameter portion are formed on the inner peripheral surface of the sintered body by pressing the enlarged diameter portion forming surface of the core against the inner peripheral surface of the sintered body. Production method.   The inner peripheral surface of the sintered body presses the enlarged-diameter portion forming surface of the sizing core against a region where the cylindrical portion forming surface slides with the press-fitting of the cylindrical portion forming surface of the sizing core. Item 2. A method for producing a sintered bearing according to Item 1.   3. The method of manufacturing a sintered bearing according to claim 1, wherein after the cylindrical portion forming surface of the sizing core is pressed into an inner peripheral surface of the sintered body, the sintered body is pressed into the die. 4. On the inner peripheral surface, a cylindrical portion having a constant diameter, a one-side enlarged portion that is disposed adjacent to one axial side of the cylindrical portion and gradually increases in diameter toward one axial side, and an axial direction of the cylindrical portion. An end portion on one side in the axial direction of the cylindrical portion and the other end in the axial direction of the one- side enlarged portion, which is disposed adjacent to the other side and gradually increases in diameter toward the other side in the axial direction. A method of manufacturing a sintered bearing in which an end on the other side in the axial direction coincides with an end on the other side in the axial direction of the cylindrical portion and an end on the one side in the axial direction of the enlarged diameter portion on the other side. When sizing a cylindrical sintered body,
In a state where the outer peripheral surface of the sintered body is constrained by a cylindrical first die, the other sizing core of the first sizing core having the other-side enlarged-diameter portion forming surface corresponding to the shape of the other-side enlarged portion is provided. By pressing a diameter forming surface against the inner peripheral surface of the sintered body, primary sizing for forming the other-side enlarged diameter portion on the inner peripheral surface of the sintered body is performed,
Next, the cylindrical portion of the second sizing core, in which the cylindrical portion forming surface corresponding to the shape of the cylindrical portion and the one-side enlarged-diameter portion forming surface corresponding to the shape of the one-side enlarged portion are connected in the axial direction. A part forming surface is press-fitted from one side in the axial direction to the inner peripheral surface of the sintered body to restrain the inner peripheral surface of the sintered body with the second sizing core and to extend the sintered body in the axial direction. the while restrict deformation by press-fitting to the inner periphery of the second die cylindrical outer peripheral surface of the sintered body outer peripheral surface of the sintered body was restrained by the second die, the second sizing in this state By moving the core relative to the second die in the axial direction and pressing the one-side enlarged-diameter portion forming surface of the second sizing core against the inner peripheral surface of the sintered body, Performing secondary sizing to form the cylindrical portion and the one-side enlarged diameter portion on a surface Method for producing a sintered bearings.   In the secondary sizing, the second sizing core is formed in an inner peripheral surface of the sintered body in a region where the cylindrical portion forming surface slides along with the press-fitting of the cylindrical portion forming surface of the second sizing core. The method for manufacturing a sintered bearing according to claim 4, wherein the one-side enlarged diameter portion forming surface is pressed.   The first sizing core is held in a non-contact state with the area of the inner peripheral surface of the sintered body where the cylindrical portion and the one-side enlarged-diameter portion are to be formed during the execution of the primary sizing. 6. The method for producing a sintered bearing according to 4 or 5. The sintering according to any one of claims 4 to 6, wherein the binding force of the second die on the outer peripheral surface of the sintered body is larger than the binding force of the first die on the outer peripheral surface of the sintered body. Manufacturing method of bearing.   8. The inner peripheral surface of the sintered body to be sized, wherein a region where the cylindrical portion, the one-side enlarged diameter portion and the other-side enlarged diameter portion are to be formed is a cylindrical surface having a constant diameter. The method for producing a sintered bearing according to claim 1.   In the inner peripheral surface of the sintered body to be sized, the forming area of the cylindrical portion and the one-side enlarged diameter portion is a cylindrical surface having a constant diameter, and the forming area of the other-side enlarged diameter portion is in the axial direction. The method for manufacturing a sintered bearing according to any one of claims 4 to 7, wherein the sintered bearing has a tapered surface whose diameter gradually increases toward the other side.

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