Sintered bearing

Abstract

A sintered body in a cylindrical shape is formed by sintering a raw material powder mainly composed of a metal material, and contains a lubricating oil. An end portion in one axial direction is provided as a first bearing portion, and an end portion in the other axial direction is provided as a second bearing portion. A sliding surface is formed by an inner diameter surface of the first bearing portion and an inner diameter surface of the second bearing portion. An intermediate portion having a larger diameter than the inner diameter surface of the first bearing portion and the inner diameter surface of the second bearing portion is formed in a bearing inner diameter central portion. The first bearing portion, the second bearing portion, and the intermediate portion are provided with a density difference.

Description

Technical Field

[0001] This invention relates to sintered bearings. Background Technology

[0002] Sintered bearings can be used, for example, in sintered oil-impregnated bearing components for small motors. Even under conditions where the lubricant supply to bearings in motors operating at low temperatures and high speeds is not smooth, sintered bearings can achieve stable rotational speeds, thereby suppressing current values. In particular, sintered bearings are suitable for bearings in automotive cooling fan motors and the like, used in a wide temperature range from low to high temperatures.

[0003] Conventionally, bearing portions are formed at both ends of the axial direction, and an intermediate portion (avoidance portion) with an inner diameter larger than that of each bearing portion is formed between the bearing portions (Patent Document 1).

[0004] By constructing the bearing as described in Patent Document 1, the inner circumferential surface of the middle portion does not contact the rotating shaft, and the sliding area in the inner circumferential surface of the bearing bore is reduced. Therefore, compared to a sintered bearing (hereinafter referred to as a "linear bearing") in which the inner diameter of the bearing bore is formed uniformly along its entire axial length, contact between the inner circumferential surface of the bearing bore and the rotating shaft is suppressed, and the fluid resistance of the lubricant during shaft rotation is reduced, thus reducing the frictional resistance generated between the bearing bore and the rotating shaft. In other words, in the sintered bearing of Patent Document 1, the frictional resistance with the rotating shaft can be reduced, and noise can be lowered.

[0005] In particular, at least one of the bearing surfaces of a pair of bearing portions supporting a rotating shaft has multiple recesses. As a result, the portion (area) of the bearing surface with each recess does not contact the rotating shaft, thus reducing the sliding area in the bearing surface. This suppresses contact between the bearing surface and the rotating shaft, while simultaneously reducing the fluid resistance of the lubricant during shaft rotation, thereby reducing the frictional resistance generated between the bearing surface and the rotating shaft. Therefore, without reducing the axial dimension of the bearing surface, the sliding area in the inner circumferential surface of the bearing bore can be reduced, thereby suppressing the decrease in oil film strength and reducing the frictional resistance generated between the bearing surface and the rotating shaft.

[0006] Furthermore, it is shown that the lubricant contained therein is stored in each recess, and when the rotating shaft rotates, the stored lubricant is drawn out between the bearing surface and the rotating shaft, thereby reducing the coefficient of friction of the bearing surface.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 6253134 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, when pits are formed on the bearing surface, plastic processing such as shot peening, rolling, and embossing is required. This presents problems in terms of productivity and cost, such as the need for additional processing equipment and processing time, and the manufacture of tools for plastic processing with protrusions.

[0012] Therefore, in view of the above-mentioned problems, the present invention provides a sintered bearing and bearing device that have excellent lubrication performance (sliding characteristics) without requiring plastic processing such as shot peening, rolling, or stamping.

[0013] Methods for solving problems

[0014] This invention relates to a sintered bearing having a sliding surface that slides with a shaft component on the opposite side. The bearing is formed by sintering a cylindrical sintered body, which is mainly composed of metal powder, and contains lubricating oil. One axial end is designated as a first bearing portion, and the other axial end is designated as a second bearing portion. The sliding surface is formed by the inner diameter surfaces of the first and second bearing portions. An intermediate portion is formed at the center of the bearing's inner diameter, and this intermediate portion has a clearance portion with a diameter larger than that of the inner diameter surfaces of the first and second bearing portions. A density difference is provided between the first bearing portion, the second bearing portion, and the intermediate portion.

[0015] According to the sintered bearing of the present invention, by providing a clearance portion, the sliding area of ​​the shaft component relative to the sintered bearing can be reduced, thereby reducing the sliding resistance. By providing a density difference, oil is actively supplied to the direction of high density and fine pores due to capillary action. Therefore, in the sintered bearing of the present invention, a circulation path can be formed in which lubricating oil circulates from the middle portion side to the first bearing portion and from the middle portion side to the second bearing portion.

[0016] Preferably, the first bearing portion is a high-density region, the second bearing portion is a low-density region with a lower density than the high-density region, and between the high-density region and the low-density region, there is a minimum density region with a lower density than the low-density region and a density gradient region where the density increases from the minimum density region to the high-density region.

[0017] In this way, by setting a density difference, the circulation of lubricating oil from the clearance section to the first bearing section and from the clearance section to the second bearing section can be stably achieved.

[0018] The density of the first bearing section is set to be 0.08 g / cm³ higher than that of the second bearing section. 3 0.56 (g / cm³) 3The oil content of the first bearing section is 1% to 7% lower than that of the second bearing section, or the density difference between the first and second bearing sections is set to 0.08 g / cm³. 3 0.48 (g / cm³) 3 The difference in oil content is 1% to 6%, or the difference in surface opening ratio between the inner diameter surface of the first bearing part and the inner diameter surface of the second bearing part is set to 5% to 45%. By setting it in this way, a stable oil circulation can be obtained.

[0019] The present invention is a bearing device that uses the sintered bearing, wherein the first bearing portion is the output side of the motor and the second bearing portion is the opposite side of the output side of the motor.

[0020] By configuring a high-density area on the output side of the motor where sliding resistance increases, a large amount of lubricating oil can be supplied to the output side, thereby reducing the coefficient of friction of the bearing surface. Therefore, even when used over a wide temperature range, oil circulation and supply function smoothly, improving oil cut-off and achieving good sliding. Especially at low temperatures where oil viscosity increases and oil circulation and supply are difficult to achieve smoothly, oil circulation and supply still function smoothly, improving oil cut-off and achieving good sliding.

[0021] This allows the density of the first bearing portion to be 0.08 g / cm³ higher than that of the second bearing portion. 3 0.48 (g / cm³) 3 The oil content of the first bearing portion is 1% to 6% lower than that of the second bearing portion, or the density of the first bearing portion is 0.16 g / cm³ higher than that of the second bearing portion. 3 0.40 (g / cm³) 3 The oil content of the first bearing portion is 2% to 5% lower than that of the second bearing portion, or the surface opening ratio of the inner diameter surface of the first bearing portion is 5% to 45% lower than that of the inner diameter surface of the second bearing portion.

[0022] Invention Effects

[0023] In this invention, a sliding component can be provided that does not require special processing equipment, processing tools, or special plastic processing tools. By giving the sintered bearing a density tilting function, a circulation path for lubricating oil is formed, thereby achieving excellent lubrication performance / sliding characteristics.

[0024] In particular, by using the sintered bearing of the present invention in a bearing assembly where the first bearing portion is on the output side of the motor and the second bearing portion is on the opposite side of the motor's output side, oil circulation and supply function smoothly even when used in a wide temperature range, improving oil cut-off and achieving good sliding. As a result, it is possible to improve the reduction of motor speed and speed instability. It is also possible to reduce power consumption. Attached Figure Description

[0025] Figure 1 This is a cross-sectional view of the sintered bearing of the present invention.

[0026] Figure 2 This is an explanatory diagram showing the density distribution of the sintered bearing of the present invention.

[0027] Figure 3 This is an explanatory diagram of the oil circulation in the sintered bearing of the present invention.

[0028] Figure 4 This is a manufacturing process diagram of the sintered bearing of the present invention.

[0029] Figure 5 This is a simplified diagram of the core pin used in the compression molding process.

[0030] Figure 6 This is a top view of a motor using a bearing assembly with the sintered bearing of the present invention. Detailed Implementation

[0031] The following is based on Figures 1-6 The embodiments of the present invention will be described. Figure 6 A motor (fan motor) using the bearing assembly of the present invention is shown. The bearing assembly 1 includes: a sintered bearing 2 of the present invention; a housing 3 having a cylindrical portion 3a that holds the sintered bearing 2 on its inner circumference; and a shaft member 4 supported by the sintered bearing 2 for rotational freedom. In addition, the shaft member 4 is disposed at the bottom of the housing 3 and is received by a thrust receiving portion 5.

[0032] The fan motor has a bearing assembly 1, a rotor 10 attached to one end (output side) of a shaft member 4 attached to the bearing assembly 1, and a stator 11 disposed in a housing 3. The rotor 10 has a rotor yoke 12 fixed to the shaft member and a rotor magnet 13 fixed to the inner surface of the peripheral wall 12a of the rotor yoke 12. In addition, the stator 11 has a laminated iron core 15 externally fixed to the cylindrical portion 3a of the housing 3 and a coil 16 wound on the laminated iron core 15.

[0033] The sintered bearing 2 is configured such that a cylindrical sintered body, formed by sintering raw material powder with metal as the main component, contains lubricating oil, such as... Figure 1 and Figure 3As shown, one end along the axial direction is designated as the first bearing portion 21, and the other end along the axial direction is designated as the second bearing portion 22. The inner diameter surface 21a of the first bearing portion 21 and the inner diameter surface 22a of the second bearing portion 22 form a sliding surface 23 that slides against the shaft component 4 on the opposite side. In addition, the sintered bearing 2 is formed with an intermediate portion 24, which has a clearance portion 24a that is larger than the inner diameter surface of the first bearing portion 21 and the second bearing portion 22 at the center.

[0034] Furthermore, a narrowing portion 25 is formed on the outer diameter surface of the second bearing portion 22 of the sintered bearing 2. The narrowing portion 25 is composed of a cylindrical portion 25a on the axially outward side of the second bearing portion 22 and a tapered portion 25b that expands axially inward from the cylindrical portion 25a. Therefore, the second bearing portion 22 includes a portion from the cylindrical portion 25a to the tapered portion 25b. In this case, the outer diameter of the second bearing portion 22 is smaller than the outer diameter of the first bearing portion 21.

[0035] The inner diameter of the first bearing portion 21 and the inner diameter of the second bearing portion 22 are set to be the same, and the inner diameters of the first bearing portion 21 and the second bearing portion 22 are set to be slightly larger than the outer diameter of the shaft component 4. That is, the inner diameter of the first bearing portion 21 is set to D1, the inner diameter of the second bearing portion 22 is set to D2, and the outer diameter of the shaft component 4 is set to D (refer to...). Figure 6 When the outer diameter surface of the second bearing portion 22 is narrowed (D1=D2>D), the wall thickness of the second bearing portion 22 is smaller than that of the first bearing portion 21 because a narrowing portion 25 is formed on the outer diameter surface of the second bearing portion 22. Furthermore, the gap C between the outer diameter surface of the shaft component 4 and the inner diameter surface of the first bearing portion 21 and the inner diameter surface of the second bearing portion 22 is, for example, about 2μm to 8μm. Also, the same dimensions include those falling within dimensional tolerances.

[0036] However, in sintered bearing 2, such as Figure 2 As shown, in this case, the density of the first bearing portion 21 is set to be higher than the density of the second bearing portion 22. The first bearing portion adjacent to the first bearing portion 21 and the intermediate portion 24 is a high-density region H1, and the second bearing portion adjacent to the second bearing portion 22 and the intermediate portion 24 is a low-density region H2. A density variation region H3 is formed between the high-density region H1 and the low-density region H2, such that the density of the high-density region H1 is higher than the density of the density variation region H3. The density variation region H3 has a lowest density portion 28 near the low-density region H2 (a portion with a density set to be lower than the density of the low-density region H2) and a density gradient portion 29 from the lowest density portion 28 toward the high-density region H1.

[0037] The density of the first bearing section 21 is set to be 0.08 g / cm³ higher than the density of the second bearing section 22. 3 0.56 (g / cm³) 3 The oil content of the first bearing section 21 is 1% to 7% lower than that of the second bearing section 22. The density difference between the first bearing section 21 and the second bearing section 22 is set to 0.08 g / cm³. 3 0.48 (g / cm³) 3 The difference in oil content is 1% to 6%. The difference in surface opening ratio between the inner diameter surface of the first bearing part and the inner diameter surface of the second bearing part is set to 5% to 45%. Surface opening ratio refers to the ratio of the total area of ​​all openings to the area per unit area.

[0038] By balancing the pressure during molding and designing the die, the density after sintering and precision pressing can be set to [specific value]. Figure 2 The density distribution is as shown. Furthermore, for example, by making the inner diameter of the output side after in-mold pressing different from that of the opposite side, the finishing allowance during rotary finishing of the output side is increased, which can reduce the surface opening ratio. Therefore, by making the finishing allowance during rotary finishing different in different locations, the surface opening ratio can be varied in different locations.

[0039] In addition, such as Figure 4 As shown, the sintered bearing 2 is formed by performing a powder mixing process S1, a compression molding process S2, a sintering process S3, a precision pressing / rotation finishing process S4, and a cleaning / oiling process S5.

[0040] As the raw material powder in the powder mixing process S1, for example, Figure 4 As shown, copper powder, tin powder, iron powder, etc., are mixed to form a mixed powder. In this case, various molding aids, such as lubricants (e.g., metal soaps) for improving mold release, are added to the mixed powder as needed. Furthermore, the raw material powder used is not limited to these; raw material powders commonly used in cylindrical sintered bearings can be used.

[0041] In compression molding process S2, a pressed powder is formed by stamping using a die device. This die device has cylindrical upper and lower punches and a core pin 30 that shapes the internal form of the pressed powder (see reference). Figure 5This includes a die for shaping the compressed powder. In this case, during the compression molding process, an inner diameter step (avoidance portion 24a) is formed only on one side (the inner diameter surface 21a side of the first bearing portion 21) between the core pin body 30c and the core pin body 30c. During the precision pressing process described later, the other side (the inner diameter surface 22a side of the second bearing portion 22) is narrowed and deformed from the outer diameter direction to reduce its diameter, forming an avoidance portion 24b in the inner diameter. That is, the core pin 30 has a first forming portion 30a for forming one of the bearing surfaces (the inner diameter surface 21a of the first bearing portion 21), and the outer diameter of this forming portion 30a is smaller than the outer diameter of the core pin body 30c. Furthermore, this differs from the forced punching method in the compression molding process, which utilizes the undercut portion that springs back when the die is released.

[0042] In the sintering process S3, a sintered body is obtained by heating the pressed powder obtained in the pressing process (compression molding process) to the sintering temperature of the metal powder used. That is, the specified atmosphere for sintering under specified atmosphere and specified temperature conditions can be selected from various options, such as vacuum, reducing gas, and inactive gas, depending on the metal powder used.

[0043] In the precision pressing process S4, the sintered body, which has undergone dimensional deformation due to sintering, is compressed and dimensionally shaped. In this case, the dimensional changes (expansion and contraction) of the sintered body vary depending on the material composition, sintering temperature, and sintering atmosphere. Specifically, a mandrel is inserted into the inner circumference of the sintered body, and the axial width of the sintered body is defined to a specified size using upper and lower punches, and they are integrally pressed into the inner circumference of the die. As a result, the outer circumferential surface of the sintered body is formed by the die, and the inner circumferential surface of the sintered body is pressed against the outer circumferential surface of the mandrel and formed (in-die precision pressing). That is, using a mandrel (not shown) that has plastic deformation allowance on the other side (the inner diameter surface 22a side of the second bearing portion 22) through this precision pressing process, it is narrowed and deformed from the outer diameter direction, causing the inner diameter to shrink, forming a relief portion 24b in the inner diameter. That is, the mandrel in the precision pressing process is an inverted version of the mandrel 30 used in the compression forming process. Through the precision pressing process, the relief portion 24b is formed in the inner diameter and the dimensional accuracy is improved. Alternatively, after the precision pressing process, the voids opening on the inner circumferential surface of the sintered body can be further reduced by performing a rotary precision pressing. The precision pressing process includes a first precision pressing process (in-mold precision pressing process) and a second precision pressing process. The second precision pressing process includes either a rotary precision pressing process or an in-mold precision pressing process.

[0044] However, in the embodiment, the sintered bearing has a narrowing portion 25 formed on the outer diameter surface of the second bearing portion 22. Therefore, during precision pressing, a die with an inner diameter side bulge for forming the narrowing portion 25 is used.

[0045] The second bearing section 22 is deformed by in-mold precision pressing, which easily increases its density. Therefore, by balancing the pressure during molding and designing the mold, the final density after sintering and precision pressing is set to be lower than that of the output side.

[0046] After the precision pressing / rotary finishing process S4, a cleaning / oiling process S5 is performed. That is, after cleaning and other processes, the lubricating oil is applied.

[0047] In the oil impregnation process S5, lubricating oil is impregnated into the sintered bearing 2, which has been formed into a specified shape through the precision pressing process. This completes the process of impregnating the internal pores of the sintered bearing 2 with lubricating oil. Alternatively, the impregnation of lubricating oil into the internal pores of the sintered bearing 2 can be performed, for example, by immersing the sintered bearing 2 in a lubricating oil bath filled with lubricating oil for a certain period of time under a specified reduced pressure environment. In this case, to ensure reliable and short-term lubricating oil impregnation, the impregnation operation can also be performed while the lubricating oil is heated.

[0048] However, by setting a density difference, oil is actively supplied to the direction with higher density and smaller pores due to capillary action. Therefore, in the sintered bearing of the present invention, as... Figure 3 As indicated by the arrow, a circulation path can be formed in which lubricating oil circulates from the middle part 24 to the first bearing part 21 and from the middle part 24 to the second bearing part 22.

[0049] According to the sintered bearing of the present invention, by providing the clearance portion 24a, the sliding area of ​​the shaft component relative to the sintered bearing can be reduced, thereby reducing the sliding resistance. Moreover, by forming an oil circulation path, the supply of lubricating oil in the sliding portion is stable.

[0050] Therefore, in the sintered bearing of the present invention, a sliding component can be provided that does not require special processing equipment, processing tools, or special plastic processing tools, and by giving the sintered bearing a density tilting function, a circulation path for lubricating oil is formed, thereby achieving excellent lubrication performance / sliding characteristics.

[0051] The preferred configuration is as follows: the first bearing portion 21 is a high-density region H1, the second bearing portion 22 is a low-density region H2 with a lower density than the high-density region H1, and between the high-density region H1 and the low-density region H2, the vicinity of the low-density region H2 has a minimum density portion 28 with a lower density than the low-density region H2 and a density gradient portion 29 with a density that increases from the minimum density portion 28 to the high-density region H1.

[0052] By setting the density difference in this way, the circulation of lubricating oil from the clearance section to the first bearing section 21 and from the clearance section to the second bearing section 22 can be stably achieved.

[0053] A density gradient section 29, where the density increases from the lowest density section 28 towards the high density region H1, is particularly preferred. In this way, by setting a density gradient, lubricating oil is supplied sequentially from the lowest density section 28 towards the high density region H1, ensuring stable oil circulation.

[0054] The density of the first bearing section 21 and the second bearing section 22 is set to be 0.08 (g / cm³) higher than the density of the lowest density section. 3 0.56 (g / cm³) 3 The oil content of the first bearing portion 21 and the second bearing portion 22 is 1% to 7% lower than the oil content of the lowest density portion, or the density difference between the first bearing portion 21 and the second bearing portion 22 is set to 0.08 (g / cm³). 3 0.48 (g / cm³) 3 The difference in oil content is 1% to 6%, or the difference in surface opening ratio between the inner diameter surface of the first bearing portion 21 and the inner diameter surface of the second bearing portion 22 is 5% to 45%. By setting it in this way, a stable oil circulation can be obtained.

[0055] The bearing device of the present invention uses a sintered bearing 2, with the first bearing section 21 on the output side of the motor and the second bearing section 22 on the opposite side of the motor's output side. Therefore, by configuring a high-density region H on the output side of the motor where sliding resistance is high, a large amount of lubricating oil can be supplied to the output side, reducing the coefficient of friction of the bearing surface. Thus, even when used in a wide temperature range, oil circulation and supply function smoothly, improving oil cut-off and achieving good sliding. In particular, when the oil viscosity increases, oil circulation and supply become difficult to function smoothly; even at low temperatures, oil circulation and supply function smoothly, improving oil cut-off and achieving good sliding.

[0056] As such a bearing device, the density of the first bearing section 21 can be 0.08 (g / cm³) higher than the density of the second bearing section 22. 3 0.48 (g / cm³) 3 The oil content of the first bearing portion 21 is 1% to 6% lower than that of the second bearing portion 22, or the density of the first bearing portion 21 is 0.16 g / cm³ higher than that of the second bearing portion 22. 3 0.40 (g / cm³) 3 The oil content of the first bearing portion 21 is 2% to 5% lower than that of the second bearing portion 22, or the surface opening ratio of the inner diameter surface of the first bearing portion 21 is 5% to 45% lower than that of the inner diameter surface of the second bearing portion 22.

[0057] The embodiments of the present invention have been described above, but the present invention is not limited to the described embodiments and can be modified in various ways, and may not include the narrowing portion 25. In addition, in the embodiments, a density gradient is provided in the density variation region H3, where the density increases from the lowest density portion 28 toward the high density region H1, but such a gradient may not be provided.

[0058] Furthermore, the sintered bearings of the present invention can be used not only in spindle motors for HDD and other disk drive devices, but also in fan motors for cooling fans, multi-faceted scanner motors for laser beam printers, and the like. In particular, they are suitable for use in automotive cooling fan motors and the like over a wide temperature range, from low to high temperatures.

[0059] Example 1

[0060] The motor characteristics when the sintered bearing of the present invention is used in a fan motor were investigated. The results are shown in Table 1. In this case, sintered bearings of Examples 1 to 5 and Comparative Examples 1 to 3 were manufactured. The sintered bearings of Examples 1 to 5 and Comparative Examples 1 to 3 are... Figure 1 The sintered bearing shown has a first bearing portion 21 as the output side and a second bearing portion 22 as the opposite side of the output side. The inner diameter of the first bearing portion 21 and the second bearing portion 22 is set to Φ3mm, the outer diameter of the bearing is set to Φ8mm, the width (axial length) is set to 10mm, the gap between the bearing surface 23 (the inner diameter surface of the first bearing portion 21 and the inner diameter surface 22a of the second bearing portion 22) and the shaft component 4 is set to 4μm, and the gap between the clearance portion 24a and the shaft component 4 is set to approximately 100μm.

[0061] Table 1

[0062] As for the bearing density, in Example 1, the density on the output side of A is 6.59 (g / cm³). 3 The density on the opposite side of the output side of B is 6.11 (g / cm³). 3 The density of the lowest density part of C is 6.03 (g / cm³). 3 In Example 2, the density on the output side of A is 6.51 (g / cm³). 3 The density on the opposite side of the output side of B is 6.11 (g / cm³). 3 The density of the lowest density part of C is 6.03 (g / cm³). 3 In Example 3, the density of A on the output side was 6.43 (g / cm³). 3 The density on the opposite side of the output side of B is 6.19 (g / cm³). 3The density of the lowest density part of C is 6.11 (g / cm³). 3 In Example 4, the density of A on the output side is 6.35 (g / cm³). 3 The density on the opposite side of the output side of B is 6.19 (g / cm³). 3 The density of the lowest density part of C is 6.11 (g / cm³). 3 In Example 5, the density of A on the output side was 6.35 (g / cm³). 3 The density on the opposite side of the output side of B is 6.27 (g / cm³). 3 The density of the lowest density part of C is 6.19 (g / cm³). 3 ).

[0063] As for the bearing density, in Comparative Example 1, the density on the output side of A is 6.27 (g / cm³). 3 The density on the opposite side of the output side of B is 6.35 (g / cm³). 3 The density of the lowest density part of C is 6.19 (g / cm³). 3 In Comparative Example 2, the density on the output side of A was 6.19 (g / cm³). 3 The density on the opposite side of the output side of B is 6.43 (g / cm³). 3 The density of the lowest density part of C is 6.11 (g / cm³). 3 In Comparative Example 3, the density on the output side of A was 6.11 (g / cm³). 3 The density on the opposite side of the output side of B is 6.51 (g / cm³). 3 The density of the lowest density part of C is 6.03 (g / cm³). 3 ).

[0064] exist Figure 1 In sintered bearings of uniform shape, the opposite side of the output side is reduced in size through in-mold precision pressing, thus generally resulting in a higher density. Therefore, in Examples 1 to 5 and Comparative Example 1, by balancing the pressure during molding and designing the mold, the density of the opposite side of the output side is reduced in advance, and the final density after precision pressing is adjusted to be lower than that of the output side. In Comparative Example 2, the density of the molded body is adjusted to be output side ≒ output side, and in Comparative Example 3, the density of the molded body is adjusted to be output side < output side.

[0065] As for the oil content, in Example 1, it was 19% on the output side of A, 25% on the opposite side of the output side of B, and 26% in the lowest density section of C. In Example 2, it was 20% on the output side of A, 25% on the opposite side of the output side of B, and 26% in the lowest density section of C. In Example 3, it was 21% on the output side of A, 24% on the opposite side of the output side of B, and 25% in the lowest density section of C. In Example 4, it was 22% on the output side of A, 24% on the opposite side of the output side of B, and 25% in the lowest density section of C. In Example 5, it was 22% on the output side of A, 23% on the opposite side of the output side of B, and 24% in the lowest density section of C.

[0066] Regarding the oil content, in Comparative Example 1, it was 23% on the output side of A, 22% on the opposite side of the output side of B, and 24% in the lowest density section of C. In Comparative Example 2, it was 24% on the output side of A, 21% on the opposite side of the output side of B, and 25% in the lowest density section of C. In Comparative Example 3, it was 25% on the output side of A, 20% on the opposite side of the output side of B, and 26% in the lowest density section of C.

[0067] The density difference (AB) between part A and part B in Example 1 was 0.48 (g / cm³). 3 In Example 2, it was 0.40 (g / cm³). 3 In Example 3, it was 0.24 (g / cm³). 3 In Example 4, it was 0.16 (g / cm³). 3 In Example 5, it was 0.08 (g / cm³). 3 The density difference (AB) between part A and part B in Comparative Example 1 was -0.08 (g / cm³). 3 In Comparative Example 2, it was -0.24 (g / cm³). 3 In Comparative Example 3, it was -0.40 (g / cm³). 3 ).

[0068] The difference in oil content (AB) between part A and part B was -6% in Example 1, -5% in Example 2, -3% in Example 3, -2% in Example 4, and -1% in Example 5. The difference in oil content (AB) between part A and part B was +1% in Comparative Example 1, +3% in Comparative Example 2, and +5% in Comparative Example 3.

[0069] As for the motor characteristics (-30°C environment), in Example 1, the speed is 820 rpm, the current is 64 mA, and the starting voltage is 7.9 V; in Example 2, the speed is 890 rpm, the current is 62 mA, and the starting voltage is 7.5 V; in Example 3, the speed is 910 rpm, the current is 61 mA, and the starting voltage is 7.5 V; in Example 4, the speed is 880 rpm, the current is 62 mA, and the starting voltage is 7.5 V; and in Example 5, the speed is 830 rpm, the current is 65 mA, and the starting voltage is 7.8 V.

[0070] As for motor characteristics (-30°C environment), in Comparative Example 1, the speed was 770 (rpm), the current was 68 (mA), and the starting voltage was 8.3 (V); in Comparative Example 2, the speed was 720 (rpm), the current was 70 (mA), and the starting voltage was 8.5 (V); and in Comparative Example 3, the speed was 650 (rpm), the current was 72 (mA), and the starting voltage was 8.9 (V).

[0071] In Table 1, ◎ (Excellent) indicates a speed of 860 rpm or higher, a current of 62 mA or lower, and a starting voltage of 7.6 V or lower; 〇 (Good) indicates a speed of 800 rpm or higher, a current of 66 mA or lower, and a starting voltage of 8.0 V or lower; △ (Acceptable) indicates a speed of 700 rpm or higher, a current of 70 mA or lower, and a starting voltage of 8.6 V or lower; and × (Unacceptable) indicates a speed of less than 700 rpm, a current exceeding 70 mA, and a starting voltage exceeding 8.6 V. In other words, for a product, ◎, 〇, and △ are acceptable, while × is unacceptable.

[0072] Thus, the density difference between the output side and the opposite side of the output side is preferably set to 0.08–0.48 (g / cm³). 3 The difference in oil content between the output side and the opposite side is preferably set to 1% to 6%, and the density difference between the output side and the opposite side is preferably set to 0.16 to 0.40 (g / cm³). 3 The oil content difference between the output side and the opposite side of the output side is preferably set to 2% to 5%.

[0073] Next, the surface opening ratio of the bearing surface and the motor characteristics (-30°C environment) were investigated. In this case, Examples 6 to 9, as well as Comparative Examples 4 and 5, were prepared with varying surface opening ratios relative to the same dimensions, shape, and density specifications as the sintered bearing of Example 3, and their results were investigated. The surface opening ratio of Example 6 was 10% on the output side of A and 55% on the opposite side of the output side of B; the surface opening ratio of Example 7 was 25% on the output side of A and 55% on the opposite side of the output side of B; the surface opening ratio of Example 8 was 35% on the output side of A and 55% on the opposite side of the output side of B; the surface opening ratio of Example 9 was 50% on the output side of A and 55% on the opposite side of the output side of B; the surface opening ratio of Comparative Example 4 was 5% on the output side of A and 55% on the opposite side of the output side of B; and the surface opening ratio of Comparative Example 5 was 55% on the output side of A and 55% on the opposite side of the output side of B.

[0074] The difference in surface opening ratio (BA) between part A and part B was 45% in Example 6, 30% in Example 7, 20% in Example 8, 5% in Example 9, 50% in Comparative Example 4, and 0% in Comparative Example 5. Furthermore, in Examples 6, 7, and 4, by creating a difference in the inner diameter of the output side after in-mold pressing and the opposite side of the output side, and by increasing the finishing allowance during rotary finishing of the output side, the surface opening ratio could be reduced.

[0075] Table 2

[0076] In Table 2, "Inner Diameter NG" indicates that the opening of the inner diameter surface on the output side has been blocked or charred, indicating that the condition of the inner diameter surface is not good. In addition, "Unable to manufacture" means that a sample with the target surface opening ratio cannot be manufactured in the final rotary finishing stage. For a bearing with the same size, shape and density specifications as the sintered bearing in Example 3, the surface opening ratio can be changed by rotary finishing, but even if the finishing allowance is minimized, the surface opening ratio on side A cannot be made to 55%.

[0077] Regarding motor characteristics (-30°C environment), in Example 6, the speed was 870 rpm, the current was 63 mA, and the starting voltage was 7.6 V; in Example 7, the speed was 920 rpm, the current was 61 mA, and the starting voltage was 7.5 V; in Example 8, the speed was 910 rpm, the current was 61 mA, and the starting voltage was 7.5 V; and in Example 9, the speed was 840 rpm, the current was 64 mA, and the starting voltage was 7.7 V. In Comparative Example 4, the opening on the inner diameter surface of the output side was blocked or burned, indicating a problem with the condition of the bearing inner diameter surface. In Comparative Example 5, it was impossible to produce a surface opening ratio of 55% on side A. The ◎ and 〇 in Table 2 are the same as in Table 1.

[0078] The difference in surface aperture ratio between the output side and the opposite side of the output side is preferably set to 5% to 45%, and more preferably to 20% to 30%.

[0079] Industrial availability

[0080] Sintered bearings and bearing assemblies can be constructed to be suitable for use in a wide temperature range from low to high temperatures, such as automotive cooling fan motors, without the need for plastic processing such as shot peening, rolling, or stamping, thus exhibiting excellent lubrication performance (sliding characteristics).

[0081] Label Explanation

[0082] H1: High-density region; H2: Low-density region; H3: Density variation region; 1: Bearing assembly; 2: Sintered bearing; 21: First bearing section; 21a: Inner diameter surface; 22: Second bearing section; 22a: Inner diameter surface; 23: Sliding surface; 24a: Clearance section; 26: Bearing section adjacent section; 27: Bearing section adjacent section; 28: Lowest density section.

Claims

1. A sintered bearing having a sliding surface that slides with a shaft component on the opposite side, characterized in that, The cylindrical sintered body, which is formed by sintering raw material powder with metal material as the main component, contains lubricating oil. One end in the axial direction is designated as a first bearing part, and the other end in the axial direction is designated as a second bearing part. The sliding surface is formed by the inner diameter surfaces of the first bearing part and the second bearing part. An intermediate part is formed in the center of the bearing inner diameter. The intermediate part has a clearance portion with a diameter larger than the inner diameter surfaces of the first bearing part and the second bearing part. A density difference is provided between the first bearing part, the second bearing part, and the intermediate part.

2. The sintered bearing according to claim 1, characterized in that, The first bearing portion is a high-density region, and the second bearing portion is a low-density region with a lower density than the high-density region. Between the high-density region and the low-density region, there is a minimum density region with a lower density than the low-density region and a density gradient region where the density increases from the minimum density region to the high-density region.

3. The sintered bearing according to claim 1 or 2, characterized in that, The density of the first bearing portion is higher than the density of the second bearing portion by 0.08 (g / cm 3 ) to 0.56 (g / cm 3 ), and the oil content of the first bearing portion is lower than the oil content of the second bearing portion by 1% to 7%.

4. The sintered bearing according to claim 1 or 2, characterized in that, The density difference between the first bearing portion and the second bearing portion is 0.08 (g / cm 3 ) to 0.48 (g / cm 3 ), and the difference in oil content is 1% to 6%.

5. The sintered bearing according to claim 1 or 2, characterized in that, The difference in surface opening ratio between the inner diameter surface of the first bearing section and the inner diameter surface of the second bearing section is 5% to 45%.

6. A bearing assembly using the sintered bearing according to claim 1 or 2, characterized in that, The first bearing section is on the output side of the motor, and the second bearing section is on the opposite side of the output side of the motor.

7. The bearing device according to claim 6, characterized in that, The density of the first bearing portion is 0.08 g / cm³ higher than that of the second bearing portion. 3 0.48 (g / cm³) 3 The oil content of the first bearing portion is 1% to 6% lower than that of the second bearing portion.

8. The bearing device according to claim 6, characterized in that, The density of the first bearing portion is 0.16 g / cm³ higher than that of the second bearing portion. 3 0.40 (g / cm³) 3 The oil content of the first bearing portion is 2% to 5% lower than that of the second bearing portion.

9. The bearing device according to claim 6, characterized in that, The surface opening ratio of the inner diameter surface of the first bearing portion is 5% to 45% lower than that of the inner diameter surface of the second bearing portion.

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