KR20200038438A - Sintered bearing - Google Patents

Abstract

Provided is a sintered bearing capable of reducing the resistance applied to a rotating shaft. According to the present invention, a sintered bearing (1) comprises: a first bearing portion (21) having a first bearing surface (21a) for supporting the outer circumferential surface of a rotating shaft (10); a second bearing portion (22) having a second bearing surface (22a) for supporting the outer circumferential surface of the rotating shaft (10); and an intermediate portion (23) formed between the first bearing portion (21) and the second bearing portion (22). The inner diameter of the intermediate portion (23) is formed to be larger than each of the inner diameter of the first bearing portion (21) and the inner diameter of the second bearing portion (22), and a plurality of dimples (d) are formed on the first bearing surface (21a) and/or the second bearing surface (22a).

Description

Sintered bearing {SINTERED BEARING}

The present invention relates to a sintered bearing formed by compacting a metal powder in a mold and then sintering and impregnated with a lubricant, and more particularly, to a sintered bearing capable of reducing frictional resistance with a rotating shaft and reducing noise.

Sintered bearings are inexpensive and highly reliable bearings, and are widely used in motors for home appliances, motors for automobiles, and OA equipment. As an example, the fan motor includes a cooling fan inside a household appliance such as a computer or a television, a fan for circulation and cooling in a refrigerator, a fan for vehicle installation used for cooling a battery or suctioning an in-car sensor, and the demand is increasing year by year.

Since these fan motors are used for a long period of time, the long-term service life and reduction of power consumption are important requirements. In particular, it is necessary to suppress power consumption as much as possible when driving with a battery such as a mobile device.

On the other hand, the fan motor has a particularly high level of demand for silent sound. In general, in order to silence the motor, first, in a sintered bearing, the clearance between the rotating shaft and the bearing is narrowed to suppress noise caused by the runaway of the shaft, and secondly, the oil film generated on the inner diameter sliding surface by increasing the viscosity of the lubricant impregnated in the bearing. It is effective to increase the strength.

However, in a low-torque motor, such as a fan motor, and in a low-torque motor, the frictional resistance between the rotating shaft and the bearing is dominated by the fluid resistance of the lubricant impregnated with the bearing. Therefore, if the clearance between the rotating shaft and the bearing is too narrow, the fluid resistance of the lubricant at the rotation of the shaft increases, and the power consumption of the motor increases. Further, even if the viscosity of the lubricant is increased, power consumption increases due to an increase in fluid resistance, and thus the viscosity of the selected lubricant is also limited.

Conventionally, what is shown in patent document 1 is known as a sintered bearing which can reduce the frictional resistance with a rotating shaft, for example.

In this sintered bearing, in the bearing hole rotatably supporting the rotating shaft, the inner diameter of the intermediate portion in the axial direction is formed larger than the inner diameter of each of both ends in the axial direction (hereinafter referred to as "bearing portion"). Thereby, since the inner peripheral surface of the intermediate portion does not come into contact with the rotating shaft, the area of the portion corresponding to the rotating shaft in the inner peripheral surface of the bearing hole (hereinafter referred to as "sliding area") is reduced. Therefore, since the contact between the inner circumferential surface of the bearing hole and the rotating shaft is suppressed and the fluid resistance of the lubricant during shaft rotation is also suppressed, it is possible to reduce frictional resistance generated between the rotating shaft. Here, the "part corresponding to the rotating shaft" does not mean a portion that is in constant contact with the rotating shaft when the rotating shaft is rotating, and may have contact with the rotating shaft, and at the same time, the fluid resistance of the lubricant at the time of rotating the shaft strongly affects it. It means a part (hereafter, the same applies).

Japanese Patent Publication No. Hei 7-332363

However, conventional sintered bearings have limitations in reducing frictional resistance with the rotating shaft.

That is, in the conventional sintered bearing, the sliding area can be made smaller as the range of the intermediate portion is widened in the axial direction to narrow the range of both bearing portions. However, if the axial dimension of each bearing portion (each bearing surface) is too small, the hydraulic pressure generated by the wedge effect will escape from both ends of the axial direction of each bearing surface, and oil film strength cannot be maintained. Further, when the oil film strength decreases, contact between the bearing surface and the rotating shaft tends to occur, and as a result, frictional resistance generated between the rotating shaft increases and noise is promoted. Therefore, in the conventional sintered bearing, there is a limit to reduction of frictional resistance with the rotating shaft.

An object of the present invention is to provide a sintered bearing capable of reducing frictional resistance with a rotating shaft.

In order to solve the above problems, the sintered bearing according to the first invention is formed by sintering a metal powder in a mold and then sintering it, having a bearing hole rotatably supporting a rotating shaft, and a sintered bearing impregnated with lubricant, wherein the rotating shaft Has a first bearing portion having a first bearing surface for supporting, a second bearing portion having a second bearing surface for supporting the rotary shaft, and an intermediate portion formed between the first bearing portion and the second bearing portion, The inner diameter of the intermediate portion is larger than the inner diameter of the first bearing portion and the inner diameter of the second bearing portion, and a plurality of dimples are formed on at least one bearing surface of the first bearing surface and the second bearing surface. It is characterized by being.

In the sintered bearing according to the first invention, an intermediate portion is formed between the first bearing portion and the second bearing portion, and the inner diameter of the intermediate portion is larger than that of each bearing portion.

Thereby, the inner circumferential surface of the intermediate portion does not come into contact with the rotating shaft, and the sliding area on the inner circumferential surface of the bearing hole decreases. Therefore, compared with the sintered bearings (hereinafter referred to as "straight bearings") in which the inner diameter of the bearing hole is equally formed over the entire length in the axial direction, the contact between the inner circumferential surface of the bearing hole and the rotating shaft is suppressed, and at the same time the shaft rotates By reducing the fluid resistance of the lubricant, it becomes possible to reduce the frictional resistance generated between the rotating shafts.

In particular, in the sintered bearing according to the first invention, a plurality of dimples are formed on at least one bearing surface of the first bearing surface and the second bearing surface rotatably supporting the rotating shaft.

Thereby, since the part (range) in which each dimple is formed in the bearing surface does not contact the rotating shaft, the sliding area on the bearing surface is reduced. Therefore, the contact between the bearing surface and the rotating shaft is suppressed, and at the same time, it is possible to reduce the frictional resistance generated between the rotating shaft by reducing the fluid resistance of the lubricant when rotating the shaft.

Therefore, the sliding area on the inner circumferential surface of the bearing hole can be reduced without reducing the axial dimension of the bearing surface, and it is possible to reduce the frictional resistance generated between the rotating shafts while suppressing a decrease in oil film strength. .

In addition, in the sintered bearing according to the first invention, a plurality of dimples are formed on the bearing surface so that the impregnated lubricant is stored in each dimple. Then, when the rotating shaft rotates, lubricant stored in each dimple is drawn between the bearing surface and the rotating shaft. As a result, when the rotating shaft rotates, oil film formation is particularly facilitated at the beginning of operation, and it becomes possible to reduce the friction coefficient of the bearing surface.

In addition, in the sintered bearing according to the first invention, since a plurality of dimples are formed on the bearing surface, the average clearance between the bearing surface and the outer peripheral surface of the rotating shaft increases. This makes it possible to reduce the fluid resistance of the lubricant present between the bearing surface and the rotating shaft when the rotating shaft rotates.

As described above, according to the sintered bearing according to the first invention, it is possible to reduce frictional resistance generated between the rotating shaft by suppressing the contact between the bearing surface and the rotating shaft and reducing the fluid resistance of the lubricant.

In particular, by applying the sintered bearing according to the first invention, it is possible to improve the characteristics of a motor with a small driving torque. That is, in general, in the motor, as the driving torque decreases, the magnitude of the frictional resistance generated between the bearing surface and the rotating shaft has greatly influenced the motor characteristics. Specifically, when the frictional resistance increases, the number of revolutions of the motor decreases, the target number of revolutions cannot be achieved, and the power consumption of the motor increases. On the other hand, according to the sintered bearing according to the first invention, as described above, frictional resistance generated between the bearing surface and the rotating shaft can be reduced. Therefore, by applying the sintered bearing according to the first aspect of the invention, even if the driving torque of the motor is made small, it is possible to suppress a decrease in the number of motor revolutions, and at the same time, it is also possible to reduce power consumption.

Further, by applying the sintered bearing according to the first invention, it becomes possible to construct a motor having a smaller clearance between the bearing surface and the outer peripheral surface of the rotating shaft. That is, in general, in a motor, as the clearance between the bearing surface and the outer circumferential surface of the rotating shaft decreases, the fluid resistance of the lubricant during rotation of the shaft increases, and the frictional resistance generated between the rotating shaft increases. Then, the number of revolutions of the motor decreases, so that the target number of revolutions cannot be achieved, and the power consumption of the motor increases. On the other hand, according to the sintered bearing according to the first invention, it is possible to reduce the fluid resistance of the lubricant during shaft rotation as described above. Therefore, even when the clearance between the bearing surface and the outer circumferential surface of the rotating shaft is reduced by applying the sintered bearing according to the first invention, it is possible to suppress a decrease in the number of motor revolutions, and also to suppress an increase in motor power consumption. Becomes And, as a result of being able to reduce the clearance between the bearing surface and the outer circumferential surface of the rotating shaft, congestion of the rotating shaft within the clearance between the bearing surface and the outer circumferential surface of the rotating shaft can be suppressed, and motor noise can be reduced.

Further, by applying the sintered bearing according to the first invention, it becomes possible to use a lubricant of higher viscosity. That is, in general, as the viscosity of the lubricant used in the motor increases, the fluid resistance of the lubricant existing between the bearing surface and the rotating shaft increases. Then, the number of revolutions of the motor decreases, so that the target number of revolutions cannot be achieved, and the power consumption of the motor increases. On the other hand, according to the sintered bearing according to the first invention, as described above, the fluid resistance of the lubricant present between the bearing surface and the rotating shaft can be reduced. Therefore, even if the viscosity of the lubricant used by applying the sintered bearing according to the first invention is increased, it is possible to suppress a decrease in the number of motor revolutions, and also to suppress an increase in motor power consumption. In addition, as a result of being able to increase the viscosity of the lubricant to be used, the wear resistance of the bearing can be improved, and evaporation suppression, deterioration suppression, and leakage suppression of the lubricant under high temperature can also be made, so that the motor life can be extended. In particular, it is possible to increase the oil film strength generated on the inner diameter sliding surface by using a lubricant having a high viscosity, thereby making it possible to reduce motor noise.

The sintered bearing according to the second invention is characterized in that in the sintered bearing according to the first invention, the plural dimples are formed by plastic working.

In the sintered bearing according to the second invention, a plurality of dimples are formed by plastically deforming the bearing surface. This makes it possible to improve the processing precision of each dimple.

In particular, the sintered bearing has a porous structure because it is formed by sintering the metal powder. For this reason, by forming each dimple by plastic working, the deformed portion is absorbed into the micropores, so that it is possible to prevent the bearing surface from rising.

Further, there are laser processing and etching (partial corrosion) processing as methods for forming dimples other than plastic processing, but these methods require large-scale equipment and increase the number of processing steps. On the other hand, plastic processing does not require large-scale equipment, and since the processing steps are small, it is relatively inexpensive and can be processed in large quantities.

The sintered bearing according to the third invention is characterized in that in the sintered bearing according to the first or second invention, the dimple is installed spaced apart from the end of the axial direction of the bearing surface.

According to the sintered bearing according to the third invention, since the dimples are formed to be spaced apart from the axial end of the bearing surface, it is possible to suppress hydraulic pressure from escaping from the axial end of the bearing surface, thereby suppressing a decrease in oil film strength. Becomes

In the sintered bearing according to the fourth invention, in the sintered bearing according to any one of the first to third inventions, the clearance between the bearing surface on which the plurality of dimples are formed and the outer peripheral surface of the rotating shaft is set to 6 µm or less. It is characterized by being.

In general, in a motor driven at a light load such as a fan motor, if the clearance between the bearing surface and the outer circumferential surface of the rotating shaft is made larger than 6 µm, there is a fear that the rotating shaft may run out of this clearance and noise may increase. On the other hand, if the clearance between the bearing surface and the outer circumferential surface of the rotating shaft is 6 µm or less, the fluid resistance of the lubricant at the time of rotation of the shaft increases, and the frictional resistance generated between the rotating shaft increases.

Here, in the sintered bearing according to the present invention, even if the clearance between the bearing surface and the outer circumferential surface of the rotating shaft is 6 µm or less as described above, friction generated between the rotating shaft by reducing the fluid resistance of the lubricant during rotation of the shaft The resistance can be reduced, so that the power consumption of the motor can be kept low, and at the same time, it is possible to reduce noise when the rotating shaft is rotated.

The sintered bearing according to the fifth invention is the sintered bearing according to any one of the first to fourth inventions, wherein the average microhardness (MHv) of the bearing surface on which the plurality of dimples is formed is within a range of 50 to 200 It is characterized by.

That is, when the average microhardness (MHv) of the bearing surface is lower than 50, the wear resistance of the sintered bearing deteriorates and the durability decreases. On the other hand, if the average microhardness (MHv) of the bearing surface is higher than 200, the circumference of each dimple is raised when each dimple is formed, so that a predetermined dimension or precision cannot be obtained.

Therefore, by setting the average microhardness (MHv) of the bearing surface on which a plurality of dimples is formed within a range of 50 to 200, the durability of the sintered bearing is not reduced, and the dimple is dipped on the bearing surface without deteriorating the dimension or precision of the sintered bearing. It becomes possible to form.

The sintered bearing according to the sixth invention is applied to the fan motor in the sintered bearing according to any one of the first to fifth inventions.

According to the sintered bearing according to the sixth invention, it is possible to improve the characteristics of the fan motor having a small driving torque, and at the same time to reduce power consumption. In addition, since a fan motor having a smaller clearance between the bearing surface and the rotating shaft can be configured, congestion of the rotating shaft within the clearance between the bearing surface and the outer peripheral surface of the rotating shaft can be suppressed, and noise of the fan motor can be reduced. Becomes In addition, since it is possible to use a lubricant having a higher viscosity, it is possible to improve the wear resistance of the bearing, and also to suppress evaporation of the lubricant under high temperature, suppress deterioration, and suppress leakage, thereby extending the motor life. In particular, it is possible to increase the oil film strength generated on the inner diameter sliding surface by using a lubricant having a high viscosity, thereby making it possible to further reduce the noise of the fan motor.

According to the sintered bearing according to the present invention, it is possible to reduce frictional resistance with the rotating shaft and reduce noise.

1 is a partial cross-sectional view of a fan motor according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of the sintered bearing provided in the fan motor shown in FIG. 1.
3 is a partially enlarged view of the bearing surface of the sintered bearing shown in FIG. 2.

Hereinafter, the sintered bearing 20 according to the embodiment of the present invention will be described with reference to the drawings.

The sintered bearing 20 can be applied over a wide range of various motors, such as household appliances and automobiles, and OA equipment. In this embodiment, an example in which the sintered bearing 20 is applied to the fan motor 1 is shown.

[Configuration of fan motor 1]

1 is a partial cross-sectional view of a fan motor according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the sintered bearing provided in the fan motor shown in FIG. 1. 3 is a partially enlarged view of the bearing surface of the sintered bearing shown in FIG. 2.

The fan motor 1 shown in FIG. 1 includes a housing holder 2, a sintered bearing 20 held in the housing holder 2, and a rotating shaft 10 rotatably supported by the sintered bearing 20 Doing.

The housing holder 2 has a cylindrical portion 2a that holds the sintered bearing 20 inside. A laminated core (stator) 3 formed by winding the coil 3a is disposed on the outer circumferential surface of the cylindrical portion 2a.

The rotating shaft 10 is formed in a cylindrical shape by metal (alloy steel such as carbon steel or stainless steel). A magnet (rotor) 5 is attached to the rotating shaft 10 through the rotor yoke 4. The magnet 5 is arranged to face the laminated core 3 disposed on the outer circumferential surface of the housing holder 2. An impeller (fan) 6 is attached to the outer circumference of the rotor yoke 4. Further, a thrust plate 7 is fitted into the inner bottom of the cylindrical portion 2a of the housing holder 2 to support the semi-output side end of the rotating shaft 10 in the thrust direction.

1 and 2, the sintered bearing 20 supports a portion between the rotor yoke 4 and the thrust plate 7 in the rotating shaft 10. The sintered bearing 20 is made of sintered metal (including a sintered alloy) and has a porous structure. The sintered bearing 20 is impregnated with a lubricant, such as lubricant or lubricating grease.

The sintered bearing 20 is formed in a substantially cylindrical shape, and has a bearing hole h for rotatably supporting the rotating shaft 10. The bearing hole h is formed so as to penetrate in the axial direction (up and down direction shown in Fig. 1).

The sintered bearing 20 has a first bearing portion 21, a second bearing portion 22, and an intermediate portion 23 formed between the first bearing portion 21 and the second bearing portion 22. . The inner circumferential surface of the first bearing portion 21 is a first bearing surface 21a that supports the outer circumferential surface of the rotating shaft 10. In addition, the inner circumferential surface of the second bearing portion 22 is a second bearing surface 22a that supports the outer circumferential surface of the rotating shaft 10.

The inner diameter of the first bearing portion 21 and the inner diameter of the second bearing portion are respectively formed to be larger than the outer diameter of the rotating shaft 10. Moreover, the inner diameter of the 1st bearing part 21 and the inner diameter of the 2nd bearing part 22 are formed in substantially the same dimension. In this embodiment, the inner diameter of the first bearing portion 21 and the inner diameter of the second bearing portion 22 are dimensioned such that the clearance between each bearing surface 21a, 22a and the outer peripheral surface of the rotating shaft 10 is 6 µm or less. Is set. In addition, the inner diameter of the intermediate portion 23 is formed to have a larger size than each of the inner diameter of the first bearing portion 21 and the second bearing portion 22.

The rotating shaft 10 is disposed in a state inserted into the bearing hole h of the sintered bearing 20. In addition, the sintered bearing 20 has a first bearing portion 21 supporting an output side end of the rotating shaft 10, and a second bearing portion 22 supporting a half output side end of the rotating shaft 10. In addition, in the sintered bearing 20, each of the first bearing surface 21a and the second bearing surface 22a rotatably supports the rotating shaft 10, and the inner circumferential surface 23a of the intermediate portion 23 has a rotating shaft 10 ) Does not come into contact (slip contact).

As shown in FIG. 3, a plurality of dimples d are formed on at least one of the first bearing surface 21a and the second bearing surface 22a. In the present embodiment, a plurality of dimples d are formed in each of the first bearing surface 21a and the second bearing surface 22a. In addition, dimples are formed substantially on the entire bearing surfaces 21a and 22a, and a plurality of dimples are regularly arranged. Further, the dimple d is not formed on the inner circumferential surface 23a of the intermediate portion 23.

Each dimple d is formed by plastic processing such as pinning, rolling, and stamping. Each dimple d is formed as a concave portion such as a substantially hemispherical shape, a substantially semi-elliptical shape, or a substantially semi-cylindrical shape. In this embodiment, each dimple d is formed in a substantially semi-ellipsoidal shape with a shorter diameter in the range of 10 to 500 µm and a longer diameter in the range of 10 to 1000 µm. In addition, the maximum depth of each dimple d is formed within a range of 1 to 50 μm. Further, each dimple d is formed to extend along the circumferential direction (direction perpendicular to the axial direction).

In this embodiment, each dimple d is formed to be spaced apart from the axial end of each bearing surface 21a, 22a. That is, each dimple d is formed so as not to be exposed (not communicated with) on each end surface in the axial direction of each bearing portion 21 and 22.

Here, when the average microhardness (MHv) of each bearing surface (21a, 22a) is lower than 50, the wear resistance of the sintered bearing (20) deteriorates and the durability decreases. On the other hand, if the average microhardness (MHv) of each bearing surface (21a, 22a) is higher than 200, when forming each dimple (d) by plastic working, the circumference of each dimple (d) is raised to give a predetermined dimension. I can't get precision. Therefore, it is preferable that the average microhardness (MHv) of each bearing surface 21a, 22a is in the range of 50-200.

In addition, when the dimple area ratio is less than 10%, the effect of reducing the friction coefficient cannot be sufficiently obtained. On the other hand, when the dimple area ratio exceeds 60%, the sliding area is insufficient on each of the bearing surfaces 21a and 22a, resulting in insufficient load resistance. Therefore, it is preferable that the dimple area ratio is in the range of 10 to 60%. Here, the dimple area ratio is the sum of the projected areas of the dimples (d) formed in the corresponding bearing surfaces (21a, 22a) relative to the total area of each bearing surface (21a, 22a) (formed in the corresponding bearing surfaces (21a, 22a) The ratio of the projection area of each dimple d to the sum of all dimples d formed in the bearing surfaces 21a and 22a.

[Method of manufacturing sintered bearing 20]

Next, a method for manufacturing the sintered bearing 20 will be described.

In addition, in the following, the manufacturing method of an internal-diameter internal relief bearing uses the manufacturing method shown in Unexamined-Japanese-Patent No. 2-8302 or Unexamined-Japanese-Patent No. 7-332363.

That is, in the production of the sintered bearing 20, a mold lubricant is first added to the metal powder as a raw material, followed by stirring and mixing. Here, as the metal powder, copper powder, bronze powder, brass powder, nickel silver powder, iron powder, copper nickel alloy powder, copper-coated iron powder, stainless steel powder, mixed powders thereof, and the like can be used.

Further, the mold lubricant may be a powder of a metal soap represented by zinc stearate or lithium stearate, a fatty acid amide powder such as ethylenebisstearic acid amide, or a wax-based lubricant powder such as polyethylene. Depending on the use of the bearing, a powder of a solid lubricating component, such as graphite, molybdenum disulfide, or boron nitride, may be added separately from the metal powder.

In addition, the metal powder as a raw material, a solid lubricant component, and a mold lubricant are not limited to these.

Subsequently, the raw material powder mixed with stirring is press-molded in a mold at a pressure of about 100 to 500 MPa to form a green compact.

Further, the green compact is sintered in a predetermined atmosphere and at a predetermined temperature to form a sintered body. By sintering the green compact, adjacent metal particles are diffusion-bonded, and the metal particles are combined to form a porous sintered body.

The atmosphere is suitably in accordance with the raw material composition in a vacuum, in a reducing gas (ammonia decomposition gas, hydrogen gas, endochemical gas, etc.), in an inert gas (nitrogen gas, argon gas, etc.), or a mixture gas of reducing gas and inert gas. Choose. The sintering temperature is practically about 600 to 1200 ° C, for example, about 600 to 800 ° C in the case of bronze (Cu-Sn), and the material mainly made of iron is about 700 to 1200 ° C, and this is also used for raw material composition. It is selected accordingly.

Further, the sintered body is sized (recompressed) in a mold to form a recompressed body. By sizing the sintered body, dimensional accuracy can be improved, and surface roughness can also be improved.

Then, a plurality of dimples d are formed on the bearing surfaces 21a and 22a of the compression molded body. The formation of dimples d on the bearing surfaces 21a, 22a uses plastic processing such as pinning, rolling, and stamping. For example, the formation of dimples d on the bearing surfaces 21a, 22a can be performed using a tool for plastic working. The tool includes a mandrel having a convex portion, a retainer external to the mandrel, and a rolling element held by the retainer and rolling and moving the outer circumferential surface of the mandrel. Thereby, the retainer is inserted into the inner circumferential surface of the bearing hole h, and by rotating the mandrel, the rolling element protrudes or is buried from the outer surface of the retainer by the convex portion of the mandrel, and the protruding rolling element engages the bearing surfaces 21a, 22a. Dimples can be formed by plastic deformation.

Further, rotation sizing (burning processing) may be performed on the bearing surfaces 21a and 22a on which the dimple d is formed. By performing re-sizing of the bearing surfaces 21a and 22a to refinish the inner diameter of the bearing hole h, not only can the dimensional accuracy be further improved, but also characteristics such as surface roughness and conformity at the beginning of operation can be improved. .

Then, the compressed molded body after the dimple forming process or the compressed molded body subjected to the rotation sizing after the dimple forming process is subjected to a cleaning treatment to remove metal debris generated by the processing, lubricant for sizing, and the like.

Thereafter, the sintered bearing 20 is completed by impregnating the cleaned compressed molded body with a lubricant.

[Effects of the fan motor 1]

Next, the effect of the fan motor 1 (sintered bearing 20) will be described.

In the fan motor 1, the rotating shaft 10 is rotated by applying current to the coil 3a of the laminated core 3, and accordingly, the impeller 6 disposed on the output side of the rotating shaft 10 is rotated.

At this time, in the sintered bearing 20, the inner diameter of the intermediate portion 23 formed between both bearing portions 21 and 22 is formed in a larger dimension compared to the inner diameter of each bearing portion 21 and 22, thereby forming the intermediate portion ( The inner circumferential surface 23a of 23) does not come into contact with the rotating shaft 10 (sliding contact). Therefore, the contact between the inner circumferential surface of the bearing hole h and the rotating shaft 10 is suppressed as compared to a straight bearing, and at the same time, the frictional resistance generated between the rotating shaft 10 is reduced by reducing the fluid resistance of the lubricant during shaft rotation. It becomes possible to do.

Here, as a method of reducing the frictional resistance generated between a bearing and a rotating shaft in a conventional motor, a method of supporting the rotating shaft by two bearings arranged apart is known. However, in this method, it is difficult to suppress the unevenness of the coaxiality of two independent bearings, and if the coaxiality is poor, the clearance between the rotating shaft and the inner diameter sliding surface becomes too narrow even if the rotating shaft cannot or cannot penetrate both bearings. This increases, and the power consumption of the motor increases. For this reason, although the clearance design must inevitably be widened, when the coaxiality can be improved within a range of non-uniformity, the clearance between the rotating shaft and the inner diameter sliding surface becomes too large, and motor noise is generated due to congestion of the rotating shaft. Here, the coaxiality means the size shifted from the reference axis of the axis to be on the same straight line as the reference axis.

On the other hand, in the sintered bearing 20, the first bearing part 21 and the second bearing part 22 are integrally formed through the intermediate part 23, so that the coaxiality of both bearing parts 21, 22 It becomes possible to decrease the value of. And, by making the value of the coaxiality of both bearing parts 21 and 22 small, it becomes possible to further suppress the contact between both bearing surfaces 21a and 22a and the rotating shaft 10. In particular, in the sintered bearing 20, the first bearing portion 21 and the second bearing portion 22 are integrally formed, so that the coaxiality of both bearing portions 21 and 22 can be made 3 µm or less. . Therefore, in the fan motor 1, it is preferable to form the coaxiality of both bearing parts 21 and 22 to 3 µm or less. Thus, by adjusting the clearance level of both bearing parts 21 and 22 (clearance between the bearing surfaces 21a and 22a and the rotating shaft 10), the noise characteristics and power consumption of the fan motor 1 are mass produced. Nonuniformity can be suppressed, and it becomes possible to obtain equivalent motor quality.

Further, in the sintered bearing 20, a plurality of dimples d are formed on at least one of the first bearing surface 21a and the second bearing surface 22a rotatably supporting the rotating shaft 10. As a result, the sliding area on the bearing surfaces 21a and 22a is prevented from coming into contact with the rotating shaft 10 in the portion (range) in which the dimples d are formed among the bearing surfaces 21a and 22a. Decreases. Therefore, the contact between the bearing surfaces 21a, 22a and the rotating shaft 10 is suppressed, and at the same time, it is possible to reduce frictional resistance generated between the rotating shaft 10 by reducing the fluid resistance of the lubricant during the rotating shaft. It is done. Therefore, the sliding area on the inner circumferential surface of the bearing hole h can be reduced without reducing the axial dimension of the bearing surfaces 21a, 22a, and while suppressing the decrease in oil film strength, the rotational axis 10 is interposed. It becomes possible to reduce the frictional resistance generated at.

In addition, in the sintered bearing 20, a plurality of dimples d are formed on the bearing surfaces 21a and 22a, so that the impregnated lubricant is stored in each dimple d. Then, when the rotating shaft 10 rotates, the lubricant stored in each dimple d is drawn out between the bearing surfaces 21a, 22a and the rotating shaft 10. This makes it easy to form an oil film at the beginning of operation, especially when the rotating shaft 10 is rotated, and it becomes possible to reduce the friction coefficients of the bearing surfaces 21a and 22a.

In addition, in the sintered bearing 20, a plurality of dimples d are formed on the bearing surfaces 21a and 22a, thereby increasing the average clearance between the bearing surfaces 21a and 22a and the outer peripheral surface of the rotating shaft 10. This makes it possible to reduce the fluid resistance of the lubricant present between the bearing surfaces 21a, 22a and the rotating shaft 10 when the rotating shaft 10 rotates.

In addition, in the sintered bearing 20, a plurality of dimples d are formed by plastically deforming the bearing surfaces 21a, 22a, so that it is possible to improve the processing precision of each dimple d. In particular, the sintered bearing has a porous structure because it is formed by sintering metal powder. For this reason, by forming each dimple d by plastic working, since the deformed portion is absorbed by the micropores, it is possible to prevent the swelling of the bearing surfaces 21a and 22a.

Here, there are laser processing and etching (partial corrosion) processing as a method of forming the dimple by plastic processing, but a large-scale facility is required for these methods, and the processing process increases. On the other hand, plastic processing does not require large-scale equipment, and since the processing steps are small, it is relatively inexpensive and can be processed in large quantities.

In particular, in the sintered bearing 20, the average microhardness (MHv) of the bearing surfaces 21a and 22a is within the range of 50 to 200, so that durability of the sintered bearing is not deteriorated, and dimensions and precision of the sintered bearing are not deteriorated. Without it, it becomes possible to form a dimple on the bearing surface.

In addition, in the sintered bearing 20, each dimple d is formed to be spaced apart from the axial ends of the bearing surfaces 21a, 22a, so that the hydraulic pressure escapes from the axial ends of the bearing surfaces 21a, 22a. It is suppressed and it becomes possible to suppress the fall of the oil film strength.

As described above, according to the sintered bearing 20, contact between the bearing surface and the rotating shaft is suppressed, and at the same time, it is possible to reduce the frictional resistance generated between the rotating shaft by reducing the fluid resistance of the lubricant during the rotating shaft. . Thereby, it becomes possible to obtain the effects shown below in the fan motor 1.

It is possible to improve characteristics of a motor having a small driving torque, such as the fan motor 1. That is, in general, in the motor, as the driving torque decreases, the magnitude of the frictional resistance generated between the bearing surface and the rotating shaft has greatly influenced the motor characteristics. When the frictional resistance increases, the number of revolutions of the motor decreases, so that the target number of revolutions cannot be achieved and the power consumption of the motor increases.

On the other hand, in the sintered bearing 20, the frictional resistance generated between the bearing surfaces 21a, 22a and the rotating shaft 10 can be reduced as described above. Therefore, by applying the sintered bearing 20 to the fan motor 1, even if the driving torque of the fan motor 1 is reduced, it is possible to suppress a decrease in the rotational speed of the fan motor 1, and at the same time, it is also possible to reduce power consumption. Becomes

In addition, in the fan motor 1, it becomes possible to make the clearance between the bearing surfaces 21a and 22a and the outer peripheral surface of the rotating shaft 10 smaller. That is, in general, in a motor, as the clearance between the bearing surface and the outer circumferential surface of the rotating shaft decreases, the fluid resistance of the lubricant during rotation of the shaft increases, and the frictional resistance generated between the rotating shaft increases. Then, the number of revolutions of the motor decreases, so that the target number of revolutions cannot be achieved, and the power consumption of the motor increases.

On the other hand, in the sintered bearing 20, the fluid resistance of the lubricant present between the bearing surfaces 21a, 22a and the rotating shaft 10 can be reduced as described above. Therefore, by applying the sintered bearing 20 to the fan motor 1, even if the clearance between the bearing surfaces 21a, 22a and the outer circumferential surface of the rotating shaft 10 is made small, it is possible to suppress the decrease in the rotational speed of the fan motor 1 It becomes possible, and it is also possible to suppress the increase in the power consumption of the fan motor 1. And, as a result of being able to reduce the clearance between the bearing surfaces 21a, 22a and the outer peripheral surface of the rotating shaft 10, the rotating shaft 10 within the clearance between the bearing surfaces 21a, 22a and the outer peripheral surface of the rotating shaft 10 Congestion of can be suppressed, and the values of the coaxiality of both the bearing parts 21 and 22 described above can be reduced, and noise of the motor can be reduced.

In general, in a motor driven at a light load such as a fan motor, if the clearance between the bearing surface and the outer circumferential surface of the rotating shaft is made larger than 6 µm, there is a fear that congestion of the rotating shaft occurs within this clearance and noise increases. On the other hand, if the clearance between the bearing surface and the outer circumferential surface of the rotating shaft is 6 µm or less, the fluid resistance of the lubricant at the time of rotation of the shaft increases, and the frictional resistance generated between the rotating shaft increases. On the other hand, in the fan motor 1, frictional resistance generated between the bearing surfaces 21a, 22a and the rotating shaft 10 can be reduced by applying the sintered bearing 20, so that the bearing surfaces 21a, 22a The clearance between the outer peripheral surfaces of the rotating shaft 10 can be 6 µm or less. Therefore, in the fan motor 1, it is preferable that the clearance between the bearing surfaces 21a and 22a and the outer peripheral surface of the rotating shaft 10 is 6 µm or less in order to reduce noise.

In addition, it is possible to use a lubricant having a higher viscosity in the fan motor 1. That is, in general, as the viscosity of the lubricant used in the motor increases, the fluid resistance of the lubricant existing between the bearing surface and the rotating shaft increases. Then, the number of revolutions of the motor decreases, so that the target number of revolutions cannot be achieved and the power consumption of the motor increases.

On the other hand, in the sintered bearing 20, the fluid resistance of the lubricant present between the bearing surfaces 21a, 22a and the rotating shaft 10 can be reduced as described above. Therefore, by applying the sintered bearing 20 to the fan motor 1, even if the viscosity of the lubricant used is high, it is possible to suppress a decrease in the number of revolutions, and also to suppress an increase in power consumption. In addition, as a result of being able to increase the viscosity of the lubricant to be used, the wear resistance of the bearing can be improved, and evaporation suppression, deterioration suppression, and leakage suppression of the lubricant under high temperature can also be made, so that the motor life can be extended. In particular, it is possible to increase the oil film strength generated on the inner diameter sliding surface by using a lubricant having a high viscosity, thereby making it possible to reduce motor noise.

In general, a motor with a small driving torque uses a lubricant of 32 kPa / s or less to reduce the fluid resistance of the lubricant. On the other hand, since the fluid resistance of the lubricant can be reduced by applying the sintered bearing 20 in the fan motor 1, the viscosity of the lubricant used within the range of the specified current value of the motor can be increased up to 70 kPa / s. You can. On the other hand, if the viscosity of the lubricant is lower than 10 mm / s ² , the evaporation characteristics of the lubricant decrease. Therefore, in the fan motor 1, it is preferable that the viscosity of the lubricant is within the range of 10 to 70 kPa / s. Here, the viscosity (mm / s ² ) means a value at 40 ° C.

Further, in the fan motor 1, the use temperature range from low temperature to high temperature can be widened. That is, in general, in a motor, as the operating temperature decreases, the viscosity of the lubricant increases significantly, so that the fluid resistance of the lubricant existing between the bearing surface and the rotating shaft increases. Then, the number of revolutions of the motor decreases, so that the target number of revolutions cannot be achieved, and the power consumption of the motor increases. Especially, in the case of a low-torque motor, there is a fear that a worst-case starting failure (non-starting state) may occur. There is. Conversely, when the motor operating temperature increases, the viscosity of the lubricant decreases significantly, and the oil film strength generated on the sliding surface of the bearing inner diameter decreases, so that the wear resistance of the bearing or noise of the motor tends to occur. In addition, the evaporation, deterioration, and leakage of the lubricant also tend to occur, resulting in a reduction in motor life.

On the other hand, in the sintered bearing 20, the fluid resistance of the lubricant present between the bearing surfaces 21a, 22a and the rotating shaft 10 can be reduced as described above. Therefore, by applying the sintered bearing 20 to the fan motor 1, it is possible to suppress a decrease in the number of revolutions even when the viscosity of the lubricant increases at a low temperature, and it is also possible to suppress an increase in power consumption. Here, when a lubricant having the same viscosity as a conventional bearing is selected, it becomes possible to improve the low temperature characteristics while maintaining the high temperature characteristics of the motor. On the other hand, when a lubricant having a viscosity higher than that of a conventional bearing is selected, it becomes possible to improve the high temperature characteristics while maintaining the low temperature characteristics of the motor.

For example, the sintered bearing 20 is suitable for application to a fan motor of a refrigerator. That is, in recent refrigerators, defrosting control is performed to increase the temperature at regular intervals to remove frost. As a result, in a fan motor used in a refrigerator, if the viscosity of the lubricant is high, starting failure may occur. On the other hand, when the viscosity of the lubricant is too low, evaporation, deterioration and leakage of the lubricant are likely to occur when defrosting control is performed. There is a risk of losing the life. On the other hand, by using the fan motor 1 which can be used at a wider range of temperatures in the refrigerator, it is possible to suppress the decrease in life while preventing the occurrence of starting failure.

(Modified example)

The embodiments of the present invention have been described above, but various modifications can be made in the above embodiments.

For example, in the above embodiment, a plurality of dimples d are formed in each of the first bearing surface 21a and the second bearing surface 22a. However, a plurality of dimples d may be formed only on the first bearing surface 21a among the two bearing surfaces 21a, 22a, and the second bearing surface 22a among the two bearing surfaces 21a, 22a It does not matter even if a plurality of dimples d are formed. Particularly, by forming a plurality of dimples d only on the second bearing surface 22a among the two bearing surfaces 21a and 22a, the decrease in the oil film strength at the first bearing surface 21a on the output side where the load is increased It is possible to reduce the friction coefficient in the second bearing surface 22a on the half output side where the load is lowered while preventing.

In the above embodiment, the dimple d formed in the first bearing surface 21a and the dimple d formed in the second bearing surface 22a have the same shape, dimension, and maximum depth. However, at least one of shape, dimension and maximum depth may be different from the dimple d formed in the first bearing surface 21a and the dimple d formed in the second bearing surface 22a. For example, at least one of the dimension and the maximum depth of the dimple d is reduced in the first bearing surface 21a on the output side where the load is increased, and the dimple (in the second bearing surface 22a on the half-output side where the load is lowered) is reduced. It does not matter even if at least one of the dimension and the maximum depth of d) is increased.

Further, the range, density, and the like in which the dimples d are formed on both bearing surfaces 21a and 22a may be different. For example, the range or density in which the dimple d is formed in the first bearing surface 21a on the output side where the load is increased is reduced, and the dimple (d) in the second bearing surface 22a on the half output side where the load is lowered is reduced. It is also possible to increase the range or density in which the) is formed. Here, the density means the number of dimples per unit area (hereafter, the same is done).

Further, in the above-described embodiment, a plurality of dimples d are formed in substantially the entire area of each bearing surface 21a, 22a. However, an area in which the dimple d is not formed may be formed in a part of each of the bearing surfaces 21a and 22a. For example, by forming an area where no dimple d is formed at at least one of the axial end portions of each bearing surface 21a, 22a, the oil film strength of each bearing surface 21a, 22a is determined. It becomes possible to suppress the drop.

Further, in the above embodiment, each dimple d is formed in a substantially semi-ellipsoidal shape (the shape of the projection surface is elliptical). However, each dimple d may be formed in a shape of a projection plane in a circular shape, a fan shape, a triangle shape, a square shape, or a rhombus shape.

In the above-described embodiment, the shape, dimension and maximum depth are the same in the plural dimples d formed on the bearing surfaces 21a and 22a. However, in a plurality of dimples d formed on each bearing surface 21a, 22a, it is possible to mix at least one of shape, dimension, and maximum depth.

In addition, in the above embodiment, a plurality of dimples d are regularly arranged on each bearing surface 21a, 22a. However, a plurality of dimples d may be irregularly arranged on the bearing surfaces 21a and 22a.

In the above embodiment, each dimple d is formed to extend along the circumferential direction. However, each dimple d may be formed to extend along the axial direction, or may be formed to extend along a direction inclined at a predetermined angle with respect to each of the axial and circumferential directions.

Further, in the above embodiment, after sizing (recompression) of the sintered body, a plurality of dimples d are formed on the bearing surfaces 21a and 22a of the compression molded body. However, sizing (recompression) may be performed after forming a plurality of dimples d on the bearing surfaces 21a and 22a of the sintered body.

In addition, in the above embodiment, an example in which the sintered bearing 20 is applied to the fan motor 1 is shown, but the sintered bearing 20 is considered to be applied to a wide range of applications as follows, particularly among motors of high-speed rotation. The application is considered suitable.

[Household appliances]

Cooling fans for computers, televisions, digital video, projectors, LED lights, color wheel motors for DLP, small-diameter stepping motors for digital cameras or digital video, fans for refrigerators, fans for microwave ovens, fans, ventilation fans, air conditioners, dryers , Vacuum cleaner, juicer / mixer, food processor, vibration motor, spindle motor for ODD, spindle motor for HDD, etc.

[For vehicle installation]

Fan for battery cooling, fan for temperature control seat, fan for in-sensor, cooling fan for audio or navigation equipment, blower, actuator for air conditioner, washer pump, door mirror, door closer, seat reclining, seat slide, power window, wiper, Starters, motors of intake and exhaust devices such as ETC and EGR, EPS (electric power steering), EPB (electronically controlled parking brake), etc.

[For OA equipment]

Polygon mirror scanner motor, stepping motor, etc.

1: Fan motor 2: Housing holder
2a: cylindrical portion 3: laminated core
3a: coil 4: rotor yoke
5: Magnet 6: Impeller
7: thrust plate 10: rotating shaft
20: sintered bearing 21: first bearing portion
22: second bearing portion 23: intermediate portion
21a: 1st bearing surface 22a: 2nd bearing surface
23a: inner peripheral surface h: bearing hole
d: dimple

Claims (1)

A sintered bearing having a bearing surface rotatably supporting a rotating shaft, wherein the rotating shaft slides relative to the bearing surface during rotation of the rotating shaft,
The first bearing surface of the first bearing portion of the porous structure,
The second bearing surface of the second bearing portion of the porous structure,
A lubricant impregnated into the first bearing portion and the second bearing portion,
It has an intermediate portion provided between the first bearing portion and the second bearing portion,
The inner diameter of the intermediate portion is formed larger than the inner diameter of the first bearing portion and the inner diameter of the second bearing portion, respectively.
A plurality of dimples are formed in the entire circumferential direction on at least one of the first bearing surface and the second bearing surface,
The dimple is a sintered bearing, characterized in that extending along a direction inclined with respect to the circumferential direction.

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