TW201532712A - Sintering bearing - Google Patents

Abstract

Provided is a sintering bearing capable of reducing the rotating shaft resistance. The sintering bearing 20 of the present invention comprises a first bearing part 21, a second bearing part 22 and a middle part 23. The first bearing part 21 comprises a first bearing surface 21a supporting an outer peripheral surface of the rotating shaft 10. The second bearing part 22 comprises a second bearing surface 22a supporting an outer peripheral surface of the rotating shaft 10. The middle part 23 is positioned between the first bearing part 21 and the second bearing part 22. The internal diameter of the middle part 23 is larger than the internal diameter of the first bearing part 21 and the internal diameter of the second bearing part 22. Besides, a plurality of pits d are formed on at least one bearing surface 21a, 22a of the first bearing surface 21a and the second bearing surface 22a.

Description

Sintered bearing

The present invention relates to a sintered bearing which is formed by sintering powder metal powder in a mold and then sintered, and impregnated with a lubricant. More particularly, the present invention relates to a sintered bearing capable of reducing noise while reducing frictional resistance between a bearing and a rotating shaft.

As a low-cost and highly reliable bearing, sintered bearings are widely used in electric motors for home appliances, electric motors for vehicles, and OA equipment (office automation equipment). Examples of the fan motor include a cooling fan inside a home appliance such as an electronic computer or a television, a fan for circulating and cooling inside the refrigerator, cooling of the battery, and suction of the interior sensor. The demand for fan motors, etc., is increasing every year.

Since the equipment using the fan motor has a long service life, the fan motor not only needs to have a long service life, but also needs to have an important characteristic that the power consumption can be reduced. In particular, in a battery-driven device such as a mobile device, it is necessary to minimize power consumption.

On the other hand, in recent years, the requirement for quieting of the fan motor has been greatly improved. In general, in order to achieve the quieting of the motor, it is necessary to achieve a sintered bearing: first, the noise generated by the sway of the shaft is suppressed by reducing the gap between the rotating shaft and the bearing, and second, by impregnating the impregnation The viscosity of the lubricant in the bearing to increase the strength of the oil film produced on the sliding surface of the inner diameter Therefore, it is possible to effectively achieve the quieting of the fan motor.

However, in a motor having a low operating load such as a fan motor and a small torque, the frictional resistance between the rotating shaft and the bearing mainly depends on the fluid resistance of the lubricant impregnated in the bearing. Therefore, if the gap between the rotating shaft and the bearing is too small, the fluid resistance of the lubricant when the shaft rotates increases, resulting in an increase in the power consumption of the motor. On the other hand, as the viscosity of the lubricant increases, the fluid resistance increases, which also causes the power consumption of the motor to become large. Therefore, there is a limit to the viscosity of the available lubricant.

In the prior art, as a sintered bearing capable of reducing the frictional resistance between the rotating shaft and the bearing, for example, Patent Document 1 discloses a sintered bearing.

In the sintered bearing, the inner diameter of the axially intermediate portion of the bearing hole that supports the rotatable shaft so as to be rotatable is formed to be larger than the inner diameters of both axial end portions (hereinafter referred to as "bearing portions"). Thereby, since the inner peripheral surface of the intermediate portion can be prevented from coming into contact with the rotating shaft, the area of the portion corresponding to the rotating shaft on the inner peripheral surface of the bearing hole (hereinafter referred to as "sliding area") can be reduced. Since the contact between the inner circumferential surface of the bearing hole and the rotating shaft can be suppressed, and the fluid resistance of the lubricant at the time of the shaft rotation can be suppressed, the frictional resistance generated between the rotating shaft and the bearing can be reduced. Here, the "portion corresponding to the rotating shaft" means a portion which is likely to come into contact with the rotating shaft when the rotating shaft rotates, and the influence of the fluid resistance of the lubricant received when the shaft is rotated, rather than rotating. The part that always touches the rotating shaft when the shaft rotates (the same applies below).

Patent literature

Patent Document 1 Japanese Patent Laid-Open No. Hei 7-332363

However, in the existing sintered bearings, the friction between the rotating shaft and the bearing is reduced. There is a limit to the resistance to rubbing.

Specifically, in the conventional sintered bearing, the range of the two bearing portions is reduced by expanding the range of the intermediate portion in the axial direction of the sintered bearing. At this time, the smaller the range of the two bearing portions, the smaller the sliding area can be reduced. . 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 the axial ends of the respective bearing faces, so that the strength of the oil film cannot be maintained. Further, as the strength of the oil film is lowered, contact between the bearing surface and the rotating shaft is likely to occur, and as a result, not only the frictional resistance generated between the bearing surface and the rotating shaft is increased, but also noise is generated. Therefore, in the conventional sintered bearing, there is a limit in reducing the frictional resistance between the rotating shaft and the bearing.

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

In order to solve the above problems, the sintered bearing according to the first aspect of the invention is formed by subjecting a metal powder to powder compaction in a mold and then sintering, and has a bearing hole that supports a rotatable shaft so as to be rotatable, and is impregnated with a lubricant. The sintered bearing is characterized by having a first bearing portion having a first bearing surface supporting the rotating shaft, and a second bearing portion having a support a second bearing surface of the rotating shaft, the intermediate portion being disposed between the first bearing portion and the second bearing portion, the inner diameter of the intermediate portion being formed to be larger than an inner diameter of the first bearing portion The inner diameter of the second bearing portion is large, and a plurality of dimples are formed on a bearing surface of at least one of the first bearing surface and the second bearing surface.

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

Thereby, it is possible to prevent the inner peripheral surface of the intermediate portion from coming into contact with the rotating shaft, and it is possible to reduce the sliding area in the inner peripheral surface of the bearing hole. Therefore, compared with a sintered bearing (hereinafter referred to as a "linear bearing") in which the inner diameter of the bearing hole is the same in the axial direction, not only the contact between the inner peripheral surface of the bearing hole and the rotating shaft is suppressed, but also the lowering is achieved. Since the fluid resistance of the lubricant when the shaft rotates, the frictional resistance generated between the bearing and the rotating shaft can be reduced.

In particular, in the sintered bearing according to the first aspect of the invention, a plurality of pits are provided on a bearing surface that supports at least one of the first bearing surface and the second bearing surface that can rotate the rotating shaft.

Since the portion (range) of the bearing surface where each pit is provided does not come into contact with the rotating shaft, the sliding area in the bearing surface can be reduced. Therefore, not only the contact between the bearing surface and the rotating shaft is suppressed, but also the fluid resistance of the lubricant when the shaft rotates is reduced, so that the frictional resistance generated between the bearing surface and the rotating shaft can be reduced.

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

Further, in the sintered bearing according to the first aspect of the invention, since a plurality of pits are provided on the bearing surface, the lubricant impregnated in the sintered bearing can be stored in each of the pits. When the rotating shaft rotates, the lubricant stored in each of the pockets is attracted between the bearing surface and the rotating shaft. Therefore, when the rotating shaft rotates, especially in the initial stage of operation, the formation of the oil film can be facilitated, and the friction coefficient of the bearing surface can be reduced.

Further, in the sintered bearing according to the first invention, since a plurality of concaves are provided on the bearing surface The pit can increase the average gap between the bearing surface and the outer peripheral surface of the rotating shaft. Thereby, when the rotating shaft rotates, the fluid resistance of the lubricant existing between the bearing surface and the rotating shaft can be reduced.

As described above, according to the sintered bearing of the first aspect of the invention, it is possible to suppress the contact between the bearing surface and the rotating shaft and to reduce the fluid resistance of the lubricant, so that the frictional resistance generated between the bearing surface and the rotating shaft can be reduced.

In particular, by applying the sintered bearing according to the first aspect of the invention, it is possible to improve the characteristics of a motor having a small driving torque. That is to say, in general, the smaller the driving torque of the motor, the greater the influence of the frictional resistance generated between the bearing surface and the rotating shaft on the characteristics of the motor.

Specifically, as the frictional resistance increases, the rotational speed of the motor decreases, which not only makes it impossible to achieve the target rotational speed, but also causes an increase in the power consumption of the motor. On the other hand, according to the sintered bearing according to the first aspect of the invention, as described above, the 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 when the driving torque of the motor is reduced, the reduction in the number of rotations of the motor can be suppressed, and the power consumption can be reduced.

Further, by applying the sintered bearing according to the first aspect of the invention, it is possible to configure a motor having a small gap between the bearing surface and the outer peripheral surface of the rotating shaft. That is to say, in general, in the motor, as the gap between the bearing surface and the outer peripheral surface of the rotating shaft is reduced, the fluid resistance of the lubricant when the shaft rotates increases, so that the bearing surface and the rotating shaft are The frictional resistance generated between them increases. At this time, not only the rotation speed of the motor is reduced, but the target rotation speed cannot be achieved, and the power consumption of the motor is increased. On the other hand, according to the sintered bearing according to the first aspect of the invention, as described above, the fluid resistance of the lubricant at the time of the shaft rotation can be reduced. So by application In the sintered bearing according to the first aspect of the invention, even when the gap between the bearing surface and the outer peripheral surface of the rotating shaft is reduced, the reduction in the number of revolutions of the motor can be suppressed. In addition, it is also possible to suppress an increase in power consumption of the motor. Further, since the gap between the bearing surface and the outer peripheral surface of the rotating shaft can be reduced, it is possible to suppress the occurrence of rattling of the rotating shaft in the gap between the bearing surface and the outer peripheral surface of the rotating shaft, thereby reducing the noise of the motor.

Further, by applying the sintered bearing according to the first invention, a lubricant having a higher viscosity can be used. That is, in general, in the motor, as the viscosity of the lubricant used increases, the fluid resistance of the lubricant existing between the bearing surface and the rotating shaft increases. At this time, not only the rotation speed of the motor is reduced, but the target rotation speed cannot be achieved, and the power consumption of the motor is increased. On the other hand, according to the sintered bearing according to the first aspect of the invention, as described above, the fluid resistance of the lubricant existing 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, it is possible to suppress a decrease in the number of revolutions of the motor even if a lubricant having a high viscosity is used. In addition, it is also possible to suppress an increase in power consumption of the motor. Further, since a highly viscous lubricant can be used, it is possible to suppress the evaporation of the lubricant at a high temperature while suppressing the wear resistance of the bearing, suppress the aging, and also suppress the leakage of the lubricant, thereby extending the motor. Service life. In particular, by using a highly viscous lubricant, the strength of the oil film formed on the inner diameter sliding surface can be increased, and the noise of the motor can also be reduced.

According to the sintered bearing according to the first aspect of the invention, the sintered bearing according to the second aspect of the invention is characterized in that the plurality of pits are formed by plastic working.

In the sintered bearing according to the second aspect of the invention, a plurality of pits are formed by plastically deforming the bearing surface. Thereby, the processing precision of each pit can be improved.

In particular, since the sintered bearing is formed by sintering the metal powder, it has many Porous structure. Therefore, each of the dimples is formed by plastic working, and the deformed portion can be absorbed by the micropores, so that the bearing surface can be prevented from bulging.

In addition to plastic working, as a method of forming the pits, laser processing and etching (partial etching) processing and the like are also exemplified, but these methods require not only large-scale equipment but also an increase in processing steps. On the other hand, plastic processing does not require the use of large equipment, and the number of processing steps is small, so that it is possible to perform large-scale processing at a relatively low cost.

According to a sintered bearing according to the first or second aspect of the invention, in the sintered bearing according to the third aspect of the invention, the recess is provided at an interval from an axial end portion of the bearing surface.

According to the sintered bearing of the third aspect of the invention, since the dimples are spaced apart from the axial end portions of the bearing surfaces, it is possible to suppress the escape of the hydraulic pressure from the axial end portions of the bearing surfaces, thereby suppressing the decrease in the strength of the oil film. .

The sintered bearing according to any one of the first to third aspects of the present invention, characterized in that the sintered bearing according to the fourth aspect of the present invention is characterized in that a bearing surface provided with the plurality of pits and the rotating shaft The gap between the outer peripheral faces is set to be 6 μm or less.

In general, in a motor driven by a light load such as a fan motor, if the gap between the bearing surface and the outer peripheral surface of the rotating shaft is larger than 6 μm, the rotating shaft may be shaken in the gap, thereby making the noise large. . On the other hand, if the gap between the bearing surface and the outer peripheral surface of the rotating shaft is set to 6 μm or less, the fluid resistance of the lubricant at the time of the shaft rotation increases, which causes friction between the bearing surface and the rotating shaft. The resistance increases.

However, in the sintered bearing according to the present invention, as described above, even when the gap between the bearing surface and the outer peripheral surface of the rotating shaft is set to 6 μm or less, the running of the shaft can be reduced. Since the fluid resistance of the lubricant is reduced, the frictional resistance generated between the bearing surface and the rotating shaft can be reduced, the power consumption of the motor can be suppressed, and the noise at the time of rotation of the rotating shaft can be reduced.

The sintered bearing according to any one of the first to fourth aspects of the present invention, characterized in that the sintered bearing according to the fifth aspect of the invention is characterized in that the average microhardness of the bearing surface on which the plurality of pits are provided (MHv) ) in the range of 50 to 200.

Specifically, when the average microhardness (MHv) of the bearing surface is less than 50, the wear resistance of the sintered bearing is deteriorated, resulting in a decrease in durability. On the other hand, if the average microhardness (MHv) of the bearing surface is more than 200, when each pit is formed, the periphery of each pit is caused to bulge, so that the prescribed size and precision cannot be obtained.

Therefore, by setting the average microhardness (MHv) of the bearing surface provided with a plurality of pits in the range of 50 to 200, it is possible to avoid the deterioration of the durability of the sintered bearing and to avoid the decrease in the size and precision of the sintered bearing. In the case, a pit is formed on the bearing surface.

A sintered bearing according to a sixth aspect of the present invention provides the sintered bearing according to the sixth aspect of the invention, characterized in that the sintered bearing is applied to a fan motor.

According to the sintered bearing of the sixth aspect of the invention, not only the characteristics of the fan motor having a small driving torque but also the power consumption can be reduced. Further, since the fan motor can be configured to have a smaller gap between the bearing surface and the outer peripheral surface of the rotating shaft, it is possible to suppress the occurrence of rattling of the rotating shaft in the gap between the bearing surface and the outer peripheral surface of the rotating shaft, and it is possible to reduce the fan motor. The noise. Further, since a lubricant having a higher viscosity can be used, it is possible to suppress the evaporation of the lubricant at a high temperature while suppressing the wear resistance of the bearing, suppress the aging, and also suppress the leakage of the lubricant, thereby being prolonged. The service life of the motor. Especially by using high The viscosity of the lubricant can increase the strength of the oil film formed on the inner diameter sliding surface, and can further reduce the noise of the motor.

According to the sintered bearing of the present invention, the frictional resistance between the bearing and the rotating shaft can be reduced, and noise can be reduced.

1‧‧‧Fan motor

2‧‧‧Shell bracket

2a‧‧‧Cylinder

3‧‧‧Laminated iron core

3a‧‧‧ coil

4‧‧‧ rotor yoke

5‧‧‧ magnet

6‧‧‧ Impeller

7‧‧‧Thrust plate

10‧‧‧Rotary axis

20‧‧‧Sintered bearings

21‧‧‧First Bearing Department

22‧‧‧Second bearing

23‧‧‧Intermediate

21a‧‧‧First bearing surface

22a‧‧‧second bearing surface

23a‧‧‧ inner circumference

H‧‧‧ bearing hole

D‧‧‧ pit

Fig. 1 is a partial cross-sectional view showing a fan motor according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view showing a sintered bearing of the fan motor shown in Fig. 1.

Fig. 3 is a partial enlarged view of a bearing surface of the sintered bearing shown in Fig. 2;

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

The sintered bearing 20 can be widely applied to various electric motors such as various home electric appliances and vehicles, and OA equipment (office automation equipment). An example in which the sintered bearing 20 is applied to the fan motor 1 is shown in the present embodiment.

(Structure 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 of the fan motor shown in FIG. 1, and FIG. 3 is a bearing surface of the sintered bearing shown in FIG. Partial enlarged view.

The fan motor 1 shown in Fig. 1 has a housing holder 2, a sintered bearing 20 held by the housing holder 2, and a rotating shaft 10 supported by the sintered bearing 20 so as to be rotatable.

The housing holder 2 has a cylindrical portion 2a that holds the sintered bearing 20 therein. In the cylindrical portion 2a A laminated core (stator) 3 formed by winding the coil 3a is provided on the outer peripheral surface.

The rotating shaft 10 is made of metal (alloy steel such as carbon steel or stainless steel) and is formed in a cylindrical shape. A magnet (rotor) 5 is attached to the rotating shaft 10 via the rotor yoke 4. The magnet 5 is disposed to face the laminated core 3 provided on the outer peripheral surface of the casing holder 2. An impeller (fan) 6 is attached to the outer circumference of the rotor yoke 4. Further, a thrust plate 7 is fitted to the inner bottom portion of the cylindrical portion 2a of the casing bracket 2, and pivotally supports the end portion of the rotating shaft 10 opposite to the output side in the thrust direction.

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

The sintered bearing 20 is formed substantially in a cylindrical shape, and has a bearing hole h that supports the rotating shaft 10 so as to be rotatable. The bearing hole h is provided to penetrate the sintered bearing 20 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 provided between the first bearing portion 21 and the second bearing portion 22. The inner circumferential surface of the first bearing portion 21 serves as a first bearing surface 21a that supports the outer circumferential surface of the rotating shaft 10, and the inner circumferential surface of the second bearing portion 22 serves as 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 formed to be larger than the outer diameter of the rotating shaft 10, respectively. Further, the inner diameter of the first bearing portion 21 and the inner diameter of the second bearing portion are formed to be substantially the same size. In the present embodiment, the inner diameter of the first bearing portion 21 and the inner diameter of the second bearing portion 22 are set such that the gap between the respective bearing surfaces 21a, 22a and the outer peripheral surface of the rotary shaft 10 is 6 μm or less. . Further, the inner diameter of the intermediate portion 23 is formed to be larger than the first bearing portion 21 Both the inner diameter and the inner diameter of the second bearing portion 22 are large.

The rotary shaft 10 is disposed in a state of being inserted into the bearing hole h of the sintered bearing 20. Further, in the sintered bearing 20, the first bearing portion 21 supports the end on the output side of the rotating shaft 10, and the second bearing portion 22 supports the end portion of the rotating shaft 10 on the side opposite to the output side. Further, in the sintered bearing 20, the rotary shaft 10 is rotatably supported by the first bearing surface 21a and the second bearing surface 22a, and the inner peripheral surface 23a of the intermediate portion 23 is not in contact with the outer peripheral surface of the rotary shaft 10 (sliding contact) ).

As shown in FIG. 3, a plurality of dimples d are provided on a bearing surface of at least one of the first bearing surface 21a and the second bearing surface 22a. In the present embodiment, a plurality of pits d are provided on the first bearing surface 21a and the second bearing surface 22a, respectively. Further, the dimples are provided substantially over the entire area of the respective bearing faces 21a, 22a, and a plurality of dimples are regularly arranged. No pit d is provided on the inner peripheral surface 23a of the intermediate portion 23.

Each of the pits d is formed by plastic working such as shot blasting, rolling processing, and embossing. Each of the dimples d is formed into a substantially hemispherical concave portion, a substantially semi-ellipsoidal concave portion, or a substantially semi-cylindrical concave portion. In the present embodiment, each of the pits d is formed into a substantially semi-ellipsoidal concave portion having a short diameter of 10 to 500 μm and a long diameter of 10 to 1000 μm. Further, the maximum depth of each pit d is formed in the range of 1 to 50 μm. Further, each of the dimples d is provided to extend in the circumferential direction (direction orthogonal to the axial direction).

In the present embodiment, each of the dimples d is provided at a certain interval from the axial end portions of the respective bearing faces 21a, 22a. That is, each of the dimples d is not exposed on each of the end faces of the respective bearing portions 21, 22 in the axial direction (not communicating with the respective end faces).

Here, if the average microhardness (MHv) of each of the bearing faces 21a, 22a is less than 50, the wear resistance of the sintered bearing 20 is deteriorated, so that the durability is lowered. On the other hand, each bearing surface 21a, 22a If the average microhardness (MHv) is higher than 200, when the respective pits d are formed by the plastic working method, the periphery of each of the pits d is swelled, so that the prescribed size and precision cannot be obtained. Therefore, it is preferable to set the average microhardness (MHv) of each of the bearing faces 21a, 22a in the range of 50 to 200.

Further, if the area ratio of the pits is less than 10%, the effect of lowering the friction coefficient cannot be sufficiently obtained. On the other hand, if the area ratio of the pits exceeds 60%, the sliding area of each of the bearing surfaces 21a and 22a is insufficient, and the load resistance is insufficient. Therefore, it is preferable to set the area ratio of the pits to be in the range of 10 to 60%. Here, the area ratio of the pits means the total projected area of the pits d formed on the respective bearing faces 21a, 22a (for all the pits d formed on the bearing faces 21a, 22a, which will be formed) The ratio of the value obtained by totaling the projected areas of the respective pits d on the bearing surfaces 21a and 22a with respect to the total area of the respective bearing surfaces 21a and 22a.

(Method of Manufacturing Sintered Bearing 20)

Hereinafter, a method of manufacturing the sintered bearing 20 will be described.

In the following manufacturing method, a manufacturing method disclosed in Japanese Laid-Open Patent Publication No. Hei. No. Hei.

That is, in manufacturing the sintered bearing 20, a metal lubricant is first added to the metal powder as a raw material, and stirred and mixed. 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 or a mixed powder of these powders can be used.

Further, as the mold lubricant, a powder of a metal soap typified by zinc stearate or lithium stearate, a powder of a fatty guanamine such as vinyl bis- saponin or a paraffin such as polyethylene may be used. A powder of lubricant. Depending on the use of the bearing, in addition to the metal powder, a powder of a solid lubricating component typified by graphite, molybdenum disulfide, and boron nitride may be added.

The metal powder, the solid lubricating component, and the mold lubricant as raw materials are not limited to the above.

Next, the stirred and mixed raw material powder is press-molded in a mold under a pressure of about 100 to 500 MPa to form a green compact.

Thereafter, the green compact is sintered in a predetermined environment in accordance with predetermined temperature conditions to form a sintered body. By sintering the green compact, adjacent metal particles are diffusion-bonded, and the metal particles are bonded to each other to form a porous sintered body.

The environment is a vacuum environment, a reducing gas environment (ammonia decomposition gas, hydrogen gas, endothermic gas, etc.), an inert gas atmosphere (nitrogen gas, argon gas, etc.), and a mixed gas of the reducing gas and the inert gas, etc., according to The raw material components are appropriately selected. As the sintering temperature, a practical sintering temperature of about 600 to 1200 ° C, for example, when using bronze (Cu-Sn), a sintering temperature of about 600 to 800 ° C can be used, and when a material mainly composed of iron is used, The sintering temperature of about 700 to 1200 ° C is used, and the sintering temperature can also be appropriately selected according to the raw material composition.

Further, the sintered body may be subjected to Sizing (recompression) in a mold to form a recompressed body. By coining the sintered body, it is possible to improve the surface roughness while improving the dimensional accuracy.

Thereafter, a plurality of dimples d are formed in the bearing faces 21a, 22a of the compression molded body. When the recesses d are formed in the bearing faces 21a and 22a, the pits d can be formed by plastic working such as shot blasting, rolling, and embossing. For example, when the bearing faces 21a, 22a form the dimples d, the plastic-machined tool can be used to form the dimples d. The tool has a mandrel, a cage and a rolling body, the mandrel has a convex portion, the cage is sleeved outside the mandrel, the rolling body is held by the cage, and is on the outer circumference of the mandrel Scroll up. By inserting the retainer into the inner peripheral surface of the bearing hole h and rotating the mandrel, the rolling element is protruded or retracted from the outer surface of the retainer by the convex portion of the mandrel, and the bearing surface is made by the protruding rolling element. 21a, 22a are plastically deformed, whereby pits can be formed.

Further, it is also possible to perform rotational sizing processing (polishing processing) on the bearing faces 21a, 22a after the formation of the pit d. By performing the rotary sizing processing on the bearing surfaces 21a and 22a, the inner diameter of the bearing hole h is again finished, which not only improves the dimensional accuracy, but also improves the surface roughness and the wearability at the initial stage of operation.

Then, the compression molded body after the pit forming process or the compression molded body subjected to the rotary sizing process after the pit forming process is subjected to a cleaning process to remove metal scraps and fine pressure lubricating oil generated during the processing. .

Thereafter, the lubricant is impregnated in the compressed molded body after washing, thereby completing the manufacture of the sintered bearing 20.

(The function and effect of the fan motor 1)

The action and effect of the fan motor 1 (sintered bearing 20) will be described below.

When the coil 3a of the laminated core 3 of the fan motor 1 is energized, the rotating shaft 10 is rotated, whereby the impeller 6 provided on the output side of the rotating shaft 10 is rotated.

At this time, in the sintered bearing 20, since the inner diameter of the intermediate portion 23 provided between the two bearing portions 21, 22 is formed to be larger than the inner diameter of each of the bearing portions 21, 22, the middle is The inner peripheral surface 23a of the portion 23 does not come into contact (sliding contact) with the rotating shaft 10. Therefore, compared with the linear bearing, not only the contact between the inner circumferential surface of the bearing hole h and the rotating shaft 10 but also the fluid resistance of the lubricant during the rotation of the shaft can be suppressed, whereby the bearing surface and the rotating shaft 10 can be reduced. The frictional resistance generated between them.

In the conventional electric motor, as a method of reducing the frictional resistance generated between the bearing and the rotating shaft, a method of supporting the rotating shaft by two bearings provided independently is known. However, in this method, it is difficult to suppress the coaxiality deviation of two independent bearings. If the deviation of the coaxiality is large, the rotating shaft cannot pass through the two bearings, or although it is able to pass through the two bearings, due to the rotation The gap between the shaft and the inner diameter sliding surface is too small to cause an increase in fluid resistance, so that the power consumption of the motor becomes large. At this time, it is necessary to enlarge the size of the gap in the design, and if the size of the gap is enlarged in design, the rotation axis and the inner diameter sliding surface of the bearing having good coaxiality within the deviation range of the coaxiality The gap between them becomes too large, causing the rotating shaft to sway and causing noise in the motor. Here, the coaxiality refers to the magnitude of the deviation from the reference axis of the axis which should be on the same straight line as the reference axis.

On the other hand, since the first bearing portion 21 and the second bearing portion 22 of the sintered bearing 20 are integrally formed by the intermediate portion 23, the value of the coaxiality of the two bearing portions 21, 22 can be reduced. By reducing the value of the coaxiality of the two bearing portions 21, 22, the contact between the two bearing faces 21a, 22a and the rotating shaft 10 can be further suppressed. In particular, since the first bearing portion 21 and the second bearing portion 22 are integrally formed in the sintered bearing 20, the coaxiality of the two bearing portions 21, 22 can be controlled to be 3 μm or less. Therefore, in the fan motor 1, it is preferable to form the coaxiality of the two bearing portions 21, 22 to be 3 μm or less. As described above, by forming the gap between the two bearing portions 21, 22 (the gap between the bearing surfaces 21a, 22a and the rotating shaft 10) to the same size, it is possible to suppress noise characteristics and mass production of the motor 1 when mass production is performed. The deviation of power consumption can obtain the same quality motor.

Further, in the sintered bearing 20, a plurality of dimples d are provided on at least one of the first bearing surface 21a and the second bearing surface 22a that support the rotatable shaft 10 so as to be rotatable. Since the portions (ranges) of the bearing faces 21a, 22a in which the respective pits d are provided do not overlap with the rotating shaft 10 Contact occurs, so that the sliding area in the bearing faces 21a, 22a can be reduced. Thereby, not only the contact between the bearing surfaces 21a and 22a and the rotating shaft 10 is suppressed, but also the fluid resistance of the lubricant at the time of the shaft rotation is reduced, so that the frictional resistance generated between the bearing surface and the rotating shaft 10 can be reduced. Therefore, it is possible to reduce the sliding area in the inner circumferential surface of the bearing hole h without reducing the axial dimension of the bearing faces 21a, 22a, and it is possible to reduce the strength of the oil film while reducing the bearing surface and the rotating shaft 10 Frictional resistance generated between.

Further, in the sintered bearing 20, since a plurality of pits d are provided on the bearing faces 21a, 22a, the lubricant impregnated in the sintered bearing 20 can be stored in each of the pits d. When the rotary shaft 10 rotates, the lubricant stored in each of the pockets d is attracted between the bearing faces 21a, 22a and the rotary shaft 10. Thereby, when the rotating shaft 10 rotates, especially in the initial stage of operation, formation of an oil film can be made easy, and the friction coefficient of the bearing surfaces 21a and 22a can be reduced.

In the sintered bearing 20, since a plurality of dimples d are provided in the bearing faces 21a and 22a, the average gap between the bearing faces 21a and 22a and the outer peripheral surface of the rotating shaft 10 can be increased. Therefore, when the rotary shaft 10 rotates, the fluid resistance of the lubricant existing between the bearing surfaces 21a, 22a and the rotary shaft 10 can be reduced.

In the sintered bearing 20, a plurality of pits d are formed by plastically deforming the bearing faces 21a, 22a. Thereby, the processing precision of each pit d can be improved. In particular, since the sintered bearing is formed by sintering the metal powder, it has a porous structure. Therefore, each of the dimples d is formed by plastic working, and the deformed portion can be absorbed by the micropores, so that the bearing faces 21a, 22a can be prevented from bulging.

Further, in addition to plastic working, as a method of forming the pits, laser processing and etching (partial etching) processing and the like can be cited, but these methods require not only large-scale equipment but also The number of processing steps has increased. On the other hand, plastic processing does not require the use of large equipment, and the number of processing steps is small, so that it can be processed in large quantities at a relatively low cost.

In particular, in the sintered bearing 20, by setting the average microhardness (MHv) of the bearing faces 21a, 22a in the range of 50 to 200, it is possible to avoid the deterioration of the durability of the sintered bearing and to avoid the size and size of the sintered bearing. When the accuracy is lowered, pits are formed on the bearing surface.

Further, in the sintered bearing 20, since the respective pits d are spaced apart from the axial end portions of the bearing surfaces 21a and 22a, it is possible to suppress the escape of the hydraulic pressure from the axial end portions of the bearing surfaces 21a and 22a, and it is possible to suppress The strength of the oil film is reduced.

As described above, according to the sintered bearing 20, since the contact between the bearing surface and the rotating shaft can be suppressed and the fluid resistance of the lubricant when the shaft is rotated can be suppressed, the frictional resistance generated between the bearing surface and the rotating shaft can be reduced. Therefore, the following effects can be obtained in the fan motor 1.

It is possible to improve the characteristics of a motor having a small driving torque such as the fan motor 1. That is to say, in general, the smaller the driving torque of the motor, the greater the influence of the frictional resistance generated between the bearing surface and the rotating shaft on the characteristics of the motor. As the frictional resistance increases, the rotational speed of the motor decreases, which not only makes it impossible to achieve the target rotational speed, but also causes an increase in the power consumption of the motor.

On the other hand, in the sintered bearing 20, as described above, the frictional resistance generated between the bearing faces 21a, 22a and the rotating shaft 10 can be reduced. Therefore, by using the sintered bearing 20 in the fan motor 1, even when the driving torque of the fan motor 1 is lowered, the decrease in the number of revolutions of the fan motor 1 can be suppressed, and the power consumption can be reduced.

Further, in the fan motor 1, the gap between the bearing faces 21a, 22a and the outer peripheral surface of the rotary shaft 10 can be further reduced. That is to say, in general, in the motor, As the gap between the bearing surface and the outer peripheral surface of the rotating shaft is reduced, the fluid resistance of the lubricant when the shaft rotates increases, and the frictional resistance generated between the bearing surface and the rotating shaft increases. At this time, not only the rotation speed of the motor is reduced, but the target rotation speed cannot be achieved, and the power consumption of the motor is increased.

On the other hand, in the sintered bearing 20, as described above, the fluid resistance of the lubricant existing between the bearing faces 21a, 22a and the rotating shaft 10 can be reduced. Therefore, by using the sintered bearing 20 in the fan motor 1, even when the gap between the bearing faces 21a, 22a and the outer peripheral surface of the rotating shaft 10 is reduced, the decrease in the number of revolutions of the fan motor 1 can be suppressed. Further, it is also possible to suppress an increase in power consumption of the fan motor 1. Further, since the gap between the bearing surfaces 21a and 22a and the outer circumferential surface of the rotating shaft 10 can be reduced, it is possible to suppress the rotation of the rotating shaft 10 in the gap between the bearing surfaces 21a and 22a and the outer circumferential surface of the rotating shaft 10, and it is possible to The noise of the motor is reduced while reducing the value of the coaxiality of the two bearing portions 21, 22.

In general, in a motor driven by a light load such as a fan motor, if the gap between the bearing surface and the outer peripheral surface of the rotating shaft is larger than 6 μm, the rotating shaft may be shaken in the gap, thereby making the noise large. . On the other hand, if the gap between the bearing surface and the outer peripheral surface of the rotating shaft is set to 6 μm or less, the fluid resistance of the lubricant when the shaft rotates increases, which causes frictional friction between the bearing surface and the rotating shaft. Increase. On the other hand, by using the sintered bearing 20 in the fan motor 1, the frictional resistance generated between the bearing surfaces 21a and 22a and the rotating shaft 10 can be reduced, so that the bearing surfaces 21a and 22a and the outer circumference of the rotating shaft 10 can be provided. The gap between the faces is set to be 6 μm or less. Therefore, in the fan motor 1, in order to reduce noise, it is preferable to set the gap between the bearing surfaces 21a and 22a and the outer peripheral surface of the rotating shaft 10 to 6 μm or less.

Further, in the fan motor 1, a lubricant of a higher viscosity can be used. and also That is, in general, in the motor, as the viscosity of the lubricant used increases, the fluid resistance of the lubricant existing between the bearing surface and the rotating shaft increases. At this time, not only the rotation speed of the motor is reduced, but the target rotation speed cannot be achieved, and the power consumption of the motor is increased.

On the other hand, in the sintered bearing 20, as described above, the fluid resistance of the lubricant existing between the bearing faces 21a, 22a and the rotating shaft 10 can be reduced. Therefore, by using the sintered bearing 20 in the fan motor 1, even if a high-viscosity lubricant is used, the reduction in the number of revolutions of the motor can be suppressed. In addition, it is also possible to suppress an increase in power consumption of the motor. Further, since a highly viscous lubricant can be used, it is possible to suppress the evaporation of the lubricant at a high temperature while suppressing the wear resistance of the bearing, suppress the aging, and also suppress the leakage of the lubricant, thereby extending the motor. Service life. In particular, by using a highly viscous lubricant, the strength of the oil film formed on the inner diameter sliding surface can be increased, and the noise of the motor can also be reduced.

Generally, in a motor having a small driving torque, in order to reduce the fluid resistance of the lubricant, a lubricant of 32 mm ² /s or less is used. On the other hand, by using the sintered bearing 20 in the fan motor 1, the fluid resistance of the lubricant can be reduced, so that the viscosity of the lubricant to be used can be increased up to 70 mm ² /s within a predetermined current value range of the motor. On the other hand, if the viscosity of the lubricant is lowered to less than 10 mm ² /s, the evaporation characteristics of the lubricant are lowered. Therefore, in the fan motor 1, it is preferable to set the viscosity of the lubricant to be in the range of 10 to 70 mm ² /s. Here, the viscosity (mm ² /s) means the viscosity at 40 °C.

Further, in the fan motor 1, it is possible to expand the use temperature range from a low temperature to a high temperature. That is to say, in general, in the motor, as the temperature of use decreases, the viscosity of the lubricant increases greatly, resulting in lubrication between the bearing surface and the rotating shaft. The fluid resistance of the agent increases. At this time, not only the rotation speed of the motor is reduced, but the target rotation speed cannot be achieved, and the power consumption of the motor is increased. In particular, in a low-torque motor, in the worst case, a startup failure (in a state in which it cannot be started) may occur. On the contrary, as the use temperature of the motor increases, the viscosity of the lubricant is drastically lowered, resulting in a decrease in the strength of the oil film generated on the sliding surface of the inner diameter of the bearing. At this time, the wear resistance of the bearing is lowered, so that the motor is prone to noise. In addition, since the lubricant is prone to evaporation, aging, and leakage, the life of the motor is degraded.

On the other hand, in the sintered bearing 20, as described above, the fluid resistance of the lubricant existing between the bearing faces 21a, 22a and the rotating shaft 10 can be reduced. Therefore, by using the sintered bearing 20 in the fan motor 1, even if the viscosity of the lubricant is increased by the low temperature, the reduction in the number of revolutions of the motor can be suppressed. In addition, it is also possible to suppress an increase in power consumption of the motor. Here, in the case where a lubricant having the same viscosity as that of the conventional bearing is used, the low-temperature characteristics of the motor can be improved while maintaining the high-temperature characteristics of the motor. On the other hand, in the case of using a lubricant having a higher viscosity than the conventional bearing, it is possible to improve the high-temperature characteristics of the motor while maintaining the low-temperature characteristics of the motor.

The sintered bearing 20 is suitable, for example, for use in a fan motor of a refrigerator. That is to say, in recent years, in order to perform defrosting in a refrigerator, defrosting control for increasing temperature is periodically performed. Therefore, when the fan motor is used in a refrigerator, if the viscosity of the lubricant is too high, the motor may be inferior in starting. On the other hand, if the viscosity of the lubricant is too low, the lubricant is liable to evaporate, deteriorate, and leak during the defrosting control, resulting in a decrease in the service life of the motor. On the other hand, by using the fan motor 1 which can be used in a larger temperature range in the refrigerator, it is possible to suppress the deterioration of the life of the motor while preventing the start failure of the motor.

(Modification)

The embodiments of the present invention have been described above. The above embodiment can be variously modified.

For example, in the above embodiment, a plurality of pits d are provided on the first bearing surface 21a and the second bearing surface 22a, respectively. However, it is also possible to provide a plurality of dimples d only on the first bearing faces 21a of the two bearing faces 21a, 22a, and it is also possible to provide only a plurality of the second bearing faces 22a of the two bearing faces 21a, 22a. a pit d. In particular, by providing a plurality of dimples d only on the second bearing surface 22a of the two bearing surfaces 21a, 22a, it is possible to prevent the oil film strength of the first bearing surface 21a on the output side where the load is heavy from decreasing, The coefficient of friction of the second bearing surface 22a on the side opposite to the output side of the lighter load is lowered.

Further, in the above embodiment, the shape, size, and maximum depth of the dimple d formed on the first bearing surface 21a are the same as the shape, size, and maximum depth of the dimple d formed on the second bearing surface 22a. However, it is also possible to set at least one of the shape, the size, and the maximum depth of the dimples d formed on the first bearing surface 21a to be different from the dimples d formed on the second bearing surface 22a. For example, at least one of the size and the maximum depth of the recess d is reduced in the first bearing surface 21a on the load side of the load on the load side, and is increased in the second bearing surface 22a on the side opposite to the output side where the load is lighter. At least one of the size and the maximum depth of the large pit d.

Further, the setting range, density, and the like of the pits d in the two bearing faces 21a, 22a may be different from each other. For example, the setting range and density of the dimples d are reduced in the first bearing surface 21a on the load side where the load is heavy, and the dimples are enlarged in the second bearing surface 22a on the side opposite to the output side where the load is lighter. The setting range and density of d. Here, the density refers to the number of pits per unit area (the same applies hereinafter).

Further, in the above embodiment, the plurality of pits d are provided on the respective bearing faces 21a, 22a. The entire area. However, a region where the pit d is not formed may be provided in a part of each of the bearing faces 21a and 22a. For example, by providing at least one end portion of each of the bearing surfaces 21a, 22a in the axial direction at a portion where the pit d is not formed, it is possible to suppress a decrease in the oil film strength of each of the bearing surfaces 21a, 22a.

Further, in the above embodiment, the shape of each of the pits d is formed substantially in a semi-ellipsoidal shape (the shape of the projection surface is an elliptical shape). However, the shape of the projection surface of each pit d may be formed into a circular shape, a sector shape, a triangle shape, a quadrangular shape, or a diamond shape.

Further, in the above embodiment, the shapes, sizes, and maximum depths of the plurality of pits d provided in the respective bearing faces 21a, 22a are the same. However, in the plurality of pits d provided in the respective bearing faces 21a, 22a, at least one different shape d, d, d, d

In the above embodiment, a plurality of dimples d are regularly provided on the respective bearing faces 21a, 22a. However, a plurality of dimples d may also be irregularly disposed on the respective bearing faces 21a, 22a.

In the above embodiment, each of the dimples d is provided to extend in the circumferential direction. However, each of the dimples d may be provided to extend in the axial direction, and may also be provided to extend in a direction inclined by a predetermined angle with respect to the axial direction and the circumferential direction.

Further, in the above embodiment, after the sintered body is subjected to coining (recompression), a plurality of pits d are formed on the bearing faces 21a and 22a of the compression molded body. However, it is also possible to perform a fine press (recompression) after forming a plurality of pits d on the bearing faces 21a and 22a of the sintered body.

In the above embodiment, an example in which the sintered bearing 20 is applied to the fan motor 1 is shown, but as described below, the sintered bearing 20 is widely used, and is particularly suitable for use in a motor that rotates at a high speed.

(for home appliances)

Cooling fans for electronic computers, televisions, digital video cameras, projectors, LED lighting, DLP color wheel motors, small-diameter stepping motors for digital cameras and digital video cameras, fans for refrigerators, fans for microwave ovens, electric fans, exhaust fans , air conditioners, hair dryers, vacuum cleaners, juice blenders, food processing machines, vibration motors, spindle motors for ODD, and spindle motors for HDD.

(for car use)

Battery cooling fan, temperature adjustment sheet fan, in-vehicle sensor fan, cooling fan for audio and navigation equipment, blower, air conditioner actuator, cleaning pump, mirror, door closer, seat back tilt adjustment Motors, seat slides, power windows, wipers, starters, motors for intake and exhaust mechanisms such as ETC and EGR, EPS (electric steering wheel), EPB (electronically controlled parking brake), etc.

(for OA equipment)

Multi-angle mirror scanner motor, stepper motor, etc.

21a‧‧‧First bearing surface

22a‧‧‧second bearing surface

D‧‧‧ pit

Claims (6)

A sintered bearing formed by sintering powder metal powder in a mold, having a bearing hole that supports a rotatable shaft, and impregnated with a lubricant, characterized by having: a first bearing portion a first bearing surface supporting the rotating shaft; a second bearing portion having a second bearing surface supporting the rotating shaft; and an intermediate portion disposed between the first bearing portion and the second bearing portion The inner diameter of the intermediate portion is formed to be larger than an inner diameter of the first bearing portion and an inner diameter of the second bearing portion, in the first bearing surface and the second bearing surface At least one of the bearing surfaces is formed with a plurality of dimples. A sintered bearing according to claim 1, wherein the plurality of dimples are formed by plastic working. A sintered bearing according to claim 1 or 2, wherein the recess is partially provided with an axial end portion of the bearing surface. The sintered bearing according to any one of claims 1 to 3, wherein a gap between a bearing surface on which the plurality of pits are provided and an outer peripheral surface of the rotating shaft is set to 6 μm or less. The sintered bearing according to any one of claims 1 to 4, wherein the bearing surface provided with the plurality of dimples has an average microhardness (MHv) in the range of 50 to 200. A sintered bearing according to any one of claims 1 to 5, wherein the sintered bearing is suitable for a fan motor.