CN104895926B - Sintered bearing - Google Patents

Sintered bearing Download PDF

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Publication number
CN104895926B
CN104895926B CN201410074753.7A CN201410074753A CN104895926B CN 104895926 B CN104895926 B CN 104895926B CN 201410074753 A CN201410074753 A CN 201410074753A CN 104895926 B CN104895926 B CN 104895926B
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bearing
sintered
rotating shaft
dimples
motor
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CN104895926A (en
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田边重之
古川智庸
麻生忍
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PORITE CORP
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PORITE CORP
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Abstract

The invention provides a sintered bearing capable of reducing resistance of a rotating shaft. The solution is as follows: a sintered bearing (20) according to the present invention has a first bearing section (21), a second bearing section (22), and an intermediate section (23), wherein the first bearing section (21) has a first bearing surface (21 a) that supports the outer peripheral surface of a rotating shaft (10), the second bearing section (22) has a second bearing surface (22 a) that supports the outer peripheral surface of the rotating shaft (10), and the intermediate section (23) is provided between the first bearing section (21) and the second bearing section (22). The inner diameter of the intermediate portion (23) is formed larger than both the inner diameter of the first bearing portion (21) and the inner diameter of the second bearing portion (22). A plurality of dimples (d) are formed in at least one of the bearing surfaces (21 a,22 a) of the first bearing surface (21 a) and the second bearing surface (22 a).

Description

Sintered bearing
Technical Field
The present invention relates to a sintered bearing which is formed by compacting metal powder in a die and then sintering the metal powder, and which contains a lubricant. More particularly, the present invention relates to a sintered bearing capable of reducing noise while reducing frictional resistance between the bearing and a rotating shaft.
Background
Sintered bearings are widely used as inexpensive and reliable bearings in motors for home appliances, motors for vehicles, OA equipment (office automation equipment), and the like. Examples of the Fan Motor (Fan Motor) include a cooling Fan inside a home appliance such as a computer and a television, a Fan for circulation and cooling inside a refrigerator, and a vehicle-mounted Fan used for cooling a battery and sucking a sensor inside a vehicle, and the demand for the Fan Motor is increasing every year.
Since the devices using the fan motors have a long life, the fan motors are required to have not only a long life but also an important characteristic of reducing power consumption. In particular, in a device driven by a battery such as a mobile device, it is necessary to suppress power consumption to the maximum.
On the other hand, in recent years, demands for noise reduction of the fan motor have been greatly increased. In general, in order to reduce noise of a motor, it is necessary to provide a sintered bearing with: first, noise generated by shaft vibration is suppressed by reducing the gap between the rotating shaft and the bearing, and second, the strength of the oil film generated on the inner diameter sliding surface is increased by increasing the viscosity of the lubricant impregnated in the bearing, thereby effectively achieving noise reduction of the fan motor.
However, in a motor such as a fan motor having a low running load and a small torque, the frictional resistance between the rotating shaft and the bearing is mainly determined by the fluid resistance of the lubricant impregnated in the bearing. Therefore, if the clearance 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 leads to an increase in the power consumption of the motor. Therefore, there are constraints on the viscosity of alternative lubricants.
Conventionally, as a sintered bearing capable of reducing frictional resistance between a rotating shaft and a bearing, for example, patent document 1 discloses a sintered bearing.
In this sintered bearing, the inner diameter of the axially intermediate portion of the bearing hole that supports the rotating shaft so as to be rotatable is formed larger than the inner diameters of both axially end portions (hereinafter referred to as "bearing portions"). Accordingly, 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 of the inner peripheral surface of the bearing hole corresponding to the rotating shaft (hereinafter referred to as "sliding area") can be reduced. Since the contact between the inner peripheral surface of the bearing hole and the rotary shaft can be suppressed and the fluid resistance of the lubricant during the rotation of the shaft can be suppressed, the frictional resistance generated between the rotary shaft and the bearing can be reduced. Here, the "portion corresponding to the rotating shaft" refers to a portion that may come into contact with the rotating shaft when the rotating shaft rotates and that is greatly affected by the fluid resistance of the lubricant when the shaft rotates, and does not refer to a portion that is always in contact with the rotating shaft when the rotating shaft rotates (the same applies hereinafter).
Prior art documents
Patent document
Patent document 1 Japanese patent application laid-open No. Hei 7-332363
Disclosure of Invention
However, in the conventional sintered bearing, there is a limit to reduce the frictional resistance between the rotating shaft and the bearing.
Specifically, in the conventional sintered bearing, the range of the two bearing portions is narrowed by widening the range of the intermediate portion in the axial direction of the sintered bearing, and in this case, the sliding area can be reduced as the range of the two bearing portions is narrowed. However, if the axial dimension of each bearing portion (each bearing surface) is too small, the hydraulic pressure generated by the wedge effect escapes from both axial ends of each bearing surface, and the strength of the oil film cannot be maintained. Further, as the oil film strength decreases, the bearing surface and the rotating shaft are likely to come into contact with each other, and as a result, not only is the frictional resistance generated between the bearing surface and the rotating shaft increased, but also noise generation is promoted. Therefore, in the conventional sintered bearing, there is a limit to reduce the frictional resistance between the rotating shaft and the bearing.
The invention provides a sintered bearing capable of reducing frictional resistance between a rotating shaft and a bearing.
Technical scheme
In order to solve the above problem, a sintered bearing according to a first aspect of the present invention includes a bearing surface that supports a rotating shaft to be rotatable, the sintered bearing including: a first bearing surface which is a bearing surface of a first bearing portion having a porous structure; a second bearing surface which is a bearing surface of a second bearing portion having a porous structure; a lubricant impregnated in the first bearing portion and the second bearing portion; and an intermediate portion provided between the first bearing portion and the second bearing portion, the intermediate portion having an inner diameter larger than both the inner diameter of the first bearing portion and the inner diameter of the second bearing portion, wherein a plurality of dimples are formed in at least one of the first bearing surface and the second bearing surface over substantially the entire circumferential region of the at least one bearing surface, the dimples extending in the circumferential direction, and a gap between the bearing surface provided with the dimples and the outer circumferential surface of the rotating shaft is set to 6 μm or less.
In the sintered bearing according to the first aspect of the invention, the intermediate portion is provided between the first bearing portion and the second bearing portion, and the inner diameter of the intermediate portion is formed larger than the inner diameter of each of the bearing portions.
Thereby, the contact between the inner peripheral surface of the intermediate portion and the rotary shaft can be avoided, so that the sliding area in the inner peripheral surface of the bearing hole can be reduced. Therefore, compared to a sintered bearing (hereinafter, referred to as a "linear bearing") in which the inner diameter of the bearing hole is the same over the entire length in the axial direction, not only contact between the inner peripheral surface of the bearing hole and the rotating shaft is suppressed, but also the fluid resistance of the lubricant during rotation of the shaft is reduced, so that 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 present invention, a plurality of dimples are provided in at least one of the first bearing surface and the second bearing surface that rotatably support the rotating shaft.
Since the portion (range) of the bearing surface where each dimple is provided does not contact the rotating shaft, the sliding area in the bearing surface can be reduced. Therefore, not only contact between the bearing surface and the rotating shaft is suppressed, but also fluid resistance of the lubricant during rotation of the shaft is reduced, and frictional resistance generated between the bearing surface and the rotating shaft can be reduced.
Therefore, the sliding area in the inner peripheral surface of the bearing hole can be reduced without reducing the axial dimension of the bearing surface, and the frictional resistance generated between the bearing surface and the rotating shaft can be reduced while suppressing the decrease in the strength of the oil film.
In the sintered bearing according to the first aspect of the present invention, since the plurality of dimples are provided on the bearing surface, the lubricant impregnated in the sintered bearing can be retained in each of the dimples. When the rotating shaft rotates, the lubricant stored in each of the dimples is attracted between the bearing surface and the rotating shaft. Therefore, when the rotating shaft rotates, particularly at the initial stage of operation, formation of an oil film can be facilitated, and the friction coefficient of the bearing surface can be reduced.
In the sintered bearing according to the first aspect of the present invention, since the plurality of dimples are provided on the bearing surface, the average clearance between the bearing surface and the outer peripheral surface of the rotating shaft can be increased. This reduces 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 of the first aspect of the present invention, the contact between the bearing surface and the rotating shaft can be suppressed, and the fluid resistance of the lubricant can be reduced, 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 invention, the characteristics of the motor with a small driving torque can be improved. That is, in general, the smaller the driving torque of the motor, the greater the influence of the magnitude of the frictional resistance generated between the bearing surface and the rotating shaft on the motor characteristics.
Specifically, as the frictional resistance increases, the rotation speed of the motor decreases, which not only makes it impossible to achieve the target rotation speed, but also increases the power consumption of the motor. On the other hand, according to the sintered bearing of the first aspect, 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 present invention, even when the drive torque of the motor is reduced, the reduction in the motor rotation speed can be suppressed, and the power consumption can be reduced.
Further, by applying the sintered bearing according to the first aspect of the present invention, it is possible to construct a motor in which the gap between the bearing surface and the outer peripheral surface of the rotating shaft is small. That is, in general, in a motor, as a gap between a bearing surface and an outer peripheral surface of a rotating shaft is reduced, a fluid resistance of a lubricant at the time of rotation of the shaft is increased, so that a frictional resistance generated between the bearing surface and the rotating shaft is increased. In this case, the rotation speed of the motor is reduced, and 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 of the first aspect, as described above, the fluid resistance of the lubricant during rotation of the shaft can be reduced. Therefore, by applying the sintered bearing according to the first aspect of the present invention, it is possible to suppress a decrease in the motor rotational speed even when the gap between the bearing surface and the outer peripheral surface of the rotating shaft is reduced. Further, an increase in power consumption of the motor can be suppressed. Further, since the gap between the bearing surface and the outer peripheral surface of the rotating shaft can be reduced, the rotating shaft can be suppressed from wobbling in the gap between the bearing surface and the outer peripheral surface of the rotating shaft, and the noise of the motor can be reduced.
In general, in a motor driven by a light load such as a fan motor, if a gap between a bearing surface and an outer peripheral surface of a rotating shaft is larger than 6 μm, the rotating shaft may be shaken in the gap, and noise may be increased. On the other hand, if the clearance 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 increases when the shaft rotates, resulting in an increase in the frictional resistance generated between the bearing surface and the rotating shaft.
However, in the sintered bearing according to the present invention, as described above, even 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 during the rotation of the shaft can be reduced, so that 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 during the rotation of the rotating shaft can be reduced.
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 a motor, as the viscosity of a lubricant used increases, the fluid resistance of the lubricant existing between a bearing surface and a rotating shaft increases. In this case, the rotation speed of the motor is reduced, and 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 of the first aspect, 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 invention, it is possible to suppress a decrease in the motor rotation speed even if a lubricant having a high viscosity is used. Further, an increase in power consumption of the motor can be suppressed. Further, since a lubricant having a high viscosity can be used, the wear resistance of the bearing can be improved, the evaporation of the lubricant at a high temperature can be suppressed, the deterioration can be suppressed, the leakage of the lubricant can be suppressed, and the service life of the motor can be extended. In particular, by using a lubricant having a high viscosity, the strength of the oil film formed on the inner-diameter sliding surface can be increased, and the noise of the motor can be reduced.
According to the sintered bearing of the first aspect, the sintered bearing of the second aspect is characterized in that the depth of the dimples is set to 50 μm or less.
In the sintered bearing according to the second aspect of the present invention, the plurality of dimples are formed by plastically deforming the bearing surface. This can improve the machining accuracy of each pit.
In particular, the sintered bearing has a porous structure because it is formed by sintering metal powder. Therefore, by forming each dimple by plastic working, the deformed portion can be absorbed by the minute hole, and the bearing surface can be prevented from bulging out.
In addition to plastic working, laser working, etching (local etching) working, and the like are also cited as methods for forming pits, but these methods not only require the use of large-scale equipment, but also increase the number of working steps. In contrast, plastic working does not require large-scale equipment and requires a small number of working steps, and therefore can be carried out at a relatively low cost in a large amount.
According to the sintered bearing of the first or second aspect, the sintered bearing of the third aspect is characterized in that the circumferential size of the dimples is within a range of 10 to 1000 μm.
According to the sintered bearing of the third aspect of the present invention, since the dimples are provided at intervals from the axial end portions of the bearing surface, it is possible to suppress the escape of the hydraulic pressure from the axial end portions of the bearing surface, and thereby suppress the decrease in the strength of the oil film.
A sintered bearing according to a fourth aspect of the present invention is the sintered bearing according to any one of the first through third aspects of the present invention, wherein an average microhardness (MHv) of a bearing surface on which the plurality of dimples are provided is in a 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 deteriorates, so that the durability is lowered. On the other hand, if the average microhardness (MHv) of the bearing surface is more than 200, the periphery of each dimple bulges when each dimple is formed, and thus a predetermined size and accuracy cannot be obtained.
Therefore, by setting the average microhardness (MHv) of the bearing surface provided with a plurality of dimples to be within a range of 50 to 200, it is possible to form dimples on the bearing surface while avoiding a decrease in the durability of the sintered bearing and a decrease in the size and accuracy of the sintered bearing.
The sintered bearing according to the fifth aspect of the present invention is the sintered bearing according to any one of the first to fourth aspects of the present invention, wherein the sintered bearing is applied to a fan motor.
According to the sintered bearing of the fifth aspect of the present invention, not only can the characteristics of the fan motor with a small driving torque be improved, but also the power consumption can be reduced. Further, since the fan motor can be configured such that the gap between the bearing surface and the outer peripheral surface of the rotating shaft is smaller, the rotating shaft can be suppressed from wobbling in the gap between the bearing surface and the outer peripheral surface of the rotating shaft, and the noise of the fan motor can be reduced. Further, since a lubricant having a higher viscosity can be used, the wear resistance of the bearing can be improved, the lubricant can be prevented from evaporating at a high temperature, the deterioration of the bearing can be prevented, and the lubricant can be prevented from leaking, whereby the service life of the motor can be prolonged. In particular, by using a lubricant having a high viscosity, the strength of the oil film formed on the inner diameter sliding surface can be increased, and the noise of the motor can be further reduced.
Advantageous effects
According to the sintered bearing of the present invention, frictional resistance between the bearing and the rotating shaft can be reduced, and noise can be reduced.
Drawings
Fig. 1 is a partial sectional view of a fan motor according to an embodiment of the present invention.
Fig. 2 is a sectional view of a sintered bearing provided in the fan motor shown in fig. 1.
Fig. 3 is an enlarged partial view of the bearing surface of the sintered bearing shown in fig. 2.
Description of the symbols
1 Fan Motor
2 casing support
2a cylindrical part
3 laminated iron core
3a coil
4 rotor yoke
5 magnet
6 impeller
7 thrust plate
10 rotating shaft
20 sintered bearing
21 first bearing part
22 second bearing part
23 intermediate part
21a first bearing surface
22a second bearing surface
23a inner peripheral surface
h bearing hole
d pit
Detailed Description
A sintered bearing 20 according to an embodiment of the present invention will be described below with reference to the drawings.
The sintered bearing 20 can be widely used for various household electric appliances, various motors for vehicles, OA equipment (office automation equipment), and the like. In the present embodiment, an example in which the sintered bearing 20 is applied to the fan motor 1 is shown.
(Structure of Fan Motor 1)
Fig. 1 is a partial sectional view of a fan motor according to an embodiment of the present invention, fig. 2 is a sectional view of a sintered bearing included in the fan motor shown in fig. 1, and fig. 3 is a partial enlarged view of a 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 by the housing holder 2, and a rotary shaft 10 supported by the sintered bearing 20 so as to be freely rotatable.
The housing holder 2 has a cylindrical portion 2a in its interior that holds the sintered bearing 20. A laminated core (stator) 3 formed by winding a coil 3a is provided on the outer peripheral surface of the cylindrical portion 2 a.
The rotating shaft 10 is made of metal (alloy steel such as carbon steel and stainless steel) and is formed in a cylindrical shape. A magnet (rotor) 5 is attached to the rotary shaft 10 via a rotor yoke 4. The magnet 5 is provided to face the laminated core 3 provided on the outer peripheral surface of the case holder 2. An impeller (fan) 6 is attached to the outer periphery of the rotor yoke 4. Further, a thrust plate 7 that pivotally supports an end portion of the rotating shaft 10 on the side opposite to the output side in the thrust direction is fitted into the inner bottom portion of the cylindrical portion 2a of the housing holder 2.
As shown in fig. 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 a sintered metal (including a sintered alloy) and has a porous structure. The sintered bearing 20 is impregnated with a lubricant such as a lubricating oil or grease.
The sintered bearing 20 is formed in a substantially cylindrical shape and has a bearing hole h for rotatably supporting the rotary shaft 10. The bearing hole h is provided to penetrate the sintered bearing 20 in the axial direction (the up-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 peripheral surface of the first bearing portion 21 serves as a first bearing surface 21a that supports the outer peripheral surface of the rotary shaft 10, and the inner peripheral surface of the second bearing portion 22 serves as a second bearing surface 22a that supports the outer peripheral surface of the rotary shaft 10.
The inner diameter of the first bearing portion 21 and the inner diameter of the second bearing portion are respectively formed larger than the outer diameter of the rotary shaft 10. 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 to have a dimension such that the clearance between each of the 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 both the inner diameter of the first bearing portion 21 and the inner diameter of the second bearing portion 22.
The rotary shaft 10 is inserted into the bearing hole h of the sintered bearing 20. In the sintered bearing 20, the first bearing portion 21 supports an end portion on the output side of the rotary shaft 10, and the second bearing portion 22 supports an end portion on the opposite side of the rotary shaft 10 from the output side. 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 does not contact (slide-contact) the outer peripheral surface of the rotary shaft 10.
As shown in fig. 3, a plurality of dimples d are provided on at least one of the first bearing surface 21a and the second bearing surface 22 a. In the present embodiment, a plurality of dimples 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 each of the bearing surfaces 21a,22a, and a plurality of dimples are regularly provided. The inner peripheral surface 23a of the intermediate portion 23 is not provided with the dimples d.
Each pit d is formed by plastic working such as shot peening, rolling, embossing, and the like. Each pit d is formed as a concave portion having a substantially hemispherical shape, a concave portion having a substantially hemiellipsoidal shape, or a concave portion having a substantially semi-cylindrical shape. In the present embodiment, each pit d is formed as a concave portion having a substantially hemiellipsoidal shape with a short diameter in the range of 10 to 500 μm and a long diameter in the range of 10 to 1000 μm. Further, the maximum depth of each pit d is set to be in the range of 1 to 50 μm. Each of the dimples d is provided so as to extend in the circumferential direction (direction orthogonal to the axial direction).
In the present embodiment, the dimples d are provided at a predetermined interval from the axial ends of the bearing surfaces 21a and 22 a. That is, the respective recesses d are not exposed at (do not communicate with) the respective end surfaces of the respective bearing portions 21,22 in the axial direction.
Here, if the average microhardness (MHv) of each of the bearing surfaces 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, if the average microhardness (MHv) of each of the bearing surfaces 21a,22a is higher than 200, when each of the dimples d is formed by plastic working, the periphery of each of the dimples d is bulged, so that a prescribed size and accuracy cannot be obtained. Therefore, the average microhardness (MHv) of each of the bearing surfaces 21a,22a is preferably set to be in the range of 50 to 200.
Further, if the area ratio of the dimples is less than 10%, the effect of reducing the friction coefficient cannot be sufficiently obtained. On the other hand, if the area ratio of the dimples exceeds 60%, the sliding area of each of the bearing surfaces 21a,22a is insufficient, resulting in insufficient load resistance. Therefore, the area ratio of the pits is preferably set within a range of 10 to 60%. Here, the pit area ratio is a ratio of a total projected area of the pits d formed in the bearing surfaces 21a and 22a (a value obtained by summing the projected areas of the pits d formed in the bearing surfaces 21a and 22a for all the pits d formed in the bearing surfaces 21a and 22 a) to the total area of the bearing surfaces 21a and 22 a.
(method of manufacturing sintered bearing 20)
The method for manufacturing the sintered bearing 20 will be described below.
In the following production methods, as the production method of the bearing having the concave inner diameter, the production methods disclosed in Japanese patent laid-open Nos. Hei 2-8302 and Hei 7-332363 are used.
That is, in manufacturing the sintered bearing 20, the 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.
As the die lubricant, a powder of a metal soap typified by zinc stearate, lithium stearate, or the like, a powder of a fatty amide such as vinyl bis stearamide, or a powder of a paraffin-based lubricant such as polyethylene can be used. Depending on the use of the bearing, powders of solid lubricating components typified by graphite, molybdenum disulfide, boron nitride, and the like may be added in addition to the metal powder.
The metal powder, the solid lubricating component and the die lubricant as the raw materials are not limited to the above.
Then, the stirred and mixed raw material powder is subjected to compression molding in a mold under a pressure of about 100 to 500MPa to form a powder compact.
Thereafter, the green compact is sintered under a predetermined temperature condition in a predetermined environment to form a sintered body. By sintering the green compact, adjacent metal particles are diffusion-bonded to each other, and the metal particles are bonded to each other to form a porous sintered body.
The atmosphere is a vacuum atmosphere, a reducing gas atmosphere (ammonia decomposition gas, hydrogen gas, endothermic gas, etc.), an inert gas atmosphere (nitrogen gas, argon gas, etc.), a mixed gas of these reducing gas and inert gas, etc., and may be appropriately selected depending on the raw material components. As the sintering temperature, a practical sintering temperature is about 600 to 1200 ℃, and for example, when bronze (Cu — Sn) is used, a sintering temperature of about 600 to 800 ℃ may be used, when a material mainly composed of iron is used, a sintering temperature of about 700 to 1200 ℃ may be used, and the sintering temperature may be appropriately selected depending on the raw material components.
Further, the sintered body may be subjected to coining (Sizing) (recompression) in a die to form a recompressed body. By coining the sintered body, the surface roughness can be improved while the dimensional accuracy is improved.
Thereafter, a plurality of dimples d are formed in the bearing surfaces 21a,22a of the compression-molded body. When the dimples d are formed in the bearing surfaces 21a,22a, the dimples d may be formed by plastic working such as shot peening, rolling, and embossing. For example, when the dimples d are formed on the bearing surfaces 21a,22a, the dimples d may be formed by using a tool for plastic working. The tool has a mandrel having a convex portion, a retainer fitted around the outside of the mandrel, and a rolling body held by the retainer and rolling on the outer peripheral surface of the mandrel. By inserting the cage into the inner peripheral surface of the bearing hole h and rotating the spindle, the rolling elements are caused to protrude or retract from the outer surface of the cage by the convex portion of the spindle, and the bearing surfaces 21a,22a are plastically deformed by the protruding rolling elements, thereby forming the dimples.
Further, the bearing surfaces 21a and 22a on which the dimples d are formed may be subjected to rotary coining (burnishing). By performing rotary coining of the bearing surfaces 21a,22a and then finishing the inner diameter of the bearing hole h, not only dimensional accuracy but also properties such as surface roughness and running-in property at the initial stage of operation can be improved.
Next, the compression-molded body after the dimple forming process or the compression-molded body after the dimple forming process and the rotary coining process is subjected to a cleaning process to remove metal chips, a lubricating oil for coining, and the like generated during the process.
Thereafter, the cleaned compression molded body is impregnated with a lubricant, thereby completing the production of the sintered bearing 20.
(action and Effect of Fan Motor 1)
The operation and effect of the fan motor 1 (sintered bearing 20) will be described below.
The rotation shaft 10 is rotated by energizing the coil 3a of the laminated core 3 of the fan motor 1, and the impeller 6 provided on the output side of the rotation shaft 10 is rotated.
In this case, 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 inner peripheral surface 23a of the intermediate portion 23 does not come into contact (sliding contact) with the rotary shaft 10. Therefore, as compared with the linear bearing, not only contact between the inner peripheral surface of the bearing hole h and the rotary shaft 10 can be suppressed, but also fluid resistance of the lubricant during rotation of the shaft can be reduced, whereby frictional resistance generated between the bearing surface and the rotary shaft 10 can be reduced.
In a conventional motor, as a method of reducing frictional resistance generated between a bearing and a 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 occurrence of the misalignment of the coaxiality of the two independent bearings, and if the misalignment of the coaxiality is large, the rotating shaft cannot pass through the two bearings, or although the rotating shaft can pass through the two bearings, the clearance between the rotating shaft and the inner diameter sliding surface is excessively small, and the fluid resistance is increased, so that the power consumption of the motor becomes large. In this case, it is necessary to increase the size of the gap by design, and if the size of the gap is increased by design, the gap between the rotating shaft and the inner diameter sliding surface becomes excessively large in a bearing having a good coaxiality within a variation range, and the rotating shaft is shaken, which causes noise in the motor. Here, the coaxiality is a deviation of a reference axis from an axis to be aligned with the reference axis.
In contrast, 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, contact between the two bearing surfaces 21a,22a and the rotary shaft 10 can be further suppressed. In particular, since the sintered bearing 20 is formed by integrating the first bearing portion 21 and the second bearing portion 22, the coaxiality of the two bearing portions 21 and 22 can be controlled to be 3 μm or less. Therefore, in the fan motor 1, the coaxiality of the two bearing portions 21 and 22 is preferably set to 3 μm or less. As described above, by forming the gaps between the two bearing portions 21 and 22 (the gaps between the bearing surfaces 21a and 22a and the rotary shaft 10) to have the same size, it is possible to suppress variations in noise characteristics and power consumption when mass-producing the motor 1, and to obtain a motor of the same quality.
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 rotatably support the rotary shaft 10. Since the portions (ranges) of the bearing surfaces 21a,22a where the respective dimples d are provided do not come into contact with the rotary shaft 10, the sliding area in the bearing surfaces 21a,22a can be reduced. This suppresses contact between the bearing surfaces 21a and 22a and the rotary shaft 10, and reduces the fluid resistance of the lubricant during rotation of the shaft, thereby reducing the frictional resistance generated between the bearing surfaces and the rotary shaft 10. Therefore, the sliding area in the inner peripheral surface of the bearing hole h can be reduced without reducing the axial dimension of the bearing surfaces 21a,22a, and the frictional resistance generated between the bearing surfaces and the rotary shaft 10 can be reduced while suppressing the decrease in the oil film strength.
In the sintered bearing 20, since the plurality of dimples d are provided on the bearing surfaces 21a,22a, the lubricant impregnated in the sintered bearing 20 can be stored in each dimple d. When the rotary shaft 10 rotates, the lubricant stored in each pocket d is attracted between the bearing surfaces 21a,22a and the rotary shaft 10. This makes it possible to facilitate formation of an oil film and reduce the friction coefficient of the bearing surfaces 21a and 22a when the rotary shaft 10 rotates, particularly at the initial stage of operation.
In the sintered bearing 20, since the plurality of dimples d are provided on the bearing surfaces 21a,22a, the average clearance between the bearing surfaces 21a,22a and the outer peripheral surface of the rotary 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, the plurality of dimples d are formed by plastically deforming the bearing surfaces 21a,22 a. This can improve the machining accuracy of each pit d. In particular, the sintered bearing has a porous structure because it is formed by sintering metal powder. Therefore, by forming the respective dimples d by plastic working, the deformed portions can be absorbed by the minute holes, so that the bearing surfaces 21a,22a can be prevented from bulging.
In addition to plastic working, laser working, etching (local etching) working, and the like are given as examples of a method for forming pits, but these methods not only require the use of large-scale equipment, but also increase the number of working steps. In contrast, plastic working does not require the use of large-scale equipment, and requires a small number of working steps, so that it is possible to perform large-scale working at a relatively low cost.
In particular, in the sintered bearing 20, by setting the average microhardness (MHv) of the bearing surfaces 21a,22a within the range of 50 to 200, it is possible to form dimples on the bearing surfaces while avoiding a decrease in the durability of the sintered bearing and a decrease in the size and accuracy of the sintered bearing.
In the sintered bearing 20, since the dimples d are provided at intervals from the axial ends of the bearing surfaces 21a and 22a, the escape of the hydraulic pressure from the axial ends of the bearing surfaces 21a and 22a can be suppressed, and the decrease in the strength of the oil film can be suppressed.
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 during the rotation of the shaft can be reduced, 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.
The characteristics of a motor having a small driving torque, such as the fan motor 1, can be improved. That is, in general, the smaller the driving torque of the motor, the greater the influence of the magnitude of the frictional resistance generated between the bearing surface and the rotating shaft on the motor characteristics. As the frictional resistance increases, the rotation speed of the motor decreases, not only making it impossible to achieve the target rotation speed, but also causing 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 surfaces 21a,22a and the rotary shaft 10 can be reduced. Therefore, by using the sintered bearing 20 for the fan motor 1, it is possible to reduce the power consumption while suppressing a decrease in the rotational speed of the fan motor 1 even when the drive torque of the fan motor 1 is reduced.
In the fan motor 1, the clearance between the bearing surfaces 21a and 22a and the outer peripheral surface of the rotary shaft 10 can be further reduced. That is, in general, in a motor, as a gap between a bearing surface and an outer peripheral surface of a rotating shaft is reduced, a fluid resistance of a lubricant during rotation of the shaft is increased, and a frictional resistance generated between the bearing surface and the rotating shaft is increased. In this case, the rotation speed of the motor is reduced, and 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 surfaces 21a,22a and the rotary shaft 10 can be reduced. Therefore, by using the sintered bearing 20 in the fan motor 1, even when the clearance between the bearing surfaces 21a,22a and the outer peripheral surface of the rotary shaft 10 is reduced, the reduction in the rotation speed of the fan motor 1 can be suppressed. Further, an increase in power consumption of the fan motor 1 can be suppressed. Further, since the clearance between the bearing surfaces 21a,22a and the outer peripheral surface of the rotary shaft 10 can be reduced, the occurrence of rattling of the rotary shaft 10 in the clearance between the bearing surfaces 21a,22a and the outer peripheral surface of the rotary shaft 10 can be suppressed, and the motor noise can be 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 a gap between a bearing surface and an outer peripheral surface of a rotating shaft is larger than 6 μm, the rotating shaft may be shaken in the gap, and noise may be increased. On the other hand, if the clearance 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 increases when the shaft rotates, resulting in an increase in the frictional resistance generated between the bearing surface and the rotating shaft. In contrast, since the sintered bearing 20 is used for the fan motor 1, the frictional resistance generated between the bearing surfaces 21a and 22a and the rotary shaft 10 can be reduced, and the clearance between the bearing surfaces 21a and 22a and the outer peripheral surface of the rotary shaft 10 can be set to 6 μm or less. Therefore, in the fan motor 1, in order to reduce noise, it is preferable to set the clearance between the bearing surfaces 21a,22a and the outer peripheral surface of the rotating shaft 10 to 6 μm or less.
In the fan motor 1, a lubricant having a higher viscosity can be used. That is, in general, in a motor, as the viscosity of a lubricant used increases, the fluid resistance of the lubricant existing between a bearing surface and a rotating shaft increases. In this case, the rotation speed of the motor is reduced, and 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 surfaces 21a,22a and the rotary shaft 10 can be reduced. Therefore, by employing the sintered bearing 20 in the fan motor 1, even if a lubricant with high viscosity is used, a decrease in the motor rotation speed can be suppressed. Further, an increase in power consumption of the motor can be suppressed. Further, since a lubricant having a high viscosity can be used, the wear resistance of the bearing can be improved, the evaporation of the lubricant at a high temperature can be suppressed, the deterioration can be suppressed, the leakage of the lubricant can be suppressed, and the service life of the motor can be extended. In particular, by using a lubricant having a high viscosity, the strength of the oil film formed on the inner-diameter sliding surface can be increased, and the noise of the motor can be reduced.
Generally, in a motor with a small driving torque, 32mm is used to reduce the fluid resistance of a lubricant2Lubricants below/s. In contrast, since the sintered bearing 20 is used in the fan motor 1, the fluid resistance of the lubricant can be reduced, and the viscosity of the lubricant used can be increased to 70mm at the maximum within a predetermined current value range of the motor2And s. On the other hand, if the viscosity of the lubricant is reduced to less than 10mm2And/s, the evaporation characteristics of the lubricant are reduced. Therefore, in the fan motor 1, it is preferable to set the viscosity of the lubricant to 10 to 70mm2In the range of/s. Here, the viscosity (mm)2The term,/s) means the viscosity at 40 ℃.
In addition, in the fan motor 1, the range of the use temperature from a low temperature to a high temperature can be expanded. That is, in general, in a motor, as the use temperature decreases, the viscosity of the lubricant greatly increases, which results in an increase in the fluid resistance of the lubricant existing between the bearing surface and the rotating shaft. In this case, the rotation speed of the motor is reduced, and 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 start failure (a state in which the start cannot be performed) may occur. On the contrary, as the use temperature of the motor increases, the viscosity of the lubricant is greatly reduced, and the strength of the oil film generated on the inner diameter sliding surface of the bearing is reduced. In this case, the wear resistance of the bearing is reduced, and the motor is likely to generate noise. In addition, since the lubricant is easily evaporated, aged and leaked, it may cause a reduction in the life span of the motor.
On the other hand, in the sintered bearing 20, as described above, the fluid resistance of the lubricant existing between the bearing surfaces 21a,22a and the rotary shaft 10 can be reduced. Therefore, by using the sintered bearing 20 in the fan motor 1, even if the viscosity of the lubricant increases due to a low temperature, it is possible to suppress a decrease in the motor rotation speed. Further, an increase in power consumption of the motor can be suppressed. Here, when a lubricant having the same viscosity as that of a 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, when a lubricant having a higher viscosity than that of a conventional bearing is used, the high-temperature characteristics of the motor can be improved while maintaining the low-temperature characteristics of the motor.
The sintered bearing 20 is suitable for use in a fan motor of a refrigerator, for example. That is, in recent years, in order to perform defrosting in a refrigerator, defrosting control for raising the temperature is periodically performed. Therefore, if the viscosity of the lubricant is too high when the fan motor is used in a refrigerator, a start failure of the motor may occur. On the other hand, if the viscosity of the lubricant is too low, the lubricant is liable to be evaporated, aged and leaked at the time of defrosting control, resulting in a reduction in the service life of the motor. In contrast, by using the fan motor 1 that can be used in a wider temperature range in a refrigerator, it is possible to prevent the occurrence of a start failure in the motor and suppress a decrease in the service life of the motor.
(modification example)
The embodiments of the present invention have been described above. The above embodiment can be variously modified.
For example, in the above embodiment, the dimples d are provided on the first bearing surface 21a and the second bearing surface 22a, respectively. However, the dimples d may be provided only on the first bearing surface 21a of the two bearing surfaces 21a,22a, or may be provided only on the second bearing surface 22a of the two bearing surfaces 21a,22 a. 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 reduce the friction coefficient of the second bearing surface 22a on the side opposite to the output side, which is relatively light in load, while preventing the oil film strength of the first bearing surface 21a on the output side, which is relatively heavy in load, from decreasing.
Further, in the above-described embodiment, the shape, size, and maximum depth of the dimples d formed on the first bearing surface 21a are the same as those of the dimples d formed on the second bearing surface 22 a. However, at least one of the shape, size, and maximum depth of the dimples d formed on the first bearing surface 21a may be set to be different from the dimples d formed on the second bearing surface 22 a. For example, at least one of the size and the maximum depth of the dimples d is reduced in the first bearing surface 21a on the output side where the load is heavy, and at least one of the size and the maximum depth of the dimples d is increased in the second bearing surface 22a on the side opposite to the output side where the load is light.
Further, the arrangement range, density, and the like of the dimples d in the two bearing surfaces 21a,22a may be different from each other. For example, the range and density of the arrangement of the dimples d are reduced in the first bearing surface 21a on the output side where the load is heavy, and the range and density of the arrangement of the dimples d are increased in the second bearing surface 22a on the opposite side to the output side where the load is light. Here, the density refers to the number of pits per unit area (the same applies hereinafter).
In the above embodiment, the plurality of dimples d are provided over substantially the entire area of each of the bearing surfaces 21a and 22 a. However, a region where the dimples d are not formed may be provided in a part of each of the bearing surfaces 21a and 22 a. For example, by providing a region where the dimples d are not formed in at least one of the two axial ends of each of the bearing surfaces 21a,22a, a decrease in oil film strength of each of the bearing surfaces 21a,22a can be suppressed.
In the above embodiment, each pit d is formed in a substantially semi-ellipsoidal shape (the shape of the projection surface is an elliptical shape). However, the projection surface of each pit d may have a circular, fan-shaped, triangular, quadrangular or rhombic shape.
Further, in the above embodiment, the shape, size, and maximum depth of the plurality of dimples d provided on the respective bearing surfaces 21a,22a are the same. However, the dimples d having different shapes, sizes, and maximum depths may be mixed with each other among the plurality of dimples d provided on the respective bearing surfaces 21a,22 a.
In the above embodiment, the plurality of dimples d are regularly provided on the respective bearing surfaces 21a,22 a. However, the plurality of dimples d may be irregularly provided on the respective bearing surfaces 21a,22 a.
In the above embodiment, the respective dimples d are provided so as to extend in the circumferential direction. However, each of the dimples d may be provided so as to extend in the axial direction, or may be provided so as to extend in a direction inclined at a predetermined angle with respect to the axial direction and the circumferential direction.
In the above embodiment, after the sintered body is subjected to the coining (recompression), the plurality of dimples d are formed in the bearing surfaces 21a,22a of the compression-molded body. However, after forming a plurality of dimples d in the bearing surfaces 21a,22a of the sintered body, the pressing (recompression) may be performed.
In the above embodiment, the sintered bearing 20 is applied to the fan motor 1, but as described below, the sintered bearing 20 is widely used, and is particularly suitable for use in a motor that rotates at high speed.
(for household electrical appliances)
A cooling fan for a computer, a television, a digital video camera, a projector, LED lighting, etc., a color wheel motor for DLP, a small-diameter stepping motor for a digital camera, a digital video camera, etc., a fan for a refrigerator, a fan for a microwave oven, an electric fan, an exhaust fan, an air conditioner, a blower, a vacuum cleaner, a juice mixer, a food processor, a vibration motor, a spindle motor for ODD, and a spindle motor for HDD.
(for vehicle)
A battery cooling fan, a temperature adjustment sheet fan, an in-vehicle sensor fan, an audio and navigation device cooling fan, a blower, an air conditioning actuator, a washer pump, a rearview mirror, a door closer, a seat back tilt adjuster, a seat slider, a power window, a wiper, a starter, an electric motor of an intake and exhaust mechanism such as ETC and EGR, an EPS (electric power steering), an EPB (electronically controlled parking brake), and the like.
(for OA equipment)
Polygon scanner motors, stepper motors, etc.

Claims (5)

1. A sintered bearing having a bearing surface that supports a rotating shaft so as to be freely rotatable, said sintered bearing being such that: during rotation of the rotating shaft, the rotating shaft slides relative to the bearing surface; in the sintered bearing, a metal powder is pressed in a die to form a pressed powder body, the pressed powder body is sintered to form a sintered body, the sintered body is impregnated with a lubricant to form a sintered bearing, the impregnated lubricant is drawn out to form an oil film, the sintered bearing is a sintered bearing having no oil supply hole, and the sintered bearing is characterized by comprising:
a first bearing surface which is a bearing surface of a first bearing portion having a porous structure;
a second bearing surface which is a bearing surface of a second bearing portion having a porous structure;
a lubricant impregnated in the first bearing portion and the second bearing portion; and
an intermediate portion disposed between the first bearing portion and the second bearing portion,
the inner diameter of the intermediate portion is formed larger than both the inner diameter of the first bearing portion and the inner diameter of the second bearing portion,
a plurality of dimples are formed in at least one of the first bearing surface and the second bearing surface over substantially the entire circumferential area of the at least one bearing surface,
the dimples extend in a direction inclined with respect to the circumferential direction,
a clearance between the bearing surface provided with the plurality of dimples and the outer peripheral surface of the rotating shaft is set to 6 [ mu ] m or less.
2. The sintered bearing as claimed in claim 1, wherein the maximum depth of said dimples is set in the range of 1 to 50 μm.
3. The sintered bearing as claimed in claim 1 or 2, wherein said dimples are formed in a hemiellipsoidal shape having a minor diameter in the range of 10 to 500 μm and a major diameter in the range of 10 to 1000 μm.
4. The sintered bearing of claim 1 or 2, wherein the bearing surface provided with said plurality of dimples has an average microhardness in the range of 50 to 200.
5. Sintered bearing according to claim 1 or 2, wherein the sintered bearing is applied to a fan motor.
CN201410074753.7A 2014-03-03 2014-03-03 Sintered bearing Active CN104895926B (en)

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