JP2003120674A - Sintered oil-impregnated bearing for electric motor and method of manufacturing the same - Google Patents

Abstract

(57) [Problem] To provide a sintered oil-impregnated bearing having a relatively high oil content, which does not generate squeal even when an electric motor is operated in a low-temperature environment. SOLUTION: As a sintered oil-impregnated bearing structure, a sintered alloy of a bearing material has a cross-sectional structure in which a Cu alloy phase containing Sn and P and a ferrite phase of Fe are present in a mixed state in which an area ratio is almost equal. Containing 0.7% by mass or less of graphite particles,
The area of the iron portion exposed on the inner peripheral surface of the sized bearing is 2 to 6%, the effective porosity is 20 to 30%, and the air permeability of the bearing is 6 to 50 × 10 ⁻¹¹ cm ^2. 40
In kinematic viscosity at ℃ 61.2~74.8mm ² / s (c
St) synthetic oil is contained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered oil-impregnated bearing for an electric motor, which is suitable for use in an environment such as an automobile, in a cold region, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Sintered oil-impregnated bearings used in electric motors such as fan motors and seat drive motors for indoor blowers installed in automobiles are available in iron-based materials, copper-based materials, iron-copper-based materials, etc. Among them, iron-copper-based materials are preferred. This is because it has the characteristics of copper alloy such as slip characteristics, conformability and heat dissipation, and the characteristics of iron such as relatively hard, relatively low specific gravity and low cost. The content of the iron portion and the content of the copper portion of such a sintered alloy are approximately the same.

[0003]

An electric motor using the above-mentioned sintered oil-impregnated bearing operates normally when it is operated in a warm environment. For example, a cold region such as 20 ° C below zero or 30 ° C below zero is used. When driving in an environment, there was a problem that a squeaking noise was generated for a while after the driving started. It is considered that such squeal noise is generated because the shaft rotates while vibrating when it is started in the initial stage of operation with insufficient lubrication on the sliding surface. It was not possible to solve the problem simply by replacing the lubricating oil which is said to exist. Further, this type of bearing has a structure in which an oil-impregnated felt for storing lubricating oil is attached (Japanese Patent Laid-Open No. 7-231001, Japanese Patent Laid-Open No. 9-14085, etc.), but the bearing element becomes complicated and the number of assembling steps and There is also a demand for simplification because it will increase costs.

The present inventors have found that the above problems can be solved by devising the oil-impregnated bearing structure and the like. That is, an object of the present invention is to provide a sintered oil-impregnated bearing having a relatively high oil content that does not generate a squeal even when the electric motor is operated in a low temperature environment.

[0005]

[Means for Solving the Problems] To achieve the above object
In the sintered oil-impregnated bearing for an electric motor of the present invention,
A Cu alloy that is composed of bonded gold and that contains Sn and P
The gold phase and the ferrite phase of Fe are almost equal in area ratio
Cross-sectional structure presenting a mixed state of proportion, 0.7 mass% or less
It contains graphite particles of
Area of exposed iron part is 2-6%, effective porosity 20-30
%, And the air permeability of the bearing is 6 to 50 × 10 ^-11cm^Twoso
There is a kinematic viscosity of 61.2 to 7 in the pores at 40 ° C.
4.8 mm^Two/ S (cSt) synthetic oil
It is characterized by that.

As a method for producing the sintered oil-impregnated bearing for an electric motor, as described in claim 2, a sponge-like reduced iron powder having a particle size of 145 mesh sieve 42 to 50 mass% and a particle size of 145 mesh. Under the sieve 350 mesh is 5
Electrolytic copper powder 41 to 43% by mass, which is 0 to 90% by mass, foil-like copper powder having a particle size of 100 mesh, 2 to 10% by mass, tin powder 1.4 to 2.7% by mass, and P content 8 A mixed powder containing 3 to 5% by mass of phosphorous copper alloy powder of 9 to 9% by mass, graphite powder of 0.7% by mass or less, and molding lubricant of 1% by mass or less is used, and the mixed powder is compressed to have a density of 5. A molded body in the range of ^{3 to} 6.1 g / cm ³ is manufactured, the molded body is sintered at a temperature at which the phosphor copper alloy powder is melted, and the obtained sintered body is sized to have a density of 5.8 to 6.5 g / cm ³ and air permeability 6 to 50 × 10
A sizing body having a size of ⁻¹¹ cm ² was used, and the kinematic viscosity at 40 ° C. was 61.2 to 74.8 mm in the pores of the sizing body.
It is characterized by containing ² / s (cSt) of synthetic oil.

The above-mentioned sintered oil-impregnated bearing is based on the following test results which were obtained by examining the relationship between the properties of conventional bearings and sliding noise. (1) The effective porosity of the bearing itself does not significantly affect the sliding noise. (2) Permeability of sintered sintered alloy is related to sliding noise. The relationship between air permeability and noise level is similar to a quadratic function, and the higher the air permeability, the higher the noise level. (3) The noise level increases as the amount of lubricating oil contained decreases. In this case, when the lubricating oil becomes less than half of the effective porosity, the increase becomes extremely large. (4) If there is sufficient lubricating oil, there is no difference in noise level between the bronze bearing and the pure iron bearing. (5) When the amount of lubricating oil impregnated decreases, the noise level of pure iron bearings becomes higher than that of bronze bearings. (6) The higher the viscosity of lubricating oil, the lower the noise level.

Based on the above test results, the structure of the sintered oil-impregnated bearing of the present invention and the manufacturing method for realizing the structure are derived from the following technical ideas from empirical rules. (1) The sintered alloy has a composite structure in which iron particles are dispersed in a copper alloy phase. (2) The above-mentioned volume ratio, that is, the ratio in the cross-sectional structure, is a structural figure of about 1: 1 so as to have an intermediate property between them. (3) The bearing sliding surface (inner peripheral surface) can improve the initial conformability of shaft sliding by mainly exposing the copper particles while exposing the iron particles, but considering wear resistance Part of the iron particles are exposed and scattered to a predetermined degree. (4) The effective porosity should be as high as possible in order to secure the oil retaining ability. (5) In order to ensure oil lubrication on the bearing sliding surface, the pores on the inner peripheral surface of the bearing should have pores in the iron phase and in the copper alloy phase in addition to the relatively large pores between particles or phases. The organization is scattered. (6) In order to reduce the exposed iron particles on the bearing surface, the iron particles should be appropriately wrapped with a copper alloy, and foil-shaped copper powder should be used as the raw material. (7) In order to form pores in the iron phase and the copper alloy layer, spongy reduced iron powder and copper powder having a small powder particle size and a relatively large amount are used. (8) The copper alloy phase should be a relatively soft material, and the number of additive elements and the amount of additive should be small. Specifically, Sn and P are used. (9) Liquid phase sintering is used to secure effective porosity and strength, and low melting point tin powder and phosphor copper alloy are used. (10) In order to complement oil lubrication during sliding, the characteristics of the mixed powder,
A solid lubricant is added to the sintered alloy as long as the alloy strength and the lubricating oil are not contaminated. (11) Sizing so that the pores on the bearing sliding surface remain. (12) Sintered alloy has a relatively high effective porosity (lower density), but its air permeability is relatively low because it has a structural pattern with pores in the iron phase and copper alloy phase. State,
Suppress excessive oil bleeding due to sliding. (13) As the lubricating oil, select a synthetic oil that is excellent in low temperature characteristics and thermal stability and that is compatible with high temperature environments.

Specifically, the sintered oil-impregnated bearing which does not generate the above-mentioned squeaking noise can be obtained by having the following constitutional requirements. 1. Iron particles in the sintered alloy As the iron particles, spongy reduced iron powder is used so that pores also exist in the particles. The iron phase has a soft ferrite structure in which no bonded carbon is observed. The amount of iron particles in the alloy excluding pores is dispersed in the copper alloy phase in the range of 45 to 53% by volume to form a framework of the alloy. The particle size of the iron powder is 145 to prevent coarse iron particles from being exposed on the bearing surface.
Be under the mesh sieve. Here, the iron particle volume amount is 45 to 53.
% Is a range in which the distribution state of the iron particles as viewed from the cross-sectional structure and the exposed state on the surface are almost the same, and outside this range, the surface exposed state described later cannot be secured. This iron particle volume amount of 45 to 53% corresponds to 42 to 50 mass% in the entire structure.

2. The copper alloy phase copper alloy in the sintered alloy is Cu-Sn-P because of its appropriate hardness and strength.
System. Of these, Sn is added in the form of tin powder, melted by sintering, and diffused in copper. S in copper alloy system
The n content is 3 to 5% by mass, which is a small amount for a bronze system. This corresponds to 1.4 to 2.7 mass% in the total composition. P is added in the form of phosphorous copper alloy powder, melted during sintering and diffused into copper. As the phosphorus-copper alloy, the P content is 8 to 9 mass% which is the eutectoid portion of the binary system phase diagram. JIS H2501 (1979) Phosphor copper ingot 3 type (symbol: 8PCu) can be adopted for this. The addition amount of the phosphorous copper alloy powder is set to about 6 to 8 mass% in the copper alloy system in consideration of the amount of liquid phase generated by sintering. This corresponds to 3 to 5 mass% in the whole mixed powder containing iron powder. Also, P
The content corresponds to 0.18 to 0.4 mass% in the copper alloy system and 0.24 to 0.45 mass% in the overall composition.

As the copper powder, electrolytic copper powder and foil copper powder are used. As the former electrolytic copper powder, a relatively fine powder (a powder containing a large amount of subsieve powder) is used. As a result, fine pores are formed in the copper alloy phase of the sintered body. The particle size of such electrolytic copper powder is
Electrolyzed copper powder having 50 to 80 mass% under 145 mesh sieve and 350 mesh sieve is preferable, and commercially available electrolytic copper powders include, for example, CE25 and CE15 manufactured by Fukuda Metal Foil & Powder Industry. The total amount of electrolytic copper powder added is 4
41-43 which is approximately 80-95% of 5-51 mass%
Mass% The latter foil-shaped copper powder uses 1/20 to 1/5 (5 to 20 mass%) by weight of the total amount of copper powder. The foil-shaped copper powder increases the amount of copper alloy phase exposed on the sliding surface. As a result, there is an effect that the area of the iron particles exposed on the sliding surface is appropriately suppressed. The particle size used is under 100 mesh.

3. Cross-sectional structure of bearing and sliding surface of bearing The cross-sectional structure of the bearing is such that the iron phase and the copper alloy phase are mixed in a ratio of about 1: 1 by area, and relatively large pores between the particles are compared in each phase. Small pores are dispersed. Further, the surface layer portion is in a state in which some iron particles are exposed on the bearing surface. The sized inner peripheral surface of the bearing is a state in which pores (recesses) between metal particles and fine pores are observed in the metal part, especially in the copper alloy part, like the general sintered alloy. The area of pores on the moving surface is about 5 to 20%. Most of the metal surface of the inner peripheral surface of the bearing is a copper alloy surface, and iron is exposed in spots, and the exposed area of iron is 2 to 6 area%. This corresponds to a state in which about 10 to 25 iron particles having an average diameter of about 30 μm are observed within a visual field having an area of 0.2 mm ² when observed with a microscope. Such a surface is mainly composed of a copper alloy surface and has a shape reinforced with iron at intervals, and there are relatively small pores in the particles as well as relatively large pores between the particles. There is a state.

4. From the standpoint of solid lubricant lubrication, graphite particles can be included to supplement the lubrication of the impregnated oil. This content is 0.7 mass% or less in the entire composition. The inclusion of graphite reduces friction when oil lubrication is insufficient, but the inclusion of a large amount reduces the strength of the alloy and prevents it from having a high effective porosity. May deteriorate performance.

5. Sintering temperature The sintering condition is set to a temperature at which the tin powder and the phosphor copper alloy powder are melted or more, and the density increase due to sintering is 0.1 to 0.2 g / cm ^3.
The temperature and time are about the same. Sintering temperature is 720-78
It is 0 ° C.

6. Density, effective porosity, and air permeability The effective porosity is set to a region having a high oil impregnation capacity so that the strength of the sintered alloy satisfies the design values and oil supplementation means such as oil impregnation is not required. -30%. This value corresponds to a density of 5.8 to 6.5 g / cm ³ . In addition, the air permeability is compared to the density and effective porosity by comparing the density and effective porosity as the air permeability by using sponge-like reduced iron powder as raw material powder and copper powder with relatively fine particle size and foil-like copper powder. It becomes a sintered alloy in an extremely low state. Density 5.8-6.5 g /
The air permeability corresponding to cm ³ is 6 to 50 × 10 ⁻¹¹ cm ²
(× 10 ⁻³ darkness).

7. Lubricating oil Lubricating oil is a synthetic oil that can be used at low temperatures as well as at high temperatures, and has a viscosity grade of ISO VG
Equivalent to 68 is used. This has a kinematic viscosity at 40 ° C. of 61.2 to 74.8 mm ² / s (cSt).
This synthetic oil preferably contains PAO (poly-α-olefin) as a base oil having excellent lubricating properties, low-temperature properties, and thermal stability, and an ester as an oiliness improver as main components. Commercial products corresponding to such synthetic oils include, for example, the product name Anderol 465 (manufactured by Anderor Japan),
The trade name is All Time J-652 (manufactured by NOK CRYVA) and the like.

[0017]

EXAMPLES Next, examples to which the present invention is applied will be described. This example is an example in which the manufacturing method of the above-mentioned sintered oil-impregnated bearing and the physical properties of the produced sintered oil-impregnated bearing were examined and compared with the comparative example. Here, Examples and Comparative Examples of the invention will be described in the order of production of mixed powder, powder molding, sintering, sizing, oil impregnation treatment, physical properties of the produced oil impregnated bearing, and performance test.

1. Production of Mixed Powder (Example) As the raw material powder, the following (1) to (6) were used and mixed. The mixing ratio of each raw material powder is 45% by mass of iron powder,
Electrolytic copper powder 44%, foil copper powder 4.5%, tin powder 2%, phosphor copper alloy powder 4%, and graphite powder 0.5%. Further, 0.5% of zinc stearate powder which is a molding lubricant was additionally added. (1) Iron powder: Dowa iron powder, name DNC-180, particle size 14
5 mesh sieve (2) Electrolytic copper powder: Fukuda Metal Foil & Powder Industry, name CE-25,
80 under 145 mesh sieve and under 350 mesh sieve
~ 90% by mass (3) Foil-like copper powder: Fukuda Metal Foil & Powder Co., Ltd., name Cu-S-1
35 to 55% by mass of those under 00, 100 mesh sieve and 350 mesh sieve (4) Tin powder: manufactured by Japan Atomize Processing, name Sn-325 (5) Phosphor copper alloy powder: manufactured by Fukuda Metal Foil Powder Industry, name 8P-C
u-At-200 (6) Graphite powder: manufactured by Nippon Graphite Industry Co., Ltd., CPB (comparative example) The following raw material powders (1) to (4) were used and mixed. The mixing ratio of each raw material powder is, by mass, iron powder 48%, electrolytic copper powder 48%, tin powder 3.5%, and graphite powder 0.5%.
In addition, 0.5% of zinc stearate powder as a molding lubricant was added in the same manner as in the example. (1) Iron powder: made by Heganes, name NC100-24, grain size 8
0 mesh sieve (2) Electrolytic copper powder: Fukuda Metal Foil & Powder Industry, name CE-56,
15% under 350 mesh under 80 mesh sieve (3) Tin powder: manufactured by Nippon Atomize Co., Ltd., name: Sn-325 (4) Graphite powder: manufactured by Nippon Graphite Industry Co., Ltd., CPB

2. Powder Forming (Examples and Comparative Examples) Each of the mixed powders was compression-molded into a bearing shape using a mold. The compact density was set to 6.0 g / cm ³ .

3. Sintering (Examples and Comparative Examples) Each of the powder-compacted compacts was sintered at a temperature of 760 ° C. in a mixed gas of hydrogen gas and nitrogen gas.

4. Sizing (Examples and Comparative Examples) Negative sizing was performed on each of the sintered bodies. The plastic deformation of the metal surface of the bearing inner diameter was such that the sealing due to plastic flow did not proceed. In addition,
According to the method of the invention, the density at the time of compacting is 5.3 to 6.1.
The density was set to 5.5 by sintering within the range of g / cm ^3.
Up to 6.2 g / cm ³ and by sizing to a density of 5.8 to 6.5 g / cm ³ ,
It is preferable that the effective porosity is in the range of 20 to 30%.

5. Oil Impregnation (Examples and Comparative Examples) Each sizing body was vacuum impregnated with Anderol 465 (trade name, manufactured by Anderol Japan) as an oil impregnation treatment.

6. The properties of the sintered oil-impregnated bearings of Examples and Comparative Examples manufactured under the above conditions such as the physical properties of the sintered oil-impregnated bearing are as follows. (1) The density is 6.2 g / cm for both the example and the comparative example.
It was ³ . (2) The air permeability of the example is 20 × 10 ⁻¹¹ cm ^2.
(× 10 ⁻³ darkness), the comparative example is 60 × 10
^{It was -11} cm < ² > (* 10 < ^-3 > darcy). (3) The effective porosity was 25% in both the example and the comparative example. (4) The oil content was 25% in both the examples and the comparative examples. (5) The metal surface area of the bearing inner peripheral surface is 90% in the embodiment.
And that of the comparative example was 65%. (6) In the example, the area of exposed iron particles on the inner peripheral surface of the bearing is 3
%Met. In the comparative example, the area of the iron portion was 20% of the metal surface as the area of the copper alloy portion and the iron portion on the inner peripheral surface of the bearing. (7) In the example, as the exposed pore state of the inner peripheral surface of the bearing,
The pore area was 10%, and small pores were observed on the surface of the copper alloy particle in addition to the pores between the metal particles. In the comparative example, the exposed pores on the inner peripheral surface of the bearing have a pore area of 35%,
Most of the pores were between the metal particles, and the copper alloy had few pores and was smooth.

7. The low-temperature operation test evaluation method for an electric motor was carried out when the sintered oil-impregnated bearings of the above-mentioned Examples and Comparative Examples were mounted for a motor shaft shaft of an electric motor, and the electric motor was cooled to 30 ° C. below zero and then operated in that temperature environment. This is a mounting test in which the presence or absence of noise is checked. The motor has a shaft axis diameter of 8 mm, a sliding speed of 0.8 m / s, and a PV
The value is 0.08 MPa · m / s. The test results show that when the sintered oil-impregnated bearing of the example is used, no squeaking noise is generated from the initial stage of operation, but when the sintered oil-impregnated bearing of the comparative example is used, squeaking noise is generated, and the superiority of the invention product is remarkably recognized. Was given.

As described above, the bearing structure is a sintered alloy having a relatively large effective porosity and a relatively low air permeability in a state where the copper alloy phase, the iron phase and the pores are appropriately dispersed on the sliding surface. By combining with a lubricating oil having excellent low temperature characteristics and relatively high kinematic viscosity, a bearing element for an electric motor that does not generate a squeaking noise during operation in a low temperature environment can be realized.

[0026]

As described above, according to the present invention, by devising the structure of the sintered oil-impregnated bearing and the manufacturing method thereof,
For example, it is possible to improve the quality and reliability of the applied electric motor without generating a squeaking noise in the initial stage of operation of the electric motor used in a cold region of about 30 ° C. below zero.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H02K 5/167 H02K 5/167 A 15/14 15/14 AF term (reference) 3J011 AA07 AA08 AA20 BA02 DA01 DA02 JA02 KA02 LA01 MA02 MA22 RA03 SB19 4K018 AA04 AA25 BA02 BA14 BB04 CA02 DA21 5H605 AA04 BB05 CC04 EB06 EB13 GG21 5H615 AA01 BB01 PP25 SS01 SS26 SS31 TT16

Claims (2)

[Claims] 1. A cross-sectional structure in which the bearing material is made of a sintered alloy, and the sintered alloy exhibits a mixed state of a Cu alloy phase containing Sn and P and a ferrite phase of Fe in an approximately equal ratio in area ratio, The area of the iron part exposed on the inner peripheral surface of the sized bearing containing graphite particles of 0.7% by mass or less is 2 to
6%, effective porosity 20-30%, and bearing air permeability 6
50 is a × ¹⁰ -11 cm ^2, electric motors for oil-impregnated sintered bearing, wherein a synthetic oil of 61.2~74.8mm ² / s at a kinematic viscosity are oil-impregnated at 40 ° C. The pores . 2. Electrolytic copper powder 41 having a sponge-like reduced iron powder having a particle size of 145 mesh sieve of 42 to 50% by mass, and a particle size of 145 mesh sieve and 350 mesh sieve having a particle size of 50 to 90% by mass. 43 mass%, 2 to 10 mass% of foil-like copper powder having a particle size of 100 mesh sieve, 1.4 to 2.7 mass% of tin powder,
Phosphorous copper alloy powder having a P content of 8 to 9% by mass, 3 to 5% by mass,
Using a mixed powder containing 0.7% by mass or less of graphite powder and 1% by mass or less of a molding lubricant, the mixed powder is compressed to obtain a molded body having a density of 5.3 to 6.1 g / cm ^3. Made,
The formed body is sintered at a temperature at which the phosphor copper alloy powder is melted, and the obtained sintered body is sized to have a density of 5.8 to 6.5 g / c.
A sizing body having m ³ and an air permeability of 6 to 50 × 10 ⁻¹¹ cm ² is prepared, and synthetic oil having a kinematic viscosity at 40 ° C. of 61.2 to 74.8 mm ² / s is contained in the pores of the sizing body. A method of manufacturing a sintered oil-impregnated bearing for a motor.