JPH11256206A - Small-sized motor and manufacture of sintered alloy-made oil impregnated bearing thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a small-sized motor and a sintered alloy-made oil impregnated bearing thereof in which the wear resistance of a sliding bearing is improved and also, the noise of the motor developed with wearing can be reduced. SOLUTION: In this small-sized motor in which a permanent magnet 3 is fitted on the inner peripheral surface 2 of a casing 4 and a rotor 5 is disposed in the inner part of the casing 4 and the rotating shaft 6 of the motor is supported to be freely rotated with the bearing parts 7 and 8 provided in the casing 4, sliding bearings 19 and 22 in the bearing parts are the sintered alloy- made oil imprgnant bearing, in which a mixture blended into the blended composition so as to be 4-27 wt.% at least one side of powder between a single element of Ni and an alloy containing the Ni element, 3-5 wt.% a single element powder of Sn, 18-55 wt.% an alloy powder containing the Sn element and the balance, a single element of Cu with inevitable impurities, is formed by compressing and sintering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor,
In particular, small motors used in optical precision equipment such as small cameras, audio / video equipment such as CD players, OA equipment such as copying machines, home electric equipment such as hair dryers, electric equipment for automobiles, and toys. The present invention relates to a method for manufacturing the oil-impregnated bearing made of a sintered alloy.

[0002]

2. Description of the Related Art Small motors are widely used in various fields in addition to the above-mentioned devices, and are required to reduce bearing wear, motor noise (motor noise, etc.) and current consumption. For small motors, a stator is mounted on the inner peripheral surface of the casing, and a rotor is arranged inside the casing,
A rotating shaft of the rotor is rotatably supported by a bearing provided on the casing. Oil bearings made of a sintered alloy (hereinafter, referred to as sintered oil bearings) are often used as sliding bearings in the bearing portion.

[0003]

The sintered alloy is made of an iron-based material or a copper-based material. In the case of a sintered oil-impregnated bearing made of an iron-based material, the wear resistance is good, but the rotation speed is high. Since the frequency of the sliding sound when the shaft rotates is high, a relatively hard sound is generated. On the other hand, in the case of a sintered oil-impregnated bearing made of a copper-based material, a relatively soft sound is generated because the frequency of the sliding noise is low, but the wear resistance is lower than that of an iron-based material. There is a problem in durability of the motor, and there is a problem that motor noise increases due to wear. For this reason, conventionally, a sintered oil-impregnated bearing made of an iron-based material and a copper-based material has been selectively used depending on the use of the motor.

Japanese Patent Application Laid-Open No. 6-264110 discloses a technique relating to a bronze-based sintered oil-impregnated bearing in which the friction coefficient and conformability are improved. However, the sintered oil-impregnated bearing described in this publication may not have sufficient strength to withstand a high load in some cases. In addition, when a large side pressure load or the like is applied to the sintered oil-impregnated bearing at the time of eccentric side pressure or low rotation, since the effect of the lubricating oil impregnated in the sintered oil-impregnated bearing is not so much exhibited, the wear resistance is sufficient. Not always.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has a small motor having a sintered alloy oil-impregnated bearing capable of improving abrasion resistance and reducing motor noise caused by abrasion. An object of the present invention is to provide a method for manufacturing the oil-impregnated bearing made of the sintered alloy.

[0006]

Hereinafter, the present invention will be described with reference to FIGS. First, the overall configuration of the small motor according to the present invention will be described. FIG. 1 is a front view showing a cross section of one side of a small motor. As shown in FIG.
The small DC motor 1 as a small motor includes a casing 4 having a pair of stators 3 attached to an inner peripheral surface 2 and a rotor 5 disposed inside the casing 4. The rotating shaft 6 of the rotor 5 is rotatably supported by bearings 7 and 8 provided on the casing 4.

The casing 4 has a housing 9 formed in a hollow cylindrical shape with a bottom, and a lid member 11 fitted into an opening 10 of the housing 9. The housing 9 is integrally formed of a metal plate, and the lid member 11 is
It is integrally formed of the same metal material or resin material as the housing 9. The bearings 7 and 8 are provided at both ends of the casing 4. One bearing 7 is attached to the housing 9, and the other bearing 8 is attached to the lid member 11. The pair of stators 3 are fixed to the inner peripheral surface 2 of the housing 9 and are opposed to each other.

The rotor 5 includes a rotating shaft 6 extending in the direction of a central axis serving as a center of rotation, an armature 12 in which an armature winding is wound around a core attached to the rotating shaft 6 in a coil shape, A commutator 13 attached to the shaft 6 and electrically connected to the armature winding. A plurality (for example, two) of brushes 14 are slidably engaged with the commutator 13, and each brush 14 has a plurality (for example, two) of connection terminals 15.
Are electrically connected to each other. The connection terminal 15 is attached to the lid member 11, protrudes outward from the lid member 11, and is connected to a wiring or the like. A cylindrical projection 17 is integrally formed at the center of the flat surface 16 of the housing 9. On the inner peripheral surface 18 of the protruding portion 17, one sliding bearing 19 which forms one bearing portion 7 and has a sliding surface is press-fitted and fixed. The slide bearing 19 rotatably supports the output side of the rotating shaft 6.

The other bearing portion 8 that rotatably supports the non-output side of the rotating shaft 6 includes a thrust receiving member 20 that supports the end 21 of the rotating shaft 6 in the thrust direction and a rotating shaft end 21 that rotates. And the other sliding bearing 22 that freely supports the bearing. The thrust receiving member 20 is formed of a synthetic resin or the like having good lubricity. The slide bearing 22 is press-fitted and fixed to an inner peripheral surface 24 of a protrusion 23 formed on the lid member 11. Sintered oil-impregnated bearings (sintered alloy oil-impregnated bearings) are used for the slide bearings 19 and 22. In the motor 1, the brush 14 and the commutator 1
When a current is passed through the armature winding of the armature 12 via the armature 3, a rotational force is applied to the rotor 5 existing in the magnetic field formed by the pair of stators 3, and the rotor 5 rotates. do. Thereby, the motor 1 drives an optical precision device or the like via the output section of the rotating shaft 6.

Next, the sintered oil-impregnated bearing used for the slide bearings 19 and 22 will be described. FIG. 2 is a block diagram showing a manufacturing process of the sintered oil-impregnated bearing, and FIG. 3 is a graph showing an example of a temperature change of the material to be sintered in the sintering process. Indicates the temperature of the object.

[0011] Oil-impregnated bearings made of sintered alloys are defined as "sintered oil-impregnated bearings" in Japanese Industrial Standards in JIS B1581-1976, and the types of bearings are classified by component composition and oil content. For example, in the case of a bronze-based bearing “SBK-1218”, Sn is defined as 8 to 11% by weight, C is 2% by weight or less, and the rest is Cu or the like. Conventionally, these bronze-based sintered oil-impregnated bearings are made of Cu,
It is manufactured by compounding each powder of Cu-Sn and Sn into a predetermined compounding composition, compressing and then sintering. However, when this bronze-based sintered oil-impregnated bearing is used for a plain bearing of a motor, it is insufficient in terms of wear resistance and reduction of motor noise caused by wear.

By the way, the sintering is not performed by completely melting the entire material powder into an alloy, but by heat-treating a metal or alloy powder (powder) under pressure at a temperature lower than the melting point. In addition, the powder is baked and solidified by utilizing a phenomenon in which the bonding between powders occurs and the powder is solidified in a molded form. for that reason,
Even if the component composition is the same, if the composition of the material powder is different, the physical properties of the product will be different. Therefore, in the present invention,
As a material for the sintered oil-impregnated bearing, a material obtained by further adding Cu-Ni powder to each powder of Cu, Cu-Sn and Sn is used. Then, these powders are blended into a predetermined blending composition,
The obtained mixture is compression-molded into a green compact, and the green compact is sintered under predetermined conditions to form a sintered body, thereby producing a sintered oil-impregnated bearing having excellent physical properties.

More specifically, in the sintered oil-impregnated bearings constituting the sliding bearings 19 and 22 in the present invention, powder of at least one of an alloy containing a single element of Ni and an element containing Ni is 4 to 27% by weight. , Sn single element powder is 3 to 5
Compression molding and sintering of a mixture in which the powder of the alloy containing the element of Sn is 18 to 55% by weight and the balance is a powder of the single element of Cu and unavoidable impurities. It is molded by. The composition of the sintered oil-impregnated bearing is preferably such that Ni is 3 to 13% by weight, Sn is 7.5 to 12% by weight, and the remainder is Cu and inevitable impurities. Further, in the sintered oil-impregnated bearing, a part or the whole of the Cu—Ni—Sn alloy of the sintered body is formed of a θ phase (an intermetallic compound composed of Ni and Sn, for example, Ni ₃ S
It is preferable to have at least one of the structure of n) and a modulation structure formed by spinodal decomposition.

[0014] The method for manufacturing the sintered oil-impregnated bearing is as follows.
Powder of at least one of the alloy containing the single element of Ni and the element of Ni is 4 to 27% by weight, and the powder of the single element of Sn is 3 to 27% by weight.
The powder of the alloy containing the element of Sn is 18 to 55% by weight.
% By weight, and a mixture blended in a composition such that the balance is a powder of a single element of Cu and unavoidable impurities.
After sintering at about 800 ° C. for a predetermined time to form a sintered body, when the sintered body is cooled to about 300 ° C., a part or the whole of the Cu—Ni—Sn alloy of the sintered body is Cu-
In the ternary equilibrium diagram of the Ni-Sn alloy, "α (Cu-Ni-
(Sn solid solution) + θ (intermetallic compound consisting of Ni and Sn) ”, and gradually cools the sintered body at a cooling rate such that the θ phase is precipitated. After sizing to a predetermined shape, oil immersion processing is performed.

In the sintered oil-impregnated bearing and the method for manufacturing the same, the compounding composition of the raw material powder is such that at least one of the powder of the alloy containing the single element of Ni and the alloy containing the element of Ni is 7%.
~ 15 wt%, Sn single element powder 3-5 wt%, S
It is preferable that the powder of the alloy containing the element n is 36 to 50% by weight, and the balance is a powder of a single element of Cu and unavoidable impurities. The composition of the composition is as follows: Ni is 6 to 10% by weight;
Is preferably 8 to 10% by weight, and the balance is Cu and inevitable impurities.

In the above manufacturing method, the green compact is sintered in a reducing atmosphere at about 750 ° C. for about 1 hour to form a sintered body, and the sintered body is cooled at a rate of about 3 to about 5 ° C./min. It is preferred to cool slowly at a rate. The porosity of the sintered body is about 18 to about 28% by volume, or the oil content after oil immersion is about 18 to about 28% by volume, or the porosity of the sintered body is It is preferred that the oil content be about 18 to about 28% by volume and the oil content after the oil immersion treatment be about 18 to about 28% by volume. Here, the “porosity” is a percentage of the volume of all pores to the total volume of the porous body.

As described above, in the present invention, one or both of the intermetallic compound which is not completely dissolved in the copper alloy by cooling after sintering and the modulation structure formed by spinodal decomposition are precipitated. This precipitate suppresses the dislocation movement (ie, plastic deformation) of the metal crystal, and thus has higher heat resistance (ie, high-temperature strength) and hardness than other phase structures. Here, "spinodal decomposition"
This is a process of two-phase separation that occurs when a mixed system of two or more components is cooled from a high temperature to an unstable state, and causes remarkable hardening. Spinodal decomposition occurs as an initial stage of the precipitation process of the second phase, and a solid solution structure that is periodically separated into two phases is called a modulated structure.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a sintered oil-impregnated bearing and a method of manufacturing the same according to the present invention will be described. As shown in FIGS. 2 and 3, in the mixing step 101,
The raw material powder (raw material powder) is blended into a predetermined blending composition and component composition, and the mixture is sufficiently mixed so that the whole becomes uniform. Tables 1 and 2 below show the composition of the mixture when molding the sintered oil-impregnated bearing and the component composition of the sintered oil-impregnated bearing, respectively.

[0019]

[Table 1]

[0020]

[Table 2]

In the mixing step 101, the raw material powder is blended so as to have the composition shown in Table 1 and the component composition shown in Table 2, and the mixture obtained by adding zinc stearate to the raw material powder and mixing is subjected to the compacting step 102. send. Zinc stearate is a lubricant that is temporarily added in order to prevent seizure with a mold and the like, and has a low boiling point (about 250 ° C.) and is evaporated off during sintering. The zinc stearate is added at about 1% by weight of the total mixture. In the compacting step 102, a compact is formed by putting the mixture into a mold and compression-molding the mixture into a predetermined shape.

Next, the green compact is sent to a sintering step 103. In the sintering step 103, for example, a conveyor type continuous sintering furnace is used. By setting the inside of the sintering furnace to a reducing atmosphere filled with a reducing gas such as an ammonia decomposition gas, the sintering object (that is, the green compact and the sintered body) is prevented from being oxidized. The object to be sintered is continuously moved in a furnace while being placed on a belt conveyor, and is subjected to a sintering process. In the sintering step 103, the green compact compacted in the compacting step 102 is sintered in a reducing atmosphere at about 700 to about 800 ° C. for a predetermined time to form a sintered body.

In the sintering step 103 of this embodiment, first, pre-sintering for heating the green compact to about 400 to about 450 ° C. to evaporate zinc stearate is performed for about 1 hour. Next, in the main sintering, the green compact is heated from about 400 to about 450 ° C. to about 750 ° C., and sintered at the sintering temperature of about 750 ° C. for about 1 hour to form a sintered body. Thereafter, the sintered body is heated from about 750 ° C. to about 40 ° C. in about 3 hours, for example, about 3.9 ° C.
After gradually cooling at a cooling rate of ° C / min, the material is discharged into the atmosphere outside the furnace.

On the surface of the sintered body carried out of the sintering furnace,
An oiling process 104 for preventing rust is performed. In a sizing process 105 after the oiling process 104, a sizing process is performed so that the sintered body has a predetermined shape, and then a cleaning process for removing dust, impurities, oil, and the like attached to the surface of the sintered body. Perform 106. After the cleaning process 106, the clean sintered body is immersed in lubricating oil and subjected to an oil immersion process 107 in which the sintered body is heated under vacuum, so that the porosity of the sintered body is about 18%.
About 28% by volume, or an oil content of about 18 to
About 28% by volume, or a porosity of about 18 to about 28
Thus, a sintered oil-impregnated bearing having an oil content of about 18 to about 28% by volume after the oil immersion treatment is completed. In the present embodiment, the sintered body is sized so as to have a cylindrical shape with an inner diameter of 2 mm and a sliding length of 2 mm, and the cylindrical sintered body having an oil content of 20.8 to 22.2% by volume. The present invention bearing N- which is an oil-impregnated bearing
Comparative bearings S-1 to S-3 corresponding to conventional sintered oil-impregnated bearings were prepared (Tables 1 to 4).

As shown in Tables 1 and 2, the present bearing N
-1 to N-5 are Cu-N containing 70% by weight of Ni.
i is used, and the other bearings of the present invention N-6 to
For N-8, a Cu-Ni alloy powder having a Ni content of 30% by weight is used. Each of the comparative bearings S-1 to S-3 was prepared under conditions outside of the scope of the present invention in both the compounding composition and the component composition, and did not contain Ni. In particular, the comparative bearing S-1 is the SB of JIS B1581-1976.
It is a conventional bronze-based sintered oil-impregnated bearing corresponding to K-1218.

Table 3 below shows the bearings N-1 to N-8 of the present invention.
5 shows measurement results of oil content, hardness, and the like in comparative bearings S-1 to S-3.

[0027]

[Table 3]

In Table 3, Cu—Ni—Sn alloy, C
The hardness of the u-Sn alloy and the Cu-Sn alloy containing a relatively large amount of Sn is not the apparent hardness, which is the indentation hardness including the effect of the pores of the sintered material, but the pores of the sintered material are avoided. It was measured by "matrix hardness", which measures only metal parts. The matrix hardness (Hv) was measured with a Vickers hardness tester, and the measurement conditions were such that the test load was 9.8.
1 × 10 ⁻² N and the holding time was 5 seconds. As shown in Table 3, in the bearings N-1 to N-8 of the present invention, the sintered body is C
u-Sn alloy (contains a small amount of Ni,
Or Cu-Sn alloy) and Cu-Ni-S
n-alloy (a portion that was Ni or Cu-Ni alloy at the time of green compacting). This Cu-Ni-Sn alloy has a higher hardness than the Cu-Sn alloy and a matrix hardness of 25.
It is 0Hv or more and has excellent wear resistance. In the sintered body, the Cu—Ni—Sn having high hardness and excellent wear resistance is used.
About 4.3 to 26.7% by weight of the alloy (preferably 5 to 2%);
5% by weight). Cu-Ni-Sn alloy is a portion that was Ni or Cu-Ni powder at the time of compacting,
The above numerical values are based on the amounts of the Cu-Ni powder shown in Table 1.

In the bearings N-1 to N-8 of the present invention, C
The matrix hardness of the u-Ni-Sn alloy is Cu-Sn
The alloy is about 1.5 to about 3 times harder than the alloy, but at room temperature, Cu in the comparative bearings S-1 to S-3 has a relatively large amount of Sn.
-Since there is no great difference from the matrix hardness of the Sn alloy, even if the bearings N-1 to N-8 of the present invention are used for the motor 1, it is almost impossible to damage or wear the rotary shaft 6 more than the comparative bearing. Absent.

FIG. 4 is a graph showing the effect of the oil content on the radial crushing strength. The horizontal axis represents the oil content and the vertical axis represents the radial crushing strength. Generally, as shown in FIG. 4, when the oil content is 18% by volume or less, the sintered oil-impregnated bearing has a sufficient radial crushing strength, but since the amount of the impregnated lubricating oil is small, the lubricating oil can be lubricated in a short time. Oil is consumed and the life of the sintered oil-impregnated bearing is shortened. On the other hand, in general, when the oil content is 28% by volume or more, the sintered oil-impregnated bearing is impregnated with a sufficient amount of lubricating oil. May be distorted or cracked when press-fitted.
Therefore, when the oil content of the sintered oil-impregnated bearing is about 18 to about 28% by volume, the sintered oil-impregnated bearing has both an appropriate oil content and a radial crushing strength. In the bearing of the present invention, the oil content is 21.3.
Since it is ２２22.2% by volume, the radial crushing strength is almost the same as that of the comparative bearing.

Next, the change of the metal structure during sintering will be described. FIG. 5 is a ternary system diagram of a Cu—Ni—Sn alloy at 780 ° C. (hereinafter referred to as an equilibrium diagram), FIG. 6 is a schematic explanatory diagram showing an example of a state of a change in a metal structure in a sintering process, 7 is a schematic explanatory view showing an example of the state of the atomic structure of the metal structure in FIG. 6, FIG. 8 is a structural diagram of the metal surface of the sintered oil-impregnated bearing according to the present invention (that is, the sliding surface of the bearing of the present invention),
FIG. 9 is a graph showing the results of the eccentric side pressure load test.

In the mixing step 101 and the compacting step 102, Cu
After powder, Cu-Ni powder, Cu-Sn powder and Sn powder are mixed and the mixture is compression-molded, the green compact is sintered in a sintering step 103 to obtain a sintering temperature (about 700 to about 800).
C.), the Sn powder having a lower melting point melts and diffuses around. Thereby, Cu powder, Cu-Ni powder and Cu-
Sn powders are Cu-Sn alloy and Cu-Ni-S, respectively.
It becomes n alloy and Cu-Sn alloy. In addition, the melting Sn
To a lesser extent, Ni also diffuses around, so Cu-Sn
An alloy (including a trace amount of Ni) and a Cu-Ni-Sn alloy are formed. The Cu-Sn alloy (containing a trace amount of Ni) is a portion that was a Cu powder or Cu-Sn powder before sintering,
The u-Ni-Sn alloy is a portion that was a Cu-Ni powder before sintering.

The Cu—Ni alloy is an all-solid solution,
Can form a solid solution in Cu, so Cu-
The Ni alloy does not precipitate Ni no matter how much the amount of Ni is increased. However, Cu-Ni since alloy Sn becomes not a complete solid solution and will diffuse Cu-Ni-Sn alloy, or solid solution limit of Ni, Sn is Cu-Ni-Sn intermetallic compound Ni ₃ Sn Precipitates on the alloy.

In the equilibrium diagram of FIG.
The solid solubility curve of the α phase at 0 ° C. is shown, and the dashed line C shows the solid solubility curve of the α phase at 300 ° C. As shown, α
Since the solid solubility curves B and C of the phases are greatly different from each other, when the sintered body is gradually cooled from 780 ° C. to 300 ° C., the θ phase (Ni ₃ Sn or other Ni) is removed from the Cu—Ni—Sn alloy. And Sn), and spinodal decomposition occurs.

More specifically, when the α solid solution (Cu—Ni—Sn alloy) in which Ni and Sn are dissolved to the solid solution limit is gradually cooled from a high temperature, the solid solution limit becomes small. And Sn cannot be completely dissolved in the Cu-Ni-Sn alloy.
As a result, the θ phase (for example, an intermetallic compound of Ni ₃ Sn)
And spinodal decomposition, that is, precipitation of a modulated structure. Cu-Ni-
In the case of Sn alloy, not the mixing ratio of Ni and Sn, but Cu
It is important that Ni and Sn form a solid solution up to the solid solubility limit of. For this purpose, in the present invention, the amounts of Ni and Sn in the composition and composition of the raw material powder are defined so that the Cu-Ni-Sn alloy becomes a saturated solid solution. However, Ni
If too much Sn and Sn are added, problems such as increased wear occur, so the upper limits are set for the amounts of Ni and Sn.

FIG. 6 shows an example of the state of the change of the metal structure taking the bearing N-8 of the present invention as an example. Inventive bearing N
The mixture at the time of producing -8 (mixture having the composition shown in Table 1 and having the composition shown in Table 2) is in a state shown in FIG. 6A before sintering. About 75 of this mixture
After sintering at 0 ° C. for about 1 hour, as shown in FIG.
It becomes a Cu-Sn alloy (containing a trace amount of Ni) and an α solid solution (that is, a Cu-Ni-Sn alloy). The α solid solution at this time is indicated by the symbol E in the equilibrium diagram D at about 750 ° C.

Next, the sintered body is heated from about 750 ° C. to about 30 ° C.
When gradually cooled at a predetermined cooling rate to 0 ° C., FIG.
As shown in (c), precipitation of a θ phase (for example, an intermetallic compound of Ni ₃ Sn) and precipitation of a modulated structure due to spinodal decomposition occur. In equilibrium diagram D ₁ of the at about 300 ° C. shown in FIG. 6 (c), since the solid solubility limit curve F of alpha phase is moving in the figure below the case 750 ° C., alpha solid solution position E
Changes from the component range of the α phase to the component range of the α + θ phase, causing precipitation of the θ phase and spinodal decomposition.

As can be seen from the equilibrium diagrams shown in FIG. 5 and FIG. 6C, in order to cause this change reliably, it is better to increase the Sn composition rather than the Ni composition. is important. That is, if the mixture is blended in a blended composition containing a large amount of Sn, the position E of the α solid solution becomes α
The composition range of the phase changes to the composition range of the α + θ phase, and the precipitation of the θ phase and spinodal decomposition are easily caused. By the way, if the sintered body is rapidly cooled as shown in FIG. 6 (d), there is not enough time for the precipitation of the θ phase and the spinodal decomposition, so that the structural change does not occur or is insufficient. become. Therefore, it is preferable to gradually cool the sintered body at a predetermined cooling rate or lower.

FIG. 7A shows the atomic structure when the α solid solution is sintered at about 750 ° C. and becomes unstable. When this α solid solution is gradually cooled at a predetermined cooling rate, spinodal decomposition occurs as shown in FIG. 7B, and a Cu—Ni—Sn alloy with a high Sn concentration and a Cu—Ni—Sn alloy with a high Ni concentration Two-phase separation occurs. The state at this time is a metastable state. The atomic radius of Sn (1.41 × 10 ⁻¹⁰ or 1.51 × 10 ⁻¹⁰ m) is
Ni atomic radius (1.25 × 10 ^-10 m) and atomic radius (1.28 × 10 ^-10 m) of Cu large compared to, cyclic elastic stress field since there is a difference in the lattice constant of each atom Is generated. Spinodal decomposition greatly contributes to the improvement of the strength of the alloy, as this is an effective obstacle to dislocation movement.

Further, when this sintered body is gradually cooled at a predetermined cooling rate, as shown in FIG. 7 (c), in addition to the progress of the spinodal decomposition, the θ phase precipitates in the α phase and becomes stable. . The precipitated structure has high heat resistance and hardness because it suppresses the movement of the dislocation of the metal crystal. As shown in FIG. 8, the sintered alloy oil-impregnated bearing 30 of the present invention thus manufactured has a Cu-Sn alloy phase 31 containing a small amount of Ni and an intermetallic compound (Ni ₃ It has a metal structure mainly including two phases of a Cu-Ni-Sn alloy phase 32 in which Sn) is precipitated, and voids in the structure are oil holes 33 impregnated with lubricating oil.

In order to gradually cool the sintered body to precipitate the intermetallic compound consisting of Ni and Sn, Ni and Sn are dissolved in the material to be sintered at the time of sintering in a high temperature environment. Must be dissolved to near the limit. For this purpose, the composition of the raw material powder is set so that at least one of the powders of the alloy containing a single element of Ni and the element containing Ni is 4 to 27% by weight,
3 to 5% by weight of a single element powder of n, 18 to 55% by weight of an alloy powder containing an element of Sn, and a powder of a single element of Cu and inevitable impurities (for example, a single element of Cu and an inevitable impurity) Ni and Sn which form a solid solution in the Cu-Ni-Sn alloy by making the composition so that the impurity powder is 38 to 50% by weight.
Need to be increased.

If the amount of the Cu—Ni powder or Sn powder is too large, the proportion of the Cu—Ni—Sn alloy in the sintered oil-impregnated bearing increases and the Cu—Ni
The intermetallic compound precipitates in a large amount in the -Sn alloy. As a result, the hardness of the sintered oil-impregnated bearing and the entire inner peripheral surface becomes too high, and the conformability is deteriorated, and the rotating shaft 6 may be damaged. On the other hand, if the compounding amount of the Sn powder is too large, the Cu-Sn alloy containing a relatively large amount of Sn can be formed. Therefore, if the composition of the raw material powder is set as in the present invention, Cu
-The ratio of the Ni-Sn alloy and the Cu-Sn alloy becomes moderate, and the precipitation amount of the intermetallic compound composed of Ni-Sn becomes moderate (see the eccentric load test results in Table 4).

Therefore, the Cu-metal having the intermetallic compound and the modulated structure formed by spinodal decomposition precipitated.
The Ni-Sn alloy has significantly improved heat resistance and hardness compared to the Cu-Sn alloy (see Table 3). That is, in the sintered oil-impregnated bearing 30, since the structure of the intermetallic compound and the modulation structure are precipitated and dispersed in the copper alloy, heat resistance and hardness are improved.

As described above, since the Cu—Ni—Sn alloy has excellent heat resistance, when the sintered oil-impregnated bearing 30 is applied to the sliding bearings 19 and 22 of the motor 1, the matrix hardness shown in Table 3 is obtained. As shown in the data, the maximum hardness at room temperature is not much different from that of the conventional product, but the sliding bearings 19 and 22 and the rotating shaft 6
When the temperature of the sliding surface rises due to sliding with
Changes in hardness are smaller than those of Cu-Sn alloys containing a relatively large amount of. In particular, such a severe condition that the eccentric side pressure load or the high side pressure load at the time of low rotation is applied to the sintered oil-impregnated bearings of the slide bearings 19 and 22 so that the lubricating oil impregnated in the sintered oil-impregnated bearing does not exert much lubricating effect. Under the conditions, the ratio of the characteristics of the metal structure of the sintered oil-impregnated bearing becomes larger than the characteristics of the lubricating oil. Therefore, according to the sintered oil-impregnated bearing of the present invention,
Wear of the slide bearing is reduced, and noise (mechanical noise) of the motor 1 can be reduced by reducing the wear.

Next, the results of the eccentric side pressure load test and the side pressure load test of the bearings N-1 to N-8 of the present invention and the comparative bearings S-1 to S-3 are shown in Table 4 below and FIG.

[0046]

[Table 4]

The test conditions for the eccentric side pressure load test were as follows. A motor 1 in which the present bearings N-1 to N-8 and comparative bearings S-1 to S-3 were mounted on sliding bearings 19 and 22 was prepared.
When the rotor 5 is rotated at 9000 min ^-1 (that is, the sliding speed of the slide bearing is 56.5 m / min), the eccentric pressure load of 8.44 N (that is, the load is 209 N / cm ² ) is applied to the slide bearing 19. The eccentric pulley was set on the rotor 5. Then, the motor 1 is continuously rotated 96 in the same rotation direction.
The characteristics of the sintered oil-impregnated bearing were evaluated by measuring the mechanical noise (motor noise) and the inner diameter of the bearing before and after the eccentric pressure test by rotating at 9000 min ^-1 for a time. Mechanical noise is 2.4V applied to the motor with the eccentric pulley removed.
And rotate at about 7600 min ^-1
-Measured under the condition of the A characteristic. The PV value under the eccentric side pressure load test condition is 11792 N / cm ² · m / min.

The side pressure load test was performed by mounting the sintered oil-impregnated bearing of the present invention not on a small motor but on a friction coefficient measuring device. The mating shaft member that slides by engaging with the sintered oil-impregnated bearing was made of the same material as the rotating shaft used for the small motor. The friction coefficient measuring device has a load of 280 N / cm ²
(A weight of 1.14 kg) and a sliding speed of 3.1 m / min (that is, a rotational speed of 500 min ^-1 ). It was measured under conditions where the effect was not so significant. In addition,
The PV value under the friction coefficient measurement condition is 878 N / cm ² · m / min.
The friction coefficient was measured one hour after the start of rotation in order to measure the friction coefficient after the initial adaptation. Each test condition of the eccentric side pressure load test and the side pressure load test is a severe condition in which the effect of the lubricating oil impregnated in the sintered oil-impregnated bearing is not so much exerted. Since the ratio of the properties of the metal of the oil-impregnated bearing increases, this is a convenient condition for examining the properties of the metal itself.

As can be seen from Table 4, in the bearing of the present invention,
The amount of change in mechanical noise (ie, motor noise) before and after the test is about 1 to about 5 dB (decibel) lower than that of the comparative bearing. In the bearing of the present invention, except for the bearing N-5,
The amount of change in the bearing inner diameter before and after the test (that is, the amount of wear) is about 1 to 2 more than the best bearing S-1 among the comparative bearings.
μm, it can be seen that the wear resistance is greatly improved. The coefficient of friction of the bearing of the present invention is about 0.02 to 0.10 lower than that of the comparative bearing. In particular, the coefficient of friction of the bearing N-8 of the present invention is about 0.
07 low. As described above, since the bearing of the present invention has a smaller friction coefficient than the comparative bearing, the current consumption of the small motor can be reduced. In the bearing of the present invention and the comparative bearing, in any of the eccentric side pressure load test and the side pressure load test, no damage due to sliding was observed when the rotating shaft after the test was observed.

FIGS. 9A and 9B are graphs showing the change in the bearing inner diameter before and after the test in the eccentric side pressure load test shown in Table 4. The vertical axis indicates the change in the bearing inner diameter before and after the test. (That is, the amount of wear). The horizontal axis indicates the component composition (% by weight), and FIG. 9A shows the comparative bearing S-1.
9B shows the Sn content of Comparative Bearing S-1.
And the Ni content of the bearings N-1 to N-8 of the present invention are shown. In general, a substance such as a Cu-Ni powder having a high melting point (for example, containing 70% of Ni and having a melting point of about 1380 ° C.) has a large bonding force between atoms. , Which means that the bond is hard to break. In general, the higher the melting point of a substance, the better the heat resistance tends to be.

As shown in FIG. 9A, the comparative bearing S-2
When the composition of Sn is set to 7.5% or less as described above, the sintered body becomes an α solid solution and becomes an alloy having high ductility. Although this alloy is excellent in conformability, the amount of Sn having an effect of improving the hardness is small, so that the hardness is low and the wear resistance is poor. On the other hand, when the component composition of Sn is set to 12% or more as in the comparative bearing S-3, a δ phase (intermetallic compound of Cu ₃ Sn) formed by decomposition of a β solid solution precipitates in an α solid solution. Cu-Sn alloy with a relatively large amount of Sn (about 410 ° C
To form a liquid phase).

Since the δ phase is a hard and brittle metal structure, this alloy has high hardness but low melting point Sn (melting point is about 232 ° C.)
, The heat resistance is poor. The value of Vickers hardness of this alloy is almost the same as that of Cu-Ni-Sn alloy, but when the temperature of the sliding surface rises due to sliding of the sintered oil-impregnated bearing and the rotating shaft, the hardness decreases and the sintered oil-impregnated The wear of the bearing increases, and as shown in FIG. 9 (A), the wear resistance may decrease and the sintered oil-impregnated bearing may be seized. When the composition ratio of Sn is 9.5% as in the comparative bearing S-1, an alloy having high hardness and relatively excellent heat resistance improves wear resistance. Therefore, it can be seen that in the sintered oil-impregnated bearing, when the composition of Sn is 7.5 to 12% by weight, the wear resistance is excellent.

As shown in FIG. 9B and Table 2, when the composition of Ni is 3% or less as in the case of the bearings N-1 and N-6 of the present invention, Cu having excellent heat resistance and hardness is obtained. -Ni-Sn
The alloy accounts for a small percentage of the whole, and the Cu-Sn alloy (N
(i.e., a small amount of i) is emphasized, so that the effect of adding Ni is reduced. If the Ni composition is less than 3%, the abrasion resistance tends to decrease, and the difference in abrasion resistance between the present invention and the comparative bearing S-1 is reduced.

On the other hand, when the component composition of Ni is 13% or more as in the bearing N-5 of the present invention, the proportion of the Cu—Ni—Sn alloy excellent in heat resistance and hardness becomes large, The properties of this alloy are emphasized. Inventive bearing N-5
When the component composition of Ni is 13% or more as in
n diffuses preferentially in Cu-Ni powder over Cu powder. Further, the addition amount of Sn itself may be small, so that the Sn amount in the Cu-Sn alloy (the portion which was Cu powder before sintering) will be small. Therefore, Table 2
As can be seen from Table 3 and Table 3, as the amount of Ni increases, C increases.
The matrix hardness of the u-Sn alloy decreases, and the wear resistance of this portion decreases. As a result, as shown in FIG. 9B, when the Ni composition is 13% or more, the wear resistance of the sintered oil-impregnated bearing as a whole decreases.

On the other hand, the bearings N-1 to N-4, N-6 of the present invention
To N-8, when the composition of Ni is 3 to 13% by weight, a Cu—Ni—Sn alloy excellent in heat resistance and hardness and a Cu—Sn alloy excellent in conformability (Ni (Including a very small amount) and the excellent characteristics of the two are emphasized at a favorable ratio, and the wear resistance is clear even in comparison with the best wear resistant bearing S-1 among the comparative bearings. Is excellent. Among the bearings of the present invention having a Ni composition of 3 to 13% by weight, those having a Ni composition of about 8%, such as the present invention bearings N-3 and N-8, are the most excellent in wear resistance. You can see that there is. Therefore, the component composition of the sintered oil-impregnated bearing is
If Ni is 3 to 13% by weight, Sn is 7.5 to 12% by weight, and the remainder is Cu and unavoidable impurities (for example, 75 to 89.5% by weight of Cu and unavoidable impurities), wear resistance is improved. It turns out that it is excellent.

As described above, when the sintered oil-impregnated bearing of the present invention is applied to a sliding bearing of a small motor, wear of the sliding bearing is reduced, and mechanical noise and current consumption of the motor are reduced.
Since this sintered oil-impregnated bearing is a bearing made of copper-based material, it produces a soft sliding noise and has good wear resistance and durability. Even if the oil-impregnated bearings are not used properly, one kind of the sintered oil-impregnated bearing of the present invention can be used regardless of the use of the motor. The sintered oil-impregnated bearing of the present invention can be applied to a small motor such as a brushless motor or a stepping motor using a plain bearing, in addition to the above-described motor with a commutator. The same reference numerals in the drawings indicate the same or corresponding parts.

[0057]

As described above, according to the present invention, the wear resistance of the sliding bearing is improved and the motor noise caused by the wear can be reduced.

[Brief description of the drawings]

FIGS. 1 to 9 are views showing an example of an embodiment of the present invention, and FIG. 1 is a front view showing a cross section of one side of a small motor.

FIG. 2 is a block diagram showing a manufacturing process of a sintered alloy oil-impregnated bearing.

FIG. 3 is a graph showing an example of a temperature change of an object to be sintered in a sintering step.

FIG. 4 is a graph showing the effect of oil content on radial crushing strength.

FIG. 5 is a ternary equilibrium diagram of a Cu—Ni—Sn alloy at 780 ° C.

FIG. 6 is a schematic explanatory view showing a state of a change in a metal structure in a sintering step.

7 is a schematic explanatory view showing an example of a state of an atomic structure of a metal structure in FIG.

FIG. 8 is a structural diagram of a metal surface of the oil-impregnated bearing made of a sintered alloy according to the present invention.

9A is a graph showing the relationship between the Sn content and the wear amount of the comparative bearing, and FIG. 9B is a graph showing the relationship between the Ni content and the wear amount of the present invention bearing and the comparative bearing S-1. It is a graph which shows a relationship.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Small DC motor (Small motor) 2 Inner peripheral surface 3 Stator 4 Casing 5 Rotor 6 Rotating shaft 7,8 Bearing part 19,22 Sliding bearing 30 Sintered alloy oil impregnated bearing 107 Oil immersion treatment

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H02K 5/167 H02K 5/167 A // C22C 1/04 C22C 1/04 A

Claims (4)

[Claims] 1. A stator (3) is mounted on an inner peripheral surface (2) of a casing (4), a rotor (5) is disposed inside the casing, and a bearing (7) provided on the casing is provided. , 8), the small-sized motor rotatably supporting the rotating shaft (6) of the rotor, wherein the sliding bearings (19, 22) of the bearing portion are made of an alloy containing a single element of Ni and an element of Ni. 4 to 27% by weight of at least one powder, 3 to 5% by weight of a single element powder of Sn, 18 to 18% by weight of an alloy containing Sn element.
An oil-impregnated bearing made of a sintered alloy (30) formed by compression-molding and sintering a mixture blended in such a composition that 55% by weight, with the balance being a powder of a single element of Cu and inevitable impurities. A small motor characterized by the following. 2. A stator is mounted on the inner peripheral surface of the casing,
A small motor in which a rotor is disposed inside the casing and the rotating shaft of the rotor is rotatably supported by bearings (7, 8) provided in the casing. , 22) is an oil-impregnated bearing made of a sintered alloy having a composition of 3 to 13% by weight of Ni, 7.5 to 12% by weight of Sn, and the remainder being Cu and inevitable impurities. motor. 3. A stator is mounted on the inner peripheral surface of the casing,
A small motor in which a rotor is disposed inside the casing and the rotating shaft of the rotor is rotatably supported by bearings (7, 8) provided in the casing. , 22) are at least one powder of 4 to 27% by weight of the alloy containing the single element of Ni and the element containing Ni, 3 to 5% by weight of the single element powder of Sn, and 3% by weight of the alloy containing the element of Sn. Powder 18 ~
The mixture is formed by compression-molding and sintering a mixture having a composition of 55% by weight, with the balance being a powder of a single element of Cu and unavoidable impurities.
It is an oil-impregnated bearing made of a sintered alloy having a component composition such that the content of Sn is 7.5 to 12% by weight, and the remainder is Cu and unavoidable impurities. A motor having at least one of a structure of a θ phase (intermetallic compound composed of Ni and Sn) and a structure of a modulation structure formed by spinodal decomposition. 4. A stator is mounted on an inner peripheral surface of the casing,
A rotor is disposed inside the casing, and the bearing (7, 8) provided in the casing rotatably supports the rotating shaft of the rotor. 22) A method for producing a sintered alloy-made oil-impregnated bearing constituting item 22), wherein at least one powder of a single element of Ni and an alloy containing an element of Ni is 4 to 27% by weight, and the single element powder of Sn is 3-5% by weight of alloy powder containing Sn element is 18-
A mixture having a composition of 55% by weight, with the balance being a powder of a single element of Cu and unavoidable impurities, is compression-molded, and the compression-molded green compact is reduced to about 700 to about 8 in a reducing atmosphere.
After sintering at 00 ° C. for a predetermined time to form a sintered body, when the sintered body is cooled to about 300 ° C., a part or the whole of the Cu—Ni—Sn alloy of the sintered body becomes Cu −Ni
-(Sn alloy ternary equilibrium diagram "α (Cu-Ni-Sn
Solid solution) + θ (intermetallic compound composed of Ni and Sn), and gradually cools the sintered body at a cooling rate at which the θ phase is precipitated. A method for producing an oil-impregnated bearing made of a sintered alloy for a small motor, wherein the oil-impregnated bearing for a small motor is subjected to oil immersion treatment after sizing to the shape of the above.