JPH1113765A - Magnetic fluid-impregnated sintered slide bearing and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic fluid-impregnated sintered slide bearing to have excellent slide performance and prevent outflow of lubrication oil, in a composite material of a bronze alloy, having excellent slide characteristics, and a permanent magnet. SOLUTION: Mixture powder with metal powder forming a bronze alloy, containing 30-70 wt.% Alnico powder, on which age hardening treatment is applied, and 10-50 wt.% foil powder of copper is green-molded at temperature of 700 deg.C or less in reduction atmosphere, and sizing, magnetizing treatment, and magnetic fluid-impregnation are effected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintered sliding bearing impregnated with a magnetic fluid and a method of manufacturing the same. It can be used for a motor for video equipment, a polygon motor for scanning, a spindle motor for a magneto-optical disk and the like.

[0002]

2. Description of the Related Art As a sintered bearing element utilizing a magnetic fluid, a permanent magnet is disposed adjacent to a bronze-based porous sintered bearing, or as disclosed in Japanese Utility Model Laid-Open No. 3-49416. Further, there are known porous sintered bearings in which permanent magnets are buried, or magnetized ferromagnetic particles dispersed in a matrix alloy of the porous sintered bearings.

[0003]

Among the prior arts, a sintered bearing made of a composite material of a sliding bearing alloy and ferromagnetic particles and impregnated with a magnetic fluid has a structure in which permanent magnet members are arranged adjacent to each other. Compared to the bearings, the bearing element has a simpler structure, and the magnets are dispersed near the sliding surface. Is done. However, in a sintered bearing using a mixed powder of a normal metal powder and a magnetic powder, relatively hard magnetic particles are exposed on a sliding surface, so that the compatibility with the shaft is poor,
It also causes abrasive wear and is not practical.

[0004] Therefore, the present invention provides a magnetic fluid impregnated sintered sliding bearing which is excellent in sliding performance and can prevent outflow of lubricating oil in a composite material of a bronze alloy and a permanent magnet having excellent sliding characteristics. Is a technical issue.

[0005]

SUMMARY OF THE INVENTION The present invention has been developed to solve the above-mentioned problems, and its technical means consists of a composite alloy of 30 to 70% by weight of magnetized alnico particles and the balance of a bronze alloy, A magnetic fluid impregnated sliding bearing characterized in that pores of a porous sintered alloy whose surface alnico particles are covered with a bronze alloy are impregnated with a magnetic fluid based on lubricating oil. The bronze alloy may be any alloy, but a particularly preferred bronze alloy is phosphor bronze. This is because the bearing performance and durability are excellent.

Here, Alnico has a composition of Al: 8 to 1
An iron alloy containing 3% by weight, Ni: 1 to 28% by weight, Co: 2 to 24% by weight, and if necessary, Cu and Ti. After being powdered by atomization, it is heated and subjected to aging treatment to precipitate. It is cured. The aging treatment may be performed at a normal temperature and time, but it is preferable that the aging treatment is performed in an incomplete state with a small temperature and time so that the aging is further advanced by sintering the green compact. The particle size is not particularly limited, but commercially available ones contain 35 to 45% by weight of sub-sieve powder,
It passes through a mesh sieve.

[0007] The amount of alnico particles in the bearing alloy is
The content is 30 to 70% by weight, optimally around 50% by weight. When the content of the alnico particles is less than 30% by weight, the amount of leakage magnetic flux of the entire bearing decreases, and the holding force of the magnetic fluid decreases. Therefore, 30% by weight or more is suitable as a bearing. However, when the content exceeds 70% by weight, the alnico particles are likely to be exposed on the bearing sliding surface, and the bearing performance is deteriorated.

Next, in the present invention, a member made of a non-magnetic material and having a higher effective porosity than a sintered sliding bearing and impregnated with a magnetic fluid based on lubricating oil is brought into contact with the end face of the sintered sliding bearing. This configuration is preferable because this member functions as an oil reservoir and extends the life of the bearing. The above-mentioned method for manufacturing a plain bearing includes 30 to 70% by weight of an alnico powder subjected to age hardening treatment and 10 to 50% by weight of a copper foil powder.
Of a mixed powder with a metal powder forming a bronze alloy containing aluminum is compacted into a bearing shape, and the compact is subjected to a temperature of 700 in a reducing atmosphere.
It is characterized in that sintering is performed at a temperature of not more than ℃ and sizing, magnetization treatment and magnetic fluid impregnation are performed.

[0009] The bronze alloy part has a normal composition having an Sn content of about 7 to 11% by weight, or a P content of 0.1 to 11% by weight.
It has a phosphor bronze composition of about 0.5% by weight. The latter is superior in durability. The bronze alloy part is made of copper and tin powder, and phosphor bronze is further Cu-P (for example, P: 15% by weight).
Content) alloy powder mixed, of which
Copper must be added in the form of foil powder of at least 10 to 50% by weight of the mixed powder. This technique is described in Japanese Patent Application Laid-Open No. 60-128201 and Japanese Patent Application Laid-Open No. 3-166303 disclosed by the present applicant, and a mixed powder that wraps the alnico powder with the foil powder is used. After being obtained and compacted and sintered, the sliding surface forms a porous surface of a bronze alloy without exposing the alnico powder on the surface of the bearing. The amount of copper foil powder may be adjusted depending on the content of alnico powder, but if the amount of foil powder is less than 10% by weight, coating may be incomplete, which is not preferable. A bearing can be manufactured even if the amount of foil powder is all of the required amount of Cu. However, if it exceeds 50% by weight of the mixed powder, the apparent density of the mixed powder becomes low, and the workability of compression molding becomes poor. The required shortage of the amount of Cu is added in the form of ordinary electrolytic or atomized copper powder and, if necessary, in the form of bronze alloy powder.

The reason that alnico is selected as the permanent magnet particles is that the amount of remanent magnetization does not decrease even when sintering at a temperature required for obtaining a bronze alloy. Other permanent magnet materials are unsuitable because of their small residual magnetization. For Alnico, the leakage flux of a material heat-treated at 700 ° C. is reduced by only about 10% with respect to the leakage flux of a material obtained by magnetizing a material subjected to normal aging. Similarly 770
When heated to ℃, it becomes about 50%. From this, sintering of the green compact is performed at a temperature of 700 ° C. or less,
50-700C is a preferred temperature. The bronze alloy is liquid phase sintered. If the surface of the alnico powder is plated with copper, less exposure to the sliding surface can be used, but it is not preferable because the number of processing steps increases and the cost increases.

The sizing of the sintered body of the present invention controls the size, density, surface exposed porosity and the like. Either the magnetization of the bearing or the impregnation of the magnetic fluid may be performed in the previous step. The magnetization of the bearing is such that by placing the bearing in a magnetic field, the alnico particles in the bearing are magnetized into permanent magnets. The magnetization direction may be axial or radial, but for bearing applications, the inner diameter is about several mm, so if formed in the radial direction, adjacent magnetic poles will act and the desired magnetism will be obtained. It may not be obtained, and it is desirable to form in the axial direction.

The sintered sliding bearing impregnated with the magnetic fluid thus produced and containing the permanent magnet particles has a high efficiency of retaining the magnetic fluid in the pores and on the sliding surface, and has a lubricating oil film. It is strongly formed and less lubricating oil leaks out of the bearing elements. Since the surface of the bearing is made of a bronze alloy, the same sliding characteristics as those of a normal sintered sliding bearing can be obtained.

The end surface (one or both surfaces as necessary) of the sintered bearing impregnated with the magnetic fluid is impregnated with the same magnetic fluid as that impregnated in the sintered bearing in the porous body made of a nonmagnetic material. When the above-mentioned members are configured to be in contact with each other, the porous member plays a role of an oil reservoir, and can significantly extend the lubrication life of the bearing. When the porous member is made of a non-magnetic material, the magnetic fluid is held in the pores mainly by capillary action, and when the magnetic fluid in the adjacent magnetic sliding bearing is reduced by operation or wear, the capillary is used. The decrease is compensated for by attracting by magnetic force against the phenomenon. If the rotation of the shaft stops and the magnetic fluid around the sliding bearing becomes excessive, it is sucked into the porous member. It is desirable that the porous member has a higher effective porosity and a larger porosity than the sintered plain bearing.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to examples.

[0015]

EXAMPLES The following powders were prepared as raw materials. (1) Alnico 2 powder: the total composition is 12% C by weight.
o, 18% Ni, 10% Al, 6% Cu and balance Fe,
Particle size -80 mesh (2) Copper foil powder: Particle size -200 mesh (3) Copper powder: Particle size -100 mesh, electrolytic copper powder (4) Tin powder: Particle size -200 mesh (5) Copper phosphorus alloy powder: Overall composition 15% P in weight ratio and the balance Cu, particle size -150 mesh These are in weight ratio, alnico powder 50%, copper foil powder 15%,
Copper powder 28.8%, tin powder 4.5%, and copper phosphorous powder 1.7% were mixed. When converted to the two-phase alloy composition after sintering, the alnico described in (1) above was 50% and 9% S.
Phosphor bronze consisting of n-0.6% P-remainder Cu is 50%.

As a comparative example, a mixed powder of 9% of tin powder, 2.4% of copper-phosphorus alloy powder and 87.6% of electrolytic copper powder was prepared. The size of each mixed powder is 10 mm in inner diameter, 16 mm in outer diameter,
It was formed into a cylindrical shape having a length of 10 mm, and each was sintered at a temperature of 690 ° C. in an ammonia decomposition gas. The sintered body was sized with a mold, adjusted in size, and had an effective porosity of 18%.

The former sizing body of the embodiment was magnetized in an electromagnet ring, and then impregnated with a lubricating oil-based magnetic fluid using an ordinary vacuum impregnating apparatus. The latter phosphor bronze bearing sample was impregnated with a low-viscosity lubricating oil. Each of these samples was set in a housing of a bearing test device, and a rotary shaft of a heat-treated stainless steel SUS420J2 was used, and a radial load on the bearing was 196 kP.
a, The operation was performed for 100 hours at a shaft rotation speed of 4000 rpm, and the average value of the temperature rise of the bearing during the operation and the lubricating oil consumption rate after the operation were compared.

The temperature rise was 5 ° C. or less in the bearing of the embodiment, but was 15 ° C. in the bearing of the comparative example. Further, the lubricating oil consumption rate is 4% in the bearing of the example and 11% in the bearing of the comparative example, and the former is about 1/3. Observation of the bearing element from the axial direction shows that the latter has lubricant flowing down to the housing and is contaminated, while the former has magnetic fluid accumulated in the rotating shaft and the chamfered part of the bearing, but has leaked to the outside. Not.

The bearings of the embodiment and the comparative example are made of phosphor bronze having the same sliding surface. However, since the bearing of the embodiment contains permanent magnet particles and pores containing a magnetic fluid lubricant, the sliding face and the pores are made. It is considered that the temperature rise and the consumption of the lubricant are reduced because the lubricant is held firmly therein. Next, a bearing test was performed on a sample manufactured in the same manner as in the previous example using a mixed powder having the same overall composition as the above-described bearing sample according to the present invention but using only electrolytic copper powder without using copper foil powder. went. In the case of this sample, the temperature rise was high, a lot of magnetic fluid accumulated in the portion of the chamfer of the rotating shaft and the bearing, and was scattered by the shaft rotation, and the lubricating oil consumption rate was 8%. The temperature rise of the bearing is considered to be due to the effect of the alnico particles exposed on the bearing sliding surface, and is considered to be due to the fact that the sliding characteristics are disadvantageous as compared with bronze when metal contact occurs with the shaft.

Further, a cylindrical sintered bronze ring having an effective porosity of 22%, impregnated with the same magnetic fluid as that impregnated in the bearing sample, is brought into contact with the end surface of the bearing sample according to the present invention described above. And a bearing test was performed.
The lubricating oil consumption rate is 2%, which is 1/2 that of the bearing of the above embodiment.
It can be expected that the bearing life will be prolonged.

[0021]

As described above, in the magnetic fluid impregnated sintered plain bearing of the present invention according to the manufacturing method of the present invention, the sliding surface is made of bronze having good sliding properties, and the permanent magnet particles are dispersed in the bearing material. As a result, the oil is efficiently retained in the bearing pores and the sliding surface, so that the lubricating oil is not scattered and consumed, the periphery of the bearing element is not stained, and a long life can be obtained. In addition, the manufacturing method and assembling means of the bearing are the same as ordinary oil-impregnated bearings,
There is also an advantage that it can be manufactured efficiently.

Claims (4)

[Claims] 1. The method according to claim 1, wherein a lubricating oil is contained in pores of a porous sintered alloy comprising a composite alloy of 30 to 70% by weight of magnetized alnico particles and the rest of the bronze alloy, the alnico particles on the surface being covered with a bronze alloy. A magnetic fluid-impregnated sintered plain bearing characterized by being impregnated with a magnetic fluid based on. 2. A magnetic member, wherein a porous member made of a non-magnetic material impregnated with a lubricating oil-based magnetic fluid is in contact with an end surface of the sintered plain bearing according to claim 1. Fluid impregnated sintered plain bearing. 3. The sintered sliding bearing as claimed in claim 1, wherein the bronze alloy is phosphor bronze. 4. An aging-hardened alnico powder is mixed with 3
A mixed powder of 0 to 70% by weight and a metal powder forming a bronze alloy containing 10 to 50% by weight of copper foil powder is compacted into a bearing shape, and the compact is subjected to a temperature of 700 ° C. in a reducing atmosphere. A method for producing a sintered sliding bearing with magnetic fluid impregnation, comprising sintering, sizing, magnetizing, and impregnating with magnetic fluid.