JPH0711302A - Production of double layer bearing - Google Patents

Abstract

PURPOSE:To produce the double layer bearing which is improved in critical load and cavitation resistance by forming a porous metallic sintered layer on steel sheet and further forming a lubricating layer consisting of a tetrafluoroethylene resin and solid lubricant thereon under specific conditions. CONSTITUTION:The tetrafluoroethylene resin is made into an emulsified state of 0.2 to 0.4mu particle size and the powder of the solid lubricant, such as lead-tin alloy, is mixed uniformly therewith and further the mixture is integrated by co-coagulation, by which the resin powder consisting of about 70 to 95vol.% tetrafluoroethylene resin and about 5 to 30vol.% solid lubricant is formed. On the other hand, the porous layer 6 consisting of bronze powder is sintered on the band-shaped steel sheet 7 and the resin powder previously wetted with an org. solvent is sprayed on the porous layer 6 and is pressed by a roll pressure to coat the porous layer with the resin layer 5. After the org. solvent is removed from the resin layer 5, the resin layer is baked for about 10 minutes at about 380 deg.C and further, the size is adjusted under the roll pressure, by which the double layer bearing 4 having the resin layer 5 on the surface is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multi-layer bearing, and more particularly to a method for manufacturing a multi-layer bearing suitable for a shock absorber bush for an automobile.

[0002]

2. Description of the Related Art Conventionally, various multilayer bearings have been proposed and implemented. For example, in JP-A-54-86041, a tetrafluoroethylene resin (hereinafter referred to as PTFE resin), lead fluoride, and lead-tin alloy or lead are provided on a porous layer lined with a metal backing. The bearing material is described in which the mixture is applied and impregnated into the porous material by roll rolling or the like. This bearing is a good material because it has excellent lubricity and high load. However, in this bearing, the mixture applied on the porous material is in a mixed state, and the binding force between the PTFE resin powder and the powder such as lead fluoride is weak, and especially the limit load is low and the cavitation resistance is low. -It is not very effective. For this reason, it is not always satisfactory in the case of reciprocating motion such as a shock absorber in which a fluctuating load is applied.

Recently, shock absorbers have severer lubrication conditions than before due to 1) reduction of oil viscosity as a countermeasure against cold regions, 2) cost reduction, and higher load of sliding motion due to weight reduction. It has become a thing. For this reason, in the sliding portion, the oil film is often cut off in the one-sided contact portion, and the boundary lubrication state occurs, so that friction resistance increases, smooth sliding cannot be obtained, and the amount of wear tends to increase.

Under such circumstances, the conventional multi-layer bearing as described above has a problem in load bearing capacity and wear resistance of the bearing surface, and the resin forming the bearing surface is worn away in the boundary lubrication state. It may be burned. The reason for this is that the strength of the resin layer existing as a film having a thickness of several tens of microns in the porous sintered body is weak. The reason for this is that the mixture forming the resin layer is in a mixed state, so that the PTFE
This is because the bonds between the PTFE resin and the filler such as lead fluoride are weak, in addition to the weak bonds between them.

More specifically, in a multi-layer bearing composed of a porous layer and a resin layer, (1) a dispersion of PTFE resin (PTFE) is used to form the resin layer.
A method in which an aqueous colloidal suspension of a resin and a filler such as lead fluoride are mixed in a dispersion state, and the dispersion state is applied and impregnated and coated as an agglomerated paste, (2) PTFE resin powder There is known a method of impregnating and covering a porous layer with a mixed powder composed of and a filler powder.

In the method (1), PTFE in the paste is used.
The particle size of the resin is as small as 0.2-0.4μ,
In particular, since the PTFE particles are dispersed in water or an organic solvent, even if they are heated and baked after coating and impregnating,
The bonding strength between the PTFE resin particles is weak. Furthermore, PT
The force of holding and fixing the filler powder by the particles of the FE resin is weak, and a strong resin layer cannot be obtained.

According to the method (2), the average particle size of the PTFE resin powder particles is as large as about 500 μ, but the particle size of lead fluoride or the like to be mixed is uniformly dispersed, and the mixing effect is exerted. Therefore, 50μ or less, especially 5μ
It is necessary to be below, and the particle size becomes extremely small.
For this reason, even if lead fluoride or the like is uniformly dispersed, even if fine lead fluoride or the like is attached to the periphery of the PTFE particles, there is a limit in itself. There is a problem that stable film strength cannot be obtained.

[0008]

The present invention aims to solve these problems. Specifically, seizure in the boundary lubrication state is prevented, and the lead-tin alloy is evenly distributed in the resin layer. A method for producing a multi-layer bearing in which the powder of PTFE resin is dispersed and firmly bonded, and the powder of lead-tin alloy is firmly held by this resin powder to improve the limit load and cavitation resistance. The purpose is to provide.

[0009]

That is, according to the method of the present invention, a porous metal sintered layer is formed on a steel plate, and the porous metal sintered layer is impregnated with a solid lubricant together with a tetrafluoroethylene resin. When forming the resin layer, the tetrafluoroethylene resin is made into an emulsified state with a particle diameter of 0.2 to 0.4 μ in advance, and a powder of a solid lubricant is uniformly mixed and co-coagulated with the powder. , Forming a resin powder, wetting this resin powder with an organic solvent, spraying it on a porous metal and then coating by indentation, then heating to remove the organic solvent, and then firing. Characterize.

The structure and operation of the bearing according to the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged view of an example of resin powder used for forming a resin layer in the method of the present invention.
FIG. 3 is an enlarged vertical sectional view of an example of a multi-layer bearing manufactured by the method of the present invention.

First, the resin powder used for forming the resin layer in the present invention is made of PTFE as described later with reference to FIG.
It consists of a resin powder and a solid lubricant powder such as a lead-tin alloy powder, but this is manufactured as will be shown later, and they are not simply mixed in a powder state. That is, one resin powder contains two component powders co-coagulated together, and two resin component powders are uniformly dispersed in one resin powder. Therefore, since the lead-tin alloy powder is uniformly dispersed in the powder containing the PTFE resin as a main component, the effect of adding the lead-tin alloy can be further increased, and the PTFE resin and lead -The effects of tin alloy and the like can be sufficiently exhibited, and since the bonding is integrated, the mechanical strength and wear resistance can be improved, and the effect of improving cavitation can also be achieved.

More specifically, first, in order to obtain a bearing having excellent load resistance and wear resistance, for example, PTF is formed on a porous layer made of metal powder such as bronze powder.
The resin powder containing the E resin and the primary particles of each powder of the lead-tin alloy in the co-coagulated and integrated state is coated and fired to form a resin layer as a bearing layer on the surface.

This resin powder is a PTFE resin powder 70.
.About.95% by volume (hereinafter simply referred to as "%") and 5 to 30% of powder of solid lubricant such as lead-tin alloy. In addition, powders of these components are particularly co-coagulated and integrated,
This formed powder. Therefore,
The resin powder is a powder formed by uniformly dispersing the PTFE resin powder and the lead-tin alloy fine powder and co-coagulating these powders. That is, as shown in FIG. 1, the resin powder 1 has a structure in which the PTFE resin powder 2 and the lead-tin alloy powder 3 are uniformly dispersed and integrated by co-coagulation. This resin powder is manufactured as follows.

Generally, PTFE resins are roughly classified into three types according to their molding methods. Compression molding powder mode
Luding powder, fine powder of powder for paste extrusion, and dispersion for coating / coating. Of these, fine powder and dispersion are used for impregnating and coating the porous layer such as the multilayer bearing.

Both the fine powder and the dispersion are obtained from an emulsion polymerization product of an intermediate product of the PTFE resin. Fine powder can be obtained by coagulating the emulsion polymerization product, and by concentration. Disperser
John can.

On the other hand, the resin powder forming the resin layer in the method of the present invention is a co-coagulated powder, which is co-coagulated as follows.

That is, PTF in the state of emulsion polymer
Powder of primary particles of E resin (diameter 0.2 to 0.4 μ) and powder of solid lubricant such as lead-tin alloy are uniformly mixed, and further co-coagulated to be integrated. That is, one particle of the resin powder is apparently formed as a secondary particle by uniformly mixing and agglomerating the solid lubricant powder such as a lead-tin alloy with the powder of the primary particle of the PTFE resin. The particle size is about the same as the particle size of the fine powder of PTFE resin, and the average particle size is about 500 μm.

Therefore, unlike the conventional one, it can be dispersed uniformly, the filling rate of the powder of the solid lubricant such as lead-tin alloy can be increased, and the resin layer can be formed by the paste extrusion as the molding method. Can be formed. For this reason, as the strength of the resin layer, it is possible to perform molding by paste extrusion using a roller or the like, and at that time, the resin powders are easily fibrillated and entangled with each other, and a filler is provided between the fiberized structures. It was easy to wrap, and the physical properties were greatly improved by strengthening the bond between the PTFE resin powders and the bond between the PTFE resin powder and the filler.

The solid lubricant used here is one that improves the load bearing capacity without impairing the low wear resistance of the PTFE resin.
And it is chemically stable with oil. That is, graphite, carbon powder, carbon fiber, molybdenum disulfide, lead-tin alloy and the like.

[0021]

EXAMPLES Next, examples will be described.

In advance, 85% of PTFE resin powder was made into an emulsified state, and 15% of lead-tin alloy powder was uniformly mixed and co-coagulated together to prepare a resin powder (16 mesh or less).

Further, as shown in FIG. 2, a porous layer 6 (thickness of bronze: 0.3 mm) was sintered on a strip steel plate 7 (thickness: 1.20 mm). A resin powder moistened with an organic solvent in advance was placed on the porous layer 6, and the resin powder was sprayed on the porous layer 6 and then pressed with a roll to form a resin layer.

Next, the organic solvent is heated and removed from the molded resin layer, and then baked at 380 ° C. for 10 minutes,
The PTFE resin powders were closely adhered to each other in the resin layer, and then the size was adjusted by rolling with a roll to obtain a multi-layer bearing 4 having the resin layer 5 on the surface. On the other hand, as a comparative material, as shown in Table 3, 85% of PTFE resin powder (fine powder) and 15% of lead-tin alloy powder were mixed, and a resin layer was formed from this mixed powder in the same manner as described above. Formed (Comparative Sample No. 7), PTFE resin 8
5% and 15% of lead-tin alloy powder was obtained as a paste by mixing lead-tin alloy powder with PTFE resin dispersion, and a resin layer was formed in the same manner. (Comparative sample No. 6) was prepared.

The various multi-layer bearings thus obtained were evaluated for load resistance, wear resistance and friction under the test conditions shown in Table 1 using a Suzuki type friction wear tester. Specifically, the load was accumulated by 20 kgf / cm ² per hour in a low-viscosity strut oil that tends to be in a boundary lubrication state, and a limit load was obtained and compared. At the same time, a cavitation test was conducted under the conditions shown in Table 2 for the purpose of evaluating the film strength of the resin layer, and comparison was attempted.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

The test results are shown in Table 3. As shown in Table 3, the multi-layer bearing according to the present invention has a comparative material no. 6, No. It was found that the limit load was larger than that of No. 7 and the cavitation resistance was also superior to that of the comparative sample.

Further, in order to further compare the effects of the present invention, the PTFE resin and tetrafluoroethylene-perfluoroalkylvinyl ether shown in Japanese Patent Application No. 58-014315 are used.
A co-coagulated powder (comparative sample No. 8) of a tercopolymer resin (hereinafter referred to as PFA resin) was impregnated under the same conditions as above, coated and baked to produce a multi-layer bearing. When a Suzuki type friction and wear test and a cavitation test were conducted on this multi-layer bearing, it was found to be equivalent in cavitation, but inferior in load bearing capacity to that of the present invention. Further, the same test was conducted in the multi-layer bearing according to the present invention by changing the compounding amount of the lead-tin alloy powder.
%, The load bearing capacity and cavitation were the same. The criteria for cavitation in Table 3 are as follows. A: Almost no change B: Part of the resin layer has been removed. C: The resin layer is completely removed and the sintered body is exposed.

[0031]

As described above, according to the method of the present invention, a porous metal sintered layer is formed on a steel sheet, and the porous metal sintered layer is impregnated with a solid lubricant together with a tetrafluoroethylene resin. When the resin layer is formed by using the tetrafluoroethylene resin in an emulsified state having a particle diameter of 0.2 to 0.4 μ,
The powder of the solid lubricant is uniformly mixed with this, co-coagulated to form a resin powder, the resin powder is wetted with an organic solvent, then sprayed on the porous metal, and then press-coated. After that, heating is performed to remove the organic solvent, and then baking is performed. Therefore, according to the method of the present invention, the solid lubricant can be uniformly dispersed and can be stably impregnated, and the impregnation can be achieved to the same extent as the impregnation of the PTFE powder itself.

Further, the obtained multi-layer bearing has excellent wear resistance even under a basic condition in which the oil becomes low in viscosity due to reciprocating motion to which a fluctuating load is applied and the load is increased to cause boundary lubrication. Since it has friction characteristics, it has a particularly large effective limit load and is excellent in cavitation resistance when applied to a place where a high load is applied such as a shock absorber bush or piston ring. There is.

Needless to say, this multi-layer bearing is also effective when applied to bearings used in general machine tools and the like.

[Brief description of drawings]

FIG. 1 is an enlarged view of an example of resin powder pre-coagulated by the method of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view of an example of a multi-layer bearing manufactured by the method of the present invention.

[Explanation of symbols]

 1 Co-coagulated resin powder 2 PTFE resin 3 Lead-tin alloy 4 Multi-layer bearing material 5 Resin layer 6 Sintered porous layer 7 Steel plate backing

Claims (1)

[Claims] 1. When a porous metal sintered layer is formed on a steel plate and a resin layer is formed by impregnating and coating a solid lubricant with a tetrafluoroethylene resin on the porous metal sintered layer, This tetrafluoroethylene resin has a particle size of 0.2 to 0.
A solid lubricant powder is uniformly mixed and co-coagulated to form a resin powder in an emulsified state of 4μ, and the resin powder is wetted with an organic solvent and then sprayed on the porous metal. A method for producing a multi-layer bearing, which comprises indenting and coating, then heating to remove the organic solvent, and then firing.