JPH0155667B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a bearing material, and more specifically, to a resin bearing material containing tetrafluoroethylene resin as a main component. Resin bearing materials are used, for example, in guide bushes and piston rings of automobile shock absorbers. In addition, with the recent increase in engine output and increased emphasis on ride comfort in automobiles, improving the performance of shock absorbers has become an important issue, and further improvement in the sliding performance of guide bushes and the like is desired. (Prior Art) Abrasion of materials that may occur when resin sliding materials are used for guide bushes and piston sliding parts of shock absorbers used in automobiles will be explained with reference to the drawings. In the shock absorber,
Although it can be attached to a struc- ture type suspension, a double-width suspension type suspension, etc., the struc- ture type will be described here as a representative example with reference to Fig. 2. In Fig. 2, 1 is the cylinder of the shock absorber (only the upper part of the whole is shown);
2 is a piston, 3 is a piston ring part that slides on the cylinder 1 provided on the outer periphery of the piston 2, 4 is a piston rod fixed to the piston 2, 5 is a guide bush that slides on the piston rod 4, and 6 is a piston ring part that slides on the cylinder 1 provided on the outer periphery of the piston 2. 7 is a ring nut, and 8 is a sealing member.
As shown in the figure, while the vehicle is running, the piston rod 4 moves up and down with the piston rod 4 in partial contact with the guide bush 5 and the piston ring 3 with the inner surface of the cylinder 1. As is well known, the purpose of a shock absorber is to soften the return force of the suspension coil or leaf spring to improve the ride comfort of the car.
It is important to improve the sliding properties of The problems that occur in these sliding parts are as follows. (b) When the distance traveled by a car exceeds a certain level,
The frictional force of the sliding parts increases, resulting in poor riding comfort. (b) As a result of frictional flaws occurring on the piston rod 4 and cylinder 1, which are the mating materials, the frictional force increases and riding comfort deteriorates, and the mating materials (1, 4)
As the shock absorber wears, the damping amount of the shock absorber decreases, and the damping performance of vibrations and vibrations during cornering decreases. As a bearing material used in automobile shock absorbers, lift bearings for forklifts, etc.
Japanese Patent Publication No. 54-26655 proposes a material in which a mixture of tetrafluoroethylene resin, zinc, and aluminum oxide is impregnated on a steel backing plate in which a porous portion is formed by a sintered layer of Cu and Fe. There is. Furthermore, as a multi-layer bearing used in similar applications, a material in which the back metal is coated with tetrafluoroethylene resin and tetrafluoroethylene-perfluoroakyl vinyl ether copolymer resin has been proposed in Japanese Patent Application Laid-Open No. 58-28016.
It is proposed in the Publication No. In the field of so-called resin materials for bearings, tetrafluoroethylene resin (hereinafter referred to as PTFE) is widely used due to its low friction properties. However, since PTFE does not have very good wear resistance, it
As shown in Japanese Patent No. 26655, it is often used as a bearing material in combination with additives. Further, as the additive material, a resin material is used as disclosed in Japanese Patent Application Laid-open No. 58-28016. Furthermore, it is known that aromatic polyester (Sumitomo Chemical's product name ECONOL) mixed with PTFE or alone is used as a bearing material for piston rings or sliding parts such as typewriters and motors. There is. The present invention improves the performance of the various bearing materials mentioned above and provides a material that is particularly suitable for use in guide bushes for shock absorbers (FIG. 2, 5) and piston rings (FIG. 2, 3). (Problems to be Solved by the Invention) Al ₂ O ₃ -containing PTFE, which has been proposed as a sliding material for shock absorbers, has the following problems. Higher loads tend to increase the coefficient of friction and reduce wear resistance, making the shock absorber less effective under severe operating conditions. Next, since the coefficient of friction tends to increase as the test time increases, the riding comfort tends to deteriorate as the distance traveled by the vehicle increases. moreover,
It has a strong tendency to damage the mating material. On the other hand, aromatic polyester-PTFE mixed materials generally alleviate the above-mentioned problems of Al ₂ O ₃ -containing PTFE, but cannot sufficiently meet the performance of automobile shock absorbers, where ride comfort is important in recent years. has not been reached yet. In particular, when large loads or small loads are repeatedly applied, the performance of aromatic polyester-PTFE mixed materials deteriorates significantly, so even if aromatic polyester-PTFE is considered to be used in shock absorbers, Considering that aromatic polyester is currently more than twice as expensive as PTFE, it can be said that there is no particular advantage in using this mixed material. (Means for solving the problem) In order to solve the above-mentioned problem, the present inventors
Preliminary experiments were conducted to investigate the sliding properties of various materials. Figure 1 shows the PTFE + 3% Al ₂ O ₃ mixed material (▲
) and PTFE + 3% Al ₂ O ₃ + 20% aromatic polyester (Sumitomo Chemical brand name ECONOL) (○)
The graph shows the change in friction coefficient obtained by testing under the following conditions. Test machine: Thrust test machine Load: 100, 200, 300, 400, 500Kg gradual increase Test material peripheral speed: 0.2m/S (rotation speed 200rpm) Compatible material: SUJ2 (Hv700-800) Lubrication method: 3 drops of shock absorber oil Dripping From FIG. 1, it can be seen that aromatic polyester is effective in lowering the absolute value of the coefficient of friction and increasing its load-bearing stability. Figure 3 shows PTFE in addition to the same materials as in Figure 1.
The graph shows the change in friction coefficient obtained by testing +10% Zn + 3% Al ₂ O ₃ mixed material (marked with □) under the following conditions. Testing machine: Thrust tester Load: 500Kg (constant) Test material peripheral speed: 0.002m/S Compatible material: SUJ-2 (Hv700~800) Lubrication: One drop of shock absorber oil The test was conducted by simulating a state of uneven contact, that is, boundary lubrication. From FIG. 3, it can be seen that aromatic polyester lowers the absolute value of the coefficient of friction and stabilizes it from the initial stage of the test to the entire test time. Under the same conditions as in the case of Fig. 3 above, changes in the coefficient of friction were investigated for the following materials in addition to the materials shown in Fig. 3. PTFE + 20% aromatic polyester + 3% Al ₂ O ₃
+2% MoS ₂ - mark ● PTFE + 2% aromatic polyester - mark △ The results are shown in Figure 4. As can be seen from Figure 4, adding aromatic polyester to PTFE (△) stabilizes the friction coefficient, but under long-term friction, the friction reaches the same level as materials without aromatic polyester (▲, □). The coefficient increases gradually. On the other hand, when Al ₂ O ₃ and aromatic polyester are simultaneously added to PTFE, the friction coefficient is stabilized at a low level for a long time. The present invention was completed based on the above-mentioned knowledge, and its gist is (a) PTFE, (b)
One or more of alumina (Al ₂ O ₃ ), SIC, Cr ₂ O ₃ , TiN, and (iii) aromatic polyester are mixed together. The configuration of the present invention will be explained below. The sliding material of the present invention can be used by itself, that is, by itself, or can be used by bonding to a backing steel plate. As the backing steel plate, carbon steel or any other material can be used, and the surface thereof has sintered porous Fe or Cu formed as shown in Figure 1 of Japanese Patent Publication No. 54-26655, or mechanically or chemically It is also possible to use a plate that has a porous part, such as a plate with unevenness or a plate made of multi-layered sintered particles, so that it can be impregnated with PTFE or the like. When a sintered porous layer of Cu is used on a back metal steel plate, it consists of a back metal 1, a porous portion 2, and a resin layer 3, as shown in FIG. The composition of the resin layer, which is a feature of the present invention, will be explained below. PTFE is a basic component of the resin layer and provides low friction properties. It is desirable that the amount of PTFE is no less than 35% (all percentages are by weight). When the amount of PTFE is less than 35%, the coefficient of friction increases. Al ₂ O ₃ is a component that mainly imparts wear resistance to the resin layer, increases the load bearing capacity of the PTFE-aromatic polyester two-component composition, and further stabilizes the coefficient of friction over a long period of time. In addition to Al ₂ O ₃ , SiC, Cr ₂ O ₃ and TiN also have the same effect as Al ₂ O ₃ , and therefore one or more of these can be used in the present invention. Al ₂ O ₃ , SiC, Cr ₂ O ₃ TiN
Even small amounts (the total amount if two or more types) are effective in imparting wear resistance, improving load carrying capacity, and lowering the coefficient of friction, but the effect becomes noticeable at 0.5% or more, especially 3% or more. . However, the amount of Al ₂ O ₃ etc.
If it exceeds 10%, there is a tendency to damage the mating material, so it is preferably 5% or less for soft mating materials. The aromatic polyester is a component that imparts wear resistance to the resin layer and makes the mating material less susceptible to scratches. Furthermore, aromatic polyester is PTFE-
It is a component that stabilizes the frictional properties of the Al ₂ O ₃ two-component composition both over time and with increasing load. Even a small amount of aromatic polyester is effective, but 3%
Above that, the effect becomes particularly noticeable when the content is 5% or more. however,
If the amount of aromatic polyester exceeds 60%, friction increases and stable properties cannot be obtained, which is not desirable. Econol (trade name of Sumitomo Chemical) and the like are known as aromatic polyesters, and these materials can be used as one component in the present invention. However, general formula

Most preferred is an aromatic polyester represented by the formula: According to the present invention, in addition to the above three components, graphite and
One or more components of MoS ₂ can be added to the resin layer as an optional component. These components are components that improve the lubricity of the resin layer, and are particularly effective when the lubrication conditions of the bearing material are poor. If the amount of graphite etc. exceeds 5%, wear resistance will deteriorate, so it is preferably 3% or less. The above additive components become the base material (matrix)
It is mixed intimately with PTFE, processed into a predetermined shape, such as a ring shape, either as a solid or with a backing metal, and, if necessary, after adjusting the surface roughness, is incorporated into various devices. There is no particular restriction on the particle size of the solid content in the above ingredients as long as it is a common size.
Al ₂ O ₃ , SiC, Cr ₂ O ₃ , TiN, graphite, and MoS ₂ are all desirably -(200) meshes. Method of forming a porous part on the backing metal and forming the porous part
As a method for impregnating PTFE, etc., the method described in Japanese Patent Publication No. 54-26655 can be adopted (column 3, line 30 to column 4, line 15 of the same publication). Note that a multilayer porous part may be obtained. Next, the uses and performance of the resin bearing material of the present invention will be described. A bearing material according to the present invention was prepared into a ring shape with a cross-sectional structure as shown in FIG. 5, and was subjected to a reciprocating friction test and a reciprocating wear test that reproduced the usage conditions of a guide bush. The test conditions were as shown in the table below.

【table】 The bearings tested were of the following fifth type.

[Table] Figure 6 shows the change in friction coefficient over time. From FIG. 6, the bearings according to the present invention (marked No. 3○ and No. 4●
The coefficient of friction stabilized at a low level in a short period of time (marked), and it is clear that the effect of the aromatic polyester is remarkable. Next, the mating material SUJ-2 (Hv700-800) was applied under the conditions shown in Table 1 for 3 hours and the number of repetitions -54 x 10 ³ times.
Table 3 shows the measured wear depths of the test bearings after repeated wear tests were carried out under these conditions.

[Table] Wear in this table means that the surface of the mating material, which was smooth at the beginning of the test, was scratched by the resin layer of the bearing, and as a result, the surface flaws of the mating material scraped off the resin layer, resulting in wear. From Table 3, it can be seen that aromatic polyester forms a resin layer to prevent scratches on the mating material. In addition, among the components of the resin layer, hard Al ₂ O ₃ is the most likely to damage the mating material, so aromatic polyester alleviates the influence of such hard substances on the mating material, as shown in Table 3. I understand more. Furthermore, in order to conduct a physical test of the shock absorber, a ring-shaped bearing was incorporated into the shock absorber as a guide bush, and the frictional resistance and wear depth were measured under the following conditions.

[Table] The test bearings are No. 1 (▲ mark) and No. 3 (○ mark) in Table 2.
No. 4 (● mark) and No. 5 (△ mark). The friction coefficient measurement results are shown in Figure 7. From FIG. 7, it can be seen that the aromatic polyester suppresses the increase in frictional resistance caused by repeated friction. Next, the wear depth is shown in the table below.

[Table] From Table 5, it can be seen that, as in the case of the reproduction experiment, the aromatic polyester achieved a reduction in the wear depth in the actual shock absorber test. In addition, the guide bush of a shock absorber is prone to wear because it is in uneven contact with the shaft, which is the mating material, but the results in Table 5 show that aromatic polyester is effective in reducing the depth of wear even when it is in uneven contact. It shows. Furthermore, in test bearings No. 3 and 4 of the present invention, the porous sintered layer was not exposed and was covered by the resin layer, and there were few defects on the shaft. The above-mentioned excellent properties of the bearing material of the present invention meet the requirements not only for guide bushes for shock absorbers but also for sliding parts such as piston rings. It also meets the demands of sliding parts, especially bearings that require wear resistance.
Furthermore, the bearing material of the present invention satisfies the required performance of rotary bearings for industrial machinery and the like. (Function) Aluminum oxide, etc. added to PTFE has the advantage of improving wear resistance, but has the disadvantage of damaging the mating material (Japanese Patent Publication No. 54-26655), while aromatic polyester added to PTFE has the advantage of improving wear resistance. is said to improve heat resistance. Aluminum oxide, etc. and aromatic polyester added simultaneously to PTFE according to the present invention maintain the above-mentioned advantages, while the latter eliminates the disadvantages of the former (aluminum oxide, etc.). The present invention will be further explained below with reference to Examples. Examples PTFE, aromatic polyester (Sumitomo Chemical brand name ECONOL), Al ₂ O ₃ , SiC, Cr ₂ O ₃ , TiN, graphite (Gr), MoS ₂ and Zn (particle size (200)
Mesh Under) was used and mixed in the ratio (weight percentage) shown in Table 6 to prepare a sample.
The friction coefficient and wear amount (μm) of these samples were measured under the conditions shown in Table 1.

【table】

[Table] Nos. 36 to 39 in the table are comparative examples. The following can be seen from Table 6. (a) Aromatic polyester ("Polyester" in the table)
) is in the range of about 15% to about 25%. (b) The optimum amount of Al ₂ O ₃ etc. is in the range of about 3-6%. (c) The optimum amount of graphite etc. is in the range of about 1-2%. (d) Compared to the PTFE-aromatic polyester sample (No. 36), the sample of the present invention exhibits about twice as much wear resistance and about 10% or more of low friction, and also
Approximately 3% compared to Al ₂ O ₃ added PTFE (No. 37, 38)
It exhibits more than double the wear resistance and approximately 20% less friction. (e) By comparing 39, 37, 36, and 10, it can be seen that polyester and Al ₂ O ₃ act synergistically to improve performance. (Effects) The resin bearing material of the present invention has excellent properties such as low friction, stable friction coefficient, and does not damage mating materials and has little wear on itself, so it is suitable for sliding of various equipment. Contributes to improving the performance of moving parts. In one embodiment of the present invention, even when the bearing material is used in a state of uneven contact, that is, a state of boundary lubrication, there is little uneven wear and excellent sliding characteristics are achieved over a long period of time. When the bearing material of the present invention is used in the sliding part of a shock absorber for an automobile as an example of the above-mentioned embodiment, good riding comfort is maintained over a long period of time. A wide variety of materials, mainly PTFE, have been proposed as bearing materials for the sliding parts of automobile shock absorbers.
It is of great significance that we have provided a material that far exceeds these performances.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between load and friction coefficient.
Figure 2 is a partial sectional view of the shock absorber, Figures 3 and 4 are graphs showing changes in the coefficient of friction over time, Figure 5 is an enlarged cross-sectional view of the bearing material, and Figure 6 shows changes in the coefficient of friction over time. The graph shown in FIG. 7 is a graph showing changes in frictional resistance due to repeated sliding.

Claims (1)

[Claims] 1 (a) Tetrafluoroethylene resin, (b) Al ₂ O ₃ , SiC,
A bearing material comprising a mixture of one or more of Cr ₂ O ₃ , TiN, and (c) aromatic polyester. 2. The bearing material according to claim 1, wherein the mixture further contains one or more of graphite and _MoS2 .