JP7475309B2 - Sliding member used in bushing for shift fork, bushing for shift fork, manufacturing method of sliding member used in bushing for shift fork, and manufacturing method of bushing for shift fork - Google Patents

Description

The present invention relates to a sliding member used in a bushing for a shift fork , a bushing for a shift fork, a method for manufacturing a sliding member used in a bushing for a shift fork, and a method for manufacturing a bushing for a shift fork.

The material disclosed for use in the sliding members is a bearing material made of polytetrafluoroethylene resin (hereinafter abbreviated as "PTFE"), zinc, and aluminum oxide.

Japanese Patent Application Laid-Open No. 50-43005

However, with conventional technology, it was difficult to improve wear resistance.

An object of the present invention is to provide a sliding member used in a bushing for a shift fork , a bushing for a shift fork, a manufacturing method for a sliding member used in a bushing for a shift fork , and a manufacturing method for a bushing for a shift fork, which are capable of improving friction resistance.

In order to solve the above-mentioned problems and achieve the object, the sliding member used in the bushing for a shift fork of the present invention is provided on a base material and includes polytetrafluoroethylene resin, zinc particles dispersed in the polytetrafluoroethylene resin, and zinc fluoride interposed between the polytetrafluoroethylene resin and the zinc particles.

According to the present invention, it is possible to provide a sliding member used in a bushing for a shift fork , which has improved friction resistance, a bushing for a shift fork, a method for manufacturing a sliding member, and a method for manufacturing a bushing for a shift fork.

FIG. 1 is a diagram showing an example of a sliding member. FIG. 2 is a cross-sectional view of the sliding member. FIG. 3A is a graph showing the results of an X-ray diffraction investigation of the sliding member. FIG. 3B is a graph showing the results of an X-ray diffraction investigation of the sliding member. FIG. 3C is a graph showing the results of an X-ray diffraction investigation of the sliding member. FIG. 4 is a diagram showing the internal structure of a manual transmission. FIG. 5 is a perspective view showing the configuration of the shift fork. FIG. 6 is an explanatory diagram of the wear test.

The following describes in detail an embodiment of the sliding member according to the present invention with reference to the attached drawings.

The sliding member of this embodiment is composed of polytetrafluoroethylene resin (hereinafter sometimes abbreviated as PTFE), zinc (Zn) particles dispersed in the PTFE, and zinc fluoride (ZnF ₂ ) interposed between the PTFE and the zinc particles.

As a result, the sliding member of this embodiment can improve its wear resistance. Furthermore, the sliding member of this embodiment can improve its low friction and wear resistance, particularly when used in reciprocating sliding conditions with grease lubrication or poor lubrication.

The reason why the above effect is achieved is speculated to be as follows. However, the present invention is not limited to the speculation below.

By interposing zinc fluoride between the PTFE and the zinc particles, at least a portion of the gap between the PTFE and the zinc particles is filled with zinc fluoride. This is believed to strengthen the bond between the PTFE and the zinc particles. The stronger bond prevents the zinc particles from falling off during sliding. The suppression of the zinc particles from falling off is believed to improve the wear resistance of the sliding member.

The sliding member of this embodiment is described in detail below.

Figure 1 is a schematic diagram showing an example of a sliding member 41 according to the present embodiment. In this embodiment, an embodiment in which the sliding member 41 is applied to a bushing for a shift fork will be described as an example. Figure 1 shows an example of a cross-sectional structure of a bushing for a shift fork that includes the sliding member 41. Hereinafter, the bushing for a shift fork will be described as a bushing 19. Details of the application will be described later.

The bushing 19 comprises a base material 8 and a sliding member 41.

The substrate 8 has, for example, a steel plate 2 and a sintered layer 3.

The steel plate 2 is a layer that provides mechanical strength to the bushing 19. The steel plate 2 may be referred to as a backing metal or a backing metal layer. The steel plate 2 may be, for example, a metal plate such as an Fe alloy, Cu, or Cu alloy.

The sintered layer 3 is a porous layer produced by sintering. The sintered layer 3 is produced by scattering a copper alloy, such as copper-tin, copper-lead-tin, phosphor bronze, or a mixed powder of iron, copper, tin, etc., on the steel plate 2 and sintering it. By providing the sintered layer 3 on the steel plate 2, it is possible to improve the adhesion between the sliding member 41 and the steel plate 2. Note that the bushing 19 is not limited to a configuration having a sintered layer 3.

Next, the sliding member 41 will be described. The sliding member 41 is provided on the substrate 8.

Figure 2 is a schematic diagram showing a cross section of a sliding member 41. The sliding member 41 is made of PTFE 5, zinc particles 61 dispersed in the PTFE 5, and zinc fluoride 62 interposed between the PTFE 5 and the zinc particles 61.

The sliding member 41 may use PTFE5 as the resin material, but may also contain the following synthetic resins in addition to PTFE5 as the main component. For example, it may further contain one or more types selected from PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer), FEP (perfluoroethylenepropene copolymer), low molecular weight PTFE, PI (polyimide), PAI (polyamideimide), PBI (polybenzamidazole), PA (polyamide), phenolic resin, epoxy resin, POM (polyacetal), PEEK (polyetheretherketone), PE (polyethylene), PPS (polyphenylene sulfide), and PEI (polyetherimide).

The zinc particles 61 are dispersed in PTFE 5. The shape and size of the zinc particles 61 are not limited.

The content of zinc particles 61 is preferably 5% by weight or more and 15% by weight or less relative to 100% by weight of PTFE5. By setting the content of zinc particles 61 within the above range, the wear resistance of the sliding member 41 can be improved.

The zinc fluoride 62 is interposed between the PTFE 5 and the zinc particles 61. Interposed means that the zinc fluoride 62 is present in at least a portion of the area between the PTFE 5 and the zinc particles 61. The zinc fluoride 62 is generated around the zinc particles 61 by a manufacturing method described below. Therefore, the zinc fluoride 62 is interposed between the PTFE 5 and the zinc particles 61.

Note that the zinc fluoride 62 may be provided in at least a portion of the area around the zinc particle 61, but it is preferable that it is present over the entire circumference of the zinc particle 61. Present over the entire circumference of the zinc particle 61 means that the zinc fluoride 62 is present around the zinc particle 61 over the entire circumference of the zinc particle 61. In other words, it means that the zinc fluoride 62 is generated so as to surround the entire area of the outer surface of the zinc particle 61. Note that in this case, the zinc fluoride 62 may be present over the entire circumference of the zinc particle 61, and at least a portion of the zinc fluoride 62 may be in contact with the zinc particle 61, or at least a portion of the zinc fluoride 62 may not be in contact with the zinc particle 61. In other words, it is preferable that the zinc particle 61 is covered with the zinc fluoride 62 over the entire circumference.

Since zinc fluoride 62 is present all around the zinc particle 61, zinc fluoride 62 is interposed between the zinc particle 61 and the PTFE 5 all around the zinc particle 61. Therefore, the gap between the zinc particle 61 and the PTFE 5 is filled with zinc fluoride 62 all around the zinc particle 61. This further improves the wear resistance of the sliding member 41.

From the viewpoint of further improving the wear resistance, it is preferable that the sliding member 41 further contains aluminum oxide (Al ₂ O ₃ ) 7. As shown in Fig. 2, it is preferable that the aluminum oxide 7 is further dispersed in the PTFE 5. The shape and size of the aluminum oxide 7 are not limited.

The content of aluminum oxide 7 is preferably 2% by weight or more and 4% by weight or less relative to 100% by weight of PTFE 5.

Other additives may be added to the sliding member 41. For example, one or more additives selected from salts such as _BaSO4 , _CaSO4 , calcium phosphate, magnesium phosphate, magnesium silicate, and the like, resins such as aromatic polyester, _polyimide , and PEEK, oxides such as aluminum oxide ( _Al2O3 ), _FeO3 , and _TiO2 , sulfides such as ZnS, carbides such as TiC, glass fiber, carbon fiber, and carbon can be added.

The thickness of the sliding member 41 is not limited. For example, the thickness of the sliding member 41 is 80 μm or more and 400 μm or less. The thickness of the sliding member 41 specifically means the length L in FIG. 1. L represents the thickness of the sliding member 41.

Next, we will explain the manufacturing method of the sliding member 41.

The sliding member 41 of this embodiment is manufactured, for example, by the following process.

The manufacturing method of the sliding member 41 includes a firing process in which a mixture of the raw material PTFE 5 powder and additives such as zinc particles 61 and aluminum oxide 7 is fired at 390°C or higher and 500°C or lower.

By baking a mixture of PTFE5 powder and at least zinc particles 61 within the above temperature range, zinc fluoride 62 is generated around the zinc particles 61 due to a reaction between PTFE5 and Zn. In other words, zinc fluoride 62 is interposed between PTFE5 and zinc particles 61.

The firing temperature may be 400°C or higher and 500°C or lower. By setting the firing temperature to 400°C or higher, zinc fluoride 62 is generated around the zinc particles 61 over the entire circumference of the zinc particles 61.

Note that if the firing temperature exceeds 500°C, decomposition of PTFE5 will begin, so it is preferable that the firing temperature be 500°C or less.

An X-ray diffraction study was conducted on a sliding member 41 manufactured by firing a mixture of PTFE 5 and zinc particles 61 at each of the firing temperatures of 370°C, 380°C, 390°C, 400°C, 410°C, 420°C, and 430°C. In X-ray diffraction (XRD), when a sample is irradiated with X-rays, the diffraction that occurs as a result of the X-rays being scattered or interfered with by electrons surrounding the atoms is analyzed. By analyzing this diffraction, it is possible to identify and quantify the constituent components of the sample.

Figures 3A to 3C are diagrams showing the results of an X-ray diffraction study of the sliding member 41. In Figures 3A to 3C, the horizontal axis represents the angle at which the X-rays are irradiated, and the vertical axis represents the strength of the bonds between each component (peak intensity).

Figure 3A shows the results of an X-ray diffraction study of a sliding member 41 produced by firing a mixture of PTFE 5, zinc particles 61, and aluminum oxide 7 at 370°C. Figure 3B shows the results of an X-ray diffraction study of a sliding member 41 produced by firing the above mixture at 400°C. Figure 3C shows the results of an X-ray diffraction study of a sliding member 41 produced by firing the above mixture at 430°C.

When the above mixture was sintered at 370°C or 380°C, zinc fluoride 62 was not produced. Specifically, as shown in FIG. 3A, PTFE 5, zinc from zinc particles 61 as an additive, aluminum oxide 7, and copper as a component of sintered layer 3 were detected, but zinc fluoride 62 was not detected.

On the other hand, when the above mixture was fired at 390°C, 400°C, 410°C, 420°C, or 430°C, zinc fluoride 62 was produced. Specifically, as shown in Figures 3B and 3C, zinc fluoride 62 was detected in addition to PTFE 5, zinc from zinc particles 61 as an additive, aluminum oxide 7, and copper as a component of sintered layer 3.

From these investigation results, it can be said that zinc fluoride 62 is produced on the surface of zinc particles 61 by baking a mixture of PTFE5 and at least zinc particles 61 at a temperature of 390°C or higher and 500°C or lower.

The cross section of the sliding member produced by firing the mixture at 370°C and the cross section of the sliding member 41 produced by firing the mixture at 430°C were also observed using an electron microscope.

As a result, zinc fluoride 62 was not generated in the sliding member sintered at 370°C, and gaps were observed between the zinc particles 61 and the PTFE 5. On the other hand, zinc fluoride 62 was generated in the sliding member 41 sintered at 430°C, and gaps were not confirmed between the zinc particles 61 and the PTFE 5. This is because zinc fluoride 62 (ZnF ₂ ) was present between the zinc particles 61 and the PTFE 5. The presence of this zinc fluoride 62 strengthens the bond between the zinc particles 61 and the PTFE 5, and the wear resistance of the sliding member 41 can be improved.

Next, the identification of the zinc fluoride 62 contained in the sliding member 41 will be described. The zinc fluoride 62 contained in the sliding member 41 is identified, for example, by point analysis using a SEM (scanning electron microscope).

Point analysis was performed for each of positions A, B, and C in the sliding member 41 shown in Figure 2. Position A is the position where only PTFE 5 is present. Position B is the position where zinc particles 61 are present. Position C is the position on the outer periphery of zinc particles 61. Table 1 shows the weight percentages of elemental components at each of positions A, B, and C.

As shown in Table 1, carbon (C) and fluorine (F), which are components of PTFE5, were detected at position A. Zn from zinc particles 61 was detected at position B. Fluorine (F) and zinc (Zn) were detected at position C. From this, it was analyzed that zinc fluoride 62 was generated by defluorination of PTFE5 at position C.

Next, an example of an application form of the sliding member 41 will be described.

The sliding member 41 is applied to various components that require high wear resistance. For example, the sliding member 41 is applied to bushings for shift forks in manual transmissions for automobiles, various bearings, compressors, etc.

In this embodiment, an example is described in which the sliding member 41 is applied to a bushing (bush 19) for a shift fork. In addition, in this embodiment, an example is described in which the sliding member 41 is applied to a situation in which it is used for reciprocating sliding with grease lubrication or poor lubrication. Specifically, an example is described in which the bushing 19 is provided on a shift fork that changes gears in a manual transmission of an automobile.

Figure 4 shows an example of the internal structure of a manual transmission.

The manual transmission 1 includes a lever 12, a fork shaft 13, a shift fork 14, and a gear 17 for shifting. The fork shaft 13 is a cylindrical support shaft.

The shift fork 14 is slidably attached to the outer circumferential surface 13a of the fork shaft 13. The lever 12 is a lever for sliding the shift fork 14 in the axial direction of the fork shaft 13, and is operated by the driver of the vehicle. When the shift fork 14 slides, the gear 17 changes the gear it meshes with, and the manual transmission 1 shifts gears.

Next, we will explain the shift fork 14.

Figure 5 is a perspective view showing the configuration of the shift fork 14. The shift fork 14 has a cylindrical hole portion 15 and an action portion 18. The fork shaft 13 passes through the hole portion 15. The action portion 18 slides the gear 17 along the axis.

A hollow cylindrical bush 19 (shift fork bush) is attached to the inner circumferential surface 16 of the hole 15. For convenience of explanation, the bush 19 is shown in a flat shape in FIG. 1, but the actual bush 19 has a cylindrical shape with the inner circumferential surface 4a on the inside as shown in FIG. 5. Therefore, the outer circumferential surface 13a of the fork shaft 13 contacts the inner circumferential surface 4a of the bush 19 (see FIG. 4). When the shift fork 14 is slid relative to the fork shaft 13, the bush 19 slides against the outer circumferential surface 13a of the fork shaft 13. Therefore, whether the shift fork 14 slides smoothly relative to the fork shaft 13 depends on the frictional force between the outer circumferential surface 13a of the fork shaft 13 and the inner circumferential surface 4a of the bush 19 (see FIG. 4).

As explained with reference to FIG. 1, in this embodiment, the bushing 19 includes a base material 8 and a sliding member 41. Therefore, the bushing 19 of this embodiment can improve its wear resistance. Furthermore, the bushing 19 of this embodiment can effectively exhibit low friction and wear resistance in a situation where it is used in reciprocating sliding with grease lubrication or poor lubrication.

The bushing 19 can be manufactured by forming the sliding member 41 on the base material 8 using the manufacturing method described above.

For example, the sintered layer 3 is formed on the steel plate 2. The sintered layer 3 is formed by scattering constituent particles of the sintered layer 3 (e.g., copper alloy powder, etc.) on the steel plate 2 and sintering it. Then, a mixture of PTFE 5 and additives such as zinc particles 61 and aluminum oxide 7 is supplied to the sintered layer 3 to impregnate it, and then sintered under the above-mentioned sintering conditions.

As described above, the bushing 19 is not limited to a configuration including a sintered layer 3. In other words, the base material 8 is not limited to a configuration in which a sintered layer 3 is provided on a steel plate 2, and may be composed of only the steel plate 2.

In this case, for example, a roughening treatment such as shot blasting may be performed on the steel plate 2, and a mixture of PTFE 5 powder and additives such as zinc particles 61 and aluminum oxide 7 may be supplied directly to the roughened area. There are no limitations on the method of supplying the mixture. The mixture may then be fired under the firing conditions described above.

In addition, a wire mesh may be used instead of the steel plate 2. When a wire mesh is used, the method of impregnating the porous fired layer is basically the same as that described above.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

A steel plate 2 was prepared, the surface of which had been sanded and then degreased. Phosphor bronze powder was spread on the steel plate 2, and then sintering was performed at 920°C to 950°C to form a sintered layer 3 having a thickness of 0.2 mm to 0.25 mm. Through these steps, a substrate 8 was produced.

A mixture of PTFE 5 powder of 500 μm or less, zinc particles 61 with an average particle size of 75 μm or less, and aluminum oxide 7 with an average particle size of 35 μm or less was applied to the substrate 8 by a roll, thereby impregnating and coating the substrate 8. Next, the mixture was fired (firing process), and a sliding member 41 was formed on the substrate 8. The thickness of the sliding member 41 was 0.08 mm to 0.40 mm.

Example 1
In Example 1, the content of zinc particles 61 and aluminum oxide 7 in the mixture was 10% by weight for zinc particles 61 and 3% by weight for aluminum oxide 7. The mixture was fired at 390° C. to produce slide member 41.

(Examples 2 to 6)
In Examples 2 to 6, the sliding members 41 were produced in the same manner as in Example 1, except that the firing temperatures of the mixture were 400°C, 420°C, 450°C, 450°C, 480°C, 420°C, and 420°C, respectively.

(Example 7-Example 8)
In Examples 7 and 8, the content of zinc particles 61 and aluminum oxide 7 in the mixture was 15% by weight for zinc particles 61 and 4% by weight for aluminum oxide 7. The firing temperature of the mixture was set to 420° C. to produce slide member 41.

(Example 9-Example 10)
In Examples 9 and 10, the sliding members 41 were produced in the same manner as in Example 1, except that the mixture was fired at 510°C.

(Comparative Example 1-Comparative Example 2)
In Comparative Examples 1 and 2, comparative sliding members were produced in the same manner as in Example 1, except that the mixture was fired at 370°C.

The wear resistance of the sliding member 41 and the comparative sliding member produced in the above examples and comparative examples was evaluated. The wear resistance was evaluated using the wear tester shown in Figure 6.

Figure 6 is an explanatory diagram of the wear test. A test piece corresponding to the sliding member 41 was brought into contact with a mating material corresponding to the fork shaft 13, and rotated while applying a load to measure the amount of wear and the friction coefficient as an evaluation of wear resistance. The evaluation was performed under the following conditions.

・Testing machine: Thrust friction and wear testing machine (see Figure 6)
Load: 5 MPa
Sliding speed: 0.3 m/s
Test time: 3 hours Test temperature (ambient temperature): 40°C
Lubricant: None; Mating shaft material: SCM415 (Hv500 or higher)
Shaft roughness: 0.8 to 1.0 μm Rz JIS

The friction coefficient was calculated by measuring the friction force during the abrasion resistance test and calculating the average friction force after the friction force stabilized. The evaluation results are shown in Table 2.

As shown in Table 2, the evaluation results showed that in Examples 1 to 10, in which zinc fluoride 62 was produced, the amount of wear was smaller and the friction coefficient was lower than in Comparative Examples 1 and 2.

As a result, the sliding members 41 produced in Examples 1 to 10 were able to achieve improved wear resistance compared to the comparative sliding members produced in Comparative Examples 1 and 2.

In addition, in Examples 9 and 10, where the firing temperature was 510°C, the abrasion resistance was improved, but decomposition of PTFE5 was confirmed. On the other hand, in Examples 1 to 7, where the firing temperature was 390°C or higher and 500°C or lower, decomposition of PTFE5 was not confirmed. Therefore, it was confirmed that the firing temperature is preferably 390°C or higher and 500°C or lower.

The various materials and their compositions used in the above examples are merely examples, and the present invention is not limited to these. The sliding member 41 according to this embodiment may contain unavoidable impurities. Furthermore, the specific structure of the sliding member 41 is not limited to those exemplified in Figures 1 and 2.

Although the embodiment of the present invention has been described above, this embodiment and the modifications are merely examples and are not intended to limit the scope of the invention. This new embodiment and modifications can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. This embodiment and modifications, and the modifications thereof, are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

5 PTFE
7 Aluminum oxide 41 Sliding member 61 Zinc particles 62 Zinc fluoride

Claims (6)

A sliding member for use in a bushing for a shift fork, the sliding member being provided on a substrate and comprising: polytetrafluoroethylene resin; zinc particles dispersed in the polytetrafluoroethylene resin; and zinc fluoride interposed between the polytetrafluoroethylene resin and the zinc particles. The zinc fluoride is present over the entire circumference of the zinc particles.
A sliding member used in the bushing for a shift fork according to claim 1. 5% by weight or more and 15% by weight or less of the zinc particles;
2% by weight or more and 4% by weight or less of aluminum oxide dispersed in the polytetrafluoroethylene resin;
3. A sliding member used in the bushing for a shift fork according to claim 1 or 2, comprising: A bushing for a shift fork, comprising a sliding member for use in the bushing for a shift fork according to any one of claims 1 to 3, disposed on a base material. A firing step of firing the mixture of zinc particles and polytetrafluoroethylene resin at 390° C. or more and 500° C. or less;
The manufacturing method of a sliding member provided on a substrate and used in a bushing for a shift fork, comprising: A firing step of firing the mixture of zinc particles and polytetrafluoroethylene resin supplied onto the substrate at 390° C. or more and 500° C. or less;
A method for manufacturing a bushing for a shift fork, comprising:

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