JPH02277733A - Shift fork for transmission - Google Patents

Abstract

PURPOSE:To develop the shift fork having the excellent wear resistance of the sliding surfaces pawl parts of the shift fork for transmission by using a composite material formed by impregnating an Al alloy in a composite molding consisting of graphite particles and reinforcing material to constitute the sliding surfaces in the pawl parts of the above-mentioned shift fork. CONSTITUTION:The fine graphite particles 10 and SiC whiskers 12 are mixed and the molding 14 having the U-shaped section substantially corresponding to the surface shape in the pawl parts of the shift fork 32 is formed. The molding 18 consisting of short fibers 16 of an Al2O3-SiO2 system is fitted into the recess thereof to form the composite molding 20. This molding 20 is put into a molding cavity 4 of a die casting device 22 and a melt 26 of an Al alloy is supplied by a plunger 28 into the cavity and is pressurized, impregnated and solidified by the pressure thereof. The sliding surfaces of the pawl parts 30 consist of the Al alloy matrix combined and reinforced by the graphite particles 10 and the SiC whiskers 12. The shift fork 32 having the pawl parts 30 made of the composite material having the excellent wear resistance is thus produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a shift fork for a transmission, and more particularly to a shift fork for a transmission in which at least the pawl portion is made of a composite material.

Problems to be Solved by the Prior Art and the Invention Since the pawl portion of a shift fork for a transmission is exposed to severe sliding conditions, for example, as described in JP-A-62-35925, the entire pawl portion is Alternatively, attempts have been made in the past to construct only the surface portion of the claw portion from a composite material made of a light alloy reinforced with reinforcing fibers such as alumina-silica fibers. However, shift forks whose pawls are made of a composite material made of aluminum alloy reinforced with reinforcing fibers such as alumina-silica fibers have insufficient durability as shift forks for modern high-speed transmissions. In particular, when such a shift fork is subjected to a high surface pressure load at high speed and high oil temperature, seizure is likely to occur on the sliding surface of the pawl portion.

Furthermore, as described in, for example, Japanese Patent Application Laid-Open No. 63-243237, it has already been proposed to use a self-lubricating material such as graphitic carbon fiber together with reinforcing fibers. Composite materials using such self-lubricating materials and reinforcing fibers have superior wear resistance compared to composite materials using only alumina-silica fibers as reinforcement materials, but solid lubricants are generally made from molten aluminum alloys. Since the wettability of the solid lubricant is poor, and the strength of the molded product containing the solid lubricant is low, when manufacturing a shift fork whose claw portion is made of a composite material using a pressure casting method such as die casting, Poor impregnation and damage to the molded body are likely to occur.

In view of the above-mentioned problems in conventional shift forks in which the pawl portion is made of reinforcing fibers or a light alloy composite reinforced with reinforcing fibers and a solid lubricant, the present invention aims to improve the wear resistance of the sliding surface of the pawl portion. It is an object of the present invention to provide a shift fork for a transmission which has excellent properties and can be manufactured without causing problems such as poor impregnation of an aluminum alloy as a matrix metal or breakage of a molded body.

Means for Solving the Problems According to the present invention, the sliding surface of the claw is made of a composite material in which an aluminum alloy is impregnated into a molded body made of graphite particles and a reinforcing material. The other part is achieved by a transmission shift fork made of a composite material in which aluminum alloy is impregnated into a reinforced molded body.

Effects and Effects of the Invention According to the present invention, the sliding surface portion of the claw portion is formed of a composite material in which an aluminum alloy is impregnated into a molded body made of graphite particles and a reinforcing material, and the other portions of the claw portion are It is made of a composite material in which aluminum alloy is impregnated into a reinforced molded body. Graphite particles have excellent self-lubricating properties, so the wear resistance of the sliding surface can be improved compared to when the sliding surface is compositely reinforced with only reinforcing material, and the entire claw part is made of graphite. Compared to a composite material in which aluminum alloy is impregnated into a compact made of particles and reinforcing material, the risk of problems such as poor impregnation of the aluminum alloy and breakage of the compact is reduced. be able to.

The volume fraction of the graphite particles and the reinforcing material may be set appropriately depending on the application, but the volume fraction of the graphite particles is about 15 to 40%, and the volume fraction of the reinforcing material is 2 to 15%, especially 2 to 40%. 10%
It is preferable that the degree of

In addition, the average particle size of the graphite particles is 1 to 150μ, especially 5 to 10μ.
Preferably it is 5μ. The reinforcing material may also be short ceramic fibers, ceramic whiskers, ceramic particles, short metal fibers, metal particles, and the like.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Example 1 As shown in FIG. 1, graphite particles 10 (manufactured by Graphite Co., Ltd., Japan) with an average particle size of 1 μm and silicon carbide whiskers 1
2 ("Tokai Whisker" manufactured by Tokai Carbon Co., Ltd.) and suction molding the mixture, a molded body 14 having a U-shaped cross section that substantially corresponds to the surface shape of the pawl of the shift fork is produced. Formed. The volume percentages of graphite particles and silicon carbide whiskers in this compact were 20% and 10%, respectively. In addition, alumina staple fiber (IC)
By performing suction molding on "Saphir" manufactured by one company, an alumina short tli16 with a volume ratio of 10% and a shape and dimensions that fit into the molded body 14 as shown in FIG.
A molded body 18 was formed. Next, by fitting the molded body 18 into the molded body 14, a composite molded body 20 made of these molded bodies was formed as shown in FIG.

Next, after preheating the composite molded body 20 to 400°C, the 40th
As shown in the figure, the composite molded body is placed in the part that defines the claw part of the mold cavity 24 of the die-casting device 22, and an aluminum alloy (JIS standard ADc12) with a hot water temperature of 730°C is placed in the mold cavity. The molten metal 26 was supplied by the plunger 28, and the molten metal was pressurized at about 500 atmospheres, and the pressurized state was maintained until the molten metal completely solidified.

After the molten metal has completely solidified, the solidified body is taken out from the die-casting device, and the solidified body is subjected to a predetermined machining process, thereby allowing the claw portion 30 to slide as shown in FIGS. 5 and 6. A shift fork 32 was formed in which the face part was made of an aluminum alloy compositely reinforced with graphite particles lo and silicon carbide whiskers 12, and the inside of the claw part was made of an aluminum alloy compositely reinforced with alumina short fibers 16. A total of 100 shift forks were manufactured using the above method, and the composite pawl portion was cut as shown in Figure 6 to investigate the internal condition. It was observed that the alloy had penetrated well into the compact, and no defects such as deformation or cracking occurred in the compact.

For the purpose of comparison, 100 shift forks were manufactured in the same manner and under the same conditions as in the above example except that the molded body 18 was not used, and the condition of the pawls was investigated. It was observed that the molded body 14 of the shift fork was deformed and cracked. Furthermore, for the purpose of comparison, a molded body having the same shape and dimensions as the composite molded body 20 and consisting of graphite particles with a volume fraction of 20% and silicon carbide whiskers with a volume fraction of 10% was used. 100 shift forks were manufactured in the same manner and under the same conditions as in the example, and the condition of their pawls was investigated.
It was found that in two shift forks, there was insufficient impregnation of the aluminum alloy into the molded bodies, and in ten shift forks, the molded bodies were deformed or cracked.

Example 2 By compression molding titanium powder (manufactured by Osaka Titanium Co., Ltd.) with an average particle size of 40 μm, the shape of the portion of the claw portion other than the sliding surface portion was substantially changed as shown in FIG. A molded body 36 made of titanium powder 34 having dimensions and shape corresponding to the dimensions and a volume fraction of 30% was formed. Next, by suction molding using this molded body 36 as a filter element, as shown in FIG. "Kao Wool" manufactured by Isolite Kogyo Co., Ltd.)
Two molded bodies 42 and 44 are formed by forming the molded body 36 and the molded body 4 integrally formed on both sides thereof.
A composite molded body 46 consisting of 2 and 44 was formed.

Next, a total of 100 shift forks were manufactured using the composite molded body 46 in the same manner and under the same conditions as in Example 1, and the condition of the pawl portion was examined in the same manner as in Example 1. As a result, as shown in FIG. 9, it was found that no defects such as deformation or cracking of the molded body occurred in any of the shift forks.

Although the present invention has been described above in detail with reference to two embodiments, the present invention is not limited to these embodiments, and various embodiments of the pond are possible within the scope of the present invention. This will be obvious to those skilled in the art.

[Brief explanation of drawings]

1 to 5 are process diagrams showing an example of the manufacturing process of a shift fork according to the present invention, and FIG. 6 is a line Vl-V in FIG. 5.
7 is a sectional view showing a molded body made of titanium powder, and FIG. 8 is a cross-sectional view showing a molded body made of titanium powder. FIG. 9 is a cross-sectional view corresponding to FIG. 6 showing a cross-section of a pawl portion of another embodiment of the shift fork of the present invention. 10...graphite particles, 12...silicon carbide whiskers. 14... Molded object, 16... Alumina-silica short fiber. 18... Molded body, 20... Composite molded body, 22...
Die casting device, 24...Mold cavity, 2
6 molten aluminum alloy, 28... plunger, 3
0...Claw portion, 32...Shift fork, 34...
Titanium powder 36... Molded body, 38... Graphite particles,
40...Alumina-silica short fiber, 42.44...
Molded object, 46... Composite molded object patent application Attorney Toyota Motor Corporation

Claims (1)

[Claims] The sliding surface of the claw is made of a composite material in which aluminum alloy is impregnated into a molded body made of graphite particles and reinforcing material.
A shift fork for a transmission in which the other part of the pawl is made of a composite material in which a molded body of reinforcing material is impregnated with an aluminum alloy.