The present invention relates to a carbon-carbon composite plate for stamping and a process for producing a multiple plate wet clutch friction plate using the composite plate.
When a plate-shaped member such as, for example, a multiple plate wet clutch friction plate is produced from a carbon-carbon composite plate, if the friction plate can be obtained by subjecting the carbon-carbon composite plate to stamping, it is possible to greatly improve the production efficiency.
However, since a conventional carbon-carbon composite plate has a high density and is rigid, when it is subjected to stamping there are the problems of cracking in sheared sections and peeling-off of a matrix occurring.
It is an object of the present invention to provide a carbon-carbon composite plate for stamping, the carbon-carbon composite plate being capable of giving an intact plate-shaped member by stamping.
In order to attain this object, in accordance with the present invention, there is provided a carbon-carbon composite plate for stamping, the carbon-carbon composite plate having a porosity P of 20% or greater, and the stamping being carried out in the absence of water.
Since the composite plate having the above porosity P can be plastically deformed, it is possible to obtain an intact plate-shaped member by stamping in the absence of water. However, when the porosity P is less than 20%, cracking, etc., occurs in sheared sections.
Furthermore, in accordance with the present invention, there is provided a carbon-carbon composite plate for stamping, the carbon-carbon composite plate having a porosity P of 10% or greater, and the stamping being carried out in the presence of water.
Although when the porosity P is at the lower limit value or in the vicinity thereof, for example, when it is at least 10% but less than 20%, the composite plate has a relatively high density, an intact plate-shaped member can be obtained by virtue of a slipping action due to water during stamping. However, when the porosity P is less than 10%, even in the presence of water, cracking, etc. occurs in sheared sections. On the other hand, when P is equal to or greater than 20%, as described above, even without using water an intact plate-shaped member can be obtained.
It is also an object of the present invention to provide a process for efficiently producing an intact multiple plate wet clutch friction plate using a carbon-carbon composite plate.
In order to attain this object, in accordance with the present invention, there is provided a process for producing a multiple plate wet clutch friction plate having an annular plate shape with a spline on an inner peripheral section, and having, in a flat section between the inner peripheral section and an outer peripheral face, at least either a plurality of through holes arranged in the peripheral direction, or a plurality of slits that are arranged in the peripheral direction, extend from the inner peripheral section side, and open on the outer peripheral face, the process including subjecting a carbon-carbon composite plate having a porosity P of 20% or greater to a single stamping operation in the absence of water.
Furthermore, in accordance with the present invention, there is provided a process for producing a multiple plate wet clutch friction plate having an annular plate shape with a spline on an inner peripheral section, and having, in a flat section between the inner peripheral section and an outer peripheral face, at least either a plurality of through holes arranged in the peripheral direction, or a plurality of slits that are arranged in the peripheral direction, extend from the inner peripheral section side, and open on the outer peripheral face, the process including subjecting a carbon-carbon composite plate having a porosity P of 10% or greater to a single stamping operation in the presence of water.
In accordance with these production processes, the desired object can be achieved.
A carbon-carbon composite plate 1 shown in
(1) A preformed yarn disclosed in Example 1 of Japanese Patent Publication No. 4-72791, that is, a bundle of carbon fibers with attached thereto a petroleum-based pitch powder binder and a coke powder, the bundle having been covered with a polyethylene sleeve having an outer diameter of 3 mm and a thickness of 8 μm, was cut into lengths of 1 to 30 mm and superimposed to give a mat-form material.
(2) The mat-form material was placed in a mold of a hot press and kept at a mold temperature of 250° C. for 10 minutes, the mold was subsequently tightened so as to apply a pressure of 10 MPa to the mat-form material, and the mold was cooled to room temperature in this state to give a rectangular molded plate.
(3) The molded plate was placed in a calcining furnace and carbonized under a nitrogen atmosphere at 600° C. to give the carbon-carbon composite plate 1.
(4) This composite plate 1 was subjected to finishing.
The carbon-carbon composite plate 1 obtained by this method had a porosity P of 5%. Using the same method as above, various types of carbon-carbon composite plate having a porosity P of greater than 5% were produced.
Table 1 shows the starting material composition, the porosity P, etc. of the various types of composite plate. In Table 1, Example 1 corresponds to the above embodiment, CF denotes carbon fiber, and Mx denotes a matrix. The carbon fiber does not change in volume.
In Table 1, the Mx volatile ratio C was obtained from the decrease in weight at 600° C., the Mx proportion D after calcining was obtained from D=B·(1−C), the CF volume fraction Vf was obtained from Vf={A/(A+D)}·100, and the porosity P was obtained from P=B·C. As is clear from Table 1, the porosity P was adjusted by changing the Mx volatile ratio C and the starting material composition. In Examples 1 to 3, the Mx volatile ratio C was changed by changing the ratio by weight of the petroleum-based pitch powder binder to the coke powder. In Examples 4 to 8, the ratio by weight of the petroleum-based pitch powder binder to the coke powder was set so as to be constant.
It can be seen from Table 2 that, in order to obtain a usable friction plate 3 by stamping in the absence of water, the porosity P of the carbon-carbon composite plate 1 should be greater than that in Example 2, that is, P should be equal to or greater than 20%. In stamping in the presence of water, a usable friction plate 3 can be obtained by setting the porosity P of the composite plate 1 so that it is greater than that in Example 1, that is, so that P is equal to or greater than 10%. While taking into consideration the strength, coefficient of friction, etc., it is desirable for the porosity P of the friction plate 3 to be at least 10% but not greater than 70%. In this case, if the porosity P is less than 10% stamping cannot be performed, and if P is greater than 70% the strength is degraded.
The friction plate 3 shown in
Such a friction plate 3 can be produced in the same manner as above by subjecting the carbon-carbon composite plate 1 having a porosity P equal to or greater than 20% to a single stamping operation in the absence of water, or by subjecting a carbon-carbon composite plate having a porosity P equal to or greater than 10% to a single stamping operation in the presence of water. By forming the plurality of through holes 5 on the flat section 4, it is possible to improve the ease of removal of an oil film when connecting the clutch, reduce the drag torque and, moreover, enhance the cooling performance of the friction plate 3.
Since the temperature of this type of friction plate 3 increases due to the heat of friction generated when connecting the clutch, a temperature variation is caused on the flat section 4. A range A in which the peak of this temperature variation is present is, when the width in the radial direction of the flat section 4 is defined as a, a range of about 0.5a to about 0.78a from the inner periphery (the tip of the spline 2) 6. By arranging each of the through holes 5 within the range A, it is possible to efficiently carry out cooling of the friction plate 3.
The friction plates 3 shown in
The eight slits 7 in
With regard to other plate-shaped members obtained by stamping, there can be cited as an example a plate-shaped material for a gear having a porosity P of at least 10% but not greater than 70%.
Number | Date | Country | Kind |
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2002-43668 | Feb 2002 | JP | national |
2002-361200 | Dec 2002 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP03/01777 | 2/19/2003 | WO |