Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-09-15
2001-06-26
Edwards, N. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S221000, C428S375000, C188S25100R, C188S073370
Reexamination Certificate
active
06251519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention generally relates to a friction member. More specifically, the present invention relates to a friction member used in a clutch device of an automobile or the like.
2. Background Information
A dry clutch device of an automobile is provided with a friction facing, which is pressed against a flywheel for frictionally transmitting power.
The friction facing for a dry clutch device is produced in the following manner. First, glass yarn made of, e.g., only glass fibers or a mixture of glass fibers and metal lines twisted together is prepared. Then, the glass yarn is moved into an impregnation tank containing a composition of rubber, curing agent, thermosetting resin and other materials dissolved in a solvent. Thus, the glass yarn is impregnated and coated with the above composition. The yarn for the friction member thus prepared is wound and preshaped into an annular form (i.e., a product form). Thereafter, the final product of the friction facing is completed through thermal pressing, curing, polishing and other steps.
In the manufacturing method of the friction facing described above, the glass yarn is immersed in the impregnation tank. The glass yarn is impregnated and coated with the composition. Therefore, the resin composition moves into the glass yarn.
It has been known that when starting a vehicle, automobile clutch judder is affected by the amount of spaces which are present within the facing. To suppress the judder, it is necessary to increase the porosity by increasing a ratio of spaces within the molded portion. However, it is difficult to increase the porosity of the yarn in conventional methods of facing manufacture because the resin is present within the glass yarn.
In the prior art, therefore, the porosity of the molded portion is controlled by controlling the pressure during the thermal molding. However, although the judder can be suppressed, an increase in porosity of the molded portion lowers the resistance against wearing, and thus shortens the life of the facing.
In view of the above, there exists a need for a friction member which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
SUMMARY OF THE INVENTION
An object of the invention is to suppress judder without impairing wear resistance.
According to an aspect of the present invention, a friction member is prepared by impregnating or coating base fibers with a composition containing rubber and/or resin to prepare yarn for the friction member, preshaping the yarn into an annular form, and then thermally molding the preshaped yarn. The friction member preferably has porosity in a range from about 10% to 20%. A porosity of or larger than about 10% can provide a sufficient amount of spaces in a molded portion. Thus, the friction member which is used as a friction facing for an automobile clutch device can suppress judder. Since the porosity does not exceed about 20%, impairment of wear resistance can be prevented. The porosity is a rate of spaces within the facing, and is expressed as a percentage of a volume of absorbed oil with respect to a volume of a specimen, as will be described in greater detail.
According to another aspect of the present invention, the friction member of the aforementioned aspect of the present invention further has a feature such that an apparent density is about 1.75 or less. This can reduce weight when compared to the density of conventional friction members. The apparent density is calculated from the weight and the volume.
According to another aspect of the present invention, the friction member of either of the previous aspects of the present invention further has a feature such that the yarn for the friction member is formed of strands of base fibers with a twist of about 10-90 T/M. If the twist were smaller than about 10 T/M, twisting could not provide adequate porosity. If it were larger than about 90 T/M, twist-back would occur, resulting in problems while manufacturing.
According to another aspect of the present invention, the friction member of any of the previous aspects of the present invention further has a feature such that the composition containing the rubber and the resin has a viscosity of about 300000 CPS or more. In this aspect of the present invention, the high viscosity suppresses entry of the composition into the yarn of the friction member. Therefore, the friction member having a viscosity of about 10% or more can be produced without difficulty.
According to another aspect of the present invention, the friction member of any of the first three aspects of the present invention further has a feature such that the yarn for the friction member is formed by coating the base fibers with a clay-like composition containing rubber and resin supplied by an extruder. In this aspect of the present invention, the composition covers the outer peripheries of the base fibers. Thus, the rate of entry of the composition into the base fibers is very small. Consequently, the friction member having the porosity of about 10% or more can be easily obtained.
According to another aspect of the present invention, the friction member of any one of the aforementioned aspects of the present invention further has a feature such that the base fibers are made of only glass fibers.
According to another aspect of the present invention, the friction member of any one of the first five mentioned aspects of the present invention further has a feature such that the base fibers are made of a mixture of glass fibers and organic fibers. Alternatively, metal fibers can be included in the mixture.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.
REFERENCES:
patent: 355086933A (1980-07-01), None
patent: 401234629A (1989-09-01), None
patent: 402209635A (1990-08-01), None
patent: 41102270A (1999-01-01), None
Hata Takashi
Sanai Hisao
Yamamura Shozo
Edwards N.
Exedy Corporation
Shinjyu Global IP Counselors, LLP
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