Patent Application
20070295574
According to the present invention, there is provided a multi plate clutch in which at least one separator plate and at least one friction plate, in which two different kinds of friction materials are adhered to respective front and rear surfaces of a core plate, are alternately arranged. By combining the separator plate with the friction plate, in which the two different kinds of friction materials are adhered to the respective front and rear surface of the core plate, the same kind of friction surface of the friction plate oppose to both surface of the separator plate. Therefore, thermal balance of both surfaces of the separator plate can be made uniform.
Moreover, use of a highly-heat-resistant friction material enables prevention of occurrence of a heat spot in the separator plate, which is located in the center of the clutch and subjected to sever thermal condition, thus, a clutch having superior heat-resistant can be acquired.
In the friction member, a single friction material may also be applied to different thicknesses over both surfaces of the friction plate. Further, different types of materials having different elastic modulus may also be used as the friction member. In addition, different types of materials having different wear rates may also be used as the friction member.
When different types of materials are used as the friction members, it is better to take into account the following points.
In general, a material having a high content of fibrous component and a material having a low content of fibrous component have hitherto been known as a friction material. The material having a high content of fibrous component has a small friction coefficient but exhibits characteristics of high mechanical strength and high heat resistance. Meanwhile, the material having a low content of fibrous component has a large friction coefficient but exhibits characteristics of low mechanical strength and low heat resistance. Further, the material including a high content of fibrous component causes high frictional engagement in the early stage of engagement, but the material including a low content of fibrous component exhibits a large frictional coefficient after completion of engagement.
Consequently, the amount of fibrous component is a trade-off between the frictional coefficient and the mechanical strength and heat resistance.
In consideration of these characteristics of the friction materials, combined use of these friction materials is useful for obtaining a friction plate or a clutch which exhibits a high frictional coefficient, high mechanical strength and heat resistance, simultaneously.
However, in a case where different types of materials are affixed to a single surface as in the related art when the friction materials are combined with each other, there arises a problem of difficulty in alignment of positions where the materials are to be affixed and a failure to maintain uniform thickness.
Particularly, different types of materials have different coefficients of thermal expansion, respectively. Hence, when the friction materials are heated, a difference arises between the friction materials in terms of thickness. Consequently, the thickness of the friction materials of different types varies between the initial stage of engagement at low temperature and the time of completion of engagement at high temperature. Specifically, irregularities due to uneven thickness are occurred on a single surface.
When such a friction plate is used, partial wear in the friction plate or vibration at the time of engagement of the clutch may be occurred, and thus such the situation is not preferable.
Therefore, different friction materials are affixed to different surfaces of the friction plate as described in the present invention, whereby the problem of uneven thickness induced by the coefficients of thermal expansion can be solved. The reason for this is that, since a single type of friction material is present on a single surface, the thickness of the friction material on the single surface changes as a whole even when the friction material is heated, thereby preventing occurrence of irregularities in the single surface.
There may also be adopted a configuration in which a friction plate is provided with a single ring-shaped friction material. In this case, punching and affixing processes can be simplified.
Alternatively, a configuration in which a friction plate is provided with a plurality of small pieces of friction material may also be adopted. In this case, friction members can be efficiently punched from a sheet-shaped friction material, and enhanced yield is achieved.
Embodiments of a clutch formed by incorporation of a plurality of friction plates of the present invention will be described below.
As mentioned above, friction materials of different types are affixed to the respective front and rear surfaces of the core plate of the friction plate, so that the present invention can address various frictional characteristics and that a friction plate having stable quality can be provided at low cost. Specifically, provided that a friction material on the left side of the drawing is taken as the friction material 21, and a friction material on the right side of the same is taken as the friction material 22, a left-side surface 31 of the separator plate 30 engages with the friction material 22, and a right-side surface 32 of the same engages with the friction material 21. Thus, the both surfaces of the separator plate 30 engage with the friction materials of different types. Reference numeral 34 designates spline teeth provide along an outer periphery of the separator plate 30.
As mentioned above, if the friction plate of the present invention is used, a material which exhibits great frictional force at the initial stage of engagement and a material which exhibits great frictional force after completion of engagement are combined together. Hence, a clutch, which can exhibit a frictional characteristic of desired magnitude which is constant during the time period from the initial stage of engagement to the time of completion of engagement, can be built.
In the embodiment shown in
In the core plate 23 of a friction plate 20 located on the right side of the core plate 23′, the friction materials 21 and 22 are affixed to the same sides where their counterparts are affixed to the leftmost core plate 23. Therefore, surfaces 30l and 30r of the separator plate 30 sandwiched between the core plates 23′ and 23 engage with the friction material 21 of the single type.
According to the present embodiment, both sides of that separator plate 30 are engaged with the friction material 21 of a single type. Since the friction material of a single type exhibits the same heat characteristic, the same frictional heat arises between the separator plate 30 and the friction material 21. Accordingly, both surfaces 30l and 30r of the separator plate 30 are heated to the same temperature.
However, when both surfaces of the separator plate 30 engage with friction materials of different types as in the second embodiment shown in
Consequently, according to the present embodiment, both sides of the separator plate 30 are heated to the same temperature, and hence deformation of the separator plate 30, which would otherwise be caused by thermal expansion, can be prevented.
The wet multi plate clutch 110 of the third embodiment has two friction plates 20L and 20R; three separator plates 30L, 30C, and 30R; and a friction material 121 which exhibits high heat resistance and high heat radiation and is provided on a surface 23Lr of that friction plate 20L and a surface 23Rl of that friction plate 20R which contact the center separator plate 30c.
A friction material including a large amount of fibrous component is preferably used as a high-heat-radiation friction material for the friction material 121.
In the multi plate clutch using a plurality of friction plates and separator plates, radiation is less likely to arise in a space inside the clutch as in the case of, e.g., the separator plate 30C, and the space tends to become heated to a higher temperature when compared with other locations in the clutch. When the friction material becomes heated, seizing of the separator plate or deterioration of the friction material will arise undesirably.
However, according to the third embodiment, the friction material exhibiting high radiation and high heat resistance is provided in the clutch that is to be heated, thereby effectively preventing occurrence of the above-mentioned problems.
Since the friction material including a large amount of fibrous component usually exhibits a small frictional coefficient, a friction material which includes a small amount of fibrous component but a large amount of filler is preferably provided on the respective surfaces 23Lr and 23Rl of the friction plates in order to compensate for the frictional coefficient. With such a configuration, the clutch can exhibit a high frictional coefficient. The outside of the internal space of the clutch is likely to dissipate heat to peripheral members such as a housing or the like. Even when a friction material which exhibits inferior heat radiation and inferior heat resistance is used in this space, seizing up of the previously-described member or deterioration of the material wilt less likely to take place.
The wet multi plate clutch and the wet friction plate of the present invention have the configurations, such as those mentioned above, and can be manufactured in a comparatively-easy manner, thereby avoiding an increase in cost. Moreover, requests for various heat characteristics and engagement characteristics can be readily met.
While the invention has been described in connection with the exemplary embodiments, it will be obvious to those skilled in the art that various changes and modification may be made therein without departing from the present invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-172179 | Jun 2006 | JP | national |
