Field of the invention:
The present invention relates to automobile clutches in general and to clutch disc for automobile clutches in particular.
Background of the invention:
Clutches are well known mechanisms used in vehicles. They are used to connect a driven means and a rotational power source, which is usually the crankshaft of an automobile engine. The clutches work as a flexural member between the engine and transmission of a vehicle. Generally the clutch assembly consists of one or more clutch disc and a pressure plate assembly. The pressure plate assembly is bolted to flywheel. One or more clutch disc(s) are sandwiched between the pressure plate assembly and the flywheel. The clutch disc transfers the engine torque to the input shaft of the gear box. The clutch disc generally has an annular body having friction plates on both the sides attached with the clutch disc using some means like rivets or may be bonded using some adhesive. The friction plate on one side, faces the flywheel and on the other side, faces the pressure plate of pressure plate assembly. The thickness of friction plate generally defines the wear life of the clutch. More particularly, the height of friction material above the rivet is the wear allowance in the clutch disc.
During engagement the pressure plate moves axially to clamp the clutch disc between the pressure plate and the flywheel. The friction plates on the clutch disc engage with the flywheel on one side and pressure plate on the other. When the clutch is released, the pressure plate is pulled back away from the flywheel allowing the clutch disc to spin freely. The continuous engagement/disengagement process causes the friction plate on the clutch disc to wear. A point comes when the thickness of friction plate above the rivet wears and there is a metal to metal contact with the flywheel and/or the pressure plate. This condition is however undesirable and clutch needs to be replaced at this point.
The flywheel generally has a greater mass as compared to a pressure plate. Also pressure plate being movable part with reference to flywheel causes high heat generation due to friction at pressure plate side than flywheel side. Being heavier mass flywheel is able to dissipate the heat faster than the pressure plate. High heat at pressure plate side causes friction plate material to fade and thus the wear rate increases. This results in early worn out of the friction plate on the pressure plate side as compared to flywheel side, forcing the user to change the clutch disc even if the friction plate on the flywheel side is in working condition as there is friction material left above the rivets.
This differential wear rate phenomenon has been largely seen in failed clutches and practically found on all type of clutches for passenger cars, commercial vehicles, agricultural tractors, buses, etc.
From the cost economics, the friction plate material cost is very high and is nearly 60% to the cost of complete clutch disc. Thus, there is wastage of expensive material on flywheel side friction plate.
In order to obviate the aforementioned problems there is a need to provide a clutch mechanism that enhances the wear life of the friction plate.
The subject matter disclosed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.
Summary of the Invention:
The principal object of the present invention is to optimize the usage of friction plate material to enhance wear life clutch disc and to enhance the usable life of the clutch.
To achieve aforementioned objective an improved clutch disc is provided wherein the friction plate on one side is thicker as compared to the other side.
According to an embodiment of the invention a clutch disc for dry friction clutch assembly have a flywheel facing side and a pressure plate facing side. Both the sides have a friction material provided thereon of a specific thickness wherein the thickness of the friction material on the pressure plate facing side is greater then the thickness of the friction material on the flywheel facing side.
Additional features of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The features and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the present invention will become more apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
Brief Description of the drawings:
To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by references to exemplary embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be exemplified with reference to the accompanying drawings, wherein:
FIG. 1 is a sectional side view of the clutch system fitted on a flywheel according to an embodiment of the present invention; and
FIG. 2 is a sectional side view of the clutch disc according to an embodiment of the present invention.
Detailed Description of the invention:
The following detailed description does not limit the invention. The scope of the invention remains defined by the appended claims.
Figure 1 discloses a cross section view of a clutch 10 according to an embodiment of the present invention. The clutch 10 have a clutch disc 20 and a pressure plate assembly 30 bolted to a flywheel 40. An input shaft 50 of a gear box 60 is connected to central hub 70 of the clutch disc 20. The Pressure plate assembly 30 essentially has a pressure plate 35, which has to move along the clutch axis 45 as the clutch 10 moves from engagement to disengagement. It must be appreciated that figure 1 illustrate an exemplary single plate push type diaphragm clutch. However the invention may be implemented in any push or pull type clutches, diaphragm or coil type clutches, single plate or multi plate clutches etc., without going beyond the scope of the invention defined by the appended claims
Figure 2 illustrates a cross section view of a clutch disc 20 according to an embodiment of the present invention. The clutch disc 20 has a core 100, a pressure plate side facing friction material 80 and a flywheel side facing friction material 90. The friction material may be provided in the form of friction buttons, friction plates, friction cookies etc and may be attached to the body 100 by one or more rivets 110. In yet another embodiment the friction material may be attached using an adhesive to the body 100. According to yet another embodiment, the friction material may be selected from a group comprising organic friction material in the form of pads or full rings, cerametallic friction material in the form of pads or full rings, ceramic friction material in the form of pads or full rings.
The thickness of the friction plate on the pressure plate side is kept greater then the thickness on the other side. According to one embodiment the thickness of the friction plate of the clutch disc facing the flywheel is 'a' wherein the thickness of the friction plate of the clutch disc facing the pressure plate is 'b' wherein 'b' is greater then 'a'. The rate of wear on two sides is different because of different masses of flywheel and pressure plate and also because flywheel does not reciprocate while pressure plate does. According to another embodiment the thickness of the friction material on the pressure plate facing side is approximately 10 to 70 % greater then the thickness of the friction material on the flywheel facing side.
Since the wear rate on both side friction materials is different, this invention discloses the optimum use of expensive friction material by distributing the material so that overall clutch disc thickness remains same. This also ensures interchangeability.
The above-described exemplary embodiments are intended to be illustrative in all respects, rather than restrictive, of the present invention. Thus the present invention is capable of many variations in detailed implementation that can be derived from the description contained herein by a person skilled in the art. All such variations and modifications are considered to be within the scope and spirit of the present invention as defined by the following claims. No element, act, or instruction used in the description of the present application should be construed as critical or essential to the invention unless explicitly described as such. Also, as used herein, the article "a" is intended to include one or more items.

We Claim:
1. A clutch disc for dry friction clutch assembly comprising:
a flywheel facing side and a pressure plate facing side having a friction material provided thereon, characterized in that the thickness of the friction material on the pressure plate facing side is greater then the thickness of the friction material on the flywheel facing side.
2. The clutch disc as claimed in claim 1, wherein the thickness of the friction
material on the pressure plate facing side is approximately 10 to 70 % greater then
the thickness of the friction material on the flywheel facing side.
3. The clutch disc as claimed in claim 1, wherein the friction material can be of any type in terms of frictional properties like organic, cerametallic or ceramic friction material.