Flexible plate for transmitting torque

Abstract: A flexible plate 3 transmits torque from a crank shaft 4 in an engine to a fly wheel main body 2 while absorbing axial vibration, and includes a first disc element 7 and a second disc element 8. The first disc element 7 comes is fixed to a distal end of the crank shaft 4. A second disc element 8 has its inner circumferential portion is connected to the first disc element 7, with both being connected to the crank shaft 4 at their respective inner circumferential portions. The outer circumferential portion of the second disc element 8 is longer in the radial direction than the first disc element 7 and is connected to the fly wheel main body 2. The second disc element 8 can be flexibly transformed in axial directions.

Description: The present invention relates to a flexible plate, and more particularly, it relates to a flexible plate for transmitting torque from an engine crankshaft to other components while absorbing axial vibration. In a typical motor vehicle, a flywheel is attached to a distal end of an engine crankshaft, and a clutch disc assembly and clutch cover assembly are attached to the flywheel. The flywheel is provided with a frictional surface which opposes the frictional facing of the clutch disc assembly. When the friction facing is pressed against the frictional surface of the flywheel, torque from the engine is transmitted to the clutch disc assembly and applied to the transmission of the vehicle. A disc-like flexible plate has conventionally been used as an element to connect the distal end of the crankshaft with the flywheel. This type of flexible plate is excellent in rigidity in radial directions and is capable of being flexibly deformed in axial directions. The flexible plate effectively absorbs axial vibration transmitted from the engine. For a given torque, the circumferential forces increase sharply as the diameter diminishes, so stress concentration tends to occur in the radially inner circumferential portion of the flexible plate, which comes in contact with the end portion of the crankshaft. Hence, the flexible plate must be increased in thickness in that area so as to improve its durability. Such an increase in thickness, however, increases the rigidity of the flexible plate as a whole and prevents it from effectively absorbing axial vibration. The situation is aggravated for flexible plates to be arranged at the distal end of a crankshaft. To provide for the necessary durability under the circumferential forces of the transmitted torque together with the required axial elasticity of the flexible plate, in GB 1 001 538 and DE 44 02 257 A1 the diameter of the distal end portion of the crankshaft had to be enlarged beyond the diameter of the adjacent bearing, thus bringing the circumferential forces to values durably transmittable to the flexible plate by means of bolts connecting the flexible plate to the distal end of the crankshaft. Accordingly, the object of the present invention is to permit the flexible plate to effectively absorb axial vibration while preventing the concentration of excessive amounts of stress in the flexible plate. Correspondingly, the invention includes a flexible plate for transmitting torque from a crankshaft in an engine to other components while absorbing axial vibration, comprising: a first disc element connected to a distal end of a crankshaft by means of first fixing elements, and a second disc element capable of being flexibly transformed in axial directions and having its inner circumferential portion interconnected with that first disc element by means of second fixing elements; wherein these first fixing elements connect the inner circumferential portions of both first and second disc elements to the distal end of that crankshaft; and the outer circumferential portion of said second disc element is longer in the radial direction than said first disc element and may be fixed to other components. Advantageously, the first and second disc elements can be composed of sheet metal. For easy centering of the flexible plate, the first disc element may have an annular projection such that its inner portion comes in contact with an outer circumferential edge of the distal end of the crankshaft. To enhance the torque transmission, the first and second fixing elements are arranged at different diameters, the diameter for the second fixing elements being greater than that for the first fixing elements. Other objects, features, aspects and advantages of the present invention will be apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which like reference numerals designate the same or similar parts throughout. BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a cross-sectional top elevation showing a flexible plate according to a preferred embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 depicts a fly wheel 1 employing a preferred embodiment of the present invention. The fly wheel 1 includes a fly wheel main body 2 and a flexible plate 3, and it is attached to a distal end of a crank shaft 4. The fly wheel main body 2 is provided with an annular frictional surface 2a. On the right of the frictional surface 2a in the drawing, a clutch disc assembly and a clutch cover assembly are disposed, both of which are not shown. The fly wheel main body 2 has an annular outer circumferential wall 2b extending away from the crank shaft in the axial direction. A bolt hole 2c is disposed in the outer circumferential wall 2b, at which a clutch cover of the clutch cover assembly is fixed. The flexible plate 3 couples the crank shaft 4 to the fly wheel 2 and is comprised primarily of a first disc element 7 and a second disc element 8. Both the first and second disc elements 7 and 8 are sheet metal disc-shaped components having a center hole. The second disc element 8 is greater in outer diameter than the first disc element 7. The first disc element 7 and the second disc element 8 are fixed to each other in an inner circumferential portion of the second disc element 8 by a plurality of rivets 9. The first and second disc elements 7 and 8 are fixed at their respective inner circumferential portions to the distal end of the crank shaft 4 by bolts 11. In the first disc element 7, an annular drawing socket 7a is formed, protruding toward the crank shaft 4. The inner portion of drawing socket 7a is in contact with an outer circumferential edge of the distal end of the crank shaft 4. The drawing socket 7a enables the flexible plate 3 to be centered relative to the crank shaft 4. An outer circumferential portion of the second disc element 8 extends to an outer circumferential portion of the fly wheel main body 2 the second disc element 8 being fixed to the fly wheel main body 2 by bolts 10. In the area on the second disc element 8 located between bolt 10 and bolt 11, a plurality of round holes 8a are formed. Washers 12 are placed between heads of the bolts 11 and an inner circumferential portion of the second disc element 8. The operation of the fly wheel will now be described. Torque is transmitted from the crank shaft 4 to the fly wheel main body 2 through the flexible plate 3. When axial vibration is transmitted to the flexible plate 3, the second disc element 8 is primarily flexed to absorb the axial vibration. The second disc element 8 is the same thickness as the prior art flexible plate, and therefore it is of low rigidity and flexible enough to effectively absorb the axial vibration. Since the first disc element 7 is fixed to the inner circumferential portion of the second disc element 8, the inner circumferential portion of the flexible plate 3, as a whole, is of high rigidity. Thus, stress concentration in an inner circumferential portion of the flexible plate 3 is relieved. In addition to that, stress concentration by torsional vibration is also relieved in that area. Moreover, since the drawing socket 7a is formed in the first disc element 7, the flexible plate 3 is accurately centered relative to the crank shaft 4. The first disc element 7 and the second disc element 8 are composed of sheet metal, and therefore their fabrication is simplified and their cost of fabrication is reduced. Since the first disc element 7 and the second disc element 8 are fixed by the rivets 9, the flexible plate 3 is integral with those components. In addition, the first disc element 7 and the second disc element 8 are fixed by the rivets 9 and the bolts 11, and hence, even if the rivets 9 are damaged, both the elements will still be coupled to each other. Various details of the invention may be changed without departing from its scope as defined in the claims. Furthermore, the foregoing description of the embodiments according to the present invention is provided for the purpose of illustration only, and not for the purpose of limiting the invention as defined by the appended claims.

Claims: A flexible plate (3) for transmitting torque from a crankshaft (4) in an engine to other components (2) while absorbing axial vibration, comprising: a first disc element (7) connected to a distal end of a crankshaft (4) by means of first fixing elements (11), and a second disc element (8) capable of being flexibly transformed in axial directions and having its inner circumferential portion interconnected with that first disc element (7) by means of second fixing elements (9); wherein these first fixing elements (11) connect the inner circumferential portions of both first and second disc elements (7 and 8) to the distal end of that crankshaft (4), and the outer circumferential portion of said second disc element (8) is longer in the radial direction than said first disc element (7) and may be fixed to other components (2). A flexible plate (3) according to claim 1, wherein the first and second disc elements (7 and 8) are composed of sheet metal. A flexible plate (3) according to claim 1 or 2, wherein said first disc element (7) has an annular projection (7a) such that its inner portion comes in contact with an outer circumferential edge of the distal end of said crankshaft (4). A flexible plate (3) according to claim 1, wherein these first and second fixing elements (11; 9) are arranged at different diameters, the diameter for the second fixing elements (9) being greater than that for the first fixing elements (11). The flexible plate according to one of claims 1 to 4, further comprising a second fixing element (9) for fixing said first and second disc elements (7, 8) to each other. The flexible plate according to one of claims 2 to 5, wherein said first' flexible disc element (9) is formed with an annular indentation corresponding to said annular protrusion with said annular protrusion on one side of said first flexible plate and said annular indentation formed on an opposite side of said first flexible plate. The flexible plate according to claim 6, wherein a radially inner portion of said second flexible disc element (8) is formed with an annular protrusion (8b) that extends into said annular indentation of said first flexible plate (7). The flexible plate according to one of claims 5 to 7, wherein said second fixing element (9) for fixing said first and second disc elements (7, 8) to each other comprises a plurality of rivets circumferentially spaced apart from each other, said rivets extending through a radially outward portion of said first flexible disc element (7) and said rivets extending through a proximate radial mid-portion of said second flexible disc element, (8).

Inventors: FUKUSHIMA HIROTAKA, FUKUSHIMA, HIROTAKA
Applicants: EXEDY CORP, EXEDY CORPORATION
Application year: 1995
Main classification: F16D13
IPC codes: F16D3, F16D13, F16F15