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United States Patent  [ii] Patent Number: 4,667,793
Kunz et al.  Date of Patent: May 26, 1987
U. S. Patent May 26,1987 Sheet 1 of2 4,667,793
U.S. Patent May26,1987 Sheet2 of2 4,667,793
 FRICTION CLUTCH AND DIAPHRAGM SPRING THEREFOR
 Inventors: Martin Kunz, Buhl/Eisental; Dieter Pretzel, Baden-Baden, both of Fed. Rep. of Germany
 Assignee: Luk LameUen und Kupplungsbau GmbH, Biihl/Baden, Fed. Rep. of Germany
 Appl. No.: 829,294
 Filed: Feb. 13,1986
 Foreign Application Priority Data
Aug. 13, 1985 [DE] Fed. Rep. of Germany 5 MR
Jan. 30, 1986 [DE] Fed. Rep. of Germany 3602716
 Int. Q.4 F16D 13/72
 U.S. CI 192/70.12; 192/89 B;
 Field of Search 192/113 A, 113 R, 89 B,
192/70.12, 70.27, 70.28; 188/71.6, 264 R, 264
A; 267/161, 167
 References Cited
U.S. PATENT DOCUMENTS
2,171,829 9/1939 Haupt 192/113 AX
3,417,846 12/1968 Cook 192/89 B
4,241,819 12/1980 Babcock et al 192/70.27
4,300,669 11/1981 Browne 192/109 A
FOREIGN PATENT DOCUMENTS
6606711 11/1970 Fed. Rep. of Germany . ^
Primary Examiner—George H. Krizmanich
Attorney, Agent, or Firm—Peter K. Kontler
A friction clutch wherein the prongs of the diaphragm spring are formed with half spoon-shaped vanes each of which is adjacent to one edge face of the respective prong and serves to circulate air when the spring rotates. Each prong is further formed with a reinforcing rib which extends radially outwardly from the respective vane and into the ring-shaped main section of the spring. The ribs stiffen the prongs and prevent them from bending during actuation of the clutch, namely while the tips of the prongs are pushed or pulled in a direction to relax the bias of the spring upon the pressure plate of the clutch.
18 Claims, 2 Drawing Figures
FRICTION CLUTCH AND DIAPHRAGM SPRING THEREFOR
CROSS-REFERENCE TO RELATED CASE
The friction clutch of the present invention constitutes an improvement over and a further development of the friction clutch which is disclosed in the commonly owned copending patent application Ser. No. 465,783 filed Feb. 11, 1983 by Phong Lu for "Friction clutch and diaphragm spring therefor" and in the commonly owned copending patent application Ser. No. 531,930 filed Sept. 13, 1983 by Wolfgang Reik for "Friction clutch and diaphragm spring therefore".
BACKGROUND OF THE INVENTION
The present invention relates to friction clutches in general, and more particularly to improvements in diaphragm springs which are utilized in friction clutches, especially in friction clutches for transmission of torque between the engine and the change-speed transmission of a motor vehicle.
As a rule, the diaphragm spring of a friction clutch for use in motor vehicles or the like comprises a ringshaped main section and a set of radially inwardly extending prongs or fingers which are separated from each other by slots and whose free end portions or tips define a centrally located opening. The diaphragm spring is tiltably mounted on a support, e.g., on the housing or cover of the friction clutch, and bears against a pressure plate so as to urge the latter axially toward engagement with the friction linings of a clutch disc. The pressure plate is driven by the crankshaft and the clutch disc transmits torque to the input shaft of the change-speed transmission if the friction clutch is installed in a motor vehicle.
The trend in the automobile industry is toward the making of high-performance lightweight and compact vehicles. This involves a reduction of the weight and space requirements of practically all components including the friction clutch. Thus, the working capacity of the clutch should be increased, and such increase should take place simultaneously with a reduction in dimensions and weight. Since the manufacturer of a friction clutch does not have too much freedom in the selection of materials for component parts of the friction clutch (rather narrow limits are imposed by the cost of raw materials as well as by the ability of materials to be treated in an economical way). One of the important parameters of a satisfactory friction clutch for use in motor vehicles is its ability to stand pronounced thermal stresses for extended intervals of time and/or to dissipate heat before the elevated temperatures could adversely affect sensitive friction linings and certain other heat-sensitive parts. The operating temperature of a modern compact engine for motor vehicles is sufficiently high to greatly reduce the useful life of friction linings and/or to cause undesirable and pronounced thermally induced distortion of the cover, pressure plate, clutch disc and/or other parts of the friction clutch. Therefore, rapid dissipation of frictioninduced heat in a friction clutch is of utmost importance.
German Utility Model No. 66 06 711 proposes to provide the diaphragm spring of a friction clutch with openings in the region of slots between the prongs. The openings are supposed to allow for circulation of air and attendant cooling of the friction clutch. The dimensions
of such openings cannot be increased at will because this would entail undue weakening of the spring. Furthermore, and in the absence of any additional undertakings, mere provision of openings in the prongs contributes little, if anything, to the dissipation of heat.
U.S. Pat. No. 3,417,846 proposes to provide bentover portions at one or both sides of each prong of the diaphragm spring. The purpose of such configuration of the prongs is to reduce the lift-off losses which develop as a result of bending of the prongs. The bent-over portions are supposed to reinforce the prongs and to thus ensure predictable disengagement of the clutch while minimizing the distance which the prongs must cover in order to effect a disengagement of the pressure plate from the adjacent linings of the clutch disc.
OBJECTS AND SUMMARY OF THE
An object of the invention is to provide a novel and improved friction clutch wherein the dissipation of heat is more satisfactory than in heretofore known friction clutches.
Another object of the invention is to provide a novel and improved diaphragm spring for use in a friction clutch for motor vehicles or the like.
A further object of the invention is to provide a simple, compact and inexpensive friction clutch which has a built-in automatic cooling or heat-dissipating system and which can be used as a pull-type or push-type clutch.
An additional object of the invention is to provide a diaphragm spring which is constructed and configurated in such a way that the lift-off losses are minimal as well as that the prongs of the spring automatically effect a cooling of the spring as well as of the entire clutch when the spring is set in rotary motion.
Still another object of the invention is to provide a novel and improved method of reinforcing and/otherwise improving the characteristics and adding to the utility of prongs in a diaphragm spring for use in friction clutches.
Another object of the invention is to provide a novel and improved method of enhancing the rigidity of prongs in a diaphragm spring.
A further object of the invention is to prolong the useful life of a friction clutch and its components, to shield the components of the friction clutch from overheating, and to ensure a predictable disengagement of the friction clutch.
An additional object of the invention is to provide a friction clutch wherein the diaphragm spring is constructed and mounted in such a way that it can perfrom the functions of conventional diaphragm springs plus one or more additional desirable functions, particularly ensuring adequate cooling and predictable disengagement of the clutch.
The invention is embodied in a friction clutch which comprises a rotary pressure plate, a support (e.g., a cover or housing) which is adjacent to the pressure plate; and a diaphragm spring which is mounted on the support and serves to normally bias the pressure plate axially (particularly against the linging or linings of a clutch disc). The diaphragm spring comprises a ringshaped main section and a plurality of prongs or fingers which extend substantially radially inwardly from the main section and have free end portions or tips defining a centrally located opening. The prongs of the dia