Torque transmitting and torsion damping apparatus for use in motor vehicles

Abstract

A torsion damping apparatus between the crankshaft of the engine and the input shaft of the change-speed transmission of a motor vehicle has two flywheels one of which is driven by the crankshaft and the other of which drives the input shaft by way of a friction clutch which generates heat. In order to prevent the transfer of heat from the friction clutch to the antifriction bearing between the flywheels, which are rotatable relative to each other against the opposition of a damper, the bearing is at least partially surrounded by a thermal barrier of synthetic plastic, ceramic or metallic material which prolongs the useful life of the bearing and enhances the torsion damping action of the damper. The thermal barrier can constitute or form part of the damper. The bearing can be disposed radially inwardly of the location of engagement between the clutch and the other flywheel and can be cooled by streams of air flowing through an annulus of passages each having a first end disposed radially inwardly of the friction surface of the other flywheel and a larger second end in a second surface of the other flywheel opposite the friction surface. Heat barriers in the other flywheel can alternate with the passages in the circumferential direction of the other flywheel.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The torsion damping apparatus 1 of FIG. 1 comprises a composite flywheel 2 including a first flywheel 3 receiving torque from an internal combustion engine 105 by way of a crankshaft 5 which is secured thereto by an annulus of bolts 6 or analogous fasteners, and a second flywheel 4 which transmits torque to the input element 10 of a change-speed transmission 110 in a motor vehicle by way of a friction clutch 7. The friction clutch 7 comprises an axially shiftable pressure plate 8, an axially fixed pressure plate which constitutes the second flywheel 4, a clutch plate or disc 9 with two friction linings 9a, a cover or housing 11 and a diaphragm spring 12 which normally urges the pressure plate 8 against the adjacent lining 9a so that the friction- and heat-generating (second) surface 9b of the other lining 9a bears against the adjacent friction- and heat-generating (first) surface 4a of the flywheel 4. The diaphragm spring 12 is tiltably mounted between two wire-like ring-shaped seats on the cover 11 by rivets 12a, and the axially movable pressure plate 8 is non-rotatably affixed to the flywheel 4 or to the cover 11 by leaf springs 8a. The cover 11 rotates with the flywheel 4 and with the pressure plate 8. The central portion of the clutch disc 9 transmits torque to the input element 10 of the transmission 110. The means for disengaging the clutch 7 can comprise a bearing (not shown) which can act against the radially inwardly extending prongs 12b of the diaphragm spring 12 in order to move the radially outermost portion of the diaphragm spring axially in a direction away from the flywheel 4 so that the leaf springs 8a can move the pressure plate 8 axially and away from the flywheel 4 to thus terminate the torque-transmitting connection between the flywheel 4 and the clutch disc 9, i.e., between the crankshaft 5 and the input element 10.

The flywheels 3 and 4 are or can be coaxial and can perform limited or unlimited angular movements relative to each other against the opposition of a composite damper including a damper unit 13, a friction generating unit 13a and a slip clutch 14 which is connected in series with the damper unit 13.

The torsion damping apparatus 1 further comprises a bearing means 15 which is interposed between the flywheels 3 and 4 and, in the embodiment of FIG. 1, comprises an antifriction ball bearing 16 with an inner race 19, an outer race 17 spacedly surrounding the inner race 19 and a single row of spherical rolling elements 16a in the bearing clearance between the two races. The outer race 17 is installed in a centrally located recess or bore 18 of the flywheel 4, and the inner race 19 is mounted on a centrally located cylindrical protuberance or hub 20 which is an integral part of the flywheel 3, which extends axially in a direction away from the crankshaft 5, and at least a portion of which is received in the recess 18. The inner race 19 is a press fit on the protuberance 20 of the flywheel 3 and is held against any axial movement relative to the protuberance 20 by a shoulder 21 of the flywheel 3 as well as by an annular washer-like retaining element 22 which is affixed to the protuberance 20 by screws 23 so that its left-hand end face bears against the end face 20a of the protuberance 20.

The improved torsion damping apparatus 1 further comprises means for impeding the transfer of heat from the friction- and heat-generating surfaces 9b, 4a to the bearing means 15. In the embodiment of FIG. 1, the heat transfer impeding means includes a thermal insulator or barrier 24 which is installed between the outer race 17 of the antifriction bearing 16 and the adjacent portion of the flywheel 4, namely that portion of the flywheel 4 which directly surrounds the recess 18 therein. The construction, composition and mounting of the thermal barrier 24 are such that it at least strongly interferes with and appreciably reduces the transfer of heat from the clutch disc 9 to the antifriction bearing 16. This reduces the likelihood of excessive thermal stressing of the lubricant (e.g., grease) for the antifriction bearing 16 as well as the likelihood of excessive thermally induced distortion (expansion) of the antifriction bearing 16 which could result in jamming of spherical rolling elements 16a between the races 17 and 19. The diameter of the recess 18 in the central portion of the flywheel 4 is selected in such a way that the recess can receive the outer race 17 of the antifriction bearing 16 as well as the components of the thermal barrier 24. In other words, the diameter of the recess 18 exceeds the outer diameter of the outer race 17.

The illustrated thermal barrier 24 comprises two rings 25, 26 which are mirror symmetrical to each other with reference to a plane that is disposed between them and is normal to the axes of the flywheels 3, 4 and antifriction bearing 16. Each of the rings 25, 26 has a substantially L-shaped cross-sectional outline with a cylindrical section 25a, 26a which surrounds the external surface of the outer race 17 and a radially inwardly extending washer-like section 25b, 26b which extends along the respective end face of the outer race 17 and toward and along the respective end face of the inner race 19. The radially innermost annular portions or lips of the radial sections 25b, 26b bear axially against the respective end faces of the inner race 19. Thus, the sections 25b, 26b constitute sealing elements which reduce the likelihood of penetration of foreign matter into the annular bearing clearance between the races 17, 19 as well as the likelihood of escape of lubricant from such clearance. The sealing action of radial sections 25b, 26b of the rings 25, 26 is enhanced by discrete means for biasing the radially innermost portions of such radial sections against the adjacent end faces of the inner race 19. The biasing means comprises two diaphragm springs 27, 28. The radially outermost portion of the diaphragm spring 27 reacts against a shoulder provided therefor on a disc 30 which is affixed to the flywheel 4 by rivet-shaped distancing elements 29, and the radially innermost portion of the diaphragm spring 27 bears against the radially innermost portion of the radial section 25b of the ring 25. The radially outermost portion of the diaphragm spring 28 reacts against a shoulder of the flywheel 4, and its radially innermost portion bears against the radially innermost portion of the radial section 26b of the ring 26.

In order to simplify and facilitate the assembly of the antifriction bearing 16 with the flywheels 3 and 4, the cylindrical sections 25a, 26a of the rings 25, 26 are forcibly fitted onto the outer race 17 of the antifriction bearing 16 in a first step before the bearing 16 and the rings 25, 26 thereon are forcibly inserted into the recess 18 of the flywheel 4. The bearing 16 and the rings 25, 26 are thereupon additionally secured against axial movement relative to the flywheel 4 in that the radial section 26b of the ring 26 bears against an internal shoulder 31 of the flywheel 4 and the radial section 25a of the ring 25 is caused to abut against the disc 30 which, as mentioned above, is affixed to the flywheel 4 by the distancing elements 29.

The damper unit 13 includes the disc 30 and a second disc 33 which is held at a fixed distance from the disc 30 by the aforementioned rivet-shaped distancing elements 29 which are anchored in the flywheel 4. The shanks of such distancing elements extend through a flange 32 which is disposed between the discs 30 and 33. The discs 30, 33 cannot rotate relative to each other and share all angular movements of the flywheel 4. The flange 32 shares all angular movements of the flywheel 3. The discs 30, 33 and the flange 32 are provided with neighboring windows for energy storing devices in the form of circumferentially acting coil springs 34 which oppose angular movements of the flywheels 3 and 4 relative to each other, i.e., such coil springs resist angular movements of the discs 30, 33 with reference to the flange 32 and vice versa.

The composite damper further includes the friction generating unit 13a which is active during each and every stage of angular movement of the flywheel 3 relative to the flywheel 4 and/or vice versa. The friction generating unit 13a acts axially between the disc 30 on the flywheel 4 and the flywheel 3, and includes an energy storing member in the form of a diaphragm spring 35 which is installed in prestressed condition between the disc 30 and a pressure applying washer 36. The diaphragm spring 35 can react against the flywheel 3 to bear against the washer 36 which, in turn, urges a friction ring 37 against the adjacent side of the disc 30 on the flywheel 4. The axial stress which is applied by the diaphragm spring 35 is taken up by the antifriction bearing 16.

The flange 32 constitutes the input element of the damper unit 13 as well as the output element of the slip clutch 14. The input element of the slip clutch 14 is constituted by two discs 38, 39 which are maintained at a fixed axial distance from each other and are non-rotatably secured to the flywheel 3. The means for non-rotatably securing the disc 39 to the flywheel 3 comprises an annulus of rivets 40. The disc 38 is provided with an annulus of axially extending peripheral fingers or lugs 38a which extend into adjacent peripheral notches 41 of the disc 39 so that the two discs are held against angular movement relative to one another. The flange 32 has radially outwardly extending arms 42 which are clamped between the discs 38 and 39 by a diaphragm spring 43 which urges the discs 38 and 39 toward each other. The diaphragm spring 43 reacts against the flywheel 3 and bears against the disc 38 in a direction to urge the latter axially toward the disc 39. The arms 42 of the flange 32 alternate with windows which are provided in the discs 38, 39 and receive energy storing devices in the form of coil springs 44 which can be engaged by the respective arms 42 and constitute stops that determine the extent of angular displacement of the parts of the slip clutch 14 relative to each other.

It has been found that the thermal barrier 24 between the friction clutch 7 and the bearing means 15 is capable of prolonging the useful life of the bearing means as well as of ensuring more satisfactory operation of the damper (13, 13a, 14) between the flywheels 3 and 4. This is due to the fact that the thermal barrier 24 greatly reduces the transfer of heat to the bearing means 15 even though it takes up little room and is assembled of a small number of simple, compact and inexpensive parts each of which can be mass-produced in available machinery. Extensive experiments with the improved torsion damping apparatus (wherein the bearing means is installed directly between the two flywheels 3 and 4 and wherein the angular movements of the flywheels relative to each other must be damped by one or more discrete or interlinked dampers) indicate that, in the absence of any preventive or precautionary measures, heat energy which is released when the friction clutch 7 is engaged subjects the bearing means between the flywheels to very pronounced thermal stresses which entail unsatisfactory operation and frequently rapid destruction of the bearing means as well as unsatisfactory operation of the damper or dampers. The likelihood of rapid destruction of the bearing means is especially pronounced if the bearing clearance or tolerance between the inner and outer races is small or very small. Repeated pronounced heating and cooling of the parts cf such bearing means entails substantial thermally induced expansion and contraction whereby the rolling elements between the two races are likely to seize in response to expansion cf the races which, in turn, entails rapid destruction of the rolling elements and of the tracks which are machined into the races. All this can be avoided by the advent of the present invention, i.e., by the provision of a thermal barrier which at least impedes the transfer of heat to the bearing means.

Another important advantage of the improved apparatus is that the lubricant (such as oil or grease) in the bearing clearance between the races of the bearing is much less likely to be overheated and to escape from the bearing. This, too, contributes to longer useful life of the bearing means and of the entire torsion damping apparatus. Moreover, portions or sections of the rings 25, 26 which constitute or form part of the improved thermal barrier 24 can serve as an effective means for sealing the bearing clearance between the races 17 and 19 to thereby even further reduce the likelihood of escape of excessive quantities of lubricant from the interior of the antifriction bearing 16. The aforediscussed plastic, ceramic and/or metallic materials have been found to constitute highly satisfactory thermal insulators which can protect the antifriction bearing 16 and the units of the composite damper for extended periods of time, even if the friction clutch 7 is continuously engaged and/or is caused or permitted to slip (with attendant pronounced generation of heat) at frequent and relatively long intervals.

It was further ascertained that the placing of the thermal barrier directly between the antifriction bearing 16 and the adjacent portion of the flywheel 4 (i.e., of that flywheel which is directly heated by the friction clutch 7) contributes significantly to adequate shielding of the bearing means 15 from excessive heat while, at the same time, allowing for relatively simple and inexpensive installation of the thermal barrier in the torsion damping apparatus. Of course, it is equally possible to employ two or more thermal barriers or to provide one or more thermal barriers in the body of the flywheel 4 and out of direct contact with the antifriction bearing 16 but in the path of transfer of heat energy from the friction generating surfaces 9b, 4a to the bearing 16.

The positions of the recess 18 and protuberance 20 can be reversed, i.e., the protuberance can be provided on the central portion of the flywheel 4 and the flywheel 3 is then formed with a recess which receives at least a portion of the protuberance on the flywheel 4, at least a portion of the bearing means on such protuberance and at least a portion of the thermal barrier. The thermal barrier is then preferably installed within the inner race (which surrounds the protuberance of the flywheel 4) in order to prevent overheating of the bearing means 15. This is shown in FIG. 5.

The thermal barrier 24 of FIG. 1 can be replaced with a thermal barrier which comprises a single ring having a cylindrical section which surrounds the major portion of or the entire outer race 17, and a radial section which is adjacent one end face of the race 17 and extends radially inwardly toward and at least in part along one end face of the inner race 19. The illustrated two-piece thermal barrier 24 is preferred in many instances because the two radially extending sections 25b, 26b constitute effective and relatively simple as well as compact sealing elements which prevent the escape of lubricant from the bearing clearance for the rolling elements 16a and also reduce the likelihood of overheating of the confined lubricant and/or rolling elements. The provision of biasing means (such as the aforementioned diaphragm springs 27 and 28) even further reduces the likelihood of escape of excessive quantities of lubricant and/or of overheating of the lubricant and/or rolling elements in the bearing clearance between the races 17 and 19. The diaphragm springs 27, 28 can be provided even if the sections 25b and 26b are elastically deformable and the rings 25, 26 are installed in such a way that the sections 25b, 26b are prestressed and bear against the respective end faces of the inner race 19 even if the diaphragm springs 27, 28 are omitted; however, these diaphragm springs are then optional.

FIG. 2 shows a portion of a modified torsion damping apparatus with coaxial flywheels 3, 4, a modified bearing means having an antifriction ball bearing 116 between the two flywheels, and a modified thermal barrier between the antifriction bearing 116 and that portion of the flywheel 4 which is immediately adjacent the outer race 117 of the bearing 116. Such portion of the flywheel 4 has a recess 118 which receives a portion of the outer race 117 as well as portions of two mirror symmetrical insulating rings 125, 126 which constitute component parts of the thermal barrier. The inner race 119 of the antifriction bearing 116 is a press fit on the protuberance or hub 120 of the flywheel 3. The manner in which the flywheel 4 cooperates with the friction clutch (not shown in FIG. 2), and the manner in which the flywheel 3 receives torque from the crankshaft of the engine is or can be the same as shown in FIG. 1. The outer race 117 of the antifriction bearing 116 has circumferentially extending annular chambers in the form of grooves or recesses 117a, 117b which are overlapped in part by the cylindrical sections 125a, 126a and in part by the inwardly extending radial sections 125b, 126b of the respective rings 125, 126. Each of these rings has a substantially L-shaped cross-sectional outline, the cylindrical sections 125a, 126a engage with the peripheral surface of the outer race 117, and the radial sections 125b, 126b extend radially inwardly along the respective end faces of the races 117, 119 and have radially innermost annular portions or lips 125c, 126c which are biased axially against the adjacent end faces of the inner race 119 by two diaphragm springs 127, 128 which respectively react against the a disc 130 and flywheel 4 and bear against the adjacent lips 125c, 126c. The disc 130 has a shoulder for the radially outermost portion of the diaphragm spring 127, and the flywheel 4 has a shoulder for the radially outermost portion of the diaphragm spring 128.

The chambers 117a, 117b respectively receive discrete sealing means in the form of O-rings 145, 146 which cooperate with the lips 125c, 126c and diaphragm springs 127, 128, to prevent penetration of foreign matter into the bearing clearance between the races 117, 119 as well as to prevent the escape of lubricant (e.g., grease) from such clearance. The dimensions of the chambers 117a, 117b and of the O-rings 145, 146 are selected in such a way that the O-rings are at least slightly compressed so as to reliably prevent the escape of lubricant from the clearance for the rolling elements of the antifriction bearing 116.

FIG. 2 further shows that the thickness of the intermediate portion of each of the radial sections 125b, 126b is less than the thickness of the radially outermost or the radially innermost (125c, 126c) portion of each such section. This enhances the elasticity of the radial sections 125b, 126b and enables the diaphragm springs 127, 128 to reliably hold the lips 125c, 126c in sealing contact with the adjacent end faces of the inner race 119. The cylindrical sections 125a, 126a can be a press fit in the recess 118 of the flywheel 4, and they can be assembled with the outer race 117 of the antifriction bearing 116 before the latter is fitted onto the protuberance 120 and before the protuberance 120 is introduced into the recess 118.

The diaphragm spring 127 and/or 128 can be omitted if the corresponding radial section 125b and/or 126b is sufficiently elastic to adequately bear against the respective end face of the inner race 119 when the antifriction bearing 116 is properly mounted on the protuberance 120 of the flywheel 3 and is adequately received in the recess 118 of the flywheel 4. The same applies for the radial sections 25b, 26b of the rings 25, 26 and for the diaphragm springs 27, 28 of the apparatus 1 which is shown in FIG. 1. Thus, all that is necessary is to make the rings 25, 26 and/or 125, 126 of a suitable elastomeric material and to mount these rings in such a way that their radial sections 25b, 26b and/or 125b, 126b are elastically deformed in fully assembled condition of the respective apparatus to adequately bear against the inner race 19 or 119 and to thus prevent escape of lubricant from the clearance between the races 17, 19 or 117, 119.

The O-rings 145 and 146 even further reduce the likelihood of escape of lubricant from the bearing clearance between the races 117 and 119, even if the lubricant is subjected to the action of very pronounced centrifugal forces.

Referring to FIG. 3, there is shown a portion of a further torsion damping apparatus wherein the antifriction bearing 216 between the coaxial flywheels 3 and 4 has an outer race 217 with a frustoconical external or peripheral surface 217' abutting against a complementary frustoconical internal surface 225a' of the tubular section 225a of a split ring-shaped thermal barrier 225. The section 225a has a frustoconical external surface 225a" whose taper is counter to that of the internal surface 225a' and which is in contact with a complementary frustoconical surface in the recess 218 of the flywheel 4. The illustrated section 225a can be replaced with a section having a cylindrical internal surface and a frustoconical external surface or vice versa. The external surface of the outer race 217 or the surface in the recess 218 is then a cylindrical surface.

The diaphragm spring 227 reacts against the disc 230 and biases the ring-shaped thermal barrier 225 in the direction of taper of its frustoconical surfaces 225a', 225a", i.e., in a direction to cause the section 225a to penetrate deeper into the recess 218.

The thermal barrier of FIG. 3 further comprises a first sealing element 226 which is a separately produced washer and extends radially inwardly from the thinnest portion of the cylindrical section 225a along the right-hand end faces of the races 217, 219 and carries at its radially innermost end an annular lip 226c which is biased against the right-hand end face of the race 219 due to innate elasticity of the sealing element 226 or due to the provision of a suitable diaphragm spring (not specifically shown). The radially inwardly extending section 225b of the ring-shaped thermal barrier 225 constitutes a second washer-like sealing element which is adjacent the left-hand end faces of the races 217, 219 and has a radially innermost portion in the form of an annular lip bearing against the adjacent end face of the race 219 under the action of the diaphragm spring 227, i.e., because the spring 227 urges the cylindrical section 225a deeper into the recess 218 of the flywheel 4. The disc 230 is affixed to the flywheel 4, e.g., in a manner as described for the disc 30 of FIG. 1. The sealing elements 226 and 225b flank the antifriction bearing 216 and reduce the likelihood of escape of lubricant from the annular clearance for the rolling elements of the bearing 216. Portions of the sealing elements 226, 225b have reduced thicknesses (see the portion 226b) to enhance their elasticity and to further reduce the likelihood of uncontrolled escape of lubricant from the clearance for the rolling elements. In lieu of spheres, the antifriction bearing 16, 116 or 216 can also employ barrel-shaped or needle-like rolling elements without departing from the spirit of the invention. Furthermore, the antifriction bearing can be provided with two or more rows of antifriction rolling elements.

The material of the ring-shaped thermal barrier 225 and of the sealing element 226 is preferably a good insulator of heat.

The torsion damping apparatus which embodies the structure of FIG. 3 exhibits the advantage that the frustoconical parts 217 and 225 compensate for certain machining tolerances and ensure automatic centering of the antifriction bearing 216 and thermal barrier when the diaphragm spring 227 is caused to bear against the left-hand side of the cylindrical tubular section 225a and radial section or sealing element 225b. Moreover, the structure which is shown in FIG. 3 can automatically compensate for wear upon the parts of the antifriction bearing 216, upon the ring-shaped part 225 of the thermal barrier as well as upon the sealing element 226. The spring 227 ensures that the cylindrical tubular section 225a is wedged in the recess 218 of the flywheel 4, that the outer race 217 is wedged in the cylindrical section 225a, and that the sealing element 226 is adequately held between the outer race 217 and the adjacent shoulder 231 of the flywheel 4 as well as that its lip 226c sealingly engages the right-hand end face of the inner race 219. The provision of a split ring 225 even further ensures adequate wedging of the parts 225, 217 in the recess 218 of the flywheel 4.

It is further within the purview of the invention to provide the improved torsion damping apparatus with a thermal barrier which need not include any prefabricated parts in the form of rings and/or washer-like sealing elements. For example, and as shown in FIG. 4, the thermal barrier 324 can constitute a single piece of thermoplastic or thermosetting material which is injected into the recess 318 of the flywheel 4 around the outer race 317 of the antifriction bearing 316. All that is necessary is to dimension the outer race 317 and the recess 318 in such a way that the surfaces bounding the recess and the surfaces bounding the outer race define an annular space or compartment which can receive flowable plastic material. When the plastic material sets, the resulting thermal barrier 324 adequately fills the space between the race 317 and the surfaces surrounding the recess 318 and impedes or totally prevents the transfer of heat from the clutch disc (not shown) to the antifriction bearing 316. The illustrated plastic thermal barrier 324 can be replaced with a barrier which consists of sintered ceramic or metallic material. In each instance, the thermal barrier is an integral part of the antifriction bearing 316 and/or of the flywheel 4. It is also possible to apply an integral plastic, ceramic or metallic thermal barrier to the inner race and/or outer race of the antifriction bearing 316 before the latter is inserted into the recess 318 or to apply the thermal barrier to the surfaces bounding the recess 318 (so that the thermal barrier becomes an integral part of the flywheel 4) before the antifriction bearing 316 is inserted into the thus obtained thermal barrier in the recess 318.

The injection or another mode of introduction of a flowable plastic, metallic or ceramic material into the space between the surfaces bounding the recess 318 of the flywheel 4 and the exterior of the antifriction bearing 316 is especially advantageous and desirable if the bearing 316 is a commercially available antifriction bearing which is already provided with sealing elements 360 that prevent uncontrolled escape of lubricant from the space between the two races. As mentioned above, all that is necessary is to adequately select the dimensions of the surfaces bounding the recess 318 so as to provide sufficient room for introduction of a flowable material which is to form the thermal barrier 324 and is to be integral with the outer race 317 and/or with the flywheel 4.

The disc 330 is applied subsequent to introduction of the outer race 317 into the recess 318, and the disc 320 is attached to the flywheel 3 to hold the inner race 319 against axial movement.

Referring to FIGS. 6 and 7, there is shown an apparatus 401 which transmits torque from a rotary output element 405 (such as the crankshaft of an internal combustion engine in a motor vehicle) to a rotary input element 410 (e.g., the input shaft of a change-speed transmission in a motor vehicle). In order to render it possible to absorb shocks which develop during transmission of torque, the apparatus 401 comprises a composite flywheel 402 having two coaxial flywheels 403 and 404 which have limited or full freedom of angular movement relative to each other. The flywheel 403 is coaxially secured to the output element 405 by a set of bolts 406 or by other suitable fasteners. The flywheel 404 can transmit torque to the input element 410 by way of a friction clutch 407 whose housing or cover 411 is secured to the flywheel 404 by bolts, screws or like fasteners, not shown. The clutch 407 further comprises a pressure plate 408, a clutch disc 409 whose linings are disposed between a radially extending surface 404a of the flywheel 404 and the pressure plate 408 and whose hub is non-rotatably affixed to the input element 410, and a diaphragm spring 412 which reacts against the cover 411 and bears against the pressure plate 408 to bias the latter against the respective friction lining whereby the other friction lining bears against the surface 404a and the flywheel 404 rotates the input element 410 as long as the friction clutch 407 remains engaged. The diaphragm spring 412 is installed between two ring-shaped seats in the form of wire rings which are supported by the cover 411.

A damper 413 is installed between the flywheels 403 and 404 to yieldably oppose the aforementioned angular movements of the flywheels relative to each other. The apparatus 401 further comprises antifriction bearing means 414 here shown as comprising a ball bearing 415 with a single row of spherical rolling elements 415a between an outer race 416 and an inner race 418. The race 416 extends into an internal annular groove 417 of the flywheel 404, and the race 418 surrounds a hub-shaped central portion or protuberance 419 of the flywheel 403. The protuberance 419 extends axially of the flywheel 404 in a direction away from the output element 405.

The inner race 418 is a press fit on the protuberance 419 and is held against axial movement on such protuberance by a radially outwardly extending shoulder 420 of the flywheel 403 in cooperation with a washer-like retainer 421 which abuts the adjacent end face 422 of the protuberance 419 and is separably affixed to the latter by screws 423 or by analogous fastener means.

In accordance with a feature of the embodiment of FIGS. 6 and 7, the apparatus 401 further comprises a thermal barrier 424 which is interposed between the race 416 of the ball bearing 415 and the flywheel 404 so as to impede or fully prevent the transmission of heat which is generated primarily as a result of frictional engagement of the clutch plate 409 with the surface 404a of the flywheel 404 when the friction clutch 407 is operative to transmit torque from the flywheel 404 to the input element 410 of the change-speed transmission. The purpose of the thermal barrier 424 is to prevent heat, which is generated in response to engagement of the friction clutch 407, from adversely influencing (i.e., from exerting excessive thermal stresses upon) the lubricant (grease) which is used for the rolling elements 415a of the ball bearing 415. Furthermore, the barrier 424 prevents excessive thermally induced deformation and radial expansion of the bearing 415 when the left-hand lining of the clutch disc 409 is in frictional engagement with the surface 404a of the flywheel 404. Excessive radial expansion of the races 416 and 418 could entail a jamming of the rolling elements 415a between the races. The diameter of the surface in the deepmost portion of the recess 417 in the flywheel 404 is selected in such a way that certain parts of the thermal barrier 424 can be installed in such recess and surround the outer race 416 of the antifriction bearing 415.

As can be best seen in FIG. 7, the thermal barrier 424 comprises two substantially or exactly mirror symmetrical rings 425, 426 each of which has a substantially L-shaped cross-sectional outline. The axially extending (annular) portions or legs 425a, 426a of the rings 425, 426 are radially outwardly adjacent the outer race 416 of the ball bearing 415, and the radially inwardly extending (washer-like) portions or legs 425b, 426b of these rings flank the respective end faces of the race 416 and have radially innermost parts or lips 434, 435 which abut the respective end faces 437, 438 of the inner race 418 to thereby oppose angular movements of the race 418 and flywheel 403 relative to the race 416 and flywheel 404. Thus, the lips 434, 435 form part of the thermal barrier 424 as well as of the aforementioned damper 413 between the flywheels 403 and 404.

The radially extending legs 425b, 426b of the rings 425, 426 perform the additional function of confining the lubricant (normally grease) for the rolling elements 415a in the space between the races 416 and 418 of the ball bearing 415. The damping and confining or sealing action of the legs 425b, 426b can be enhanced and maintained at a selected optimum value or within a predetermined optimum range by the provision of means for biasing the lips 434, 435 against the respective end faces 437, 438 of the inner race 418. Such biasing means comprises a first dished spring 427 whose radially outermost portion reacts against an internal shoulder 430a of a disc 430 and whose radially innermost portion bears against the lip 434 of the leg 425b, and a second dished spring 428 whose radially outermost portion reacts against an internal shoulder 431 of the flywheel 404 and whose radially innermost portion bears against the lip 435 of the leg 426b. The disc 430 is affixed to the flywheel 404 by a set of rivets 429.

FIG. 7 shows that the thickness of the median portions of the legs 425b, 426b is reduced so that such median portions constitute two relatively thin and hence more readily flexible membranes 432, 433. The lips 434, 435 are disposed radially inwardly of the respective membranes 432 and 433 and bear against the respective end faces 437 and 438 of the inner race 418 with a force which is determined by the bias of the respective dished springs 427 and 428. The initial stressing of the dished springs 427 and 428 is selected in such a way that the axially oriented force which is applied by the spring 428 exceeds the axially oriented force which is applied by the spring 427. This ensures that the races 416 and 418 tend to move axially and in opposite directions whenever the friction clutch 407 is idle whereby the rolling elements 415a are clamped between the two races. The inner race 418 tends to move to the left, as viewed in FIG. 7, because the bias of the dished spring 428 prevails over that of the dished spring 427.

In order to simplify the assembly of the thermal barrier 424 with the antifriction bearing 415, the annular portions 425a, 426a of the rings 425, 426 are first force-fitted onto the peripheral surface of the outer race 416 before the rings 425, 426 are introduced into the recess 417 of the flywheel 404. The antifriction bearing 415 is maintained in a predetermined axial position with reference to the flywheel 4 404 because the outer side of the properly installed radially extending leg 426b abuts an internal shoulder 431a of the flywheel 404 and the radially outermost portion of the outer side of the leg 425b abuts the adjacent side of the aforementioned disc 430.

The damper 413 between the flywheels 403 and 404 further comprises the aforementioned disc 430 as well as a second disc 440 whose inner diameter is larger than that of the disc 430. The rivets 429 are configurated in such a way that they maintain the discs 430, 440 at a fixed axial distance from the surface 404a of the flywheel 404 as well as from each other. The discs 430, 440 flank (i.e., they are disposed at the opposite sides of) a flange 439 whose radially outwardly extending prongs 439a are secured to the flywheel 403 by rivets 442. The flange 439 and the discs 430, 440 have registering windows for energy storing elements in the form of coil springs 441 whose function is to oppose angular movements of the discs 430, 440 and flange 439 relative to each other.

The arrow 443 denotes in FIG. 6 the direction in which the tips of the radially inwardly extending fingers of the diaphragm spring 412 must be shifted in order to move the radially outermost portion of the diaphragm spring axially and away from the flywheel 404 in order to disengage the friction clutch 407. The force which is applied in the direction of the arrow 443 must overcome the force with which the prestressed spring 412 urges the pressure plate 408 against the respective friction lining of the clutch disc 409. The bias of the springs 427, 428 is selected in such a way that the resulting axial force acting upon the race 418 (namely the difference between the axially applied larger force of the spring 428 and the axially applied smaller force of the spring 427) is smaller than the force which must be applied in the direction of the arrow 443 in order to disengage the clutch 407. This ensures that the spring 428 ceases to urge the inner race 418 axially relative to the outer race 416 when the friction clutch 407 is engaged to transmit torque from the flywheel 404 to the input element 410 of the change-speed transmission. In other words, the rolling elements 415a are not clamped between the races 416 and 418 when the flywheels 403, 404 are to transmit torque from the output element 405 to the input element 410. The just discussed selection of the bias of the springs 412, 427, 428 and of the force which must be applied in the direction of the arrow 443 is desirable and advantageous because this ensures that the rolling elements 415a come into contact with different portions of the tracks which are defined by the races 416 and 418 and also that the angular positions of the rolling elements 415a change with attendant reduction of pronounced localized wear upon the antifriction bearing 415 and the longer useful life of the torque transmitting apparatus 401.

The extent to which the flywheels 403 and 404 can turn relative to each other is determined by the length of circumferentially extending slots in the flange 439. Such slots receive portions of the respective rivets 429.

FIG. 8 shows a portion of a modified torque transmitting apparatus wherein the dished spring 527 which bears upon the bead 534 reacts against the corresponding end face of the outer race 516 and urges the bead 534 against a friction generating washer 503b so that the latter bears against a shoulder 503a of the flywheel 503. Thus, the spring 527 is disposed between the median portion or membrane of the radially extending leg 525b of the ring 525 and the respective end faces of the races 516 and 518. The washer 503b can be made of steel and is preferably mounted in such a way that it cannot rotate relative to the flywheel 503. The construction which is shown in FIG. 8 ensures that the axially oriented force which is generated by the spring 527 is added to the axially oriented force which is generated by the spring 528 so as to urge the inner race 518 axially of the outer race 516 when the friction clutch (not shown in FIG. 8) is disengaged i.e., the races 516 and 518 then clamp the rolling elements 515a of the antifriction bearing 515. The leg 525b is integral with the axially extending annular leg 525a of the ring 525. The ring 526 has an axially extending portion 526a and the radially extending leg 526b with bead 535. The rings 525, 526 are installed in the flywheel 504.

An important advantage of the torque transmitting apparatus of FIGS. 6-8 is that the thermal barrier 424 of FIGS. 6-7 or the barrier of FIG. 8 can also serve as (or as a component part of) a means for opposing angular movements of the flywheels 403 and 404 or 503 and 504 relative to each other. This contributes to simplicity, compactness and lower cost of the apparatus. The rings 425, 426 or 525, 526 and the springs 427, 428 or 527, 528 can constitute the sole means for frictionally damping the angular movements of the flywheel 403 or 503 relative to the flywheel 404 or 504 and/or vice versa. This entails a substantial reduction of the overall number of component parts of the torque transmitting apparatus and simplifies the assembly and/or dismantling of such apparatus. If the improved thermal barrier 424 or the barrier of FIG. 8 constitutes the sole means for functionally damping the angular movements of the flywheels 403 or 503 and 404 or 504 relative to each other, the conventional damper or dampers can be omitted in their entirety. On the other hand, if the apparatus comprises one or more conventional dampers plus the thermal barrier which also serves as or includes a means for opposing angular movements of the flywheels 403, 404 or 503, 504 relative to each other, the damping action can be enhanced by a unit (the improved torque transmitting apparatus) which also performs another important, desirable and advantageous (thermal insulating) function. It has been found that the improved thermal barrier (either alone or in combination with one or more conventional dampers) can ensure an ideal or nearly ideal progress of the damping action. Proper thermal insulation of the lubricant (normally grease) in the annular space between the races 416, 418 or 516, 518 of the antifriction bearing 415 or 515 contributes significantly to a longer useful life of the entire apparatus, and such insulation also reduces the need for frequent inspection of the bearing. Proper lubrication of the tracks which are defined by the races 416, 418 or 516, 518 and of the rolling elements 415a or 515a is one of the most important factors insofar as the useful life of the bearing means (and hence of the entire torque transmitting apparatus) is concerned.

The apparatus of FIGS. 6-8 can be simplified still further by omitting the spring 427 and/or 428 of FIGS. 6-7 and/or the spring 527 and/or 528 of FIG. 8. All that is necessary is to ensure that the rings 425, 426 or 525, 526 are made of a material which exhibits a requisite degree of springiness so that the radially extending arms 425b, 426b or 525b, 526b bear against the respective end faces of the race 418 or 518 and/or directly against the flywheel 403 and/or against a part (such as 503b) which rotates with the flywheel 503 when the improved thermal barrier is properly installed between the friction clutch and the bearing 415 or 515, normally between the flywheel 404 or 504 and the respective race (416 or 516) of the bearing means. The utilization of dished springs or otherwise configurated biasing means is often preferred because such springs ensure a more predictable generation of friction between the ring or rings of the thermal barrier and the flywheel 403 or 503. The springs 427, 428 or FIG. 7 further ensure an even more reliable sealing of both axial ends of the annular space which is defined by the races 416, 418 and serves for reception of the rolling elements 415a.

The improved thermal barrier can operate satisfactorily with a single ring 425, 525 or 426, 526. The utilization of two rings is preferred at this time because two rings ensure a more satisfactory sealing of the aforediscussed annular space between the races 416, 418 or 516, 518, because two rings can establish a highly satisfactory thermal barrier between the flywheel 404 or 504 and the bearing 415 o 515, and also because two rings (especially when used with two discrete dished springs or the like) can provide a highly satisfactory damping action by opposing the angular movements of the flywheels 403, 404 or 503, 504 relative to each other.

FIGS. 9 and 10 show an apparatus 601 for controlled transmission of torque from the crankshaft 605 (indicated by phantom lines) of the internal combustion engine to the input shaft 610 (shown by phantom lines) of the change-speed transmission in a motor vehicle. The apparatus 601 comprises a composite flywheel 602 including coaxial first and second components 603, 604 which are rotatable relative to each other within predetermined limits. The component 603 is coaxially secured to the crankshaft 605 by a set of bolts 606, and the component 604 carries the housing or cover 611 of a friction clutch 607 whose clutch disc or clutch plate 609 has a hub which is non-rotatably secured to the input shaft 610. The component 603 drives the input shaft 610 in response to engagement of the clutch 607 in a manner not forming part of the present invention. FIG. 9 shows an axially movable pressure plate 608 which is normally biased toward the component 604 by a diaphragm spring 612 tiltably mounted at the inner side of the housing 611. The clutch plate 609 carries linings which are in frictional engagement with the adjacent surface of the pressure plate 608 and with an annular friction surface 604a of the component 604 when the clutch 607 is engaged, namely when the component 603 drives the input shaft 610 through the medium of the component 604 and clutch plate 609.

The apparatus 601 further comprises means for yieldably opposing angular movements of the components 603 and 604 relative to each other. Such opposing means comprises a first damping unit 613, a second damping unit 614 in series with the unit 613, and a friction generating device 613a. The exact construction of the units 613, 614 and friction generating device 613a forms no part of the present invention. Reference may be had to the aforementioned copending applications of the assignee and to the embodiments of FIGS. 1-8.

The apparatus 601 still further comprises bearing means 615 including at least one radial antifriction bearing 616 having an outer race 617, an inner race 619 and an annulus of spherical rolling elements 616a between the two races. The outer race 617 is disposed in an axial recess or bore 618 of the component 604, and the inner race 619 is preferably a press-fit on a centrally located cylindrical protuberance 620 of the component 603. The protuberance 620 extends axially in a direction away from the crankshaft 605 and into the bore 618 of the component 604. The inner race 619 abuts a stop in the form of a shoulder 621 of the protuberance 620 and is held against axial movement away from such shoulder by a disc-shaped retainer 622 which is secured to the adjacent end face 620a of the protuberance 620 by a set of screws 623 or other suitable fasteners.

The apparatus 601 also comprises a number of means for impeding or preventing the transmission of heat between the friction surface 604a and the radial antifriction bearing 616. The latter is disposed radially inwardly of the friction linings on the clutch plate 609. One of the heat transmission preventing or impeding means comprises a thermal barrier 624 composed of two coaxial rings 625 and 626 each having a substantially L-shaped cross-sectional outline. The axially extending (cylindrical) portions 625a, 626a of the rings 625, 626 surround the major part of the external surface of the outer race 617 and are received in the bore 618 of the second component 604. The radially extending (washer-like) portions 625b, 626b of the rings 625, 626 are adjacent the respective end faces of the races 617, 619 and are biased against the corresponding end faces of the inner race 619 by energy storing elements in the form of diaphragm springs 627, 628, respectively. The radially extending portions 625b, 626b not only intercept some of the heat but also serve to seal the space between the races 617, 619 so as to prevent uncontrolled escape of grease for the rolling elements 616a. The radially outermost portion of the diaphragm spring 627 reacts against a shoulder of a disc 630 which is affixed to the component 604 by rivets 629, and the radially innermost portion of the spring 627 bears against the radially innermost part of the portion 625b. The diaphragm spring 628 has a radially outermost portion which reacts against an internal shoulder of the component 604 and a radially innermost portion which bears against the radially innermost part of the portion 626b. The diameter of the surface surrounding the bore 618 is sufficiently large to allow for the placing of rings 625, 626 onto the outer race 617 in a manner as shown in FIG. 9. The material of the rings 625, 626 is selected in such a way that they constitute a thermal insulator which impedes the transfer of heat between the friction surface 604a of the component 604 and the radial bearing 616. The bearing 616 is held against axial movement relative to the component 604 by the rings 625, 626 in that the ring 625 abuts the disc 630 and the ring 626 abuts an internal shoulder 631 of the component 604. As mentioned before, the rivets 629 fix the disc 630 to the component 604.

The damping unit 613 comprises the aforementioned disc 630 and a second disc 633. The discs 630, 633 are disposed at the opposite sides of a flange 632 and are held (by the rivets 629) against axial movement relative to each other and relative to the component 604. The flange 632 has windows (not specifically referenced) which register with windows in the discs 630, 633 and serve to receive energy storing elements in the form of coil springs 634. The coil springs 634 yieldably oppose angular movements of the flange 631 and discs 630, 633 relative to each other. The flange 632 is rotatable relative to the component 604, together with the component 603.

The friction generating device 613a can be said to constitute a part of the damping unit 613 and is designed to resist each and every angular movement of the components 603 and 604 relative to each other. This friction generating device is installed between the disc 630 and the component 603 and comprises an energy storing device in the form of a diaphragm spring 635 which reacts against the disc 630 and bears upon a ring 636. The ring 636, in turn, urges a washer 637 against the component 603. The force which is transmitted by the diaphragm spring 635 to the disc 630 is taken up by the radial bearing 616.

The flange 632 is the input member of the damping unit 613 as well as the output member of the damping unit 614. The input member of the damping unit 614 includes two axially spaced-apart discs 638, 639 which are non-rotatably secured to the component 603. The disc 639 is affixed to the component 603 by rivets 640. The periphery of the disc 638 is provided with integral projections in the form of axially extending lugs 638a which extend into complementary recesses 641 of the disc 639. This ensures that the discs 638, 639 can move axially toward and away from each other but cannot perform any angular movements with respect to one another. The flange 632 has radially extending arms or teeth 642 which are clamped between the discs 638 and 639. For this purpose, the discs 638, 639 are biased toward each other by a diaphragm spring 643. The spring 643 reacts against the component 603 and bears upon the disc 638 in a direction to urge the disc 638 toward the disc 639. The discs 638, 639 have windows which register with each other and with tooth spaces between the arms 642 and serve to receive energy storing elements in the form of coil springs 644.

In accordance with a feature of the invention which is shown in FIGS. 9 and 10, the component 604 is provided with axially extending passages 645 which are disposed between the bore 618 for the radial bearing 616 and the friction surface 604a of the component 604, as considered in the radial direction of the composite flywheel 602. The passages 645 serve to prevent the transfer of substantial quantities of heat from the friction surface 604a of the component 604 to the bearing 616. As can be seen in FIG. 10, the passages 645 can constitute slots which are elongated in the circumferential direction of the component 604 and together form an annulus whose diameter 650 is smaller than the minimum diameter of the friction surface 604a but greater than the diameter of the surface surrounding the bore 618 of the component 604. The passages 645 are preferably adjacent, and most preferably closely adjacent, the bearing 616.

In accordance with a presently preferred embodiment of the invention, the cross-sectional areas of the passages 645 increase in a direction from a surface 646 radially inwardly of the friction surface 604a toward an additional surface 647 of the component 604 opposite the friction surface 604a. The surface 647 faces the damping units 613 and 614. The component 604 has internal surfaces which surround the passages 645 and each of which includes a first or inner portion 648 nearer to the common axis of the components 603, 604 and extending in at least substantial parallelism with such axis, and a second or outer portion 649 which is more distant from the common axis of the components 603, 604 and diverges radially outwardly away from the common axis toward the periphery of the component 604. At least a portion of each surface portion 649 has a substantially convex outline as can be readily seen in the lower portion of FIG. 9. The shallow leftmost portion of each passage 645 is provided in the second surface 647 of the component 604 and extends radially at least along a portion (x) of the width of the friction surface 604a as considered in the radial direction of the flywheel 602. The surfaces bounding the passages 645 resemble those of air circulating vanes or blades on an air impeller and cause streams of air to flow through the passages 645 in a direction from the friction surface 604a toward the additional surface 647 of the component 604. This entails a pronounced cooling of the entire flywheel 602 and greatly reduces the amount of heat which is transmitted from the friction surface 604a to the bearing 616. Thus, that portion of the component 604 which is formed with the passages 645 can be said to constitute a thermal barrier which impedes the transfer of heat from the surface 604a to the antifriction bearing 616. In addition, streams of air flowing through the passages 645 effect a substantial cooling of component parts of the damping means 613, 614, 613a because such streams flow along the discs 633 and 639 and a portion of each such stream can escape, for example, through the windows of the discs 630, 633 and flange 632. As mentioned before, such windows are provided for the energy storing springs 634.

FIG. 10 shows that the rivets 629 form an annulus whose diameter equals or approximates the diameter 650 of the circle formed by the annulus of passages 645. FIG. 10 further shows that each fastener 629 alternates with pairs of slit-shaped passages 645 which have identical lengths. The length of each of the webs 652 through which the fasteners 629 extend exceeds the length of a passage 645. For example, the length of a web 652 (as measured in the circumferential direction of the component 604) can be between 0.5 and 2.5 times the length of a passage 645. In the embodiment which is shown in FIGS. 9 and 10, the component 604 is provided with two sets of webs, namely the aforementioned relatively long webs 652 which carry the rivets 629 and shorter webs 651 which alternate with the longer webs 652. Any heat which is generated at the friction surface 604a and is to reach the antifriction bearing 616 must be transmitted through the webs 651 and 652. Such webs can be said to constitute small heat barriers because they are being cooled by streams of air flowing through the passages 645. That (innermost) portion of the component 604 which defines the bore 618 and surrounds the radial bearing 616 is denoted by the character 653. The portion 653 is surrounded by the annulus of passages 645 and by the webs 651 and 652 of the component 604. The length of a web 652 can equal or approximate the combined length of two shorter webs 651 (as measured in the circumferential direction of the radially innermost portion 653 of the component 604). The length of a passage 645 can equal or exceed (at least slightly) the length of a shorter web 651.

The combined length of the passages 645 (in the circumferential direction of the component 604) can be between 20 and 70% of the total length of the corresponding portion of the component 604. In the embodiment of FIGS. 9 and 10, the combined length of the passages 645 can be at least 50% of the circumferential length of the corresponding portion of the component 604. In other words, at least one-half of the circle whose diameter is shown at 650 can extend through the passages 645.

It is also within the purview of the invention to increase the length of the passages 645. For example, if the radial bearing 616 can stand reasonably pronounced thermal stresses, or if the transmission of pronounced thermal stresses is impeded in another way, the length of the illustrated passages 645 can be increased as shown in FIG. 10 at 654, i.e., the shorter webs 651 can be omitted so that the rivets 629 alternate with relatively long passages each of which can extend along an arc in excess of 45 degrees. For example, the component 604 can be provided with four relatively long passages 645 which alternate with four webs 652, and each web 652 is traversed by at least one fastener in the form of a rivet 629.

Since the webs 651 and/or 652 constitute relatively narrow portions of the component 604 and alternate with passages 645, they act not unlike restrictors or throttles to the transmission of heat from the friction surface 604a toward the bearing 616. Thus, the corresponding portion of the component 604 is cooled by streams of air flowing through the passages 645, and the webs 652 constitute restrictors in that they oppose the transmission of heat to the radial bearing 616 so that the useful life of such bearing is much longer than in conventional apparatus. In view of the aforediscussed distribution of material of the component 604 in the region of the circle whose diameter is shown at 650, and in view of the distribution of passages 645 in the form of an annulus which is disposed between the friction surface 604a and the radially innermost portion 653 of the component 604 (i.e., radially outwardly of the bearing 616), heat which is generated in response to engagement of the friction clutch 607 can entail some rise in the temperature of the radially innermost portion 653 but not to a value which could entail damage to the bearing 616. The feature that the bearing 616 is not subjected to excessive thermal stresses is attributable, to a considerable extent, to the fact that the major part of the mass of the component 604 is located radially outwardly of the passages 645.

The placing of rivets 629 into the webs 652 exhibits the advantage that the rivets dissipate substantial quantities of heat which would otherwise pass through the webs 652 and into the radially innermost portion 653 of the component 604. Moreover, the rivets 629 transmit heat to the discs 630, 633 which dissipate such heat into the surrounding atmosphere. In other words, the rivets 629 ensure that a substantial percentage of heat which would have passed through the webs 652 and into the portion 653 is transmitted to parts (630, 633) having large exposed surfaces to ensure rapid dissipation of transmitted heat to atmospheric air.

The heat barrier 624 including the rings 625, 626 constitutes an optional feature of the apparatus of FIGS. 9-10. Thus, if the bearing 616 is furnished with conventional sealing rings, the rings 625, 626 can be omitted and the bearing 616 can be fully assembled on the component 603 before the component 603 is assembled with the component 604. In such apparatus, the outer race 617 of the bearing 616 is or can be a press-fit in the bore 618 of the component 604. The just described mounting of the bearing 616 in the bore 618 (without the rings 625, 626) reduces the initial cost and simplifies the assembly of the apparatus 601.

The passages 645 are provided in addition to those passages which are desirable or necessary in the component 604 for other purposes, for example, to facilitate assembly of the apparatus 601 by providing paths for the tool which is to rotate the bolts 605 and/or other tools. It is also known to provide the components of a composite flywheel with openings for withdrawal of lubricant and for other purposes. The passages 645 are provided for the specific purpose of reducing the transfer of heat between the antifriction bearing which is interposed between the components of the flywheel and the friction surface of the component which comes into contact with the linings of the clutch plate 609. The passages 645 extend all the way between the surfaces 604a and 647 of the component 604 so as to ensure the aforedescribed desirable circulation of air streams and attendant cooling of the corresponding portion of the component 604 radially outwardly of the portion 653 which supports and surrounds the outer race 617 of the antifriction bearing 616. It has been found that the passages 645 contribute significantly to the useful life of the bearing 616 because the bearing is shielded from excessive thermal stresses which develop when the friction clutch 607 is actuated and which are likely to rapidly destroy the bearing in the absence of any remedial measures in addition to those which are already known in the art. The provision of passages 645 is particularly desirable in apparatus which employ antifriction bearings whose components are assembled with a minimum of play so that pronounced and rapid heating or cooling of such bearings could entail extensive thermally induced distortion and attendant jamming of the parts. In fact, such excessive thermally induced distortion can lead to seizing with immediate destruction of the bearing. The streams of air which flow through the passages 645 further ensure adequate cooling of lubricant for the rolling elements 616a of the bearing 616 regardless of whether such lubricant is oil or grease. Adequate cooling (or prevention of overheating) of the lubricant also prolongs the useful life of the bearing 616.

The passages 645 can be configurated in a number of different ways without departing from the spirit of the invention. It has been found that elongated passages in the form of arcuate slots are particularly advantageous because they ensure the flow of large quantities of air and reduce the combined length of webs 652 or webs 651, 652. The aforedescribed configuration of surfaces 648, 649 which surround the passages 645 is desirable and advantageous because such surfaces act not unlike the surfaces of vanes or blades and ensure forced circulation of air in the region of the circle including the diameter 650. The placing of passages 645 close to the radially innermost portion 653 of the component 604 also contributes to a more reliable prevention of overheating of the bearing 616. The provision of relatively shallow recesses which are provided in the surface 647 and constitute the radially outermost portions of the passages 645 ensures that a large percentage of air which is heated during flow through the passages is caused to flow radially outwardly and away from the bearing 616. The surfaces surrounding the passages can be said to constitute a radial fan which draws air from the space radially inwardly of the friction surface 604a and causes streams of air to flow first axially and thereupon radially outwardly toward the periphery of the component 604. This effectively reduces the likelihood of flow of large quantities of heated air toward the bearing 616. The aforementioned configuration (convexity) of the surface portions 649 in the passages 645 also contributes to a desirable flow of heated air radially outwardly and away from the radially innermost portion 653.

While it is possible to provide the passages 645 in non-uniform or irregular distribution, a uniform or regular distribution is preferred at this time because it ensures predictable cooling of each and every portion of the component 604 in the region of the webs 651 and 652.

As mentioned before, the mass of the component 604 radially outwardly of the passages 645 is much larger than the mass of the radially innermost portion 653. Since the flow of heated air is radially outwardly, eventual heating of the major part of the component 604 radially outwardly of the passages 645 does not entail an overheating of the portion 653 and bearing 616.

The streams of air which flow through the passages 645 bring about a desirable cooling of the elements of the damping means 613, 613a, 614. This prolongs the useful life of such damping means and hence the useful life of the entire apparatus. Moreover, the streams of air can adequately cool the first component 603 of the composite flywheel 602.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the appended claims.

Claims

1. Apparatus for compensating for variations of torque, especially for fluctuations of torque which is transmitted between a combustion engine and an input means of a transmission, comprising at least two flywheels which are rotatable relative to each other, one of which is connectable with the engine and the other of which is connectable with the input means of the transmission and carries a disengageable friction clutch; antifriction bearing means interposed between said flywheels; a substantially disc-shaped member non-rotatably connected with said other flywheel; and damper means arranged to oppose rotation of said flywheels relative to each other, said damper means at least comprising energy storing means acting in the circumferential direction of said flywheels, and a friction generating device which is disposed between said flywheels, said friction generating device operating with friction axially between said member and said one flywheel and comprising a friction ring and a stressed energy storing element acting in the axial direction of said flywheels.

2. The apparatus of claim 1, wherein the stressing of said energy storing element of said friction generating device is such that said energy storing element exerts a force having a component acting against said other flywheel in a direction at least substantially counter to the direction of action of force which is to be applied to disengage the friction clutch.

3. The apparatus of claim 1, wherein said energy storing element reacts against said antifriction bearing means.

4. The apparatus of claim 1, wherein said other flywheel has a shoulder and said antifriction bearing means is disposed between said shoulder and said member in a predetermined axial position relative to said flywheels.

5. The apparatus of claim 4, wherein said antifriction baring means comprises an inner race and an outer race surrounding said inner race, and further comprising a thermal barrier between said antifriction bearing means and said other flywheel, said thermal barrier comprising heat-insulating rings each having a substantially L-shaped cross-sectional outline and each including an annular portion surrounding said outer race and a radially extending portion sealingly engaging said inner race.

6. The apparatus of claim 5, wherein one of said heat-insulating rings is adjacent said member and another of said heat-insulating rings is adjacent said shoulder.

7. The apparatus of claim 1, wherein said member includes a portion which is adjacent said antifriction bearing means and is disposed at a first radial distance from the axes of said flywheels, said friction generating device being disposed at a second radial distance from said axes and said second distance at least approximating said first distance, said friction generating device engaging said portion of said member.

8. The apparatus of claim 1, wherein said one flywheel comprises an axial protuberance having an external shoulder and an end face, and further comprising a disc at said end face, said antifriction bearing means including a race disposed between said shoulder and said disc.

9. Apparatus for compensating for variations of torque, especially for fluctuations of torque which is transmitted between a combustion engine and an input means of a transmission, comprising a first and a second flywheel, said flywheels being rotatable relative to each other, said first flywheel being connectable with the engine and said second flywheel being connectable with the input means of the transmission; a friction clutch carried by one of said flywheels; antifriction bearing means between said flywheels; damper means arranged to oppose rotation of said flywheels relative to each other and including series-connected first and second dampers, at least one of said dampers having energy storing means acting in the circumferential direction of said flywheels; and a disc non-rotatably connected with said one flywheel to maintain said bearing means in a predetermined axial position relative to said one flywheel, said disc having means for stressing said energy storing means.

10. The apparatus of claim 9, wherein said one flywheel has a shoulder and said antifriction bearing means abuts said shoulder and said disc.

11. Apparatus for compensating for variations of torque, especially for fluctuations of torque which is transmitted between a combustion engine and an input means of a transmission, comprising at least two flywheels including first and second flywheels, said flywheels being rotatable relative to each other, said first flywheel being connectable with the engine and said second flywheel being connectable with the input means of the transmission; a friction clutch carried by one of said flywheels; a damper device arranged to oppose rotation of said flywheels relative to each other and consisting at least of energy storing elements acting in the circumferential direction of said flywheels; an antifriction bearing disposed between said first and second flywheels and axially secured by said one flywheel, said bearing having an inner race and an outer race and said one flywheel having a first shoulder; a disc-shaped member form-lockingly and nonrotatably connected with said one flywheel, said outer race being confined between said first shoulder and said disc-shaped member and the other of said flywheels having a second shoulder engaged by said inner race and provided on a protuberance of said other flywheel, said protuberance extending from an output element of the engine; a sheet metal member; and fastener means securing said sheet metal member to said other flywheel, said sheet metal member including a radially outer portion and said inner race being secured between said radially outer portion and said second shoulder.

12. The apparatus of claim 11, further comprising a thermal insulator having means for at least reducing the transfer of heat between said one flywheel and said bearing.

13. Apparatus for compensating for variations of torque, especially for fluctuations of torque which is transmitted between a combustion engine and an input means of a transmission, comprising at least two flywheels including first and second flywheels, said flywheels being rotatable relative to each other, said first flywheel being connectable with the engine and said second flywheel being connectable with the input means of the transmission; a damper device arranged to oppose rotation of said flywheels relative to each other and consisting at least of energy storing elements acting in the circumferential direction of said flywheels; a friction clutch carried by one of said flywheels; an antifriction roller bearing disposed between said flywheels and axially fixed by said one flywheel; a substantially disc-shaped member; and means for form-lockingly and nonrotatably connecting said member to said one flywheel radially inwardly of said energy storing elements, said one flywheel having a shoulder and said bearing being confined between said shoulder and said member.

14. The apparatus of claim 13, further comprising a thermal insulator having means for at least reducing the transfer of heat between said one flywheel and said bearing.

15. The apparatus of claim 14, wherein said means for at least reducing the transfer of heat comprises at least one insulating ring which is disposed between said substantially disc-shaped member and said shoulder, said at least one insulating ring having a first section surrounding an outer race of said bearing and at least one second section extending substantially radially inwardly of said first section toward an inner race of said bearing.

16. The apparatus of claim 15, wherein said at least one second section includes a portion in sealing engagement with said inner race.

17. The apparatus of claim 15, wherein said at least one second section is resilient and bears against said inner race.

18. The apparatus of claim 15, further comprising means for biasing said at least one second section against said inner race, said biasing means comprising a diaphragm spring.

19. The apparatus of claim 14, wherein said bearing includes an outer race and further comprising a seal between said insulator and said outer race.

20. Apparatus for compensating for variations of torque, especially for fluctuations of torque which is transmitted between a combustion engine and an input means of a transmission, comprising at least two flywheels including a first and a second flywheel, said flywheels being rotatable relative to each other, said first flywheel being connectable with the engine and said second flywheel being connectable with the input means of the transmission; a friction clutch carried by one of said flywheels; damper means arranged to oppose rotation of said flywheels relative to each other and comprising energy storing elements acting in the circumferential direction of said flywheels; an antifriction bearing between said flywheels; a thermal insulator having means for at least reducing the transfer of heat between said bearing and said one flywheel; and a disc nonrotatably connected with said one flywheel to axially secure said bearing on said one flywheel, said disc having means for stressing said energy storing elements.

21. The apparatus of claim 20, wherein said means for at least reducing the transfer of heat comprises at least one insulting ring between said disc and a shoulder of said one flywheel, said at least one insulating ring having a first section surrounding an outer race of said bearing and at least one second section extending substantially radially inwardly of said first section toward an inner race of said bearing.

22. The apparatus of claim 21, wherein said at least one second section includes a portion in sealing engagement with said inner race.

23. The apparatus of claim 21, wherein said at least one second section is resilient and bears against said inner race.

24. The apparatus of claim 21, further comprising means for biasing said at least one second section against said inner race, said biasing means comprising a diaphragm spring.

25. The apparatus of claim 20, wherein said bearing includes an outer race and further comprising a seal between said insulator and said outer race.