GB2320954A - Dual-mass flywheel assembly - Google Patents

Abstract

A flywheel assembly comprises a first flywheel (1) connected to an input drive, a second flywheel (24) engaging it through a torsional vibration damper (13) and allowed limited relative angular movement in relation to the first and a damping device (105) which contains at least one vibration damper (50), by means of which a frictional connection between the two flywheels can be produced under predetermined conditions of operation. The frictional connection is produced at a predetermined position of an engaging or withdrawal mechanism of a friction clutch (32) associated with the flywheel assembly, the engaging or withdrawal mechanism having an additional travel in at least one direction of movement in which it is operative to actuate an actuating device (62) to actuate the vibration damper (50).

Description

FLYWHEEL ASSEMBLY The invention relates to a flywheel assembly of the kind comprising a first flywheel adapted to be connected to an input drive, a second flywheel engaging the first flywheel through a torsional vibration damper and able to move through a limited angular distance relative to the first flywheel, and a damping device including at least one vibration damper adapted to produce a frictional connection between the two flywheels under predetermined operating conditions.

A flywheel assembly of the kind set forth for a motor vehicle is known for example from DE-A-39 41 251, in which the torsional vibration damper comprises a torsion spring arrangement and a friction device. The vibration damper of the damping device is actuated at a predetermined speed, preferably at the speed corresponding to the resonance speed to be passed through in the starting and gear-changing sequences of the engine, in such a way that a predetermined torque is transmitted from the first to the second flywheel. This means that when passing through the resonance speed extreme relative angular movements between the two flywheel can be suppressed by means of the frictional effect of the vibration damper, thereby preventing the springs of the torsion spring arrangement connected between the two flywheels becoming "solid" and thus possibly being damaged. The amount of frictional torque exerted between the two flywheels by the vibration damper can, according to the published specification, be selected as required, and it can be set by the selection of an axial spring which bears on the vibration damper and by the withdrawal force exerted on a housing of a friction clutch associated with the flywheel assembly. However, when the axial spring for the vibration damper is installed in the clutch it can no longer adjust the characteristics of the vibration damper. This is because the withdrawal force by which an actuating device, such as a diaphragm spring, is loaded on withdrawal is dependent on the diaphragm spring and consequently acts with a constant force on the clutch housing urging it axially towards the axial spring.

This known flywheel assembly has a so-called "dry" construction. In contrast DE-A-41 28 868 shows a flywheel assembly in which a circumferentially-acting torsional vibration damper provided between the two flywheels is arranged within a sealed chamber filled with viscous medium, which provides a speed-proportional damping of any relative rotation between the two flywheels.

Because of this the circumferential region is provided with a torsion spring arrangement having extremely long-stroke springs. This torsion spring arrangement can make the resonance frequency of the flywheel assembly very close to the starting speed of the input drive, such as an internal combustion engine, so that on passing through the resonance frequency during starting the energy introduced by the drive is too small to produce any damage to the flywheel assembly. As this low resonance frequency is passed through during starting it clearly lies below the idling speed, and so will not be reached during continued operation of the drive.

Accordingly, a flywheel assembly with a chamber for viscous medium does not need to have an additional vibration damper acting between the two flywheels, but because of the presence of the chamber it is substantially larger than the "dry" version mentioned above and furthermore the chamber must be sealed, making the construction substantially more expensive.

For damping torsional vibration it is known to combine a friction clutch with a device which positions an engaging or withdrawal device through an actuating drive of an automatic clutch. Such a device is illustrated and described in DE-A36 24 755. The actuating drive is controlled in such a way that torsional vibrations which give rise to noise are damped by a predetermined amount of slip between friction linings of the clutch plate and the associated clutch elements. A disadvantage of this way of operating a friction clutch is that the operating range in which slip takes place in order to damp vibrations is relatively large. Since the operating range includes higher torque loading, the result is rapid lining wear and a marked generation of heat.

The invention is based on solving the problem of constructing a flywheel assembly of the kind set forth in such a way that it takes up minimum space, has a simple and cheap construction and a low energy vibration damper, and a damping device which can be operated without the danger of damage at resonance speed.

According to the present invention, in a flywheel assembly of the kind set forth the frictional connection between the two flywheels is produced at a predetermined position of an engaging or withdrawal mechanism of a friction clutch associated with the flywheel assembly, the engaging or withdrawal mechanism having an additional travel in at least one direction of movement, the additional travel being in addition to that necessary for engagement or withdrawal, the mechanism being operative in the additional travel to actuate an actuating device to activate the vibration damper.

Thus, it is simply the travel of the actuating device and thereby of the engaging or withdrawal mechanism in the additional travel which actuates the vibration damper. This results in a particularly simple damping device by which torsional vibrations on passing through a resonance frequency are effectively suppressed.

Preferably, the friction clutch has actuating means whose state of deformation is dependent on the axial position of the engaging or withdrawal mechanism, and a predetermined range of deformation of the actuating means is associated with the additional travel of the engaging or withdrawal mechanism. This means that the actuating means are also used to activate the vibration damper.

By the arrangement of the additional travel on the end of the travel of the engagement or withdrawal mechanism for disengagement the vibration damper is activated before engagement of the clutch.

In contrast, if the additional travel is at the other end of the engaging or withdrawal travel the vibration damper is only activated after the engaged condition has been reached.

If the additional travel of the actuating device, engaging or withdrawal mechanism or actuating means lies outside the travel necessary for the engaging or withdrawal sequence, the vibration damper does not necessarily have to be activated on each engaging or disengaging sequence.

It may only be activated when actually necessary.

Where the engaging or withdrawal mechanism is moved by the actuating device which acts as the actuating drive of an automatic clutch system, the actuating device only activates the vibration damper at the start or finish of the driving operation. Where the engaging or withdrawal mechanism is moved by a clutch pedal, the pedal may have an additional travel which is only utilised by the driver by appropriate movement of the pedal at the start or finish of the driving operation.

The vibration damper preferably comprises at least one damper element projecting beyond one flywheel and capable of being brought into engagement with the other flywheel by substantially axial movement by means of the actuating device.

There are various advantageous embodiments of the damping device in which the vibration damper may have a damper element such as a thrust rod, or a claw, or the actuating means may form the damper element.

Where the activation of the vibration damper takes place through the actuating means, it is of advantage if the actuating means is held by a wear compensating arrangement in a constant position in relation to the clutch housing and the second flywheel which carries this clutch housing. Such a wear compensating arrangement is known for example from DE-A-43 37 613.

For activation of the vibration damper between the flywheels the actuating device co-operates with the actuating means to reduce the force exerted by the actuating means through a pressure plate on a clutch plate and to activate a second vibration damper on the occurrence of torsional vibrations.

This makes it possible to regulate or control the actuating drive of an automatic clutch system within the travel available for engagement or withdrawal in such a way that the associated actuating means, such as a diaphragm spring in the clutch housing or a withdrawal mechanism acting on a diaphragm plate mounted on the clutch housing, is set so that the friction linings of the clutch plate are pressed against the associated elements of the clutch with a predetermined amount of slip, so that the friction damps torsional vibrations introduced from the input drive, and the connection between the clutch plate an elements of the friction clutch is accordingly effective as a second vibration damper. This damper is preferably activated in the speed range above the resonance speed of the flywheel assembly.

If the torsional vibrations which are introduced become so large that they themselves can no longer be damped on maximum slip between the friction linings of the clutch plate and the associated elements of the clutch, the actuating device acts on the actuating means through the engaging or withdrawal mechanism in such a way that on release of the pressure plate from the clutch plate the engaging or withdrawal mechanism causes at least a transitory interruption in torque transmission. This interruption is preferably applied during a predetermined time interval, after which renewed engagement is possible without the danger of destruction of the friction linings on the clutch plate.

Various embodiments of the invention are illustrated by way of example, in the accompanying drawings in which: Figure 1 shows a flywheel assembly with an actuating drive of an actuating device acting on a withdrawal mechanism and a damping device which has a push rod as a vibration damper; Figure 2 shows the damping device of Figure 1 on a larger scale; Figure 3 is like Figure 2 but with a direct drive as the actuating device on the housing of a friction clutch; Figure 4 is like Figure 2 but with a damping device having the actuating means of the friction clutch as the vibration damper; Figure 5 is like Figure 2 but with a damping device containing a claw as the vibration damper; Figure 6 shows a switching device in the form of a regulating arrangement; and Figure 7 is like Figure 6 but in the form of a control arrangement.

The flywheel assembly shown in Figure 1 is associated with a friction clutch 32 and is for a motor vehicle. The assembly has a first flywheel 1 and a second flywheel 24. The first flywheel 1 comprises a primary disc 2 connected to a hub 3, which is detachably mounted on the crankshaft 4 of a drive, not shown, for example an internal combustion engine of the vehicle. The primary disc 2 is provided in the region of its outside diameter with a ring 5 which has a substantially cylindrical inside wall 6. Substantially parallel to the primary disc 2 and axially spaced from it is a cover plate 7 which is rigidly secured to the ring 5 round its outside diameter. A starter ring gear 8 is formed integrally on the first flywheel 1 and meshes with a starter, not shown. All the components that are connected to the hub 3 rotate together with the crankshaft 4 of the engine about an axis 9.

The inner wall 6 of the ring 5, the radially outer region of the primary disc 2 and the cover plate 7 form a chamber 10 concentrically around the axis 9. Spring elements 11 of a torsion spring arrangement 12 are arranged in this chamber and together with a friction device which is of conventional construction and therefore not illustrated they form a torsional vibration damper 13.

The control or actuation of the spring elements 11 takes place from the first flywheel 1 through segments, not shown, secured to the insides of the primary disc 2 and cover plate 7 and acting on each spring element 11 with the interposition of a respective spring pot 14 against which the spring element engages. The chamber 10 is at least partially filled with a viscous medium. Insofar as the spring elements 11 in the present flywheel assembly have a relatively large spring stiffness, it is not essential that the chamber 10 should be filled with a viscous medium.

The torques taken by the torsion spring arrangement 12 are fed to a hub disc 17 which acts as a torque transmitter 25 for a second flywheel 24 which is rigidly secured to it through rivets 23.

The second flywheel 24 is mounted radially inwards of the rivets 23 on a bearing 28, preferably a roller bearing, fixed in an axial direction on the hub 3. The second flywheel 24 is axially secured on one side by a flange 30 and on the other side by the radially inner region of the hub disc 17. The second flywheel 24 receives the friction clutch 32 which has a clutch housing 33 secured on the second flywheel 24 and in which is clamped a diaphragm spring 35 acting as an actuating means 34. The radially outer region of the spring 35 acts with one side against a pressure plate 37 which has a friction surface engaging with a friction lining 38 on one side of a clutch plate 39. The clutch plate 39 has a friction lining 38 on its other side, which has a friction surface with an associated region of the second flywheel 24. The clutch plate 39 has a hub 40 by which it is mounted on a gearbox-side output shaft 41 to rotate with it.

The radially outer region of the diaphragm spring 35 can be brought into engagement with its side remote from the pressure plate 37 against one end of a lever 43 which is mounted to pivot in its middle region on the clutch housing 33. At its other end the lever 43 engages the adjacent end of a push-rod 44. The push-rod 44 has a shank 45 passing through the clutch housing 33 and the second flywheel 24 and a head 46 extending transverse to the shank 45 and engaging in a space 47 between the first flywheel 1 and the second flywheel 24. The push-rod 44 is held in its rest position, as shown in Figure 2, by a retaining element 48. The element 48 is formed by a spring which engages in recesses in the shank 45. The lever 43 and the push-rod 44 form a first vibration damper 50 of a damping device 105.

Radially inwards of the vibration damper 50 the diaphragm spring 35 is located on one side against a nose 51 on the clutch housing 33 and on the other side against a retaining ring 52. Radially inwardly extending tongues 53 of the diaphragm spring 35 engage in a withdrawal bearing 54 of a withdrawal mechanism 55 which is arranged concentric with the output shaft 41 and has a piston 56 which acts on the withdrawal bearing 54 and is guided sealingly between an inner cylindrical wall 57 and an outer cylindrical wall 58. The cylinder space 59 between the two walls 57 and 58 is connected to a pressure fluid connection 60 which leads through a pipe 61 to an actuating drive 62, such as is known from DE-A-37 06 849. This actuating drive is part of an actuating device 101 connected with a switchingdevice 63 acting for control or regulation of the vibration damper. The switching device is shown in Figure 6 as a regulator. It has a regulator 110 acting as a switching element 128 connected to a memory 111. The regulator 110 is connected to the actuating drive 62 as well as to a sensing device 120 which will be described in detail later and through which the regulator 110 receives information with regard to the operating state of the flywheel assembly. A regulating section 180 feeds back actual values obtained by the regulator 110 for subsequent correcting regulation as necessary.

For better understanding of this circuit arrangement the sensing device 120 will first be described. The device comprises a first mark 121 provided in the circumferential region of the first flywheel 1 and extending circumferentially and a first rotary speed pick-up 126 co-operating with it to monitor the mark 121 and secured to a gearbox bell-housing 133 indicated in broken lines. The sensing device 120 also has a second mark 123 provided on the peripheral region of the second flywheel 24 and extending circumferentially and, cooperating with it, a second rotary speed pick-up 127 for monitoring the mark 123, the pick-up 127 also being secured to the gearbox bell-housing 133 and like the first-mentioned pick-up 126, lying on its inner face opposite the associated marks 121, 123.

In a circumnferential direction the marks comprise bright/dark zones for optical monitoring or Halleffect devices for electromagnetic monitoring. The teeth of the starter ring 8 may also be used as the first marks 121.

On the introduction of torsional vibrations into the flywheel assembly the two flywheels 1 and 24 move relatively angularly, and this movement is recognised by the rotary speed pick-ups 126, 127 as a result of the different speeds detected in the form of a relative speed. The known physical connection between speed and acceleration makes possible, knowing the relative speed and a measured time interval, to determine the relative acceleration of the flywheels. This is determined by the switching device 63. The determination of the value of the relative acceleration is of great significance as high relative acceleration can damage the flywheel assembly.

The assembly operates as follows. When torsional vibrations are applied to the first flywheel 1 from the input drive on passing through a resonance frequency, the relative acceleration between the two flywheels 1, 24 rises. This rise continues until an excessive relative acceleration of the flywheels 1, 24 is detected through the pickups 126, 127. When this happens the sensing device 120 sends a signal to the switching device 63, which in turn causes the actuating drive 62 of the withdrawal mechanism 55 to be moved to actuate the vibration damper 50. Operation of the damper 50 is dependent on the signal, and so the relative acceleration between the two flywheels is reduced or even eliminated. As soon as the relative acceleration between the two flywheels 1, 24 is reduced to a predetermined permissible level as a result of the damping action of the damper 50, the damper 50 is de-activated. The de-activation can be performed in dependence on the speed of the flywheels 1, 24. For this purpose there is a speed sensor 125 on the radially outer part of the flywheel 1 and a speed pick-up 124 aligned with it and lying radially on the inside of the gearbox bell housing indicated in broken lines in Figure 1. The speed pick-up 124 is connected to the switching device 63. At least one speed at which a resonance frequency is no longer to be expected is stored in the memory 111 as a reference value for setting the switching device 63.

On the detection of relative acceleration of the flywheels 1, 24 by the sensing device 120, signals are sent to the regulator 110. Each signal has associated with it a predetermined relative acceleration. The regulator reads out from the memory 111 the reference value associated with the measured characteristic corresponding to this relative acceleration and passes it on to the actuating device 101, which thereupon causes actuation of the actuating drive 62 by which the vibration damper 50 acts between the flywheels 1, 24 with a friction force appropriate to the relative acceleration between the flywheels 1, 24. To complete the explanation it should be pointed out that the reference values in the memory 111 are determined by previous experiments and then can be fed into the memory.

In a modification the marks 121, 123 and the speed pickups 126, 127 can be eliminated, and it is then sufficient to evaluate the values obtained from the speed pick-up 124 and feed them into the regulator 110. In this case both the speed sensor 125 and also the speed pick-up 124 are part of the sensing device 120. The sensing device 120, on receiving a speed value as a measured characteristic, sends a signal corresponding to it to the regulator 110 which calls up from the memory 111 a reference value corresponding to this signal and controls accordingly the actuating device 101 and thereby the actuating drive 62 in such a way that in frequency ranges in which one must expect the resonance frequency the vibration damper 50 is activated, whilst in the remaining frequency ranges it remains out of action. Corresponding to the information from the reference values, the regulator 110 in this arrangement can control the actuating drive 52 in such a way that within a region of the resonance frequency the vibration damper 50 is regulated in response to the prevailing speed.

In a modification shown in Figure 7, the switching device 63 is formed by a control device.

The regulator 110 is replaced by a control 130 as a switching element 128 of which the function corresponds substantially to that of the regulator but has the difference that because there is no regulating section 180, there is no feedback from the sensing device 120 for subsequent correction of the vibration damper 50. On receipt of a signal from the sensing device 120 the control 130 can merely call up from the memory 111 a reference value corresponding to this signal and control the actuating device 101 in accordance with this reference value for operating the vibration damper 50.

In accordance with the information from the switching device 63 the actuating drive 62 of the actuating device 101 is preferably controlled at speeds in the range between the starting speed and the idling speed of the engine in such a way that hydraulic fluid in the pipe 61 is forced into the cylinder space 59 of the hydraulic withdrawal mechanism 55. This forces the piston 56 of the withdrawal mechanism 55 to move towards the flywheel assembly, causing the withdrawal bearing 54 to displace the tongues 53 of the diaphragm spring to the left as viewed in Figures 1 and 2. The diaphragm spring 35 therefore pivots about its pivot points on the clutch housing 33 formed by the noses 51 and the retaining ring 52. This results in a reduction in the force exerted on the pressure plate 37 in a displacement of the lever 43 about its pivotal axis on the clutch housing 33. The lever 43 displaces the push-rod 44 of the vibration damper 50 towards the first flywheel 1 against the action of the retaining element 48 until the head 46 of the push-rod 44 comes into engagement with the first flywheel 1.

Depending on the travel of the piston 56 and thus the amount of movement of the diaphragm spring 35, the push-rod 44 is pressed against the flywheel 1 with a greater or smaller force. It produces at this point friction reducing or completely preventing the amount of relative movement of the flywheels 1 and 24. The amount of movement of the diaphragm spring 35 is a measure of how much the pressure plate 37 is relieved of the force previously acting on it. The amount of displacement of the diaphragm 35 can be chosen to ensure that slip takes place between the friction linings 38 and the associated friction faces on the second flywheel 24 and the pressure plate 37, so that the connection between the clutch plate 39 and the clutch elements 24, 37 of the clutch acts as a second damping device 100. The friction between the friction linings 38 and the elements 24, 37 and the friction which is produced against the flywheel 1 by the push rod 44, damps torsional vibrations which cannot be reduced by a friction device provided and acting in a conventional manner. This is particularly true for when the assembly passes through a resonance frequency.

After the return of the torsional vibrations to a permissible level, the sensing device 120 acts on the actuating drive 62 through the switching device 63 for causing operation in the opposite direction.

Hydraulic fluid then leaves the cylinder space 59 of the withdrawal mechanism 55 through the connection 60 and the pipe 61. The piston 56 is then pushed back to its starting position by the tongues 53 of the diaphragm 35 acting through the withdrawal bearing 55. The lever 43 is then relieved of the force of the diaphragm spring 35, so that the pushrod 44 returns to its starting position under the action of the retaining element 48. At the same time, the return movement of the diaphragm spring 35 again loads the pressure plate 37 until, when the diaphragm spring 35 has reached its starting position, it is urged with its full force against the friction linings 38 and through these against the second flywheel 24.

In a modification (not shown) the diaphragm spring 35 could be replaced by a diaphragm plate which itself would not be able to apply the necessary force to cause engagement of the pressure plate 37 with the friction linings 38 and between the friction linings and the flywheel 24, acting as a counter-pressure plate 131. Using a diaphragm plate as the actuating means 34 means that instead of the withdrawal mechanism 55 a correspondingly constructed and accordingly not illustrated engaging mechanism is used in which the supply of pressure medium is the other way round in that the engaging mechanism is moved to the left in Figure 1 in order to engage the diaphragm plate and is moved to the right for withdrawal. The inherent stress in the diaphragm plate is just sufficient in order, on movement of the engaging mechanism to the right, to keep the tongues 53 in engagement with it. Such a diaphragm plate is described for example in DE-A44 14 033.

It will be understood that with the use of a diaphragm spring 35 as the actuating means 34 in combination with a withdrawal mechanism 55 the vibration damper 50 is activated on withdrawal, whereas with the use of a diaphragm plate as the actuating means 34 in conjunction with an engaging mechanism, it is activated on engagement. Depending on the layout of the lever ratios in the actuating means 34 the vibration damper 50 in this arrangement can be activated during the engaging or withdrawal sequence but it can equally be activated before or after this sequence. In accordance with the invention, the engaging or withdrawal mechanism 55 is constructed so that it can perform an additional travel beyond its actual actuating travel, within which the actuating means 34 actuates the vibration damper 50 before or after an engagement or withdrawal. According to which side of the actual operating travel this additional travel is provided, in conjunction with the construction of the engaging or withdrawal mechanism 55 and of the actuating means as a diaphragm spring 53 or diaphragm plate the vibration damper 50 is brought into action substantially before or after a clutch actuation.

Where the actuating device 101 has a clutch pedal instead of an actuating drive 62 the pedal can be used for an engaging or withdrawal sequence along a first portion of pedal travel, in which the withdrawal mechanism 55 is operated and for an additional travel beyond that of the engaging or withdrawal mechanism 55, the vibration damper 50 is brought into action. According to whether this additional pedal travel is directed towards the drivers foot or away from it, the damper 50 is activated before or after engagement.

Figure 3 shows a different arrangement in which the actuating device 101 has a direct drive attached to the clutch housing 33 and acting directly on the shank 45 of the push-rod 44 of the vibration damper 50. The lever 43 shown in Figures 1 and 2 can then be omitted. Where such an actuating device 101 is used with a clutch pedal it is of advantage for the engaging or withdrawal mechanism 55 to have associated with it a position indicator 135 which, as shown in Figure 1, is provided radially outwards of the engaging or withdrawal mechanism and cooperates with a position pick-up 136 secured on the radially inside of the gearbox bell-housing 133.

The position indicator 135 forms together with the position pick-up 136 part of the sensing device 120 and indicates when, on depression of the clutch pedal, the actual clutch travel for engagement or withdrawal is complete and the clutch pedal is in the portion of travel in which the withdrawal mechanism 55 is in its additional travel. As soon as the sensing device 120 registers through the position pick-up 136 the presence of the withdrawal or engaging mechanism 55 within the additional travel, the direct drive 132 for activating the vibration damper 50 is switched on. On a return movement of the clutch pedal into its actual clutch actuating travel the signal indication from the sensing device 120 terminates so that the direct drive 132 is de-activated and thereby the vibration damper 50 is retracted to its starting position.

The direct drive 132 functions in the same way when the switching device 63 is formed, instead of by a sensing device 120 equipped with a position indicator 135 and position pick-up 136 by the kind of sensing device which has the speed sensor 125 and pick-up 124.

It is advantageous to provide the clutch with a wear-compensating device. This is because in the actuation of the vibration damper 50 through the engaging or withdrawal mechanism 55 and the actuating means 34, it is important to achieve a constant position of the actuating means 34 within the clutch housing 33 for any state of wear of the friction linings 38 and in relation to the second flywheel 24. Such wear compensation devices are in themselves known and accordingly will not be further described. Attention is simply drawn by way of example to DE-A-43 37 613, in which such a wearcompensation is described. Equipping the clutch 32 with wear c particularly compact, whilst where a clutch pedal is used as the actuating device 101 the force which it needs to apply is kept small.

Figure 4 shows a further flywheel assembly which shows a modified vibration damper 50. The withdrawal mechanism 55, the actuating device 101 and the switching device 63 correspond to those of the flywheel assembly shown in Figure 1.

Accordingly they are not shown in Figure 4 or described further but corresponding reference numerals have been applied to corresponding parts.

In Figure 4 the primary disc 2 is secured through the hub 3 on the crankshaft 4 of an input drive, not shown, and carries in its radially outer region a heavy ring 137 which has the starter ring 8 on its periphery. In the right hand part of Figure 4 it has radially outwards an element 140 secured to rotate with it in the form of a covering 141 with a radially inwardly extending flange portion 138. The primary disc 2 has, like an associated cover pressing 142, a window 144 which is aligned with a corresponding window 145 in a hub disc 143. The hub disc 143 is mounted on the hub 3 of the first flywheel 1 through a roller bearing 28 and receives in its radially outer region a counter-pressure plate 131 that rotates with it. The plate 131 is in operative connection with one friction lining 38 whilst the other friction lining 38 engages the pressure plate 37. The clutch plate 39 itself is mounted through splines 147 on a gearbox shaft, not shown. Between hub disc 143 and cover pressing 142 the flywheel assembly has a friction device 134 of conventional construction which forms together with the torsional spring arrangement 12 part of the torsional vibration damper 13.

The necessary frictional connection between pressure plate 37, friction linings 38 and counterpressure plate 131 is produced by a diaphragm spring 35 which acts as the actuating means 34 and is mounted in a known manner through pins 148 on the clutch housing 33. The housing 33 has an extension 150 extending axially towards the first flywheel 1 and enclosing the counter-pressure plate 131. The clutch housing 33 has in its radially extending region openings 152 through which pass radially extending finger-like projections 154 on the diaphragm spring 35. The openings 152 are matched in shape to the projections 154. On displacement of the radially inwardly extending spring tongues 53 of the diaphragm spring 35 for withdrawal (to the left in Figure 4) the spring 35 is pivoted about the pins 148 and in this way relieves the load on the pressure plate 37. If the spring tongues 53 are displaced still further in this direction, so that the withdrawal mechanism is moved into its additional travel after completion of its normal travel, the projections 154 come into engagement with the flange 138 of the covering 141. As the covering 141 is rotatable with to the first flywheel 1 and clutch housing 33 which carries the diaphragm spring 35 is rotatable with the second flywheel 24, which carries the pressure plate 37, the clutch plate 39 and the counter-pressure plate 131 as well as the hub disc 143, a friction connection exists between the projections 154 of the diaphragm spring 35 and the flange 138 of the covering 141. The projections 154 of the diaphragm spring 35 are accordingly, like the covering 141, part of a vibration damper 50. To remove the friction connection it is sufficient to retract the withdrawal mechanism 55 out of its additional travel and into its normal travel.

Figure 5 shows a further modification, in which, as in Figure 4, disengagement takes place before activation of the vibration damper 50. The primary disc 2 of the first flywheel 1 carries in its radially outer region the starter ring 8 as well as a ring 156 which has an engaging part 160 with a radial engaging face 172 for engagement of a claw 161 which is secured in a manner to be described below to the second flywheel 24 and acts as part of the vibration damper 50.

In addition to the primary disc 2, the hub 3 and the ring 156, the flywheel 1 also has a hub disc 158. This engages between two cover pressings 162 and 163 which, like the hub disc 158, have respective windows 164, 165 for receiving spring elements 11 of a torsion spring arrangement 12. The latter abuts at one end, looking circumferentially, against one end of the window 164 and at its other end against the respective other end of the window 165. The cover pressings 162, 163 form part of the second flywheel 24, the left hand pressing 162 in Figure 5 being arranged on a roller bearing 28 seated on the hub 3 of the first flywheel 1 whilst the pressing 163 receives between itself and the hub disc 158 a friction device 166 made up of a plate spring 167 and a friction member 168. This friction device is constructed and operates in a known manner.

The two cover pressings 162 and 163 are rigidly connected together through rivets 170, the pressing 163 carrying the clutch housing 33. The clutch plate 39 and friction linings 38 are arranged between the counter-pressure plate 131 and the pressure plate 37. The clutch plate 39 is in its turn secured to the hub 40 which is mounted on a gearbox shaft, not shown, to rotate with it.

The actuating force between pressure plate 37, clutch plate 39 and counter-pressure plate 131 is produced by a diaphragm spring 35 which acts as actuating means 34. The spring is pivotally mounted on pins 148 and can be withdrawn by a withdrawal mechanism 55, not shown, corresponding to that of Figure 1. On withdrawal the radially inner ends of the spring tongues 53 of the diaphragm spring 35 are displaced to the left in Figure 5 and to relieve the pressure plate 37 of its load. An axial spring 171 arranged with predetermined pre-loading axially between the cover pressing 163 of the flywheel 24 and the counter-pressure plate 131 of the clutch 32, acts to displace the counter-pressure plate 131, the clutch plate 39 and the pressure plate 37 towards the diaphragm spring 35. At least one claw 161 secured by rivets 182 to the counter-pressure plate 131, acting as a vibration damper 50 and having its free end engaging behind the abutment face 172 on the abutment member 160, is likewise axially displaced, as it is carried along by the counter pressure plate 131, and its free end comes frictionally into engagement with the abutment face 172 of the abutment member 160. The vibration damper 50 is thereby activated. In a contrary manner on relief of the load on the spring tongues 53 of the diaphragm spring 35 by a return movement of the withdrawal mechanism the pressure plate 37 and thereby the counter-pressure plate 131 are urged axially so that the latter is shifted back to its starting position with an increase in the pre-load of the energy-storing device 171 between the cover pressing 163 and the counter-pressure plate 131.

When the friction clutch 32 is engaged, the vibration damper 50 is lifted away from the abutment face 172 on the abutment member 160 and thereby released.

Our co-pending application No. 2 291 487, from which this application is divided, describes and claims a flywheel assembly of the kind set forth in which the vibration damper of the damping device is activiated by a sensing device for sensing the duration of a predetermined operating condition of the flywheels and determining a reference characteristic.

Claims (18)

1. A flywheel assembly of the kind set forth, in which the frictional connection between the two flywheels is produced at a predetermined position of an engaging or withdrawal mechanism of a friction clutch associated with the flywheel assembly, the engaging or withdrawal mechanism having an additional travel in at least one direction of movement, the additional travel being in addition to that necessary for engagement or withdrawal, the mechanism being operative in the additional travel to actuate an actuating device to activate the vibration damper.

2. A flywheel assembly as claimed in claim 1, in which the friction clutch has actuating means whose state of deformation is dependent on the axial position of the engaging or withdrawal mechanism, and a predetermined range of deformation of the actuating means is associated with the additional travel of the engaging or withdrawal mechanism.

3. A flywheel assembly as claimed in claim 1 or claim 2, in which the additional travel lies at the end of the travel of the engaging or withdrawal mechanism for clutch disengagement.

4. A flywheel assembly as claimed in claim 1 or claim 2, in which the additional travel lies at the end of the travel of the engaging or withdrawal mechanism for clutch engagement.

5. A flywheel assembly as claimed in any preceding claim, in which the engaging or withdrawal mechanism is moved by the actuating device which acts as the actuating drive of an automatic clutch system.

6. A flywheel assembly as claimed in any preceding claim, in which the engaging or withdrawal mechanism is moved by a clutch pedal.

7. A flywheel assembly as claimed in any preceding claim, in which the vibration damper comprises at least one damper element projecting beyond one flywheel and capable of being brought into engagement with the other flywheel by substantially axial movement by means of the actuating device.

8. A flywheel assembly as claimed in claim 7, in which the clutch actuating means is formed with at least one projection which extends through an associated opening in the clutch housing, the projection being adapted to engage frictionally with an element of the first flywheel by appropriate deformation of the actuating means when the engaging or withdrawal mechanism is in its additional travel.

9. A flywheel assembly as claimed in claim 8, in which the element of the first flywheel comprises a covering which is fitted in an axial direction on the circumferential region of the other flywheel to rotate with it.

10. A flywheel assembly as claimed in claim 9, in which the covering is of one-piece construction.

11. A flywheel assembly as claimed in claim 9 or claim 10, in which the covering is guided on the actuating means in a radially inward direction and its side adjacent the actuating means forms a stop for the actuating means.

12. A flywheel assembly as claimed in claim 7 and any of claims 2 to 6, in which the two flywheels are relatively movable in an axial direction, and with the actuating means in the engaged position a predetermined spacing is maintained between at least one vibration damper secured on a flywheel and an engaging member rigidly secured on the other flywheel, whilst with the actuating means in the withdrawn position the vibration damper is brought into engagement with an engaging face of the engagement member by means of an axial spring acting between the flywheels.

13. A flywheel assembly as claimed in claim 12, in which the vibration damper has a claw which engages behind a radial engaging face of the engaging member.

14. A flywheel assembly as claimed in claim 12, in which the axial spring is arranged in an axial direction between a counter-pressure plate of the clutch housing and a cover pressing connected to a bearing which locates the two flywheels coaxially relative to one another.

15. A flywheel assembly as claimed in claim 14, in which the cover pressing and a further cover pressing receive the spring elements of a torsional spring arrangement of the torsional vibration damper.

16. A flywheel assembly as claimed in any preceding claim, in which the friction clutch is associated with the second flywheel, the clutch having an actuating means and incorporating a wear compensating arrangement associated with the actuating means.

17. A flywheel assembly as claimed in claim 5, in which the actuating device co-operates with the actuating means to reduce the force exerted by the actuating means through a pressure plate on a clutch plate and to activate a second vibration damper on the occurrence of torsional vibrations.

18. A flywheel assembly as claimed in claim 17, in which when the torsional vibrations exceed a predetermined limiting value, the actuating device acts on the actuating means through the engaging or withdrawal mechanism in such a way that on release of the pressure plate from the clutch plate the engaging or withdrawal mechanism causes at least a transitory interruption in torque transmission.