GB2467802A - Torque transfer coupling - Google Patents

Abstract

A torque transfer coupling 34 of a clutch assembly 20 comprises a receptacle 44 that comprises arms 48, 50 extending from a base 46 of the receptacle 44, and a protruding tongue 76 for inserting between the arms 48, 50. The base 46 of the receptacle 44 is attached to a first disc 22 of the clutch assembly 20 and the protruding tongue 76 is attached to a second disc of the clutch assembly 20. At least one self-locking element 65, 66 which is caused to lock by centrifugal force due to use of the torque transfer coupling, may be provided. The self locking element is preferably due to tapered keys 65,66 acting against surfaces 86,88 of the protruding tongue 76.

Description

Torque transfer coupling of a clutch assembly The present application relates to a torque transfer coupling of a clutch assembly. The present application also relates to a method of assembling the clutch assembly with the torque transfer coupling.

A clutch assembly transmits torque from a crankshaft of an engine to an input shaft of a gearbox in an automobile. The clutch assembly connects the two shafts so that the two shafts can either be engaged together and spin at the same speed, or be disengaged and spin at different speeds. There exist a need to make the clutch assembly to be compact and easily assembled inside a clutch housing.

The present application provides a torque transfer coupling of a clutch assembly. The torque transfer coupling comprises a receptacle that comprises two arms extending from opposite ends of a base of the receptacle in a longitudinal axial di-rection of the clutch assembly. The arms and the base form the receptacle in a U-shaped profile such that the two arms are substantially perpendicular to the base respectively. The longitudinal axis of the clutch assembly is the rotation axis of the clutch assembly. The torque transfer coupling further comprises a protruding tongue for inserting between the two arms such that the protruding tongue can be clamped between the two arms.

The clutch assembly and the flywheel comprise a first disc and a second disc. Any of these discs can be a dual mass fly-wheel, a clutch disc, a clutch pressure plate, and a clutch case. For example, the first disc is the dual mass flywheel that can be mounted onto a crankshaft of an engine for re-ceiving a driving torque. The second disc can be the clutch pressure plate that can be mounted onto an input shaft of a gearbox from providing a driven torque of the clutch assem-bly, transmitted from the driving torque. In fact, the clutch assembly includes any type of clutch that transmits torque between two shafts, including a single clutch and a dual clutch. For example, the flywheel includes a dual mass fly- wheel. Here, the torque is force or power that makes compo-nents of the clutch assembly rotate around its longitudinal axis.

The torque transfer coupling avoids using fasteners for join-ing the flywheel and a clutch assembly together. The clutch assembly comprises the clutch disc, the clutch pressure plate, and the clutch case. The fasteners tend get loose over long-term use, which can cause determination in torque trans-mission performance of the clutch assembly. Multiple torque transfer couplings that are evenly distributed around circum-ferential edge of the flywheel reduce vibration of the clutch assembly when in use.

The arms can comprise two plates that face each other in a lateral direction of the clutch assembly. Each of the plates comprises a broad area that is aligned to the lateral direc- tion of the clutch assembly. The lateral direction is perpen-dicular to the longitudinal axis of the clutch assembly. Any of the plates that is in contact with the protruding tongue can receive or exert force such that torque transmission is enabled by the protruding tongue and the plate in contact.

The two plates offer wide area for reliable and steady torque transmission.

The receptacle can comprise a bolt, which holds the two arms at its two ends. The bolt can be solid or hollow that holds a fixed distance between its two opposite ends. When the oppo- site ends of the bolt are attached to the two arms of the re-ceptacle respectively, the bolt confines these two arms in a longitudinal direction of the bolt. When in use, engine speed variation and gear ratio shifting result the receptacle bump-ing against the protruding tongue frequently. The arms can be forced wide open in usage. However the bolt holds the two arms at a predetermined gap even over long-term usage. Reli-able coupling of the clutch assembly can be achieved.

A longitudinal axis of the bolt is perpendicular to a radial direction of the clutch assembly. Since broad surfaces of the plates are preferred to be perpendicular to the longitudinal axis of the bolt, the arms can transmit force that is in line with the bolt. Torque transmission can be more efficient.

Furthermore, centrifugal force at two opposite ends of the bolt become equal when the longitudinal axis of the bolt is perpendicular to both the radial direction and the longitudi-nal axis of the clutch assembly.

The receptacle can further comprise two tapered keys that are next to the two arms respectively. The two tapered keys form a wedge-shaped cavity in-between the two tapered keys. The wedge-shaped cavity tapers towards the longitudinal axis of the clutch assembly. Correspondingly, the protruding tongue comprises two external surfaces that are lateral to the lon- gitudinal axis of the clutch assembly. The two external sur-faces are detached from the two tapered keys when the clutch assembly is stationary. Lateral gaps exist between each of the two tapered keys and the protruding tongue. When in use, the gaps gradually diminish as the two tapered keys move in a radial direction of the clutch assembly under the influence of centrifugal force. In other words, the tapered keys lock the protruding tongue when the clutch assembly rotates. Al-though there are multiple torque transfer couplings on the clutch assembly, tapered keys of each of these torque trans- fer couplings self-aligned to their respective inserted pro-truding tongues for torque transmission.

The receptacle can further comprise two flat springs on the two arms respectively. The two flat springs are coupled to the two tapered keys for forcing the two tapered keys towards the longitudinal axis of the clutch assembly. Each of the ta-pered keys can comprise an outer pillar and an inner pillar.

The outer pillar tapers resides at an entrance of the recep- tacle and tapers towards the base of the receptacle. A ta- pered area of the outer pillar guides insertion of the pro-truding tongue.

The two arms can further comprise two top portions that have a larger distance in-between than that of the two arms at the base. The two top portions extend from the two arms respec-tively that the two top portions move away from each other in the direction of the longitudinal axis direction of the clutch assembly. In other words, the two top portions flare out away from the base. The two top portions have a distance at their tips such that the protruding tongue can be guided into the receptacle during assembling.

The protruding tongue can comprise two external surfaces for contacting the arms of the receptacle. The two external sur-faces match with the two tapered keys when in use. Torque transmission of the clutch assembly is achieved by surface contact between the two external surfaces and the two tapered keys. The two external surfaces form an angle that points to-ward the longitudinal axis of the clutch assembly. The two eternal surfaces lock with the tapered keys for smooth and robust torque transmission when in use.

The protruding tongue can comprise two branches that extend toward the receptacle, following the direction of longitudi- nal axis of the clutch assembly. The two branches form a bi-furcated fork. In fact, the protruding tongue can comprise an upper arm and a lower arm for receiving the bolt in-between.

The bolt is inserted between the upper arm and the lower arm that prevents lateral shift between the first disc and the second disc.

The upper arm and the lower arm can comprise two internal surfaces respectively, the two internal surface forming a wedge-shaped cavity in-between. The two internal surfaces face each other that enclose the bolt. The two internal sur-faces further form a wedge-shaped cavity that tapers towards a joint of the two arms. The joint is contiguous to the sec-ond disc. In other words, the upper arm and the lower arm of the bifurcated fork has V-shaped opening if viewed from its side. The V-shaped opening tapers towards the first disc of the clutch assembly. The V-shaped opening eases the insertion of the bolt into the bifurcated fork.

The two external surfaces can form an angle in-between such that the angle points towards the longitudinal axis of the clutch assembly. This provides a wider end near the circum- ferential edge of the second disc. In other words, the pro-truding tongue tapers towards a centre of the second disc.

This arrangement enables to the tapered keys to engage and the protruding tongue easily.

The protruding tongue can comprise a narrower end towards the receptacle and wider end towards the second disc. In other words, the protruding tongue tapers from the second disc to-wards the first disc. The protruding tongue can be guided easily into the receptacle on the first disc.

There can be provided a power train that comprises the torque transfer coupling. The torque transfer coupling eliminates the need connection between the flywheel and other disc com- ponents of the clutch assembly, thus obviating problems asso-ciated with fasteners for the coupling. Since the torque transfer coupling has the ability of self-aligning when in use, the torque transfer between the first disc and the sec-ond disc of the clutch assembly become more reliable.

There can be provided a vehicle comprising the torque trans- fer coupling. The vehicle can have less vibration over long-term usage.

The present application provides a method of assembling a torque transfer coupling on a clutch assembly. The method comprises a step of aligning receptacles on a first disc of the clutch assembly to protruding tongues on a second disc of the clutch assembly. The method further comprises a step of inserting the protruding tongues into the receptacles respec-tively. There is no requirement for screw fastening the first disc to the second disc of the clutch assembly. Therefore, coupling between the first disc and the second disc will not suffer problems resulted deterioration of the screw fasten-ing. During the assembling, a reliable coupling between two discs can be achieved efficiently.

The method can further comprise a step of fixing a distance between the first disc and the second disc in a longitudinal axis direction of the clutch assembly. The first disc can be a flywheel that is mounted onto an engine. The second disc can be a clutch pressure plate that is mounted onto a gear-box. The engine and the gearbox can be held onto a common supporting base, which determines the longitudinal distance between the first disc and the second disc. Screws are used to fasten the engine and the gearbox onto the common support-ing base. The screws do not revolve together with the clutch assembly such that the screws fix the longitudinal distance between the first disc and the second disc in the long-term.

The application further provides a powertrain assembly of a vehicle which comprises such a clutch assembly. The power-train assembly being preferably provided in a vehicle.

For mounting the powertrain assembly of such a vehicle, the step of mounting a fly wheel to a crankshaft of a an engine is provided wherein the flywheel preferably comprises a first part of the torque transfer coupling. The method further com-prises the step of mounting a friction coupling device to one or more input shafts of a gearbox of the powertrain, wherein the friction coupling device comprises at least a second part of the torque transfer coupling. The first part of the torque transfer device and the second part of the torque transfer device provide a keyed mating connection so that the torque transfer coupling is completed upon mounting the gearbox to engine.

The application further provides a method of making a clutch assembly that has a torque transfer coupling. The method com- prises a step of providing a receptacle of the torque trans- fer coupling onto a first disc of the clutch assembly. Multi-pie receptacles can be mounted onto the first disc. The method further comprises a step of providing a protruding tongue of the torque transfer coupling onto a second disc of the clutch assembly. Equal number of protruding tongues can be provided on the second disc at places corresponding to the receptacles on the first disc. Parts of the torque transfer coupling can be moulded onto the first disc and the second disc, which reduces secondary processes.

Fig. 1 illustrates a side view of a clutch assembly having torque transfer couplings, Fig. 2 illustrates an exploded view of the clutch assembly having the torque transfer couplings, Fig. 3 illustrates a receptacle of the torque transfer coupling that is attached onto a dual mass flywheel of the clutch assembly, Fig. 4 illustrates a side view of a bifurcated fork, Fig. 5 illustrates a cross sectional view of the torque transfer coupling at the position A-A, Fig. 6 illustrates the torque transfer coupling in an en-gaged state, Fig. 7 illustrates an enlarged view of the torque transfer coupling, Fig. 8 illustrates a cross sectional view of the torque transfer coupling, Fig. 9 illustrates an alternative embodiment of a bifur-cated fork, Fig. 10 illustrates a further alternative of a bifurcated fork, and Fig. 11 illustrates an alternative embodiment of a double clutch and a gearbox 126 that are connected via torque transfer couplings.

In the following description, details are provided to de- scribe the embodiments of the application. It shall be appar-ent to one skilled in the art, however, that the embodiments may be practised without such details.

Figs. 1-8 shows an embodiment of the torque transfer coupling of a clutch assembly. In particular, Fig. 1 illustrates a side view of a clutch assembly 20 having torque transfer cou-plings. The clutch assembly 20 comprises, from left to right, a dual mass flywheel 22 of a car engine which is not shown here, a clutch disc 24, a clutch pressure plate 26, and a clutch case 28 in an axial direction 30 of the clutch assem- bly 20. These components of the clutch assembly 20 can re-volve around the axis 32.

There are three torque transfer couplings 34, 36, 38 evenly provided around circumference of the clutch assembly 20. Only one 34 of the three torque transfer couplings 34, 36, 38 is visible in Fig. 1.

Fig. 2 illustrates an exploded view of the clutch assembly 20 having the torque transfer couplings 34, 36, 38. The clutch assembly 20 is separated into two parts 40, 42. A left part of the clutch assembly 20 comprises the dual mass flywheel 22 that is attached with a receptacle 44 of the torque trans-fer coupling 34. A right part 42 of the clutch assembly 20 comprises the clutch disc 24, the clutch pressure plate 26, and the clutch case 28 that are bolted together.

The torque transfer coupling 34 is also split into two parts in the exploded view. On the left side, the receptacle 44 is formed by a metal strip that is bent into U shape. The recep-tacle 44 has a rectangular base 46 that is attached to the dual mass flywheel 22. At the opposite ends of the rectangu-lar base, arms 48, 50 are extended from these opposite ends respectively such that these two extensions 48, 50 face each other. Tip portions 52, 54 of these two extensions 48, 50 are bent away from each other such that a distance between tip portions 52, 54 is larger than a distance between the two ex-tensions 48, 50 at the base 46. A bolt 56 is provided near the rectangular base 46 that each end of the bolt 56 is in-serted into an aperture 58, 60 on each of the extensions 48, 50. The bolt 56 is further held in the two extensions 48, 50 respectively by two flat springs 62, 64 at its two ends.

These two flat springs 62, 64 forces the bolt 56 towards In an area that is between the two extensions 48, 50, there is a tapered key 65, 66 attached to each of the two exten-sions 48, 50. The two tapered keys 65, 66 have identical shapes, although only the remote tapered key 65 is visible in Fig. 2. The tapered key 65 has two parallel pillars 68, 70 that are jointed at top by a pin 72. The pin 72 passes through one of the flat springs 62, 64. A bridge 74 at bottom also connects the two pillars 68, 70. An outer pillar 68 is more remote to the dual mass flywheel 22. It has a tapered area that follows the curvature of its contiguous arm 48, 50.

The inner pillar 70 is positioned between the bolt 56 and the rectangular base 46. Surfaces of the tapered keys 64, 66 that are facing each other form an angle in-between, which is bet-ter seen in Fig. 5. In other words, the two tapered keys 64, 66 close the wedge-shaped gap in a radial direction of the dual mass flywheel 22.

The right part of the torque transfer coupling 34 comprises a bifurcated hook or fork 76 that is U-shaped. The bifurcated fork 76 comprises two arms 78, 80. The two arms 78, 80 com-prise internal surfaces 82, 84 respectively that are facing each other in a radial direction of the clutch assembly 20.

The two internal surfaces 82, 84 form an angle in-between, which is better seen in Fig. 4. The two arms 78, 80 also have external surfaces 86, 88 that are opposite to each other as seen in a circumferential direction of the clutch assembly 20. The bolt 56 can be inserted into the two arms 78, 80 of the torque transfer coupling 34, which is better seen in Fig. 1.

Fig. 3 illustrates the receptacle 44 of the torque transfer coupling 34 that is attached onto the dual mass flywheel 22 of the clutch assembly 20. The lower part 40 of the DMF/clutch assembly 20 is viewed from the same side as in Fig. 1. In Fig. 3, the two arms 48, 50 of the receptacle 44 are shown to be parallel. An axis 90 of the bolt 56 is paral-lel to a right end surface of the dual mass flywheel 22.

Fig. 4 illustrates a side view of the bifurcated fork 76. The bifurcated fork 76 has a wedge-shaped recess 92 that opens towards left. The wedge-shaped recess 92 has a narrow bottom that is configured to receive the bolt 56. The wedge-shaped recess 92 also has an opening that is wider than a diameter of the bolt 56. A cut-off line A-A is given in Fig. 4 that passes through a longitudinal axis 90 of the bolt 56.

Fig. 5 illustrates a cross sectional view A-A of the torque transfer coupling 34 at the position A-A. The torque transfer coupling 34 holds the dual mass flywheel 22 and the cen-ter/pressure plate 26, the clutch pressure plate 24 and the clutch case 28 together, as it is also shown in Fig. 1 and 2.

Only cut-ff portions of the two arms 78, 80 of the bifurcated fork 76 are visible in Fig. 5. According to Fig. 5, the bolt 56 is securely inserted into the wedge-shaped recess 92 (see Fig. 4) of the bifurcated fork 76. The left flat spring 62 and the right flat spring 64 are clamped by the topsides of the bolt 56, respectively. The flat springs 62, 64 engage pins 72 which are provided in the radially outer parts of the tapered keys 65, 66. The forces of the springs 62, 64 drive the tapered keys 65, 66 to an inner diameter of the DMF which facilitates mounting of the clutch assembly to the flying wheel by keeping the tapered keys away from the bifurcated fork 76. The pins 72 also limit the movement of the tapered keys 65, 66 as they make contact with the bolt 56.

A bridge 96 of the tapered key 66 is visible in Fig. 5. The bridge 96 is further joined to an inner pillar 97 of the ta-pered key 66 on top.

The internal surfaces 84 of the bifurcated fork 76 form an angle in-between (Fig. 4) . A narrow end of the angle points towards the rotation axis 32 of the clutch assembly 20. On the left side (Fig. 5), there is a left uniform gap 98 pro-vided between the left tapered key 66 and the arms 78, 80 of the bifurcated fork 76. Similarly, on the right side, there is a right uniform gap 100 provided between the right tapered key 65 and the arms 78, 80 of the bifurcated fork 76. Both the Fig. 1 & Fig. 5 show the clutch assembly in a stationary condition after assembling.

In particular, the left gap 98 is formed between a left ramp surface 114 of the left tapered key 66 and a left external surface 88 of the bifurcated fork 76. The right gap 100 is formed between a right external surface 86 of the bifurcated fork 76 and a right ramp surface 116 of the tapered key 66.

The gaps 98, 100 provide overall rotational clearance for taking up the bifurcated fork 76.

The torque transfer coupling 34 of Fig. 5 shows that the bi-furcated fork 76 and the receptacle 44 are disengaged in a loosened state when the dual mass flywheel 22 is still sta-tionary. Dash lines in Fig. 5 indicate the positions of the tapered keys 65, 66 in an engaged state.

The gaps 98, 100 will be closed later upon rotation of the flywheel by driving the tapered keys 65, 66 into the gaps 98, 100, thereby providing a locking interconnection between the elements of the receptable 44. The fixed ends of the bolt 56 then prevent the two arms 48, 50 from spreading under the wedge forces of the tapered keys 65, 66. This is similarly illustrated in Fig. 6 below.

Fig. 6 illustrates the torque transfer coupling in the en- gaged state. The engaged state occurs when the dual mass fly- wheel 22 rotates at a predetermined speed. Both the right ta- pered key 65 and left tapered key 66 move in a radial direc-tion of the dual mass flywheel 22 under the centrifugal force. The gaps 98, 100 disappear as the bifurcated fork 76 comes in contact with the tapered keys 65, 66. Dash lines in Fig. 6 indicate the positions of the tapered keys 65, 66 in the loosened state. The radial displacements of the two ta-pered keys 65, 66 need not necessarily be identical. For equalizing tolerances, they can move independently of each other as necessary. The overall center of gravity for the ta-pered keys 65, 66 is for different radial locations the same so that they are subjected to the same radial forces. No un-balance of the clutch system is caused. If the left tapered key 66 should radially at a position which is different from the radial position of the right tapered key 65, e.g. the left tapered key 66 is more outside than the right tapered key 65, there is -with respect to the other torque transfer couplings 36, 38 -no unbalance as far as the rotation is concerned. The displacement of the one tapered key to the ra-dial outside is the same as the corresponding displacement of the other tapered key to the inside, providing a common cen-ter of gravity which has the same distance from the axis 32 as the tapered keys of the other torque transfer couplings 36, 38.

Fig. 7 illustrates an enlarged view of the torque transfer coupling 34. The torque transfer coupling 34 comprises the receptacle 44 that encloses the bifurcated fork 76 between its two arms 48, 50. The upper arm 78 of the bifurcated fork 76 is provided on top of the bolt 56, whilst the lower arm 80 (not shown) of the bifurcated fork 76 is provided below the bolt 56.

A front end of the bifurcated fork 76, which is close to the rectangular base 46, has its two corners 106 rounded off. Al-though a left corner 106 of the upper arm 78 is visible in Fig. 7, a right corner 106 of the upper arm 78 is also rounded off. Similarly, both a left corner 106 and a right corner 106 of the lower arm 80 (not shown) are also rounded off whose images overlap with that of the upper arm 78. The tip portion 54 and the inner surface of the tapered key 66 are essentially aligned so that the rounded surfaces of the bifurcated fork 76 smoothly glides into the final position during assembly.

A cut-off line B-B is shown in Fig. 7 that is aligned to the longitudinal axis 90 of the bolt 56.

Fig. 8 illustrates a cross sectional view B-B of the torque transfer coupling 34. The gaps 98, 100 are closed here. The bolt 56 is firmly gripped between the upper arm 78 and the lower arm 80 of the bifurcated fork 76. The tapered key 65 is in close contact with the right external surface 86 of the bifurcated fork 76, whilst the tapered key 66 is also closely attached to the left external surface 88 of the bifurcated fork 76. It is shown that the two external surface 86, 88 of the bifurcated fork 76 form an angle narrowing towards the rotation axis 32 of the clutch assembly 20. When the torque transfer coupling 34 tightens, the receptacle 44 engages the bifurcated fork 76 such that torque from the flywheel 22 can be transmitted to the clutch for rotating around the longitu-dinal axis 32 of the clutch assembly 20.

The receptacle 44 receives torque from the dual mass flywheel 22. The extended arms 48, 50 of the receptacle 44 provides expanded contact areas for transmitting force that is lateral to the dual mass flywheel 22. The tip portions 52, 54 of the receptacle offers an opening that is wider than the bifur- cated fork 76 in the lateral direction such that the bifur-cated fork 76 can be easily guided into the receptacle 44 during an assembling procedure. The bolt 56 holds the arms 48, 50 with predetermined distance in-between even when transmitting large torque. The large torque tends to open the two arms 48, 50. The two tapered keys 65, 66 further provide a wedge shaped cavity for receiving the bifurcated fork 76 such that the bifurcated fork 76 is locked inside the recep-tacle 44 when transmitting the torque. The bifurcated fork 76 comprises the external surfaces 86, 88 on its lateral side.

The external surfaces 86, 88 are contiguous to the two ta-pered keys 65, 66 respectively such that the bifurcated fork 76 locks the two tapered keys 65, 66 when the clutch assembly rotates. The internal surfaces 82, 84 of the bifurcated fork 76 also form a wedge shaped cavity that has a wider opening towards the bolt 56.

In an assembling procedure, the dual mass flywheel 22 is mounted onto a crankshaft of an engine. A longitudinal axis 32 of the flywheel 22 is aligned to an output end of the crankshaft such that the flywheel 22 and the crankshaft are coaxially attached.

The clutch disc 24, the clutch pressure plate 26, the clutch case 28 are also aligned to their longitudinal axes 32 such that the clutch pressure plate 26 and the clutch case 28 en-close the clutch disc 24. The clutch disc 24, the clutch pressure plate 26, the clutch case 28 form a clutch system 112. The clutch system 112 is mounted onto an input shaft of a gearbox such that the longitudinal axis 32 of the clutch system 112 is aligned to a longitudinal axis of the input shaft.

The clutch assembly 112 and the dual mass flywheel 22 are then brought to alignment that the longitudinal axis 32 of the dual mass flywheel 22 is aligned to the longitudinal axis 32 of the clutch assembly 112. Both the dual mass flywheel 22 and the clutch system 112 can be slowly rotated that three receptacles on the dual mass flywheel 22 are aligned to the three bifurcated forks on the clutch assemblies respectively.

The three bifurcated forks subsequently are inserted into the three receptacles on the dual mass flywheel 22 respectively.

The dual mass flywheel 22 and the clutch system 112 are then kept at an axial distance from each other, because the hous-ings of the car engine and the vehicle's gearbox are fixed to each other, respectively.

In the first use of the engine, the dual mass flywheel 22 re-ceives torque from a crankshaft of an engine and rotates around its longitudinal axis 32. Within a short period, the dual mass flywheel 22 reaches a certain speed so that the two tapered keys 65, 66 move in the radial direction outside. The two tapered keys 65, 66 thus engage the bifurcated fork 76 and close the lateral gap between the two tapered keys 65, 66 and the bifurcated fork 76. As a result, torque from the dual mass flywheel 22 is transmitted to the clutch system 112. An input shaft of a gearbox thus receives the torque from the crankshaft via the clutch assembly 20.

The angle alpha of the wedge-shaped tapered keys 65, 66 and the surfaces 86, 88, 114, 16 is such that the connection be- comes self-locking after engagement. This means that the tao- ered keys can essentially only be removed by applying an ex- ternal force, e.g. when dismantling the gearbox from the en-gine.

This self-locking feature can be supported by an additional locking element which is not shown here. The additional ele-ment can be a spring, a screw, a magnet which may interact with an additional magnet on the fork 76 or on the recepable, such that the additional element creates a radial force to- wards the outside. The spring can be an actuated spring, ac-tuated during the assembly process. The extra load can-be provided by actuating and releasing a pre-loaded spring dur-ing the assembly. The triggering of the extra spring can be provided by reaching a certain position such as a ratchet element or the additional locking element can be triggered or released by a centrifugal force upon rotation of the assem- bly. The pre-loaded spring can also be actuated manually dur-ing after the assembly process.

A polymer can also be provided in the gap 98, 100, the poly-mer being hardened after assembly.

Fig. 9 illustrates an alternative embodiment of a bifurcated fork 76'. The alternative embodiment contains parts that are similar to that of the previous embodiment. The similar parts are labelled with similar reference part numbers, and having a prime symbol for differentiation. Description of the simi-lar parts is hereby incorporated by reference.

The bifurcated fork 76' is shown three views that are corre- sponding to each other. View (a) is a top view of the bifur- cated fork 76' that is in a radial direction of a clutch as- sembly 20'. View (b) is a side view which is seen from a lat-eral side of the clutch assembly 20'. View (c) is a back view that is seen from a broken off side of the bifurcated fork 76'. The bifurcated fork 76' comprises a left external sur-face 86 and a right external surface 88. These two faces 86', 88' form an angle which points in the radial direction of the clutch assembly 20'. These two faces 86', 88' are symmetrical with respect to the radial direction that each of these two faces 86', 88' has an angle of c. In other words, the bifur-cated fork 76' tapers in an opposite direction of the radial direction. An upper arm 78' and the lower arm 80' of the bi-furcated fork 76' have equal width 116. A joint 118 of the two arms 78', 80' has a narrower width 120 than that of the two arms 78', 80'.

Fig. 10 illustrates a further alternative of a bifurcated fork 76". The alternative embodiment contains parts that are similar to that of the previous embodiments. The similar parts are labelled with similar reference part numbers, and having a prime symbol for differentiation. Description of the similar parts is hereby incorporated by reference.

Fig. 10 illustrates a view (a) and a view (b) of the bifur- cated fork 76". The bifurcated fork 76" seen in a radial di-rection of a clutch assembly 20" according to the view (a).

In contrast, the bifurcated fork 76" seen in an opposite di-rection of the radial direction according to the view (b) Similar to the bifurcated fork 76' of Fig. 9, a left external surface 86" and a right external surface of the bifurcated fork 76" has an equal angle c with respect to a radial direc-tion of the clutch assembly 20". Furthermore, each of the left external surface 86" and a right external surface also forms an angle 13 with respect to a longitudinal axis direc-tion of the clutch assembly 20". As shown in Fig. 10, a front end of the bifurcated fork 76" is narrower than its back end.

In other words, a width of the front end 120 is shorter than a width of the back end 122. The left tapered key 66" and the right tapered key 65" are also shown in Fig. 10 for illus-trating matching relationship between them.

Fig. 11 illustrates an alternative embodiment of a double clutch 124 and a gearbox that are connected via torque trans-fer couplings 34"', 36"', 38"'. The alternative embodiment contains parts that are similar to that of the previous em- bodiments. The similar parts are labelled with similar refer- ence part numbers, and having a prime symbol for differentia-tion. Description of the similar parts is hereby incorporated by reference.

A gearbox is provided on a right side and the gearbox has a solid input shaft 126 and a hollow input shaft 128. The solid input shaft 126 is enclosed by the hollow input shaft 128.

These two shafts 126, 128 are connected to an inner disc 130 and an outer disc 132 of a double clutch 124. Outer edges of the inner disc 130 and the outer disc 132 are between two ac-tuating devices 134 of the double clutch. A bell-shaped clutch case 28"' encloses the inner disc 130, the outer disc 132 and the two actuating devices 134. Three bifurcated forks 34"', 36"', 38"' are evenly distributed around a circumferen-tial edge of the clutch case 28"' evenly. The double clutch 124 is enclosed by a cover 140 laterally.

On the left side, a flywheel 22"' is mounted onto a crank- shaft 136 of an engine. The flywheel 22"' has three recepta-cles 44"' that encloses each of the three bifurcated forks 34"', 36"', 38"' respectively. The engine and the flywheel 22"' are enclosed by an engine housing 138 from a lateral side.

The cover of the gearbox 140 and the housing of the engine 138 are bolted by screws 142 that are even distributed around a circumferential edge of the housing 140. When in use, these screws 142 remain stationary, and are prevented from high-speed rotational movements of the double clutch 124.

This assembly also comprises torque transfer couplings with self-locking tapered keys and forks that are similar to those in the above mentioned embodiments. These torque transfer couplings are not shown in Fig. 11, however.

Although the above description contains much specificity, these should not be construed as limiting the scope of the embodiments but merely providing illustration of the foresee-able embodiments. Especially the above stated advantages of the embodiments should not be construed as limiting the scope of the embodiments but merely to explain possible achieve-ments if the described embodiments are put into practise.

Thus, the scope of the embodiments should be determined by the claims and their equivalents, rather than by the examples given.

Reference Numbers clutch assembly 22 dual mass flywheel 24 clutch disc 26 clutch pressure plate 28 clutch case axial direction 32 axis 34 torque transfer coupling 36 torque transfer coupling 38 torque transfer coupling left part 42 right part 44 receptacle 46 rectangular base 48 arm arm 52 tip portion 54 tip portion 56 bolt 58 aperture aperture 62 flat spring 64 flat spring tapered key 66 tapered key 68 outer pillar inner pillar 72 pin 74 bridge 76 bifurcated fork 78 upper arm lower arm 82 internal surface 84 internal surface 86 external surface 88 external surface axis 92 wedge-shaped recess 94 cut-off line A-A 96 bridge 97 inner pillar 98 left gap right gap 102 inner pillar 104 outer pillar 106 corners 108 centre line lateral direction 112 clutch system 114 left ramp surface 116 width 118 joint width of a front end 122 width of a back end 124 double clutch 126 solid input shaft 128 hollow input shaft inner clutch disc 132 outer clutch disc 134 actuating devices 136 crank shaft 138 engine housing cover of a gearbox 142 screws