DESC:TECHNICAL FIELD

[0001] The present invention relates generally to an engine with an automatic transmission system, and more particularly, but not exclusively, to an engine with automatic transmission system having electrically operable clutch.

BACKGROUND

[0002] Straddle type vehicles such as motorcycles generally have a manual transmission system to carry the power generated by an internal combustion (IC) engine, in a controllable way, to a wheel of the vehicle. The manual transmission system comprises a system of interlocking gears such that by operating a gear shift lever manually, the driver can choose one of the several ratios of speed between the input shaft and the output shaft. To allow smooth and gradual shifting of gears, a clutch is provided to isolate the engine from the transmission momentarily. When the driver releases the clutch lever manually, the plates in the clutch assembly are squeezed with each other and thus the transmission is engaged with the engine.

[0003] Off lately, automated manual transmission (AMT) systems have come into use for ease of operation of clutch actuation and gearshift. The ride on such vehicle is less tiring for the vehicle rider. Conventionally, a vehicle fitted with an AMT engine has an electrically actuating clutch operation and gearshift operation, powered by a battery and controlled by a control unit. But, a limp home mode in the form of a manual clutch actuation system is also provided to ‘de-clutch’ the AMT engine and moves the vehicle. The manual clutch actuation system is particularly helpful in the event of malfunction of the control unit or during any other electrical fault when the vehicle would be stuck in a geared state in the clutch engaged position.

[0004] Generally, in any clutch actuation system, the ratio of angle of swivel of a rotatable member of the clutch actuation system actuating the clutch to the clearance between the rotatable member and clutch (hereafter referred to as ratio) is critical to disengage the clutch. The ratio is critical in the design of the clutch actuation system. The ratio contributes in determining the amount of work to be done on clutch actuation and acts a parameter to accommodate for various inconsistencies in dimensions of various components during manufacturing and assembly. The ratio helps determining the time required for engagement and disengagement and contributes in providing optimum velocity of travel of gear during gear shifts (march off parameter). Further, the ratio is important to design other allied components forming part of the clutch actuation system such as crankcase housing and clutch shaft float adjustment. Furthermore, due to prolonged use, the clutch may wear out. The design of clutch bases on the ratio helps determine clutch life. The ratio should be always a constant and be within limits of a predetermined range to provide overall optimum clutch performance.

[0005] In manual transmission system, variations in the ratio can be rectified by adjusting clutch-handle lever play on the vehicle handlebar. Additionally, there is an adjusting screw disposed on the clutch-cable pulley support, which on adjustment can increase the tension of a clutch cable to bring the ratio within predetermined limits. On the other hand, in AMT engines, due to automatic clutch disengagement operation, provision for such adjustment can be accommodated. Further, the need for maintaining accurate ratio within critical limits of a predetermined range is extremely crucial as the control unit is pre-programmed to operate at a fixed ratio. Furthermore, one cannot adopt similar conditions of ratio of manual transmission system to AMT engines as the below drawbacks are observed. 1.) In manual transmission systems, the rider will actuate the clutch by operating the clutch lever and hence will be able to adjust the clutch engagement and disengagement rate by varying the force and rate of application on the clutch lever. But, in AMT engines, since the control unit is programmed to operate at a fixed rate, this actuation may take a longer time thus affecting drivability and providing a sluggish feel to the rider. 2.) During change of gears, predominantly during change from neutral position to first gear, it is important that velocity of travel is optimum for proper and smooth transition from stationary position to moving position. These characteristics are represented as March off parameter. In manual transmission system, the rider controls the clutch engagement and hence can provide better march off of the vehicle. But, in AMT engine the march off parameter is dependent on the ratio. 3.) There can be instances of time delay due to higher ratio as the swivel and length of travel is more. Hence, it is pertinent to design an AMT engine having the ratio within a critical predetermined range which ensures an optimum performance and helps alleviate the above drawbacks and is the primary object of the present subject matter.

[0006] In addition to having the ratio within the critical predetermined range, in AMT engine which comprises of a plurality of components, the ratio may vary due manufacturing inconsistencies in the components. For instance, the ratio may increase during the assembly of the engine due to tolerance variation in clutch actuation components. An increase in the ratio interferes in the process of clutch actuation because the control unit is programmed to operate at a fixed ratio, any change in the ratio will cause the motor to swivel exceeding the required amount and the distance between the clutch actuation components and the clutch is disturbed. Hence, it is probable that the clutch is not fully disengaged causing hindrance in the gear shift. Ultimately, it affects the drivability of the vehicle having such engine. Further, such ratio also varies with each engine unit due to manufacturing inconsistencies. Therefore, drivability changes from engine to engine and is not uniform across the engine units. Hence, providing a means to alleviate the above drawbacks is also another aspect of the present subject matter.

SUMMARY OF THE INVENTION

[0007] The present subject matter is directed to overcoming one or more problems as set forth above and thereby to obviate a lacunae in the prior art. It is an object of the present invention to provide an automatic transmisison engine having a clutch and a clutch actuation system such that the ratio of the angle of swivel of a rotatating member of the clutch actuation system and the clearance between the components of clutch actuation system and the clutch before the actuation of the clutch is set to a predertermined value. The clutch actuation system can actuate the clutch by electrical means or manual means. It is also an object of the present invention to improve the drivability of an automatic transmission engine by avoiding the problems caused due to manufacturing inconsistencies.

[0008] The present invention discloses an apparatus for controlling a clutch for an internal combustion (IC) engine with automatic transmission, comprising: a first covering unit supporting a clutch actuation system comprising a rotatable member configured to swivel by a clutch actuation motor, and a clutch disengaging member operably connected to the rotatable member and configured to move axially relative to the extent of swivel of the rotatable member; a second covering unit supporting the clutch, said clutch operated by a clutch release pin and mounted on a clutch bearing; said clutch disengaging member operatively engaged to the clutch release pin, and said clutch is capable of being engaged and disengaged on the axial movement of the clutch disengaging member to the clutch release pin; a clearance between the clutch disengaging member and the clutch release pin in the clutch engaged condition when the first covering unit is assembled with the second covering unit; and said rotatable member having a predetermined angle of swivel, said angle of swivel is determined based on the rotation of the rotatable member from a first position to a second position; wherein, the ratio of the angle of swivel and the clearance is set to a predetermined value. The predetermined value is in a range of 70° and 72°, the angle of swivel measured in degrees and the clearance measured in millimeters.
[0009] Further, another important aspect of the present invention is that, the clearance is set by disposing an adjusting member between the clutch release pin and the clutch bearing to bring the ratio to the predetermined value. The construction of the engine unit according to the present invention ensures that the clearance between the clutch and the clutch disengaging member remains within a predefined range and any undesirable change detected in the clearance during the assembly of the engine is compensated by providing the adjusting member. The components of the clutch actuation system are fabricated with negative tolerances in the present invention. There are dimensional variances mainly in two critical areas, namely due to presence of shaft float on the clutch shaft on which the clutch is supported and the clutch release pin is mounted. Another area is in the variation of dimensions in the first covering unit and the second covering unit. The adjusting member ensures the above two variations are taken care to set to the predetermined ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

[00010] The present invention will now be briefly described with reference to the accompanying drawings in which:

[00011] FIG. 1 shows a side view of an AMT engine with an electrically and manually operable clutch according to the present invention.

[00012] FIG. 2 shows an exploded view of an embodiment of the AMT engine of FIG. 1 according to the present invention.

[00013] FIG. 3 shows an inner view of a first covering unit of the engine comprising a clutch.
[00014] FIG. 4 shows an exploded view of assembly of clutch actuation system and manual disengagement system in a second covering unit.

[00015] FIG. 5 shows a illustrative sectional view of the engine according to an embodiment of the present invention.
[00016] FIG. 6 shows a illustrative front view of a rotatable member according to an embodiment of the present invention.

BRIEF DESCRIPTION OF THE INVENTION
[00017] The present invention disclosed herein is usable with an engine with an automatic, electrically or manually operable clutch. It is to be noted that “front” and “rear”, unless mentioned otherwise, refer to front and rear directions as seen in a state of being seated on a seat of the vehicle carrying the present invention and looking forward. The vehicle is installed with the engine with its cylinder head facing towards the front as shown by the directional arrows. Further, “left” and “right”, unless mentioned otherwise, refer to left and right directions of an onlooker standing in front of the vehicle and looking towards it. A lateral axis refers generally to a side to side, or left to right axis relative to the vehicle. Various other features of the present subject matter here will be discernible from the following further description thereof, set out hereunder.
[00018] FIG. 1 and FIG. 2 respectively show an side view and an exploded view of an IC engine 100 with an automatic transmission (AMT). The engine 100 comprises of a cylinder head 101, a first covering unit 150, a second covering unit 110 and a third covering unit 105. In an embodiment, the first covering unit 150, the second covering unit 110 and the third covering unit 105 are provided rearward or below the cylinder head 101. The third covering unit 105 supports and covers a crankshaft of the engine. In an embodiment, the second covering unit 110 is located between the first covering unit 150 and the third covering unit 105. The second covering unit 110 supports the crankshaft from the opposite side of the third covering unit 105 and comprises of a clutch 113 supported within the second covering unit 110. The clutch 113 works with the help of plurality of clutch plates 111 and through which it is engaged to and disengaged from a primary driven gear 112 taking its drive from the crankshaft of the engine 100. The construction and the working of crankshaft is known in the prior art and hence not included here for the purposes of brevity.

[00019] The AMT engine 100 is provided with an electrically operated gearshift actuation system comprising a gearshift actuation motor 160 which controls the gearshift after the clutch 113 is engaged or disengaged. The engine 100 is also provided with a clutch actuation system for actuating the operation of clutch disengagement and re-engagement either electrically or manually. In an embodiment, the first covering unit 150 houses and supports the clutch actuation system having a clutch disengaging member 171 operatively engageable to the clutch 113. The first covering unit 150 has an inner surface 151 facing towards the clutch 113 and an outer surface 152 opposed to the inner surface 151. FIG. 3 shows the inner view of the second covering unit 110 which houses and supports the clutch 113. The clutch 113 includes a clutch release pin 114 which on being operated allows the clutch plates 111 to slip and the clutch 113 to disengage. The clutch release pin 114 is supported on a clutch bearing 115. When the first covering unit 150 and second covering unit 110 are assembled along with the third covering unit 105, a clearance 116 is maintained between the clutch disengaging member 171 and the clutch release pin 114 (FIG. 5).
[00020] The clutch actuation system includes an automatic clutch actuation system for electrically operating the clutch and a manual clutch actuation system for manually operating the clutch in the event of failure of the automatic clutch actuation system. The clutch actuation system is now explained. The automatic clutch actuation system includes a clutch actuation motor 161, a reduction gear box, a power transmission mechanism which transmits the rotational driving force of the clutch actuation motor 161 to the clutch 113 and a clutch position sensor 158 which detects the clutch position and state. The clutch actuation motor 161 is mounted and secured to the outer surface 152 of the first covering unit 150 and sealed against ingress of oil. The clutch actuation motor 161 is electrically connected to a control unit (not shown) which is programmed to control the direction of rotation of the clutch actuation motor 161 as well as the duration of its operation. The reduction gear box comprises of a plurality of reduction gears connecting the clutch actuation motor 161 and the power transmission mechanism. In an embodiment, the power transmission mechanism comprises of a worm gear 162 mechanically meshed with an electrically operable rotatable member 163. The reduction gear box is mechanically connected to the worm gear 162 through a thrust bearing, a ball bearing and a washer.
[00021] As shown in FIG. 4, the rotatable member 163 in turn is operatively connected to the clutch disengaging member 171 through a caging member 168. The rotatable member 163 can only rotate along its central axis but cannot move axially to and fro. In an embodiment, the rotatable member is a worm wheel and the caging member 168 is a plate like structure having one or more balls 169, and disposed between the clutch disengaging member 171 and rotatable member 163. The one or more balls 169 are caged within the caging member 168 and are rotatable along their own axis. In an embodiment, the one or more balls 169 include ramped balls and protrude in both directions of the central axis of the caging member 168. The rotational driving force from the clutch actuation motor 161 is transmitted to the clutch disengaging member 171 through the rotatable member 168 by use of the ramped balls 169. The clutch disengaging member 171 then actuates the clutch 113 and disengages it from an engaged position.

[00022] In an embodiment, the clutch disengaging member 171 is a circular plate structure formed integrally as a single piece. It can only move to and fro towards the clutch release pin 114 and away from clutch release pin 114 axially but cannot rotate along its own axis. Further, the clutch disengaging member 171 is engaged on one side to the rotatable member 163 and on the other side to the clutch release pin 114. As shown in FIG. 2 and FIG. 4, the clutch disengaging member 171 includes a clutch facing surface proximal to the clutch 113 and a non-clutch surface distal to the clutch 113 opposed to the clutch facing surface. A clutch portion 172 protrudes out of a clutch facing surface and is engageable with the clutch release pin 114. In an embodiment, the clutch portion 172 of the clutch disengaging member 171 protrudes centrally from the clutch facing surface.

[00023] Further, the non-clutch surface of the clutch disengaging member 171 has a first set of grooves. The electrically operable rotatable member 163 comprises of a second set of grooves 164 corresponding to the first set of the grooves. In an embodiment, a portion of the clutch disengaging member 171 is slidably fitted to the rotatable member 163. The caging member 168 is rotatably supported on the clutch disengaging member 150 and not fixed to it.

[00024] The one or more balls 169 of the caging member 168 are sandwiched between the rotatable member 163 and the clutch disengaging member 171 such that in the assembled state, the one or more balls are oriented to remain in the maximum depth respectively in first set of grooves and the second set of grooves. Each ball 169 traverses within the depth provided in each groove of the first set of grooves 164 and the second set of grooves 118.

[00025] During the electrical operation of the clutch 113, the clutch actuation motor 161 rotates in the direction controlled by the control unit and operates the clutch 113 through the power transmission mechanism. The torque from the clutch actuation motor 161 is transferred to the rotatable member 163 through the worm gear 162. The one or more balls 169 in the caging member 168 rotate between the second set of grooves 118 and the first set of grooves 164 resulting in axial movement of the clutch disengaging member 171 for the angular displacement of the clutch actuation motor 161. The linear displacement forces the clutch portion 172 of the clutch disengaging member 171 to push the clutch release pin 114 due to which the clutch 113 is electrically disengaged. The rotation of clutch actuation motor 161 in opposite direction by the control unit withdraws the force on the clutch release pin 114 and the clutch is re-engaged again. The clutch disengaging member 171 therefore axially operates the clutch release pin 114 thereby disengaging the clutch 113.

[00026] The clutch actuation system of the engine 100 also includes the manual clutch actuation system as shown in FIG. 4 for manually operating the clutch in the event of failure of the automatic clutch actuation system to help the rider to manually disengage the clutch and move the vehicle. Both the automatic clutch actuation system and the manual clutch actuation system act on the clutch disengaging member 171 to actuate the clutch 113. In an embodiment, the manual clutch actuation system operates the clutch disengaging member 171 through a clutch release shaft 156. In an embodiment, the clutch release shaft 156 is manually operable and mechanically connected to a manually operable clutch release lever 155. In an embodiment, the clutch release lever 155 is rotatably connected to the clutch release shaft 125 and is provided external to the first covering unit 150 for ease of access to the rider of the vehicle. Further, the clutch release shaft 156 includes an end portion 157 configured to engage with the clutch portion 172 of the clutch disengaging member 171. The clutch release shaft 156 is received in a supporting boss formed integral with the first covering unit 150. The manual clutch actuation system further includes a preloaded return spring 159 to bring the clutch release shaft 156 to its original position after the withdrawal of manual force on the clutch release lever 155. One end of the return spring 159 is held on the inner surface 151 of the first covering unit 150.
[00027] In an embodiment, the end portion 157 engages with the clutch portion 172 through a rack and pinion arrangement. The clutch portion 172 of the clutch disengaging member 171 comprises a rack 173, the end portion 157 of the clutch release shaft 156 comprises a pinion having a plurality of grooves that intermesh with the grooves of the rack. The rack and pinion arrangement prevents the rotational movement of the clutch disengaging member 171 and hence it can only move axially. The manual disengagement system further comprises of a guide-cum-holder member 175 which partially covers and supports the end portion 157 and the clutch portion 172, and keeps them guided towards their intended path. The guide-cum-holder member 175 is supported on the inner surface 151 and maintains the central distance between the rack and pinion arrangement of the clutch release shaft and the clutch disengaging member. It prevents the misalignment between the rack and pinion arrangement and guides the clutch portion 157 to move axially and also provides rigidity to the system.
[00028] When the rider of the vehicle detects that the automatic clutch actuation system has failed due to any reason whatsoever (including electrical failures) and the vehicle comes to a stop with clutch in engaged position with the engine in geared state, he may use the present manual disengagement system to disconnect the drive to the wheel. During the operation of the manual clutch actuation system, the clutch release lever 155 is manually rotated which in turn rotates the clutch release shaft 156. Since the pinion 157 of the clutch release shaft 156 is intermeshed with the rack 173 of the clutch disengaging member 171, the clutch release shaft ‘directly’ operates the clutch disengaging member 171 due to which it moves axially forward to operate the clutch release pin 114 to disengage the clutch 113. Thus, the rotatory motion of the clutch release lever 155 is converted to the axial motion of the clutch disengaging member 171. The preloaded return spring 159 brings the clutch release shaft 125 to its original position after the withdrawal of manual force on the clutch release lever 155. However, the extent of rotation of the clutch release lever 155 is predetermined due the constant ratio. It rotates only to that extent as the axial movement required by the clutch portion 172 of the clutch disengaging member 171 to operate the clutch release pin 114. However, in the manual operation, the rotatable member 163 and the caging member 168 has no role to play because the clutch release shaft 156 acts ‘directly’ on the clutch disengaging member 171.

[00029] As shown in FIG. 5, when the first covering unit 150 and second covering unit 110 are assembled along with the third covering unit 105 to develop into the complete engine 100, the clearance 116 is maintained between the clutch disengaging member 171 and the clutch release pin 114. As shown further in FIG. 6, during operation, the clutch actuation system (automatic or manual) overcomes this clearance 116 by the swivel of the rotatable member 163 by swiveling at an anlge of swivel ? and thus actuates the clutch 113. In automatic clutch actuation system, the clutch is actuated through the r.p.m of clutch actuation motor 161 which is controlled by the control unit through varying the current to the clutch actuation motor 161. By varying the current correspondingly the r.p.m of the clutch actuation member 161 changes and the time taken for axial movement of clutch disengaging member 171 changes. But, the ratio of angle of swivel ? of the rotatable member 163 and the clearance 116 is always a constant. This ratio is fixed to a predetermined value and in one embodiment of the present invention, the predetermined value is between a range of 70° and 72°, the angle of swivel ? measured in degrees and the clearance 116 measured in millimeters.
[00030] If the ratio changes, the angle of swivel remians a constant but the clearance 116 between the clutch release pin 114 and the clutch actuation system (read clutch disengaging member’s clutch portion 172) varies, and hence the current distribution to the clutch actuation motor varies because the control unit takes reference from the contact point of the clutch disengaging member 171 and the clutch release pin 114. Since, the control unit is programmed to drive the actuation motor to cover a fixed distance of clearance, such variation in current distribution may lead to jerking of engine 100 and affects ridability and reduces smoothness and feel of the rider whiling driving the vehicle. Such variations in the gap may occur due to variations in tolerance of dimensions during manufacture of first covering unit 150 and second covering unit 110 and the combined tolerance is compounded during their assembly and will lead to change in the length of the clearence 116 and affect the ratio which needs to maintained to the predetermined value and within specified range.

[00031] Therefore, the first covering unit 150 also comprises of an adjusting member 121 which is disposed between the clutch release pin 114 and the clutch bearing 115. The adjusting member 121 is of predefined width for that particular engine 100. The width of the adjusting member 121 is dependent on the clearance 116 between the clutch disengaging member 171 and the clutch release pin 114. During the assembly of the first covering unit with the second covering unit, the clearance 116 is calculated from the clutch position sensor 158. Therefore, if the clearance 116 is more, the adjusting member 121 having more width is assembled with the first covering unit 150. It is to be noted that, the first covering unit (150) and second covering unit 110 are always manufactured having negative tolerance, which ensures that, always length of the clearance 116 is found to be equal to or lesser than the required length of the clearance 116.

[00032] Hence, to assemble the engine, the second covering unit 110 is first assembled with the third covering unit 105, and this subassembly is then assembled along with the first covering unit 150. The clutch 113 is initially in engaged position. The clutch actuation motor 161 is then powered so that the clutch disengaging member 171 touches the clutch release pin 114 but does not disengage the clutch 113. Thereafter, the value of clearance 116 is calculated from the clutch position sensor 158. Based on the value of clearance which is more than the predefine clearance value due to negative tolerance of assembled components, the adjusting member 121 of adequate width is inserted into the assembly by reopening the first covering unit 150. In an embodiment of the present invention, the adjusting member is a shim.

[00033] It will be appreciated that the present invention and its equivalent thereof offers many advantages, including those which have been described forthwith. The inclusion of adjusting member counters any increase in the clearance 116 during assembly because it maintains adequate distance between the clutch actuation components and the clutch. Thus any interference in the process of clutch actuation does not arise and the clutch is fully disengaged without affecting the drivability of the vehicle. Further addition of adjusting member is a simple, cost effective way of adjusting said clearance. The aforementioned invention is also usable in engine units with semi-automatic transmission having automatic clutch actuation and manual gearshift.
[00034] The present invention is thus briefly described. It will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the present invention.

,CLAIMS:We claim:

1. An apparatus for controlling a clutch (113) for an internal combustion (IC) engine with automatic transmission, comprising:
a first covering unit (150) supporting a clutch actuation system comprising a rotatable member (163) configured to swivel by a clutch actuation motor (161), and a clutch disengaging member (171) operably connected to the rotatable member (163) and configured to move axially relative to the extent of swivel of the rotatable member (163);
a second covering unit (110) supporting the clutch (113), said clutch (113) operated by a clutch release pin (114) and mounted on a clutch bearing (115);
said clutch disengaging member (171) operatively engaged to the clutch release pin (114), and said clutch (113) is capable of being engaged and disengaged during the axial movement of the clutch disengaging member (171) with respect to the clutch release pin (114);
a clearance (116) between the clutch disengaging member (171) and the clutch release pin (114) in the clutch engaged condition when the first covering unit (150) is assembled with the second covering unit (110); and
said rotatable member (163) having a predetermined angle of swivel (?), said angle of swivel is determined based on the rotation of the rotatable member (163) from a first position to a second position;
wherein, the ratio of the angle of swivel (?) and the clearance (116) is set to a predetermined value.

2. The apparatus for controlling the clutch (113) for the IC engine with automatic transmission as claimed in claim 1, wherein the predetermined value is in a range of 70° and 72°, the angle of swivel (?) measured in degrees and the clearance (116) measured in millimeters.

3. The apparatus for controlling the clutch (113) for the IC engine with automatic transmission as claimed in claim 2, wherein the clearance (116) is set by disposing an adjusting member (121) between the clutch release pin (114) and the clutch bearing (115) to bring the ratio to the predetermined value.

4. The apparatus for controlling the clutch (113) for the IC engine with automatic transmission as claimed in claim 3, wherein the adjusting member (121) is a shim.
5. The apparatus for controlling the clutch (113) for the IC engine with automatic transmission as claimed in claim 3, wherein the width of the adjusting member (121) is dependent on the clearance between the clutch disengaging member (171) and the clutch release pin (114).

6. The apparatus for controlling the clutch (113) for the IC engine with automatic transmission as claimed in claim 1, wherein the clutch release pin (114) is also manually operable in addition to being electrically operable.

7. The apparatus for controlling the clutch (113) for the IC engine with automatic transmission as claimed in claim 1, wherein the first position of said rotatable member (163) is a rest position, and said second position of the rotatable member (163) corresponds to the clutch disengaging member (171) covering the entire length of the clearance (116).

8. A method of assembling an internal combustion engine having automatic transmission comprising the steps of:
assembling a third covering unit (105) with a second covering unit (110), the second covering unit (110) supports a clutch (113), said clutch (113) operated by a clutch release pin (114) and mounted on a clutch bearing (115);
assembling a first covering unit (150) which supports a clutch actuation system comprising a rotatable member (163) operably connected to a clutch actuation motor (161), and a clutch disengaging member (171) operably connected to the rotatable member (163);
assembling the first covering unit (150) with the second covering unit (110) and measuring a clearance (116) between the clutch disengaging member (171) and the clutch release pin (114) in the engaged condition of the clutch (113), and measuring an angle of swivel (?), said angle of swivel (?) determined based on the rotation of the rotatable member (163) from a first position to a second position;
comparing the measured value of the ratio of the angle of swivel and the clearance (116) against a first predefined range; and
inserting an adjusting member (121) in the first covering unit (150) of width which is corresponding to the measured value of the ratio, if the measured value of the ratio is more than the first predefined range.

9. The method as claimed in claim 7, wherein the first predefined range is between 70° and 72°, the angle of swivel measured in degrees and the clearance measured in millimeters and wherein the first position of said rotatable member (163) is a rest position, and said second position of the rotatable member (163) corresponds to the clutch disengaging member (171) covering the entire length of the clearance (116).

10. The method as claimed in claim 7, wherein the adjusting member (121) is a shim.