JP2012047273A - Vehicular power unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of the simultaneous engagement of a pair of clutches with a simple constitution for reducing the number of part items, in a vehicular power unit for arranging a gear train of a plurality of selectively establishing shift stages between coaxially juxtaposed first and second main shafts and a counter shaft and arranging the first and second clutches for disengaging-engaging rotational power transmitted to the first and second main shafts from a crankshaft, in opposite side end parts of the mutual first and second main shafts.SOLUTION: An alternate disengagement-engagement assist mechanism 90A having at least a rod 91 coaxially inserted into the first and second main shafts 33 and 34, is interposed between switching operation members 69 and 84 respectively possessed by the first and second clutches 41 and 42 for switching disengagement-engagement by operating in the axial direction of the first and second main shafts 33 and 34 so as to assist the alternate disengagement-engagement of the first and second clutches 41 and 42.

Description

  The present invention includes a crankshaft that extends in the left-right direction of a vehicle, first and second main shafts that are arranged coaxially with an axis parallel to the crankshaft, and parallel to the first and second main shafts. A countershaft having an arbitrary axis is rotatably supported by the engine case, and a gear train of a plurality of shift stages that is selectively established is provided between the first and second main shafts and the countershaft, A vehicle in which first and second clutches for connecting / disconnecting rotational power transmitted from the crankshaft to the first and second main shafts are disposed at opposite ends of the first and second main shafts. It relates to the power unit.

  A gear train of a plurality of shift stages that is selectively established is provided between a pair of main shafts arranged coaxially and a counter shaft having an axis parallel to the main shafts. A vehicle power unit in which a pair of clutches for connecting / disconnecting rotational power transmitted to the main shaft is disposed at opposite ends of the main shafts is known from Patent Document 1. .

JP 2010-106983 A

  However, in the one disclosed in Patent Document 1, a pair of clutches are both connected in a state where a gear train between one main shaft and the counter shaft and a gear train between the other main shaft and the counter shaft are established. In order to avoid this, a back torque limiting device is provided for both clutches. For this reason, it is necessary to incorporate a dedicated part for the back torque limiting device into each clutch, and the problem is that the structure of the clutch is complicated, the weight is increased, and the number of parts and the cost are increased.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a vehicular power unit in which a pair of clutches are not simultaneously connected with a simple configuration with a reduced number of parts.

  In order to achieve the above object, the present invention includes a crankshaft extending in the left-right direction of a vehicle, first and second main shafts arranged coaxially with an axis parallel to the crankshaft, A countershaft having an axis parallel to the first and second main shafts is rotatably supported by the engine case, and a plurality of transmissions are selectively established between the first and second main shafts and the countershaft. The first and second clutches, which are provided with stepped gear trains and connect / disconnect rotational power transmitted from the crankshaft to the first and second main shafts, are on opposite sides of the first and second main shafts. In the vehicle power unit disposed at the end, the disconnection / connection is switched by operating in the axial direction of the first and second main shafts. And an alternate assisting / contact assisting mechanism having at least a rod inserted coaxially into the first and second main shafts between the switching actuating members provided in each of the first and second clutches. -The first feature is that it is provided so as to assist contact.

  According to the present invention, in addition to the configuration of the first feature, the alternate disconnection / contact assist mechanism is interposed between at least one of the switching operation members of the first and second clutches and the rod. The second feature is that an elastic member is provided.

  According to the present invention, in addition to the configuration of the second feature, the elastic member is interposed between any one of the switching operation members of the first and second clutches and the rod. Three features.

  In the present invention, in addition to any of the first to third features, the alternate disconnection / contact assist mechanism directly pushes the switching operation member of the first and second clutches at the end of the rod. Thus, a fourth feature is that the first and second clutches are configured to assist in disengagement / connection.

  Furthermore, in addition to any of the configurations of the first to fourth features, the present invention provides a length between the two switching operation members when both the first and second clutches are in a connected state. The fifth feature is that the length is set to be shorter than the length between the two switching operation members when only one of the first and second clutches is in the connected state.

  The crankcase 21 of the embodiment corresponds to the engine case of the present invention, the first lifter 69 and the second lifter 84 of the embodiment correspond to the switching operation member of the present invention, and the coil spring 92 of the embodiment. Corresponds to the elastic member of the present invention.

  According to the first aspect of the present invention, the alternate disconnection / contact assist having at least a rod inserted coaxially into the first and second main shafts between the switching operation members provided in the first and second clutches, respectively. Since the mechanism is interposed and the alternate disengagement / contact assist mechanism assists the alternate disengagement / contact of the first and second clutches, switching between the first and second clutches is performed more smoothly and the number of parts is increased. It is possible to prevent simultaneous connection of a pair of clutches with a simple configuration in which the above is reduced.

  According to a second aspect of the present invention, the alternate disconnection / contact assist mechanism includes an elastic member interposed between at least one of the first and second clutch switching operation members and the rod. In addition, it is possible to reduce the operation noise by the elastic member when the alternate cutting / contact assist mechanism is operated, and the rod can be positioned in the axial direction by the elastic member.

  According to the third aspect of the present invention, since the elastic member is interposed between one of the first and second clutch switching operation members and the rod, the first and second clutch switching. The number of parts can be reduced as compared with the case where the elastic member is interposed between both the working member and the rod.

  According to the fourth aspect of the present invention, the alternate disconnection / contact assist mechanism is configured to directly push the switching operation member of the first and second clutches at the end of the rod. Position accuracy is improved.

  According to the fifth feature of the present invention, the length of the rod is longer than the length between the switching operating members when both the first and second clutches are in the connected state, and the first and second clutches Since only one of them is shorter than the length between the switching operating members when in the connected state, it is possible to reliably prevent both clutches from being in the connected state and to alternately disconnect the first and second clutches.・ Does not interfere with contact.

1 is an overall side view of a motorcycle according to a first embodiment. It is a side view of a power unit. It is sectional drawing which follows the 3-3 line of FIG. It is a principal part enlarged view of FIG. It is sectional drawing corresponding to FIG. 4 of 2nd Embodiment.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

  A first embodiment of the present invention will be described with reference to FIGS. 1 to 4. First, in FIG. 1, a body frame F of a motorcycle as a vehicle steers a front fork 11 that supports a front wheel WF. A head pipe 12 that is supported, a pair of left and right main frames 13 that extend rearwardly downward from the head pipe 12, and a pair of left and right pivot plates 14 that are connected to the rear of both main frames 13 and extend downward. The rear wheel WR is pivotally supported on the rear portion of the swing arm 15 whose front end is pivotably supported on the pivot plate 14. In addition, a link 16 is provided between the lower part of the pivot plate 14 and the front part of the swing arm 15, and a cushion unit 17 is provided between the upper part of the pivot plate 14 and the link 16.

  A power unit P is suspended from the main frames 13 and the pivot plates 14. Rotational power output from the power unit P is transmitted to the rear wheel WR via a drive shaft 18 extending in the front-rear direction. A side stand 19 is attached to the lower part of the left pivot plate 14 in the vehicle body frame F.

  In FIG. 2, the engine main body 20 of the engine E constituting a part of the power unit P includes a front bank BF positioned in the front in a mounted state on the motorcycle, and a rear part positioned rearward of the front bank BF. It has a bank BR and is configured as a V-type water-cooled type, and a crankshaft 22 along the left-right direction of the motorcycle is rotatable in a crankcase 21 as an engine case common to both banks BF and BR. It is supported by.

  The crankcase 21 is formed by combining an upper case half 21a and a lower case half 21b, and is integrated with the upper case half 21a so that the front and rear cylinder blocks BF and BR are V-shaped. The axis of the crankshaft 22 is disposed on the coupling surface of the upper case half 21a and the lower case half 21b.

  The front bank BF includes a front cylinder block 23F, a front cylinder head 24F coupled to the front cylinder block 23F, and a front head cover 25F coupled to the front cylinder head 24F. The rear bank BR Is composed of a rear cylinder block 23R, a rear cylinder head 24R coupled to the rear cylinder block 23R, and a rear head cover 25R coupled to the rear cylinder head 24R, and an oil pan 26 is disposed below the crankcase 21. Combined.

  Referring also to FIG. 3, a pair of pistons 27 is slidably fitted to the front cylinder block 23F of the front bank BF, and a pair of pistons (see FIG. 3) is also attached to the rear cylinder block 23R of the rear bank BR. (Not shown) are slidably fitted, and the pistons 27 are connected to the crankshaft 22 in common.

  A left cover 28 forming a first clutch chamber 31 is fastened between the crankcase 21 and the left side surface of the crankcase 21, and a second clutch chamber is formed between the crankcase 21 and the right side surface of the crankcase 21. The right cover 29 forming 32 is fastened. Further, one end of the crankshaft 22 passes through the crankcase 21 rotatably and protrudes into the first clutch chamber 31, and the other end of the crankshaft 22 passes through the crankcase 21 and rotates second. Project into the clutch chamber 32.

  The crankcase 21 is rotatably supported by first and second main shafts 33 and 34 that are arranged coaxially with an axis parallel to the crankshaft 22, and rotate on the left side wall of the crankcase 21. One end of the first main shaft 33 penetrating freely projects into the first clutch chamber 31, and a first ball bearing 35 is interposed between the intermediate portion of the first main shaft 33 and the crankcase 21, and the first main shaft 33 A second ball bearing 36 is interposed between the other end of 33 and the crankcase. The second main shaft 34 has one end portion coaxially disposed opposite the other end portion of the first main shaft 33 and the other end portion protruding into the second clutch chamber 32 so that the right side wall of the crankcase 21 is provided. A third ball bearing 37 is interposed between one end of the second main shaft 34 and the crankcase 21, and an intermediate portion of the second main shaft 34 and the right side of the crankcase 21. A fourth ball bearing 38 is interposed between the walls.

  The rotational power of the crankshaft 22 is transmitted to the first main shaft 33 via the first primary reduction gear train 39 and the first clutch 41 disposed in the first clutch chamber 31, and the second clutch 42 chamber 32. Is transmitted to the second main shaft 34 via the second primary reduction gear train 40 and the second clutch 42 arranged at the same position, and is transmitted from the crankshaft 22 to the first and second main shafts 33, 34. The first and second clutches 41 and 42 that connect and disconnect the rotational power are disposed at opposite ends of the first and second main shafts 33 and 34 that are aligned on the same axis.

  A countershaft 43 having an axis parallel to the crankshaft 22 is rotatably supported on the crankcase 21. One end of the countershaft 43 is connected to the left side wall of the crankcase by a fifth ball bearing. The other end portion of the counter shaft 43 is rotatably supported on the right side wall of the crankcase 21 via a roller bearing 45.

  Between the first main shaft 33 and the counter shaft 43, first, third and fifth speed gear trains G1, G3, G5 are provided to be alternatively established, and the second main shaft 34 and the counter Between the shafts 43, second, fourth and sixth speed gear trains G2, G4, G6 are provided so as to be alternatively established.

  A final shaft 48 having an axis parallel to the counter shaft 43 is rotatably supported in the crankcase 21, and one end portion of the final shaft 48 that rotatably penetrates the left side wall of the crankcase 21 is The drive shaft 18 is linked and connected via a bevel gear mechanism 49. Thus, a sixth ball bearing 50 is interposed between one end of the final shaft 48 and the left side wall of the crankcase 21, and a seventh ball bearing 50 is interposed between the other end of the final shaft 48 and the right side wall of the crankcase 21. A ball bearing 51 is interposed.

  The rotational power of the counter shaft 43 is transmitted to the final shaft 48 via a final gear train 52 and a torque damper 53 that absorbs excessive torque generated in the torque transmission path from the crankshaft 22 to the rear wheel WR. .

  Thus, the final gear train 52 is disposed between the right side wall of the crankcase 21 and the second speed gear train G2 and meshes with the final drive gear 54 that rotates together with the counter shaft 43. And a final driven gear 55 supported on the final shaft 48 so as to be relatively rotatable.

  The torque damper 53 is opposed to the final driven gear 55 so as to be supported by the final shaft 48 so as not to rotate relative to the final shaft 48 but to allow relative movement in the axial direction. The cam member 56 faces the final driven gear 55 side. And a damper spring 57 for biasing.

  A concave portion 58 is provided on a side surface of the final driven gear 55 facing the cam member 56, and an output side cam portion 60 that abuts on an input side cam portion 59 formed at the closed end of the concave portion 58 is provided on the cam member 56. It is formed. The damper spring 57 is a coil spring that surrounds the final shaft 48. A retainer 61 that receives one end of the damper spring 57 is fixed to the final shaft 48, and the other end of the damper spring 57 is connected to the final driven gear 55 from the opposite side. It abuts on the cam member 56.

  According to the torque damper 53, although the final driven gear 55 and the cam member 56 are integrally rotated when a torque equal to or lower than a predetermined torque acts between the final driven gear 55 and the cam member 56, the engine of the motorcycle is used. When a torque exceeding a predetermined torque is applied between the final driven gear 55 and the cam member 56 during deceleration of the engine E during braking or the like, slip in the rotational direction occurs between the final driven gear 55 and the cam member 56, and The cam member 56 absorbs the excessive torque while moving to the side away from the final driven gear 55 against the spring force of the damper spring 57.

  Referring also to FIG. 4, the first clutch 41 accommodated in the first clutch chamber 31 so as to cut off / connect the transmission of the rotational power from the crankshaft 22 to the first main shaft 33 is the first clutch 41. A first clutch outer 62 that is rotatably supported on one end of the main shaft 33, a plurality of first friction plates 63, 63... Engaged with the first clutch outer 62, and the first main shaft 33. The first clutch inner 64 coupled so as not to be relatively rotatable, and the plurality of second friction plates 65, 65,... Alternately engaged with the first friction plates 63, 63,. .., 65, 65... Of the first and second friction plates 63, 63... 65, 65. And alternately Of the first and second friction plates 63, 63... 65, 65... Between the first pressure-receiving plate 66 and the dish-shaped first pressing member 67 whose outer peripheral portion is opposed to the axially outer friction plate. First and second friction plates 63, 63... 65, 65... Are interposed between the first clutch inner 64 and the first pressing member 67 so as to urge the first pressing member 67 toward the side to be crimped. One end of the clutch spring 68 and the left cover 28 are slidably fitted and a cylindrical portion 69a slidably fitted to the cylindrical first main shaft 33 is provided on the other end side. And a first lifter 69 serving as a switching actuating member disposed coaxially with the first pressing member 67 and coupled to the inner peripheral portion of the first pressing member 67 via a first release bearing 70. One end of the lifter 69 has an actuator (not shown) Therefore, the first rotation shaft 71 that is slidably fitted to the left cover 28 so as to be rotationally driven is interlocked and connected so as to drive the first lifter 69 in the axial direction by the rotation. The

  In such a first clutch 41, when the actuator is in an inoperative state, the first pressing member 67 is urged toward the engagement side by the first clutch spring 68, so the first clutch 41 is in a power transmission state. Next, when the actuator is operated to operate the first lifter 69 in the axial direction, the driving force is transmitted from the first release bearing 70 to the first pressing member 67, and the first pressing member 67 causes the first clutch spring 68 to move. The first and second friction plates 63, 63... 65, 65... Are pressed toward the side where the pressure-bonding force is weakened while being compressed, and the power transmission between the first clutch outer 62 and the first clutch inner 64 is cut off. It becomes.

  By the way, the rotational power from the crankshaft 22 is transmitted to the first main shaft 33 via the first primary reduction gear train 39 and the first clutch 41. The first primary reduction gear train 39 The first primary drive gear 72 is fixed to one end of the crankshaft 22, and the first primary driven gear 73 is meshed with the first primary drive gear 72 and arranged coaxially with the first main shaft 33. The first primary driven gear 73 is supported on the first main shaft 33 so as to be relatively rotatable, and is connected to the first clutch outer 62 via a first damper spring 74.

  The second clutch 42 housed in the second clutch chamber 32 is connected to the other end portion of the second main shaft 34 so that the transmission of the rotational power from the crankshaft 22 to the second main shaft 34 is disconnected and connected. A second clutch outer 77 that is rotatably supported, a plurality of third friction plates 78 that are engaged with the second clutch outer 77, and a second main shaft 34 that is relatively non-rotatably coupled. Are arranged alternately with the two clutch inners 79 and the third friction plates 78, 78... And are engaged with the second clutch inners 79. And fourth friction plates 78, 78..., 80, 80... Are arranged alternately with second pressure receiving plates 81 provided integrally with the second clutch inner 79 so as to face the axially inner friction plates. 3 and 4th friction plate 7 , 78...; 80, 80... Third and fourth friction plates 78, 78 of a dish-shaped second pressing member 82 whose outer peripheral portion is opposed to the axially outer friction plate and a second pressure receiving plate 81. ..., 80, 80 ..., a second clutch spring 83 interposed between the second clutch inner 79 and the second pressing member 82 so as to urge the second pressing member 82 toward the side to be crimped, and a cylindrical shape. A cylindrical portion 84a slidably fitted to a certain second main shaft 34 is provided on one end side, and the other end is slidably fitted to the right cover 29 and arranged coaxially with the second pressing member 82. And a second lifter 84 as a switching actuating member connected to the inner peripheral portion of the second pressing member 82 via a second release bearing 85, and the other end of the second lifter 84 is not shown. As it is driven to rotate by an actuator Second turning axis 86 slidably fitted in the right cover 29 and is interlocked with the second lifter 84 by the rotation to drive the axial direction, are connected.

  Rotational power from the crankshaft 22 is transmitted to the second main shaft 34 via a second primary reduction gear train 40 and a second clutch 42. The second primary reduction gear train 40 is The second primary drive gear 87 is fixed to the right end portion of the shaft 22, and the second primary driven gear 88 is meshed with the second primary drive gear 87 and arranged coaxially with the second main shaft 34. The second primary driven gear 88 is supported by the second main shaft 34 so as to be relatively rotatable, and is connected to the second clutch outer 77 via a second damper spring 89.

  Between the first and second lifters 69, 84 of the first and second clutches 41, 42 configured to be connected by the spring biasing force of the first and second clutch springs 68, 83, the first and second mains An alternate disengagement / contact assist mechanism 90A having at least a rod 91 inserted coaxially into the shafts 33, 34 is interposed so as to assist the alternate disengagement / contact of the first and second clutches 41, 42. .

  The alternate break / contact assist mechanism 90A includes a coil spring 92 as an elastic member interposed between at least one of the first and second lifters 69 and 84 and the rod 91. In this embodiment, the coil spring 92 is interposed between the first lifter 69 of the first and second lifters 69 and 84 and the rod 91.

  That is, one end of the rod 91 is slidably fitted into the cylindrical portion 69a of the first lifter 69, and a coil spring 92 provided between the one end of the rod 91 and the first lifter 69 is placed in the cylindrical portion 69a. Be contained. The other end of the rod 91 is fitted into the cylindrical portion 84 a of the second lifter 84, and the other end of the rod 91 is in contact with the second lifter 84.

  According to such an alternate disengagement / contact assist mechanism 90A, the second lifter 84 is connected to the third and fourth friction plates 78, 78 to bring the second clutch 42 out of the first and second clutches 41, 42 into an engaged state. When 80, 80... Are moved to the pressure-bonding side, the rod 91 moves to the side that compresses the coil spring 92 on the first clutch 41 side. For this reason, when the operation of driving the first lifter 69 is delayed to the side where the first clutch 41 is disengaged or the first clutch 41 cannot be disconnected due to an actuator failure or the like, the first lifter 69 is compressed. The load of the coil spring 92 is applied. Thus, when the load of the first clutch spring 68 in the first clutch 41 is F1, and the load of the coil spring 92 when the first and second clutches 41 and 42 are both in the connected state is FC, The effective load in one clutch 41 is (F1-FC), and the clutch capacity is reduced. Further, when the first lifter 69 moves to the side where the first and second friction plates 63, 63... 65, 65. When the operation of driving the second lifter 84 is delayed or the second clutch 42 cannot be disconnected due to an actuator failure or the like, the load of the compressed coil spring 92 acts on the second lifter 84. Therefore, when the load of the second clutch spring 83 in the second clutch 42 is F2, the effective load in the second clutch 42 is (F2-FC), and the clutch capacity is reduced.

  Moreover, the length of the rod 91 is longer than the length between the lifters 69 and 84 when the first and second clutches 41 and 42 are both connected, and only one of the first and second clutches 41 and 42 is present. Is set to be shorter than the length between the lifters 69 and 84 in the connected state.

  Next, the operation of this embodiment will be described. First and second lifters 69 of the first and second clutches 41 and 42 configured to be connected by the spring biasing force of the first and second clutch springs 68 and 83. , 84 includes an alternate disengagement / contact assist mechanism 90A having at least a rod 91 that is coaxially inserted into the first and second main shafts 33, 34, and alternately disengages the first and second clutches 41, 42. Since it is provided so as to assist the contact, the switching between the first and second clutches 41 and 42 can be performed more smoothly, and the pair of clutches 41 and 42 can be configured with a simple configuration with a reduced number of parts. Can be prevented from occurring simultaneously.

  Further, since the alternate breaking / contact assist mechanism 90A includes a coil spring 92 interposed between at least one of the first and second lifters 69, 84 and the rod 91, the alternate breaking / contacting mechanism 90A. The operation sound can be reduced by the coil spring 92 when the assist mechanism 90A is operated, and the axial positioning of the rod 91 can be achieved by the coil spring 92.

  In addition, since the coil spring 92 is interposed between one of the first and second lifters 69 and 84 and the rod 91, the gap between both the first and second lifters 69 and 84 and the rod 91 is provided. The number of parts can be reduced as compared with the case where the coil spring 92 is interposed.

  Further, the length of the rod 91 is longer than the length between the lifters 69 and 84 when both the first and second clutches 41 and 42 are in the connected state, and only one of the first and second clutches 41 and 42 is present. Is set to be shorter than the length between the lifters 69 and 84 in the connected state, so that even if the first and second clutches 41 and 42 cannot be disconnected due to an actuator failure or the like, the rod 91 Is in contact with both the first and second lifters 69 and 84 to prevent both the first and second clutches 41 and 42 from being connected to each other. It does not hinder 42 alternate disconnection and contact.

  The second embodiment of the present invention will be described with reference to FIG. 5, but the parts corresponding to the first embodiment are only shown with the same reference numerals, and the detailed description is omitted. To do.

  Between the first and second lifters 69, 84 of the first and second clutches 41, 42 configured to be connected by the spring biasing force of the first and second clutch springs 68, 83, the first and second mains An alternate disengagement / contact assist mechanism 90B having at least a rod 93 inserted coaxially into the shafts 33, 34 is interposed so as to assist alternate disengagement / contact of the first and second clutches 41, 42. .

  The alternate disengagement / contact assist mechanism 90B is configured to assist the disengagement / contact of the first and second clutches 41, 42 by directly pushing the first and second lifters 69, 84 at the ends of the rod 93. Between the rod 93 and one of the first and second lifters 69 and 84, positioning of the rod 93 in the first and second main shafts 33 and 34, and tolerance absorption The coil spring 94 for achieving the above is interposed so as to exert a very weak spring force.

  According to the second embodiment, the alternate break / contact assist mechanism 90B is configured to directly push the first and second lifters 69, 84 of the first and second clutches 41, 42 at the end of the rod 93. Therefore, the positional accuracy of the first and second lifters 69 and 84 is improved.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. Is possible.

21 ... Crankcase 22 as an engine case ... Crankshaft 33 ... First main shaft 34 ... Second main shaft 41 ... First clutch 42 ... Second clutch 43 ... Counter shafts 69, 84... Lifters 90A, 90B as switching operation members. Alternate cutting / contact assist mechanisms 91, 93... Rod 92 .. Coil springs G1, G2, G3 which are elastic members. G4, G5, G6 ... Gear train P ... Power unit

Claims (5)

  A crankshaft (22) extending in the left-right direction of the vehicle, first and second main shafts (33, 34) arranged in parallel and coaxially with an axis parallel to the crankshaft (22); A counter shaft (43) having an axis parallel to the second main shaft (33, 34) is rotatably supported by the engine case (21), and the first and second main shafts (33, 34) and the counter are supported. A gear train (G1, G2, G3, G4, G5, G6), which is selectively established, is provided between the shaft (43) and the first and second gear trains from the crankshaft (22). The first and second clutches (41, 42) that connect and disconnect the rotational power transmitted to the main shaft (33, 34) are opposed to each other between the first and second main shafts (33, 34). In the vehicular power unit disposed at the end of the first and second clutches (41 and 41), the first and second clutches (41) are switched by operating in the axial direction of the first and second main shafts (33, 34). , 42) between the switching actuating members (69, 84) respectively provided at least with rods (91, 93) inserted coaxially into the first and second main shafts (33, 34). A power unit for a vehicle, wherein the assist mechanism (90A, 90B) is interposed so as to assist alternate disconnection / contact of the first and second clutches (41, 42).   The alternate disconnection / contact assist mechanism (90A) is interposed between at least one of the switching operation members (69, 84) of the first and second clutches (41, 42) and the rod (91). The vehicular power unit according to claim 1, further comprising an elastic member (92).   The elastic member (92) is interposed between any one of the switching operation members (69, 84) of the first and second clutches (41, 42) and the rod (91). The vehicle power unit according to claim 2.   The alternate disengagement / contact assist mechanism (90B) directly pushes the switching operation members (69, 84) of the first and second clutches (41, 42) at the end of the rod (93). 4. The vehicle power unit according to claim 1, wherein the vehicle power unit is configured to assist disconnection / connection of the second clutch (41, 42).   The length of the rods (91, 93) is longer than the length between the switching operation members (69, 84) when both the first and second clutches (41, 42) are in the connected state. And the length of the switching member (69, 84) when only one of the second clutches (41, 42) is in a connected state is set to be shorter. A power unit for a vehicle according to any one of the above.

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