WO2023053305A1

WO2023053305A1 - Power unit

Info

Publication number: WO2023053305A1
Application number: PCT/JP2021/036001
Authority: WO
Inventors: 大荒井; 飛鳥伊東; 直樹石井
Original assignee: 本田技研工業株式会社
Priority date: 2021-09-29
Filing date: 2021-09-29
Publication date: 2023-04-06

Abstract

In a shift drive mechanism (60) of this power unit, when driving, by means of a shift driven gear (83), a drum center (82) that is connected to an end portion of a shift drum (80) and rotates synchronously with the shift drum, a driving engagement portion (83d) formed in the shift driven gear (83) and a driven engagement portion (82d) formed in the drum center (82) can be engaged in the circumferential direction while having an idle angle (θ) therebetween in the circumferential direction, so that the rotation of the shift drum (80) is ultimately set by the drum center (82) and a stopper mechanism (90). Accordingly, the driving accuracy of a shift motor (61) can be roughly set and no improvement in the performance of the shift motor (61) or accuracy of an angle sensor, etc., of a control system is required, whereby cost reduction can be achieved.

Description

power unit

The present invention relates to a power unit in which an internal combustion engine and a transmission are integrally supported by a crankcase, and in which the transmission has a transmission drive mechanism that shifts the transmission by moving a shift fork caused by rotation of a shift drum. .

In the transmission drive mechanism of the transmission in this type of power unit, there are examples (for example, Patent Document 1, etc.) that use a motor (shift motor) as a drive source for rotating the shift drum.

Japanese Patent Application Laid-Open No. 2017-48908

In the transmission drive mechanism of the transmission disclosed in Patent Document 1, between the motor gear integrally attached to the output shaft of the motor and the actuator gear integrally engaged with the gear shift cam (corresponding to the shift drum), the An idle gear (reduction gear) is interposed.

In the transmission drive mechanism disclosed in Patent Document 1, rotation of the output shaft of the motor rotates the actuator gear through meshing of the gears of the idle gear, thereby rotating the gear shift cam integrated with the actuator gear.

That is, since the rotation of the output shaft of the motor is always transmitted to the rotation of the gear shift cam at a constant speed reduction ratio, it is necessary to improve the driving accuracy of the motor in order to accurately rotate the gear shift cam. Therefore, as the performance of the motor becomes higher, the rotation angle sensor for detecting the rotation angle of the gear shift cam or the like for controlling the drive of the motor is required to have higher accuracy, resulting in an increase in cost.

In addition, when the motor malfunctions, the gear shift cam (shift drum) rotates through the gear in synchronization with the motor malfunction, which may affect the gear shift cam.

The present invention has been made in view of this point, and its purpose is to enable rough setting of the driving accuracy of the motor, to reduce the cost, and to reduce the influence on the shift drum, etc., even when the motor malfunctions. to provide a power unit having a transmission that does not provide

In order to achieve the above object, the present invention
A power unit in which an internal combustion engine and a transmission are integrally supported by a crankcase,
The transmission is
a transmission having gear pairs with different gear ratios for power transmission;
a shift drive mechanism that rotates a shift drum by driving a shift motor, and shifts gears by changing a pair of gears for transmitting power of the transmission by movement of a shift fork guided by the shift drum;
In the power unit equipped with
a drum center connected to an end of the shift drum and rotating in synchronization with the shift drum;
a stopper mechanism for positioning the drum center;
a shift driven gear that rotates in synchronism with the shift motor and is arranged to be engageable with the drum center;
prepared,
A driving engagement portion formed on the shift driven gear and a driven engagement portion formed on the drum center are circumferentially engageable with a play angle therebetween. We provide a power unit that

According to this configuration, the stopper mechanism is provided, and the drive engagement portion of the shift driven gear and the driven engagement portion of the drum center can be engaged in the circumferential direction with a play angle therebetween. Because of this play angle, the rotation of the shift drum is finally set by the drum center and the stopper mechanism. High accuracy of the rotation angle sensor of the control system is not required, and the cost can be reduced.

Further, when the shift motor operates abnormally, the drive of the shift motor can be stopped before the play angle between the driving engagement portion and the driven engagement portion is reduced and the shift drum starts rotating. It is possible to prevent the abnormal operation from affecting the drum or the like.
Furthermore, since the shift motor rotates the drive engagement portion so as to reduce the play angle between the drive engagement portion and the driven engagement portion immediately after the start of driving, the shift motor can be accelerated until the play angle is reduced. The drum center can be rotated by acceleration, and the driving force of the shift motor can be set small.

In a preferred embodiment of the invention,
The shift driven gear and the drum center have a plurality of the driving engagement portions and the driven engagement portions that are engaged with each other at equal intervals in the circumferential direction.

With this configuration, the force applied from the shift driven gear to the drum center can be dispersed, and durability can be improved.

In a preferred embodiment of the invention,
The driven engagement portion of the drum center is formed to protrude in the direction of the rotation axis in a fan shape that widens outward in the radial direction around the rotation center axis.

According to this configuration, when the drive engagement portion of the shift driven gear engages with the driven engagement portion of the drum center to transmit the power, the driven engagement portion forms a fan shape projecting in the direction of the rotation axis. force can be received by the entire side portion of the drum center, and concentration of the load on a part of the drum center can be suppressed.

In a preferred embodiment of the invention,
The shift driven gear has a hollow disk shape, and is recessed in the direction of the rotation axis in a fan shape that widens outward in the radial direction around the center axis of rotation in the hollow disk portion on the outer periphery of the hollow circle. A fan-shaped recess is formed,
a pair of side sides forming a pair of side sides of the fan-shaped concave portion of the hollow disc portion of the shift driven gear are a pair of the driving engagement portions;
When the fan-shaped driven engagement portion of the drum center is fitted into the fan-shaped recessed portion of the shift driven gear, the drum is positioned between the pair of drive engagement portions, which are the pair of side portions of the shift driven gear. The driven engagement portion of the center is loosely fitted with the play angle in the circumferential direction.

According to this configuration, when the fan-shaped driven engagement portion of the drum center is fitted into the fan-shaped recessed portion of the shift driven gear, the fan-shaped drum center is positioned between the pair of fan-shaped driving engagement portions of the shift driven gear. Since the driven engagement portion is loosely fitted with the play angle in the circumferential direction, the shift driven gear and the drum center can be combined compactly in the rotation axis direction.

In the present invention, the stopper mechanism is provided, and the drive engagement portion of the shift driven gear and the driven engagement portion of the drum center are engageable in the circumferential direction with a play angle therebetween. Since the rotation of the drum is finally set by the drum center and stopper mechanism, the drive accuracy of the shift motor can be roughly set, and the performance of the motor and the accuracy of the rotation angle sensor of the control system can be improved. is not required, and the cost can be reduced.

In addition, since the drive engagement portion of the shift driven gear and the driven engagement portion of the drum center can be engaged with each other in the circumferential direction with a play angle in the circumferential direction, when the shift motor is abnormally The drive of the motor can be stopped before the play angle between the engaging portion and the driven engaging portion is reduced and the shift drum starts to rotate, thereby preventing the shift drum from being affected by abnormal operation. can be prevented.

Furthermore, since the driving engagement portion of the shift driven gear and the driven engagement portion of the drum center can engage with each other in the circumferential direction with a play angle in the circumferential direction, the shift motor immediately after the start of driving is Since the drive engagement portion is moved so as to reduce the play angle between the drive engagement portion and the driven engagement portion, the drum center can be rotated by accelerating until the play angle is reduced. , the driving force of the shift motor can be set small.

1 is a right side view of a motorcycle equipped with a power unit according to an embodiment of the invention; FIG. It is a right side view of the same power unit. It is a left side view of the same power unit. FIG. 3 is an exploded cross-sectional view of the same power unit taken along line IV-IV in FIG. 2; It is a left view which shows the reduction gear mechanism part of the same power unit. It is a partial right side view of the lower crankcase of the same power unit. FIG. 6 is an exploded cross-sectional view of the main parts of the same power unit taken along the line VII-VII in FIG. 5; It is a right side view of a drum center. It is a left side view of the same drum center. FIG. 10 is a cross-sectional view of the drum center taken along line XX of FIGS. 8 and 9; It is a left side view of a shift driven gear. FIG. 11 is a left side view showing a state in which the drum center and the shift driven gear are loosely fitted when the 1st gear position is set; FIG. 5 is a left side view showing the state of the drum center and the shift driven gear when the driving engagement portion of the shift driven gear comes into contact with the driven engagement portion of the drum center; FIG. 10 is a left side view showing a state in which the drum center and the shift driven gear are loosely fitted when set to a next gear position;

An embodiment according to the present invention will be described below with reference to FIGS. 1 to 14. FIG.
FIG. 1 is a side view of a motorcycle 1, which is a straddle-type vehicle equipped with a power unit according to one embodiment to which the present invention is applied.
In the description of this specification, the front, rear, left, and right directions are based on the normal standard that the straight traveling direction of the motorcycle 1 according to the present embodiment is the front. In the drawings, FR indicates the front, and RR indicates the rear. , LH indicates left and RH indicates right.

As shown in FIG. 1, a vehicle body frame 10 of a motorcycle 1 includes a head pipe 11 disposed in the front portion, and extends obliquely downward to the rear from the head pipe 11, bends in the middle, and extends rearward. A main frame 12, a center frame 13 extending downward from the rear end of the main frame 12, a seat rail 14 extending rearward from the upper portion of the center frame 13, and a rear portion of the center frame 13 and the seat rail. A midstay 15 that bridges the rear part of 14 and a down frame 16 that extends downward from the head pipe 11 are provided.

A front fork 17 that rotatably supports a front wheel 18 is steerably supported at the lower end of the head pipe 11 .
A steering handle 19 is connected to the upper end of the front fork 17 . A swing arm 21 is swingably supported by the center frame 13 via a pivot shaft 20 .
A rear wheel 23 is rotatably supported at the rear end of the swing arm 21 via a rear wheel axle 22 .

An occupant's seat 24 is attached above the seat rails 14, and a fuel tank 25 is mounted in front of the occupant's seat 24 and above the main frame 12.

In the motorcycle 1, a power unit P for driving the rear wheels 23 is supported by a plurality of mounting brackets 10a provided on the vehicle body frame 10, and is horizontally placed with the rotation axis of the crankshaft 32 oriented in the lateral direction of the vehicle body. is installed.
An endless chain 26 is stretched between the drive sprocket 42a fitted to the output shaft (counter shaft 42) of the power unit P and the driven sprocket 22a fitted to the rear wheel shaft 22 (Fig. 3).

As shown in FIG. 2, the power unit P integrally includes a water-cooled 2-cylinder 4-stroke cycle internal combustion engine 3 and a transmission 4 connected to the rear of the internal combustion engine 3 .
In the power unit P, a crankcase 31 that rotatably supports a crankshaft 32 extends rearward to accommodate the transmission 4 .
The crankcase 31 is vertically divided into an upper crankcase 31U and a lower crankcase 31D.

The upper crankcase 31U consists of a left case side wall _31UL , a right _case side wall _31UR facing each other, and an upper case peripheral wall 31US formed integrally with each of the upper peripheral edges except for the split surfaces thereof and extending left and right. The lower crankcase 31D is composed of a left case side wall 31D _L and a right case side wall 31D _R which face each other on the left and right sides, and a lower case peripheral wall formed integrally with each lower side peripheral edge except for the split surface thereof so as to extend to the left and right. 31D _S.

A cylinder block 34, a cylinder head 35, and a head cover 36 are successively stacked obliquely forward and upward on the front half of the upper case peripheral wall 31US of the upper crankcase _31U , and project obliquely forward.
The bottom of the lower case peripheral wall 31DS of the lower crankcase _31D is open, and an oil pan 37 is provided so as to protrude downward.
The right opening of the cylinder wall formed by combining the upper case peripheral wall _31US and the lower case peripheral wall _31DS of the crankcase 31 is covered with a right crankcase cover 38R (see FIG. 4), and the left opening of the cylinder wall is It is covered by the left crankcase cover 38L.

A crankshaft 32 oriented in the lateral direction of the vehicle body is pivotally supported between the split surfaces of the upper crankcase 31U and the lower crankcase 31D.
That is, the left and right case side walls _31UL and _31UR of the upper crankcase 31U are separated from the left and right case side walls _31DL and _31DR of the lower crankcase 31D. They are put together and axially supported so that the crankshaft 32 is sandwiched therebetween.

The transmission 4 that shifts the driving force of the internal combustion engine 3 to a predetermined gear shift includes a constant mesh transmission 40, a shift drive mechanism 60 that operates the gear shift of the transmission 40, and a clutch mechanism 53. I have.
Referring to FIG. 4, transmission 40 includes a constant mesh gear group 50 provided on main shaft 41 and counter shaft 42 .

As shown in FIGS. 2 and 4, the main shaft 41 is arranged in the upper crankcase 31U in parallel with the rotation axis of the crankshaft 32, obliquely upward to the rear of the crankshaft 32. As shown in FIGS.
The left end of the main shaft 41 is connected to the left case side wall 31UL of the upper crankcase 31U via a ball bearing ₄₃ , the center is connected to the right case side wall 31UR of the upper crankcase 31U _via a ball bearing 44, and the right end is connected to a ball bearing 45. are rotatably supported by the right crankcase cover 38R via the .

The counter shaft 42 is arranged in parallel with the main shaft 41, sandwiched between the upper and

lower crankcases

31U and 31D, at a position obliquely below the rear of the main shaft 41. As shown in FIG.
The left end of the counter shaft 42 passes through a ball bearing 46, the left end of the counter shaft 42 passes through the ball bearing 46, and the right end of the counter shaft 42 passes through the needle bearing 47. there is
The left end of the counter shaft 42 is fitted with a drive sprocket 42a.

As shown in FIG. 4, the main shaft 41 is composed of a long main shaft inner shaft 41A, a main shaft outer shaft 41B, and a clutch portion outer shaft 41C.
The main shaft outer shaft 41B covers the main shaft inner shaft 41A from the center to the center of the left half thereof via a needle bearing 48 so as to be relatively rotatable.
The clutch portion outer shaft 41c covers the main shaft inner shaft 41a from the center to the right end thereof via a needle bearing 49 so as to be relatively rotatable.

The main shaft 41 is provided with six driving gears m1 to m6 having gear ratios from 1st to 6th, and the counter shaft 42 is provided with 6 driven gears c1 to c6 from 1st to 6th. It is
The driving gears m1 to m6 and the driven gears c1 to c6 are arranged in the order of second, sixth, fourth, third, fifth, and first gears from the right side and mesh with each other. and the driven gears c1 to c6 constitute a gear group 50. As shown in FIG.
The drive gears m2, m4 and m6 for even-numbered gears are provided on the outer main shaft 41B, and the drive gears m1, m3 and m5 for odd-numbered gears are provided on the inner main shaft 41A.

In FIG. 4, the suffix x attached to the reference numerals of the driving gears m1 to m6 and the driven gears c1 to c6 indicates fixed gears integrally molded with the shaft 41, and the suffix w indicates the supported

shafts

41 and 42. The suffix s indicates a free gear supported so as to be relatively rotatable, and the suffix s indicates a shifter gear that rotates integrally with the supported

shafts

41 and 42 and is movable in the axial direction.
That is, the first-speed drive gear m1 and the second-speed drive gear m2 are fixed gears, the fifth-speed drive gear m5, the sixth-speed drive gear m6, the first-speed driven gear c1, the second-speed driven gear c2, the third-speed driven gear c3 and the fourth-speed driven gear c3. The speed driven gear c4 is a free gear, and the third speed drive gear m3, fourth speed drive gear m4, fifth speed driven gear c5 and sixth speed driven gear c6 are shifter gears.

A dog clutch 51 is provided between each shifter gear m3, m4, c5, c6 and each free gear m5, m6, c1, c2, c3, c4 adjacent to each shifter gear m3, m4, c5, c6, When the shifter gears m3, m4, c5, and c6 approach the adjacent free gears m5, m6, c1, c2, c3, and c4, the dog clutch 51 engages to connect both gears so as not to rotate relative to each other.
Fork grooves 52 with which fork portions of a shift fork 87 (to be described later) are engaged are formed along the circumferential direction on the outer peripheral surfaces of the respective shifter gears m3, m4, c5 and c6.

A first hydraulic clutch 53A and a second hydraulic clutch 53B are arranged on the right half of the main shaft 41 with a primary driven gear 54 fitted in the center of the clutch outer shaft 41C so as not to rotate relative to each other. A clutch mechanism 53 of a dual-clutch transmission is provided.
The power of the crankshaft 32 is transmitted to the clutch mechanism 53 via the primary drive gear 33 fitted on the crankshaft 32 and the primary driven gear 54, and the first hydraulic clutch 53A and the second hydraulic clutch 53B are connected to the hydraulic circuit. By selectively connecting through 55, power is transmitted from the crankshaft 32 to the main shaft inner shaft 41A and the main shaft outer shaft 41B.

As shown in FIG. 7, the shift drive mechanism 60 for moving the shifter gears m3, m4, c5, and c6 of the transmission 40 to switch gear stages includes a shift motor 61, a reduction gear mechanism 70, a shift spindle 75, and a shift drum. 80, a shift fork shaft 86 and a shift fork 87.

The shift drum 80 _consists of a cylindrical drum main body 80A and a left drum shaft 80B. ing.
A drum center 82 is coaxially fixed by a bolt 81 to the right end of the right cylindrical portion 80A _R on the right side of the portion of the drum main body 80A where the lead groove 80v is formed. is pivotally supported on the right case side wall 31D _R via the .

The shift drum 80 is arranged below the main shaft 41 in parallel with the main shaft 41, that is, oriented in the left-right direction, and is rotatably supported by a needle bearing 84 and a ball bearing 85. As shown in FIG.
The end of the drum left shaft portion 80B passing through the needle bearing 84 of the shift drum 80 is attached to a drum angle sensor 89 provided on the gear case cover 65, which will be described later.
The rotation angle of the shift drum 80 is detected by this drum angle sensor 89 .

Referring to FIGS. 8 to 10, a drum center 82 fixed to the right end of a shift drum 80 has a cylindrical portion 82a with an enlarged outer diameter on the right side to form an enlarged diameter disk portion 82b. A star-shaped cam 82c is formed by enlarging the outer diameter of the right opening end on the right side of the enlarged diameter disc portion 82b of the cylindrical portion 82a, and the rotation center is located on the left side of the enlarged diameter disc portion 82b of the cylindrical portion 82a. A driven engagement portion 82d is formed so as to protrude leftward from the diameter-enlarged disc portion 82b, forming a fan shape that widens toward the outside in the radial direction with the shaft as the core of the fan.

Three driven engagement portions 82d radially protrude from the outer peripheral surface of the cylindrical portion 82a at equal intervals in the circumferential direction.
In the drum center 82, a diameter-reduced portion 82e formed by reducing the diameter of the left open end of the cylindrical portion 82a is in contact with the right end portion of the right cylindrical portion _80AR of the shift drum 80 and fixed by a bolt 81. As shown in FIG.

A shift driven gear 83 is rotatably supported on the outer peripheral surface of the cylindrical portion 82a of the drum center 82. As shown in FIG.
As shown in FIG. 11, the shift driven gear 83 is in the shape of a hollow disc, and spreads radially outward on a hollow disc portion 83b on the outer periphery of the hollow circle 83a, with the central axis of rotation being the center of a fan. A fan-shaped recessed portion 83c recessed in the rotation axis direction is formed.
The fan-shaped recessed portion 83c penetrates the hollow disk portion 83b by recessing it in the rotation axis direction.

A pair of side portions forming a pair of side sides of the fan-shaped recessed portion 83c in the hollow disk portion 83b of the shift driven gear 83 are a pair of driving engagement portions 83d.
The sector-shaped concave portions 83c of the shift driven gear 83 are formed so as to radially protrude from the hollow circle 83a at equal intervals in the circumferential direction.
Gear teeth 83e are formed on the outer peripheral edge of the hollow disk portion 83b of the shift driven gear 83. As shown in FIG.

Referring to FIG. 12, the inner diameter of the hollow disc portion 83b of the shift driven gear 83 (the outer diameter of the hollow circle 83a) is substantially equal to the outer diameter of the cylindrical portion 82a of the drum center 82. The cylindrical portion 82a of the drum center 82 is fitted into the hollow circle 83a inside the shift driven gear 83b, and the three driven engagement portions 82d of the drum center 82 are fitted into the three fan-shaped recessed portions 83c of the shift driven gear 83.

The angle α between the pair of sides of the fan-shaped recessed portion 83c of the shift driven gear 83 (the angle between the pair of fan-shaped drive engagement portions 83d) is Between a pair of drive engagement portions 83d, which are the pair of side portions of the shift driven gear 83, the driven engagement portion 82d of the drum center 82 forms a play angle θ in the circumferential direction. and loosely fitted so as to be relatively rotatable.

FIG. 12 shows the state when stopped at a certain gear position, and there are a first play angle θ1 and a second play angle θ2 on both sides of the driven engagement portion 82d.
The sum of the first play angle .theta.1 and the second play angle .theta.2 is the so-called play angle .theta.(=.theta.1+.theta.2=.alpha.-.beta.).

As shown in FIG. 3, the left crankcase cover _38L , which covers the left side of the left case side wall 31DL of the lower crankcase 31D, is provided with a reduction gear mechanism 70 which is covered with the gear case cover 65 slightly behind the center. It is
As shown in FIG. 7, the reduction gear mechanism 70 is provided as a reduction gear train within the gear case between the left crankcase cover 38L and the gear case cover 65 attached to the left side thereof.

A shift motor 61 is attached to the lower part of the gear case cover 65 so as to protrude leftward, and a drive gear 71 formed on the drive shaft of the shift motor 61 penetrates the gear case cover 65 rightward and protrudes into the gear case. (See Figure 7).
On the other hand, in the vicinity of the lower part of the shift drum 80, a shift spindle 75 is oriented in the left-right direction and mounted on the left case side wall _31DL and the right case side wall _31DR of the lower crankcase 31D, and is rotatably supported. there is

As shown in FIG. 7, the shift spindle 75 penetrates the right case side wall 31D _R rightward, reaches the right crankcase cover 38R at its right end, and reaches the spindle angle sensor 78 provided on the right crankcase cover 38R. attached to the
The rotation angle of the shift spindle 75 is detected by this spindle angle sensor 78 .

A shift drive gear 76 is fitted to a portion of the shift spindle 75 which penetrates the right case side wall 31D _R to the right.
This shift drive gear 76 meshes with (the gear teeth 83e of) a shift driven gear 83 which is loosely fitted in a drum center 82 integrally attached to the right end of a shift drum 80 with a play angle in the circumferential direction so as to be relatively rotatable. do.
The shift driven gear 83 has more teeth than the shift drive gear 76, and power is transmitted at a reduced speed.

As shown in FIG. 7, the shift spindle 75 penetrates the left case side wall _31DL to the left, and the left end is inserted into the gear case.
A reduction gear mechanism 70 is formed between a spindle driven gear 74 fitted to the left end of the shift spindle 75 and a drive gear 71 of the drive shaft of the shift motor 61 .

Between the drive gear 71 and the spindle driven gear 74, two first and

second gear shafts

72, 73 are oriented in the left-right direction and are rotatably supported at both ends by the gear case cover 65 and the left crankcase cover 38L. erected.
The drive gear 71 of the shift motor 61 meshes with the large diameter gear 72L of the first gear shaft 72, the small diameter gear 72S of the first gear shaft 72 meshes with the idle gear 73I of the second gear shaft 73, and the second gear shaft 73 The idle gear 73I meshes with the spindle driven gear 74 of the shift spindle 75 to form a reduction gear mechanism 70. As shown in FIG.

Therefore, the rotation of the drive gear 62 of the shift motor 61 is decelerated through the reduction gear train of the reduction gear mechanism 70 and transmitted to the rotation of the shift spindle 75, and the rotation of the shift spindle 75 meshes with the shift drive gear 76. Rotate the driven gear 83 .
The rotation of the shift driven gear 83 rotates together with the shift drum 80 a drum center 82 which has a play angle θ in the circumferential direction and is loosely fitted so as to be relatively rotatable.

By rotating the shift drum 80, the shift fork 87 is guided by the lead groove 80v formed on the outer peripheral surface of the shift drum 80 and moves in the axial direction, thereby moving the shifter gears m3, m4, c5, The gear stage of the transmission 40 is switched by moving c6 in the axial direction.

Referring to FIG. 8, a star-shaped cam 82c formed on a drum center 82 fixed to the right end of a shift drum 80 has a concave-convex cam surface in which a plurality of concavities and convexities are alternately arranged at regular intervals on its outer peripheral surface. It is

As shown in FIG. 6, the uneven cam surface of the star-shaped cam 82c is provided with a stopper mechanism 90 for pressing a stopper roller 93 pivotally supported at the tip of a stopper arm 92 which is biased to swing. .
The stopper mechanism 90 positions the shift drum 80 at the rotation position of the required shift stage by fitting the stopper roller 93 into the concave portion of the uneven cam surface of the star-shaped cam 82c.

In a dual-clutch transmission, when shifting from 1st to 2nd, the gear position of the shift drum changes from the 1st speed position (1-N) to the 1st speed and 2nd speed preliminary shift position (1-2). It switches to the second speed position (N-2).

Since this transmission 40 is of a dual-clutch type and has six speed stages, there are 12 gear positions (N - N, 1-N, 1-2, N-2, 3-2, 3-N, 3-4, N-4, 5-4, 5-N, 5-6, N-6) are set on the shift drum 80 Therefore, each gear position interval is 30 degrees.
Therefore, twelve recesses are formed at intervals of 30 degrees on the concave-convex cam surface of the star-shaped cam 82c for positioning the shift drum 80 by the stopper mechanism 90. As shown in FIG.

As described above, referring to FIG. 12, the drum center 82 integrated with the shift drum 80 and the shift driven gear 83 are loosely fitted with a play angle .theta.
In order to smoothly transmit power from the shift driven gear 83 to the shift drum 80, it is desirable that the play angle θ (=α−β) is about 10 to 30% of the gear position interval.
In this transmission 4, since the gear position interval is 30 degrees, the play angle θ is set to about 3 to 9 degrees.

FIG. 12 shows a state when the drum center 82 is stopped at a certain gear position, the drum center 82 is positioned by the stopper mechanism 90, and the shift driven gear 83 has the first play on both sides of the driven engagement portion 82d. A neutral state in which the angle θ1 and the second play angle θ2 are equal is shown.

In order to switch the gear position from this state, the shift motor 61 is driven and the shift driven gear 83 is controlled to rotate toward the neutral position (target position) of the next gear position.
When the shift motor 61 is driven to rotate the shift driven gear 83 via the reduction gear mechanism 70, the shift spindle 75, and the shift drive gear 76, the pair of driving engagement portions 83d of the shift driven gear 83 rotates backward in the rotational direction. The engaging portion 83d abuts against the driven engaging portion 82d of the drum center 82 with the first play angle θ1.

FIG. 13 shows a state in which the drive engaging portion 83d abuts against the driven engaging portion 82d.
After the driving engagement portion 83d of the shift driven gear 83 collides with the driven engagement portion 82d of the drum center 82, the driven engagement portion 82d is pushed and dragged with the driven engagement portion 82d. is separated from the drive engagement portion 83d and positioned at the next gear position rotated 30 degrees, and after a delay the shift driven gear 83 stops at the next gear position rotated to the neutral position, as shown in FIG. Enter the next gear position shown.

In the state shown in FIG. 14, the shift driven gear 83 is also in the neutral state where the first play angle .theta.1 and the second play angle .theta.2 on both sides of the driven engagement portion 82d are equal.
The above shows the ideal gear position state and operation when switching gear positions.

The embodiment of the power unit according to the present invention, which has been described in detail above, has the following effects.
As shown in FIG. 12, a drive engagement portion 83d formed on the shift driven gear 83 and a driven engagement portion 82d formed on the drum center 82 have a circumferential play angle θ therebetween. Because of this play angle θ, the rotation of the shift drum 80 is finally set by the drum center 82 and the stopper mechanism 90, so the drive accuracy of the shift motor 61 is can be roughly set, and high performance of the shift motor 61 and high accuracy of the angle sensor of the control system are not required, and the cost can be reduced.

Further, if the shift motor 61 has a relay that cuts off when the shift motor 61 is abnormally operated, the driving engagement portion 83d of the shift driven gear 83 and the driven engagement portion 82d of the drum center 82 are arranged circumferentially between each other. Since the drive engaging portion 83d has the play angle, an abnormality can be detected while the play angle is being reduced, the relay can be cut off, and the abnormal operation of the shift motor 61 can be stopped. It is possible to suppress the driving due to the abnormal operation of 61.

Furthermore, the shift motor 61 rotates the drive engagement portion 83d so as to reduce the play angle between the drive engagement portion 83d and the driven engagement portion 82d immediately after the start of driving, so the shift motor 61 accelerates until the play angle is reduced. It is possible to rotate the drum center 82 by acceleration, and the driving force of the shift motor 61 can be set small.

As shown in FIG. 12, the shift driven gear 83 and the drum center 82 have three driving engagement portions 83d and three driven engagement portions 82d that engage with each other at equal intervals in the circumferential direction. The force applied to the center 82 can be dispersed, and durability can be improved.

As shown in FIGS. 8 to 10, the driven engagement portion 82d of the drum center 82 is formed so as to protrude in the direction of the rotation axis in the shape of a fan that widens outward in the radial direction around the rotation center axis. Therefore, when the driving engagement portion 83d of the shift driven gear 83 engages with the driven engagement portion 82d of the drum center 82 to transmit power, the driven engagement portion 82d forms a fan shape and protrudes in the direction of the rotation axis. The entire fan-shaped side portion can receive force, and concentration of the load on a part of the drum center 82 can be suppressed.

Referring to FIGS. 7 and 12, shift driven gear 83 has a hollow disk shape, and spreads radially outward in a hollow disk portion 83b on the outer periphery of the hollow circle with the central axis of rotation serving as a fan. A fan-shaped recessed portion 83c recessed in the rotation axis direction is formed, and a pair of side portions forming a pair of fan-shaped sides of the fan-shaped recessed portion 83c in the hollow disk portion 83b of the shift driven gear 83. However, since the pair of driving engagement portions 83d are provided, when the fan-shaped driven engagement portion 82d of the drum center 82 is fitted into the fan-shaped recessed portion 83c of the shift driven gear 83, the pair of drive engagement portions 83d opened in the fan-shape of the shift driven gear 83 is engaged. Since the fan-shaped driven engagement portion 82d of the drum center 82 is loosely fitted between the engagement portions 83d with a play angle in the circumferential direction, the shift driven gear 83 and the drum center 82 can be made compact in the rotation axis direction. Can be combined.

Although the power unit according to one embodiment of the present invention has been described above, aspects of the present invention are not limited to the above-described embodiment, and may be implemented in various aspects within the scope of the gist of the present invention. includes.

P... power unit, m1 to m6... drive gear, c1 to c6... driven gear, m3, m4, c5, c6... shifter gear,
DESCRIPTION OF SYMBOLS 1... Motorcycle, 3... Internal combustion engine, 4... Transmission,
10... Body frame, 11... Head pipe, 12... Main frame, 13... Center frame, 14... Seat rail, 15... Mid stay, 16... Down frame, 17... Front fork, 19... Steering handle, 20... Pivot axis , 23 ... rear wheel, 24 ... passenger seat, 25 ... fuel tank,
31 Crankcase 31U Upper crankcase _31UL Left case _{side wall 31UR Right case side wall 31U S} _Upper case peripheral wall 31D Lower crankcase 31D _L Left case side wall 31D _R Right Case side wall, 31D _S ... lower case peripheral wall, 31D _SR ... right rear case peripheral wall portion, 32 ... crankshaft, 33 ... primary drive gear, 34 ... cylinder block, 35 ... cylinder head, 36 ... head cover, 37 ... oil pan, 38R...Right crankcase cover, 38L...Left crankcase cover,
40...Transmission, 41...Main shaft, 42...Counter shaft, 43...Ball bearing, 44...Ball bearing, 45...Ball bearing, 46...Ball bearing, 47...Needle bearing,
50... gear group, 51... dog clutch, 52... fork groove, 53... clutch mechanism, 54... primary driven gear, 55... hydraulic circuit,
60... gear shift drive mechanism, 61... shift motor, 62... drive gear, 65... gear case cover,
70...reduction gear mechanism, 71...drive gear, 72...first gear shaft, 72L...large diameter gear, 72S...small diameter gear, 73...second gear shaft, 73I...idle gear, 74...spindle driven gear, 75...shift spindle , 76 ... shift drive gear, 78 ... spindle angle sensor,
80... shift drum, 80A... drum main body, 80v... lead groove, 80A _R ... right cylindrical part, 80B... left drum shaft part, 80d... recessed part, 81... bolt,
82... Drum center 82a... Cylindrical part 82b... Expanded disc part 82c... Star-shaped cam 82d... Driven engaging part 82e... Reduced diameter part
83... shift driven gear, 83b... hollow disk portion, 83c... fan-shaped recessed portion, 83d... driving engaging portion, 83e... gear tooth,
84...needle bearing, 85...ball bearing, 86...shift fork shaft, 87...shift fork, 88...neutral switch, 89...drum angle sensor,
90... Stopper mechanism, 92... Stopper arm, 93... Stopper roller.

Claims

A power unit in which an internal combustion engine (3) and a transmission (4) are integrally supported by a crankcase (31),
The transmission (4) is
a transmission (40) having gear pairs with different gear ratios for power transmission;
The shift drum (80) is rotated by driving the shift motor (61), and the shift fork (87) guided by the shift drum (80) shifts the gear pair for power transmission of the transmission (40). a speed change drive mechanism (60) that changes and changes speed;
In the power unit equipped with
a drum center (82) connected to an end of the shift drum (80) and rotating in synchronization with the shift drum (80);
a stopper mechanism (90) for positioning the drum center (82);
a shift driven gear (83) that rotates in synchronism with the shift motor (61) and is arranged to engage with the drum center (82);
prepared,
A drive engagement portion (83d) formed in the shift driven gear (83) and a driven engagement portion (82d) formed in the drum center (82) form a circumferential play angle (θ) therebetween. A power unit, characterized in that it has and is circumferentially engageable.
The shift driven gear (83) and the drum center (82) each have a plurality of the driving engagement portions (83d) and the driven engagement portions (82d) that are engaged with each other at equal intervals in the circumferential direction. The power unit according to claim 1, wherein
The driven engagement portion (82d) of the drum center (82) is formed to protrude in the direction of the central axis of rotation, forming a fan shape that widens radially outward with respect to the central axis of rotation. The power unit according to claim 1 or 2, wherein
The shift driven gear (83) is in the shape of a hollow disc, and rotates in a fan shape that expands outward in the radial direction around the central axis of rotation in a hollow disc portion (83b) on the outer periphery of the hollow circle. A fan-shaped recessed portion (83c) recessed in the axial direction is formed,
A pair of side portions forming a pair of side sides of the fan-shaped recessed portion (83c) in the hollow disc portion (83b) of the shift driven gear (83) are connected to the pair of drive engagement portions (83d). ) and
When the fan-shaped driven engagement portion (82d) of the drum center (82) is fitted into the fan-shaped recessed portion (83c) of the shift driven gear (83), the pair of side portions of the shift driven gear (83) The driven engagement portion (82d) of the drum center (82) is loosely fitted with the play angle (θ) in the circumferential direction between the pair of drive engagement portions (83d). A power unit according to claim 3, characterized by: