JP4849554B2 - Engine unit and saddle riding type vehicle equipped with the same - Google Patents

Description

  The present invention relates to an engine unit and a straddle-type vehicle including the same.

  An engine unit including a belt type continuously variable transmission (hereinafter referred to as CVT) has been used as an engine unit of a saddle-type vehicle such as a motorcycle. The CVT includes a primary sheave that rotates together with the crankshaft, and a secondary sheave connected to the primary sheave via a belt. In the engine unit, the rotation of the crankshaft of the engine is transmitted to the output shaft via the CVT.

  A pair of crank webs are provided at the center of the crankshaft. The pair of crank webs are connected by a crank pin, and a connecting rod is connected to one end of the crank pin. The piston of the engine is connected to the other end of the connecting rod. In the engine unit, the reciprocating motion of the piston is converted into rotational motion by the connecting rod and the crankpin, and the crankshaft rotates.

  By the way, the above-mentioned piston reciprocates at high speed. Therefore, when the piston is at the top dead center or the bottom dead center, a large inertial force acts near the crankpin of the crankshaft. As a result, when the crankshaft rotates, the crankshaft swings, causing vibration. Such vibration is a problem because it adversely affects precision machines such as control devices and also causes noise.

  In view of this, an engine unit has been proposed in which a balance weight is provided on a crankshaft or a balancer shaft provided in parallel with the crankshaft, thereby eliminating the unbalance of rotation around the crankshaft (see, for example, Patent Document 1).

In the engine unit shown in Patent Document 1, the inertial force generated by the high-speed reciprocation of the piston is reduced by the centrifugal force of the balance weight that rotates at the same speed as the crankshaft, thereby suppressing vibration and the like.
JP 2006-214551 A

  However, if the balance weight is provided to eliminate the unbalance as in the engine unit disclosed in Patent Document 1, there is a problem that the weight of the engine unit increases and the entire vehicle body becomes heavy. Further, if the balance weight is provided for each location where the unbalance is generated to cancel the unbalance, the number of parts increases, so that there is a problem that it takes time and effort for mounting.

  The present invention has been made in view of such points, and an object of the present invention is to achieve a rotation balance around the crankshaft without increasing the weight and the number of parts in the engine unit.

  An engine unit according to the present invention includes a crankshaft having a crankpin eccentric from a rotation center, a connecting rod having one end connected to the crankpin, and a piston reciprocating connected to the other end of the connecting rod. A primary sheave that rotates together with the crankshaft, a secondary sheave, and a belt-type continuously variable transmission that includes a belt wound around the primary sheave and the secondary sheave. Is formed so that the weight on the side opposite to the crankpin side with respect to the center of rotation of the crankshaft increases in the axial direction of the crankshaft.

  When the engine unit is started, the piston reciprocates at a high speed over a short stroke. Therefore, when the piston is at the top dead center or the bottom dead center, a large inertia force acts on the crankshaft. That is, a large force is applied to the crankshaft from the center of rotation toward the crankpin, and the rotation balance is lost. However, the primary sheave of the engine unit is formed so that the weight on the side opposite to the crankpin side with respect to the rotation center of the crankshaft is increased. Therefore, when the crankshaft rotates, a large centrifugal force is generated in the vicinity of the primary sheave in the direction opposite to the crankpin side with respect to the rotation center as compared with the crankpin side direction. Thereby, the rotation imbalance caused by the reciprocating motion of the piston can be reduced by the centrifugal force imbalance caused by the primary sheave. Therefore, the balance of rotation around the crankshaft can be achieved. Therefore, according to the engine unit, it is possible to suppress the occurrence of vibration or noise due to rotation imbalance.

  According to the present invention, in the engine unit, the rotation balance around the crankshaft can be achieved without increasing the weight and the number of parts.

(First embodiment)
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, a scooter type motorcycle 1 shown in FIG. 1 will be described as an example of the saddle riding type vehicle. However, the straddle-type vehicle according to the present invention is not limited to this. For example, a so-called motorcycle type motorcycle in which a fuel tank is arranged in front of the seat, an off-road type motorcycle, a so-called moped type motorcycle, or the like may be used. The straddle-type vehicle according to the present invention is not limited to a motorcycle, but may be another straddle-type vehicle such as a four-wheel buggy.

  FIG. 1 is a side view of a motorcycle 1 according to this embodiment. First, the overall configuration of the motorcycle 1 will be described with reference to FIG. In the following description, the front, rear, left, and right directions refer to directions viewed from the occupant seated on the seat 2.

  As shown in FIG. 1, most of the front surface and both side surfaces of the motorcycle 1 are covered with a cowl 30 for preventing wind. The motorcycle 1 includes a front wheel 3 and a rear wheel 4 that is a driving wheel, and a seat 2 is provided between the front wheel 3 and the rear wheel 4. An engine unit 5 is provided below the seat 2. The engine unit 5 of this embodiment includes an engine 6 (see FIG. 2) that is a gasoline engine using gasoline as fuel. However, the engine 6 of the motorcycle 1 according to the present invention is not limited to an internal combustion engine using gasoline as fuel. For example, a motor engine or the like may be used.

  FIG. 2 is a cross-sectional view of engine unit 5 of motorcycle 1 shown in FIG. As shown in FIG. 2, the engine unit 5 includes an engine 6, a belt-type continuously variable transmission (hereinafter referred to as CVT) 10 coupled to a crankshaft 11 of the engine 6, and a driven shaft 21 that is rotationally driven by the CVT 10. And an output shaft 13 connected to the driven shaft 21 via a speed reduction mechanism 12 composed of a gear train. The output of the engine 6 is shifted by the CVT 10, the driven shaft 21, and the speed reduction mechanism 12 and transmitted to the output shaft 13.

  The engine 6 includes a crankshaft 11, a crankcase 14 that houses the crankshaft 11, a cylinder block 17, a cylinder head 18, and a cylinder head cover 9. The crankcase 14 includes a left case 14a and a right case 14b.

  The crankshaft 11 is disposed so as to penetrate the left case 14a and the right case 14b of the crankcase 14, and is rotatably supported by both cases 14a and 14b. The crankshaft 11 has two parts, a left part 11a and a right part 11b. A crank web 8a is formed at the right end of the left portion 11a, and a crank web 8b is formed at the left end of the right portion 11b. The crank web 8 a and the crank web 8 b are connected by a crank pin 7. With such a configuration, when the crankpin 7 is turned in the circumferential direction of the crankshaft 11, the left side portion 11a and the right side portion 11b of the crankshaft 11 rotate integrally.

  A piston 19 is slidably provided in a space 16 surrounded by the cylinder block 17 and the cylinder head 18. One end of a connecting rod 20 is connected to the piston 19, and the other end of the connecting rod 20 is connected to the crank pin 7 described above. As a result, the crankshaft 11 rotates as the piston 19 reciprocates.

  A generator case 22 is attached to the right case 14b. The right end portion of the right side portion 11b of the crankshaft described above is rotatably supported by the generator case 22. A generator 24 is provided in a space 23 formed by the right case 14 b and the generator case 22. The generator 24 includes a rotor 24a that is fixed to the right side portion 11b of the crankshaft 11 and rotates together, and a stator 24b that is fixed to the generator case 22 inside the rotor 24a. With such a configuration, the generator 24 generates power by the rotation of the crankshaft 11. The electricity generated by the generator 24 is supplied to electric parts, batteries, and the like mounted on the motorcycle 1 (see FIG. 1).

  The left case 14a extends rearward from the right case 14b. A transmission case 15 is attached to the left case 14a. The transmission case 15 is provided so as to face the left case 14a, and the left case 14a and the transmission case 15 form a first space 25 and a second space 26 arranged in the front-rear direction. The first space 25 and the second space 26 communicate with each other, and the aforementioned CVT 10 is stored in both spaces.

  In the first space 25, the left side portion 11a of the crankshaft 11 described above is disposed, and in the second space 26, the driven shaft 21 is provided in parallel to the crankshaft 11. A partition wall 27 is provided in the second space 26, and a third space 28 is partitioned by a part of the left case 14 a and the partition wall 27. The driven shaft 21 is provided so as to penetrate the third space 28, and the driven shaft 21 is rotatably supported by the left case 14a, the partition wall 27, and the transmission case 15. Inside the third space 28, an output shaft 13 that rotationally drives the rear wheel 4 (see FIG. 1), which is a drive wheel, is provided. The output shaft 13 is rotatably attached to each of the partition wall 27 and the left case 14a. The driven shaft 21 and the output shaft 13 are connected by a speed reduction mechanism 12 composed of a plurality of gears. The output shaft 13 is driven to rotate when the driven shaft 21 is driven to rotate.

  The CVT 10 includes a primary sheave 31 attached to the crankshaft 11, a secondary sheave 32 attached to the driven shaft 21, and a V belt 33 wound around the primary sheave 31 and the secondary sheave 32.

  FIG. 3 is an enlarged view of the vicinity of the primary sheave 31 of the CVT 10. As shown in FIG. 3, the primary sheave 31 includes a fixed sheave half 34 fixed to one end side of the crankshaft 11 and a movable sheave half 35 slidably attached in the axial direction of the crankshaft 11. I have. The fixed sheave half 34 has a conical surface 34a, and the movable sheave half 35 has a conical surface (sheave surface) 35a. The conical surface 34a and the conical surface 35a form a substantially V-shaped belt groove 36 around which the V-belt 33 is wound.

  The movable sheave half 35 of the primary sheave 31 includes a main body 37 having the aforementioned conical surface 35 a and a cylindrical boss portion 38 that covers the outer periphery of the crankshaft 11. A substantially cylindrical collar 39 is provided between the outer peripheral side of the crankshaft 11 and the inner peripheral side of the boss portion 38. The collar 39 is spline-fitted with a part of the crankshaft 11. Further, the boss portion 38 is fixed so as not to rotate relative to the collar 39. Therefore, the boss portion 38 and the collar 39 of the movable sheave half 35 rotate together with the rotation of the crankshaft 11.

  FIG. 4A is a side view of the movable sheave half 35, and FIG. 4B is a side sectional view of the movable sheave half 35. As shown in FIG. 4A, a key groove 40 extending in the longitudinal direction is formed in the boss portion 38 of the movable sheave half 35. Further, as shown in FIG. 3, the collar 39 is formed with a holding groove 41 at a position overlapping the key groove 40 as viewed from the radial direction. An end portion on the outer peripheral side of the key 42 is inserted into the key groove 40 of the boss portion 38 so as to be slidable in the axial direction. The inner peripheral side end of the key 42 is held immovably in the holding groove 41 of the collar 39. Thereby, the torque of the crankshaft 11 and the collar 39 is transmitted to the boss portion 38 via the key 42. As described above, the boss portion 38 is not rotatable relative to the collar 39, but is configured to be relatively movable in the axial direction.

  A substantially cylindrical support member 43 is provided on the outer peripheral side of the boss portion 38 of the movable sheave half 35, and the key groove 40 is covered with the support member 43. The support member 43 is regulated by the circlip 38a protruding from the boss portion 38 of the movable sheave half 35 so as not to move relative to the boss portion 38 in the axial direction.

  A bearing 44 is provided on the outer peripheral side of the support member 43. A feed screw 45 is provided on the outer peripheral side of the bearing 44. The movable sheave half 35, the support member 43, the bearing 44, and the feed screw 45 are configured to operate integrally in the axial direction. More specifically, the bearing 44 is regulated by the circlip 46 so as not to move relative to the support member 43 and the feed screw 45 in the axial direction. Further, as described above, the support member 43 is restricted so as not to move relative to the boss portion 38 of the movable sheave half 35 in the axial direction.

  A housing 57 is fixed to the left case 14a, and a feed guide 48 having an internal thread 49 formed on the inner peripheral surface thereof is fixed to the housing 57. On the other hand, a male screw 47 is formed on the outer peripheral surface of the feed screw 45 described above. The feed screw 45 and the feed guide 48 are arranged so that the male screw 47 and the female screw 49 are always meshed with each other. The feed screw 45 is formed so that the male screw 47 advances in the axial direction on the female screw 49 when driven in rotation.

  A driven gear 50 is fitted on the outer peripheral side of the feed screw 45 so as not to be relatively rotatable. The driven gear 50 is always meshed with the speed change drive gear 52 of the speed change drive shaft 51 arranged in parallel with the crankshaft 11. The transmission drive gear 52 is always in mesh with a gear portion 53 a of an idler shaft 53 disposed in parallel with the crankshaft 11 and the transmission drive shaft 51. Further, a gear 54 is engaged with the idler shaft 53 so as not to be relatively rotatable, and the gear 54 is always meshed with a rotating shaft 56 of the electric motor 55.

  With such a configuration, the movable sheave half 35 is received by the driving force of the electric motor 55 by the support member 43, the bearing 44, the feed screw 45, the feed guide 48, the driven gear 50, the transmission drive shaft 51, and the idler shaft 53. A power conversion mechanism that slides in the axial direction of the crankshaft 11 is configured. Thus, when the driven gear 50 is rotationally driven by the electric motor 55, the movable sheave half 35, the support member 43, the bearing 44, the feed screw 45, and the driven gear 50 reciprocate in the axial direction integrally. As a result, the movable sheave half 35 approaches or separates from the fixed sheave half 34, and the width (axial distance) of the belt groove 36 formed by both sheave halves 34, 35 changes. Therefore, the position in the radial direction of the V belt 33 wound around these changes, and the gear ratio is changed.

  On the other hand, as shown in FIG. 2, similarly to the primary sheave 31, the secondary sheave 32 is fixed to the driven shaft 21 with respect to the axial direction, and is attached to be slidable in the axial direction of the driven shaft 21. The movable sheave half 62 is provided. The fixed sheave half 61 has a conical surface 61a, and the movable sheave half 62 has a conical surface 62a. The conical surface 61a and the conical surface 62a form a substantially grooved belt groove 66 around which the V belt 33 is wound.

  The fixed sheave half 61 has a cylindrical guide 63. The guide 63 is provided on the outer peripheral side of the driven shaft 21 via the bearing 64 and is supported by the driven shaft 21 so as to be relatively rotatable. A centrifugal clutch 65 is interposed between the fixed sheave half 61 and the driven shaft 21. The centrifugal clutch 65 is fixed to the left end of the driven shaft 21 with the centrifugal plate 67 that rotates integrally with the guide 63 of the fixed sheave half 61, the centrifugal weight 68 supported by the centrifugal plate 67, and the driven shaft 21. A rotating clutch housing 69 is provided.

  With such a configuration, when the rotational speed of the centrifugal plate 67 that rotates integrally with the fixed sheave half 61 reaches a predetermined value, the centrifugal weight 68 moves radially outward due to centrifugal force. As a result, the centrifugal weight 68 comes into contact with the clutch housing 69 and the rotation of the stationary sheave half 61 is transmitted to the driven shaft 21. That is, even if the primary sheave 31 is rotationally driven by the crankshaft 11 and the secondary sheave 32 is rotationally driven via the V-belt 33, the secondary sheave 32 rotates idly with respect to the driven shaft 21 until the rotational speed reaches a predetermined value. . When the rotational speed reaches a predetermined value, the secondary sheave 32 and the driven shaft 21 are connected by the centrifugal clutch 65 and rotate together.

  Further, when the secondary sheave 32 and the driven shaft 21 are rotating together, the width of the belt groove 66 of the secondary sheave 32 is changed by driving the electric motor 55 to change the width of the belt groove 36 of the primary sheave 31. Fluctuate and the gear ratio is changed. Specifically, when the width of the belt groove 36 of the primary sheave 31 is reduced, the position of the V belt 33 is shifted forward, and the width of the belt groove 66 of the secondary sheave 32 is increased. Thereby, the gear ratio becomes small. On the other hand, when the width of the belt groove 36 of the primary sheave 31 is increased, the V belt 33 is shifted rearward, and the width of the belt groove 66 of the secondary sheave 32 is decreased. This increases the gear ratio.

  With the above configuration, when the engine 6 is started and the crankshaft 11 is rotationally driven, the driven shaft 21 rotates via the CVT 10. Then, the rotation of the driven shaft 21 is transmitted to the output shaft 13 via the speed reduction mechanism 12. Thereby, the rear wheel 4 which is a drive wheel is rotationally driven, and the motorcycle 1 travels.

  FIG. 5 is a drawing schematically showing the relationship between the piston 19, the connecting rod 20, the crankpin 7 and the key groove 40 when the crankshaft 11 is viewed in the axial direction. Hereinafter, a line drawn from the rotation center C1 of the crankshaft 11 toward the center C2 of the crankpin 7 in the axial direction view of the crankshaft 11 shown in FIG. Further, with the rotation center C1 of the crankshaft 11 as the center, the angle on the rotation direction B side of the crankshaft 11 from the reference line A is a positive angle, and the angle on the opposite side of the rotation direction B of the crankshaft 11 from the reference line A is set. This will be described below as a negative angle.

The keyway 40 is provided on the crankpin 7 side with the rotation center C1 of the crankshaft 11 as the center. Here, “provided on the crankpin 7 side” means that the keyway 40 forms an angle of the reference line A (0 degree) and the angle X (°) with the rotation center C1 of the crankshaft 11 as the center. If it is arranged at a position, it means that X is in the angular range shown in the following formula (1). FIG. 5 shows a case where the key groove 40 is provided on the reference line A (X = 0).
−90 <X <+90 (1)

  By the way, when the engine 6 is started, the air-fuel mixture (fuel-containing air) burns, a large force is applied to the piston 19, and the piston 19 reciprocates at high speed. Since the piston 19 reciprocates at a high speed over a short stroke, a large inertial force acts on the crankshaft 11 when the piston 19 is at the top dead center or the bottom dead center. That is, when the engine 6 is operated, a large force is applied to the crankshaft 11 in the direction from the rotation center C1 to the crankpin 7, so that the balance of rotation is lost.

  However, in the engine unit 5 according to the present invention, the key groove 40 is provided on the crankpin 7 side with respect to the center C1 when viewed in the axial direction. Thereby, in the boss | hub part 38, the weight by the side of the crankpin 7 becomes small with respect to the center C1 by the part of the keyway 40. Therefore, when the crankshaft 11 rotates, the centrifugal force applied to the key groove 40 side is smaller at the boss portion 38 than at the other portions. Thereby, in the boss portion 38, the centrifugal force around the axis does not cancel out, and a force in the direction opposite to the key groove 40 with respect to the center C1 is generated. Therefore, in the engine unit 5 according to the present embodiment, the inertial force generated in the direction from the rotation center C1 toward the crankpin 7 due to the reciprocating motion of the piston 19 is caused by the key groove 40 to be opposite to the crankpin 7 from the center C1. It can be reduced by the force generated in the direction. Therefore, the key groove 40 can reduce the unbalance of the rotation around the crankshaft due to the reciprocating motion of the piston 19. Thereby, the balance of rotation around the crankshaft 11 can be achieved. Therefore, according to the engine unit 5, it is possible to suppress the occurrence of vibration or noise due to rotation imbalance.

  In the engine unit 5, the inertia force generated by the reciprocating motion of the piston 19 can be reduced by providing the key groove 40 on the crankpin 7 side. Therefore, unlike the conventional case, it is possible to balance rotation around the crankshaft 11 without providing a new member such as a balance weight and increasing the number of parts. Therefore, according to the engine unit 5, since it is not necessary to attach a balance weight, it is possible to reduce assembling work. Furthermore, the cost in production can be reduced by the above effects.

  In the engine unit 5, a collar 39 that is spline-fitted to the crankshaft 11 is provided between the outer peripheral side of the crankshaft 11 and the inner peripheral side of the boss portion 38, and the key 42 is attached to the collar 39. The formed holding groove 41 is held immovably. Therefore, according to the engine unit 5, the key 42 can be easily rotated integrally with the crankshaft 11 by using the collar 39 that is easy to manufacture. In addition, the manufacturing cost can be reduced.

  In the engine unit 5, the key groove 40 provided in the boss portion 38 of the primary sheave 31 is arranged at a position that forms an angle greater than −90 degrees and less than +90 degrees with the reference line A (0 degree). ing. Therefore, due to the presence of the key groove 40, the direction opposite to the crankpin 7 side (the direction within the angular range of −180 degrees to −90 degrees and 90 degrees to 180 degrees and radially outward). A large centrifugal force will work. Thereby, according to the engine unit 5, the large inertia force generated by the reciprocating motion of the piston 19 can be reduced by the key groove 40. Thereby, the balance of rotation around the crankshaft 11 can be achieved.

  In the present embodiment, in particular, the key groove 40 is provided at an angular position (0 degrees) equal to the crankpin 7 when the crankshaft 11 is viewed in the axial direction. Thereby, according to the engine unit 5, the inertia force generated by the reciprocating motion of the piston 19 can be more effectively reduced by the key groove 40.

  In the present embodiment, a single cylinder engine is used as an example of the engine 6, but the engine 6 is not limited to a single cylinder engine. However, the present invention aiming at balancing the rotation around the crankshaft can exhibit the above-described effects more in an engine unit using a single cylinder engine.

  As described above, by providing the engine unit 5, it is possible to provide the motorcycle 1 in which generation of vibration and noise is suppressed.

(Second Embodiment)
As shown in FIGS. 6A and 6B, the engine unit 5 according to the second embodiment has a notch 71 in the main body 37 of the movable sheave half 35 of the engine unit 5 according to the first embodiment. Is provided. As shown in FIG. 6B, the notch 71 is provided in the same direction as the key groove 40 of the main body 37 when the rotation center C <b> 1 of the crankshaft 11 is centered when viewed in the axial direction.

  As a result, in the engine unit 5 according to the second embodiment, when the crankshaft 11 is viewed in the axial direction, a notch portion 71 is further formed on the crankpin 7 side in addition to the key groove 40. Therefore, according to the engine unit 5, the centrifugal force generated on the opposite side of the crankpin 7 when the crankshaft 11 rotates is further increased, and the inertial force due to the reciprocating motion of the piston 19 can be more effectively reduced. .

  Further, according to the present embodiment, the main body 37 is formed to have a larger diameter than the boss portion 38, so that the cutout portion 71 can be provided on the outer peripheral side of the boss portion 38. By providing the notch 71 on the outer peripheral side of the crankshaft 11 in this way, the centrifugal force generated on the opposite side of the notch 71 (crank pin 7 side) when the crankshaft 11 rotates is further increased. Is possible. Therefore, the inertial force due to the reciprocating motion of the piston 19 can be reduced more effectively.

  In the present embodiment, the notch 71 of the engine unit 5 is provided at the radially outer end of the main body 37. Therefore, the cutout portion 71 can be formed large without impairing the strength of the main body 37. Therefore, the centrifugal force generated on the side opposite to the crankpin 7 can be further increased, and the inertial force due to the reciprocating motion of the piston 19 can be more effectively reduced. The notch 71 may be provided not in the radially outer end of the main body 37 but in the radially inner portion.

  As described above, the present invention is useful for an engine unit and a straddle-type vehicle including the engine unit.

1 is a side view of a motorcycle according to a first embodiment. It is sectional drawing of the engine unit which concerns on 1st Embodiment. It is a figure which expands and shows the primary sheave vicinity of FIG. (A) is a side view of a movable sheave half, (b) is a side sectional view showing a part of the movable sheave half. It is the figure which represented typically the relationship between a piston, a connecting rod, a crankpin, and a keyway in the axial direction view of a crankshaft. (A) is side sectional drawing which shows a part of movable sheave half body of the engine unit which concerns on 2nd Embodiment, (b) is a side view which shows a part of movable sheave half body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motorcycle 5 Engine unit 6 Engine 7 Crankpin 10 CVT (belt-type continuously variable transmission)
11 Crankshaft 19 Piston 20 Connecting rod 21 Driven shaft 31 Primary sheave 32 Secondary sheave 33 V belt (belt)
34 Fixed sheave half 35 Movable sheave half 37 Main body 38 Boss part 39 Collar 40 Keyway 41 Holding groove 42 Key 55 Electric motor

Claims (9)

An engine having a crankshaft having a crankpin eccentric from a rotation center, a connecting rod having one end connected to the crankpin, and a piston reciprocating connected to the other end of the connecting rod;
A belt-type continuously variable transmission having a primary sheave rotating with the crankshaft, a secondary sheave, and a belt wound around the primary sheave and the secondary sheave;
With
The primary sheave is an engine unit formed so that a weight on a side opposite to the crankpin side with respect to a center of rotation of the crankshaft is increased when viewed from an axial direction of the crankshaft.   2. The engine unit according to claim 1, wherein the primary sheave has a notch on the crankpin side of the crankshaft centered on the rotation center of the crankshaft as viewed in the axial direction of the crankshaft. The primary sheave is
A fixed sheave half fixed to the crankshaft;
A movable sheave half having a boss covering the outer periphery of the crankshaft and movable in the axial direction of the crankshaft;
With
A key groove extending in the axial direction of the crankshaft is formed in the boss portion,
A motor,
A key that is slidably inserted into the key groove, rotates with the crankshaft, and transmits the rotational force of the crankshaft to the boss portion;
A power conversion mechanism that connects the motor and the movable sheave half, and receives the driving force of the motor to slide the movable sheave half in the axial direction of the crankshaft;
With
The engine unit according to claim 2, wherein the notch is the keyway. The primary sheave is
A fixed sheave half fixed to the crankshaft;
A movable sheave half having a boss covering the outer periphery of the crankshaft and movable in the axial direction of the crankshaft;
With
A key groove extending in the axial direction of the crankshaft is formed in the boss portion,
A collar that is disposed between the outer peripheral side of the crankshaft and the inner peripheral side of the boss portion, is a spline fitted to the crankshaft, and has a holding groove formed;
A motor,
One end portion located on the inner circumferential side is held immovably in the holding groove, and the other end portion located on the outer circumferential side is slidably inserted into the key groove, and the crankshaft rotates through the collar. A key for transmitting force to the boss,
A power conversion mechanism that connects the motor and the movable sheave half, and receives the rotational force of the motor to slide the movable sheave half in the axial direction of the crankshaft;
With
The engine unit according to claim 2, wherein the notch is the keyway. When viewed from the axial direction of the crankshaft, a line drawn from the center of rotation of the crankshaft toward the center of the crankpin is used as a reference line, and further, the crankshaft from the reference line is centered on the center of rotation of the crankshaft. When the angle on the rotation direction side of the shaft is a positive angle and the angle on the opposite side to the rotation direction of the crankshaft from the reference line is a negative angle,
The engine unit according to claim 3 or 4, wherein the keyway is provided within an angle range of greater than -90 degrees and less than +90 degrees.   The engine unit according to claim 5, wherein the keyway is provided on the reference line. The movable sheave half includes a main body formed with a larger diameter than the boss portion and having a sheave surface that comes into contact with the belt;
5. The engine unit according to claim 3, wherein the main body is provided with a notch on the crankpin side when the crankshaft is viewed in the axial direction.   The engine unit according to claim 7, wherein the notch is provided at a radially outer end of the main body.   A straddle-type vehicle comprising the engine unit according to claim 1.

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