JP3155809U - Engine and saddle type vehicle - Google Patents

Abstract

An engine capable of revealing primary vibration in a low rotational speed region and reducing primary vibration in a high rotational speed region is provided. A balancer 60A provided in an engine 10 causes a difference between a rotation speed of a balancer shaft and a rotation speed of a center of gravity GB of the balancer 60A by a movable weight movable in a circumferential direction. Since the difference decreases as the rotation speed of the balancer shaft increases, the degree of suppressing the primary vibration of the engine 10 can be gradually increased. [Selection] Figure 2

Description

  The present invention relates to an engine including a balancer and a straddle-type vehicle.

  An engine applied to a motorcycle or the like may be provided with a balancer for reducing vibration caused by reciprocation of a piston. The balancer is provided on a balancer shaft that rotates in conjunction with the crankshaft, and generates an inertial force in a direction opposite to the inertial force generated by the reciprocation of the piston, thereby reducing engine vibration.

JP 2005-172215 A

  By the way, in recent years, in an American type (cruiser type) motorcycle or the like, a feeling such as a beating feeling or a pulse feeling when idling or accelerating the vehicle is required by the user. Such a sensation can be obtained from vibrations in the low engine speed range.

  However, when the conventional balancer is provided in the engine, the vibration is reduced over the entire rotational speed range, so that the vibration in the low rotational speed range is also reduced. Can't get.

  On the other hand, in order to leave the vibration in the low rotation speed region, the balance between the inertial force of the piston and the inertial force of the balancer may be intentionally broken, but in this case, the vibration in the high rotation speed region also remains, There is a risk that the user may feel uncomfortable during high-speed driving.

  Patent Document 1 discloses a technique for improving a balancer in order to reduce the secondary couple vibration of an engine. However, a document that mentions a technique for making vibrations in a low rotation speed range obvious. There is no.

  The present invention has been made in view of the above circumstances, and provides an engine and a straddle-type vehicle including a balancer that can manifest vibrations in a low rotational speed range and reduce vibrations in a high rotational speed range. One of its purposes is to do.

  In order to solve the above problems, an engine of the present invention includes a crankshaft, a balancer shaft that is linked to the crankshaft, a balancer that is rotationally driven by the balancer shaft and suppresses vibrations synchronized with the rotation of the crankshaft, The balancer is supported by the balancer shaft and is supported by the support portion, and at least in the circumferential direction of the balancer shaft according to a change in the rotation speed of the balancer shaft. And a movable weight movable relative to the support portion.

  A straddle-type vehicle of the present invention is a straddle-type vehicle including the engine. The straddle-type vehicle is, for example, a motorcycle (including a scooter), a four-wheel buggy (all-terrain vehicle), a snowmobile, or the like.

  In general, it is known that the rotational speed of the crankshaft periodically varies when viewed on a microscopic time scale (so-called rotational unevenness). This is because the rotational speed of the crankshaft increases in the combustion stroke during one cycle and decreases in the subsequent stroke. Further, it is known that the fluctuation amount of the periodic fluctuation becomes smaller as the rotational speed of the crankshaft increases.

  Therefore, by providing a movable weight on the balancer as in the present invention, a difference can be generated between the rotational speed of the balancer shaft that is linked to the crankshaft and the rotational speed of the center of gravity of the balancer.

  That is, when the rotational speed of the balancer shaft increases, the movable weight moves in the direction opposite to the rotational direction, so the rotational speed of the balancer's center of gravity decreases with respect to the rotational speed of the balancer shaft. On the other hand, when the rotational speed of the balancer shaft decreases, the movable weight moves in the same direction as the rotational direction, so the rotational speed of the center of gravity of the balancer increases relative to the rotational speed of the balancer shaft.

  As a result of the difference in rotational speed, there is a difference between the inertial force that causes vibration in the engine and the inertial force of the balancer that cancels it. It can be left.

  As the rotational speed of the crankshaft increases, the amount of fluctuation in the rotational speed decreases as described above, so the amount of movement of the movable weight decreases and the difference in rotational speed decreases. For this reason, the difference of the said inertia force becomes small and an engine vibration reduces. As a result, it is possible to realize an engine and a straddle-type vehicle that can manifest vibrations in a low rotational speed range and can reduce vibrations in a high rotational speed range.

1 is a side view of a motorcycle according to an embodiment of a straddle-type vehicle of the present invention. It is sectional drawing of the engine which concerns on one Embodiment of this invention. It is sectional drawing of the III-III line in FIG. It is a perspective view of the balancer of the 1st example. It is a front view of the balancer of the 1st example. It is a side view of the balancer of the 1st example. It is operation | movement explanatory drawing of the balancer of a 1st example. It is sectional drawing of the modification of the balancer of a 1st example. It is a perspective view of the balancer of the 2nd example. It is a front view of a 2nd balancer. It is sectional drawing of the balancer of a 2nd example. It is operation | movement explanatory drawing of the balancer of a 2nd example. It is explanatory drawing of the rotational speed of the gravity center of a balancer.

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

  FIG. 1 shows a side view of a motorcycle 1 according to an embodiment of a saddle riding type vehicle of the present invention. The motorcycle 1 has a double cradle type body frame 2, and a front fork 3 is pivotally supported by a head pipe (not shown) provided at a front end portion of the body frame 2. A front wheel 4 is pivotally supported at the lower end portion of the front fork 3, and a handle 5 is attached to the upper end portion.

  A fuel tank 6 is disposed on the front side of the vehicle body frame 2 and a seat 7 is disposed on the rear side. A swing arm 8 is pivotally supported at the lower rear end portion of the vehicle body frame 2 so as to swing up and down, and a rear wheel 9 is pivotally supported at the rear end portion of the swing arm 8.

  An engine 10 according to an embodiment of the present invention is mounted in the cradle of the body frame 2. The engine 10 is an air-cooled four-cycle V-type two-cylinder engine.

  FIG. 2 shows a longitudinal cross section of the engine 10 according to an embodiment of the present invention as viewed from the left side of the vehicle. FIG. 3 is a sectional view taken along line III-III in FIG.

  In the engine 10, the front cylinder block 14 </ b> F and the rear cylinder block 14 </ b> B are arranged on the upper part of the crankcase 12 so as to form a bank angle smaller than 90 degrees in the vehicle front-rear direction. In addition, a front cylinder head 16F and a rear cylinder head 16B are respectively disposed on these upper portions.

  The crankcase 12 is divided into a left and right case, and includes a left case 12L and a right case 12R. A clutch cover 17 is attached to the outer side of the right case 12R, and a generator cover 18 is attached to the front side of the outer side of the left case 12L.

  Pistons 42F and 42B are slidably disposed in the cylinder blocks 14F and 14B, respectively. The pistons 42F and 42B are connected together to the crankpin 21a of the crankshaft 21 via connecting rods 46F and 46B, respectively.

  The crankshaft 21 has a crankpin 21a at a position eccentric from the center of rotation of the crankshaft 21, and is counterclockwise as viewed from the left side of the vehicle (in FIG. 2) in conjunction with the reciprocating motion of the pistons 42F and 42B. Rotate in the direction of arrow ωC).

  Here, the reciprocating motion of the pistons 42F and 42B has a phase difference corresponding to the bank angle of the cylinder blocks 14F and 14B. For example, after the piston 42B in the rear cylinder block 14B reaches the top dead center, the piston 42F in the front cylinder block 14F reaches the top dead center after the rotation angle of the crankshaft 21 has changed by the bank angle. To do.

  The crankshaft 21 has a pair of balance weights 21c and 21d arranged so as to sandwich the crankpin 21a. These balance weights 21c and 21d have a weight distribution having a center of gravity GC on the opposite side of the crankpin 21a with respect to the center of rotation.

  The crankshaft 21 has a pair of journal portions 21e and 21f provided outside the balance weights 21c and 21d in the vehicle width direction. These journal portions 21 e and 21 f are rotatably supported by the crankcase 12 and serve as the rotation center of the crankshaft 21. Specifically, the left journal portion 21e is pivotally supported by the rib 12e of the left case 12L. The right journal portion 21f is pivotally supported by the rib 12f of the right case 12R.

  The crankshaft 21 extends further leftward from the left journal portion 21e to drive the generator 22. The crankshaft 21 extends further to the right side from the right journal portion 21f, and a clutch drive gear 21g is provided at the right end portion.

  The rotation of the crankshaft 21 is transmitted from the clutch drive gear 21g to the main shaft 25 via the clutch 23, and is transmitted to the drive shaft 27 via the transmission gear portion 26. The drive shaft 27 has a sprocket 29 attached to the left end. The sprocket 29 meshes with a chain (not shown) that drives the rear wheel 9.

  Next, the engine 10 has primary balancers 60 </ b> A (hereinafter simply referred to as balancers) on the left and right sides of the front side of the crankcase 12. These balancers 60A are respectively attached to balancer shafts 48L and 48R provided in parallel with the crankshaft 21, and rotate together. The balancer 60A has a center of gravity GB at a position eccentric with respect to the balancer shafts 48L and 48R.

  The balancer shafts 48L and 48R are pivotally supported by the crankcase 12 on the left and right sides obliquely below and forward of the crankshaft 21, respectively. Specifically, the left balancer shaft 48L is pivotally supported by ribs 12a and 12b formed on the left case 12L on both sides of the portion to which the balancer 60A is attached. Similarly, the right balancer shaft 48R is pivotally supported by ribs 12c and 12d formed on the right case 12R on both sides of the portion to which the balancer 60A is attached.

  Further, the balancer shafts 48L and 48R are respectively attached to the balancer driven gears 38L and 38R at outer ends in the vehicle width direction and rotate together. The balancer driven gears 38L and 38R mesh with the balancer drive gears 36L and 36R attached to the left and right ends of the crankshaft 21, respectively. Here, the balancer driven gears 38L and 38R have the same diameter and the same number of teeth as the balancer driving gears 36L and 36R. Therefore, the balancer shafts 48L and 48R rotate at the same rotational speed as that of the crankshaft 21 and rotate in the opposite direction. It rotates in the direction (direction of arrow ωB in FIG. 2).

  The two balancers 60 </ b> A suppress primary vibration generated by the reciprocation of the pistons 42 </ b> F and 42 </ b> B together with balance weights 21 c and 21 d provided on the crankshaft 21.

  The pistons 42F and 42B generate primary vibrations mainly in the vertical direction by reciprocating motion. For example, as shown in FIG. 2, when the crank pin 21a is located above the center of rotation of the crankshaft 21 (in the middle of the bank angle), the inertial force FP by the pistons 42F and 42B has an upward maximum magnitude. . On the other hand, when the crankpin 21a is positioned below the rotation center of the crankshaft 21, the inertial force FP by the pistons 42F and 42B is downward and has a maximum magnitude.

  The balance weights 21c and 21d generate an inertial force (centrifugal force) FC corresponding to the rotational speed ωC of the crankshaft 21. Here, since the balance weights 21c and 21d have the center of gravity GC on the opposite side of the crankpin 21a with respect to the rotation center of the crankshaft 21, for example, as shown in FIG. 2, the inertial force FP by the pistons 42F and 42B is generated. In the case of upward, an inertial force FC is generated in the downward direction, which is a direction to cancel this. On the other hand, when the inertial force FP due to the pistons 42F and 42B is downward, the inertial force FC is generated upward, which is a direction to cancel this.

  Each balancer 60A generates an inertial force (centrifugal force) FB corresponding to the rotational speed of the center of gravity GB. In the present embodiment, the rotational speed of the center of gravity GB of the balancer 60A is not always the same as the rotational speed ωB of the balancer shafts 48L and 48R, as will be described later.

  Here, as with the balance weights 21c and 21d, the phase of the center of gravity GB is set so that each balancer 60A generates an inertial force FB in a direction to cancel the inertial force FP by the pistons 42F and 42B. That is, for example, as shown in FIG. 2, each balancer 60 </ b> A generates an inertial force FB in a downward direction, which is a direction to cancel out the inertial force FP caused by the pistons 42 </ b> F and 42 </ b> B. On the other hand, when the inertial force FP due to the pistons 42F and 42B is downward, the inertial force FB is generated upward, which is a direction to cancel the inertial force FP.

  Since each balancer 60A rotates in the direction opposite to the balance weights 21c and 21d, an inertial force FB is generated in a direction to cancel the longitudinal component of the inertial force FC of the balance weights 21c and 21d.

  Therefore, the total sum of the magnitudes of the inertia forces FB of the two balancers 60A and the sum of the magnitudes of the inertia forces FC of the balance weights 21c and 21d is the maximum magnitude of the inertia force FP by the pistons 42F and 42B. In the case corresponding to the above, the primary vibration in the vertical direction is most suppressed. Further, when the sum of the magnitudes of the inertia forces FB of the two balancers 60A corresponds to the sum of the magnitudes of the inertia forces FC of the balance weights 21c and 21d, the primary vibration in the front-rear direction is most suppressed. Furthermore, when both of these conditions are satisfied, the primary vibration in the vertical direction and the primary vibration in the front-rear direction are most suppressed.

  In the present embodiment, the sum of the magnitudes of the inertia forces FC of the balance weights 21c and 21d is set to be half of the maximum magnitude of the inertia force FP by the pistons 42F and 42B.

  Further, the sum of the magnitudes of the inertial forces FB of the two balancers 60A is the sum of the magnitudes of the inertial forces FC of the balance weights 21c and 21d when the rotational speed of the center of gravity GB is the same as the rotational speed ωC of the crankshaft 21. It is set to be the same level.

[Balancer of the first example]
Hereinafter, a specific configuration of the balancer 60A of the first example will be described. FIG. 4 is a perspective view of the balancer 60A. FIG. 5 is a front view of the balancer 60A. FIG. 6 is a side view of the balancer 60A.

  FIG. 7 is an explanatory diagram of the operation of the balancer 60A. FIG. 7A shows a state when the rotational speed ωB of the balancer shafts 48L and 48R increases. FIG. 7B shows a state when the rotational speed ωB of the balancer shafts 48L and 48R is decreased.

  The balancer 60A includes a support portion 64A that is fixed to the balancer shafts 48L and 48R, and a movable weight 62A that is supported by the support portion 64A so as to be rotatable about positions eccentric from the balancer shafts 48L and 48R.

  The support portion 64A has a cylindrical fixing portion 641 in which an insertion hole 641a is formed, and the balancer shafts 48L and 48R are inserted into the insertion hole 641a.

  Further, the support portion 64A has two extending portions 643 that extend from the both end portions of the balancer shafts 48L and 48R in the radial direction of the balancer shafts 48L and 48R in the fixed portion 641, respectively. A shaft support portion 631 that supports the movable weight 62C is provided between the distal end portions of the extending portions 643.

  The movable weight 62A has a substantially fan shape, and the corner portion 622a is sandwiched between the tip ends of the two extending portions 643 of the support portion 64C and is pivotally supported by the shaft support portion 631. Thus, the movable weight 52C can be rotated around the axis parallel to the balancer shafts 48L and 48R by the shaft support portion 531.

  The center of gravity GB of the balancer 60A is mainly determined by the movable weight 62A. For this reason, the center of gravity GB of the balancer 60A changes in the circumferential position with respect to the balancer shafts 48L and 48R as the movable weight 62A rotates.

  FIG. 13 shows a variation example of the rotation speed ωC of the crankshaft 21 and a variation example of the rotation speed of the center of gravity GB of the balancer 60A when the rotation speed ωC of the crankshaft 21 gradually increases with time.

  The rotational speed ωC of the crankshaft 21 undergoes periodic fluctuations (so-called rotational unevenness). The periodic variation decreases with the cycle as the rotational speed ωC of the crankshaft 21 gradually increases.

  In addition, the rotational speed ωB of the balancer shafts 48L and 48R that rotate in conjunction with the crankshaft 21 also varies periodically as does the rotational speed ωC of the crankshaft 21.

  Here, when the rotation speed ωB of the balancer shafts 48L and 48R increases, as shown in FIG. 7A, the acceleration dωB in the same direction as the rotation direction of the balancer shafts 48L and 48R acts on the support portion 64A. The movable weight 62A receives an inertial force in a direction opposite to the acceleration dωB, and is displaced in the direction opposite to the rotation direction.

  When the movable weight 62A is displaced in this way, the center of gravity GB of the balancer 60A is similarly displaced to the side opposite to the rotation direction of the balancer shafts 48L and 48R. As a result, when the rotational speed ωB of the balancer shafts 48L and 48R increases, the rotational speed of the center of gravity GB of the balancer 60A decreases with respect to the rotational speed ωB of the balancer shafts 48L and 48R.

  On the other hand, when the rotational speed ωB of the balancer shafts 48L and 48R decreases, the acceleration dωB in the direction opposite to the rotational direction of the balancer shafts 48L and 48R acts on the support portion 64A as shown in FIG. The weight 62A receives an inertial force in the direction opposite to the acceleration dωB and is displaced to the same side as the rotational direction.

  When the movable weight 62A is thus displaced, the center of gravity GB of the balancer 60A is similarly displaced to the same side as the rotation direction of the balancer shafts 48L and 48R. As a result, when the rotational speed ωB of the balancer shafts 48L and 48R decreases, the rotational speed of the center of gravity GB of the balancer 60A increases with respect to the rotational speed ωB of the balancer shafts 48L and 48R.

  As a result, the rotational speed of the center of gravity GB of the balancer 60A is different from the rotational speed ωC of the crankshaft 21 as shown in FIG. Specifically, the rotational speed of the center of gravity GB of the balancer 60A becomes smaller when the rotational speed ωC of the crankshaft 21 increases, and on the other hand when the rotational speed ωC of the crankshaft 21 decreases. growing.

  Further, as the rotational speed ωC of the crankshaft 21 gradually increases, the fluctuation amount of the periodic fluctuation of the rotational speed ωC decreases with the period. Accordingly, the displacement amount of the movable weight 62A also decreases, and the balancer The difference between the rotational speed of the center of gravity GB of 60A and the rotational speed ωC of the crankshaft 21 becomes smaller.

  Here, the inertial force FB of the balancer 60A has a magnitude corresponding to the rotational speed of the center of gravity GB, and the inertial force FC of the balance weights 21c and 21d has a magnitude corresponding to the rotational speed ωC of the crankshaft 21. The magnitude of the inertial force FB also differs from the magnitude of the inertial force FC of the balance weights 21c and 21d, similarly to the relation of the rotational speed in FIG.

  The difference between the magnitude of the inertial force FB of the balancer 60A and the magnitude of the inertial force FC of the balance weights 21c and 21d causes the primary vibration of the engine 10 to remain. Further, as the rotational speed ωC of the crankshaft 21 is gradually increased, this difference is reduced. Accordingly, the primary vibration of the engine 10 is reduced.

  As described above, the balancer 60A of the present embodiment can gradually increase the degree of suppressing the vibration of the engine 10 as the rotational speed ωB of the balancer shafts 48L and 48R increases. The vibration becomes obvious and the primary vibration can be reduced in the high rotation speed region.

  In addition, as shown in FIG. 8, the balancer 60A may be provided with an elastic member 66 (an example of a suppressing portion) made of a spring or the like. The elastic member 66 is disposed between the two extending portions 643 of the support portion 64A, one end is attached to the fixed portion 641 of the support portion 64A, and the other end is attached to the corner portion 622a of the movable weight 62A.

  When the center of gravity GB of the balancer 60A is farthest from the balancer shafts 48L and 48R is the reference position PC (see FIG. 8), the movable weight 62A is moved from the elastic member 66 when displaced from the reference position PC. A biasing force toward the reference position PC is received. Thereby, an excessive displacement of the movable weight 62A is suppressed.

  In addition to the elastic member 66, as another example of the suppressing portion, a stopper that restricts a predetermined displacement or more from the reference position PC of the movable weight 62A is provided between the two extending portions 643 of the support portion 64A. It may be.

  Note that the balancer 60B of the second example described below may be applied to the engine 10 without being limited to the balancer 60A of the first example described above.

[Balancer of the second example]
Hereinafter, a specific configuration of the balancer 60B of the second example will be described. FIG. 9 is a perspective view of the balancer 60B. FIG. 10 is a front view of the balancer 60B. FIG. 11 is a cross-sectional view of the balancer 60B.

  FIG. 12 is an explanatory diagram of the operation of the balancer 60B. FIG. 12A shows a state when the rotational speed ωB of the balancer shafts 48L and 48R increases. FIG. 12B shows a state when the rotational speed ωB of the balancer shafts 48L and 48R is decreased.

  The balancer 60B includes a support portion 64B fixed to the balancer shafts 48L and 48R, and a movable weight 62B supported by the support portion 64B.

  The support portion 64B includes a fixed portion 641 through which the balancer shafts 48L and 48R are inserted, and a deformable portion 645 interposed between the fixed portion 641 and the movable weight 62B.

  The deformable portion 645 includes a wire-shaped metal member 645a and an elastic member 645b made of rubber or the like. One end of the wire-shaped metal member 645a is attached to the side portion of the corner portion 622a of the movable weight 62B, and the other end is attached to the side portion of the fixed portion 641 to connect the movable weight 62B and the fixed portion 641.

  The elastic member 645b is formed so as to surround the periphery of the wire-like metal member 645a, and one side is fixed to the side portion of the corner portion 622a of the movable weight 62B, and the other side is fixed to the side portion of the fixed portion 641. Has been. These wire-like metal member 645a and elastic member 645b have flexibility and are deformed according to the external force received by the movable weight 62B.

  The center of gravity GB of the balancer 60B is mainly determined by the movable weight 62B. For this reason, when the movable weight 62B is displaced in the circumferential direction with respect to the balancer shafts 48L, 48R, for example, the center of gravity GB of the balancer 60B changes in the circumferential direction.

  Such a balancer 60B causes a difference between the rotational speed of the center of gravity GB of the balancer 60B and the rotational speed ωC of the crankshaft 21 as in the balancer 60A of the first example (see FIG. 13). .

  Specifically, when the rotational speed ωB of the balancer shafts 48L and 48R increases, as shown in FIG. 12A, the balancer 60B receives the inertia force in the direction opposite to the acceleration dωB when the movable weight 62B receives The deforming portion 645 is deformed accordingly, and the movable weight 62B is displaced to the opposite side to the rotation direction of the balancer shafts 48L and 48R. As a result, the center of gravity GB of the balancer 60B is similarly displaced in the direction opposite to the rotation direction of the balancer shafts 48L and 48R. descend.

  On the other hand, when the rotational speed ωB of the balancer shafts 48L and 48R decreases, as shown in FIG. 12 (b), the balancer 60B receives the inertia force in the direction opposite to the acceleration dωB. Accordingly, the movable weight 62B is displaced to the same side as the rotation direction of the balancer shafts 48L and 48R. As a result, the center of gravity GB of the balancer 60B is similarly displaced in the same direction as the rotation direction of the balancer shafts 48L and 48R. To do.

  The magnitude of the inertial force FB of the balancer 60B is also different from the magnitude of the inertial force FC of the balance weights 21c and 21d, similarly to the relation of the rotational speed in FIG.

  The primary vibration of the engine 10 can remain due to the difference between the magnitude of the inertial force FB of the balancer 60B and the magnitude of the inertial force FC of the balance weights 21c and 21d. Further, as the rotational speed ωC of the crankshaft 21 is gradually increased, this difference is reduced. Accordingly, the primary vibration of the engine 10 is reduced.

  As described above, the balancer 60B of the present embodiment can also gradually increase the degree of suppressing the vibration of the engine 10 as the rotational speed ωB of the balancer shafts 48L and 48R increases. The vibration becomes obvious and the primary vibration can be reduced in the high rotation speed region.

  In addition, the elastic member 645b of the deformable portion 645 has a certain width in the circumferential direction of the balancer shafts 48L and 48R around the wire-shaped metal member 645a, so that the movable weight 62B is positioned at the reference position PC ( In the case of displacement from (see FIG. 11), an urging force toward the reference position PC is applied to the movable weight 62B.

  Specifically, as shown in FIG. 11, when the movable weight 62B is displaced from the reference position PC where the center of gravity GB of the balancer 60B is farthest from the balancer shafts 48L and 48R, the displacement direction of the elastic member 645b. Since the same side portion is compressed, an urging force for pushing back the movable weight 62B toward the reference position PC is generated from this portion. Further, since the portion of the elastic member 645b opposite to the displacement is stretched, an urging force for pulling the movable weight 62B toward the reference position PC is generated from this portion. Thereby, excessive displacement of the movable weight 62B is suppressed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the format of the said embodiment. For example, the balancer 60A of the first example or the balancer 60B of the second example may be applied as a secondary balancer that suppresses secondary vibration of the engine.

  1 Motorcycle (an example of a saddle type vehicle), 2 body frame, 3 front fork, 4 front wheels, 5 handles, 6 fuel tank, 7 seats, 8 swing arms, 9 rear wheels, 10 engine, 12 crankcase, 12L Left case, 12R Right case, 14F, 14B Cylinder block, 16F, 16B Cylinder head, 17 Clutch cover, 18 Generator cover, 21 Crankshaft, 21c, 21d Balance weight, 22 Generator, 23 Clutch, 25 Main shaft, 26 Mission gear section, 27 drive shaft, 29 sprocket, 36L, 36R balancer drive gear, 38L, 38R balancer driven gear, 42F, 42B piston, 46F, 46B connecting rod, 48L, 48R balancer shaft, 60A balancer, 60B balancer, 6 A movable weight, 62B movable weight, 622a corner, 631 shaft support, 64A support, 64B support, 641 fixing, 641a insertion hole, 643 extension, 645 deformation, 645a metal member, 645b elastic member, 66 elasticity Member (an example of a suppression unit), PC reference position.

Claims (9)

A crankshaft,
A balancer shaft linked to the crankshaft;
A balancer that is rotationally driven by the balancer shaft and suppresses vibrations synchronized with the rotation of the crankshaft;
An engine with
The balancer is
A support attached to the balancer shaft;
A movable weight supported by the support portion and movable relative to the support portion at least in the circumferential direction of the balancer shaft according to a change in the rotational speed of the balancer shaft;
An engine characterized by including. The engine according to claim 1,
The support part is
Including a shaft support portion that supports the movable weight at a position eccentric from the balancer shaft;
An engine characterized by that. The engine according to claim 1,
The support part is
Including a deformed portion that is interposed between the balancer shaft and the movable weight and is formed of at least one material that is deformable at least in a circumferential direction of the balancer shaft.
An engine characterized by that. The engine according to claim 3,
The deformation part includes a flexible metal member,
An engine characterized by that. The engine according to claim 3,
The deformation part includes an elastic member,
An engine characterized by that. The engine according to claim 5, wherein
The elastic member is
The movable weight biases the movable weight toward the reference position when the balancer moves from a reference position where the center of gravity of the balancer is farthest from the balancer shaft;
An engine characterized by that. The engine according to claim 1,
The movable weight further includes a suppressing unit that suppresses the movement of the movable weight when the center of gravity of the balancer moves from a reference position that is most distant from the balancer shaft.
An engine characterized by that. The engine according to claim 1,
The engine is a V-type engine having a bank angle smaller than 90 degrees.
An engine characterized by that.   A straddle-type vehicle comprising the engine according to any one of claims 1 to 8.

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