JPH0617649B2 - Motorcycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a set of cylinders are arranged in a V shape with a crank pin in common at an included angle of less than 90 °, and a plurality of sets of cylinders are arranged in parallel in a vehicle width direction. The present invention relates to a motorcycle engine having an overhead camshaft type valve operating mechanism arranged therein, and related structures such as an accommodating portion of a chain for driving the camshaft, a crank pin, and a balance weight.

Conventionally, in a V-type engine with a cylinder included angle of 90 °,
The crankpin was shared by one set of cylinders arranged in a V shape, and the balance weight attached to the crank eliminated the residual unbalanced inertial force primary term of the reciprocating mass of the piston, etc.
In the case of a compact engine with a cylinder included angle of 90 ° or less, the balance weight formed on the crank cannot eliminate the primary term of the residual unbalanced inertial force, resulting in engine vibration. Was transmitted to the motorcycle body and the riding comfort was poor.

A motorcycle engine equipped with a balancer has been considered to overcome the above-mentioned difficulties. However, the provision of such a balancer causes a problem in the bearing strength of the crankshaft in the crankcase due to the positional relationship with the balancer shaft, and even if the effect of suppressing the vibration is achieved, a large amount of lubricating oil is used on the other hand. The lubricating oil falling from the cylinder head, which requires the air-conditioning, hits the balancer, causing so-called air trapping. As a result, there is a possibility that the entire engine may malfunction such as damage to the oil pump and wear of parts due to insufficient oil supply.

The present invention is provided with such a balancer,
The crankshaft bearing for a pair of V-shaped cylinders is reinforced by a rib that communicates with the front wall of the crankcase, and the accommodating portion for the chain that drives the camshaft of the intake / exhaust valve through this rib is used as a balance weight or crank. By separating from the pin disposition part, the lubricating oil falling from the cylinder head above the chain storage part does not directly collide with and spread on the balance weight or crank pin,
This is to prevent the drop of lubricating oil from adversely affecting the entire engine.

An embodiment of the present invention shown in the drawings will be described below.

Reference numeral 1 is a motorcycle, in which the crankshaft 4 of a 4-cylinder V-type 4-cycle gasoline engine 3 is oriented in the width direction of the vehicle body, and the cylinder 6 is a V-type with an included angle of 70 ° forward and backward. The engine 3 is mounted on the frame 2 of the wheeled vehicle 1.

In the four-cylinder V-type cycle gasoline engine 3, the cylinder sets 6a, 6b and the cylinder sets 6c, 6d arranged in the V-type front and rear have the crank pins 5a, 5b in common, and the front cylinders 6a, 6c are Each is slightly biased to the right of the rear cylinders 6b and 6d.

In the crankcase 7, the crankshaft 4
A balancer 8 is rotatably pivoted forward in parallel with the crankshaft 4 and the balancer 8 while the gears 11 and 12 having the same pitch circle and the same number of teeth are meshed with each other.
The balance weights 10a and 10b of the balancer 8 are integrally fitted to the left ends of the shafts 9 of the crankpin 5a,
The balance weight is installed at the position facing 5b.
The gears 11, 10a, 10b have an angular relationship such that the first-order term of the residual unbalanced inertial force of the reciprocating mass in the engine 3 is eliminated.
Twelve meshed.

As another embodiment, the shaft 12 may be rotated by engaging the gear 12 with the drive gear 19 having a larger mesh width.

Further, as will be described later, sprockets 13a and 13b are integrally formed substantially at the center of the crankshaft 4, and camshafts 15a and 15b are rotatably supported by the front cylinder head 14a and the rear cylinder head 14b, respectively. Cam sprockets 16a and 16b are integrally fitted to the cam sprockets 16a and 16b, and cam chains 17a and 17b are bridged between the sprockets 13b and 13a and the cam sprockets 16a and 16b, respectively. The camshaft 15 through the cam chains 17a and 17b and the cam sprockets 16a and 16b.
The intake and exhaust valves (not shown) are driven to open and close by being transmitted to a and 15b. Furthermore, at the left end of the crankshaft 4, an AC generator 18 is provided outside the gear 11.
Is provided.

A drive gear 19 is fitted on the right end of the crankshaft 4, and a main shaft 20 and a countershaft 21 are rotatably supported behind the crankshaft 4 in parallel therewith, and the main shaft 20 is rotatable. The input gear 23 of the clutch 22, which is pivotally attached to, is meshed with the drive gear 19.

Further, the output portion (not shown) of the clutch 22 is directly connected to the main shaft 20, the main shaft gear group 24 is spline-fitted or fitted to the main shaft 20, and the counter shaft gear group 25 is splined to the counter shaft 21. The main shaft gear group 24 is selectively engaged with any gear of the counter shaft gear group 25 by a shift fork (not shown) so that a predetermined reduction ratio is achieved. The counter shaft 21 and the drive sprocket 26 integrated with the counter shaft 21 are rotationally driven.

Furthermore, the final driven sprocket 28 is integrally fitted to the rear wheel 27, and the drive sprocket is
A drive chain 29 is provided between the 26 and the final driven sprocket 28.

Moreover, the crankcase 7 has a split surface that passes through the crankshaft 4, the main shaft 20 and the countershaft 21, and is vertically divided into two parts.
It is divided and connected to each other with bolts 31.

The crankshaft 4 and the balancer shaft 9 are supported by bearings provided on the split surface of the crankcase 7, respectively, and the crankshaft 4 supports the one set of cylinders 6a, 6b and 6c, 6d.
Are supported by bearings 34a, 38a and bearings 34b, 38b, respectively, and the balancer shaft 9 is supported by bearings 35a, 35b at both ends thereof.

The sprocket 13b, 13a for winding the cam chains 17a, 17b is formed on the crankshaft 4 between the bearings 38a, 38b on the center side among the four bearings supporting the crankshaft 4. .

The ribs 3 pass from the front wall of the crankcase 7 to the insides of the balancer weights 10a and 10b on the balancer shaft 9, respectively.
9a and 39b are extended and connected to the central bearing portions 38a and 38b.

Ribs 39a, 39b extending from the bearings 38a, 38b to the front wall of the crankcase 7 reinforce the bearings 38a, 38b and form a space for accommodating the chains 17a, 17b, that is, a chain storage part 40. The storage section 40 is separated from the balancer weights 10a and 10b on the balancer shaft 9 and the crank pins 5a and 5b of the crankshaft 4 by ribs 39a and 39b.

The balancer shaft 9 has one bearing portion 35a inside the one bearing portion 35a.
A larger diameter protrusion 36 is formed, and the bearing portion 35a is formed by the protrusion 36 and the gear 12 fitted to the balancer shaft 9.
After the balancer shaft 9 is placed on the bearing portion 35a so as to sandwich the nut, the nut 37 is screwed from the outside of the gear 12, and the balancer shaft 9 is attached to the bearing portion 35a so that the axial movement thereof is restricted. It is installed. The protrusion 36 may be a bulge or a flange that supports another member such as a gear.

Further, side covers 32, 33 are detachably fitted on both sides of the crankcase 7.

Since the illustrated embodiment is configured as described above, the output of the engine 3 is from the drive gear 19 integrated with the crankshaft 4 to the input gear 23 of the clutch 22, the clutch 22, the main shaft 20, the main shaft gear group 24. , The counter shaft gear group 25, the counter shaft 21, the drive sprocket 26, and the drive chain 29 to the final driven sprocket 28, and the rear wheel 27 is driven.

As a result of setting the cylinder included angle to 70 °, even if the crank weight 30 formed integrally with the crankshaft 4 cannot eliminate the first-order term of the residual unbalanced inertial force of the reciprocating mass in the engine 3, The balancer 8 connected to the crankshaft 4 can eliminate the first-order term of the residual unbalanced inertial force and improve the riding comfort.

Furthermore, since the cylinders 6 are arranged in a V-shape in the front-rear direction to reduce the dimension in the width direction and the cylinder angle is set to 70 °, the engine 3
The engine 3 can be made compact by shortening not only the width but also the front-rear length, so that the motorcycle 1 can be made compact and lightweight.

Furthermore, since the balancer 8 is disposed below the front cylinders 6a and 6c and in front of the crankshaft 4, even if the balancer 8 is attached, the front-rear length of the engine 3 does not change.

In addition, the sprockets 13a, 1
3b is integrally formed, and the cam sprockets 16a, 16b and the cam chains 17a, 17b of the front cylinders 6a, 6c and the rear cylinders 6b, 6d are arranged substantially in the center in the width direction of the engine 3, so that the appearance of the engine 3 is left and right. It is not emphasized that there is a discrepancy between the front and back, and the noise can be suppressed as much as possible by moving the cam chain, which is a noise source, inward.

Further, a gear 11, which connects the crankshaft 4 and the balancer shaft 9,
Since the 12 is arranged on one side of the engine 3, the assembling property and the maintainability are improved.

Since the balancer shaft 9 is attached to the one bearing portion 35a so that the movement in the axial direction is restricted, it is sufficient to simply mount the balancer shaft 9 on the other bearing portion 35b.

In the present invention, since the balancer shaft is arranged in front of the crank shaft, the crank shaft is held in a state of floating in the middle of the crank case, which causes a problem in the strength of the bearing portion in the middle. To make it easier, since the intermediate bearing portions (38a and 38b) of the crankshaft are connected to the front wall of the crankcase by ribs, respectively, the bearing portion of this intermediate portion is reinforced and the crankshaft supporting structure is strengthened. Can be sufficient.

In addition, the chain storage portion communicating with the camshaft to which a large amount of lubricating oil is supplied includes the bearing portion (38a, 38b) and the rib (39a,
39b) separates the balance weight of the balancer shaft from the crank pin, and the piston reciprocating portion of each cylinder, and the lubricating oil that falls from the cylinder head where the cam shaft is arranged has these balance weight, crank pin, Since it rarely collides with the piston reciprocating part and diffuses, it is possible to suppress air entrapment (air mixing) of the lubricating oil, and damage to the oil pump and failure of the entire engine such as wear of parts due to insufficient oil supply occur. Can be prevented.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a balancer for a motorcycle engine according to the present invention, FIG. 2 is an enlarged view of an essential part thereof, and FIG. 3 is a partially longitudinal side view thereof. DESCRIPTION OF SYMBOLS 1 ... Motorcycle, 2 ... Frame, 3 ... 4-cylinder V-type 4-cycle gasoline engine, 4 ... Crank shaft, 5 ... Crank pin, 6 ... Cylinder, 7 ... Crank case, 8 ... Balancer, 9 ... Balancer shaft, 10 ... Balance weight, 11 ... Gear, 12 ... Gear, 13 ... Sprocket, 14 ... Cylinder head, 15 ... Cam shaft, 16 ... Cam sprocket, 17 ... Cam chain, 18 ... Alternator, 19 ... Drive gear, 20 ... Main Shaft, 21 ... Counter shaft, 22 ... Clutch, 23 ...
Input gear, 24 ... Main shaft gear group, 25 ... Counter shaft gear group, 26 ... Drive sprocket, 27 ... Rear wheel, 28 ... Final driven sprocket, 29 ... Drive chain, 30 ... Crank weight, 31 ... Bolt, 32
… Side cover, 33… Side cover, 34… Bearing part, 35…
Bearing part, 36 ... Projection part, 37 ... Nut, 38 ... Bearing part, 39 ... Rib, 40 ... Chain storage part.

Claims (1)

[Claims] 1. A crankshaft is oriented in the width direction of a vehicle body, and a pair of cylinders are arranged in a V-shape with a common crank pin and an included angle of less than 90 ° in the front-rear direction. In a motorcycle engine having a plurality of overhead camshaft type valve operating mechanisms arranged in parallel in a direction, a balancer shaft driven by the crankshaft is installed in front of the crankshaft in parallel with the balancer shaft. Is provided with a balance weight at a position facing the crank pin, and a chain on the crank shaft for driving the cam shaft is arranged between bearing portions for the cylinder set. The bearing portions on both sides of the chain are forwardly moved by ribs. It is connected to the crankcase wall of the crankcase, and the chain storage section is separated from the balance weight on the balancer shaft and the crankpin of the crankshaft by the bearing section and ribs. A motorcycle engine to be used.