JPH0228510B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motorcycle mainly used for racing, and particularly aims to reduce the weight of the vehicle and lower the center of gravity to improve running stability.

Generally, motorcycles used for road races need to turn while running at high speed, and it is preferable that the allowable tilting angle is as large as possible. Furthermore, in order to improve stability and maneuverability when turning, it is necessary to lower the center of gravity of the vehicle as much as possible. Conventionally, this kind of motorcycle was
As shown in Publication No. 3806, the engine is mounted on the tower with a large cylinder that is either upright or tilted slightly forward, which not only raises the center of gravity, but also supports the steering shaft tube that supports the front fork and the rear fork. The main frame member that connects the engine to the main frame must be bent upward to avoid the engine, which not only increases the weight but also contributes to raising the center of gravity.

In order to eliminate the above-mentioned problems, this invention connects the steering shaft tube and the bracket at the rear of the vehicle body frame by a main tube member that is configured substantially linearly and is disposed downward from the rear, and is formed on the lower surface of the main tube member. The unique feature is that the engine is rationally suspended within a triangular space.

The present invention will be explained below with reference to illustrated embodiments.

Figure 1 is a side view of a motorcycle 1 used for road racing, Figure 2 is a plan view of its main parts, Figure 3 is a partially cutaway side view of the engine, and Figure 4 is its power system diagram. be. That is, a separately formed steering shaft tube 3 is attached to a bracket 2a in front of the vehicle body frame 2 by bolts 4, and the steering shaft tube 3 allows a front fork 6 having a front wheel 5 to be turned left and right. It is pivoted. 7 is a steering handle attached to the front fork 6. The front bracket 2a
A main frame member 8, which is made by welding and assembling a plurality of steel pipes, extends rearward and downward, and a rear bracket 2b is fixed to the rear end thereof. The rear part of the engine 9 is fixed to the rear bracket 2b, and a rear fork 11 having a rear wheel 10 is supported by a pivot shaft 11a so as to be vertically swingable.
A drive chain 12 is spanned between the rear wheel 10 and the rear wheel 10. 14 is a radiator for engine cooling water, and 15, 15 are exhaust pipes. An arm 16 is rotatably attached to the upper cross member 8a of the main frame member 8, and the free end of the arm 16 is connected to the rod 1.
7 is connected and fixed to the rear bracket 2b, and the other end of the buffer spring 18 is connected. 19 is a fuel tank, and 20 is a passenger seat.

The engine 9 is arranged in a substantially triangular space formed between the lower surface of the main frame member 8, which extends substantially linearly from the steering shaft tube 3 toward the rear bracket 2b with a downward slope, and the ground. ing. That is, the crankcase 9b is supported on the rear lower surface of the main frame member 8, and the front surface of the crankcase 9b has an upper side extending obliquely upward along the left and right main pipes of the main frame member 8 and facing between the left and right main pipes. A cylinder 9e and a lower cylinder 9f located below the cylinder 9e and extending substantially horizontally are provided, and these form a V-type engine. That is, the engine 9 has a V-shaped cylinder when viewed from the side and has a V-shape when viewed from the side of the vehicle body.
The V-shaped cylinders are arranged one above the other so that the V-shaped space formed between the cylinders is opened to the front. The buffer spring 18 is mounted so that its axis is substantially parallel to the axis of the upper cylinder 9e. 9d is both cylinders 9e, 9
This shows an air-fuel mixture generating means such as a carburetor or a fuel injection device arranged between f. To explain the engine 9 in more detail, the two cylinders 9e and 9f have substantially the same configuration, and as shown in FIG.
and a piston 23 slidably fitted therein, and a combustion chamber 24 is formed in the top surface of the piston 23. 25 is a spark plug. A crankshaft 26 is housed in a crank chamber 27 and connected to the piston 23 via a connecting rod 26a. 28 is a scavenging passage, and 29 is an exhaust passage. Reference numeral 30 denotes an intake passage leading into each crank chamber 27, and two of the intake passages 30 are arranged side by side. Reference numeral 31 denotes a throttle valve provided in the intake passage 30, which is controlled to open and close by the driver. A disk valve 32 is provided downstream of the throttle valve 31 in the intake passage 30. That is, the disc valve 32 is disposed with a slight gap between the case of the crank chamber 27 and the lid member 33, and is connected by the valve shaft 34 so as to rotate once for every revolution of the crankshaft 26. Reference numeral 35 indicates two valve ports provided symmetrically on the disk valve 32 with the valve shaft 34 in between. Valve stem 3
4 has a bevel gear 37 at the shaft end, and an intermediate gear member 38
It meshes with the reduction large gear 39 via. The large reduction gear 39 is connected to the input shaft 41 of the transmission via a clutch 40 and to the crankshaft 26 via a small reduction gear 42. Reference numeral 43 denotes an output shaft driven by the input shaft 41 via a group of transmission gears 44, which is the same as the output shaft 9a of the engine, and a sprocket 45 for driving the drive chain 12 is engaged therewith. A cooling water pump 46 circulates cooling water between the cooling jacket 21 and the radiator 14.

Next, the operation of this embodiment will be explained. When the crankshaft 26 is cranked and the piston 23 begins its upward stroke, the disk valve 32 rotates and allows the valve port 35 to communicate with the intake passage 30. Therefore, the air-fuel mixture generated by the air-fuel mixture generating means 9d and metered by the throttle valve 31 is introduced into the crankshaft 27. When the piston 23 moves to the downward stroke, the disk valve 32 blocks the intake passage 30, so the air-fuel mixture introduced into the crank chamber 27 is compressed, and as the piston 23 further descends, the scavenging passage 28 closes to the combustion chamber. When it opens in 24, it flows into the interior at once. Piston 23
starts to rise and reaches the end of the compression stroke, spark plug 2
Ignition is effected by 5, and the resulting high pressure forces the piston 23 down with an acceleration. When the downward stroke reaches the middle stage, the exhaust passage 29 opens and the burnt gas in the combustion chamber 24 is discharged.

The engine output thus obtained is transmitted from the crankshaft 26 to the speed change gear group 44 via the small reduction gear 42 and the large gear 39, and is taken out from the sprocket 45 provided at the end of the output shaft, and then sent to the drive chain 12. The rear wheels 10 are driven through the rear wheels 10.

The two-stroke engine described above is mounted on the motorcycle 1 with the two cylinders 9e and 9f at the front, and the disk valve 32 is positioned above the crankshaft of the lower cylinder 9f. . In addition, the intake passage 30 is oriented in the direction in which the vehicle is traveling, and can receive the wind pressure of the traveling wind while the vehicle is running. Incidentally, out of the running wind that has flowed between the cylinders 9e and 9f, the running wind that does not flow into the intake passage 30 flows toward the rear of the vehicle around the air-fuel mixture generating means 9d. When the vehicle travels and the rear wheels pass over unevenness on the road surface, the rear wheels 10 move up and down, and the rear fork 11 swings about the pivot shaft 11a. Since this rocking motion is absorbed by the buffer spring 18, no large impact is applied to the vehicle body frame 2.

Note that the rod 17 connected to the arm 16 has a turnbuckle shape, and its overall length can be changed. In other words, loosen the lock nut,
When the rod 17 is rotated and extended, the arm 16 rotates counterclockwise to move the initial position of the rear fork 11 upward, thereby lowering the vehicle height. Conversely, by shortening the rod 17, the vehicle height, that is, the minimum ground clearance, can be adjusted higher, and the vehicle settings can therefore be easily changed according to the weight of the occupants and the size of the unevenness of the road surface.

As described above, the present invention includes a main frame member that is tilted substantially linearly downward from the steering shaft tube toward the rear bracket, and upper and lower cylinders arranged vertically below the main frame member. The V-shaped engine is suspended with the upper cylinder facing between the main frame members, and an air-fuel mixture generating means is disposed between the upper and lower cylinders, and an upper cylinder is disposed behind the upper cylinder. Since the rear wheel buffer member is arranged approximately parallel to the axis of the cylinder, the main frame member is made approximately straight to improve buckling strength, and the approximately triangular space formed between the main frame member and the ground is reduced. It can be used effectively to accommodate the engine.

Therefore, compared to conventional bent main frame members, the strength margin can be reduced, and the upper cylinder faces between the left and right main frame members, reducing the minimum ground height of the engine. can be secured. Therefore, not only the weight of the vehicle body frame can be reduced, but also the center of gravity of the vehicle can be lowered by lowering the main frame member and the engine. Moreover, since the axis of the rear wheel shock absorbing member is made substantially parallel to the axis of the upper cylinder of the engine, the engine and the shock absorbing member, which are relatively heavy, can be brought close to each other without interfering with each other. In this way, the center of gravity is moved closer to the center of the vehicle body (mass concentration), and steering stability can be improved. Furthermore, the V-shaped space between the V-shaped cylinders is open to the front, allowing running air to flow around the air-fuel mixture generating means, so that the air-fuel mixture is not heated by heat radiation from the cylinders. can be suppressed and increase intake efficiency.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a side view of a motorcycle, FIG. 2 is a plan view of its main parts, and FIG. 3 is a partially cutaway side view of the engine.
Figure 4 is its power system diagram. 2...Vehicle frame, 2b...Rear bracket, 3...
Steering shaft tube, 5...front fork, 8...main frame member.

Claims (1)

[Claims] 1. A front fork having a front wheel of a steering shaft tube located at the front is supported so as to be able to freely turn left and right, and a rear fork having a rear wheel is supported on a rear bracket so as to be swingable up and down. In the vehicle body frame which is connected to the bracket by left and right main frame members, the main frame member is tilted substantially linearly rearward downward from the steering shaft tube toward the rear bracket,
Below this main frame member, the upper side arranged vertically,
A V-shaped engine having a lower cylinder is suspended with the upper cylinder facing between the main frame members, and an air-fuel mixture generating means is disposed between the upper and lower cylinders. A motorcycle characterized in that a rear wheel buffer member is arranged on the side substantially parallel to the axis of the upper cylinder.