JPH031194B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a motorcycle.

[Conventional technology]

Conventionally, as this type of motorcycle, for example, Jikosho
As shown in Publication No. 38-3806, there is an engine equipped with a large cylinder that stands upright or tilts slightly forward. The frame member had to be bent upward to avoid the engine.

[Problem to be solved by the invention]

However, with this structure in which the main frame member is bent, not only does the weight of the body frame increase in order to provide the desired strength to the bent and elongated main frame member, but also the weight of the main frame member disposed above the engine increases. The frame member contributes to raising the center of gravity of the vehicle. On the other hand, in order to improve the stability and maneuverability of motorcycles when turning at high speed, it is necessary to lower the center of gravity of the vehicle as much as possible. The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a motorcycle that not only has a lightweight body frame but also can lower the center of gravity of the vehicle.

[Means to solve the problem]

The motorcycle according to the present invention connects the steering shaft tube and the rear bracket that supports the rear fork with a pair of left and right main frame members that extend substantially linearly from the steering shaft tube toward the rear bracket. An engine is disposed in a generally triangular space formed below the main frame member, and the head portion of the engine is interposed between the left and right main frame members.

[Effect]

In the present invention, the buckling strength of the main frame member is improved. Further, the engine is accommodated by effectively utilizing the substantially triangular space formed between the main frame member and the ground, and interference between the main frame member and the head portion of the engine can be avoided.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. 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. From the front bracket 2a, there is a main frame member 8 which is assembled by welding a plurality of steel pipes.
extends rearward and downward, and a rear bracket 2b is fixed to the rear end. That is, the main frame member 8 includes a pair of left and right members 8a and 8b that face each other at a constant interval in the vehicle width direction, a cross member 8c that connects these left and right members, and the like. In addition, the main frame member 8 is attached to the front bracket 2a.
The steering shaft tube 3 extends from the steering shaft tube 3 toward the rear bracket 2b via the steering shaft tube 3 and extends toward the rear of the vehicle body while being inclined downwardly and connects the steering shaft tube 3 and the rear bracket 2b. 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 able to swing vertically. A drive chain 12 is spanned between them. 1
4 is a radiator for engine cooling water, and 15 is an exhaust pipe. An arm 16 is rotatably attached to the cross member 8c at the upper part of the main frame member 8, and the free end of the arm 16 is connected and fixed to the rear bracket 2b by a rod 17. The other end is connected. 19 is a fuel tank, and 20 is a passenger seat.

The engine 9 is disposed in a substantially triangular space formed between the lower surface of the main frame member 8 that slopes downward toward the rear and the ground. That is, a crankcase 9b is supported on the rear lower surface of the main frame member 8, and on the front side of the crankcase 9b there is an upper cylinder 9e extending obliquely upward along the main frame member 8, and an approximately horizontal cylinder located below the upper cylinder 9e. A lower cylinder 9f extending in the direction is provided, forming a V-shaped engine. Here, the angle of inclination of the upper cylinder 9e with respect to the ground is larger than the angle of inclination of the main frame member 8, and the head portion of the upper cylinder 9e is interposed between the left and right members 8a and 8b of the main frame member 8. 9
d indicates an air-fuel mixture generating means such as a carburetor or a fuel injection device disposed between the cylinders 9e and 9f. To explain the engine 9 in more detail, the two cylinders 9e and 9f have substantially the same configuration, and as shown in FIG. The piston 23 has a piston 23 that is freely inserted.
A combustion chamber 24 is formed on the top surface. 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. In other words, the disc valve 32 is connected to the crank chamber 2.
1 of the crankshaft 26 by the valve shaft 34.
They are connected so that they rotate once per rotation. 35
are two valve ports provided symmetrically on the disk valve 32 with the valve shaft 34 in between. The valve shaft 34 has a bevel gear 3 at the shaft end.
7, and meshes with a large reduction gear 39 via an intermediate gear member 38. The large reduction gear 39 is connected to the input shaft 41 of the transmission via a clutch 40, and is connected to the crankshaft 2 via a small reduction gear 42.
6. 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. 46 is the cooling jacket 21 and the radiator 1
This is a cooling water pump that circulates cooling water between 4 and 4.

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. Thereupon, the air-fuel mixture generated by the air-fuel mixture generating means 9d and metered by the throttle valve 31 is introduced into the crank chamber 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
5, and the resulting high pressure forces the piston 23 downwards 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 reduction small 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 transferred 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 facing forward, and the disc valve 32 is positioned above the crankshaft of the lower cylinder 9f. Further, the intake passage 30 is oriented in the direction in which the vehicle is traveling, so that it can receive the wind pressure of the traveling wind while the vehicle is running. 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 you turn the rod 17 and extend it, arm 1
6 rotates counterclockwise to shift the initial position of the rear fork 11 upward, thereby lowering the vehicle height. Conversely, if the rod 17 is shortened, the vehicle height, that is, the minimum ground clearance, can be adjusted higher, and the vehicle settings can therefore be easily changed in accordance with the weight of the occupant and the size of the unevenness of the road surface.

Moreover, since the main frame member 8 is made substantially straight,
Improves buckling strength compared to bending structures,
Since the strength margin can be reduced, the weight of the main frame member 8 can be reduced. By accommodating the engine 9 by effectively utilizing the approximately triangular space formed between the main frame member 8 and the ground,
The engine 9 can be arranged below. Furthermore, by interposing the head portion of the upper cylinder 9e between the left and right members 8a and 8b of the main frame member 8, the main frame member 8 can be placed as downwardly as possible while avoiding interference with the engine 9. Can be done.

〔Effect of the invention〕

As explained above, according to the present invention, a pair of left and right main frame members extend rearwardly downward in a substantially straight line from the steering shaft tube toward the rear bracket between the steering shaft tube and the rear bracket that supports the rear fork. Connect with
Since the engine is disposed in the approximately triangular space formed below the main frame member, and the head portion of the engine is interposed between the left and right main frame members, the buckling strength of the main frame member is improved. The engine can be accommodated by effectively utilizing the space below the main frame member, and interference between the main frame member and the head portion of the engine can be avoided.

Therefore, the strength margin for the main frame member can be reduced compared to a conventional bent type main frame member, and the main frame member and the engine can be lowered, in particular, the main frame member can be lowered as much as possible. This not only reduces the weight of the vehicle body frame, but also lowers the center of gravity of the vehicle.

[Brief explanation of the drawing]

Fig. 1 is a side view showing a motorcycle according to the present invention, Fig. 2 is a plan view showing its main parts, Fig. 3 is a side view with a part of the engine cut away, and Fig. 4 is a power system diagram thereof. be. 2...Vehicle frame, 2b...Rear bracket, 3...
Steering shaft tube, 6...front fork, 8...main frame member,
9...Engine, 9e...Upper cylinder, 11...
...Ryahuoak.

Claims (1)

[Claims] 1. Connect the steering shaft tube from the steering shaft tube to the rear between the steering shaft tube, which is located at the front of the vehicle body frame and supports the front fork so that it can turn left and right, and the rear bracket, which is located at the rear and supports the rear fork so that it can swing vertically. They are connected by a pair of left and right main frame members that extend backward and downward in a substantially straight line toward the bracket, and the engine is disposed in a substantially triangular space formed below the main frame members. A two-wheeled motor vehicle in which the main frame members are interposed between the left and right main frame members.