JPH02117486A - Body frame of motor bicycle - Google Patents

Abstract

PURPOSE:To improve its frame rigidity and sufficiently secure its handle cutting inclination, by inwardly bending and connecting the front ends of the pair of right and left main pipes to its frame member located behind its head pipe, and axially supporting its rear arm to the rear end portions of the pair of main pipes. CONSTITUTION:A frame member (cleaner box 4) is connected to the rear side of a head pipe 3 for axially supporting a front fork 11 and the front ends of the pair of right and left main pipes 5 are connected to the respective rear end portions of the frame member while being bent inwards. In this case, the crossing point of an extension line in the direction of bending of the right and left main pipes 5 with the vehicle axis is positioned behind the above head pipe 3. The front ends of a rear arm 14 for axially supporting rear wheels 15 are axially supported via an arm bracket 6 to the respective rear ends of the main pipes 5 both passing above an engine 18 and extending rearwards. Spaces for on-vehicle parts are thus formed and also a space for rotation of the front fork 11 is provided in the vicinity of the rear side of the head pipe 3.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a body frame for a motorcycle, and in particular to a structure around a head pipe that can significantly improve frame rigidity and ensure a large steering angle. .

[Conventional technology]

Conventionally, as a body frame for a motorcycle, a front fork is pivotally supported by a head pipe at the front end, an engine is suspended and supported by a main pipe connected to the hend pipe, and a rear arm is pivoted by the rear end of the main pipe. There are things that are designed to support it.

In this case, in order to improve the frame rigidity and to secure space for mounting in-vehicle components above the engine, a pair of the above-mentioned main pipes is provided, one on the left and one on the right, and these are arranged so as to extend rearward above the engine. For example, JP-A-61
(Refer to Publication No.-275078).

In this vehicle body frame, the frame rigidity can be improved by having two main pipes, and the space sandwiched between the two main pipes becomes a space for arranging a carburetor, an air cleaner, and the like.

[Problem that the invention attempts to solve]

By the way, for trial motorcycles that compete for drivability on extremely uneven terrain such as rocky areas, steep slopes, and large steps, the turning angle of the steering wheel should be, for example, 60 degrees or more in total on both sides, and two-wheeled motorcycles for public roads. It is common to make it about twice as large.

On the other hand, there has recently been a desire for a significant improvement in frame rigidity for this type of motorcycle, and a body frame equipped with a pair of left and right main pipes as described above is advantageous for improving this rigidity. . However, with this conventional body frame, when you turn the steering wheel, the left side of the front fork
The right pair of fork bodies interfere with the left and right main pipes, making it impossible to obtain a sufficient steering angle.

The present invention has been made in view of the above-mentioned conventional situation, and an object of the present invention is to provide a motorcycle body frame that can significantly improve frame rigidity and ensure a sufficient steering angle.

[Means for solving problems]

The present invention connects a frame member extending rearward to the rear side of a head pipe that pivotally supports a front fork, and connects the front ends of a pair of left and right main pipes to the rear end of the frame member as an extension of this. Connect by bending the line so that it intersects the vehicle axis and the head pipe behind the head pipe, extend both main pipes to the rear so as to pass above the engine, and pivot the rear arm at the rear end of the main pipe. This is a body frame for a motorcycle, characterized in that it is designed to

[Effect]

According to the motorcycle body frame according to the present invention, the left,
By providing the right pair of main pipes, frame rigidity can be improved accordingly, and the arrangement of in-vehicle parts can be improved! You get space.

In the present invention, the main pipe is not directly connected to the hend pipe, but is connected to the head pipe through one frame member, and the front end of the main pipe is bent inward, so that the frame member By setting the length appropriately, a rotation space for the front fork can be created near the rear of the head pipe, and as a result, a sufficient steering angle can be secured.

〔Example〕

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

FIGS. 1 to 4 are diagrams for explaining the body frame of a motorcycle according to an embodiment of the present invention. In this embodiment, a motorcycle used in a trial competition in which running ability is competed on rocky areas etc. An example will be explained.

In the figure, l is a motorcycle in which the structure of this embodiment is adopted, and a steering shaft 11a of a front fork 11 is pivotally supported at the front end of a body frame 2 of the motorcycle l. The front fork 11 is attached to the steering shaft 11a with upper and lower brackets Il.
b, a pair of left and right fork body lids through LLC,
It has a configuration in which ie is installed. Further, a steering handle llf is fixed to the upper bracket 11°b, a front end 12 is pivotally supported between the lower ends of the fork bodies lid and lie, and a front fender 1 covering the upper surface of the front wheel 12 is located in the middle.
3 is installed.

Further, the front end of a rear arm 14 is pivotally supported at the rear end of the vehicle body frame 2, and the rear end of the rear arm 14 is supported by a rear wheel 15.
is pivoted. Note that 16 is a link mechanism that connects the rear arm 14 and the vicinity of the lower end of the arm bracket 6, and 17 is a buffer that connects the link mechanism 16 and the upper cross pipe 7, which constitute a rear wheel suspension system. There is.

Furthermore, an engine unit 18 is suspended and supported below the vehicle body frame 2. This engine unit 18 includes a cylinder 18b on a crankcase 18a,
This is a water-cooled two-stroke single-cylinder engine made up of stacked heads 18c. The lower surface of the crankcase 18a is covered with an undercover 19. Further, the exhaust pipe 20a of the engine unit 18 passes between the unit 18 and the vehicle body frame 2 and extends to the vicinity of the rear wheel 15.

The vehicle body frame 2 has the following configuration.

That is, a cleaner box 4 as a frame member is installed on the rear side of the cylindrical hend pipe 3 that pivotally supports the front fork 11.
The front ends of the pair of left and right main pipes 5 are connected to the left and right side walls 4C of the box 4, and the arm brackets 6 are connected to the rear ends of each main vibe 5. The upper and lower parts of .6 are connected by upper and lower cross pipes 7.8, and the upper end of the engine suspension down tube 9 is connected to the side wall 4C of the cleaner box 4.

The cleaner box 4 has a box shape with a narrow front portion to match the diameter of the head pipe 3 when viewed from above, and has an air intake port 4b formed in the ceiling wall 4a.
An air cleaner 10 is provided inside. The left and right main pipes 5 are rectangular in cross section, and their front ends are bent inward and welded to the wide center of the side wall 4c of the cleaner box 4. , both communicate through a communication hole 4d. As a result, the intersection of the line extending the front end portions of the left and right main pipes 5.5 along the bending direction and the longitudinal axis of the vehicle is located at the rear of the head pipe 3, and as a result,
A rotation space for the front fork 11 is formed in front of each main pipe 5.

Also, on the rear side of the cylinder 18b is the left cylinder.

A carburetor 21 located between the right main pipes 5.5 is connected to the carburetor 21, and a box-shaped air chamber 22 having a relatively large capacity is connected to the carburetor 21. The left and right side walls of this air chamber 22 communicate with the left and right main pipes 5.5, so that the cleaner box 4 is connected to the main pipes 5.5. It will be connected to the vaporizer via the air chamber 22.

A fuel tank 23 is arranged above the air chamber 22. This fuel tank 23 is made of resin and is similar to the carburetor 21. It has a long shape in the front-rear direction and covers the air chamber 22 and the shock absorber 17. Further, the fuel in the rear half 23a is sent to the front half 23b by a fuel pump 24 provided in the rear half 23a, and from there the fuel is supplied to the carburetor 21 by gravity. Also, this fuel tank 2
3 is fixed at its bottom to the vehicle body frame 2, and has a rear fender 29 attached to its rear end.

In addition, a radiator 25 is installed in the upper part of the cylinder 18b in the space sandwiched between the left and right main pipes 5.5.
is installed. The radiator 25 has a flat plate shape and is formed by connecting head boxes 25b and 25c to both ends of a heat radiating element 25a, and is parallel to the main pipe 5. Further, a blower fan 26 is disposed above the radiator 25, and is bolted to the main pipe 5 together with the radiator 25.

In addition, the vehicle body frame 2. The upper and side surfaces of the fuel tank 23 are covered with a resin vehicle body cover 27, and a seat 28 is disposed on the rear upper surface of the cover 27.

Note that this seat 28 is supported by the fuel tank 23 mentioned above. Further, an air exhaust opening 27a is formed near the blower fan 26 on the front side surface of the vehicle body cover 27.
There is an air inlet 27b near the air cleaner 10 on the top surface.
is formed.

Here, in FIG. 3, numeral 30 is a variable valve for setting the exhaust timing of the engine, and this variable valve is rotationally controlled by a control device (not shown) so as to close the upper part of the exhaust boat 18d at a low speed.

Further, 31 is a manual knob for setting the initial position of the variable valve 3o, and this is provided near the side wall of the cylinder 18b. By means of this knob 31, the variable valve 30 is initially set to be closed when used at low speed or medium speed rotation, and set to the open state when used at high speed rotation.

Note that it is of course possible to use a structure in which the variable valve is set simply by a knob, without providing the above-mentioned control device.

Further, in FIG. 4, reference numeral 32 denotes a front wheel brake disc, which is supported in a floating state by a stand bolt 33 implanted in the hub 12a, and is locked by an e-ring 34.

According to this structure, even if the disk 32 has a small diameter, it can be supported in a floating state on the container.

Next, the effects of this embodiment will be explained.

The motorcycle 1 of this embodiment is a competition vehicle for competing on running ability on rocky areas, etc., and a large steering angle is required.
Also, sufficient frame rigidity is required. Therefore, in this embodiment, a pair of left and right main pipes 5.5 are provided, so that
The frame rigidity can be significantly improved compared to the case where there is only one main pipe, which is common in conventional motorcycles of this type. On the other hand, if a pair of left and right main pipes are provided, there is a concern that the steering angle will become narrower, but in this embodiment, a cleaner box 4 as a frame member for rear extension is connected to the front pipe 3, The main pipes 5.5 are connected to this, and the front ends of each pipe 5 are bent inward, so that the outwardly expanding part of the main pipe 5 is located at the rear by this cleaner box 4, and the front end of each pipe 5 is bent inward. A rotation space for the fork 11 will be formed. Therefore, when the steering handle llf is rotated, the fork bodies lid and lie do not immediately interfere with the main pipe 5, and as a result, a sufficient steering angle (60
degree or higher).

Further, since the pair of left and right main pipes 5.5 are arranged on the left and right sides, a space is created above the engine, which can be used as a space for arranging in-vehicle components.

In this embodiment, a radiator 25. Air chamber 22. A fuel tank 23 and the like are arranged.

Further, in this embodiment, since the cleaner box 4 is formed into a box shape, this can be used as a space for arranging the air cleaner 1o, and the space can be used effectively.

In the above embodiment, the frame member was formed into a box shape to form an air cleaner box, but the frame member of the present invention is not limited to such a shape (the connecting point of the pair of left and right main pipes is Any shape may be used as long as it can be positioned behind the head pipe and avoid interference with the fork body.

Further, in the above embodiment, a competition vehicle was used as an example, but the present invention can of course also be applied to a regular public road vehicle.

〔Effect of the invention〕

As described above, according to the body frame of a motorcycle according to the present invention, the frame member is connected to the head pipe, and the front ends of the pair of left and right main pipes are bent inward and connected to this, so that the frame rigidity is improved. This has the effect of ensuring a sufficient steering angle while significantly improving the steering angle.

[Brief explanation of drawings]

1 to 4 are diagrams for explaining a vehicle body frame according to an embodiment of the present invention, and FIG. 1 is a plan view thereof;
FIG. 2 is a left side view of a motorcycle to which the structure is applied, FIG. 3 is a cross-sectional side view of its engine portion, and FIG. 4 is a cross-sectional view of its disc brake portion. In the figure, 1 is a motorcycle, 3 is a head pipe, 4 is a cleaner box (frame member), 5°5 is a pair of left and right main pipes, 11 is a front fork, 14 is a rear arm, and 18 is an engine unit. . Figure 1 Patent applicant Yamaha Motor Co., Ltd. agent Patent attorney Tsutomu Shimofu

Claims (1)

[Claims] (1) Connect a frame member extending rearward to the rear side of the head pipe that pivotally supports the front fork, and connect the front ends of the pair of left and right main pipes to the rear end of the frame member as an extension of this. are bent and connected so that they intersect with the vehicle axis at the rear of the head pipe, both main pipes are extended rearward to pass above the engine, and the rear arm is pivotally supported at the rear end of the main pipe. A motorcycle body frame characterized by: