JPH0641270B2 - Motorcycle frame - Google Patents

Description

TECHNICAL FIELD The present invention relates to a frame for a motorcycle.

[Prior art]

In the frame of the type in which the engine is mounted between the left and right main pipes extending obliquely downward and rearward from the steering head pipe and the down tubes extending rearward through the lower parts of the main pipes, the present applicant has recently been trying to reduce the weight and increase the weight. In order to achieve both the rigidity and rigidity, it has been proposed to construct the main pipe by a flat aluminum alloy square pipe whose longitudinal dimension is vertically long, and Japanese Patent Application No. 59-
The application has been completed as No. 156868.

[Problems to be solved by the invention]

However, in this prior art frame, the main pipe is formed to be vertically long as it goes forward, and the longitudinal dimension of the front end portion that is the joint end with the steering head pipe is formed to be substantially equal to the axial length of the head pipe. Therefore, it is very difficult to obtain a space for attaching the down tube to the steering head pipe, and there are problems such as various restrictions on the frame structure.

[Means for solving problems]

Therefore, in the present invention, in forming the longitudinal dimension of the front end portion of the main pipe substantially equal to the axial length of the steering head pipe, a cross member is bridged between the front end portions of the main pipe,
The upper end of the down tube is connected to the cross member.

[Action]

According to this configuration, since the rigidity around the steering head is secured by the main pipe, it is possible to secure a mounting space for the down tube in this highly rigid portion. Moreover, since it is sufficient for the down tube to support the engine, the position with respect to the steering head pipe is not so restricted, so that there is no problem in terms of strength and the degree of freedom in the frame structure is increased.

Example of Invention

The present invention will be described below based on an embodiment shown in the drawings.

In the figure, 1 is a frame made of aluminum alloy, and a front fork 4 pivotally supporting a front wheel 3 is pivotally supported on a steering head pipe 2 (hereinafter referred to as a head pipe) vertically installed at a front end thereof with a predetermined caster angle. Has been done. The head pipe 2 is welded with a pair of left and right main pipes 5, 5 extending obliquely downward and rearward in a substantially straight line in a side view. As shown in FIG. 5, the main pipes 5 and 5 are a thin wall and a pair of frame materials 6a and 6b having a substantially U-shaped cross section with one side open, are abutted and welded from the vehicle width direction. It is formed into a flat rectangular tube shape whose cross-sectional shape is vertically long in the vertical direction. The vertical dimension of each of the main pipes 5 and 5 is continuously increased as it goes to the head pipe 2, and the vertical dimension of the front end opening abutted on the head pipe 2 is equal to that of the head pipe 2.
The front end opening is welded to the head pipe 2 over the entire circumference. Further, as shown in FIG. 2, the main pipes 5 and 5 are opened toward the outer side in the vehicle width direction immediately after the head pipe 2 and are bent so as to be parallel to each other from the middle of the head pipe 2 and rearward as they are. A bracket 8 for pivotally supporting the rear arm 7 is welded to the rear end of the bracket.

A seat rail 9 extending rearward is welded to the upper surface of the rear portion of the main pipes 5 and 5, and a back stay 10 is provided between the rear portion of the seat rail 9 and the bracket 8.

By the way, a cross member 11 made of an extruded material of an aluminum alloy is bridged between the front ends of the main pipes 5 and 5. The cross member 11 crosses right and left immediately after the head pipe 2, and a down tube 12 is installed between the cross member 11 and the bracket 8. The down tube 12 of the present embodiment includes a pair of left and right front tubes 13 and 13 extending downward from the cross member 11 and a portion extending between the lower ends of the front tubes 13 and 13 to the rear below the main pipes 5 and 5. Book the back tube 14 and this down tube
Engine 15 in the space between 12 and the main pipes 5, 5.
Is installed. Square tubes made of aluminum alloy are used for the front tubes 13 and 13 and the rear tube 14.

The front tubes 13 and 13 extend vertically on the front surface side of the engine 15, and boss portions 16 and 16 welded to the upper ends thereof are abutted on the front surface of the cross member 11 and bolted. The lower ends of the front tubes 13 and 13 are connected by a cross pipe 17, and the crank case 15a of the engine 15 is supported by the cross pipe 17 via brackets 19 and 19, and the front end of the rear tube 14 is also connected. Are welded.
The rear tube 14 passes below the crankcase 15a of the engine 15 and is located on the center line along the front-rear direction of the vehicle body. A boss portion 22 welded to the rear end of the rear tube 14 is attached to the bracket 8. It is bolted to a cross member 18 that connects the lower ends.

A radiator 20 is installed in front of the front tubes 13 and 13, and an engine 15 is installed on both left and right sides of the rear tube 14.
The exhaust pipes 21, 21 derived from are inserted and arranged.

Further, in the case of this embodiment, a wire 22 such as an accelerator wire or a choke wire is introduced between the front ends of the main pipes 5 and 5 as shown in FIGS. A harness 23, which is a bundle of various electrical cords, is introduced from below the pipe 2. The wire 22 and the harness 23 are guided into the space 24 between the head pipe 2 and the cross member 11,
After passing through the space 24, 22 is pulled out below the main pipes 5 and 5 and is routed to the engine 15 side,
After the harness 23 passes through the space 24, the main pipe 5,
It is led to the battery (not shown) side at the rear through the space 5.

According to this structure, the cross member 11 is bridged between the front ends of the main pipes 5 and 5, and the front tubes 13 and 13 of the down tube 12 are connected to the cross member 11. Even if it is difficult to obtain a mounting space for the down tube 12 in the head pipe 2 due to an increase in the vertical dimension, a mounting space for the down tube 12 can be secured around the steering head.

In this case, the longitudinal dimension of the front end openings of the main pipes 5 and 5 is substantially equal to the axial length of the head pipe 2,
The joint area between the head pipe 2 and the main pipes 5, 5 is increased, and the rigidity and strength around the steering head are sufficiently secured by the main pipes 5, 5. Therefore, since the cross member 11 is located between the front ends of the highly rigid main pipes 5 and 5, it is possible to secure a mounting space for the down tube 12 in a highly rigid portion, and there is no problem in terms of strength. There is no.

Moreover, with this frame configuration, the down tube 12
Since it suffices to support the engine 15, the position with respect to the head pipe 2 is not so restricted, and this has the advantage of increasing the degree of freedom in the frame structure in combination with the fact that the mounting space can be secured.

Further, since the down tube 12 of the present embodiment has only one rear tube 14 that passes below the crankcase 15a, the spaces on both sides of the rear tube 14 are exhaust pipes 21, 21.
It can be used as an insertion space. Therefore, the exhaust pipe
21 and 21 can be easily handled and the exhaust pipe 21,
The 21 can be moved to the inside of the car body, and a sufficient bank can be secured.

The configuration of the down tube is not limited to the above-described embodiment, and the whole down tube may be two on the left and right, or may be one, and the attachment is not limited to bolting and may be welding.

Further, the material of the frame is not limited to aluminum alloy and may be general steel.

〔The invention's effect〕

According to the present invention described in detail above, a mounting space for the down tube can be secured in a highly rigid portion, and the position of the down tube with respect to the steering head pipe is not so restricted, so that the degree of freedom in designing the frame is increased. There is.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a side view of a frame, FIG. 2 is a plan view around a steering head, and FIG.
The figure shows the front view of the down tube, FIG. 4 shows the front view of the engine mounted on the frame, and FIG. 5 shows VV in FIG.
FIG. 6 is a sectional view taken along the line, and FIG. 6 is a side view of the motorcycle. 1 ... Frame, 2 ... Steering head pipe, 4
... front fork, 5 main pipe, 11 cross member, 12 down tube, 15 engine.

Claims (1)

[Claims] 1. A steering head pipe vertically supported in a vertical direction for pivotally supporting a front fork, a pair of left and right main pipes extending obliquely rearward and downward from the steering head pipe, and passing below the main pipes. In a motorcycle frame having a down tube extending rearward and having an engine mounted between the main pipe and the down tube, the main pipe is formed in a vertically-elongated rectangular tube shape having a flat cross section. , The longitudinal dimension of the front end portion of the main pipe connected to the steering head pipe is formed to be substantially equal to the axial length of the steering head pipe, and a cross member is bridged between the front end portions of the main pipes, and A motorcycle frame characterized by connecting the upper end of the down tube. Mu.