JPH0686232B2 - Motorcycle frame - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a motorcycle frame, and more particularly to a structure of a main pipe extending rearward from a steering head pipe thereof.

[Conventional technology]

In this type of motorcycle frame, the present applicant has a pair of left and right main pipes that connect the steering head pipe and the pivotal support of the rear arm in order to achieve both lightweight and high rigidity of the frame. We proposed that the pipe be made of a flat aluminum alloy pipe that is vertically long in the vertical direction, and the application has already been completed as “Japanese Patent Application No. 59-156868”.

[Problems to be solved by the invention]

By the way, the main pipe of the frame is formed by fitting a pair of frame materials, which are sheet-metal processed into a substantially U-shaped cross section, from the left and right directions along the vehicle width direction so that the upper and lower flange walls are abutted with each other, and the flange walls are joined together. It is assembled by welding the upper and lower edge portions of the whole length thereof.
In this case, the main pipe is expanded in the vehicle width direction as it goes behind the steering head pipe, and is bent so as to be parallel to each other from the middle of the steering head pipe. It is pressed so as to follow the bent shape of.

However, stress is often accumulated in the bent portion of this frame material due to press working, so if the frame material is welded after this processing, the accumulated stress will suddenly increase due to the temperature rise due to welding heat input to the frame material. It will be diverged. In particular, the welded portion of the flange wall has a long welding distance over the entire length of the main pipe, so the welding heat input is large, and the stress accumulated in the bent portion is more easily dissipated, and the main pipe is deformed. May occur.

The present invention has been made based on such circumstances, and can prevent deformation of the main pipe due to heat during welding,
It is an object of the present invention to provide a motorcycle frame that does not require major modification of the main pipe after this welding and can sufficiently secure rigidity against vertical and lateral loads applied to the main pipe during traveling.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention connects a pair of left and right main pipes extending rearward and obliquely downward in a substantially straight line shape in a side view to a steering head pipe pivotally supporting a front fork. The front part on the head pipe side has a bent part that protrudes outward in the vehicle width direction as it goes backward, and has bent parts that are bent from the protruding end in directions close to each other. It has a flat rectangular tube shape that is vertically long in the direction, and the longitudinal dimension of this main pipe is such that the front end portion that is continuous with the steering head pipe is set to be approximately equal to the axial length of the steering head pipe.
It is premised on a motorcycle frame whose vertical dimension is gradually reduced from the front end of the main pipe to the rear.

The main pipe is provided with a pair of sheet metal frame materials having a U-shaped cross section having side walls extending in the vertical direction and upper and lower flange walls extending in the vehicle width direction from the upper and lower edges of the side walls. The materials are arranged side by side in the vehicle width direction, and the flange wall of the other frame material located inside the vehicle width direction is fitted inside the flange wall of one frame material located outside the vehicle width direction. Together, this fitting portion is formed by welding over the entire length of the frame material, and is positioned on the side wall of one of the frame materials positioned on the outer side in the vehicle width direction at a portion corresponding to the bent portion. To form a concave portion in which the side wall is integrally concave while keeping the thickness constant, and the concave portion is
The front end of the recess is formed to have the largest vertical dimension, and the vertical dimension is gradually reduced from the front end of the recess toward the rear so as to correspond to the vertical direction of the main pipe.

[Action]

With such a configuration, since the side wall surface of the frame material located outside in the vehicle width direction has the recessed portion at the position corresponding to the bent portion of the main pipe, the recessed portion is accumulated during the processing of the frame material. To counter the applied stress. Therefore, the rigidity of the bent portion of the main pipe is particularly enhanced, and the deformation of the main pipe after welding can be prevented.

Further, since the recess is formed on the side wall of the frame material located outside in the vehicle width direction, the distance from this recess to the vertical line passing through the center of the frame in the vehicle width direction becomes long,
The second moment of area of the main pipe with respect to this vertical line becomes large. That is, since the main pipe receives a lateral load along the vehicle width direction when the motorcycle is turning, the bending stress of the bending portion of the main pipe is a distance from a vertical line passing through the center of the frame in the vehicle width direction. Will be proportional to. Therefore, if the second moment of area of the main pipe becomes large, the main pipe can withstand a larger lateral load, and the lateral bending rigidity of the main pulp is improved.

Further, with respect to the vertical load applied to the main pipe, since the concave portion functions as a rib, the main pipe itself has a vertically long cross-sectional shape, the deformation of the side wall is suppressed, and the rigidity is high. Become. In addition, the vertical dimension of the concave portion is gradually reduced as it goes backward from the front end portion thereof so as to correspond to the change in the vertical dimension of the main pipe, so that the concave portion corresponds to the vertical dimension of the main pipe. And can be formed large. Therefore, the rigidity of the main pipe with respect to the load in the vertical direction can be further increased as compared with the case where the recess has a constant narrow width.

Further, according to the above configuration, by denting the side wall, the rigidity around the main pipe can be secured, so that it is not necessary to increase the thickness of the frame material or use a special reinforcing material, and reduce the weight of the frame. It will be convenient for you.

Example of Invention

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

In the figure, reference numeral 1 is a frame made of aluminum alloy, and a front fork 4 is pivotally supported on a steering head pipe 2 which is vertically installed at the front end thereof. The front wheel 3 is supported at the lower end of the front fork 4.

The steering head pipe 2 has a pair of left and right main pipes 5 and 5 extending obliquely rearward and extending straight in a side view.
Are connected. As shown in FIG. 2, these main pipes 5 and 5 are opened immediately after the steering head pipe 2 toward the outside in the vehicle width direction as they move rearward, and their rear ends are parallel to each other. It is bent inward in the width direction in an arc shape, and a portion behind the bent portion 17 extends straight in a rearward direction.
The portions of the main pipes 5, 5 that are behind the bent portion 17 are arranged at a large distance in the vehicle width direction of the frame 1.

Therefore, in the frame 1, the main pipe 5,
The distance from the portion behind the bent portion 17 in 5 to the vertical line X1 passing through the center of the frame 1 in the vehicle width direction becomes long,
That is, the arrangement intervals of the main pipes 5, 5 are set wide, and the rear arm brackets 6, 6 are connected to the rear ends of the widened main pipes 5, 5, respectively.

A pair of left and right seat rails 7, 7 extending rearward are connected to the rear side upper surfaces of the main pipes 5, 5 as described above. Back stays 8, 8 are provided between the rear portions of the seat rails 7, 7 and the upper portions of the rear arm brackets 6, 6.

As shown in FIG. 2, a bracket 9 is installed between the front ends of the main pipes 5, 5. This bracket 9
A pair of left and right down tubes 10, 10 are installed between the rear arm brackets 6, 6 and the rear arm brackets 6, 6. Down tube 1
0, 10 are arranged below the main pipes 5, 5, and an engine 11 is arranged in a space surrounded by the main pipes 5, 5, the rear arm brackets 6, 6 and the down tubes 10, 10. ing.

A front end of a rear arm 12 made of aluminum alloy is pivotally supported between the rear arm brackets 6, 6. A chain-driven rear wheel 13 is supported at the rear end of the rear arm 12.

By the way, as shown in FIG. 3, the main pipes 5 and 5 have a frame material 14 having a substantially U-shaped cross section with one side open.
The a and 14b are abutted against each other in the vehicle width direction and welded, and are formed into a flat rectangular tube shape whose cross-sectional shape is vertically long in the vertical direction.

That is, the frame materials 14a and 14b are formed by processing a long plate material made of an aluminum alloy into a metal plate, and a side wall 15 extending in the vertical direction and upper and lower side walls extending in the vehicle width direction from the upper and lower edges of the side wall 15. The flange walls 16a and 16b are integrally provided. Then, the one frame material 14 located on the outer side in the vehicle width direction
The flange walls 16a, 16b of the other frame material 14b located on the inner side in the vehicle width direction are fitted inside the flange walls 16a, 16b of a.

In this case, the frame materials 14a and 14b are bent in advance so as to follow the bent shape of the main pipes 5 and 5. By welding the fitting portions of the flange walls 16a, 16b over the entire length, the main pipe 5 having a flat cross section,
Assembled as 5.

Further, the main pipes 5, 5 have the axial length of the steering head pipe 2 so that the longitudinal dimension of the front end portion connected to the steering head pipe 2 increases the strength and rigidity of the connecting portion with the steering head pipe 2. And the longitudinal dimension of the main pipes 5, 5 is gradually reduced toward the rear. For this reason,
The side faces 5a of the main pipes 5, 5 facing the side of the vehicle body are tapered toward the rear side.

By the way, on the side surface 5a of the main pipes 5, 5, there are formed recesses 18 that are recessed inward over a certain range before and after the bent portion 17 of the main pipes 5, 5. The recess 18 is formed by inserting the side wall 15 of the frame material 14a located on the outer side in the vehicle width direction,
The concave portion 18 is provided with a stepped portion 19 that extends inward at a peripheral edge portion that is continuous with the side surface wall 15, while being configured to be recessed inward while keeping its thickness substantially constant. Further, as shown in FIG. 1, the recess 18 has the largest vertical dimension at its front end portion, and the vertical dimension is gradually reduced from this position toward the rear. For this reason, the recess 18 is tapered toward the rear, and has a shape substantially corresponding to the side surface shape of the main pipes 5, 5.

A gusset 20 is welded to the upper surface between the front ends of the main pipes 5, 5 to reinforce the connecting portion with the steering head pipe 2.

In FIG. 1, reference numeral 21 is a fuel tank, 22 is a seat, and 23 is a radiator.

According to such a configuration, since the concave portion 18 is formed in the side wall 15 of the frame material 14a located outside in the vehicle width direction, the frame materials 14a and 14b are heated by heat input when welding the frame materials 14a and 14b. Even if the stress accumulated therein is dissipated, the stepped portion 19 located at the peripheral edge of the recess 18 functions as a rib against the stress.

Therefore, since the rigidity of the frame material 14a itself is increased due to the presence of the recess 18, the deformation of the frame materials 14a and 14b after welding is suppressed, and the main pipes 5 and 5 need not be largely modified.

Further, according to the frame 1 having the above-described configuration, the left and right main pipes 5, 5 are arranged in the vehicle width direction at the rear of the steering head pipe 2 so as to be separated from the main pipes 5, 5 in the vehicle width direction center of the frame 1. The distance to the vertical line X1 passing through is long. Therefore, even when the frame 1 receives a lateral load along the vehicle width direction when the motorcycle is turning, the lateral bending rigidity of the main pipes 5, 5 can be sufficiently ensured.

Further, the main pipes 5 and 5 are disposed inside the flange walls 16a and 16b of the frame material 14a located outside in the vehicle width direction, and on the inside of the flange material 16b of the frame material 14b located inside in the vehicle width direction.
Since the flat pipes are assembled by fitting a and 16b together, the vertical dimension of the side faces 5a of the main pipes 5 and 5 is increased. Since the concave portion 18 is formed in the side wall 15 of the frame material 14a that constitutes the side surface 5a, the step portion 19 at the peripheral edge of the concave portion 18 is farthest from the vertical line X1 passing through the center of the frame 1 in the vehicle width direction. Therefore, the second moment of area of the main pipes 5, 5 with respect to the vertical line X1 becomes large.

That is, when the motorcycle turns around, the main pipe
Since 5 and 5 receive a lateral load along the vehicle width direction, the bending stress generated in the bent portion 17 of the main pipes 5 and 5 is proportional to the distance from the vertical line X1. Therefore, if the second moment of area of the main pipes 5, 5 increases, the main pipes 5, 5 can withstand a larger lateral load, and the lateral bending rigidity of the frame 1 improves accordingly.

Further, with respect to the vertical load applied to the main pipes 5, 5, since the stepped portion 19 of the recess 18 functions as a rib, together with the main pipes 5, 5 themselves having a vertically long cross-sectional shape, The deformation of the side wall 15 can be suppressed. With that,
The vertical dimension of the recess 18 is gradually reduced as it goes backward from the front end thereof so as to correspond to the change in the vertical dimension of the main pipes 5, 5, so that the recess 18 of the main pipes 5, 5 is It can be formed large corresponding to the side surface 5a. Therefore, the rigidity of the main pipes 5, 5 with respect to the load in the vertical direction can be further increased as compared with the case where the recess 18 has a certain narrow width.

Further, according to the above configuration, it is possible to increase the rigidity around the main pipes 5 and 5 by simply recessing the side wall 15, so that the wall thickness of the frame materials 14a and 14b can be increased or a special reinforcing material can be provided. It is not necessary to use the frame 1, and the frame 1 can be reduced in weight while ensuring the rigidity of the frame 1.

Moreover, since the recess 18 is formed on the side surface 5a of the main pipe 5, 5 at a position corresponding to the bent portion 17 immediately after the steering head pipe 2, the legs of the driver seated on the seat 22 are It will be located behind the recess 18. Therefore, the legs do not enter or touch the recess 18, and the ride feeling of the driver is not impaired.

Further, since the concave portion 18 is recessed from the side surface 5a of the main pipes 5, 5, compared to the case where the convex portion is provided on the side surface 5a,
The surface of the recess 18 is less likely to be scratched, and the appearance of the frame 1 can be favorably maintained.

The frame according to the present invention is not limited to the aluminum alloy, but can be made of steel as well.

〔The invention's effect〕

According to the present invention described in detail above, since the concave portion resists the stress accumulated during the processing of the frame material, the rigidity around the bent portion of the main pipe is enhanced, and the deformation of the main pipe after welding is prevented. You can

Further, since the recess is formed on the side wall of the frame material located on the outer side in the vehicle width direction, the shape of the recess can be enlarged, and the vertical line passing through the center of the frame in the vehicle width direction from the recess. The longer the distance to, the larger the moment of inertia of area of the main pipe with respect to this vertical line. That is, when the main pipe receives a lateral load along the vehicle width direction during turning of the motorcycle, the bending stress of the bending portion of the main pipe is proportional to the distance from the vertical line. If the second moment of area of the main pipe becomes large, the main pipe can withstand a larger lateral load, and the lateral bending rigidity of the main pipe is improved accordingly. Further, with respect to the vertical load applied to the main pipe, the concave portion functions as a rib, so that the main pipe itself has a vertically long cross-sectional shape, deformation of the side wall is suppressed, and rigidity is high. Become.

In addition, the vertical dimension of the concave portion is gradually reduced as it goes backward from the front end portion thereof so as to correspond to the change in the vertical dimension of the main pipe, so that the concave portion corresponds to the vertical dimension of the main pipe. Can be made larger. Therefore, the rigidity of the main pipe with respect to the load in the vertical direction can be further increased as compared with the case where the recess has a constant narrow width.

Further, according to the above configuration, since the rigidity around the main pipe can be secured by simply recessing the side wall, there is no need to increase the wall thickness of the frame material or use a special reinforcing material, and the rigidity of the frame can be improved. There is an advantage that the frame can be lightened while ensuring the sufficient amount.

[Brief description of drawings]

 The drawings show an embodiment of the present invention. Fig. 1 is a side view of a motorcycle, Fig. 2 is a plan view of a frame, and Fig. 3 is a sectional view taken along line III-III in Fig. 2. is there. 1 …… frame, 2 …… steering head pipe, 4 …… front fork, 5 …… main pipe, 14a, 14b …… frame material, 15 …… side wall, 16a, 16b …… flange wall, 17 …… bend Part, 18 ... recessed part.

Claims (1)

[Claims] 1. A steering head pipe pivotally supporting a front fork is connected to a pair of left and right main pipes extending rearward and obliquely downward in a substantially straight line shape in a side view, and each of these main pipes is a front portion on the steering head pipe side. In addition, it has a bent portion that extends outward in the vehicle width direction as it goes rearward, and has a bent portion that is bent from the protruding end in a direction close to each other. The vertical dimension of the main pipe is such that the front end portion connected to the steering head pipe is set to be approximately equal to the axial length of the steering head pipe, and the vertical dimension is set to the front end portion of the main pipe. In the frame of the motorcycle, which is gradually reduced as it goes backward from the main pipe, the main pipe extends in the vertical direction. A pair of sheet metal frame materials having a U-shaped cross section having a face wall and upper and lower flange walls extending in the vehicle width direction from the upper and lower edges of the side wall are provided, and these frame materials are arranged side by side in the vehicle width direction. , The flange wall of the other frame material located inside the vehicle width direction is fitted to the inside of the flange wall of one frame material that is located outside the vehicle width direction, and this fitting part is the entire length of the frame material. The side wall of one of the frame materials located outside in the vehicle width direction is located at a portion corresponding to the bent portion, and the thickness of the side wall is kept constant. A recess is formed by integrally denting the recess, and the front end of the recess is formed to have the largest vertical dimension. As the vertical dimension advances from the front end of the recess to the rear side, A frame for a motorcycle characterized by being successively reduced so as to correspond to the vertical dimension of the motorcycle.