JP2694538B2 - Motorcycle frame - Google Patents

Description

TECHNICAL FIELD The present invention relates to a frame of a motorcycle including a front fork.

[Conventional technology]

Conventionally, a frame used for a motorcycle that travels on an uneven terrain is made to have high rigidity by relatively thickening a diameter of a pipe used. Further, an inverted front fork having high rigidity and long cushion stroke may be attached to this type of frame.
This inverted front fork has a structure in which the inner cylinder is inserted into the outer cylinder from below, and the lower bracket connecting the left and right outer cylinders is larger than the upright one. For this reason, conventionally, when the front fork of this type is provided, the down tube of the frame is formed of a single round pipe to avoid interference between the down tube and the lower bracket.

[Problems to be solved by the invention]

However, even if the down tube is formed from a single round pipe, if the pipe diameter is increased in order to increase the rigidity of the frame, the steering angle of the handle becomes smaller. That is,
This is because when the outer diameter of the down tube is increased, the down tube and the lower bracket of the front fork interfere with each other, and the steering angle of the handle is reduced accordingly. This tendency is remarkable when an inverted front fork is used. Also, by increasing the outer diameter of the down tube, not only the rigidity in the vehicle front-rear direction required for the frame increases, but also
Since the rigidity in the vehicle width direction also becomes higher than the required rigidity, there is also a problem that the frame weight increases by the amount of the material that increases the rigidity. The present invention has been made in view of such circumstances, and provides a frame of a motorcycle capable of ensuring a steering wheel turning angle and increasing rigidity.

[Means for solving the problem]

In the motorcycle frame according to the present invention, the down tube is formed in a flat plate shape by plastically deforming an upper tube formed of a tubular material having a rectangular cross-section in the longitudinal direction of the vehicle body and an upper end of the pipe portion. A flat plate portion formed of two lower tubes welded to the side surface of the lower end portion of the upper tube, and a part of both side surfaces of the lower end portion of the upper tube is cut out in a triangular shape to form one of the front and rear directions of the cutout portion. Of the lower tube is bent toward the other side and the notched edges are welded to each other, so that the lower end of the upper tube is formed so that the length in the front-rear direction of the vehicle gradually becomes shorter. The abutting portion is located near the bent portion.

[Action]

In the present invention, the upper tube of the down tube does not expand in the vehicle width direction, and the rigidity required in the motorcycle in the vehicle front-rear direction is increased. In addition, the portion of the upper tube where the stress is greatest when the force is transmitted from the lower tube to the upper tube, in other words, the side surface facing the abutting portion of the lower tube at the lower end of the upper tube has a longitudinal length. Is shorter than other parts,
Higher rigidity against bending load in the vehicle width direction.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a second view showing a frame of a motorcycle according to the present invention.
Fig. 2 is a sectional view taken along the line I-I in Fig. 2, Fig. 2 is a side view showing the frame of the motorcycle, Fig. 3 is a side view showing the entire motorcycle, and Fig. 4 is a sectional view taken along the line IV-IV in Fig. 3. In these figures, reference numeral 1 indicates a frame. The frame 1 includes a head pipe 2, a tank rail 4 that forms an upper portion of the frame 1 and supports a fuel tank 3, and a down tube 6 that is disposed below the tank rail 4 and supports a front side of an engine 5. Has been done. Tank rail 4
Is made of a single pipe material having a circular cross section, the front end of which is connected to the upper portion of the head pipe 2 by welding and extends rearward and downward toward the rear of the vehicle.

On the other hand, as shown in the front view of FIG. 5, the down tube 6 includes one upper tube 6a welded to the lower part of the head pipe 2 and a pair of left and right lower parts branched from the lower part of the upper tube 6a to the left and right. It consists of a tube 6b. In the lower tube 6b, a flat plate part formed by plastically deforming the upper end of the pipe part to form a flat plate is welded to the lower end side face of the upper tube 6a, and the upper end of the pipe part is projected to the lower end side face of the upper tube 6a. It is applied and extends downward along the front side of the engine and then extends substantially horizontally rearward along the lower side of the engine.

A connecting member 7 is connected to the rear end of the tank rail 4. The connecting member 7 is formed by facing a pair of upper and lower halves each having a groove shape in cross section, and is connected to a pair of left and right seat pillar tubes 8 as shown in FIG. It has a letter shape. A support bracket 9 for pivotally attaching the upper end of a shock absorber, which will be described later, is fixed to the back surface thereof.

Reference numeral 11 is a rear arm support bracket having a pivotally supporting portion 11a for supporting the rear arm 12. The rear arm support bracket 11 is formed by facing a pair of left and right halves having a groove shape in cross section, and by connecting the seat pillar tubes 8 and the rear end of the lower tube 6b, a frame is formed. Form a part of. Reference numeral 13 denotes a shock absorber for buffering the swing of the rear arm 12, the lower end of which is connected to the rear arm 12 via a link mechanism 14, and the upper end of which is pivotally attached to the support bracket 9. Reference numeral 15 is a seat rail that supports the seat 16, and 17 is a backstay that supports the rear portion of the seat rail 15. The seat rails 15 are welded to both side surfaces of the support bracket 9 and extend rearward and upward toward the rear.

Reference numeral 21 is a front fork rotatably supported by the head pipe 2. The front fork 21 is an inverted type in which an inner cylinder is inserted into the outer cylinder from below, and a pair of left and right outer cylinders are connected to each other by a lower bracket 22. The upper tube 6a of the down tube 6 located immediately behind the lower bracket 22 is made of a tubular material having a rectangular cross-sectional shape that is long in the vehicle front-rear direction as shown by an arrow L in the figure as shown in FIG. Has been formed. In this embodiment, the ratio of the width w and the length l of the upper tube 6a is w: l = 7: 1.
It is set to be about 1 and is narrower than the tank rail 4. Here, the upper tube 6a is bent in a V shape toward the front slightly above the upper end of the engine 5. Therefore, the bending rigidity improves the torsional rigidity of the upper tube 6a, and the space between the upper tube 6a and the engine 5 is secured as much as possible to improve the maintainability. Further, the lower end portion of the upper tube 6a is formed so as to gradually taper downward in the front-rear direction of the vehicle body. To describe this in detail, triangular notches 23 are provided on both side surfaces of the lower end portion of the upper tube 6a, and a rear member forming the rear surface of the upper tube 6a is folded forward so that the notches 23 are crushed from the rear. The taper is made by bending and welding the back surface member and the side surface member. Further, the abutting portion of the lower tube 6b is positioned near the bent portion. Therefore, the strength of both side portions is improved, and the joining strength of the lower tube 6b is obtained even when the lower end of the upper tube 6a is left open.

Incidentally, 24 is a connecting pipe for connecting the tank rail 4 and the upper tube 6a, 25 is a supporting member for supporting the rear portion of the tank rail 4, and 26 is a triangular shape for reinforcing the space between the tank rail 4 and the upper tube 6a. Is a reinforcing plate. The rigidity of the frame 1 is improved by these reinforcing members.

In the motorcycle frame thus configured, since the upper tube 6a is formed of a tubular material having a long rectangle in the vehicle front-rear direction, the second moment of area of the upper tube 6a in the vehicle front-rear direction can be increased. Therefore, without expanding the upper tube 6a in the vehicle width direction, the rigidity of the upper tube 6a against the bending moment generated in the vehicle body front-rear direction required for the motorcycle can be increased.

Therefore, even if the rigidity of the upper tube 6a in the longitudinal direction of the vehicle body is increased, it is possible to prevent the upper tube 6a from expanding in the vehicle width direction. Therefore, as shown by the chain line in FIG. 22 can be prevented from interfering with each other and a steering wheel turning angle can be secured. Moreover, by increasing the cross-sectional shape of the upper tube 6a in the front-rear direction of the vehicle body, an increase in the weight of the upper tube 6a can be effectively contributed to the improvement of the rigidity in the front-rear direction of the vehicle body. Can be suppressed.

Further, in the embodiment, since the lower portion of the upper tube 6a is bent forward in a V shape, this bending portion can not only increase the torsional rigidity of the upper tube 6a but also bend the upper tube 6a. A space can be secured between the engine 5 and a portion below the portion to facilitate maintenance work around the engine. Further, since the lower end portion of the upper tube 6a is tapered, the space between the upper tube 6a and the engine 5 can be made larger than the structure in which the upper tube 6a is simply bent as described above. Moreover, the strength of both sides of the upper tube 6a can be improved, and the bonding strength of the lower tube 6b can be improved.

〔The invention's effect〕

As described above, according to the present invention, the down tube is formed in a flat plate shape by plastically deforming an upper tube formed of a tubular material having a rectangular cross-section in the longitudinal direction of the vehicle body and the upper end of the pipe portion. Consisting of two lower tubes welded to the side surface of the lower end of the upper tube, which is formed by notching a part of both side surfaces of the lower end of the upper tube in a triangular shape in the front-back direction of the notch. By bending one side toward the other side and welding the notched edges together, the lower end of the upper tube is formed so that the length in the vehicle front-rear direction gradually decreases as it goes downward.
Since the abutting portion of the lower tube is positioned in the vicinity of the bent portion, the rigidity of the upper tube in the vehicle longitudinal direction required for the motorcycle can be increased without expanding the upper tube of the down tube in the vehicle width direction. it can.

Therefore, even if the rigidity of the upper tube in the front-rear direction of the vehicle body is increased, the upper tube can be prevented from expanding in the vehicle width direction, and the increase in weight can be effectively contributed to the improvement in rigidity. As a result, it is possible to increase the rigidity of the frame while suppressing a decrease in steering wheel turning angle and an increase in weight. Therefore, even if the inverted front fork is used, the steering wheel turning angle can be secured.
In addition, the side surface of the lower tube that faces the butting portion of the lower tube has a shorter length in the front-rear direction than other portions, and the rigidity against bending load in the vehicle width direction is high, so The tube can be firmly welded to the lower end of the upper tube.

[Brief description of the drawings]

FIG. 1 is a second view showing a frame of a motorcycle according to the present invention.
Fig. 2 is a sectional view taken along the line I-I of Fig. 2, Fig. 2 is a side view showing the frame of the motorcycle, Fig. 3 is a side view showing the entire motorcycle, and Fig. 4 is a sectional view taken along the line IV-IV of Fig. 3. FIG. 5 is a front view showing the down tube, and FIG. 6 is a plan view showing the rear portion of the tank rail. 1 ... frame, 2 ... head pipe, 4 ... tank rail, 6 ... down tube, 6a ... upper tube, 6b
...... Lower tube, 21 …… Front fork, 22 …… Lower bracket.

Claims (1)

(57) [Claims] 1. A motorcycle having a front fork, wherein the down tube is a flat tube formed by plastically deforming an upper tube formed of a tubular material having a rectangular cross-section in the longitudinal direction of the vehicle body and an upper end of a pipe portion. A flat plate part formed in a shape of two lower tubes welded to the lower end side surface of the upper tube, and a part of both side surfaces of the lower end part of the upper tube is cut out in a triangular shape to form a cutout portion. By bending one side in the front-rear direction toward the other side and welding the notched edges together, the lower end of the upper tube is formed so that the length in the front-rear direction of the vehicle gradually decreases as it goes downward. A frame for a motorcycle, wherein the abutting portion of the lower tube is positioned in the vicinity of the bent portion.