JPH0674071B2 - Motorcycle frame - Google Patents

Description

TECHNICAL FIELD The present invention relates to a vehicle body frame of a motorcycle, and more particularly to improvement of a so-called cradle type frame.

(Prior Art) Generally, a so-called double cradle type or semi-double cradle type frame, which has a shape in which an engine is mounted on a cradle, is widely used as a vehicle body frame of a motorcycle because of its relatively high strength and rigidity.

By the way, especially in motorcycles, the height of the vehicle body from the ground, that is, the minimum ground clearance must be secured by a predetermined amount, but as described above, in the case of the double cradle type frame, the down tube exists under the engine. Therefore, it may be difficult for the design to obtain a sufficient minimum ground clearance.

In addition, there is a general demand for shortening the wheelbase in order to make the entire body smaller, but for those with a downtube, it is necessary to prevent contact between the downtube and the steering wheel. It was difficult to shorten.

Furthermore, recently, in order to emphasize the frame itself as an exterior design, there is a demand for exposing the frame on both outer side surfaces of the vehicle body. However, when a pipe is used as the frame in order to increase the mechanical strength and rigidity of the frame, it is conceivable to provide a reinforcing rib having a surface orthogonal to the surface to be bent in the longitudinal direction inside the frame (not known). However, assuming a configuration in which the frame itself is exposed on both outer side surfaces of the vehicle body as described above, the pair of frames are curved so as to have a bulge corresponding to the engine part when viewed from the top surface, and thus the bending process causes the surface to be exposed. It is easy to cause unevenness or rough skin that is unaesthetic. This is because the existing portion of the reinforcing rib exerts a tensioning action on the outer surface to be stretched during bending of the pipe.
In particular, this becomes remarkable in the case of a square pipe having a partial flat surface.

(Object of the Invention) The present invention has been made in view of the above problems, strength,
It is excellent in rigidity, and it is easy to design enough to secure the minimum ground clearance and shorten the wheel base. Moreover, it tries to emphasize the frame made of tank rails without spoiling the aesthetics by reinforcing the pipe. The present invention provides a motorcycle body frame that can meet the requirements of the exterior design.

(Structure of the Invention) The present invention has a layout in which a pair of left and right tank rails that linearly extend rearward from the steering head pipe and obliquely downward in a side view are continuously provided, and the tank rails are exposed to both outer side surfaces of the vehicle body. In addition, a vertically long flat pipe made of extruded aluminum is used as the tank rail, and the wall of the tank rail on the outer side of the vehicle body is made thicker than the wall of the inner side.

With this configuration, sufficient strength and rigidity can be secured even if the down tube in the conventional double cradle type frame is omitted, and even if the tank cler is bent, the rigidity of the outer side wall is high. However, it is less likely that things that would impair their aesthetic appearance will occur.

(Example) Hereinafter, the present invention will be described with reference to the drawings illustrating an example.

1 to 4, reference numeral 1 denotes a steering head pipe, and a front fork 3 to which a front wheel steering 2 is attached is rotatably held on the head pipe 1. Reference numeral 4 is a steering wheel operated by a driver of the front fork 3, and 5 is curved so as to extend rearward and obliquely downward from the head pipe 1 substantially linearly when viewed from the side and have a bulge when viewed from the top. A pair of left and right tank rails. The tank rails 5, 5 are made of vertically elongated flat aluminum extruded pipes and are laid out so as to be exposed on both outer side surfaces of the vehicle body. A bracket rear arm 6 is welded and fixed to the rear ends of the tank rails 5 and 5 by a welded portion 6a. Reference numeral 7 denotes a rear arm pivotally connected to the bracket rear arm 6 by a shaft 8, and a rear wheel 9 is supported at a rear end portion of the rear arm 7. 10 is a radiator, 11 is an engine, and these are suspended below the tank rails 5, 5. 12 is seat rail, 13
Is a back stay and is fixed to the tank rails 5 and 5 and the bracket rear arm 6 by bolting or the like.

Further, as shown in FIG. 4, the tank rail 5 which is a vertically long flat pipe made of the aluminum extruded material has a reinforcing rib 5a which has a surface in the longitudinal direction and orthogonal to the vertically long surface as shown in FIG.
Is provided and is thicker than the wall (o) located on the outer side surface of the vehicle body and the wall (i) located on the inner side surface of the vehicle body to increase the rigidity of the outer side wall. When the tank rail 5 is bent as shown in FIGS. 2 and 3, the wall (o) on the outer side in the bending direction tends to be elongated and thin and weak. Since the wall (o) is formed thick as described above, the strength is prevented from being weakened by the bending process, and the appearance is deteriorated by being stretched. As a concrete example of this tank rail 5, the height dimension of the vertically long is 140 mm, the width dimension of the left and right is 30 mm,
The outer wall thickness is 2.5 to 3.5 mm, the inner wall thickness is 2 mm, and the reinforcing ribs 5a and other wall thicknesses are about 2 mm. In the drawings, the drive mechanism for transmitting the drive output of the engine 11 to the rear wheels 9, the fuel tank held by the tank rails 5, 5, the seat on which the driver rides, such as the seat rail 12, are shown. Omitted.

Since a pair of left and right flat pipes made of aluminum extruded material that is vertically long as described above is used as the tank rails 5, 5,
The torsional rigidity with the head pipe 1 as a fulcrum is increased, and therefore, sufficient strength and rigidity are provided without using a down tube unlike the conventional double cradle type frame. Since the body frame is composed of the pair of left and right tank rails 5, 5, the bracket rear arm 6, the rear arm 7, etc., and it is not necessary to provide a down tube under the engine 11 as in the conventional case, a minimum ground clearance above the ground is designed. It can be easily and sufficiently ensured, and the front wheel steering 2 may be largely offset to the rear, so that it is extremely easy to shorten the wheel base.

Also, since the vertically long tank rails 5 and 5 are exposed on both outer side surfaces of the vehicle body, the frame can be emphasized in terms of appearance design.Furthermore, the reinforcing ribs 5a are extruded inside the tank rails 5 and 5 during extrusion. Since it is integrally molded, its mechanical strength and torsional rigidity are further enhanced due to its vertical flatness, and the tank rails 5, 5 are bent so that they have a bulge when viewed from above. , Even if the reinforcing rib 5a is partially stretched on its outwardly extending surface, the wall thickness of the tank rails 5, 5 located on both outer sides of the vehicle body should be made thicker than the wall thickness of the inner wall. As a result, it is possible to prevent the surface exposed to the outside from having irregularities and skin roughness that are unaesthetic, and also to increase the rigidity of the pair of tank rails as a whole. Therefore, in the layout in which the frame is exposed on both outer side surfaces of the vehicle body, it is almost impossible to reduce the commercial value.

Further, as described above, by providing the reinforcing ribs 5a inside the hollow tank rails 5, 5, there is also an effect of preventing the generation of resonance noise that is likely to occur in the case of a relatively large pipe cavity. In addition, since the outer wall (o) of the hollow tank rail 5 is formed thick, there is also an advantage that the internal sound is hard to come out to the outside.

Further, it is extremely difficult to bend the three-dimensional flat pipe that constitutes the tank rail 5 in three dimensions due to its structure, but it is relatively easy to bend it in two dimensions. It is almost straight when viewed from above and there is no bending on that surface, while when viewed from above the engine 11
Corresponding to the situation, the two tank rails 5 and 5 were curved so as to have a bulge at the middle part, and the bending process was performed only in two dimensions. Although the thicker one is used, it is easy to process.

Further, by using the pipe made of aluminum extruded material as described above, the die cost can be significantly reduced and the overall cost can be reduced as compared with a tank rail having a so-called hollow structure, which is formed by press punching.

In the above-described embodiment, the notch 5b is provided in the lower portion of the rear end of the tank rail 5, and by providing the notch 5b, even if the rear portion of the tank rail 5 is lowered largely obliquely downward, the engine 11 The part can be suspended at an appropriate height position, and the rear part of the tank rail 5 is lowered obliquely so that the tank rail does not interfere with the foot contact when the driver rides on the motorcycle. ing. Further, a recess 5c is integrally formed in the wall (i) on the inner side surface of the vehicle body of the tank rail 5 in the lengthwise direction, and the recess 5c can be used for laying a wire harness or the like.

(Effect of the Invention) As described above, according to the present invention, a pair of left and right tank rails are continuously provided rearward and obliquely downward from the steering head pipe, and a vertically long flat pipe made of aluminum extruded material is used as the tank rail. As a result, the torsional rigidity and strength are extremely high without using the down tube in the conventional double cradle type frame, etc., moreover, the minimum ground clearance can be sufficiently secured, and it is also extremely easy to design the wheel base to be short.

In addition, the layout of the tank rail frame itself exposed on both outside surfaces of the vehicle body emphasizes the frame in the exterior design, and the wall thickness of the tank rail outside surface of the vehicle body is increased to the inside surface. By making it thicker than the thickness, the rigidity of this outer wall increases and
The rigidity of the entire tank rail also increases.

[Brief description of drawings]

FIG. 1 is a schematic side view showing an embodiment of a vehicle body frame of a motorcycle of the present invention, FIG. 2 is a top view of a main part of the vehicle body frame, and FIG. 3 is a tank rail as viewed in the direction of arrow A in FIG. The top view and FIG. 4 are sectional views taken along line IV-IV in FIG. 1 ... Head pipe, 5 ... Tank rail, 5a ... Reinforcing rib, o ... Wall of tank rail on outer side of vehicle, i ... Wall of tank rail on inner side of vehicle.

Claims (1)

[Claims] A pair of left and right tank rails extending linearly rearward from the steering head pipe and obliquely downward in a side view are continuously provided, and the tank rails are exposed to both outer side surfaces of the vehicle body. A body frame for a motorcycle, wherein a vertically long flat pipe made of extruded aluminum is used as a tank rail, and a wall of an outer surface of the tank rail is thicker than a wall of an inner surface of the tank rail.