JPH0771952B2 - 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 driver generally rides with the fuel tank sandwiched between both legs, but at this time, it must be designed so that no obstructive member is located at the contact portion of both legs, and Since the minimum clearance, that is, the minimum ground clearance, must be ensured by a certain amount, a compact design of the equipment around the engine is required, and in the case of the double cradle type frame, the down tube exists under the engine as described above. Therefore, it may be difficult in design to secure a sufficient minimum ground clearance.

Even if the down tube is omitted from this background, strength,
A frame structure that can solve the problem of rigidity has been demanded.

On the other hand, 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.

In order to meet any of the above requirements, the down tube is omitted, and a pair of tubes (frames) inclined downward from the head pipe to the pivot part of the swing arm has a vertically long dimension to increase the strength and strengthen the strength. A frame configuration using tank rails is conceivable (not known), but using tank tanks that are vertically long,
In addition, assuming that the tank rail is exposed on both outer side surfaces of the vehicle body, the layout must allow the carburetor to largely escape above or below the tank rail, and such a design is impossible due to the positional relationship with the engine. Therefore, the layout has to be such that the frame has a bulge in the middle portion when viewed from above and holds the carburetor. In such a layout, it is necessary to design the frame so that it does not interfere with the operation of the carburetor itself or the operation part of the carburetor, for example, the sliding part of the choke. Therefore, the width between the pair of frames should be increased or the carburetor should be increased. It is conceivable that the tank rail has a bent shape so as to escape. However, such a configuration causes new problems such as hindering the foot contact portion of the driver and lowering the frame strength and rigidity.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems to be solved.
It has excellent rigidity, and it is easy to secure a minimum ground clearance by design, and it does not interfere with the placement of the carburetor itself or the operation of the carburetor's operating part, or increase the width between frames. The present invention provides a vehicle body frame of a motorcycle capable of exposing the frame to both outer side surfaces of the vehicle body in response to a request for external design.

(Structure of the Invention) According to the present invention, a pair of left and right tank rails linearly extending rearward from the steering head pipe and obliquely downward in a side view are continuously provided, and an engine is suspended below the tank rail. As the rail, a pipe having a vertically long flat shape made of an aluminum extruded material and having a concave portion formed in the length direction on at least one of the facing surfaces of the pair of tank rails is used.

With this configuration, sufficient strength and rigidity can be secured even if the down tube in the conventional double cradle type frame etc. is omitted, and even though the tank rail has a large vertical dimension, the carburetor placement or It does not hinder the operation of the operating part, and the width between the frames does not increase.

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

1 to 5, 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 denotes a steering wheel operated by a driver of the front fork 3, and 5 extends substantially linearly from the head pipe 1 rearward and obliquely downward when viewed from the side, and is curved so as to hold the carburetor when viewed from the upper surface. As the tank rail, as shown in FIG. 4, the tank rails 5 and 5 are made of an extruded aluminum pipe having a vertically long flat shape and a recess 5c formed in the longitudinal direction on at least one of a pair of opposing surfaces. Has been. Further, the tank rails 5, 5 are integrally provided with reinforcing ribs 5a in the length direction. 6 is a placket rear arm, and the above tank rails 5, 5
It is welded and fixed to the rear end of the 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 a carburetor and an engine, which are suspended under the tank rails 5, 5. A seat rail 12 and a back stay 13 are fixed to the tank rails 5 and 5 and the bracket rear arm 6 by bolting or the like. Reference numeral 14 is a wire harness, which is set so as to pass through a recess 5c provided on one of the facing surfaces of the pair of tank rails 5,5. Reference numeral 15 is a choke slide portion of a carburetor that slides in the direction of the arrow in FIG. Further, a cutout portion 5b is provided in the lower portion of the rear end of the tank rail 5 so as to avoid contact with the engine 11. By providing the cutout portion 5b, the rear portion of the tank rail 5 is greatly inclined downward. Engine 11 even when lowered
The part is designed so that it can be suspended at an appropriate height.

In the drawings, the fuel tank mounted on the tank rails 5, 5, the seat on which the driver is seated mounted on the seat rail 12, the drive mechanism for transmitting the drive output of the engine 11 to the rear wheels 9, etc. are not shown. Omitted.

As described above, since a pair of vertically oriented flat aluminum extruded pipes are used as the tank rails 5, 5, the torsional rigidity with the head pipe 1 as a fulcrum is increased. Therefore, the down tube like the conventional double cradle type frame is used. It will have sufficient strength and rigidity without using.

The tank rails 5, 5, the placket rear arm 6, the rear arm 7 and the like constitute a vehicle body frame, which does not require a down tube below the engine 11 as in the conventional case. Therefore, a sufficient minimum ground clearance above the ground should be secured. Can be easily designed. Furthermore, the vertically long tank rails can be exposed on both outer side surfaces of the vehicle body to emphasize the frame in terms of external design, and the concave portions 5c are provided on the opposite surfaces of the tank rails 5, so that the concave portions 5c can be used. Since the wire harness 14 is passed through and there is no hindrance to the operation of the choke slide portion 15, a pair of tank rails can be used to set the wire harness 14 even if the lengthwise dimension of the tank rail 5 is considerably increased. 5,5,
The lateral (left and right) width does not become large, and it is not necessary to make a hole to escape the choke slide portion 15. Moreover, since the recess 5c may be provided at the time of extrusion molding of the tank rail 5, it is easy to manufacture,
Moreover, by providing the recess 5c, the strength and rigidity of the tank rail 5 are further increased.

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 pair of tank rails 5 and 5 were curved so as to have a bulge at the middle part, and bending was performed only in two dimensions. Will be easier.

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 by press punching.

(Effects of the Invention) As described above, according to the present invention, a pair of left and right tank rails extending rearward and obliquely downward from the steering head pipe are continuously provided, 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., and it is also extremely easy in design to secure a sufficient minimum ground clearance. By forming a recess on the opposing surface integrally, this recess is used as a clearance for the carburetor itself or as a clearance for the carburetor's operating part, exposing the frame itself, which is the tank rail, to both outer surfaces of the vehicle body. Even when the frame is emphasized in the exterior design, the frame This has the effect that the width between the frames does not increase.

[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. Top view, Fig. 4 is IV of Fig. 3 on the same tank rail.
-IV sectional view, FIG. 5 is a sectional view of the tank rail and the choke slide portion of the carburetor. 1 ... Head pipe, 5 ... Tank rail, 5c ... Recess, 11 ... Carburetor and engine, 14 ... Wire harness.

Claims (1)

[Claims] 1. A pair of left and right tank rails linearly extending rearward from a steering head pipe and obliquely downward in a side view are continuously provided, an engine is suspended below the tank rails, and an aluminum extrusion is used as the tank rails. A body frame for a motorcycle, comprising: a pipe having a vertically long flat shape made of a material, the pipe having a recessed portion formed in a longitudinal direction on at least one of opposing surfaces of a pair of tank rails.