JPH0678074B2 - 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-dull cradle type frame, which has a shape in which an engine is mounted on a cradle as a vehicle body frame of a motorcycle, is relatively strong,
It is widely used because of its high 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 in the case of the double cradle type frame, as described above, the down tube exists under the engine. Therefore, in some cases, it may be difficult for the design to sufficiently attain the minimum price increase.

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 side surfaces of the vehicle body. However, when a pipe is used as a frame in order to increase the mechanical strength and rigidity of the frame, a reinforcing rib having a surface orthogonal to the surface to be bent in the longitudinal direction inside the frame is provided (not known).
Assuming a configuration in which the frame itself is exposed to 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, The surface is apt to have unevenness or rough skin that is unaesthetic due to the processing. 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 plan view.

(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) According to the present invention, at least a pair of left and right tank rails extending rearward and obliquely downward from the steering head pipe and curved so as to have a bulge when viewed from the upper surface are connected, and the tank rails are provided on both outer side surfaces of the vehicle body. The tank rail is made of an extruded aluminum material and has a vertically long flat cross section, and the tank length has a horizontal surface in the cross section. A reinforcing rib continuous in the direction is integrally formed, and a thin portion in the longitudinal direction is provided in a part of the reinforcing rib.

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 if the tank rail is bent, the mechanical strength of the thin portion of the reinforcing ribs Bending stress is absorbed by the weaker portion, and the appearance of the tank rail surface is less likely to be impaired.

(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 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 rail 5 is formed of a pipe made of an aluminum extruded material having a vertically long flat cross section (cross section orthogonal to the length direction) shown in FIG. The left and right tank rails 5, 5 are laid out so as to be exposed on both outer sides 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. 7 is a bracket 8 on the rear arm 6
A rear wheel is pivotally coupled to the rear arm 7, and a rear wheel 9 is supported at the rear end of the rear arm 7. 10 is a radiator, 11 is an engine, and these are suspended below 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.

A reinforcing rib 5a is integrally formed inside the tank rail 5 which is a vertically long flat pipe made of the aluminum extruded material, as shown in FIGS. This reinforcement rib
5a has a surface that is continuous in the lengthwise direction of the pipes that form the tank rail 5 and that is a horizontal direction in the cross section shown in FIG.
In other words, it is formed so as to cross the inside of the pipe at a right angle to the vertical walls (o, i) on both sides. A thin portion (n) in the longitudinal direction is provided on a part of the reinforcing rib 5a, and the mechanical strength thereof is partly weakened. In this embodiment, the thin portion (n) is the wall (o) on the vehicle body outer side surface of the tank rail 5.
It is provided with a suitable width at a position far from the wall (i) on the inner surface of the vehicle body. Further, FIG. 6 shows a view corresponding to FIG. 5 of another embodiment different from the above, and a thin portion (n) is provided at a substantially intermediate portion between the wall (o) and the wall (i). 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. Combined with the vertically long flat shape, the mechanical strength and torsional rigidity are further increased, and the tank rails 5 and 5 are bent so that they have a bulge when viewed from above. Even if the reinforcing rib 5a is stretched by its outwardly extending surface, the reinforcing rib 5a inside the tank rails 5, 5 is provided with a thin portion (n), so Will be absorbed as a change in width due to the bending or bending of the thin portion (n), and the surface exposed on the outer side of the tank rails 5, 5 may have unevenness or rough skin that is unaesthetic. Suppressed. Therefore, in the layout in which the frame is exposed on both outer side surfaces of the vehicle body, the commercial value is hardly reduced.

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 tends to occur in the case of a relatively large pipe cavity.

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 portion, and bending was performed only in two dimensions, so a vertically long flat pipe was used. Processing becomes easy.

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 parts 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. I have to. Further, a recess (5c) in the lengthwise direction is integrally formed on the wall (i) on the inner surface of the vehicle body of the tank rail (5), and this recess allows the use of the recess (5c) for laying a wire harness.

(Effects of the Invention) 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 the tank rail is vertically elongated by an aluminum extruded material having reinforcing ribs inside. By using the flat pipe of, the torsional rigidity and strength are extremely high without using the down tube in the conventional double cradle type frame etc., and moreover, the minimum ground clearance can be sufficiently secured, and the wheel base can be shortened. This is extremely easy in design.

In addition, by laying out the frame itself consisting of the tank rail on both outer sides of the vehicle body, the frame is emphasized in the exterior design and a thin wall part is provided in a part of the reinforcing rib inside the tank rail. ,
Although the tank rail is bent for the above-mentioned layout, its bending stress is absorbed by the thin portion, so that the reinforcing rib portion may be stretched to cause unpleasant aesthetics. This has the effect of lowering the range of restraint and loss of commercial value.

[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. FIG. 4 is a top view, FIG. 4 is a cross section taken along line IV-IV in FIG. 3, and FIG.
FIG. 6 is an enlarged cross-sectional view of the reinforcing rib portion of the tank rail shown in the figure, and FIG. 6 is a view corresponding to FIG. 5 according to another embodiment of the present invention. 1 ... Head pipe, 5 ... Tank rail, 5a ... Reinforcing rib, n ... Thin-walled part.

Claims (1)

[Claims] 1. At least a pair of left and right tank rails extending rearward and obliquely downward from the steering head pipe and curved so as to have a bulge when viewed from the upper surface are continuously provided, and the tank rails are exposed on both outer side surfaces of the vehicle body. With this layout, a pipe made of extruded aluminum and having a horizontally long flat cross section is used as the tank rail. A vehicle body frame for a motorcycle, characterized in that continuous reinforcing ribs are integrally formed, and a longitudinal thin portion is provided in a part of the reinforcing ribs.