JPH03121987A - Body frame structure for motorcycle - Google Patents

Abstract

PURPOSE:To attain light weight and rigidity as well as hold the height of a seat placed above low by forming a main frame formed of rectangular tapered pipe in such shape as to have its sectional area corresponding to longitudinal load distribution. CONSTITUTION:A main frame 6, extended from a head pipe 2 straight down diagonally backward as far as above a rear arm pivot 13, is formed into approximately rectangular cylindrical shape in its cross section, and the head pipe 2 side is made longitudinally wider with large sectional area. On the other hand, the rear arm pivot 13 side is formed of an approximately rectangular tapered pipe molded longitudinally narrow with small sectional area in order to correspond to the longitudinal load distribution of a body. In addition, the height of a seat 22 extended backward in the approximately horizontal direction from above the intermediate part of the main frame 6 is held down low.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a body frame structure for a motorcycle that is particularly suitable for traveling off-road.

[Prior Art] Some motorcycle body frames have a main frame connected to a head pipe so as to extend rearward.A front fork that suspends the front wheel is rotatably supported on this head pipe, and the main frame is connected to a head pipe so as to extend rearward. The engine is mounted on the frame, and the seat rail is further connected to the main frame.

When looking at the body frame of such a motorcycle from the viewpoint of the load acting state, a concentrated load acts on the head pipe side of the main frame.

Therefore, for example, if the main frame is made of a round pipe, it will not be possible to secure the joint strength with the head pipe, and it will be necessary to reinforce it with a reinforcing plate, and when joining these, the weld line will be curved. Moreover, it is necessary to weld from the front side to the rear side of the head pipe, making the welding work troublesome, difficult to automate, and increasing manufacturing costs.

There is also a main frame made of a rectangular pipe, but this makes the welding line with the head pipe a straight line, making welding easy and automation possible, but the cross-sectional shape is made by press-forming aluminum. A rectangular frame is formed by forming a character-shaped split frame and welding the joints together, and welding is used to form the frame itself, which poses problems such as increased production costs.

[Problems to be Solved by the Invention] For this reason, a split frame is formed by casting into two parts in the axial direction, and the split frames are joined and integrated by welding to form a main frame with a rectangular cross section. It is possible to weld it to the head pipe, but if the main frame is made of a cast rectangular frame, the welding strength with the head pipe can be improved to some extent, but if it is made of cast material, the wall thickness is thick to a certain extent due to casting technology. Therefore, there is a problem that the weight reduction effect is inhibited.

In addition, since the frame itself is a welded structure, stress concentration at the weld bead area occurs. Material softening occurs due to welding heat.In addition to improving rigidity and reducing weight, it is possible to lower the seat height.
Another object of the invention is to provide a motorcycle body frame structure in which the main frame is optimal for storing oil and fuel.

[Means for Solving the Problems] In order to solve the above problems, the invention according to claim 1 includes a main frame extending in a straight line from the head pipe to above the rear arm pivot rearward and diagonally downward, and The main frame has a sheet extending substantially horizontally from the upper part to the rear, and the main frame is made of a cylindrical pipe having a substantially rectangular cross section and a head pipe side having a large cross-sectional area.
The rear arm pivot side is characterized by being constructed from a substantially rectangular tapered tube formed into a shape with a vertically narrow width and a small cross-sectional area.

The substantially rectangular tapered tube of the present invention can be manufactured, for example, by the following method. In other words, the so-called rotor, in which the round pipe is rotated and struck with a striking member in a direction perpendicular to its axis, gradually changing the amount of protrusion of the striking member of the bracket, is unavoidable, and this tends to cause cracks and other problems in terms of strength and reliability. There is a problem with being inferior. Further, there are problems in that the weight increases due to the weld bead and that productivity is low due to the need for welding work that requires relatively skill.

Furthermore, in motorcycles that travel off-road, it is necessary to lower the seat height to improve riding stability, but when a square frame is used for the main frame, the rear arm pivot side of the main frame is vertical and wide. There is a problem with the seat height being too high.

In addition, the main frame is sometimes used as a container such as a tank for storing oil or fuel, but if the main frame is formed by welding, the number of welded parts increases and defects such as leaks are likely to occur. In addition to being unfavorable for storing oil or fuel, if the oil or fuel bubbles, there are problems such as the bubbles being sucked in when the pump is driven and the pump not working.

This invention was made in view of such circumstances, and Claim 1
In the invention described above, the main frame is formed into a Taber round vibrator with a larger diameter toward one end by Freley swaging, and then an inner mold of a predetermined shape is inserted into this pipe, and then the main frame is processed from the outside with an outer mold. It can be manufactured by pressing.

Further, the approximately rectangular tapered tube of the present invention includes one in which the wall is thicker toward one end and one in which the side wall is curved so as to bulge outward.
The end portion side can be thickened, and by forming the inner mold into a curved shape that bulges outward, the side wall can be curved outward.

Further, the invention according to claim 2 is characterized in that oil or fuel is stored in the main frame formed of a substantially rectangular tapered tube.

[Operations] In the invention described in claim 1, the main frame is constituted by a substantially rectangular tapered tube, and the head vibe side is vertically wide and has a large cross-sectional area, and the rear arm pivot side is vertically narrow and has a small cross-sectional area. It is molded into a shape with a cross-sectional area that corresponds to the load distribution in the front-rear direction, making it lightweight and highly rigid.

Additionally, the rear arm pivot side of the main frame is vertically narrow, allowing the height of the seat placed on top to be reduced accordingly.

Furthermore, the main frame is composed of a substantially rectangular tapered tube, and has few welded parts, making it suitable for use as a sealed container for storing oil or fuel. In addition, in this main frame, when oil or fuel decreases, the liquid surface area also decreases, which reduces the generation of air bubbles, making it possible to prevent air bubbles from entering the pump.

[Example] Hereinafter, an example of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a side view of the motorcycle, FIG. 2 is a side view of the vehicle body frame, and FIG. 3 is a cutaway plan view of the rear end of the main frame.

In the figure, reference numeral 1 denotes a vehicle body frame, and a front fork 4 on which a front wheel 3 is suspended is rotatably attached to a head vibrator 2 constituting the vehicle body frame 1.A main frame 6 extends rearward from the head vibrator 2 to above the rear arm pivots 1-13. The main frame 6 extends diagonally downward in a straight line, and the main frame 6 is made of a cylindrical tube with a substantially rectangular cross section and a head vibrator 2.
It is constituted by a substantially rectangular tapered tube formed into a shape in which the side is vertically wide and the cross-sectional area is large, and the rear arm pivot 13 side is vertically narrow and the cross-sectional area is small. By being constituted by this approximately rectangular tapered tube, the main frame 6 has a wide end portion 6a and a narrow end portion 6b, and the long sleeve direction of the wide end portion 6a extends in the axial direction of the head vibe 2. The wide end portions 6a are matched and welded against each other. The front end 5a of the subframe 5 is welded to the head vibe 2 and the wide end 6a of the main frame 6, and a tension vibe 20 is further disposed between the main frame 6 and the subframe 5.
is welded.

A fuel tank 21 is provided on the main frame 6 so as to straddle the entire frame, and a seat 22 is placed on the seat rail 15 from the fuel tank 21, and the seat 22 is supported above the middle part of the main frame. A subframe 5 and a main frame 6 extending downward are welded to the head vibe 2, and a pair of left and right seat leaflet tubes 7 are welded to the rear end of the main frame 6. Also,
A rear arm bracket 9 is welded between the lower frame 8 and the seat frame tube 7, which are welded to the subframe 5.
An engine 10 is mounted on these. A rear arm 12 on which a rear wheel 11 is suspended is supported by the rear arm bracket 9 via a rear arm pivot 13, and this rear arm 12 is supported by the rear arm bracket 9 via a link mechanism 14. A reaction 17 is provided between the link mechanism 14 and a bracket 16 provided between the left and right pair of seat rails 15 connected to the upper portions of the left and right pair of seat villa tubes 7. The pair of left and right seat rails 15 are each connected to a pair of support frames 1.
8 and is supported by the rear arm bracket 9.

Further, a side stand 19 is provided below the rear arm bracket 9.

It extends approximately horizontally from the rear.

As described above, the main frame 6 is formed of a substantially rectangular tapered tube, and the head vibe 2 side is vertically wide and has a large cross-sectional area, and the rear arm pivot 13 side is vertically narrow and has a small cross-sectional area. As a result, the cross-sectional area corresponds to the load distribution in the front-rear direction, making it lightweight and highly rigid. Further, the rear arm pivot 13 side of the main frame 6 is vertically narrow, and the height of the seat 22 placed thereon is correspondingly low.

In addition, an oil cap 2 is attached to the front end of the main frame 6.
4 is provided, and oil can be injected into the main frame 6 from the filler tube 25 by removing the oil cap 24. A cap 26 is fixed to the rear end of the main frame 6 by welding, so that oil can be stored inside the main frame 6. A filter 27 is attached to the cap 26.
An oil hose 28 having a diameter is taken out via a joint 29 (=j), and the oil hose 28 is connected to an oil pump 30 provided in the engine 10, and each part of the engine is lubricated by the drive of this oil pump 30. The oil for lubricating the main frame 6 is returned to the main frame 6 via an oil hose 31, and this oil hose 31 is connected to the front end of the main frame 6 via a joint 32.

The main frame 6 is made of a substantially rectangular tapered tube, and has few welded parts, making it suitable for use as a sealed container. Further, the rear end of the main frame 6 is lower than the front end, and the surface area of the liquid level becomes smaller toward the rear end. For this reason, when the oil decreases, the liquid surface area also decreases, so the generation of air bubbles can be reduced, making it possible to prevent air bubbles from entering the oil pump.

In this embodiment, oil is stored in the main frame 6, but fuel may be stored in the main frame 6.

In addition, the substantially rectangular tapered pipe has a structure in which a raw pipe such as a round pipe is formed into a rectangular tapered shape, and the height of a sheet in which the frame itself is press-formed to have a U-shaped cross section can be reduced.

In the invention as claimed in claim 2, the main frame is composed of a substantially rectangular tapered pipe, and there are few welded parts, and the main frame can be preferably used as a sealed container for storing oil or fuel.
Moreover, in this main frame, when oil or fuel decreases, the liquid surface area also decreases, which reduces the generation of air bubbles, making it possible to prevent air bubbles from entering the pump.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the motorcycle, FIG. 2 is a side view of the vehicle body frame, and FIG. 3 is a cutaway plan view of the rear end of the main frame. In the figure, 1 is the body frame, 2 is the head vibe, 6 is the main frame, 5 is the subframe, 9 is the rear arm bracket, 10 is the engine, 13 is the rear arm pivot,
21 is a fuel tank, 22 is a seat, 28.31 is an oil hose, and 3o is an oil pump. Patent Applicant: Yamaha Motor Co., Ltd. Compared to the case where a square frame is formed by joining a pair of frames, no welding work is required. Therefore, the problem of softening of the stress-concentrated material due to the weld bead does not occur, and reliability in terms of strength can be improved, as well as productivity. [Effects of the Invention] As described above, the invention according to claim 1 has a main frame extending in a straight line from the head vibrator to the upper part of the rear arm pivot rearward and diagonally downward. The head vibe side is vertically wide and has a large cross-sectional area, and the rear arm pivot side is vertically narrow and has a small cross-sectional area.The main frame is made of a rectangular tapered tube with a vertically narrow width and a small cross-sectional area. It is wide and has a large cross-sectional area, and the rear arm pivot side is narrow vertically and has a small cross-sectional area.The cross-sectional area corresponds to the load distribution in the front and rear direction, making it lightweight and highly rigid. In addition, the rear arm pivot side of the main frame is vertically narrow, so the two

Claims (1)

[Scope of Claims] 1. A main frame that extends in a straight line from the head pipe to above the rear arm pivot rearward and diagonally downward, and a seat that extends rearward and approximately horizontally from an upper part of the main frame midway; The frame is made of a substantially rectangular tapered tube formed by forming a cylindrical raw tube into a shape with a substantially rectangular cross section, the head pipe side being wide vertically and having a large cross-sectional area, and the rear arm pivot side being narrow vertically and having a small cross-sectional area. A motorcycle body frame structure characterized by comprising: 2. The body frame structure for a motorcycle according to claim 1, wherein oil or fuel is stored in the main frame formed of the substantially rectangular tapered tube.