JPS62184980A - Car body frame structure of motorcycle - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a body frame structure for a motorcycle.

[Prior art]

As the body frame of a motorcycle, a pair of left and right main frames are connected to the steering shaft tube, and the main frames have a hollow rectangular cross-section, and the shape in side view is wide at the front end.
Some are designed to become narrower towards the rear. Such a main frame not only changes in vertical width in the longitudinal direction, but also has a curved shape in plan view, so it cannot be made into an integrally molded product with only a single member. In order to manufacture such a main frame, the left and right halves are split into U-shaped cross-sections, and their edges are partially overlapped in a step-like manner and welded together.

However, in general, welded parts are more brittle than other parts, and in addition to this, if the welded part has a stepped weld structure as described above, dust and water droplets tend to accumulate especially in the stepped welded part on the top side. (This has the disadvantage that it tends to promote corrosion.

Furthermore, since the welded parts are located on both the upper and lower sides of the main frame, the welded parts on the upper side in particular are easily visible from the outside, which impairs the appearance and lowers the product value.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a body frame structure for a motorcycle that prevents accelerated corrosion of the welded parts of a main frame having a hollow rectangular cross section as described above and has a good appearance.

[Structure of the invention]

To achieve the above object, the present invention has a pair of left and right main frames connected to a steering shaft tube, each of which has a hollow rectangular cross section, and has a shape in side view that is wide at the front end and becomes narrower toward the rear. In the body frame of a motorcycle, the main frame is formed of an outer plate part whose outer surface and an upper surface are integrally formed, and an inner plate part whose inner surface and lower surface are integrally formed, and the upper surface of the outer plate part. The edge and the inner side edge of the inner plate part are welded by overlapping the latter inward at least within the inner side, and the outer side edge of the outer plate part and the lower side edge of the inner plate part are welded together at least within the lower side. The latter is characterized by being polymerized and welded to the inside.

〔Example〕

In the motorcycle shown in FIG. 2, 1 is a steering shaft tube, 2 is a main frame, 3 is a back stay, and 4 is a down tube that connects the lower part of the front end of the main frame 2 and the lower part of the back stay 3. Reference numeral 5 denotes an engine mounted on a vehicle body frame made up of these members. Among the above members, the steering shaft tube 1, the main frame 2, and the backstay 3 are made of a light alloy such as aluminum.

As shown in FIG. 3, the main frames 2 are provided in a pair on the left and right, each having a front end welded to the oblique rear surface of the steering shaft tube 1, extending outward, and further curved and extending rearward. Further, the main frame 2 has a hollow rectangular cross-sectional shape as shown in FIGS. The width is narrow and has a so-called delta box shape.

The main frame 2, which has a hollow rectangular cross section, has a structure in which two left and right half members, an outer plate part 6 and an inner plate part 7, are welded to each other. As shown in FIGS. 1A and 1B, the outer plate portion 6 has an integral cross-sectional shape with an outer surface 6a and an upper surface 6b, and the edges of the outer surface 6a and the upper surface 6b are slightly curved. It has an inwardly curved shape. On the other hand, the inner plate part 7 has an inner side surface 7a and a lower surface 7b formed in an integral cross-sectional shape, and the edges of the inner surface 7a and the lower surface 7b are slightly curved inward. Further, the upper edge of the inner surface 7a is provided with protrusions 9 at multiple locations along the longitudinal direction that extend until they come into contact with the inner wall of the outer surface 6a of the outer plate part 6. -...-19
are integrally formed.

Both plate parts 6 and 7 are welded together by making the curved edge of the upper surface 6b and the curved edge of the inner surface 7a overlap inward, and using 8 as the welding part. Similarly, the curved edge of the outer surface 6a and the curved edge of the lower surface 7b are overlapped inward and welded together at 8'. Moreover, since the protrusion 9 of the inner plate part 7 comes into contact with the inner wall of the outer surface 7a of the outer plate part 6 together with the edge of the lower surface 7b, the both plate parts 6.7 can be simply pinched from both sides during welding work. The width of the main frame 2 can be set to a predetermined width by simply folding the main frame 2.

In this embodiment, the welded parts 8 and 8'' are one welded part 8.
is located at the uppermost corner of the inner surface 7a, and the other is located at the lowermost corner of the lower surface 6b.
It is located in the outermost corner of the interior. This welded part 8.8'
It is sufficient if they are arranged separately within the inner surface 7a and the lower surface 6b, respectively, and do not necessarily have to be limited to the corners. For example, as in the embodiment of FIG. 5, the weld 8 may be located below the uppermost corner in the inner surface 7a, and this also applies to the weld 8'.

According to the main frame 2 described above, in the step portions at the welding portions 8° and 8′, the supports facing upward do not form surfaces;
All are facing downwards. Therefore, dust and water droplets do not accumulate in the welded parts 8.8', and although these welded parts 8.8' are more brittle than other parts, the dust and water droplets do not accelerate corrosion. do not have.

Further, in the main frame 2, the welded portions 8,8' are located on the inner side and the lower surface of the frame, respectively, so that they are not visible from the outside, and the appearance can be improved.

In addition, when welding the outer plate part 6 and the inner plate part 7 at the welding part 8.8', both edges of the inner plate part 7 are overlapped inside both edges of the outer plate part 6, but Since the width in the direction changes in the length direction, the inner plate part 7 is slightly offset in the length direction from the outer plate part 6 as shown by the chain line in FIG. It can be easily set in the correct position by inserting it and then moving it in the direction of the arrow.

〔Effect of the invention〕

As described above, the present invention provides an automatic transmission system in which the cross section of the pair of left and right main frames connected to the steering shaft tube is hollow and rectangular, and the shape in side view is wide at the front end and becomes narrower toward the rear. In the body frame of a two-wheeled vehicle, the main frame is formed from an outer plate part whose outer surface and an upper surface are integrally formed, and an inner plate part whose inner surface and lower surface are integrally formed, and the upper surface edge of the outer plate part. and the inner side edge of the inner plate part are welded by overlapping the latter inward at least within the inner side, and the outer side edge of the outer plate part and the lower edge of the inner plate part are welded together at least within the lower side. Since the structure is made by polymerizing and welding on the inside, dust and water droplets do not accumulate in the step-like welded parts, which prevents corrosion from accelerating in the welded parts, which are more brittle than other parts.

In addition, since the two welding points are located on the inside and the bottom surface of the main frame, respectively, they are not visible from the outside, and the appearance can be improved.

[Brief explanation of drawings]

FIGS. 1A and 1B show a main frame according to an embodiment of the present invention.
The parts corresponding to the 1-1 arrow in the figure are A in Fig. 3, respectively.
- A sectional view taken along arrows A and B-B; Figure 2 is a side view of a motorcycle having the same main frame; and Figure 3 is a plane view showing essential parts of the steering shaft tube and main frame of the motorcycle. FIG. 4 is an explanatory diagram showing how the main frame is assembled, and FIG. 5 is a sectional view corresponding to FIG. 1 in another embodiment. 1.--.Steering shaft tube, 2-.-.Main frame,
6.-Outer plate part, 6a...outer surface, 6b...
Top surface, 7-inner plate portion, 7a--inner surface, 7b--
Lower surface, 88'-・Welded part.

Claims (1)

[Claims] In a motorcycle body frame, a pair of left and right main frames connected to a steering shaft tube have a hollow rectangular cross section, and a side view shape is wide at the front end and narrows toward the rear. The frame is formed from an outer plate part whose outer surface and an upper surface are integrally formed, and an inner plate part whose inner surface and lower surface are integrally formed, and the upper surface edge of the outer plate part and the inner surface of the inner plate part. The outer surface edge of the outer plate part and the lower surface edge of the inner plate part are welded by overlapping the latter inward at least within the lower surface. Motorcycle body frame structure.