JPH0577777A - Motorcycle frame - Google Patents

Abstract

PURPOSE:To improve the rigidity of a frame of a motorcycle. CONSTITUTION:The upper end part of a rear cushion unit 19 is connected to the rear end part of a main pipe 5 extending from a head pipe 4 to the rear side of a motorcycle body through a rear cushion bracket 20. The rear cushion bracket 20 and the right and the left down tubes 6, 7 are connected to each other by the right and the left tension pipes 21. The respective pipes are positioned at the top of a trigonal pyramid. When the rear cushion unit 19 extends/contracts, the force exerted from the rear cushion unit 19 to a frame 2 is transmitted in a diversified manner from the rear cushion bracket 20 to the respective pipes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorcycle frame, and more particularly to a structure of a portion connected to an upper end portion of a rear cushion unit.

[0002]

2. Description of the Related Art Conventionally, in a frame assembled by welding steel pipes together, there is a frame in which an upper end portion of a rear cushion unit is connected to a main pipe extending from a head pipe to a rear side (for example, Japanese Patent Application No. Sho 63). -168969
No.).

In this motorcycle frame, a connecting bracket is welded to the rear end portion of one main pipe which is linearly formed and extends rearward and downward from the head pipe, and the seat pillar is attached to the main pipe through the connecting bracket. The tube and seat rail were connected. The upper end of the rear cushion unit is pivotally supported by the connecting bracket.

Further, the rear cushion unit is disposed on the extension line of the main pipe so as to be inclined rearward and downward so that its axis line is substantially along the axis line of the main pipe.

By arranging the rear cushion unit in this way, it is possible to reduce the vertical bending load applied to the main pipe during the cushion stroke, which is advantageous in terms of rigidity of the frame.

[0006]

However, in the conventional motorcycle frame thus constructed, the main cushion and the rear cushion unit are positioned on substantially the same axis, so that the rear cushion is used during the cushion stroke. The center of gravity moves back and forth due to the expansion and contraction of the unit.

In order to eliminate such a problem, the axial direction of the rear cushion unit may be set to the vertical direction. However, in such a case, the rear cushion unit interferes with the engine and the lower end of the rear cushion unit is positioned near the pivot shaft of the rear arm, so that the rear cushion unit cannot be mounted. It is also possible to extend the rear end of the main pipe rearward and connect the upper end of the rear cushion unit to the rear end, but the cantilevered part of the main pipe becomes longer and joins the main pipe during the cushion stroke. The bending load in the vertical direction increases, which causes a problem in frame rigidity.

[0008]

In a motorcycle frame according to the present invention, a rear end of one main pipe linearly extending from the head pipe to the rear side of the vehicle body has an upper end portion of a rear cushion unit via a bracket. The rear cushion unit connecting portion and the left and right down tubes extending downward from the head pipe are connected by the left and right tension pipes.

[0009]

[Operation] Since the main pipe, the left and right down tubes, and the left and right tension pipes are positioned on the top side of the triangular weight, the force applied from the rear cushion unit to the frame when the rear cushion unit expands and contracts is It will be distributed from the connecting portion to each of the pipes and transmitted.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to FIGS. 1 is a side view of a motorcycle equipped with a frame according to the present invention, FIG. 2 is a side view of a motorcycle frame according to the present invention, FIG. 3 is a plan view of the same, and FIG.
2 is a sectional view taken along line IV-IV in FIG. 2, and FIG. 5 is V in FIG.
It is a -V line sectional view. In these figures, 1 is an off-road motorcycle, and 2 is a frame of this motorcycle.

As shown in FIG. 2, the frame 2 includes a head pipe 4 for supporting a front fork 3 in a steerable manner,
One main pipe 5 extending downward from the head pipe 4, left and right down tubes 6 and 7 extending downward from the head pipe 4, and connected to the rear end portion of the main pipe 5. The left and right seat pillar tubes 8 and 9, the left and right seat rails 10 and 11 extending rearward from the rear end portion of the main pipe 5, and the left and right back stays 12 and 13 and the like. ..

The rear ends of the down tubes 6 and 7 and the lower ends of the seat pillar tubes 8 and 9 are connected via a rear arm bracket 14.

The left and right down tubes 6 and 7 are connected by a cross tube 2a, and the left and right rear arm brackets 14 are connected by a cross tube 2b.

Each of the pipe members constituting the frame 2 is a pipe member having a circular cross section except that the main pipe 5 is formed in a rectangular tube shape.

Reference numeral 15 is an engine, and this engine 15 is
The front portion is supported by the down tubes 6 and 7, and the rear portion is supported by the seat pillar tubes 8 and 9.

Reference numeral 16 denotes a rear arm that supports a rear wheel 17 so as to be vertically swingable, and the rear arm 16 is supported by the rear arm bracket 14 via a pivot shaft 18. A rear cushion unit 19 is interposed between the rear arm 16 and the frame 2.

The left and right arm portions 16a of the rear arm 16 are slightly bent at the portions connected to the rear cushion unit 19, and are bent in a downward convex shape when viewed from the side. Is formed in.

The rear cushion unit 19 is mounted with its axis oriented substantially vertically so that it is substantially parallel to the seat pillar tubes 8 and 9 of the frame 2 when viewed from the side, and the upper end portion thereof is attached to the frame 2 It is pivotally supported by a rear cushion bracket 20 welded to the rear end portion.

Here, the rear cushion bracket 2
The structure of 0 will be described in detail. The rear cushion bracket 20 is formed by bending a plate material, and the central portion in the longitudinal direction is formed into a substantially rectangular tube shape with a size into which the main pipe 5 can be fitted, and both front and rear ends have a downward U-shaped cross section. Has been formed. In addition, a portion formed in a rectangular tube shape is indicated by reference numeral 20a in the drawing, and a portion formed in a rearward downward U-shaped cross section is indicated by a reference numeral 20b.

The rear cushion bracket 2
As shown in FIG. 4, 0 is welded to the main pipe 5 with the rear end of the main pipe 5 fitted in the rectangular tubular portion 20a. Further, as shown in FIG. 5, the rear cushion unit 1 is provided on the rearward downward U-shaped section 20b.
The upper end of 9 is pivotally supported.

Further, this rear cushion bracket 2
On the left and right sides of 0, seat pillar tubes 8 and 9,
The seat rails 10 and 11 are welded to each other. That is, the rear cushion bracket 2 is provided between each member connected to the rear end of the main pipe 5 and the main pipe 5.
0 will intervene.

In addition, the rear cushion bracket 2
A pair of left and right tension pipes 21 and 21 are welded to the lower surface of the square tubular portion 20a of 0.

The rear end of the tension pipe 21 is passed between the left and right seat pillar tubes 8 and 9 and welded to the lower surface of the rear cushion bracket 20 as described above, and the front end thereof is welded to the down tubes 6 and 7. There is. Also, the tension pipe 21 and the down tubes 6, 7
The welding position with is a portion of the down tubes 6 and 7 which is substantially in front of the cylinder head of the engine 15,
The cross tube 2a is a connected portion.

Reference numeral 22 is a reinforcing plate interposed between the tension pipe 21 and the main pipe 5, and 23 is a reinforcing plate for reinforcing the welded portion between the front end of the tension pipe 21 and the down tubes 6 and 7.

Reference numeral 24 is a carburetor of the engine 15, and 25 is an air cleaner. This air cleaner 25 is used for the frame 2
Seat pillar tubes 8 and 9, seat rails 10 and 1
The air cleaner element 25a, which is arranged in a portion surrounded by 1 and the back stays 12 and 13, and is incorporated therein, is positioned in front of the rear cushion unit 19.

Therefore, in the frame 2 thus constructed, the main pipe 5, the left and right down tubes 6,
7 and the left and right tension pipes 21 and 21 are positioned on the top side of the triangular pyramid.
The force applied from the rear cushion unit 19 to the frame 2 when swinging is distributed and transmitted from the rear cushion bracket 20 to the pipes.
It

Further, since the main portion of the air cleaner 25 (the air cleaner element 25a portion) is positioned in front of the rear cushion unit 19, the duct portion for guiding the intake air to the carburetor 24 can be formed linearly and shortly. Therefore, the intake system members can be continuously arranged in a row to reduce the intake resistance as much as possible.

[0028]

As described above, in the motorcycle frame according to the present invention, the upper end portion of the rear cushion unit is provided with the bracket at the rear end portion of one main pipe extending straight from the head pipe to the rear side of the vehicle body. Since the rear cushion unit connecting portion and the left and right down tubes extending downward from the head pipe are connected by the left and right tension pipes, the main pipe, the left and right down tubes, and the left and right tension pipes have a triangular pyramid shape. Therefore, the force applied from the rear cushion unit to the frame when the rear cushion unit expands and contracts is dispersed and transmitted from the rear cushion unit connecting portion to the pipes.

Therefore, the rigidity is high against the vertical force and the twisting force applied to the rear cushion unit connecting portion. Therefore, the axial direction of the rear cushion unit can be oriented vertically, and the center of gravity can be prevented from moving in the front-rear direction during the cushion stroke.

[Brief description of drawings]

FIG. 1 is a side view of a motorcycle equipped with a frame according to the present invention.

FIG. 2 is a side view of the motorcycle frame according to the present invention.

FIG. 3 is a plan view of a motorcycle frame according to the present invention.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

5 is a sectional view taken along line VV in FIG.

[Explanation of symbols]

 1 Motorcycle 2 Frame 4 Head Pipe 5 Main Pipe 6 Down Tube 7 Down Tube 19 Rear Cushion Unit 20 Rear Cushion Bracket 21 Tension Pipe

Claims (1)

[Claims] 1. An upper end portion of a rear cushion unit is connected via a bracket to a rear end portion of one main pipe linearly extending from the head pipe to the rear side of the vehicle body, and the rear cushion unit connecting portion and the head. A motorcycle frame characterized by connecting left and right down tubes extending downward from the pipes by means of left and right tension pipes.