JPH05178254A - Car body frame of motorcycle - Google Patents

Abstract

PURPOSE:To increase rigidity by connecting the front half parts of two square shaped pipes in the car width direction through welding, installing a tank rail for separating the rear half part into the left and right parts, and connecting the vicinity of the lateral separation part and a down tube by a tension pipe. CONSTITUTION:A semidouble cradle type car body frame is constituted of a head pipe 3, tank rail 4 which extends aslantly downward and rearward, rear arm bracket 5 connected at the rear edge part of the tank rail 4, down tube 6 for connecting the lower edge of the bracket 5 and the head pipe 3, and a tension pipe 7 for connecting the down tube 6 and the tank rail 4. The tank rail 4 is formed by superposing the front half parts 4a of two square shaped pipes in the car width direction, joining two pipes into one piece by welding the upper and lower surfaces, and then separating the rear half part 4b into the left and right parts, and the vicinity of the lateral separation part of the tank rail 4 and the down tube 6 are connected by the tension pipe 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle body frame of a motorcycle, and more particularly, to an improvement in the structure of a tank rail portion which can be made more lightweight and more rigid.

[0002]

2. Description of the Related Art There are various types of motorcycle body frames. For example, in the case of a motorcycle intended for off-road running, it is required to be particularly lightweight and highly rigid. In order to improve the rigidity of the entire body frame of this type, it is particularly effective to improve the rigidity of the tank rail that connects the head pipe and the rear arm bracket. As such a vehicle body frame, conventionally, a large-diameter round pipe and a pair of small-diameter round pipes that are welded to the rear end of the large-diameter round pipe and spread diagonally downward left and right are arranged. It is common to construct a tank rail by welding the front end of the large-diameter round pipe to the head pipe and connecting the rear arm bracket to the rear end of the small-diameter round pipe (for example, Japanese Patent Laid-Open No. 59-59). No. 120585).

[0003]

However, in the above-mentioned conventional body frame, it is necessary to further increase the diameter of the large diameter round pipe in order to further improve the rigidity.
There is a problem that the request for weight reduction is impaired. Also, because it is a structure that welds a small diameter round pipe to a large diameter round pipe,
There is also a problem that stress concentration is likely to occur in the welded portion and the weld strength greatly affects the frame strength.

The present invention has been made in view of the above conventional circumstances, and an object of the present invention is to provide a body frame of a motorcycle which can be improved in rigidity and strength while achieving weight reduction.

[0005]

According to the present invention, there are provided tank rails in which the front halves of two square pipes are overlapped in the vehicle width direction and welded together, and the rear halves are separated into left and right.
A head pipe to which the front end of the tank rail is connected,
A rear arm bracket to which each rear end of the tank rail is connected, a down tube extending obliquely downward from the head pipe, and a tension pipe connecting the down tube and the left and right separation parts of the tank rail. It is characterized by having.

[0006]

According to the vehicle body frame of the motorcycle of the present invention, the tank rail is welded to the front half portions of the two square pipes in the width direction of the vehicle so as to be welded to each other and the rear half portions are separated left and right. It has a structure. For this square pipe,
By making the cross-sectional shape vertically long, the ratio of the increase in rigidity to the increase in weight is large as compared with the conventional pipe made of a round pipe, and the rigidity can be increased while suppressing the increase in weight.

The tank rail of the present invention has a structure in which the front half of a pair of left and right rectangular pipes are overlapped in the vehicle width direction, and the rear half is separated into left and right pipes. The frame strength is not affected by the welding strength as in the above conventional structure in which the frame is welded, and the frame strength can be improved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 9 are views for explaining a vehicle body frame of a motorcycle according to an embodiment of the present invention. FIG. 1 is a side view, and FIGS. 2 to 8 are II-II lines of FIG. 1, respectively. View, III
-III line view, IV-IV line sectional view, VV line view, VI-VI
A line sectional view, a VII-VII line sectional view, a VIII-VIII line sectional view, and FIG. 9 are left side views of a motorcycle equipped with the frame of the embodiment.

In the figure, 1 is a motorcycle in which the frame of the embodiment is adopted. In the motorcycle 1, a head pipe 3 of a body frame 2 pivotally supports a front fork (not shown) that pivotally supports a front wheel to the left and right, and a rear arm bracket 5 pivotally supports a rear wheel 26. A rear arm 21 is pivotally supported so as to be vertically swingable, an engine 12 is mounted in a cradle of the vehicle body frame 2, a fuel tank 10 is mounted above the engine 12, and a seat 11 is mounted behind the tank 10. In addition, 14a and 14b are a vaporizer and an air cleaner.

The engine 12 is of a water-cooled two-cycle single-cylinder type, and a cylinder block 14 and a cylinder head 15 are laminated and fastened in a forwardly inclined state on a front portion of a crankcase 13 integrated with a transmission case. It has a structure. This engine 12 has the above crankcase 13
The front and bottom bosses 13a and 13b of the down tube 6
Of the left and right branch portions 6a are bolted and fixed to the support bracket 61 fixed to the rising portions of the left and right branch portions 6a, and the bracket 6c welded and fixed to the bottom portion of the crankcase 13.
The rear boss portion is supported by a pivot shaft 27, which will be described later, and the suspension boss portion 15a of the cylinder head 15 is mounted on the vehicle body frame 2 by bolting and fixing it to the tank rail 4 via the suspension bracket 15b.

The rear arm 21 has a pair of left and right prismatic arm bodies 20a, 20a, each of which has a pivot portion 23 formed at a front end portion thereof, and portions of the arm body 20 rearward of the pivot portion 23 are prismatic portions. The left and right arm bodies 20a, 20a are connected and fixed by the cross member 24 of FIG.
A rear wheel 26 is pivotally supported by an axle 25 that is inserted and fixed between the rear ends. The pivot portion 23 is pivotally supported by a pivot shaft 27 inserted through the bearing through a bearing, and the pivot shaft 27 supports the left and right rear arm brackets 5.
It is fastened and fixed with a nut. The rear boss portion of the crankcase 13 is located between the left and right pivot portions 23, 23.

A rear wheel suspension device 29 is arranged from below the front part of the rear arm 21 to below the engine. The rear wheel suspension device 29 is disposed between the rear arm 21 and the rear arm bracket 5, and is provided with a rotary damper 30 for suppressing irregular vertical vibration of the rear wheel 26, the rear arm 21 and the body frame 2. It is arranged between the Dunun tube 6 and a leaf spring 31 for absorbing a shock transmitted from the road surface to the rear wheel 26.

In the rotary damper 30, a substantially plate-shaped wing-shaped piston 33 which defines two chambers inside the case is arranged and housed in a damper case 32 which is composed of a case body and a lid and which is substantially fan-shaped in a side view. The drive shaft 3 is attached to the lower end 33a of the piston 33.
4 is inserted and spline-fitted, and the drive shaft 34 is rotatably supported by the damper case 32. The damper case 32 is fixed to the rear arm bracket 5 by bolts.

The rear end of the leaf spring 31 has a link mechanism 56.
Is connected to the rear arm 21 via a front end portion of the support bracket 6 via an initial load adjusting mechanism 57.
Supported by 1. The link mechanism 56 includes a support bracket 24a of the cross member 24 for supporting the left side,
A pair of right intermediate links 38, and a pair of left and right damper arms 37 connecting the intermediate links 38 and the drive shaft 34.
And a pair of left and right spring links 39 connecting the intermediate link 38 and the leaf spring 31. Reference numerals 62 and 63 denote front and rear pillows that serve as fulcrums when the leaf spring is deformed, and these are made of relatively hard rubber, foamed urethane or the like.

The body frame 2 is of a so-called semi-double cradle type, and includes the head pipe 3 and
A tank rail 4 extending obliquely downward and rearward from the head pipe 3, a rear arm bracket 5 connected to a rear end portion of the tank rail 4, and a down tube 6 connecting a lower end of the rear arm bracket 5 and the head pipe 3.
And a tension pipe 7 that connects the down tube 6 and the tank rail 4. In addition,
8 and 9 are seat rails and back stays.

In the tank rail 4, the front half portions 4a of two rectangular pipes are overlapped in the vehicle width direction and the upper and lower surfaces thereof are welded to be joined to one, and the rear half portions 4b are separated into left and right. The front end of the front half portion 4a is welded and fixed to the head pipe 3. Reference numeral 4c is a gusset for reinforcing the connecting portion with the head pipe 3, 4d is a gusset for reinforcing the branch portion, and 4e is a lightening lightening hole formed in the joint portion of the rectangular pipes.

The rear arm bracket 5 has a rectangular cross section in which sheet metal halves are butted against each other and welded,
The left and right rear arm brackets 5, 5 are welded to each other by upper and lower cross pipes 5b, 5c made of a round pipe. In addition, 5d is a pivot boss portion through which the pivot shaft 27 is inserted and supported.

The down tube 6 is composed of a single center tube 6b made of a rectangular pipe and a left end of the center tube 6b.
The center tube 6b is welded to the upper end of the center tube 6b, and the rear end of the side tube 6a is connected to the lower side tube 6a. Cross pipe 5
It is welded to c. Also, the lower ends of the left and right rear arm brackets 5 are attached to the left and right side tubes 6 respectively.
It is welded to the rear side surface of a.

A reinforcing plate 7a having a box cross-section with the rear surface is welded and fixed to the rear surface of the center tube 6b, and the upper portion 7b of the reinforcing plate 7a has the head pipe 3, the tank rails 4, and Down tube 6
And form a box cross-section. The tension pipe 7 is composed of one round pipe connecting the reinforcing plate 7a and the tank rail 4 near the left and right separating portions. Note that reference numerals 4f and 4g are lightening weight reduction holes, which are formed at the connecting portion between the reinforcing plate 7a and the tank 4 and the connecting portion between the reinforcing plate 7a and the center tube 6b, respectively.

Next, the function and effect of this embodiment will be described. According to the vehicle body frame 2 of the present embodiment, the tank frame 4 has a structure in which the front half portions 4a of two square pipes are overlapped in the vehicle width direction by welding and the rear half portions 4b are separated left and right. I am trying. In order to improve the vertical rigidity that is particularly required for the off-road motorcycle in the tank rail 4, it is effective to make the cross-sectional shape of the square pipe long, and in such a case, the cross-sectional area is increased too much. The rigidity can be improved without causing it. As a result, it is possible to increase rigidity while suppressing an increase in weight as compared with a conventional frame made of a round pipe. Further, since the rectangular pipes are stacked, the vertical wall is formed in the center, so that the vertical rigidity can be improved. By the way, this effect cannot be obtained when the diameter of the round pipe is increased.

Further, in this embodiment, a reinforcing plate 7a is arranged on the back side of the down tube 6 and the down tube 6 is provided.
Since the box cross section is formed by and the box cross section is formed by the upper portion 7b of the reinforcing plate 7a at the connecting portion of the head pipe 3, the tank rail 4, and the down tube 6, the rigidity around the head pipe where a large load acts is formed. Can be improved.

Further, the tank rail 4 of this embodiment adopts a structure in which the front half 4a of a pair of left and right rectangular pipes are aligned in the vehicle width direction so as to be aligned, and the rear half 4b is separated left and right. The frame strength is not affected by the welding strength as in the conventional structure in which the large diameter pipe and the small diameter pipe are welded, and the frame strength can be improved.

Furthermore, in this embodiment, the tank rail 4
Can be linearly connected to the rear arm bracket 5 in a side view, the length of the tank rail itself can be short, and the weight can be reduced in this respect as well.

In the above-mentioned embodiment, the semi-cradle type frame in which the down tube is separated from the middle is described, but the scope of application of the present invention is not limited to this. The present invention can be applied to a so-called double cradle type in which two pipes are provided near the head pipe and a diamond type in which a part of the down tube is interrupted and the crankcase is used as a part of the frame.

As described above, according to the motorcycle body frame of the present invention, the tank rail is connected such that the front half portions of the two square pipes are overlapped in the vehicle width direction and the rear half portion is left, Since the structure is separated to the right, there is an effect that rigidity can be improved while suppressing an increase in weight, and the front half and the rear half of the tank rail are made up continuously by a pair of left and right square pipes. There is no place. Therefore, the frame strength is not affected by the welding strength, and the frame strength can be improved.

[Brief description of drawings]

FIG. 1 is a side view showing a vehicle body frame of a motorcycle according to an embodiment of the present invention.

FIG. 2 is a view taken along the line II-II of FIG.

FIG. 3 is a view taken along the line III-III in FIG.

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

5 is a view taken along the line VV of FIG.

6 is a sectional view taken along line VI-VI of FIG.

7 is a sectional view taken along line VII-VII of FIG.

8 is a sectional view taken along line VIII-VIII of FIG.

[Fig. 9] Fig. 9 is a left side view of a motorcycle including the frame of the embodiment.

[Explanation of symbols]

 1 Motorcycle 2 Body Frame 3 Head Pipe 4 Tank Rail 4a 1st Half 4b 2nd Half 5 Rear Arm Bracket 6 Down Tube 7 Tension Pipe

Claims (1)

[Claims] 1. A tank rail in which the front halves of two square pipes are overlapped with each other in the vehicle width direction and welded together, and the rear halves are separated left and right, and a front end of the tank rail is connected. A head pipe, a rear arm bracket to which each rear end of the tank rail is connected, a down tube extending obliquely downward from the head pipe, and the down tube and the left and right separation parts of the tank rail are connected. A motorcycle body frame characterized by having a tension pipe.