JP3689980B2 - Motorcycle frame structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a motorcycle frame structure, and more particularly to a motorcycle frame structure in which an engine is suspended as a strength member.
[0002]
[Prior art]
Conventionally, an example of this type of frame structure is shown in FIG.
In the drawing, an upper tube b extending obliquely downward is connected to an upper end portion of a head pipe a through which a steering shaft is inserted, and a body frame c is connected to a rear end portion of the upper tube b. It is connected. Below the upper tube b, a lower tube d connecting the head pipe a and the body frame c is provided substantially parallel to the upper tube b. The lower tube d includes a front lower tube d1 connected to the head pipe a, a front suspension portion d2 welded to the lower surface portion thereof, a rear suspension portion d3 welded to a rear end portion of the front lower tube d1, and the rear suspension. It consists of a rear lower tube d4 formed by welding both ends to the part d3 and the body frame c.
The engine e is suspended by the front suspension part d2 and the rear suspension part d3 of the lower tube d and the upper and lower suspension parts c1 and c2 of the body frame c.
[0003]
As described above, in the frame structure of the conventional motorcycle, the engine e is suspended by the lower tube d and the body frame c, whereby the engine e acts as a strength member and the frame structure The strength can be secured.
A cushion unit f is disposed between the rear lower tube d4 and the engine e in the width direction (left-right direction) of the motorcycle. The front end portion of the cushion unit f is connected to the vicinity of the rear suspension portion d3 via a predetermined mounting member, and the rear end portion is connected to a swing arm supported on the body frame c by a pivot c1 so as to be vertically movable. ing.
[0004]
[Problems to be solved by the invention]
However, in the above conventional frame structure, the rear lower tube d4 and the portion (front lower tube) d1 positioned in front of it have the same size and shape, so this rear lower tube d4 and the engine e It is extremely difficult to arrange the cushion unit f so as to avoid interference with the engine e and the rear lower tube d4 in this narrow space. Even if it is possible, if the gap formed between the cushion unit f and the engine e is narrow, there arises a problem that the characteristics of the cushion unit f change due to the heat of the engine e. In particular, when an oil damper (not shown) is incorporated in the cushion unit, there is a problem that the viscosity of the oil changes and the cushion characteristics are remarkably deteriorated. Therefore, the degree of freedom of design regarding the arrangement of the cushion unit f is very low, and it is extremely difficult to make a setting that can satisfy all of the positional relationship with the engine, cushion characteristics, and the like.
[0005]
The present invention has been made to solve the above-described problems of the prior art. A cushion unit can be appropriately and easily disposed between the engine and the frame, and the influence of heat from the engine can be reduced. An object is to provide a frame structure for a motorcycle.
[0006]
[Means for Solving the Problems]
The present invention includes a pair of left and right upper tubes that connect a head pipe through which a steering shaft is inserted and a body frame behind the head pipe, and a pair of left and right lower tubes that connect the head pipe and the body frame below the upper tube. And an engine suspension provided in an intermediate portion of the lower tube and a body frame, and a cushion unit formed by connecting both ends to the body frame and the vicinity of the suspension portion, and the cushion unit, In a frame structure of a motorcycle in which the expansion and contraction direction is attached so as to be substantially parallel to a portion located behind the suspension portion of the lower tube, and the engine is suspended from the suspension portion so that the engine is a strength member. , In the lower tube That the portion positioned behind the suspension unit, and is obtained by forming the small becomes outside dimension than the portion located in front of the suspension unit.
[0007]
Therefore, in the present invention, the space between the lower tube and the engine is increased by downsizing the lower tube, so that the cushion unit can be disposed with a margin and the degree of freedom in design is increased. For this reason, by disposing the cushion unit away from the engine, the influence of the engine heat can be reduced, and a stable cushion characteristic can be obtained.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing the overall structure of a motorcycle frame structure according to a first embodiment of the present invention, FIG. 2 is an enlarged side view of what is shown in FIG. 1, and FIG. 3 is a bottom view of what is shown in FIG. 4 is a cross-sectional view taken along line AA of FIG.
[0009]
In each figure, a head pipe 2 is provided at a front end portion of a frame 1 that forms the skeleton of the motorcycle M. A steering shaft is inserted into the head pipe 2 and is supported by the steering shaft. The front wheel Hf is rotatably supported by the fork Ff.
Further, as shown in FIGS. 2 and 3, front end portions of a pair of left and right upper tubes 3a and 3b extending obliquely downward toward the rear are fixed to the upper end portion of the head pipe 2, respectively. A fuel tank T is provided above. A body frame 4 is fixed to the rear ends of the upper tubes 3a and 3b, and a pair of left and right swing arms SA that rotatably support the rear wheel Hr are pivoted on the body frame 4. Is supported so as to be swingable in the vertical direction.
[0010]
A pair of lower tubes 5a and 5b are provided below the upper tubes 3a and 3b so as to be substantially parallel to the upper tubes 3a and 3b in a side view. The lower tubes 5a and 5b have a front end portion fixed to the lower portion of the head pipe 2 and a rear end portion fixed to the body frame 4, respectively, and are configured as follows.
That is, the lower tubes 5a and 5b in this embodiment include a front lower tube (a portion positioned in front of the suspension portion) 51 whose front end portion is connected to the head pipe 2, and a front suspension portion welded to the lower surface portion thereof. 52, a rear suspension portion 53 welded to the rear end portion of the front lower tube 51, a rear lower tube (portion located behind the suspension portion) 54 and a connection pipe 55 welded to the rear suspension portion 53, The body frame 4 is welded to the rear end portion of the rear lower tube 54.
[0011]
The upper tubes 3a, 3b and the front lower tubes 5a, 5b are all cylindrical, and the front lower tube 51 is larger than the outer diameter of the upper tube 3a as shown in FIG. 4 (a). The rear lower tube 54 is formed to have an outer diameter dimension, and is formed to have a smaller outer dimension than the front lower tube 51. The outer dimension t1 of the rear lower tube 54 is smaller than the outer diameter t2 of the conventional rear lower tube d4 shown by the two-dot chain line in FIGS. However, since the positions of the side end portions of both the rear lower tubes 54 and 54 are in the same position as the conventional rear lower tube 54 in plan view, the facing distance between the two rear lower tubes 54 and 54 is the same as that of the conventional rear lower tube. It is increased by 2 (t2-t1) as compared to the facing distance of 5a and 5b.
[0012]
Further, of the pair of swing arms SA, one end of the cushion rod 11 is pivotally attached to the upper front end of the right swing arm SA, and the other end of the cushion rod 11 is in the middle of the cushion lever 12. It is attached to the part. The cushion lever 12 has an upper end rotatably supported by the body frame 4 and a lower end pivotally attached to the rear end of the cushion unit Cu. The cushion unit Cu is located in a gap formed between the left rear lower tube 54 and the rear cylinder 6 c of the engine 6. The upper end of the front part of the left swing arm SA is connected to a rotary damper 15 fixed to the body frame 4 via a cushion rod 13 and a damper arm 14.
[0013]
In the motorcycle frame structure configured as described above, the engine 6 including the engine block 6a and the cylinders 6b and 6c is suspended by the lower tubes 52 and 53 and the body frame 4 as shown in FIGS. Is done. The engine 6 shown here is a V-type engine in which cylinders 6b and 6c are arranged before and after a cylinder block 6a. The front cylinder 6b is suspended on the front suspension 52 of the lower tube 5a, and the engine block 6a is rearwardly suspended. 53 and the suspension portions 4a and 4b of the body frame 4, and the rear cylinder 6c is suspended by a suspension portion 55a protruding from the connecting pipe 55.
[0014]
Thereby, the engine 6 also acts as a strength member of the entire frame structure, and there is no problem in strength even if the diameter of the rear lower tube 54 located between the rear suspension portion 53 and the body frame 4 is reduced. By reducing the diameter of the rear lower tube 54, the weight of the entire vehicle body can be reduced.
Although the load from the engine 6 is applied to the lower tubes 5a and 5b, the lower tubes 5a and 5b are set to have outer diameters larger than those of the upper tubes 3a and 3b, and have sufficient strength in advance. Therefore, the load from the engine 6 can be reliably supported.
[0015]
In addition, in this embodiment, the lower tubs 5a and 5b are reduced in diameter so that the cushion unit Cu can be easily disposed.
That is, as shown in FIGS. 1 and 3, the cushion unit Cu is disposed between the left rear lower tube (the lower tube on the opposite side of the mission) 54 and the rear cylinder 6c of the engine 6a. However, as described above, the outer diameter t1 of the rear lower tube 54 in this embodiment is the same as that of the conventional rear. The lower tube (indicated by a two-dot chain line in FIG. 3) has an outer diameter t2, and the distance between the rear lower tube 54 and the cylinder 6c is increased by the outer diameter difference (t2-t1). Therefore, the arrangement of the cushion unit Cu can be easily set.
[0016]
Further, as the distance between the rear lower tube 54 and the rear cylinder 6c increases, the cushion unit Cu can be set on the left side, and heat conduction from the rear cylinder 6c to the cushion unit Cu is greatly increased. Can be reduced. For this reason, the cushion characteristics of the cushion unit Cu are stabilized, and the service life is greatly improved. In particular, when the cushion unit Cu is provided with an oil damper whose cushion characteristics are easily changed by heat, the effect of stabilizing the cushion characteristics becomes remarkable.
[0017]
5 and 6 are diagrams showing a second embodiment of the present invention. In each figure, the same or equivalent parts as those shown in the first embodiment are denoted by the same reference numerals.
In this embodiment, the portions 73, 74, 75 excluding the front side lower tube 51 out of the front side lower tube 51, the suspension portion 73, the rear lower tube 74, and the connecting pipe 75 constituting the lower tube 5 a, 5 b are included. As shown in FIG. 6, they are integrally formed.
[0018]
For this reason, the strength of the lower tubes 5a and 5b can be further increased, and the number of parts can be reduced. In addition, since the number of welding parts is reduced, the number of assembling steps is reduced, and the accuracy of the frame is increased, so that it is possible to accurately align with the engine, greatly improving productivity and improving the appearance of the product. To do. In the second embodiment, the suspending portion 73 is provided with a scraping portion 73a, and a shaft for engine suspension is inserted through the insertion hole 73b, and then the fastening portion 73c formed at the lower end is bolted. Since it is fixed by fastening, the suspension work of the engine 6 can be performed more easily.
[0019]
In each of the above embodiments, the case where the cushion unit Cu is connected to the rotary solenoid 15 via the link 12 has been described as an example. However, the cushion unit Cu does not use the rotary solenoid 15 and the cushion unit Cu includes an oil damper. The present invention is effective even for non-existing devices and the like, and is not limited to the above embodiment.
[0020]
【The invention's effect】
As described above, according to the present invention, the portion of the lower tube that is located behind the suspension portion is formed to have a smaller outer dimension than the portion that is located in front of the suspension portion, and therefore the cushion unit can be easily arranged. Since the distance between the engine and the cushion unit can be increased, the influence of heat from the engine can be reduced, stable cushioning characteristics can be obtained, and the life of the cushion unit can be increased. Can be improved.
[Brief description of the drawings]
FIG. 1 is a side view showing an overall configuration of a frame structure of a motorcycle according to a first embodiment of the present invention.
FIG. 2 is an enlarged side view of the main part of what is shown in FIG.
3 is a bottom view of what is shown in FIG. 2. FIG.
4A is a cross-sectional view taken along line AA of what is shown in FIG. 2, and FIG. 4B is a cross-sectional view taken along line BB of what is shown in FIG.
FIG. 5 is a side view showing an overall configuration of a frame structure of a motorcycle according to a second embodiment of the present invention.
6 is an enlarged perspective view of a main part of what is shown in FIG. 5. FIG.
FIG. 7 is a side view showing an overall configuration of a frame structure of a conventional motorcycle.
[Explanation of symbols]
2 Head pipe 3a, 3b Upper tube 4 Body frame 5a, 5b Lower tube 6 Engine 51 Front lower tube 52, 53 Engine suspension 54 Rear lower tube

Claims (1)

A pair of left and right upper tubes connecting the head pipe through which the steering shaft is inserted and the body frame behind the head pipe;
A pair of left and right lower tubes connecting the head pipe and the body frame below the upper tube;
A suspension part of the engine provided in the middle part of the lower tube and the body frame;
A cushion unit formed by connecting both end portions to the body frame and the vicinity of the suspension,
The cushion unit is attached so that its expansion / contraction direction is substantially parallel to a portion located behind the suspension portion of the lower tube,
In the frame structure of a motorcycle in which the engine is a strength member by suspending the engine on the suspension part,
A frame structure for a motorcycle, wherein a portion of the lower tube located behind the suspension portion is formed to have a smaller outer dimension than a portion located in front of the suspension portion.

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