JP2940791B2 - Motorcycle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorcycle having an improved swing arm support structure.

[0002]

2. Description of the Related Art Generally, a rear wheel of a motorcycle is attached to a rear end of a swing arm. The swing arm has a front end rotatably mounted around a pivot shaft and is elastically supported by a main frame of the vehicle body by a rear suspension. Here, conventionally, the center of the pivot shaft is located on the rear wheel side or substantially at the same position as the center of the drive sprocket connected to the output shaft of the engine in the longitudinal direction of the vehicle body (for example, see Japanese Utility Model Publication No. -47721 or JP-A-5-286777). Further, in the prior art, one pivot shaft penetrates the main frame, which is bifurcated into right and left, in the width direction of the vehicle body to support a swing arm (for example, Japanese Utility Model Application No. 03-094567).
No.).

[0003]

In the prior art, when accelerating or decelerating, the relationship between the moment applied to the rear suspension about the pivot center of the swing arm and
There is a characteristic that the posture change of the vehicle body increases. In addition, in the conventional swing arm support structure, sufficient support strength cannot be secured unless one pivot shaft penetrates the main frame, which is divided into left and right forks, in the width direction of the vehicle body.
Therefore, the structure must be complicated. The present invention has been made in view of the above circumstances, and provides a motorcycle having a swing arm support structure that can travel without increasing the posture change of a vehicle body even during acceleration or deceleration, and that is simple and lightweight and has sufficient support strength. With the goal.

[0004]

In order to achieve the above object, in the motorcycle according to the present invention, a swing arm is rotatably mounted around a pivot shaft, and the center of the pivot shaft is located at the center of the vehicle body. In the front-rear direction, the front sprocket is set closer to the front wheel than the center of the drive sprocket connected to the output shaft of the engine. Accordingly, the vehicle body can travel without increasing the posture change even during acceleration or deceleration due to the relationship between the moment applied to the rear suspension around the pivot center of the swing arm during acceleration or deceleration.

It is preferable that the left and right swing arms are sandwiched between the main frame of the vehicle body and the engine on each of the left and right sides. As a result, the engine becomes a support member of the swing arm, so that sufficient support strength can be ensured even if one pivot shaft does not penetrate the main frame which is divided into right and left branches, so that the pivot shaft can be shortened,
The swing arm support structure is also simplified. Further, since the engine also functions as a cross member of the main frame, a cross pipe conventionally required for securing the rigidity of the main frame can be omitted, and the weight and cost of the entire vehicle body can be reduced.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the fork 31 is rotatably attached to the head pipe 32 and supports the front wheel 13. As shown in the plan view of FIG. 2, the swing arm 24 is bifurcated into left and right sides, and is attached to the engine 12 and supports the rear wheel 4. Returning to FIG. 1, the main frame 6 is joined to the head pipe 32 by welding. The main frame 6 supports the engine 12 and also supports the rear wheel 4 via a swing arm 24. A rear frame 34 that supports the seat 33 is attached to the main frame 6 with bolts (not shown). Here, the center O of the pivot of the swing arm 24, that is, the center O of the pivot shaft 11 (FIG. 3) is located in the front-rear direction A of the vehicle body more than the front center of the drive sprocket 2 connected to the output shaft of the engine.
It is set to be located on the third side.

FIG. 3 is a plan sectional view of a support structure of the swing arm 24 in this embodiment. In the present embodiment, two left and right pivot shafts 11 composed of seated bolts are coaxially located on the engine 12 on each of the left and right sides, for example, the engine sprocket cover mounting portion 14 on the left side, and the engine clutch cover on the right side. 16 screwed. Although not shown, the sprocket cover 15 and the clutch cover 16 are screwed to the engine body 17 with, for example, three or ten bolts.

The seats of the pivot shaft 11 are, on the left and right sides, one of the main frame 6 which is bifurcated from the outside, the collar 18 holding the inner race of the bearing 19, the inner race of the bearing 19, and the bearing 19. Another collar 20 that holds the inner race is fastened to the engine 12. The swingarm 24, which is an integral object and is bifurcated,
On each of the left and right sides, the outer race of the bearing 19 is press-fitted and retained by a retaining ring 21, whereby the swing arm 24 is rotatably mounted around the pivot shaft 11.

With the swing arm 24 supporting structure as in the present embodiment, the engine 12 is used as a supporting member.
Sufficient support strength can be ensured without penetrating one pivot shaft through the main frame 6 which is divided into right and left forks, so that the pivot shaft can be shortened and the swing arm support structure is simplified. Further, since the engine 12 also functions as a cross member of the main frame 6, a cross pipe conventionally required for securing the rigidity of the main frame 6 can be omitted, and the weight and cost of the entire vehicle body can be reduced.

Next, the operation of the prior art and the present embodiment will be described by taking an example of acceleration. Swing arm 2
4 is, for example, as shown in FIG.
7, a link 26, and a support member 28 integrated with the main frame 6, are elastically supported on the main frame 6 by the rear suspension 25. The drive sprocket 2 is connected to a driven sprocket 5 of a rear wheel 4 via an endless drive chain 3. Here, the rear suspension 2 around the center of the pivot shaft 11 of the swing arm 24 during acceleration
Consider the moment M applied to 5.

First, in FIG. 5 showing the prior art, the force applied during acceleration is indicated by a thick solid line arrow, and the force applied during deceleration is indicated by a thick broken line arrow. At the time of acceleration, the rear suspension 2 around the pivot center O of the swing arm 24
5 (FIG. 4) is expressed by the following equation (1). _{M = F1 · H GP -F1 ·} H P + F C 1 · H C 1 ... (1) where the direction to reduce the rear suspension 25 (Fig. 4) is positive. F1: driving force (force in the forward acting force or the rear wheels 4 of the rearward acting on the center of gravity G) H _GP: distance from the pivot center O to the center of gravity G H _P: distance from the ground 30 to pivot center O F _C 1: Tension of drive chain 3 during acceleration H _C 1: Distance from pivot center O to upper part of drive chain 3

Here, the drive chain tension F _C 1
And the forward force F1 acting on the rear wheel 4 have the relationship of the following equation (2). F _C 1 = F1 · (R / r) (2) where R: radius of the rear wheel 4 r: radius of the driven sprocket 5 According to the above equations (1) and (2), the rear around the pivot center O during acceleration. The moment M applied to the suspension 25 (FIG. 4) is expressed by the following equation (3). M = F1 · {H _GP −H _P + (R / r) · H _C 1} (3)

Here, when the moment M in the above equation (3) is close to zero, the rear suspension 25 is accelerated by the acceleration operation.
Since no extra force is applied to (FIG. 4), the posture change of the vehicle body is natural and the riding comfort is improved. The magnitude of the moment M changes according to the position of the pivot center O, as can be seen from the equation (3). When the moment M becomes positive during acceleration, the rear suspension 25 (FIG. 4)
And the change in the attitude of lowering the vehicle body backwards increases.

[0014] However, in the conventional art, if the moment due to the tensile force Fc 1 drive chain is applied strongly during acceleration, when the swing arm 24 rear suspension is compressed is lifted upward, H _C 1 is increased H _P
From the equation (3), the rear suspension 25
The moment for shrinking (FIG. 4) further increases, and the posture change that lowers the vehicle body further increases.

On the other hand, in the present embodiment, equations (1) to (3) hold in FIG. 1 as in the prior art, but a strong moment due to the drive chain tension Fc 1 is applied during acceleration. In this case, when the rear suspension (FIG. 4) is compressed and the swing arm 24 is lifted upward, for example, H _C1 decreases by about 10% and H _P decreases by 4%.
%, The moment for shrinking the rear suspension 25 (FIG. 4) is reduced from the equation (3). Therefore, when the rear suspension 25 (FIG. 4) is slightly compressed, the posture of the vehicle body is balanced. I do.

According to the same principle, even if the moment due to the tension Fc2 of the drive chain is strongly applied during deceleration, in the conventional technique, the moment for extending the rear suspension 25 (FIG. 4) is further increased and the vehicle body is lowered forward. In contrast, in the present embodiment, the posture of the vehicle body is balanced when the rear suspension 25 (FIG. 4) is slightly extended. Therefore, according to the present invention, the change in the posture of the vehicle body does not increase even during acceleration or deceleration.

[0017]

As described above, according to the first aspect of the present invention, the moment of acceleration applied to the rear suspension about the pivot center of the swing arm at the time of acceleration or deceleration indicates that the body of the vehicle body is accelerated or decelerated. The vehicle can travel without increasing the change in posture.

In the swing arm supporting structure according to the second aspect of the present invention, since the engine is used as a supporting member, one pivot shaft does not have to penetrate the main frame divided into two right and left branches. Sufficient support strength can be secured, so the pivot shaft can be shortened,
The swing arm support structure is also simplified. Further, since the engine also functions as a cross member of the main frame, a cross pipe conventionally required for securing the rigidity of the main frame can be omitted, and the weight and cost of the entire vehicle body can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a motorcycle according to the present invention.

FIG. 2 is a schematic plan view of a swing arm according to the present invention.

FIG. 3 is a plan sectional view of a swing arm support structure according to the present invention.

FIG. 4 is a schematic side view of a conventional swing arm support structure.

FIG. 5 is a schematic side view of a motorcycle according to the related art.

[Explanation of symbols]

2 ... Drive sprocket, 6 ... Main frame, 12 ... Engine, 13 ... Front wheel, 24 ... Swing arm, A ... Back and forth direction of vehicle body, O ... Center of pivot shaft.

Claims (2)

(57) [Claims] 1. A motorcycle in which a swing arm is rotatably mounted around a pivot shaft, wherein the center of the pivot shaft is in the front-rear direction of the vehicle body.
A motorcycle characterized by being set on a front wheel side of a shaft center of a drive sprocket connected to an output shaft of an engine. 2. The motorcycle according to claim 1, wherein the left and right bifurcated swing arms are sandwiched between a main frame of the vehicle body and the engine on each of the left and right sides.