JPH1081288A - Body construction of motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make improvements in the suspension performance of two- suspension construction by installing the body side coupling part of a shock absorber in a main frame connecting an arm pivoting part and a steering device support part to each other, in a device equipped with the shock absorber, to be installed over a range between a body frame and a rocking arm bearing a rear wheel, at both symmetrical sides of the rear wheel. SOLUTION: In a two-suspension specification suspension construction where both shock absorbers 9L and 9R of a motorcycle are set up at both symmetrical sides of a rear wheel 3, each body side coupling part A of these shock absorbers 9L and 9R is installed in two brackets 10 and 11 and each arm side coupling part B in the rear of a rocking arm 2, respectively. At this time, for example, when the shock absorber 9L is installed, a boss 22 is pierceably attached tight to a left pipe 2L of the rocking arm 2, and this boss 22 is bolted, constituting the arm side coupling part B. In addition, the bracket 10 is projectingly installed from a main pipe 33 at the left, and a body side mounting part 9a of the shock absorber 9L is pinched in and bolted tight, thereby marking up the body side coupling part A, and then a lower pipe of an auxiliary frame is bolted to the tip side of the bracket 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorcycle (hereinafter, referred to as a motorcycle) having a structure in which two shock absorbers for rear wheels are provided on a pair of right and left rear wheels.
For more details, refer to the body structure of
The present invention relates to a technique for improving the suspension performance of a rear wheel.

[0002]

2. Description of the Related Art In a conventional two-suspension vehicle, Japanese Utility Model Publication No. 62-4
As shown in Japanese Patent No. 6397 or the like, an intersection (referred to as a triangle top) of a seat rail extending rearward from the horizontal frame member and a side rail extending obliquely upward from the lower portion of the horizontal frame member. It is a general structure to install a shock absorber over the swing arm and the rear part of the swing arm.

[0003]

As a rear wheel suspension system for a motorcycle, one shock absorber is disposed roughly at the center of the vehicle body on the front side of the rear wheel, and a link mechanism is used to move the swing arm up and down. There is a so-called single suspension structure that converts the effective stroke of the shock absorber through a so-called single suspension structure, and a double suspension structure that includes shock absorbers on the left and right sides of the rear wheel as described above. When both are compared, it is known that the single suspension structure is more advantageous than the two suspension structure in terms of shock absorption, ground grip, and suspension performance such as ride comfort. In particular, models for off-roads where suspension performance is important have almost completely a single suspension structure.

However, in the single suspension structure, a space for disposing the link mechanism and the shock absorber and a space for moving the link mechanism and the shock absorber must be secured inside the vehicle body, so that the space for auxiliary equipment such as an air cleaner is easily restricted. In addition to the design difficulties, there are disadvantages that the setting, inspection and maintenance of the shock absorber are extremely difficult due to its internal structure. On the other hand, the two-suspension structure has an advantage that it functions reliably because there is no link mechanism, and that the shock absorber is exposed to the outside so that setting, inspection and maintenance can be easily performed. That is, in the single suspension structure and the two suspension structure,
These strengths and weaknesses are almost reversed, and models that require a high level of suspension performance (such as off-road vehicles) adopt a single suspension structure and models that do not require much suspension performance (road models and business models). , Etc.), two suspension vehicles are still mainstream even today.

[0005] It is desirable to provide a suspension system that provides excellent suspension performance and is excellent in maintainability and design. However, it is fundamentally difficult to improve maintainability and design in a single suspension structure. However, there seems to be room for improvement in improving the suspension performance of the two-suspension structure, which is excellent in maintainability and design. Accordingly, an object of the present invention is to provide a vehicle body structure in which the suspension performance of a two-suspension structure is improved to the same level as that of a one-suspension structure, and an overall excellent rear wheel suspension device can be obtained.

[0006]

[Means for Solving the Problems]

[Configuration] A first aspect of the present invention is a motorcycle body structure provided with a shock absorber erected between a swing arm for rotatably supporting a rear wheel and a body frame on each of the left and right rear wheels.
The vehicle body-side connection portion of the shock absorber is provided on a main frame that connects an arm pivot support portion that supports the swing arm so that the swing arm can swing up and down, and a steering device support portion.

According to a second aspect of the present invention, in the first aspect, the vehicle-body-side connecting portion is provided on a single front-falling elongated member that directly connects the arm pivot portion and the head pipe.

[0008] A third invention is the first or second invention, wherein
It is characterized in that the arm side connecting portion of the drive side shock absorber on the side where the endless turning band for driving the rear wheel of both shock absorbers is disposed is disposed above the upper moving portion of the endless turning band. is there.

According to a fourth aspect of the present invention, in the third aspect, the non-drive-side shock absorber of the two shock absorbers, on which the endless rotating band is not provided, is connected to an arm-side connecting portion thereof. The height of the arm relative to the swing arm is lower than the height of the arm-side connecting portion of the drive-side shock absorber relative to the swing arm.

In a fifth aspect based on the first to fourth aspects, the rear frame supporting the rear fender is detachably attached to the main frame to form a body frame.
The rear frame is attached to a connection member for connecting the shock absorber in the main frame.

[Operation] According to the configuration of the first aspect, the suspension performance of the rear wheel is improved, the degree of freedom in designing the rear portion of the frame, and the weight of the rear portion of the frame can be reduced.

[0012] The reason for improving the rear wheel suspension performance will be briefly described. Since the vehicle body-side mounting portion of the shock absorber is provided on the main frame, when compared with the conventional structure provided on the rear frame,
If the thrust load acting on the rear wheel is the same, the force itself acting on the shock absorber of the present invention is larger than that of the shock absorber due to the steep fall of the front of the shock absorber and the loosening of the mounting angle. However, since the distance between the point where the force acts and the arm pivot (hereinafter abbreviated as pivot) is smaller in the present invention, "the moment of inertia with respect to a certain axis of the object is determined by the mass of the object and its mass. from the portion of the product of the square of the distance from the axis "hereinafter theorem (I = mr ^2), as the moment of inertia by dampers reaction force is the direction of application of those conversely decreases.

Therefore, at the moment when the rear wheel is pushed up from the road surface due to the riding on a convex portion or the like, the influence of the moment of inertia that the vehicle body (spring) receives from the shock absorber, that is, the couple that tries to rotate the vehicle body forward, It is smaller than the two suspension cars. In other words, dynamically, the sprung weight is relatively large, and the influence of road surface unevenness or undulation is less likely to be exerted on the vehicle body that is sprung. The detailed description of the suspension performance improvement will be described in the section of the embodiment.

As described above, the suspension performance can be improved by reducing the distance between the pivot and the action vector of the shock absorber. From this point, FIGS. 10 (a), (b), and FIG. Structure is conceivable. FIG. 10A shows a structure in which the mounting portion on the upper side of the shock absorber is moved to the pivot side without changing the mounting position on the upper side of the shock absorber so much as before, and the shock absorber is tilted backward. The structure of (1) is a structure in which the shock absorber is translated forward from the state of the conventional structure. The structure shown in FIG. 4 has a structure in which the mounting portion on the upper side of the shock absorber is shifted toward the pivot side so that the front inclination angle of the shock absorber is remarkable.

In the structure shown in FIG. 10A, the included angle between the swing arm 2 and the shock absorber 9 on the front side becomes obtuse, and the included angle α increases as the swing arm 2 is displaced upward. Characteristic and poor feasibility. FIG.
In the structure shown in (b), it is good that the front included angle between the swing arm 2 and the shock absorber 9 is an acute angle, but the mounting portion 9a on the upper side of the shock absorber is located at a considerably high position and the main frame Fa From the rear frame F as shown in the figure.
The shock absorber 9 must be attached to the triangular top formed in b. Therefore, as in the conventional case, it is necessary to provide the rear frame with considerable strength, and the handling of the frame is restricted, which is inconvenient. In addition, since the swing arm has a point of application of a load in the middle between the front and rear thereof, a strong arm that can withstand a large bending moment due to the load is required, which is disadvantageous in terms of cost and weight. For comparison,
FIG. 10A shows the position of the shock absorber 9 according to the present invention by a virtual line.

In the structure of the present invention shown in FIG. 4, since the vehicle body side mounting portion 9a is sufficiently lowered by being remarkably tilted forward, there is no disadvantage such as a reverse progressive characteristic or a heavy swing arm. The position of the shock absorber is low, the center of gravity can be lowered, and there is no shock absorber mounting part at the rear of the frame, so there is no restriction, so the design with priority on the placement of auxiliary equipment can be done, so the design flexibility of the rear of the frame Is improved.
In addition, since the connection point between the shock absorber and the main frame can be set at a low position, the position of the lower connection portion q (see FIG. 10) to the main frame at the rear portion of the frame can also be lowered, and the vertical support strength of the rear portion of the frame can be reduced. This is advantageous, and the weight of the rear part of the frame can be reduced. In addition, the main frame portion connecting the steering device support portion and the arm pivot portion, that is, the strength and
Since the shock absorber is connected to the main frame part having high rigidity, the vehicle body side connection part can be configured without special reinforcement or with a small amount.

According to the second aspect of the present invention, since the vehicle body-side connecting portion of the shock absorber is provided on the single long front-end member which directly connects the arm pivot portion and the head pipe, the longitudinal direction of the shock absorber can be reduced. The longitudinal direction of the long member can be matched as much as possible,
The component in the bending direction of the force acting on the long member due to the shock absorber reaction force can be reduced. In other words, the reaction force of the shock absorber is received by the long member as a tensile direction that is mainly advantageous in strength, and the reaction force of the shock absorber can be sufficiently received without performing special treatment such as partial reinforcement. Can be. For example, as shown in Japanese Utility Model Publication No. Sho 62-38476, the shock absorber connecting portion is clearly provided with an advantage in terms of frame strength and almost no reinforcement is required as compared with a means in which a shock absorber connecting portion is provided in a frame portion that falls backward. Therefore, the weight can be reduced.

According to the configuration of the third aspect, the vehicle body width (straddling width) at the shock absorber portion can be reduced. In the conventional two-suspension vehicle, the shock absorber can be as close as possible to the rear wheel side on the side where the endless turning band is not provided, but on the side where the endless turning band is provided, the shock absorber is provided to avoid interference with the rear wheel side. It was arranged on the lateral outside of the endless rotating belt. Therefore, the position of the shock absorber with respect to the center of the vehicle body is different on the left and right, and the shock absorber on the endless rotation band side protrudes sideways, but the position of the shock absorber itself is far away from the pilot, especially to hinder the riding posture It wasn't. On the other hand, in the case of the present application, since the arm-side connection portion of the drive-side shock absorber on the side where the endless rotation band is provided is arranged above the endless rotation band, the same horizontal position as the non-drive-side shock absorber is used. Thus, the horizontal distance from the center of the vehicle body to the shock absorber can be reduced without interfering with the endless turning band. Therefore, even if the present invention is configured such that the shock absorber is likely to be arranged forward so that the driver's foot and the shock absorber interfere with each other in the front-rear direction, the lateral protrusion amount of the drive side shock absorber can be suppressed, and the shock absorber is placed on the footrest. The straddling width can be made sufficiently narrow, such that the rider does not care about contact with the foot (calf portion), and can take a good riding posture.

According to a fourth aspect of the present invention, the position of the shock absorber on the side where the endless rotating band is not disposed is lowered with respect to the position of the shock absorber on the side where the endless rotating band is disposed. That is, there is no endless rotation band on the non-arranged side, and there is no factor that requires the shock absorber and the rear wheel to be largely separated in the left-right direction. Can be brought close enough. Therefore, the connecting portion between the non-drive-side shock absorber and the swing arm can be made smaller and lighter than that of the drive-side shock absorber, and can also contribute to lowering the position of the center of gravity.

According to the fifth aspect of the present invention, since the rear frame supporting the rear fender can be attached to and detached from the main frame portion, the restriction on the interference when attaching / detaching the accessories to the rear frame is relaxed, and the air cleaner, the silencer, etc. And the inspection and maintenance of these accessories can be performed easily. Further, since the rear frame is attached to the shock absorber connecting member of the main frame portion having sufficient strength, it is not necessary to separately provide a dedicated attaching member or a reinforcing member. Thereby, the appearance can be improved.

[Effect] In the vehicle body structure according to any one of the first to fifth aspects, by providing the vehicle body-side connecting portion of the shock absorber on the main frame, the degree of freedom in layout around the rear portion of the vehicle body is increased and the rear wheel suspension is provided. It is possible to provide a two-suspension vehicle with improved performance.

The vehicle body structure according to the second aspect has the advantage that the weight of the main frame portion can be reduced or the strength is advantageous.

In the vehicle body structure according to the third aspect, the amount of protrusion of the drive-side shock absorber in the left-right direction can be suppressed,
There is an advantage that the width of the vehicle body of the shock absorber portion can be reduced without increasing the straddling width, such as maintaining a good riding position without strongly hitting the foot even if the shock absorber is arranged forward than before.

The vehicle body structure according to the fourth aspect has the advantage that the position of the non-drive-side shock absorber can be made lower than that of the drive-side shock absorber, which contributes to lowering the center of gravity and reducing the weight.

In the vehicle body structure according to the fifth aspect, the capacity of auxiliary devices and the detachability can be improved, and the main frame can be simplified by eliminating the need for a dedicated mounting portion. There is an advantage that the handling property is improved.

[0026]

1 and 2 show an on / off motorcycle. 1 is an OHC engine, 2 is a swing arm that supports the rear wheel 3, 4 is a front fork that supports the front wheel 5, 6 is a fuel tank, 7 is a first seat, and F is a body frame. Carburetor 8 with engine 1 leaning forward
And the drive sprocket 34 is close to the pivot P, which is the pivot axis of the pivot arm 2. Thereby, the minimum liquid level of the fuel is lowered to increase the tank capacity and lower the center of gravity.

The body frame F is formed by connecting a main frame Fa and an auxiliary frame Fb by bolts. The main frame Fa is formed by integrating a head frame (an example of a steering device support portion) 32 supporting the front fork 4, a main body frame f formed by integrating a pair of left and right main pipes 33, 33, and the like with a down frame d. It is composed. The bifurcated down frame d is a transmission case 1
The m front part and the front part of the underguard 17 are supported by bolts. Brackets 10 and 11 for mounting shock absorbers 9L and 9R for the rear wheel 3 are formed on the left and right main pipes 33 and 33, respectively.

The auxiliary frame Fb includes the left and right brackets 1.
Left and right lower pipes 12, 1 bolted to 0, 11
2, and upper and lower pipes 13, 13 which are bolted to the main pipe 33, and the connecting pipe 14, are integrally formed, and support auxiliary devices such as the rear fender 15 and the silencer 16. Also, the second sheet 18 for off-road use
The first seat 7 for on-road use and the like are also supported by the auxiliary frame Fb. The tandem step 19 is supported by the swing arm 2, but may be supported by the auxiliary frame Fb. The first seat 7 includes a tail lamp (including a direction indicator and a license plate attaching portion) 20 and a tool box 2.
1 and a sheet ASSY integrated and integrated, and as shown in JP-A-4-358978,
It is configured such that two types of riding positions are obtained by attaching and detaching the sheet ASSY.

Since the load of the driver or tandem occupant and the load in the vertical direction due to running are applied to the auxiliary frame Fb, it is preferable to connect the auxiliary frame Fb to the main frame with sufficient vertical strength. Therefore, the lower pipe 12 is connected to the bracket 1
By connecting to 0,11, the shock absorber 9L,
As a structure that does not interfere with 9R, the lower connection point of the auxiliary frame Fb can be set at the lowest position, which is advantageous in strength. or,
It is desirable that the brackets 10, 11 have sufficient strength to receive the load of the shock absorbers 9L, 9R, and that the lower pipes 12, 12 can be connected without any additional reinforcing members.

Next, the suspension structure of the rear wheel will be described. The shock absorbers 9L and 9R are of a two-suspension type provided on the left and right sides of the rear wheel 3, and the vehicle body side connecting portions A of the shock absorbers 9L and 9R are brackets 10 and 11 fixed to the main pipe 33.
Further, the arm-side connecting portions B are respectively formed at the rear portions of the swing arm 2. The left and right distances a and b between the centers of the left and right shock absorbers 9L and 9R and the center BC of the vehicle body are set at equal intervals a = b. For this reason, the attachment of the left shock absorber 9L is devised.

Attaching the left-side shock absorber (drive-side shock absorber) 9L As shown in FIGS. 3 and 4, the left pipe 2L of the swing arm 2
A pair of front and rear bosses 22, 22 are fixedly penetrating therethrough, and these bosses 22, 22 are sandwiched between an outer plate 23 and an inner plate 24 and bolted to form an arm-side connecting portion B. The arm-side mounting portion 9b of the shock absorber 9L is mounted between the inner and outer plates 24 and 23 with the bolt 25 and the nut portion 24a of the inner plate 24, and the bolt 25 can be inserted and removed from the left outside of the vehicle body. A space for an upper moving portion 26a of a drive chain (an example of an endless rotating band) 26 is secured between the inner and outer plates 24 and 23, and a chain case 27 is attached to the inner plate 24. In addition, tandem step 19
May be fastened to the boss 22 together. A U-shaped bracket (an example of a connecting member) 10 is protruded from the left main pipe 33, and the vehicle body-side connecting portion A is configured by sandwiching the vehicle-body-side mounting portion 9a of the shock absorber 9L and bolting the same. I have. On the tip side of this bracket 10,
The lower pipe 12 of the auxiliary frame Fb is bolted.

Attaching the right-side shock absorber (non-drive side shock absorber) 9R As shown in FIGS. 3 and 4, the right pipe 2R of the swing arm 2
The U-shaped bracket 28 welded to the upper surface of the
The arm-side connecting portion B is formed by bolting the arm-side mounting portion 9b. Note that a support stay (not shown) of the tandem step 19 may be jointly supported with the arm-side mounting portion 9b. A U-shaped bracket (an example of a connecting member) 11 protrudes from the right main pipe 33, and a vehicle-body-side connecting portion A is configured by bolting a vehicle-body-side mounting portion 9a of the shock absorber 9R. The auxiliary frame Fb
Are bolted.

In order to avoid interference with the drive chain 26, the lower mounting portion 9b of the left shock absorber 9L is arranged at a high distance above the left pipe 2L. There is no such restriction, and the arm-side mounting portion 9b is disposed close to the upper surface of the right pipe 2R. FIG.
As shown in the figure, the angle difference between the positions of the left and right brackets 10 and 11 with respect to the pivot P of the left and right vehicle body-side mounting portions 9a and 9a is θ10, and the angle difference between the positions of the left and right arm-side mounting portions 9b and 9b with respect to the pivot P is If θ20, then θ
10 = θ20, and the buffers 9L and 9R are the same. In FIG. 4, the solid line represents the shock absorber 9L,
9R is in the most extended state where it has extended most, and the imaginary line is the shock absorber 9
L and 9R show the maximum pressure states compressed to the limit, respectively.

* [Improvement of rear wheel suspension performance] The reason why the suspension performance is better than that of the conventional two suspensions will be described in detail below. FIG. 5A shows a rear wheel suspension model according to the present invention, and FIG. 5B shows a simplified rear wheel suspension model. The sprung mass M is a value obtained by subtracting the unsprung mass m of the rear wheel system from the total mass, and it is assumed that the center of gravity is located at the drawn position. It is assumed that the center of gravity of the rear wheel system m also coincides with the center of the rear axle for simplicity. And
When the force acting on each point at the moment when the reaction force F from the road surface acts in the vertical direction is obtained, the identification symbol is 1 for the present application and 2 for the conventional one.

Reaction force of shock absorber: F1 = F / sin θ1 F2 = F / sin θ2 Moment of inertia around pivot P due to reaction force of shock absorber: IF IF1 = d1 ² · F1 IF2 = d2 ² · F2 Mass over spring M ( Moment of inertia about pivot P of vehicle body): IM IM1 = R1 ² · M = R2 ² · M = IM2 Moment of inertia about pivot P of unsprung mass (rear wheel): Im Im1 = L1 ² · m = L2 ² · m = Im2. In the shock absorber, the reaction force is replaced by the mass.

Here, as an example, M = 75 kg, m = 1
5 kg, L1 = L2 = 0.45 m, R1 = R2 = 0.2
6 m, θ1 = 65 degrees, d1 = 0.15 m, θ2 = 15
Assuming that d2 = 0.43 m, F1 = 2.37F F2 = 1.04F IM1 = IM2 = 5.07 kgm ² Im1 = Im2 = 3.04 kgm ² IF1 = 0.053 Fkgm ² IF2 = 0.192 Fkgm ² ( ≒ 3.61IF1), and the moment of inertia due to the reaction force of the shock absorber is reduced to 1 / 3.61 compared to the conventional case.

When the moment of inertia increases, the amount of change per unit time with respect to the input decreases.
Both when the rear wheel rises due to thrust from the road surface and the shock absorber is compressed, and when the shock absorber compressed to separate the vehicle body and the swing arm extends,
If the input to the rear wheel is the same, the swing movement amount per unit time around the pivot will be
That is, the rate of change of the attitude of the vehicle body becomes slow. Therefore,
The change in vehicle attitude when the rear wheel passes through the gap momentarily is reduced.Of course, even when running on a continuous uneven road surface, the attitude change is suppressed, and it is easy to maneuver, and the riding comfort and ground grip Is improved.

Since the moment of inertia I = mr ² is proportional to the mass m and proportional to the square of the distance r,
It can be seen that, even if the road surface reaction force at the rear wheels is the same, the couple to turn the vehicle body around the pivot P is smaller in the present application. In conventional two suspensions, shock absorbers 9L and 9R
Acts far away from the pivot P,
In the case of the present application, it acts on a position close to the pivot P. Therefore, the value of the reaction force load is larger in the present application, but the moment of inertia obtained by multiplying the square of the distance is smaller in the present application.

In order to reduce the moment of inertia due to the reaction force of the shock absorber, the connecting portion A of the shock absorbers 9L and 9R is connected to the pivot P.
, That is, r (d at I = mr ²
1, d2) is reduced. Actually, there is a limit due to the absolute stroke amount of the shock absorber and the lever ratio with respect to the rear wheel stroke. However, the position of the shock absorber connecting portion A is made as close as possible to the pivot P in the up-down direction, and the like.
It is only necessary to reduce the distance between the push-pull vector and the pivot P. Therefore, it is structurally desirable to provide the vehicle body-side connecting portion A on the main pipe 33 connecting the pivot P and the head pipe 32. Next, specific examples of the operation and effect by the reduction of the moment of inertia will be described.

Example (1) Difference in posture change of the vehicle body when passing through the convex portion In the two-suspension structure of the present application shown in FIG. 6A, the front inclination angle α of the vehicle body around the front axle 5a due to the riding on the convex portion.
Assuming that the rising amount of the rear wheel 3 by ha1 and the rising amount of the rear wheel 3 by compression of the shock absorbers 9L and 9R are hb1, then ha1 + hb1 = height Ht of the convex portion C. Further, in the conventional two-suspension structure shown in FIG. 6 (b), the rising amount of the rear wheel 3 due to the front inclination angle β of the vehicle body centering on the front axle 5a due to the riding on the convex portion is represented by ha2,
If the amount of rise of the rear wheel 3 due to the compression of L and 9R is hb2, then ha2 + hb2 = height Ht of the convex portion C.

As described above, the protrusion C
When the vehicle rides, the rear wheel 3 is caused by the upward swing of the swing arm 2 due to the compression of the shock absorbers 9L and 9R and the change of the front leaning posture of the vehicle body around the front axle 5a due to the compression reaction force of the shock absorbers 9L and 9R. However, the relationship of ha1 <ha2 hb1> hb2 α <β is established in the case of the present invention in which the moment of inertia is small as compared with the conventional one. In other words, in the case of the present application, the change in the sprung relative to the change in the unsprung becomes slower than before, and therefore, the change in the sprung during the time required for the rear wheel to ride over the convex portion which operates instantaneously is obtained. Become smaller. Therefore, most of the rear wheel stroke is absorbed by the shock absorber, and the rate of change in the posture of the vehicle body is reduced, so that the feeling of thrust is reduced and the riding comfort is improved.
Also, in the return operation from the state of floating in the air after passing the convex part,
As described above, both the sprung and unsprung swinging movement speeds are slower than those of the related art, the posture change of the vehicle body is moderated, the disturbance of the balance can be suppressed, and the steering becomes easy.

Example (2) Trial step (steer) is exceeded. In this case, if the height is the same, the height can be increased more easily than before, and the limit height at which the height can be increased becomes higher than before. As described above, the dynamic unsprung mass has become lighter, so the grip time from when the rear wheel comes into contact with the vertical wall of the step to when the rear wheel substantially separates is longer than in the conventional two suspension, This is because the rear lifting action is enhanced. In the past, when the rear wheel hit the steer, the rear of the vehicle body was bounced and the grip was lost immediately (for this reason, it was important to lift the rear wheel as much as possible before hitting the vertical wall due to gravity removal) . However, in the case of the present application, it is as if the rear wheels are attached to the vertical wall and the driving force is transmitted to the vertical wall, and the rear of the vehicle body feels as if it were lifted up (so-called push-out). Unequal heights are possible.

An example of oversteering in the conventional structure will be described. First, in a state in which the rider is approaching the steer S in a standing posture (see FIG. 7A), when the steer S approaches to a certain extent, the accelerator is opened and the upper body is pulled backward by pulling the steering wheel. Retreat to (or
The front wheels are lifted up by operating the clutch (Fig. 7 (b)
reference〕. When the front wheel 5 comes into contact with the upper part of the vertical wall t, the body is left behind (see FIG. 7 (c)). Is quickly moved upward and forward (see FIG. 8D).

At this time, the rear wheel 3 collides with the vertical wall t and the shock absorber 9L (9R) is compressed, and the rear wheel 3 is stroked from the position of the virtual line to the position of the solid line, and the driving force of the rear wheel 3 is reduced. Vertical wall t
To start lifting the rear of the vehicle. While the rear part of the vehicle body is being lifted, the compressed shock absorber 9L extends, and a forward-turning couple acts on the vehicle body, and finally, the pressing force of the rear wheel 3 against the vertical wall t, that is, the grip is lost, and FIG. As shown in (e), the lifting action by the driving force of the rear wheel 3 disappears at the position where the rear wheel 3 has risen above the ground by h. Thereafter, the rear wheel 3 is steered S by the inertia of the vehicle body and the rider's center of gravity.
Although it is lifted upward, since the drive lift height of the rear wheel 3 is lower than the steer height (= h), as shown in FIG. It will fail.

Next, although the steering is exceeded by the structure of the present invention, since the behavior up to FIG. 7C is almost the same as that of the conventional structure, the following state will be described. The state shown in FIG. 9 (g) corresponds to the conventional state shown in FIG. 8 (d). The rear wheel 3 collides with the vertical wall t to compress the shock absorber 9L (9R), and the rear wheel 3 is indicated by an imaginary line. From the position to the position indicated by the solid line (this stroke amount is often larger than that of the conventional two-suspension structure), and the driving force of the rear wheel 3 is transmitted to the vertical wall t to move the rear portion of the vehicle body. Start lifting.

While the rear portion of the vehicle body is being lifted, a forward couple couple acts on the vehicle body by the extension operation of the compressed shock absorber 9L (9R), and finally the pressing force of the rear wheel 3 against the vertical wall t, that is, the grip However, since the component that causes the vehicle body to lean forward acts slowly due to the decrease in the moment of inertia, the rear wheels 3
As shown in FIG. 9 (h), the grip time of
The height H at which the driving force of the rear wheel 3 to the vertical wall t disappears is larger than the conventional height h. Therefore, due to the inertia of the movement of the vehicle body and the inertia of the center of gravity of the rider, as shown in FIG. 9 (i), the steer S having a height that cannot be climbed as shown in FIG. The rear wheel 3 can be lifted and successful.

[Another Embodiment] As shown in FIG. 3, mounting portions 9a and 9b at both ends of the shock absorbers 9L and 9R are provided in a ring-like elastic member 30 such as a rubber ring in an outer cylinder 29 fixed to the shock absorber. And the inner cylinder 31 is press-fitted and integrated. Therefore, the vehicle body side mounting portion 9a is
The inner cylinder 31 of each of the mounting portions 9a and 9b is arranged so as to be closer to the inside in the left-right direction than the arm-side mounting portion 9b.
Conveniently, the shock absorber is configured to be parallel to the mounting bolt 25 in the most extended state.

That is, to reduce the width of the vehicle body at the front of the shock absorber so as not to hinder riding, the shock absorber 9L,
If the 9R is inclined in a C-shape in plan view, the inclination angle changes due to expansion and contraction of the shock absorber, and the rubber ring 30
Are twisted not only in the circumferential direction but also in the axial direction. Therefore, if the upper and lower inner cylinders 31 and the mounting bolts 25 are parallel to each other in a state where the shock absorbers 9L and 9R are in the most extended state, that is, in a free state, the most extended state in which the rear wheels are levitated to the ground when attaching and detaching the shock absorbers 9L and 9R. In this state, the shock absorber can be easily and easily attached and detached without torsional deformation of the rubber ring 30.
With this structure, the more the shock absorbers 9L and 9R are compressed, the greater the amount of axial twisting of the rubber ring 30.
There is an advantage that while the a and 9b are inexpensive elastic member interposed structures, the elastic members can be effectively used by a part of the buffer function.

[0049] Buffers 9R and 9L for pivot P
May be the same as that on the side where the drive chain 26 is disposed (ie, θ10 = θ20 = 0). Further, by making the positions of the mounting portions 9a and 9b of the shock absorber with respect to the pivot P different from each other on the left and right and by making the shock strokes different, as a result, the swing arm by the left and right shock absorbers 9L and 9R different from each other is obtained. The swing angles of 2 may be the same.

As a frame structure, as shown in FIG. 11 (a), a main frame f in the form of a forward leaning formed by integrating a thick main frame 33A and left and right side frames 33B, 33B, or FIG. ), Left and right main pipes 33, 33 directly connecting the head pipe 32 and the pivot P are provided, and the vehicle body-side connecting portion A (10 or 11) is provided in a rear-falling portion below the main pipe 33. The provided main body frame f may be used. Further, the vehicle body frame F may have a structure in which two or three of the main frame f, the down frame d, and the auxiliary frame Fb are fixed.

As described above, the gist of the present application is to make the reaction force vector of the shock absorber closer to the pivot P. Then, it seems that the forward lean of the shock absorber in the conventional two-suspension vehicle is merely extreme, but it is not so simple. Because, as mentioned above, simply tilting the shock absorber forwards often causes the shock absorber to be located exactly inside the foot and abuts the calf, easily hindering the riding posture, and It is difficult to remove from the vicinity of the pivot, which is disadvantageous in terms of dynamics. On the chain side, the shock absorber further protrudes to the side. In addition, as described above, since there was no awareness that the suspension performance would be improved by the forward tilt of the shock absorber, conventionally, the extreme forward tilt arrangement of the shock absorber "has no particular advantage only with design difficulties". There was no problem to adopt the configuration shown in the present application. Therefore,
The present application conceived with the elucidation of the theory that the suspension performance is improved has a sufficient “unpredictability of purpose” and should not be judged to be poor in inventive step due to the simplicity of the structure.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a left side view of a motorcycle.

FIG. 2 is a right side view of the motorcycle.

FIG. 3 is a partially cutaway rear view showing the structure of a rear wheel suspension.

FIG. 4 is a side view showing a relative positional relationship between left and right shock absorbers.

FIG. 5 is a diagram of a rear wheel suspension model according to the related art and the present application.

FIG. 6 is an operation diagram showing a change in behavior at the time of riding on a convex portion according to the related art and the present application.

FIG. 7 is an operation view showing a first half of the conventional over-steer.

FIG. 8 is a function diagram showing a second half of the conventional steering-over state.

FIG. 9 is an operation view showing the latter half of oversteer according to the present application.

FIG. 10 is a side view showing a comparative example of a rear wheel suspension device.

FIG. 11 is a side view showing another structure of the frame.

[Explanation of symbols]

 Reference Signs List 2 swing arm 3 rear wheel 9L, 9R shock absorber 10, 11 connecting member 15 rear fender 26 endless turning band 26a upper moving portion 32 steering device support portion 33 long member A vehicle body side connecting portion B arm side connecting portion F Body frame Fa Main frame Fb Auxiliary frame P Arm pivot

Claims (5)

[Claims] A pair of left and right shock absorbers (9L) and (9R) are provided between a swing arm (2) rotatably supporting a rear wheel (3) and a vehicle body frame (F). A vehicle body structure of a motorcycle, wherein a body-side connecting portion (A) of the shock absorbers (9L) and (9R) connected to the vehicle body frame (F) is vertically swung by the swing arm (2). A motorcycle body structure provided on a main frame (Fa) for connecting an arm pivot portion (P) that freely supports and a steering device support portion (32). 2. The vehicle-body-side connecting portion (A) is connected to a single front-elongated long member (33) that directly connects the arm pivot portion (P) and the steering device support portion (32). The vehicle body structure of a motorcycle according to claim 1, wherein the vehicle body structure is provided. 3. The drive-side shock absorber (9L) of the two shock-absorbers (9L) and (9R), on which the endless turning band (26) for driving the rear wheel (3) is disposed. The arm-side connecting portion (B) connected to the swing arm (2) in (1) is disposed above an upper moving portion (26a) of the endless rotating band (26). The body structure of the motorcycle according to the description. 4. The non-drive-side shock absorber (9R) of the two shock absorbers (9L) and (9R), on which the endless rotation band (26) is not provided, is connected to an arm-side connecting portion thereof. The state in which the height position of (B) with respect to the swing arm (2) is lower than the height position of the arm-side connecting portion (B) with respect to the swing arm (2) in the drive-side shock absorber (9L). The vehicle body structure of a motorcycle according to claim 3, wherein the vehicle body structure is provided with: 5. A vehicle body frame (F) comprising a rear frame (Fb) supporting a rear fender (15) detachably attached to the main frame (Fa), and a main frame (Fa). The shock absorber (9
L), (9R) Connecting members for connection (10), (11)
The rear frame (Fb) is mounted on the rear frame.
The vehicle body structure of a motorcycle according to any one of claims 1 to 4.