JPH054279B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a motorcycle, and particularly to a rear arm having a shape that can increase the bank angle by securing piping space for an exhaust system while ensuring rigidity;
The present invention also relates to an improvement in the arrangement position of an exhaust valve that can suppress the adhesion of mud and the like to the shock absorber.

[Conventional technology]

BACKGROUND ART Conventionally, in a motorcycle, an exhaust device is disposed so as to pass below an engine body and below the front of a rear arm, and may be further led out to the rear outside of the rear arm. In a motorcycle with such an arrangement structure, the outwardly extending part of the exhaust system passes below the rear arm, so this part is located on the outside in the vehicle width direction and at a low location, which makes the motorcycle's This tends to be a factor that narrows the bank angle. Particularly in the case of vehicles equipped with two-stroke engines, the expansion pipe that serves as this lead-out portion has a large diameter, so
The minimum ground clearance will be lower accordingly, and there is a risk that the bank angle will not be secured from this point of view.

Therefore, as an exhaust system for motorcycles that can relax the bank angle regulation by expansion pipes, conventionally, two expansion pipes are installed below the engine unit, as described in, for example, Japanese Patent Application Laid-Open No. 62-23889. It has been proposed that the expansion tubes are arranged in a V-shape when viewed in cross section, and the outer corner of the lower end of each expansion tube is cut along the bank angle line determined by the footrest.

[Problem to be solved by the invention]

According to the exhaust device described in the above-mentioned publication, since the portion of each expansion tube that first contacts the ground during banking is cut off, the bank angle can be increased accordingly. However, in this structure, as the bank angle increases, the cut area needs to be increased, so there is a risk that the required expansion chamber size will be sacrificed, and there is a limit to the increase in the bank angle.

Therefore, the inventor of the present invention has developed a rear arm that can solve the above problem by bending one arm part upward in a convex manner and using the concave space formed below this bending part as the piping space for the exhaust system. There is.

However, with the rear arm developed above, the left,
The shape of the right arm is different, and there is a concern that the weight and rigidity of the left and right arms will be unbalanced. Moreover, in order to solve this problem of balance, it is necessary to specially reinforce one of the arm parts or add a weight member, which also causes the problem that the shape becomes complicated.

In view of the above-mentioned conventional problems and concerns, it is an object of the present invention to increase the bank angle while securing the necessary expansion chamber volume, to ensure the rigidity of the rear arm, and to prevent the adhesion of mud etc. to the shock absorber. The point is to provide a motorcycle that can be controlled.

[Means to solve the problem]

The present invention connects the front parts of a pair of left and right arm parts with a cross member part, and connects the pivot part of the rear arm, which is formed by bending one of the arm parts in an upwardly convex substantially V-shape, to the vehicle body frame. In a motorcycle in which a rear wheel suspension device arranged approximately at the center of the vehicle body is connected to the vicinity of the cross member portion, and the rear wheel is pivotally supported at the rear end of the arm portion, the rear wheel suspension device is forming a through hole made of a cylindrical body that passes downward through the lower part of the shock absorber of the rear wheel suspension system, and locating the through hole near the front end of a concave space formed below the bend of the arm portion; A boss portion for connecting the shock absorber via a link plate is formed in a portion between the through hole of the cross member portion and the arm portion, and an exhaust pipe is connected from one side of the vehicle body to the boss portion and the rear wheel. It is characterized in that the pipe is laid across the other side through a concave space formed between the arm part and the tire and below the bend of the arm part.

Here, the piping space in the present invention means a space for piping a part of the exhaust system, that is, a part that crosses the lower part of the rear arm, and 2
In the case of an exhaust system for a cycle engine, a large-diameter expansion pipe portion is generally located in this piping space.

[Effect]

In order to secure the bank angle, parts that must be located low due to the shape of the exhaust pipe itself or the way it is placed should be placed near the center line of the vehicle and outward in the vehicle width direction. It is important to place the parts where it is necessary to do so in a high place. For example, as mentioned above, if the exhaust pipe is piped from below the engine to cross below the rear arm, this crossing section will be located outward and at a low location, which will not meet the above requirements from the viewpoint of securing the bank angle. It is difficult to answer.

In contrast, in the present invention, one of the arm parts is bent upward in a convex manner, and the concave space formed below the bent part is used as the piping space for the exhaust system.
The cross section of the exhaust pipe, which must be located outward due to its arrangement structure, can be located upward, meeting the above-mentioned requirements, and the bank angle can be increased accordingly.

In addition, in the present invention, the arm part is bent to actively secure piping space, and the boss part for connecting the shock absorber is formed between the shock absorber through hole and the arm part, so the shock absorber and link Mechanisms can be placed as far forward as possible. As a result, the problem of the concave space below the arm being substantially narrowed by a shock absorber or the like can be avoided, and the concave space can be effectively used as a piping space. As a result, even in the case of an exhaust system for a two-stroke engine, there is no restriction on the cross-sectional shape of the expansion tube portion, a sufficient volume of the expansion chamber can be ensured, and engine performance is not affected.

Further, since the boss portion is located between the through hole of the cross member portion and the arm portion, the surface rigidity can be improved at the location where the boss portion is formed. In other words, the above-mentioned through hole has a structure in which the top plate and the bottom plate of the cross member part are connected by a cylindrical body, so the vicinity of the boss part has a closed cross section with the cylindrical body, the top plate, the bottom plate, and the arm part. It is curved and has extremely high surface rigidity.

In this case, even if the rear wall of the cross member portion is positioned rearward, the rigidity of the boss portion does not decrease, so that a large longitudinal width of the vehicle body can be secured for the cross member portion. Incidentally, in the case where the boss portion is provided on the rear side of the through hole, if the rear wall of the cross member portion is to be positioned rearward, additional reinforcement is required since the surface rigidity of the location where the boss portion is formed will decrease.

Furthermore, since the exhaust pipe is arranged to cross the rear of the boss section, this exhaust pipe functions to block mud thrown up from the rear wheels, and prevents mud from adhering to the shock absorber connection area. can.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1 to 6 are diagrams for explaining a rear arm of a motorcycle according to an embodiment of the present invention.

In the figure, reference numeral 1 denotes a motorcycle in which the rear arm of this embodiment is adopted, and its body frame 2 is made of cast material, and has a cylindrical steering shaft tube 3 and a pair of left and right main frames 4 of a box-like structure made of sheet metal. The front parts of the main frame 4 are welded together, and the rear ends of the main frame 4 are welded and connected with a back stay 5. The upper left end of the back stay 5,
A seat rail 6 made of a square pipe is connected to the rear end of a connecting portion 5a formed on the right side. Note that 7 is a reinforcing member that connects the backstay 5 and the main frame 4, and 8 is a reinforcing member that connects the rear wall of the backstay 5 and the seat rail 6.

Further, a front fork 10 that pivotally supports a front wheel 9 is supported at the lower end of the steering shaft cylinder 3 of the vehicle body frame 2, and a fuel tank 11 and a seat 12 are mounted on the upper part of the main frame 4, seat rail 6, etc. has been done. Furthermore, a water-cooled two-stroke V-type four-cylinder engine unit 13 is suspended below the rear half of the main frame 4, and the engine unit 13 and the body frame 2 are surrounded by a rectifying cowling 31. .

The front end of the rear arm 14 of this embodiment is pivotally supported at the rear end of the main frame 4. This rear arm 14 is constructed by welding the front parts of left and right arm parts 15 and 16 together at a cross member part 17, and fixing a pivot tube (pivot part) 18 by welding to the front end of the cross member part 17. The pivot tube 18 is pivotally supported by a pivot shaft 18a inserted into a pivot hole formed in the rear end of the main frame 4. Further, a shock absorber 32 of the rear wheel suspension system is inserted into a through hole 17b made of a cylindrical body formed in the cross member portion 17, and the upper end of the shock absorber 32 is formed in the backstay 5. The lower ends of the shock absorber support parts are each connected to a link mechanism 33.
This link mechanism 33 connects the connecting bracket 4e at the lower end of the main frame 4 and the boss portion 17c on the lower surface of the cross member portion 17. Here, the boss portion 17c is formed in a portion between the through hole 17b and the arm portions 15 and 16 on the lower surface of the cross member portion 17. Further, an axle support bracket (wheel part) 19 is fixed to the rear ends of the left and right arm parts 15, 16, and the rear wheel 21 is supported by the rear wheel inserted into the support hole 19a of the bracket 19. It is pivoted.

Further, the left arm portion 15 is connected to the pivot tube 1.
It has an upwardly convex triangular shape whose base is a straight line connecting 8 and support bracket 19, and a reinforcing arm 23 which forms the rear oblique side of the triangle is attached to the upper surface of the linear main arm 22 which forms the base. is arranged in an inclined manner such that the front side is higher, and its rear end is welded and fixed to the main arm 22 and its front end to the rear wall of the cross member portion 17, which forms the front oblique side of the triangle. . The space surrounded by the base of the triangle and the front and rear hypotenuses is a chain arrangement space 25 for passing the rear wheel drive chain 26.
It is becoming. Note that 24 is a reinforcing member.

On the other hand, the right arm part 16 is box-shaped, which is formed by welding a pair of left and right U-shaped sheet metal members 16a and 16b against each other, and is bent into an upwardly convex shape when viewed from the side. The front and rear hypotenuses of an upwardly convex triangle whose base is the straight line connecting the pivot tube 18 and the support bracket 19 described above are formed. Further, the right end of the cross member portion 17 is welded and connected to the front inclined portion 16c of the right arm portion 16, and the lower surface shape of the connecting portion 17a is as follows.
The front inclined portion 16c has an inclined shape that continues to the lower surface of the front inclined portion 16c. In this way, the right arm section 16
The space below the bent portion is a piping space 30 for leading out an expansion pipe of an exhaust device to be described later. Note that 16d is a bead-shaped recess for improving strength.

Further, the left and right exhaust devices 28 and 29 connected to the left and right cylinders 27a located below the engine unit 13 are connected to the left and right cylinders 27a located below the engine unit 13, as shown in FIG. The exhaust pipes 28a and 29a intersect at a lower position. The expansion pipe 28b portion of the left exhaust device 28 is guided outward in the vehicle width direction at the front side of the piping space 30 formed in the right arm portion 16.
It extends diagonally upward on the side of the right arm portion 16, and a muffler 28c is connected to the rear end.
Further, the expansion pipe 29b portion of the right exhaust device 29 is curved below the cross member portion 17 so as to bypass the link mechanism 33, and then curved in the piping space 30 along the rear part of the left expansion pipe 28b. It is led out and extends obliquely upward, and a muffler 29c is also connected to the rear end. Although not shown, the upper cylinder 2
The left and right exhaust devices connected to 7b extend rearward along the upper side of the vehicle.

Next, the effects of this embodiment will be explained.

As described above, in order to increase the bank angle of the motorcycle, parts located outward in the vehicle width direction need to be placed upward. On the other hand, when the exhaust system is arranged below the rear arm so as to cross it in the vehicle width direction, especially when the large-diameter expansion pipe section is located at the above-mentioned crossing position, as in the case of a two-stroke exhaust system, this part is located in a low place, and the minimum ground clearance is low, which is disadvantageous in gaining a bank angle. In contrast, in this embodiment, the entire right arm portion 16 of the rear arm 14 is bent in an upwardly convex F-shape to actively form the piping space 30.
Exhaust devices 28, 29 in the space 30 part
Since the expansion tubes 28b and 29b were led out,
The minimum ground clearance can be increased while ensuring sufficient expansion chamber capacity, and the bank angle can be increased.

In addition, in this embodiment, the left and right arm portions 15,
16 are formed in an upwardly convex triangular shape with the base being a straight line connecting the pivot tube 18 and the support bracket 19 when viewed from the side, and having substantially the same height.As for the left arm portion 15, a chain arrangement space 25 is formed. The piping space 30 is provided for the right arm section 16.
, the amount of parts used for each arm portion is approximately equal. Therefore, the weight of the left and right arm sections is balanced, and the section modulus, that is, the rigidity, is also balanced. Therefore, there is no need to specially reinforce any of the arm portions to balance the rigidity, or add any extra members to balance the weight, and the shape does not become complicated.

Furthermore, the left arm portion 1 located on the chain side
Regarding No. 5, since the chain placement space 25 is between the bottom part and the oblique part, the chain 26
can be passed through without difficulty.

Further, in this embodiment, since the boss portion 17c connecting the link mechanism 33 is formed between the through hole 17b on the lower surface of the cross member portion 17 and the left and right arm portions 15 and 16, the shock absorber 32 and the link Mechanism 33
etc. can be placed as far forward as possible. As a result, the problem that the concave space below the arm is substantially narrowed by the shock absorber 32 etc. can be avoided, and the concave space can be effectively used as a piping space.

Furthermore, since the boss portion 17c is located between the through hole 17b of the cross member portion 17 and the arm portions 15, 16, the rigidity of both the positions where the boss portion 17c is formed can be improved. That is, this boss portion 17c
Nearby are the cylindrical body forming the through hole 17b, the top plate and bottom plate of the cross member part 17, and the arm part 15,
16 and has a closed cross section, and has extremely high surface rigidity.

〔Effect of the invention〕

As described above, according to the rear arm of a motorcycle according to the present invention, one arm portion is bent upwardly in a convex manner, and the concave space below the bend is used as the piping space for the exhaust device, so that large diameter expansion is possible. Even when the pipe section is placed in this space, the minimum ground clearance can be increased and a sufficient bank angle can be ensured, and the shock absorber connection boss section can be placed between the shock absorber through hole and the arm section. Since it is formed in between, it is possible to avoid the problem of a shock absorber or the like substantially narrowing the concave space below the arm, and it is also possible to improve the surface configuration near the position where the boss is formed.

[Brief explanation of drawings]

1 to 6 are diagrams for explaining a rear arm according to an embodiment of the present invention. FIG. 1 is a right side view of the rear arm, and FIG.
Line sectional view, Figure 3 is a left side view of the rear arm, Figure 4 is a plan view of the rear arm, Figure 5 is a bottom view of the rear arm showing the arrangement of the exhaust system, and Figure 6 is the rear arm of this example adopted. FIG. 2 is a side view of the motorcycle. In the figure, 1 is a motorcycle, 4 is a main frame (body frame), 14 is a rear arm, 15,
16 is the left and right arm parts, 17 is the cross member part,
18 is a pivot tube (pivot part), 19 is a support bracket (axle part), 21 is a rear wheel, 22 is a main arm (lower pipe part), 23 is a reinforcement arm (upper pipe part), 25 is a chain arrangement space, 26 is a chain, 28b and 29b are expansion pipes (exhaust device),
30 is a piping space.

Claims (1)

[Claims] 1. The front parts of the left and right pair of arm parts are connected by a cross member part, and the pivot part of the rear arm, which is formed by bending one of the arm parts into an upwardly convex substantially V-shape, is pivotally supported by the vehicle body frame. In addition, in a motorcycle in which a rear wheel suspension device disposed approximately at the center of the vehicle body is connected to the vicinity of the cross member portion, and the rear wheel is pivotally supported at the rear end portion of the arm portion, the rear wheel suspension device is connected to the cross member portion. A through hole made of a cylindrical body is formed to pass downward through the lower part of the shock absorber of the device, and the through hole is located near the front end of the concave space formed below the bend of the arm portion, and the cross member portion A boss part is formed between the through hole and the arm part to connect the shock absorber via a link plate, and an exhaust pipe is connected from one side of the vehicle body between the boss part and the rear wheel diamond. and a concave space formed below the bend of the arm portion, and piping is provided so as to cross to the other side.