JPH03114989A - Rear arm for motorbicycle - Google Patents

Abstract

PURPOSE:To increase a minimum height and ensure a sufficient bank angle even when an expanded pipe portion of large diameter is laid in space formed with one of arm parts so bent as to be turned down at both ends, by bending the arm part as aforementioned and using the recessed space below the bent part as piping space for an exhaust device. CONSTITUTION:One arm part 16 is so formed as to have the oblique line of a triangle projected upward with a line between a pivot part 18 and an axis part 19 as a base viewed from the side. Recessed space formed under the bent part is used as piping space 30 for an exhaust pipe so laid as to be extended out from the inner side of a body. Furthermore, the other arm part 17 is formed with a linear lower pipe part 22 forming the base of the triangle and an upper pipe part 23 forming the oblique line thereof, and space between the upper and lower pipe parts 22 and 23 is used as the chain arrangement space 25 where a chain 26 passes.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is installed in the rear arm of a motorcycle, and in particular, by securing piping space for the exhaust system, the bank angle can be increased, and the left and right arm portions can be This invention relates to an improvement in the shape of the arm part that can balance the weight of the vehicle and secure a space for disposing a rear wheel drive chain.

[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 under 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 This tends to narrow the bank angle of the engine, especially in the case of vehicles equipped with 2-stroke engines, because the expansion pipe that leads to this part has a large diameter, which lowers the minimum ground clearance. There is a possibility that the bank angle cannot be secured.

Therefore, as an exhaust system for motorcycles that can relax the bank angle regulation by the expansion pipe, conventionally, as described in Japanese Patent Application Laid-Open No. 62-23889,
The expansion tubes are arranged below the engine unit in a reverse cross section when viewed in cross section, and the outer corners of the lower ends of each expansion tube are cut along the bank angle line determined by the footrest. is proposed.

[Problem to be solved by the invention]

According to the exhaust device described in the above-mentioned publication, the portion of each expansion tube that first contacts the ground during banking has a canted shape, so that the bank angle can be increased accordingly. However, in this structure, as the bank angle increases, the cant area needs to be increased, so there is a risk that the required expansion chamber capacity 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, in the rear arm developed above, the left side.

The shape of the right arm is different, so the left,
There is a concern that the weight and rigidity of the right arm may 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, an object of the present invention is to provide a motorcycle that can increase the bank angle while securing the necessary expansion chamber volume, and that can ensure a balance between the weight and rigidity of the left and right arm sections. The point is that it provides a rear arm.

(Means for solving !III) The present invention connects the front parts of a pair of left and right arm parts with a cross member part, and the front end pivot part is pivotally supported on the vehicle body frame, and the rear In a rear arm of a motorcycle that pivotally supports a rear wheel with an axle portion at the end, when one of the arm portions is viewed from the side, the hypotenuse side of an upwardly convex triangle whose base is a line connecting the pivot portion and the axle portion. The concave space formed below the bent part is used as a piping space in which the exhaust pipe is arranged to extend from the inside of the vehicle body to the outside. It is characterized in that it is formed by a linear lower pipe part and an oblique upper pipe part, and the space between the upper and lower pipe parts is used as a chain arrangement space through which the chain 7 passes.

Here, the piping space in the present invention refers to a space for piping a part of the exhaust system, that is, the part that crosses the lower part of the rear arm.In the case of an exhaust system for a two-stroke engine, generally this piping space is The expansion tube portion of the diameter will be located.

[For production]

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 that are unavoidable at a high location.For example, as mentioned above, when piping the exhaust pipe from below the engine to cross below the rear arm,
This cross section will be located outward and at a low location,
As it is, it is difficult to meet the above request from the viewpoint of securing a bank angle.

In contrast, in the present invention, one of the arm parts is bent convexly upward, and the concave space formed below the bent part is used as the piping space for the exhaust system, so that it is located outside due to the arrangement structure. The cross section of the exhaust pipe, which is unavoidable, can be positioned upward, meeting the above-mentioned requirements, and the bank angle can be expanded accordingly.

In addition, in the present invention, the arm portion is bent to actively secure piping space, so 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 pipe portion, and sufficient piping space is secured. The expansion chamber volume can be secured and engine performance will not be affected.

In the present invention, both the left and right arm sections have a triangular shape that is upwardly convex and has substantially equal heights, with the base being the straight line connecting the pivot section and the axle section when viewed from the side, and one A piping space is formed for the arm portion, and a chain arrangement space is formed for the other arm portion. Therefore, the amounts of parts used in the left and right arm portions are approximately equal, resulting in a balance in weight and rigidity. Further, since a chain placement space is formed in the other arm portion located on the side of the rear wheel drive chain, the chain 7 can be passed therethrough without any problem.

〔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 ends of the main frame 4 are connected by welding, and the back stay 5 is welded and connected between the rear ends of the main frame 4. A seat rail made of a square pipe is attached to the rear end of the connection part 5a formed on the left and right upper ends of the back stay 5. It is constructed by connecting 6. In addition, 7
8 is a reinforcing member connecting the backstay 5 and the main frame 4, and 8 is the rear wall of the backstay 5 and the seat rail 6.
This is a reinforcing member that connects the

Further, a front fork 1O which pivotally supports a front end 9 at its lower end is supported on the steering shaft tube 3 of the vehicle body frame 2, and a fuel tank 11.
A seat 12 is mounted.

Further, below the rear half of the main frame 4, a water-cooled type 2
A cycle V-type four-cylinder engine unit 13 is suspended, and the engine unit 13 and the vehicle 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 1
4 connects the front parts of the left and right arm parts 15 and 16 by welding with a cross member part 17, and the cross member part 17
A pivot tube (pivot part) 18 is welded and fixed to the front end of the main frame 4, and the pivot tube 18 is pivotally supported by a pivot shaft 18a inserted into a pivot size formed at the rear end of the main frame 4. ing. Further, a shock absorber 32 of the rear wheel suspension system is inserted into the through hole 17b formed in the cross member portion 17, and the upper end of the shock absorber 32 is connected to the shock absorber 32 formed in the backstay 5. The support portion and the lower end are connected to a link mechanism 33, respectively. This link mechanism 33 connects the connecting bracket 4e at the lower end of the main frame 4 and the connecting bracket 17c at the lower surface of the cross member portion 17. Also, above left.

An axle support bracket (axle part) 19 is fixed to the rear end of the right arm part 15, 16, and a rear wheel 21 is pivotally supported by a rear wheel fitted into a support hole 19a of the bracket 19.

Further, the left arm portion 15 has an upwardly convex triangular shape whose base is a straight line connecting the pivot cylinder 18 and the support bracket 19, and the upper surface of the linear main arm 22 forming the base is A reinforcing arm 23 forming the rear oblique side of the triangle is arranged in an inclined manner such that the front side is higher.The rear end of the reinforcing arm 23 is connected to the main arm 22, and the front end is connected to the rear of the cross member portion 17 forming the front oblique side of the triangle. Each is welded and fixed to the wall. The space surrounded by the base of the triangle and the front and rear hypotenuses is a chain arrangement space 25 through which the rear wheel drive chain 26 is passed. Note that 24 is a reinforcing member.

On the other hand, the right arm section 16 is box-shaped, formed by welding a pair of left and right U-shaped sheet metal members 16a and 16b, and is bent into an upwardly convex U-shape when viewed from the side. The above-mentioned pivot cylinder 18 and support bracket 1
It forms the front and rear oblique sides of an upwardly convex triangle whose base is the straight line connecting 9. In addition, the above cross member part 1
The right end of 7 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 an inclined shape that continues to the lower surface of the front inclined portion 16c.

In this way, the space below the bent portion of the right arm portion 16 serves as 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 circular portion for improving strength.

In addition, the left side located below the engine unit 13,
Left and right exhaust devices 28 connected to the right cylinder 27m.
29, as shown in FIG. 5 when viewed from the bottom, the exhaust pipe 28a,
The portions 29a intersect. 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 I6.
It extends diagonally upward on the side of the right arm portion 1G, and a muffler 28C is connected to the rear end. Further, the expansion pipe 29b portion of the right exhaust device 29 is connected to the cross member portion 1.
After curving to bypass the link mechanism 33 below 7, the left expansion pipe 28b is opened in the piping space 30.
The muffler 29C is guided outward along the rear portion and extends diagonally upward, and the muffler 29C is also connected to the rear end. Although not shown, the left and right exhaust devices connected to the upper cylinder 27bg extend rearward along the upper side of the vehicle.

Next, the effects of this embodiment will be explained.

As mentioned above, to increase the bank angle of a motorcycle,
Components located outward in the vehicle width direction need to be placed upward. On the other hand, when the exhaust system is placed below the rear arm and across the vehicle width direction,
When a large-diameter expansion pipe section is located at the above-mentioned crossing position, as in a cycle exhaust system, this section is located at a low location, resulting in a low minimum ground clearance, which is disadvantageous in gaining a bank angle. In contrast, in this embodiment, the right arm portion 16 of the rear arm 14
By bending the entire structure in an upwardly convex F-shape, a piping space 30 is actively formed, and the expansion pipes 28b and 29b of the exhaust device 28, 29 are led out to the outside in the space 30, so that the expansion The minimum ground clearance can be increased while ensuring sufficient room capacity, and the bank angle can be increased.

In addition, in this embodiment, the left and right arm portions 15° and 16 are
Pivot tube 1B and support bracket 19 in both side views
It is formed into an upwardly convex triangular shape with a straight line connecting them as its base and approximately the same height, and a chain placement space 25 is provided for the left arm portion 15, and a piping space 30 is provided for the right arm portion 16. Therefore, 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 specifically reinforce any of the arm sections to balance the rigidity, or add any extra members to balance the weight, and the shape etc. does not become complicated.

Furthermore, regarding the left arm portion 15 located on the chain side, a chain placement space 25 is provided between the bottom side and the oblique side, so that the chain 26 can be passed through easily.

〔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 and #sW
! Since the concave space below the i-curve is used as the piping space for the exhaust system, the minimum ground clearance can be increased and a sufficient bank angle can be secured even when a large-diameter expansion pipe is placed in the space. In addition, the left and right arms are triangular in side view with an empty piping space or chain placement space, so it is possible to balance the weight and rigidity of the left and right arms, and it is possible to balance the weight and rigidity of the left and right arms, making it possible to use a rear-wheel drive chain. It has the effect of being able to be inserted without any problems.

[Brief explanation of drawings]

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

Claims (1)

[Claims] (1) The front parts of a pair of left and right arm parts are connected by a cross member part, and the pivot part at the front end is pivotally supported by the vehicle frame, and the rear wheel is pivotally supported by the axle part at the rear end. In the rear arm of a motorcycle, one of the arm portions is formed into a bent shape forming an oblique side of an upwardly convex triangle whose base is a line connecting the pivot portion and the axle portion when viewed from the side, and the bent portion The concave space formed below is used as a piping space for arranging the exhaust pipe so as to extend from the inside of the vehicle body to the outside, and the other arm part forms the oblique side of the straight lower pipe part that forms the base of the triangle. A rear arm for a motorcycle, characterized in that the rear arm is formed with an upper pipe part, and the space between the upper and lower pipe parts is used as a chain placement space through which the chain passes.