JPH03135890A - Frame for motorcycle - Google Patents

Abstract

PURPOSE:To arrange an exhaust pipe near the center part by dividing down tubes on the right and left into two, respectively, by forming a lower side down tube in such a manner that the width thereof is formed narrower as it goes downward from a connection part with an upper side down tube, and by arranging the rear part of the lower side down tube near the center part in an engine width direction. CONSTITUTION:A down tube 8 supporting the front side of an engine 6 is divided into two, into upper side and lower side down tubes 8a, 8b, and the right and left lower side down tubes 8b are formed in such a manner that the interval thereof becomes narrower as they go downward from a connection bolt 9. The rear side part thereof is extended near the center part in the engine 6 direction, horizontally, on the lower part of the engine 6. Right and left exhaust pipes 30, 31 are crossed with each other in such a manner that they are dislocated in a back-and-forth direction, whereby chamber parts 30a, 31a of large cross sectional area can be arranged near the center part in the engine 6 width direction, and in the vicinity of the lower part of the engine 6. Bank angle can thus be enlarged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a frame for a motorcycle, and particularly to the structure of a down tube thereof.

[Conventional technology]

Conventionally, one of the frames for motorcycles is a double cradle type, in which a pair of left and right down tubes that support the engine pass from the head pipe under the engine and are connected to the main frame near the rear arm support part. .

The down tubes used in this double cradle type frame extend diagonally from the head pipe to the front of the engine to the rear and lower side, and the distance between them gradually widens as they move downward from the head pipe. It was extended near the lower corner of the engine to provide reliable support for the engine.

[Problem to be solved by the invention]

However, if a parallel two-stroke engine, in which the exhaust pipe passes below the engine, is mounted on a frame in which the downtube is placed near the lower corner of the engine, the large diameter of the two exhaust pipes will increase. To avoid interference with the downtube, move the part below the engine and outward in the vehicle width direction.
Alternatively, it must be shifted to the bottom of the engine. Therefore, the distance between the exhaust pipe and the road surface becomes smaller, and the bank angle becomes narrower. Additionally, there is a problem in that if the down tube is bent and formed into a complicated shape like the conventional down tube, the manufacturing cost increases.

[Means to solve the problem]

In the motorcycle frame according to the present invention, a pair of left and right down tubes that pass under the engine and are connected near the rear arm support portion of the main frame are connected from the head pipe to the front of the engine with an interval wider than the width of the cylinder portion. It is divided into two parts: an extending upper down tube and a lower down tube connected to the lower end of the upper down tube and detachably attached to the main frame,
The distance between the left and right lower down tubes is gradually narrowed downward from the connecting portion with the upper down tube, and the rear part of the lower down tube is
It is arranged in a space surrounded by the engine and an exhaust pipe extending in the front-rear direction below the engine.

[For production]

Since the rear portions of the left and right lower down tubes are placed closer to the center in the width direction of the engine, the exhaust pipe can be placed closer to the bottom of the engine and closer to the center in the width direction of the engine. .

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 to 9.

FIG. 1 is a side view showing a motorcycle employing the motorcycle frame according to the present invention, FIG. 2 is an enlarged side view showing the main parts of the motorcycle frame according to the present invention, and FIG. 3 is the same. A front view, FIG. 4 is a side view showing an enlarged seat rail portion of the motorcycle frame according to the present invention, FIG. 5 is a plan view, and FIG. 6 is a cushion of the motorcycle frame according to the present invention. FIG. 7 is an enlarged plan view showing the unit connecting portion; FIG. 7 is an exploded perspective view showing the connecting portion between the upper down tube and the lower down tube used in the motorcycle frame according to the present invention; FIG. 8 is an enlarged plan view showing the connecting portion of the unit; 9 is a plan view showing the exhaust pipe, and FIG. 9 is a sectional view taken along the line IX-f in FIG. 1. In these figures, l indicates a frame for a motorcycle according to the present invention, and this frame 1 includes a head pipe 2, a pair of left and right main pipes 4 connected to the head pipe 2 and supporting a fuel tank 3, and A rear arm bracket 7 is connected to the rear end of the main pipe 4 and supports the rear side of the engine 6 via a bracket 5 for mounting the engine, and a rear arm bracket 7 is disposed below the main pipe 4 and supports the front side of the engine 6. It is composed of a pair of left and right down tubes 8, etc.

The main pipe 4 is made of a single pipe material with a circular cross section,
The front end is welded to the head pipe 2 and extends downward toward the rear of the vehicle body. Further, the engine 6 is a two-stroke parallel two-cylinder engine, and includes a cylinder portion 6a and a crankcase 6b.

The down tube 8 includes an upper down tube 8a that is welded to the lower part of the head pipe 2 and extends obliquely from the hend pipe 2 to the rear and lower side in front of the engine 6, and from the lower end of the upper down tube 8a to the engine 6. The frame is divided into two parts, including a lower down tube 8b which passes through the lower side of the frame and extends to the rear arm bracket 7. The left and right upper down tubes 8a are each formed of a tube material having a circular cross section, and the distance between them gradually increases as you go downward from the head pipe 2, and the distance at the lower end is larger than the width of the cylinder portion 6a of the engine 6. It is designed to be wide. Further, a reinforcing cross pipe 8C is horizontally suspended at the widest part of the upper down tube 8a. The lower down tube 8b is formed of a tubular material with a circular cross section, and its front end is connected to the lower end of the upper down tube 8a by a connecting bolt 9, and its rear end is attached to the rear arm by a bolt 1-10. It is fixed to the lower part of the bracket 7. Further, as shown in FIGS. 2 and 3, the front portions of the left and right lower down tubes 8b are oriented substantially directly above in side view, and as they go downward from the tips, the left and right lower down tubes 8b The intervals are gradually narrowed, and the rear portion is bent along the crankcase 6b of the engine 6 so as to extend rearward substantially horizontally below the engine 6. A cross vibe 8d equipped with a bracket 11 for mounting the engine is mounted horizontally on the bent portion of the left and right lower down tubes 8b, and a portion extending below the engine 6 is attached to the vehicle body frame. A cross pipe 8e is brought into contact with a compression member 12 that counteracts the chain tension of the elastically supported engine 6.
is suspended horizontally. Furthermore, at the connecting portion between the upper down tube 8a and the lower down tube 8b, a pair of connecting members 13.14 are fastened by two upper and lower connecting bolts 9.9, as shown in FIG. It has been intervened. These connecting members 13 and 14 connect to the upper down tube 8.
The connecting portions 13a and 14a have a substantially oval shape in side view and are formed to have a thickness approximately half the diameter of a, and are inserted and fixed into the respective tip openings of the upper and lower down tubes 8a and 3b. The connecting portion 13a of the connecting member 13 attached to the upper down tube 8a is positioned outward in the vehicle width direction from the axis of the upper down tube 8a, and has two bolt holes 13b, upper and lower, through which the connecting bolts 9 are inserted. ing. This bolt hole 13b is connected to the frame 1. When the lower down tube 8b and the upper down tube 8a become misaligned due to machining errors in the lower down tube 8b, etc., the opening dimensions of the connecting bolts 9 are adjusted so that the mounting position can be slightly changed. It is set larger than the diameter. Furthermore, in this embodiment, the connecting portion 14a of the connecting member 14 attached to the lower down tube 8b is inserted into a position corresponding to the upper bolt hole of the two bolt holes 13b in the connecting member 13. A bolt hole 14b is drilled, and a screw hole 14c into which the connecting bolt 9 is screwed is provided at a position corresponding to the lower bolt hole. That is, in order to connect the upper down tube 8a and the lower down tube 8b, first, the connecting portion 13a is installed inside the connecting member 13.

The connecting members 14 are arranged with the 14a overlapped, and then the two connecting bolts 9.9 are inserted into the bolt holes 13 from the outside.
Insert it into b. Then, the lower connecting bolt 9 is screwed onto the connecting member 14, and the upper connecting bolt 9 is passed through the reconnecting parts 13b and 14b and tightened with a nut on the inside. In this way, the upper and lower down tubes 8a and 8b can be connected.

15 is a seat rail for supporting the seat 16; 17;
is a backstay that supports the rear part of the seat rail 15. The seat rail 15 includes a front seat rail 15a which is butt welded to the main vibe 4 of the frame 1, and is connected to the rear end of the front seat rail 15a via a back stay connecting tube 18 and extends rearward. and the rear seat rail 15b. The back stay 17 has a front end connected to the rear end of the main vibe 4 via a tube 4a, and a rear end connected to the tube 18. As shown in FIGS. 4 and 5, the tubular body 18 is arranged so that its axis is substantially parallel to the vehicle width direction, and has a rear end of the front seat rail 15a and a front end of the rear seat rail 15b. and the rear ends of the pack stay 17 are butt welded. The welding position of the rear seat rail 15b to the tubular body 18 is set to a position shifted inward in the vehicle width direction from the welding position of the front seat rail 15a. Further, a lid 18a is provided inside the tubular body 18 to close the hollow portion thereof. In addition,
A tail cowl 19 is fixed to the seat rail 15 and the backstay 17. This tail cowl 1
9 is formed to cover the sides of the rear seat rail 15b and expose the back stay 17 and tube body 18. Further, the portion of the tail cowl 19 that corresponds to the back stay 17 and the tube body 18 is formed such that the most outwardly protruding portion thereof is substantially continuous with the outermost portion of the back stay 17 and the tube body 18. The bumps on the sides of the vehicle body are designed to be as small as possible.

20 is an outer pipe of a front fork that suspends the front wheel 21; 22 is a handle for operating this front fork; these are attached to the head pipe 2 of the frame 1;
It is rotatably supported. Note that 23 is a front fender attached to the outer pipe 20 of the front fork.

Reference numeral 24 denotes a rear arm for supporting a rear wheel 25, and this rear arm 24 is swingably supported by the rear arm bracket 7 of the frame 1. A cushion unit 26 is interposed between the rear arm 24 and the frame 1. The lower end of the cushion unit 26 is connected to the rear arm 24 via a link 27, and the upper end is connected to the frame 1. The support bracket 28 is pivotally connected to the support bracket 28 . This support bracket 28, as shown in FIG.
A gate-shaped cross pipe 28a that projects upward and is hung horizontally between the left and right main pipes 4, and this cross pipe 28
a gate-shaped cross pipe 2 that is connected to the top of
8b, and a connecting plate 28c that is provided at the top of both of these cross pipes 28a, 28b and supports a cushion unit connecting bolt. By using this support bracket 28, the cushion unit 26
The upper end portion of can be supported above the main pipe 4.

Reference numerals 30 and 31 denote exhaust pipes connected to the two cylinders of the engine 6, respectively. These exhaust pipes 30 and 31 are connected to the front sides of the left and right cylinder parts 6a of the engine 6, respectively, and extend from the front to the bottom of the engine 6. It is passed through and extended to the rear right side of the vehicle body. Further, both the exhaust pipes 30
．． In the part located below the engine 6 in 31,
Chamber portions 30a and 31a, each having a nearly circular cross-section and a larger cross-sectional area than other portions, are provided substantially parallel to each other. In addition, both left and right exhaust pipes 30.31 are
From the exhaust port of the engine 6 to the channel section 30a, 31a
The dimensions are set to be approximately equal to the rear end. As shown in FIG. 3, the front parts of these exhaust pipes 30 and 31 intersect with each other in front of the engine 6.
The exhaust pipe 30 connected to the right cylinder of the engine 6 is bent in front of the engine 6 and extends to the left, and the exhaust pipe 31 connected to the left cylinder is bypassed in front of the exhaust pipe 30 and extends to the right. It is set up.

The exhaust pipe 30 extending to the left side has a relatively short front bent portion and the chamber part 30a is disposed on the rear side.
5 and the link 27, and extends to the right side of the vehicle body. In addition, since the exhaust pipe 31 extending to the right side passes through the front side of the exhaust pipe 30, the front bent portion has a long dimension, so that the chamber part 31a is connected to the other exhaust pipe. 30 is disposed on the front side of the chamber part 30a. That is, both chamber parts 30a, 31a
Since the thickest part of the chamber is shifted forward and backward, both chamber parts 30a and 31a can be arranged closer to the center in the vehicle width direction.

32 is a silencer provided at the rear end of each exhaust pipe 30.31; 33 is an exhaust pipe stay for supporting the rear part of both exhaust pipes 30.31;
．． It is configured to hold 31 silencers 32 from both sides at once, and is connected to the back stay 17 or attached to the lower end of the footrest bracket 34. 35 is a fuel cock of the fuel tank 3;
This fuel cock 35 is disposed within the recess 3a of the fuel tank 3. The recess 3a of the fuel tank 3 is
It is formed by recessing a portion of the bottom portion of the frame 1 upward that corresponds to the connecting portion between the main pipe 4 and the front seat rail 15a.

In addition, 36 is a radiator attached to the upper down tube 8a of the frame 1, 37 is a carburetor attached to the crankcase 6b of the engine 6, and 38 and 39 are connecting pipes connecting the main pipe 4 and the upper down tube 8a. It is. Further, a chain double-dashed line A in FIG. 1 indicates the position of the front fender 23 when the front fork is most retracted.

In order to mount the engine 6 on the motorcycle frame constructed in this way, first, the rear side of the engine 5 is attached to the engine mounting bracket 5 of the rear arm bracket 7. Next, attach the rear end of the lower down tube 8b to the rear arm bracket 7 with bolts 10.
It is attached to the lower part of the rear arm bracket 7 and held by the rear arm bracket 7. To attach the engine to the lower down tube 8b, attach the front side of the engine 6 to the bracket 11, and finally fix the front end of the lower down tube 8b to the lower end of the upper down tube 8a with a connecting bolt 9. It will be equipped with engine 6.

That is, when the engine 6 is mounted on the motorcycle frame according to Zero's invention in this manner, the rear part of the lower down tube 8b is disposed closer to the center of the engine 6 in the width direction.

Therefore, in the motorcycle frame according to the present invention, since the space below both lower side portions of the engine 6 can be widened, the large diameter portions of the exhaust pipes 30 and 31 can be brought close to the lower part of the engine 6. As well as being able to
It can be placed closer to the center of the engine 6 in the width direction.

In addition, as shown in this embodiment, the lower down tube 8b
The front part of 1. By bending the tip so that it points substantially directly above when viewed from the side, the lower end of the upper down tube 8a can be brought closer to the cylinder portion 6a of the engine 6, so the radiator 36 can be brought closer to the engine 6. . That is, by bringing the radiator 36 closer to the engine 6, the front fork can be placed rearward to the extent that the front fender 23 and the radiator 36 do not come into contact when the front fork is fully retracted. By shortening the base, the vehicle body can be made smaller.

Furthermore, according to this embodiment, the rear seat rail 15
b is welded to the tube body 18 while being shifted inward in the vehicle width direction from the front seat rail 15a, so that the side part of the tail cowl 19 is on approximately the same plane as the front seat rail 15a and the side edge of the tube body 18. can be placed. Therefore, the side portions of the tail cowl 19 can be formed substantially flat without extending outward in the vehicle width direction in order to avoid interference with the seat rail 15.
The width of the vehicle body can be reduced.

Further, in this embodiment, the front parts of the exhaust pipes 30 and 31 are crossed with each other in front of the engine 6, so that the chamber parts 30a and 31
Since the position of the maximum diameter part a is shifted back and forth, both chamber parts 30a and 31a can be arranged closer to the center in the vehicle width direction.

Therefore, it is possible to prevent the large-diameter portions of the chamber parts 30a and 31a from being recessed inwardly so that they do not contact the road surface. The large diameter portions of 30a and 31a can be formed so that the cross section has a shape close to circular. Further, the chamber part 30a disposed on the left side of the vehicle body has its rear part passed between the rear wheel 25 and the link 27 and extends to the right side of the vehicle body, so that a portion of the chamber part 30a on the left and right side is disposed on the left side of the vehicle body. Since the large diameter portions of the exhaust pipes 30a and 31a do not overlap vertically, the minimum ground height can be lowered without the exhaust pipes 30 and 31 coming into contact with the road surface.

Also, if the front parts of the left and right exhaust pipes 30 and 31 intersect in front of the engine, and the chamber part 30a of the exhaust pipe 30 located on the rear side is passed through the front of the rear wheel 25 at the intersection, it crosses the vehicle body. Even if the rear part of the re-exhaust pipe is arranged on one side of the vehicle body and the position of the silencer 32 is approximately the same in the front and rear direction, the lengths from the connection part of the left and right exhaust pipes 30, 31 to the rear end of the tail pipe are made approximately equal. be able to.

Although this embodiment shows an example in which the rear portions of the exhaust pipes 30 and 31 extend to the right side of the vehicle body, they may also extend to the left side of the vehicle body. In this case, the exhaust pipe whose rear part of the chamber does not cross the vehicle body, in other words, the exhaust pipe whose part is connected to the right cylinder of the engine, is located in front of the other exhaust pipe at the front of the engine. will be passed through. In addition, in this embodiment, the front seat rail 15a
An example has been shown in which the left and right pipe bodies 18 connecting the rear seat rails 15b and 15b are formed separately, but this pipe body 18 is formed of a long pipe material that extends horizontally between the left and right seat rails 15 and 15. You can also.

In this way, the rigidity of the frame 1 can be increased.

〔Effect of the invention〕

As explained above, the motorcycle frame according to the present invention includes a pair of left and right down tubes that pass below the engine and are connected near the rear arm support portion of the main frame.
An upper down tube that extends from the head pipe toward the front of the engine with an interval wider than the width of the cylinder, and a lower down tube that is connected to the lower end of the upper down tube and is detachably attached to the main frame. The space between the left and right lower down tubes is gradually narrowed from the connecting part with the upper down tube toward the lower side, and the rear part of the lower down tube is formed so that the rear part of the lower down tube extends downwardly of the engine. Because the exhaust pipes are placed in a space surrounded by the engine and the exhaust pipes that extend along the direction of the It can be placed close to the engine, and it can also be placed closer to the center in the width direction of the engine.

Therefore, since the distance between the exhaust pipe and the road surface can be increased, the bank angle can be increased. Furthermore, since the down tube is formed in two parts, the shapes of the individual members are simple, which facilitates processing and reduces manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a motorcycle employing the motorcycle frame according to the present invention, FIG. 2 is an enlarged side view showing the main parts of the motorcycle frame according to the present invention, and FIG. 3 is the same. 4 is an enlarged side view showing the seat rail portion of the motorcycle frame according to the present invention, FIG. 5 is a plan view of the same, and FIG. 6 is a motorcycle frame glue 7 seat unit according to the present invention. FIG. 7 is an enlarged plan view showing the connection part, FIG. 7 is an exploded perspective view showing the connection part between the upper down tube and the lower down tube used in the motorcycle frame according to the present invention, and FIG. A plan view showing the exhaust pipe, FIG. 9 is a sectional view taken along the line IX-IX in FIG. 1. 1... Frame, 4... Main pipe, 6...
・・Engine, 7・・Rear arm bracket, 8・
...Down tube, 8a...Upper down tube, 8b...Lower down tube, 13.14...
...Connecting member, 30.31...Exhaust pipe, 30a, 3
1a... Part of the chamber.

Claims (1)

[Claims] A pair of left and right down tubes that pass under the engine and are connected near the rear arm support part of the main frame are connected to an upper down tube that extends from the head pipe to the front of the engine with an interval wider than the width of the cylinder part. The lower down tube is connected to the lower end of the upper down tube and is detachably attached to the main frame. The lower down tube is gradually narrower as it goes downward, and the rear part of the lower down tube is located in a space surrounded by the engine and an exhaust pipe that extends below the engine in the front-rear direction. Frame for motorcycles.