JP2777397B2 - Arrangement structure of intake and exhaust system of two-cycle engine for motorcycle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Applications) The present invention relates to a two-stroke engine for a motorcycle,
The present invention relates to an exhaust system arrangement structure.

(Prior Art) Conventionally, there is a motorcycle disclosed in Japanese Patent Application Laid-Open No. 59-53228.

According to this, the body frame of the motorcycle includes a main frame extending rearward and downward from a head pipe constituting a front portion thereof, and a rear arm bracket extending downward from a rear end of the main frame. A rear arm supporting a rear wheel is pivotally supported by a lower end of the rear arm bracket so as to be vertically swingable by a pivot shaft.

An engine is provided below the main frame and supported by the vehicle body frame. The engine includes a crankcase and a cylinder protruding forward and upward from the crankcase, and supplies fuel to the engine. A fuel supply device is provided, while an exhaust pipe extending rearward from the upper surface of the cylinder is provided. A power transmission case is attached to a rear portion of the crankcase, and the fuel supply device is disposed in a space sandwiched between upper surfaces of the crankcase and the power transmission case and the exhaust pipe.

Further, in the above configuration, conventionally, an output gear that supports a kick shaft that extends in the vehicle width direction and that inputs a kick force at an upper portion in the power transmission case, and that outputs a kick force input to the kick shaft, There is a type in which a return spring for urging the kick shaft around its axis opposite to the direction of action of the kick force is disposed in the power transmission case coaxially with the kick shaft.

(Problems to be Solved by the Invention) By the way, in the conventional technology, the rear wall of the crankcase and the output gear do not interfere with each other.
If the output gear is disposed in the power transmission case away from the rear of the crankcase, the following problem may occur.

That is, first, when the front and rear dimensions of the power transmission case become longer as the output gear moves away from the crankcase to the rear thereof, the mass can be concentrated between the engine and the power transmission case. And the drivability may be reduced accordingly.

Further, when the dimension in the front-rear direction of the power transmission case is increased as described above, there is a possibility that the rear end of the main frame descending rearward interferes with the rear upper end of the power transmission case in the vertical direction. In order to avoid this, the rear end of the main frame needs to be positioned higher. However, in this case, the rear end of the main frame and the pivot shaft, which is the pivot portion of the rear arm with respect to the rear arm bracket, move up and down. In the direction. Then, since the main frame does not extend linearly from the head pipe side toward the pivot shaft side, a large external force from the rear wheel is applied to the main frame via the rear arm and the pivot shaft. When the main frame is loaded, the main frame cannot support the external force as its axial force, and therefore, there is a possibility that the support cannot be strengthened.

Secondly, since the output gear has a large outer diameter, simply including the output gear in the power transmission case increases the vertical dimension of the power transmission case. The vertical dimension of the assembly of the power transmission case and the fuel supply device and the exhaust pipe disposed above the power transmission case becomes large, and it may be impossible to secure a sufficient ground clearance for the motorcycle. There is.

(Purpose of the Invention) The present invention has been made in view of the above-mentioned circumstances, and rationally arranges a fuel supply device and an exhaust pipe so as to concentrate mass of a vehicle body and to provide sufficient ground. The purpose is to be able to secure the height.

(Structure of the Invention) A feature of the present invention for achieving the above object is that a main frame 4 in which a body frame 2 extends rearward and downward from a head pipe 3 constituting a front portion thereof, And a rear arm bracket 6 extending downward from the rear end of the main frame 4. A rear arm 14 supporting a rear wheel 15 is pivotally supported by a pivot shaft 13 at the lower end of the rear arm bracket 6 so as to be vertically swingable. The engine 24 is disposed below the vehicle body frame 2 and supported by the vehicle body frame 2. The engine 24 includes a crankcase 33 and a crankcase 33.
A carburetor (fuel supply device) that includes a cylinder 35 that projects forward and upward from 33, and that supplies fuel to the engine 24.
On the other hand, an exhaust pipe 47 extending rearward from the upper surface of the cylinder 35 is provided, and a power transmission case 55 is attached to the rear of the crankcase 33.
The carburetor (fuel supply device) 42 is disposed in a space sandwiched between the upper surfaces of the power transmission case 33 and the power transmission case 55 and the exhaust pipe 47, and extends in the vehicle width direction at an upper portion in the power transmission case 55 To support the kick shaft 69 for inputting the kick force.
A first intermediate gear (output gear) 72 for outputting the kick force input to 69, and a return spring for urging the kick shaft 69 about its axis in the opposite direction to the action of the kick force
75 and the power transmission case on the same axis as the kick shaft 69.
(1) The first intermediate gear (output gear) 72 is disposed at one end of the kick shaft 69, and the return spring 75 is disposed at the other end of the motorcycle. The side of the crankcase 33
An intermediate portion in the axial direction of the kick shaft 69 is brought close to the rear wall of the crankcase 33 so that the front portion of the first intermediate gear (output gear) 72 overlaps the rear portion of the kick shaft 69. A middle part of the upper wall of the power transmission case 55 in the vehicle width direction is approached to a middle part of the power transmission case 55, and a concave portion 77 is formed on the upper surface of the power transmission case 55.
The lower part 81 of the carburetor (fuel supply device) 42 is fitted in the lower part 81.

(Operation) The operation of the above configuration is as follows.

(1) A first intermediate gear (output gear) 72 is provided at one end of the kick shaft 69, and a return spring 75 is provided at the other end of the kick shaft 69. An axial intermediate portion of the kick shaft 69 is made to approach the rear wall of the crankcase 33 so that the front portion of the first intermediate gear (output gear) 72 overlaps with the front portion.

Therefore, in order to prevent the first intermediate gear (output gear) 72 from interfering with the rear wall of the crankcase 33, the first intermediate gear (output gear) is moved away from the rear of the crankcase 33. In comparison with the arrangement of the power transmission case 72, the size in the front-rear direction of the power transmission case 55 including the first intermediate gear (output gear) 72 can be reduced.

Therefore, the assembly of the crankcase 33 and the power transmission case 55 is made compact, and mass concentration is achieved to improve the maneuverability.

Further, as described above, when the dimension of the power transmission case 55 in the front-rear direction is reduced, the rear end position of the power transmission case 55 moves to the front side, which is the crankcase 33 side, and the rear frame of the main frame 4 is lowered. The power transmission case from the rear end
55, the rear upper end part moves forward, and these vertical gaps increase. Therefore, the rear end of the main frame 4 can be lowered correspondingly, and can be approached to the pivot 13.

Therefore, the main frame 4 can be extended more linearly from the head pipe 3 side toward the pivot shaft 13 side, and the rear wheel 14 can be extended through the rear arm 14 and the pivot shaft 13. When a large external force from 15 is applied to the main frame 4, this kind of frame 4 can support the external force as its axial force, so that the support is strong.

(2) A midway portion of the upper wall of the power transmission case 55 in the vehicle width direction is made to approach an intermediate portion of the kick shaft 69 in the axial direction, and a concave portion 77 is formed on the upper surface of the power transmission case 55; The lower portion 81 of the vaporizer (fuel supply device) 42 is fitted into the recess 77.

For this reason, the power transmission case 55 and the carburetor (fuel supply device) disposed above the power transmission case 55 by the amount that the lower portion of the carburetor (fuel supply device) 42 is fitted into the recess 77 formed in the power transmission case 55. The vertical dimension of the assembly including the device 42 and the exhaust pipe 47 can be reduced, so that the motorcycle 1 can have a sufficient ground clearance.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 1, 1 is a motorcycle, and 2 is its body frame. The vehicle body frame 2 has a head pipe 3 at a front portion thereof, and a pair of left and right main frames 4 extends from the head pipe 3 toward a rear lower part. Each main frame 4 has a rectangular box shape in cross section and a vertically long shape. Then, rear arm brackets 6 extend downward from the rear ends of the main frames 4, respectively. Further, a pair of left and right down tubes 7 are provided for connecting the front portion of each of the main frames 4 and the corresponding lower end of the rear arm bracket 6, respectively. A pair of seat rails 8,
8 are protruding.

An inverted front fork 9 is supported on the head pipe 3 so as to be steerable. A front wheel 10 is supported on a lower end of the front fork 9, and a handle 11 is mounted on an upper end of the front fork 9. on the other hand,
At the lower ends of the rear arm brackets 6, 6, a rear arm 14 is pivotally supported by a pivot shaft 13 so as to be vertically swingable. A rear wheel 15 is supported on the swing end of the rear arm 14. A shock absorber 16 is provided between the rear portion of the main frame 4 and the rear arm 14.
Are provided via a link mechanism 17.

Reference numeral 22 denotes a seat, and the seat 22 is supported by front portions of the main frames 4, 4 and seat rails 8, 8.

Reference numeral 24 denotes a two-stroke engine for driving the rear wheels 15. This engine 24 is disposed below the main frames 4, 4 and is firmly supported by the body frame 2. A power transmission device 25 is connected to a rear portion of the engine 24, and the rear wheel 15 is linked to the power transmission device 25 by a chain transmission means 29. The chain transmission means 29 includes a drive wheel 26, a driven wheel 27 attached to the rear wheel 15, and a power chain 28 wound around the two wheels 26, 27. The power of the engine 24 is transmitted to the rear wheels 15 via the power transmission device 25, the transmission chain 28, and the like.

1 to 3, the engine 24 has a crankcase 33, in which a crankshaft 34 is supported. A cylinder 35 projects from the crankcase 33 so as to tilt forward, and a piston 36 inserted into the cylinder 35 and the crankshaft 34 are connected by a connecting rod 37.

An intake port 39 is formed at the front upper part of the crankcase 33, a reed valve 40 is attached to the intake port 39, and a carburetor 42 as a fuel supply device is attached to the reed valve 40 by an intake pipe 41. I have. The carburetor 42 is connected to an air cleaner 43 by an intake pipe (not shown). 44 is a fuel tank, and this fuel tank 44
The fuel inside is sent to the carburetor 42.

On the other hand, an exhaust port is provided on the upper surface of the cylinder 35 tilted forward.
An exhaust pipe 47 extends rearward from the exhaust port 46, and has a muffler 48 at the rear end. 49 is a scavenging port and 50 is a spark plug.

During the operation of the engine 24, the outside air is supplied to the air cleaner 43.
Which is mixed with fuel in the carburetor 42,
This air-fuel mixture passes through the reed valve 40, the crankcase 33, and the scavenging port 49 in order, and is sucked into the cylinder 35. Then, it burns here, and the subsequent exhaust gas is exhausted to the rear of the vehicle body through the exhaust pipe 47.

Further, a cooling water passage 52 is formed in the cylinder 35,
The cooling water in the cooling water passage 52 is cooled by the radiator 53 after cooling the cylinder 35, and is returned to the cylinder 35 again. The upper and lower surfaces of the radiator 53 are both recessed in the middle part in the vehicle width direction, the concave portion on the upper surface is fitted with the left and right down tubes 7, 7, and the concave portion on the lower surface is attached to the front end of the cylinder 35. Is fitted.

1, 2, and 4, the power transmission device 25 will be described in detail.

The power transmission device 25 has a power transmission case 55 formed integrally with the rear part of the crankcase 33, the right side of the power transmission case 55 is covered with a right case cover 5a, and the left side of the power transmission case 55 is a crankcase. Along with the left side of the case 33, it is covered with a left case cover 55b.

In the power transmission case 55, an intermediate shaft 56, a main shaft 57, and an output shaft 58 are respectively supported in parallel with the crankshaft 34,
At this time, the cylinder 35 is inclined forward until the axis A of the cylinder 35 is located above the intermediate shaft 56. For this reason, the space between the front end 79 of the exhaust pipe 47 and the upper surfaces of the crankcase 33 and the power transmission case 55 is large,
That is, the vaporizer 42 can be sufficiently installed in this space. The output shaft 58 is provided on the same axis B as the pivot shaft 13.

A drive gear 60 is attached to the right end of the crankshaft 34, while a driven gear 61 that meshes with the drive gear 60 is freely rotatably supported on the intermediate shaft 56. A multi-plate clutch 62 is provided between the driven gear 61 and the intermediate shaft 56, and the clutch 62 is located in the right case cover 55a.

On the other hand, a hydraulic cylinder 63 for connecting and disconnecting the clutch 62 is provided. The cylinder tube of the hydraulic cylinder 63 is fitted to the left case cover 55b, and is fastened together with the left case cover 55b to the power transmission case 55 by bolts 63a. When the rider operates the hydraulic cylinder 63 to connect the clutch 62, power is transmitted from the crankshaft 34 to the intermediate shaft 56.

A drive-side intermediate gear 64 is attached to the intermediate shaft 56, while a driven-side intermediate gear 65 meshing with the drive-side intermediate gear 64 is attached to the main shaft 57. Further, the main shaft 57 and the output shaft 58 are interlocked and connected to each other by a transmission gear set 66, and the drive wheel 26 is attached to the output shaft 58.

The power transmitted to the intermediate shaft 56 is transmitted to the output shaft 58 via the drive-side intermediate gear 64, the driven-side intermediate gear 65, and the speed change gear set 66. It is transmitted to the rear 15 via the transmission chain 28, the transmission chain 28, and the driven wheel 27.

In all the figures, a kick starter 68 for driving the engine 24 is provided. This kick starter 68 is an intermediate shaft
A kick shaft 69 is provided above the main shaft 57 and above the main shaft 57, and is supported at an upper part in the power transmission case 55. The kick shaft 69 extends in the vehicle width direction. The left end of this kick shaft 69 is the left case cover 55b
Protruding from here, the kick pedal 70 is attached here,
In other words, the kick pedal 70 is provided opposite to the clutch 62 on the left and right so as not to interfere with each other. In the power transmission case 55, the kick shaft
A kick dog 71 is spline-fitted to the right end of 69 in an axially slidable manner, and a first intermediate gear 72 is slidably supported on the kick dog 71. The gear 72 is detachably engaged with the gear 72.

The second intermediate gear 73 meshing with the first intermediate gear 72
Are freely rotatably supported on the intermediate shaft 56, and the driven gear 61 and the second intermediate gear 73 are integrally formed. Further, a return spring 75 for urging the kick shaft 69 in a counterclockwise rotation direction as viewed from the left side is provided. The return spring 75 is provided in the power transmission case 55 so as to correspond to the left side of the kick shaft 69. Have been.

As shown in FIGS. 3 and 5, the kick dog 71 is normally disengaged from the first intermediate gear 72. In this case, the kick pedal 70 is as shown by a solid line in FIG. When the kick pedal 70 is depressed, the kick pedal 70 is once turned outward as shown by the phantom line in FIG. Then, if the pedal operation of the kick pedal 70 is performed from this state,
The kick force is input to the kick shaft 69, and the kick shaft 69 rotates clockwise as viewed from the left side. As a result, the kick dog 71 slides in the axial direction and engages with the first intermediate gear 72. I do. Then, with the rotation of the kick shaft 69, the kick pedal 70
Is output from the first intermediate gear 72, that is, the first intermediate gear 72 is used as an output gear,
The power is transmitted from the intermediate gear 72 to the crankshaft 34 via the second intermediate gear 73, the driven gear 61, and the drive gear 60, so that the engine 24 can be started. When the stepping operation on the kick pedal 70 is released, the return spring 75 urges the kick shaft 69 in the opposite direction of the action of the kick force, and the kick pedal 70 is returned to the original position.

In the above case, the kick dog 71 and the return spring 75 are coaxial with the kick shaft 69 and the power transmission case 55
The kick dog 71 and the first intermediate gear 72 are disposed at one end (right end) of the kick shaft 69 and housed in the right case cover 55a.
Is disposed on the other end (left end) side of the kick shaft 69 and housed in the left case cover 55b. In other words, these kick dogs 71 and the like are divided right and left so as not to interfere with the crankcase 33.
In the figure, the axial middle part of the kick shaft 69 is made closer to the rear wall of the crankcase 33 so that the front part of the first intermediate gear 72 overlaps the rear part of the crankcase 33.

As a result, the power transmission case 55 is made compact back and forth. When the power transmission case 55 becomes compact, the position of the kick pedal 70 moves forward accordingly, so that the main frame 4 is moved from the head pipe 3 side to the pivot shaft 13 as much as possible. It can be extended linearly. Therefore, when an external force from the rear wheel 15 is applied to the main frame 4 via the rear arm 14, the main frame 4 supports the external force as an axial force. Thus, this support is made strong, which is beneficial in strength.

In FIGS. 1 to 3, a midway portion of the upper wall of the power transmission case 55 in the vehicle width direction is recessed downward so as to approach the outer peripheral surface of the axially intermediate portion of the kick shaft 69. Therefore, a concave portion 77 is formed on the upper surface of the power transmission case 55.
Are formed. On the other hand, kick dog 71
, The first intermediate gear 72, and the respective portions of the upper wall of the power transmission case 55 corresponding to the return spring 75, respectively, bulge upward to accommodate them. Protrusions 78, 78 are respectively formed on the upper surfaces of the left and right sides.

The carburetor 42 is disposed in a space sandwiched between the upper surfaces of the crankcase 33 and the power transmission case 55 and the exhaust pipe 47 from above and below in a side view. Further, in this case, the suction pipe 41 is bent in an arc shape so that the vaporizer 42 leans toward the left side as it faces rearward.
The front end 79 of the exhaust pipe 47 protruding from the cylinder 35 is a carburetor.
The carburetor 42 and the exhaust pipe 47 are provided so as to be separated from each other so as not to interfere with each other so as to bypass the right side of the upper portion 80 of the 42. Further, in this case, the upper portion 80 of the vaporizer 42 and the front end 79 of the exhaust pipe 47 are overlapped in a side view, that is, the vaporizer 42 and the exhaust pipe 47 are overlapped.
And are compactly arranged up and down.

Further, in the above case, the lower portion 81 of the vaporizer 42 is fitted into the concave portion 77, and the lower portion 81 and the convex portion 78 of the vaporizer 42 overlap with each other in a side view, that is, the vaporizer 42 and the power transmission case.
55 and compactly arranged up and down.

Further, since the exhaust pipe 47 extends from the upper surface of the cylinder 35 inclined forward as described above, an extra space is generated in front of the cylinder 35. Therefore, using the surplus space, the cylinder 35 is tilted sufficiently forward, that is, the center of gravity is lowered. In addition, the fuel tank 44 described above is disposed in this surplus space, and the cylinder 35 and the fuel tank 44 are brought close to each other. That is, since both of them are heavy, the mass is concentrated by the above configuration.

Although the above description is based on the illustrated example, the fuel supply device may be a fuel injection device. Further, the front end 79 of the exhaust pipe 47 may be bent in an arc shape protruding upward, and the vaporizer 42 and the front end 79 may be arranged vertically. Further, if the suction pipe 41 and the front end 79 are displaced to the left and right, they can be formed into a simple shape that linearly extends rearward.

(Effect of the Invention) According to the present invention, the main body frame includes the main frame extending rearward and downward from the head pipe constituting the front part thereof, and the rear arm bracket extending downward from the rear end of the main frame. A rear arm for supporting a rear wheel is pivotally supported on a lower end of the rear arm bracket by a pivot shaft so that the rear arm can swing up and down. An engine is disposed below the main frame and supported by the vehicle body frame. A crankcase and a cylinder protruding forward and upward from the crankcase are provided, and a fuel supply device for supplying fuel to the engine is provided, while an exhaust pipe extending rearward from an upper surface of the cylinder is provided. A power transmission case is attached to a rear portion of the crankcase, and upper surfaces of the crankcase and the power transmission case, the exhaust pipe, The fuel supply device is arranged in a space sandwiched by the above, and a kick shaft that extends in the vehicle width direction and inputs a kick force is supported at an upper portion in the power transmission case, and the kick force input to the kick shaft is An automatic output gear, which is provided in the power transmission case coaxially with the kick shaft, includes an output gear for outputting, and a return spring for urging the kick shaft around its axis in a direction opposite to the direction in which the kick force acts. In the motorcycle, (1) the output gear is provided at one end of the kick shaft, and the return spring is provided at the other end of the kick shaft. The axial middle portion of the kick shaft is made closer to the rear wall of the crankcase so that the front portion overlaps.

For this reason, in order to prevent the output gear from interfering with the rear wall of the crankcase, the output gear is included in comparison with disposing the output gear behind the crankcase. The dimension of the power transmission case in the front-rear direction can be reduced.

Therefore, the assembly of the crankcase and the power transmission case is made compact, and the mass is accordingly concentrated, and the maneuverability is improved.

Moreover, as described above, when the dimension of the power transmission case in the front-rear direction is shortened, the rear end position of the power transmission case moves to the front side which is the crankcase side, and the rear end of the power transmission case moves downward from the rear end of the main frame. The rear upper end of the power transmission case separates forward, and these vertical gaps increase. Therefore, the rear end of the main frame can be lowered accordingly, and can be brought closer to the pivot.

Therefore, the main frame can be extended more linearly from the head pipe side toward the pivot shaft side, and a large external force from the rear wheel is applied via the rear arm and the pivot shaft. When the main frame is loaded, the main frame can support the external force as an axial force, so that the support is firmly provided.

(2) A midway portion of the upper wall of the power transmission case in the vehicle width direction approaches an intermediate portion of the kick shaft in the axial direction,
A recess is formed in the upper surface of the power transmission case, and the lower portion of the fuel supply device is fitted into the recess.

Therefore, an assembly of the power transmission case and the fuel supply device and the exhaust pipe disposed above the power transmission case by an amount corresponding to the lower portion of the fuel supply device carburetor fitted into the recess formed in the power transmission case. The vertical dimension of the can be reduced,
Therefore, the ground clearance of the motorcycle can be sufficiently secured.

[Brief description of the drawings]

1 shows an embodiment of the present invention. FIG. 1 is an overall side view of a motorcycle, FIG. 2 is a partially enlarged sectional view of FIG. 1, FIG. 3 is a plan view of FIG. 2, and FIG. 2 is a sectional view taken along line IV-IV of FIG. 2, and FIG. 5 is a sectional view taken along line VV of FIG. 1 ... motorcycle, 2 ... body frame, 3 ... head pipe, 4 ... main frame, 6 ... rear arm bracket, 13 ... pivot shaft, 14 ... rear arm, 15 ... rear wheel, 24
… Engine, 33… Crank case, 35… Cylinder, 42… Vaporizer (fuel supply device), 44… Fuel tank, 47… Exhaust pipe, 55… Power transmission case, 69… Kick shaft , 72: first intermediate gear (output gear), 75: return spring, 77: recess, 81: lower part.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B62K 11/00-11/04 B62M 7/02 F02M 17/34

Claims (1)

(57) [Claims] 1. A vehicle body frame comprising: a main frame extending rearward and downward from a head pipe constituting a front portion thereof; and a rear arm bracket extending downward from a rear end of the main frame, and a lower end of the rear arm bracket. A rear arm for supporting the rear wheel is pivotally supported by a pivot shaft so that the rear arm can swing up and down. An engine is arranged below the main frame and supported by the body frame. A cylinder protruding forward and upward from the case, and a fuel supply device for supplying fuel to the engine is provided, while an exhaust pipe extending rearward from an upper surface of the cylinder is provided, and a rear portion of the crankcase is provided. A power transmission case is attached to the upper surface of the crankcase and the power transmission case, and the space is sandwiched between the exhaust pipe. An output gear for providing a kick shaft extending in the vehicle width direction and inputting a kick force at an upper portion in the power transmission case, and outputting a kick force input to the kick shaft; A motorcycle in which a return spring for urging the kick shaft around its axis in a direction opposite to the direction of action of the kick force is provided in the power transmission case coaxially with the kick shaft. The output gear is disposed at one end of the kick shaft, and the return spring is disposed at the other end of the kick shaft.The crank is arranged such that the front of the output gear overlaps the rear of the crankcase in a side view. (2) approaching the axially intermediate portion of the kick shaft to the axially intermediate portion of the kick shaft near the rear wall of the case; On this power transmission case In a recess, absorption of a motorcycle 2-cycle engine is fitted at the bottom of the fuel supply device in the recess, the exhaust system disposition structure.