JP2875267B2 - Exhaust control valve device for motorcycle - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a motorcycle having an exhaust control valve that changes an opening area near a downstream end of a first exhaust pipe from an engine to an expansion chamber in accordance with an operation state. The present invention relates to an exhaust control valve device.

(Background of the Invention) An exhaust control valve for changing an opening area is provided at a downstream end of an exhaust pipe of an engine, that is, near an opening end to an expansion chamber. Improvements are known.

Generally, the exhaust gas expands rapidly near the opening end where the exhaust pipe opens to the expansion chamber, and the negative reflected wave at this time flows back through the exhaust pipe and acts on the exhaust valve of the engine. In a high-speed type engine, the exhaust system is set such that the negative reflected wave flowing backward at a high speed acts to promote the exhaust to increase the high-speed output. However, in this high-speed engine, at a middle speed, the negative reflected wave acts to hinder exhaust, and the output decreases. Therefore, at medium speed, the exhaust control valve is almost half-open,
A negative reflected wave generated at the downstream end of the exhaust pipe and flowing backward is canceled out by a positive reflected wave reflected and returned by the exhaust control valve, thereby increasing the torque in the middle speed range.
In a low-speed range, the exhaust valve is closed to prevent fresh air from flowing through the combustion chamber, thereby stabilizing idling operation.

In order to sufficiently exert the above-described effects, it is necessary to secure the exhaust pipe to a certain length or more. For this reason, when the present invention is applied to a motorcycle equipped with an engine in the lower part near the center of the vehicle body, the exhaust control valve has conventionally been arranged below and behind the engine. However, in this case, the position of the exhaust control valve is lowered, the load clearance is reduced, and the bank angle is disadvantageously reduced. Further, there is also a problem that the exhaust pipe located in front of the exhaust control valve impedes the flow of the traveling wind that impinges on the exhaust control valve, thereby obstructing the cooling of the exhaust control valve.

(Object of the Invention) The present invention has been made in view of such circumstances,
When such an exhaust control valve is provided on a motorcycle, the exhaust pipe length is sufficiently secured to ensure a large load clearance without sacrificing performance, and the traveling wind easily hits the exhaust control valve to cool it. It is an object of the present invention to provide a motorcycle exhaust control valve device capable of improving performance.

(Constitution of the Invention) According to the present invention, an object of the present invention is to provide a crankshaft side-by-side parallel multi-cylinder engine having a plurality of cylinders mounted near the center of a vehicle body and having a plurality of cylinders rising obliquely forward from an upper surface of a front portion of a crankcase; A single exhaust expansion chamber disposed below the crankcase, a plurality of first exhaust pipes that communicate with and open to the front of the expansion chamber independently of each cylinder of the engine; and the expansion of the first exhaust pipes An exhaust control valve formed of one valve shaft and a valve body in the vehicle width direction located near an opening end in the front of the compartment, the exhaust control valve changing an exhaust passage area according to an engine operating state; The front portion of the exhaust expansion chamber is located forward of the crankcase and the upper surface of the front portion is located above the lower surface of the crankcase, and the first exhaust pipe is located forward and downward from the front surface of each cylinder. Towards The first exhaust pipe is connected to the front side of the exhaust expansion chamber while being bent so as to be bent forward and then to the rear, and then inclined downward and rearward. The exhaust control valve device for a motorcycle, characterized in that a substantially triangular space in a side view that gradually increases in the front-rear direction is formed downward with the upper end of the first exhaust pipe as the apex.

(Embodiment) FIG. 1 is a side view of a motorcycle to which an embodiment of the present invention is applied, FIG. 2 is a side view of the exhaust system, and FIG.

In FIG. 1, reference numeral 10 denotes a parallel four-cylinder four-stroke engine. The engine 10 is mounted near the center of the vehicle body, and its left and right sides are covered by a cowling 12.
14 is a front wheel, 16 is a rear wheel, 18 is a steering handlebar, 20 is a cover which covers the air cleaner 22 and the fuel tank 24.
Reference numeral 26 denotes an operation seat.

The engine 10 is a side-by-side crankshaft four-cylinder engine having a plurality of cylinders that stand up from the front upper surface of the crankcase 28 obliquely upward. Therefore, the cylinder block is formed by assembling four cylinders arranged in the engine width direction. The cylinder head 30 mounted on the cylinder block incorporates intake / exhaust valves and a valve operating mechanism thereof. Body frame
Numeral 32 extends obliquely downward and rearward from the steering shaft tube 34, and its rear end is bent downward. The upper and lower corners of the rear part of the crankcase 28 are fixed to the body frame 32, and the left and right side surfaces of the cylinder head 30 are fixed to the body frame 32 by U-shaped pipe brackets 36 (only one is shown). A downdraft type carburetor 38 is connected to the rear surface of the cylinder 36.
The carburetor 38 is of a four-unit configuration in which four carburetors are connected to each cylinder. The upper end of the carburetor 38 is connected to the air cleaner 22 located above it.

The vertical movement of the rear arm 40 holding the rear wheel 16 is transmitted to the lower end of one cushion unit 42 by using a link mechanism.

Next, the exhaust system 50 will be described. The exhaust system 50 includes four first exhaust pipes 52 (52a) independently connected to each cylinder of the engine 10.
To d), an exhaust control valve 54 located below the front part of the crankcase 28, one exhaust expansion pipe 56 surrounding the exhaust control valve 54 vertically and forward and extending rearward, and the expansion pipe 56 And a second exhaust pipe 58 extending from the second exhaust pipe 58 to the right side of the rear wheel 16.
And a muffler 60 connected to the exhaust pipe 58. Each first exhaust pipe 52 is led forward and downward from the front surface of each cylinder, and then bent twice in the front-rear direction so as to bend once forward and then bend rearward, thereby forming the first exhaust pipe 52 and the cylinder block. A substantially triangular space is formed between the front surface and the front surface of the crankcase 28, with the upper end of the first exhaust pipe 52 being the apex and gradually expanding downward in the front-rear direction. The downstream end of each of these first exhaust pipes 52 is integrated with a branch pipe 62 described later to form a vertically-long rectangular cross-sectional shape.
It opens to the front of 54 at an angle rear-down.

The expansion tube 56 is formed by vertically stacking a pair of upper and lower pressed stainless steel halves and welding a flange portion at a peripheral edge thereof, and an exhaust expansion chamber 56A is formed therein. The front part of the exhaust expansion pipe 56 is a bracket 57 (FIG. 1).
By the engine 10. Therefore, the front portion of the exhaust expansion chamber 56A is located forward of the crankcase 28 and the upper surface of the front portion is located above the lower surface of the crankcase 28. A branch pipe 62 (62a to 62a) which substantially becomes a part of the first exhaust pipe 52 is provided on the front surface of the exhaust expansion pipe 56.
d) is welded. Each of the branch pipes 62 is formed in a tubular shape by welding a pair of left and right pressed stainless steel halves to each other, and has a front end connected to the first exhaust pipe 52 with a circular cross section, and a downstream side in the vertical direction. It becomes a long rectangle and is inclined backward and downward.

A bearing plate 64 made of stainless steel is fixed to the right side surface of the expansion chamber 56A, and the bearing plate 66 is bolted to the left side surface.

The exhaust control valve 54 includes one stainless steel valve body 68 having an arc-shaped cross section held by each bearing plate 64, 66, and one valve shaft is held by bearing plates 64, 66. The left end of the shaft projects from the bearing plate 66, and a pulley 70 is fixed here.
The pulley 70 is connected to a servomotor 72 (FIG. 1) via a wire, and the valve body 68 is controlled to close in a low-to-medium speed range of the engine 10 and open in a high-speed range.

The row of openings of the branch pipes 62 arranged in parallel is formed in an arc shape so as to be close to the outer peripheral surface of the valve body 68, and leakage of exhaust gas from the gap between the opening and the valve body 68 is prevented.

Next, the operation will be described. When the diameter and length of the first exhaust pipe 52 are set so that the volume efficiency of the engine 10 is high in the high speed range, the servo valve is closed so that the exhaust control valve 54 closes in the middle speed range and opens in the high speed range. It is driven by a motor 72. engine
The positive pressure wave due to the opening of the 10 exhaust valves is sonic and the first exhaust pipe
The negative pressure wave generated by the rapid expansion at the opening to the expansion chamber 56A propagates through the first exhaust pipe 52 and the branch pipe 62 in the opposite direction at the speed of sound. Return to the exhaust valve. If the valve body 68 facing the opening closes the opening, the positive pressure wave due to the opening of the exhaust valve is reflected by the valve body 68 and returned to the exhaust valve at the speed of sound as a positive pressure wave. Therefore, if the valve element 68 is controlled so that the exhaust flow path area is reduced to about 1/2 in a medium speed range where the dynamic effect acts in reverse, a negative pressure wave generated and returned by the opening and the valve element 68
And the sum with the positive pressure wave reflected by the zero is zero. At this time, the pulsation effect is canceled, and a decrease in volumetric efficiency (generation of torque valley) in the medium speed range can be suppressed.

When idling, the valve element 68 is 5% of the exhaust path when fully open.
It is closed to the extent that the exhaust pressure waves between the cylinders interfere with each other to prevent the operation from becoming unstable due to the exhaust interference.

On the other hand, the traveling wind impinges on the plurality of first exhaust pipes 52. Since a wide space is formed between the first exhaust pipes 52 and the crankcase 28, the traveling wind smoothly flows between the first exhaust pipes 52. And hits a cylinder block or a crankcase 28 and is guided downward. Therefore, the traveling wind satisfactorily hits the exhaust control valve 54 located below the front part of the crankcase 28, and the cooling performance of the exhaust control valve 54 is improved.

(Effect of the Invention) As described above, the invention of claim 1 is arranged such that the front portion of the exhaust expansion chamber accommodating the exhaust control valve is located forward of the crankcase and the upper surface of the front portion is located above the lower surface of the crankcase. A first exhaust pipe extending from the engine to the exhaust control valve is led forward and downward from the front of each cylinder and then bent forward and backward twice so as to be bent once and then backward. Since they are connected, the length of the first exhaust pipe necessary for obtaining sufficient engine performance can be secured. Further, since the exhaust control valve has one valve body and a valve shaft in the vehicle width direction, a sufficiently large load clearance can be ensured. Further, since a large space of a substantially triangular shape in a side view is formed between the first exhaust pipe and the crankcase, which is gradually enlarged downward and forward in the front-rear direction with the upper end of the first exhaust pipe as an apex. The air flows well into this space through the space between the exhaust pipes, is guided to the front of the cylinder block and the front of the crankcase, and is guided obliquely downward. Below the front of the crankcase, the front of the exhaust expansion chamber accommodating the exhaust control valve is located forward of the crankcase, and the upper surface of the front is located above the lower surface of the crankcase. The exhaust air is connected to the front of the exhaust expansion chamber so that the traveling wind satisfactorily hits the exhaust control valve and the first exhaust pipe, thereby improving the cooling performance.

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle to which one embodiment of the present invention is applied, FIG. 2 is a side view of an exhaust system thereof, and FIG. 3 is a partially sectional plan view thereof. 10 ... engine, 28 ... crankcase, 30 ... cylinder head, 50 ... exhaust system, 52 ... first exhaust pipe, 54 ... exhaust control valve, 56 ... exhaust expansion pipe, 56A ... exhaust expansion Room.

Claims (1)

(57) [Claims] A crankshaft side-by-side multi-cylinder engine mounted near the center of a vehicle body and having a plurality of cylinders rising from a front upper surface of the crankcase toward an obliquely forward direction, and disposed below the crankcase. A single exhaust expansion chamber, a plurality of first exhaust pipes which communicate with and open to the front of the expansion chamber independently of each cylinder of the engine, and are located near the opening ends of the first exhaust pipe on the front of the expansion chamber. A motorcycle comprising: an exhaust control valve formed of one valve shaft and a valve body in a vehicle width direction and changing an exhaust passage area according to an engine operating state; a front part of an exhaust expansion chamber accommodating the exhaust control valve; Are arranged so that the upper surface of the front part is located above the lower surface of the crankcase and the front of the crankcase.
The exhaust pipe is led forward and downward from the front of each cylinder, and then bent once to be bent forward and then bent backward, and is connected to the front of the exhaust expansion chamber while being inclined obliquely downward and backward. A substantially triangular space is formed between the exhaust pipe and the front surface of the engine cylinder block and the front of the crankcase. Exhaust control valve device for motorcycles.