JPH076390B2 - Exhaust control device for motorcycles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is applied to a motorcycle in which an exhaust control valve is provided below the engine near the center of the vehicle body and one exhaust muffler is provided on one side of the vehicle body rear side. Exhaust control device.

(Background of the Invention) In a 4-cycle engine, a 2-cycle engine, etc., it is known that exhaust gas is intermittently guided to an exhaust pipe by opening and closing an exhaust valve, and an inertial effect and a pulsating effect of the exhaust gas are generated in the exhaust pipe. . These effects (called dynamic effects) change depending on the engine speed. Therefore, if the dynamic effect is maximized and the volumetric efficiency is increased at a certain rotation speed, the dynamic effect is adversely affected and the volumetric efficiency is significantly reduced at other rotation speeds. For this reason, when the exhaust system specifications (exhaust pipe length, exhaust pipe diameter, etc.) are set so that this dynamic effect is optimal in the high rotation range, the torque is significantly reduced in the middle speed range (torque valley). There was a problem that occurs.

Therefore, an exhaust control valve that changes the exhaust flow passage area is provided near the opening end of the exhaust pipe to the expansion chamber to reduce the flow passage area in the rotational speed range where the volumetric efficiency decreases and to change the flow passage area in other rotation speed regions. It is considered to increase.

Further, in a multi-cylinder engine, if the downstream side of each exhaust pipe is joined in the expansion chamber, the volume efficiency and the torque may be reduced due to exhaust interference between the cylinders. Therefore, it is considered that an exhaust control valve is provided for each exhaust pipe and the exhaust flow passage area is reduced by closing this control valve in a rotational speed range where adverse effects due to exhaust interference occur.

It is also considered to improve combustion by controlling the back pressure of the exhaust pipe or to control the exhaust gas component by controlling self-EGR (exhaust gas recirculation).

Thus, it is conceivable to provide the exhaust pipe with an exhaust control valve for changing the exhaust passage area for various purposes such as improvement of volumetric efficiency, improvement of combustion, and control of exhaust components. However, particularly in a motorcycle in which the engine is disposed near the center of the vehicle body and one exhaust muffler is disposed on one side of the rear portion of the vehicle body, when the exhaust control valve is disposed near the center of the vehicle body width direction below the engine,
The curvature of the exhaust passage becomes large downstream of the exhaust control valve. For this reason, there arises a problem that the flow of exhaust gas is not smooth. Particularly in the case of a multi-cylinder engine, when a plurality of exhaust pipes are joined near this exhaust control valve, the curvature of the exhaust flow path changes significantly for each exhaust pipe on the downstream side of the exhaust control valve for each exhaust pipe. There is also a problem that the combustion characteristics of each cylinder are likely to be non-uniform.

(Object of the Invention) The present invention has been made in view of the above circumstances, and from an exhaust control valve provided in the vicinity of the center of the vehicle body width direction below the engine to one exhaust muffler provided at one side of the rear part of the vehicle body. When guiding the exhaust, the curvature of the exhaust flow path on the downstream side of the exhaust control valve is reduced to smooth the flow of the exhaust, and in the case of a multi-cylinder engine, it is effective for uniforming the combustion characteristics of each cylinder. An object of the present invention is to provide an exhaust control device for a motorcycle.

(Structure of the Invention) According to the present invention, an object of the present invention is to provide a plurality of exhaust pipes, which are guided from the front of an engine mounted near the center of a vehicle body to the lower part of the engine, with an exhaust control valve and an expansion valve located below the engine. In a motorcycle connected to one exhaust muffler arranged on one side of the rear part of the vehicle body through a chamber, the valve body of the exhaust control valve has its shaft end on the exhaust muffler side displaced forward in a horizontal plane. The exhaust control device for a motorcycle is characterized in that the valve element is obliquely arranged on a horizontal plane.

(Embodiment) FIG. 1 is a partially sectional plan view of an exhaust control valve according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line II-II, FIG. Figures 4 and 5 show IV-I in Figure 1.
Fig. 6 is a side view of the exhaust system of a motorcycle using this exhaust control valve, Fig. 7 is a plan view of the same, and Fig. 8 shows this exhaust system. It is a side view of the used motorcycle.

In FIGS. 6 and 8, reference numeral 10 is a 4-cycle 4-cylinder engine, which is mounted near the center of the vehicle body. This engine
Cylinder 10 extends diagonally upward and forward from crankcase 12
Have 14. The exhaust system includes four exhaust pipes 16 (16a to 16d) extending from the front surface of the cylinder 14 to the lower side of the crankcase 12.
An exhaust control valve 20 connected to the rear end of the exhaust pipe 16 and an exhaust muffler 18 connected to the exhaust control valve 20 and located on the right side of the rear part of the vehicle body.

As shown in FIG. 1, a body 22 of the exhaust control valve 20 is connected to each of the four exhaust pipes 16 and forms branch pipes 24 (24a to 24d) together with the exhaust pipes 16, and the branch pipe portions 24a to 24d. The expansion chamber 26 in which the downstream open ends 16A to 16D of 24 are open, and one collecting pipe portion 28
And are integrally cast from stainless steel for casting. The upstream end of the branch pipe portion 24 is the fifth
As shown in the figure, it has a circular cross section and is connected to each exhaust pipe 16. The downstream open ends 16A to 16D of the branch pipe 24 are the fourth
As shown in the figure, it has a vertically long rectangular opening, and the expansion chamber
It opens in parallel with 26. The silencer 18 is a collecting pipe section 28.
It is detachably attached to.

Reference numeral 28 denotes a crank-shaped valve body (Fig. 1). The valve body 28 is rotatably supported by the left and right walls of the expansion chamber 26 behind the open ends 16A to 16D, and the intermediate portion 30 has an arcuate cross section. Is formed in. Circular openings are formed in the left and right walls of the expansion chamber 26, and these openings are closed by bearing plates 32 and 34. Both shaft ends 28a, 28b of the valve body 28 are axially supported by bearing plates 32, 34, respectively, and the shaft end on the side of the exhaust muffler 18, that is, the right shaft end 28a is biased forward of the left shaft end 28b on a horizontal plane. I am ranked. As a result, the valve element 28 is arranged obliquely so that the right side thereof is located forward in the horizontal plane. The left shaft end 28b penetrates the bearing plate 34 and projects outward, and the pulley 36 is fixed to the projecting end. The intermediate portion 30 faces the downstream opening of the branch portion 24, that is, the downstream opening ends 16A to 16D of the exhaust pipe 16. The outer peripheral surface of the intermediate portion 30 and the downstream opening end 16A of the exhaust pipe 16
As shown in FIGS. 2 and 3, the symbols .about.16D are formed in an arc shape around the center of rotation of the valve body 28 and are close to each other.
The pulley 36 is rotated via a wire by a servo motor (both not shown) in accordance with the rotation speed of the engine 10, and the exhaust control valve 20 is closed in the low and medium speed range of the engine 10 and opened in the high speed range. Controlled.

The body 22 of the exhaust control valve 20 is attached to the vehicle body frame 40 as shown in FIGS. Ie body frame
The reference numeral 40 includes a pair of left and right hanging parts 42 (only one is shown) extending downward along the rear part of the engine 10, and a bracket 46 is fixed to a cross member 44 connecting the both hanging parts 42. A link 48 and a hanging plate 50 are fastened together to the bracket 46, and a bracket 52 fixed to the body 22 is fixed to the lower end of the hanging plate 50. The exhaust muffler 18 is fixed to a stay 40a (see FIG. 8) hanging from the vehicle body frame 40.

In FIG. 6, 54 is a rear arm, the front end of which is pivotally supported by the hanging portion 42 of the vehicle body frame 40, and the rear wheel 56 is attached to the rear end (FIG. 8). The pivot end of the link 48 is connected to the rear arm 54 by a pair of left and right links 58, 58 (FIG. 7). A support arm 60, on which the lower end of a shock absorber (not shown) is rotatably supported, is provided at the rotating end of the link 48.

In FIG. 8, 62 is a front wheel, 64 is a steering wheel, 66
Is a fuel tank and 68 is a driving seat.

Therefore, when the diameter and length of the exhaust pipe 16 are set so that the volumetric efficiency of the engine 10 is high in the high speed range, the exhaust control valve 20 is controlled to close in the low and medium speed range and open in the high speed range. It is driven by a motor.

The positive pressure wave due to the opening of the exhaust valve of the engine 10 propagates in the exhaust pipe 16 at the speed of sound, and the negative pressure wave generated by the rapid expansion at the opening ends 16A to 16D causes the exhaust pipe 16 to travel in the opposite direction at the speed of sound. And propagates back to the exhaust valve of the engine 10. If the exhaust control valve 20 located near the open ends 16A to 16D is closed, a positive pressure wave due to the opening of the exhaust valve will cause this exhaust control valve 20
It is reflected by and returns to the exhaust valve at the speed of sound as a positive pressure wave.
Therefore, if the exhaust control valve 20 is controlled so that the exhaust flow passage area is halved, the negative pressure wave generated by the open end of the exhaust pipe and returned and the positive pressure wave reflected by the exhaust control valve 20 The sum of and becomes zero. At this time, the pulsating effect is canceled out,
It is possible to suppress a decrease in volumetric efficiency (occurrence of a torque valley) in the medium speed range.

Further, when the exhaust control valve 20 is used for the purpose of preventing the torque reduction due to the exhaust interference between the cylinders, the exhaust control valve 20 may be closed in the rotation region where the torque reduction due to the exhaust interference is remarkable. When closing the exhaust control valve 20 in the low speed range, it is possible to use the exhaust control valve 20 by reducing the exhaust flow passage area by about 70 to 90% to about 30 to 10%.

Since the valve 28 is obliquely arranged so that the right shaft end 28a is displaced forward, each branch pipe portion 24 is also opened so as to be directed slightly to the right side, and as a result, each branch pipe portion 24 is opened. The angle between the center line of the center of the pipe and the center line of the collecting pipe portion 28 increases. Therefore, the exhaust gas flowing from each branch pipe portion 24 into the expansion chamber 26 is guided to the collecting pipe portion 28 with a large curvature, and the flow of the exhaust gas becomes smooth.

In this embodiment, the four exhaust pipes 16 are connected in parallel to each other to the exhaust control valve 20.
Therefore, the exhaust control valve 20 has a wide width. However, if the valve body 28 is obliquely arranged on the horizontal plane as in the present invention, the lateral width of the valve body 28 is reduced, and a large bank angle of the vehicle body can be secured.

(Effects of the Invention) As described above, the present invention is configured so that the exhaust muffler side shaft end of the valve body of the exhaust control valve disposed below the engine is displaced forward from the other shaft end on the horizontal plane. Since it is arranged, the exhaust gas flowing from the exhaust pipe into the expansion chamber draws a large curvature and flows to the downstream side of the expansion chamber. Therefore, the flow of exhaust gas becomes smooth. Further, in the case of a multi-cylinder engine, the exhaust gas from each exhaust pipe can smoothly flow in the expansion chamber, which is effective in making the combustion characteristics of each cylinder uniform.

[Brief description of drawings]

FIG. 1 is a plan view in which an exhaust control valve according to an embodiment of the present invention is partially sectioned, FIG. 2 is a sectional view taken along the line II-II, FIG. 3 is a view taken along arrow III, FIG. 4 and FIG. Figure 5 shows IV-I in Figure 1.
Fig. 6 is a side view of the exhaust system of a motorcycle using this exhaust control valve, Fig. 7 is a plan view of the same, and Fig. 8 shows this exhaust system. It is a side view of the used motorcycle. 10 …… Engine, 16 …… Exhaust pipe, 18 …… Exhaust muffler, 20 …… Exhaust control valve, 26 …… Expansion chamber, 28 …… Valve element, 28a, 28b …… Shaft end.

Claims (1)

[Claims] 1. A plurality of exhaust pipes, which are installed in the vicinity of the center of a vehicle body and are guided from the front side of the engine to the lower side of the engine, through one side of a rear portion of the vehicle body via an exhaust control valve and an expansion chamber located below the engine. In the motorcycle connected to one exhaust muffler arranged at, the valve body of the exhaust control valve has its shaft end on the exhaust muffler side biased forward on a horizontal plane, and the valve body is slanted on the horizontal plane. An exhaust control device for a motorcycle, characterized in that