JPH0689672B2 - Engine exhaust control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control device for an engine in which an exhaust control valve is provided in each of a plurality of exhaust pipes extending from an exhaust port of the engine to an expansion chamber.

(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 specifications of the exhaust system (exhaust pipe length, exhaust pipe system, etc.) are set so that this dynamic effect is optimal in the high speed region, the torque is significantly reduced in the medium speed region (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, and the flow passage area is reduced in the rotational speed range where the volumetric efficiency is reduced, and the flow passage area is changed in other rotational 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 provide an exhaust control valve in the middle of the exhaust pipe to improve combustion by controlling the back pressure or control self-EGR (exhaust gas recirculation) to control exhaust components.

In this way, it is conceivable to provide an exhaust control valve for changing the exhaust flow passage area in the exhaust pipe for various purposes such as improving volumetric efficiency, improving combustion, and controlling exhaust components. In this case, each exhaust pipe must be provided with an exhaust control valve, and if each is controlled independently, the control device becomes complicated. If the exhaust control valves have the same valve axis,
Since the valve shaft becomes long, its elongation due to heat increases, which causes a problem that the valve plate provided on the valve shaft and the exhaust pipe interfere with each other when the engine is hot or cold.

(Object of the invention) The present invention has been made in view of the above circumstances, and when the exhaust control valves are provided in a plurality of exhaust pipes respectively, the control device can be simplified, and even if the valve shaft expands and contracts due to heat. An object of the present invention is to provide an exhaust control device for an engine that can prevent a valve plate provided on a valve shaft from interfering with an exhaust pipe. (Construction of the Invention) According to the present invention, one end thereof is an exhaust port of the engine. In an engine including a plurality of exhaust pipes, the other ends of which are respectively connected to expansion chambers, and an exhaust control valve which is provided in each of the exhaust pipes and changes the exhaust flow passage area of each of the exhaust pipes, each of the exhaust control valves, One valve shaft that traverses each exhaust pipe, a plurality of valve plates fixed to the valve shaft corresponding to each exhaust pipe, and one thrust receiver that regulates axial movement of the valve shaft. And a shape in which the valve plate is elongated in a direction orthogonal to the valve axis. The exhaust control device for an engine is characterized in that a gap is formed between the valve plate and the inner wall of the exhaust passage to avoid interference between the valve plate and the inner wall of the exhaust passage due to expansion of the valve shaft due to heat. To be done.

(Operation) When the valve shaft is rotated in accordance with the operating state of the engine, the exhaust passage area of each exhaust pipe is changed based on the operating state of the engine.

As the temperature of the engine rises, the valve shaft extends and the valve plate shifts from the center of the exhaust pipe in the direction opposite to the thrust receiver.

(Embodiment) FIG. 1 is a rear view of an exhaust control valve assembly, which is an embodiment of the present invention, with a partial cross section, FIG. 2 is a plan view of the same, and FIG. 3 is an exhaust system of a motorcycle using the same. Is a plan view, FIG. 4 is a side view of the same, and FIG. 5 is a side view of a motorcycle using this exhaust system.

In FIGS. 4 and 5, 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.
And an exhaust control valve assembly 18 connected to the rear end of each exhaust pipe 16.
And the exhausts of the two exhaust pipes 16a, 16b and 16c, 16d connected to the rear surface of the exhaust control valve assembly 18
Two expansion chambers 22 (22a, 2b) leading to the silencer 20 (20a, 20b)
2b) and.

In FIG. 5, 24 is a front wheel, 26 is a steering wheel, and 28 is a steering wheel.
Is a rear wheel, 30 is a cover for covering the intake cleaner and the fuel tank, and 32 is an operating seat.

The exhaust control valve assembly 18 is formed by integrating a plurality of exhaust control valves 34 (34a to 34d) for changing the exhaust passage area of each exhaust pipe 16, and a main body 36 fixed to the rear end of the exhaust pipe 16. Each exhaust pipe
Circular holes 38 (38a-3
8d), one valve shaft 40 penetrating each circular hole 38, and valve plates 42 (41a to 42d) fixed to the valve shaft 40.

The right end of the valve shaft 40 is restricted from moving in the axial direction by a thrust receiver 44. That is, the retaining ring 46 fixed to the right end of the valve shaft 40, the bottom surface of the recessed chamber 48 provided on the right side of the main body 36,
The thrust receiver 44 is formed by sandwiching the thrust receiver 44 with the lid member 50 press-fitted into the recessed chamber 48.

The valve plate 42 is formed in an elliptical shape that is long in a direction orthogonal to the valve axis 40, and its center substantially coincides with the center of the exhaust pipe 16 when the engine 10 is cold. As a result, a gap 1 is formed between the valve plate 42 and the inner wall of the circular hole 38 which is the exhaust passage, as shown in FIG. The gap 1 is determined so that the valve plate 42a of the exhaust control valve 34a farthest from the thrust receiver 44 does not interfere with the inner wall of the circular hole 38a in the hot state of the engine 10.

A pulley 52 is fixed to the left end of the valve shaft 40, and the pulley 52 is forcibly rotated in both directions by a servo motor 56 via a wire 54. The servo motor 56 is, for example, an ignition device.
Based on the engine rotation speed detected from 58 (see FIG. 3), each control valve 34 is closed in the rotation region where the volumetric efficiency deteriorates,
It is controlled by the control circuit 60 to open in the other rotation area.

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 control circuit 60 causes the servo motor 56 to close the exhaust control valve 34 in the medium speed range. To drive. Each exhaust control valve 34 is controlled to have the same opening degree by one valve shaft 40 in synchronization.

The positive pressure wave generated by opening 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 open end propagates in the exhaust pipe 16 in the opposite direction at the speed of sound. Back to the exhaust valve of engine 10. If the exhaust control valve 34 located near this opening end is closed, the positive pressure wave due to the opening of the exhaust valve is reflected by this exhaust control valve 34 and returns to the exhaust valve as a positive pressure wave at the speed of sound. Therefore, if the exhaust control valve 34 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 34 The sum of and becomes zero.
At this time, the pulsating effect is canceled out, and a decrease in volumetric efficiency (occurrence of a torque valley) in the medium speed range can be suppressed.

When the exhaust control valve 34 is used for the purpose of preventing the torque decrease due to the exhaust interference between the cylinders, the exhaust control valve 34 may be closed in a rotation region where the torque decrease due to the exhaust interference is significant. When closing the exhaust control valve 34 at a low speed, the exhaust control valve 34 reduces the exhaust flow passage area by about 90% to 10%.
Anything can be used.

When the engine 10 is cold, the valve plate 42 is located near the center of the exhaust passage as shown in FIG. As the engine 10 warms up, the valve shaft 40 extends leftward in FIG. That is, the deviation amount of the valve shaft 40 increases as the distance from the thrust receiver 44 increases. Since the valve plate 42, which is farthest from the thrust receiver 44, is determined so as to avoid interference with the inner wall of the circular hole 38a when the engine is hot, all the valve plates 42 are exhaust pipes when the engine is hot. 16 does not interfere with the inner surface.

Although the exhaust control valve 34 is provided near the opening end of the exhaust pipe 16 to the expansion chamber 22 in the above embodiments, it may be provided at another position of the exhaust pipe 16 depending on the purpose of the exhaust control valve. For example, for back pressure control or self-EGR, it is desirable to provide it at a position close to the engine 10. Further, it may be arranged close to the downstream side of the open end of the exhaust pipe 16.

(Effects of the Invention) As described above, the present invention provides one valve shaft so as to traverse the exhaust pipe, restricts the axial movement of the valve shaft by one thrust receiver, and It is formed in a long shape in the direction orthogonal to the valve axis. Therefore, even if the engine temperature rises and the valve shaft extends, interference between the valve plate and the inner wall of the exhaust passage can be prevented. Further, each exhaust control valve can be controlled by one drive means such as a servo motor, which simplifies the control device.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional rear view of an exhaust control valve assembly according to an embodiment of the present invention, FIG. 2 is a plan view of the same, and FIG. 3 is a plan view of an exhaust system of a motorcycle using the same. FIG. 4 is a side view of the same, and FIG. 5 is a side view of a motorcycle using this exhaust system. 10 …… Engine, 16 …… Exhaust pipe, 18 …… Exhaust control valve assembly, 22 …… Expansion chamber, 34 …… Exhaust control valve, 40 …… Valve shaft, 42 …… Valve plate, 44 …… Thrust receiver l ... gap.

Claims (1)

[Claims] 1. A plurality of exhaust pipes, one end of which is connected to an exhaust port of an engine, and the other end of which is connected to an expansion chamber, and an exhaust control valve which is provided in each of the exhaust pipes and changes an exhaust passage area of each exhaust pipe. In the engine provided, each exhaust control valve includes one valve shaft that traverses each exhaust pipe, a plurality of valve plates fixed to the valve shaft corresponding to each exhaust pipe, and an axial direction of the valve shaft. A thrust receiver for restricting the movement of the valve shaft to the valve shaft, and the valve plate is formed in a shape elongated in a direction orthogonal to the valve shaft. An exhaust control device for an engine, characterized in that a gap is provided to avoid interference between the valve plate and the inner wall of the exhaust passage.