JPH0689671B2 - 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 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 this control valve is closed in a rotational speed range where an adverse effect due to exhaust interference occurs to reduce the exhaust flow passage area.

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 element 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 such circumstances, and when the exhaust control valves are respectively provided in a plurality of exhaust pipes, 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, which can prevent a valve element provided on a valve shaft from interfering with an exhaust pipe.

(Structure of the Invention) According to the present invention, an object is to provide 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. In an engine including an exhaust control valve that changes a passage area, each exhaust control valve includes one valve shaft that traverses each exhaust pipe, and a plurality of valves fixed to the valve shaft corresponding to each exhaust pipe. A body and one thrust receiver for restricting the axial movement of the valve shaft, and the width of the valve body is set smaller than the inner diameter of the exhaust pipe, while the valve body is in a cold state of the engine. The deviation amount in the thrust receiving direction from the exhaust pipe center at the center of
This is achieved by an exhaust control device for an engine, which is set to be larger as the distance from the thrust receiver increases.

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

As the temperature of the engine rises, the valve shaft extends and the valve body 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
The circular holes 38 (38a to 38
d), one valve shaft 40 penetrating each circular hole 38, and a valve plate 42 (42a to 42d) as a valve body 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 a circular shape having a diameter smaller than the inner diameter of the exhaust pipe 16, and its center A _{1 to} A ₄ is the center B ₁ to the exhaust pipe 16 when the engine 10 is cold.
It is deviated to the thrust receiving 44 side from B ₄ , and the deviation amount l _{1 to} l ₄
Is set so that it becomes larger as it goes away from the thrust receiver 44 (FIG. 1). That is, l ₁ > l ₂ > l ₃ > l ₄ is set.

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 opposite direction at the speed of sound in the exhaust pipe 16. 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 in the low speed range,
As the exhaust control valve 34, it is possible to use a valve that reduces the exhaust flow passage area by about 90% to about 10%.

When the engine 10 is cold, the valve plate 42 is deviated to the thrust receiver 44 side as shown in FIG. As the engine 10 warms up, the thrust valve shaft 40 extends leftward in FIG. That is, the valve shaft becomes farther from the thrust receiver 44.
The deviation amount of 40 becomes large. As the valve plate 42 becomes farther from the thrust receiver 44, the amount of deviation l from the center of the exhaust pipe 16 during cold
Is set to be large, so that the valve plate 42 does not interfere with the inner surface of the exhaust pipe 16 when the engine is hot.

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.

(Effect of the invention) As described above, the present invention provides one valve shaft so as to traverse the exhaust pipe, restricts axial movement of the valve shaft by one thrust receiver, and The amount of deviation from the center of the exhaust pipe increases toward the thrust receiving side as the distance from the thrust receiving increases in the engine cold state. Therefore, even if the engine temperature rises and the valve shaft extends, it is possible to prevent interference between the valve body and the exhaust pipe. Also, each exhaust control valve can be controlled by one driving means such as a servo motor,
The control device becomes simple.

[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 as valve body, 44 ... Thrust receiver, A ... Valve plate center, B ... Exhaust pipe center, l ... Deviation amount.

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 bodies fixed to the valve shaft corresponding to each exhaust pipe, and an axial direction of the valve shaft. And a thrust receiver for restricting the movement of the valve body to the exhaust pipe inner diameter, and the width of the valve body is set to be smaller than the inner diameter of the exhaust pipe. An exhaust control device for an engine, wherein an amount of deviation in a thrust receiving direction is set to be larger as the distance from the thrust receiving is increased.