JPH0689670B2 - 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 element provided on the valve shaft and the exhaust pipe interfere with each other when the engine is hot or cold.

Furthermore, depending on the location of the exhaust pipes, the arrangement of the exhaust pipes is limited, and the degree of freedom in designing when deciding the arrangement of the exhaust pipes is reduced.

(Object of the invention) The present invention has been made in view of such circumstances, and when the exhaust control valves are provided in a plurality of exhaust pipes, respectively, the control device can be simplified, and the valve shaft expands and contracts due to heat. It is an object of the present invention to provide an exhaust control device for an engine that can reduce the inconvenience and increase the degree of freedom in arranging the exhaust pipes. One or more exhaust gases in an engine including a plurality of exhaust pipes whose other ends are respectively connected to expansion chambers at their mouths, and an exhaust control valve which is provided in each exhaust pipe and changes an exhaust flow passage area of each exhaust pipe A plurality of valve shafts traversing the pipes are arranged so that their center lines intersect each other, and a valve element corresponding to each exhaust pipe is fixed to each of these valve shafts and provided between the valve shafts. Each valve by rotation transmission mechanism It is achieved by an exhaust control system for an engine, characterized in that to link the.

(Operation) When one valve shaft is rotated corresponding to the operating state of the engine, the other valve shafts are also rotated in conjunction with each other, and the exhaust passage area of each exhaust pipe is changed.

The valve shaft extends as the engine temperature rises, but the valve shaft
Since it is divided as described above, it becomes shorter and the amount of expansion and contraction due to heat is small.

(Embodiment) FIG. 1 is a plan view of an exhaust system using an embodiment of the present invention, FIG. 2 is a side view of a motorcycle using the same, and FIG. 3 shows a part of an exhaust control valve assembly. It is the rear view which carried out the cross section.

In FIG. 2, reference numeral 10 is a 4-cycle 4-cylinder engine, which is mounted near the center of the vehicle body. The engine 10 has a cylinder 14 extending obliquely upward and forward from a crankcase 12. 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 assembly 18 connected to the rear end of each exhaust pipe 16, and the exhaust pipes. Two exhaust pipes 16 connected to the rear surface of the control valve assembly 18
Two expansion chambers 22 (22a, 22b) are provided to collect the exhaust gases of a, 16b and 16c, 16d respectively and guide them to the two silencers 20 (20a, 20b).

In FIG. 2, 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 an integrated body of a plurality of exhaust control valves 34 (34a to 34d) that change the exhaust passage area of each exhaust pipe 16, and is fixed to the rear ends of the exhaust pipes 16a and 16b. 36a,
Main body 36b fixed to the rear ends of the exhaust pipes 16c and 16d, and each exhaust pipe
A circular hole 38 provided in each main body 36a, 36b so as to communicate with 16.
(38a to 38d), two valve shafts 40 (40a, 40b) penetrating the circular holes 38a, 38b and 38c, 38d, and a valve plate 42 (a valve body fixed to each valve shaft 40 ( 42a to 42d). The two valve shafts 40a and 40b intersect so that their center lines form an obtuse angle. A bevel gear 44, which serves as a rotation transmission mechanism, is arranged at opposite ends of both valve shafts 40.
Both valve shafts 40a and 40b are interlocked with each other.

A pulley 46 is fixed to the left end of the left valve shaft 40a, and the pulley 46 is forcibly rotated in both directions by a servo motor 50 via a wire 48. The servomotor 50 operates the control valves 34 in the rotation region where the volumetric efficiency deteriorates based on the engine rotation speed detected from the ignition device 52 (see FIG. 1), for example.
Is controlled by the control circuit 54 to close and open in the other rotation regions.

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 54 causes the servo motor 50 to close the exhaust control valve 34 in the medium speed range. To drive. Each of the exhaust control valves 34 is controlled to have the same opening degree in synchronization by two valve shafts 40 that are interlocked with each other.

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.

Further, when the exhaust control valve 34 is used for the purpose of preventing the torque reduction due to the exhaust interference between the cylinders, the exhaust control valve 34 may be closed in a rotation region where the torque reduction due to the exhaust interference is remarkable. When closing the exhaust control valve 34 in the low speed range, the exhaust control valve 34 reduces the exhaust flow passage area by about 90% to 10%.
It is possible to use the one set to about%.

In the above embodiment, the two valve shafts 40a, 40b are arranged in a V shape as shown in FIG. 3, and the exhaust pipe outside the center in the engine width direction is arranged at a position higher than the inside exhaust pipe. Particularly, when applied to an exhaust system that passes under the engine of a motorcycle, there is an effect that a large bank angle of the vehicle body can be secured.

Further, the rotation transmission mechanism may be composed of not only the bevel gear 44 but also another mechanism such as a universal joint.

Further, the present invention also includes one having two or three exhaust pipes.

Although each shaft 40 is driven by the pulley 46 fixed to the outer end of one valve shaft 40a in the above embodiment, the present invention may be driven from the rotation transmission mechanism side between both valve shafts 40.

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 arranges a plurality of valve shafts so as to cross one or more exhaust pipes so that their center lines intersect with each other, and between the valve shafts. Since each valve shaft is interlocked by the rotation transmission mechanism provided, it can be controlled by one driving means such as a servo motor, and the control device is simplified. Also, since the valve shaft is divided into two or more, each valve shaft becomes shorter,
The amount of expansion / contraction change due to heat is reduced. For this reason, measures against expansion and contraction become simple or unnecessary.

Further, the shape of the space occupied by the exhaust pipe can be changed by changing the angle formed by the plurality of valve shafts, and there is an effect that the degree of freedom in designing when the exhaust pipe is housed in the predetermined housing space is increased.

[Brief description of drawings]

FIG. 1 is a plan view of an exhaust system using an embodiment of the present invention, FIG. 2 is a side view of a motorcycle using the same, and FIG. 3 is a rear view showing a part of an exhaust control valve assembly in section. Is. 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 ...... Bevel gear as a rotation transmission mechanism.

Claims (3)

[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 an equipped engine, a plurality of valve shafts that cross one or more exhaust pipes are arranged so that their center lines intersect each other, and a valve element corresponding to each exhaust pipe is fixed to each of these valve shafts. At the same time, an engine exhaust control device is characterized in that each valve shaft is interlocked by a rotation transmission mechanism provided between each valve shaft. 2. The engine is a motorcycle engine having a cylinder extending obliquely upward and forward from a crankcase, and the plurality of exhaust pipes are juxtaposed so as to extend rearward from a front surface of the cylinder through a lower portion of the crankcase. Is
The exhaust control device according to claim 1, wherein each of the exhaust control valves is disposed below the crankcase. 3. An exhaust control valve having at least three exhaust pipes, wherein an exhaust control valve located outside from a center of a width direction of the engine is arranged above an exhaust control valve located inside. 2. The exhaust control device according to claim 2.