JPH0730702B2 - 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, when the downstream side of each exhaust pipe is joined in the expansion chamber, the volume effect 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.

In particular, in the case of an engine mounted on a vehicle and this exhaust control valve is arranged below the engine, it is necessary to make the vertical dimension of the exhaust control valve as small as possible in order to ensure a sufficient clearance with the road surface, that is, a road clearance. is there.

Further, when the exhaust control valves have the same valve shaft, there is a problem that the expansion of the valve shaft due to heat increases. 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 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 a sufficiently large load clearance can be secured. It is an object of the present invention to provide an exhaust control device for an engine, which is suitable for the above-mentioned conditions, can reduce the elongation of the valve shaft due to heat, and can increase the degree of freedom in the arrangement of the exhaust pipes.

(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, and the exhaust pipes disposed below the engine. In an exhaust control device of an engine for a vehicle, comprising an exhaust control valve for changing an exhaust flow passage area, a valve shaft of an exhaust control valve, which is provided substantially horizontally and penetrates one of two adjacent exhaust pipes, Displaced in the valve axis direction to the valve axis of the exhaust control valve that is installed almost horizontally through the pipe and is arranged non-coaxially and substantially parallel to each other. A rotation transmission mechanism that is operably connected is provided near the middle of the adjacent exhaust pipes,
This is achieved by an exhaust control system for an engine, characterized in that one valve shaft is driven by one drive means.

(Embodiment) FIG. 1 is a plan view of an exhaust system of a motorcycle according to an embodiment of the present invention, FIG. 2 is a side view of the same, and FIG. 3 is a side view of a motorcycle using this exhaust system. FIG. 4 is a side view in which a part of the exhaust control valve is cross-sectioned, and FIG. 5 is a cross-sectional view taken along line VV thereof.

In FIG. 3, 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). These expansion chambers 22 are located below or below the engine 10 and the exhaust control assembly 18 is located near below the engine 10.

In FIG. 3, 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 includes a plurality of butterfly type exhaust control valves 34 (34a to 34d) that change the exhaust passage area of each exhaust pipe 16. That is, the assembly 18 is a circular hole (36a ~ 36d) arranged in parallel laterally so as to communicate with each exhaust pipe 16, and a valve shaft 38a, 38c horizontally penetrating each circular hole 36a, 36d, Circular holes 36b and 36c
Through the valve shaft 38b, levers 40a and 40d fixed to the inner ends of the valve shafts 38a and 38c, and levers 40 fixed to both ends of the valve shaft 38b.
b, 40c and links 42a, 42b connecting the turning ends of the levers 40. That is, with the lever 40 and the link 42, each valve shaft 38
A link mechanism A is formed as a rotation transmission mechanism that rotates the gears in synchronization with each other. The circular holes 36a and 36d are located above and behind the 36b and 36c. Further, the link mechanism A crosses planes B, B connecting the centers of two adjacent exhaust pipes 16a, 16b and 16c, 16d (Fig. 5). A circular valve plate 44 (44a to 44d) located in each circular hole 36 is fixed to each valve shaft 38.

A pulley 46 is fixed to the outer end of the valve shaft 38a.
Is forcibly rotated in both directions by a servomotor 50 via a wire 48. The servomotor 50 controls the control valve so as to close each control valve 34 in a rotation region where the volumetric efficiency deteriorates and open it in other rotation regions based on the engine rotation speed detected from the ignition device 52 (see FIG. 2), for example. Controlled by 54.

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 exhaust control valve 34 is controlled by the link mechanism A in synchronization with each other so as to have the same opening degree.

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 the opening end is closed, the positive pressure wave due to the opening of the exhaust valve is reflected by the exhaust control valve 34 and returned to the exhaust valve as a sound wave as a positive pressure wave. 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 controlled.

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 one that is set to about%.

In this embodiment, four exhaust pipes 16 are arranged side by side below a crankcase 12 of an engine 10 for a motorcycle, and exhaust pipes 16a and 16d farther outward from the center of the engine 10 in the width direction are provided inside. Since it is located above 16b and 16c, a large bank angle can be secured for the vehicle, and turning performance is improved. It should be noted that this effect can be similarly obtained when three exhaust pipes are provided and the left and right exhaust pipes are arranged higher than the central exhaust pipe.

Also, as in this embodiment, some exhaust control valves (34a, 34d)
Is displaced to the rear of the other exhaust valves (34b, 34c),
The degree of freedom in design is increased in that an appropriate exhaust control stool 34 can be shifted back and forth to be placed at an optimum position in accordance with the difference in length due to the layout of the exhaust pipes 16.

In particular, when the position of each exhaust control valve 34 is changed up and down, traveling wind easily hits each exhaust control valve 34, and the cooling performance is improved accordingly.

It is desirable that the rotation transmission mechanism has a link structure,
The present invention is not limited to this, and gears may be used to interlock each valve shaft.

Further, the present invention is not limited to the case where four exhaust pipes are provided,
It also includes those suitable for the case of having two exhaust pipes.

(Advantages of the Invention) As described above, according to the present invention, when the exhaust control valve provided for each exhaust pipe is arranged below the engine, each valve shaft that penetrates two adjacent exhaust pipes substantially horizontally is provided. The valve shafts are arranged so as to be eccentric to each other in a non-coaxial manner and substantially parallel to each other, and opposite end portions of both valve shafts are connected to each other by a rotation transmission mechanism so as to be interlocked with each other. Therefore, the plurality of exhaust control valves can be controlled by one drive means such as a servo motor, and the control device is simplified.

In addition, since each valve shaft is connected so that the end parts work together,
The vertical dimension of the exhaust control valve can be made smaller than in the case where the exhaust control valves provided for each exhaust pipe are driven separately. Therefore, when the exhaust control valve is provided below the engine, a large load clearance can be secured.

Further, since each valve shaft is shortened, measures against expansion of the valve shaft due to heat of exhaust gas are simple or unnecessary. Further, since the positions of the adjacent exhaust control valves can be changed relatively freely in the length direction of the exhaust pipe or the direction orthogonal to the exhaust pipe, there is an effect that the degree of freedom in design is increased.

[Brief description of drawings]

FIG. 1 is a plan view of an exhaust system of a motorcycle which is an embodiment of the present invention, FIG. 2 is a side view of the same, FIG. 3 is a side view of a motorcycle using this exhaust system, and FIG. FIG. 5 is a sectional view taken along line VV of the exhaust control valve of FIG. 10 ... Engine, 16 ... Exhaust pipe, 18 ... Exhaust control valve assembly, 22 ... Expansion chamber, 34 ... Exhaust control valve, 38 ... Valve shaft, A ... Link mechanism as rotation transmission mechanism, B: A plane that connects the centers of the exhaust pipes.

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 disposed below the engine and changes an exhaust passage area of each exhaust pipe. In an exhaust control device for a vehicle engine, the valve shaft of an exhaust control valve that is provided substantially horizontally through one of two adjacent exhaust pipes is provided substantially horizontally through the other exhaust pipe. The rotation transmission mechanism is arranged so as to be eccentric to the valve axis of the exhaust control valve in the valve axis direction and non-coaxial and substantially parallel to each other, and the opposite end portions of the two valve axes are connected so as to be interlocked with each other. An exhaust control device for an engine, which is provided in the vicinity of the middle of the exhaust pipe, and drives one valve shaft by one drive means. 2. The engine is a motorcycle engine having a cylinder that extends obliquely upward and forward from a crankcase, and the plurality of exhaust pipes extend rearward from the front surface of the cylinder through a lower portion of the crankcase and under the engine. Side by side so as to be connected to the expansion chamber arranged near the rear,
The engine exhaust control device according to claim 1, wherein the exhaust control valves are disposed below the crankcase. 3. An exhaust gas 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. An exhaust control device for an engine according to claim 2.