JPH0791989B2 - 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 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.

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, there also arises a problem that the elongation due to the heat becomes large.

(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 a decrease in volumetric efficiency can be suppressed to reduce the torque valley. It is an object of the present invention to provide an engine exhaust control device capable of improving the torque characteristics by reducing the valve ratio and further reducing the elongation of the valve shaft due to heat.

(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 an exhaust flow of each exhaust pipe provided in each of the exhaust pipes. In an engine exhaust control device including an exhaust control valve that changes a passage area, each exhaust control valve includes a mutually parallel valve shaft that penetrates near the opening end on the expansion chamber side of each exhaust pipe. , Passing through one end of each valve shaft and orthogonal to each valve shaft 1
A book control rod, a transmission mechanism that converts the movement of the control rod into rotation of each valve shaft, a valve element that is attached to each valve shaft, and narrows the exhaust flow passage area of each exhaust pipe at its closed position, One servo motor that synchronously opens and closes all the valve elements via the control rod and the transmission mechanism, and a flow passage area of each exhaust control valve of about 1 in a medium speed range where the volumetric efficiency of the engine decreases. / 2
And a control circuit for controlling the servomotor in accordance with the engine rotation speed so as to limit the above.

(Operation) The linear movement or the rotational movement of the control rod causes each valve shaft to rotate synchronously by the transmission mechanism, and changes the exhaust passage area of each exhaust pipe based on the operating state of the engine.

(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 plan view of the exhaust control valve, FIG. 5 is a rear view with a partial cross section, and FIG.
VI-VI sectional view, and FIG. 7 is an exploded perspective view near the exhaust control valve.

1 to 3, 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. 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 is an integration of a plurality of exhaust control valves 34 (34a to 34d) that change the exhaust passage area of each exhaust pipe 16, and is arranged side by side so as to communicate with each exhaust pipe 16. Circular holes 36 (36a to 36d), valve shafts 38 (38a to 38d) that vertically pass through the circular holes 36, and levers 40 (40a to 40d) fixed to the upper ends of the valve shafts 38. , A control rod 42 connecting the turning ends of the levers 40. That is, with the lever 40 and the control rod 42,
A link mechanism is formed as a transmission mechanism that rotates each valve shaft 38 in synchronization. A valve plate 44 (44
a to 44d) are fixed.

A pulley 46 is fixed to the upper 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. The respective exhaust control valves 34 are controlled by the control rod 42 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 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 passage area is halved, the sum of the negative pressure wave returned by the open end of the exhaust pipe and the positive pressure wave reflected by the exhaust control valve 34. Is 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. In this case, it is possible to use the exhaust control valve 34 in which the exhaust flow passage area is reduced to about 90% to about 10%.

In the above embodiment, the exhaust control valves 34 are located on a straight line, but when the heights of the exhaust control valves 34e to 34h are changed as shown in FIG. 8, the lengths of the valve shafts 38e to 38h are changed. Can be coped with by changing, and when it is arranged below the engine of the motorcycle, the turning traveling performance can be improved by increasing the bank angle of the vehicle, and the present invention also includes such a thing.

Although it is desirable that the transmission mechanism has a link structure, the present invention is not limited to this, and the rack and pinion is used to change the parallel movement of the control rod into the rotation of the valve shaft, or the bevel gear is used to control the control rod. The rotation may be changed to the rotation of the valve shaft.

(Effects of the Invention) As described above, the present invention provides the exhaust control valve valve shafts provided in the exhaust pipes separately and in parallel for each exhaust pipe, passing near one end of each valve shaft and orthogonal to each valve shaft. Opening and closing of each exhaust control valve is synchronized by a single control rod via a transmission mechanism. Therefore, each exhaust control valve can be controlled by one servomotor, which simplifies the control device. In addition, each exhaust control valve closes its flow passage area to about 1/2 in the medium speed rotation speed range where the volumetric efficiency is reduced, and in particular, suppresses the torque decrease in the middle speed range and improves the torque characteristics. be able to. Further, since each valve shaft is provided separately for each exhaust control valve, the valve shaft becomes short, and measures against expansion of the valve shaft due to exhaust heat become simple or unnecessary.

[Brief description of drawings]

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, FIG. 3 is a side view of a motorcycle using this exhaust system, and FIG. 4 is an exhaust system. FIG. 5 is a plan view of the control valve, FIG.
FIG. 7 is a sectional view taken along line VI-VI, FIG. 7 is an exploded perspective view of the vicinity of the exhaust control valve, and FIG. 8 is a view showing an exhaust control valve arrangement of another embodiment of the present invention. 10 …… Engine, 16 …… Exhaust pipe, 18 …… Exhaust control valve assembly, 34 …… Exhaust control valve, 38 …… Valve shaft, 42 …… Control rod, 44 …… Valve plate as valve body, 50 ...... Servomotor, 54 …… Control circuit.

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 the exhaust control device for an engine, the exhaust control valves include valve shafts that are parallel to each other and that are provided independently through the expansion chamber side opening ends of the exhaust pipes and that are provided near one end of the valve shafts. One control rod that is orthogonal to each valve shaft, a transmission mechanism that converts the motion of the control rod into the rotation of each valve shaft, and the exhaust flow of each exhaust pipe attached to each valve shaft and in its closed position. A valve body for narrowing the road area and all of the valve bodies are opened and closed synchronously through the control rod and the transmission mechanism 1
Two servo motors and the servo motors are controlled corresponding to the engine speed so as to limit the flow passage area of each exhaust control valve to about 1/2 in the medium speed range where the volumetric efficiency of the engine decreases. An exhaust control device for an engine, comprising: a control circuit. 2. The engine is a motorcycle engine having a cylinder extending obliquely upward and forward from the crankcase, and the plurality of exhaust pipes extend rearward from the front surface of the cylinder through a lower portion of the crankcase. The exhaust emission control device for an engine according to claim 1, wherein the exhaust emission control valves are arranged in parallel and 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.