JPS5968520A - Exhaust device for internal-combustion engine with multi-cylinders - Google Patents

Abstract

PURPOSE:To maintain a high torque characteristics over the entire engine speed range from low speed to high speed with minimum torque change by connecting exhaust pipes from respective cylinders through a connecting pipe having a control valve. CONSTITUTION:When an internal combustion engine 1 is operated under low and medium loads, the control valve 10 is closed to interrupt the connection of exhaust pipes 4, 5, and the exhaust gas from respective cylinders 2, 3 is separately routed through the exhaust pipes 4, 5 and mufflers 6, 7 to the atmosphere. When the internal combustion engine 1 is operated under high load and the engine speed exceeds 5,000rpm, the control valve 10 is opened by a signal from a control unit. The exhaust gas from respective cylinders 2, 3 is also routed into the connecting pipe 8 to enlarge the area of exhaust gas passage and to enhance the interference of the exhaust gas between the respective cylinders 2, 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust system for a multi-cylinder internal combustion engine in which exhaust pipes led out from each cylinder are connected by a connecting pipe.

In a multi-cylinder internal combustion engine, when the exhaust pipes leading out from each cylinder are connected with a connecting pipe, the passage area of the exhaust pipe is substantially increased, which improves exhaust efficiency and has the advantage of increasing maximum output. There is. However, during low-load and medium-load operation, the exhaust pulsation may not be utilized effectively because the exhaust air escapes too well.
As shown by the broken line in the figure, a problem occurs in which the torque temporarily decreases during the transition period to high-load operation.

The present invention was made based on the above circumstances, and an object of the present invention is to provide an exhaust system for a multi-cylinder internal combustion engine that has little temporary torque fluctuation and can obtain high torque over the entire operating range.

That is, in order to achieve the above object, the present invention is characterized in that a control valve is provided in the exhaust passage of the connecting pipe connecting the exhaust pipes, and the control valve is opened during high-load operation of the internal combustion engine.

The present invention will be explained below based on an embodiment shown in the drawings.

1 in the figure is an internal combustion engine, and in this example, two cylinders 2
．． It has two cylinders with three cylinders installed in parallel.

Exhaust pipes 4.5 are led out from each cylinder 2, 3, respectively, and mufflers 6.7 are connected to the leading ends of the exhaust pipes 4, 5. The exhaust pipes 4.5 are connected to each other by a connecting pipe 8.
are interconnected. A control valve 10 is provided in the exhaust passage 9 within the connecting pipe 8, and the exhaust passage 9 is opened and closed by this control valve 10. Control valve 1
0 is operated in the opening direction depending on the operating status of the internal combustion engine 1, that is, when transitioning from low load or medium load operation to high load operation, and in the case of this embodiment, the rotation speed of the internal combustion engine 1 ( γpm) is detected from the ignition pulse of the ignition unit 11, and when this detection signal reaches a predetermined level or higher, that is, as shown in FIG.
2 gives an operating signal to a pulse motor 13, which is a drive source for the control valve 10, so that the control valve 10 is opened.

Next, the operation of the configuration described in item 1 will be explained.

Since the control valve 10 is closed during low or medium load operation of the internal combustion engine 1, communication between the exhaust pipes 4.5 is cut off, and the exhaust from each cylinder 2, 3 is independently routed to the exhaust pipe 4.5. 5 and is discharged into the atmosphere through a silencer 6.7. Therefore, the exhaust gas from each cylinder 2.3 does not interfere with each other, so the exhaust pressure in the exhaust pipes 4 and 5 is kept high due to the effect of exhaust pulsation, and therefore, as shown by the solid line in Fig. 3, There is no temporary drop in torque, and torque is improved during low and medium load operation.

On the other hand, the internal combustion engine 1 shifts to high-load operation, and the rotational speed of the internal combustion engine 1 increases to 50.
When the temperature exceeds 00 γpm, the control valve 10 is opened by an activation signal from the control unit 12. Since the control valve 10 opens the exhaust passage 9 in response to an increase in the rotational speed and causes the exhaust pipes 4.5 to communicate with each other, the exhaust gas from each cylinder 2.3 also flows into the connecting pipe 8. Therefore, the surface roughness of the exhaust passage increases, and the exhaust interference between the cylinders 2 and 3 is enhanced. As a result, exhaust efficiency is improved and high torque and high output are obtained. Therefore, as shown by the solid line in FIG. 3, a high torque characteristic with little torque fluctuation can be obtained over the entire rotation range from low speed to high speed.

In the above-described embodiment, the state of transition to high-load operation was detected from the rotational speed of the internal combustion engine, but it may also be detected from, for example, the exhaust pressure, and the means for detecting the rotational speed of the internal combustion engine may also be electrical. The method is not limited to a mechanical type. Further, the control valve is not limited to one that completely closes the exhaust passage, but may be a throttle valve that increases or decreases the area of the passage, for example.

Further, in the above-described embodiment, only the exhaust pipes are connected, but the silencers may also be connected to each other by a connecting pipe or a chamber.

However, the internal combustion engine according to the present invention is not limited to two cylinders, and can be similarly implemented even if it is a multi-cylinder internal combustion engine with three or more cylinders.

As detailed above, according to the present invention, a control valve is provided in the exhaust passage of the connecting pipe connecting the exhaust pipes, and this control valve is opened during high-load operation of the internal combustion engine.
There is no sudden drop in torque during the transition period from low-medium load operation to high-load operation, and high torque characteristics can be obtained over the entire rotation range from low speed to high speed.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic configuration diagram;
FIG. 2 is a block diagram showing the control system of the throttle valve, and FIGS. 3 and 4 show characteristic teeth, respectively. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2, 3... Cylinder, 4, 5... Exhaust pipe, 8... Connecting pipe, 9... Exhaust passage, 1o.
...Control valve.

Claims (1)

[Claims] In a multi-cylinder internal combustion engine in which exhaust pipes led out from each cylinder are connected by a connecting pipe, a control valve is provided in the exhaust passage in the connecting pipe, and this control valve is opened during high load operation of the internal combustion engine. An exhaust system for a multi-cylinder internal combustion engine.