JPH01262319A - Exhaust device of four-cycle four-cylinder engine - Google Patents

Abstract

PURPOSE:To improve output by a method wherein two pairs of exhaust pipes whose ignition periods are different from each other are jointed by respective exhaust chambers and the respective exhaust chambers are jointed by a communicating pipe provided with a switch valve, while the switch valve is driven according to the number of engine rotations. CONSTITUTION:An engine 1 has a cylinder head 2 jointed with four exhaust pipes 3. In this case, two pairs of exhaust pipes 3 whose ignition periods are different from each other are connected by respective exhaust chambers 4. The respective exhaust chambers 4 are connected by a communicating pipe 6 and a switch valve 7 is provided at the middle of the communicating pipe 6. The switch valve 7 is driven according to the number of engine 1 rotations so that it is opened in low and medium speed ranges and closed in a high speed range. This eliminates a valley of output in the low and medium speed ranges while preventing the output from dropping in the high speed range so that the output and drivability can be totally improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an improvement in an exhaust system for a four-stroke, four-cylinder engine.

[Conventional technology and its problems]

In a four-cylinder four-cylinder engine, the tail ends of the exhaust pipes connected to the exhaust holes of each cylinder are gathered together and connected to the muffler. In an engine, the frequency of the exhaust pulsating wave changes depending on the engine speed, the exhaust valve (Ex) is open, and the intake valve (IN) is open.
) near the top dead center (TDC>) and in the medium to low speed range, positive pressure is generated on both the exhaust valve side and the intake valve side as shown in Figure 3 (B), and the intake efficiency and exhaust efficiency increase. In order to prevent this, an on-off valve is provided at the collecting part of the exhaust pipe, and it is opened and closed depending on the rotation speed.
Attempts have been made to effectively change the pulsating waves of the exhaust by creating negative pressure near the exhaust hole by connecting two sets of oval trachea with delayed exhaust timing in a chamber. For example, JP-A-61-212622, Jikai 0116
See Publication No. 2-58017. According to these methods, it is possible to improve the output so that the output can be increased, but it is still not satisfactory.

[Purpose of the invention]

An object of the present invention is to obtain an exhaust system for a four-stroke, four-cylinder engine that can improve the output by eliminating valleys in the low-to-medium speed range, and can also improve the output so that there is no drop or decrease in the output even in the high-speed range.

[Structure of the invention]

The present invention will be explained below with reference to the embodiments shown in FIGS. 1 and 2.

Connect the tips of the exhaust pipes 3 to the four exhaust hole ends of the cylinder head 2 of the four-cycle, four-stroke engine 1, respectively. The ignition types of the engine 1 are as follows: 1, 3, # 2, 4. An exhaust damper 4 is welded to two sets of exhaust pipes 3 with different ignition timings, and a communication hole 5 is formed in the exhaust pipes 3.
is connected to the inside of the exhaust chamber 4. Further, the two exhaust chambers 4 are communicated with each other through a communication pipe 6, and an open valve 7 is provided in the middle of the communication pipe 6. The on-off valve 7 is I! This is a rotational speed responsive switch that detects the rotational speed of the engine 1 using a magnetic solenoid, etc., and opens in the low to medium speed range and closes in the high speed range. The rear ends of the two sets of exhaust pipes 3 are connected to a collecting pipe 8, and a muffler 9 is further connected to the collecting pipe 8.

In the figure, a silencer 9 is connected to each of the two collecting tubes 8, but the rear ends of the two collecting tubes 8 can also be connected to one silencer 9.

(Operation of the invention) When the two exhaust chambers 4 are opened and the valve 7 is opened and communicated with each other through the communication pipe 6, the intake side (IN) and the exhaust side (
The pressure curve of Ex) changes as shown in Figure 3 (A), and the pressure becomes negative near the top dead center where the intake valve starts to hear before the exhaust valve closes. Comparing with B), it can be seen that positive pressure changes to negative pressure. Looking at the output curve, as shown in Figure 4, the valley in the low and medium speed range shown by the dotted line can be improved as shown by the solid line, and the output can be increased. lFf! If you leave valve 7 open in the high speed range,
As shown by the two-dot chain line in FIG. 4, a decrease in output is observed. Therefore, when the on-off valve 7 is closed in the high speed range, the output decrease in the high speed range is also eliminated, as shown by the solid line in FIG.

〔Effect of the invention〕

As explained above, the present invention connects two sets of exhaust pipes whose ignition timings are different among the trachea connected to the exhaust hole of each cylinder of a four-stroke, four-cylinder engine through an exhaust chamber. The exhaust chambers were connected by a communication pipe, and an opening m valve was provided in the middle of the communication pipe, and the IJ11m valve was opened in the low and medium speed range and opened in the high speed range in relation to the engine speed. Therefore, the valley in the output in the low and medium speed range can be improved and high output can be achieved, and the drop in output in the high speed range can also be prevented, resulting in an engine with high overall output and good drivability.

[Brief explanation of the drawing]

1 and 2 show one embodiment of the present invention, FIG. 1 is a perspective view, FIG. 2 is a cross-sectional view of the main part, and FIG. 3 shows pressure measurements of the intake and exhaust boats, (A> is the one of the present invention (
B) shows a conventional example, and FIG. 4 shows an output curve of the present invention. DESCRIPTION OF SYMBOLS 1...Engine, 3...Exhaust pipe, 4...Exhaust chamber, 6...Communication pipe, 7...Opening/closing valve. Applicant's agent Hiroshi Fujiki (A) (B) $3 n

Claims (1)

[Claims] Among the exhaust pipes connected to the exhaust holes of each cylinder of a four-stroke, four-cylinder engine, two sets of exhaust pipes with different ignition timings are connected by an exhaust chamber, and the two exhaust chambers are connected by a communicating pipe. An exhaust system for a four-cycle, four-cylinder engine, characterized in that an on-off valve is provided in the middle of a communicating pipe, and the on-off valve is opened in a low to medium speed range and closed in a high speed range in relation to the engine speed.