JPS6220621A - 2-cycle engine - Google Patents

Abstract

PURPOSE:To relieve a sudden rise in a pressure and to reduce a fluctuation in torque due to irregular combustion, by a method wherein an on-off valve is located in a bypass passage running from the upper area of cylinder to an exhaust passage, and the valve is opened in a middle and low speed range and a middle and low load range. CONSTITUTION:A bypass passage 10 is so formed as to extend from a position above an exhaust port 8 in a cylinder 1 to the middle of an exhaust passage 9. An electromagnetic valve 11 is located to the middle of a bypass passage 10, and the bypass passage 10 is opened and closed by a valve part 11a of the electromagnetic valve. In which case, operation of the electromagnetic valve 11 is controlled depending upon the rotation speed or the load of an engine, and is so constituted as to be opened at a middle and low speed range and a middle and low load range, and closed at a high speed range and a high load range. Since the upper range of the cylinder 1 is brought into a state in that it is communicated with an exhaust passage 9 through the bypass passage 10 at a middle and low speed range and a middle and low load range, a sudden rise in a pressure during a compression stroke and an expansion stroke is leaked through the bypass passage 10, and this enables relief of the sudden rise in the pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a two-stroke engine installed in a motorcycle or the like.

[Prior art]

It is known that a two-stroke engine is prone to misfire intermittently and to cause asymmetric combustion in its medium to low speed range, medium to low load range, and the like. When such irregular combustion occurs in a two-stroke engine installed in a vehicle such as a motorcycle, the fuel accumulated in the cylinder due to irregular combustion is burned all at once at the next ignition, which increases the torque fluctuation per cycle. The vibrations generated at this time cause discomfort to passengers.

[Purpose of the invention]

An object of the present invention is to provide a two-stroke engine that reduces torque fluctuations caused by irregular combustion as described above.

[Structure of the invention]

The two-stroke engine of the present invention that achieves the above object is provided with a bypass passage leading from the upper region of the cylinder to the exhaust passage, and a valve for opening and closing this bypass passage. This is characterized by a structure in which the valve opens in any one of the regions.

〔Example〕

Hereinafter, the present invention will be explained with reference to embodiments shown in the drawings.

In the two-stroke engine shown in FIG. 1, 1 is a cylinder, 2 is a piston, and 3 is a crankshaft. cylinder 1
A combustion chamber 4 is provided in the upper part of the combustion chamber 4, and a spark plug 5 is provided on the upper surface of the combustion chamber 4.

Further, an intake boat 6 and an intake passage 7 communicating therewith are provided on one side of the cylinder 1, and an exhaust boat 8 and an exhaust passage 9 communicating therewith are provided on the other side. There is.

Reference numeral 10 denotes a bypass passage bent in an L shape, which communicates with the cylinder 1 from a position above the exhaust boat 8 to the middle of the exhaust passage 9.

A solenoid valve 11 is provided in the middle of this bypass path 10,
The bypass passage 10 is opened and closed by the valve portion 11a crossing the bypass passage 10. This solenoid valve 11 is controlled to open and close according to the rotational speed or load of the 5 engines, and is opened in the medium-low speed range and medium-low load range.
The valve closes in high speed and high load ranges.

Such rotational speed and load signals can be obtained from, for example, a generator or a throttle potentiometer (not shown).

According to the two-stroke engine described above, in the medium-low speed range and medium-low load range, the upper region of the cylinder 1 is in communication with the exhaust passage 9 via the bypass passage 10, so that the compression stroke is carried out via the bypass passage 10. The rapid pressure rise during the expansion stroke is relieved by IJ. Therefore, torque fluctuations due to irregular combustion are reduced, and the vehicle occupants do not feel uncomfortable.

FIG. 2 shows a two-stroke engine showing another embodiment of the present invention.

Similar to the first embodiment, this two-stroke engine is provided with a bypass passage 10 extending from the upper part of the cylinder 1 to the middle of the exhaust passage 9, and a rotary valve 12 is provided at the part that opens into the exhaust passage 9. ing. This rotary valve 12
The rotation is controlled according to the engine speed or load, and in the high speed range or high load range, the bypass path 1 is closed as shown by a.
0 is in the closed state, and again in the medium and low speed range.

In the medium to low load range, a part of the rotary valve 12 closes the upper end of the exhaust boat 8, as shown in c, thereby minimizing intake air blow-through and improving fuel efficiency and output. I have to. Especially in the medium speed range under low load,
As shown in C, the open circuit 10° is communicated with the bypass passage 10 so that the upper region of the cylinder 1 leaks. Similar to the first embodiment, such rotational speed and load signals can be taken out from a generator, a throttle potentiometer, or the like.

In the case of this embodiment as well, as in the first embodiment, torque fluctuations due to irregular combustion can be reduced in the low load and medium speed range.

〔Effect of the invention〕

As described above, the two-stroke engine of the present invention is provided with a bypass path leading from the upper region of the cylinder to the exhaust passage, and is also provided with a valve that opens and closes this bypass path, and this valve is operated in the medium and low speed range of the engine.

Since the valve is configured to open in either the medium or low load range, the sudden pressure rise during the compression stroke or expansion stroke is alleviated by leaking into the exhaust passage through the bypass passage, thereby reducing torque fluctuations caused by irregular combustion. Decrease. Further, this reduction in torque fluctuation does not cause discomfort to vehicle occupants.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a two-stroke engine according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of a two-stroke engine according to another embodiment. 1- cylinder, 4- combustion chamber, 5 single spark plug, 8-
Exhaust boat, 9-Exhaust passage, 10-Bypass passage, 11-Solenoid valve, 12-Rotary valve.

Claims (1)

[Claims] In addition to providing a bypass passage from the upper area of the cylinder to the exhaust passage, a valve is provided to open and close this bypass passage, and this valve is configured to open in either the medium-low speed range or the medium-low load range of the engine. Features a 2-stroke engine.