JPS6346665Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a starting pressure reducing device for a two-stroke gasoline engine that is manually started using a recoil starter or the like.

[Prior Art] Small two-stroke gasoline engines used for various tasks are mainly started by hand using a recoil starter, etc., and gasoline engines have a lower compression ratio than diesel engines. Due to the small size of the engine, at present there are almost no pressure reducing devices installed during startup. However, even with 2-cycle engines, the displacement may be large or the compression ratio may be high in order to produce high output, and for this reason it may not be easy to start by pulling the starter rope even when starting with a recoil starter. .

Therefore, attempts have been made to facilitate starting by releasing a portion of the compressed gas during the compression stroke to reduce the pressure. As a prior art related to this, for example, Japanese Utility Model Application Publication No. 53-14025 is known.

[Problem to be solved by the invention] This prior art provides another sub-exhaust port above the exhaust port to directly release a portion of the compressed gas, but according to this method, the compressed gas has no resistance There is a risk that the pressure will be reduced not only during startup but also during normal operation. Also, during depressurization, unburned air-fuel mixture is discharged into the atmosphere, causing air pollution.

In view of these circumstances, the present invention is a two-cycle engine that facilitates starting so as not to cause air pollution problems during hand-cranked starting and to make effective use of fuel, while achieving the specified engine performance during normal operation. The purpose of this invention is to provide a starting pressure reducing device for a gasoline engine.

[Means for solving the problem] For this purpose, the device according to the present invention focuses on the fact that air pollution and fuel waste can be prevented by letting a part of the compressed gas escape to the scavenging port side during depressurization. , a zigzag relief passage is connected from the inside of the cylinder to the scavenging port through the wall, piston skirt and piston pin hole for a certain period of time during compression.During normal operation, the gas flow rate and piston movement are high. The feature is that the pressure reduction effect is ignored and the pressure reduction effect is effective only when the engine starts relatively slowly.

[Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In Fig. 1, reference numeral 1 is a cylinder, 2 is a cylinder head, 3 is a combustion chamber, and 4 is an ignition ignition for spark ignition. A plug 5 is a piston that reciprocates within the cylinder 1, and a scavenging port 6 and the like are opened at the bottom of the cylinder 1. Further, the piston 5 is connected to a connecting rod 9 by a piston pin 8 inserted into a piston pin hole 7.

Therefore, in such a two-stroke gasoline engine, a small gas inlet 10 is opened in the upper part of the wall 1a of the cylinder 1 near the combustion chamber 3, and a gas outlet 11 is opened in the upper part of the scavenging port 6 below. The inflow and outflow ports 10 and 11 are communicated through a passage 12. Also, piston 5
A vertical groove 13 is formed in the skirt portion 5b under the head 5a at a location corresponding to the gas outlet 11 above the piston pin hole 7, and these gas inlets 10, passages 12, gas outlets 11, A relief passage 1 bent in a zigzag manner from the inside of the cylinder 1 toward the scavenging port 6 by a vertical groove 13 and a piston pin hole 7
4. Incidentally, reference numeral 15 is a blind plug that closes the small hole.

Next, the operation of the starting pressure reducing device configured as described above will be explained with reference to FIGS. 2 to 4. During starting, when the starting pulley is manually turned by the recoil starter, the piston 5 reciprocates up and down within the cylinder 1. It becomes like this. And when the piston rises,
The compression stroke begins when the piston 5 reaches the position of the scavenging port 6 and closes it, and immediately after this, the piston head 5a closes the gas outlet 11 and normal compression is performed. Next, when the piston head 5a passes the position of the gas outlet 11 as shown in FIG. The passage 14 is brought into communication, and a portion of the compressed gas in the cylinder 1 escapes from the scavenging port 6, starting a pressure reducing action. Here, since the escape passage 14 is configured in a zig-sag pattern and given a flow resistance, only a small amount of the compressed gas escapes little by little. As shown in FIG. 2b, this pressure reducing action continues until the piston head 5a reaches the position of the gas inlet 10 and closes it, after which the normal compression state resumes.

Such an action is illustrated in FIG. 3, where the pressure reducing action is performed for a certain period of time during the compression stroke. Therefore, the compressive force decreases only during the decompression period, as shown by the broken line in FIG.
Thereafter, the compression pressure increases along the normal compression characteristic shown by the solid line, and a compression pressure that allows ignition to be started by spark ignition from the ignition plug is secured.

On the other hand, during normal operation after starting, the relief passage 14 temporarily becomes in communication as described above during the reciprocating movement of the piston 5, but the moving speed of the piston 5 is significantly higher than that at the time of starting, and this causes The communication time of the escape passage 14 becomes extremely short. Further, since the escape passage 14 itself is narrow and has a flow resistance, the effect of the escape passage 14 is ignored, and escape of compressed gas and combustion gas is substantially eliminated. Therefore, a normal compression pressure as shown by the solid line in FIG. 4 is obtained, and no problem arises with respect to engine performance.

[Effects of the invention] As is clear from the above explanation, according to the invention, the pressure is reduced when starting a two-stroke gasoline engine by hand using a recoil starter, etc.
Easy to start. Since a part of the compressed gas is released to the scavenging port 6 when the pressure is reduced, there is no problem of air pollution caused by being discharged into the atmosphere, and the gas is again taken into the cylinder 1 and used effectively. The pressure reduction action is performed only for a certain period of time during compression, and a compression pressure that allows ignition start is finally secured, so that deterioration in startability can be prevented. During normal operation after startup, the depressurization effect is ignored and the engine can achieve the desired performance. Further, since the piston pin hole 7 is used to construct the relief passage 14, the vertical groove 13 of the piston skirt portion 5b can be short, which is advantageous in terms of strength.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the device according to the present invention, FIGS. 2 a and b are cross-sectional views of the main parts showing each operating state, and FIG. 3 is a diagram showing the depressurization timing in the compression stroke.
FIG. 4 is a diagram showing changes in compression pressure. 1...Cylinder, 2...Cylinder head, 3...Combustion chamber, 4...Spark plug, 5...Piston, 5a...Head, 5b...Skirt portion, 6...Scavenging port, 7...Piston pin hole, 8...Piston pin, 9 …conrod,
10... Inlet, 11... Outlet, 12... Passage, 13
...Vertical groove, 14...Escape passage, 15...Blind plug.

Claims (1)

[Scope of utility model registration request] Only for a certain period during the compression stroke, the inside of the cylinder is communicated with the scavenging port through a narrow, zigzag-curving relief passage formed in the cylinder wall, piston skirt, and piston pin hole, allowing some of the compressed gas to escape. A starting pressure reducing device for a two-stroke gasoline engine, characterized in that it is configured as follows.