JPH0511301Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a two-stroke engine equipped with a variable exhaust timing device.

[Prior art]

As shown in FIGS. 7 and 8, the two-stroke engine has a valve body 3 removably disposed on the upper wall 2a of the housing 2 that forms the exhaust passage 1, so that the valve body 3 is retractably disposed in the upper wall 2a of the housing 2 forming the exhaust passage 1. The valve body 3 is made to protrude, and the tip 3a of the valve body 3 is made to face the upper part of the exhaust port 5 of the cylinder 4 to block the upper part of the exhaust port 5, thereby delaying the exhaust timing and reducing the exhaust timing in the high speed range of the engine. Some devices are equipped with an exhaust timing variable device that retracts the tip 3a of the valve body 3 from the exhaust port 5 of the cylinder, thereby accelerating the exhaust timing.

By the way, in a two-stroke engine equipped with such a variable exhaust timing device, when the engine is stopped, the valve body 3 protrudes and closes the upper part of the exhaust port 5.

Therefore, when starting the engine, the compression ratio is high, making it difficult to start, especially when starting with a kick starter.

[Purpose of invention]

An object of the present invention is to provide a two-stroke engine with a variable exhaust timing device that has good startability.

[Structure of the idea]

The two-stroke engine with a variable exhaust timing device of the present invention includes a bypass means that substantially communicates the upper part of the exhaust port with the exhaust passage when the valve body is actuated to completely block at least the upper part of the exhaust port. There is.

In other words, if you try to start the engine in such a state, even if the piston closes the exhaust port (the open part), the inner space of the cylinder formed on the top surface of the piston will be blocked by the bypass means. Since the compressor is connected to the exhaust passage, compression resistance is small and large force is not required.

〔Example〕

1, 3 and 5 show a two-stroke engine equipped with a variable exhaust timing device according to the present invention.

This engine 10 has a cylinder 12 in a housing 11, and the cylinder has a cylinder 12 shown in FIG.
As shown in FIGS. 4 and 6, two exhaust ports 13 are formed. On the other hand, housing 11
An exhaust passage 14 continuous from the exhaust port 13 is formed in the upper wall 1 forming the exhaust passage 14.
Two circular holes 15 are bored in 1a toward the exhaust port 13. The two holes 15,1 mentioned above
A roughly semi-cylindrical guide sleeve 1 is provided on the upper peripheral surface of the guide sleeve 5.
6 and 16 are attached, and the guide sleeve 1
6, 16 guide surfaces 16a, 16a and holes 15, 1
Approximately semi-cylindrical valve bodies 17, 17 are slidably disposed in the hollow portion defined by the lower peripheral surface of the valve body 5.

Furthermore, the engine 10 shown in FIGS. 1, 3, and 5 has bypass means 20, 3, respectively.
It is equipped with 0.40.

Bypass means 2 for the engine 10 shown in FIG.
0 has a ventilation port 21 at the upper side edge of the exhaust port 13, as shown in FIG. The vent 21 is communicated with the exhaust passage 14 via a groove (vent passage) 22 formed in the side wall 11b of the exhaust passage 14.

Further, the bypass means 30 of the engine 10 shown in FIG. 3 is connected to the exhaust port 1 as shown in FIG.
3 has a ventilation port 31 independent from the air vent 31. The ventilation port 31 is communicated with the exhaust passage 14 via a ventilation passage 32 formed within the housing 11 .

Furthermore, the bypass means 40 of the engine 10 shown in FIG. 5 has a ventilation passage 41 formed in the valve body 17, as also shown in FIG. It has an opening in the closed surface 17a and the opposite side 17b, and is exposed in the exhaust passage 14 at the maximum operating position of the valve body 17 (the position shown in FIG. 5).

The operation of the two-stroke engine 10 equipped with the variable exhaust timing device described above will be explained below.

First, when starting the engine 10, the valve body 1
7 protrudes as shown in FIGS. 1, 3, and 5, and is in a state of closing the exhaust port 13. However, the upper part of the exhaust port 13 or the exhaust port 1
Ventilation hole 2 is formed at almost the same height as the top of 3.
1 and 31 are in communication with the exhaust passage 14 via the ventilation passages 22, 32, and 41, so that even if the piston 18 closes the open part of the exhaust port 13, the piston 18 is formed on the upper surface of the piston 18. The cylinder interior space is not completely sealed. Therefore, the piston 18
Compression resistance is small and starting is easy.

Even when the engine 10 is started, the valve body 17 remains in a state where the upper part of the exhaust port 13 is closed in the low speed range of the engine 10. Therefore, the exhaust timing is delayed, and the optimum output performance of the engine 10 in the low speed range is maintained. In this state, the upper part of the cylinder 12 is communicated with the exhaust passage 14 by the bypass means 20, 30, 40, but the ventilation holes 21, 31, the ventilation passage 22,
The cross-sectional areas of 32 and 41 are made small so that they do not have much influence on the effect of delaying the exhaust timing.

When the engine 10 reaches a high speed range, the valve body 17 is recessed into the housing 11, thereby completely opening the exhaust port 13. Therefore,
The exhaust timing becomes earlier, and optimal output performance in the high speed range of the engine 10 can be obtained.

In addition, in the above embodiment, the valve body 17 was shown to be actuated linearly to open and close the upper part of the exhaust port 13.
Of course, the valve body 17 may be rotatably operated.

[Effect of idea]

As described above, the two-stroke engine with a variable exhaust timing device according to the present invention has low compression resistance when starting, and therefore has good startability. Furthermore, if the exhaust timing is delayed, the compression ratio will increase and there is a risk that abnormal combustion will occur in the extremely low rotational speed region of the engine, but in the engine according to the present invention, abnormal combustion can be prevented.

[Brief explanation of drawings]

Figures 1 and 2 show an embodiment of a two-stroke engine according to the present invention, with Figure 1 being a vertical sectional view of the main parts of the engine, and Figure 2 showing the exhaust port in a closed state. Partially enlarged front view of cylinder, 3rd
4 and 4 show another embodiment of the two-stroke engine according to the present invention, FIG. 3 is a longitudinal cross-sectional view of the main part of the engine, and FIG. 4 is a cylinder showing a closed state of the exhaust port. 5 and 6 show still other embodiments of the two-stroke engine according to the present invention, FIG. 5 is a longitudinal cross-sectional view of the main parts of the engine, and FIG. FIGS. 7 and 8 are partially enlarged front views of the cylinder showing a closed state of the exhaust port, and show a conventional two-stroke engine. FIG. 7 is a longitudinal cross-sectional view of the main parts of the engine, and FIG. FIG. 2 is a partially enlarged front view of the cylinder showing a closed state of the exhaust port. 10...Engine, 11...Housing, 12
... cylinder, 13 ... exhaust port, 14 ... exhaust passage, 17 ... valve body, 20 ... bypass means, 21
...Vent, 22...Vent, 30...Bypass means, 31...Vent, 32...Vent, 40...
...bypass means, 41...ventilation path.

Claims (1)

[Claims for Utility Model Registration] (1) An exhaust timing variable device is provided, in which a valve body is arranged in relation to the exhaust port, and the valve body blocks the upper part of the exhaust port, thereby delaying the exhaust timing. In a cycle engine, an exhaust gas comprising a bypass means that substantially communicates the upper part of the exhaust port with an exhaust passage when the valve body is actuated to completely block at least the upper part of the exhaust port. 2-stroke engine with variable timing device. (2) The bypass means has a ventilation port separate from the exhaust port in the cylinder and at approximately the same height as the top of the exhaust port, and the ventilation port passes through the wall forming the exhaust passage. A two-stroke engine with a variable exhaust timing device as set forth in claim (1) of the registered utility model, characterized in that the engine is always in communication with the exhaust passage. (3) The bypass means has a ventilation passage in the valve body, and the ventilation passage communicates the upper part of the exhaust port with the exhaust passage. A two-stroke engine with a variable exhaust timing device as described in item 1). (4) The above-mentioned ventilation passage is formed in a position where the upper part of the above-mentioned exhaust port and the above-mentioned exhaust passage communicate with each other only at the maximum operating position of the above-mentioned valve body. A two-stroke engine with a variable exhaust timing device as described in 3).