JPH0517371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-stroke engine, and particularly to an improvement in its exhaust system structure.

[Conventional technology]

In a 2-stroke engine, exhaust is performed by adding a so-called scavenging process in which the combustion gas is pushed out by the air-fuel mixture, and this allows for more moderate gas exchange and more efficient gas exchange than in an engine with an independent exhaust valve like a 4-stroke engine. That is, there is a drawback that the air-fuel mixture cannot be exchanged with the exhaust gas.

For this reason, in conventional two-stroke engines, part of the air-fuel mixture exits from the exhaust port during exhaust (so-called blow-by phenomenon), reducing the filling efficiency of the air-fuel mixture and resulting in an engine with reduced output.

Conventionally, in order to prevent this type of blow-by phenomenon, an expansion chamber was formed in the exhaust pipe, and the exhaust pressure pulsations generated in this expansion chamber were used to prevent the air-fuel mixture from blow-by, thereby improving the filling efficiency of the air-fuel mixture. However, the optimal volume for forming this expansion chamber differs depending on the rotation range of the 2-cycle engine, and as a result, the output of the 2-cycle engine can be increased over a wide range of rotation speeds. I couldn't improve it.

[Purpose of the invention]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide a two-stroke engine that improves output over a wide range of engine speeds from low speeds to high speeds.

[Structure of the invention]

In order to achieve the above-mentioned object, this invention:
A subchamber is branched and connected to an exhaust passage connected to an exhaust port opening on the inner surface of the cylinder, and a first subchamber is provided between the subchamber and the exhaust passage.
A second valve is disposed at the upper edge of the exhaust port, and interlocking means is interposed between the first and second valves, so that when the engine rotates at low speed, the first valve is disposed at the upper edge of the exhaust port. A valve opens between the exhaust passage and the subchamber, and the second valve is held at a position that delays exhaust timing, and when the engine rotates at high speed, the first valve opens between the exhaust passage and the subchamber. and the second valve is held in a position that accelerates the exhaust timing via the interlocking means, thereby obtaining an exhaust pipe volume and exhaust timing suitable for each engine speed range. This is how it was done.

〔Example〕

An embodiment of the two-stroke engine according to the present invention will be described in detail below.

FIG. 1 is a sectional view of essential parts of a two-stroke engine 10 according to the present invention.

This two-stroke engine 10 has a subchamber 16 formed across a cylinder block 12 and a cylinder head 14. This subchamber 16 communicates with an exhaust passage 20 connected to an exhaust port 26 through a communication hole 18 formed in the cylinder block 12, and this communication hole 18 has a connection between the subchamber 16 and the exhaust passage 20. A cylindrical first valve 22 that opens or closes the gap is rotatably supported.

Note that a through hole 22b is formed in the circumferential surface 22a of the first valve 22, extending between the circumferential surfaces 22a, and the through hole 22b is connected to the communication hole 1.
8, the subchamber 16 and the exhaust passage 20 are opened, and when the through hole 22a and the communication hole 18 are not aligned, the peripheral surface 22a of the valve 22 opens the subchamber 16 and the exhaust passage 20.
The relationship between the two is closed.

On the other hand, the exhaust port 26 located on the cylinder 24 side of the exhaust passage 20 is provided with a second valve 30 that changes the position of the upper edge 26a of the exhaust port 26. This second valve 30 is formed of a plate-shaped valve that slides along the moving direction (arrow A) of a piston (not shown), and the circumferential surface 30a of this second valve 30 is the circumferential surface of the cylinder 24. It is curved along. Further, an interlocking means 40 is interposed between the second valve 30 and the first valve 22, and the interlocking means 40 allows which of the first and second valves 22, 30 to be operated. If one of them is rotated or moved, the other will also be moved or rotated.

The interlocking means 40 includes a pinion 44 fixed to a shaft 42 supporting the first valve 22, and a pinion 44 that meshes with the pinion 44 and is connected to the second valve 30.
It is constituted by a rack 46 formed on the back side of the holder.

In FIG. 1, reference numerals 12a and 12b are relief grooves for the pinion 44, and 48 is a water jacket. Further, since the second valve 30 is engaged with a guide groove (not shown), it will not fall into the cylinder 24.

Next, the operation of the two-stroke engine 10 described above will be explained, and the configuration will also be explained in more detail.

Figure 2 mainly shows the first and second
2 showing the rotation and movement positions of the valves 22, 30 of
This is a sectional view of the main parts of the cycle engine 10, and the same parts as in FIG. 1 are designated by the same reference numerals.

From the start of the two-stroke engine 10 to a predetermined low/medium speed range, the first valve 22 is rotated by a drive device including a servo motor (not shown), as shown in FIG. the valve 22
The through hole 22b and the communication hole 18 are stopped at a matching position.

On the other hand, when this first valve 22 rotates, the interlocking means 4 composed of a pinion 44 and a rack 46
0, the second valve 30 moves below the cylinder 24, and therefore the upper edge 26a of the exhaust port 26 moves downward by a predetermined distance.

In this way, the first and second valves 22, 30
When the engine stops at the position shown in FIG. 2 and is held at that position, the space between the subchamber 16 and the exhaust passage 20 is opened, which increases the exhaust pipe volume, which is required mainly in the low rotation range. The exhaust pipe volume is secured, and the second valve 30 is lowered to lower the upper edge 26a of the exhaust port 26 by a predetermined distance, thereby delaying the exhaust timing. You will get the timing.

On the other hand, when the two-stroke engine 10 reaches a predetermined rotation speed or higher, the first valve 22 is reversely rotated by a drive device (not shown), and the first valve 22 is rotated from the position shown in FIG.
It is rotated to the position shown and held there. Then, the second valve 30 is also moved upward by the interlocking means 40, and the upper edge 2 of the exhaust port 26 is moved upward.
6a is held in the uppermost position.

The first and second valves 22 shown in FIG.
According to the stop position 30, the peripheral surface 22a of the first valve 22 connects the subchamber 16 and the exhaust passage 2.
0 is closed and the exhaust pipe volume decreases,
A suitable exhaust pipe volume for the high rotation range of the two-stroke engine 10 is secured, and the second valve 30
moves upward to speed up the exhaust timing,
This makes it possible to obtain suitable exhaust timing in the high rotation range.

〔Effect of the invention〕

As explained above, in the two-stroke engine of the present invention, a first valve that changes the volume of the exhaust pipe and a second valve that changes the position of the upper edge of the exhaust port are arranged, and these first and second valves are arranged to change the position of the upper edge of the exhaust port. interlocking with the second valve by an interlocking means;
By ensuring suitable exhaust pipe volume and exhaust timing for low/medium rotation range and high rotation range,
It is possible to improve the output of a 2-cycle engine over a wide rotation speed range from low rotation to high rotation.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are sectional views each showing a two-stroke engine according to the present invention. 10...2 cycle engine. 14... Cylinder head, 20... Exhaust passage, 22... First valve, 24... Cylinder, 26... Exhaust port, 26a... Upper edge, 30... Second valve, 40... Interlocking means .

Claims (1)

[Scope of Claims] 1. A subchamber is branched and connected to an exhaust passage connected to an exhaust port opening on the inner surface of the cylinder, and a first valve is disposed between the subchamber and the exhaust passage, and the exhaust port A second valve is disposed on the upper edge, and interlocking means is interposed between the first and second valves, and when the engine rotates at low speed, the first valve connects the exhaust passage and the subchamber. and the second valve is held at a position that retards the exhaust timing, and when the engine rotates at high speed, the first valve closes the gap between the exhaust passage and the subchamber and the interlocking operation is performed. A two-stroke engine, characterized in that the second valve is held at a position that accelerates exhaust timing through means. 2. The two-stroke engine according to claim 1, wherein the first valve is a cylindrical valve with a through hole formed between its peripheral surfaces. 3. The two-stroke engine according to claim 1, wherein the second valve is a plate-shaped valve that moves along the vertical movement direction of the piston. 4. The interlocking means according to claim 1, wherein the interlocking means is a pinion fixed to the first valve and a rack formed on the second valve and meshing with the pinion. 2 cycle engine.