JPH0519009B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an exhaust system for an engine in which the piston itself acts as an exhaust valve, that is, a two-stroke engine.

[Prior Art] Conventionally, in a two-stroke engine, an auxiliary exhaust passage is provided in addition to the main exhaust passage, and the auxiliary exhaust passage is closed at low speeds and opened at high speeds to reduce the cross-sectional area of the exhaust passage ( There is an exhaust system that aims to improve output by making the area (hereinafter referred to as passage area) commensurate with the rotational speed of the engine. However, in this prior art, no consideration is given to medium speeds, so the output at medium speeds decreases.

Therefore, there is an exhaust control device that increases the passage area of the auxiliary valve steplessly by gradually opening the auxiliary valve that opens and closes the auxiliary exhaust passage in accordance with the increase in engine speed. 60-249614). By doing so, this prior art attempts to maintain the output over a wide range from low speed to high speed.

[Problems to be Solved by the Invention] However, the above-mentioned auxiliary valve has been designed to avoid interference between the stand bolt that connects the cylinder block and the cylinder head and the drive rod of the auxiliary valve, or to reduce the thickness of the cylinder wall. For reasons such as maintaining sufficient exhaust gas, it is provided at a position away from the cylinder in the auxiliary exhaust passage. For this reason,
Although the auxiliary exhaust passage between the cylinder and the auxiliary valve is long, the distance narrowed by the auxiliary valve is extremely short. Therefore, the actual passage area of the auxiliary exhaust passage is almost the same when the auxiliary exhaust passage is slightly opened by the auxiliary valve and when it is fully opened, so the area in between is suitable for high speed operation. become. As a result, a passage area suitable for medium speeds cannot be obtained, resulting in a decrease in output at medium speeds.

This invention was made in view of the above-mentioned conventional problems, and can be applied over a wide range from low speed to high speed.
The object of the present invention is to provide an exhaust system for a two-stroke engine that can improve output.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a common auxiliary valve in the middle of a plurality of auxiliary exhaust passages disposed close to each other to reduce the rotational speed of the engine. Depending on the increase, the above common auxiliary valves
The number of auxiliary exhaust passages to be opened is increased in multiple stages.

[Operation] According to the present invention, since the number of auxiliary exhaust passages to be opened is increased in multiple stages, the passage area of the auxiliary exhaust passages is controlled in two or more stages, so that substantially all the exhaust passages are The area can be controlled in three or more stages. Therefore, it is possible to improve the output over a wide range from low speed to high speed. Further, since the plurality of auxiliary exhaust passages are arranged close to each other and are opened and closed by one auxiliary valve, the number of auxiliary valves does not increase.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, two auxiliary exhaust ports 4, 5 and 6, 7 are provided on both sides of a main exhaust port 3 of a main exhaust passage 2 that communicates with the inside of a cylinder 1, respectively. The auxiliary exhaust ports 4, 6 and 5, 7 are provided with first and second auxiliary exhaust passages 8, 10 and 9, 11 having small passage areas.
Each of them communicates with the main exhaust passage 2. In other words, the auxiliary exhaust passages 8...11 connect the cylinder 1 and the main exhaust passage 2 as auxiliary exhaust passages. In addition, the two auxiliary exhaust passages 8 on the left side,
9, as well as the two auxiliary exhaust passages 10 on the right side,
11 are both arranged close to each other.

Auxiliary valves 12 and 13 are provided in the middle of the auxiliary exhaust passages 8, 9 and 10, 11, respectively. In other words, the auxiliary valves 12, 13
is arranged at a distance from the cylinder 1 for reasons such as maintaining a sufficient thickness of the cylinder wall. The auxiliary valves 12 and 13 are rotary valves that rotate in both directions, and the valve body 12a,
13a and valve passages 12b, 13b. As will be described later, the auxiliary valves 12 and 13 increase the number of auxiliary exhaust passages 8...11 that are opened in multiple stages as the engine speed increases. In the state shown in FIG. 1, which indicates low speed, the resonance chamber 1 provided on the side of the auxiliary exhaust passages 9 and 11
4 and 15 are communicated with the main exhaust passage 2 via the valve passages 12b and 13b, thereby preventing a decrease in output at low speeds. In addition, 40 is an auxiliary exhaust mechanism, which includes a first auxiliary exhaust passage 8 or 10 and a second auxiliary exhaust passage 9 or 1.
1 and an auxiliary valve 12 or 13, one on each side of the main exhaust passage 2.

In FIG. 2 showing a longitudinal cross section of FIG. 1, the auxiliary valves 12, 13 have valve bodies 12a, 13a
, cylindrical parts 12c, 13c, and shaft parts 12d, 13
d and valve pinions 12e and 13e are integrally formed. The auxiliary valves 12 and 13 have shaft portions 12d and 13d rotatably supported by the engine body 16.

Reference numeral 17 denotes a drive rod, which moves the inside of a sliding hole 30 provided in the engine body 16 by the drive device 25 shown in FIG. 3 as the rotational speed of the engine increases.
It is moved to the left side. This driving rod 1
At 7 there is a first rack 1 which engages the pinion 18.
7a and a second rack 17b which engages the right-hand valve pinion 13e. The pinion 18 shown in FIG. 2 is rotatably supported on the engine body 16 by its shaft portion 18a, and is also engaged with the left valve pinion 12e as shown in FIG. 3. Numeral 19 is a low speed stopper, and 20 is a high speed stopper, which positions the drive rod 17 at low speed or high speed, respectively.

The drive device 25 moves the steel balls along the inclination of a dish-shaped spherical plate when the rotational speed of the crankshaft exceeds a predetermined value by rotation of a governor (not shown) connected to the crankshaft. This is a well-known device (see the above-mentioned prior literature). Further, the drive device 25 may have a well-known structure that detects the rotational speed of the engine with a detector (not shown) and operates the actuator of the motor. Furthermore, for example,
By providing a step part in the middle of the slope of the dish-shaped spherical plate, the movement of the steel ball is temporarily stopped at this step part, so that the drive rod 17 is in the middle speed state shown in FIG. A structure may be adopted in which the rotation speed is stopped within a predetermined range of rotation speeds.

Next, the operation of the above configuration will be explained.

At low speed in Figure 1, four auxiliary exhaust ports 4
... 7 are closed by the auxiliary valves 12 and 13, and exhaust is exhausted only from the main exhaust passage 2. For this reason,
As shown in FIG. 4, the output at low speed changes like a curve L.

After that, when the engine speed reaches N1,
As the drive rod 17 in FIG. 3 gradually moves to the left, the pinion 18 and the right valve pinion 13e are each rotated counterclockwise. At this time, the left valve pinion 12
e is rotated clockwise by pinion 18. With this rotation, the auxiliary valves 12 and 13 in FIG.
are in opposite directions, that is, arrow A,
It rotates in direction B until it reaches the position shown in FIG. 5, which indicates medium speed. At this time, the first auxiliary exhaust passages 8, 1
0 communicates with the main exhaust passage 2 via valve passages 12b and 13b. On the other hand, the second auxiliary exhaust passages 9 and 11 are closed by valve bodies 12a and 13a. From when the first auxiliary exhaust passages 8, 10 are slightly opened until they are completely opened, that is, at medium speeds, exhaust is exhausted from the first auxiliary exhaust passages 8, 10, and from the second auxiliary exhaust passages. Since there is no exhaust air from ports 9 and 11, the substantial passage area becomes large enough for medium speeds, and the output changes as shown by curve M in FIG.

Furthermore, by setting the inclination of the spherical plate mentioned above, when the engine speed reaches N1, the auxiliary valves 12 and 13 shown in Fig. 1 are opened rapidly rather than gradually, and the auxiliary valves 12 and 13 shown in Fig. 5 are opened rapidly. It may be stopped for a predetermined period of time in this state.

Furthermore, as the rotational speed of the engine increases, the auxiliary valves 12 and 13 continue to rotate, and when the rotational speed reaches N2 in FIG. 4, the second auxiliary exhaust passages 9 and 11 in FIG. It will be released. Eventually, the drive rod 17 in FIG. 3 moves to the high speed stopper 2.
0, the valve pinions 12e, 13e and the auxiliary valves 12, 13 shown in FIG. 6 stop rotating, and the second auxiliary exhaust passages 9, 11 are completely opened. Therefore, the above rotation speed is N2
At high speeds greater than , all exhaust passages 2,
Since the air is exhausted from 8...11, the substantial passage area becomes large enough to be suitable for high-speed operation, and the output changes as shown by curve H in FIG.

In the above configuration, the present invention provides, for example, the first
As shown in the figure, first and second auxiliary exhaust passages 8,
10, 9, and 11 are provided and are sequentially opened as the engine speed increases, so that the substantial passage area of the auxiliary exhaust passages 8...11 can be increased in two stages. In other words, the substantially total area of the exhaust passages 2, 8, . . . , 11 can be controlled in three stages. Therefore, even at medium speeds, the passage area can be made commensurate with the medium speeds, so that the output corresponding to the perspective part S in FIG. 4 can be improved. In other words, the output can be improved over a wide range from low speed to high speed, and the output from low speed to high speed can be smoothly connected.

In addition, the first auxiliary exhaust passage 8 or 1 in FIG.
0 and the second auxiliary exhaust passage 9 or 11 are provided adjacently, and both auxiliary exhaust passages 8, 9 or 10, 11
Since the auxiliary valves 12 or 13 are opened and closed by one auxiliary valve 12 or 13, the number of auxiliary valves 12 or 13 does not increase compared to the conventional one. Therefore, there is no fear that the structure will become complicated or large.

Note that it is also possible to increase the number of auxiliary exhaust passages to increase the number of auxiliary exhaust passages that are opened to three or more stages, and this is included in the present invention.

[Effects of the Invention] As explained above, according to the present invention, the number of auxiliary exhaust passages that are opened increases in multiple stages as the engine rotational speed increases, so it can be used in a wide range from low speed to high speed. It is possible to improve the output over a period of time, and it is also possible to smoothly connect the output from low speed to high speed. Furthermore, since the number of auxiliary valves does not increase compared to the conventional one, there is no risk of the structure becoming complicated or increasing in size.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, in which a plan sectional view of the engine at low speed, Fig. 2 a longitudinal sectional view at low speed, Fig. 3 a sectional view taken along the - line in Fig. 2, and Fig. 4 The output characteristics of the engine are shown in FIG. 5, a plan sectional view at medium speed, and FIG. 6, a plan sectional view at high speed. 1...Cylinder, 2...Main exhaust passage, 8, 9, 1
0, 11... Auxiliary exhaust passage, 12, 13... Auxiliary valve, 40... Auxiliary exhaust mechanism.

Claims (1)

[Scope of Claims] 1. A main exhaust passage that communicates with the inside of the cylinder, and a plurality of auxiliary exhaust passages that connect the inside of the cylinder and the main exhaust passage as auxiliary exhaust passages, and that are provided close to each other. A two-stroke engine that includes a passage and a common auxiliary valve that is provided in the middle of the plurality of auxiliary exhaust passages and increases the number of auxiliary exhaust passages that are opened in multiple stages according to an increase in the rotational speed of the engine. exhaust system. 2. The exhaust of a two-stroke engine according to claim 1, wherein the auxiliary exhaust mechanism having the plurality of auxiliary exhaust passages and the common auxiliary valve is arranged one on each side of the main exhaust passage. Device.