JPH0551765B2 - - Google Patents

Description

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

[Conventional technology]

In the two-stroke engine mentioned above, there is an exhaust control device that aims to improve the output at high speed rotation by reducing the cross-sectional area of the exhaust passage in the engine body at low speed rotation and increasing it at high speed rotation (for example, (Refer to Japanese Patent Application Laid-Open No. 60-249614). This control method includes a method of controlling the cross-sectional area of a single exhaust passage and a method of controlling a plurality of cross-sectional areas.

[Problem to be solved by the invention]

However, the above-mentioned conventional technology has the disadvantage that mechanical noise is large when the engine is in a no-load operating state where the engine does not stop rotating, that is, when the engine is idling. This is presumed to be due to irregular combustion in which combustion occurs once for every 3 to 5 strokes of the piston during idling. Therefore, the inventor conducted various studies regarding the operating state of the engine during idling. As a result, it was found that under certain conditions, combustion occurs once for every two or three strokes of the piston.

This invention was made in view of the above-mentioned conventional problems, and it is possible to improve the flow of combustion gas during idling and suppress the generation of mechanical noise, as well as to smoothly operate the valve used for exhaust control. The purpose of the present invention is to provide a method for controlling the exhaust gas of a two-stroke engine, which can maintain the exhaust gas level.

[Means to solve the problem]

In order to achieve the above object, two according to this invention
The exhaust control method for a cycle engine includes: a main exhaust passage communicating with a main exhaust port of a cylinder; an auxiliary exhaust port provided on the side of the main exhaust port in the cylinder in the circumferential direction; An auxiliary exhaust passage that connects with the main exhaust passage as an auxiliary exhaust passage, and an auxiliary valve that opens and closes this auxiliary exhaust passage, and opens and closes the auxiliary valve according to changes in engine speed. A two-stroke engine exhaust control method that controls exhaust gas by: when the engine power switch is turned on, the auxiliary valve is first turned from a fully open state to a closed state, and then returned to a fully open state again;
When the engine is idling, the auxiliary valve is kept open, when the engine is rotating at low speed, the auxiliary valve is closed, and when the engine is rotating at high speed, the auxiliary valve is fully open.

[Effect]

According to this invention, when the engine power switch is turned on, the auxiliary valve provided in the auxiliary exhaust passage is moved from a fully open state to a closed state, and then returned to a fully open state again. By doing so, carbon and the like adhering to the auxiliary valve are removed. During idling, the auxiliary valve is opened, which improves the flow of combustion gas and stabilizes combustion, with combustion occurring once every two or three strokes of the piston. In other words,
Engine rotation fluctuations (unevenness) are reduced, and mechanical noise generation is suppressed.

〔Example〕

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

FIG. 1 shows a longitudinal section of a two-cylinder two-stroke engine, in which 1 is a cylinder head, 2 is a cylinder block, 3 is a piston, and 4 is a water jacket.
A main exhaust port 5 communicates the cylinder 6 with the main exhaust passage 7 shown in FIG. 2a. The above cylinder 6
On the side of the main exhaust port 5 in the circumferential direction,
Two auxiliary exhaust ports 8 are provided. An auxiliary exhaust passage 9 connects the auxiliary exhaust port 8 and the main exhaust passage 7 as an auxiliary exhaust passage. That is, the cross-sectional area of the auxiliary exhaust passage 9 is smaller than that of the main exhaust passage 7. Note that 30 is a resonance chamber that communicates with the main exhaust passage 7 at low speeds to prevent a decrease in output at low speeds. Although only one side of the resonance chamber 30 is illustrated,
It may be provided on both sides, and it is not always necessary to provide it.

Reference numeral 10 denotes an auxiliary valve, which is provided in the middle of the auxiliary exhaust passage 9 and is rotationally driven by a drive device 11 (FIG. 3), which will be described later, to open and close the auxiliary exhaust passage 9 according to changes in the engine speed. It is. This auxiliary valve 10 includes a valve passage 10a.
and a valve body 10b are formed in the cylindrical portion 10c of FIG. This auxiliary valve 10 has its axial direction set in the sliding direction of the piston 3 of the engine,
This is a rotary valve whose shaft portion 10d is pivotally supported by a cylinder head 1 and a cylinder block 2, and which rotates in both directions around this shaft portion 10d. The shaft portion 10d of this auxiliary valve 10 projects from the cylinder block 2 through the cylinder head 1,
Above the cylinder head 1, it is connected to a transmission device 12 of the drive device 11. Although not shown, the right engine is also provided with the above-mentioned auxiliary valve and transmission device.

For example, as shown in FIG. 3, this two-stroke engine is supported obliquely by a frame (not shown) of a motorcycle. In addition, in this figure,
13 is an exhaust pipe, and 14 is a reed valve case.

Next, the drive device 11 (FIG. 3) will be explained.

The drive device 11 includes a motor 15 that can rotate in forward and reverse directions.
and the transmission device 12 described above. Above motor 1
5 is provided with a potentiometer 40 for detecting the rotation angle position thereof. The above transmission device 1
Reference numeral 2 denotes a pulley 16 that is connected to the motor 15 and rotates, first and second cables 17 and 18 that engage with this pulley 16, and this cable 17,
first levers 19 respectively connected to 18;
, the second lever 20 shown in FIG. 4, etc.
The driving force of the motor 15 (Fig. 3) is transferred to the auxiliary valve 10.
The signal is transmitted to the shaft portion 10d.

Both cables 17 and 18 have cable outer 17a and 18a and cable inner 1
7b and 18b, and the cable outer 1
7a and 18a are fixed to the cylinder head 1 of FIG. 3 via a bracket 21. Note that the bracket 21 is integrally formed with the cylinder head 1.

In FIG. 4, the first and second levers 19, 20 are connected to each other via a first rod 22, and a third lever is connected via a second and third rod 23, 24, respectively. and the fourth
The levers 25 and 26 are connected to each other. The four levers 19, 20, 25, 26 are each
It is screwed and fixed to the shaft portion 10d of the auxiliary valve 10 shown in FIG. 1, and protrudes in the radial direction of this shaft portion 10d.
27 in Fig. 5 is a synthetic resin connector, and the rod 2
2 and 24 and the levers 19 and 26 by resin elasticity so as to be rotatable. As described above, since the shaft portion 10d is connected to the motor 15 shown in FIG. , 18b are pulled in opposite directions, and the levers 19, 2 in FIG.
0, 25, and 26 rotate in the direction of the arrow, and
auxiliary valve 10 is rotated.

In FIG. 3, reference numeral 28 denotes a control means, which is composed of, for example, a microcomputer, and essentially controls the ignition timing of the engine. This control means 28 receives the engine rotational speed signal a detected by the detector 41 and the potentiometer 40.
The rotation angle signal b of the motor 15 detected by the motor 15 is input, and a drive signal c for rotating the motor 15 is output in accordance with changes in the engine speed.

Next, the control method of the present invention will be explained.

First, before starting the engine, the auxiliary valve 10 is kept fully open as shown in FIG. 2b.
Then, at the same time as the engine power switch is turned on, the motor 15 shown in FIG. After reaching the fully closed state shown in Figure a, it returns to the fully open state shown in Figure 2b. This reciprocating rotation of the auxiliary valve 10 causes the auxiliary valve 10 to
Carbon and other substances adhering to the surface are removed.

During idling time T1 in FIG. 6 until the engine rotates at a low speed, the opening degree of the auxiliary valve is kept fully open. Here, the present invention opens the auxiliary valve 10 of the auxiliary exhaust port 8 provided on the circumferential side of the main exhaust port 5 in the cylinder 6 in FIG. 1 at T1 during idling. Improves the flow of combustion gas. Therefore, combustion is stable, and the engine burns once for every two or three strokes of the piston 3. Therefore, mechanical noise is reduced.

When the rotational speed of the engine exceeds the rotational speed N1 shown in FIG. 6, the auxiliary valve 10 shown in FIG. 2b is rotated and becomes fully closed as shown in FIG. 2a.
Thereafter, during low speed rotation T2 until the rotational speed reaches the rotational speed N2 in FIG. 6, the opening degree of the auxiliary valve 10 is maintained in the fully closed state. For this reason, as is well known,
The cross-sectional area of the entire exhaust passage is made small enough to be suitable for low-speed rotation, and a decrease in output at low speed is prevented.

When the rotational speed of the engine reaches a predetermined rotational speed N2, the auxiliary valve 10 (FIG. 1) is driven to rotate and becomes fully open. After that, during high-speed rotation T3 until the rotational speed reaches the rotational speed N3, as shown in Fig. 2 b.
As in, the auxiliary valve 10 is kept fully open. For this reason, exhaust is exhausted from all the exhaust passages 7 and 9, so that, as is well known, the cross-sectional area of all the exhaust passages becomes large enough to correspond to high-speed rotation, and the output is improved.

When the rotational speed of the engine reaches the predetermined rotational speed N3 shown in FIG. 6, the auxiliary valve 10, which is in the fully open state shown in FIG. 2b, is rotated to the half-open state as shown in FIG. 2c. In other words, at T4 during overrun exceeding T3 at high speed rotation in Fig. 6, the valve opening is 1/
It is kept at 2. This causes the output peak to be at the 7th point.
As shown in the figure, the engine moves to the overrun side, and as a result, the output increases by an amount corresponding to the shaded area S2. Incidentally, if the auxiliary valve 10 (FIG. 1) is opened even slightly at T4 during overrun in FIG. 6, the output can be improved to some extent. The control to maintain the half-open state is performed by the control means 8 shown in FIG. 3 controlling the rotation angle of the motor 15 using the rotation angle signal b of the motor 15.

Incidentally, in the above embodiment, an electric drive device as shown in FIG. 3 was used to control the opening and closing of the auxiliary valve 10, but it is possible to use a mechanical drive device. This mechanical drive device is
For example, as is well known, a pair of governor devices are connected to a crankshaft (not shown) and move steel balls along the slope of a dish-shaped spherical plate when the rotational speed of the crankshaft exceeds a predetermined value. It is possible to use a device in which the auxiliary valve 10 of FIG. 1 is fully closed by one governor device and fully opened again by the other governor device.

By the way, the valve opening degree during idling does not necessarily need to be fully open, but may be 1/2 or more. Note that the effects of the present invention are obtained when the auxiliary exhaust port 8 is provided on the side of the main exhaust port 5 in the cylinder 6 in the circumferential direction.

〔Effect of the invention〕

As described above, according to the present invention, by opening the auxiliary valve provided in the auxiliary exhaust passage connected to the main exhaust passage during idling, the flow of combustion gas during idling is improved and the combustion As a result, it is possible to sufficiently suppress the occurrence of mechanical noise due to fluctuations in engine rotation. Moreover,
When the power switch of the engine is turned on, the auxiliary valve can be rotated back and forth, such as fully open, closed, and fully opened, to remove carbon and the like adhering to the auxiliary valve. Therefore, the opening and closing operations of the auxiliary valve can be maintained in a smooth state, and the exhaust gas control by opening and closing the auxiliary valve can always be performed properly and smoothly.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a two-stroke engine according to an embodiment of the present invention, and FIG.
Line sectional view, Figure 2b is a plane sectional view with the auxiliary valve fully open, Figure 2c is a plane sectional view with the auxiliary valve half open, Figure 3 is an external view of the entire engine, and Figure 4 is the 1st Fig. 5 is a sectional view taken along the - line in Fig. 4, Fig. 6 is a time chart showing the relationship between the opening degree of the auxiliary valve and the engine speed, Fig. 7 is a characteristic diagram showing the relationship between output and rotation speed. 5...Main exhaust port, 6...Cylinder, 7...Main exhaust passage, 8...Auxiliary exhaust port, 9...Auxiliary exhaust passage,
10...Auxiliary valve, T1...When idling, T2
...at low speed rotation, T3...at high speed rotation.

Claims (1)

[Claims] 1 a main exhaust passage communicating with the main exhaust port of the cylinder; an auxiliary exhaust port provided on the side of the main exhaust port in the cylinder in the circumferential direction;
an auxiliary exhaust passage connecting the auxiliary exhaust port and the main exhaust passage as an auxiliary exhaust passage;
The auxiliary exhaust passage is equipped with an auxiliary valve that opens and closes the auxiliary exhaust passage, and exhaust is controlled by opening and closing the auxiliary valve according to changes in engine speed.
A cycle engine exhaust control method, wherein when the engine power switch is turned on, the auxiliary valve is turned from a fully open state to a closed state, and then returned to a fully open state again, and when the engine is idling, the auxiliary valve is opened. At the same time, the auxiliary valve is closed during low-speed rotation, and the auxiliary valve is fully opened during high-speed rotation.
Cycle engine exhaust control method.