JPH03199625A - Two-cycle engine - Google Patents

Abstract

PURPOSE:To restrain the compression release of mixture at the time of the compression stroke of a piston by controlling the apparent volume of an expansion chamber which has been provided in the midway of an exhaust pipe in response to the operating timing of the piston. CONSTITUTION:In a two-cycle engine 1, an expansion chamber 16 is provided in the midway of an exhaust pipe 11. When the engine speed is low, the core 22 in the inside of the expansion chamber 16 is placed in the position of the mark I. As the engine speed increases, a motor 27 is turned by the signal from an engine speed sensor 8, so that the position of the core 22 is successively changed together with a slide plate 23 from the mark I to the mark IV via a wire 32. Thereby the the exhaust gas quantity to be released through the outlet 17 of the expansion chamber 16 can be regulated, and the apparent volume of the expansion chamber 16 is changed. Accordingly, the pressure of reflected waves produced in the inside of the expansion chamber 16 is controlled into a condition corresponding to the speed, so that the compression release of mixture at the time of the compression stroke of a piston 5 can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a two-stroke engine that can prevent decompression of an air-fuel mixture during piston compression.

(Prior art) A two-stroke engine has air intake (t!) on the cylinder wall.
It has an air port and an exhaust port, and each port opens and closes as the piston moves up and down, allowing gas to enter and exit from there. The positions of the intake port and the exhaust port are such that the exhaust port is shifted upward to a greater extent than the intake port, and the intake stroke is set when the piston moves up.

To explain further, in a two-stroke engine, when the piston rises, the intake port connects to the inside of the crankcase, and as the piston rises, the air-fuel mixture is sucked into the crankcase, which has a negative pressure. On the other hand, above the intake port, the raised piston blocks the exhaust port and compresses the air-fuel mixture introduced into the combustion chamber, which is then ignited by the spark plug. Then, it explodes, the i-tension gas pushes down the piston, and this stroke becomes an output. As the piston nears the end of its downward movement, the exhaust port at the bottom of the cylinder that was previously blocked by the piston becomes visible, and the waste gas from the explosion begins to blow out from there. Also, when the piston moves down a little more, the intake port that was previously blocked by the piston appears. Then, the air-fuel mixture that had already been sucked into the crankcase is compressed by the downward movement of the piston and ejected into the cylinder. In addition, after the air-fuel mixture ejected into the cylinder collides with the inside of the combustion chamber, which is the ceiling of the cylinder, it turns around and uses its momentum to push out the remaining waste gas through the exhaust port. By repeating this series of operations, the two-cycle The engine is driven continuously.

In this way, in the exhaust of a two-stroke engine, waste gas is pushed out by the air-fuel mixture from the intake port, but at this time, part of the air-fuel mixture exits from the exhaust port together with the waste gas.

To solve this problem, two-stroke engines generally have a hollow llj with a small outlet in the middle of the exhaust pipe.
By providing an expansion chamber, most of the waste gas that comes out from the exhaust port is stopped and reversed in this expansion chamber, and due to the reverse flow, the unburned mixture that follows the waste gas from the exhaust port is returned to the cylinder. A method of reversal is being taken.

This expansion chamber has a shape in which the internal space gradually expands and swells as it goes from the inlet side connected to the exhaust port to the rear side, and narrows again halfway toward the outlet side. The shape of this expansion chamber, that is, the tapered shape that widens from the inlet side and the tapered shape that narrows toward the outlet side, the diameter and length of the tail pipe, etc., affect the output characteristics of the engine. This is well known in boat fishing.

Therefore, in order to control the output characteristics of the engine,
Some engines have rotary valves or valves that slide up and down in the exhaust port of the engine body to vary the exhaust timing and prevent air-fuel mixture from escaping when the piston is compressed.

[Problems to be Solved by the Invention] However, with the above-mentioned conventional structure in which a pulp mechanism is provided at the exhaust port of the engine body to change the exhaust timing, it is difficult to completely push the air-fuel mixture into the cylinder. The problem was that it could not be kept in place.

In addition, although the exhaust timing is changed according to the engine speed, the engine characteristics (output and torque increase rapidly at certain rotations) as shown in Figure 3 (b), which will be described later.
has not yet been resolved.

For this reason, for example, if the exhaust port is provided at a lower position closer to the crankcase side to form a low-speed engine body, and an expansion chamber that matches the characteristics of this engine body is installed, the shaft output L ( The relationship between shaft torque T (kg・■) and engine speed N (rpII) is as shown in Figure 3(a).In other words, the characteristics shown in Figure 3(a) are as follows: Both the shaft power and the shaft torque T increase gradually, but the maximum shaft power obtained at the rotation speed N and the maximum shaft torque Ll obtained at the rotation speed N1 are small.

On the other hand, the exhaust port is placed in the upper position closer to the cylinder head side to form a high-speed engine body, and the shaft output is increased when an 11 tension chamber that matches the characteristics of this engine body is installed. The relationship between the shaft torque T and the engine rotational speed N has a characteristic as shown in FIG. 3(b). In the characteristics shown in Fig. 3 (b>), both the maximum output L2 obtained at the rotation speed N5 and the maximum shaft torque T2 obtained at the rotation speed N4 become large, but the rising curve is not smooth, and at a certain engine speed There has been a problem that the number increases rapidly when the number exceeds the number.

The present invention has been made in view of the above-mentioned problems, and its purpose is to eliminate compression loss of the air-fuel mixture during piston compression, and to maintain the shaft output and shaft torque at smooth and high values over the range from low speed rotation to high speed rotation of the engine. The objective is to provide a two-stroke engine that can obtain the following.

(Means for Solving the Problems) In order to achieve the above object, the present invention exhausts an expanded expansion chamber in which the internal space gradually expands from the inlet side connected to the exhaust port and narrows halfway toward the outlet side. The two-cycle engine is provided in the middle of a pipe, and includes an adjusting means provided in the expansion chamber to adjust the timing of a reflected wave generated in the expansion chamber by an exhaust pulsating wave, and a means for detecting the actuation timing of the piston and adjusting the timing. and control means for controlling the amount of adjustment by the means.

(Function) According to this configuration, when the apparent volume inside the expansion chamber is changed by adjusting the adjustment means, the magnitude of the reflected wave pressure inside the expansion chamber can be changed. Since the actuation timing of the piston is controlled by means, that is, according to the exhaust pulsation wave, the reflected wave pressure can also be adjusted in proportion to the rotation speed, and when the piston is compressed, the air-fuel mixture is decompressed and flows out from the cylinder exhaust port. can be held in the cylinder by the pressure of this reflected wave.Therefore, increasing the apparent volume of the expansion chamber will increase engine characteristics such as high rotation, high output, and high torque; When the upper volume is reduced, the engine characteristics become low rotation, low output, and low torque, and regardless of the high or low engine speed, it is possible to always obtain maximum efficiency and smooth high values for both shaft output and shaft torque. I can do it.

<Example> Hereinafter, an example of the present invention will be described in detail using the drawings.

FIG. 1 is a side view schematically showing a two-stroke engine according to an embodiment of the present invention.

In the figure, this engine 1 includes a crankcase 3 at the bottom of an engine body 2, and a cylinder 4 connected to the crankcase 3 at the top. A piston 5 is disposed within the cylinder 4, and the piston 5 is linked to a crankshaft 7 via a connecting rod 6 extending into the crankcase 3. In addition,
An engine rotation sensor 8 is attached to the crankshaft 7 to detect the engine rotation speed.

Further, the cylinder 4 is composed of a cylinder body 4A and a cylinder head 4B attached to the upper part of the cylinder body 4A.

Furthermore, an intake port 9 and an exhaust port 10 are provided on the wall surface of the cylinder body 4A. Among these, the intake port 9 is formed below the exhaust port 10. The air-fuel mixture that has passed through a carburetor (not shown) is introduced from the intake port 9, and the exhaust gas after combustion can be discharged from the exhaust port 10 through an exhaust pipe 11.

On the other hand, the cylinder head 4B is attached to the upper part of the cylinder body 4A so as to form a combustion chamber 12 inside the cylinder 4. Further, a spark plug 13 is attached to the cylinder head 4B so that the electrode is located at the apex of the combustion chamber 12.

Next, a muffler 15 is attached to the tail vibe 14 of the exhaust pipe 11 connected to the exhaust port 10, and an expansion chamber 16 is formed between the exhaust port 10 and the tail vibe 14.

This expansion chamber 16 is hollow, and the inner diameter on the outlet 17 side is smaller than the inner diameter on the inlet 1811tll. The shape of this expansion chamber 16 includes a tapered first region 19 whose inner diameter gradually widens as it goes from the inlet 18 side to the rear, and an inner diameter approximately equal to the rear end side of this first region 19. A second region 20 having the same inner diameter toward the rear side and a third region 21 having a tapered shape in which the inner diameter gradually narrows from the rear end of the second region 20 toward the outlet 17 are continuous. It is made in a state where it is provided. Further, inside the expansion chamber 16, a core 22 is provided which serves as an adjusting means for adjusting the amount of exhaust gas to be extracted through the outlet 17.

This core 22 is disposed corresponding to the inside of the third region 21 in the expansion chamber 16, and has an outer dimension smaller than the inner dimension of the third region 21 as shown in the figure, and the diameter increases toward the rear. It is formed into a substantially funnel shape so that its dimensions are reduced. Further, a through hole 22 a having a size substantially equal to the inner diameter of the outlet 17 is provided at the center of the core 22 . The core 22 is supported from outside the expansion chamber 16 via a slide plate 23 that is integrated with the core 22 and extends outside the expansion chamber 16, and is controlled by the control means 26. It is adjustable to move forward and backward. Note that a core slide guide 2 is provided outside the expansion chamber 16 to guide the movement of the slide plate 23.
4 is formed integrally with the expansion chamber 16. Further, a sealing gasket 25 is interposed between the core slide guide 24 and the slide plate 23.

Next, the control means 26 is composed of the engine rotation sensor 8, the motor 27, the power transmission T1128, etc., and the motor 27 is connected to the engine rotation sensor 8 via a wire harness 29, and the engine rotation sensor 8
It can rotate in two directions, forward and reverse, depending on the output. The power transmission mechanism 28 also includes a pulley 30 that is rotatably attached to the output shaft of the motor 27, an idler boot 31, and a wire 32 that is passed between the pulley 30 and the pulley 31. ing. When the pulley 30 is rotated by the motor 27, the wire 32° pulley 31 is rotated integrally with the pulley 30. Furthermore, a slide puto 23 is attached to the wire 32, and when the wire 32 rotates, the core 22 can also move integrally in the front and rear directions within the expansion chamber 16 via the slide plate 23. ing. In addition, in FIG. 1, the symbols 1, n,
The positions Ill and IV indicate the positions to which the slide plate 23 has moved together with the core 22, respectively.

In a two-stroke engine with a tank bottom as described above, when the engine speed is low, the motor 27 is placed at the position I, and as the speed increases, the motor 27 is turned on by a signal from the engine speed sensor 8. The core 22 is rotated, and the core 22 and the slide plate 23 are sequentially changed from the position I to the positions n, m, and rv via the wire 32. Then, the amount of exhaust gas discharged through the outlet 17 of the expansion chamber 16 is adjusted, and the apparent volume inside the expansion chamber 16 changes. Further, in this regard, the reflected wave pressure generated in the expansion chamber 16 is controlled in a state C2 according to the rotation of the engine, and it is possible to suppress decompression of the air-fuel mixture when the piston is compressed.

Figure 2 shows the relationship between shaft power, shaft torque T, and engine speed N when the structure according to this embodiment is applied, and the conventional characteristics shown in Figure 3 (a>, (b)) and actual measured values. The output values LL, L2.TI, and T21 rotational speeds N1 to N5 are shown in comparison based on the third
This corresponds to FIG. As can be seen from this characteristic diagram, by configuring as in this embodiment, in the present invention, the engine rotational speed is N5, which is the same as the rotational speed at which the maximum shaft output L2 was obtained in the case of a conventional high-speed engine. The same maximum shaft output L2 is obtained when
The same maximum shaft torque T2 was obtained smoothly when the rotation speed N2 was the same as that at which engine speed 2 was obtained, and the shaft output and shaft torque could be obtained with maximum efficiency regardless of the high or low engine speed. .

Note that the core 22 and the power transmission mechanism 28 as the control means 26 shown in the above structure are not limited to the i-structure of the above embodiment, and may be implemented with various modifications.

(Effects of the Invention) As explained above, according to the two-cycle engine according to the present invention, the magnitude of the reflected wave pressure from the expansion chamber can be changed by adjusting the adjustment means. Since this adjustment is controlled by the control means according to the piston operation timing, that is, the exhaust pulsating wave, the reflected wave pressure can also be adjusted in proportion to the rotation speed, and when the piston is compressed, the air-fuel mixture flows from the cylinder exhaust port. This reflected wave pressure can be used to keep the compressor from flowing out inside the cylinder. As a result, it is possible to obtain smooth and high values for both shaft output and shaft torque with maximum efficiency, regardless of the high or low engine speed, which has the effect of improving engine performance.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway schematic side view of a two-cycle engine according to an embodiment of the present invention, and FIG. Characteristic diagram showing the relationship, Figure 3 (a), (
b) is a characteristic diagram showing the relationship between shaft output, shaft torque, and engine rotation speed in a conventional low-speed two-stroke engine and a high-speed two-stroke engine. DESCRIPTION OF SYMBOLS 1... Engine, 2... Engine body, 4... Cylinder, 5... Piston, 8... Engine rotation sensor, 9... Intake port, 10... Exhaust port,
11... Exhaust pipe, 16... Expansion chamber, 17... Expansion chamber outlet, 18... Expansion chamber inlet, 22... Core (
adjustment means), 26... control means, 27... motor,
29...Wire harness, 32...Wire

Claims (1)

[Claims] (1) A 2-stroke engine with an expansion chamber in the middle of the exhaust pipe, in which the internal space gradually expands from the inlet side connected to the exhaust port and narrows from the middle toward the outlet side.
The engine includes an adjusting means that is provided to be able to vary the apparent volume of the expansion chamber and adjusts the timing of a reflected wave generated in the expansion chamber by an exhaust pulsating wave, and an adjusting means that detects the actuation timing of the piston. A two-cycle engine characterized by comprising: control means for controlling the amount of adjustment by.