JPH0131008B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a port control device for a two-stroke engine that can change the port time area and port timing according to the engine speed.

In a piston-valve type two-stroke gasoline engine (hereinafter referred to as a two-stroke engine), during low-speed operation including idling,
When the intake port is open for too long compared to when driving at high speed, and as a result, the air-fuel mixture flows in and the internal pressure in the crankcase rises to a certain level, some of the air-fuel mixture is blown back into the intake pipe, resulting in fuel loss. There is a problem that arises. Similarly, as a result of the exhaust port opening time being too long, the opening time of the exhaust port before the scavenging port opens becomes faster and longer, resulting in a decrease in output, and the time from when the scavenging port closes until the exhaust port closes becomes shorter. There is a problem in that as the time increases, part of the air-fuel mixture in the cylinder blows through to the exhaust pipe side, causing fuel loss. Further, a two-stroke engine is known from Japanese Patent Publication No. 38-6506 in which the vertical position of the port is changed between high speed and low speed so that high output can be obtained at both high speed and low speed. However, in this prior art example, the port control member itself constitutes a part of the cylinder, which makes the cylinder structure complicated, and furthermore, there is a specific structure in which the port control member is moved up and down in relation to the rotation of the engine. has not been disclosed or taken measures.

In view of these problems, an object of the present invention is to interpose a port control member displaceably between the outer circumference of the cylinder liner and the inner circumference of the cylinder block in conjunction with the throttle valve, and to control the port control member according to the engine speed. By making it possible to change the time area and port timing, for example, the intake port can be controlled without complicating the cylinder structure to prevent the air-fuel mixture from blowing back into the intake pipe, which occurs at low engine speeds, thereby reducing fuel consumption. It is an object of the present invention to provide a port control device for a two-stroke engine that aims to reduce the amount of water used.

Another object of the present invention is that by controlling the exhaust port with the configuration described above, it is possible to prevent a decrease in output due to the exhaust port opening too quickly at low engine speeds, and further to reduce the opening time of the exhaust port. It is an object of the present invention to provide a port control device for a two-stroke engine that can prevent the air-fuel mixture in the cylinder from blowing through to the exhaust pipe side due to the cylinder being too long, and can reduce fuel consumption.

The present invention will be specifically described below with reference to the drawings. 1 to 3 show one embodiment of the present invention. In these figures, numeral 1 is the cylinder block, 2 is the cylinder liner, 3 is the intake port, 4 is the exhaust port, and 5 is the scavenging port. A gap G is formed therein. This gap G includes an intake port control port 6, an exhaust port control port 7, and a scavenging port communication port 8.
A cylinder 9 having a diameter is rotatably interposed therein. This cylinder 9 is connected to a throttle valve 13 of a carburetor 12 via a lever 10 and a link mechanism 11, and is configured to rotate by a predetermined angle depending on the opening degree of the throttle valve 13. As shown in FIG. 3, the intake port control port 6 and exhaust port control port 7 of the cylinder 9 are tapered from the top side to the rear end, and the top side is above and below the intake port 3 and the exhaust port 4. It is wider than the width, and narrows at the rear end. Also, the left and right width of the port control ports 6 and 7 is
It is wider than the left and right widths of the intake port 3 and exhaust port 4. At high speeds, that is, when the opening degree of the throttle valve 13 is large, as shown in FIG. , the exhaust port 4 is not throttled, and at low speeds, that is, when the opening degree of the throttle valve 13 is small, the rear end sides of the port control ports 6 and 7 are located at the intake port 3 and the exhaust port 4, as shown in FIG. The upper sides of these intake ports 3 and exhaust ports 4 are constricted.

In the figure, reference numeral 14 indicates a chiyoke valve, 15 indicates a piston, and 16 indicates a crankcase.

In such a configuration, the cylinder 9 rotates by a predetermined angle in conjunction with the throttle valve 13, and at low speeds, the upper sides of the intake port 3 and exhaust port 4 are controlled by the intake port control port 6 and the exhaust port control port 7. narrowed down. When the upper side of the intake port 3 is narrowed, the port time area decreases accordingly, and the intake port 3
As the opening time becomes shorter, the inflow of the air-fuel mixture into the crankcase 16 is reduced, and as a result, the air-fuel mixture is prevented from blowing back into the intake pipe, which occurs at low speeds. On the other hand, if the upper side of the exhaust port 4 is narrowed,
The port time area is reduced accordingly, and the opening time of the exhaust port 4 until the scavenging port 5 opens is delayed and shortened, making it possible to improve the output. This shortens the time it takes for the cylinder to close, thereby preventing the air-fuel mixture in the cylinder from blowing through to the exhaust pipe side.

Next, at high speeds, the intake port control port 6 and exhaust port control port 7 on the narrow rear end side are retracted from the intake port 3 and exhaust port 4, and these ports 3 and 4 are fully opened to achieve the mixing required for high speed rotation. It takes in air and exhausts exhaust gas.

In the present invention, the area of the throttle that controls the intake port 3 and the exhaust port 4, as well as its shape and position, are determined by the engine displacement, load, etc. Further, the control member may be a plate-shaped member instead of a cylinder like the cylinder, and the method of displacement thereof and the means of connection and interlocking with the throttle valve are not limited.

Further, the port control may be performed not only on both the intake port 3 and the exhaust port 4 as in the embodiment, but also on either one of them.

Thus, according to the present invention, the port control member is interposed between the outer periphery of the cylinder liner and the inner periphery of the cylinder block so as to be freely displaceable in conjunction with the throttle valve, so that the structure of the cylinder is not complicated. It is possible to change the port time area and port timing according to the engine speed, and as a result, the intake port and exhaust port are controlled at low speeds, and the air-fuel mixture that occurs at low speeds is blown back into the intake pipe and away from the cylinder. This has the effect that fuel consumption can be reduced by preventing blow-by to the exhaust pipe side, and moreover, it is possible to improve output by delaying the opening time of the exhaust port.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a port control device according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line A-A in FIG. 1, and FIG. 3 is an explanatory diagram showing a port and a port control port. A shows the state at low speed, and B shows the state at high speed. 1... Cylinder block, 2... Cylinder liner, 3... Intake port, 4... Exhaust port, 6...
...Intake port control port, 7...Exhaust port control port,
9... cylinder, 13... throttle valve.

Claims (1)

[Claims] 1 In a piston-valve type two-stroke gasoline engine, a port control member provided with a port control port for controlling port opening is interposed between the outer circumference of the cylinder liner and the inner circumference of the cylinder block so as to be freely displaceable in conjunction with a throttle valve. The upper side of the port control port is tapered from the tip to the rear end, and the tip side is wide or equal to the vertical width of the port,
The rear end side is formed to be narrow, and when the opening degree of the throttle valve is large, the tip side of the port control opening of the port control member is located at the port and the port is not throttled. When it is small, the rear end side of the port control port is located at the port, and the upper side of the port is throttled, so that the port time area and port timing can be changed according to the opening degree of the throttle valve. 2-stroke engine port control device.