JPS6151647B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates primarily to two-stroke internal combustion engines for motorcycles and other vehicles.

Conventionally, this kind of engine has a cylinder with a slidable piston inside, an exhaust port on one side, a third scavenging port on the other side, and a pair of left and right main scavenging ports in the middle. In this case, the air-fuel mixture introduced from the main scavenging port is introduced into the cylinder in the opposite direction to the exhaust port, rises, and then reversed before being introduced to the exhaust port. On the other hand, the air-fuel mixture led from the third scavenging port travels almost straight inside the cylinder and is led to the exhaust port, and therefore the time required for scavenging tends to be different. Particularly in the low rotational speed range of the engine, this has the disadvantage of easily causing poor scavenging.

The object of the present invention is to obtain an engine free of such inconveniences, and includes a cylinder having a slidable piston inside, an exhaust port on one side, and a third scavenging port on the other side. In the device in which a pair of left and right main scavenging ports are arranged in the middle, a throttle is inserted in the passage communicating the third air supply port with the crank chamber, apart from the opening on the cylinder side of the scavenging port. It is characterized by

An example of implementing the present invention will be explained with reference to the attached drawings.

In the drawing, 1 is a cylinder, 2 is a slidable piston inside the cylinder, 3 is a cylinder head at the top, and 4 is a cylinder head.
5 indicates a spark plug provided therein, 5 indicates a crank chamber on the lower side thereof, 6 indicates an internal crankshaft, 7 indicates a connecting rod connecting this to the piston 2, and an exhaust port 8 on one side of the cylinder 1; The third scavenging port 10 on the other side and a pair of left and right main scavenging ports 9, 9 in the middle are provided, and this is configured in a uniform type. The main scavenging ports 9, 9 and the third scavenging port 10 are connected to each other through passages 11, 11 extending downward and having approximately the same cross-sectional area, and a passage 12 having a cross-sectional area smaller than that of the passage 11. The crank chamber 5 is connected to the inside of the crank chamber 5 through which the air-fuel mixture is introduced, and the crank chamber 5 is further provided with an intake passage 14 for introducing the air-fuel mixture into the crank chamber 5.

The above is not particularly different from the conventional one. For example, as clearly shown in Fig. 2, the air-fuel mixture led through each main scavenging port 9 is opposite to the exhaust port 8 as shown by arrow A in the figure. The air-fuel mixture is guided into the cylinder 1 in the direction shown by arrow B in the figure, and then reversed and guided to the port 8. The scavenging gas is guided approximately straight through the cylinder 1 to the port 8, and since the path lengths of the two are greatly different, the time required for scavenging tends to be different. In other words, Scavenging through the third port 10 is performed in a relatively short time, whereas scavenging through the main port 9 takes a relatively long time, and the time difference may result in poor scavenging, especially in the low engine speed range. It's a win.

The present invention eliminates such inconvenience by intervening a throttle 13 in the passage 12 described above, that is, the passage 12 communicating the third scavenging port 10 with the crank chamber 5, so that the mixture guided through this I tried to reduce the flow velocity to some extent. The throttle 13 has a tapered portion 13a that gradually and smoothly expands on the downstream side to form an expansion chamber, and the degree of restriction of the throttle 13 is 40 to 20% of the maximum effective cross-sectional area of the third port 10. It is preferable to do so.

Thus, to explain its operation, the air-fuel mixture guided through the third port 10 has its flow velocity reduced to some extent by the throttle 13, in other words, the scavenging by the air-fuel mixture is more or less reduced. By increasing the time, the time difference between the air-fuel mixture and the scavenging air introduced through the main scavenging air port 9 is reduced as much as possible.

As described above, the present invention eliminates the inconvenience caused by the time difference of the conventional method, and is particularly effective in eliminating poor scavenging in the low rotation range, and its configuration is extremely simple, simply by intervening a throttle in the passage. It has the effect of being obtained at a low cost.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway side view of an example of the engine of the present invention, and FIG. 2 is a cutaway side view illustrating its operation. 1... Cylinder, 2... Piston, 8... Exhaust port, 9, 9... Main scavenging port, 10... Third
Scavenging port, 12... passage, 13... throttle.

Claims (1)

[Claims] 1. In a cylinder having a slidable piston therein, an exhaust port on one side, a third scavenging port on the other side, and a pair of left and right main scavenging ports in between, the above-mentioned A two-stroke internal combustion engine, characterized in that a throttle is inserted into a passage communicating a third air supply port with a crank chamber at a distance from an opening on the cylinder side of the scavenging port.