JPH0712669Y2 - Exhaust timing control valve for two-cycle engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to improvement of an exhaust timing control valve of a two-cycle engine.

[Conventional technology and its problems]

In a two-cycle engine, a scavenging hole and an exhaust hole are opened on the wall surface of the cylinder, and the piston is reciprocated to open and close, the piston opens near the bottom dead center, and the burned exhaust gas is discharged to the exhaust hole. At the same time, new gas is filled into the cylinder through the scavenging hole. Therefore, the performance of the engine is determined by the opening / closing timing depending on the opening areas of the exhaust hole and the scavenging hole, and the exhaust hole plays a large role. In general, if the upper edge of the opening of the exhaust hole is made high and the opening area is made large, the exhaust can be performed quickly and a high rotation and high output type can be obtained. Conversely, if the upper edge of the opening of the exhaust hole is lowered to reduce the opening area, the amount of blow-through gas is reduced, and a low-speed high-power type can be obtained. For this reason, valves have been developed that control the exhaust timing so that both low speeds and high speeds can be of high output type. FIG. 4 shows an example of the exhaust timing control valve. In this case, the valve hole C is obliquely provided above the exhaust hole B opening to the cylinder A.
And insert the valve guide D into the valve hole C,
The valve E is slidably inserted into the valve guide D, and the valve E is moved forward and backward at a predetermined rotation in response to engine rotation. When the valve E is pulled, the opening upper edge of the exhaust hole B is the timing when the exhaust hole is opened, and when the valve E is projected, the tip of the valve E is opened,
The exhaust timing can be adjusted by α. In this structure,
The tip of the valve guide D is slightly recessed from the wall so that it does not get caught by the ring of the piston.
There is an inconvenience that gas leakage occurs and the output is reduced. FIG. 5 shows another conventional example. In this case, a cylindrical valve hole C is formed above the exhaust hole B opening in the cylinder A, and the valve E is slidably inserted into the valve hole C so as to move forward and backward depending on the number of rotations. . In this case, the upper end of the tip of the valve E is exposed on the wall surface of the cylinder A, and it is recessed in a gap to provide a gap t so that the piston ring does not bite, and the output is reduced due to gas leakage. Further, when the valve E is pulled, there is a disadvantage that a pocket is formed.

[Purpose of device]

It is an object of the present invention to obtain an exhaust timing control valve for a two-cycle engine that can prevent gas leakage and increase output by preventing the valve hole of the cylinder from penetrating to the wall surface.

[Constitution of device]

The present invention will be described below with reference to the embodiments shown in FIGS. 1 and 2 show an embodiment of the present invention. The cylinder 1 is cast from a light alloy, the sleeve 2 is inserted inside, and the wall surface 3 has an exhaust hole 4 and a scavenging hole 5. Then, it is opened and closed by a piston that slides back and forth on the wall surface 3, and is opened near the bottom dead center of the piston. On the upper side of the exhaust hole 4, a valve hole 6 is formed obliquely toward the upper edge of the opening of the exhaust hole 4.
The upper end of the valve hole 6 is stopped by the stepped portion 7,
The lower end of the tip is passed through the exhaust hole 4. The valve guide 8 is inserted into the valve hole 6, and the valve 9 is slidably inserted into the lower portion of the valve guide 8. The tip of the valve 9 is located below the upper edge of the opening of the exhaust hole 4 by α and is projected so as to be close to the wall surface 3. The valve 9 protrudes in the low rotation range and becomes the opening / closing timing, and in the high rotation range,
An electromagnetic solenoid or the like that responds to the number of revolutions is slid to draw it in, and the upper edge of the exhaust hole 4 becomes the opening / closing timing. FIG. 3 shows another embodiment of the present invention. In this case, the valve hole 6 provided above the exhaust hole 4 of the cylinder 1
The stepped portion 7 at the upper end of the is parallel to the sleeve 2. Others are the same as those shown in FIGS. 1 and 2, and the same reference numerals are given.

[Function of device]

In the low engine speed region, the exhaust hole 4 is opened and closed at the tip of the valve 9 and the timing at which the exhaust hole 4 is opened is shortened by α, so that the amount of blow-through gas is small and the output can be increased. In the high speed rotation range, the valve 9 is retracted, the opening upper edge of the exhaust hole 4 determines the opening / closing timing, the opening timing is lengthened, the exhaust can be speeded up, and high output can be achieved in the high speed range. Further, since the tip of the valve guide 8 is not exposed on the upper wall surface 3 at the upper edge of the opening of the exhaust hole 4 and no gap is formed, gas leakage can be prevented and the output does not decrease.

[Effect of device]

As described above, according to the present invention, the valve hole is obliquely provided on the upper side of the exhaust hole of the cylinder toward the upper edge of the opening of the exhaust hole. Through the exhaust hole, insert the valve guide in the valve hole, and let the tip of the valve slidably inserted in the valve guide face the lower side of the upper edge of the opening of the exhaust hole, so the exhaust timing can be changed. Therefore, high output can be achieved from low speed range to high speed range. Further, the valve guide does not appear on the wall surface of the cylinder, there is no gap for gas leakage, and a decrease in output can be prevented.

[Brief description of drawings]

1 and 2 show an embodiment of the present invention, FIG. 1 is a vertical sectional side view, FIG. 2 is an outer side view of a valve portion, and FIG. 3 is a vertical sectional view showing another embodiment of the present invention. A side view, FIG. 4 is a vertical side view showing a conventional example, and FIG. 5 is a vertical side view showing another conventional example. 1 ... Cylinder, 4 ... Exhaust hole, 6 ... Valve hole, 7
…… Step, 8 …… Valve guide, 9 …… Valve.

Claims (1)

[Scope of utility model registration request] 1. A valve hole is obliquely provided on the upper side of an exhaust hole of a cylinder toward an upper edge of an opening of the exhaust hole, and an upper end of the valve hole is stopped at a step and a lower end of the valve hole penetrates the exhaust hole. The exhaust timing control of a two-cycle engine is characterized in that the valve guide is inserted into the valve hole, and the tip of the valve slidably inserted into the valve guide is made to face below the upper edge of the opening of the exhaust hole. valve.