JPH0427369B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust valve device for a two-stroke engine that can vary the exhaust timing in accordance with the rotational speed of the engine.

[Prior Art] In a two-stroke engine, a movable valve that changes the exhaust timing is provided at the upper edge of the exhaust port opened in the cylinder wall, and this movable valve is operated in accordance with the rotational speed of the engine, so that the entire rotation is maintained. There are some that attempt to obtain high output over a wide range of areas.
Examples thereof include those shown in Japanese Utility Model Application Publication No. 51-163314 and US Pat. No. 4,121,552.

That is, a member is provided that allows an operating portion to change between a position immediately below the upper edge of the inlet of an exhaust port provided in the cylinder and a position retracted into a recess provided on the exhaust port wall, and the action of this member is There is a performance selection device for a two-stroke engine that slightly delays the timing of exhaust start when the exhaust port takes a position just below the upper edge of the inlet of the exhaust port.

Further, in order to pivotally support the movable valve, a bearing is provided in a hole formed in a recess of a main cylinder block divided into an inner and outer cylinder block, for example,
It is known from the publication No. 74623.

Further, there is also known a valve in which an on-off valve is provided in the middle of the exhaust pipe, with one side supported by a through hole and the other side supported by a blind hole, as shown in Japanese Utility Model Publication No. 53-46411.

[Problems to be Solved by the Invention] These conventional techniques can be summarized as follows: ``The valve rotation axis is It is possible to create an exhaust valve device for a two-stroke engine in which a plate-shaped valve is attached to the shaft and the bottom surface of the valve is flush with the upper edge of the exhaust passage and the road surface when the valve is opened. , It is difficult to insert the valve rotating shaft because the through hole and blind hole have almost the same diameter.

The bearings that support the valve rotation shaft have almost the same diameter, so if the valve drive member is installed on the through-hole side, the bearing on the through-hole side will be subjected to a large bearing load under conditions that are likely to cause seizure or galling. A strong force will come into play.

Since the seal portion is disposed within the through hole, the seal is likely to deteriorate due to heat.

There is a problem.

This invention was made in view of the problems of the conventional technology, and its objectives are to provide a structure that is easy to assemble, does not apply excessive force to the bearing, and has minimal seal deterioration. The present invention aims to provide an exhaust valve device for a two-stroke engine.

[Means for Solving the Problems] In order to achieve the above object, the exhaust valve device for a two-stroke engine according to the present invention includes a large diameter hole penetrating one side of the cylinder block at the upper part of the exhaust passage near the exhaust port. and a small-diameter blind hole provided on the other side to support a valve rotating shaft, and a plate-shaped valve is attached to the shaft so that when the valve is open, the bottom surface of the valve is flush with the upper edge of the exhaust passage and the road surface. A sealing material is housed on the cylinder block side around the large-diameter hole, and the valve drive section is provided outside the large-diameter shaft support.

[Function] When the valve is opened during high-speed operation, the tip of the plate-shaped valve is located at approximately the same position as the inner surface of the cylinder, and the bottom surface of the valve is approximately flush with the upper edge of the exhaust passage. There is nothing in the passage that causes particular flow resistance, and even though there is a valve device, this does not cause any problems during high-speed operation. Further, even during low-speed operation, the exhaust timing can be continuously changed by sequentially moving the valves in the closing direction in accordance with the rotational speed of the engine.

Since the through hole has a larger diameter than the blind hole, when the valve rotation shaft is inserted, the tip of the shaft passes through the through hole, making it easier to assemble the shaft.

In addition, even if the valve seizes or galls due to heat or adhesion of carbon, etc., and a large force is applied to the bearing part of the through hole on the drive side, the bearing part is larger than the bearing part of the blind hole, so both bearing parts Bearing pressure will be about the same.

Further, since the seal of the shaft support of the valve rotating shaft is housed on the cylinder block side around the through hole, the cylinder block is constantly cooled, so deterioration of the seal portion due to heat is prevented.

[Example] An example of the present invention will be described below with reference to the drawings.

In the figure, the reference numeral 1 indicates a cylinder block, and this cylinder block 1 has an intake passage 3 communicating with an intake port 2 and an exhaust passage communicating with an exhaust port 4, as is well known as a cylinder of a two-stroke engine. A passage 5 and scavenging ports 6, 7 are provided, each of these openings 2, 4, 6, 7 being connected to a piston 8.
It is opened and closed by the vertical movement of. 9 is a crankcase, 10 is a cylinder head, and a spark plug 12 facing a combustion chamber 11 is screwed into the cylinder head 10.

Reference numeral 20 indicates an exhaust valve device according to the present invention, and this valve device 20 includes a valve rotation shaft 21 pivotally supported at the upper part of the exhaust passage 5 near the exhaust port 4, and a plate-shaped valve 22 attached to the shaft. It is composed of: This valve rotation shaft 21 is disposed between a large diameter through hole 1b drilled from one side of the cylinder block 1 close to the exhaust port 4 and a small diameter blind hole 1a provided on the other side and is pivotally supported. It has a small diameter part 21a and a large diameter part 21b, and the large diameter part 21b is provided with a cutout part 21c which serves to form a part of the inner surface of the exhaust passage 5. Note that 23 is a sealing material made of an O-ring for preventing leakage of exhaust gas, and is arranged in an O-ring holder 24 housed within the cylinder block 1. On the other hand, the plate-shaped valve 22 fixed to the valve rotation shaft 21 is formed so that its tip edge 22a has approximately the same curvature as the inner surface of the cylinder 1, and its side edges 22b
is formed with a curved surface that substantially follows the inner wall surface of the exhaust passage 5. And this plate-shaped valve 22
The valve 22 is attached to the notch 21c of the valve rotating shaft 21 by a screw 25 when the valve is opened.
is attached so that its bottom surface is substantially flush with the upper edge of the exhaust passage 5.

Therefore, when the valve rotating shaft 21 is rotated clockwise in FIG. 1 in accordance with the rotational speed of the engine, the plate valve 22 sequentially moves to the position indicated by the chain line. As a result, the exhaust port 4 is gradually narrowed from its upper edge side. Therefore, when the piston 8 descends from the top dead center position, the timing at which the exhaust port 4 begins to open, that is, the exhaust timing is delayed, and this delay can be continuously adjusted.

The shaft end 21d of the valve rotation shaft 21 is connected to a motor unit or control system that varies the rotation angle in accordance with the rotational speed of the engine, and by controlling the rotation of the shaft end 21d, the rotational speed of the engine is increased. The engine's maximum output can always be extracted throughout the entire range.

Furthermore, even if the valve 22 is seized or galled due to heat or adhesion of carbon, etc., and a large force is applied to the bearing part of the through hole 1b on the drive side (because it is close to the drive side),
Since this bearing portion is larger than the bearing portion of the blind hole 1a, the bearing pressures of both bearing portions are approximately the same.

Furthermore, a seal 23 on the shaft support of the valve rotation shaft 21
Since the cylinder block 1 is housed on the side of the cylinder block 1 around the through hole 1b, the cylinder block 1 is constantly cooled, thereby preventing deterioration of the seal 23 due to heat.

[Effects of the Invention] In this invention, the valve can be closed continuously and the exhaust gas can be controlled during low-speed operation so that the engine performance can be continuously maintained at the optimum state at all times. Of course, since the valve rotation shaft is supported by a large diameter hole passing through one side of the cylinder block and a small diameter blind hole provided on the other side at the upper part of the exhaust passage near the exhaust port, Since the tip of the shaft passes through the through hole when the valve rotation shaft is passed through, the shaft can be easily assembled and the weight of the shaft can be reduced.

In addition, even if the valve seizes or galls due to heat or adhesion of carbon, etc., and a large force is applied to the bearing part of the through hole on the drive side, the bearing part is larger than the bearing part of the blind hole, so both bearing parts Since the bearing pressure is about the same, no particular problem arises with the drive-side bearing.

Furthermore, since the seal of the shaft support of the valve rotation shaft is housed on the cylinder block side around the through hole, the cylinder block is constantly cooled, preventing deterioration of the seal part due to heat and preventing high temperatures. There is no need to prepare expensive materials that can withstand

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an embodiment according to the present invention, FIG. 2 is a cross-sectional view thereof, and FIG. 3 is a cross-sectional view of FIG.
A cross-sectional view is shown. 1...Cylinder block, 1a...Blind hole, 1b
...Through hole, 4...Exhaust port, 5...Exhaust passage, 2
1... Valve rotation shaft, 22... Plate valve, 23
……sticker.

Claims (1)

[Claims] 1. The valve rotating shaft is pivotally supported by a large-diameter hole penetrating one side of the cylinder block and a small-diameter blind hole provided on the other side at the upper part of the exhaust passage near the exhaust port, and a plate-shaped shaft is attached to the shaft. When the valve is installed, the bottom surface of the valve when the valve is open is flush with the upper edge of the exhaust passage and the road surface, and a sealing material is stored on the cylinder block side around the large diameter hole, and the seal material is placed on the outside of the large diameter shaft support. An exhaust valve device for a two-stroke engine, characterized by being provided with a valve drive.