JPS62189319A - Exhaust timing controller 2-cycle engine - Google Patents

Abstract

PURPOSE:To blast exhaust flow to a valve body housing chamber to prevent carbon from deposition therein by providing a through hole from the opening side end face of the valve body to the upper surface of valve body in the swing valve body for opening and closing the upper edge of an exhaust port of a 2-cycle engine. CONSTITUTION:An exhaust port 10 of a 2-cycle engine is provided with a valve body 16 swung about a shaft 15 to open and close the upper edge of a port opening 10a. The valve body 16 is provided in the opening 10a side end face 19 with a hole 17 which extends through the upper surface of valve body 16 to communicate to a housing chamber 14 in the valve body 16. A portion of exhaust flow is blasted directly into the housing chamber 14 through the through hole 17 to prevent carbon from deposition in said chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust timing control device for an engine, and in particular, by opening and closing the upper part (top dead center side) of the exhaust port in a two-stroke engine, the upper edge of the exhaust port is controlled by the piston. This invention relates to an exhaust timing control device that changes the timing of communication between the inside of the cylinder and the exhaust passage as the piston slides by changing the sliding direction of the piston.

"Conventional Technology" In general, the engines installed in vehicles, etc. are roughly divided into low-speed types that emphasize power characteristics in the low-speed range, and high-speed types that emphasize power characteristics in the high-speed range. It is divided into two parts, the former is designed so that the peak of engine output is obtained in the low rotation range, and the latter is designed so that the peak of engine output is obtained in the high rotation range.
In the former, the output in the high rotation range peaks out, and in the latter, the output in the low rotation range is lower than the former. Maintaining high output in the rotation range Improving power characteristics in a wide range from the rotation range to the high rotation range is being considered.

One specific solution to this problem is to change the exhaust timing of the engine between the low and high rotation ranges, but if this method is to be applied to a 2-cycle engine, Exhaust in the engine is performed by opening the exhaust port with the piston, so in order to change the exhaust timing, move the upper edge of the exhaust port (i.e. the edge on the top dead center side of the piston) in the sliding direction of the piston. Need to be moved.

Therefore, the present inventors proposed the structure shown in FIG. 1 as a means for changing the upper edge of the exhaust port as described above.

In this proposal, as shown in FIG.
The upper part of the exhaust passage 2 (hereinafter, upper means the top dead center side of the piston, and the lower means the lower dead center side of the piston) A shaft 3 is rotatably provided in the vicinity of the exhaust port 2a, which is an opening to the inner surface of the cylinder l, so as to be orthogonal to the center line of the cylinder l, and a valve body 4 is integrally attached to this shaft 3. A recess 5 for accommodating the valve body 4 is formed in the upper part of the exhaust passage 2 facing the body 4, and the recess 5 extends toward the inside of the recess 5 at the upper part of the swinging end of the valve body 4. A protrusion 6 is integrally formed to fill the gap between the swing end of the valve body 4 and the upper edge of the exhaust port 2a when the valve body 4 is protruded from the recess 4, and the four parts 5 are provided with the protrusion 6. It has a structure in which a deep bottom part 5a that accommodates the protrusion 6 of the valve body 4 is arranged in series, and when the engine is operated at low rotation speed, as shown in FIG.
By swinging the valve body 4 about the shaft 3 and closing the upper part of the exhaust port 2a with its swing end, the upper edge 2b of the exhaust port 2a is moved to the lower end of the swing end of the valve body 4. distance 9 to the bottom dead center side to delay the exhaust timing,
In addition, when the engine speed reaches high speeds, the valve body 4 is housed in the recess 5 and the upper part of the exhaust port 2a is opened to advance the exhaust timing, thereby improving the output characteristics in the entire rotation range. We are working to improve this.

"Problems to be Solved by the Invention" The present invention aims to improve the following points that remain for further improvement of characteristics in the above-mentioned proposal.

That is, during exhaustion (during scavenging), a phenomenon occurs in which a portion of the combustion gas discharged to the exhaust passage 2 slightly enters into the recess 5 through the gap between the valve body 4 and the inner surface of the recess 5.
Carbon contained in the combustion gas stays in the recess 5 and adheres to and hardens on the inner surface of the recess 5 and the upper surface of the valve element 4, and this adhered carbon causes the inner surface of the valve element 4 and the recess 5 to become separated. It is conceivable that the gap set in between is filled, and the storage position of the valve body 4 is shifted from the predetermined position, or that the reciprocating inertia weight of the valve body 4 increases. .

"Means for Solving the Problems" The present invention aims to provide an exhaust timing control device for a two-stroke engine that can effectively eliminate the improvements and points to be solved in the above-mentioned proposal, and which A recess is formed in the upper wall of the exhaust passage provided with the exhaust passage toward the downstream side from the vicinity of the exhaust port, and a valve body having a swing axis along a direction perpendicular to the cylinder is swingably provided in the recess. ,
The timing of communication between the inside of the cylinder and the exhaust port is changed by swinging the valve body in the direction of protruding from the recess and the direction of retracting, and opening and closing the upper part of the exhaust port with the swing end. The exhaust timing control device is characterized in that a through hole communicating from the end face to the upper surface of the valve body is formed in the swinging end portion of the valve body.

"Function" The exhaust timing control device for a two-stroke engine according to the present invention allows a part of the gas to be blown into the recess through the through hole formed at the swinging end of the valve body during exhaust (scavenging). Accordingly, carbon adhering to the inner wall of the recess and the upper surface of the valve body is removed by cleaning the blowhole with gas before solidification.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 is a longitudinal cross-sectional view of a two-stroke engine equipped with an exhaust timing control device according to the present invention, and FIG. 3 is a cross-sectional view taken along the line ■-■ in FIG.

In the figure, reference numeral 7 indicates a cylinder, which includes a cylinder block 7a and a cylinder head 7b attached to the cylinder block 7a to form a combustion chamber A. Further, reference numeral 8 denotes a piston slidably fitted in the cylinder 7, 9 a scavenging passage for sending the air-fuel mixture into the combustion chamber A, and 10 an exhaust for discharging combustion gas from the combustion chamber A. It is a passage.

Inside the exhaust passage 10, there is a reinforcing rib 11 that has a predetermined length toward the downstream side from the exhaust port LOa, which is an opening to the inside of the cylinder 7, and that extends along the length direction of the cylinder 7. As shown in FIG. 3, the exhaust passage 10 is divided into two in the circumferential direction of the cylinder 7. This rib 11 reinforces the vicinity of the exhaust port 10a of the exhaust passage 10, and when the piston 8 is slid, the piston ring 12 attached to the piston 8 expands radially outward due to its own elasticity. and exhaust port
It functions to prevent Oa from hitting the E edge 10b or the lower edge LOc. Further, a water passage W for passing cooling water is formed along the length of the rib 11 to suppress a rise in temperature of the rib 11.

The exhaust port 10 is located at the upper part of the exhaust passage 10.
An air timing control device 13 according to this embodiment is provided near a.

Next, the exhaust timing control device 13 will be explained as follows.

The exhaust timing control device 13 is provided on the upper wall of the exhaust passage 10,
A recess 14 is formed from the vicinity of the exhaust port 10a toward the downstream side, and a sleeve 15 is rotatably arranged in the recess 14 along the direction orthogonal to the cylinder 7, and is integrally attached to the axis I5. A valve body 16 is provided and is swung by the shaft 15, and a through hole 17 is formed at the swinging end of the valve body 16 to communicate from the end surface to the upper surface of the valve body 16. The valve body 16 is connected to the drive mechanism (not shown) for rotating the shaft 5 back and forth within a predetermined angle range according to the engine operating condition. By swinging it in the direction of protruding from the recess 14 and the direction of retracting it, and opening and closing the upper part of the exhaust port lOa with the swinging end, the timing of communication between the inside of the cylinder 7 and the exhaust port lOa is changed. It looks like this.

More specifically, as shown in FIG. 3, the two valve bodies 16 are arranged in the circumferential direction of the cylinder 7 with the rib 11 in between, and are each attached to the shaft 15 and integrally formed. It is designed so that it can be swayed. Further, the swing end portion of each valve body 16 has a width that is equal to or greater than the width of the exhaust port 10a.
The length is such that the upper part of the cylinder 7 can be completely covered in the circumferential direction of the cylinder 7, and a protrusion 18 extending inward of the recess 14 is provided at the upper part of the swinging end. The protrusion 18 and the end face of the swinging side of the valve body 16 on the inside of the cylinder 7 are continuous, so that the valve body 16 is swung to the protruding position. The control surface 19 is substantially continuous with the inner surface of the cylinder 7, and the through hole 17 is formed so as to pass through the protrusion 18 from the control surface 19. The size of the through-hole 17 is determined in consideration of the degree of improvement in the engine's horn characteristics in the low speed range.

On the other hand, the inner surface of the recess 14 has a shape corresponding to the upper surface of the valve body 16, and the valve body 16 is located near the exhaust port log when the valve body 16 is swung to the storage position.
A deep bottom portion 14a with a triangular cross section in which the protrusion 18 of No. 6 is accommodated.
is formed. From the deep bottom portion 14a toward the downstream side of the exhaust passage 10, there is a flat portion 14b in which the intermediate portion of the i7i valve weight 6 is accommodated, and a semicircular cross section in which the center of the valve body 16 is accommodated. It has a shape in which shaped wall portions 14c are provided in order, and when the valve body 16 is housed, a minute gap is formed over the entire surface between the valve body 16 and the upper surface of the valve body 16. ing.

According to the exhaust timing control device 13 of this embodiment configured in this way, the output characteristics of the engine are increased in the entire rotation range by operating the valve body 6 based on the operating state of the engine. In addition, adhesion of carbon to the inner surface of the recess 14 and the valve body 16 is suppressed.

That is, when the engine is operated at low rotation speed, the shaft 15 is rotated in a predetermined direction and the valve body 16 is swung to project into the exhaust passage IO.

This movement of the valve body 16 positions the control surface 19 above the exhaust port 10a, thereby causing the second
As shown in the figure, the upper part of the exhaust port 10a is closed, and the upper edge 10b of the exhaust port 10a is apparently lowered by the distance ML to the lower edge of the control surface 19 of the rising body 16.

Therefore, as the upper edge 10b of the exhaust port LQa is lowered, the opening timing of the exhaust port 10a by the piston 8 is reduced.
In other words, the exhaust timing is delayed.

On the other hand, when the engine reaches a high speed range, the valve body 16
is moved in the opposite direction to that described above and stored in the recess 14.

As a result, the upper part of the exhaust port 10a is opened and the exhaust timing is advanced.

By such an operation, appropriate exhaust is performed over a wide range from a low engine speed range to a high engine speed range, and the output characteristics of the engine are improved over the entire engine speed range.

Then, while the above-mentioned exhaust action, that is, the scavenging action is being performed, the combustion gas is discharged to the exhaust passage lO,
A part of the carbon in the combustion gas enters the recess 14 through the gap between the valve body 16 and the fourth part 14, and carbon in the combustion gas enters the recess 14.
It is conceivable that the liquid may adhere to the inner surface of the valve body 16 or the upper surface of the valve body 16.

However, during the above-mentioned exhaust (scavenging), a part of the unburned gas together with the combustion gas is exhausted as gas from the atrium. The gas is blown into the recess 14 through the hole 17, and the gas is used to clean the inner surface of the recess 14 and the upper surface of the valve body 16, thereby removing carbon attached thereto and removing the carbon from the valve body. The gas is discharged into the exhaust passage 10 from the gap between the downstream side of the exhaust gas 16 and the recess 14 .

Therefore, the protruding position and the retracted position of the valve body 16 are maintained at the set values for a long period of time, and an increase in the reciprocating inertial mass of the valve body 16 is suppressed, so that the above-mentioned exhaust timing control is performed with high precision. .

It should be noted that the shapes and dimensions of each component shown in the above embodiments are merely examples, and can be changed in various ways based on design requirements and the like.

For example, although an example has been shown in which the opening area is secured by making the cross-sectional shape of the through hole 17 flat, it is also possible to provide a plurality of independent through holes at intervals in the width direction of the valve body 16. It is a good thing.

"Effects of the Invention" As explained above, the exhaust timing control device for a two-stroke engine according to the present invention is arranged so that the exhaust timing control device for a two-stroke engine according to the present invention is installed on the upper wall of the exhaust passage having an exhaust port opening on the inner surface of the cylinder, from the vicinity of the exhaust port to the downstream side. A concave portion is formed toward the cylinder, and a valve body having a pivot axis along a direction perpendicular to the cylinder is swingably provided in the concave portion, and the valve body is pivoted in a direction in which the valve body protrudes from the concave portion and in a direction in which it is housed. and by opening and closing the upper part of the exhaust port with its swinging end,
A mechanical timing control device that changes the timing of communication between the inside of the cylinder and the exhaust port, and includes a rotary end portion of the valve body that communicates with the upper surface of the valve body from the end surface thereof. It is characterized by having a through hole formed therein. During exhaust (scavenging), unburned gas discharged together with the combustion gas, that is, a part of the gas, flows from the through hole formed in the end face of the valve body to the recessed part. The blowing gas cleans the inner surface of the recess and the upper surface of the valve body to prevent carbon from adhering to these surfaces, thereby controlling the swing of the valve body within a set range. This has excellent effects, such as being able to reliably perform the exhaust timing within the engine, suppressing an increase in the reciprocating inertial mass of the valve body, and maintaining stable exhaust timing control over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an example of the structure of a two-stroke engine equipped with a conventional exhaust timing control device, and FIGS. 2 and 3 show a two-stroke engine to which an embodiment of the present invention is applied. So, Figure 2 is a vertical cross-sectional view, and Figure 3 is the ■-
3 is a cross-sectional view taken along the line. 7...Cylinder, 7a...Cylinder block, 7b...
Cylinder head, 10...exhaust passage,
10a... Exhaust port, 10b... Upper edge, 13... Exhaust timing control device, 14...
Recessed part...15...shaft, 16...
... Valve body, 17 ... Through hole,
18... Protrusion.

Claims (1)

[Claims] A recess is formed in the upper wall of an exhaust passage having an exhaust port opening into the inner surface of the cylinder of a two-stroke engine, extending from the vicinity of the exhaust port toward the downstream side, and a rocker is inserted into the recess along a direction perpendicular to the cylinder. A valve body having a moving axis is swingably disposed, and the valve body is swung in the direction of protruding from the recess and the direction of being retracted, and the swing end portion opens and closes the upper part of the exhaust port. , an exhaust timing control device that changes the timing of communication between the inside of the cylinder and the exhaust port, wherein a through hole is formed in the swinging end of the valve body, leading from the end surface to the upper surface of the valve body. Features: Exhaust timing control device for two-stroke engines.