JPS62271926A - Exhaust timing control device for two-cycle engine - Google Patents

Abstract

PURPOSE:To enhance sealability and controllability by constituting an exhaust timing control device which opens or closes the upper periphery of the exhaust port of a two-cycle engine with a seal part which is engaged with the projected part of a cylinder, and a control part which is projected so as to be gradually thinned in the direction of the cylinder. CONSTITUTION:On the upper periphery of the exhaust port 15 of a two-cycle engine, an exhaust timing control device 18 which turns making a shaft 20 as the center is provided. The exhaust timing control device 18 is comprised of a seal part 22a which a engaged with the projected part 19 of a cylinder, and a control part 23a which is projected from the seal part 22a in the radial direction of the cylinder. The control part 23 is so formed that it is gradually thinned as it approaches inside the cylinder. Thus, a secure seal can be obtained by the seal part and the projected part of the cylinder, and since the end of the control part 23 is formed so as to be thin, the accuracy of the exhaust timing control can be enhanced.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention "Field of Industrial Application" The present invention relates to an engine exhaust timing control device, and in particular,
The present invention relates to an exhaust timing control device applied to a two-cycle engine.

"Conventional technology" Generally speaking, engines used in vehicles, etc., operate at low speeds (
They are roughly divided into two types: low-revving types that focus on power characteristics during high-speed driving (high-speed range), and high-revving types that emphasize power characteristics during high-speed driving (high-speed range). In the latter case, the peak of engine output is obtained in the low rotation range, and in the former case, the output peaks in the high rotation range. In addition, the latter also has the characteristic that the output in the low rotation range is lower than the front sound.

Therefore, by increasing the output in the low rotation range while maintaining high output in the high rotation range, the
Improvements in output characteristics over a wide range of speeds, from low to high speeds (high speeds) are being considered, and one example of a specific solution is to reduce engine exhaust It is suggested that the timing changes.

By the way, in a two-stroke engine, the exhaust operation is performed by communicating the exhaust passage with the inside of the cylinder by opening the exhaust port as the piston moves toward the bottom dead center side. In order to change the exhaust timing, the upper edge of the exhaust port, which is the opening of the exhaust passage into the cylinder (hereinafter, the top dead center side of the piston is taken as the top, and the bottom dead center side of the piston is taken as the bottom). It is necessary to change the position in the direction of movement of the piston.

In order to change the position of the upper edge of the exhaust port of the two-stroke engine as described above, conventionally, for example,
A technique shown in US Pat. No. 4,391,234 has already been proposed 9).

As shown in Fig. 1, this technique is applied to the upper wall of an exhaust passage 4 that is continuous with an exhaust port 3 opened on the inner surface of the cylinder 2 of a two-cycle engine, and directed from the vicinity of the exhaust port 3 to the downstream side. A recess 5 is formed in the recess 5, and a rotatable drive shaft 6 is provided at the downstream end of the recess 5 so as to be substantially orthogonal to the center line of the navigation cylinder 2 and the air passage 4. The shaft 6 has a groove structure integrally provided with a plate-shaped valve body 7 which is accommodated in the four parts 5 and projected from the recess 5 into the exhaust passage 4 by being swung by the drive shaft 6. with the valve body 7 protruding from the recess 5,
By closing the upper part of the exhaust port 3 with the swinging end of the valve body 7, the piston 8 is opened as shown in FIG.
The timing of communication between the inside of the cylinder 2 and the exhaust passage 4 due to the lowering of the cylinder 2, that is, the exhaust timing, is delayed by the distance between the upper edge 3a of the exhaust port 3 and the lower edge 7a of the swinging end of the valve body 7, and
By housing the valve body 7 in the four parts 5 and opening the upper part of the exhaust port 3, the above-mentioned exhaust timing is brought forward.

"Problems to be Solved by the Invention" The present invention aims to solve the following problems in the conventional technology described above.

That is, in the conventional technology described above, the exhaust timing is changed by swinging the plate-shaped valve body 7 and opening and closing the upper edge 3a of the exhaust port 3 with the swinging end thereof. However, when the valve body 7 swings in this manner, the swinging end of the valve body 7 draws an arc-shaped movement locus, and the valve body 7 is in a state in which it protrudes into the exhaust passage 4. In,
In order to prevent leakage of combustion gas, it is necessary to bring the swinging end of the valve body 7 as close to the inner surface of the cylinder 2 as possible, so the inner surface of the recess 5 housing the valve body 7 and the inner surface of the cylinder 2 are The problem is that the cylinder wall between the two ends up being edge-shaped, resulting in poor heat drainage.

In particular, since the above-mentioned edge portion is formed at a portion where the temperature rise is the highest, such as the upper part of the exhaust port 3, countermeasures are required.

On the other hand, as a means to solve these problems,
It is conceivable that the aforementioned edge portion may be made smaller by thinning the valve body 7 and making the recess 5 shallower.
According to this means, since the amount of change in the exhaust timing, that is, the amount of protrusion of the valve body 7 is set in advance, when the valve body 7 is made to protrude by the set amount into the exhaust passage 4, the swing end of the valve body 7 is The part is completely separated from the recess 5, and the space formed between the recess 7 and the upper part of the valve body 7 is communicated with the inside of the cylinder 2 and the combustion chamber, so that a so-called dead space is created. A space is formed, and as a result, part of the combustion gas flows into the space before the regular exhaust timing set by the valve body 7 is reached, and there is a risk that the control accuracy of the exhaust timing will deteriorate. Therefore, it cannot be an effective solution.

"Means for Solving the Problems" The present invention can effectively solve the above-mentioned conventional problems.
Provided is an exhaust timing control device for a cycle engine, in particular, in the upper wall of an exhaust passage formed in a cylinder of a two-stroke engine, near the exhaust port that is the opening to the seventh ring of the exhaust passage. a valve body formed in the concave portion toward the downstream side of the exhaust passage, and provided with a rotating shaft substantially perpendicular to the center line of the cylinder, and a valve body that is swung by the rotating shaft. an exhaust timing control device, wherein the valve body is oscillated to close the upper part of the exhaust port by the oscillating end of the valve body, thereby changing the communication timing between the exhaust passage and the inside of the cylinder. The valve body has a base portion formed with a sealing surface that is brought into sliding contact with the inner wall surface of the cylinder of the recessed portion, and the base portion includes:
It is characterized by comprising a control part that protrudes outward in the radial direction of swing of the valve body from the lower end of the sealing surface, and that gradually becomes thinner toward the end on the protruding side. .

"Operation" The exhaust timing control device for a two-stroke engine according to the present invention has the following functions:
By overlapping the sealing surface provided at the base of the valve body and the inner surface of the recess, communication between the space formed between the upper surface of the valve body and the recess and the inside of the cylinder is cut off, and the base A control section protruding outward in the radial direction of the valve body's swing allows the sealing surface to be repositioned toward the center of the valve body's swing, thereby allowing the inner surface of the recess and the inner surface of the cylinder This increases the thickness of the cylinder wall above the exhaust port.

``Example'' An example of the present invention will be described below with reference to FIGS. 2 to 4.

In FIGS. 2 and 3, the symbol lO indicates a two-stroke engine to which one embodiment is applied, and is composed of a cylinder block lla and a cylinder head llb attached to the upper part of the cylinder block lla. a cylinder 11, a piston 12 slidably fitted in the cylinder block lla, a combustion chamber 13 formed by the piston 12, the cylinder block lla, and the cylinder head ttb, and the cylinder block lla.
a, a plurality of scavenging passages 14 and a single exhaust passage 15, and a scavenging port 16 and an exhaust port 17 which are openings to the combustion chamber 13, and the exhaust passage 15
An exhaust timing control device 18 according to this embodiment is provided on the upper wall of the exhaust port 17 in the vicinity of the exhaust port 17.

The exhaust timing control device 18 has a recess 19 formed in the upper wall of the exhaust passage 15 from near the exhaust port 17 toward the downstream side, and has a recess 19 that is substantially orthogonal to the center line of the cylinder 11. A rotation shaft 20 is provided, a valve body 21 is provided on the rotation shaft 20, and the valve body 21 is attached to the wall surface 1 of the four parts 19 on the combustion chamber 13 side.
A base 22 is provided with a sealing surface 22a formed therein to be brought into sliding contact with the valve body 9a, and the base 22 is provided with a base 22 that protrudes outward in the radial direction of swing of the valve body 21 from the lower end of the sealing surface 22a. It has a general configuration formed by a control part 23 that becomes gradually thinner toward the side end.

Next, to explain these details, the recess 1
In this embodiment, as shown in FIG. 3, 9 is a first recess 19b formed along the circumferential direction of the cylinder 11 and spaced apart from the inner surface of the combustion chamber 13 by a predetermined distance in the radial direction;
and a second recess 19c formed along the length direction of the exhaust passage 15 from the first recess 19b, and the first four parts 19b are slightly larger than the width of the exhaust port 17. As shown in FIG. 3, the wall surface 19a on the side of the combustion chamber 13 is curved about the axis of the rotary wheel 2o, and as described above, the wall surface 19a on the side of the combustion chamber 13 is curved around the axis of the rotary wheel 2o. is formed along the inner surface of the combustion chamber 13, resulting in a three-dimensional curved surface. The distance between the wall surface 19a and the inner surface of the combustion chamber 13 is set in consideration of heat shrinkage in the cylinder wall between the two.

The rotation shaft 20 includes a cylindrical portion 24a rotatably supported on the upper wall of the cylinder 11, and a non-circular attachment portion 24b extending in the length direction from one end of the cylindrical portion 24a.
a first axial groove member 24 having a first axial groove member 24;
A non-circular through hole 25a is formed to be fitted into the fitting portion 24bh of the exhaust passage 15.
A second shaft groove body 25 is rotatably supported on the upper wall of the shaft.

The second shaft lateral body 25 is attached to the first shaft lateral body 24 by being brought into contact with a stopper 27 that is locked by a nut 26 screwed onto one end of the mounting portion 24b.
The stopper 2 is prevented from leaving the stopper 2.
7, between the cylindrical part 24a of the first shaft transverse body 24 and the step part 24c formed at the boundary between the mounting part 24b, the mounting part 24b
The length is set so that the image can be exposed for a predetermined length.

Further, as shown in FIG. 3, a small diameter portion 24d is provided in a portion of the first shaft side body 24 that protrudes to the outside of the cylinder 11.
A stopper 28 fixed to the cylinder 11 is fitted into the small diameter portion 24d so as to be relatively rotatable, and an operating lever 29 is integrally rotatable toward one end. The collar 30 is fitted in order, and the stopper 28, operating lever 29 and collar 30 are locked by a nut 31 screwed onto the end of the small diameter portion 24d.

Therefore, with this configuration, the first shaft-side body 24 and the second shaft-side body 25 are positioned with respect to the cylinder 11, and are prevented from separating from the cylinder 11.

Further, the columnar portion 24a of the first shaft-side body 24 and the externally protruding portion of the second shaft-side body 25 and the cylinder 1
Seal members 32 and 33 are interposed between the outer wall surfaces of the first and second outer walls to airtightly close them.

In this embodiment, as shown in FIGS. 3 and 4, the valve body 21 is divided into two parts in the length direction of the rotating shaft 20, and extends from the exhaust port 17 to the downstream side of the exhaust passage 15. It is provided so as to sandwich reinforcing ribs 34 provided facing toward it.

The base portion 22 constituting these valve bodies 21 is
As shown in FIGS. 2 and 3, a non-circular through hole 35 having the same cross-sectional shape as the portion 24b is formed at one end of the shaft for mounting the first shaft lateral body 24. By fitting the mounting portions 24b into these through holes 35, each valve body 21 is integrally attached to the rotation shaft 20, and the rotation shaft 20 allows the valve body 21 to be rotated within a predetermined angle range. It is designed to be able to rotate back and forth.

Further, as shown in FIG. 3, the base portion 22 is formed to have substantially the same shape as the four portions 19 when viewed from the center line direction of the cylinder 11, so that it can be accommodated in the recess portion 19. The lower surface (the surface exposed in the exhaust passage 15) is continuous with and forms a part of the inner wall surface of the exhaust passage 15 when the exhaust passage 15 is housed in the recess 19. In this case, the end surface of the part accommodated in the first recess 19b on the combustion chamber 13 side is connected to the sole surface 22.
a, and the sealing surface 22a is formed in the first recess 19.
It is formed into a three-dimensional curved surface similarly to the wall surface 19a of FIG.

Both valve bodies 21 are attached to the first shaft side body 24 when the portion 24b is inserted through the first shaft side body 24.
By being sandwiched between the stepped portion 24c and the inner end surface of the second shaft lateral body 25, it is attached to the rotating shaft 20 and positioned with respect to the cylinder 11, the exhaust passage 15, the exhaust port 17, and the recess 19. It is supposed to be done. In addition, in this way, both valve bodies 21 are connected to the rotation shaft 2G.
As shown in FIG. 2, each sealing surface 22a is shaped as shown in FIG.

As shown in FIG. 3, the control section 23 is provided in the width direction (circumferential direction of the cylinder 11) of the sealing surface 22a, and its lower surface is continuous with the lower surface of the base 22.
In addition, the upper surface 23a is located at one point on the center line of the combustion chamber 13.
It is a curved part that follows a part of a conical surface with the point as its apex. When the valve body 21 is housed in the recess 19, the i4 upper surface 23a is connected to the inner surface of the combustion chamber 13 and the wall surface 1 of the first recess 19b, as shown in FIG.
9a, so as to be in contact with the lower surface of the cylinder wall over almost the entire surface.

On the other hand, an actuator (not shown) is connected to the rotating shaft 20 via an operating lever 29, and the actuator is operated based on the rotational speed of the engine 10.
For example, a governor actuated by the crankshaft of the engine [0], or an electrically actuated servo motor, the rotation shaft 20
By rotating it back and forth, ζ)-Etiquette 21 can be changed to p]'r within the node of the fixed mountain degree.

As the engine 1O starts, combustion gas is continuously discharged to the outside through the exhaust port 17 and the exhaust passage 15, and this discharged combustion gas causes the cylinder wall above the exhaust port 17 to However, in the engine IO to which the exhaust timing control device 18 of this embodiment is applied, the valve body 2
1 is spaced apart from the inner surface of the combustion chamber 13, and the thickness of the cylinder wall above the exhaust port 17 is increased, so that the heat given by the combustion gas is transferred to the cylinder. 11 to prevent overheating. Therefore, the durability against heat of the engine IO is improved. Also,
Since the control portion 23 is formed so as to gradually become thicker toward the downstream side of the exhaust passage 15, heat is efficiently transferred to the lower temperature portion, and the valve body 21 itself is prevented from becoming excessively thick. Temperature rise is suppressed.

When the engine 10 is operated in a low rotation range, the rotation shaft 20 is rotated by the actuator, and as shown by the chain line in FIG.
0 causes the valve body 21 to swing and protrude from the four parts 19 into the exhaust passage 15, so that the upper edge of the exhaust port 17 is closed by the swing end of the valve body 21, and the piston 12 is The opening timing of the exhaust port 17 as it descends, that is, the exhaust timing, is delayed by the distance between the control section 23 of the valve body 21 and the upper IJ 11a of the exhaust port 17.

During such an exhaust timing delay operation, the sealing surface 22a of the valve body 21 in the protruding state and the wall surface 19a of the recess 19
Communication between the combustion chamber 13 and the recess 19 is cut off at the overlapped portion with the recess 19, thereby ensuring that the aforementioned exhaust timing delay operation by the control unit 23 is carried out reliably. This is done to improve the output characteristics in the low rotation range.

Here, a slight space is formed between the valve body 21 in the protruding state and the inner surface of the exhaust passage 15 and the upper surface of the control section 23, but the volume of this space is compared to that of the combustion chamber 13. The effect on the exhaust timing control mentioned above is very small.

Furthermore, when the engine 10 reaches a high speed range, an actuator operated based on the information causes the valve body 21 to be housed in the four parts 19 as shown by the solid line in FIG. The upper part of the port 17 is opened, the exhaust timing is advanced, and the exhaust is properly performed in the high rotation range, and the output characteristics in the high rotation range are improved.

Note that the layers, dimensions, etc. of each component shown in the above embodiments are merely examples, and can be variously changed based on the type of engine to be applied, design requirements, etc.

"Effects of the Invention" As explained above, the exhaust timing control device for a two-stroke engine according to the present invention has an exhaust port that is formed continuously with an exhaust port that is opened and closed by a piston that is slidably fitted in a cylinder. A recess is formed in the upper wall of the exhaust passage from the vicinity of the exhaust port toward the downstream side of the exhaust passage, and the recess is provided with a rotation axis substantially orthogonal to the center line of the cylinder, and the rotation axis is provided with a rotation axis substantially perpendicular to the center line of the cylinder. , a valve body is provided that is swung by the rotation shaft, and by swiveling the valve body, the swing end portion closes the upper part of the exhaust port, and the exhaust passage and the inside of the cylinder are closed. The exhaust timing control device is configured to change the timing of communication with the valve body, and the valve body includes a base portion formed with a sealing surface that is brought into sliding contact with a wall surface on the inner side of the cylinder of the recessed portion, and a base portion that includes: The valve body is characterized by comprising a control portion that protrudes outward in the radial direction of swing of the valve body from the lower end of the sealing surface, and that gradually becomes thinner toward the end on the protruding side. It has the following excellent effects:

■By separating the control unit that sets the exhaust timing from the sealing surface that blocks communication between the combustion chamber and the recess, the
The thickness of the cylinder wall located between the recess and the inside of the combustion chamber, where a large amount of heating heat is generated, is made as large as possible to improve the heat sink of the cylinder wall, and to greatly improve its durability against heat. can be improved.

■By providing the control section protruding from the sealing surface, the control section can be placed as close to the extension of the inner surface of the combustion chamber as possible to accurately open and close the exhaust port. It is possible to reliably prevent communication with the exhaust gas and to reliably control the exhaust timing while maintaining the effect (2) above.

■6 When the component is set to the low rotation range side, the volume of the space created above the exhaust port that communicates with the combustion chamber, the so-called dead space, is minimized so that the dead space can be used at the exhaust timing. The effect on control operations can be made slight, and in combination with the above effects,
The control accuracy of exhaust timing can be greatly improved.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view showing a conventional example of a two-stroke engine equipped with an exhaust timing control device, and Figs. 2 to 4 show an embodiment of the present invention, so Fig. 2 shows the main parts. longitudinal section,
FIG. 3 is a sectional view taken along the line ■-■ in FIG. 2, and FIG. 4 is an external perspective view of the valve body. 10...2-cycle engine, 11...
・Flick, 11a...Cylinder block) tib...Cylinder head, 12...Piston, L5...Exhaust passage, 17...
...Exhaust port, 17a...Top edge, 18...Exhaust timing control device, 19...
・Concavity, 19a...Wall surface, 19b...
・First recess, 19c...Second recess, 20
... Rotation shaft, 21 ... Valve body,
22... Base, 22a... Seal surface,
23...Control unit, 23a...Top surface.

Claims (1)

[Claims] On the upper wall of an exhaust passage formed continuously with an exhaust port that is opened and closed by a piston that is slidably fitted in a cylinder of a two-stroke engine, from the vicinity of the exhaust port toward the downstream side of the exhaust passage. forming a recess, and providing the recess with a rotation axis substantially perpendicular to the center line of the cylinder;
The rotating shaft is provided with a valve body that is swung by the rotating shaft, and by swinging the valve body, the swinging end portion closes the upper part of the exhaust port, and the exhaust passage is closed. The exhaust timing control device is configured to change the timing of communication with the inside of the cylinder, and the valve body includes a base portion formed with a sealing surface that is brought into sliding contact with the wall surface on the inside side of the cylinder of the recessed portion, and The control portion is provided at the base and protrudes outward in the radial direction of swing of the valve body from the lower end of the sealing surface, and the control portion gradually becomes thinner toward the end on the protruding side. Features: Exhaust timing control device for 2-stroke engines.