JPH0674742B2 - Exhaust timing control device for 2-cycle engine - Google Patents

Description

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.

"Prior Art" In general, engines used in vehicles, etc., focus on power characteristics during low speed running (low speed range) and low speed type, and focus on power characteristics during high speed running (high speed range). It is roughly divided into a high rotation type and a former type so that the peak of engine output can be obtained in the low rotation range.
Also, in the latter, the peak of the engine output is obtained in the high rotation range, but in the former case, the output peaks at the high rotation range, and in the latter case,
It also has the characteristic that the output in the low rpm range becomes lower than the former.

Therefore, while maintaining a high output in the high speed range, by increasing the output in the low speed range, low speed running (low speed)
It has been studied to improve the output characteristics in a wide rotation range from high speed to high speed (high speed), and as an example of a concrete means for solving the problem, engine exhaust at low speed and high speed is considered. It is mentioned that the timing is changed.

By the way, in the two-cycle engine, the exhaust operation is performed by the communication between the exhaust passage and the inside of the cylinder due to the opening of the exhaust port by the movement of the piston toward the bottom dead center side. To change the exhaust timing, set the position of the upper edge of the exhaust port, which is the opening of the exhaust passage into the cylinder (hereafter, the top dead center side of the piston is up and the bottom dead center side is down). , It is necessary to change the direction of movement of the piston.

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

As shown in FIG. 1, this technique is applied to an upper wall of an exhaust passage 4 continuous with an exhaust port 3 which is opened in an inner surface of a cylinder 2 of a two-cycle engine 1 from a vicinity of the exhaust port 3 toward a downstream side. A recess 5 is formed, 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 lines of the cylinder 2 and the exhaust passage 4. By being swung by the drive shaft 6,
The exhaust passage 4 is accommodated in the recess 5 and is also provided from the recess 5.
It has a structure in which a plate-shaped valve body 7 that is projected inside is integrally provided, and in a state where the valve body 7 is projected from the recess 5, the upper end of the exhaust port 3 is formed by the swinging end of the valve body 7. As shown in FIG. 1, when the piston 8 descends, the communication timing between the inside of the cylinder 2 and the exhaust passage 4,
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 swing end of the valve body 7, and the valve body 7
Is exhausted in the recess 5 and the upper portion of the exhaust port 3 is opened to expedite the exhaust timing.

"Problems to be Solved by the Invention" The present invention is intended to solve the following problems in the above-described conventional techniques.

That is, in the above-described conventional technique, the plate-shaped valve body 7 is swung, and the swinging end portion opens and closes the upper edge 3a of the exhaust port 3 to change the exhaust timing. However, when swinging the valve body 7 as described above,
In the state where the swing end of the valve body 7 draws an arcuate movement locus and the valve body 7 is projected into the exhaust passage 4,
In order to prevent the combustion gas from leaking, it is necessary to bring the swinging end of the valve body 7 as close as possible to the inner surface of the cylinder 2. Therefore, the inner surface of the recess 5 for accommodating the valve body 7 and the inner surface of the cylinder 2 are required. There is a problem that the cylinder wall between and becomes edge-shaped, and heat dissipation is reduced.

In particular, since the above-mentioned edge portion is formed at a portion where the temperature rises the highest, such as the upper portion of the exhaust port 3, it is necessary to take measures against it.

On the other hand, as one means for solving such problems,
It is conceivable that the above-mentioned edge portion is made smaller by thinning the valve body 7 and making the recess 5 shallower. According to this means, the change amount of the exhaust timing, that is, the protruding amount of the valve body 7 is set in advance. Therefore, when the valve body 7 is projected into the exhaust passage 4 by the set amount, the swinging end portion of the valve body 7 is completely separated from the concave portion 5, and the concave portion 7 and the upper portion of the valve body 7 are separated from each other. The space formed between the two is communicated with the inside of the cylinder 2, that is, the combustion chamber, so that a so-called dead space is formed, and as a result, at the regular exhaust timing set by the valve body 7. Before reaching it, a part of the combustion gas may flow into the space, and the control accuracy of the exhaust timing may be reduced, so that it is not an effective solution.

"Means for Solving Problems" The present invention can effectively solve the above-mentioned conventional problems 2
An exhaust timing control device for a cycle engine is provided, and in particular, an exhaust passage is formed in an upper wall of an exhaust passage formed in a cylinder of a two-cycle engine from a vicinity of an exhaust port which is an opening of the exhaust passage to the cylinder. A concave portion is formed toward the downstream side of the cylinder, a rotary shaft that is substantially orthogonal to the center line of the cylinder is provided in the recess, and a valve body that is swung by the rotary shaft is provided in the rotary shaft. An exhaust timing control device, which swings the valve body to close an upper portion of the exhaust port by a swing end portion thereof to change a communication timing between the exhaust passage and the inside of the cylinder. ,
The valve body has a base portion formed with a seal surface that is brought into sliding contact with the inner wall surface of the cylinder of the recess, and the base portion extends outward in the swinging radial direction of the valve body from the lower end portion of the seal surface. And a control unit that is gradually thinned toward the protruding end.

[Operation] In the exhaust timing control device for a two-cycle engine according to the present invention, when the valve element is projected into the exhaust passage,
By overlapping the sealing surface provided on the base of the valve body and the inner surface of the recess, the communication between the space formed between the upper surface of the valve body and the recess and the inside of the cylinder is blocked, and the base The control portion projecting outward from the valve body in the swinging radial direction enables the position of the sealing surface to be shifted toward the swinging center of the valve body, whereby the inner surface of the recess and the inner surface of the cylinder can be changed. Are separated from each other to increase the wall thickness of the cylinder wall above the exhaust port.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

In FIGS. 2 and 3, reference numeral 10 indicates a two-cycle engine to which one embodiment is applied, which is a cylinder block.
A cylinder 11 constituted by 11a and a cylinder head 11b attached to the upper part of the cylinder block 11a,
A piston 12 slidably fitted in the cylinder block 11a, and a combustion chamber 1 formed by the piston 12, the cylinder block 11a and a cylinder head 11b.
3, a plurality of scavenging passages 14 and a single exhaust passage 15 formed in the cylinder block 11a, a scavenging port 16 and an exhaust port 17 which are openings to these combustion chambers 13, and the upper portion of the exhaust passage 15 An exhaust timing control device 18 according to this embodiment is provided on the wall near the exhaust port 17.

The exhaust timing control device 18 is provided on the upper wall of the exhaust passage 15,
A recess 19 is formed from the vicinity of the exhaust port 17 toward the downstream side, and the recess 19 is provided with a rotary shaft 20 substantially orthogonal to the center line of the cylinder 11, and the rotary shaft 20 is rotated by the rotary shaft 20. A valve body (21) swingable by a shaft (20) is provided, and the valve body (21) is brought into sliding contact with a wall surface (19a) of the recess (19) on the combustion chamber (13) side.
2 on which the seal surface 22a is formed.
Has a schematic structure formed by a control portion 23 which is provided so as to project outward from the lower end portion in the swinging radial direction of the valve body 21 and which gradually becomes thinner toward the projecting end portion.

Next, these will be described in detail.
In this embodiment, as shown in FIG.
A first concave portion 19b formed along the circumferential direction of 11 and at a predetermined distance from the inner surface of the combustion chamber 13 in the radial direction, and formed from the first concave portion 19b along the length direction of the exhaust passage 15. And the second recess 19c, the first recess 19b is formed to be slightly larger than the width of the exhaust port 17, and the wall surface 19a on the combustion chamber 13 side is
As shown in FIG. 3, it is curved about the axis of the rotary shaft 20, and as described above, the first recess 19b is formed along the inner surface of the combustion chamber 13. Together, they form a three-dimensional curved surface. And the wall surface
The distance between 19a and the inner surface of the combustion chamber 13 is set in consideration of the heat sink property of the cylinder wall between them.

The rotating shaft 20 includes a column portion 24a rotatably supported on the upper wall of the cylinder 11 and a non-round attachment portion 24b extending in the length direction from one end of the column portion 24a. First
Is formed with a non-round through hole 25a into which the shaft forming body 24 of the first shaft forming body 24 and the mounting portion 24b of the first shaft forming body 24 are fitted, and is rotated on the upper wall of the exhaust passage 15. It is composed of a second shaft structure 25 which is freely supported.

The second shaft structure 25 is brought into contact with a stopper 27 locked by a nut 26 screwed to one end of the mounting portion 24b, so that the second shaft structure 25 can be separated from the first shaft structure 24. The cylindrical portion 24 of the first shaft forming body 24 in the state of being blocked and being brought into contact with the stopper 27.
The length is set so that the mounting portion 24b can be exposed for a predetermined length between the step portion 24c formed at the boundary between the a and the mounting portion 24b.

Further, as shown in FIG. 3, a small diameter portion 24d is formed in a portion of the first shaft structure 24 projecting to the outside of the cylinder 11, and the small diameter portion 24d has a small diameter portion 24d. A fixed stopper 28 is rotatably fitted in the stopper 28, and is integrally rotatable toward one end.
9. The collar 30 is successively fitted, and the stopper 28, the operating lever 29 and the collar 30 are locked by the nut 31 screwed to the end of the small diameter portion 24d.

Therefore, with such a configuration, the first shaft component 24 and the second shaft component 25 are positioned with respect to the cylinder 11 and are prevented from being separated from the cylinder 11.

Further, the cylindrical portion 24a of the first shaft forming body 24 and the second
Between the portion of the shaft structure 25 projecting to the outside and the outer wall surface of the cylinder 11, a sealing member 32 for hermetically closing them is provided.
33 are installed.

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

And, the base portion 22 constituting these valve bodies 21 is
As shown in FIGS. 3 and 4, at one end thereof, the first
Non-circular through holes 35 similar to the cross-sectional shape of the mounting portion 24b of the shaft component 24 are formed, and by fitting the mounting portion 24b in these through holes 35, each valve body 21 is integrally attached to the rotary shaft 20, and can be reciprocally rotated within the range of a predetermined angle by the rotary shaft 20.

In addition, the base 22 is, as shown in FIG.
Seen from the center line direction of, is formed to have a shape substantially similar to the recessed portion 19, so that it can be stored in the recessed portion 19, in the state of being stored in the recessed portion 19,
The lower surface (the surface exposed in the exhaust passage 15) is configured to be continuous with the inner wall surface of the exhaust passage 15 to form a part thereof, and the combustion of the portion housed in the first recess 19b. The end surface on the chamber 13 side is the sealing surface 22a, and the sealing surface 22a is formed into a three-dimensional curved surface like the wall surface 19a of the first recess 19b.

Both valve bodies 21 are attached to the mounting portion 24 of the first shaft forming body 24.
b is inserted, and the step portion 24c of the first shaft forming body 24 is inserted.
It is attached to the rotary shaft 20 by being sandwiched by the inner end surface of the second shaft component 25 and is positioned with respect to the cylinder 11, the exhaust passage 15, the exhaust port 17 and the recess 19. Has become. Further, as described above, in the state where both valve bodies 21 are attached to the rotary shaft 20 in this manner, as shown in FIG.
It is adapted to be brought into sliding contact with the wall surface 19a of the concave portion 19b.

As shown in FIG. 3, the control unit 23 controls the sealing surface 22.
It is provided in the full width direction of a (circumferential direction of the cylinder 11), the lower surface of which is continuous with the lower surface of the base portion 22, and the upper surface 23a is a cone whose apex is one point on the center line of the combustion chamber 13. The curved surface is formed so as to follow a part of the surface. The upper surface 23a is a cylinder wall between the inner surface of the combustion chamber 13 and the wall surface 19a of the first recess 19b in the state where the valve body 21 is housed in the recess 19, as shown in FIG. It is designed to come into contact with the lower surface of the, almost all over.

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 rotation speed of the engine 10. Is a governor that is operated by the crankshaft of the above, or is a servomotor that is electrically operated by swinging the rotary shaft 20 back and forth to swing the valve body 21 within a predetermined angle range. It is designed to let you.

Then, when the engine 10 is started, the combustion gas is continuously discharged to the outside through the exhaust port 17 and the exhaust passage 15, and the exhausted combustion gas causes the cylinder wall above the exhaust port 17 to move to another Compared with the part, there is a phenomenon of being particularly heated, but the exhaust timing control device 18 of this embodiment is
In the engine 10 to which is applied, the wall surface 19a of the recessed portion 19 that houses the valve body 21 is separated from the inner surface of the combustion chamber 13, and the wall thickness of the cylinder wall above the exhaust port 17 is increased. Therefore, the heat given by the combustion gas is quickly transferred to the other parts of the cylinder 11 to prevent overheating. Therefore, the durability of the engine 10 against heat is improved. In addition, the control unit 23 controls the exhaust passage.
Since it is formed so as to gradually increase in thickness toward the downstream side of 15, the heat is satisfactorily transferred to the low temperature portion, and an excessive temperature rise of the valve body 21 itself is suppressed.

When the engine 10 is operated in the low rotation range, the rotary shaft 20 is rotated by the actuator, and the rotary shaft 20 causes the valve body 21 to move as shown by the chain line in FIG. By being swung and projected from the recess 19 into the exhaust passage 15, the swinging end of the valve body 21 closes the upper edge of the exhaust port 17, and the exhaust port 17 accompanying the lowering of the piston 12 is closed. The opening timing, that is, the exhaust timing, is delayed by the distance between the control unit 23 of the valve body 21 and the upper edge 17a of the exhaust port 17.

In such an operation of delaying the exhaust timing, the communication between the combustion chamber 13 and the recess 19 is interrupted at the overlapping portion of the sealing surface 22a of the valve body 21 and the wall surface 19a of the recess 19 that are in the protruding state. The above-mentioned delay operation of the exhaust timing is surely performed by the control unit 23, and the exhaust is appropriately performed in the low rotation speed range, so that the output characteristic in the low rotation speed range is improved.

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 unit 23, but the volume of the space is smaller than that of the combustion chamber 13. It is extremely small, and its influence on the control of the exhaust timing is slight.

Furthermore, when the engine 10 reaches a high speed range, an actuator that is operated based on the information,
As shown by the solid line in FIG. 2, the valve body 21 is housed in the recess 19, so that the upper portion of the exhaust port 17 is opened and the exhaust timing is advanced, so that the exhaust is appropriately performed in the high rotation range. The output characteristics are improved in the high rotation range.

It should be noted that the shapes, sizes, and the like of the constituent members shown in the above embodiment are examples, and can be variously changed based on the type of engine to be applied, design requirements, and the like.

[Advantages of the Invention] As described above, the exhaust timing control device for a two-cycle engine according to the present invention is formed continuously with the exhaust port opened and closed by the piston slidably fitted in the 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 a rotary shaft that is substantially orthogonal to the center line of the cylinder is provided in the recess. A valve element that is swung by the rotating shaft is provided, and by swinging the valve element, an upper end of the exhaust port is closed by the swing end, and the exhaust passage and the inside of the cylinder are connected. An exhaust timing control device for changing a communication timing, wherein the valve body includes a base portion having a seal surface that is slidably contacted with a wall surface of the recessed portion on the inner side of the cylinder, and the seal portion provided on the base portion. Valve from the bottom edge of the surface It is characterized in that it is formed so as to project outward in the swinging radial direction of the body, and is composed of a control section that gradually becomes thinner toward the end of the projecting portion. Produce the effect.

By separating the control unit that sets the exhaust timing and the sealing surface that blocks the communication between the combustion chamber and the recess,
The thickness of the cylinder wall located between the recess and the inner surface of the combustion chamber, where the amount of heat to be heated is large, is maximized to improve the heat sink of the cylinder wall, thereby significantly improving the durability against heat. You can do it.

By providing the control unit so as to project from the sealing surface, the control unit can be brought as close as possible to the extension line of the inner surface of the combustion chamber to open and close the exhaust port with high accuracy, and the sealing surface allows communication between the recess and the combustion chamber. Can be reliably prevented, and the exhaust timing can be reliably controlled while maintaining the above effect.

When each component is set to the low rotation speed side, the volume of the so-called dead space, which is a space generated above the exhaust port that communicates with the combustion chamber, is minimized, and the dead space controls the exhaust timing. The influence on the operation can be made slight, and in combination with the above effect,
The control accuracy of the exhaust timing can be greatly improved.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a conventional example of a two-cycle engine equipped with an exhaust timing control device, FIGS. 2 to 4 show one embodiment of the present invention, and FIG. Longitudinal section,
3 is a sectional view taken along the line III-III in FIG. 2, and FIG. 4 is an external perspective view of the valve body. 10 …… 2-cycle engine, 11 …… cylinder, 11a …… cylinder block, 11b …… cylinder head, 12 …… piston, 15 …… exhaust passage, 17 …… exhaust port, 17a …… upper edge, 18 …… Exhaust timing control device, 19 ... Recess, 19a ... Wall surface, 19b ... First recess, 19c ... Second recess, 20 ... Rotating shaft, 21 ... Valve body, 22 ... Base, 22a …… Seal surface, 23 …… Control part, 23a …… Top surface.

Claims (1)

[Claims] 1. An upper wall of an exhaust passage formed continuously with an exhaust port opened and closed by a piston slidably fitted in a cylinder of a two-cycle engine, the exhaust passage extending from the vicinity of the exhaust port. A recess is formed toward the downstream side, a rotary shaft that is substantially orthogonal to the center line of the cylinder is provided in the recess, and a valve body that is swung by the rotary shaft is provided on the rotary shaft. An exhaust timing control device that swings a valve element to close an upper portion of the exhaust port by a swing end thereof to change a communication timing between the exhaust passage and the inside of a cylinder. The valve body has a base portion formed with a seal surface that is brought into sliding contact with the inner wall surface of the cylinder of the recess, and the base portion extends outward in the swinging radial direction of the valve body from the lower end portion of the seal surface. And the protruding side Exhaust timing control apparatus of a two-stroke engine, characterized in that towards the end is composed of a gradually thin to become controller.