JPS62271925A - Exhaust timing control device for two-cycle engine - Google Patents

Abstract

PURPOSE:To obtain a secure seal of exhaust gases by providing an exhaust timing control device which opens or closes the upper periphery of the exhaust port of a two-cycle engine so as to form a seal part with the outer wall of a cylinder, and providing a control part projected from the seal part in the direction of the cylinder. CONSTITUTION:On the upper periphery of the opening of the exhaust port 15 of a two-cycle engine, an exhaust timing control device 21 which turns making a turning shaft 20 as the center is provided. The end part of the exhaust timing control device 21 is comprised of a seal part 22a which is engaged with the projected part 19a of the outer wall of a cylinder, and a control part 23a which extends from the seal part 22a in the direction of the cylinder. Even if the exhaust timing control device turns in the clockwise direction at the time of low speed of the engine to lower the control part 23a, since the seal part 22a is engaged with the projected part 19a of the outer wall of the cylinder, exhaust gases can be securely sealed.

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-stroke engine.

"Conventional technology" Generally speaking, engines used in vehicles, etc., operate at low speeds (
They are roughly divided into two types: the low-speed type, which focuses on power characteristics at high speeds (low speed range), and the high-speed type, which focuses on power characteristics at high speeds (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 peak output in the high rotation range is obtained. The latter also has the characteristic that the output in the low rotation range is lower than the former.

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, change the position of 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 direction of movement of the piston.

In order to change the position of the upper edge of the exhaust boat 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.

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 a cylinder 2 of a two-cycle engine 1, from near the exhaust port 3 toward the 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 the exhaust passage 4 is contained in the recess 5.
It has a structure in which a plate-shaped valve body 7 that is projected inward is integrally provided, and when the valve body 7 is projected from the recess 5, the swinging end of the valve body 7 is connected to the exhaust port 3. By closing the upper part of the piston 8, as shown in FIG.
The timing of communication between the inside of the cylinder 2 and the exhaust passage 4 due to the lowering 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 recess 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 part 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 arcuate movement locus, and
With the valve body 7 protruding into the exhaust passage 4, in order to prevent combustion gas from leaking, it is necessary to bring the swinging end of the valve body 7 close to the inner surface of the cylinder cylinder 2.
The problem is that the cylinder wall between the inner surface of the recess 5 that accommodates the valve body 7 and the inner surface of the cylinder 2 is thinned in an edge-like manner, resulting in a reduction in dryness.

In particular, since the above-mentioned edge portion is formed at a portion where the temperature rise is 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 fully projected 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, that is, the combustion chamber, and a so-called dead space is formed. As a result, part of the combustion gas may flow into the space before the regular exhaust timing set by the valve body 7 is reached, reducing the accuracy of controlling the exhaust timing. It cannot be a solution.

"Means for Solving the Problems" The present invention can effectively solve the above-mentioned conventional problems.
It is an object of the present invention to provide an exhaust timing control device for a cycle engine. In particular, it is an object of the present invention to provide an exhaust timing control device for a two-stroke engine. A recessed portion is formed toward the downstream side of the exhaust passage, a rotating shaft substantially orthogonal to the center line of the cylinder is provided in the recessed portion, and a valve body that is swung by the rotating shaft is mounted on the rotating shaft. The exhaust timing control device is configured to swing the valve body to open and close the upper part of the exhaust boat using the swinging end thereof, 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 a base portion that protrudes outward in a swinging radial direction of the valve body from below the sealing surface. and a control section integrally attached to the lower surface of the base.

"Function" The exhaust timing control device for a two-stroke engine according to the present invention, in a state where the valve body is protruded into the exhaust passage,
By overlapping the seal 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 seal A projecting piece protruding outward in the radial direction of the valve body's swing from below the surface controls the timing of communication between the inside of the cylinder and the exhaust passage, and causes the sealing surface to move toward the center of the valve body's swing. This makes it possible to change the position, thereby separating the inner surface of the recess and the inner surface of the cylinder to increase the wall thickness of the cylinder wall above the exhaust boat, and further, to reduce the machining of the base and the control section. As much as possible, the machining accuracy and manufacturability are improved.

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

In FIG. 2 and FIG. 3, the symbol IO indicates a two-cycle ennon to which one embodiment is applied, so the cylinder block lla and the cylinder head Ilb attached to the second part of the cylinder block lla. A cylinder 11. The piston 12 is slidably fitted in the cylinder block Ila, the combustion chamber 13 is formed by the piston 12, the cylinder block Ila, and the cylinder head Ilb, and the number of membranes formed in the cylinder block I1g. A scavenging passage 14 and a single exhaust passage 15, a scavenging boat 16 which is an opening to these combustion chambers 13, and an exhaust port 17 are provided, and in the vicinity of the exhaust port 17 on the upper wall of the exhaust passage 15, a An example exhaust timing control device 18 is provided.

The exhaust timing control device 18 includes a concave portion L9 formed in the upper wall of the exhaust passage 15 from near the exhaust port 17 toward the downstream side, and a concave portion L9 formed in the concave portion 19 so as to be substantially perpendicular to the center line of the cylinder 1. A rotation shaft 20 is provided on the rotation shaft 20, and 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 side of the combustion chamber 13.
The base portion 22 includes a base portion 22 on which a seal surface 22a is formed to be brought into sliding contact with the valve body 9a, and a projection piece 23a that protrudes outward in the swinging radial direction of the valve body 21 from below the seal surface 22a. It has a general configuration formed by a control section 23 that is integrally attached to the lower surface of the controller.

Next, to explain these details, the above four parts 1
In this embodiment, as shown in FIG. 3, 9 is a first four part 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;
A second recess 19c is formed along the length of the exhaust passage 15 from the first recess 19b. Further, the first recess 19b is located at the exhaust port 1.
7, and the wall surface 19a on the side of the combustion chamber 13 is curved around the axis of the rotating shaft 20, as shown in FIG. In combination with the fact that the first recess 19b is formed on the inner surface of the combustion chamber 13 at an angle of tO, a three-dimensional curved surface is formed. The wall surface 19a and the combustion chamber 1
The distance from the inner surface of No. 3 is set in consideration of heat shrinkage on the cylinder wall between the two.

EFi rotation shaft 20 includes a cylindrical portion 24a that is rotatably supported on the upper wall of the cylinder 11 and a non-circular attachment portion 2 that extends in the length direction from one end of the cylindrical portion 24a.
4b, and a non-circular through hole 25a into which the fitting portion 24b of the first shaft groove member 24 is fitted are formed, and the exhaust passage 1
A second shaft horizontal body 25 rotatably supported on the upper wall of 5
It is composed of.

The second shaft cross body 25 is prevented from detaching from the first shaft cross body 24 by being brought into contact with a stopper 27 which is secured to one end of the mounting portion 24b by a nut 26. At the same time, in the state in which the stopper 27 is brought into contact with the stopper 27, between the cylindrical part 24a of the first shaft horizontal body 24 and the step part 24c formed at the boundary part with the mounting part 24b, The length of the attachment is set so that the portion 24b 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. Collar 30h (sequentially fitted, these stopper 28, operating lever 29 and collar 30,
It is 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
Sole members 32 and 3'A are interposed between the outer wall surfaces of the sole members 1 and 1 to airtightly close them.

In this embodiment, the valve body 21 is divided into two parts in the length direction of the rotating wheel 20, as shown in FIGS. The reinforcing ribs 34 provided toward the downstream side of the exhaust passage 15 are sandwiched therebetween.

As shown in FIGS. 2 and 3, the front Ad base 22 constituting these valve bodies 21 has a cross-sectional shape of a portion 24b to which the first shaft-side body 24 is attached at one end. Through-holes 35 having a non-perfect circular shape similar to those shown in FIG. As the rotation shaft 20 rotates, it can be rotated reciprocally within a predetermined angle range.

This rotation angle is an angle at which the amount of overlap between the seal member 22a and the wall surface 19a of the recess 9 reaches a set distance, with reference to the state in which each valve body 21 is housed in the recess 19.

Further, as shown in FIG. 3, the base 22 may be formed to have substantially the same shape as the recess 9 when viewed from the center line direction of the cylinder 11, and may be accommodated in the recess 19. A notch 2 is provided on the lower surface (exposed in the exhaust passage 15) for attaching the control section 23.
2b is formed, and the first recess 19b
The end of the part housed in the combustion chamber 13 side serves as the seal 22a, and the round surface 22a is formed into a three-dimensional curved surface similar to the wall surface 19a of the first recess 19b. There is.

The mounting portion 24b of the first shaft lateral body 24 is inserted into the through hole 35 of both valve bodies 21, and the step portion 24c of the first shaft lateral body 24 and the second shaft lateral body 24 are inserted. Lateral adult body 25
By being sandwiched between the inner end of the cylinder 11 and the exhaust passage 15, the
, and the exhaust boat 17 and the recess 19 (I''LL).In addition, in this way, both valve bodies 2
1 attached to the rotating shaft 20, each seal 22a is brought into sliding contact with the wall surface 19a of the first recess 19b, as shown in FIG.

As shown in FIGS. 3 and 4, the control section 23 is formed so that the shape viewed from the center line direction of the cylinder U is almost the same as the base 22, and the notch of the base 22 22b, it is aligned with the base 22 and is integrated by a plurality of rivets 36 passing through both pieces. When the control section 23 is housed in the recess 19 along with the base 22, the lower surface thereof is continuous with and forms a part of the inner surface of the exhaust passage 15.

On the other hand, the protrusion 23a provided on the control section 23 is
When the control section 23 is attached to the base 22, it is formed to protrude from the sealing surface 22a of the base 22 as described above, and the upper surface 37 has a point on the center line of the combustion chamber 13 as its apex. It is a curved surface that forms part of a conical surface. Further, when the valve body 21 is housed in the recess 19, the upper surface 37 is connected to the inner surface of the combustion chamber 13 and the first recess 19b, as shown in FIG.
The lower surface of the cylinder wall between the cylinder wall and the wall surface 19a is brought into contact over almost the entire surface thereof.

On the other hand, an actuator (shown in the figure) is connected to the rotation shaft 20 via an operating lever 29, and the actuator is operated based on the rotation speed of the engine 1O. A governor operated by a crankshaft, or a servo motor electrically operated, rotates the rotation shaft 20 back and forth to move the valve body 21 within a predetermined angle range. It is made to float.

As the engine 1O starts, combustion gas is continuously discharged to the outside via the exhaust boat 17 and the exhaust passage 15, and the cylinder wall above the exhaust boat 17 is affected by the discharged combustion gas. Although there is a phenomenon that the sealing surface 22a of the valve body 21 is heated to a higher temperature than other parts, in the engine 10 to which the exhaust timing control device 18 of this embodiment is applied, the sealing surface 22a of the valve body 21 is Since the wall surface 19a of the recess 19 that accommodates the valve body 21 is spaced apart from the end of the combustion chamber 13, the thickness of the cylinder wall above the exhaust boat 17 is reduced. The cylinder 11 is formed large so that the heat provided by the combustion gas is rapidly transferred to other parts of the cylinder 11, thereby preventing overheating. Therefore, the durability against heat of the engine 10 is improved. Furthermore, since the protruding piece 23a is formed so as to gradually become thicker toward the downstream side of the exhaust passage 15, heat is efficiently transferred toward the lower temperature portion, and the valve body 21 itself is Excessive temperature rise is suppressed.

When the engine IO 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 recess 19 into the exhaust passage 15, so that the swing end of the valve body 2L closes the upper part of the exhaust boat 17.
The opening timing of the exhaust boat 17 as the piston 12 descends;
That is, the exhaust timing is delayed by the distance between the protrusion 23a of the control section 23 and the upper edge 17a of the exhaust boat 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
The 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, and that the exhaust is properly discharged in the low rotation range. As a result, the output characteristics in the low rotation range are improved. Moreover, when forming the valve body 21, the sealing surface 2 is manufactured separately and integrated with the base 22 and the control part 23.
2a and the end of the protrusion 37 on the side of the combustion chamber 13 can be processed with sufficient accuracy, and from this point of view, the sealing performance described above can be improved, or the exhaust timing can be set reliably.
Highly accurate exhaust timing control is implemented.

By the way, when the valve body 21 is made to protrude as described above, the valve body 21, the inner surface of the exhaust passage 15, and the protruding piece 23a
A space communicating with the inside of the combustion chamber 13 is formed between the space and the upper surface 37, but its volume is extremely small compared to that of the combustion chamber 13, and its influence on the exhaust timing control described above is slight. It is something.

Furthermore, when the engine IO reaches a high speed range, an actuator operated based on the information causes the valve body 21 to be accommodated in the recess 19, as shown by the solid line in FIG. The upper part of the boat 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 shapes, 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 rotating wheel substantially orthogonal to the center line of the cylinder, and the rotation axis is A valve body is provided that is swung by the rotating shaft, and by swiveling the valve body, the swinging end portion closes the upper part of the exhaust port, thereby communicating the exhaust passage with the inside of the cylinder. The exhaust timing control device is configured to change the timing, and the valve body includes a base portion formed with a sealing surface that is brought into sliding contact with the inner wall surface of the four cylinders, and a base portion that is formed with a sealing surface that is brought into sliding contact with the inner wall surface of the four cylinders, and a valve body that is configured to change the timing of the exhaust timing. It is characterized by comprising a protruding piece that protrudes outward in the radial direction of the body's swing, and a control unit that is integrally attached to the lower surface of the base. It has excellent effects.

■By separating the protrusion that sets the exhaust timing from the sealing surface that blocks communication between the combustion chamber and the recess, it can be located between the fourth part and the inner surface of the combustion chamber, which is a location that receives a large amount of heating heat. By increasing the thickness of the cylinder wall as much as possible, it is possible to improve the heat sink of the cylinder wall, thereby greatly improving the durability against heat.

■ By providing the protruding piece protruding from the sealing surface, the protruding piece can be placed as close as possible to the extension of the inner surface of the combustion chamber to accurately open and close the exhaust port, and the sealing surface allows the recess to be connected to the combustion chamber. to ensure communication is cut off,
The exhaust timing can be reliably controlled while maintaining the effect (2) above.

■By making the base and the control part separate members, we can process the sealing surface, which affects the sealing performance between the combustion chamber and the recess, and
It not only makes it easier to process the edge of the protrusion, which greatly affects the setting of the exhaust timing, but also enables high-precision machining.
The effect can be further enhanced.

■When the valley-groove member is set to the low rotation range side, the volume of the so-called dead space, which is the space created above the exhaust port that communicates with the combustion chamber, is minimized to minimize the volume of the dead space. The effect on the control operation can be made negligible, and in combination with the above effects,
It is possible to significantly improve the control accuracy of exhaust timing.

[Brief explanation of the drawing]

Fig. 1 is a vertical cross-sectional view showing a conventional example of a two-cycle ennon 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 cross-sectional view of
FIG. 3 is a sectional view taken along arrows lll-[line tf] in FIG.
FIG. 4(A) is an exploded perspective view of the valve body, and FIG. 4([3) is an external perspective view. 10...2-cycle engine, 11...Mountain cylinder, 11a...Cylinder block, 11b
...Cylinder head, 12...Piston, 15...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, 22b ... Notch,
23...Control unit, 23a...
... protrusion, 36 ... rivet, 3
7...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. An exhaust timing control device configured to change communication timing with the inside of a cylinder, wherein the valve body includes a base portion formed with a sealing surface that is brought into sliding contact with a wall surface on the inside side of the cylinder of the recessed portion, and 2, comprising a protruding piece projecting outward in the swinging radial direction of the valve body from below the sealing surface, and a control unit integrally attached to the lower surface of the base. Cycle engine exhaust timing control device.