JPH0565690B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an exhaust timing control valve for an engine, and particularly to an exhaust timing control valve used in a two-stroke engine.

"Conventional technology" Generally, engines installed in vehicles, etc.
They are roughly divided into two types: low-revving types that emphasize power characteristics when running at low speeds, and high-revving types that emphasize power characteristics when driving at high speeds.
In the case of the former, the peak of engine output is obtained in the low rotation range of the engine, and in the latter case, the peak of engine output is obtained in the high rotation range. The output reaches a plateau, and in the case of the latter, the output in the low rotation range becomes lower than that of the former.

Therefore, it is being considered to improve the power characteristics in the entire range from low speed driving to high speed driving by increasing the output at low speed while maintaining high power in the high speed range. One method is to change the exhaust timing of the engine between low and high engine speeds.

Conventionally, a technique disclosed in Japanese Patent Publication No. 47-36047, for example, has been proposed as a means for changing the position of the upper edge of the opening of the exhaust passage.

This technology provides a support shaft at a position spaced downstream from the opening to the cylinder at the upper part of the inner wall surface of the exhaust passage, and is attached to the support shaft so as to be slidable along a plane perpendicular to the length direction of the support shaft. a control member comprising a shank portion which is connected to the shank portion and extends toward the opening, and an action portion which is integrally attached to the swinging end portion of the shank portion and is curved in substantially the same manner as the inner wall surface of the cylinder; A recess is formed in the vicinity of the opening at the bottom of the exhaust passage, in which the operating portion of the control member is accommodated.

By moving the operating portion up and down along the moving direction of the piston by the swinging motion of the shank portion of the control member, the recess formed in the upper edge of the opening of the exhaust passage and the lower part of the inner wall of the exhaust passage is connected. By this, the operating portion is retracted from the exhaust passage and positioned in the recess during high rotation, thereby opening the entire surface of the opening. and raise its upper edge, and also position the acting part above the opening of the exhaust passage during low rotation to close the upper part of the opening and align the curved surface of the acting part with the inner wall surface of the cylinder. By placing them on the same level,
The upper edge of the opening is apparently shifted downward to delay the timing of communication between the inside of the cylinder and the exhaust passage as the piston descends.

"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, when the operating part is located in the recess, in other words, when the engine is in a high rotation state, the shank part is located so as to cross the exhaust passage. In addition, when the working part is located at the upper edge of the opening, that is, when the engine is in a low rotation state, the recess that accommodates the working part is inside the exhaust passage. The problem is that since the shank portion is left open, it creates resistance to exhaust air like the shank portion described above, which may lead to a decrease in exhaust efficiency.

In addition, there is a tendency to increase the opening area of the exhaust passage as much as possible from the perspective of improving output, but if this method is applied to the prior art described above, the piston ring or oil that is constantly in pressure contact with the inner surface of the cylinder. The support surface for the rings, etc. will be reduced, and there is a risk that these rings will protrude into the exhaust passage and become caught on the upper or lower edge of the exhaust passage as the piston moves. There is.

And in order to eliminate such problems,
It has been proposed to provide a reinforcing rib along the direction of movement of the piston approximately in the middle of the opening of the exhaust passage, but this rib obstructs the movement of the control member, making it difficult to control the exhaust timing. This can lead to problems such as the inability to perform effectively.

"Means for Solving the Problems" The present invention aims to provide an exhaust timing control valve for a two-stroke engine that can effectively solve the problems in the conventional techniques described above. In particular, a slit is provided in the upper part of the exhaust passage so as to be movable back and forth, has a control surface at the inner end of the cylinder with approximately the same curvature as the inner surface of the cylinder, and extends from the end along the length direction of the exhaust passage. It is characterized by having the following.

"Function" By attaching the control valve according to the present invention to the upper part of the exhaust passage so as to be able to move forward and backward, the internal shape of the exhaust passage becomes smooth in both the protruding and retracting states, and also when the control valve moves The reinforcing rib provided at the opening of the exhaust passage is fitted into the slit formed in the valve piece to eliminate interference with the reinforcing rib and ensure control of the exhaust timing. At the same time, the area of the opening can be expanded as much as possible.

"Embodiment" Hereinafter, a preferred embodiment of the present invention will be described in detail based on FIGS. 1 to 3.

In FIG. 1, reference numeral 1 indicates a two-stroke engine to which the exhaust timing control valve according to the present embodiment is applied, which includes a cylinder 2, a piston 3 slidably inserted into the cylinder 2, and a cylinder 2, a piston 3 slidably inserted into the cylinder 2, A plurality of scavenging passages 4 are provided at intervals in the circumferential direction of the cylinder 2 and open on the inner surface of the cylinder 2, an exhaust passage 5 having an opening 5a on the inner surface of the cylinder 2, and an opening 5a of the exhaust passage 5. The opening 5 of the exhaust passage 5 is provided with a reinforcing rib H that divides the cylinder 2 into two in the circumferential direction.
Near a, there is an exhaust timing control valve 6 according to this embodiment.
(hereinafter abbreviated as a control valve) is provided, and in this embodiment, it is constituted by two control valves 7 and 8, a first and a second control valve.

To explain these details, the cylinder 2 is formed with a recess 9 continuous to the exhaust passage 5 at a position near the opening 5a at the upper part of the exhaust passage 5, and a recess 9 continuous to the recess 9 and connected to the cylinder 2. 2
A guide hole 10 is formed along a direction oblique to the length direction of the guide hole 10 .

A rotation shaft 11 is provided in the upper part of the recess 9 in parallel with a plane perpendicular to the cylinder 2, and a slit 12 into which the rib H is fitted is formed in the rotation shaft 11. The first control valve 7 is attached (see FIG. 2).

The first control valve 7 is swingable in the longitudinal direction of the cylinder 2 about the rotation shaft 11,
A control surface 7a having approximately the same curvature as the inner surface of the cylinder 2 is formed at its swinging end, and when it is swung toward the recess 9, the control surface 7a is It is positioned so as to fill the interior and constitute a part of the inner wall surface of the exhaust passage 5.

On the other hand, a drive means (not shown) for rotating the rotation shaft 11 is connected to an end of the rotation shaft 11 located outside the cylinder 2. The driving means is an actuator such as a governor, a servo motor, or a fluid pressure cylinder, which is controlled based on the rotational state of the engine 1, and is adapted to reciprocate the rotation shaft 11 within a predetermined angle range.

The guide hole 10 includes a first guide portion 10a that is continuous with the recess 9 and curved along the circumferential direction of the cylinder 2, and a second guide portion that is circular and continuous with the first guide portion 10a. 10b, and the second control valve 8 is fitted into the guide hole 10.

The second control valve 8 has a second guide portion 10b of the guide hole 10, as shown in FIGS.
A cylindrical sliding rod 13 that is slidably inserted into the
and a valve piece 14 which is connected to the inner end of the cylinder 2 of the sliding rod 13 and is slidably inserted into the first guide portion 10a of the guide hole 10. has been done. The valve piece 14 is formed into a curved shape similar to the first guide part 10a, and is integrally formed with the sliding rod 13 on both sides in the length direction by welding or the like, as shown in FIG. As shown in FIGS. 2 and 3, a slit 15 is formed extending from the end of the sliding rod 13 toward the inside of the cylinder 2 and having an interval approximately equal to the thickness of the rib H. is beginning to form. Further, a coil spring 16 is interposed between the sliding rod 13 and the cylinder 2,
The second control valve 8 is urged toward the swinging end of the first control valve 7 and is kept in constant contact with the first control valve 7 to follow the swinging motion of the first control valve 7. It's summery. Furthermore, a control surface 8a having approximately the same curvature as the inner surface of the cylinder 2 is formed on the end surface of each valve piece 14 on the inner side of the cylinder 2, and the first control valve 7 is swung in the projecting direction. When the first control valve 7 is removed, it enters between the upper edge of the first control valve 7 and the upper edge 5b of the exhaust passage 5 and blocks the space between them.
Further, as shown in FIGS. 1 to 3, the control surface 7a of the first control valve 7 is continuous with the inner wall surface of the cylinder 2 and forms a part thereof.

Thus, the control valve 6 of this embodiment configured as described above is moved in a predetermined direction by the driving means based on the operating state of the engine 1, thereby adjusting the output characteristics of the engine 1 over the entire rotation range. can be increased.

That is, when the engine 1 is operated at low rotation speed, the rotation shaft 11 is driven to open the first control valve 7.
is swung to protrude into the exhaust passage 5. With this movement of the first control valve 7, the second control valve 8, which is urged by the coil spring 16, also follows the first control valve 7 and slides toward the inside of the cylinder 2. However, since the reinforcing rib H provided in the opening 5a is fitted into the slits 12 and 15 formed in each control valve 7 and 8, each control valve 7 and 8 is The control surfaces 7a and 8a thereof are located in continuity with the inner surface of the cylinder 2, as shown in FIGS. 1 to 3. As a result, the upper part of the opening 5a of the exhaust passage 5 is closed, and as shown in FIGS. 1 and 2, the upper edge 5b of the opening 5a is apparently It is lowered by a distance L to the lower edge 7b.

Then, at the same time that the piston 3 descends and its upper end passes the lower end edge 7b of the first control valve 7, communication between the cylinder 2 and the exhaust passage 5 is established, so that the exhaust timing is delayed. As a result, proper exhaust gas is carried out at low rotation speeds, resulting in improved engine output in the low rotation range.

On the other hand, when the engine 1 reaches a high speed range, each component of the control valve 6 is moved in the opposite direction to the above, and the upper part of the opening 5a is opened to advance the exhaust timing. Appropriate exhaust gas is performed during high rotations, and engine output in the high rotation range can be improved.

Therefore, the exhaust timing of the engine 1 is controlled by the lower edge 7b of the first control valve 7, and the output characteristics are improved in the entire rotation range.

Since the control valve 6 is moved forward and backward in the upper part of the exhaust passage 5 during the control operation described above, the recess 9 in which the control valve 6 is accommodated is always maintained in a closed state. This allows for smooth exhaust flow. Further, in this embodiment, when each component is set corresponding to low rotation, the control surface 7a of the first control valve 7 is controlled by the control surface 8a of the second control valve 8 to control the cylinder 2. Since the space on the back side of both control valves 7 and 8, that is, the recess 9, is disconnected from the inside of the cylinder 2 by being connected to the inner surface, the swing range of the first control valve 7 is increased. Even if the above-described amount of change in the exhaust timing is made large, no accumulation will be formed in the exhaust passage 5, and furthermore, even when set to correspond to high rotation, the recess 9 will remain in the first position.
The first control valve 7 is filled in by the control valve 7, and the surface of the first control valve 7 on the exhaust passage 5 side is continuous with and forms a part of the inner wall surface of the exhaust passage 5, so as in the case of low rotation, No accumulation is formed in the exhaust passage 5, and smooth exhaust is maintained.

Furthermore, even when the area of the opening 5a of the exhaust passage 5 is expanded and a rib H is provided in the opening 5a in order to improve exhaust efficiency, the control valve 6 of this embodiment has a slit when moving. 12 and 15 prevents interference with the rib H, so that the exhaust timing control described above is performed reliably. This prevents deterioration of the strength of the cylinder 2 due to the enlargement of the opening 5a and deformation of the ring due to the reduction of its support surface, thereby significantly expanding the range in which the area of the opening 5a can be expanded. Therefore, it is possible to simultaneously achieve an output increase by controlling the exhaust timing described above and an output increase by improving the exhaust.

Note that the shapes, dimensions, combinations, etc. of each component shown in the above embodiments are merely examples, and can be variously changed based on design requirements and the like.

"Effects of the Invention" As explained above, the exhaust timing control valve of the two-stroke engine according to the present invention is provided in the upper part of the exhaust passage so as to be movable back and forth, and the end on the inside of the cylinder is provided with a valve that is almost flush with the inner surface of the cylinder. Since it has a curvature control surface and a slit extending from the end along the length of the exhaust passage, it can be applied to an engine having a reinforcing rib at the opening of the exhaust passage. Even when the exhaust timing is controlled by opening and closing the upper part of the opening, interference between the rib and the control valve can be prevented and the control valve can be operated reliably. In addition to being able to reliably control the exhaust timing described above, it is also possible to improve exhaust efficiency by enlarging the opening area of the exhaust passage. Therefore, it is possible to significantly improve the output of the engine over a wide rotation range. In addition, by providing ribs, it is possible to obtain effects such as securing the engine strength and preventing interference between the piston ring or oil ring and the opening of the exhaust passage, thereby ensuring smooth engine operation. It has excellent effects such as being able to secure

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a longitudinal cross-sectional view, FIG. 2 is a view taken along the - line with a part of FIG. The figure is a sectional view taken along the - line in which a part of FIG. 1 is omitted. 1... (2 cycle) engine, 2... cylinder, 3... piston, 5... exhaust passage, 5a...
Opening, 5b... upper edge, 6... (exhaust timing) control valve, 7... first control valve, 7a... control surface, 7b...
... lower edge, 8 ... second control valve, 8a ... control surface,
9... recess, 10... guide hole, 10a... first
Guide portion, 10b...Second guide portion, 11...
... Rotating shaft, 12 ... Slit, 13 ... Sliding rod, 14 ... Valve piece, 15 ... Slit, 16
……coil spring.

Claims (1)

[Claims] 1 Opening and closing the upper part of the opening of the exhaust passage communicating with the inside of the cylinder of a two-stroke engine to change the timing of communication between the inside of the cylinder and the exhaust passage by a piston fitted slidably inside the cylinder. The exhaust timing control valve is provided in the upper part of the exhaust passage so as to be movable back and forth, and has a control surface having approximately the same curvature as the inner surface of the cylinder at the end on the inside side of the cylinder, and has a control surface having a curvature that is approximately the same as the inner surface of the cylinder, and the exhaust timing control valve is provided so as to be movable in the upper part of the exhaust passage. An exhaust timing control valve for a two-stroke engine, comprising a slit extending along the length of the valve.