JPH0420984Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] This invention is an exhaust control system for a two-stroke engine that opens and closes the gap between the subchamber and the exhaust port at a predetermined engine speed to change the volume of the exhaust pipe. Regarding equipment.

[Prior art]

FIG. 5 is a conceptual diagram of a two-stroke engine 10 with a subchamber equipped with a conventional exhaust control device.

In this two-stroke engine 10, a subchamber 16 is formed in the cylinder head 12 and communicates with an exhaust port 14. Further, the passage 18 that communicates between the subchamber 16 and the exhaust port 14 has a communication hole 2 between the circumferential surfaces.
A cylindrical valve 22 with a hole extending through it is rotatably supported. Further, one end of this valve 22 is connected to interlocking means 24 consisting of a link mechanism,
The other end of the interlocking means 24 is connected to a rotation means 26 for switching the valve 22 at a predetermined engine speed. The rotating means 26 includes a governor mechanism (not shown) that is displaced in accordance with the rotational speed of the engine, and a cam mechanism that converts the displacement of the governor mechanism into rotational motion. In addition,
In FIG. 5, reference numeral 28 is an arm of a link mechanism fixed to one end of the valve 22, and one end 28a of this arm 28 engages with stoppers 29a and 29b attached to the side of the cylinder block 29. Rotation of the valve 22 beyond a certain rotation angle is restricted.

According to such a conventional exhaust control device, when the engine 10 reaches a predetermined rotation speed, the rotation means 26 and the interlocking means 24 operate the valve 2.
2 is exhaust port 14 and subchamber 16
The subchamber 16 and the exhaust port 14 are rotated from the initial position where the subchamber 16 and the exhaust port 14 are in communication with each other. Further, when the engine speed falls below a predetermined speed, the valve 22 returns to its initial position by the action of a return spring (not shown).
Therefore, the engine 10 can obtain an optimum exhaust pipe volume according to each rotation speed range, and can obtain a high output two-stroke engine with flat output characteristics.

By the way, in the conventional exhaust control device mentioned above,
A rotating means 26 constituted by a governor mechanism and a cam mechanism serves as a driving means for switching the valve 22.
Since the interlocking means 24 constituted by a link mechanism that connects the rotation means 26 and one end of the valve 22 is used, when the rotational speed of the engine 10 increases, each part constituting the driving means Due to manufacturing errors and the like, an excessive load is applied through the governor mechanism, particularly to the link mechanism, and there is a risk that the rod, arm 28, etc. that make up the link mechanism may be damaged.

[Purpose of invention]

In view of the above-mentioned problems, it is an object of this invention to provide an exhaust gas control device for a two-stroke engine that does not apply excessive load to a cylindrical valve and a driving means for switching the valve.

[Structure of the invention] In the exhaust control device of this invention, an overload prevention means is provided at one end of the valve that opens and closes between the exhaust port and the subchamber, and the valve is linked to the drive means via the overload prevention means. There is.

〔Example〕

Hereinafter, one embodiment of the exhaust gas control device according to the present invention will be described in detail.

1 to 4 show the main parts of a two-stroke engine showing the exhaust gas control system of the present invention, and the same parts as in FIG. 5 are designated by the same reference numerals.

In this two-stroke engine 30, a groove 22b is formed in one end 22a of the cylindrical valve 22 that changes the volume of the exhaust pipe, and the groove 22b is used to return the valve 22 to the initial position where the exhaust port 14 and the subchamber 16 are communicated with each other. One end 32a of the return spring 32 is engaged. This return spring 32 is a coil spring with both sides formed in a “◯” shape as shown in Fig. 2.
The other end 32b engages with a rotating plate 36 that adjusts the biasing force of the return spring 32 and constitutes a part of the adjusting means 34. This rotating plate 36 is a disc-shaped plate having a predetermined thickness,
Inside thereof, there is an annular groove 36a for accommodating the return spring 32, and the return spring 32
A linear groove 36b that engages with the other end 32b is formed. Further, on the side of this rotary plate 36, there is a linear knob 3 integrally formed with the plate 36.
6c is formed.

Further, a disk-shaped fixed plate 38 that constitutes the other part of the adjustment means 34 is disposed on the side of the rotation plate 36. This fixed plate 3
8 is a knob 36c of the rotating plate 36 in the center.
A hole 38a is formed through which the fixing plate 38 is exposed, and an insertion hole 38b for a mounting screw 42 for fixing the fixing plate 38 to the side of the cylinder block 29 shown in FIG. 1 is formed at the periphery.

According to the adjustment device 34 described above, the mounting screw 42
When the rotation plate 34 is loosened and then rotated in either direction via the knob 36c, the return spring 32 is twisted accordingly, the urging force of the return spring 32 against the valve 22 is strengthened, and the rotation plate 34 is rotated in the other direction. If you do so, the urging force will weaken. Note that when the mounting screw 42 is tightened again after adjusting the urging force of the return spring 32, the rotating plate 36 is pressed between the fixed plate 38 and the recess 29c formed in the cylinder block 29, as shown in FIG. It is clamped and its rotation is restricted.

As shown in FIG. 1, an O-ring 44 is fitted to the outer peripheral edge of the rotating plate 36 to prevent exhaust gas, oil, etc. from leaking between the rotating plate 36 and the recess 29c that accommodates it. It prevents you from doing so.

On the other hand, the other end 22c of the valve 22 disposed in the two-stroke engine 30 is connected to the overload prevention means 5.
0, the valve 22 is connected to a mechanical drive means 60 for opening and closing the valve 22 at a predetermined engine speed (FIG. 1). Note that this driving means 60 is constituted by an interlocking means 24 constituted by a link mechanism, and a rotation means 26 connected to this interlocking means 24. Of these, the rotating means 26 includes a mechanical governor mechanism 62 that uses ball centrifugal force and is displaced in the direction of arrow A according to the rotation speed of the engine 30;
It is comprised of a cam mechanism 64 that converts the displacement of the governor mechanism 62 into rotational motion. Further, this cam mechanism is composed of a ball 64a and cam plates 64b and 64c forming inclined ball races (not shown) in which the ball 64a runs concentrically, and constitutes the interlocking means 24. One end 66a of the link mechanism rod 66 is supported by a rotating cam plate 64b, and the other end 66b is connected to the valve 22 via the overload prevention means 50.

On the other hand, as shown in FIG. 2, which is an exploded perspective view of main parts in FIG.
, a coil-shaped spring 54 fitted into the other end 22c, and a second arm 56 having an L-shaped cross section and rotatably supported by the other end 22c. . Among these, each one end 54a, 54b of the spring 54 extends in a direction perpendicular to the axial direction, and the one end 54a is connected to a side 52 of a bent portion 52a formed on the first arm 52.
a', and the other end 54b engages with a side 56a' of a bent portion 56a formed on the second arm 56. Therefore, when the second arm 56 is rotated in the direction of arrow B via the rod 66 supported on the other end 56b of the second arm 56, the first arm 52 is rotated in the same direction (arrow B) via the spring 54. direction). Note that in FIG.
Nut 72 is the crankshaft.

Next, the operation of the above-mentioned overload prevention means 50 will be explained, and the structure will also be explained in more detail.

FIG. 3 is a conceptual side view of FIG.
Through subchamber 16 and exhaust port 1
4 is positioned at the position where the communicating hole is formed. The other end 52b of the first arm 52 constituting the overload prevention means 50 engages with a stopper 74 protrudingly formed at a predetermined position on the side of the cylinder block 29, and its rotation in one direction is restricted. There is.

On the other hand, when the engine 30 reaches a predetermined rotation speed,
The second arm 56 is rotated clockwise in the drawing by the rotation means 26 constituting the drive means 60 and the rod 66 of the interlocking means 24. This second
When the arm 56 rotates clockwise in the drawing, the rotational force of the second arm 56 is transmitted to the first arm 52 via the spring 54, and the valve 22 is rotated through the first arm 52. Resisting the biasing force of the return spring 32, it rotates in a direction that closes the space between the subchamber 16 and the exhaust port 14 on its peripheral surface, as shown in FIG. When the valve 22 rotates to a predetermined position where its peripheral surface closes the subchamber 16 and the exhaust port 14, the other end 52b of the first arm 52 moves to a stopper 76 formed to protrude to the side of the cylinder block 29. Since the rotation angle is engaged with, rotation beyond a predetermined rotation angle is restricted. On the other hand, the engine 30 rotates further, and the second arm 5 is rotated through the rod 66.
6 further clockwise in the drawing, each end 5 of the spring 54 will rotate as shown in FIG.
4a and 54b are expanded and deformed to absorb the rotational force applied to the first arm 52 and the valve 22, and also absorb the overload applied to each part of the drive means 60. Note that when the rotational speed of the engine 30 becomes lower than a predetermined rotational speed, the valve 22 is moved to a predetermined initial position (a predetermined initial position where the subchamber 16 and the exhaust port 14 are communicated with each other) due to the biasing force of the return spring 32 shown in FIG. Return to Figure 3).

Note that when the valve 22 returns to the predetermined initial position, if a force acts through the rod 66 to further rotate the second arm 56 in the counterclockwise direction in the drawing, each of the springs 54 will be One end 54a, 54
b expands and deforms, absorbing the rotational force applied to the first arm 52 and the valve 22, and
Excessive loads applied to each part of the drive means 60 are also absorbed.

[Effect of idea]

As explained above, in this invention, the cylindrical valve that opens and closes between the subchamber and the exhaust port is connected to the mechanical drive means consisting of the governor mechanism via the overload prevention means. Overload applied to the valve and drive means is absorbed, and the durability of the exhaust control device can be improved.

In addition, because the overload prevention means is placed on the side (one end) of the cylindrical valve located perpendicular to the direction in which the exhaust port extends, the longitudinal dimensions of the engine do not increase. Therefore, the overload prevention means can be compactly mounted on the engine.

[Brief explanation of the drawing]

FIG. 1 is a cutaway cross-sectional view of the essential parts of a two-stroke engine showing the exhaust control device according to the present invention, FIG. 2 is an enlarged assembled perspective view of the essential parts of FIG. 1, and FIGS. 3 and 4 are the same as those shown in FIG. 1. FIG. 5 is a conceptual side view of a two-stroke engine showing a conventional exhaust control device. 14...Exhaust port, 16...Subchamber, 20...Communication hole, 22...Valve, 22
b... One end, 50... Overload prevention means, 52...
First arm, 54... Spring, 56... Second arm, 60... Drive means, 62... Governor mechanism,
64...Cam mechanism, 64b...Rotating side cam plate, 66...Rod.

Claims (1)

[Scope of claims for utility model registration] Exhaust port 14 and subchamber 1
6, the shaft is arranged perpendicular to the extending direction of the exhaust port 14, and the communication hole 2 is disposed between the peripheral surfaces in a direction perpendicular to the axial direction.
A first arm 52 having an L-shaped cross section is fixed to one end of the valve, and a second arm 52 having an L-shaped cross section is rotatably supported at one end of the valve. an arm 56, and a stopper 74 that comes into contact with one end of the first arm 52 when the first arm 52 rotates by a predetermined rotation angle to restrict rotation of the first arm beyond a predetermined rotation angle; 76, and both end portions 54a and 54b that are fitted into one end of the valve 22 and extended connect the L-shaped one end 56a of the second arm 56 and the L-shaped one end 52a of the first arm 52. The rotational force of the second arm 56 is transmitted to the first arm 52 via the extended ends 54a, 54b, and
When the second arm 52 comes into contact with one of the stoppers 74, 76 and is restricted from rotating beyond a predetermined rotation angle, over-rotation of the second arm 56 is prevented by widening the space between the two ends 54a, 54b. Overload prevention means 50 consisting of an absorbing coil spring 54
, a mechanical governor mechanism 62 that is displaced according to the engine rotation speed, a cam mechanism 64 that converts the displacement of the governor mechanism 62 into rotational motion, and one end of which is connected to the second arm 56 of the overload prevention means. The other end is connected to the rotating side cam plate 64 of the cam mechanism 64.
and a rod 66 connected to the exhaust port 14 from the initial position where the valve 22 communicates between the exhaust port 14 and the subchamber 16 via the overload prevention means 50 at a predetermined engine speed. and a drive means 60 for rotating in a direction to close the space between the subchamber 16 and the subchamber 16.