JPH0531215Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial application field" The invention relates to an engine exhaust timing control device, and more specifically, the upper part of the exhaust port (top dead center side of the piston) in a two-stroke engine is By opening and closing with a valve body, the upper edge position of the exhaust port is substantially changed in the sliding direction of the piston, and the timing of communication between the inside of the cylinder and the exhaust passage is changed as the piston slides. The present invention relates to an exhaust timing control device as described above.

"Conventional technology" Generally, engines installed in vehicles, etc.
The engine is roughly divided into two types: the low-rev type, which focuses on power characteristics in the low-rpm range, and the high-rpm type, which focuses on power characteristics in the high-rpm range. In addition, in the latter case, the peak of engine output is obtained in the high rotation range, but in the former case, the output reaches a peak in the high rotation range, and in the latter case, the peak output is obtained in the high rotation range. Since it also has the characteristic that the output in the rotation range is lower than the former, by increasing the output in the low rotation range while maintaining high output in the high rotation range, it is possible to increase the output in the low rotation range. Improving power characteristics over a wide range of speeds, from the rotation range to the high rotation range, is being considered.

One specific solution to this problem is to change the exhaust timing of the engine between the low and high rotation ranges, but if this method is applied to a two-stroke engine, the Since this is performed by opening the exhaust port by the piston, in order to change the exhaust timing, it is necessary to move the upper edge position of the exhaust port in the sliding direction of the piston.

By the way, as described above, the applicant has proposed, as a means for changing the upper edge position of the exhaust port,
He devised an exhaust timing control device disclosed in Japanese Patent Application No. 121026/1983.

This exhaust timing control device has a recessed portion in the upper part of the exhaust passage and near the exhaust port, a rotating shaft provided in the recessed portion so as to be substantially orthogonal to the axis of the cylinder, and a rotary shaft that rotates integrally with the recessed portion. A plate-shaped valve body is provided so that the valve body rotates, and a drive mechanism is provided that rotates the rotating shaft in accordance with the rotational speed of the engine.

According to this device, the rotating shaft is rotated by a drive mechanism according to the rotational speed of the engine. For example, when the engine rotates at a low speed, the tip of the valve body is caused to protrude downward from the upper edge of the exhaust port. On the other hand, when the engine rotates at high speed, the valve body is operated to be housed in the recess. In this way, the position of the upper edge of the exhaust port is substantially moved up and down in accordance with the rotational speed of the engine, thereby controlling the exhaust timing of the engine and improving the output over the entire rotational range of the engine.

``Problems to be solved by the invention'' By the way, it has been found that the above-mentioned exhaust timing control device has the following problems.

That is, in the above-mentioned exhaust timing control device, the recess for accommodating the valve body provided at the upper part of the exhaust passage is formed to be slightly wider than the valve body, taking manufacturing errors into consideration in advance. Therefore, the valve body can move freely within the recess in the thrust direction (the axial direction of the rotating shaft that supports the valve body) by the amount of clearance, and the valve body is protected from the effects of engine vibration. When affected by exhaust gas, it moves in the thrust direction,
There was a problem in that the drum collided with the inner surface of the recess, producing a tapping sound.

The present invention has been developed in view of the above circumstances, and is a two-stroke engine that can restrict the free movement of the valve body in the thrust direction and prevent the hammering noise caused by the valve body colliding with the inner surface of the recess. The purpose of the present invention is to provide an exhaust timing control device.

"Means for Solving the Problem" In the exhaust timing control device according to the present invention, the rotating shaft supporting the valve body is urged in the axial direction by the biasing member, and the valve body is pushed against the inner surface of the recess. I try to keep them in contact at all times.

"Operation" Since the valve body is biased in one direction by the biasing member, it will not move unnecessarily in the thrust direction even when affected by engine vibration or exhaust gas. Therefore, there is no rattling of the valve body in the thrust direction, and there is also no knocking sound caused by the valve body colliding with the inner surface of the recess.

"Embodiment" Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

Fig. 1 is a longitudinal cross-sectional view of an engine equipped with an exhaust timing control device according to the present invention, and Fig. 2 is a - of Fig. 1.
A sectional view taken along the line, and FIG. 3 is an enlarged view of a part thereof.

In these figures, reference numeral 1 indicates a cylinder block, 2 a cylinder head, 3 a piston slidably inserted into the cylinder, 4 a scavenging passage, and 5 an exhaust passage. A reinforcing rib 6 is provided at the center of the exhaust passage 5 in the left-right direction, extending from an exhaust port 7 opening to the inner surface of the cylinder to a predetermined location downstream of the exhaust passage 5. This rib 6 reinforces the vicinity of the exhaust port 7 of the exhaust passage 5, and the piston ring fitted on the outer periphery of the piston 3 expands radially outward due to its own elasticity.
It functions to prevent bumps from hitting the upper or lower edges of the surface.

A recess 8 is provided at the upper part of the exhaust passage 5 and slightly downstream of the exhaust port 7. A rotation shaft 9 is provided in the recess 8 so as to extend in a direction substantially perpendicular to the central axis of the cylinder so as to cross the recess 8 and to be freely rotatable. The upper and lower parts of the central part of the rotating shaft 9 are shaved to form a flat part, and valve bodies 10, 10 for exhaust timing control are placed on both sides of the rib 6 so as to sandwich the rib 6 between the central parts. It is positioned and fixed to a bolt or the like by a fixing means.

The valve bodies 10, 10 are symmetrical to each other. The valve body 10 has a shaft insertion portion 1 as shown in FIG.
1, and a flat plate portion 12 extending from the shaft insertion portion 11 to one side.
and a collar portion 13 erected at the tip of the flat plate portion 12. The surface 14 of the flange 13 facing toward the cylinder center is a surface that functions as a control surface that substantially moves the upper end position of the exhaust port 7 up and down when the valve body 10 is oscillated, and is approximately the same as the inner surface of the cylinder. It is formed to have a curvature of. Flat plate part 1
A through hole 15 is formed approximately in the center of 2.
This through hole 15 serves to guide exhaust gas into the upper space S of the valve body 10 and to prevent carbon from adhering to this portion.

The lower surface of the recess 8 has a shape corresponding to the upper surface of the valve body 10, that is, a recess 8a having a triangular cross section, a flat portion 8b, and a recess 8c having an arcuate cross section are provided in this order from the upstream side to the downstream side of the exhaust passage 5. , and the width l of the recessed portion 8 is formed to be slightly wider than the length of the valve bodies 10, 10 connected together.

One end of the rotating shaft 9 is rotatably fitted into a hole formed in the cylinder block 1 via a sleeve 16. The other end of the rotating shaft 9 passes through a hole 17 formed in the cylinder block 1 and projects to the outside.

A recess 17a is formed near the outer opening of the hole 17 in the cylinder block 1. Inside the recess 17a, an E clip 18 and a disc spring 1 are placed in order from the back side.
9, a washer 20 and a sealing material 21 are arranged. The E-clip 18 is fitted into a groove 9a of the rotating shaft 9, and is configured to move integrally with the rotating shaft 9 in the axial direction. The sealing material 21 is prevented from coming off by a casing 22 bolted to the cylinder block 1. Further, the washer 20 is urged in the A direction by the disc spring 19, while the E clip 18 is urged in the B direction, and the washer 20 is prevented from moving in the A direction by the casing 22 via the sealing material 21. Since the E-clip 18 and the rotating shaft 9 integrated therewith are urged in the B direction, the valve body 10 fixed to the rotating shaft 9 is eventually moved in the B direction. Its side portion is in contact with the inner surface of the recess 8.

Here, the strength of the disc spring 19 is such that even when the valve body 10 is affected by engine vibration or exhaust gas, the valve body 10 is always moved in the direction B and attached to the inner surface of the recess 8. It is set to such an extent that the abutting state can be maintained, and at the same time, a very strong frictional force is not generated when the valve body 10 swings as the valve body 10 comes into contact with the inner surface of the recess.

A wire guide 23 is fixed to the protruding end of the rotating shaft 9 with a bolt 24, and the wire guide 23 is connected to a servo motor 26 via a wire 25. Also, servo motor 2
6 is operated in forward and reverse directions by a controller (not shown) according to the rotational speed of the engine. That is, the wire guide 23, the wire 25, the servo motor 26, and the controller constitute a drive mechanism 27 that rotates the rotation shaft 9 according to the rotational speed of the engine.
Note that the portion where the washer guide 23 is connected to the wire 25 is covered by the casing 22.

According to the exhaust timing control device configured in this manner, the output characteristics of the engine can be improved over the entire rotation range by swinging the valve body 10 based on the operating speed of the engine.

That is, when the engine is operated at low rotation speed, the valve body 10 is brought into a state in which the control surface 14 is lowered toward the bottom dead center, that is, in a closed state, as shown by the two-dot chain line in FIG. . When the valve body 10 is in the closed state in this manner, the upper edge position of the exhaust port 7 is apparently lowered to the lower edge of the valve body control surface 14 . Therefore, by lowering the control surface 14, the exhaust port 7, which is opened and closed by the movement of the piston 3, can be opened later and closed earlier.

In this way, when the engine 3 is at low rotation speed,
In response to the long vertical movement period of the piston, the exhaust port 7 is opened slowly and closed quickly, so that the exhaust reflected wave is returned to the exhaust port 7 just before the exhaust port 7 is closed, and the combustion gas is Improves filling efficiency.

On the other hand, when the engine reaches a high rotation range,
Drive the servo motor 26 to drive the wire guide 23
and rotating the valve body 10 via the rotation shaft 9,
The valve body 10 is housed in a recess 8 formed in the upper part of the exhaust passage 5. As a result, the upper end position of the exhaust port 7 is substantially moved upward.

In other words, in this case, as the vertical movement period of the piston 3 becomes shorter, the exhaust port 7
to open earlier and close later than in the case described above. Therefore, in this case as well, the exhaust reflected waves are returned to the exhaust port 7 just before the exhaust port 7 is closed, and as in the case described above, the combustion gas filling efficiency can be increased by effectively utilizing the reflected waves.

In this way, the exhaust timing of the engine is controlled by the control surface 14 of the valve body 10, thereby improving the output characteristics at both high speed rotation and low speed rotation.

Further, according to the above control device, the rotary shaft 9 is biased in the direction B by the disc spring 19 disposed between the E clip 18 fixed to the rotary shaft 9 and the washer 20, and the valve body 10 is biased. It is always brought into contact with the inner surface of the recess 8. Therefore, even if the valve body 10 is affected by engine vibrations, it is possible to suppress rattling in the thrust direction (A, B direction), and the valve body 10 collides with the inner surface of the recess 8. It is possible to prevent conspicuous hitting sounds.

Also, if the disc spring 19 is placed at the above location,
The sealing material 21 is pressed from both sides by the reaction force of the disc spring 19, and the inner circumferential surface of the sealing material 21 can be strongly pressed against the rotating shaft 9, thereby improving the sealing performance between the two.

Furthermore, by arranging the disc spring 19 as far away from the exhaust passage 5 as possible, it is possible to prevent the disc spring 19 from being affected by heat from the exhaust gas, thereby improving the durability of the disc spring 19. can be achieved.

In the above embodiment, a recess 17a is provided near the outer opening of the hole 17 through which the rotating shaft 9 of the cylinder block 1 is inserted, and the disc spring 19 is placed in the recess 17a together with the sealing material 21, etc. This disc spring 1
The rotation shaft 9 is biased by the rotation shaft 9.
The member for biasing is not limited to a disk spring, but may be any other member such as a wave washer or a coil spring, and the location where these biasing members are placed is not limited to the recess 17a, but may be any other member such as a casing. It may be within 23.

"Effect of the invention" As explained above, according to the invention, the rotating shaft supporting the valve body is urged in the axial direction by the urging member, and the valve fixed to the rotating shaft is Since the body is always brought into contact with the inner surface of the recess, it is possible to eliminate rattling of the valve body in the thrust direction, and it is also possible to eliminate the generation of tapping sounds caused by movement of the valve body.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional side view illustrating the control device for a two-stroke engine according to the present invention, Fig. 2 is a sectional view taken along the - line in Fig. 1, and Fig. 3 is an enlarged view of the circular part in Fig. 2. be. 1...Cylinder block, 5...Exhaust passage, 7
...Exhaust port, 8...Recess, 9...Rotation axis, 1
0... Valve body, 19... Belleville spring, 26... Servo motor, 27... Drive mechanism.

Claims (1)

[Scope of utility model registration request] A recess is provided in the upper part of the exhaust passage and near the exhaust port, a rotating shaft is provided in the recess so as to be substantially orthogonal to the axis of the cylinder, and a plate-shaped valve body is attached to the rotating shaft so that the tip thereof is connected to the exhaust port. The rotating shaft is rotated in accordance with the rotational speed of the engine, and the swinging tip of the valve body substantially moves the upper end position of the exhaust port up and down, thereby changing the exhaust timing of the engine. 2, further comprising a biasing member that biases the rotation shaft in its axial direction to bring the valve body into contact with the inner surface of the recess.
Cycle engine exhaust timing control device.