JPH0350264Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to an exhaust timing control device for an engine, and particularly to an exhaust timing control device 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 former, the peak of engine output occurs when the engine output peaks at low engine speeds. In addition, in the latter case, the output peak is obtained in the high rotation range, but in the former case, the output peaks out in the high rotation range,
The latter also has the characteristic that the output in the low rotation range is lower than 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, and there are specific solutions. One method is to change the exhaust timing of the engine between low and high engine speeds.

By the way, when such a means is applied to a two-stroke engine, the exhaust operation is performed by communication between the exhaust passage and the inside of the cylinder as the piston descends, so that the exhaust passage is It is necessary to change the position of the upper edge of the opening (hereinafter, the top dead center side of the piston is taken as the top, and the bottom dead center side is taken as the bottom) in the direction of movement of the piston.

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 swingable 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 lower part of the exhaust passage and near the opening, in which the operating part of the control member is accommodated.

In response to the operating state of the engine, the operating portion of the control member is moved up and down along the moving direction of the piston by the rocking operation of the shank portion of the control member, thereby connecting the upper edge of the opening of the exhaust passage and the exhaust passage. and a recess formed in the lower part of the inner wall of the exhaust passage, whereby during high rotation, the operating portion is retracted from the exhaust passage and positioned within the recess. By doing so, the entire surface of the opening is opened and its upper edge is raised, and
By positioning the acting part above the opening of the exhaust passage to close the upper part of the opening during low rotation, and by positioning the curved surface of the acting part at the same level as the inner wall surface of the cylinder, the opening can be closed. The upper edge is apparently shifted vertically to delay the communication between the inside of the cylinder and the exhaust passage as the piston descends.

On the other hand, as a method for driving the above-mentioned control member in accordance with the operating state of the engine, for example,
It has been considered to connect a control member to a throttle lever of an engine and to control the position of the control member in conjunction with the amount of operation of the throttle lever.

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

That is, when performing blipping (in other words, rapid throttle operation) in a no-load state such as during warm-up, it is desirable to stop the operation of the control member. By connecting the control member to the throttle lever of the engine, the control valve can be driven in accordance with the operating state of the engine, and even during the above-mentioned blipping, the control member will follow the movement of the throttle lever. The problem is that there is a risk that the optimum exhaust timing cannot be controlled. Another problem is that if the exhaust timing changes too much in response to sudden throttle ON/OFF operations, the power feeling changes greatly, leading to a so-called jerky feeling.

"Means for Solving the Problems" The present invention aims to provide an exhaust timing control device for a two-stroke engine that can effectively solve the problems in the conventional techniques described above. In particular, a control valve that opens and closes the upper part of the opening by being driven by a throttle lever is provided above the opening of the exhaust passage communicating with the inside of the cylinder of the two-cycle engine, and the control valve and the throttle lever The invention is characterized in that a buffer means is provided in the middle of the power transmission path between the control valve and the control valve to reduce the driving force transmitted to the control valve.

"Operation" The present invention uses a control valve driven by a throttle lever to delay the exhaust timing by closing the upper part of the exhaust passage and lowering the upper edge of the opening of the exhaust passage. By unblocking the upper part of the opening and raising the upper edge of the opening, the exhaust timing is accelerated, the output characteristics of the engine are improved in the entire rotation range, and the driving force transmitted to the control valve is increased. The damping means provided in the middle of the power transmission path suppresses the movement of the control valve in response to rapid throttle changes during blipping and normal driving, thereby improving practicality.

"Embodiment" Hereinafter, a preferred embodiment of the present invention will be described in detail based on FIGS. 1 to 5.

Reference numeral 1 in the figure indicates a two-stroke engine to which the exhaust timing control device according to the present embodiment is applied, and the two-stroke engine 1 (hereinafter simply referred to as engine 1) has cylinder 2. A piston 3 slidably inserted into the cylinder 2, a plurality of scavenging passages 4 provided at intervals in the circumferential direction of the cylinder 2 and open to the inner surface of the cylinder 2, As shown in FIG. 3, an exhaust passage 5 having an opening 5a on its inner surface, a carburetor 6 for producing an air-fuel mixture to be supplied into the combustion chamber of the cylinder 2, and a throttle lever 7 for operating the carburetor 6. an opening 5a of the exhaust passage 5;
An exhaust timing control device 8 according to this embodiment is provided between the vicinity and the carburetor 6.

First, to explain the cylinder 2, as shown in FIG.
A continuous recess 9 is formed, and a guide hole 10 continuous with the recess 9 and inclined with respect to the longitudinal direction of the cylinder 2 is formed.

The guide hole 10 has a first hole that is continuous with the recess 9 of the exhaust passage 5 and is curved along the circumferential direction of the cylinder 2.
A guide part 10a that is continuous with the first guide part 10a and a perfectly circular second guide part 10b that is connected to the cylinder head attached to the cylinder 2. 11.

Next, the exhaust timing control device 8 according to this embodiment
To explain, the exhaust timing explaining device 8 is as follows.
As shown in FIG. 1, a first control valve 12 is swingably fitted into the recess 9 and has a control surface 12a having approximately the same curvature as the inner surface of the cylinder 2.
and is slidably fitted into the guide hole 10,
A second control valve 13 having a control surface 13a having approximately the same curvature as the inner surface of the cylinder 2; Drive mechanism 1 that swings the valve 12
4, and a throttle drum 15 connected to the drive mechanism 14 and the throttle (not shown) of the carburetor 6.
and a wire 16 disposed between the two to form a power transmission path between the two and to connect the two in an interlocking state, the schematic configuration is such that the driving force transmitted to the drive mechanism 14 is alleviated. In order to reduce the driving force, a buffer 17 is provided in the middle of the wire 16 in this embodiment.

To explain this in more detail, the first control valve 12 has a support tube 18 integrally attached to the side opposite to the side on which the control surface 12a is formed. A rotary shaft 19 composing the drive mechanism 14 that penetrates the cylinder 2 and projects into the recess 9 is connected to the support tube 18, and the rotary shaft 19 reciprocates within a predetermined angle range. By being rotated, the support cylinder 18 is integrally rotated, and the rotation of the support cylinder 18 causes the first control valve 12 to move into the recess 9.
The opening 5a is accommodated in the opening 5a or projected at a predetermined position above the opening 5a. and the first control valve 12 is housed in the recess 9 and fills the recess 9 together with the support tube 18;
The wall surface of the exhaust passage 5 is formed.

On the other hand, the second control valve 13 controls the guide hole 1
Similarly to the first guide portion 10a of No. 0, the cylinder 2
It is curved along the circumferential direction of the second
The cylinder head 10 is integrally attached to a sliding rod 20 that is slidably inserted into the guide portion 10b of the cylinder head 11, and is provided with a coil spring 21 interposed between the sliding rod 20 and the cylinder head 11. ,
Together with the sliding rod 20, it is constantly ejected toward the first control valve 12.

Therefore, the second control valve 13 is always in contact with the upper part of the swinging end of the first control valve 12,
The guide hole 10 follows the swinging of the first control valve 12.
When the first control valve 12 is swung to the position where it closes the opening 5a, the upper end of the first control valve 12 and the opening 5a
It enters between the upper edge 5b and closes the gap between the two, and its control surface 13a allows the first control valve 1
In cooperation with the control surface 12a of the cylinder 2, a surface continuous with the inner wall surface of the cylinder 2 is formed at the upper part of the opening 5a (see FIG. 1).

As shown in FIGS. 2 and 3, the drive mechanism 14 includes a rotation shaft 19 integrated with the support tube 18, and a rotation shaft 19 attached to the outer end of the rotation shaft 19. One end of the wire 16 is wound around the rotating drum 22, and the drum 22 is rotated by the tension or driving force acting on the wire 16. 1 control valve 12 is oscillated.

One end of the wire 16 is wound around the rotating drum 22 of the drive mechanism 14, as described above, and the other end is wound around the throttle drum 15 of the carburetor 6. The buffer 17 is divided into two parts at the part where the buffer 17 is provided.
are interconnected through.

Furthermore, the buffer 17 is the fourth buffer in this embodiment.
As shown in the figure, a cylindrical casing 23 with a bottom,
A movable plate 24 slidably mounted in the casing 23, a cover 25 that closes the open end of the casing 23, and a bellows made of an elastic material provided between the cover 25 and the movable plate 24. 26
It is equipped with Further, an end of one wire 16 that penetrates the cover 25 and is drawn into the bellows 26 is fixed to the movable plate 24, and an end of the other wire 16 is fixed to the bottom of the casing 23. is fixed. Furthermore, the casing 23 and the cover 25 are provided with orifices 2 that connect the inside of the casing 23 and the bellows 26 to the outside.
7 and 28 are provided.

The bellows 26 deforms significantly when a sudden tension is applied to the other wire 16, thereby relieving the tension and transmitting it to the one wire 16, and also suppressing the increase in the tension applied to the other wire 16. If the tension is gentle, most of the tension is transmitted to one wire 16 through small deformation, and the orifice 27 is provided to adjust the tension transmission to one wire 16. When the movable plate 24 moves, the casing 23
This is provided in order to adjust the buffering effect generated by the bellows 26 by limiting the amount of air flowing out from the inside of the bellows 26 to the outside.

On the other hand, reference numeral 29 in the figure indicates a rib that is provided to divide the opening 5a into two in the circumferential direction of the cylinder 2 and also serves to reinforce the cylinder 2. It is designed to be inserted into S ₁ and S ₂ . Also, code 3
0 indicates a throttle wire that connects the throttle drum 15 of the carburetor 6 and the throttle lever 7 in an interlocked manner.

Control device 8 of this embodiment configured in this way
For example, when casting the cylinder 2, the exhaust passage 5
At the same time, a recess 9 is formed in the upper part of the recess 9 , a guide hole 10 is bored, and a first control valve 12 is inserted into the recess 9 .
At the same time, a drive mechanism 14 is connected to the first control valve 12, and a rotating drum 22 of the drive mechanism 14 is connected to the first control valve 12.
and the throttle drum 15 of the carburetor 6 are connected by a wire 16 to which a buffer 17 is attached, and a second control valve with a sliding rod 20 attached in the guide hole 10. 13 and coil spring 21 in sequence,
It is attached to the engine 1 by attaching a cylinder head to the cylinder 2 so as to compress and lock the coil spring 21.

The exhaust timing control device 8 of this embodiment installed in this manner is activated to follow the operation of the throttle lever 7 when the operation of the throttle lever 7 is gentle, such as during normal driving. do,
To set the exhaust timing of an engine 1 to a state suitable for its operating condition.

That is, when the engine 1 is in a low rotation state and the operation amount of the throttle lever 7 is within the set range, the first control valve 12 is positioned above the opening 5a, and the second control valve 12 is positioned above the opening 5a. Control valve 13
is brought into contact with the upper part of the first control valve 12 by the elastic force of the coil spring 21, and both control valves 1
The control surfaces 12a and 13a of the cylinders 2 and 13 are positioned flush with the inner surface of the cylinder 2. Therefore,
The upper part of the opening 5a is closed, and as shown in FIG.
The distance _L1 to the lower edge 12b of the control valve 12 is lowered. As a result, the piston 3 descends and its upper end passes the lower end edge 12b of the first control valve 12, and at the same time, the cylinder 2 and the exhaust passage 5 are communicated with each other, so that the exhaust timing is delayed. This allows appropriate exhaust to be carried out at low speeds, thereby improving engine output in the low speed range.

Furthermore, when the rotation of the engine 1 is increased by gradually increasing the amount of operation of the throttle lever 7, the amount of operation of the throttle lever 7 is transmitted to the throttle drum 15 via the throttle wire 30, and the amount of operation of the throttle lever 7 is transmitted to the throttle drum 15 via the throttle wire 30. 15 is driven to rotate, and the rotation of the throttle drum 15 is caused by the rotation of the other wire 1.
6. The tension is transmitted to the drive mechanism 14 via the buffer 17 and one of the wires 16, but since the increase in tension generated in the wire 16 is gradual, the amount of deformation of the bellows 26 of the buffer 17 is small, and the throttle The drum 15 and the rotating drum 22 of the drive mechanism 14 are rotated almost synchronously. Due to such rotation of the rotary drum 22, the first control valve 12 is swung and housed in the recess 9, and the second control valve 13, which is in constant contact with the first control valve 12, is moved into the coil. It is slid while compressing the spring 21 and is housed in the recess 9 similarly to the first control valve 12 . As a result, the upper part of the opening 5a is opened as shown in FIG. 5, and the cylinder 2
The communication timing between the engine and the exhaust passage 5, that is, the exhaust timing is advanced, and appropriate exhaust is performed at high rotation speeds.

On the other hand, since the ribs 29 fit into the slits S ₁ and S ₂ formed in each of the control valves 12 and 13 when the control valves 12 and 13 are operated, the movement of the control valves 12 and 13 is not obstructed. .

Therefore, the exhaust timing of the engine 1 is controlled by the lower end 12b of the first control valve 12, and the output characteristics are improved in the entire rotation range.

In this embodiment, in the case where each component is set corresponding to low rotation speed as in the former case, the control surface 12a of the first control valve 12 is controlled by the control surface 13a of the second control valve 13. The control valves 12 and 1 are connected to the inner surface of the cylinder 2.
The space on the back side of 3, that is, the recess 9 and the cylinder 2
There is no communication between the exhaust passage 5 and the inside of the exhaust passage 5, so that no accumulation is formed in the exhaust passage 5, and exhaust can be smoothly carried out. Further, even when set for high rotation, the recess 9 is filled with the first control valve 12 and the surface of the first control valve 12 on the exhaust passage 5 side is connected to the exhaust passage 5. Since it forms a part of the inner wall surface continuously, there is no accumulation in the exhaust passage 5 as in the case of low rotation, and smooth exhaust can be maintained.

Next, the operation when the throttle lever 7 is rapidly operated such as blipping in a no-load state will be explained as follows.

As mentioned above, the gentle throttle lever 7
The operation is performed using the throttle wire 3 as described above.
0, throttle drum 15, other wire 16,
The signal is transmitted to one wire 16 through the shock absorber 17 to generate rotation of the rotating drum 22. However, when the throttle lever 7 is rapidly operated, the bellows 26 of the shock absorber 17 is suddenly compressed. Due to the application of a load, the bellows 26 is greatly deformed before the movable plate 24 in a stopped state moves, and until the amount of deformation reaches a set value, the wire 16 is transferred from the other wire 16 to the one wire 16. Tension transmission is relieved. As a result, a time lag occurs between the operation of the throttle lever 7 and the operation of the drive mechanism 14. Therefore, considering the duration of blipping (for example, 0.05 seconds to 0.3 seconds) and the operating speed of the throttle lever 7 during blitting,
By adjusting the function of the buffer 17 by adjusting the elasticity of the bellows 26 and the shapes of the orifices 27 and 28, the control valves 12 and 13 can be maintained in a stopped state.

On the other hand, FIG. 6 shows another embodiment of the present invention, in which a variable discharge type oil pump 31 attached to the engine 1 is vaporized together with the drive mechanism 14 via a single shock absorber 17. It is connected to the throttle drum 15 of the device 6.

In a two-stroke engine, the discharge amount of the oil pump 31 is changed in response to changes in load, and in the case of blipping in the no-load state as described above, the discharge amount must be kept constant. However, in this embodiment, the control valve 1 at the time of blipping is
Similar to the operation stop actions 2 and 13, a time lag is generated between the operation of the throttle lever 7 and the operation of the oil pump 31 to maintain the amount of oil discharged at an appropriate amount.

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. For example, by driving the first control valve 12, the first control valve 1
2 was made to follow the second control valve 13, but
The second control valve 13 is driven and the first control valve 12
may be made to follow. In this case,
The drive mechanism 14 is changed slightly to the second control valve 13.
need to be connected to. Further, although the biasing member is shown as a coil spring 21, a torsion spring or the like may also be used. Further, although an example has been shown in which the drive mechanism 14 is driven via the carburetor 6, it may be connected to the throttle lever 7 via a shock absorber 17 instead. In short, any configuration is sufficient as long as the operation of the control valve is linked to the carburetor throttle.

"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 timing control device that is connected to the carburetor throttle at the upper part of the opening of the exhaust passage communicating with the inside of the cylinder of the two-stroke engine. A control valve is provided to open and close the upper part of the opening, and the driving force transmitted to the control valve is relaxed by a buffer means provided in the middle of the power transmission path, as follows. It has excellent effects.

Even if the engine reaches a high speed range due to rapid throttle lever operation during blipping, the control valve operation is maintained at almost a low speed position to ensure proper exhaust timing during blitting. It can be in a state of

When the engine is in a low rotation state, by closing the upper part of the opening with the control valve, the timing of communication between the cylinder and the exhaust passage can be changed and the exhaust timing can be delayed. When increasing the number to high rotation range,
By almost synchronizing the operation of the throttle lever and the operation of the control valve and moving the control valve in a direction away from the opening of the exhaust passage, the upper part of the opening is opened and the timing of communication between the cylinder and the exhaust passage is determined. It is possible to advance the exhaust timing and perform appropriate exhaust at high rotation speeds.

Therefore, due to the synergistic effect mentioned above, the output characteristics of the engine can be maintained in a good condition over a wide rotation range from low speed to high speed, and the exhaust gas can be kept in an appropriate state under various operating conditions. can be maintained.

[Brief explanation of the drawing]

Figures 1 to 5 show an embodiment of the present invention, with Figure 1 being a vertical cross-sectional view of the main parts, and Figure 2 being a cross-sectional view taken along the line - in Figure 1 with a portion omitted. Figure, 3rd
The figure is a schematic diagram of one embodiment, FIG. 4 is a detailed view of the buffer, FIG. 5 is a diagram similar to FIG. FIG. 4 is a diagram similar to FIG. 3 showing an embodiment of the present invention. 1... (2 cycle) engine, 2... cylinder, 3... piston, 5... exhaust passage, 5a...
Opening, 5b...upper edge, 8...exhaust timing control device,
9... recess, 10... guide hole, 10a... first
Guide portion, 10b...Second guide portion, 12...
...First control valve, 12a...Control surface, 12b...Lower edge, 13...Second control valve, 13a...Control surface,
14... Drive mechanism, 15... Throttle drum,
16...Wire, 17...Buffer (buffer means),
18... Support tube, 19... Rotating shaft, 20... Sliding rod, 21... Coil spring, 22... Rotating drum, 23... Casing, 24... Movable plate, 25... Cover, 26... …Bellows, 27,
28... Orifice, 30... Throttle wire.

Claims (1)

[Scope of utility model registration request] A control valve that opens and closes the upper part of the opening when driven by a throttle lever is provided above the opening of the exhaust passage communicating with the inside of the cylinder of the two-cycle engine, and the control valve and the throttle lever are connected to each other. An exhaust timing control device for a two-stroke engine, characterized in that a buffer means is provided in the middle of a power transmission path between the control valves to reduce the driving force transmitted to the control valve.