JPS6235020A - Discharge timing controller of two-cycle engine - Google Patents

Abstract

PURPOSE:To reduce a space between valves on the cylinder side surface at the closing time of the valves by composing a sliding valve-type exhaust timing control valve to be provided on the upper part of an exhaust port of a two-cycle engine, with a plurality of valves arranged in the vertical direction. CONSTITUTION:In the case of the cylinder opening part of an exhaust port 10 of a two-cycle engine 6, an exhaust timing control valve 14 with its upper part made to open and close is composed of a plurality of valves 18, 19, and is arranged in the vertical direction to a cylinder side surface and almost parallel to the cylinder side surface for closing and matching to an inclined exhaust port side surface for opening. The valves 18, 19 are kept open at high engine speed as indicated in the diagram. A lever 28 is swung by an actuator 24 at low engine speed. Pins 22, 23 of the valves 18, 19 engaging with the groove of the lever 28 are transferred, and the top edge of the valve is moved until it parallels the cylinder side surface.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] 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" In general, the engines installed in vehicles are of the low-speed type, which focuses on power characteristics when driving at low speeds (low speed range), and those that emphasize power characteristics when driving at high speeds (high speed range). It is roughly divided into two types: the high-speed engine that focuses on high engine speeds, and the former is designed to achieve peak engine output in the low engine speed range, while the latter is designed to achieve peak engine output in the high engine speed range. However, the former has the characteristic that the output in the high rotation range reaches a plateau, and the latter has the characteristic that the output in the low rotation range is lower than the former. ing.

Therefore, it is being considered to improve the power characteristics in the entire range from low-speed waiting to high-speed driving by maintaining high output in the high-speed range and increasing output in the low-speed range. A specific solution is to change the exhaust time of the engine between low and high rotations, and a conventional example of this is disclosed in Japanese Patent Application Laid-Open No. 56-9
A technique disclosed in Japanese Patent No. 2314 has already been proposed.

As shown in FIG. 1, this technology is based on a method in which a piston 4 is placed near the opening 3a of the exhaust passage 3 in the upper part of the exhaust passage 3 communicating with the inside of the cylinder 2 of the two-stroke engine 1 in the sliding direction of the piston 4. A through hole 2a is formed which is inclined at an angle and communicates with the exhaust passage 3, and the opening 3a is formed in the through hole 2a.
A control valve 5 is slidably provided in the upper part of the piston 4 so that the upper edge 3b of the opening 3a can be changed in the sliding direction of the piston 4. Here, as shown by the solid line in FIG. 1, by retracting the control valve 5 from the opening 3a of the exhaust passage 3,
The entire surface of the opening 3a is opened and its upper edge 3b is raised, and the control valve 5 is made to protrude above the opening 3a of the exhaust passage 3 as shown by the chain line in FIG. When a part of the opening 3a is closed, the protruding end 5a of the control valve 5 is positioned at approximately the same level as the extension line of the inner surface of the cylinder 2, so that the upper edge 3b of the opening 3a is closed to the control valve. The projecting end 5a of the piston 5 is apparently moved upward by a distance, and is shifted downward by a certain distance.
The timing of communication between the inside of the exhaust passage 3 and the exhaust passage 3 is delayed by the above-mentioned distance.

"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 above-mentioned technique, when the control valve 5 is in a protruding state, a recess is formed in the vicinity of the upper part of the opening 3a by the upper surface of the control valve 5 and the inner wall surface of the exhaust passage 3; The problem is that the recesses may act as a flow resistance in the exhaust passage, leading to a decrease in exhaust efficiency.Furthermore, if the recesses are large, the recesses may act as expansion chambers for the exhaust gas. This poses a problem in that if it is slow, it may adversely affect the expansion pattern of the combustion gas and cause the output characteristics to change slowly when switching from a low rotation range to a high rotation range.

"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, and the exhaust timing control device has the following features: In particular, a through hole is formed in the upper wall of the exhaust passage along the radial direction of the cylinder and communicates with the upper part of the opening of the exhaust passage. - a control valve that changes the upper edge of the opening up and down is slidably fitted therein, and a driving means for moving the control valve forward and backward is connected to the control valve; A first control valve and a second control valve, which are movable relative to each other in the radial direction, are stacked in the sliding direction of the piston, and the driving means moves the two control valves forward and backward in an interlocked manner. It is characterized by having a section.

``Function J'' The exhaust timing control device according to the present invention has a recess formed in the upper part of the opening of the exhaust passage by inserting the upper control valve between the lower control valve and the inner wall surface of the exhaust passage. The purpose is to reduce the volume as much as possible, thereby reducing the flow path resistance of the exhaust passage, and making the change in output characteristics more sharp.

"Example" Hereinafter, a first example of the present invention will be described in detail based on FIGS. 2 and 3. In the following description, the top dead center side of the piston will be referred to as the top, and the bottom dead center side will be referred to as the bottom.

In FIG. 2, reference numeral 6 indicates a two-stroke engine to which this embodiment is applied, which includes a cylinder 7, a piston 8 slidably inserted into the cylinder 7, and a piston 8 that is spaced apart in the circumferential direction of the cylinder 7. The exhaust passage 10 includes a plurality of scavenging passages that are spaced apart from each other and open to the inner surface of the cylinder 7, and an exhaust passage IO that has an opening LOa on the inner surface of the cylinder 7.
An exhaust timing control device 11 according to this embodiment is provided near the top of the opening LOa.

To explain these in detail, a through hole 12 is formed in the cylinder 7 along the radial direction of the cylinder 7 from near the opening 10a at the upper part of the exhaust passage 1O to the outside of the cylinder 7. A stepped portion 12a that is perpendicular to the length direction of the through hole 12 is formed at the inner end of the through hole 12.

The exhaust timing control device 11 includes a guide portion 4. which is fitted and fixed in each of the through holes 12 and has a guide hole 13a having a substantially rectangular cross section. -113, a control valve 14 slidably fitted into each guide member 13, and a driving means 15 connected to the control valve 14.

Each of the guide members 13 is made of a material with higher hardness and strength than aluminum, which is a general material for forming the cylinder 7;
For example, it is made of iron or the like, and one end located inside the cylinder 7 has a shape that follows the inner peripheral shape of the cylinder 7 and the inner surface shape of the exhaust passage 10, and one end edge has a A stepped portion 16 that is perpendicular to the length direction of the guide hole 13a is formed inside the guide hole 13a.

On the other hand, the other end of the guide member 13 outside the cylinder 7 has a flange 17 that is brought into contact with the outside surface of the cylinder 7.
The guide portion (A1
A slight gap is formed between one end surface of 3 and the step 11ζ12a of the rY through hole 12. First, the kite member 13 is positioned relative to the cylinder 7.

The purpose of forming a gap between one end surface of the guide member 13 and the stepped portion 12a of the through hole 12 in this way is to absorb the difference in thermal expansion that occurs between the cylinder 7 and the guide portion +A13. This is to do so.

The control valve 14 includes first control valves 18 stacked vertically.
and the second control valve 19 (, 14).

The control valves 18 and 19 are connected to the kite hole 1 at the end of each control valve 18 and 19 located inside the cylinder 7.
, a, the exhaust passage 1
A curved surface 1 that is substantially continuous with and forms a part of the inner wall surface of 0.
8a and 19a, and in this embodiment, one end edge located inside the cylinder 7 of the first control valve 18 located below has a slight width in the vertical direction. Further, an arc-shaped control surface 18b is formed along the inner circumferential surface of the cylinder 7.

On the other hand, on the other end side of each of the control valves 18 and 19, through holes 20 and 21 are formed along the thickness direction of the control valves 18 and 19, and projecting into the respective through holes 20 and 21. The drive means 15 is connected to the control valves 18 and 19 via the respective pins 22 and 23.

The driving means 15 includes an actuator 24 such as a governor, a servo motor, or a fluid pressure cylinder that is operated based on the operating state of the engine 6, and the control valves 18 and 1 that are driven by the actuator 24.
The operating section 25 is configured to move forward and backward as shown in FIG.

In this embodiment, the operating portion 25 includes a drive shaft 26 rotatably supported by the cylinder 7 in a state perpendicular to the sliding direction of the control valves 18 and 19, and a radius of the drive shaft 26 from the drive shaft 26. The control valves 18 and 19 are integrally protruded in the direction and inserted into the through holes 20 and 21 of each control valve 18 and 19 through an N through hole 27 formed across the cylinder 7 and the guide member 13. The pins 22 and 22 of each of the control valves 18 and 19 are inserted into an engagement hole 29 formed in the swing arm 28 along its length.
The control valves 18 and 19 are connected to each other by being slidably fitted into the control valves 23. Then, by the swinging of the swinging arm 28, each control valve 18, 19 is
The guide member 13 is slid in an interlocking manner toward the inside of the cylinder 7 to a position where one end edge of each abuts against the stepped portion 16 of the guide member 13. Further, the distance between the drive shaft 26 and each pin 22 and 23 fitted in the engagement hole 29 can be adjusted by swinging the swinging arm 28 to adjust the distance between each of the control valves 18 and 9.
The control valves 18 and 19 are set in such a relationship that one end edge of the control valves 18 and 19 is brought into contact with the stepped portion 16 of the guide member 13 at the same time when the control valves 18 and 19 are in the most protruding state toward the inside of the cylinder 7.

On the other hand, in FIGS. 2 and 3, the reference numeral 30 indicates the through hole 2.
7 shows a cover attached to the cylinder 7,
Reference numeral 31 designates a support plate that covers the outer end of the guide member 13 and clamps the flange 17 between the cylinder 7 and prevents the guide member 13 from coming off. It is.

In addition, the exhaust timing control device 11 of this embodiment, which has such a groove configuration, is configured so that when the cylinder 7 is cast, the exhaust passage l.
A through hole 12 is simultaneously molded at a predetermined position in the upper part of the O, and the guide member I3 is fitted and fixed in the through hole 12, and then the first and second control valves 18 and 19 are laminated inside the guide member 12. the through hole 27 of the cylinder 7.
The drive shaft 26 of the operating section 25 is attached to the portion where the control valves 18 and 19 are formed.
23, and then the actuator 24 is attached to the drive shaft 26, and the cover 30 and support plate 31 are attached to the cylinder 7.

By moving the control valve 14 in a predetermined direction based on the operating state of the engine 6, the output characteristics of the engine 6 can be improved over the entire rotation range.

That is, when the engine 6 is operated in a low rotation range, the driving means! The actuator 24 of No. 5 is caused to rotate the drive shaft 26 and swing the swinging arm 28 toward the inside of the cylinder 7, thereby causing the control valves 18 and 19 to be in the interlocked state. Opening 1 of exhaust passage 10
0a, and when one end edge of each control valve 18, 19 comes into contact with the stepped portion 16 of the guide member I3, the movement of these control valves 18 and 19 is stopped and held at that position. By such movement of each control valve 18 and 19, as shown in FIG. 3, the control surface tab of the first control valve 18 is located near the inner surface of the cylinder 7, and the control surface tab of the second control valve is the first
By entering between the upper surface of the control valve 18 and the inner wall surface of the exhaust passage 10, the upper part of the opening 10a of the exhaust passage 10 is closed, and the upper edge 10b of the opening 10a is apparently The control surface 18a of the control valve 18 is lowered by a distance L2 to the lower end edge 18c, and the second control valve I9 forms a space between the upper surface of the first control valve 18 and the inner wall surface of the exhaust passage lO. The volume of the recess D° is reduced.

As a result, the position of the piston 8 for establishing communication between the cylinder 7 and the exhaust passage 10 is at the distance described above.

As a result, the exhaust timing of the engine 6 is delayed so that appropriate exhaust gas is obtained at low rotation speeds, and the output of the engine 6 in the low rotation range is improved. Furthermore, since the volume of the recess D' is reduced by the second control valve 19, an increase in the flow resistance of the exhaust passage IO is suppressed to the utmost, and from this point of view as well, the output of the engine 6 can be improved.

On the other hand, when the engine 6 reaches a high rotation range,
Each control valve 1 is controlled by the actuator 24 and the operating section 25.
Move 8/19 in the opposite direction to the direction described above. As a result, as shown in FIG. 2, both the control valves 18 and 19 are housed in the guide member 13 and the upper part of the opening 10a is opened, thereby preventing communication between the inside of the cylinder 7 and the exhaust passage 10. , at the upper edge 10b of the opening 10a, the exhaust timing of the engine 6 is brought forward, appropriate exhaust is carried out at high rotations, and the engine output in the high rotation range is improved.

Therefore, it is possible to improve the output characteristics of the engine 6 over the entire rotation range, and by reducing the extra expansion volume, when transitioning from a low rotation range to a high rotation range or from a high rotation range to a low rotation range, A sharp change in output characteristics can be obtained.

Next, a second embodiment of the present invention will be described based on FIGS. 4 to 7. In the following explanation, the same reference numerals are used for the same parts as in the first embodiment to simplify the explanation.

In the second embodiment, in place of the drive means 15 in the first embodiment, a drive means 32 having a differential function for varying the operating timing of the two control valves 18 and 19 is used.

That is, as shown in FIGS. 4 and 5, the drive means 32 includes a drive arm 33 that is integrally provided with the drive shaft 26 and swings within a plane passing through the center line of the cylinder 7 by rotation thereof. Both sides of the drive arm 33 are attached to the drive shaft 26 so as to be relatively rotatable, and one end is attached to the first and second control valves 18 and 19 for their respective bins 22 and 23.
driven arms 34 and 35 engaged via the first
The first control valve 18 is attached to the other end of the driven arm 34 that has been engaged with the control valve 18, and by pressing and rotating the driven arm 34, the first control valve 18 is constantly urged in the backward direction. a set spring 36 and a driven arm 3 engaged with the drive arm 33 and the second control valve 19;
A connecting member 37 is provided between the drive arm 33 and the driven arm 34 which is engaged with the drive arm 33 and the first control valve 18. The operating part 25 is constituted by an engaging member 38 that follows the rotation of the drive arm 33 and the driven arm 34 when the drive arm 33 is rotated by a predetermined angle or more. be.

Next, to explain these details, a pin 39 is provided at the swinging end of the drive arm 33 to protrude toward the driven arm 35, and a pin 39 that faces the drive arm 33 of each of the driven arms 34 and 35 is provided. Pins 40 and 41 that extend toward the drive arm 33 are provided on the surfaces, respectively.

In this embodiment, a coil spring is used as the front connecting member 37, which is attached between the drive arm 33 of the drive shaft 26 and the driven arm 1.35, and has both ends 3
7a and 37a are extended toward the 1° 1° swing portion of the drive arm 1833 to elastically clamp the pins 39 and 41 of the drive arm 33 and the driven arm 35. Then, the one end 37a of the connecting member 37 is not engaged with the first control valve 18, and is placed in the same position as the rotation 11uL of the pin 40 provided on the driven arm 34. With the relative rotation of the driving arm 33 and the driven arm 34 described in 111j, they are configured to engage with each other. The engagement member 38 is constituted by the pin 40.

On the other hand, as shown in FIG. A spring seat 43 installed (on the cover 30 in the illustrated example)
The driven arm 34 is rotated as described in Section 17I, and the first control valve 18 is always urged toward the retracted position.

Thus, in the exhaust timing control device 11 of this embodiment configured as described above, in addition to the effect of the first embodiment, the effect of controlling the exhaust timing of the engine 6 in two stages can be obtained.

That is, when the drive shaft 26 is rotated by the actuator 24, the drive arm 33 is swung together with the drive shaft 26, but one driven arm 35 is integrated with the drive arm 33 via a connecting member 37. Yes, and
A second control valve 1 is connected to the driven arm 35 via a pin 23.
9 is engaged, as the drive arm 33 swings, the second control valve 19 closes the opening 1 of the exhaust passage 10.
It is made to protrude toward the top of 0a. And the second
As shown in FIG. 6, the movement of the control valve 19 is stopped and held at that position when its protruding end comes into contact with the stepped portion 16 of the guide portion +4'13.

On the other hand, until the second control valve 19 is stopped at the above-described position, the one end 37a of the connecting member 37 constituting the engaging member 38 and the pin 40 are not engaged.
The driven arm 34 is maintained in a stopped state by a centrifugal spring 36, and the first control valve 18 is housed in the retracted position, that is, in the guide member 13, and is maintained in this state.

The upper edge 10b of the opening 10a is thus lowered to the projecting end of the second control valve 19, with a distance of 1.
The exhaust timing of the engine 6 is avoided by being delayed by 2 minutes, and the exhaust timing is controlled at an intermediate level between the desired exhaust timing control amount shown in the first embodiment.

By further rotating the drive shaft 26, the drive arm 33
When the swing angle of the drive arm 33 is increased, the pin 3 of the drive arm 33
9 presses one end 37a of the connecting member 37, but since the connecting member 37 is constituted by a coil spring, the other end 37b of the connecting member 37 is locked by the pin 41 in a stopped state. Despite that,
The elasticity of the connecting member 37 allows the ifI first end 37a to move and engage with the pin 40 of the driven arm 34. This allows the driven arm 34 or the driving arm 33 to
is integrated with the set spring 36 and rotated against the elastic force of the set spring 36, and as a result of the rotation, the first control valve 18 or, as shown in FIG. 7, the second control valve 19. Similarly, it is made to protrude to the upper part of the opening 10a. Since the second control valve 19 is held in the protruding position by the elastic force of the elastically deformed connecting member 37, the second control valve 19 connects the upper surface of the first control valve 18 with the exhaust gas. aisle 10
The volume of the recess D° formed between the inner wall portion of the recess D° is reduced.

Therefore, similarly to the first embodiment described above, the exhaust passage 1
The upper edge 10b of the opening 10a of the first control valve 18 is lowered by a distance of 3 minutes to the protruding end of the first control valve 18, thereby obtaining the desired exhaust timing and suppressing an increase in the flow resistance of the exhaust passage 10. , thereby suppressing the decline in exhaust efficiency.

As described above, in this embodiment, the first control valve 18 controls the exhaust timing by a desired amount, and the second control valve 19 reduces the volume between the first control valve 18 and the exhaust passage 10. In addition to this effect, it is also possible to obtain an exhaust timing control effect at an intermediate stage using the second control valve 19.

It should be noted that the various shapes, dimensions, combinations, etc. of the constituent members shown in each of the previous embodiments are merely examples, and can be variously changed based on design requirements and the like.

For example, in the embodiment described above, the control valve 14 was attached to the cylinder 7 via the guide member 13, but the guide member 13 is omitted and the control valve 14 is directly attached to the through hole 12.
It may also be fitted.

"Effects of the Invention" As explained above, the exhaust timing control device for a two-stroke engine according to the present invention has a through hole in the upper wall of the exhaust passage that runs along the radial direction of the cylinder and communicates with the upper part of the opening of the exhaust passage. A control valve is slidably fitted in the through hole to move the upper edge of the opening upward and downward, and the control valve is driven to move the control valve upward and downward. The control valve is formed by stacking a first control valve and a second control valve that are relatively movable along the radial direction of the cylinder in the sliding direction of the piston, and The means is characterized in that it is provided with an operation part that slides and moves both the control valves in an interlocked state, and by moving the control valves forward and backward, the appropriate exhaust timing is set according to the operating state of the engine. By setting the control valve as two stacked control valves, the volume of the four parts formed near the top of the exhaust passage opening is minimized to suppress an increase in the flow resistance of the exhaust passage. As a result, the output characteristics of the engine can be improved in the entire rotation range, and the excessive expansion amount in the expansion process can be suppressed to provide excellent exhaust timing control.

[Brief explanation of the drawing]

In the drawings, FIG. 1 is a vertical sectional view showing an example of the structure of a two-cycle engine equipped with a conventional exhaust timing control device, and FIGS. 2 and 3 show a first embodiment of the present invention. FIG. 2 is a diagram similar to FIG. 1 to which the first embodiment is applied, FIG. 3 is a diagram similar to FIG. 2 showing main parts for explaining the operation, and FIG.
7 to 7 show a second embodiment of the present invention, FIG. 4 is an enlarged sectional view of the main part, FIG. 5 is a sectional view taken along the line ■-■ in FIG. 4, and FIG. 7 and 7 are diagrams similar to FIG. 4 for explaining the operation. 6... (2 cycle) engine, 7...
・Cylinder, 8... Piston, 10...
Exhaust passage, 10a...Opening, Job...
...Top edge, 11...Exhaust timing control device, 12.
...Through hole, 13...Guide member, 13a
...Guide hole, 14...Control valve, 15
・32...Driving means, ■6...Step part,
18...First control valve, 18a...Curved surface, 18b...Control surface, 18c...
Lower edge, 19... Second control valve, 19a...
...Curved surface, 22, 23...Bin, 25...
...Operation unit, 26...Drive shaft, 27...
...Through hole, 28...Swing arm, 29...
...Engagement hole, 33...Drive arm, 34, 35...
...Followed arm, 36...Set spring, 37...Connecting member, 38...Engaging member, 39, 40, 41... Pin, 37a・
37b... end, 42, 43... spring seat.

Claims (1)

[Claims] An exhaust system that opens and closes the upper part of the exhaust passage that communicates with the inside of the cylinder of a two-cycle engine to change the timing of communication between the inside of the cylinder and the exhaust passage through a piston that is slidably fitted inside the cylinder. In the timing control device, a through hole is formed in the upper wall of the exhaust passage along the radial direction of the cylinder and communicates with the upper part of the opening of the exhaust passage, and the exhaust passage is moved forward and backward into the upper part of the opening in the through hole. A control valve that changes the upper edge of the opening up and down is slidably fitted therein, and a driving means for moving the upper edge of the opening up and down is connected to the control valve, and the control valve is configured to move in the radial direction of the cylinder. A first control valve and a second control valve, which are relatively movable along the piston, are stacked in the sliding direction of the piston. An exhaust timing control device for a two-stroke engine, comprising: