JPS6270619A - Exhaust timing control device of 2-cycle engine - Google Patents

Abstract

PURPOSE:To cause reliable actuation of an opening and closing control valve, by a method wherein, in a device which opens and closes the upper part, near a portion open to the inner peripheral surface of a cylinder, of an exhaust passage and changes a communicating timing between the interior of a cylinder and an exhaust passage, the opening and closing control valve is forcibly driven by a driving mechanism. CONSTITUTION:When an engine is run at, for example, low rotation, a rotary shaft 19 in a driving mechanism 17 is rotated in a direction A by means of a wire 21, and a flapper valve 13 is swung to protrude it in an exhaust port 5a. Simultaneously, a wire guide 20 attached to the end part of the rotary shaft 19 is rotated in a direction B, a shaft 35 is rotated in a direction D through the medium of link mechanisms 32, 34, and 36 in a driving mechanism 31, and a slide valve 15 is pressed by an arm 38 to move it downward. As a result, control surfaces 12 and 14 of the valves 13 and 15, respetively, are positioned about flush with the inner peripheral surface of a cylinder to close the upper part of the exhaust port 5a. This causes the exhaust port 5a to open slowly and close quickly.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to an exhaust timing control device for a two-stroke engine.

``Prior art'' In a two-stroke engine, one way to increase the combustion gas filling efficiency is to utilize reflected waves in the exhaust passage.
During the scavenging stroke, fuel gas blows from the combustion chamber to the exhaust passage (
There is a known technology for pushing gas (so-called atrium) back into the combustion chamber.

When applying this technology to an actual engine, it is important to keep in mind that the exhaust reflected wave must be returned to the exhaust boat after the scavenging port is closed but just before the exhaust boat is closed. By the way, in the case of two-stroke engines installed in motorcycles and automobiles, the rotational speed is varied, so at a certain rotational speed, the reflected waves are on the verge of blocking the exhaust boat. Even if it is possible to return the reflected wave and increase the combustion gas filling efficiency, at other rotation speeds, the timing at which the reflected wave returns and the timing at which the exhaust port or scavenging boat closes will deviate, resulting in the blowout caused by the reflected wave. When venting, a phenomenon occurs in which the gas cannot be pushed back.

In order to deal with such problems, the present inventors proposed a technique for changing the exhaust timing according to the rotational speed of the engine in the aforementioned Utility Application No. 78221/1983.

In this technology, a first control valve is provided in the upper part of the exhaust passage near the opening to the inner circumferential surface of the cylinder so as to be swingable about an axis perpendicular to the center line of the cylinder.
A drive mechanism is provided for swinging the control valve in accordance with the rotational speed of the engine, and a second control valve is provided above the first control valve so as to be movable in the length direction thereof, and the second control valve The second control valve is provided with a spring that urges the second control valve toward the first control well so that the tip of the second control valve always comes into contact with the swinging tip of the first control valve.

In this engine, when the rotational speed is low, the upper part of the exhaust port is closed by the first control valve and the second control valve that operates following the first control valve, and on the other hand,
When the rotation speed becomes high, the upper part of the exhaust boat is no longer blocked by these control valves. In this way, the position of the upper edge of the exhaust port is substantially moved up and down according to the rotational speed of the engine,
As a result, the exhaust timing is optimized to match the rotational speed, thereby increasing gas filling efficiency over the entire rotational range and improving output.

"Problems to be Solved by the Invention" Although the above-mentioned engine has the advantage of being able to improve output, it has been found that it has the following drawbacks.

In other words, if the second control valve is configured to operate simply by being biased by a spring, or if carbon contained in the exhaust gas adheres to the second control valve or to the valve housing, the carbon This is a problem in that the reaction force against the spring urging force increases due to viscosity and sticking force, making it impossible for the second control valve to operate smoothly.

``Object of the Invention'' The present invention was made in view of the above circumstances, and an object thereof is to provide a highly reliable exhaust timing control device for a two-stroke engine that can reliably operate the second control valve. do.

"Means for Solving the Problems" In order to achieve the above-mentioned object, the present invention has a configuration in which not only the first control valve but also the second control valve is forcibly driven by a drive mechanism.

"Operation" The second control valve is not operated by the biasing force of a spring as in the conventional case, but is forcibly operated by the drive mechanism, so reliable operation of the second control valve can be realized, and the reliability of the device can be improved. You can increase your sexuality.

``Chukyozono 11'' Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 5.

FIG. 1 shows a longitudinal sectional view of a two-stroke engine equipped with an exhaust timing control device according to the present invention. In the figure, l is a cylinder, 2 is a cylinder head, and 3 is a cylinder that is slidably inserted into the cylinder. The piston, 4 is a scavenging passage, and 5 is an exhaust passage. The opening (exhaust port) 5a of the exhaust passage 5 to the inner circumferential surface of the cylinder is as wide as possible so as to obtain high output, and is provided so that both left and right ends extend almost half of the inner circumferential surface of the cylinder in the circumferential direction. In the exhaust passage 5, there is a boat 5a.
A rib 6 extending from the upper surface to the lower surface is provided near the center in the left-right direction and extends to a predetermined location on the downstream side. The ribs 6 serve to reinforce the vicinity of the opening of the exhaust passage 5 to the inner circumferential surface of the cylinder, and also to prevent the piston ring from expanding radially outward and abutting against the upper or lower edges of the exhaust port 5a.

A recess 7 is formed in the upper part of the exhaust passage 5 and slightly downstream of the exhaust port 5a. In the upper part of this recess 7, guide holes 8.8 are provided, which are continuous with the recess 7 and are inclined with respect to the central axis of the cylinder 1, with intervals left and right (see Fig. 3). .

Further, a guide hole 9 is formed in the cylinder head 2 and is continuous with the guide hole 8.8. The guide hole 9 consists of a lower guide part that is bifurcated so as to be continuous with the guide hole 8.8 on the cylinder side, and an upper guide part that is provided on the upper part of the lower guide part and continuous with the lower guide parts. It has become.

Inside the recess 7 is a flap valve (first control valve) which has a control surface I2 that has approximately the same curvature as the inner circumferential surface of the cylinder l and is aligned with the inner circumferential surface of the cylinder l! 3 is arranged so as to be swingable about an axis perpendicular to the cylinder center line,
The guide hole 8.9 also has a slide valve (second control valve) 15 having a control surface 14 at its lower end that has approximately the same curvature as the inner circumferential surface of the cylinder l and is aligned with the inner circumferential surface of the cylinder.
is fitted so as to be movable in its length direction (see Figure 5).

The flap valve 13 has a structure in which it is divided into two parts at the center in the left-right direction, that is, at the portion facing the rib 6. At the swinging tip of each valve half body 13A, 13B constituting the flap valve 13, there is a collar 16 that projects upward.
is provided extending from a central portion facing the rib 6 to a midway position in the circumferential direction, and a surface of this collar 16 facing the cylinder inner circumferential surface constitutes a part of the control surface 14. The flap valve I3 having the above-mentioned configuration has a drive mechanism 1.
7, it can be selectively positioned either in a state housed in the recess 7 or in a state projected at a predetermined position above the exhaust boat 5a.

To explain the drive mechanism 17, each of the valve halves 1
A support cylinder 18 is integrally formed on the side opposite to the side on which the control surface 12 of 3A and 13B is formed. The support tube 18 has a rectangular center section of a rotating shaft 19 provided through the recess 7, and when the rotating shaft I9 is rotated, the flap valve 13 swings together with it. It is designed to be moved. The rotation shaft 19 is arranged to extend in a direction perpendicular to the center line of the cylinder 1, and is arranged on the downstream side of the rib 6.

A wire guide 20 (see FIGS. 2 and 5), which will be described later, is attached to the end of the rotating shaft 19 that projects outward from the cylinder l. Outer guide portion 2 of wire guide 20
0a, one end of the wire 21, 21 is fitted into the proximal groove 20b, 20b of the guide part through a stopper (not shown), and the other end of the wire 20 is connected to the guide part approximately half a circumference from there. It is provided so as to extend in a predetermined direction after being guided along 20a. wire 21.2
The other end of 1 is connected to a motor capable of forward and reverse rotation, and the motor is operated by a controller according to the rotational speed of the engine.

Note that the wire guide 20 and one end of the wire 21 wound around the wire guide 20 are covered by a case 22 screwed to the cylinder 1 and its lid, and are protected from rainwater and dust contained in the outside air. There is.

Meanwhile, said slide valve! 5 is composed of an action part 23.23 which is split into two parts in the left and right direction and which is inserted into the guide hole 8.8 of the cylinder l, and a base part 24 which connects these action parts 23, and the overall shape is U-shaped. It is formed. The action portion 23 is disposed on the outer side of the flange 16 of the flap valve 13 in the left-right direction. And this slide valve I5
When the flap valve 13 is swung to the position where the upper part of the exhaust port 5a is opened, that is, when the flap valve 13 is swung in the direction A in FIG. is pushed upward by the swinging tip of the flap valve 13, and on the other hand, when the flap valve 13 is swinged to the position where it closes the upper part of the exhaust boat 5a, it swings in the Chunichi direction in FIG. When the exhaust boat is caused to protrude into the exhaust boat hSa, it is moved downward by the drive mechanism 31 and enters between the upper end of the flap valve 13 and the upper edge 5b of the exhaust boat, filling the gap between the two. At the same time, the control surface 14 cooperates with the control surface I2 of the flap valve 13 to form a surface substantially continuous with the inner peripheral surface of the cylinder I at the upper part of the exhaust boat 5a. Further, as shown in FIG. 1, the cover 25 screwed to the position above the exhaust passage 5a of the cylinder head 2 is removed from the slide valve 15, and the cover 25 is opened from the opening 2a previously provided in the cylinder head 2. Set by insertion.

To explain the drive mechanism 31 that drives the slide valve 15, as shown in FIG. 5, a pin 33 is implanted at the tip of an arm 32 extending radially outward from the center of the wire guide 20. Rod 3 is attached to pin 33
One end of 4 is rotatably connected, while 35 is a shaft arranged parallel to the rotation axis 19, and one end of the shaft 35 is supported by the case 22, which covers the wire guide 20 and the rod 34. At the same time, the other end side is supported by the mating surface of the cylinder head 2 and the cover 25 so as to be freely rotatable. An arm 36 is integrally attached to one end of the shaft 35, and a pin 37 is implanted at the tip of the arm 36. And this pin 37
The other end of the rod 34 is rotatably connected to the rod 34. That is, the arm 32.36, the pin 33.37, and the rod 34 constitute a link mechanism, and when the wire guide 20 is rotated in the directions A and B in FIG. , functions to rotate in the D direction.

Further, an arm 38 is attached to the other end of the shaft 35, and the lower end of the arm 38 can come into contact with the upper surface of the base 24 of the slide valve. Also,
A spring 39 is interposed between the pin 33 and the pin 37, and the spring 39 pulls the pins 33.37 together, and the rod 34 and the pin 33.3
Arm 32.36 caused by the play (gap) between
It eliminates the gap between the two. Note that the spring 39 has a curved engagement portion formed at its end that is inserted into the gap between the bifurcated portions at both ends of the rod 34, and in this state is engaged with the engagement grooves 33a, 37a of the pin 33.37. is set.

That is, the spring 39 is attached to the pin 33.3 of the rod 34.
It also serves as a stopper from being eliminated from 7. Further, the spring 39 and the rod 34 are arranged overlapping each other so that the space for their arrangement is small.

In addition, 41 in FIG. 1 indicates a cooling water population, and the cooling water guided here passes through a cooling water passage 42 formed so as to surround the inside of the cylinder, the exhaust passage 5, and the slide valve 15, respectively. Cool them appropriately, and then the cooling water outlet 43 attached to the cylinder head 2
from there to be returned to a radiator (not shown).

However, the exhaust timing control device configured in this way is
By being operated based on the engine operating status,
The output characteristics of the engine can be improved over the entire rotation range.

That is, when the engine is operated at low rotation speed, the flap valve 13 is swung by rotating the rotating shaft 19 in the direction A in FIGS. 1 and 5 by means of a controller, motor, and wire 21 (not shown). Then, the flap valve 13 is made to protrude into the exhaust boat 5a as shown by the solid line in FIG. At this time, the above rotation axis! 9 rotates, the wire guide 20 attached to the end of the rotation shaft 19 moves to B.
The shaft 35 is rotated in the D direction via a link mechanism including the arm 32, the rod 34, the arm 36, etc., and the slide valve 1 is rotated via the arm 38.
5 to move the slide valve 15 downward. Thus, the control surfaces 12.14 of the flap valve 13 and the slide valve I5 are positioned substantially flush with the inner peripheral surface of the cylinder 1, and the exhaust boat 5a
As a result, the upper edge of the exhaust boat 5a is apparently lowered by the distance ρ to the lower edge of the upper flap valve 13. Therefore, since the upper edge of the exhaust boat 5a is apparently lowered by the upper Mρ, the exhaust boat 5a, which is opened and closed by the movement of the piston 3, opens later and closes earlier.

In this way, when the engine is running at low speed, the piston 3
In response to the long vertical movement period of the exhaust boat 5a, the exhaust boat 5a is opened late and closed late, so that the exhaust reflected wave is returned to the exhaust boat 5a just before the exhaust boat 5a is closed.
Improves combustion gas filling efficiency.

On the other hand, when the engine reaches a high speed range, the rotating shaft 1
9 in the opposite direction to that described above, that is, in the direction B, and the flap valve x3 is housed in the recess 7 as shown by the two-dot chain line in FIG. At this time, since the wire guide 20 rotates in the A direction, the rotational force of the wire guide 20 is transmitted to the shaft 36 by the link mechanism, and the shaft 36 is rotated in the direction A.
Rotate in the direction. As the shaft 36 rotates, the swinging tip of the arm 38 moves upward away from the upper surface of the base of the slide valve 15. This arm 38
In parallel with this movement, the slide valve f5 is pressed by the swinging tip of the flap valve 13 and moves upward. That is, in this case, the closure by the flap valve 13 and slide valve 15 of the exhaust boat 5aJz portion is released, and the vertical movement period of the piston 3 becomes shorter, so that the exhaust boat 5a It opened earlier than the
and closes late. Therefore, in this case as well, the exhaust reflected waves are returned to the exhaust boat 5a just before the exhaust boat 5a is closed, and as in the case described above, the combustion gas filling efficiency is improved by effectively utilizing the reflected waves.

In this way, the exhaust boat 5 is operated by the flap valve 13 and the slide valve 15 according to the rotational speed of the engine.
The upper edge position of a is substantially moved up and down to increase combustion gas filling efficiency in both low-speed and high-speed rotations, and to improve output characteristics over the entire rotation range.

In addition, in the above-mentioned exhaust timing control device, when moving the slide valve 15 downward, the drive mechanism 31 is used to forcibly move the slide valve 15, instead of using the biasing force of a spring as in the conventional case. Valve 1
Carbon in the exhaust gas adheres to slide valve 15.
Even if it becomes difficult to move the slide valve 15,
can be moved reliably.

Furthermore, in the above exhaust timing control device, since the slide valve drive mechanism 31 is connected to the shaft 19 that swings the flap valve 13, the slide valve 15 can be reliably synchronized with the movement of the flap valve 13. In addition, advantages such as a reduction in the number of parts and a reduction in size and weight can be obtained.

In addition, in the above embodiment, the slide valve 15 and the arm 3
8 are structured so that they can come into contact with and separate from each other, and the drive mechanism 31 is operated only when moving the slide valve I5 downward. When the slide valve 15 is moved upward, the drive mechanism 34 is connected freely.
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Furthermore, in the above embodiment, the control method for the flap valve 13 and the slide valve 15 is two-position control.
The present invention is not limited to this, and a proportional control method may be used in which the opening degree is continuously changed according to the engine speed.

"Effects of the Invention" As explained above, according to the present invention, not only the first control valve but also the second control well are forcibly driven by the drive mechanism. Even in the case of adhesion, both valves can be operated reliably, which has the effect of increasing the reliability of the device.

[Brief explanation of drawings]

1 to 12 show one embodiment of the present invention, and a first embodiment of the present invention is shown in FIG.
The figure is a longitudinal sectional view of the 2-stroke ennon, Figure 2 is a partially sectional side view showing the drive mechanism of the slide valve, Figure 3 is a plan view of the cylinder head, and Figure 4 is the IV-IV of Figure 1. I
FIG. 5 is a sectional view taken along line V and a perspective view illustrating a flap valve, a slide valve, and their drive mechanism. l...Cylinder, 2...Cylinder head, 4...Scavenging passage, 5...Exhaust passage, 5a...Opening (exhaust boat) 6...Rib, l2...Control surface, ! 3... Flap valve (first control valve), 14
...Control surface, 15...Slide valve (second control valve), I7
... Drive mechanism, 19 ... Rotation shaft, 20 ... Wire guide, 21 ... Wire, 31 ... Drive mechanism, 32 ...Arm, 3°4...Rod, 35...Shaft, 36...Arm, 38...Arm, 39... ···spring. Applicant Honda Motor Co., Ltd. Procedural Amendment (Method) 61,2. -5 II+1 Japanese year month day 1, case description 1985 Jikaku Application No. 211918 2, title of the invention 2-stroke engine exhaust timing control device 3, person making the amendment, applicant (j, 7.2 ) Fuda Moken Kogyo Forest Shikikisha 4, Agent

Claims (1)

[Claims] This is an exhaust timing control device that changes the timing of communication between the inside of the cylinder and the exhaust passage by a piston that is slidably fitted inside the cylinder by opening and closing the upper part of the exhaust passage near the opening to the inner peripheral surface of the cylinder. is swingably provided near the opening to the inner circumferential surface of the cylinder at the upper part of the exhaust passage, and has a control surface having approximately the same curvature as the inner circumferential surface of the cylinder at the tip of the swing; a first control valve that opens and closes the upper part of the opening; a first control valve driving mechanism that swings the first control valve according to the rotational speed of the engine;
a second control valve that is disposed above the control valve so as to be movable in its length direction and has a control surface having approximately the same curvature as the inner circumferential surface of the cylinder; When the second control valve is swung to the position where the upper part of the opening to the inner peripheral surface is closed, the second control valve is moved toward the first control valve side, and the first control valve is controlled by the control surface of the second control valve. An exhaust timing control device for a two-stroke engine, comprising: a second control valve drive mechanism that closes a gap between an upper edge of the surface and an upper edge of the opening.