JPH06146834A - Decompression device for 2-cycle engine - Google Patents

Abstract

PURPOSE:To facilitate the start of an engine and prevent the worsening of the engine performance by pulling a rope wound round a drum of a recoil starter and moving the wire via both a rope-abutting roller and a spring, thereby opening a decompression valve. CONSTITUTION:Until the middle of a compression stroke of a piston 4, a decompression port 11, which connects a combustion chamber 2 to an exhaust port 5 or a scavenging port 7, is formed in a cylinder 1. In addition, a decompression valve 21, which opens/closes a passage, is arranged in the midst of the decompression port 11. In this case, by pulling a knob 54, a rope-winding drum 52 of a recoil starter 51 is rotated so as to increase the tension of a rope 53, so that a stem 57 is pushed are pressed to shorten a spring 59. At the same time, a wire 22 is pushed and pressed by the spring 59, thereby opening a decompression valve 21. On the other hand, by releasing the knob 54, the decompression valve is closed. With this contrivance, starting of an engine can be eased, and at the same time the worsening of the engine performance can be prevented.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a starter for a two-stroke gasoline engine.

[0002]

2. Description of the Related Art A first conventional example will be described with reference to FIG. FIG. 5A is a sectional view of the first conventional example. In the figure, 1 is a cylinder, 4 is a piston, 2 is a combustion chamber, 5 is an exhaust port, 6 is an intake port, and 7 is a scavenging port, all of which are known elements of a two-cycle engine. Reference numeral 11 is a decompression port, and the exhaust port 5
It is a pipeline leading to. The operation of the first conventional example will be described. Even after the exhaust port 5 is closed in the ascending stroke of the piston 4, the decompression port 11 communicates the combustion chamber 2 with the exhaust port 11 until the decompression port 11 is closed by the piston 4, thus preventing gas compression in the combustion chamber 2. To do. After the decompression port 11 is closed by the piston 4, the combustion chamber 2 becomes a closed space and is compressed by the rise of the piston 4, so that the compression pressure at the time of starting can be lowered, and the reaction force due to this pressure is suppressed especially at the time of manual starting. it can.

A second conventional example will be described with reference to FIG. FIG. 5B is a sectional view of the second conventional example. In the figure, reference numerals 1 to 7 are the same as the sectional view of the first conventional example and FIG. Reference numeral 12 denotes a decompression (scavenging) port, which is a narrow groove communicating with the scavenging port 7 provided in the cylinder axial direction on the scavenging port 7 on the wall of the cylinder 11.
The second conventional example is the same as the first conventional example.

A third conventional example will be described with reference to FIG. FIG. 6 is a sectional view of a third conventional example. The third conventional example is found in Japanese Patent Application No. 63-48320 and Japanese Utility Model Application No. 01-152064. In the third conventional example, a valve that communicates with the atmosphere through the combustion chamber is opened while the recoil string is being pulled in conjunction with the recoil starter. In the figure, 51 is a recoil starter main body, and 53 is a recoil string which is known. 1
Reference numeral 69 denotes a valve, which is an opening / closing valve provided at the top of the combustion chamber and communicating with the atmosphere, which is normally closed and mechanically connected to the recoil starter unit. The operation of the third conventional example will be described. A mechanical connection opens valve 169 while pulling recoil starter string 53, opening the combustion chamber to atmosphere.

[0005]

In the conventional system in which the decompression port is provided in the cylinder, the decompression port is open even during normal operation after starting, so that the unburned air-fuel mixture to be burned in the compression stroke passes through the decompression port. The amount of combustion that escapes from the combustion chamber decreases, and in the expansion stroke after combustion, the combustion gas escapes from the decompression port and the work of the piston due to expansion decreases.
That is, the fuel consumption, the exhaust gas, and the like adversely affect the engine performance. For this reason, if the cross-sectional area of the decompression port is made too small in order to minimize the effect, not only the depressurizing effect at the time of starting becomes smaller, but also problems such as clogging by combustion products such as carbon medium occur.

Further, in the system in which the combustion chamber is communicated with the atmosphere through the valve while pulling the recoil string, the pressure is excessively released, so that evaporation is not promoted by compression and even if combustion occurs, due to the escape of the air-fuel mixture and the escape of combustion gas. The combustion pressure is low and the acceleration after starting becomes poor. Normally, the recoil string is held for a while even after being pulled, so the decompression valve remains open during this time.

It is an object of the present invention to provide a decompression device for a two-cycle engine, in which the engine can be started easily and the engine performance is not deteriorated.

[0008]

According to a first aspect of the present invention, a decompression port for communicating a combustion chamber with an exhaust port or a scavenging port is provided in a cylinder part up to the middle of a compression stroke of a piston to control opening / closing of a passage in the middle of the decompression port. In a decompression device for a two-cycle engine equipped with a decompression valve, a rope bending portion having a small radius of curvature provided between a rope winding drum of a recoil starter and a rope outlet, and an anti-curvature of the rope bending portion via a spring. It is characterized by having a guide-slewing roller urged toward the center and a means for opening the decompression port by guiding the movement stroke of the roller in the opposite urging direction by the spring when pulling the rope to the decompression valve via the wire. And

According to a second aspect of the invention, a decompression port for communicating the combustion chamber with the exhaust port or the scavenging port is provided in the cylinder part up to the middle of the compression stroke of the piston, and a decompression valve for controlling the opening and closing of the passage is provided in the middle of the decompression port. In a decompression device for a cycle engine, a cam is formed on the rope winding drum part of the recoil starter, and a mechanism for opening and closing the decompression port by transmitting the position of the cam follower at the time of starting and non-starting to the decompression valve via a wire is provided. It is characterized by

According to a third aspect of the present invention, a decompression port for communicating the combustion chamber with an exhaust port or a scavenging port is provided in the cylinder part up to the middle of the compression stroke of the piston, and a decompression valve for controlling the opening and closing of the passage is installed in the middle of the decompression port. In a decompression device for a two-cycle engine, fluctuating pressure in the crankcase is taken out from the + or-side through one valve and guided to an actuator, which directly controls the decompression valve and closes the decompression valve during normal operation and starts it. Is characterized by having a mechanism for opening.

[0011]

The action of the first invention is that when the rope of the recoil starter is pulled, the rope winding drum rotates and is connected to the crankshaft of the engine (not shown) to rotate, and at the same time the tension of the rope increases so that the radius of curvature of the bent portion increases. The roller is moved in the increasing direction, and the roller in contact with the inside of the bend of the bent portion of the rope is moved toward the center of curvature against the spring force.
Since the movement of the roller is guided to the decompression valve via the rope and opened, and the gas in the combustion chamber is released through the exhaust port or the scavenging port in the compression stroke of the engine, the force for pulling the rope is also reduced.

The action of the second invention is that when the rope is pulled, the rope winding drum rotates and is connected to the crankshaft of the engine (not shown) to rotate, and at the same time the cam rotates to move the cam follower. The movement of the cam follower is transmitted to the decompression valve via the wire to open / close the decompression port. Since the rope is not pulled while the engine is running, the rope winding drum returns to its original position, so the decompression valve is closed.

The operation of the third invention is that the decompression valve is opened at the time of engine start. When the engine rotates, the pressure in the crank chamber fluctuates, the one-way valve takes out only the positive side or the negative side of the pressure, and the valve is guided to the actuator, and the actuator controls the decompression valve by this pressure, and the decompression valve during engine operation. Close. When the engine stops, the actuator does not exert external pressure and the decompression valve opens.
As described above, in any of the above inventions, the torque for releasing the gas in the cylinder through the decompression port only at the time of starting to reduce the torque to rotate the engine by the external force is closed, and the decompression port is closed during the normal operation to prevent the gas in the combustion chamber from escaping. Prevents deterioration of stopping performance and deterioration of exhaust gas.

[0014]

EXAMPLE An example of the decompression device will be described with reference to FIG. 1A is a sectional view of an embodiment of the decompression device, FIG.
1B is a sectional view taken along the line AA in FIG. In the figure, 1 is a cylinder, 2 is a combustion chamber, 3 is a spark plug, 4
Is a piston, 5 is an exhaust port, 6 is an intake port, and 7 is a scavenging port, all of which are known elements of a two-cycle spark ignition engine. Reference numeral 11 denotes a decompression port, which is a passage that connects the cylinder 1 to the exhaust port 5 halfway through the compression stroke. 29
Is a decompression valve cylinder provided in the middle of the decompression port 11. Reference numeral 21 is a decompression valve, which is an opening / closing valve that is movable in the decompression valve cylinder 29 in the axial direction.
A wire 22 is attached to the end of the decompression valve 21 in the axial direction. Reference numeral 21a is a groove provided around the decompression valve 21 in the decompression valve cutout portion. 22
The wire a is attached to the decompression valve 21 at the tip of the wire.

Reference numeral 23 is a spring, and the decompression valve 21 is connected to the wire 22.
Is pushed to the direction of pulling. When no external force is applied to the wire 23, the decompression valve cutout 21a coincides with the position of the decompression port 11. That is, the decompression valve 21 is open. Reference numeral 24 is an adapter for attaching the decompression valve 21 and the wire 22 to the upper portion of the exhaust port 5 of the cylinder 1. 26 is a wire cover, the end of which is attached to the adapter 24.

A first embodiment of the detection at the time of starting for operating the decompression valve will be described with reference to FIG. FIG. 2 is a sectional view of a first embodiment of detection at the time of starting for operating the decompression valve. The first embodiment of the detection at the time of starting is installed in the recoil starter. The main body 51 of the recoil starter forms the skeleton of the entire recoil starter. Reference numeral 52 is a rope winding drum, 53 is a rope, 49 is a claw, and 54 is a knob, all of which are known elements of a recoil starter. A roller 56 is pressed against the inside of the curved portion of the rope 53.
Reference numeral 57 denotes a stem, which is connected to a roller 56 by a pin near the end and is supported so as to be movable in the axial direction. A spring 59 pushes the stem 57 toward the roller 56. Reference numeral 60 denotes a spring receiver which is attached to 57 and receives the spring 59. 58
The stop ring is provided at a position where the movement of the stem 57 in the direction of the roller 56 is stopped by the stop ring.

The operation of the first embodiment of the detection at the time of starting will be described. When the knob 24 is pulled, the rope winding drum 52 rotates, and at the same time, the tension of the rope 53 increases and the stem 57 is moved against the force of the spring 59 in the direction of contracting the spring 59 to push the wire 22. The movement is transmitted to the decompression valve 21, and the decompression valve 21 opens. When the knob 24 is released, the decompression valve 21 closes.

A second embodiment of the detection at the time of starting will be described with reference to FIG. FIG. 3 is a diagram of a second embodiment of the detection at the time of starting. FIG. 3a is a front view of the first embodiment of detection at start-up, FIG.
FIG. 3B is a sectional view of FIG. Reference numeral 5 in the figure
1, 52, 54, 22, 26, 53 are the same as those in FIG. Reference numeral 62 is a cam, which is a plate cam attached to the rope winding drum 52. Reference numeral 63 denotes a cam follower at which the rope 53 is fully rewound and is provided at a position in contact with the valley of the cam 62. A spring 66 pushes the cam follower 63 toward the cam 62. 64 is an adapter for cam follower 6
3, the spring 66, the wire 22, and the wire cover 26 are attached to the recoil starter body 51.

The operation of the second embodiment of the detection at the time of starting will be described. When the rope 53 is pulled by the knob 24, the cam 62 rotates together with the rope winding drum 52 and pushes up the cam follower 63. The cam follower 63 rises along the edge of the cam 62, pushes the wire 22 to the right in the figure, and pushes the decompression valve 21 to open it. The cam 62 is a rope winding drum 52.
At the same time, the valley of the rotating cam 62 passes through the position of the cam follower 63 once every rotation, but the movement is slow due to the friction of the wire rope 22 and the portion of the cam follower 63, and the cam 62 does not move.
It floats when the Valley of No. passes. That is, the decompression valve 21 remains open. In the operating state after starting, the knob 24 is released, the rope 53 is fully rewound, the valley of the cam 62 is returned to the position of the cam follower 63, and the decompression valve 21 is also returned via the wire 22 and closed to decompress the port. 11 will be closed. That is, in the operating state, the decompression port is closed and adverse effects on engine performance and exhaust gas are avoided.

A third embodiment of the detection at the time of starting will be described with reference to FIG. FIG. 4 is a sectional view of a third embodiment of the detection at the time of starting. The third embodiment of the detection at the time of starting utilizes the fluctuating pressure in the crankcase. In the figure, reference numeral 1
21, 21a and 11 are the same as those in FIG. A one-way valve 74 is attached to the crankcase and has a very small return hole which opens only outward of the crankcase and communicates both sides of the valve. 75 is a reed valve and one-way valve 7
No. 4 valve opens only to the outside of the crankcase, and 70 is an actuator which is gas pressure operated and is connected to one-way valve 70 and the outside communicates with the atmosphere. Reference numeral 71 is a diaphragm, which is a membrane that receives pressure from the elements of the actuator 70. Reference numeral 24 is an adapter for attaching the actuator 70 to the cylinder 1. Reference numeral 33 denotes a compression spring which, together with the adapter 24, places the decompression valve 21 at a position where the decompression valve notch 21a coincides with the decompression port 11. A rod 34 is attached to the diaphragm 71 at one end and to the decompression valve 21 at the other end.

The operation of the third embodiment of the detection at the time of starting will be described. When the engine is started, the decompression valve notch 21a is aligned with the decompression port 11, the decompression valve 21 is open, and the decompression port 11 communicates the combustion lid with the exhaust port. When the engine starts and a pressure fluctuation occurs in the crankcase 1, the positive pressure of the crankcase 1 acts on the actuator 70 by the action of the one-way valve 74, and the diaphragm 71 swells to the right in the figure and the decompression valve 21 is inserted through the rod 34. By moving it to the right, the decompression valve notch 21a is removed from the position of the decompression port 11, the decompression port 11 is shut off, and this state is maintained during engine operation. When the engine stops, the pressure in the crankcase 1 becomes atmospheric pressure. The positive pressure in the actuator 70 gently passes through the minimum return hole to become atmospheric pressure, the diaphragm returns to the left, the decompression valve 21 is pulled to the left via the rod 34, and the decompression valve notch 21a is aligned with the decompression port 11. Decompression port 11 is open.

[0022]

The engine can be started by a small pulling force of the rope of the recoil starter and does not adversely affect the engine performance during normal operation. Since the detection at the time of starting is automatically performed, the operator does not need any operation for reducing the rope pulling force. The decompression valve actuating device is a simple mechanism, and there are few obstacles in manufacturing and assembling. Therefore, the present invention makes it easy to start the engine and does not deteriorate the engine performance.
A decompression device for a cycle engine can be provided.

[Brief description of drawings]

FIG. 1 is a diagram of a decompression device according to an embodiment of the present invention.

FIG. 2 is a diagram of a first embodiment of a detection unit at the time of starting for opening and closing the decompression valve.

FIG. 3 is a diagram of a second embodiment of the detection unit at the time of starting.

FIG. 4 is a diagram of a third embodiment of the detection unit at the time of starting.

FIG. 5 is a diagram of a decompression device according to a first conventional example.

FIG. 6 is a diagram of a decompression device according to a second conventional example.

[Explanation of symbols]

1 ... Cylinder, 2 ... Combustion chamber, 4 ... Piston, 5 ... Exhaust port, 7 ... Scavenging port, 11 ... Decompression port, 21 ...
Decompression valve, 21a ... Decompression valve notch, 22 ... Wire, 23 ... Spring, 51 ... Recoil starter body, 52 ...
Rope winding drum, 53 ... Rope, 56 ... Roller, 54
... knob, 70 ... actuator, 71 ... diaphragm.

Claims (3)

[Claims] 1. A decompression port (11) for connecting a combustion chamber (2) to an exhaust port (5) or a scavenging port (7) halfway through a compression stroke of a piston (4) is provided with a cylinder section (1).
And a decompression valve (12) for controlling the opening and closing of the passage in the middle of the decompression port.
1) A rope bending portion having a small radius of curvature provided between the rope winding drum (52) and the rope outlet portion, and the rope bending portion is biased toward the anti-curvature center via a spring (59). And a means for guiding the moving stroke in the direction opposite to the biasing direction of the roller (56) by the spring when pulling the rope to the decompression valve (12) to open the decompression port (11). A two-cycle engine decompression device. 2. A decompression port (11) for communicating the combustion chamber (2) with the exhaust port (5) or the scavenging port (7) up to the middle of the compression stroke of the piston (4).
In a decompression device for a two-cycle engine, in which a decompression valve (12) for controlling the opening and closing of a passage is installed in the decompression port provided in the decompression port, a cam (62) is formed in the rope winding drum (52) of the recoil starter (51). The position of the cam follower (63) at the time of starting and when not starting is transmitted to the decompression valve (1) via the wire (22).
A decompression device for a two-cycle engine having a mechanism for opening and closing 1). 3. A decompression port (11) for communicating the combustion chamber (2) with the exhaust port (5) or the scavenging port (7) up to the middle of the compression stroke of the piston (4), the cylinder part (1).
In a decompression device for a two-cycle engine, in which a decompression valve (12) for controlling the opening and closing of a passage is installed in the middle of the decompression port, the fluctuation pressure inside the crankcase can be changed only through the one valve (74) to the + or-side. The decompression of a two-cycle engine having a mechanism of taking out and guiding it to an actuator (70), which directly controls the decompression valve (21) to close the decompression valve (70) during normal operation and open it at startup. apparatus.