JPH10184407A - Automatic decompression device of small engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the startability by closing a valve automatically against a spring when an engine starts and a pressure in a combustion chamber rises, and constituting this engine so as to produce an intermediate state between valve opening and valve closing of an automatic decompression device till it is normally operated. SOLUTION: A tip part 3a of a cylindrical body, having a valve seat 3b at the tip and installed with a communicating hole 3f in a part of the rear end 3c, is screwed in a combustion chamber 2 of a cylinder 1, and a slider 4 is fitted in this cylindrical body 3 free of slide motion in a direction along a shaft. A main valve 6 in contact or separate to or from the valve seat 3b is combinedly installed in this slider 4 via a main valve fulcrum shaft 5, and this main valve 6 is opened and separated from the valve seat 3b via a slide valve 7 installed with a communicating hole 7a being connectable to the communicating hole 3f of the cylindrical body 3. When the engine is started and pressure in the combustion chamber 2 is raised high, the main valve 6 is gradually closed, and thus an engine start is facilitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine, such as a small engine used in a brush cutter or a chain saw, for example, for reducing the pulling force when pulling a starting rope of a recoil starter during an engine starting operation. The present invention relates to an improvement in an auto decompression device for a small engine for reducing a rotational force required for starting at the time of starting.

[0002]

2. Description of the Related Art As a conventional decompression device for a small engine of this type, there is a device as shown in FIG. 5, wherein FIG. 5A shows a valve open state and FIG. 5B shows a valve closed state. . In this figure, reference numeral 11 denotes a cylindrical body which is a component member of the decompression device. A screw 11a screwed into a combustion chamber 20 of a cylinder 19 is formed at the tip of the cylinder, and a mortar-shaped valve seat 1 is formed at the tip.
1b, a communication hole 11e communicating from the inner circumference 11c to the outer circumference 11d is formed in the middle part, and a ball receiving part 11f opening from the inner circumference 11c to the outer circumference 11d is formed at the rear end.

Reference numeral 12 denotes a sliding body which is slidably inserted in a direction along an axis into a rear portion of the cylindrical body 11, and has a rear end 12a.
Protrudes rearward from the cylindrical body 11, and an inclined portion 12 b having a diameter decreasing toward the front is formed at the distal end.
13 is a valve support shaft integrally formed at the tip of the inclined portion 12b, 14 is a flared valve integrally formed at the tip of the valve support shaft 13 and comes into contact with and separates from the valve seat 11b at the tip of the cylindrical body 11. Reference numeral 15 denotes a ball disposed on the ball receiving portion 11f of the cylindrical body 11, reference numeral 16 denotes a cover covering an outer periphery of a rear portion of the cylindrical body 11 so as to hold the ball 15 so as not to fall off.
Reference numeral 7 denotes a spring contracted between the inner periphery of the cover 16 and the ball 15, and reference numeral 18 denotes a knob attached to a rear end portion 12a of the sliding body 12 projecting rearward from the cylindrical body 11.

When the engine is started, a knob 18 attached to the rear end 12a of the sliding body 12 is manually pushed to slide the sliding body 12 forward. Then, the ball 15 is fitted into the concave portion 12c formed on the outer periphery of the sliding body 12, and the sliding state is maintained. Then, FIG.
As shown in the figure, the valve 14 at the tip of the valve shaft 13 formed integrally with the sliding body 12 is separated from the valve seat 11b at the tip of the cylindrical body 11.

In this state, when the starting rope (not shown) of the recoil starter is pulled, the piston 9
(See FIG. 2), and a part of the mixture of the fuel and the air compressed in the combustion chamber 20 by the driving of the piston is partly between the valve 14 and the valve seat 11b and in the cylindrical body 11 and the cylindrical body. Since the body 11 escapes from the inner periphery 11c of the body 11 through the communication hole 11e formed so as to communicate with the outer periphery 11d, the piston can be driven by the weak pulling force of the starting rope.

When the engine is started, the pressure in the combustion chamber 20 increases, and the tip of the valve 14 is pressed by the pressure and retreats, and the valve 14 contacts the valve seat 11b and closes.
The movement of the valve 14 slides the sliding body 12 via the valve support shaft 13, and the ball 15 comes into contact with the inclined portion 12 b of the sliding body 12 to maintain the sliding body 12 in the retracted state.

[0007]

In the above-described decompression apparatus, when the small engine is started by pulling a starting rope (not shown) of the recoil starter, it is attached to the rear end portion 12a of the sliding body 12. Knob 18
Is pressed by hand to slide the sliding body 12 forward, and the valve 14 at the tip of the valve support shaft 13 formed integrally with the sliding body 12 must be kept away from the valve seat 11b, which is troublesome. However, there is a problem that force is required when pulling the starting rope of the recoil starter while forgetting to press the knob 18. If the decompression device is easy to close at the start of the engine, the valve closes at the first explosion of the engine. If the engine does not explode continuously, the knob 18 must be pushed again by hand to open the valve. Must. Further, if the decompression device is difficult to close at the time of starting the engine, the problem that the engine is difficult to start, that is, since there is no intermediate state between the opening and closing of the valve of the decompression device, the above-described problem occurs. Had occurred. According to the present invention, before starting a small engine such as a two-cycle engine, the valve of the auto decompression device automatically opens by the urging force of the spring, and the starting rope of the recoil starter can be pulled lightly. The rotational force required for starting at the time of starting is reduced. Further, when the engine starts and the pressure in the combustion chamber increases, the valve is automatically closed against the urging force of the spring, and the engine can be operated normally. It is an object of the present invention to manufacture and provide a small, lightweight and inexpensive auto decompression device in which an intermediate state between the opening and closing of the valve of the auto decompression device occurs before the operation.

[0008]

According to the present invention, in order to achieve the above object, a front end portion 3a is screwed into a combustion chamber 2 of a cylinder 1, a valve seat 3b is formed at a front end, and a rear end portion 3c is formed. A cylindrical body 3 partially provided with a communication hole 3f communicating from the inner circumference 3d to the outer circumference 3e, a sliding body 4 slidably inserted into the cylindrical body 3 in a direction along an axis, and a sliding body 4 A main valve support shaft 5 formed in a direction along the axis, and a main valve 6 formed at the tip of the main valve support shaft 5 and coming into contact with and separating from the valve seat 3b.
And the main valve 6 slides on the outer periphery 3e of the cylindrical body 3 so as to move integrally with the sliding body 4, and the main valve 6
A slide valve 7 having a communication hole 7a communicating with the communication hole 3f of the cylindrical body 3 when it is separated from the cylinder body 3, and a spring 8 for urging the slide body 4 so that the main valve 6 is always separated from the valve seat 3b. And an auto decompression device for a small engine.

A wind generated by the rotation of the cooling fan hits the rear end of the slide valve 7 and moves the slide valve 7 so that the communication hole 7a of the slide valve 7 does not face the communication hole 3f of the cylinder 3. This is an auto decompression device for a small engine, which is provided with a wind receiving plate 7b for performing an operation.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an auto decompression device for a small engine such as a two-cycle engine according to the present invention will be described below in detail with reference to the drawings. FIG. 1A is a cross-sectional view of the auto decompression device of the first invention in a state in which a valve is opened, and FIG. 1B is XX of FIG.
1 (c) is a cross-sectional view of the auto decompression device with the valve closed, and FIG.
Is a combustion chamber, and 3 is a screw 3g formed on the outer periphery of a tip 3a of the cylinder 1 in the combustion chamber 2 of the cylinder 1. A mortar-shaped valve seat 3b is formed at the tip, and an inner periphery is formed at a part of the rear end 3c. 3d to outer circumference 3
A cylindrical body 4 having a communication hole 3f communicating with e is a sliding body which is slidably inserted into the cylindrical body 3 in a direction along an axis. A notch 4a is formed in a direction along the direction. Therefore, the notch 4a and the cylindrical body 3
A gap G is formed between the inner circumference 3d and the inner circumference 3d. The operation of the gap G will be described later.

Reference numeral 5 denotes a main valve support shaft integrally formed with the sliding member 4 in a direction along the axis. Reference numeral 6 denotes a flared main valve formed at the tip of the main valve support shaft 5 and in contact with and separated from the valve seat 3b. , 7 are in sliding contact with the outer periphery 3e of the cylindrical body 3 so as to move integrally with the sliding body 4, and when the main valve 6 is separated from the valve seat 3b, the communication hole 3f of the cylindrical body 3
A cylindrical slide valve provided with a communication hole 7a communicating with the outer periphery 3 of the cylindrical body 3
e, and one end thereof is fixed to the rear end of the sliding body 4 in a sealed state. Reference numeral 8 denotes a coil spring having one end fixed to the outer periphery of the rear end of the slide valve 7 and the other end extended to the outer periphery of the intermediate portion of the cylindrical body 3. Urges the sliding body 4 to separate from the valve seat 3b.

A gap is provided between the outer periphery 3e of the cylindrical body 3 and the inner periphery of the slide valve 7 so as to perform the operation described below, and this gap is exaggerated in the drawings. ing. FIG. 2 is a cross-sectional view of a main part of a small engine in which the auto decompression device A of the first invention is mounted in the combustion chamber 2. Reference numeral 9 denotes a piston slidably disposed in the cylinder 1. It is a spark plug attached to the chamber 2.

The auto decompression device of the first invention is
As described above, before the engine is started, the slide valve 7 is stretched between the slide valve 7 and the cylinder 3 by the tension of the coil spring 8 provided in an extended state. As shown in FIG. 1A, the main valve 6 is separated from the valve seat 3b because it is pulled toward the front end side of the tubular body 3. In this state,
The communication hole 3f of the cylinder 3 and the communication hole 7 of the slide valve 7
a and communicate with each other.

In this state, when the starting rope (not shown) of the recoil starter is pulled, the piston 9 is driven by the pulling force, and the mixture of the fuel and air compressed in the combustion chamber 2 by the driving of the piston 9 is pulled. As shown by the arrow in FIG. 1 (a), a part passes through the space between the main valve 6 and the valve seat 3b and inside the cylinder 3, and communicates from the inner circumference 3d of the cylinder 3 to the outer circumference 3e. After passing through the formed communication hole 3f,
Since the escape is performed through the communication hole 7a formed in the slide valve 7, the pulling force of the starting rope can be reduced.

When the pressure in the combustion chamber 2 rises during the first explosion of the engine, the automatic decompression device closes. 3b, the valve is opened, and the pulling force of the starting rope can be reduced again.

When the starting rope is pulled, the piston 9
Is driven, the pressure in the combustion chamber 2 increases, a part of the compressed gas presses the tip of the main valve 6, and a part of the compressed gas passes between the valve seat 3 b and the main valve 6. , Escapes to the outside air through the inside of the cylindrical body 3 and through the communication holes 3f and the communication holes 7a, and a part of the compressed gas
d and the pressure storage space I of the slide valve 7 passing between the notch 4a and a part of the outer periphery of the sliding body 4. So, still,
When the engine is not completely operated, the main valve 6 does not abut against the valve seat 3b at a stretch, and an intermediate state occurs between the opening and closing of the auto decompression device, and the auto decompression device is completely closed. As a result, the pulling of the engine starting rope does not become heavy.

When the engine is completely operated, the pressure in the combustion chamber 2 is continuously increased, and a part of the compressed gas is applied to the front end face of the main valve 6 as shown by a thick arrow in FIG. Since the compressed gas is continuously pressed strongly and a part of the compressed gas passes between the inner periphery 3d of the cylindrical body 3 and a part of the notch 4a of the outer periphery of the sliding body 4, it enters the pressure accumulating space I of the slide valve 7. The main valve 6 and the slide valve 7 are retracted, the main valve 6 abuts on the valve seat 3b and is continuously closed, and the communication hole 3f formed in the cylindrical body 3 and the slide valve 7 are connected.
The internal pressure of the pressure accumulating space H in the cylindrical body 3 and the pressure accumulating space I in the slide valve 7 further increase, so that the valve is completely closed. The engine operates normally in such a state.

When the engine is stopped, as shown in FIG. 1C, the compressed gas in the pressure accumulation space I between the sliding body 4 and the slide valve 7 is released from the outer periphery of the cylindrical body 3 and the slide valve 7.
The slide valve 7 is slid toward the distal end of the cylindrical body 3 by the pulling force of the coil spring 8, and escapes to the outside air through the gap between the inner circumference of the cylinder 3 and
(A), the main valve 6 is separated from the valve seat 3b and is opened.

FIG. 3 shows an embodiment of an automatic decompression device for a small engine according to the second invention, which is different from the first invention in that a cooling fan rotation is provided at the rear end of the slide valve 7. A wind receiving plate 7b is provided so as to move the slide valve 7 such that the communication hole 7a of the slide valve 7 does not face the communication hole 3f of the cylindrical body 3 when the wind generated by the slide valve 7 is in contact with the communication hole 3a.

The auto decompression device of the second invention is
Since it is configured as described above, in addition to the valve closing action described in the auto decompression device of the first invention,
The wind generated by the rotation of the cooling fan when the engine is in a predetermined operating state hits the wind receiving plate 7b, and the slide valve 7 prevents the communication hole 7a of the slide valve 7 from facing the communication hole 3f of the cylinder 3. And main valve 6
Is moved rightward in the figure, so that the valve can be closed more reliably and the engine can be operated normally.

FIGS. 4A and 4B show another embodiment of the automatic decompression device for a small engine according to the present invention, wherein FIG. 4A is a sectional view of the valve in an open state, and FIG. 4B is a sectional view of the valve in a closed state. The difference from the above embodiment is that the outer diameter of the rear part 4b of the sliding body 4 that slides on the inner circumference 3d of the cylindrical body 3 is reduced and the inner circumference 3d of the cylindrical body 3 A space is formed between them, and the rear end 3h of the cylindrical body 3 is brought into sliding contact with the rear part 4b of the sliding body 4, and the rear end 3h of the cylindrical body 3 and the inner circumference 3d of the cylindrical body 3 are formed.
A spring 8 is contracted in a space portion between the sliding member 4 and the rear portion 4b of the sliding member 4, and the spring 8 constantly presses and biases the sliding member 4 so that the main valve 6 is separated from the valve seat 3b. ing. By arranging the spring 8 inside the auto decompression device in this way, in addition to the operation of the auto decompression device of the above-described embodiment, there is an advantage that dust does not adhere to the spring 8.

[0022]

According to the first aspect of the present invention, an auto decompression device for a small engine has a tip portion screwed into a combustion chamber of a cylinder.
A cylindrical body having a valve seat formed at the front end and a communication hole formed in a part of the rear end part and communicating from the inner circumference to the outer circumference, and a sliding body slidably inserted in a direction along an axis in the cylindrical body. A main valve support shaft formed in a direction along an axis of the sliding body, a main valve formed at a tip of the main valve support shaft and coming into contact with and separating from the valve seat, and moving so as to move integrally with the slide body. A slide valve that slides in contact with the outer periphery of the cylindrical body and has a communication hole that communicates with the communication hole of the cylindrical body when the main valve separates from the valve seat, and the main valve always moves away from the valve seat. Before the engine is started, the valve of the auto decompression device automatically opens by the biasing force of the spring, and the starting rope of the recoil starter can be pulled lightly because the sliding body is composed of the spring that biases the sliding body. Etc. of the engine It is possible to reduce the rotational force required to start at the time of moving. Further, when the engine starts and the pressure in the combustion chamber continuously increases, the valve is automatically closed against the urging force of the spring, and the engine can be normally operated. Before the normal operation, the intermediate state between the opening and closing of the auto decompression device occurred, so that the decompression device continued to close and the engine continued after the first explosion of the engine as before. If the explosion did not occur, the problem that the decompression device had to be manually opened again was eliminated. Further, this auto decompression device can be made compact and lightweight, can be manufactured at low cost, and can be easily screwed as a single component to the combustion chamber of the cylinder.

In the automatic decompression device for a small engine according to the second aspect of the present invention, the wind generated by the rotation of the cooling fan hits the rear end of the slide valve, and the communication hole of the slide valve does not face the communication hole of the cylindrical body. Thus, in addition to the valve closing action of the auto decompression device of the first invention, the cooling fan when the engine is in a predetermined operating state is provided by providing the wind receiving plate for moving the slide valve. The wind generated by the rotation of the slide valve hits the wind receiving plate, and moves the slide valve and the main valve so that the communication hole of the slide valve does not face the communication hole of the cylindrical body. Can be activated.

[Brief description of the drawings]

FIG. 1 is a sectional view of an automatic decompression device for a small engine according to the first invention.

FIG. 2 is a sectional view showing a state in which the auto decompression device for the small engine according to the first invention is mounted on the small engine.

FIG. 3 is a sectional view of an automatic decompression device for a small engine according to a second invention.

FIG. 4 is a sectional view of another embodiment of the automatic decompression device for a small engine according to the present invention.

FIG. 5 is a cross-sectional view of a conventional automatic decompression device for a small engine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 2 Combustion chamber 3 Cylindrical body 3a Tip 3b Valve seat 3c Rear end 3d Inner circumference 3e Outer circumference 3f Communication hole 3g Screw 3h Rear end 4 Sliding body 4a Notch 4b Back 5 Main valve spindle 6 Main valve 7 Slide valve 7a Communication hole 7b Wind receiving plate 8 Coil spring 9 Piston 10 Ignition plug 11 Cylindrical body 11a Screw 11b Valve seat 11c Inner circumference 11d Outer circumference 11e Communication hole 11f Ball receiving part 12 Sliding body 12a Rear end part 12b Inclined part 12c recess 13 Valve spindle 14 Valve 15 Ball 16 Cover 17 Spring 18 Knob 19 Cylinder 20 Combustion chamber H Accumulation space I Accumulation space

Claims (2)

[Claims] 1. A cylindrical body having a front end portion screwed into a combustion chamber of a cylinder, a valve seat formed at a front end, and a communication hole formed in a part of a rear end portion to communicate from an inner periphery to an outer periphery. A sliding body slidably inserted in a direction along the axis in the cylinder, a main valve support shaft formed in the direction along the axis on the slide body, and a contact with the valve seat formed at the tip of the main valve support shaft. A main valve to be separated and a communication hole that slides on the outer periphery of the cylindrical body so as to move integrally with the sliding body and that communicates with a communication hole of the cylindrical body when the main valve separates from the valve seat. An auto decompression device for a small engine, comprising: a slide valve provided; and a spring that biases the slide body so that the main valve always moves away from the valve seat. 2. A wind receiving plate which acts to move the slide valve so that the communication hole of the slide valve does not face the communication hole of the cylindrical body when wind generated by the rotation of the cooling fan hits the rear end of the slide valve. The auto-decompression device for a small engine according to claim 1, characterized in that: