JPH0711923A - Decompression device of two cycle engine - Google Patents

Abstract

PURPOSE:To prevent any deformation and inferiority in response to the overheat of an open/close valve by closing a mushroom type valve when the rotational speed of an engine is increased. CONSTITUTION:In the start of an engine 21 at a low rotational speed, the pressure in a cylinder 22 during its compression stroke is reduced by pushing a cam member 46 through an operation ring 43 by the energizing force of a compression spring 44 and opening by pushing a mushroom type valve by the cam of the cam member 46. When the rotational speed of the engine 21 is increased, a disc 42 is push-pressed by the cetrifugal force of a pair of balls 41 in the slant hole 29a of a balance weight 29 and the cam member 46 is put in turning movement by an operation ring 43 making contact with the disc. A rod engaged with the cam member 46 down and the mushroom valve 31 is closed and also the pressure in the cylinder 22 is increased and the engine 21 can output a prescribed output by closing a passage leading to a scavensing port 27. Thereby, the deformation and inferiority in response to the overheat of an open/close valve can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a decompression device for a two-cycle engine which reduces crankshaft rotation torque at the time of starting the two-cycle engine and improves engine startability.

[0002]

2. Description of the Related Art A conventional engine in which a recoil starter is attached to an engine body, in which a decompression operation component is attached to an operation portion of the recoil starter, is proposed in Japanese Utility Model Laid-Open No. 63-86312. The conventional example will be described with reference to FIGS. 5 is a sectional view of a conventional decompression device, and FIG. 6 is a partially enlarged sectional view of a conventional decompression device. In the figure, 1 is an engine, 2 is a cylinder, which is an element of the engine 1, and 4 is a piston which is fitted in the cylinder 2. A combustion chamber 5 is an upper space of the cylinder 2. 8
Is open to the cylinder 2 at a decompression port.

Reference numeral 6 is an exhaust pipe, and 7 is an intake pipe. An operation knob 15c is provided on the end of the rope of the recoil starter. A closing member 15a is provided on the operation knob 15c and has a plug shape. A knob receiver 16 hooks the operation knob 15c. Reference numeral 16a denotes a port, which opens to the knob receiver 16 and is closed by the closing member 15a. Reference numeral 15 is a handle of the recoil starter. A communication passage 10 connects the decompression port 8 and the port 16a. Reference numeral 9 is a pipe joint provided in the decompression port 8. 1
Reference numeral 1 is a cap nut for fastening the communication passage 10 to the pipe joint 9. Reference numeral 17 is an inner lining and is attached to the inner surface of the knob receiver 16. A pipe joint 13 is provided outside the port 16a. 14 is a cap nut for fastening the communication passage 10 to the pipe joint 13. 18 is a rope.

The operation of the conventional example will be described. When the handle 15 of the recoil starter is pulled, the closing member 15a moves together and leaves the knob receiver 16 to open the port 16a, so that the combustion chamber 5 of the engine and the outside air communicate with each other through the decompression port 8, the communication passage 10 and the port 16a. Since the pressure reducing port 8 opens in the middle of the compression stroke of the piston 4 of the cylinder 2, the mixed gas in the combustion chamber 5 is decompressed and the starting torque is reduced. The piston 4 ignites and burns the compressed mixed gas in the remaining stroke after passing through the pressure reducing port 8 to start the engine. Next, the handle 15 of the recoil starter
When the valve is released, the closing member 15a returns to the knob receiver 16 to close the report 16a, the decompression is stopped, the combustion chamber becomes in a normal state, the pressure of the mixed gas rises, and the engine generates a predetermined output.

[0005]

In the conventional decompression device, the communication passage of the combustion chamber and the port of the recoil starter are always communicated with each other, and the seal portion of the port closing member is worn or tilted or a foreign substance is trapped. Occurs, the compression pressure in the combustion chamber decreases and the engine output decreases. Further, since the communication passage is thin and long, the lubricating oil and soot in the unburned gas are likely to be accumulated, and there is a problem that the diameter of the communication passage is narrowed or clogged.

The object of the present invention is to solve the above problems, to allow the decompression device to be housed in the engine compactly, and to install the opening / closing valve of the decompression device above the engine cooling air.
It is an object of the present invention to provide a decompression device for a two-cycle engine, which can prevent deformation and deterioration of the on-off valve due to overheating and can provide a highly reliable device.

[0007]

A decompression device for a two-cycle engine according to the present invention is arranged in a two-cycle single-thin-rider engine in parallel with a passage for communicating a cylinder compression chamber with a scavenging port or an exhaust port and a cylinder central axis. A balance between a mushroom-shaped valve that can open and close the passage and is normally urged to be closed by a compression spring, and a crankshaft that has a pair of holes with a bottom that are symmetrically opened and inclined forward toward the crankshaft end. A pair of balls that enter the hole of the weight and can freely move in the hole, and a disk that has an outer diameter that abuts the balance weight and can block the inclined hole of the balance weight and that can slide in the longitudinal direction of the crankshaft, It comes into contact with the disc, is fitted onto the crankshaft, is movable in the crankshaft direction, and is biased by a compression spring so as to push in the balance weight direction. An operating ring with a pin, and a pair of arms that rotatably fits on a shaft fixed to the crankcase and that fits into a pin of the operating ring with a pin through a hole. And a rod with a roller that engages with the cam of the cam member to operate the mushroom valve, and is pinned by the urging force of the compression spring at a low rotation speed at the time of engine startup. When the cam member is pushed through the actuation ring, the cam member opens the mushroom valve through the rod with the roller to reduce the pressure in the compression chamber during the compression stroke, and the engine speed increases. The circular plate is pushed by the centrifugal force of a pair of balls in the inclined hole of the balance weight, and an operating ring with a pin that abuts against the circular plate rotates a cam member to pull down a rod with a roller engaged with the cam member by a compression spring. Previous Characterized in that the operation of closing the Kinokokatachiben.

[0008]

When the engine is started and the rotational speed is low, the urging force of the compression spring pushes the cam member through the pin-equipped operating ring, and the cam of the cam member pushes the mushroom valve through the rod with a roller. When the cylinder pressure during the compression stroke is reduced by opening and the engine speed increases, the circular plate is pressed by the centrifugal force of the pair of balls in the inclined hole of the balance weight, and the operating ring with a pin that abuts this disk. The pressure inside the cylinder rises by closing the passage leading to the scavenging port or the exhaust port while closing the mushroom valve by rotating the cam member and pulling down the rod with a roller that engages with the compression spring with a compression spring. A predetermined output can be output.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a decompression device for a two-cycle single cylinder engine according to the present invention will be described with reference to FIGS.
1 is a sectional view of an engine equipped with the decompression device of the embodiment, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is taken along line B-O- of FIG.
4 is a sectional view taken along line CC of FIG. 3 and FIG. In the figure, 21 is a two-cycle single cylinder engine, 22 is a cylinder of the engine 21, 22 is a compression chamber of the cylinder, 2
7 is a scavenging port. 22b, 22a, 32a, 35
All of a are connected in the above order by passages to connect the compression chamber 25 and the scavenging port 27 or an exhaust port (not shown).
Reference numeral 31 denotes a mushroom valve which is provided between the passage 22a and the passage 32a in parallel with the cylinder 22 and opens and closes between the passage 22a and the passage 32a and is normally closed. A compression spring 33 urges the mushroom valve 31 in a closing direction. Reference numeral 34 denotes a rod with a roller that is in contact with the valve rod end of the mushroom valve 31. A roller 36 is pin-connected to the lower end of the rod 34 with a roller.

Reference numeral 28 is a crank shaft, and 29 is a balance weight fixed to the crank shaft 28. Reference numeral 29a is a hole, which is a pair of holes with a bottom formed symmetrically on the surface of the balance weight 29 toward the shaft end of the crankshaft 28 with a forward slope. 41 is a ball which is loosely inserted in each of the holes 29a. Reference numeral 42 denotes a disc having an outer diameter capable of contacting the surface of the balance weight 29 and covering the hole 29a, and is loosely fitted to the crankshaft 28. An operating ring 43 is in contact with the disc 42 and is loosely fitted to the crankshaft 28. Reference numeral 30 is a crankcase of the engine 21. 44 is a compression spring, and the operating ring 4
3 and the crank ring 30 are provided between the operating ring 4
3 is urged toward the balance weight 29. 43a
Is a column-shaped projection that protrudes on the outer circumference of the operating ring 43 with a pin on a diameter perpendicular to the axis of the cylinder 22 of the operating ring 43. Reference numeral 47 denotes a shaft, which is a support shaft provided in the crankcase 30 perpendicularly to the center line of the cylinder 22 and the center line of the crank shaft 28. Reference numeral 46 denotes a cam member, which has arms having holes for loosely fitting to the shaft 47 and loosely fitting to the pins 43a on both sides of the crankshaft 28, and a cam is provided at one end thereof. A cam 46a is provided at the tip of one arm of the cam member 46 and is in contact with the roller 36.

The operation of the above embodiment will be described. Engine 2
When 1 is stopped or at a low rotational speed, the compression spring 44 presses the actuation ring 43, and the actuation ring 43 causes the pin 43a to rotate the cam member 46 about the shaft 47, and the position shown by the two-dot chain line in FIG. The cam 46a pushes up the roller 36, thereby pushing up the rod 34 with the roller against the compression spring 33. Then, the rod 34 with rollers pushes up the valve rod end of the mushroom valve 31 to open the mushroom valve 31 and open the passage 22.
Pass between a and the passage 32a. Therefore, the compression chamber 25 communicates with the scavenging port 27 or an exhaust port (not shown) via the passage 22b, the passage 22a, the passage 32a, and the passage 35a. Therefore, in the compression stroke of the engine 21, the inside of the compression chamber 25 is not compressed until the piston 24 passes through the opening of the passage 22b, and the inside of the compression chamber 25 is decompressed and the starting torque is reduced.

In the compression stroke, the piston 24 passes through the opening of the passage 22b, and in the subsequent stroke, the compressed mixed gas is ignited and burned to start the engine 21.
When the engine 21 starts and the rotation speed rises above a set value, the centrifugal force of the pair of balls 41 in the hole 29a of the balance weight 29 exceeds the pressing force of the compression spring 44, and the disc 42
And the disk 42 pushes back the operating ring 43,
The actuating ring 43 pushes the arm by the pin 43a to rotate the cam member 46 about the shaft 47 and place it in the position shown by the solid line in FIG. Then, the cam 46a separates from the roller 36 and pulls down the roller rod 34, so that the mushroom valve 31 is closed by the force of the compression spring 33 and the space between the passage 22a and the passage 32a is closed, so that the compression chamber 25 is also exhausted to the scavenging port 27. The port is no longer connected, decompression stops, compression chamber 25 is normally compressed, and engine 21 can output a predetermined output.

[0013]

The present invention is constructed as described above, and since the decompression device can be compactly housed in the engine, the influence of dust and the like can be avoided, and
Since the opening / closing valve of the decompression device can be arranged on the windward side of the engine cooling air, deformation and deterioration due to overheating of the opening / closing valve can be prevented, and a highly reliable device can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an engine equipped with a decompression device according to an embodiment.

FIG. 2 is a sectional view taken along line AA in FIG.

3 is a cross-sectional view taken along the line BOC of FIG.

FIG. 4 is a sectional view taken along line DD in FIG.

FIG. 5 is a cross-sectional view of a conventional decompression device.

FIG. 6 is a partially enlarged cross-sectional view of a conventional decompression device.

[Explanation of symbols]

21 ... 2-cycle single cylinder engine, 22 ... Cylinder, 25 ... Compression chamber, 27 ... Scavenging port, 22a, 22
b, 32a, 35a ... passage, 24 ... piston, 28 ... crankshaft, 29 ... balance weight, 29a ... hole, 30
... crankcase, 31 ... mushroom valve, 34 ... rod, 41
... ball, 42 ... disk, 43 ... operating ring, 44 ... compression spring, 46 ... cam member, 46a ... cam, 47 ... shaft, 33
... compression spring.

Claims (1)

[Claims] 1. A passage (22b) (22a) (32) for connecting a cylinder compression chamber (25) to a scavenging port (27) or an exhaust port in a two-cycle single cylinder engine.
a) (35a), a mushroom type valve (31) that is placed parallel to the cylinder center axis and can open and close the passage, and is normally urged to close by a compression spring (33), and is directed toward the crankshaft end. And a pair of balls (41) which can freely move in the holes of the balance weight (29) of the crankshaft (28) having a pair of holes (29a) with a bottom and which are inclined symmetrically with respect to each other. A disk (42) having an outer diameter capable of abutting the balance weight and closing the inclined hole (29a) of the balance weight and slidable in the longitudinal direction of the crankshaft.
And a pin (43a) which is in contact with the disk and is externally fitted to the crankshaft, is movable in the crankshaft direction, is biased by the compression spring (44) so as to push in the balance weight direction, and is symmetrically coaxial with the outer circumference. And a pair of arms rotatably fitted to the shaft (47) fixed to the crankshaft and fitted to the pins (43a) of the pin-equipped operation ring with holes. A cam (46
and a rod (34) with a roller (36) which engages with the cam of the cam member and operates the mushroom-shaped valve. At this time, the cam member is pushed up by the urging force of the compression spring through the pin-equipped operating ring, and the cam member opens the mushroom valve through the rod-equipped rod to compress the compression chamber during the compression stroke. When the engine speed is increased and the rotational speed of the engine is increased, the centrifugal force of the pair of balls in the inclined hole of the balance weight pushes the disk, and the pin-attached operating ring that abuts the disk rotates the cam member. A decompression device for a two-cycle engine, characterized in that a rod with a roller engaged therewith is pulled down by a compression spring, and the rod valve is operated to close the mushroom valve.