JP2001329844A - Two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stratified scavenging with a simple structure and reduce the HC quantity in the exhaust in a Schnurle type two-cycle engine. SOLUTION: An intake side scavenge port 18, an exhaust side scavenge port 19, and an air inflow port 50 are formed on the inner peripheral face 12 of a cylinder block 1. The exhaust side scavenge port 19 is opened to a combustion chamber 14 at a delay after the intake side scavenge port 18. The air inflow port 50 is communicated with the atmospheric space. A groove 40 communicating the air inflow port 50 and the intake side scavenge port 18 when a piston 33 reaches near a top dead center is formed on the outer peripheral face of the piston 33. The air guided into the intake side scavenge port 18 through the groove 40 flows into the combustion chamber 14 prior to the air-fuel mixture flowing in from the exhaust side scavenge port 19 during a scavenge stroke to reduce the blow-by of the air-fuel mixture from an exhaust port 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke engine mounted on a brush cutter or the like, and more particularly to a THC (Total Hydrocarbon) in exhaust gas.
The present invention relates to a two-cycle engine that reduces the total amount of hydrocarbons.

[0002]

2. Description of the Related Art In a two-stroke engine, during a scavenging stroke, a gas mixture introduced into a combustion chamber from a scavenging port does not stay in the combustion chamber but flows out of an exhaust port as it is. Are released into the atmosphere as unburned gas containing HC (hydrocarbon), causing air pollution.

The two-stroke engine disclosed in Japanese Utility Model Laid-Open Publication No. 57-53026 has a normal scavenging port communicating with a crank chamber into which an air-fuel mixture is introduced, and a secondary scavenging port that opens at a timing earlier than the normal scavenging port. It has. The secondary scavenging port is connected to an air pump provided in the two-stroke engine without communicating with the crank chamber. The air pump sucks air in the atmosphere via the air control valve and the shutoff valve, and pumps the air to the secondary scavenging port.

[0004] In the scavenging stroke, a sub-scavenging port is opened prior to a normal scavenging port, and scavenging of the combustion chamber is performed by air pumped to an air pump. Subsequently, the normal scavenging port is opened. Scavenging by the mixture is performed. By performing such stratified scavenging, in the two-cycle engine disclosed in Japanese Utility Model Laid-Open No. 57-53026, the amount of HC in exhaust gas due to blow-by of the air-fuel mixture is reduced.

[0005]

Problems to be Solved by the Invention
In the two-stroke engine disclosed in Japanese Patent Publication No. 6-26, in order to perform stratified scavenging, an air pump or a shut-off valve for preventing a mixture in a combustion chamber from flowing back into the atmosphere via an air pump is required.
The structure becomes complicated.

An object of the present invention is to provide a two-stroke engine capable of performing stratified scavenging with a simple structure and reducing the amount of HC in exhaust gas.

[0007]

According to the two-stroke engine (10) of the present invention, the combustion chamber (14) is provided on both sides of the piston (33) reciprocating in the cylinder (11) in the reciprocating direction.
And a fuel-containing gas chamber (28), an intake port (15) for introducing the fuel-containing gas into the fuel-containing gas chamber (28), and an exhaust gas for discharging the internal gas into the combustion chamber (14). A mouth (16) is provided for each cylinder (11)
The inner circumferential surface (12) of the combustion chamber (14) is reciprocated by the piston (33) while communicating with the fuel-containing gas chamber (28).
A first scavenging port (18) whose opening and closing are controlled is formed, an air inlet (50) communicating with the atmosphere is formed, and the first scavenging port (18) is formed in the combustion chamber (14). The communication path (40) facing the air inlet (50) and the first scavenging port (18) when the piston (33) is in a position closed with respect to the piston (33) and / or the cylinder (1).
1) is formed.

The communication passage (40) may be formed only in the piston (33), or may be formed in both the piston (33) and the cylinder (11). The shape of the communication passage (40) is not limited as long as it can reach the air inlet (50) and the first scavenging port (18).
In addition to the groove (40) formed on the outer peripheral surface of the piston (33), a through hole or the like whose end is opened on the outer peripheral surface of the piston (33) may be used.

In the intake stroke, the first scavenging port (1
8) is closed to the combustion chamber (14) and the combustion chamber (1) is closed.
4) and the fuel containing gas chamber (28) are reduced and increased in volume, respectively. The fuel-containing gas chamber (28) and the first scavenging port (18) are increased by increasing the volume of the fuel-containing gas chamber (28).
Becomes negative pressure, and the fuel-containing gas is introduced into the fuel-containing gas chamber (28) from the intake port (15). When the piston (33) comes to a position where the communication passage (40) faces the air inlet port (50) and the first scavenging port (18), the air existing in the atmospheric space is released from the fuel-containing gas chamber (28) and the second air port. One scavenging port (18)
Communication path (40) from the air inlet (50) due to the negative pressure of
Through the first scavenging port (18). When the piston (33) passes this position, the communication passage (40) does not reach the air inlet (50) and the first scavenging port (18), and the air is sucked into the first scavenging port (18). Disappears. When the first scavenging port (18) opens to the combustion chamber (14) and enters the scavenging stroke, the air initially trapped in the first scavenging port (18) is transferred to the combustion chamber (14). Introduced and subsequently the fuel-containing gas in the fuel-containing gas chamber (28) is introduced into the combustion chamber (14) through the first scavenging port (18). The introduction of air into the combustion chamber (14) prior to the fuel-containing gas reduces the amount of fuel-containing gas that flows through the exhaust port (16). As described above, since the introduction of air for performing stratified scavenging is controlled by the movement of the piston (33), the amount of HC in the exhaust gas of the two-cycle engine (10) can be reduced with a simple structure.

Further, according to the two-stroke engine (10) of the present invention, the inner peripheral surface (12) of the cylinder (11) is provided.
The opening and closing of the combustion chamber (14) is controlled by the reciprocating motion of the piston (33) while communicating with the fuel-containing gas chamber (28), and the combustion proceeds later than the first scavenging port (18) in the scavenging stroke. A second scavenging port (19) opening into the chamber (14) is formed.

[0011] In the scavenging stroke, first the air that has stayed in the first scavenging port (18) is introduced into the combustion chamber (14), and then through the second scavenging port (19), the fuel-containing gas chamber. The fuel-containing gas in (28) is introduced into the combustion chamber (14). When the air remaining in the first scavenging port (18) is exhausted, the fuel-containing gas in the fuel-containing gas chamber (28) also passes through the first scavenging port (18).
Introduced to. By providing the second scavenging port, the timing and amount of introduction of the fuel-containing gas into the combustion chamber (14) in the stratified scavenging can be set to an appropriate value, and the output of the two-cycle engine (10) can be reduced. Can be improved.

Further, according to the two-stroke engine (10) of the present invention, the air inlet (50) and the air inlet (1).
5) is formed at an adjacent position on the inner peripheral surface (12) of the cylinder (11), and has a first flow control valve (54) and a second flow control valve (54) at the air inlet (50) and the inlet (15), respectively. A flow control valve (56) is provided.

The amount of the fuel-containing gas supplied from the intake port to the fuel-containing gas chamber (28) is controlled by a second flow control valve (56), and is controlled in two cycles according to the amount of the supplied fuel-containing gas. The output speed of the engine (10) is controlled. The amount of air introduced from the air inlet (50) to the first scavenging port (18) is controlled by the first flow control valve (54), and depends on the rotation speed of the two-stroke engine (10). It is desirable to be controlled. The air inlet (50) and the inlet (15) are connected to the inner peripheral surface (12) of the cylinder (11).
By forming the first flow control valve (54) and the second flow control valve (56) at adjacent positions in the first flow control valve (5), the first flow control valve (54) and the second flow control valve (56) can be arranged at adjacent positions.
4) and the second flow control valve (56) can be easily linked.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view showing a state where the piston 33 is located at a position near top dead center in the sinure type two-cycle engine 10. In FIG. 1, the piston 33 is substantially at the top dead center. The sinure type two-stroke engine 10 is mounted on, for example, a brush cutter.
In the cylinder block 11, the cylindrical inner peripheral surface 12
Extends in the cylinder block 11 along the center line of the cylinder block 11 and opens at the lower end surface of the cylinder block 11. The top recess 13 is formed at the top of the inner peripheral surface 12 and is provided with a discharge electrode such as a spark plug (not shown). The upper surface, the inner peripheral surface 12, and the top recess 13 of the piston 33 define a combustion chamber 14. The exhaust port 16 penetrates the peripheral wall of the cylinder block 11 and
And the inner peripheral surface 12 are communicated with each other. Air inlet 5
0 and the intake port 15 penetrate the peripheral wall of the cylinder block 11 at a position 180 ° away from the exhaust port 16 in the circumferential direction of the inner peripheral surface 12, and the outside of the cylinder block 11 and the inner peripheral surface 12.
And the communication. The upper end of the air inlet 50 is formed at a position slightly lower than the upper end of the exhaust port 16 in the height direction of the inner peripheral surface 12, and the intake port 15 is formed in the height direction of the inner peripheral surface 12. It is formed at a position lower than the air inlet 50. The plurality of cooling fins 17 are provided on the cylinder block 1.
In the upper half of the outer surface of the outer surface 1, the cylinder blocks 11 project outward in the radial direction of the cylinder block 11. The intake-side scavenging port 18 and the exhaust-side scavenging port 19 are formed at positions that open to the combustion chamber 14 when the piston 33 approaches the bottom dead center. The upper surface of the crankcase 27 is
Is joined to the lower surface. The lower surface of the piston 33, the inner peripheral surface 12, and the inner wall of the crankcase 27 define a crank chamber. The crank chamber 28 is provided with the scavenging port 1 on the intake side.
8 and the exhaust-side scavenging port 19 are always in communication, and when the piston 33 approaches the top dead center, the intake port 1
Connect to 5. The crankshaft 29 is rotatably supported by both end walls of the crankcase 27, and the piston 33 is slidably fitted into the inner peripheral surface 12, and reciprocates to move the combustion chamber 14.
And the capacity of the crank chamber 28 is increased or decreased. Connecting rod 35
Is rotatably connected to a piston 33 by a piston pin 36 at a small end, and a crankshaft 29 at a large end.
Is rotatably connected to the crank pin 37 of the motor.

An intake side scavenging port 18 and an exhaust side scavenging port 19
In the height direction of the inner peripheral surface 12, the upper end is formed at a position lower than the upper end of the exhaust port 16, and the upper end of the intake-side scavenging port 18 is higher than the upper end of the exhaust-side scavenging port 19. Is also formed at a higher position.

The groove 40 is formed at the lower end of the outer peripheral surface of the piston 33 and extends in the circumferential direction from the air inlet 50 to the intake side scavenging port 18. Piston 33
Is within a predetermined crank angle range close to the top dead center, the groove 40
Both ends face the air inlet 50 and the intake-side scavenging port 18 respectively, and the air introducing port 50 and the intake-side scavenging port 18 are communicated with each other.

The carburetor 52 has a through hole 58 and a through hole 60 having a pitch substantially equal to the distance between the air inlet 50 and the air inlet 15. The carburetor 52 aligns the through hole 58 and the through hole 60 with the air introduction port 50 and the intake port 15, respectively, and connects the cylinder block 11 with the respective holes.
Is fixed to the side. The through hole 58 is open to the atmospheric space, and a mixture of vaporized fuel and air is supplied to the through hole 60. The flow control valve 54 is disposed in the through hole 58 and controls the amount of air passing through the through hole 58. The flow control valve 56 is disposed in the through hole 60 and controls the amount of air-fuel mixture passing through the through hole 60. The flow control valve 54 includes the flow control valve 5
6 to increase or decrease the amount of air-fuel mixture passing through the through hole 58 by operating the flow control valve 56, and increase and decrease the amount of air passing through the through hole 60, respectively.

FIG. 2 is a diagram showing the cross section of the cylinder block 11 at the positions of the intake side scavenging port 18 and the exhaust side scavenging port 19 and the cross section of the piston 33 at the position of the groove 40. The exhaust port 16 and the air inlet 50 are centered at opposite positions on the diameter of the circular cross section of the inner peripheral surface 12. The center of the opening of the intake port 15 is located on the center of the opening of the air inlet 50 on the circular cross section of the inner peripheral surface 12. In the circular cross section of the inner peripheral surface 12, a line connecting the centers of the openings of the exhaust port 16 and the air inlet 50 is defined as a center line of the cylinder block 11 in the cross section. Intake side scavenging port 18 and exhaust side scavenging port 19
Are formed in pairs at symmetrical positions with respect to the center line of the cylinder block 11 in the transverse section. The intake-side scavenging port 18 and the exhaust-side scavenging port 19 are arranged such that the exhaust-side scavenging port 19 is closer to the exhaust port 1 than the intake-side scavenging port 18 in the circumferential direction of the inner peripheral surface 12.
It is arranged on the side close to 6. Both the intake-side scavenging port 18 and the exhaust-side scavenging port 19 are directed to the side away from the exhaust port 16 on the cross section.

The operation of the two-stroke engine 10 will be described. Hereinafter, the phase of operation of the two-stroke engine 10 will be described in terms of the rotation angle of the crankshaft 29, that is, the crank angle.

During the stroke in which the piston 33 moves from its bottom dead center toward its top dead center, the volume of the combustion chamber 14 decreases and the volume of the crank chamber 28 increases. When the crank angle becomes C1, the exhaust port 16 is closed by the piston 33, and the air-fuel mixture, which is a fuel-containing gas, is sealed in the combustion chamber 14 and compressed. Further, when the crank angle is C2 (C2> C
In 1), the intake port 15 communicates with the crank chamber 28,
In parallel with the compression of the air-fuel mixture in the combustion chamber 14, the air-fuel mixture from the carburetor 52 is supplied through the intake port 15 to the crank chamber 2.
8 is introduced.

When the piston 33 approaches the top dead center, the spark plug discharges, and the fuel in the air-fuel mixture in the combustion chamber 14 is ignited, explodes, and drives the piston 33 downward. On the other hand, when the piston 33 is in the vicinity of the top dead center, the lower end of the piston 33 reaches the height of the air inlet 50 and the intake-side scavenging port 18, and the groove 40 has the air inlet and the intake-side scavenging port 18.
Communicate with each other. At this time, the intake-side scavenging port 18 is in the same pressure state as the crank chamber 28 in the intake stroke, and has a negative pressure.
8, the air is introduced into the intake-side scavenging port 18 through the air inlet 50 and the groove 40, and the intake-side scavenging port 18 is filled with a predetermined amount.

When the piston 33 moves from the top dead center to the bottom dead center and the crank angle becomes C3 (C3> C2), the exhaust port 16 opens to the combustion chamber 14, and the burned gas is exhausted as exhaust gas. The gas is discharged from the exhaust port 16 to a muffler (not shown). Further, when the crank angle becomes C4 (C4> C3), the opening of the intake-side scavenging port 18 into the combustion chamber 14 starts. Accordingly, the air filled in the intake-side scavenging port 18 is introduced into the combustion chamber 14. The flow of air into the combustion chamber 14 from the two intake-side scavenging ports 18 existing in pairs is
And collides with each other in the combustion chamber 14 to form a reverse vortex, which in turn heads toward the exhaust port 16,
The burned gas in the combustion chamber 14 is scavenged and expelled from the exhaust port 16. Most of the air introduced from the intake-side scavenging port 18 into the combustion chamber 14 is discharged from the exhaust port 16 together with the burned gas as blow-by gas. Crank angle is C5
When (C5> C4), the exhaust-side scavenging port 19 starts to open to the combustion chamber 14, and this time, the air-fuel mixture in the crank chamber 28 is discharged from the two exhaust-side scavenging ports 19 present as a pair to the combustion chamber 1.
The gas flows into the combustion chamber 14 in a direction opposite to the exhaust port 16 into the combustion chamber 14 and collides with each other to form a reverse vortex. Since the airflow from the intake-side scavenging port 18 already exists on the exhaust port 16 side of the inversion vortex of the air-fuel mixture, blow-through from the exhaust port 16 is suppressed, and the inversion vortex stays in the combustion chamber 14. When all the air filled in the intake-side scavenging port 18 is introduced into the combustion chamber 14, the air-fuel mixture in the crank chamber 28 flows into the combustion chamber 14 from the intake-side scavenging port 18. As described above, by using the stratified scavenging in which the gas that is scavenged through the combustion chamber 14 and blows through is first air and then gas mixture, HC in the exhaust gas is significantly reduced.

The output rotation speed (the rotation speed of the crankshaft 29) of the two-stroke engine 10 is controlled by the flow control valve 5.
6 is changed by the supply amount of the air-fuel mixture to the intake port 15 controlled by the air-fuel mixture. From the air inlet 50 to the inlet side scavenging port 18
A small amount of air is required if the output rotational speed is small, and a large amount is required if the output rotational speed is large. When the flow rate control valve 56 is operated to control the output rotation speed, the flow rate control valve 54 operates in conjunction with the flow rate control valve 56, and the amount of air introduced from the air inlet 50 to the intake side scavenging port 18 is output. It is adjusted to an appropriate amount according to the rotation speed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a state in which a piston is located at a position near top dead center in a sinure type two-cycle engine.

FIG. 2 is a diagram showing a cross section of a cylinder block at a position of an intake-side scavenging port and an exhaust-side scavenging port together with a cross section of a piston at a position of a groove.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Sinula type 2 cycle engine (2 cycle engine) 11 Cylinder block (cylinder) 12 Inner peripheral surface 14 Combustion chamber 15 Intake port 16 Exhaust port 18 Intake side scavenging port (first scavenging port) 19 Exhaust side scavenging port (secondary scavenging port) 28 Crank chamber (fuel-containing gas chamber) 33 Piston 40 Groove (communication passage) 50 Air inlet 54 Flow control valve (first flow control valve) 56 Flow control valve (second flow control valve)

Claims (3)

[Claims] A combustion chamber (14) and a fuel-containing gas chamber (28) are respectively defined on both sides in a reciprocating direction of a piston (33) reciprocating in a cylinder (11), and the fuel-containing gas chamber (28) is defined. The inlet (1) for introducing fuel-containing gas
5) The combustion chamber (14) is provided with an exhaust port (16) for discharging gas therein, and the cylinder (1)
The fuel-containing gas chamber (2) is provided on the inner peripheral surface (12) of (1).
A first scavenging port (18) whose opening and closing to the combustion chamber (14) is controlled by the reciprocating motion of the piston (33) while communicating with the air inlet (8) is formed, and an air inlet port communicating with the atmospheric space. (50) is formed, and the first scavenging port (1) is formed.
8) when the piston (33) is in a position where the piston (33) is closed with respect to the combustion chamber (14).
0) and the communication passage (4) facing the first scavenging port (18).
0) is formed in the piston (33) and / or the cylinder (11). 2. An inner peripheral surface (12) of the cylinder (11).
The opening and closing of the combustion chamber (14) is controlled by the reciprocating motion of the piston (33) while communicating with the fuel-containing gas chamber (28). The two-stroke engine according to claim 1, characterized in that a second scavenging port (19) opening into the combustion chamber (14) is formed at a later time. 3. The air inlet (50) and the air inlet (15) are formed at adjacent positions on the inner peripheral surface (12) of the cylinder (11), and the air inlet (50) is formed.
3. The two-stroke cycle according to claim 1, wherein a first flow control valve (54) and a second flow control valve (56) are provided at the intake port (15), respectively. engine.