JPH05302522A - Two cycle engine - Google Patents

Abstract

PURPOSE:To enhance the fuel consumption rate by providing an intake side control valve and a scavenge side control valve, respectively in parts of a scavenge air passage on the upper and lower sides of a surge tank located in the scavenge air passage, and by incorporating an auxiliary fuel supply device. CONSTITUTION:A surge tank 16 is connected in a scavenge air passage 15 for the connection between a crankcase 12 and a cylinder 13. A scavenge air passage 15 is composed of a first scavenge air passage 31 opened to the crankcase 12, and a second scavenge air passage 32 opened to a scavenge air port 26 formed in the cylinder 13. Further, an intake control valve 28 and a scavenge control valve 29 are connected respectively to the scavenge air passages 31, 32, the intake control valve 28 being opened and closed during reciprocation of a piston 14 while the scavenge control valve 29 is opened until the initial stage of the reciprocation of the piston 14. Further, a main injection valve 36 adapted to be operated in a high load and high rotational speed range of the engine is provided in the surge tank 16, and an auxiliary injection valve 37 adapted to be operated in intermediate and low load and middle and low rotational speed ranges is provided in a cylinder head 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle engine capable of improving both the performance of a crankcase pump and the fuel consumption rate.

[0002]

2. Description of the Related Art In a two-cycle engine 1 shown in FIG. 12, the inside of a crankcase 4 is in a state where a piston 3 for compressing an air-fuel mixture in a cylinder 2 is rising (during returning from bottom dead center to top dead center). When the pressure becomes negative, the reed valve 5 opens, and the air-fuel mixture is sucked into the crankcase 4. Further, when the piston 3 descends (moves forward from the top dead center to the bottom dead center) due to the combustion of the air-fuel mixture, the air-fuel mixture in the crankcase 4 is guided into the cylinder 2 through the scavenging passage 6 and the scavenging port 7. Get burned.

In the two-cycle engine 1, the crankcase 4 functions as a crankcase pump by the reciprocating movement of the piston 3 as described above. Note that reference numeral 8 in FIG. 12 indicates an exhaust port, and reference numeral 9 indicates a crankshaft.

[0004]

Since the opening and closing of the scavenging port 7 is performed by the piston 3, the opening and closing timing of the scavenging port 7 is symmetrical with respect to the bottom dead center of the piston 3, as shown in FIG. become. Therefore, in the initial stage of the rising process of the piston 3, since the scavenging port 7 is opened, the negative pressure in the crankcase 4 is low and the reed valve 5 is not sufficiently opened, so that the air-fuel mixture in the crankcase 4 is not opened. Inhalation volume is low.

Further, since the scavenging port 7 is opened in the initial stage of the ascending process of the piston 3, the air-fuel mixture in the crankcase 4 is pumped into the cylinder 2 through the scavenging passage 6 and then in the cylinder 2. Exhaust gas may be blown back through the scavenging passage 6 due to the negative pressure in the crankcase 4.

The present invention has been made in consideration of the above circumstances, and increases the amount of intake air into the crankcase, prevents the exhaust gas from being blown back from the scavenging port, and improves the efficiency of the crankcase pump. Can be improved,
An object of the present invention is to provide a two-cycle engine capable of improving fuel consumption rate by supplying fuel according to engine load and the like.

[0007]

According to the present invention, the internal spaces of a cylinder accommodating a piston that reciprocates between a top dead center and a bottom dead center, and a crankcase in which this cylinder is installed have respective scavenging passages therebetween. In the two-cycle engine, which is connected to the inside of the crankcase and is capable of supplying the air-fuel mixture from the inside of the crankcase to the inside of the cylinder through the scavenging passage and the scavenging port, a surge tank is disposed in the middle of the scavenging passage. In the scavenging passage, an intake control valve is installed between the crankcase and the surge tank, a scavenging control valve is installed between the surge tank and the cylinder, and a main fuel supply device is installed in the surge tank. The auxiliary fuel supply device is installed adjacent to the spark plug on the cylinder head installed above the cylinder, and the intake control The valve is opened over substantially the entire section in which the piston moves from top dead center to bottom dead center, and the scavenging control valve is configured to open the scavenging port while the piston is moving forward and then The main fuel supply device is controlled so as to be opened from the bottom dead center toward the top dead center until the initial stage of returning of the piston, the main fuel supply device is operated in the engine high load / high rotation range, and the sub fuel supply device is operated. Is operated in the low load / medium / low speed range of the engine.

[0008]

Therefore, in the two-stroke engine according to the present invention, the intake control valve is controlled so that the piston is closed in almost all the section during the backward movement from the bottom dead center to the top dead center. In the case, the negative pressure increases from the time when the scavenging port is still open at the initial stage of the piston return movement,
The reed valve and the like are opened, and intake air is guided into the crankcase. Therefore, the amount of intake air into the crankcase increases.

Further, the scavenging control valve is closed at the initial stage of the backward movement of the piston. This means that at the final stage of the scavenging process, where the scavenging opening is still open, the scavenging opening is closed by the scavenging control valve. Therefore, it is possible to prevent the exhaust gas from being blown back into the surge tank or the crankcase through the scavenging port and the scavenging passage in the final stage of the scavenging process.

The crankcase has a crankcase pump function of supplying the air-fuel mixture into the cylinder through the scavenging passage and the surge tank by the reciprocating motion of the piston. However, the amount of intake air into the crankcase and the exhaust gas blowing are increased. By preventing the return, the efficiency of the crankcase pump can be improved.

In addition, since the sub fuel supply device operates in the engine low and medium load / medium / low speed region and the main fuel supply device does not operate, excessive fuel consumption is required in the medium / low load / medium / low speed region. Can be prevented, and as a result, the fuel consumption rate can be improved.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view showing an embodiment of a two-cycle engine according to the present invention. FIG. 2 shows the opening / closing operation of the intake control valve and the scavenging control valve in FIG. 1 with reference to the crankshaft rotation angle. Is a graph shown by. FIG. 5 is a sectional view showing an actual two-cycle engine to which the two-cycle engine of FIG. 1 is applied.

As shown in FIGS. 1 and 5, in a two-cycle engine 10, a cylinder 13 is installed in a crankcase 12 that rotatably accommodates a crankshaft 11.
A piston 14 is accommodated in the cylinder 13 so as to be capable of reciprocating between a top dead center and a bottom dead center, the crankcase 12 and the cylinder 13 are communicated with each other through a scavenging passage 15, and a surge tank 16 is provided in the scavenging passage 15. Are arranged. A main fuel injector 36 as a main fuel supply device is installed in the surge tank 16, and a sub-fuel injector e37 as a sub fuel supply device is installed in a cylinder head 17 described later.

The piston 14 and the crankshaft 11 are connected by a connecting rod (not shown), and the reciprocating motion of the piston 14 is converted into the rotary motion of the crankshaft 11. A cylinder head 17 is arranged above the cylinder 13, and an ignition plug 18 is installed on the cylinder head 17. The sub-fuel tank 37 is arranged adjacent to the spark plug 18. When the piston 14 reaches the top dead center, the cylinder head 17
A combustion chamber 19 is formed by being surrounded by the piston 14.

An intake passage 20 is formed in the crankcase 12, and the intake passage 20 is connected to an air cleaner 22 via an air tube 21. The air from the air cleaner 22 is sucked into the crankcase 12 as intake air. This intake air is controlled by a reed valve 23 arranged in the intake passage 20 and an intake throttle valve 24 arranged in the air tube 21.

That is, the reed valve 23 is the piston 1
In the process of 4 returning from the bottom dead center to the top dead center and compressing the air-fuel mixture in the cylinder 13, the inside of the crankcase 12 becomes a negative pressure, and this negative pressure causes the reed valve 23 to open.
Intake air is taken into the crankcase 12. Further, the combustion of the air-fuel mixture in the combustion chamber 19 compresses the intake air in the crankcase 12 while the piston 14 moves from the top dead center to the bottom dead center, and the inside of the crankcase 12 becomes a positive pressure. The reed valve 23 is closed. As described above, the crankcase 12 has a crankcase pump function of sucking intake air inside, compressing it, and discharging it into the surge tank 16.

On the other hand, the intake throttle valve 24 is closed when the engine is running at low speed or when the engine scavenging throttle valve 30, which will be described later, is operated for a long period of time. The amount of intake air into the surge tank 16 is optimally adjusted, and the internal pressure in the surge tank 16 is prevented from becoming excessive when the engine brake is activated.

In the cylinder 13, one exhaust port 25 and a plurality of, for example, five scavenging ports 26 are formed. Exhaust port 25
Is connected to the exhaust pipe 27, and as shown in FIG.
The exhaust gas in the combustion chamber 19 and the cylinder 13 is exhausted. In addition, as shown in FIG. 2B, the scavenging port 26 also moves the piston 1 during the forward movement of the piston 1.
4, the air-fuel mixture is opened slightly later than the exhaust port 25, and the air-fuel mixture is introduced into the cylinder 13 in the exhaust process from the scavenging passage 15 (scavenging). The intake control valve 2 controls this scavenging.
8, scavenging control valve 29 and scavenging throttle valve 3
Implemented by 0.

The scavenging passage 15 is composed of a first scavenging passage 31 and a second scavenging passage 32. The first scavenging passage 31 and the second scavenging passage 32 have a funnel shape whose diameter gradually increases on the surge tank 16 side. Formed in. The other end side of the second scavenging passage 32 is provided as a passage in the crankcase 12 and communicates with the inside of the crankcase 12. The other end of the second scavenging passage 32 is provided as a passage in the crankcase 12 and the cylinder 13,
It communicates with the scavenging port 26. An intake control valve 28 is provided in the first scavenging passage 31 and a scavenging control valve 29 is provided in the second scavenging passage 32. Further, as shown in FIG. 7, the scavenging throttle valve 30 is arranged in the second scavenging passage 32 on the upstream side of the scavenging control valve 29, that is, in the surge tank 16.

As shown in FIGS. 6 and 8, the intake control valve 28 and the scavenging control valve 29 are formed as through holes diametrically extending from the side peripheral surface of the cylindrical valve element 33 through the axial center thereof. The intake control valve 28 is provided at the center of the valve element 33 in the axial direction.
The scavenging control valves 29 are formed on both axial sides of the valve element 33, respectively. This valve element 33
Is connected to the crankshaft 11 via the valve gears 34 and 35, and is set to make 1/2 rotation per one rotation of the crankshaft 11.

As shown in (c) of FIGS. 2 and 3, the intake control valve 28 is operated to be opened in substantially the entire section of the forward movement of the piston 14 and closed in the other sections. 2 and 4, the scavenging control valve 29 is opened at the same time as the piston 14 opens the scavenging port 26 during the forward movement, and is opened until the initial stage of the backward movement of the piston 14. The state is maintained and the closing operation is performed in other sections.

When the intake control valve 28 is opened, intake air (air) compressed in the crankcase 12 by the crankcase pump function is discharged into the surge tank 16. In addition, by opening the scavenging control valve 29, the air in the surge tank 16 or the air-fuel mixture generated in the surge tank 16 by the fuel injection from the main fuel injector 36 is generated in the second scavenging passage 32.
And, it is guided into the cylinder 13 through the scavenging port 26 (scavenging).

As described above, the main fuel injector 36 injects fuel into the air in the surge tank 16 at a low pressure to generate a uniform mixture of fuel and air (pre-mixture) in the surge tank 16. To do. Further, the sub-fuel injector 37 directly injects the fuel into the combustion chamber 19 at high pressure to generate a stratified mixture in which the shade is clearly separated. As shown in FIG. 9, the sub-fuel injector 37 is operated in the medium-low load / medium-low rotation range of the engine, generates a stratified mixture in the combustion chamber 19, and performs stratified combustion in the combustion chamber 19. To be realized. In addition, the main fuel injector 36
Is operated in a high load / high speed region of the engine, generates a premixed gas in the surge tank 16, and realizes premixed combustion using this premixed gas.

In the stratified charge combustion region, the engine load control is performed by the fuel injection amount from the sub-fuel injector 37. In the premixed combustion region,
As shown in FIG. 10, the load of the engine is controlled by adjusting the opening degree of the intake throttle valve 24 and adjusting the amount of premixed gas scavenged from the surge tank 16 into the cylinder 13.

According to the above embodiment, as shown in FIG. 2 (c), the intake control valve 28 is opened from the first stage of the forward movement of the piston 14, so that the crankcase pump shows the solid line in FIG. Crankcase 1 compressed like
The intake air in 2 is quickly introduced into the surge tank 16 without delay. Therefore, the intake air in the surge tank 16 is sufficiently compressed.

Further, as shown in FIG. 2 (c), since the intake control valve 28 is closed over the substantially entire section of the backward movement of the piston 14, the scavenging port 26 still remains at the initial stage of the backward movement of the piston 14. Crankcase 12 from the time it is opened
The inside becomes negative pressure. As a result, the reed valve 23 starts to open at substantially the same time as the closing operation of the intake control valve 28.
(E), that is, since the scavenging port 26 is conventionally opened, the negative pressure in the crankcase 12 is low, and the section in which the reed valve 23 is not opened is eliminated, so that the intake amount into the crankcase 12 is increased. it can.

Further, as shown in FIG. 2 (d), the scavenging control valve 29 is closed at the initial stage of the backward movement of the piston 14 since the scavenging port 26 is still open. Therefore, as shown by the chain double-dashed line in FIG.
At the final stage of the scavenging process before the scavenging port 26 is closed by the piston 14, the blowback flowing toward the crankcase 12 in the second scavenging passage 32 can be eliminated as shown by the solid line in FIG. .. Therefore, cylinder 1
It is possible to prevent the exhaust gas from flowing into the surge tank 16 from flowing back into the surge tank 16.

The crankcase 12 has the above-described features because it quickly introduces intake air into the surge tank 16, increases the amount of intake air into the crankcase 12, and prevents exhaust gas from being blown back into the surge tank 16. The efficiency of the crankcase pump can be improved.

Further, in the high load / high engine speed range of the engine, the main fuel injector 36 operates and the combustion chamber 19
Since premixed combustion is realized in, high output can be achieved in this engine high load / high speed range. On the other hand, since the sub-fuel injector 37 operates in the middle and low load range of the engine to perform stratified combustion in the combustion chamber 19, lean burn can be realized in the middle and low load range. In addition, it is possible to prevent the fuel from being consumed more than necessary, improve the consumption burning rate, and prevent the illegal explosion.

Also, since the surge tank 16 is interposed between the scavenging port 26 and the crankcase 12, pressure fluctuations in the cylinder 13 and pressure fluctuations due to the crankcase pump in the crankcase 12 are transferred to the surge tank 16. Therefore, the influence of the blowback flow in the scavenging passage 15 can be reduced. Therefore, the opening / closing timing of the scavenging port 26 and the control of the crankcase pump can be simplified.

Further, by changing the length of the funnel shape in the surge tank 16 of the first scavenging passage 31 and the second scavenging passage 32, it is possible to optimally tune the intake air by the engine speed.

Further, since the intake control valve 28 and the scavenging control valve 29 are arranged in parallel in one valve element 33, each intake control valve 28 and the scavenging control valve 29 are arranged.
A complicated drive mechanism for individually activating the above is unnecessary, and the drive system of the intake control valve 28 and the scavenging control valve 29 can be made compact.

The intake control valve 28 and the scavenging control valve 29 may be plate-shaped valves as shown in FIG.

[0035]

As described above, according to the two-cycle engine of the present invention, the surge tank is arranged in the middle of the scavenging passage, and the scavenging passage is provided between the crankcase and the surge tank. An intake control valve has a scavenging control valve installed between the surge tank and the cylinder, and the intake control valve opens over substantially the entire section in which the piston moves forward from top dead center to bottom dead center. The scavenging control valve is operated to open until the initial stage in which the piston moves back from the bottom dead center toward the top dead center after the scavenging opening is opened during the forward movement of the piston. Since the intake air can be sucked into the crankcase from the initial stage of the backward movement process of the piston, the intake amount into the crankcase can be increased. In, it can be prevented blown-back of exhaust from the scavenging port in the final stage of the scavenging process. These results,
The efficiency of the crankcase pump included in the crankcase can be improved.

Further, a main fuel supply device is installed in the surge tank, and a sub fuel supply device is installed adjacent to the spark plug in a cylinder head installed in the upper part of the cylinder. Operated in the load / high rotation range, the auxiliary fuel supply device is
Since the engine is operated in the medium and low rotation speed range, it is possible to improve the fuel consumption rate without consuming the fuel more than necessary in the medium and low load and middle and low rotation speed range of the engine.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an embodiment of a two-cycle engine according to the present invention.

FIG. 2 is a graph showing opening / closing operations of the intake control valve and the scavenging control valve of FIG. 1 with reference to a crankshaft rotation angle.

FIG. 3 is a graph showing the opening operation of the intake control valve of FIG. 1 in relation to the rate of change in crankcase internal pressure.

FIG. 4 is a graph showing the opening operation of the scavenging control valve of FIG. 1 in relation to the flow in the scavenging passage.

5 is a sectional view showing an actual two-cycle engine to which the scavenging device for the two-cycle engine of FIG. 1 is applied.

6 is a sectional view taken along line VI-VI of FIG.

7 is a sectional view taken along line VII-VII of FIG.

FIG. 8 is a perspective view showing the intake control valve and the exhaust control valve of FIG.

FIG. 9 is a graph showing a combustion mode in a combustion chamber.

[Figure 10] Scavenging throttle valve opening and engine load
The graph which shows the relationship with a rotation speed.

11 is a view showing another embodiment of the intake control valve and the exhaust control valve of FIG.

FIG. 12 is a schematic sectional view showing a conventional two-cycle engine.

[Explanation of symbols]

 10 2 Cycle Engine 12 Crankcase 13 Cylinder 14 Piston 15 Scavenging Passage 16 Surge Tank 17 Cylinder Head 18 Spark Plug 23 Reed Valve 26 Scavenging Port 28 Intake Control Valve 29 Scavenging Control Valve 31 First Scavenging Passage 32 Second Scavenging Passage 36 Main Fuel Injector 37 Sub-fuel injector

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area F02M 69/00 69/10 7825-3G

Claims (1)

[Claims] 1. A crankcase in which a cylinder accommodating a piston that reciprocates between a top dead center and a bottom dead center and a crankcase in which the cylinder is installed are communicated with each other through a scavenging passage to form the crankcase. In a two-cycle engine in which an air-fuel mixture can be supplied from the inside to the inside of the cylinder through the scavenging passage and the scavenging port, a surge tank is arranged in the middle of the scavenging passage, and the crankcase is provided in the scavenging passage. An intake control valve between the surge tank and the surge tank, and a scavenging control valve between the surge tank and the cylinder.The main fuel supply device is installed in the surge tank and is installed above the cylinder. An auxiliary fuel supply device is installed on the cylinder head adjacent to the spark plug, and the intake control valve has the piston above. The scavenging control valve is opened over almost the entire section going from the dead center to the bottom dead center, and the scavenging control valve opens the scavenging port during the forward movement of the piston, and then the top dead center from the bottom dead center. The piston is controlled to open until the initial stage of returning to the point, the main fuel supply device is operated in the engine high load / high rotation range, and the sub fuel supply device is in the engine medium load / medium load. A two-cycle engine that operates in a low speed range.