JP2541304B2 - Air supply control device for two-cycle internal combustion engine - Google Patents

Description

The present invention relates to a charge control device for a two-cycle internal combustion engine.

[Prior Art] In a two-cycle internal combustion engine, a large amount of burned gas remains in the cylinder, and fresh air occupies only a part of the cylinder particularly during low load operation. The fuel supply amount is calculated based on, for example, the intake air amount so that the air-fuel mixture formed by the fresh air and the supplied fuel has a predetermined target air-fuel ratio. However, in such a two-cycle internal combustion engine, when the fuel supply is stopped during deceleration operation in order to reduce the fuel consumption amount, the residual burned gas in the cylinder is expelled into the exhaust passage by the fresh air in order to remain in the cylinder. The burned gas gradually decreases, and the inside of the cylinder is finally filled with fresh air. When the fuel supply is restarted in such a state, the fuel supply amount at this time is determined with respect to the amount of fresh air supplied to the cylinder at this time, that is, the amount of fresh air occupying only a part of the cylinder. As a result, the air-fuel mixture in the cylinder becomes considerably lean and thus misfires. In order to prevent such misfires, it is sufficient to continue filling the combustion chamber with residual burnt gas when the fuel supply is stopped, and for that purpose, when the fuel supply is stopped, the combustion chamber It would be better to block the inflow of fresh air into.

Therefore, a scavenging throttle valve is arranged in the scavenging passage in a two-cycle internal combustion engine of the crank chamber compression type, and when the fuel supply is stopped during deceleration operation, the scavenging throttle valve is fully closed to prevent fresh air from entering the combustion chamber. It is known that the inflow is shut off and then the scavenging throttle valve is fully opened when the fuel supply is restarted (see JP-A-53-109007).

[Problems to be Solved by the Invention]

However, in reality, even if the scavenging throttle valve is fully closed, some fresh air leaks, and therefore the fresh air amount in the combustion chamber gradually increases as the period during which the fuel supply is stopped becomes longer. Therefore, when the scavenging throttle valve is fully opened when the fuel supply is restarted as in the above-mentioned two-cycle internal combustion engine, a large amount of fresh air is supplied from the scavenging passage into the combustion chamber in addition to the fresh air in the combustion chamber. The air-fuel mixture in the cylinder becomes very lean, thus giving rise to the problem of misfiring.

[Means for solving the problem]

According to the present invention in order to solve the above problems, an air supply cutoff valve is arranged in an air supply passage for supplying the air into a combustion chamber,
In the two-cycle internal combustion engine, the air supply cutoff valve is fully closed when the fuel supply is stopped during the deceleration operation, and the fuel supply cutoff valve is fully opened when the fuel supply is restarted thereafter. When the supply stop period is longer than a predetermined period, when the fuel supply is restarted, the air supply cutoff valve is temporarily held in the partially open state and then fully opened.

[Work]

When the fuel supply stop period becomes longer, the amount of fresh air in the combustion chamber increases. Therefore, at this time, when the supply of fuel is restarted, the supply air cutoff valve is temporarily held in the partially opened state to suppress the inflow of fresh air into the combustion chamber.

〔Example〕

1 and 2 show an overall view of a two-cycle internal combustion engine. Referring to FIGS. 1 and 2, 1 is a cylinder block, 2 is a reciprocating piston in the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, 4 is a piston 2 and a cylinder head 3. Combustion chambers formed between them, 5 is an intake valve, 6 is an intake port, 7 is an exhaust valve, 8 is an exhaust port, and 9 is an air blast valve for injecting fuel into the combustion chamber 4 together with compressed air. Show each.
Although not shown in the drawings, an ignition plug is disposed at the center of the inner wall surface of the cylinder head 3. The air supply port 6 is connected to a surge tank 11 via an air supply branch pipe 10, and the surge tank 11 is connected to an air cleaner 15 via an engine-driven mechanical supercharger 12, an air supply duct 13 and an air flow meter 14. It A throttle valve 16 is arranged in the air supply duct 13.

FIG. 3 shows an enlarged sectional view of the air blast valve 9. Third
Referring to the drawing, a compressed air passage 31 extending straight is formed in a housing 30 of the air blast valve 9, and a nozzle port 32 located in the combustion chamber 4 (FIG. 1) is formed at a distal end of the compressed air passage 31. Is formed. An on-off valve 33 is disposed in the compressed air passage 31, and a nozzle port 32 is provided at an outer end of the on-off valve 33.
A valve body 34 for controlling the opening and closing of the valve is integrally formed. housing
A movable core 36 coaxially arranged with the on-off valve 33 and urged toward the on-off valve 33 by the compression spring 35 and a solenoid 37 for sucking the movable core 36 are arranged in the inside 30. The inner end of the on-off valve 33 is brought into contact with the end face of the movable core 36 by a compression spring 38, and the spring force of the compression spring 38 is stronger than that of the compression spring 35.
It is closed by the valve body 34. When the solenoid 37 is energized, the movable core 36 moves in the direction of the on-off valve 33, and as a result, the valve element 34 of the on-off valve 33 opens the nozzle port 32. On the other hand, a compressed air passage 39 that extends obliquely from the compressed air passage 31 is branched from the compressed air passage 31, and the compressed air passage 39 is connected to a compressed air supply port 40. A fuel injection valve 41 is attached to the housing 30, and a nozzle hole 42 of the fuel injection valve 41 is provided.
From there, fuel is injected into the compressed air passage 39.

As shown in FIG. 1, an air blast air passage 17 is branched from an air supply duct 13 between an air flow meter 14 and a throttle valve 16, and the air blast air passage 17 is an engine-driven vane pump 18 and a compressed air passage. It is connected to the compressed air distribution chamber 20 via 19. The compressed air distribution chamber 20 is connected to a compressed air supply port 40 of an air blast valve 9 provided for each cylinder. In the compressed air passage 19, a pressure regulating valve 21 for maintaining the compressed air pressure in the compressed air distribution chamber 20 at a predetermined constant pressure is arranged, and excess compressed air is supplied through a compressed air return passage 22. It is returned into the duct 13. Therefore, the compressed air passages 31, 39 of the air blast valve 9 are filled with compressed air of a constant pressure.

FIG. 4 shows the opening period of the supply valve 5 and the exhaust valve 7, the period of fuel injection from the fuel injection valve 41, and the opening period of the valve body 34 of the on-off valve 33, that is, the opening period of the air blast valve 9. . Fourth
As shown in the drawing, in the embodiment shown in FIG. 1, the exhaust valve 7 opens before the air supply valve 5 and closes first. Also, the fourth
Before the valve element 34 of the on-off valve 33 opens as shown in the figure,
That is, the fuel is injected from the fuel injection valve 41 into the compressed air in the compressed air passage 39 before the air blast valve 9 opens. Next, when the air blast valve 9 is opened, the injected fuel is injected into the combustion chamber 4 from the nozzle port 32 together with the compressed air.
On the other hand, as shown in FIG. 1, a mask wall 23 is formed on the inner wall surface of the cylinder head 3 so as to cover the opening of the air supply valve 5 on the exhaust valve 7 side during the full opening period of the air supply valve 5. Therefore, when the air supply valve 5 is opened, fresh air is supplied from the air supply port 6 into the combustion chamber 4 through the opening of the air supply valve 5 opposite to the exhaust valve 7. As a result, the fresh air flows along the inner wall surface of the combustion chamber 4 as shown by the arrow S, and thus good loop scavenging is performed.

Referring to FIG. 1 and FIG. 2, an air supply cutoff valve 50 is arranged in each air supply branch pipe 10. These air cutoff valves 50
Are supported by a common valve shaft 51, and the valve shaft 51 is rotationally controlled by an actuator 52. The actuator 52 includes a pair of diaphragms 53 and 54 and a pair of negative pressure chambers 55 and 56.
And a stopper 57 for the diaphragm 54, and a play coupling mechanism 58 provided between the pair of diaphragms 53, 54. Each negative pressure chamber 55, 56 is connected to a negative pressure tank 61 via an electromagnetic switching valve 59, 60 which is capable of communicating with the atmosphere. Each negative pressure chamber 5
When 5, 56 are both open to the atmosphere, each air supply shutoff valve 50 is in the fully open state as shown by the solid line in FIG.
On the other hand, when the negative pressure chamber 55 is connected to the negative pressure tank 61 due to the switching action of the electromagnetic switching valve 59, only the diaphragm 53 becomes the negative pressure chamber.
As a result, the supply air cutoff valve 50 is rotated clockwise to be in a partially opened state in which it is slightly opened. Further, the negative pressure chamber 56 is changed to the negative pressure tank 61 by the switching action of the electromagnetic switching valve 60.
When connected to, the diaphragm 54 moves to the negative pressure chamber 56 side,
At this time, since the diaphragm 53 is further moved to the negative pressure chamber 55 side through the play connecting mechanism 58, each air supply cutoff valve 50 is further rotated clockwise, and the fully closed state shown by the broken line in FIG. Becomes In this way, the supply switching valves 50 are controlled to the three positions of the fully open position, the partially open position and the fully closed position by the switching action of the electromagnetic switching valves 59, 60.

These electromagnetic switching valves 59, 60 are controlled by the output signal of the electronic control unit 70. The electronic control unit 70 is composed of a digital computer, and a ROM (Read Only Memory) 72 and a RAM interconnected by a bidirectional bus 71.
A (random access memory) 73, a CPU (microprocessor) 74, an input port 75 and an output port 76 are provided. The air flow meter 14 generates an output voltage proportional to the intake air amount, and this output voltage is input to the input port 75 via the AD converter 77. Throttle valve 16 has a throttle valve
A throttle switch 78 for detecting that 16 is an idling opening is connected, and an output signal of the throttle switch 78 is input to the input port 75. Further, the output signal of the rotation speed sensor 79 representing the engine rotation speed is input to the input port 75. On the other hand, the output port 76 is connected to the solenoid 37 of the air blast valve 9 and the fuel injection valve 41 via the drive circuits 80 and 81, and the output port 76 is further connected to the drive circuits 82 and 83.
Is connected to the electromagnetic switching valves 59, 60 via.

In the embodiment shown in FIG. 1, each supply air cutoff valve 50 is fully closed when fuel supply is stopped during deceleration operation, and each supply air cutoff valve 50 is opened when fuel supply should be restarted. Be blamed. When the supply air cutoff valve 50 is fully closed, the fresh air is prevented from flowing into the fuel chamber 4, so that the combustion chamber 4 is filled with a large amount of residual burned gas. Therefore, when the air supply cutoff valve 50 is opened when the fuel supply should be restarted, the amount of fresh air in the combustion chamber 4 at this time is small, and therefore, if the fuel corresponding to the intake air amount is supplied at this time, the ignition combustion is performed. Is done. That is, it is not necessary to increase the fuel supply amount when the fuel supply is restarted, and therefore the shock is not generated because the output torque generated at this time is small.

However, in reality, even if the air supply shutoff valve 50 is fully closed, some fresh air leaks, and therefore, if the period during which the fuel supply is stopped becomes long, the amount of fresh air in the combustion chamber 4 increases. Therefore, when the fuel supply is stopped for a long period of time, when the fuel supply should be restarted, the supply air cutoff valve 50 is temporarily opened partially and fresh air supplied to the combustion chamber 4 is supplied. The amount is controlled to prevent a misfire.

Further, when the period during which the fuel supply is stopped becomes longer and the amount of fresh air in the combustion chamber 4 increases, when the fuel supply is restarted and the charge cutoff valve 50 does not immediately ignite and burn even if the charge cutoff valve 50 is partially opened. There is also. Even if the ignition and combustion do not occur in this way, most of the fuel injected from the air blast valve 9 remains in the cylinder, so that the ignition and combustion will occur when the next fuel injection is performed. By the way, even if fresh air flows into the combustion chamber 4 while the fuel supply is stopped, the absolute amount is much smaller than that in the case where the air supply cutoff valve 50 is not provided, and therefore the fuel The output torque when the supply is restarted is not so large.

As described above, the output torque does not increase so much even if the ignition and combustion are not performed immediately when the fuel supply is restarted.However, compared with the case where the ignition and combustion is started immediately when the fuel supply is restarted, The combustion pressure rises by a large amount. When the combustion pressure rises, the blowdown becomes stronger, so that the amount of fresh air supplied from the air supply port 6 to that cylinder increases, and as a result, the amount of fresh air supplied to the cylinder to which ignition is next performed decreases. Therefore, the ignition combustion in the cylinder in which the ignition is performed next deteriorates. However, if the air supply shutoff valve 50 is partially opened, even if a strong blowdown occurs, the inflow of fresh air from the air supply port 6 to the cylinder is suppressed, and thus ignition is performed next. The fresh air supplied to the cylinder is never reduced.

Next, the control of the air supply shutoff valve 50 will be described with reference to the timing chart shown in FIG. 5 and with reference to FIGS. 6 to 8.

FIG. 6 shows a control routine of the air supply control valve 50,
This routine is executed, for example, by interruption at regular intervals.

Referring to FIG. 6, first, at step 100, the throttle valve is based on the output signal of the throttle switch 78.
It is determined whether 16 is the idling opening degree. If the throttle valve 16 is at the idling opening, step
Proceeding to 101, the engine speed N is the predetermined set speed N
_It is determined whether it is higher than ₀ . When N> N _0, the routine proceeds to step 102, where the flag F1 is set. That is, when the throttle valve 16 is at the idling opening and N> N ₀ , the flag F1 is set. When the flag F1 is set, the operation of the air blast valve 9 is stopped as shown in FIG. 5, and thus the injection of fuel and compressed air from the air blast valve 9 is stopped. Then step 10
In 3, the air supply shutoff valve 50 is fully closed. Next, at step 104, it is judged if the flag F1 was reset in the previous processing routine, that is, if the fuel supply was stopped in this processing routine. When the fuel supply is stopped in the present processing routine, the routine proceeds to step 105, where the comparison value A is calculated from the relationship shown in FIG. In FIG. 8, the horizontal axis represents the engine speed N, and the relationship shown in FIG. 8 is stored in the ROM 72 in advance. Next, at step 106, the count value of the counter C1 is incremented by 1. That is, as shown in FIG. 5, when the flag F1 is set, the counting operation of the counter C1 is started. Next, at step 107, it is judged if the count value of the counter C1 is larger than the comparison value A. If C1> A, the routine proceeds to step 108, where the flag F2 is entered.
Is set. The routine shown in FIG. 6 is executed by a time interrupt, so the count value of the counter C1 represents the elapsed time after the flag F1 is set, that is, the time when the fuel supply is stopped. On the other hand, the comparison value A represents the time until the amount of fresh air in the combustion chamber 4 reaches a certain constant value. When the air supply shutoff valve 50 is fully closed, fresh air is gradually supplied into the combustion chamber 4 every time the engine makes one revolution, so this comparison value A has a high engine speed N as shown in FIG. Becomes smaller. Therefore, if the time during which the fuel supply is stopped becomes longer than the time until the fresh air amount in the combustion chamber 4 reaches a certain constant value, the flag F2 is set as shown in FIG. 5 (B). Will be.

On the other hand, when it is judged at step 100 that the throttle valve 50 is open, or when it is judged at step 101 that it is NN ₀ , the routine proceeds to step 109, where the flag F1 is reset. When the flag F1 is reset, the operation of the air blast valve 9 is started as shown in FIG. 5, and the injection of fuel and compressed air from the air blast valve 9 is restarted. Next, at step 110, the counter C1 is cleared, then at step 111, it is judged if the flag F2 is set or not. When the flag F2 is reset, that is, when the time during which the fuel supply is stopped is short as shown in FIG. 5 (A), the routine proceeds to step 112, where the air supply cutoff valve 112 is immediately fully opened. Be punished.

On the other hand, when the flag F2 is set, that is, when the fuel supply is stopped for a long time as shown in FIG. 5 (B), the routine proceeds to step 113 and the counter C
2 is incremented by 1 and thus the counting up action of the counter C2 is started. Then step 114
Then, the count value of the counter C2 is the preset value B
It is determined whether or not it has become larger than. When C2B, the routine proceeds to step 115, where the supply air cutoff valve 50 is held in the partially open state. On the other hand, if it is determined at step 114 that C2> B, the routine proceeds to step 116, where the flag F2 is reset, and then at step 117, the counter C2 is cleared. Next, in step 112, the supply air cutoff valve 5
0 is fully opened. That is, when the fuel supply is stopped for a long time, the air supply cutoff valve 50 is held in the partially open state until the count value of the counter C2 reaches the set value,
When the count value of the counter C2 exceeds the set value B, the air supply cutoff valve 50 is fully opened.

FIG. 7 shows a control routine of the air blast valve 9, and this routine is executed by interruption every 360 crank angles, for example.

Referring to FIG. 7, first, at step 200, it is judged if the flag F1 is set or not. When the flag F1 is reset, the routine proceeds to step 201, where fuel is injected from the fuel injection valve 41, and then step 20
Proceeding to 2, the on-off valve 33 is opened. At this time, the fuel is injected from the nozzle port 32 together with the compressed air. On the other hand, when the flag F1 is set, the processing routine is immediately completed, so the air blast valve 9 does not operate at all and the fuel supply is stopped.

〔The invention's effect〕

Even if the fuel supply stop period becomes long and the amount of fresh air in the combustion chamber increases, it is possible to prevent misfire when the fuel supply is restarted.

[Brief description of drawings]

FIG. 1 is an overall view of a two-cycle internal combustion engine, FIG. 2 is a plan view of a two-cycle internal combustion engine, FIG. 3 is an enlarged side cross-sectional view of an air blast valve, and FIG. A diagram showing the opening period of the blast valve, etc., FIG. 5 is a time chart showing the control of the air blast valve and the air supply cutoff valve, FIG. 6 is a flow chart for controlling the air supply cutoff valve, and FIG. 7 is A flow chart for controlling the air blast valve, FIG. 8 is a diagram showing the relationship between the comparison value A and the engine speed N. 5 ... Air supply valve, 6 ... Air supply port, 7 ... Exhaust valve, 9 ... Air blast valve, 10 ... Air supply branch pipe, 11 ... Surge tank, 16 ... Throttle valve, 50 ... Air supply shutoff valve.

Front page continued (72) Inventor Takao Tate 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Inventor Yoshio Kido 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Corporation (72) Invention Hirohira Nihei, Toyota-cho, Toyota-cho, Aichi prefecture, Toyota city (56) References JP-A-53-109007 (JP, A)

Claims (1)

(57) [Claims] 1. A supply air cutoff valve is arranged in a supply air passage for supplying fresh air into a combustion chamber, and when the fuel supply is stopped during deceleration operation, the supply air cutoff valve is fully closed. , In a two-cycle internal combustion engine in which the air supply cutoff valve is fully opened when the fuel supply is resumed, when the fuel supply stop period is longer than a predetermined period, when the fuel supply is resumed An air supply control device for a two-cycle internal combustion engine in which a supply air cutoff valve is held in a partially opened state and then fully opened.