JP2522409B2 - Fuel injection control device for two-cycle internal combustion engine - Google Patents

Description

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

[Conventional technology]

In a two-cycle internal combustion engine, all of the intake air supplied to the engine cylinder does not contribute to combustion, and some intake air blows into the exhaust passage without contributing to combustion. Therefore, if the amount of intake air supplied to the engine cylinder is determined and the fuel injection amount is determined from this intake air amount so that the air-fuel ratio becomes the target air-fuel ratio, a part of the intake air will blow through, and the actual The air-fuel ratio becomes richer than the target air-fuel ratio, and the actual air-fuel ratio in the engine cylinder cannot match the target air-fuel ratio.

By the way, the blow-through amount of intake air changes according to the operating state of the engine, but the blow-through amount in a specific steady operating state is constant. Therefore, if the blow-through amount in various steady operation states is obtained in advance by experiments, the blow-through amount of the intake air can be known if the current operating state of the engine is known.

Then, the intake air amount and the blow-through amount supplied into the engine cylinder in various steady operation states are measured to measure the fresh air trapping coefficient {(intake air amount-blowing amount) / intake air amount},
That is, the ratio of the fresh air remaining in the engine cylinder is previously obtained by an experiment, the fresh air trapping coefficient obtained by this experiment is stored in advance, and the fresh air trapping coefficient corresponding to this operating state is detected by detecting the operating state of the engine. And measure the amount of intake air,
Two cycles in which the intake air amount that actually contributes to combustion is obtained from the measured intake air amount and the fresh air capture coefficient, and the fuel injection amount is determined from this intake air amount so that the air-fuel ratio becomes the target air-fuel ratio. Internal combustion engines are known (Japanese Patent Laid-Open No. 63-1832).
31 to JP-A-63-183236). In these two-cycle internal combustion engines, the fuel injection amount is determined with respect to the intake air amount that actually contributes to combustion, so that the actual air-fuel ratio in the engine cylinder can be made to match the target air-fuel ratio.

[Problems to be Solved by the Invention]

However, the blow-through amount of intake air during steady operation differs from the blow-through amount of intake air during transient operation, and the difference between the blow-through amount during steady operation increases as the transient state becomes more severe. Therefore, when the fuel injection amount is calculated based on the amount of blow-through during steady operation even during transient operation such as in the above-described two-cycle internal combustion engine, the intake air amount that actually contributes to combustion differs during transient operation. There is a problem that the actual air-fuel ratio in the engine cylinder cannot match the target air-fuel ratio.

[Means for solving the problem]

In order to solve the above problems, according to the present invention, as shown in the configuration diagram of the invention of FIG. 1, the actual air-fuel ratio in the engine cylinder during steady operation becomes a predetermined target air-fuel ratio. Fuel injection time storage means A that stores the fuel injection time according to the steady operating state, transient operating state detecting means B that detects the transient operating state, and the actual air-fuel ratio in the engine cylinder during the transient operating state is the above-mentioned space. A correction value storage unit C that stores a correction value for the above-mentioned fuel injection time according to the transient operating state so as to obtain a fuel ratio, and an actual fuel injection time according to the operating state of the engine from the above-mentioned fuel injection time and the correction value. And a fuel injection time calculation means D for calculating

[Work]

During the transient operation, the fuel injection time is corrected by the correction value so that the actual air-fuel ratio in the period cylinder becomes the target air-fuel ratio.

〔Example〕

FIG. 2 shows an overall view of the two-cycle internal combustion engine. Referring to FIG. 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, and 4 is formed between the piston 2 and the cylinder head 3. Combustion chamber, 5 air supply valve, 6 air supply port, 7 exhaust valve, 8 exhaust port,
Reference numerals 9 respectively denote air blast valves that inject fuel into the combustion chamber 4 together with compressed air. 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 Throttle valve in the air supply duct 13
16 are placed.

FIG. 3 shows an enlarged sectional view of the air blast valve 9. Third
Referring to the figure, a straight compressed air passage 31 is formed in the housing 30 of the air blast valve 9, and a nozzle port 32 located in the combustion chamber 4 (Fig. 2) is formed at the tip 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. 2, an air blast air passage 17 is branched from the air supply duct 13 between the air flow meter 14 and the throttle valve 16, and the air blast air passage 17 includes 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. 2, the exhaust valve 7 opens before the intake valve 5 and closes before the intake valve 5. 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. 2, a mask wall 23 is formed on the inner wall surface of the cylinder head 3 to cover the opening of the air supply valve 5 on the exhaust valve 7 side for 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 peripheral wall surface of the combustion chamber 4 as shown by the arrow S, and thus good loop scavenging is performed.

As shown in FIG. 2, the air blast valve 9 is controlled based on the output signal of the electronic control unit 50. The electronic control unit 50 includes a ROM (read only memory) 52, a RAM (random access memory) 53, a CPU (microprocessor) 54,
It has an input port 55 and an output port 56. The air flow meter 14 generates an output voltage proportional to the amount of intake air, and this output voltage is input to an input port 55 via an AD converter 57. A throttle sensor 24 for detecting the throttle valve opening is attached to the throttle valve 16, and the output signal of this throttle sensor 24 is input through an AD converter 58 to an input port.
Entered in 55. Further, the output signal of the rotation speed sensor 25 representing the engine rotation speed is input to the input port 55. On the other hand, the output port 56 is connected to the solenoid 37 and the fuel injection valve 41 of the air blast valve 9 via the corresponding drive circuits 59 and 60.

In the present invention, the fuel injection time TAU is calculated based on the following equation.

TAU = K ・ TP ・ Fb ・ C TP = Tb ・ Fa where K is a constant, Tb is the basic fuel injection time Fa is a fresh air capture coefficient, that is, the cylinder air residual rate Fb is a transient correction coefficient, and C is the engine cooling water temperature. It is a correction coefficient based on the above.

The basic fuel injection time Tb is a function of the engine load Q / N (intake air amount Q supplied to the engine cylinder / engine speed N) and the engine speed N, and the total intake air supplied to the engine cylinder is It represents the fuel injection time required to bring the air-fuel ratio in the engine cylinder to the target air-fuel ratio, assuming that the air-fuel ratio remains in the cylinder without being blown through.

On the other hand, the in-cylinder air residual rate Fa is an experimental value obtained by actually measuring the amount of blown-in intake air during steady operation, and this in-cylinder air residual rate Fa is {(intake air amount Q supplied to the engine cylinder Q -Blow-through amount) / intake air amount Q} supplied into the engine cylinder. This in-cylinder air residual ratio Fa is the engine load Q / N and engine speed N during steady operation.
Is a function of.

Therefore, the fuel injection time TP, which is obtained by multiplying the basic fuel injection time Tb by the in-cylinder air residual ratio Fa, represents the fuel injection time required to set the actual air-fuel ratio in the engine cylinder to the target air-fuel ratio during steady operation. Hereinafter, this fuel injection time TP will be referred to as a basic fuel injection time in consideration of blow through. The basic fuel injection time TP considering this blow-through is stored in advance in the ROM 52 in the form of a map as a function of the engine load Q / N and the engine speed N, as shown in FIG. Therefore, as long as the engine is operating steadily, the actual air-fuel ratio in the engine cylinder can be maintained at the target air-fuel ratio by calculating the fuel injection time based on the map shown in FIG.

However, when the fuel injection time is calculated based on the map shown in FIG. 5 during the transient operation, the actual air-fuel ratio in the engine cylinder deviates from the target air-fuel ratio. The reason will be described below. That is, when the engine load increases, the pressure in the exhaust passage, that is, the back pressure, increases, and the blow-through amount is greatly affected by this back pressure. Therefore, for example, if the back pressure increases in response to an increase in the opening degree of the throttle valve 16 during engine acceleration operation, the actual air-fuel ratio in the engine cylinder does not deviate from the target air-fuel ratio. However, in actuality, the back pressure does not immediately increase even when the opening degree of the throttle valve 16 increases during engine acceleration operation, and therefore when acceleration starts, the blow-through amount increases compared to during steady operation at the same throttle valve opening degree. Will be done. The rate of increase in the blow-through amount increases as the degree of acceleration increases. If the amount of blow-through increases, the actual air-fuel ratio in the engine cylinder becomes richer than the target air-fuel ratio.Therefore, in order to make the actual air-fuel ratio in the engine cylinder the target air-fuel ratio, the fuel injection increases as the degree of acceleration increases. I have to shorten the time. On the other hand, during engine deceleration operation, the back pressure does not immediately decrease even when the opening of the throttle valve 16 becomes small, and therefore the blow-through amount decreases.
If the amount of blow-through decreases, the actual air-fuel ratio in the engine cylinder becomes leaner than the target air-fuel ratio, so the degree of deceleration is large in order to make the actual air-fuel ratio in the engine cylinder the target air-fuel ratio during deceleration operation. Indeed, the fuel injection time must be lengthened.

Therefore, the transient correction coefficient Fb is introduced to correct the basic fuel injection time TP so that the actual air-fuel ratio in the engine cylinder becomes the target air-fuel ratio during transient operation. FIG. 6 shows an example of this transient correction coefficient Fb. In FIG. 6, the change rate ΔT of the opening of the throttle valve 16 is shown as a transient state.
The transient correction coefficient Fb decreases as the rate of change ΔT of the opening of the throttle valve 16 increases in the positive direction, that is, as the degree of acceleration increases.
16 As the rate of change ΔT of the opening increases in the negative direction,
That is, the transient correction coefficient Fb increases as the degree of deceleration increases. The relationship shown in FIG. 6 is stored in advance in the ROM 52. It should be noted that instead of using the rate of change ΔT of the opening of the throttle valve 16 to represent the transient state, the throttle valve 16
It is also possible to use the change rate ΔP of the downstream intake air pressure.

FIG. 7 shows a routine for calculating the rate of change ΔT of the opening of the throttle valve 16 and this routine is executed by interruption at regular time intervals.

Referring to FIG. 7, in this routine, in step 70, the throttle opening change rate ΔT is subtracted from the current throttle valve opening TA based on the output signal of the throttle sensor 24 by the throttle opening TA ₁ in the previous interruption routine. Is required.

FIG. 8 shows a routine for calculating the fuel injection time, and this routine is executed by interruption every constant crank angle.

Referring to FIG. 8, first, at step 80, the basic fuel injection time TP considering blow-through is calculated from the output signals of the air flow meter 14 and the rotation speed sensor 25 based on the map shown in FIG. Next, at step 81, the correction coefficient C by the engine cooling water temperature etc. is calculated, then at step 82, the transient correction is made from the latest throttle valve opening change rate ΔT obtained in the routine of FIG. 7 based on the relationship shown in FIG. The coefficient Fb is calculated. Next, at step 83, the actual fuel injection time TAU is calculated based on the following equation.

TAU = K / TP / Fb / C [Effect of the invention] Even during transient operation, the actual air-fuel ratio in the engine cylinder can be maintained at the target air-fuel ratio.

[Brief description of drawings]

FIG. 1 is a block diagram of the invention, FIG. 2 is an overall view of a two-cycle internal combustion engine, FIG. 3 is an enlarged side sectional view of an air blast valve, and FIG. 4 is an opening period of an air supply / exhaust valve, an air blast valve. FIG. 5 is a plug diagram showing a valve opening period, etc., FIG. 5 is a diagram showing a basic fuel injection time in consideration of blow-through, FIG. 6 is a diagram showing a transient correction coefficient,
FIG. 8 is a flowchart for calculating the throttle valve opening change rate, and FIG. 8 is a flowchart for calculating the fuel injection time. 4 ... Combustion chamber, 5 ... Air supply valve, 9 ... Air blast valve, 16 ... Throttle valve, 24 ... Throttle sensor.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Kei Nomura 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (56) Reference JP-A-63-208635 (JP, A)

Claims (1)

(57) [Claims] 1. A fuel injection time storage means for storing fuel injection time according to a steady operation state so that an actual air-fuel ratio in an engine cylinder during a steady operation becomes a predetermined target air-fuel ratio, and a transient operation. A transient operation state detecting means for detecting the state, and a correction value memory for storing a correction value for the fuel injection time according to the transient operation state so that the actual air-fuel ratio in the engine cylinder during the transient operation becomes the target air-fuel ratio. A fuel injection control device for a two-cycle internal combustion engine, comprising: a fuel injection time calculation means for calculating an actual fuel injection time according to an operating state of the engine from the fuel injection time and the correction value.