JPS62210243A - Boost pressure control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent an engine from misfiring by delaying a lead angle in ignition at the time of knocking and also by increasing fuel in supply whereby lowering boost pressure when an value of increase in fuel becomes a predetermined value or more. CONSTITUTION:In a boost pressure control device of an internal combustion engine equipped with a supercharger A, when the occurrence of knocking is judged by a knocking judging means B, a delay-in-angle control device C causes an ignition timing at the time of knocking to be delayed in angle by a specified angle, furthermore a fuel increase control means D increases fuel in supply at the time of knocking for restraining knocking. In this case, when an value of increase in fuel becomes a predetermined value or more, a supercharge control means E controls the supercharger A to lower supercharging pressure for preventing an excessively rich condition. Owing to this constitution, the misfire of an engine is prevented, accordingly the maximum boost pressure can be set up by considering only atmospheric condition and the time when fuel of a designated octane number is used for enhancing the output of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for controlling boost pressure depending on the state of occurrence of knocking.

[Conventional technology]

Knocking that occurs in spark-ignited internal combustion engines depends on factors such as fuel octane number, ignition timing, engine temperature, intake air temperature, compression pressure, and intake air humidity.

Anti-knock control methods and devices (commonly referred to as knock control systems) for preventing the occurrence of knocking or reducing the level of knocking are well known. This method determines the basic advance value (θ8) of the ignition timing according to the rotation speed and load, and retards the ignition timing according to the state of knocking detected by a vibration, sound, or cylinder pressure detection element called a knock sensor. Calculate the correction value (θK) and calculate the final execution lead angle value (θ
□) is calculated (θEX←θ6−θ), and this execution lead angle value (θ
The ignition is performed based on EX). That is, as the knocking frequency and knocking level increase, the retardation correction value (θ) is increased, and the ignition timing is controlled so that the frequency and level are below the allowable limit.

On the other hand, if the ignition timing is retarded, the exhaust gas temperature will rise, which may expose exhaust system components to high temperatures and shorten their lifespan. Therefore, conventionally, when the exhaust gas temperature is likely to rise, the air-fuel ratio of the air-fuel mixture is set to a rich state to suppress the rise in the exhaust gas temperature.

[Problem that the invention seeks to solve]

In an internal combustion engine equipped with a supercharger, even if the ignition timing retard amount is O, the air-fuel mixture is usually kept richer than the output air-fuel ratio in order to keep the exhaust temperature below a predetermined value. . Therefore, as mentioned above, if the retard amount is increased depending on the state of occurrence of knocking, and the fuel supply amount is further increased accordingly, the air-fuel ratio becomes rich beyond the misfire limit value, which causes the engine to A problem arises in that there is a risk of misfire.

[Means for solving problems]

The supercharging pressure control device according to the present invention is a supercharging pressure control device for an internal combustion engine equipped with a supercharger A, as shown in the configuration diagram of the invention in FIG. a retardation amount control means C for retarding the spark advance when knocking occurs; a fuel increase control means for increasing the amount of fuel supplied when knocking occurs; and a fuel increase value. The present invention is characterized in that it includes a supercharger control means E that reduces the supercharging pressure when the supercharging pressure is equal to or higher than a predetermined value.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments.

FIG. 2 shows an internal combustion engine to which an embodiment of the present invention is applied. In this figure, 10 is a cylinder block of a 4-cycle, 4-cylinder internal combustion engine, and 12 is a knock sensor attached to the cylinder block 10. The knock sensor 12 is
For example, it is a vibration detection element such as a piezoelectric element or an electromagnetic element. 14 is a turbocharger main body, 16 is a compressor provided in the intake passage, and 18 is an exhaust turbine provided in the exhaust passage. A wastegate valve 22 for controlling boost pressure is provided in the bypass passage 20 of the turbine 18 . The wastegate valve 22 is actuated by a diaphragm actuator 24.
operates with pressure fed from the intake passage downstream of the compressor 16 via a pressure conduit 30. Note that 26 is a pressure conduit for releasing part of the pressure to the upstream side of the compressor when the solenoid valve 28 is opened. Therefore, the solenoid valve 28
By opening and closing, the pressure applied to the actuator 24 changes, and the supercharging pressure is controlled via the wastegate valve 22. The pressure conduits 26 and 30 are provided with throttles 27 and 31 so that the above control can be performed smoothly.

32 indicates a distributor, and this distributor 32 is provided with crank angle sensors 34 and 36. The crank angle sensor 34 is for cylinder discrimination, and generates one pulse every time the distributor shaft makes one revolution, that is, every two revolutions of the crankshaft (every 720° CA).

The occurrence position is set, for example, to a position slightly before the top dead center of the first cylinder. The crank angle sensor 36 generates 24 pulses for each rotation of the distributor shaft, and thus a pulse for every 30'' of crank angle.

Electrical signals from the knock sensor 12 and crank angle sensors 34 and 36 are sent to a control circuit 38. Control circuit 3
8 is further fed with a signal representing the intake air flow rate from an air flow meter 40 provided in the intake passage upstream of the compressor.

On the other hand, the control circuit 38 outputs a fuel injection signal to the fuel injection valve 48 every rotation of the engine, and outputs a rectangular wave-like drive signal to the electromagnetic valve 28.

Further, the control circuit 38 outputs an ignition signal to the igniter 42, and the spark current generated by the igniter 42 and the ignition coil 44 is distributed to the spark plugs 46 of each cylinder via the distributor 32.

Engines are typically provided with various other sensors that detect operating condition parameters.

FIG. 3 is a block diagram showing an example of the configuration of the control circuit 38 in FIG. 2. The voltage signal from air flow meter 40 is passed through buffer 50 to analog multiplexer 52.
The signal is selected according to an instruction from the microcomputer and applied to the A/D converter 54, where it is converted into a binary signal and then taken into the microcomputer via the input/output port 56.

Pulses for every 720 degrees of crank angle from the crank angle sensor 34 and pulses for every 30' of crank angle from the crank angle sensor 36 are sent to the microcomputer via buffers 58 and 60 and input/output capotro 2, respectively.

The output signal of the knock sensor 12 has a buffer for impedance conversion and a frequency band specific to knocking (7 to 8
KH2) is sent to a peak hold circuit 66 and a rectifier circuit 68 via a circuit 64 consisting of a bandpass filter having a pass band. Peak hold circuit 66 is connected to line 78
Only when a "1" level signal is applied from the microcomputer via the input/output capotro 2, the output signal from the knock sensor 12 is taken in and the maximum amplitude is held. peak hold 1lffl road 6
The output of A 6 is sent to an analog multiplexer 70 and selected according to instructions from the integrated microcomputer.
After being applied to the /D converter 72 and changed into a binary signal,
The data is taken into the microcomputer via the input/output capotro 2. The rectifier circuit 68 performs full-wave rectification or half-wave rectification of the output signal from the knock sensor 12. The rectified signal is fed into an integration circuit 74 and integrated with respect to time. Therefore, the output of the integrating circuit 74 is
This value is the average of the amplitudes of the output signals.

The output of the integrating circuit 74 is sent to the analog multiplexer 70, selectively applied to the A/D converter 72, converted into a binary signal, and then taken into the microcomputer. However, when the A/D converter 72 starts A/D conversion,
This is done by an A/D conversion start signal applied from the microcomputer via the input/output capotro 2 and line 7-6. Furthermore, when the A/D conversion is completed, the A/D converter 72
notifies the microcomputer of the completion of A/D conversion via line 78 and input/output capotro 2.

On the other hand, when an ignition signal is outputted from the microcomputer to the drive circuit 80 via the input/output capotro 2, this is amplified and the igniter 42 is energized, causing ignition according to the duration and duration of the ignition signal. Control takes place.

Further, when a 1-bit control signal is output from the microcomputer to the drive circuit 82 via the input/output capotro 2, this is converted into a drive signal to turn on/off the solenoid valve 28, and the control signal causes the actuator 24 to be turned on and off. The applied pressure is controlled, thereby controlling the boost pressure.

Furthermore, when a fuel injection signal is output from the microcomputer to the drive circuit 84 via the input/output capotro 2, this signal is amplified and the fuel injection valve 48 is turned on and off, and the air-fuel ratio is controlled by changing the on time. Ru.

A control circuit 38 consisting of a microcomputer includes the aforementioned input/output ports 56 and 62, and a microprocessor (M
PU) 84, random access memory (RAM) 86
, a read-only memory (ROM) 88, a clock generation circuit (not shown), a memory wi control circuit, a bus 90 connecting these, etc., and performs various processing according to a control program described later stored in the ROM 8B. Execute.

Next, the operation of the microcomputer will be explained using the flowchart shown in FIG. 4(a), Cb').

The ignition control routine in Figure 4(a) is based on a crank angle of 180°.
executed every time. In steps 101 to 107, a retard angle correction value θ is determined based on the knocking occurrence state, and an execution advance angle value θI! The procedure for calculating × is shown. In step 101, it is determined whether or not knocking has occurred in the combustion that was ignited immediately before. That is, the integrating circuit 74 of the knock sensor 12
The knock judgment level is obtained by multiplying the binary value obtained by A/D converting the output from the knock sensor 12 by a predetermined value, and the binary value obtained by A/D converting the output from the peak hold circuit 66 of the knock sensor 12 is If it is higher than this determination level, it is determined that knocking has occurred, and if it is lower than this determination level, it is determined that knocking has not occurred.

When it is determined in step 101 that "knocking has occurred",
The process proceeds to step 106, where 0.5° is added to the retard angle correction value (θ←θ, 5°), and the process proceeds to step 105.

On the other hand, if it is determined in step 101 that there is no knocking, the process proceeds to step 102, where 1 is added to the value CKNOCK of the missing knocking counter provided in the IIAM 86 (GKNOGK-CKNOXK+1).
Continuation <In step 103, the counter tICKNOCK is 2.
Determine whether it is 0 or more and if “NO”, step 107
Proceed to. If the determination result in step 103 is "YES", that is, if the number of times that knocking is not detected is 20 or more, the process proceeds to step 104, where the retardation correction value θ is determined.

The value obtained by subtracting 0.5° from is set as the new retard angle correction value θ
, −0.5°), the process proceeds to step 105.

In this way, the reason why θ is not decreased unless knocking occurs 20 times or more in steps 102 to 104 is to avoid erroneous judgments, and the advance of the ignition timing (that is, the decrease in θ) is delayed. It will be held soon. On the other hand, if it is determined that knocking has occurred even once, 08 is incremented in step 106, and the ignition timing is immediately retarded.

In step 105, the counter is reset to zero, and in step 107
Proceed to. By repeating the above steps, the retardation correction value θ8 increases when knocking occurs and decreases when knocking does not occur, but the knocking sound at a predetermined minute level continues to occur while θ remains balanced. Similarly, the determination level in step 101 is set in advance.

In step 107, the execution advance value θEK is obtained by subtracting the retardation correction value θ from the ignition timing basic advance value θ.
8-θK). In this step, the crank angle sensor 34
, 36, the intake air IQ is determined from the output signal from the air flow meter 40, the engine load Q/N is determined from Q and N, and the deceptively obtained N and Q/H are determined. Based on the basic lead angle map or table, the basic lead angle value θ is determined by interpolation calculation or the like. Therefore, a basic advance angle map or table is stored in the ROM 88 in advance. This basic advance angle map or table is set so that a knocking sound of a predetermined level is generated when the engine load Q/N is high and when high octane fuel is used. Generally, when high octane fuel is used, a certain level of knocking noise is generated at high load, and the retardation correction value θ is approximately 0 to 3 degrees.On the other hand, when low octane fuel is used, θ is approximately Become bigger.

After step 107, the process proceeds to step 108, where the execution lead angle value θ is determined. The time to turn on the igniter 42 is determined from the current time, and the on time is set in the output register provided in the input/output capotro 2. This completes this ignition control routine, and when the set on time arrives, the igniter 4
A high voltage current flows from the spark plug 2 to the spark plug 46, and the air-fuel mixture is ignited by a spark.

The boost pressure control routine shown in FIG. 4(b) is started every engine revolution, and is usually 30 to
It is activated with a delay of 60°CA.

In step 201, the fuel injection valve 48 is turned on to start fuel injection.

In step 202, a basic fuel increase value FOTPB is calculated. That is, based on the engine speed N and the engine load Q/N, a basic increase value FOTPB is determined by interpolation calculation using a basic increase map or table.

For this reason, a basic increase map or table is stored in the ROM 8B in advance. This basic increase map or table is used to obtain a fuel increase value that will bring the exhaust temperature to a predetermined value when the ignition timing is set to the basic advance value determined from the basic advance angle map or table. Next, in step 203, the retard angle correction value θ is multiplied by a constant (for example, 1%/1°) to obtain a knock correction increase value FOTPK.
Calculate. This is to find the increase value necessary to achieve a predetermined exhaust temperature determined in advance by experiment.Instead of such calculation, the knock increase value FOTPK for the retardation correction value θa is prepared in advance in a table. It is also possible to calculate the value from this table by interpolation calculation or the like. Therefore, in step 204, the basic increase value FOTPB
Add the knock increase value FOTPK to and execute this to obtain the increase value FOTPII! Let it be X.

In step 205, it is determined whether the solenoid valve 28 is on, that is, whether the supercharging pressure is set high. If it is on, the process proceeds to step 208, and if it is off, the process proceeds to step 206.

In step 7 208, it is determined whether the execution increase value FOTPEX obtained in step 204 is greater than or equal to the maximum increase value FOTPMAX. This maximum increase value FOTPMAX is the maximum value of the fuel increase that will not cause a misfire even if the manufacturing error of the fuel injection valve 4 and the air flow meter 40 are taken into consideration. If the execution increase value POTPEX does not reach the maximum increase value FOTPMAX in step 208, step 211
However, if the maximum increase value FOTPMAX has been reached, the process proceeds to step 209, where the maximum increase value FOTPMAX is replaced with the effective increase value FOTPEX, and in step 210, the solenoid valve 28 is turned off, that is, the supercharging pressure is lowered, and the process proceeds to step 211.

In this way, for example, when low octane fuel is used, when the temperature is high, or when the engine temperature is abnormally high due to a failure in the engine cooling system, knocking becomes more likely to occur, and the retardation correction value θ8 becomes larger, causing the actual amount to be increased. Value FOTPEX
When the amount reaches the maximum increase value FOTPMAX, the boost pressure is set low.

On the other hand, if it is determined in step 205 that the solenoid valve 28 is in the OFF state, that is, the supercharging pressure is set low, the process proceeds to step 206. In step 206, the execution increase value F
If OTPEX is smaller than the value obtained by subtracting the old hysteresis S from the maximum increase value FOTPMAX, the solenoid valve 28 is turned on and the supercharging pressure is set high, and the process proceeds to step 211. Conversely, if the executed increase value FOTPEX is larger, the solenoid valve 28 is turned on. is maintained in that state and the process proceeds to step 211. That is, for example, steps 209 and 210 were executed during the previous execution of this boost pressure control routine, and the maximum increase i(iFOTP
When MAX is set to the execution increase value FOTPEχ and the set boost pressure is lowered, step 20 is executed in this execution.
Step 6 then proceeds to step 211. Note that when the set boost pressure decreases, knocking becomes less likely to occur (so the retardation correction value θ
, gradually decreases (see step 104 in FIG. 4(a)), and accordingly, the execution increase value FOTPHX also decreases (see steps 203 and 204 in FIG. 4(b)). Therefore, the execution increase value FOTPEX is the maximum increase value FOTPMA.
When it becomes smaller than the value obtained by subtracting the hysteresis old S from X,
In step 207, the solenoid valve 28 is turned on,
The set boost pressure is increased.

Here, the hysteresis old S is the effective increase value F when, for example, low octane fuel is used and the set boost pressure is low.
The size is selected so that OTPEK does not become smaller than (maximum increase value FOTPMAX - hysteresis old S), and therefore, if the set boost pressure decreases using low octane fuel, high octane fuel will be refueled next. The set boost pressure will not be increased until the

In step 211, the basic injection time TAUB obtained from the engine load Q/N is multiplied by the effective increase value FOTPEX to obtain the effective injection time TAU. Next, in step 212, the off time of the injection valve 48 determined from the effective injection time TAU is determined. Calculate, set, and exit this routine. When the off time comes, the power supply to the injection valve 48 is cut off, and fuel injection ends.

〔Effect of the invention〕

As described above, according to the present invention, knocking is likely to occur due to some cause such as the use of low octane fuel, and even if the amount of retardation of the ignition timing is set large and the amount of fuel is increased, the engine This prevents the risk of misfire. Therefore, the maximum boost pressure can be set taking into account only standard atmospheric conditions and when using a specified octane fuel, making it possible to improve engine output.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the invention, Fig. 2 is a sectional view showing an internal combustion engine to which an embodiment of the invention is applied, Fig. 3 is a diagram showing a control circuit, and Fig. 4(a) is a diagram of an ignition control routine. Flowchart FIG. 4(b) is a flowchart of the boost pressure control routine. 14...Turbocharger, 20...Wastegate valve, 38...Control circuit, 48 River fuel injection valve. 3 times (a) Figure 4/Id + Seal-1

Claims (1)

[Claims] 1. A supercharging pressure control device for an internal combustion engine equipped with a supercharger, comprising a knocking determination means for determining whether or not knocking is occurring, and a retardation amount for retarding the ignition advance angle when knocking occurs. An internal combustion engine characterized by comprising a control means, a fuel increase control means for increasing the amount of fuel supplied when knocking occurs, and a supercharger control means for reducing the supercharging pressure when the increase in fuel amount is equal to or higher than a predetermined value. Engine boost pressure control device.