JPH0323738B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a digital control method for an internal combustion engine, and is particularly suitable for use in an automobile engine equipped with a digital control device. This invention relates to improvements in digital methods for controlling internal combustion engines.

BACKGROUND OF THE INVENTION In recent years, with the development of electronic control technology, especially digital control technology, digital control has been introduced to internal combustion engines such as automobile engines. When introducing digital control to an automobile engine,
A computer repeatedly calculates the fuel injection amount and ignition timing depending on the engine operating state, and digitally controls the engine fuel injection amount and ignition timing. Conventionally, as a method for repeatedly calculating the fuel injection amount and ignition timing within a computer, calculations are repeatedly performed within the main routine at a fixed time interval, for example, every 2 to 6 milliseconds.According to this method, Fuel injection amount and ignition timing can be quickly calculated without using an interrupt routine.

[Problem to be achieved by the invention]

However, in general, calculation of fuel injection amount and ignition timing involves a large number of calculation items.
it takes time. Therefore, if both calculations are repeated unconditionally in the main routine, the burden on the program will be extremely large, and the cycle time on the main program will be slow to about every 10-odd milliseconds. During calculation of injection quantity or ignition timing,
For a long time, I had the disadvantage of not being able to do any other work. In order to solve the above-mentioned drawbacks, a method may be considered in which, for example, the fuel injection amount is calculated in synchronization with the engine crank angle in the interrupt routine. According to this method, there is no wasted calculation and the latest data can be obtained, but on the other hand, the burden on the interrupt routine is heavy, and other work cannot be done during that time. In addition, in the case of multiple interrupts, for example,
161926, 56-23527, 55-137358, or
It is necessary to make the interrupt routine wait temporarily. Furthermore, if the fuel injection amount is calculated at the same crank angle regardless of the engine speed, when the engine speed is high, there is a risk that the calculation of the fuel injection amount will not be in time for the fuel injection timing. On the other hand, if the fuel injection amount is always calculated early in conjunction with high engine speeds, there are problems such as calculation data becoming outdated during low engine speeds. It is also conceivable to calculate the basic injection amount, which changes rapidly, in an interrupt routine, and calculate the correction coefficient, which changes little, in the main routine, but this has the problem of increasing the burden of the interrupt routine. Furthermore, Japanese Patent Application Laid-open No. 137320/1983 discloses that the activation period of a time synchronization routine can be varied according to the engine speed, but this means that the higher the engine speed, the shorter the activation period. Therefore, the number of executions per predetermined time is simply brought closer to the number of executions with crank angle synchronization (the higher the engine speed, the greater the number of executions per unit time). The present invention has been made to solve the above-mentioned conventional drawbacks, and it is possible to substantially synchronize the calculation of the fuel injection amount with the crank angle, and to perform the calculation at the appropriate time based on the latest data without waste. It is therefore an object of the present invention to provide a digital control method for an internal combustion engine that can reduce the burden on a digital control circuit without reducing the responsiveness of engine control.

[Means to achieve the task]

The present invention provides a digital control method for an internal combustion engine in which the fuel injection amount of the engine is controlled by the fuel injection amount repeatedly determined according to the engine operating state. A fuel injection amount calculation flag is set at a crank angle of The above object is achieved by determining the state and calculating the fuel injection amount in the routine when the flag is set.

[Effect]

According to the present invention, since the engine rotation interrupt routine only sets the fuel injection amount calculation flag, the burden on the engine rotation interrupt routine, which has a high priority and little margin, is lightened, and other important tasks can also be processed. can. Furthermore, when the engine speed is low, the cycle for setting the flag will inevitably become longer, so the cycle for calculating the fuel injection amount will also become longer.
The burden on the digital control circuit is small. Furthermore, the actual calculation of the fuel injection amount is performed in the main routine, which has a lower priority than the engine rotation interrupt routine, depending on the state of the flag.
It is possible to calculate the fuel injection amount with high precision, including a large number of calculation items. Furthermore, since no calculation is performed unless the flag is set, the calculation can be performed at an appropriate time without waste. Furthermore, since the crank angle at which the flag is set is advanced when the engine speed is high,
This prevents the fuel injection amount calculation performed in a low priority routine such as the main routine when the engine speed is high from not being able to meet the fuel injection timing, or conversely, the calculation data becoming outdated when the engine speed is low. , it is possible to accurately determine the fuel injection amount based on the latest data at the appropriate time.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a digital control device for an automobile engine employing a digital control method for an internal combustion engine according to the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, this embodiment includes an air cleaner 12 for taking in outside air, an intake air temperature sensor 14 for detecting the temperature of the intake air taken in from the air cleaner 12, and a throttle body 16. A throttle valve 18 for controlling the flow rate of intake air, which opens and closes in conjunction with an accelerator pedal (not shown) disposed in the driver's seat, and whether or not the throttle valve 18 is at an idle opening. a throttle sensor 20 including a potentiometer that generates a voltage output proportional to the opening degree of an idle switch and throttle valve 18 for detecting whether or not the throttle valve 18 is open; a surge tank 22 for preventing intake air interference between cylinders; An intake pipe pressure sensor 23 for detecting intake pipe pressure from the pressure in the surge tank 22, a bypass passage 24 that bypasses the throttle valve 18, and the bypass passage 24 disposed in the middle of the bypass passage 24. an idle rotation control valve 26 for controlling the idle rotation speed by controlling the opening area of the engine 10; and an injector 3 disposed in the intake manifold 28 for injecting fuel toward the intake port of the engine 10.
0, an oxygen concentration sensor 34 disposed in the exhaust manifold 32 for detecting the air-fuel ratio from the residual oxygen concentration in the exhaust gas, and the exhaust manifold 32
A three-way catalytic converter 38 disposed in the middle of the exhaust pipe 36 on the downstream side, a distributor 40 having a distributor shaft that rotates in conjunction with rotation of the crankshaft of the engine 10, and the distributor 40. A top dead center sensor 42 and a crank angle sensor 44, which respectively output a top dead center signal and a crank angle signal in accordance with the rotation of the distributor shaft, are built in, and an engine cooling water temperature sensor is installed in the engine block. A basic injection amount per engine stroke is determined based on the engine rotational speed determined from the intake pipe pressure output from the intake pipe pressure sensor 23 and the crank angle signal output from the crank angle sensor 44. The amount of fuel injection can be calculated by correcting this according to the output of the throttle sensor 20, the air-fuel ratio of the output of the oxygen concentration sensor 34, the engine cooling water temperature of the output of the cooling water temperature sensor 46, etc. is determined and outputs a valve opening time signal to the injector 30, ignition timing is similarly determined according to the engine operating condition and an ignition signal is output to the igniter-equipped coil 52, and further, the idle rotation control is performed at idle. Digital control circuit 54 controlling valve 26
In the digital control device for the automobile engine 10, in the engine rotation interrupt routine of the digital control circuit 54, when the engine speed is high, a fuel injection amount calculation flag is set at a predetermined crank angle that is set to the advance side. is set, the state of the flag is determined in a main routine having a lower priority than the engine rotation interrupt routine, and when the flag is set, calculation of the fuel injection amount is executed in the main routine. This is how it was done. As shown in detail in FIG. 2, the digital control circuit 54 is a central processing unit (hereinafter referred to as CPU) consisting of a microprocessor that performs various arithmetic operations.
60, the intake temperature sensor 14, the potentiometer of the throttle sensor 20, and the intake pipe pressure sensor 2.
3. An analog input port 62 with a multiplexer for converting analog signals input from the oxygen concentration sensor 34, cooling water temperature sensor 46, etc. into digital signals and sequentially inputting them to the CPU 60; and an idle switch for the throttle sensor 20; Digital signals input from the top dead center sensor 42, crank angle sensor 44, etc. are sent to the CPU 60 at a predetermined timing.
a digital input port 64 for importing into the computer; a read-on memory (hereinafter referred to as ROM) 66 for storing programs or various constants, etc.;
Random access memory (hereinafter referred to as RAM) for temporarily storing calculation data etc. in the CPU 60
) 68, a backup random access memory 70 which can be supplied with power from an auxiliary power source and retain its memory even when the engine is stopped, and the calculation results of the CPU 60 are transmitted to the idle rotation control valve 26, injector 30, and coil with igniter at a predetermined timing. 52, etc., and a common bus 74 that connects each of the above-mentioned component devices. The effects of the embodiment will be explained below. The digital control circuit 54 has its ROM 66
Arithmetic processing is performed according to a main routine stored in the computer, for example as shown in FIG. That is, in steps 101 arranged at various places in the main routine, it is determined whether or not the TAU calculation flag is set, and if the determination result is positive, the TAU calculation flag is reset in step 102. Next, in step 103, the fuel injection time TAU is calculated. After the calculation is completed, or if the judgment result in step 101 is negative, the process advances to the next step in the main routine. Since it is necessary to discover the TAU calculation flag in the main routine in a short time, the steps 101 to 103 are arranged at various locations in the main routine. TAU calculation step 103 in the main routine
Setting the TAU calculation flag to activate
This is performed by an engine rotation interrupt routine synchronized with the crank angle as shown in FIG. That is, in step 201 provided in the engine rotation interrupt routine, it is determined whether the engine rotation speed NE is equal to or greater than a determination value. If the determination result is negative, the process proceeds to step 202, where it is determined whether the current crank angle is 30 degrees before the fuel injection timing. If the determination result is positive, the process advances to step 203 and the TAU calculation flag is set. On the other hand, if the judgment result in step 201 is positive, the process proceeds to step 204, where the current crank angle is 60 degrees below the fuel injection timing.
It is determined whether the crank angle is the previous crank angle. If the judgment result is positive, proceed to step 205.
Set TAU calculation flag. Step 203,
After completion of step 205, or if the results of the determinations in steps 202 and 204 are negative, the routine advances to the next step of the engine revolution interrupt routine. In this way, the fuel injection time that needs to be determined for each engine rotation in synchronization with the engine rotation.
TAU calculation is performed in the engine rotation interrupt routine according to the TAU calculation flag set at a predetermined crank angle that changes depending on the engine rotation speed.
By doing this within the main routine, the fuel injection time TAU can be calculated at the appropriate time without waste, and the fuel injection time can be calculated based on the latest data.
TAU decisions can be made. Also, if the engine speed is low, the fuel injection time will inevitably decrease.
Since the TAU calculation cycle is also longer, the burden on the digital control circuit is reduced. Furthermore, without directly calculating the fuel injection time TAU within the engine revolution interrupt routine, the engine revolution interrupt routine
Because we only set the TAU calculation flag,
The burden of the engine rotation interrupt routine is also small. In the above embodiments, the present invention was applied to a digital control device that adopted an intake pipe pressure type electronically controlled fuel injection method, but the scope of application of the present invention is not limited to this, and for example, the present invention Of course, it is also possible to apply this to a digital control device that employs an intake air type electronically controlled fuel injection method.

【Effect of the invention】

As explained above, according to the present invention, the calculation of the fuel injection amount is substantially synchronized with the engine rotation,
The engine is controlled efficiently because it is carried out at the right time and without waste based on the latest data. In particular, it is possible to reduce the burden on the digital control circuit due to calculation of the fuel injection amount when the engine is running at high speeds, and to ensure sufficient responsiveness even when the engine is at low speeds. Also, since TAU is calculated only when the fuel injection amount calculation flag is set,
An increase in the load of routines such as the main routine that have a lower priority than the engine rotation interrupt routine is also suppressed, and as a result, the responsiveness of other controls is also improved. Furthermore, it has excellent effects such as being able to create time margin in the control system.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view, including a partial block diagram, showing the configuration of an embodiment of a digital control device for an automobile engine in which the digital control method for an internal combustion engine according to the present invention is adopted, and FIG. A block diagram showing the configuration of the digital control circuit used in the embodiment, FIG. 3 is a flowchart showing a part of the main routine program in the digital control circuit, and FIG. 3 is a flowchart showing part of a routine program. 10...Engine, 18...Throttle valve, 2
0... Throttle sensor, 23... Intake pipe pressure sensor, 30... Injector, 34... Oxygen concentration sensor, 44... Crank angle sensor, 52... Coil with igniter, 54... Digital control circuit,
60... Central processing unit (CPU), 62... Analog input port with multiplexer, 64... Digital input port, 66... Read only memory (ROM), 68... Random access memory (RAM), 72... Digital Output port, 74...
…Common bus.

Claims (1)

[Claims] 1. In a digital control method for an internal combustion engine in which the fuel injection amount of the engine is controlled based on the fuel injection amount repeatedly determined according to the engine operating state, the injection is executed during the engine rotation interrupt routine. Set a fuel injection amount calculation flag at the previous predetermined crank angle, set the predetermined crank angle to the advance side when the engine speed is high, and in a main routine that has a lower priority than the engine rotation interrupt routine, A digital control method for an internal combustion engine, characterized in that the state of the flag is determined, and when the flag is set, calculation of the fuel injection amount is executed in the routine.