JPH0670401B2 - Internal combustion engine control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for controlling an internal combustion engine, and more particularly to a method for controlling an internal combustion engine that controls the internal combustion engine based on a digital conversion value of a detected value of intake pipe pressure. .

[Prior Art] Conventionally, an analog value of the intake pipe pressure (absolute pressure) is detected using a pressure sensor, and a filter (time constant of about 3 to 5 msec) is used to remove the pulsating component of the intake pipe pressure. There is known a method in which the pressure sensor output is input to a microcomputer, the filter output is converted into a digital value every 24 msec by the microcomputer, and the internal combustion engine is controlled based on the digital conversion value (for example, Japanese Patent Laid-Open No. Sho-Kaiyo).
59-201938 publication). In this internal combustion engine control method, the basic fuel injection time is calculated based on the digital conversion value of the intake pipe pressure and the digital value of the engine speed, and the time fuel injection valve is opened based on the basic fuel injection time. The ignition timing is controlled by controlling the fuel injection amount, calculating the basic ignition advance angle based on the digital conversion value of the intake pipe pressure and the digital conversion value of the engine speed, and controlling the igniter based on the basic ignition advance angle. Are in control.

[Problems to be Solved by the Invention] However, in the conventional control method, since the filter output is converted into a digital value, the acceleration is accelerated as shown in FIG. When the pressure sensor output rises as in time, the filter output has a time delay corresponding to the time constant of the filter with respect to the pressure sensor output, and the filter output is output during the digital conversion period of 24 msec. The digital conversion value of does not change. For this reason,
The digital conversion value used for control is considerably delayed from the actual change of the intake pipe pressure (pressure sensor output). Therefore, when controlling the fuel injection amount using such a digital conversion value, since the basic fuel injection amount is calculated by the digital conversion value showing a value lower than the actual intake pipe pressure, the air-fuel ratio is lower than the required air-fuel ratio. There is a problem that the exhaust emission is deteriorated by being controlled by the lean side and the driver viability is deteriorated. When controlling the ignition timing using the above digital value, for example,
Since the load is considered to be lower than the actual load at the time of sudden acceleration, there is a problem that the basic ignition advance angle is controlled to an advance side from the required ignition advance angle, which causes knocking. On the other hand, when the output of the pressure sensor drops, such as during deceleration, the air-fuel ratio is controlled to the latch side and the ignition timing is controlled to the retard side, contrary to the above.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a control method for an internal combustion engine in which the control content does not deviate from a required value during a transition during acceleration / deceleration.

[Means for solving problems]

In order to achieve the above object, the present invention provides a method for controlling an internal combustion engine that controls an internal combustion engine based on a digital conversion value of a detected value of intake pipe pressure, wherein the digital conversion value and a change in the digital conversion value are moderate. The deviation from the average value that changes in the meanwhile is calculated, and the rate of change of the deviation is calculated. Is calculated.

[Operation] According to the present invention, the deviation between the digital conversion value of the intake pipe pressure detection value and the average value that changes gently with respect to the change of the digital conversion value is obtained. This average value is obtained by weighting the weight of the weighted average value calculated in the past of the digital conversion value and calculating the weighted average value with the weighted average value calculated in the past and the current digital conversion value. Alternatively, the detected value of the intake pipe pressure can be obtained by passing it through a filter having a time constant larger than the time constant at which the pulsating component of the detected value can be removed. Since this average value changes gently with respect to the change in the digital conversion value, the change rate of the digital conversion value can be obtained by calculating the change rate of the deviation between the digital conversion value and this average value.
When the rate of change is equal to or greater than the predetermined value, that is, when the rate of change in the detected value of the intake pipe pressure is large and the digital converted value is significantly delayed with respect to the change in the detected value of the intake pipe pressure, the digital converted value And the change rate of the deviation are added, and the digital conversion value is corrected so that it approaches the detection value of the intake pipe pressure, so that the value corresponding to the delay of the digital conversion value with respect to the change rate of the detection value of the intake pipe pressure is corrected. To be done.

As described above, according to the present invention, since the digital conversion value is corrected by an amount corresponding to the delay of the digital conversion value with respect to the change in the detected value of the intake pipe pressure, the digital conversion value is accurately deviated from the required value. The effect that the internal combustion engine can be controlled so that it does not exist is obtained.

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

FIG. 2 shows an internal combustion engine (engine) to which the present invention can be applied. A throttle valve 8 is arranged downstream of an air cleaner (not shown), and the throttle valve 8 is in a fully closed state ( An idle switch 10 that is turned on at an idle position) is attached, and a surge tank 12 is provided on the downstream side of the throttle valve 8. A semiconductor strain resistance type pressure sensor 6 connected to a filter (FIG. 3) having a time constant of about 3 to 5 msec is attached to the surge tank 12. A bypass passage 14 is provided so as to bypass the throttle valve 8 and connect the upstream side of the throttle valve and the surge tank 12 on the downstream side of the throttle valve. An idle speed control (ISC) valve 16B whose opening is adjusted by a pulse motor 16A having a four-pole stator is attached to the bypass passage 14. Surge tank 12
Are communicated with the combustion chamber of the engine 20 via the intake manifold 18 and the intake port 22. A fuel injection valve 24 is attached to the intake manifold 18 for each cylinder or for each cylinder group so as to project into the intake manifold.

The combustion chamber of the engine 20 is connected via an exhaust port 26 and an exhaust manifold 28 to a catalyst device (not shown) filled with a three-way catalyst. This exhaust manifold 28 has an O ₂ sensor that outputs an air-fuel ratio signal inverted at the residual oxygen concentration in the exhaust gas corresponding to the theoretical air-fuel ratio.
30 is installed. A cooling water temperature sensor 34 is attached to the engine block 32 so as to penetrate the engine block 32 and project into the water jacket.
The cooling water temperature sensor 34 detects the engine cooling water temperature and outputs a water temperature signal.

A spark plug 38 is attached to each cylinder so as to penetrate the cylinder head 36 of the engine 20 and project into the combustion chamber. The ignition plug 38 is connected via a distributor 40 and an igniter 42 to an electronic control circuit 44 composed of a microcomputer or the like. Inside the distributor 40, a cylinder discriminating sensor 46 and a rotation angle sensor 48, each of which is composed of a signal rotor fixed to the distributor controller and a pick-up fixed to the distributor housing, are mounted. In the case of a 6-cylinder engine, the cylinder discrimination sensor 46 is, for example, 720 ° CA.
A cylinder discrimination signal is output for each (crank shaft angle), and the rotation angle sensor 48 outputs an engine speed signal for example every 30 ° CA.

As shown in FIG. 3, the electronic control circuit 44 includes a central processing unit (MPU) 60, a read / ori memory (ROM) 62, and a random memory unit.
Access memory (RAM) 64, back up plum (BU-RA
M) 66, I / O port 68, input port 70, output port 72, 74,
It is configured to include a bus 78 such as a data bus and a control bus which connect these 76 and these. The filter 7, the pressure sensor 6 and the cooling water temperature sensor 34 are connected to the input / output port 68 via an analog-digital (A / D) converter 78, a multiplexer 80 and buffers 82 and 84. MPU60
Controls the multiplexer 80 and the A / D converter 78 every predetermined time (for example, 24 msec) to sequentially convert the pressure sensor 6 output and the water temperature sensor 34 output input through the filter 7 into digital signals. Store in RAM64. To the input port 70, the O ₂ sensor 30 is connected via the comparator 88 and the buffer 86, the cylinder discrimination sensor 46 and the rotation angle sensor 48 are connected via the waveform shaping circuit 90, and the idle switch 10 is connected. ing. Output port 72
Is connected to the igniter 42 via a drive circuit 92, the output port 74 is connected to the fuel injection valve 24 via a drive circuit 94,
The output port 76 is connected to the pulse motor 16A of the ISC valve via the drive circuit 96. 98 is a clock and 100 is a timer. Programs and the like for the control routines described below are stored in advance in the ROM 62.

Next, a control routine of an embodiment in which the present invention is applied to the above engine will be described.

FIG. 4 shows a part of the main routine of the present embodiment. In step 138, it is judged whether or not the throttle valve is closed based on the output of the idle switch 10.
When it is determined in step 138 that the throttle valve is open, it is determined in step 140 whether the throttle valve was closed last time. If it is determined that the throttle valve was closed the last time, that is, if the throttle valve was opened from the closed state, it is rewritten in step 142 in steps 126 and 128 in FIG. The weighted average value PMDi stored in is reduced by a predetermined value γ.

However, PMi is the current digital conversion value of the intake pipe pressure that is input from the pressure sensor 6 through the filter 7, is A / D converted, and is stored in RAM, and PMDi on the right side is calculated and is currently stored in RAM. Is a weighted average value of the intake pipe pressure.

Then, when the throttle valve is open, the following main routine is executed.

FIG. 1 shows a routine for calculating the fuel injection amount TAU in this embodiment. This routine uses the interrupt signal generated on the basis of the cylinder discrimination signal and the engine speed signal described above to perform a pre-intake top dead center of each cylinder every 360 ° CA.
Executed at CA. First, at step 110, the current deviation FTCi is calculated by subtracting the weighted average value PMDi currently stored in the RAM from the current digital conversion value PMi. In step 112, the absolute value of the deviation FTCi is a predetermined value (for example, 9.76 mmH
g) It is judged whether it is in a transient state by judging whether it is the following or not.When the absolute value of the deviation FTCi exceeds a predetermined value, that is, in the case of a transient state, the routine proceeds to step 116, where the absolute value of the deviation FTCi is a predetermined value. When it is less than the value, that is, in the steady state, the deviation FTCi is set to 0 in step 114, and then the process proceeds to step 116.

At step 116, the current deviation FTCi is changed to the previous deviation FTCi.
-1 is subtracted to obtain the change rate PM ₂ of the deviation FTC, and in the next step 118, it is determined whether or not the change rate PM ₂ is 0 or less to determine whether or not the digital conversion value PM is greatly changed. to decide.

That is, the pressure sensor output during acceleration, the digital conversion value PM of the filter output, and the weighted average value of the digital conversion values.
Since PMD changes as shown in Fig. 5 (1), the deviation F
As shown in Fig. 5 (2), TC gradually increases from the beginning of the change of the digital conversion value PM, and becomes maximum when the digital conversion value PM changes to a substantially constant value after a large change. , Then gradually decreases. Therefore, the deviation FTC
It is possible to determine whether or not the digital conversion value PM greatly changes by determining whether or not the rate of change PM ₂ of 0 is 0 or less.

When the change rate PM ₂ deviations FTC is determined to 0 or less at step 118, i.e. when the change of the digital conversion value PM is not large and the rate of change PM ₂ to 0 at step 122, the deviation FTC rate of change PM ₂ When it is judged that the current deviation FTCi exceeds 0, that is, when the change of the digital conversion value PM is large, it is judged in step 120 whether the current deviation FTCi is 0 or less, thereby judging whether or not the vehicle is in the acceleration state. When the current deviation FTCi is 0 or less, that is, when the vehicle is in the deceleration state, the rate of change PM ₂
Is set to 0, and when the current deviation FTCi exceeds 0, that is, when the vehicle is in the acceleration state, the current deviation FTCi is set to R in step 124.
Remember in AM. At the next step 126, the current deviation FTCi
1/4 of the register stored in R _0, the weighted average PMD currently stored in RAM the value of the register R ₀ in step 128 of
i is added, and this sum is calculated in step 130 as the weighted average value PMDi
The weighted average value is rewritten by storing it in the area for storing the weighted average value of RAM. Above steps
In step 124 and step 126, since the same calculation as the above equation (1) is performed, the current digital conversion value PMi and the current R
A new weighted average value is calculated with the weighted average value stored in AM, and this new weighted average value is currently RA.
It is stored instead of the weighted average value stored in M.

In the next step 132, the above-mentioned rate of change PM ₂ is added to the current digital conversion value PMi to correct the current digital conversion value PMi. In step 134, the digital conversion value corrected in step 132 and the engine speed The basic fuel injection time TP is calculated with the engine speed obtained from the signal, and the fuel injection time TAU is calculated in step 136 according to the following equation.

TAU = TP / FTCi / α + β where α is a correction coefficient for air-fuel ratio control, and β is another correction amount such as invalid injection time.

Here, in the initial stage of acceleration, the intake pipe pressure is low, so that the amount of fuel adhering to the inner wall of the intake manifold is small, and in the latter stage of acceleration, the intake pipe pressure is high, so that the amount of fuel adhering to the inner wall of the intake manifold is large. However, in the present embodiment, by correcting the basic fuel injection amount TP using the change rate FTCi that changes as described above, the fuel injection amount is gradually increased from the initial acceleration to the final acceleration and gradually after the acceleration is completed. Therefore, considering the amount of fuel adhering to the inner wall surface of the intake manifold, the air-fuel ratio of the air-fuel mixture supplied to the engine combustion chamber becomes almost constant, and the air-fuel ratio is set to the engine required value over the entire range during acceleration. Can be approximately equal to. Then, when a predetermined crank angle (for example, 60 ° CA) has elapsed from the interruption timing of the routine of FIG. 1, the fuel injection valve is controlled and the amount of fuel corresponding to the fuel injection time TAU is injected.

In the above routine, when the throttle valve is opened from the closed state, that is, at the time of start, shift change, idle racing, etc., the weighted average value PMDi is reduced by a predetermined amount. Since the deviation FTC increases from the start of change and the digital conversion value is corrected, the digital conversion value can be corrected without a time delay from the time when the throttle valve is opened.

Next, another embodiment of the present invention will be described. In this embodiment, the ignition timing is controlled, and the main routine of this embodiment is the same as that shown in FIG. FIG. 6 shows a routine for calculating the ignition advance angle THT which is executed at a predetermined crank angle before compression top dead center and at every predetermined crank angle. In step 150, step 110 to step 13 in FIG.
The current digital conversion value PMi of the filter output as in 2.
To correct. In step 152, the basic ignition advance THTB corresponding to the digital conversion value PMi corrected as described above of the basic ignition advance map stored in the ROM and the current engine speed is calculated by the interpolation method. At step 154, the basic ignition advance angle THTB is corrected according to the intake air temperature and the engine cooling water temperature to calculate the ignition advance angle THT, and the igniter is controlled to ignite at the ignition advance angle THT in a routine not shown. .

In each of the embodiments described above, the example in which the digital conversion value is corrected at the time of acceleration has been described. However, since the delay described above occurs at the time of deceleration, the digital conversion value may be corrected at the time of deceleration. In FIG. 5 (3), the change in the correction value when the correction value is 2 PM ₂ is shown by a broken line. Furthermore, the example in which the weighted average value is reduced when the throttle valve is opened from the closed state has been described above. However, in an engine equipped with an automatic transmission, the shift lever moves from the non-driving range (N range) to the driving range. The weighted average value may be reduced when shifted to the (D or R range).

[Brief description of drawings]

FIG. 1 is a flow chart showing a fuel injection amount calculation routine of an embodiment of the present invention, FIG. 2 is a schematic diagram of an engine to which the present invention is applicable, and FIG. 3 is a block showing the details of the control circuit of FIG. 4 and 5 are flow charts showing the main routine of the above embodiment, and FIG. 5 is a diagram showing changes in various values in the above embodiment.
FIG. 6 is a flow chart showing another embodiment of the present invention. 6 ... Pressure sensor, 7 ... Filter, 10 ... Idle switch, 24 ... Fuel injection valve, 42 ... Igniter.

Claims (1)

[Claims] 1. A control method for an internal combustion engine, which controls an internal combustion engine based on a digital conversion value of a detected value of an intake pipe pressure, wherein an average value that changes gently with respect to the digital conversion value and the change of the digital conversion value. And the rate of change of the deviation, and when the rate of change is equal to or greater than a predetermined value, the control amount of the internal combustion engine is calculated based on the sum of the digital conversion value and the rate of change. A method for controlling an internal combustion engine, which is characterized.