JPS60156946A - Method of controlling injected quantity of fuel for internal-combustion engine - Google Patents

Abstract

PURPOSE:To achieve an optimal air-fuel ratio even at the transient run of an engine, by calculating the injected quantity of fuel for the engine in terms of the final pressure in an intake pipe determined from a signal produced by the A/D conversion of the output of a pressure sensor for the intake pipe. CONSTITUTION:The detection output of a sensor for the pressure in the intake pipe of an internal-combustion engine is applied to a low-pass filter for the A/D conversion of the detection output. A compensatory processing is performed on the basis of a formula PMDi=PMDi-1+K.(PMA/D-PMDi-1) wherein PMA/D denotes a signal produced by said A/D conversion. In a step 82, the pressure PMOS in the intake pipe is calculated on the basis of a formula PMOS=2PMA/D -PMDi to produce a signal PMOS, in terms of which the injected quantity of fuel for the engine is determined. This results in providing an optimal air-fuel ratio even at the transient run of the engine.

Description

TECHNICAL FIELD The present invention relates to a method for controlling fuel injection in an internal combustion engine in response to intake pipe pressure.

Prior Art In a so-called DJ fuel injection control system that uses an intake pipe internal pressure signal to calculate the fuel injection amount, the intake pipe internal pressure signal is obtained by obtaining an electrical signal corresponding to the pressure within the intake pipe using a pressure sensor, and passing this signal through a low-pass filter. The ripple caused by intake pulsation is removed by passing through the air. In this way, if the signal passed through the low-pass filter is used as the intake pipe pressure signal as it is, an error will occur during the transient operating state of the engine. That is, as shown in FIG. 1a, during acceleration operation, an error of ΔPM occurs at point A, for example, between the output PM of the pressure sensor and the signal PM after passing through the low-pass filter. Therefore, the signal PMi at point A with
If the fuel injection amount is calculated based on this, the fuel amount will be smaller than the actually required solution, and the air-fuel ratio will be controlled to the lean side. Note that since the injection timing is at point A', which is delayed from point A, the above-mentioned tendency becomes even more pronounced. On the other hand, during deceleration operation, as shown in Figure 1b, PMi deviates from PM by ΔPM', so the air-fuel ratio does not reach the desired value. It is controlled by IJ touch.

In order to prevent the above-mentioned disadvantages, there is a technique in which the phase of the signal PMi after passing through a low-pass filter is advanced using an analog circuit. There was a problem in that the above-mentioned errors ΔPM and ΔPM' could not be sufficiently compensated for due to variations.

OBJECTS OF THE INVENTION Accordingly, the present invention seeks to solve the above-mentioned disadvantages, and its purpose is to provide a fuel injection amount control method that can obtain optimal air-fuel ratio characteristics even during transient operation.

Structure of the Invention The feature of the present invention that achieves the above-mentioned object is that the pressure inside the intake pipe of an internal combustion engine is measured by a pressure sensor! l)! The detection output of the nuclear pressure sensor is applied to a low-pass filter, the signal after passing through the low-pass filter is converted from analog to digital, and the signal Pl'l' is obtained from the following equation using the converted signal PMA/D.
Calculate lDi, PMDi=PMDl-□+K-(P
MA, , -PMD, , ) However, PMD i-1
is the previous PMD, signal, K is a constant, and the obtained signal PMD
The purpose is to calculate the signal PMO8 from the following equation from i and the signal PMA/D, and calculate the fuel injection amount of the engine according to the obtained signal PMO8.

Embodiment FIG. 2 shows an electronically controlled fuel injection type internal combustion engine as an embodiment of the present invention. In the figure, 10 represents the engine body, 12 represents an intake passage, 14 represents a combustion chamber, and 16 represents an exhaust passage. The flow rate of intake air taken in through an air cleaner (not shown) is controlled by a throttle valve 18 that is also linked to an accelerator pedal (not shown). Intake air that has passed through the throttle valve 18 is guided into the combustion chamber 14 via a surge tank 20 and an intake valve 22.

In the intake passage downstream of the throttle valve 18, for example, in the portion of the surge tank 20, there is a closed pressure take-out boat 24a that communicates with a pressure sensor 24 that detects the absolute pressure in the intake pipe and generates a voltage corresponding to the detected value. are doing. The output voltage of this pressure sensor 24 is +ViIi! The signal is sent to the control circuit 28 via 26.

The fuel injection valve 30 is actually provided for each cylinder, and is controlled to open and close in response to an electrical P1 pulse that is sent from the control circuit 28 via a line 32, and is connected to a fuel supply system (not shown). Pressurized fuel sent from the intake valve 22 is intermittently injected into the intake passage 12 near the intake valve 22.

Exhaust gas after being burned in the combustion chamber 14 is discharged into the atmosphere via the exhaust valve 34 and the exhaust passage 16, and further via the catalytic converter 36.

From the crank angle sensor 40.42 provided in the distributor 38, the crankshaft (not shown) is detected at 30°, 3
A pulse signal is output every time the motor rotates by 60°, and a pulse signal for each crank angle of 30L is sent to the limiter 44, and a pulse signal for each crank angle of 360° is sent to the limiting circuit 28 via a line 46.

An intake air temperature sensor 48 that detects the temperature of intake air is provided in the intake passage 20 upstream of the throttle valve 18.
Its output voltage, representing the sensed intake air temperature, is fed to the control circuit 28 via the output voltage εO.

The engine shilling block is provided with a water temperature sensor 52 for detecting the coolant temperature, and its output voltage representing the detected coolant temperature is sent to the control circuit 28 via line 54.

FIG. 3 shows an example of the configuration of the control circuit 28 shown in FIG. In the figure, a pressure sensor 24, an intake air temperature sensor 48
, a water temperature sensor 52, crank angle sensors 40 and 42, and a fuel injection valve 30 provided for each cylinder are each represented by a block.

The output voltage of the pressure sensor 24 is applied to a low-pass filter 56 to remove ripples due to intake pulsation, and then sent to an analog-to-digital (A/D) converter 60. In the example shown in FIG. 3, the low-pass filter 56 is the simplest one consisting of a combination of a resistor and a capacitor, but other well-known configurations can be applied. The output voltages of the intake temperature sensor 48 and the water temperature sensor 52 are also connected to the A/D converter 60.
sent to. The A/D converter 60 has an analog multiplexer function and is connected to a microprocessor (MPU).
) 62, the signals from each sensor are selected and A/D converted to obtain a binary signal.

A pulse signal every 30 degrees of crank angle from the crank angle sensor 40 is sent to the MP via an input/output circuit (110 circuit) 64.
The signal is sent to U62 and serves as an interrupt request signal for the 30° crank angle II processing routine, and also serves as an increment clock for the timing counter provided in I10 circuit 64. The pulse signal every 360° of crank angle from the crank angle sensor 42 is 1! as the above-mentioned timing color/reset signal. I! Il<. The injection start timing signal obtained from this timing counter is sent to the MPU 62 and becomes an interrupt request signal for the injection processing routine.

The input/output circuit (engine 10 circuit) 66 is provided with a drive circuit that receives a 1-bit injection pulse signal having a connection time corresponding to the injection pulse width TAU sent from the MPU 62 and converts it into a drive signal. It is being A drive signal from this drive circuit is sent to the fuel injection valve 30 to energize it. As a result, an amount of fuel corresponding to the pulse width TAU is injected.

The A/D converter 60 and I10 circuits 64 and 66 are connected via a bus 72 to an MPU 62, a random access memory (RAM) 68, and a read only memory (ROM) 70, which are the main components of the microcomputer. Data is transferred via this bus 72.

The ROM 70 stores in advance a main processing routine program, an interrupt processing routine program for every 30 degrees of crank angle, and other programs, as well as various data, tables, etc. necessary for these arithmetic operations.

Next, the operation of the above-mentioned microcomputer will be explained using the flowcharts shown in FIGS. 4, 6, and 7.

The MPU 62 outputs A to the A/D converter 60 at predetermined intervals.
/ Instruct the start of D conversion, set the suction temperature THA,
The data representing the cooling water wetness THW is obtained from the A/D converter 60.
The data is taken into the computer by an A/D conversion completion interrupt from , and stored in the RAM 68 as it is. on the other hand,
When the A/D conversion of the channel regarding the intake pipe internal pressure is completed, the microcomputer executes the interrupt process shown in FIG. 4.

First, in step 80, the binary signal value after A/D conversion is
Input into the computer as MA/D.

Next, in step 81, the following equation is calculated as a smoothing process.

PMD・=PMD−, +K・(PMA, D−PMDi−
, ) ... (1) 1 1- Here, PMDI-, is the PMD at the time of the previous interrupt processing.

, and K is a constant. Furthermore, this PMD
i is made to match the current PMA/D during an initial processing routine performed immediately after the engine is started. In the next step 82, the intake pipe internal pressure PMO8 used for calculating the fuel injection pulse width is calculated from the following equation.

PMO8 = 2 PMA/DP hec Di = PMA, D
+(PMA, D-PMDi) (2) Next, in step 83, PMDi is changed to PMDI-.

It is stored in the RAM 68 as . Also, PMO8 is also RAM
68.

FIG. 5 illustrates the effects of the arithmetic processing in steps 81 and 82 in the processing routine of FIG. 4 described above.

FIG. In the figure, PM corresponds to the output of the pressure sensor 24, PMi corresponds to the output of the low-pass filter 56, and therefore this is the converted output P from the A/D converter 6°.
Corresponds to M. This PMA/DA/D is rounded in step 81 to become PMD. The difference between PMD and PMA7D (PMA/D-P
MDi) is added to PMA7D in step 82 to obtain the final intake pipe internal pressure PMO8. In addition, No. (
(PMA7D-PMDi) in equation 2) corresponds to the shaded area in FIG.

As mentioned above, by intentionally creating overshoots and undershoots during transient periods, it is possible to compensate for the deviation in the pressure signal in the intake pipe caused by passing through the low-pass filter, so that the optimal amount of fuel can be injected even during overdrive conditions. This makes it possible to prevent air-fuel ratio deviations.

Hereinafter, a description will be given of how to perform fuel injection control 1 from the intake pipe internal pressure signal obtained as described above and other parameters.

Data representing the rotational speed NE of the engine can be found, for example, in the processing routine shown in FIG. The interrupt process shown in FIG. 6 is performed in response to a pulse signal from the crank angle sensor 40 at every 30° crank angle. First, in step 90, M
The value of the free run counter provided in the PU 62 is read and the value is set as C3o. In the next step 91, '4'r? Observed value C3o
’ and the current value C3°, the difference ΔC is Δc−Cso−Cao
' to 9. In step 92, the reciprocal of the difference ΔC is calculated to obtain the rotational speed NE. That is, the calculation of NE=A/ΔC is performed in step 92. However, A is a constant.

In the next step 93, set Cso to C30' and R
Store in AM68.

On the other hand, the MPU 62 executes the process shown in FIG. 7 during the main processing routine. First step 100 and 101
At this time, the data of the suction side depth THA and the cooling water temperature THW are stored in the RAM 68, and correction coefficients FTHA, FTH, and W corresponding to these data are determined from mathematical formulas or tables, respectively. Since this method is well known, detailed explanation will be omitted.

Next, in steps 102 and 103, the data of the intake pipe internal pressure PMO8 and the rotational speed NE are fetched from the RAM 68, and the basic injection pulse width TP corresponding to these data is stored in the basic injection pulse width TPO table for the rotational speed NE and the intake pipe internal pressure PMO8. It is calculated using interpolation calculation. This method is also known. Next, in step 104, the final fuel injection pulse width TAU is set as the basic injection pulse width TP, the aforementioned correction coefficients F'THA, FTHW, other correction coefficients α and β, and the invalid injection time T of the injection valve 30.
No. 4 T is output from V according to the following formula.

TAU=TP-FTHA-FTHW・α+β+TV TAU ij thus obtained: Stored in RAM 68.

To create an injection pulse signal having a duration corresponding to TAU, for example, when the injection Iτ4 start timing signal occurs, the injection pulse signal is inverted to 'IH, and the value of the above-mentioned free run counter at that time is Know, 9, T
The value of this counter after the AU has elapsed is transferred to the conveyor register. If an interrupt is generated at the dark spot where the free run counter becomes 1111 or l< in the set value of the conveyor register, and the injection nozzle signal is inverted to 'O'', T
An injection pulse signal with a duration corresponding to AU will be obtained. As mentioned above, this injection pulse signal is I1
It is sent to the 0 circuit 66 and the group 4 closing movement of the fuel injection valve 30 is performed.

Effects of the Invention As described in detail above, according to the present invention, the following equation is used to perform the smoothing process on the signal PMA/D after A/D conversion, and PMDi=PMDi-, +K -(PMA/D- PM
Di,) From the obtained PMD・and PMA/D, the final intake pipe internal pressure PMO3 is obtained according to the following formula, so PMO8=2PMA/D−PMD.

It is possible to effectively compensate for deviations in the intake pipe internal pressure signal caused by passing through the low-pass filter, and as a result, optimum air-fuel ratio characteristics can be obtained even during transient operating conditions. That is, control deviation in the air-fuel ratio slope direction during acceleration operation is prevented, and control deviation in the rich direction during deceleration operation is also prevented. As a result, very good operating characteristics and exhaust gas purification characteristics can be obtained. Also,
By adding a special external circuit, program processing can be performed, reducing costs and stabilizing characteristics.

[Brief explanation of the drawing]

1a and 1b are characteristic diagrams of intake pipe internal pressure signals according to the prior art, FIG. 2 is a schematic diagram of an embodiment of the present invention, and FIG.
The figure is a block diagram of the control circuit of Figure 2, Figure 4 is a flowchart of a part of the control program of the microcomputer, Figure 5 is a characteristic diagram of the pressure signal in the intake pipe according to the present invention, and Figures 6 and 7 are It is a flowchart of a part of the control fjl program of a microcomputer. 10... Engine main body, 12... Suction/non-suction reverse path, 24...
Pressure unit, 28...Divided 1 circuit, 30...Fuel injection valve, 40.42...Crank angle sensor, 56...
Low-pass filter, 60...Al1) converter, 62...
...MPU. 64.66...I10 circuit, 68...RAM, 70
...RO,M. Patent Applicant Toyota Motor Corporation Patent Attorney Akira Aoki Patent Attorney Kazuyuki Nishidate Patent Attorney Matsushita Akira Akira Yamaguchi Patent Attorney Masaya Nishiyama Figure 10 1bI￥! Figure 3 248 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. Detecting the pressure inside the intake pipe of the internal combustion engine using a pressure sensor, applying the detection output of the pressure sensor to a low-pass filter, and converting the signal after passing through the low-pass filter from analog to digital; Using the converted signal PMA/D, calculate the signal PMD from the following equation, and calculate PMD・=PMI), −, +・
(PMA/D-PMDi-,') where PMD,-, is the previous PMD, signal, K is a constant, and the signal PMO8 is calculated from the obtained signal PMD and signal PMA/D by the following formula, PMO8 =2PMA/D-PMDi A method for controlling the fuel injection amount of an internal combustion engine, in which the fuel injection amount of the engine is increased according to the obtained signal PMO8.