JPS58150038A - Fuel injection method of electronically controlled engine - Google Patents

Abstract

PURPOSE:To compensate unevenness in an air-fuel ratio sensor from the characteristic standpoint, by compensating the skip of an integrating quantity with a difference between the maximum valve and the minimum value of the air-fuel ratio sensor, when the fuel injection quantity is calculated by means of a skip- bearing integrating quantity calculated from the output of the air-fuel ratio sensor. CONSTITUTION:An electronically controlled engine increases or decreases an integrating quantity in relation to a feedback signal of an air-fuel ratio sensor 16 at a control unit 20 while calculates a fuel injection quantity on a basis of this integrating quantity. Likewise, to improve the control responsiveness, a pecified skip is added to or subtracted from the integrating quantity in time of output reversion in the sensor 16. In this case, when the output of a water temperature sensor 15 is above the specified value and the engine speed by a crank angle sensor 10 is above the specified speed, both the maximum value and minimum value of the air-fuel ratio sensor 16 are detected while the value DELTAVOx is calculated. And, based on this value DELTAVOx, the skip of a skip-bearing integrating quantity is controlled so as to be compensated, in this method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel injection method for an electronically controlled engine that can compensate for variations in the characteristics of an air-fuel ratio sensor and control the fuel injection amount with high precision.

In the feedback control of the fuel injection amount, the integral amount is increased or decreased in relation to the feedback signal from the air-fuel ratio sensor, and the fuel injection amount is calculated based on this integral amount. Furthermore, in order to improve control responsiveness, general electronically controlled engines use an integral quantity with skip, which is obtained by adding or subtracting a predetermined skip to the integral quantity when reversing the output of the air-fuel ratio sensor. In conventional electronically controlled engines, this skip was constant. The output characteristics of the well-known air-fuel ratio sensor, which detects the air-fuel ratio based on the oxygen concentration in exhaust gas, deviate from normal values due to manufacturing variations, changes over time, and deterioration, which can impede control accuracy. ing.

An object of the present invention is to provide a fuel injection method for an electronically controlled engine that can control the fuel injection amount with high precision even if the output characteristics of an air-fuel ratio sensor deviate from normal ones.

To achieve this objective, the present invention provides electronic control that calculates an integral amount with skip based on the output of an air-fuel ratio sensor, and calculates a fuel injection amount based on the integral amount with skip during the feedback control period. In the engine fuel injection method,
(a) Maximum value VOx of the output voltage of the air-fuel ratio sensor during a period when the engine is at a predetermined temperature or higher, feedback control of the fuel injection amount is being performed, and the engine is rotating at a predetermined rotational speed or higher.
max and the minimum value VOx min are detected, and (11 the difference ΔVO between the maximum value VOxmax and the minimum value VOxmin
x (=VOx max - VOxmin is calculated, (
C) Correcting the skip of the integral amount with skip based on the difference ΔVOx.

The present invention will be described in detail with reference to the drawings.

Figure 1 is an overall schematic diagram of an electronically controlled fuel injection engine.
The air sucked into the intake passage 2 through the air cleaner 1 has its flow rate controlled by a throttle valve 3 that is linked to the accelerator pedal in the driver's cab, and is led to the combustion chamber of the engine body 5 via the intake branch pipe 4 and then exhausted. The system is provided with, in order from upstream, an exhaust branch pipe 6, an exhaust pipe 7, and a catalytic converter 8 that accommodates a three-way catalyst. The crank angle sensor 10 detects the rotational speed of the engine from the rotation of the crankshaft. The engine switch 11 in the driver's cab detects the ON position and the STAR (8T) position of the engine key 12. The air flow meter 13 detects the intake air flow rate, the intake temperature sensor 14 detects the intake air temperature, the water temperature sensor 15 is attached to the cylinder block and detects the cooling water temperature, and the air-fuel ratio sensor 16 is attached to the exhaust branch pipe 6. The throttle sensor 17 detects the opening degree of the throttle valve 3 by detecting the oxygen concentration in the exhaust gas.

Rank angle sensor 10, engine switch 11, air flow meter 13, intake temperature sensor 4, water temperature sensor I5
, the air-fuel ratio sensor 16, the throttle sensor 17, and the vehicle speed sensor JB are sent to the electronic control device 2θ. The fuel injection valves 21 are provided at each core portion of the intake branch pipe 4 and are opened and closed in response to electric pulses from the electronic control device 20.

FIG. 2 is a block diagram of the electronic control device 2o.

timer 25, interrupt control unit 26, rotation number counter 27,
Digital input port 28, analog input port 29, C
PU (Central Processing Unit) 30. A RAM (random access memory) 31, a ROM (read only memory) 32, and a fuel injection time control counter 33 are connected to each other via a bus 34. The revolution counter 27 traces the engine revolution speed once per revolution of the crankshaft based on the output pulse generated every time the crank angle sensor 10 rotates by 30' crank angle, and at the same time as the measurement ends. An interrupt command signal is sent to the interrupt control section 26. The interrupt control unit 26 generates an interrupt signal when the rotation number counter 27 also receives the interrupt command signal, and the CPU 30 executes an interrupt program for calculating the fuel injection amount based on the generation of the interrupt signal. The output signals of the start terminal 35 of the ignition switch 1, the throttle sensor 17, and the F speed sensor 18 are sent to the digital input port 28 as digital input signals. The start signal from the start terminal t35 is used as a signal for initialization. Air flow meter l: (, the outputs of the intake temperature sensor 14, water temperature sensor 15, and air-fuel ratio sensor 16 are sent as analog input signals to the analog input boat 29. The analog human power port 29 is connected to the analog multiplexer and A/i) /digital) converter to selectively A/D convert the analog human input signal. Color for fuel injection time control: 33
consists of a down counter including a register, and generates as an output a pulse having a pulse width corresponding to a digital input signal representing the amount of fuel to be injected. Counter for fuel injection time control,
The third output pulse is amplified by the power amplifier 36 and then sent to the fuel injection valve 21. Pulse 1 of the output pulse of the fuel injection time control counter 33 is C, )' Li2
O corresponds to the calculated final fuel injection amount. The power of the electronic discrimination device 20 is controlled by a power supply circuit 37.
7 is supplied with power from a storage battery 39 via an on terminal 38 of the engine switch 11.

FIG. 3 is a flowchart of a program implementing the present invention. In step 43, it is determined whether or not the temperature of the cooling water is higher than a predetermined temperature T. If the determination result is positive, the process proceeds to step 44, and if not, the process proceeds to step 75. The predetermined temperature T is set as the temperature at which warm-up of the engine is completed, and if the cooling water is above the predetermined temperature T, the air-fuel ratio sensor 16 has also reached the active temperature range and is generating a normal output. . Step 4
In step 4, it is determined whether or not it is the execution period for feedback control of the fuel injection amount, and if the determination result is positive, the process proceeds to step 45, and if not, the process proceeds to step 75. Feedback control is suspended during the warm-up period and deceleration period. During the warm-up period, the air-fuel ratio deviates to the rich side due to an increase in the amount of fuel injection, and during the deceleration period, the air-fuel ratio deviates to the lean side due to fuel cut-off. In this way, during the feedback control suspension period, the air-fuel ratio deviates from the stoichiometric air-fuel ratio, and the output of the air-fuel ratio sensor also deviates, making it difficult to detect the correct maximum and minimum output voltages of the air-fuel ratio sensor. becomes. In step 45, the output voltage VOx of the air-fuel ratio sensor 16 is detected. Step 46
Then, it is determined whether the engine is rotating at a predetermined rotational speed R or higher, and if the determination result is positive, the process proceeds to step 47, and if not, the process proceeds to step 54. When the engine rotates below the predetermined rotational speed R, the amount of exhaust gas is insufficient and the output of the air-fuel ratio sensor 16 is reversed at a high frequency.
In other words, it is easy to fluctuate, and it is difficult to detect an appropriate output. In step 47, the maximum output voltage VOx max is detected.

Specifically, the maximum output voltage VOx max so far is compared with the output voltage VOx detected in step 45 this time,
If VOx≧VOx max, convert VOx to new VOxm
Let it be ax. In step 48, the minimum output voltage VOxmi
Detect n. Specifically, the previous minimum output voltage VO
x min and the output voltage VO detected in step 45 this time
x, and VOx (If VOx min, then V
Let Ox be the new VOxmin. In step 49, the maximum output voltage VOxmax and the minimum output voltage VOx m i
Difference from n ΔVOx (=VOxm<ax −VOx
m1n) is calculated. In step 50, ΔVOx is stored. In step 54, if the output of the air-fuel ratio sensor 16 fluctuates and is unstable during the feedback control execution period, the previous ΔVOx is set as the new ΔVOx.

In step 58, the skip correction value ΔR8 is set to the difference ΔVOx.
The current difference ΔVOx is calculated from a predetermined table as a function of
A skip correction value ΔR8 corresponding to is calculated. FIG. 4 represents the correction value ΔR8, which is determined as a function of the difference ΔVOx. The table shows the appropriately selected difference ΔVO
Only the skip correction value ΔR8 corresponding to x is written. In step 59, it is determined whether or not the idle switch of the throttle sensor 12 is on. If the determination result is positive, the process proceeds to step 6o, and if not, the process proceeds to step '
Proceed to 61. The idle switch is on when the throttle valve 3 is at the idling opening, and is off when the throttle valve 3 is opened more than the idling opening. In step 6o, the skip correction value ΔR8 is set to o. The reason why the skip correction value ΔR8=o is set is to avoid this problem, where if the skip is increased by setting ΔIts)0 during the idle period, the fluctuation in the fuel injection amount becomes large and the engine engine operation becomes unstable. In step 61, it is determined whether the output voltage VOx of the air-fuel ratio sensor 16 is equal to or higher than a predetermined voltage Vr. If the determination result is positive, the process proceeds to step 62; otherwise, the process proceeds to step 68. If the air-fuel ratio is below the stoichiometric air-fuel ratio, that is, if the mixture is too rich,
VOx>Vr, and when the air-fuel ratio is larger than the stoichiometric air-fuel ratio, that is, when the air-fuel mixture is lean, VOx (Vr. Step 62 Te4'!, Vf - (R8 + ΔRs
) wo new t, knee Vf toss. However, Vf is an integral amount with skip, and R8 is a predetermined value for skip. R8+ΔR
8l'! This is the final skip, and the fuel injection amount is proportional to the integral amount Vf with skip. In step 63, V f
-New Ki! shall be. However, Ki is a positive predetermined value set as a change in the amount of integral with skip per unit time. In step 64, the air-fuel ratio sensor 16
It is determined whether or not the output voltage VOx is less than a predetermined value. When it comes out, R8+ΔR8 as a skip is subtracted from the integral amount Vf with skip, and thereafter, the integral amount Vf with skip decreases by Kl at every predetermined time interval until the air-fuel mixture becomes lean.In step 68, Uf-1
-(R8+ΔR8) is set as a new Vf. Step 69
Now let Vf0Ki be the new Vf. In step 7o, it is determined whether the output voltage VOx of the air-fuel ratio sensor 16 is greater than or equal to a predetermined value Vr. If the determination result is positive, this program is terminated, and if not, the process returns to step 69. In this way, when the air-fuel ratio sensor [6] outputs a lean signal, R8 + ΔR8 as a skip is added to the integral amount Vf with skip, and from then on, the integral amount Vf with skip increases Ki at every predetermined time interval until the air-fuel mixture becomes rich. It increases gradually. In step 75, open loop control is performed.

FIG. 5 shows temporal changes in the output voltage of the air-fuel ratio sensor 16 and the integral amount with skip. The solid line indicates when the output voltage of the air-fuel ratio sensor 16 is normal, the broken line indicates when the output voltage of the air-fuel ratio sensor 16 deviates from the normal value due to manufacturing variations, etc., and the two-dot chain line indicates when the air-fuel ratio sensor 16 is operated according to the present invention. This shows the characteristics when the output voltage is compensated.

Air-fuel ratio sensor 16 due to manufacturing variations, etc.
However, according to the present invention, the skip correction value ΔR8 is increased as the amplitude decreases, so the responsiveness is improved and the fuel injection amount can be controlled with almost the same accuracy as when the amplitude is normal. can.

As described above, according to the present invention, even if the output of the air-fuel ratio sensor deviates from normal output characteristics due to variations in manufacturing, etc., the difference between the maximum output voltage and the minimum output voltage of the air-fuel ratio sensor By correcting the skip amount, it is possible to compensate for deviations in the output characteristics of the air-fuel ratio sensor.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an electronic control engine to which the present invention is applied, FIG. 2 is a detailed block diagram of the electronic control device in FIG. 1, and FIG.
The figure is a flowchart of a program that implements the present invention, Figure 4 is a graph showing the relationship between the output voltage difference ΔVOx of the air-fuel ratio sensor and the skip correction value, and Figure 5 is the output characteristic of the air-fuel ratio sensor and the integral amount with skip. It is a graph showing the change over time.

Claims (1)

[Claims] 1. A fuel injection method for an electronically controlled engine that calculates an integral amount with skip based on the output of an air-fuel ratio sensor, and calculates the fuel injection amount based on the integral amount with skip during the feedback control period. In (a1), during a period when the engine is at a predetermined temperature or higher, feedback control of the fuel injection amount is being performed, and the engine is rotating at a predetermined rotational speed or higher, the maximum value VOx max of the output voltage of the air-fuel ratio sensor is Minimum value VOxmin
(bl maximum value VOxmax and minimum value VOx
Difference from min ΔVOx (=VOxmax−VOxmin
) - Calculation system, (characterized in that the skip of the integral amount with Cl skip is corrected based on the difference ΔVOx,
°Electronically controlled fuel injection method. 2 Skip the sum R8+ of the predetermined value R8 and the correction value ΔR8
ΔR8, a table is set in advance with the correction value ΔR8 as a function of the difference ΔVOx, and the difference ΔV calculated in the above (bl)
2. The fuel injection method according to claim 1, wherein the correction value ΔIts corresponding to Ox is determined from the table. 3. The fuel injection method according to claim 2, wherein the correction value ΔR8 is increased as the difference VOx decreases.