JPH0214534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air-fuel ratio control device that detects an air-fuel ratio based on engine exhaust gas components and performs feedback control on the air-fuel ratio of an air-fuel mixture supplied to the engine.

Conventional air-fuel ratio control means simply performs integral control based on the output of an air-fuel ratio sensor. Therefore, during transient operation of the engine, if the basic air-fuel ratio changes faster than the correction speed of the integral control, the correction control cannot follow it. Further, when the air-fuel ratio sensor is inactive, feedback control of the air-fuel ratio cannot be performed, so sufficient air-fuel ratio control cannot be performed and exhaust gas cannot be reliably purified.

This invention has been made in view of the above points, and is based on the fact that when the engine is within a predetermined first operating range, the output of the air-fuel ratio sensor is integrally processed to obtain integral information, and according to this integral information, The value is updated and stored as nonvolatile memory correction information for each state of the engine, and the air-fuel ratio is feedback-controlled using the correction information corresponding to the engine state at that time and the integral information at that time among the stored correction information. It is something.

In this case, the conditions for updating and storing correction information in the non-volatile memory shall be within the second operating range of the engine shown in (a) to (c) below, and the updating of information will be stopped outside this operating range. shall be taken as a thing.

Condition (a) An engine state in which the injection amount of the fuel injection valve or the injection pulse width applied to the injection valve is less than or equal to the set value.

Condition (b) Engine condition where the intake air amount of the engine is below the set value or above the set value.

Condition (c) The engine speed is below the set value or above the set value.

That is, in the device according to the present invention, updating of correction information is stopped in a state where air-fuel ratio feedback control is repeatedly executed and stopped, and highly accurate air-fuel ratio control is possible. The air-fuel ratio can be quickly controlled to a predetermined air-fuel ratio without any response delay even when the engine is in a transient state, and even when the air-fuel ratio sensor is inactive when the engine is at low temperature, the air-fuel ratio is adjusted based on the correction information stored in the non-volatile memory. The object of the present invention is to provide an air-fuel ratio control device that can accurately control the air-fuel ratio without causing deterioration of exhaust gas or drivability.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the engine section. The engine 11 is a known four-stroke spark ignition engine installed in an automobile. Combustion air is taken in sequentially through an air cleaner 12, an intake pipe 13, and a throttle valve 14. do. Further, fuel is supplied from a fuel system (not shown) through electromagnetic fuel injection valves 15a, 15b, . . . provided corresponding to each cylinder of the engine 11. The exhaust gas after combustion is transferred to exhaust manifold 1.
6, it is released into the atmosphere through the exhaust pipe 17, three-way catalytic converter 18, etc.

The intake pipe 13 includes a potentiometer-type intake air amount sensor 19 that detects the amount of intake air taken into the engine 11 and outputs an analog voltage according to the amount of intake air, and detects the temperature of the air taken into the engine 11. A thermistor-type intake temperature sensor 20 that outputs an analog voltage (analog detection signal) according to the intake temperature
is installed.

Further, a thermistor-type water temperature sensor 21 is installed in the engine 11 to detect the coolant temperature and output an analog voltage (analog detection signal) according to the coolant temperature, and the exhaust manifold 16 is further equipped with an oxygen concentration sensor 21 in the exhaust gas. Detects the air-fuel ratio and outputs a voltage of approximately 1 volt (high level) when the air-fuel ratio is lower than the stoichiometric air-fuel ratio (rich), and approximately 0.1 volt (low level) when it is higher than the stoichiometric air-fuel ratio (lean). An air-fuel ratio sensor 22 is installed. The rotational speed of the crankshaft of the engine 11 is detected by a rotational speed (number) sensor 23, and a frequency pulse signal corresponding to the rotational speed is output. As this rotational speed (number) sensor 23, for example, an ignition coil of an ignition device may be used, and an ignition pulse signal from the primary terminal of the ignition coil may be used as the rotational speed signal. The detection signals from the sensors 19 to 23 are supplied to the control circuit 24, which calculates the fuel injection amount based on the detection signals and calculates the opening time of the electromagnetic fuel injection valves 15a, 15b, etc. The amount of fuel injection is adjusted through control.

FIG. 2 explains the control circuit 24,
100 is a microprocessor (CPU) that calculates the fuel injection amount. Reference numeral 101 denotes a rotational speed counter that counts the engine rotational speed based on a signal from the rotational speed (number) sensor 23, and this rotational speed counter 101 sends an interrupt command signal to the interrupt control unit 102 in synchronization with the engine rotation. . When interrupt control section 102 receives this signal, it outputs an interrupt signal to microprocessor 100 via common bus CB. A digital input port 103 transmits to the microprocessor 100 a signal from the air-fuel ratio sensor 22 and a digital signal of a starter signal from a starter switch 25 that turns on and off the operation of a starter (not shown). Reference numeral 104 is an analog input port consisting of an analog multiplexer and an A/D converter, and has the function of A/D converting each signal from the intake air amount sensor 19, absorption temperature sensor 20, and cooling water temperature 21 and sequentially reading it into the microprocessor 100. have 105 is a power supply circuit and a RAM which will be described later.
107 is directly supplied with power from the battery 26. This battery 26 circuit is provided with a key switch 27, but the power supply circuit 105 directly connects the battery 26 without passing through the key switch 27.
6, and RAM107 is connected to key switch 27.
Power is always applied regardless of the The battery 26 is connected to the other power supply circuit 1 via the key switch 27.
This power supply circuit 106 supplies power to parts other than the RAM 107, which will be described later. This RAM 107 is a temporary storage unit that is used temporarily during program operation, but as mentioned above, power is always applied regardless of the key switch 27, so even if the key switch 27 is turned off and engine operation is stopped, the stored contents are constitutes a non-volatile memory that does not disappear. A second correction amount k3, which will be described later, is also stored in this RAM 107. A read-only memory (ROM) 108 stores programs, various constants, and the like. Reference numeral 109 denotes a fuel injection time control counter including a register, which is composed of a down counter and receives a digital signal representing the opening time of the electromagnetic fuel injection valves 15a, 15b, calculated by the microprocessor 100, that is, the fuel injection amount. It is converted into a pulse signal with a pulse time width that gives the actual opening time of the electromagnetic fuel injection valves 15a, 15b, . 110 is an electromagnetic fuel injection valve 15a, 15b
111 is a timer that measures the elapsed time and drives the microprocessor 10.
0.

That is, the rotational speed counter 101 measures the engine rotational speed, for example, once per engine rotation based on the output of the rotational speed sensor 23, and supplies an interrupt command signal to the interrupt control section 102 when the measurement is completed. The interrupt control unit 102 generates an interrupt signal based on the interrupt command, and causes the microprocessor 100 to execute an interrupt processing routine for calculating the fuel injection amount.

FIG. 3 shows a schematic flowchart of the microprocessor 100. Based on this flowchart, the functions of the microprocessor 100 will be explained, as well as the operation of the entire configuration. That is, when the key switch 27 and the starter switch 25 are turned on to start the engine, a start command is issued from the first step 120, the main routine arithmetic processing is started, and initialization is first performed at step 121. In step 122, digital values corresponding to the cooling water temperature and intake air temperature are read from the analog input port 104. In step 123, a correction amount k1, which will be described later, is calculated from the result, and this correction amount k1 is stored in the RAM 107. step
For 124, air-fuel ratio sensor 2 is input from the digital input port.
2, the timer 111 increases or decreases the correction amount k2, which will be described later, as a function of the elapsed time, and this correction amount k2, that is, the integral processing information, is stored in the RAM 107.
Store in.

Figure 4 shows the correction amount k2 as this integral processing information.
A detailed flowchart of the process step 124 for increasing, decreasing, or integrating .

First, in step 400, it is determined whether the air-heat ratio detector is in an active state or whether feedback control of the air-fuel ratio can be performed based on the cooling water temperature, etc. If feedback control is not possible, that is, in the case of an open loop, step 400 is performed. The process proceeds to step 406, where the correction amount k2 is set to k2=1, and the process proceeds to step 405. Furthermore, as shown in, for example, Japanese Patent Application Laid-Open No. 53-5333, Japanese Patent Application Laid-Open No. 53-8428, etc.
It is also known that an open loop occurs when the intake air amount and rotational speed are outside a predetermined range. Further, if feedback control is possible, proceed to step 401. In step 401, the elapsed time is the unit time Δt1
It is determined whether the k2 has passed or not, and if it has not passed, this processing step 124 is ended without correcting k2. If the time Δt1 has elapsed, the process proceeds to step 402, and if the air-fuel ratio is rich and the output of the air-fuel ratio sensor 22 is a rich high level signal, the process proceeds to step 402.
The process proceeds to step 403, where k2 obtained in the previous cycle is decreased by Δk2, and the process proceeds to step 405, where this new correction amount k2 is stored in the RAM 107. step 402
If the air-fuel ratio is lean and the output of the air-fuel ratio sensor 22 is a low level signal indicating lean, the process proceeds to step 404, where k2 is increased by Δk2, and the process proceeds to step 405. In this way, the correction amount k2 is increased or decreased. At step 125 in FIG. 3, the correction amount k3 is increased or decreased, and the result is stored in the RAM 107. FIG. 5 is a detailed flowchart of step 125 in which the correction amount k3 is processed and stored, that is, stored.

In step 499, the fuel injection valves 15a, 15b
Injection amount in ... or fuel injection 15a, 1
It is determined whether or not the pulse width applied to 5b is within the set value. If it is outside the set value, step 125 is ended, and if it is within the set value, the process proceeds to step 500. In step 500, it is determined whether the air amount detected by the intake air amount sensor 19 is within a set value. If it is other than the set value, step 125 is terminated, and if it is within the set value, the process proceeds to step 501. In this step 501, it is determined whether or not the engine rotation speed detected by the rotation speed sensor 23 is within a set value. If it is outside the set value, step 125 is ended, and if it is within the set value, the process proceeds to step 502. , determine the value of k2.
If k2=1, nothing is done and this processing step 125 is ended. Note that the correction amount k3 forms a map as shown in FIG. 6 based on the intake air amount Q and the engine rotational speed N. The correction amount k3 on the map corresponding to the m-th position for the intake air amount Q and the n-th position for the engine speed N is expressed as k ^m _o . In this embodiment, the map in the RAM 107 divides the engine speed N into every 200rpm, and the intake air amount Q from idle to full throttle into 32 parts. In step 502, select “k2
<1'', the process proceeds to step 503, where k ^m _o is decreased by Δk3, and the result is stored in the RAM 107 in step 505.
Store in. When "k2>1" in step 502, the process proceeds to step 504, where the correction amount k ^m _o obtained in the previous cycle is increased by Δk3, and the process proceeds to step 505, where this processing step 125 is ended. When step 125 in the main routine is completed, the process returns to step 122.

Note that the initialization process in step 121 also executes the following. That is, the battery may be removed when inspecting or repairing a vehicle. For this reason
The correction amount k3 stored in the RAM 107 may be corrupted and become a meaningless value. Normally, RAM10 is used to detect whether the battery has come off or not.
A constant with a predetermined pattern is placed in a specific address of 7. When the program starts, it is determined whether the value of this constant is corrupted or incorrect, and if it is an incorrect value, it is assumed that the battery has been disconnected, and all values of the correction amount k3 are calculated. Initialize it to "1" and reset the constant of the determined pattern. If the pattern constant is not corrupted at the next startup, k3 will not be initialized.

Normally, the main routine processing of steps 122 to 125 is repeatedly executed according to the control program.
In FIG. 2, when an interrupt signal for calculating the fuel injection amount is input from the interrupt control unit 102, the microprocessor 100 immediately interrupts the main routine even if it is processing the main routine, and returns to the step
Moving on to the interrupt handling routine of 130. Step 131
In step 132, a signal representing the engine speed N is fetched from the revolution counter 101, and then in step 132, a signal representing the intake air amount (intake amount) Q is fetched from the analog input port 104.
At step 133, the rotational speed N and the intake air amount Q are stored in the RAM 107 for use as parameters for storing the correction amount k3 in the calculation process of the main routine. Next, in step 134, the basic fuel injection amount (that is, the injection time width t of the electromagnetic fuel injection valves 15a, 15b, . . . ) determined from the engine speed N and the intake air amount Q is calculated. The calculation formula is “t=F×
Q/N" (F: is a constant). Next, in step 135, various correction amounts for fuel injection determined in the main routine are read out from the RAM 107, and correction calculations are made for the injection amount (injection time width) for determining the air-fuel ratio. The calculation formula for the injection time width T is "T=t×k1×k2×k3." Next, in step 136, the corrected and calculated fuel injection amount data is set in the counter 109. Next, the process advances to step 137 to return to the main routine.
When returning to the main routine, the process returns to the processing step at which it was interrupted due to interrupt processing.

The general functions of the microprocessor 100 are as described above.

As described above, a large number of second correction amounts k3 (=k ^m _o ) are prepared according to the intake air amount and engine speed, so the appropriate correction amount corresponding to the engine operating condition is immediately used. be able to. Control with quick response is possible under all operating conditions, including transient conditions. Furthermore, since the second correction amount k3 is corrected in accordance with the operating state, it can be automatically corrected for changes over time and deterioration of the engine and sensors.

In addition, in the above embodiment, if the engine continues to be operated under constant conditions, the correction amount k3 will be corrected only for the same k ^m _o out of the whole, and for k ^m _o , k ^m+1 _o+1 , k ^m-1 _o-1
In some cases, the difference between values near k ^m _o becomes too large, so it is also possible to learn and correct the surroundings of k ^m _o at the same time. In this case, in the calculation processing step 125 of the correction amount k3 of the main routine of the above embodiment, the correction amount k2 as the integral processing information is “k2>
₁ ^{" , step} _{504 in} ^FIG _. ^_ _{_} ^_ _{_} ＋Δkn k ^m±1 _o±2 = k ^m±1 _o±1 +Δkn k ^m±2 _o±2 = k ^m±2 _o±2 +Δkn. In other words, if the correction amount of the central k ^m _o is "3",
If there is only one, it is corrected by "2", and if there are two, it is corrected by "1" in the same direction. When "k2<1", subtraction processing is performed in the same manner as described above in step 503, and each is stored in the RAM 107.

In the above embodiment, the calculation process for k3 in FIG. 5 may be simplified as shown in FIGS. 7, 8, and 9. In FIGS. 7 to 9, the same steps are given the same reference numerals and their explanations will be omitted.

In addition, in the above embodiment, the correction amount "k3=k ^m _o "
is the amount of correction to the value previously written in RAM107.
A predetermined correction amount Δk3 (or
3Δkn, 2Δkn, Δkn), but it is also possible to obtain k3 by multiplying the correction amount k2 by a constant α or αn that changes depending on the engine condition.

In addition, in the above embodiment, the correction amount k3 is
Using the intake air amount and engine rotational speed as parameters for dividing and storing into 07, the map was created by dividing at predetermined intervals as shown in Fig. 6, but in this map, the number of k3, that is, Since the number of memories increases, there is a concern that the cost will increase and the reliability will decrease, so the parameter may be only the intake air amount Q, and the correction amount k3 may be set to k ¹ , k ² , k ³ , . . . ^km .

In addition, in each of the above embodiments, the correction amount k3 is
Although the intake air amount is used as an engine parameter to be divided into and stored, it is of course possible to use other factors such as the intake negative pressure throttle valve opening degree.

In addition, in the above embodiment, in step 125 where the correction amount k3 is calculated and stored, k3 is calculated and rewritten every unit time Δt ₂ , but the unit rotation of the engine is ΔN
Of course, it is also possible to rewrite the calculation of k3 every time, and in this case, the unit rotation ΔN is about 30 rotations when the engine is steady, and about 20 rotations during transients such as acceleration and deceleration, which is the control response. Good in terms of control accuracy.

As described above, the present invention includes an air-fuel ratio sensor that detects an air-fuel ratio based on exhaust gas components of an engine, and a method for controlling the air-fuel ratio based on a signal from the air-fuel ratio sensor. An integral processing step that performs integral processing with the output signal, and a value corresponding to the integral information obtained in this integral processing step is stored as engine state correction amount information in a read/write nonvolatile memory in correspondence with the engine state at the time of processing. and a storage processing step for storing the information, using the integral information obtained in the integral processing step and the correction information corresponding to the engine state at that time among the engine state correction information stored in the nonvolatile memory. It is characterized by controlling the engine air-fuel ratio, and can accurately control the air-fuel ratio over all engine conditions, even when the engine is transient or when the air-fuel ratio sensor is inactive, based on correction information stored in non-volatile memory. It also has the excellent effect of being able to control the air-fuel ratio with high precision by compensating for changes over time in the engine, deterioration of the air-fuel ratio sensor, and even variations during production.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is a block diagram of the control circuit shown in FIG. 1, FIG. 3 is a schematic flowchart of the microprocessor shown in FIG. 2, and FIG. Figure 4 is a detailed flowchart of the steps for obtaining the correction amount k2 shown in Figure 3.
FIG. 5 is a detailed flowchart of the steps for obtaining the correction amount k3 shown in FIG. 3, and FIG. 6 is a map of the correction amount k3 used to explain the operation of this embodiment.
FIGS. 7 to 9 are flow charts illustrating the operation of other embodiments of the present invention. 11...Engine, 19...Air amount sensor, 2
2...Air-fuel ratio sensor, 23...Rotational speed sensor,
24...Control circuit, 100...Microprocessor (CPU), 107...RAM (temporary storage unit forming non-volatile memory).

Claims (1)

[Scope of Claims] 1. The device includes an air-fuel ratio sensor that detects an air-fuel ratio based on engine exhaust gas components, and controls the air-fuel ratio based on a signal from the air-fuel ratio sensor, comprising: an output signal from the air-fuel ratio sensor. a step of performing an integral process, and stopping the integral process when the engine is outside a predetermined first operating range determined by an activation state of the air-fuel ratio sensor, a cooling water temperature of the engine, etc.; a step of fixing the information to a predetermined value; and an updating step of updating and storing a value corresponding to the integral information obtained in the integral processing step in a read/write nonvolatile memory as engine state correction information in correspondence with the engine state at the time of the processing. to the engine according to the processing step, the integral information obtained in the integral processing step, and the correction information corresponding to the engine state at that time among the engine state correction information updated and stored in the nonvolatile memory. correcting the amount of fuel supplied by the solenoid valve; and as a parameter not involved in the determination of the first operating range, a first operating range different from the first operating range depending on at least the amount of fuel to the engine. 2. An air-fuel ratio control system comprising the steps of: setting a second operating range, and stopping updating of the engine correction information by the updating processing step when the second operating range is outside the second operating range.