JPH0932608A - Air-fuel ratio control device for internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an air-fuel ratio control device that appropriately controls the air-fuel ratio immediately after starting. A start detection means for the internal combustion engine 1, an air-fuel ratio detection means (air-fuel ratio sensor 160) utilizing oxygen ion conduction of a solid electrolyte, an air-fuel ratio changing means, and a microcomputer 180 as air-fuel ratio control means. Have. The air-fuel ratio sensor 160 can output a first output that outputs an electromotive force and a second output that applies a desired voltage between the electrodes to obtain a current output. The control means performs the open control not depending on the output of the air-fuel ratio sensor 160 during the first predetermined time period T1, and during the second predetermined time period T2 after the passage of T1.
On / off control is performed based on the first output, and for the subsequent time zones, higher-level feedback control is performed based on the second output of the air-fuel ratio sensor 160.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine of an automobile or the like, and more particularly to an air-fuel ratio control device for starting control from an early stage after starting the internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine of an automobile or the like, it is required to control the air-fuel ratio with high accuracy over a wide range of operating conditions in order to improve the exhaust gas condition and the fuel consumption. As a sensor that detects the air-fuel ratio, in addition to the conventional oxygen sensor that outputs electromotive force, recently, a limit current type air-fuel ratio sensor that can accurately detect a wide range of air-fuel ratios is being used. Is becoming.
However, in the limiting current type air-fuel ratio sensor, since the temperature at which the sensor is activated is relatively high, it takes time to be detected at the time of starting the internal combustion engine and the start of the air-fuel ratio control is delayed. There is a problem.

Therefore, various proposals have been made to solve this problem. For example, in Japanese Unexamined Patent Publication No. 5-52140, when the air-fuel ratio sensor is in a semi-warm state (for example, 400 ° C. or higher at the sensor temperature) and the limiting current output is not stable, the classical proportional-integral (PI) A method has been proposed in which the control level is lowered by control to control the air-fuel ratio, and advanced control based on modern control theory is performed when the engine is completely warmed up.

Further, Japanese Patent Laying-Open No. 7-127502 further includes means for determining the presence / absence of an output signal from the air-fuel ratio sensor and means for determining whether or not the sensor has entered an activated state. It has been proposed to start air-fuel ratio control from an early stage when a stable limiting current output cannot be obtained from the sensor. That is, when the sensor output cannot be obtained by using a sensor that can determine whether the air-fuel ratio is rich or not in the inactive stage, open control is performed and the sensor outputs whether rich or not. Once obtained, proportional / integral control is performed.

[0005]

However, the above-mentioned Japanese Unexamined Patent Application Publication No.
The air-fuel ratio control device of Japanese Patent No. 52140 has a problem that effective control is not performed until the semi-warm state in which the rich or lean output of the limiting current of the air-fuel ratio sensor starts is started and the control is delayed. On the other hand, the method proposed in Japanese Patent Application Laid-Open No. 7-127502 starts control from an early stage, but means for judging the presence or absence of an output signal of the sensor and a judging means for judging whether or not the sensor has entered the activated state. Is required,
There is the problem of complex controls and equipment. The present invention has been made in view of such conventional problems,
An object of the present invention is to provide an air-fuel ratio control device capable of appropriately controlling the air-fuel ratio over a wide range immediately after the start of an internal combustion engine without complicating the device and control.

[0006]

According to the present invention, there is provided start detection means for detecting the start of an internal combustion engine, air-fuel ratio detection means utilizing oxygen ion conduction of a solid electrolyte, and air-fuel ratio changing means for changing the air-fuel ratio of the internal combustion engine. An air-fuel ratio control device for an internal combustion engine having an air-fuel ratio control means for receiving an output signal from both of the detection means and issuing an operation command to the air-fuel ratio changing means, wherein the air-fuel ratio detection means activates a solid electrolyte. And a voltage source for applying a desired voltage between the electrodes, and the above-mentioned desired output is provided between the electrodes and a first output that uses an electromotive force generated between the electrodes by oxygen ion conduction as an output signal. The control means is configured to be able to output two kinds of output signals, which are the second output and the current output when the voltage is applied, and the control means outputs the first predetermined time after the internal combustion engine is started. Obi T1 During the air-fuel ratio performed open control that does not depend on the output of the air-fuel ratio detection means with respect to changing means, the first second predetermined time period T after the predetermined time period T1 has elapsed
During 2, the first output of the air-fuel ratio detection means is fed back to determine whether the air-fuel ratio is rich, lean, or stoichiometric, and the air-fuel ratio is changed so that the target state is achieved. The air-fuel ratio control apparatus for an internal combustion engine is characterized in that the means is controlled to be turned on and off, and for the subsequent time zones, feedback control of the air-fuel ratio is performed based on the second output of the air-fuel ratio detection means.

The first point to be most noted in the present invention is that the air-fuel ratio detecting means has a heating means for activating the solid electrolyte and a voltage source for applying a desired voltage between the electrodes. , Two types of output signals, a first output that outputs an electromotive force generated between electrodes by oxygen ion conduction as an output signal and a second output that outputs a current output when the desired voltage is applied between the electrodes. It is possible to output.

The second point that is most noticeable in the present invention is that the control means controls the air-fuel ratio changing means during the first predetermined time period T1 immediately after the internal combustion engine is started. The open control that does not depend on the output of the air-fuel ratio detection means is performed, and during the second predetermined time zone T2 after the first predetermined time zone T1 has elapsed, the air-fuel ratio detection means is emptied based on the first output. It is judged whether the fuel ratio is rich, lean, or stoichiometric air-fuel ratio range, and the air-fuel ratio changing means is turned on and off so as to be in any of the target states. The purpose is to perform feedback control of the air-fuel ratio based on the second output.

It is known that an air-fuel ratio (oxygen concentration) detecting means using a solid electrolyte can obtain an electromotive force output signal from a relatively low temperature state. Therefore, in the air-fuel ratio detecting means according to the present invention, the detection output can be obtained early after the internal combustion engine is started by obtaining the first output. Then, the control means performs the open control of the air-fuel ratio immediately after the start of the internal combustion engine, and then, when the time period (T2) in which the first output is obtained is reached, based on the first output, the feedback of the air-fuel ratio is performed early. Start control. At this stage, since the output accuracy of the air-fuel ratio detecting means is low, relatively rough control is performed so as not to burden the control device. That is, it is judged whether the air-fuel ratio is rich, lean or stoichiometric air-fuel ratio range, and the air-fuel ratio changing means is turned on / off so as to be in any one of the target states.

Then, after the temperature of the air-fuel ratio detecting means further rises to reach a stage where a current output (second output) is obtained (second time period T2), the air-fuel ratio is determined based on the second output. Feedback control of. As described above, in the air-fuel ratio control device according to the present invention, appropriate control according to the state of the air-fuel ratio detecting means is implemented from an early stage after the internal combustion engine is started. Further, in the air-fuel ratio control device of the present invention, as a reference for switching the control mode in three stages as described above,
Using a time zone that can be predicted in advance based on the operation history of the internal combustion engine, etc.
No device for determining the presence / absence of a sensor output signal and a device for determining whether or not the sensor has entered the activated state, unlike the device disclosed in Japanese Patent No. Therefore, the device is not complicated and is extremely simple.

The first and second time zones T1 and T2
During a third predetermined time period T3 following, the proportional-integral (PI) control of the air-fuel ratio based on the classical control theory is performed based on the second output of the air-fuel ratio detecting means, and the fourth time period thereafter. For the time zone T4, it is preferable to perform the air-fuel ratio control according to the modern control theory based on the second output of the air-fuel ratio detecting means. The limiting current value (third output) obtained when a constant voltage is applied between the electrodes of the air-fuel ratio detecting means
It is preferable to perform the air-fuel ratio control in the fourth time zone T4 based on the above. The current output of the air-fuel ratio detection means is
The output becomes stable as the temperature rises, and eventually a nearly constant limiting current value can be obtained. Therefore, it is an appropriate countermeasure to shift to the advanced control mode in response to the stable output value.

In order to set the time zones T1 to T4 to appropriate values, warm-up determination means for determining or detecting the warm-up state of the internal combustion engine or the warm-up state of the air-fuel ratio detection means is provided, It is preferable to determine the predetermined time zones T1 to T4 based on the output of the warm-up determination means. This is because the time for determining the output state of the air-fuel ratio detecting means changes depending on the operating state (history). At this time, the warm-up state of the internal combustion engine is detected by, for example, the water temperature of the internal combustion engine. The warm-up state of the air-fuel ratio detecting means means the activated state of the air-fuel ratio detecting means, and is detected by, for example, measuring the resistance value of the heating means or the internal impedance of the sensor element. For example, in the case where the total value of the time zone T1 in the first control mode (open control) and the time zone T2 in the second control mode based on the voltage output of the sensor is changed according to the history of operation and the engine is started from the warm-up state. Can be zero (none),
When starting from the cold state, the value is about 40 seconds or less, and it is preferable to adjust the mounting position of the sensor and the heating means of the sensor so that the value is set to 20 seconds or less.

The target value of the air-fuel ratio detecting means in the second time period T2 in which a stable output cannot be obtained from the air-fuel ratio detecting means is lean, rich, or
Alternatively, it is preferable to set a value having a width corresponding to the stoichiometric air-fuel ratio. It is meaningless to set the width of the target value narrow at the stage when the output accuracy of the sensor is low, and it is appropriate to use a value with a width. Further, the rich or lean state of the air-fuel ratio to be the target at the initial stage of starting the internal combustion engine differs depending on the internal combustion engine.

Further, in the case of the control in the second time zone T2, a control delay element is provided to provide a predetermined delay time Td.
After that, it is preferable to perform delay control so that the target value of the first output is obtained. The air-fuel ratio detection means using a solid electrolyte has a delay in the response of the output to the change of the input,
This is because by providing the delay time Td, more appropriate control characteristics can be obtained.

A single sensor may be used to obtain the first and second outputs from the air-fuel ratio detecting means.
A first sensor for obtaining the first output and a second sensor for obtaining the second output may be separately provided. As the oxygen sensor used for the air-fuel ratio detecting means, for example, a cup type air-fuel ratio sensor (see FIG. 6 and Japanese Utility Model Laid-Open No. 60-179862) and a laminated type two-cell sensor (see FIG. 7 and JP-A-5-12).
6793, or FIG. 8 and JP-A-62-214.
347).

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment Example In this example, as shown in FIG. 1, a start detection means (engine switch or the like) (not shown) for detecting the start of the internal combustion engine 1,
An air-fuel ratio sensor 160 as an air-fuel ratio detecting means utilizing the oxygen ion conduction of the solid electrolyte, an air-fuel ratio changing means described later for changing the air-fuel ratio of the internal combustion engine 1, and an air-fuel ratio receiving means for receiving the output signals of the both detecting means. Microcomputer 18 as air-fuel ratio control means for issuing an operation command to the fuel ratio changing means
And an air-fuel ratio control device for an internal combustion engine having zero.

The air-fuel ratio sensor 160 has a heating means for activating the solid electrolyte, a diffusion resistance layer or diffusion limiting hole (pinhole) for limiting the flow of oxygen ions of the solid electrolyte, and a desired electrode between the electrodes. A current output in the case where the desired voltage is applied between the first output and an electrode which has an external voltage source (battery 81) for applying a voltage and which has an electromotive force generated between the electrodes by oxygen ion conduction as an output signal. It is possible to output two types of output signals, that is, a second output having an output signal of.

The above control means (microcomputer 18
0), as shown in FIG. 2, during the first predetermined time period T1 after the internal combustion engine 1 is started (0 to t ₁ s), the air-fuel ratio sensor 160 relative to the air-fuel ratio changing means implement open control that is not based on the output, during the second predetermined time period of the first after the predetermined time period T1 has elapsed T2 (t ₁ ~t ₂ s) is the first output from the air-fuel ratio sensor 160 Based on this, it is judged whether the air-fuel ratio is rich, lean, or stoichiometric air-fuel ratio range, and the air-fuel ratio changing means is turned on and off so as to be in any desired state, and after that, the time zone (t> t ₂ ), The air-fuel ratio feedback control is performed based on the second output of the air-fuel ratio sensor 160.

[0019] Then, the control means (microcomputer 180), the first, during a second time period T1, the third followed T2 for a predetermined time period T3 (t ₂ ~t ₃ s), the air based on the second output of the fuel ratio sensor 160 implemented proportional-integral (PI) control of the air-fuel ratio due to the classical control theory, it for the subsequent fourth time period T4 (t> t _3), the between electrodes The air-fuel ratio control according to the modern control theory is performed based on the third output that uses the limiting current value as an output signal when a constant voltage is applied. Further, warm-up determination means (water temperature sensor 140) for determining the warm-up state of the internal combustion engine 1 is further provided, and the control means (microcomputer 18
0) determines the predetermined time zones T1 to T4 based on the output of the warm-up determination means (water temperature sensor 140).

The target value of the first output of the air-fuel ratio sensor 160 in the second time zone T2 is set to a value having a width corresponding to the lean state in this example. Further, at this time, the control means (microcomputer 180) is provided with a control delay element to perform delay control such that the target value of the first output is reached after a predetermined delay time Td, and the target value or delay time of the first output is controlled. The value of Td is changed according to operating conditions such as the warm-up state (water temperature sensor 140) of the internal combustion engine 1 and the emission state (air-fuel ratio sensor 170).

Each of these will be described in detail below. Figure 1
4-cylinder 4-cycle spark ignition internal combustion engine (engine) 1
2 shows an example in which the present invention is applied to the fuel injection control system of FIG. When the engine 1 is in operation, the air flow passing through the air cleaner 10 and flowing into the intake pipe 20 is applied to the throttle valve 20a and the surge tank 30 inside the intake pipe 20.
Flow into the intake manifold 40 to mix the inflow air with the fuel from the fuel tanks injected by the fuel injection valves 41 to 44 into the intake manifold 40 to form an air-fuel mixture (air-fuel ratio changing means). . Then, this air-fuel mixture is supplied into the combustion chamber of each cylinder of the engine main body 50 and burned under the ignition of each spark plug 51, and passes through the exhaust manifold 60 and the three-way catalyst 70 to form an exhaust pipe 80 as exhaust gas. Discharge inside.

Each spark plug 51 receives a high voltage distributed from the distributor 90 in cooperation with the ignition circuit 91 and ignites. Also, the three-way catalyst 70 is a harmful component (C) in the exhaust gas from the intake manifold 60.
O, HC, NO _x, etc.).

The fuel injection system includes a rotation speed sensor 110.
This rotation speed sensor 110 is provided in the distributor 90, detects the actual rotation speed of the output shaft of the engine body 50 (corresponding to the actual rotation speed of the engine 1), and detects this. Pulse signals are sequentially generated at a frequency proportional to the result. However, the number of pulse signals generated from the rotation speed sensor 110 is 2 rotations of the engine 1 (that is, 72 rotations).
There are 24 per 0 ° CA (crank angle).

The throttle sensor 120 detects the actual opening of the throttle valve 20a and generates it as an opening detection signal. Further, the throttle sensor 120 also has a built-in idle switch, which detects this when the throttle valve 20a is fully closed and generates a fully closed detection signal. The negative pressure sensor 130 detects an actual negative pressure generated downstream of the throttle valve 20a in the intake pipe 20 and generates it as a negative pressure detection signal.

The water temperature sensor 140 detects the actual cooling water temperature in the cooling system of the engine body 50 and generates it as a water temperature detection signal. The air temperature sensor 150 generates the actual temperature of the airflow flowing into the intake pipe 20 upstream of the throttle valve 20a as an air temperature detection signal. The first air-fuel ratio sensor 160 detects the actual unburned oxygen concentration in the exhaust gas upstream of the three-way catalyst 70 in the exhaust pipe 80, and generates it as an oxygen concentration detection signal.

At this time, the oxygen concentration detection signal of the air-fuel ratio sensor 160 takes a linear value with respect to the actual air-fuel ratio λ of the air-fuel mixture supplied to the engine body 50. The second air-fuel ratio sensor 170 provided downstream of the three-way catalyst 70 detects the actual unburned oxygen concentration in the exhaust gas (emission) in the exhaust pipe 80 downstream of the three-way catalyst 70 to detect an oxygen concentration detection signal. Occurs as. However, this second air-fuel ratio sensor 17
In the oxygen concentration detection signal from 0, the air-fuel ratio λ is the theoretical air-fuel ratio λ
Represents _{0 as} rich or lean.

The microcomputer 180 has a CPU 1
81, ROM182, RAM183, backup RA
It is composed of an M184, an input port 185, an output port 186, a bus line 187 and the like. CPU18
Reference numeral 1 denotes a pulse signal from the rotation speed sensor 110, an opening detection signal and a fully closed detection signal from the throttle sensor 120, a negative pressure detection signal from the negative pressure sensor 130, a water temperature detection signal from the water temperature sensor 140, and an air temperature sensor. The air temperature detection signal from 150, the oxygen concentration signal from the first air-fuel ratio sensor 160 and the oxygen concentration detection signal from the second air-fuel ratio sensor 170 are input to the input port 185 and the bus line 18.
7 and receives the data stored in the ROM 182, RAM 183 and backup RAM 184 via the bus line 1
87, the computer program is executed, and during this execution, arithmetic processing necessary for driving and controlling the fuel injection valves 41 to 44 and the ignition circuit 91 via the bus line 187 and the output port 186 is performed.
However, the above computer program is stored in the ROM 182.
It is stored in advance.

Further, the microcomputer 180 supplies the power supplied from the battery Ba to the heaters for heating the first and second air-fuel ratio sensors 160 and 170, and obtains current outputs (second and third outputs). The power supply to the first air-fuel ratio sensor 160 is controlled.

There are various types of the air-fuel ratio sensor 160, for example, the cup type 160a shown in FIG. 6 and the laminated two-cell type 160b, 160c shown in FIGS. Etc. In FIG. 6, reference numeral 1
Reference numerals 61, 162, 163 and 164 denote a solid electrolyte, a heater for heating, an internal electrode and an external electrode, respectively. Figure 7
In the figure, reference numerals 165 to 169 and 190 respectively represent a solid electrolyte, a heater for heating, a first electrode for taking out a first output, a second electrode for taking out a second output, a diffusion limiting hole, and an atmosphere introducing section. What is shown in FIG. 8 is the same as that shown in FIG.
This is the one that eliminates the air introduction part for the cell type.

In the present embodiment configured as described above, when the fuel injection control system is in the operating state, the CPU 181 of the microcomputer 180 starts executing the computer program in step 200 according to the flowchart of FIG. In step 300, in response to each pulse signal generated from the rotation speed sensor 110 every 360 ° CA of the engine 1, the rotation speed N _{e of the} internal combustion engine 1 is changed according to the frequency of the pulse signal sequentially generated from the rotation speed sensor 110. Based on the rotational speed N _e , the value of the negative pressure detection signal from the negative pressure sensor 130, etc., the basic injection amount T _p of the fuel into the intake manifold 40 is calculated, and the computer program executes the air-fuel ratio calculation process. Routine 400 (FIG. 2
See).

FIG. 2 is a flowchart showing the processing executed in this step 400. The flow chart shown in FIG. 2 is one in which the four temperature states of the air-fuel ratio sensor 160 shown in FIG. 3 are made to correspond to four time zones and the respective control modes are changed. That is, in step 401,
When the start of the internal combustion engine 1 is detected by a signal from the start switch or the like, first, at step 402, the air-fuel ratio sensor 1
Open control (control mode 1) not depending on 60 is executed. Next, at step 403, when the predetermined time t1 has elapsed, at step 404, the air-fuel ratio sensor 160
The PI control (control mode 2) based on the first output (electromotive force) is performed.

Then, in step 405, the above t
When the predetermined time t2 (t2> t1) exceeding 1 has passed, in step 406, the PI control (control mode 3) based on the second output (current value) of the air-fuel ratio sensor 160 is executed. Then, in step 407, when the predetermined time t3 (t3> t2) exceeding t2 has passed, in step 408, the air-fuel ratio sensor 16
The control (control mode 4) based on the modern control theory is executed based on the third output (limit current value) of 0.

The setting range of the predetermined time t1 to t3 is
It is as follows. t1 = 0 to 10s t2 = 0 to 20s t3 = 0 to 30s When the internal combustion engine is cold started, t1 = 6
It is assumed that s, t2 = 12s and t3 = 20s. Further, when the internal combustion engine 1 is completely warmed up (restart or the like) based on the output of the water temperature sensor 140 instead of the cold start, t1 to t3 are set to 0 s. In other cases, t1 to t3 are set to intermediate values according to the water temperature.

Then, the control mode 3 (step 40
6), in the control mode 4 (step 408), in order to obtain the current output (second output, third output), the air-fuel ratio sensor 16
The voltage Vp applied to 0 is: Control mode 3: Vp = -1 to + 1V Control mode 4: Vp = -1 to + 1V, and normally, Control mode 3: Lean Vp = 0.8V, Rich Vp
= 0V Control mode 4: Vp = constant (or a value according to the air-fuel ratio (A / F)).

Control mode 2 (step 404)
The target value of the first output at is usually set to 0.45 V corresponding to the stoichiometric air-fuel ratio. However, internal combustion engine 1
However, in the case of a type that must be operated rich in the cold state, the target value above 0.45
Set between 1.0V so that it will be in a rich state at startup.

FIG. 4 shows an example of control in which the processing of step 404 is further decomposed. That is, when cold in step 404a, the target value is set to 0.7 in step 404b.
V is set, and when it is not cold in step 404a, the target value is set to 0.2V in step 404c.
On the other hand, when the internal combustion engine that can be operated lean even in the cold state or the leaner operation in the warmed-up state such as restarting causes lower emission, the above target value at the start is set between 0.1 and 0.45V. Set so that it will be in a lean state at the start.

Air-fuel ratio sensor 16 of the air-fuel ratio control device of this embodiment
At 0, the detection output of the air-fuel ratio sensor 160 can be obtained early after the internal combustion engine is started by obtaining the first output of the electromotive force. Then, the control means (microcomputer 180) performs the open control of the air-fuel ratio immediately after the start of the internal combustion engine 1, and then the time zone (T
When 2) is reached, the air-fuel ratio feedback control is started from an early stage based on the first output.

At this stage, the air-fuel ratio sensor 160
Since the output accuracy of is low, a relatively rough control that does not burden the controller is performed. That is, it is judged whether the air-fuel ratio is in the rich, lean or stoichiometric air-fuel ratio range, and the air-fuel ratio changing means is controlled to be turned on and off so as to be in any desired state. Then, after the temperature of the air-fuel ratio detecting means further rises and reaches the stage where current outputs (second and third outputs) are obtained (after the second time period T2 has elapsed), the second and third outputs are output. Based on this, more advanced feedback control is performed.

That is, during the third predetermined time period T3 immediately after the first and second time periods T1 and T2, the classical control theory is used based on the second (current) output of the air-fuel ratio sensor 160. Performing proportional / integral (PI) control of the air-fuel ratio, and performing air-fuel ratio control by modern control theory based on the third (limit current) output of the air-fuel ratio sensor 160 for the fourth time zone T4 thereafter. To do. As described above, in the air-fuel ratio control device according to the present example, appropriate control is performed from the early stage after the start of the internal combustion engine according to the degree of activation of the air-fuel ratio sensor 160.

In order to set the time zones T1 to T4 to appropriate values, a water temperature sensor 140 for determining the warm-up state of the internal combustion engine is provided, and the predetermined time zones T1 to T4 are set by the water temperature sensor 140. Determine based on output. And
In the air-fuel ratio control device of this example, a time schedule that can be set based on the operation history of the internal combustion engine 1 is used as a reference for switching the control mode to the four stages as described above. Unlike the conventional device shown in FIG. 3, there is no need for a means for determining the presence or absence of an output signal, a determination means for determining whether the sensor has entered the activated state, or the like. Therefore, the control mode switching procedure is extremely simple.

Second Embodiment In this embodiment, as shown in FIG. 9, in the first embodiment, a sensor for obtaining the first output of the air-fuel ratio detecting means and a sensor for obtaining the second and third outputs are separately provided. It is another embodiment example. That is, the oxygen sensor 191 that obtains the first (electromotive force) output
And an air-fuel ratio sensor 192 for obtaining the second and third outputs are arranged in the exhaust passage 80. The exhaust passage 80 of the internal combustion engine 1 is provided with a starting catalyst device 71 that is activated early and a main catalyst device 72 that is activated after a delay.
91 is arranged immediately after the internal combustion engine 1 and is activated early.
On the other hand, the air-fuel ratio sensor 192 is arranged immediately before the main catalyst device 72.

A second oxygen sensor 193 is arranged downstream of the main catalyst device 72 for detecting the oxygen concentration of the exhaust gas downstream of the main catalyst device 72. And these sensors 191, 19
By comparing the outputs of 2, 193, the catalytic device 7
It is possible to judge the deterioration and performance of 1,72. By arranging the sensors 191 and 192 as described above, it becomes possible to accurately obtain the first output of the sensor 191 from earlier and to control the air-fuel ratio after the engine is started. It is possible to detect catalyst deterioration in a system using a catalyst device, and the control accuracy of the air-fuel ratio is further improved. Others are the same as in the first embodiment.

[0043]

As described above, according to the present invention, the air-fuel ratio control capable of appropriately controlling the air-fuel ratio over a wide range after the internal combustion engine is started without complicating the device and control. You can get the device.

[Brief description of drawings]

FIG. 1 is a system configuration diagram of an air-fuel ratio control device according to an embodiment.

FIG. 2 is a control flowchart of the air-fuel ratio control device according to the embodiment.

FIG. 3 is a diagram showing the relationship between the control mode and the temperature of the air-fuel ratio sensor in the air-fuel ratio control device of the embodiment.

FIG. 4 is a detailed diagram of step 402 in FIG.

FIG. 5 is a diagram showing a general operating procedure of a microcomputer.

FIG. 6 is a schematic diagram (part 1) of the configuration of the air-fuel ratio sensor of the first embodiment.

FIG. 7 is a schematic diagram of the configuration of the air-fuel ratio sensor of the first embodiment (Part 2).

FIG. 8 is a schematic diagram (part 3) of the configuration of the air-fuel ratio sensor of the first embodiment.

FIG. 9 is a diagram showing an arrangement of sensors of an air-fuel ratio control device according to a second embodiment.

[Explanation of symbols]

 1. . . Internal combustion engine 160. . . Air-fuel ratio sensor (air-fuel ratio detecting means) 180. . . Microcomputer (control means)

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location G01N 27/419 G01N 27/46 327S

Claims (10)

[Claims] 1. A start detecting means for detecting the start of an internal combustion engine, an air-fuel ratio detecting means utilizing oxygen ion conduction of a solid electrolyte, an air-fuel ratio changing means for changing the air-fuel ratio of the internal combustion engine, and both the detecting means. And an air-fuel ratio control means for issuing an operation command to the air-fuel ratio changing means in response to the output signal from the air-fuel ratio changing means, wherein the air-fuel ratio detecting means is a heating device for activating the solid electrolyte. Means and a voltage source for applying a desired voltage between the electrodes, and applying the desired voltage between the first output and an electrode, which has an electromotive force generated between the electrodes by oxygen ion conduction as an output signal It is configured to be able to output two kinds of output signals, that is, a second output in which the current output in is the output signal, and the control means is for a first predetermined time period T1 after the internal combustion engine is started. ， Air-fuel above The open control that does not depend on the output of the air-fuel ratio detecting means is performed on the changing means, and the first output of the air-fuel ratio detecting means is provided during the second predetermined time zone T2 after the first predetermined time zone T1 has elapsed. Is fed back to determine whether the air-fuel ratio is rich, lean, or stoichiometric, and the air-fuel ratio changing means is turned on and off so that the target state is reached. An air-fuel ratio control apparatus for an internal combustion engine, which carries out feedback control of an air-fuel ratio based on a second output of an air-fuel ratio detecting means. 2. The control device according to claim 1, wherein the control means outputs the second output of the air-fuel ratio detection means during a third predetermined time zone T3 following the first and second time zones T1 and T2. Based on the classical control theory, proportional-integral (PI) control of the air-fuel ratio is performed based on the following, and for the fourth time zone T4 after that,
An air-fuel ratio control device for an internal combustion engine, which performs air-fuel ratio control according to modern control theory based on the second output of the air-fuel ratio detection means. 3. The air-fuel ratio detecting means according to claim 2, wherein the air-fuel ratio detecting means is capable of outputting a third output having a limit current value as an output signal when the constant voltage is applied between the electrodes. Is an air-fuel ratio control apparatus for an internal combustion engine, which performs air-fuel ratio control based on the third output in the fourth time period T4. 4. The warm-up determination means according to claim 1, further comprising a warm-up determination means for determining or detecting a warm-up state of the internal combustion engine or a warm-up state of the air-fuel ratio detection means. , The control means controls the predetermined time period T1 to T
4 is determined based on the output of the warm-up determination means. 5. The air-fuel ratio of an internal combustion engine according to any one of claims 1 to 4, wherein the total value of the predetermined time zones T1 and T2 is 40 seconds or less including 0. Control device. 6. The target value of the first output of the air-fuel ratio detecting means in the second time zone T2 according to any one of claims 1 to 5, wherein the target value of the first output is lean, rich, or An air-fuel ratio control device for an internal combustion engine, which is set to a value having a width corresponding to a theoretical air-fuel ratio. 7. The internal combustion engine according to claim 6, wherein the control means is provided with a control delay element to perform delay control so that the target value of the first output is reached after a predetermined delay time Td. Fuel ratio control device. 8. The target value of the first output or the value of the delay time Td according to claim 6 or 7, wherein the target value of the first output or the delay time Td is changed according to an operating state such as a warm-up state of the internal combustion engine or an emission state. An air-fuel ratio control device for an internal combustion engine, comprising: 9. The air-fuel ratio control based on the first output according to any one of claims 1 to 8, even when the air-fuel ratio is within the first time period T1. An air-fuel ratio control device for an internal combustion engine, wherein when the value exceeds a predetermined value, the operation is immediately performed. 10. The air-fuel ratio detecting means according to claim 1, wherein the air-fuel ratio detecting means separately includes a first sensor for obtaining a first output and a second sensor for obtaining a second output. An air-fuel ratio control device for an internal combustion engine, comprising: