JP2003148206A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To early activate an air-fuel ratio sensor at engine automatic starting while reducing the heater power consumption of the air fuel ratio sensor during an engine is automatically stopped. SOLUTION: When an automatic stop condition is satisfied during the engine is in operation, it is determined that an engine stop request is present, and then the engine is automatically stopped. Together with this, the target element temperature of the air-fuel ratio sensor is switched to a target preheating temperature Tb which is lower than a target activation temperature Ta and a heater current is reduced so that the element temperature T of the air-fuel ratio sensor decreases to be near the target preheating temperature Tb during the engine is automatically stopped. Then, it is determined that an engine start request is present when an automatic start condition is satisfied during the engine is automatically stopped. However, before the engine is automatically started, the target element temperature of the air-fuel ratio sensor is switched to the target activation temperature Ta to increase the heater current so as to quickly increase the element temperature T of the air-fuel ratio sensor to be the target activation temperature Ta, and the engine is automatically started after the element temperature T of the air-fuel ratio sensor reaches the target activation temperature Ta.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine equipped with an exhaust gas sensor with a heater for detecting the air-fuel ratio of exhaust gas from the internal combustion engine.

[0002]

2. Description of the Related Art In the recent electronically controlled internal combustion engine,
On the upstream side of the catalyst (or both upstream and downstream sides of the catalyst) in the exhaust passage, the gas component concentration such as oxygen concentration of the exhaust gas, the air-fuel ratio,
An exhaust gas sensor that detects either rich or lean is installed, and the air-fuel ratio is feedback-controlled to near the stoichiometric air-fuel ratio based on the output of this exhaust gas sensor to enhance the exhaust gas purification efficiency of the catalyst. In general,
The exhaust gas sensor has a poor detection accuracy unless the temperature of the sensor element (hereinafter referred to as “element temperature”) rises to an activation temperature (eg, about 600 to 700 ° C. or higher). The activation of the exhaust gas sensor is promoted by both the heat generation and the exhaust heat.

Further, there is a type that employs an automatic engine stop / start device (so-called idling stop device) for the purpose of saving fuel consumption, reducing exhaust emissions, and the like. This automatic engine stop / start device automatically stops the engine when the driver stops the vehicle, and then performs an operation (brake release operation, etc.) for the driver to start the vehicle. The engine is automatically started when

By the way, if the heater of the exhaust gas sensor is de-energized while the engine is automatically stopped, the element temperature of the exhaust gas sensor will drop to a temperature considerably lower than the activation temperature if the automatic stop time is long. After that, even if the heater of the exhaust gas sensor is energized again when the engine is automatically started, it takes a long time for the element temperature of the exhaust gas sensor to rise to the activation temperature. In such a case, the time when the air-fuel ratio feedback control can be started based on the output of the exhaust gas sensor after the automatic start is delayed, the accuracy of the air-fuel ratio control after the engine is started is reduced, and the exhaust emission is deteriorated.

As a countermeasure against this, as disclosed in Japanese Patent Application Laid-Open No. 9-88688, by energizing the heater so that the element temperature of the exhaust gas sensor is maintained at the active temperature even when the engine is automatically stopped, It has been proposed that the air-fuel ratio feedback control can be started immediately after automatic start.

[0006]

However, as described in the above publication, when the heater current required to maintain the element temperature of the exhaust gas sensor at the active temperature is continuously supplied during the automatic stop period of the engine, the automatic stop period is stopped. The power consumption in the inside increases and the burden on the battery increases. For this reason, in an operating situation in which automatic stop frequently occurs for a relatively long time, the battery may be exhausted quickly, and the battery may run out.

The present invention has been made in view of the above circumstances, and therefore an object thereof is to reduce the exhaust gas sensor heater power consumption during automatic stop of an internal combustion engine while reducing the exhaust power when the internal combustion engine is automatically started. The gas sensor can be activated early, lower power consumption (battery burden is reduced), and air-fuel ratio control accuracy is improved (exhaust emission reduction).
An object of the present invention is to provide a control device for an internal combustion engine that can satisfy both of the requirements.

[0008]

In order to achieve the above object, an internal combustion engine controller according to claim 1 of the present invention automatically stops when a predetermined automatic stop condition is satisfied during operation of the internal combustion engine. The internal combustion engine is automatically stopped by the control means, and during the automatic stop, the sensor element temperature of the exhaust gas sensor (hereinafter referred to as "element temperature") is maintained near a predetermined preheat temperature set to a temperature lower than the activation temperature. Thus, the heater control means controls the energization of the heater.

With this configuration, since the heater is controlled so as to maintain the element temperature of the exhaust gas sensor near the preheating temperature lower than the activation temperature during the automatic stop of the internal combustion engine, the element of the exhaust gas sensor during the automatic stop of the internal combustion engine. As compared with the conventional method of maintaining the temperature at the activation temperature, the power consumption of the heater during the automatic stop of the internal combustion engine can be reduced, the load on the battery can be reduced, and the battery can last longer. Moreover, by keeping the element temperature of the exhaust gas sensor near the preheating temperature during the automatic stop of the internal combustion engine, it is possible to shorten the time until the element temperature of the exhaust gas sensor is raised to the activation temperature after the automatic start of the internal combustion engine. Is completed,
It becomes possible to start the air-fuel ratio feedback control based on the output of the exhaust gas sensor early after the automatic start of the internal combustion engine, and control the air-fuel ratio accurately from the early time after the automatic start of the internal combustion engine to achieve exhaust emission. It can be reduced.

In this case, when the predetermined automatic start condition is satisfied during the automatic stop of the internal combustion engine, the element temperature of the exhaust gas sensor is set to the active temperature before the automatic start of the internal combustion engine is started. The control for raising the temperature may be started, and thereafter, the element temperature of the exhaust gas sensor may be raised to the activation temperature before the automatic start of the internal combustion engine is started. By doing this, since the exhaust gas sensor is already in the active state from the beginning of the automatic start, there is a problem of delay in the start timing of the air-fuel ratio feedback control due to the delay in activation of the exhaust gas sensor at the time of automatic start as in the past. The air-fuel ratio feedback control can be immediately started as soon as it is completely canceled and other conditions for executing the air-fuel ratio feedback control are satisfied after the automatic start.

Immediately after the start of the internal combustion engine (immediately after the complete explosion), the engine speed suddenly rises / falls and reaches a stable state. Therefore, even if the exhaust gas sensor is activated during automatic start Actually, the operating state of the internal combustion engine becomes the state in which the air-fuel ratio feedback control can be started from the time when the engine rotation speed is relatively stable after the start is completed.

In consideration of such circumstances, when the predetermined automatic start condition is satisfied during the automatic stop of the internal combustion engine, the element temperature of the exhaust gas sensor is immediately raised to the activation temperature. With the start of the control, at the same time as or after the element temperature of the exhaust gas sensor rises to the activation temperature, the operating state of the internal combustion engine becomes a state in which the air-fuel ratio feedback control can be started. You may make it start an automatic start.

With this configuration, when the predetermined automatic start condition is satisfied during the automatic stop of the internal combustion engine, the element temperature raising control is performed without waiting for the element temperature of the exhaust gas sensor to rise to the activation temperature. Since the automatic start of the internal combustion engine can be started in the middle of the process, the internal combustion engine can be automatically started with good response to the automatic start request due to the establishment of the automatic start condition, and the operating state of the internal combustion engine becomes empty after the automatic start. When the fuel ratio feedback control can be started,
It is possible to immediately start the air-fuel ratio feedback control based on the output of the exhaust gas sensor, and it is possible to achieve both quick automatic start when the automatic start condition is satisfied and early start of the air-fuel ratio feedback control.

Alternatively, when the automatic start condition is satisfied during the automatic stop of the internal combustion engine, the automatic start of the internal combustion engine is started immediately or slightly later, and the internal combustion after the automatic start is performed. The energization of the heater after the automatic start condition is satisfied is controlled so that the element temperature of the exhaust gas sensor rises to the activation temperature by the time when the operating state of the engine can start the air-fuel ratio feedback control. Is also good. Even in this case, when the predetermined automatic start condition is satisfied during the automatic stop of the internal combustion engine, the automatic start of the internal combustion engine is started without waiting for the element temperature of the exhaust gas sensor to rise to the activation temperature. It is possible to obtain the same effect as in the case of claim 3 described above.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION << Embodiment (1) >> Hereinafter, an embodiment (1) in which the present invention is applied to a vehicle (so-called hybrid vehicle) equipped with a power source such as an electric motor in addition to an engine.
Will be described with reference to FIGS.

First, a schematic structure of the entire engine control system will be described with reference to FIG. An electric motor 10 and an engine 11 (internal combustion engine) are provided as power sources of the vehicle. An air cleaner 13 is provided on the most upstream side of the intake pipe 12 of the engine 11, and an air flow meter 14 for detecting the amount of intake air is provided downstream of the air cleaner 13. On the downstream side of this air flow meter 14,
A throttle valve 15 and a throttle opening sensor 16 for detecting the throttle opening are provided.

Further, a surge tank 17 is provided on the downstream side of the throttle valve 15.
7, an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided. Further, the surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached near the intake port of the intake manifold 19 of each cylinder. There is. Further, a spark plug 21 is attached to each cylinder of the cylinder head of the engine 11, and the mixture in the cylinder is ignited by spark discharge of each spark plug 21.

On the other hand, the exhaust pipe 22 of the engine 11 is provided with a catalyst 23 such as a three-way catalyst for reducing CO, HC, NOx, etc. in the exhaust gas, and the air-fuel ratio of the exhaust gas is upstream of the catalyst 23. An air-fuel ratio sensor 24 (exhaust gas sensor) for detecting The sensor element 25 of the air-fuel ratio sensor 24 has a high activation temperature (about 600 to 700).
It is difficult to activate the sensor element 25 early after the engine is started only by the heat of the exhaust gas. Therefore, the air-fuel ratio sensor 24 has a built-in heater 26, which activates the sensor element 25 early by the heat generated by the heater 26 and maintains the temperature of the sensor element 25 within the active temperature range during engine operation. The power supply to 26 is controlled.

The cylinder block of the engine 11 is provided with a cooling water temperature sensor 27 for detecting the cooling water temperature, a crank angle sensor 28 for detecting the engine rotation speed, a starter 29 for starting the engine 11, and the like. There is. Further, a brake device (not shown) is provided with a brake switch 30 for detecting whether or not a brake pedal is depressed, and a wheel drive system (not shown) is provided with:
A vehicle speed sensor 31 that detects the vehicle speed is provided.

The outputs of these various sensors are output to the control device 32.
Entered in. The control device 32 is composed of an engine control microcomputer, an electric motor control microcomputer, an air-fuel ratio sensor control microcomputer, and the like. In addition, these engine control, electric motor control, air-fuel ratio sensor control,
It is needless to say that the control is not limited to the case of being executed by three microcomputers, and these three controls may be executed by one or two microcomputers. The control device 32 is R
By executing various control programs stored in the OM (not shown), the engine 1 can be operated according to the running state of the vehicle.
1 and the operation of the electric motor 10 are controlled.

At this time, the control device 32 executes the engine automatic stop / start control program of FIG. 2 and the heater control program of FIG. 3 stored in the ROM, so that the engine is controlled as shown in the time chart of FIG. The automatic stop and the automatic start of No. 11 are controlled, and the energization of the heater 26 of the air-fuel ratio sensor 24 is controlled.

As shown in FIG. 4, the control device 32 turns on the engine stop request signal when a predetermined automatic stop condition is satisfied during engine operation. It is determined that there is an engine stop request at the rising timing of the engine stop request signal, and first, the actual engine stop signal is turned on to automatically stop the engine 11, and the target element temperature of the air-fuel ratio sensor 24 is set during engine operation. Switching to the target preheating temperature Tb set to a temperature lower than the target activation temperature Ta,
The current of the heater 26 (hereinafter referred to as "heater current") is controlled to be lower than that during engine operation so that the element temperature T of the air-fuel ratio sensor 24 is lowered to near the target preheating temperature Tb and preheated during automatic engine stop. Perform preheat control.

After that, the control device 32 turns off the engine stop request signal when a predetermined automatic start condition is satisfied during automatic engine stop. Although it is determined that there is an engine start request at the falling timing of the engine stop request signal, the target element temperature of the air-fuel ratio sensor 24 is first switched to the target activation temperature Ta before the engine 11 is automatically started, and the air-fuel ratio sensor 24 is then activated. Element temperature T of the target activation temperature Ta
The element temperature raising control is executed to increase the heater current so as to raise the temperature quickly. After that, the air-fuel ratio sensor 24
After the element temperature T has risen to the target activation temperature Ta and the air-fuel ratio sensor 24 is activated, the actual engine stop signal is turned off and the engine 11 is automatically started.

The control described above is based on the RO of the control device 32.
The automatic engine stop / start control program of FIG. 2 and the heater control program of FIG. 3 stored in M are executed. The processing contents of each of these programs will be described below.

[Engine Automatic Stop / Start Control] The engine automatic stop / start control program shown in FIG. 2 is repeatedly executed at a predetermined cycle after the ignition switch (not shown) is turned on. When this program is started, first,
In step 101, it is determined whether the automatic stop condition is satisfied and the engine stop request signal is turned on. Here, the automatic stop condition is, for example, that all of the following conditions 1 to 4 are satisfied.

The vehicle speed is 0 km / h, that is, the vehicle is stopped. The throttle opening (accelerator opening) is fully closed. The brake pedal is depressed and the brake switch 30 is on. If all of them are satisfied, the automatic stop condition is satisfied. However, if any of the above conditions (1) to (4) is not satisfied, the automatic stop condition is not satisfied.
The automatic stop condition may be changed as appropriate, and the automatic stop condition may be satisfied when the vehicle speed becomes equal to or lower than a predetermined value and the driving range of the electric motor 10 is reached. .

When the engine stop request signal is turned on when the automatic stop condition is satisfied during engine operation, it is determined that the engine stop request is present, and the process proceeds to step 102 to turn on the actual engine stop signal to perform the automatic stop control. After executing (idling stop control), this program ends.
In this automatic stop control, fuel cut and ignition cut are performed to automatically stop the engine 11. The process of step 102 serves as an automatic stop control unit in the claims.

After that, when the automatic start condition is satisfied and the engine stop request signal is turned off during the automatic stop of the engine, the determination at step 101 is "No". here,
The automatic start condition is determined by, for example, whether the driver's foot is separated from the brake pedal and the brake switch 30 is turned off.

The automatic starting condition may be changed as appropriate.
The automatic start condition may be established when the driver can determine that the driver has performed some operation to start the vehicle, such as when the accelerator pedal is depressed. Alternatively, the automatic start condition may be established when the vehicle speed becomes equal to or higher than a predetermined value after the vehicle is started only by the driving force of the electric motor 10.

When the automatic start condition is satisfied during the automatic engine stop and the engine stop request signal is turned off (when "No" is determined in step 101), it is determined that there is an engine start request, and the step 101 to step 1
In step 03, it is determined whether or not the element temperature T of the air-fuel ratio sensor 24 has risen to the target activation temperature Ta or higher by the element temperature raising control described later. Element temperature T of the air-fuel ratio sensor 24
Since the impedance Z of the sensor element 25 (hereinafter referred to as “element impedance”) Z decreases as the value increases, it is determined whether the element temperature T of the air-fuel ratio sensor 24 has risen to the target activation temperature Ta or higher. The determination is made based on whether or not the element impedance Z has fallen below the impedance value Za corresponding to the target activation temperature Ta.

The air-fuel ratio sensor 2 is determined from the integrated value of the heater power and the elapsed time after the start of the element temperature raising control, which will be described later.
The element temperature T of 4 may be estimated. Alternatively, the element temperature T of the air-fuel ratio sensor 24 may be directly detected by the temperature sensor.

If it is determined in step 103 that the element temperature T of the air-fuel ratio sensor 24 has not risen to the activation temperature Ta, the program is terminated without executing the automatic start control of the next step 104. To do.

After that, when it is determined that the element temperature T of the air-fuel ratio sensor 24 has risen to the target activation temperature Ta, the routine proceeds from step 103 to step 104, the actual engine stop signal is turned off, and automatic start control is executed. And starter 2
9 is turned on to automatically start the engine 11, and then this program ends. The process of step 104 serves as an automatic start control means in the claims.

[Heater Control] The heater control program shown in FIG. 3 is repeatedly executed at a predetermined cycle after the ignition switch is turned on, and functions as a heater control means in the claims. When this program is started, first, in step 201, it is determined whether the automatic stop condition is satisfied and the engine stop request signal is turned on.

When the engine stop request signal is turned on when the automatic stop condition is satisfied while the engine is running, it is judged that the engine stop request is issued, and the routine proceeds to step 202, where the target element temperature of the air-fuel ratio sensor 24 is stopped. The target preheating temperature Tb is switched. This target preheating temperature Tb is lower than the lower limit value of the activation temperature range, and the air-fuel ratio sensor 24
Is set to a temperature at which the sensor element 25 can be maintained in a semi-active state.

Thereafter, the routine proceeds to step 204, and if the engine is stopped, the element temperature T of the air-fuel ratio sensor 24 is maintained near the target preheating temperature Tb lower than the activation temperature Ta (the element impedance Z is the target). Preheating temperature Tb
The preheating control (heater energization control while the engine is stopped) is performed so that the heater current is controlled to be lower than that during engine operation so as to be maintained near the impedance value Zb corresponding to

When the automatic start condition is satisfied during the automatic engine stop and the engine stop request signal is turned off (when "No" is determined in step 201), it is determined that the engine start request is made. From step 201 to step 203, the target element temperature of the air-fuel ratio sensor 24 is switched to the target activation temperature Ta during engine operation. The target activation temperature Ta is set near the optimum activation temperature at which the activation state of the sensor element 25 is the best.

After that, the routine proceeds to step 204, where the element temperature T of the air-fuel ratio sensor 24 is set as a target before the automatic start of the engine 11 is started immediately after the automatic start condition is satisfied (immediately after the engine stop request signal is turned off). In order to quickly raise the temperature to the activation temperature Ta (in order to quickly reduce the element impedance Z to the impedance value Za corresponding to the target activation temperature Ta), the element temperature rise control for increasing the heater current (the automatic start condition is satisfied). Immediately after the heater energization control) is executed.

While the engine is running, every time this program is started, the routine proceeds from step 201 to step 203, and the target element temperature of the air-fuel ratio sensor 24 is maintained at the target activation temperature Ta, so at step 204. The heater energization control is performed during engine operation, and the heater current is feedback-controlled so that the element temperature T of the air-fuel ratio sensor 24 is maintained near the target activation temperature Ta.

In the present embodiment (1) described above, the element temperature T of the air-fuel ratio sensor 24 while the engine 11 is automatically stopped.
Since the preheating control is performed such that the heater current is reduced to preheat so as to maintain near the target preheating temperature Tb lower than the target activation temperature Ta, the element temperature T is maintained at the activation temperature while the engine 11 is automatically stopped. As compared with the conventional method, the power consumption of the heater during the automatic stop of the engine 11 can be reduced, and the load on the battery can be reduced.
The battery can last a long time.

Moreover, by maintaining the element temperature T of the air-fuel ratio sensor 24 near the target preheating temperature Tb while the engine 11 is automatically stopped, the element temperature T of the air-fuel ratio sensor 24 is targeted after the engine 11 is automatically started. The time required to raise the temperature to the activation temperature Ta can be shortened, and it becomes possible to start the air-fuel ratio feedback control based on the output of the air-fuel ratio sensor 24 at an early stage after the automatic start. Exhaust emissions can be reduced by controlling the air-fuel ratio with high accuracy from an early stage.

Further, in this embodiment (1), the engine 1
Element temperature for increasing the heater current to raise the element temperature T of the air-fuel ratio sensor 24 to the target activation temperature Ta before the engine 11 is automatically started when the automatic start condition is satisfied during the automatic stop of 1. Since the temperature rise control is started and the element temperature T of the air-fuel ratio sensor 24 is raised to the target activation temperature Ta and the air-fuel ratio sensor 24 is activated, the engine 11 is automatically started. The air-fuel ratio sensor 24 has already been activated. Therefore, the problem of the delay in the start timing of the air-fuel ratio feedback control due to the delay in activation of the air-fuel ratio sensor at the time of automatic start is completely solved, and other conditions for executing the air-fuel ratio feedback control are satisfied after the automatic start. The air-fuel ratio feedback control can be immediately started immediately.

In this case, the element temperature T of the air-fuel ratio sensor 24 is set after the automatic start condition is satisfied during the automatic stop of the engine 11 and before the automatic start of the engine 11 is actually started.
There is a time delay until the temperature rises from the target preheating temperature Tb to the target activation temperature Ta, but the element temperature T of the air-fuel ratio sensor 24 is preheat-controlled to the target preheating temperature Tb during the automatic stop of the engine 11, so that the automatic start is performed. The time delay of the automatic start of the engine 11 with respect to the engine start request due to the satisfaction of the condition is small, and in the hybrid vehicle, the electric motor 10 can immediately drive the vehicle with respect to the automatic start request due to the satisfaction of the automatic start condition. The time delay of the automatic start of the engine 11 with respect to the engine start request due to the establishment is not a problem at all.

<< Embodiment (2) >> By the way, the engine 1
Immediately after the completion of the start of 1 (immediately after the complete explosion), there is a behavior in which the engine speed rapidly rises / falls and then reaches a stable state. The operation state of 11 becomes a state in which the air-fuel ratio feedback control can be started when the engine rotation speed after the start of the engine 11 is relatively stable.

In consideration of such circumstances, in the present embodiment (2), the controller 32 controls the engine automatic stop / start control program of FIG. 5 and the heater control of FIG. 3 described in the embodiment (1). By executing the program,
As shown in the time chart of FIG. 3, an element that immediately raises the element temperature T of the air-fuel ratio sensor 24 to the target activation temperature Ta when an automatic start condition is satisfied during the automatic stop of the engine 11 and an engine start request is generated. The temperature rise control is started, and thereafter, the element temperature T of the air-fuel ratio sensor 24 is raised to the target activation temperature Ta and the activation of the air-fuel ratio sensor 24 is finished at the same time or after that, the operating state of the engine 11 Starts the automatic start of the engine 11 so that the engine can start the air-fuel ratio feedback control.

The engine automatic stop / start control program of FIG. 5 is obtained by changing the process of step 103 of the engine automatic stop / start control program of FIG. 2 described in the embodiment (1) to the process of step 103a. .

In the engine automatic stop / start control program shown in FIG. 5, when the automatic start condition is satisfied during the automatic engine stop and the engine stop request signal is turned off, it is judged that there is an engine start request, and step 101 To step 103a, it is determined whether or not a predetermined time tw has passed since the engine stop request signal was turned off (after the element temperature raising control by the heater control program of FIG. 3 was started). The predetermined time tw sets a waiting time from when the engine stop request signal is turned off until the automatic start of the engine 11 is started, and the element of the air-fuel ratio sensor 24 is started after the element temperature increase control is started. The sensor activation time ts required for the temperature T to rise from the target preheating temperature Tb to the target activation temperature Ta, and the feedback waiting time required for the operating state of the engine 11 to change from the automatic start to the state in which the air-fuel ratio feedback control can be started. Considering the time tf, the operating state of the engine 11 becomes empty at the same time as or after the element temperature T of the air-fuel ratio sensor 24 rises to the target activation temperature Ta and the activation of the air-fuel ratio sensor 24 ends. It is set so that the fuel ratio feedback control can be started. tw + tf ≧ ts

When the sensor activation time ts is shorter than the feedback waiting time tf, the waiting time tw from the start of the element temperature raising control to the start of the automatic start is set to 0 to raise the element temperature. The automatic start may be started at the same time when the control is started.

Further, the sensor activation time ts and the feedback waiting time tf may be fixed values preset based on experiments or simulations, but the operating conditions at the time of automatic start (cooling water temperature, intake air temperature, outside air temperature, engine Considering that the sensor activation time ts and the feedback waiting time tf are changed according to the stop time, etc., the sensor activation time ts and the feedback waiting time tf are set by a map or a mathematical formula according to the operating conditions at the time of automatic start. It may be done. Alternatively, the sensor activation time ts and the feedback waiting time tf may be learned in advance for each operating condition at the time of automatic start, and the learning value according to the operating condition at the time of automatic start may be used.

Before the predetermined time tw has passed from the turning off of the engine stop request signal (start of the element temperature raising control), it is judged "No" in the above step 103a, and the automatic start control of the next step 104 is executed. End this program without

Thereafter, when it is determined in step 103a that the predetermined time tw has elapsed from the turning off of the engine stop request signal (start of element temperature increase control), step 10
In step 4, the actual engine stop signal is turned off and the automatic start control is executed to automatically start the engine 11.

In the embodiment (2) described above, the air-fuel ratio sensor 24 is immediately activated when the automatic start condition is satisfied during the automatic stop of the engine 11 and the engine start request is generated.
The element temperature increase control for increasing the element temperature T of the air-fuel ratio sensor 24 to the target activation temperature Ta is started, and thereafter, the element temperature T of the air-fuel ratio sensor 24 is increased to the target activation temperature Ta to increase the air-fuel ratio sensor 24.
At the same time as or after the activation of the engine ends.
Since the automatic start of the engine 11 is started so that the operation state of No. 1 becomes a state in which the air-fuel ratio feedback control can be started, when the predetermined automatic start condition is satisfied during the automatic stop of the engine 11, the air-fuel ratio is controlled. The automatic start of the engine 11 can be started in the middle of the element temperature increase control without waiting for the element temperature T of the sensor 24 to increase to the activation temperature Ta, and an automatic start request due to the establishment of the automatic start condition can be made. On the other hand, when the engine 11 can be automatically started with good response, and the operating state of the engine 11 becomes a state in which the air-fuel ratio feedback control can be started after the automatic start, the air-fuel ratio is immediately determined based on the output of the air-fuel ratio sensor 24. Feedback control can be started, and both quick automatic start when automatic start conditions are met and early start of air-fuel ratio feedback control It can be.

In the above embodiment (2), the engine 1
When the automatic start condition is satisfied during the automatic stop of No. 1, the element temperature raising control is immediately started to raise the element temperature T of the air-fuel ratio sensor 24 to the target activation temperature Ta or at the same time or thereafter. The automatic start of the engine 11 is started so that the operating state of 11 becomes a state in which the air-fuel ratio feedback control can be started. However, when the automatic start condition is satisfied during the automatic stop of the engine 11, immediately or slightly. After that, the automatic start of the engine 11 is started and the engine 1
The element temperature raising control is started so that the element temperature T of the air-fuel ratio sensor 24 is raised to the activation temperature Ta by the time when the operating state of No. 1 becomes a state in which the air-fuel ratio feedback control can be started. It is also possible (in this case, the start timing of the element temperature rise control is at the same time as or after the automatic start condition is satisfied). Even in this case, when the automatic start condition is satisfied during the automatic stop of the engine 11, the automatic start of the engine 11 is performed without waiting for the element temperature T of the air-fuel ratio sensor 24 to rise to the activation temperature Ta. The process can be started, and the same effect as the case of the above embodiment (2) can be obtained.

In this case, the heater current may be fixed to the maximum current (for example, 100% duty) during the element temperature raising control, but after the automatic start, the operating state of the engine 11 can start the air-fuel ratio feedback control. The heater current may be variably controlled according to the feedback waiting time tf until the above.

In each of the above embodiments (1) and (2), the present invention is applied to a system equipped with the air-fuel ratio sensor 24 for detecting the air-fuel ratio of exhaust gas. The present invention can be applied to a system equipped with a sensor that detects a component concentration and an oxygen sensor that detects rich / lean of exhaust gas.

Further, the scope of application of the present invention is not limited to a hybrid vehicle in which a driving force of an engine and a driving force other than the engine such as an electric motor are used together, and the present invention is applied to a vehicle traveling only by the driving force of the engine. You may.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.

FIG. 2 is a flowchart showing a processing flow of an engine automatic stop / start control program according to the embodiment (1).

FIG. 3 is a flowchart showing a processing flow of a heater control program of the embodiment (1).

FIG. 4 is a time chart showing an execution example of the embodiment (1).

FIG. 5 is a flowchart showing a processing flow of an engine automatic stop / start control program of the embodiment (2).

FIG. 6 is a time chart showing an execution example of the embodiment (2).

[Explanation of symbols]

10 ... Electric motor, 11 ... Engine (internal combustion engine), 20
... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 23
… Catalyst, 24… Air-fuel ratio sensor (exhaust gas sensor), 25
... Sensor element, 26 ... Heater, 29 ... Starter, 30 ...
Brake sensor, 31 ... Vehicle speed sensor, 32 ... Control device (automatic stop control means, automatic start control means, heater control means).

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 45/00 368 F02D 45/00 368F F term (reference) 3G084 AA00 CA01 CA07 DA02 DA10 EB16 FA29 3G092 AA00 AC02 AC03 CA01 EA08 EA17 FA17 FA18 FA24 FA30 GA01 GA10 HD03Z 3G093 AA07 AA16 BA19 BA20 BA21 BA22 CA02 DB09 3G301 HA00 JA02 KA04 NA08 ND13 NE21 PA11Z PD02Z PD13Z PE03Z PE08Z PF01Z PF05Z

Claims (4)

[Claims] 1. An exhaust gas sensor for detecting a gas component concentration such as oxygen concentration of an exhaust gas of an internal combustion engine, an air-fuel ratio, or rich / lean and an energization of a heater provided in the exhaust gas sensor to control the exhaust gas sensor. A controller for an internal combustion engine, comprising: a heater control means for raising the temperature of a sensor element of the exhaust gas sensor (hereinafter referred to as "element temperature") to an activation temperature, and controlling the internal combustion engine based on the output of the exhaust gas sensor. Equipped with an automatic stop control means for automatically stopping the internal combustion engine when a predetermined automatic stop condition is satisfied during operation of the engine, the heater control means, the element temperature of the exhaust gas sensor during automatic stop of the internal combustion engine A control device for an internal combustion engine, wherein energization of the heater is controlled so as to be maintained near a predetermined preheating temperature set to a temperature lower than an activation temperature. 2. An automatic start control means for automatically starting the internal combustion engine when a predetermined automatic start condition is satisfied during automatic stop of the internal combustion engine, wherein the heater control means satisfies the automatic start condition. When the automatic start control means starts control to raise the element temperature of the exhaust gas sensor to an activation temperature before starting the automatic start of the internal combustion engine, the automatic start control means is the element temperature of the exhaust gas sensor. The control device for the internal combustion engine according to claim 1, wherein the automatic start of the internal combustion engine is started after the temperature rises to the activation temperature. 3. An automatic start control means for automatically starting the internal combustion engine when a predetermined automatic start condition is satisfied during automatic stop of the internal combustion engine, wherein the heater control means satisfies the automatic start condition. When, immediately start the control to raise the element temperature of the exhaust gas sensor to the activation temperature, the automatic start control means, at the same time as the element temperature of the exhaust gas sensor is raised to the activation temperature or that 2. The control apparatus for an internal combustion engine according to claim 1, wherein the automatic start of the internal combustion engine is started so that the operating state of the internal combustion engine becomes a state in which the air-fuel ratio feedback control can be started thereafter. 4. An automatic start control means for automatically starting the internal combustion engine when a predetermined automatic start condition is satisfied during automatic stop of the internal combustion engine, wherein the automatic start control means satisfies the automatic start condition. The automatic control of the internal combustion engine is started immediately or with a slight delay, and the heater control means causes the emission by the time when the operating state of the internal combustion engine after the automatic start becomes a state in which the air-fuel ratio feedback control can be started. 2. The energization of the heater after the automatic start condition is satisfied is controlled so that the element temperature of the gas sensor is raised to the activation temperature.
A control device for an internal combustion engine according to.