JP4697129B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine control device having an exhaust gas sensor with a heater and an automatic stop (idle stop) function.

  In an electronically controlled internal combustion engine in recent years, any of gas component concentration such as oxygen concentration of exhaust gas, air-fuel ratio, rich / lean on the upstream side of the catalyst in the exhaust passage (or both upstream and downstream sides of the catalyst) An exhaust gas sensor for detecting the exhaust gas is installed, and the exhaust gas purification efficiency of the catalyst is improved by feedback-controlling the air-fuel ratio to the vicinity of the theoretical air-fuel ratio based on the output of the exhaust gas sensor. In general, the exhaust gas sensor has poor detection accuracy unless the temperature of the element portion is raised to the activation temperature. Therefore, a heater is incorporated in the exhaust gas sensor, and the heater is energized to promote activation of the exhaust gas sensor. Yes.

  In addition, vehicles equipped with automatic engine stop / restart devices (so-called idling stop devices) are increasing for the purpose of reducing fuel consumption and exhaust emissions. This automatic engine stop / restart device, for example, automatically stops the engine when the driver stops the vehicle, and then the driver performs an operation (such as a brake release operation) to start the vehicle. The engine is automatically started when

In this case, as described in Patent Document 1 (Japanese Patent Laid-Open No. 9-88688), in order to prevent the exhaust gas sensor from cooling and becoming inactive during the automatic stop, the heater is energized during the automatic stop. The exhaust gas sensor is maintained in an active state by continuing until the time of restart.
JP-A-9-88688 (first page, etc.)

  If the heater energization of the exhaust gas sensor is continued until the restart at the time of restart as in the above-mentioned Patent Document 1, the electrical load at the time of restart increases accordingly, so a small displacement engine mounted with a small output torque Cars have a negative effect on restartability and fuel efficiency. In addition, since a vehicle with a small displacement engine generally has a small battery capacity, if the heater energization is continued until the restart when the automatic stop time becomes long, the charged state of the battery is also adversely affected.

  In view of this, there is a technique in which the heater energization of the exhaust gas sensor is stopped during the automatic stop, giving priority to reducing the electric load and improving the restartability and fuel consumption during the automatic stop. However, if the heater energization is stopped every time the automatic stop is performed, the temperature of the exhaust gas sensor is decreased each time the automatic stop is performed, and the temperature of the exhaust gas sensor is rapidly increased by starting the energization of the heater at the subsequent restart. Since the temperature decrease / rapid increase is a temperature cycle in which stress (thermal stress) is applied to the element part of the exhaust gas sensor, the element part of the exhaust gas sensor deteriorates as the number of automatic stops (heater energization stop number) increases. It is expected that. For this reason, if the travel distance in which automatic stop / restart is frequently repeated due to waiting for a signal for traveling in an urban area, the progress of deterioration of the exhaust gas sensor with respect to the accumulated travel distance is accelerated, and the deterioration of the exhaust gas sensor is accelerated earlier than expected. Impact may appear. Since the deterioration of the exhaust gas sensor deteriorates the air-fuel ratio controllability and causes the emission and drivability to deteriorate, it is necessary to take measures to slow down the progress of deterioration of the exhaust gas sensor as much as possible.

  The present invention has been made in view of such circumstances. Accordingly, the object of the present invention is to promote the deterioration of the exhaust gas sensor while satisfying the requirements of electric load reduction and restartability / fuel efficiency improvement during automatic stop to some extent. An object of the present invention is to provide a control device for an internal combustion engine that can slow down the condition.

In order to achieve the above object, an invention according to claim 1 is directed to an exhaust gas sensor for detecting any one of a gas component concentration, such as an oxygen concentration of an exhaust gas of an internal combustion engine, an air-fuel ratio, and rich / lean, and to the exhaust gas sensor. Heater control means for controlling the energization of the heater provided to heat the exhaust gas sensor to an active state; air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the output of the exhaust gas sensor; And an automatic stop control means for automatically stopping the internal combustion engine when a predetermined automatic stop condition is satisfied during operation of the internal combustion engine, wherein the heater control means includes the automatic stop control electrical load increase during the automatic stop means to continue without stopping the heater energization of the exhaust gas sensor during the automatic stop of the internal combustion engine, the heater energizing time during the automatic stop by means And means for limiting within allowable heater energization time acceptable in view of deterioration of re-startability and fuel consumption, and means for storing a count of the automatic stop count by the automatic stop control means, the allowable according to the automatic stop count And a means for changing the heater energization time.

In short, the present invention continues without stopping the heater energization of the exhaust gas sensor at the time of automatic stop, thereby reducing the number of times the heater energization is turned off / on and slowing down the deterioration of the exhaust gas sensor. Continued energization of the exhaust gas sensor to the time of restart during automatic stop will lead to an increase in electrical load during automatic stop and deterioration of restartability and fuel consumption, so the heater energization time during automatic stop is within the allowable heater energization time. The allowable heater energization time is changed according to the progress of exhaust gas sensor degradation by changing the allowable heater energization time according to the number of automatic stops correlated with the progress of exhaust gas sensor degradation. It is possible to perform control. As a result, it is possible to slow down the progress of deterioration of the exhaust gas sensor while satisfying the requirements of electric load reduction during automatic stop, restartability and fuel consumption to some extent, and deterioration of air-fuel ratio controllability due to deterioration of the exhaust gas sensor And deterioration of emission drivability can be prevented over a long period of time.

  In this case, the longer the allowable heater energization time is, the higher the probability of restart within the allowable heater energization time (that is, the probability that the heater energization is not turned off during automatic stop and continues until the restart). There is a relationship that the longer the energization time is, the less the heater energization is turned off / on, and the slower the deterioration of the exhaust gas sensor.

  Therefore, as the number of automatic stops is increased and the allowable heater energization time is set to a longer time as in claim 2, the longer the allowable heater energization time is set as the degree of deterioration of the exhaust gas sensor proceeds. In addition, the progress of deterioration of the exhaust gas sensor can be delayed by reducing the number of times the heater energization is turned off / on.

  Alternatively, as described in claim 3, the shorter the number of automatic stops, the shorter the allowable heater energization time is set, and the smaller the degree of deterioration of the exhaust gas sensor, the shorter the allowable heater energization time. In addition, it is possible to increase the effect of reducing the electric load during automatic stop and improving the restartability and fuel consumption.

  Further, as described in claim 4, during the automatic stop, the continuation / stop of heater energization may be determined based on the electric load (power consumption) of the in-vehicle device. At this time, the electric load of the in-vehicle device may be determined based on, for example, the charging voltage of the battery, on / off of an air conditioner (air conditioner), lighting / extinguishing of lamps such as a headlamp and a rear lamp. If the continuation / stop of the heater energization is determined based on the electric load of the in-vehicle device, the continuation / stop of the heater energization can be determined so that the electric load during the automatic stop or restart is not excessively increased.

  Specifically, as in claim 5, the heater energization is stopped when the electric load of the in-vehicle device is greater than or equal to a predetermined value during automatic stop, or in automatic stop as in claim 6. In addition, when the electric load of the in-vehicle device is equal to or less than a predetermined value, the heater energization may be continued within a range not exceeding the allowable heater energization time. In this way, it is possible to reliably limit the electric load during the automatic stop or during the restart so as not to become too large.

  In a system comprising an automatic stop control device functioning as the automatic stop control device, and an engine control device functioning as the heater control device and the air-fuel ratio control device, the automatic stop control device as in claim 7. It is preferable to monitor the presence or absence of an abnormality in the operation state of the apparatus and the presence or absence of an abnormality in the communication system with the automatic stop control device, and to prohibit heater energization during automatic stop when any abnormality is detected. . In this way, when an abnormality occurs in the automatic stop control device itself or the communication system, the heater energization during the automatic stop is forcibly stopped. It is possible to avoid a situation where the number of energization off / on times abnormally increases.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 which is an internal combustion engine, and an air flow meter 14 for detecting the intake air amount is provided downstream of the air cleaner 13. A throttle valve 15 and a throttle opening sensor 16 for detecting the throttle opening are provided on the downstream side of the air flow meter 14. The intake pipe 12 is provided with a bypass passage 25 that bypasses the throttle valve 15, and an idle speed control valve (ISC valve) 26 is provided in the bypass passage 25.

  Further, a surge tank 17 is provided on the downstream side of the throttle valve 15, and an intake pipe pressure sensor 18 for detecting the intake pipe pressure is provided in the surge tank 17. 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 in the vicinity of the intake port of the intake manifold 19 of each cylinder. Yes. A spark plug 21 is attached to the cylinder head of each cylinder. A cooling water temperature sensor 27 that detects the cooling water temperature and a crank angle sensor 28 that detects the engine rotation speed are attached to the cylinder block of the engine 11.

  On the other hand, a catalyst 23 such as a three-way catalyst for reducing CO, HC, NOx, etc. in the exhaust gas is provided in the middle of the exhaust pipe 22 of the engine 11, and the exhaust is discharged upstream and downstream of the catalyst 23, respectively. Exhaust gas sensors 24 and 25 (oxygen sensor, air-fuel ratio sensor, etc.) for detecting any of gas component concentrations such as oxygen concentration of gas, air-fuel ratio, and rich / lean are provided. Since the element portions of the exhaust gas sensors 24 and 25 have a high activation temperature (about 600 to 700 ° C. or more), the element portions of the exhaust gas sensors 24 and 25 are activated early after engine startup only by the heat of the exhaust gas. It is difficult.

  Therefore, each exhaust gas sensor 24, 25 has a built-in heater (not shown), and heats the heater to quickly raise the temperature of the element portion to the active temperature range, and also enables each exhaust gas sensor 24, 25 during engine operation. Heater energization is performed by duty control or the like so as to maintain the activation temperature range. Needless to say, the present invention can be applied to a configuration in which the exhaust gas sensor 25 is not provided on the downstream side of the catalyst 23.

  The various sensor outputs described above are input to an engine control device (hereinafter referred to as “engine ECU”) 29. The engine ECU 29 is mainly composed of a microcomputer, and executes various control programs stored in a built-in ROM (storage medium) to thereby determine the fuel injection amount of the fuel injection valve 20 according to the engine operating state. The ignition timing of the spark plug 21 is controlled. The engine ECU 29 functions as air-fuel ratio control means for feedback-controlling the air-fuel ratio of the air-fuel mixture supplied to the engine 11 to the target air-fuel ratio based on the outputs of the exhaust gas sensors 24 and 25 during engine operation.

  An automatic stop control device (hereinafter referred to as “eco-run ECU”) 30 communicates with the engine ECU 29 as automatic stop control means for controlling automatic engine stop / restart for the purpose of reducing fuel consumption and exhaust emissions. It is provided so that it can. This eco-run ECU 30 is mainly composed of a microcomputer, and when a predetermined automatic stop condition (for example, the brake switch is turned on at idle after warm-up and the vehicle speed is equal to or lower than a predetermined value) is established during engine operation. An automatic stop request (fuel cut request) is output to the engine ECU 29. When the engine ECU 29 receives the automatic stop request from the eco-run ECU 30, the engine ECU 29 stops the fuel injection of the fuel injection valve 20 to stop the engine 11, and sets the automatic stop flag to ON. Thereafter, the eco-run ECU 30 resets the automatic stop flag to OFF when the driver detects an operation (for example, a brake release operation, a shift operation to the D range, etc.) to start the vehicle, and fuel injection is performed. The fuel injection of the valve 20 is restarted and the engine 11 is restarted.

  On the other hand, the engine ECU 29 functions as a heater control means for controlling the heater energization of the exhaust gas sensors 24 and 25 by duty control. When the engine 11 is cold started (when the exhaust gas sensors 24 and 25 are inactive), the heater duty is set. By setting a large duty (for example, 100% duty) and increasing the amount of heat generated by the heater, the exhaust gas sensors 24 and 25 are quickly raised to the activation temperature range, and after the exhaust gas sensors 24 and 25 are activated, the heater duty is increased. The exhaust gas sensors 24 and 25 are maintained in the active temperature range by reducing the duty to a small duty (for example, 30% duty). The heater duty when maintaining each exhaust gas sensor 24, 25 in the activation temperature range may be fixed to a predetermined constant value, or the temperature of the element part of each exhaust gas sensor 24, 25 may be set. The heater duty may be feedback-controlled according to the detected temperature by detecting the impedance of the element portion or the like.

  Further, the engine ECU 29 continues energization of the heaters of the exhaust gas sensors 24 and 25 even during the automatic stop, and reduces the electric load during the automatic stop and restarts in order to delay the progress of the deterioration of the exhaust gas sensors 24 and 25 as much as possible. In order to consider the demand for improved startability and fuel consumption, the heater energization time during automatic stop is limited within the allowable heater energization time.

  In short, by continuing the heater energization of the exhaust gas sensors 24 and 25 during the automatic stop, the heater energization is turned off / on and the progress of deterioration of the exhaust gas sensors 24 and 25 is delayed. If the heater energization of the exhaust gas sensors 24 and 25 is continued until restart, the electrical load during the automatic stop will increase and the restartability and fuel consumption will deteriorate, so the heater energization time during the automatic stop will be within the allowable heater energization time. It is limited to.

  In this case, the longer the allowable heater energization time is, the higher the probability of restart within the allowable heater energization time (that is, the probability that the heater energization is not turned off during automatic stop and continues until the restart). As the energization time becomes longer, the heater energization is turned off / on less frequently, and the progress of deterioration of the exhaust gas sensors 24, 25 is delayed.

  In consideration of this relationship, in the present embodiment, the number of automatic stops from the time of a new vehicle having a correlation with the progress of deterioration of the exhaust gas sensors 24 and 25 is counted, and data on the number of automatic stops is provided in the engine ECU 29. Stored in a rewritable non-volatile memory (such as an EEPROM that does not require a backup power source from a battery), the greater the number of automatic stops, the longer the allowable heater energization time, and the smaller the number of automatic stops, The allowable heater energization time is set to a short time. In this way, as the number of automatic stops increases and the degree of deterioration of the exhaust gas sensors 24, 25 progresses, the allowable heater energization time is set longer and the heater energization off / on times are reduced to reduce the exhaust gas sensors 24, 25. The progress of the deterioration of 25 can be delayed. In addition, the smaller the number of automatic stops (that is, the smaller the degree of deterioration of the exhaust gas sensors 24, 25), the shorter the allowable heater energization time, thereby reducing the electric load during automatic stop and improving the restartability and fuel consumption. Can be increased.

  Furthermore, in this embodiment, the continuation / stop of heater energization is determined based on the electric load (power consumption) of the in-vehicle device during the automatic stop. At this time, the electric load of the in-vehicle device may be determined based on, for example, the charging voltage of the battery, on / off of an air conditioner (air conditioner), lighting / extinguishing of lamps such as a headlamp and a rear lamp.

  Specifically, when the electric load of the in-vehicle device is greater than or equal to a predetermined value during automatic stop, the heater energization is stopped even within the allowable heater energization time, and the electric load of the in-vehicle device is less than or equal to the predetermined value during automatic stop In this case, the heater energization is continued within a range not exceeding the allowable heater energization time. In this way, it is possible to reliably limit the electric load during the automatic stop or during the restart so as not to become too large.

  The heater duty during the automatic stop may be set to the same heater duty (for example, 30% duty) as that immediately before the automatic stop, or slightly lower than the heater duty immediately before the automatic stop in order to reduce the heater power consumption. The duty may be set. In short, the temperature of the exhaust gas sensors 24 and 25 during automatic stop is maintained at or near the activation temperature range (to reduce the temperature drop of the exhaust gas sensors 24 and 25 during automatic stop). It is sufficient to set the heater duty necessary for the above.

  In addition, the engine ECU 29 is equipped with an abnormality diagnosis function that monitors whether there is an abnormality in the operating state of the eco-run ECU 30 and whether there is an abnormality in the communication system with the eco-run ECU 30, and when detecting an abnormality in the operating state of the eco-run ECU 30 The eco-run ECU abnormality flag is turned ON, and when a communication system abnormality is detected, the communication system abnormality flag is turned ON, and when any abnormality is detected, heater energization during automatic stop is prohibited (heater duty is 0%) ). In this way, when an abnormality occurs in the eco-run ECU 30 or the communication system, the heater energization during the automatic stop is forcibly stopped. It is possible to avoid a situation in which the number of ONs increases abnormally.

  The heater energization control of the exhaust gas sensors 24 and 25 described above is executed by the engine ECU 29 and the eco-run ECU 30 as follows according to the heater energization control routine of FIG. When this routine is started, first, in step 101, it is determined whether or not a predetermined time required for raising the temperature of the exhaust gas sensors 24, 25 to the activation temperature range has elapsed since the cold start of the engine 11. If the predetermined time has not elapsed, it is determined that the exhaust gas sensors 24 and 25 have not yet been heated to the activation temperature range, and the routine proceeds to step 102 where the heater duty is set to a large duty (for example, 100% duty). By increasing the amount of heat generated by the heater, the exhaust gas sensors 24 and 25 are quickly heated. At this time, the heater duty may be gradually reduced as the temperature of the exhaust gas sensors 24 and 25 approaches the activation temperature range.

  Thereafter, when a predetermined time has elapsed from the cold start of the engine 11, it is determined that the exhaust gas sensors 24, 25 have been heated to the activation temperature range, and the routine proceeds to step 103 where the heater duty is set to a small duty (for example, 30% duty). ) To supply the heater heat generation amount necessary for maintaining the exhaust gas sensors 24 and 25 in the active temperature range (or in the vicinity thereof). The processes of steps 101 to 103 are executed by the engine ECU 29.

  Thereafter, the routine proceeds to step 104, where it is determined whether a predetermined automatic stop condition (for example, the brake switch is turned on at idle after warm-up and the vehicle speed is equal to or lower than a predetermined value) is satisfied during engine operation, If the automatic stop condition is not satisfied, the process returns to step 103, and energization of the heater for maintaining the exhaust gas sensors 24, 25 in the activation temperature range (or the vicinity thereof) is continued.

  Thereafter, when the automatic stop condition is satisfied, the routine proceeds to step 105, where the eco-run ECU 30 outputs an automatic stop request (fuel cut request) to the engine ECU 29. The processing of these steps 104 and 105 is executed by the eco-run ECU 30.

  Then, in the next step 106, the engine ECU 29 stops the fuel injection of the fuel injection valve 20 to stop the engine 11, and the automatic stop flag is set to ON. Thereafter, the routine proceeds to step 107, where the number of automatic stops from the time of a new vehicle is counted, and the data of the number of automatic stops is stored in a rewritable nonvolatile memory (such as an EEPROM that does not require a backup power source from a battery). The data on the number of times of automatic stop is stored and held even when the operation of the engine 11 is stopped (when the ignition switch is turned off), and further stored and held even when the battery is removed from the vehicle.

  Thereafter, the process proceeds to step 108, where the allowable heater energization time is set according to the number of automatic stops from the time of the new vehicle to the present with reference to the map of the allowable heater energization time in FIG. continue. In the map of the allowable heater energizing time in FIG. 3, in the region where the number of automatic stops is equal to or less than the first predetermined value N1, the allowable heater energizing time is set to a shorter time as the number of automatic stops is smaller, and the number of automatic stops is the first predetermined number. In the region from the value N1 to the second predetermined value N2 larger than that, the allowable heater energization time is set to a constant time (or the rate of increase in the allowable heater energization time relative to the increase in the number of automatic stops is higher than in other regions. In a region where the number of automatic stops is equal to or greater than the second predetermined value N2, the allowable heater energization time is set to a longer time as the number of automatic stops is larger.

  Thereafter, the process proceeds to step 109, where the heater energization time counter Theat during automatic stop is counted up to measure the heater energization time (automatic stop time) during automatic stop. Then, in the next step 110, it is determined whether or not the heater energization stop condition during the automatic stop is satisfied by whether or not one of the following three conditions (1) to (3) is satisfied.

(1) The electric load (power consumption) of the in-vehicle equipment that is automatically stopped must be greater than or equal to the specified value
(2) The heater energization time Theat during automatic stop exceeds the allowable heater energization time.
(3) The eco-run ECU 30 is abnormal (the eco-run ECU abnormal flag is ON) or the communication system is abnormal (the communication system abnormal flag is ON)

  If none of these three conditions (1) to (3) is satisfied, the heater energization stop condition during the automatic stop is not satisfied, and the process proceeds to step 111 to continue the heater energization during the automatic stop and automatically stop. The process of counting up the heater energization time during automatic stop by counting up the middle heater energization time counter Theat is repeated (step 109).

  Thereafter, when any of the above three conditions (1) to (3) is satisfied, it is determined that the heater energization stop condition during the automatic stop is satisfied, and the process proceeds to step 112 to stop the heater energization during the automatic stop. (The heater duty is set to 0%).

  For example, if the electric load of the in-vehicle device is less than a predetermined value during the automatic stop and the eco-run ECU 30 and the communication system continue to be in a normal state, when the heater energization time Theat during the automatic stop exceeds the allowable heater energization time. Stop the heater energization during automatic stop. Further, even if the heater energization time Theat during the automatic stop is within the allowable heater energization time, if the electric load of the in-vehicle device exceeds a predetermined value, the heater energization during the automatic stop is stopped at that time. If an abnormality in the eco-run ECU 30 or the communication system is detected, the heater energization during the automatic stop is stopped at that time.

  FIG. 4 shows a control example of this embodiment. In the example of FIG. 4, at the time t1, the engine 11 is automatically stopped and the automatic stop flag is set to ON (the heater energization of the exhaust gas sensors 24 and 25 continues even after the automatic stop). During automatic stop, the heater energization time counter Theat during automatic stop is counted up to measure the heater energization time (automatic stop time) during automatic stop.

  In this example, the electric load of the in-vehicle device is less than a predetermined value during the automatic stop, and the eco-run ECU 30 and the communication system are in a normal state (eco-run ECU abnormality flag = OFF and communication system abnormality flag = OFF). The heater energization is continued until the heater energization time during the stop exceeds the allowable heater energization time set according to the number of automatic stops from the time of the new vehicle. Then, at the time t2 when the heater energization time during the automatic stop exceeds the allowable heater energization time, the heater energization during the automatic stop is stopped. Thereafter, at time t3 when an operation for starting the vehicle (for example, a brake release operation, a shift operation to the D range, etc.) is detected, the automatic stop flag is reset to OFF and the fuel injection valve 20 is turned off. Fuel injection is resumed and the engine 11 is restarted.

  The heater energization control during the automatic stop described above continues the heater energization of the exhaust gas sensors 24 and 25 during the automatic stop, thereby reducing the number of times the heater energization is turned off / on and the progress of deterioration of the exhaust gas sensors 24 and 25. However, if the heaters in the exhaust gas sensors 24 and 25 are always energized during the automatic stop until the restart time, the electric load increases during the automatic stop and the restartability and fuel consumption deteriorate. By limiting the heater energization time within the allowable heater energization time and changing the allowable heater energization time according to the number of automatic stops correlated with the progress of deterioration of the exhaust gas sensors 24 and 25, the exhaust gas sensor Control of changing the allowable heater energization time according to the progress of deterioration of 24 and 25 becomes possible. This makes it possible to slow down the progress of the deterioration of the exhaust gas sensors 24 and 25 while satisfying the requirements for reducing the electric load during the automatic stop and improving the restartability and fuel consumption to some extent. It is possible to prevent deterioration of air-fuel ratio controllability and emission drivability over a long period of time.

1 is a schematic configuration diagram of an entire engine control system showing an embodiment of the present invention. It is a flowchart which shows the flow of a heater energization control routine. It is a figure which shows notionally the map which sets the allowable heater energization time according to the frequency | count of automatic stop. It is a time chart explaining an example of heater energization control during automatic stop.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 15 ... Throttle valve, 20 ... Fuel injection valve, 21 ... Spark plug, 22 ... Exhaust pipe, 23 ... Catalyst, 24, 25 ... Exhaust gas sensor, 29 ... Engine ECU ( Engine control device, heater control means, air-fuel ratio control means) 30 ... automatic stop control device, automatic stop control means)

Claims (7)

An exhaust gas sensor for detecting any one of gas component concentrations such as oxygen concentration of an exhaust gas of an internal combustion engine, air-fuel ratio, rich / lean, and energization of a heater provided in the exhaust gas sensor to control the exhaust gas sensor in an active state Heater control means for heating the air, air-fuel ratio control means for controlling the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine based on the output of the exhaust gas sensor, and when a predetermined automatic stop condition is satisfied during operation of the internal combustion engine An internal combustion engine control device provided with an automatic stop control means for automatically stopping the internal combustion engine,
The heater control means includes means for continuing the heater energization of the exhaust gas sensor without stopping when the internal combustion engine is automatically stopped by the automatic stop control means, and increasing the electric load during the automatic stop of the heater energization time during the automatic stop. And means for limiting within the allowable heater energization time allowable from the viewpoint of deterioration of restartability and fuel consumption, means for counting and storing the number of automatic stops by the automatic stop control means, and depending on the number of automatic stops A control device for an internal combustion engine, comprising: means for changing an allowable heater energization time.   2. The control device for an internal combustion engine according to claim 1, wherein the heater control unit sets the allowable heater energization time to a longer time as the number of automatic stops is larger.   3. The control device for an internal combustion engine according to claim 1, wherein the heater control unit sets the allowable heater energization time to a shorter time as the number of automatic stops is smaller.   4. The control device for an internal combustion engine according to claim 1, wherein the heater control means determines whether or not the heater energization is continued / stopped based on an electric load of the in-vehicle device during the automatic stop.   5. The control device for an internal combustion engine according to claim 4, wherein the heater control unit stops energization of the heater when the electric load of the in-vehicle device is equal to or greater than a predetermined value during the automatic stop.   The heater control means continues the heater energization within a range that does not exceed the allowable heater energization time when the electric load of the in-vehicle device is equal to or less than a predetermined value during the automatic stop. Control device for internal combustion engine. An automatic stop control device functioning as the automatic stop control means, and an engine control device functioning as the heater control means and the air-fuel ratio control means,
The engine control device monitors whether there is an abnormality in the operation state of the automatic stop control device and whether there is an abnormality in the communication system with the automatic stop control device, and is automatically stopped when any abnormality is detected The control device for an internal combustion engine according to any one of claims 1 to 6, wherein the heater energization is prohibited.

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