JP2000249677A - O2 sensor heater control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the output characteristics of a sensor and to prevent the sensor and a heater from deteriorating by performing the duty control of the conduction state of a heater so that the temperature of an O2 sensor enters an active temperature range. SOLUTION: An O2 sensor heater control device 12 is provided by setting the map of a duty value for temperature based on the temperature of a first O2 sensor 34 being detected by a temperature sensor 152 to a control means 124. A control means 124 sets the duty value for temperature to 100% until the temperature of a heater 150 exceeds a lower-limit temperature for duty control when an engine 2 performs cold start, thus increasing the temperature of a first O2 sensor 34 to an active temperature at an early stage, and performs control so that the duty value for temperature can be decreased at a constant ratio as an upper-limit temperature approaches when the lower-temperature is exceeded for protection so that an allowable upper-limit temperature cannot be reached. Further, when the lower-limit temperature is close, the duty value for temperature is increased and duty control is made so that the temperature of the heater 150 cannot reach the lower-limit temperature or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater control device for an O2 sensor, and more particularly to an O2 sensor which can be activated at an early stage when a cold start of an engine is performed, the output characteristics of the O2 sensor can be stabilized, and the emission harmful component value can be reduced. Can prevent the deterioration of O2
The present invention relates to an O2 sensor heater control device capable of preventing deterioration of a sensor and a heater.

[0002]

2. Description of the Related Art An engine mounted on a vehicle is provided with an O2 sensor for detecting the oxygen concentration in order to feedback control the air-fuel ratio based on the oxygen concentration in the exhaust gas. Some O2 sensors are provided with a heater that generates heat by energization and heats the heater. The heater of the O2 sensor is duty controlled by the O2 sensor heater control unit based on the duty value. When the duty value is set to 100%, the heater generates maximum heat and heats the O2 sensor. On the other hand, when the duty value is set to 0%, the power is turned on. Will be stopped.

As shown in FIG. 7, the O2 sensor heater control device controls the O2 sensor to an active temperature early by performing duty control of the heater with a duty value of 100% until a set time t1 elapses from the start of the cold operation of the engine. By raising the temperature and reducing the duty value to a fixed value (for example, 40%) after the lapse of the set time t1, the temperature of the heater becomes the allowable upper limit temperature Tlim (for example, 800).
° C), and furthermore, when the engine is running at a high speed, the duty value is set to 0% and the power supply to the heater is stopped to prevent the heater from becoming hot.

After the set time t1 has elapsed, the O2 sensor heater controller uses the heater duty value set for the engine speed as shown in FIG.
Some also control the heater temperature.

[0005] The purpose of duty control of the heater of the O2 sensor as described above is, first, by increasing the temperature of the O2 sensor from the time when the engine is started to be cold, and by earlier starting the feedback control of the air-fuel ratio. Secondly, when the O2 sensor and the heater are heated to a high temperature, the output characteristics and the heat generation characteristics are deteriorated due to heat damage, so that the O2 sensor and the heater are protected from exceeding the allowable upper limit temperature Tlim. Further, the purpose is to stabilize the output temperature of the O2 sensor by stabilizing the temperature of the heater and stabilize the exhaust harmful component value.

[0006] Such an O2 sensor heater control device is disclosed in Japanese Patent Application Laid-Open Nos. Hei 8-228279 and Hei 10-1982.
There is one disclosed in JP-A-332628.

Japanese Unexamined Patent Publication No. Hei 8-227279 discloses a method of supplying all power at a duty value of 100% from the start of energization to a heater for heating an oxygen sensor until the temperature of the heater reaches an initial heating temperature. When the temperature reaches the initial heating temperature, the duty value is feedback-controlled so that the heater temperature reaches the target temperature, and when the oxygen sensor reaches the target temperature, the duty value is feedback-controlled so that the oxygen sensor reaches the target temperature.

[0008] Japanese Unexamined Patent Application Publication No. 10-332628 discloses an engine temperature at the end of the previous run and an engine temperature at the current start based on the engine temperature related to the ambient temperature of the oxygen sensor and the start information of the internal combustion engine. A temperature difference from the engine temperature is calculated, and a current is supplied by the first current supply mode when the temperature difference is equal to or more than the predetermined temperature difference within a predetermined period after the engine is started. The current is supplied in the second current supply mode in which the supply amount is smaller than that in the first current supply mode, and the heater is heated.

[0009]

However, in the O2 sensor heater control device shown in FIG. 7, when the engine is rapidly accelerated immediately after the start of the engine and the vehicle runs at high speed, the temperature of the heater becomes within the set time t1 as shown by the broken line. Allowable upper limit temperature Tl
There is a problem of exceeding im.

If the set time t1 is set to be short to cope with such a problem, the duty value of the heater becomes small, the temperature of the heater becomes low, and the output characteristics of the O2 sensor become unstable. There is a disadvantage that the exhaust harmful component value is deteriorated.

This is because there is a correlation between the temperature of the O2 sensor and the temperature of the heater, and when the temperature of the O2 sensor changes,
Output characteristics (TLR / TRL) of the O2 sensor shown in FIG.
However, as shown in FIG. 11, the output characteristics change due to the change to lean balance or rich balance and the output characteristics become unstable. As a result, as shown in FIG. 10, the temperature of the O2 sensor deviates from the activation temperature range RITemp, and the exhaust harmful component value decreases. Worsened,
If the temperature is outside the high temperature side, the O2 sensor and the heater may be deteriorated.

[0012]

Therefore, in order to eliminate the above-mentioned disadvantages, the present invention provides an O2 sensor for detecting the oxygen concentration in the exhaust of an engine, and heats the O2 sensor by generating heat when energized. A heater is provided, and a temperature sensor for detecting the temperature of the O2 sensor or the temperature around the O2 sensor is provided. The temperature of the O2 sensor is set to an active temperature by a temperature duty value set based on the temperature detected by the temperature sensor. Control means for duty-controlling the energization state of the heater so as to fall within the range is provided.

Further, the present invention provides an O2 sensor for detecting the oxygen concentration in the exhaust gas of the engine, a heater for heating the O2 sensor by generating heat when energized, and a load sensor for detecting a load on the engine. A control means is provided for duty-controlling the energization state of the heater so that the O2 sensor enters the activation temperature range by a load duty value set based on the load detected by the load sensor.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The O2 sensor heater control device of the present invention is provided with a temperature sensor for detecting the temperature of the O2 sensor or the temperature around the O2 sensor by the control means.
The duty state of the heater is controlled by a temperature duty value set based on the temperature detected by the temperature sensor so that the temperature of the O2 sensor falls within the activation temperature range.
Alternatively, a load sensor for detecting the load of the engine is provided, and the duty state of the heater is controlled by the load duty value set based on the load detected by the load sensor so that the O2 sensor enters the activation temperature range.

Thus, the O2 sensor heater control device can control the heater with a large duty value at the time of engine cold start to increase the calorific value, and can set the heater to a proper duty after the O2 sensor is activated. The heat value can be adjusted by duty control based on the value.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show a first embodiment of the present invention. In FIG. 4, reference numeral 2 denotes an engine mounted on a vehicle (not shown). The engine 2 includes an air cleaner 4, an intake pipe 6, a throttle body 8, a surge tank 10, an intake manifold 12, and an intake passage 14 as an intake system. The air cleaner 4 is provided with an intake air temperature sensor 16. The intake pipe 6 is provided with an intake air amount sensor 18. The throttle body 8 has a throttle valve 2
0, and a throttle sensor 22 is provided.

The engine 2 includes an exhaust manifold 24, an exhaust pipe 26, a catalytic converter 28, a rear exhaust pipe 30 as an exhaust system, and an exhaust passage 32. The exhaust manifold 24 has a first oxygen concentration detector for detecting the oxygen concentration in the exhaust gas.
O2 sensor 34 is provided. The catalyst converter 28 has a built-in catalyst 36, and a second O2 sensor 38 for detecting the oxygen concentration in the exhaust gas is provided downstream of the catalyst 36.

This engine 2 is provided with a fuel injection valve 40. The fuel injection valve 40 is connected to a fuel tank 44 by a fuel supply passage 42. In the fuel tank 44,
A level sensor 46, a tank internal pressure sensor 48, and a fuel pump 50 are provided. The fuel in the fuel tank 44 is pressure-fed to the fuel supply passage 42 by the fuel pump 50, dust is removed by the fuel filter 52, and supplied to the fuel injection valve 40.

The fuel supply passage 42 is provided with a fuel pressure adjusting valve 54 for adjusting the fuel pressure. The fuel pressure adjusting valve 54 adjusts the fuel pressure to a predetermined value by the intake pressure introduced from the pressure guiding passage 56 communicating with the intake passage 14, and returns excess fuel to the fuel tank 44 through the fuel return passage 58.

The engine 2 is provided with two evaporative fuel devices 60 and 62. The first evaporative fuel device 60 includes:
The canister 64 is provided, and the canister 64 and the fuel tank 4 are provided.
An evaporative passage 66 communicating with the evaporative passage 4 is provided.
Is provided with a tank internal pressure adjusting valve 68.

The first evaporative fuel device 60 has a purge passage 70 communicating the canister 64 with the intake passage 14 on the downstream side of the throttle valve 20, a purge control valve 72 is provided in the purge passage 70, and the canister 64 is provided with a purge control valve 72. An atmosphere passage 74 communicating with the atmosphere is provided.

The second evaporative fuel device 62 is provided with a canister 76, an evaporative passage 78 communicating the canister 76 with the fuel tank 44, and a tank internal pressure regulating valve 80 in the evaporative passage 78. The tank internal pressure regulating valve 80 is provided with a pressure control valve 84 and an intake pressure sensor 86 in a pressure passage 82 communicating with the intake passage 14.

The second evaporative fuel device 62 includes a canister 76 and the purge passage 7 of the first evaporative fuel device 60.
0, and a purge passage 88 communicating with the purge passage 88 is provided.
A purge control valve 90 is provided in the engine, and an evaporative diagnostic passage 92 is provided for communicating a purge passage 88 closer to the canister 76 with respect to the purge control valve 90 and the intake passage 14 upstream of the throttle valve 20. 94 are provided.

Further, the second evaporative fuel device 62 has an atmosphere passage 96 communicating the canister 76 with the atmosphere, and an atmosphere opening / closing valve 98 in the atmosphere passage 96.

The engine 2 is provided with an EGR passage 100 that connects the exhaust passage 32 and the intake passage 14, and an EGR control valve 102 is provided in the EGR passage 100. Reference numeral 104 denotes a blow-by gas passage, reference numeral 106 denotes a PCV valve, reference numeral 108 denotes an ignition coil, reference numeral 110 denotes an ignition plug, and reference numeral 112 denotes a water temperature sensor.

The engine 2 is provided with a bypass passage 114 which bypasses the throttle valve 20 and communicates with the intake passage 14, and an idle control valve 116 for adjusting the flow rate of bypass air is provided in the bypass passage 114. Bypass passage 11
6 is provided with an idle adjustment passage 118 bypassing the idle control valve 116 and an idle adjustment screw 120.

The intake air temperature sensor 16 and the intake air amount sensor 18
, Throttle sensor 22, first O2 sensor 34 and second
O2 sensor 38, fuel injection valve 40 and level sensor 46
, Tank pressure sensor 48, fuel pump 50, purge control valve 72, pressure control valve 84, intake pressure sensor 86, purge control valve 90, evaporation diagnostic valve 94, atmosphere open / close valve 98, EG
R control valve 102, ignition coil 108, water temperature sensor 112
The idle control valve 116 is connected to control means 124 of the O2 sensor heater control device 122.

The control means 124 includes a vehicle speed sensor 126, a crank angle sensor 128, a range position switch 130, an air conditioner 132, and a power steering pressure switch 13.
4, a diagnostic switch terminal 136, a test switch terminal 138, a starter switch 140, a range switch 142, an ignition switch 144, a main fuse 146, and a battery 148.

The O2 sensor heater control device 122 includes a first
Is provided with a heater 150 that generates heat by energization and heats the O2 sensor 34, and is connected to the control means 124.
The duty of the heater 150 is controlled by the duty value (0 to 100%).

Further, the O2 sensor heater control device 122
Is a temperature sensor 1 for detecting the temperature of the first O2 sensor 34 itself or the exhaust temperature around the first O2 sensor 34.
52 is provided and connected to the control means 124. In this embodiment, the temperature sensor 152 is provided integrally with the first O2 sensor 34 and detects the temperature of the first O2 sensor 34 itself.

The control means 124 has a temperature duty value M set based on the temperature detected by the temperature sensor 152.
The duty state of the heater 150 is controlled by ODUTY so that the temperature of the first O2 sensor 34 falls within the activation temperature range.

That is, as shown in FIG. 2, the control means 124 controls the first O2 sensor 34 detected by the temperature sensor 152.
According to the temperature duty value MODUTY of the map set based on the temperature, as shown in FIG. 3, the temperature of the first O2 sensor 34 falls within the activation temperature range RITemp between the lower limit temperature T1 and the upper limit temperature T2. This is for duty control.

The temperature duty value MODUTY is determined by the first
10 when the temperature of the O2 sensor 34 is lower than the lower limit temperature T1.
When the temperature exceeds the lower limit temperature T1, it is set so as to decrease at a constant rate as the temperature approaches the upper limit temperature T2, and becomes 0% when the temperature reaches the upper limit temperature T2.

Next, the operation of the first embodiment will be described with reference to FIG.

The O2 sensor heater control unit 122 is shown in FIG.
As shown in (1), a map of the temperature duty value MODUTY based on the temperature of the first O2 sensor 34 detected by the temperature sensor 152 is set and provided in the control means 124.

When the program is started by the control means 124 (step 200), the O2 sensor heater controller 122 starts the engine 2 (step 20).
2), the first O2 sensor 3 detected by the temperature sensor 152
(4) The duty of the heater 150 is controlled by the temperature duty value MODUTY read from the map set based on the temperature (step 204), and the heater 150 is ended (step 206).

As shown in FIG. 3, when the engine 2 starts cold operation, the control means 124 sets the temperature duty value MODUTY to 1 until the temperature of the heater 150 exceeds the lower limit temperature T1.
By controlling the duty to 00%, the first O2
The temperature of the sensor 34 is raised to the activation temperature at an early stage, and when the temperature exceeds the lower limit temperature T1, duty control is performed such that the temperature duty value MODUTY decreases at a constant rate as the temperature approaches the upper limit temperature T2. When the temperature approaches the lower limit temperature T1, the temperature duty value MODUTY is increased to prevent the temperature of the heater 150 from falling below the lower limit temperature T1. Control.

As described above, the O2 sensor heater control device 122 controls the temperature sensor 15 by the control means 124.
2, the temperature of the first O2 sensor 34 is set to an active temperature range RITemp by the temperature duty value MODUTY set based on the temperature of the first O2 sensor 34 detected by the second O2 sensor 34.
The duty state of the energized state of the heater 150 is controlled so as to enter the range.

As a result, the O2 sensor heater control device 122 of the second embodiment can increase the amount of heat generated by performing duty control of the heater 150 with the large temperature duty value MODUTY when the engine 2 starts to cool.
Further, after activation of the first O2 sensor 34, the heater 150 is activated.
Can be adjusted by an appropriate temperature duty value MODUTY to adjust the amount of heat generated so that the temperature of the first O2 sensor 34 falls within the activation temperature range RITemp.

For this reason, the O2 sensor heater control device 122 can increase the amount of heat generated by the heater 150 when the engine 2 starts cold operation.
The temperature of the sensor 34 can be quickly raised to the activation temperature range RITemp to activate the sensor, the output characteristics of the first O2 sensor 34 can be stabilized, and deterioration of the exhaust harmful component value can be prevented.

The O2 sensor heater controller 12
2 is that the heater 150 can be duty-controlled by an appropriate temperature duty value MODUTY after the activation of the first O2 sensor 34 to adjust the amount of heat generated, thereby reducing the temperature of the first O2 sensor 34 to the activation temperature range RITemp.
The temperature of the first O2 sensor 34 and the temperature of the heater 150 exceed the allowable upper limit temperature Tlim even when the engine is suddenly started and accelerated after the cold start. The first O2 sensor 34 and the heater 150 can be prevented from deteriorating due to high temperature. In this embodiment, the temperature of the first O2 sensor 34 itself is detected by the temperature sensor 152. However, the exhaust temperature around the first O2 sensor 34 may be detected to set the temperature duty value MODUTY. it can.

FIGS. 5 and 6 show a second embodiment of the present invention. As shown in FIG. 4, the O2 sensor heater control device 122 of the second embodiment controls the heater 150 for heating the first O2 sensor 34 by generating heat when energized.
4, a temperature sensor 152 for detecting the temperature of the first O2 sensor 34 is connected to the control means 124, and the load sensor for detecting the load on the engine 2, for example, the intake air amount sensor 18 is used as the load sensor. Connected to

The O2 sensor heater control unit 122 controls the load duty value MOD set by the control means based on the intake air amount as a load detected by the intake air amount sensor 18.
As shown in FIG. 3, the heater 1 is set so that the first O2 sensor 34 enters the activation temperature range RITemp by UTY1.
The duty state of the 50 energization state is controlled.

That is, as shown in FIG. 6, the control means 124 changes the temperature of the first O2 sensor 34 to the activation temperature Ts (for example, based on the intake air amount detected by the intake air amount sensor 18).
700 ° C.) according to the temperature duty value MODUTY of the map set as shown in FIG.
The temperature of the O2 sensor 34 is lower limit temperature T1 and upper limit temperature T2.
The duty control is performed so as to fall within the activation temperature range RITemp between the two.

Next, the operation of the second embodiment will be described with reference to FIG.

The O2 sensor heater control device 122 is shown in FIG.
As shown in the figure, the control means 124 instructs the load duty value M based on the intake air amount as a load detected by the intake air amount sensor 18.
The ODUTY1 map is set and provided.

When the program is started by the control means 124 (step 300), the O2 sensor heater control device 122 starts the engine 2 (step 30).
2) The duty is controlled by setting the load duty value MODUTY1 to 100% (step 304).
It is determined whether the temperature T of the sensor 34 is equal to or higher than the lower limit temperature T1 (step 306).

If the determination (step 306) is NO, the process returns to the above-mentioned processing (step 304). If the determination (step 306) is YES, the temperature of the first O2 sensor 34 becomes the activation temperature Ts (for example, 700) based on the intake air amount as a load detected by the intake air amount sensor 18.
° C), the duty of the heater 150 is controlled by the load duty value MODUTY1 read from the map (step 308), and the temperature T of the first O2 sensor 34 is lower than the lower limit temperature T1 and lower than the upper limit temperature T2. It is determined whether or not there is (Step 310).

If the determination (step 310) is NO, the process returns to the process (step 308). If this determination (step 310) is YES, the first O2
It is determined whether the temperature T of the sensor 34 has exceeded the upper limit temperature T2 (step 312).

If the determination (step 312) is NO, the process returns to the process (step 304). If the determination (step 312) is YES, the duty ratio for load MODUTY1 is set to 0%, duty control is performed (step 314), and the process returns to the step (step 310).

As a result, the O2 sensor heater control device 122 of the second embodiment can increase the amount of heat generated by performing duty control of the heater 150 with the large load duty value MODUTY1 when the engine 2 starts to cool. After activation of the first O2 sensor 34, the heater 1
The amount of heat generation can be adjusted so that the temperature of the first O2 sensor 34 falls within the activation temperature range RITemp by performing duty control on the 50 with an appropriate load duty value MODUTY1.

For this reason, the O2 sensor heater control device 122 can increase the amount of heat generated by the heater 150 when the engine 2 starts cold operation.
The temperature of the sensor 34 can be quickly raised to the activation temperature range RITemp to activate the sensor, the output characteristics of the first O2 sensor 34 can be stabilized, and deterioration of the exhaust harmful component value can be prevented.

The O2 sensor heater controller 12
2 is that the heater 150 can be duty-controlled by an appropriate load duty value MODUTY1 after the activation of the first O2 sensor 34 to adjust the heat generation amount.
The temperature of the first O2 sensor 34 is set to the activation temperature range RItem.
p, the emission harmful component value can be stabilized, and the temperature of the first O2 sensor 34 and the heater 150 can reach the allowable upper limit temperature Tlim even when the vehicle is suddenly started and accelerated after the cold start. The first O2 sensor 34 and the heater 150 can be prevented from deteriorating due to high temperature.

In the second embodiment, the intake air amount is exemplified as the engine load for setting the load duty value MODUTY1, but the throttle opening, the fuel injection amount, the charging efficiency, and the like may be used.

Further, the O2 sensor heater control device 122 in each of the above embodiments has described the control of the heater provided in the O2 sensor, but the control of the heater provided in another exhaust sensor such as an air-fuel ratio sensor for detecting an exhaust component has been described. It can also be applied to control. Furthermore, not only the O2 sensor and the air-fuel ratio sensor, but also the catalyst 36 deteriorates due to the temperature of the exhaust system, and the catalyst 36 also deteriorates. It can be applied to deterioration prevention.

Further, the O2 sensor heater control device 122 of each of the above-described embodiments uses the temperature of the first O2 sensor 34 itself or the exhaust temperature around the first O2 sensor 34 or the engine 2 as the duty value setting element of the O2 sensor. However, by setting the duty value in consideration of the cooling water temperature and the intake air temperature as a duty value setting auxiliary element, the heater 150 can be controlled in accordance with the engine state.

[0057]

As described above, according to the O2 sensor heater control apparatus of the present invention, the temperature of the O2 sensor is controlled by the control means based on the temperature of the O2 sensor or the temperature duty value set based on the temperature around the O2 sensor. Duty control the energization state of the heater so that it falls within the activation temperature range,
Alternatively, the energization state of the heater is duty-controlled by a load duty value set based on the load of the engine such that the O2 sensor enters the activation temperature range.

For this reason, the O2 sensor heater control device can control the heater with a large duty value at the start of the engine cold operation to increase the calorific value, thereby quickly raising the temperature of the O2 sensor to the activation temperature range. It can be activated by raising the temperature, thereby stabilizing the output characteristics of the O2 sensor and preventing the emission harmful component value from deteriorating. Also, this O2 sensor heater control device
After the O2 sensor is activated, the heater can be duty-controlled with an appropriate duty value to adjust the amount of heat generated, so that the temperature of the O2 sensor can be kept within the activation temperature range, and the emission harmful component value can be stabilized. It is possible to maintain the temperature of the O2 sensor and heater so that they do not exceed the allowable upper limit temperature even if the vehicle suddenly starts and accelerates after the cold start, and it is possible to stop the deterioration of the O2 sensor and heater due to the high temperature. it can.

[Brief description of the drawings]

FIG. 1 is a flowchart of control of an O2 sensor heater control device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a map of a duty value of a heater set according to a temperature of an O2 sensor.

FIG. 3 is a time chart of heater control.

FIG. 4 is a configuration diagram of an O2 sensor heater control device.

FIG. 5 is a flowchart of control of an O2 sensor heater control device according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a map of a heater duty value set based on an intake air amount.

FIG. 7 is a time chart of heater control showing a conventional example.

FIG. 8 is a diagram showing a duty value according to an engine speed and a heater temperature.

FIG. 9 is a diagram showing a relationship between an output characteristic of an O2 sensor and an air-fuel ratio.

FIG. 10 is a diagram showing a change in output characteristics with respect to the temperature of the O2 sensor.

FIG. 11 is a diagram showing the relationship between exhaust harmful component values due to changes in the output characteristics of the O2 sensor.

[Explanation of symbols]

 2 engine 34 first O2 sensor 122 O2 sensor heater control device 124 control means 150 heater 152 temperature sensor

Claims (2)

[Claims] An O2 sensor for detecting the oxygen concentration in the exhaust gas of an engine is provided, and a heater for heating the O2 sensor by generating heat when energized is provided for detecting a temperature of the O2 sensor or a temperature around the O2 sensor. A temperature sensor is provided, and control means is provided for duty-controlling the energization state of the heater so that the temperature of the O2 sensor falls within an activation temperature range by a temperature duty value set based on the temperature detected by the temperature sensor. An O2 sensor heater control device, characterized in that: 2. An O2 sensor for detecting the oxygen concentration in the exhaust gas of the engine, a heater for heating the O2 sensor by generating heat when energized, and a load sensor for detecting a load of the engine are provided. O2 according to the load duty value set based on the load detected by
An O2 sensor heater control device, further comprising control means for duty-controlling the energization state of the heater so that the temperature of the sensor falls within the activation temperature range.