JPH0348150A - Controller of heater for oxygen sensor - Google Patents

Abstract

PURPOSE:To prevent the overshoot of the temp. of a detection part, in an oxygen sensor detecting the concn. of oxygen in the exhaust gas of a vehicle, by deciding whether the control of the supply of a current to the heater of a sensor is performed corresponding to the state of the vehicle to suppress power for a predetermined period when the control is decided to be performed. CONSTITUTION:The current supply condition decision means M1 of a heater controller HC decides whether the supply of a current to the heater HT of an oxygen sensor DS is performed corresponding to the state of a vehicle for a definite time after starting, for example, when a start motor is operated in order to protect a battery or atmospheric temp. is extremely low. When it is decided to perform the control of the supply of a current, the power suppressing means of a motor power control means M2 is controlled by the means M1 and the supply of a current to the heater HT is suppressed for the first predetermined period of current supply. By this method, it is prevented that the temp. of the detection part of the sensor overshoots.

Description

Detailed Description of the Invention [Industrial Application Field] First Friend of the Invention An oxygen sensor heater for controlling the temperature of the detection part of an oxygen sensor installed in an engine exhaust system to a constant value for controlling the air-fuel ratio of an internal combustion engine. Regarding a control device.

[Prior Art] Internal Combustion Engine Output Reducing Fuel Consumption Various control devices have been developed for exhaust gas purification, and an essential part of the control is an oxygen sensor that measures the oxygen concentration in the exhaust gas. The oxygen sensor is composed of a solid electrolyte or a semiconductor, and its output depends on the temperature of the solid electrolyte ring and the detection section.

For example, in an oxygen sensor using titania (Tide) in the detection part (A), the operating air-fuel ratio (A/
It is known that F) changes like the curve in FIG. The vertical axis in Fig. 13 is 8/F, but when the value of the stoichiometric air-fuel ratio is included, if A/Fh (at or less (fuel is rich)), the hydrocarbon (HC) component in the exhaust gas On the other hand, if ^/Fh<a2 or more (fuel is lean), nitrogen oxide (NO) increases.The operating air-fuel ratio of this oxygen sensor is set in a narrow range near the stoichiometric air-fuel ratio (al -a
2) In order to keep it within (above) the temperature of the detection part must be controlled to keep it within a narrow range TI-T2.

For this reason, conventional devices have been known that control the temperature of the detection part at a constant level by providing a heater in the oxygen sensor and controlling the power supplied to the heater so that the resistance value of the heater becomes a predetermined resistance value. (Example)
No. 197459, No. 60-164241, No. 60-202
348 etc.).

[Problems to be Solved by the Invention] The conventional sensor temperature control described above utilizes the fact that the resistance value of the heater changes depending on the sensor temperature. It may not be possible to satisfactorily control the temperature of the detection unit immediately after the heater starts to be energized by simply controlling it to a predetermined value.

In other words, the heater resistance value 11 is the combined resistance of the resistance at the tip of the heater disposed around the detection part of the sensor and the resistance at the rear end of the heater located near the sensor attachment part to the exhaust pipe. Because the temperature rise rate at the tip of the heater is faster than at the rear end of the heater due to the difference in thermal evaluation, the heater resistance value (,t, at the beginning of energization, This indicates a low temperature, and if the power supplied to the heater is controlled so that the heater resistance value becomes the target resistance value even at the beginning of energization, the temperature of the detection part may exceed the target temperature (normal operating temperature). rise(
overshoot).

If the temperature of the detection section rises excessively in this manner, the air-fuel ratio cannot be accurately detected by the detection element.

[Means for Solving the Problems] A control device for an oxygen sensor heater according to the present invention, which has been accomplished in order to solve the above problems, is a control device for an internal combustion engine EG of a 1-mm vehicle, the configuration of which is illustrated in FIG. Resistance value R of heater HT installed in sensor O3 that detects oxygen concentration in exhaust gas
An oxygen sensor heater control device HC that detects H and controls the electric power PW supplied to the heater H so that the resistance value RH becomes a predetermined target heater resistance value RT includes the following means. It is characterized by

(Ml) Depending on the state of the vehicle, energization condition determining means (M2) that determines whether to perform energization control to oxygen sensor O3 (heater of oxygen sensor O3) (T). Electric power P supplied to the heater HT only during the first predetermined period
Heater power suppressing means for suppressing W [Function] When the vehicle is being operated normally, the electric power UW supplied to the heater HT of the oxygen sensor O8 (resistance value R of the heater HT) l is at a predetermined level. It is controlled to reach the target value RT. As a result, the temperature of the detection part of the oxygen sensor O3 is kept at a constant value, and accurate oxygen concentration detection is guaranteed.

This kind of power supply control to the heater HT (mountain) is carried out only when the vehicle is in a predetermined state.For example, when the starter motor is operating in order to protect the battery. Or, at certain times after starting when the temperature is very low, energization control is prohibited.0 The energization condition determining means Ml determines whether or not it is permissible to perform energization control of the heater HT in view of the current vehicle condition. Then, when the energization condition determining means Ml determines that the energization control to the heater HT may be started, the heater power suppressing means M2 suppresses the power PW supplied to the heater HT for a predetermined period from that time. , it is possible to suppress the temperature rise at the tip of the heater and prevent the temperature of the detection section of the oxygen sensor O3 from overshooting to a predetermined temperature or higher.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 2 is an electric circuit diagram showing the overall configuration of the heater control device of the embodiment.

As shown in the figure, a main battery 12 of an automobile is connected via an ignition switch 11 to a heater 10 of an oxygen sensor attached to an exhaust pipe of an automobile engine. A switching (power) transistor 14 and a comparison resistor 16 are further connected in series to the heater IO.

The potential AO (relative to ground potential) between the transistor 14 and the comparison resistor 16 is amplified by the operational amplifier 18.
It is input to an electronic control unit (ECU) 26 via an AC-DC converter (ABC) 24.

Battery voltage VB is also input to ECU 26 via ADC 24. In the following description, the resistance values of the heater lO and the comparison resistor 16 are assumed to be RH and R1, respectively.

ECt126 (friend) As shown in Figure 3, the well-known CPU
30, ROM32, RAM34, backup RAM3
5, a microcomputer equipped with an input section 36, an output section 38, etc.

Although not shown in Fig. 2, there is an idle switch (LL SW,) 40 that outputs an ON signal when the engine throttle valve closes, and a vehicle speed sensor (SPD) 42.
, a cooling water temperature sensor (THW) 44, a rotational speed sensor (NE) 46, and signals from an air flow meter (Q) 48 that measures the amount of intake air are also sent to the ECU 2 via the input section 36.
6 is input. Although not shown, ignition signals and injection signals output from the engine control device for ignition and fuel injection are also input to the ECU 26. And E.C.
U261L Based on these input signals, the following heater control processing is performed.

°, °Figure 4 is a flowchart of the heater control processing routine.
Execute every ec. When this routine starts, first in step 100 it is determined whether the current operating state is such that it is acceptable to energize the heater IO. concrete second (dai)
If three conditions are met: the starter motor is not operating, the voltage of Patch January 2 is above a predetermined value, and the temperature is above a predetermined value, it is determined that it is possible to energize the Mi heater IO. Do not turn on electricity here (NO)
If it is determined that
Substitute. This variable YHTll is output to the output port to the switching transistor 14 in another routine executed by the CPU 30. As a result, the switching transistor 14 becomes non-conductive, and the current supply to the heater IO is stopped.

If the determination in step 100 is YES (Table 1), the process advances to step 120, where it is determined whether this routine is the first execution after the energization was turned to 0 in step 100. Let's start by talking about the first execution cycle after the execution.

+1 at this time. Step! Flag X at 30, RT
Reset W to O. This flag X, RTWl&
When it is 0, it indicates that it is the time immediately after starting the energization control to the heater lO, and when it is ], it is to indicate that it is the normal time after that.

In the next step 135, the heater control target resistance value RTO at the end of the previous operation is read from the backup RAM 35 and assigned to the target resistance value variable RT.Then, in step 140, a predetermined value A is subtracted from RT, and the saved variable RT
Substitute into W. This value (or the predetermined value A to be subtracted from 1) is determined in advance through experiments and computer simulations, taking the following into account. As mentioned above, the temperature rise rate is different between the detection part and the mounting part of the oxygen sensor due to the difference in heat capacity, and the temperature of the detection part rises faster.Here, the heater resistance R) I is the resistance of the detection part. Since it is the sum of the resistance value RH and the resistance value RH2 of the mounting part, the heater 10 was energized until the overall heater resistance RH reached the target resistance value corresponding to the normal operating temperature of the sensor. The operating temperature will be exceeded.Therefore, the value A (1) when the sensor finally rises to the normal operating temperature.

In order to prevent the temperature of the detection part from overshooting, it is determined by taking into consideration the difference in temperature increase rate between the detection part and the mounting part.

At the next step +50, the value in the target resistance value variable RT (currently RTO) and the value in the saved variable RTW (RTO-
A) Replace with. As a result, the initial target resistance value (RTO-A) is entered in the target resistance value variable RT, and the heater resistance R)l is set to this value (RTO-A).
T[1-A). Save variable RTW
The target resistance value RTO in the normal operating state is entered in the box, and is stored until normal control is achieved.

1 up in step 160 Current IHT flowing through heater 10
It is determined whether or not is less than a predetermined value IB.Group T>18
In this case, energization of the heater 10 is prohibited in step 110. This is a current amount limitation, and is a measure to alleviate thermal shock caused by rush current immediately after starting energization to the sensor. K1) IT I& Calculated by the process of the IHT calculation routine shown in FIG. 5, which will be described later, based on the potential AD of the comparison resistor 16 output from the operational amplifier 18.

When IHT≦IB (at step 170, heater 10
The resistance value R1 of is calculated by the following formula.

RH=VB/IHT-R1 Here, VB is the voltage of the battery 12, and the sixth
It is calculated by the processing of the VB calculation routine shown in the figure. Then, in step 180, it is determined whether the calculated heater resistance value RH is greater than or equal to the target resistance value RT (currently the lower value).
Since it is RT, proceed to step 190 and set Y)(T to 1.
Set to . As a result, the switching transistor 14 becomes conductive, and current flows through the heater 10.

Thereafter, in step 250, it is determined whether the flag X and RTW are 1 or not. In the case of the first execution, (, t, flag This is the progress of the execution.

In the second and subsequent executions of this routine, steps 130-1
50 is not executed, the target resistance value RT remains at the lower value, and for a while R is set at step 180.
Since it is determined that H<RT, the heater IO continues to be energized (step 190). Of course, if the heater current IHT becomes the limit value 18 or more, the energization is stopped (step 160.110).

When the temperature of the sensor rises to a certain extent and RH≧RT (upper step 200 and subsequent steps are executed).

In step 200, it is determined whether the flags X, RTW are the end.
Since the value of TW remains 0 in step 130, the process proceeds to step 210 and increases the value of the target resistance value variable RT by a predetermined small value CRT (that is, the value in RT becomes RTO-A+DRT). . Then, it is determined whether the increased variable RT has become equal to or greater than the stored variable RTW (in which the target resistance value RTO in the normal state is stored). Since DRT is a sufficiently smaller value than A, RT<RTW at first, the process proceeds to step 240, sets YHT to O, and stops energizing the heater IO.

Repeat this routine several times and at step 21O
T increases little by little (by DRT), and when RT exceeds the target resistance value RTW (RTO) in the normal state (
In step 230, flag
This means that the transition from A to the normal value RTO has been completed, and declares that the initial control of the energization control for the heater IO has ended. In this case (from which step 260 is always executed), completely normal heater control is performed.

Above step 2601 and subsequent processing (step 270~
290) is a process for determining whether or not to execute learning control that corrects the target resistance value RT in order to compensate for variations in the resistance value inherent in the heater due to individual differences in oxygen sensors and changes over time. , specifically the idle switch (LL
SW, ) is ON (throttle valve is closed)
, the vehicle speed is 5 km or less, and the cooling water temperature is 70°C or less (i.e., idling state) for a predetermined period of time (for example, 2
sec, ) or more.

Then, if this condition is satisfied, in step 270, the average value PN of the heater supply power for a predetermined period of time (about several seconds) is calculated, and in step 280, from this calculated average value PN of the power, Correction value △R of target resistance value RT
T is calculated, and in the next step 290, this correction value ΔRT
Learning control is executed to update the target resistance value RT by correcting the target resistance value RT.

In this embodiment, the heater lO is turned ON or OFF every execution cycle (64m5ec) of the routine shown in FIG.
N=Σ(P-YHT)/n P = (VB-IHT-1t(D2-
Rl).

Further, the process E of step 280 for calculating the correction value ΔRT based on this average value PN is performed by storing a map as shown in FIG. 7 in advance in the ROM 32 and referring to this map. As a result, if the average power value PN is equal to the standard value PNO, the correction value ΔRT becomes 0, and if it is larger than that, a negative correction value is given.

Next, an IHT calculation routine (FIG. 5) for calculating the current IHT flowing through the heater 10 will be explained. This IH calculation routine is executed by forcibly energizing the heater l port every predetermined time (for example, 65 m5ec), and when this routine starts, first step 5
At 00, the comparison resistor 16 output from the operational amplifier 18
Based on this potential AD, the current heater current IH is calculated using a map as shown in Fig. 8.
Calculate Tn. Then, in the following step 51O, it is determined whether or not an ignition signal is currently being input. .

If it is determined in step 520 that an injection signal is input, or if it is determined in step 5!0 that an ignition signal is input, the process moves to step 530, and step 5
A value obtained by adding a predetermined value α to the heater current IHTn obtained at 0 inputs is newly set as the heater current IHTn.

Processing of steps 510 to 530 (upper) When ignition or fuel injection is executed on the engine side, battery voltage VB changes (decreases) greatly, and heater current tHTn obtained in step 500 applies normal battery voltage VB. This process is not intended to correct the variation in heater current IH1'n that occurs due to such voltage variation. If a negative determination is made in step 5401, the process moves to step 5401, where the heater current HTn obtained above and the heater current I obtained when the routine was executed last time are calculated.
Compare the size with ITn-1. So, if 1HTn≧Tn-1, lfL Proceed to step 550,
Using the following formula (% formula %), calculate the heater electric current JIHT used for heater control in the heater control processing routine described above, and conversely calculate 1H
If Tn<IHTn-1 (L), proceed to step 560, and set the value obtained by subtracting the predetermined value 1a from the previously determined h heater current lHTn-1 as the heater current IHT used for heater control.

Once the heater current group (■) has been calculated in this way, the process moves to the subsequent step 570, where this value IHT is set as the current heater current IHTn for the next process.
Terminate the process once.

Here, the process of steps 540 to 550 (above) is a process for preventing erroneous control of the heater when the heater current 1NTn is erroneously calculated in step 500.

In other words, within a predetermined time (65m5ec), the heater current IH
Since T does not usually change suddenly, the heater current 1) IT
The sudden fluctuations in the equation are removed by a so-called smoothing process.

In this embodiment, (l IHTn is the previous value fHTn-1
When the heater current IHT increases by 1, the heater current IHT is
However, when 1HTn decreases from the previous value IHTn~1, 1 friend is calculated.In step 560, IHTn-
By subtracting the predetermined value 1a from 1, the heater current IHT
is being calculated. A decrease in the heater current group means that the heater resistance RH increases.
This is because the heater tends to stop energizing, and when the heater current +Hrh<4 tends to be small,
By subtracting the predetermined value la from HTn-1, the heater current IHT is gradually reduced, thereby preventing the heater from becoming more likely to stop energizing.

Next, the VB calculation routine (FIG. 6) for calculating the battery voltage VB is executed every predetermined time period (for example, 115 m5ec), which is longer than the group T calculation routine described above.

As shown in FIG. 6, this VB calculation routine first takes in the battery voltage VB input via the ADC 24 in step 600, and then in step 610 checks whether or not the heater 10 is currently de-energized. In step 620, a value obtained by subtracting a predetermined value β from the battery voltage VB taken in in step 600 is set as the battery voltage VB used for control. If not, the process is simply terminated.

In other words, the heater current IHT is determined by energizing the heater lO, and since the battery voltage VB when the heater is energized is lower than when it is not energized, the battery voltage VB taken in step 600 (above) is used in the VB calculation routine. Even if VB is the value when heater lO is not energized (fS
By subtracting a predetermined value β from the value VB, the battery voltage VB is made to correspond to the value when the heater is energized. As a result, it becomes possible to accurately determine the heater resistance RH in the heater control processing routine.

Next, the state of heater energization control according to this embodiment will be explained with reference to the time chart of FIG. 9.

When the starter motor finishes starting the engine (time tl), it is determined that power can be applied (step 10),
When RT is set to RTO-A, 1: energization is started. Initially, the resistance value R)I of the heater IO is low and a large current flows, so the current supply is often stopped in steps 160 and 110 (see the graph of Y)IT). From a certain point t2 onwards, the heater resistance RH increases to some extent (however, it is still lower than the target value RT), so the current 1)
IT no longer exceeds the limit value IB, and the heater lO
Current will always flow through.

During this period, the temperature of the detection part of the oxygen sensor rises rapidly, and the heater resistance RH also increases at the same time, but at the time t3 when the heater resistance RH exceeds the target resistance value RT (initial value RTO-A). Power supply to the heater IO is temporarily stopped. At this time point t3, since the value A is set as described above, the temperature of the detection section has almost reached the normal operating temperature (see RHI). After that, while the energization/cutoff is repeated intermittently, the target resistance value RTli is
The temperature of the mounting part gradually increases and approaches the equilibrium temperature ((see RH2)).

In addition, the CRT value (R after the temperature of the detection part of the oxygen sensor reaches the normal operating temperature) is determined by taking into account the rising speed of In the graph of the detection part temperature in Fig. 9, the dotted line indicates the case where control as in this embodiment is not performed. (In other words, when the temperature is not corrected by the target resistance value RTe value A), it is shown that the temperature rises suddenly to an initial stage and an overshoot occurs.

As explained above, 1: In the above embodiment (1) the normal target resistance value RTO is set as the target resistance value RT at the start of heater energization.
When the resistance RH reaches the target resistance RT, the target resistance value RT is gradually increased to the normal target resistance value RTO, so that the target resistance value RT becomes the normal value. Heater 10 until reaching RTO
The power supplied to the oxygen sensor is suppressed more than usual to prevent the temperature of the detection section of the oxygen sensor from rising excessively above the target temperature at the beginning of the heater energization. By the way, in order to prevent the temperature of the detection part of the oxygen sensor from rising excessively above the target temperature, it is sufficient to suppress the power supplied to the heater, which is different from the method of correcting the target resistance value RT as in the above embodiment. It can be achieved by any method.

Therefore, as a second embodiment of the present invention, a heater control processing routine for suppressing the power supplied to the heater 10 by suppressing the energization time of the heater 10 will be explained with reference to the flowchart of FIG. 10.

Note that the heater control processing routine in FIG.
This process is executed in the ECU 26 every 16m5ec. In addition, in this routine, power control of the heater 10 is realized by duty control that repeats energization and de-energization of the heater 10 at predetermined intervals.

As shown in the figure, in the heater control processing routine of this embodiment (
First, step 300 is executed to determine whether power is currently being supplied to the heater IO. and heater l
In step 310, similarly to step 260 described above, it is determined whether the learning condition for the target resistance value RT is satisfied, and if the learning condition is satisfied, (Proceeding to step 320, the electric power PW being supplied to the heater IO is calculated using the following formula.

PW = (VB-1)IT-IHT2-R1)・(D
UTY/256) Here, DUTY is a counter corresponding to a duty ratio described later. In step 330, it is determined whether or not the power PW calculation in step 320 has been performed 256 times, and if this determination is YES, the process proceeds to step 340. Average value av(PW) of value PW
is calculated as PN, and in the next steps 350 and 360, the target resistance value RT is updated in the same manner as in steps 280 and 290 described above.

Whether the learning control of the target resistance value RT is executed in this way,
If NO is determined in step 310 or step 330, the process moves to step 370, and the step 170 described above
Similarly, the resistance value R1 of the heater 10 is calculated.

Then, in the following steps 380 to 400, depending on whether the heater resistance RH is above or below the target resistance value RT, the counter DUT corresponding to the duty ratio of the electric power supplied to the heater IO is
Increase or decrease Y by 1. DUTY (Top 11th)
As shown in Figure (B), it is the value corresponding to the ON time (b) relative to the ON/OFF cycle time (a) of the heater lO, that is, the duty ratio (b/aX Ion%),
In this embodiment (free running counter CDU described above and later)
It takes a value of 1:, 0 to 256 to correspond to TY.

Once the DUTY is set in this way, step 41
0 for a predetermined period of time (e.g. 3S) after starting the engine.
Osec, ) has elapsed. Then, if the predetermined time has not elapsed (Dai), the process moves to step 420, and it is determined whether or not the target resistance value RT has been updated in step 360, and if the target resistance value RT has not been updated ('
L At step 430, based on the target resistance value RT, the map of FIG. 12 is used to express the upper limit value of DUTY.
Ymax is calculated and the process moves to step 44υ.

On the other hand, if it is determined in step 410 that a predetermined period of time has elapsed since the engine was started, or if it is determined in step 420 that the target resistance value RT has been updated, then in step 450 the maximum value is set to DUTYmax. 256 (duty ratio: 100%), and the process moves to step 440. Then, in the following step 440, 1 table is shown in step 4 above.
Upper limit value DUTYmax set at 30 or 450 and lower limit value DυTYmin set in advance (=8.
DUTY
A guard process is executed to prevent the value from exceeding the upper and lower limit values.

Here, Stella: Process 1 of j410 to 430 r until a predetermined period of time passes after the engine starts or until the target resistance value RT is updated. i, DUTYmax is the target resistance value RT
DUTYmax is set to a value smaller than 256 according to the processing for suppressing the energization time of the heater IO (namely, the supplied power) to a value smaller than normal.

The target resistance value RT
Guard jJ and DUTYmax until the target resistance value RT is updated. Moreover, even if the target resistance value R is not updated, it can be determined that the engine has been sufficiently warmed up after a predetermined period of time (350 seconds in this embodiment) has elapsed since the engine was started. In other words, if the engine is sufficiently warmed up (the temperature at the mounting part of the heater lO will also rise, and the temperature at the detection part will not rise above the target temperature), the above step 420
and 1 friend at 430. Such a steady state is detected from the time after the engine is started and the update state of the target resistance value RT.

In addition, when these conditions are not met, setting DUTYmax based on the target resistance value RT (Target resistance value RTI; t,, due to past learning control, the heater It is set to compensate for variations in the inherent resistance value, and if the target resistance value RT is large, the amount of heat generated by the heater is small relative to the supplied power, and if the target resistance value RT is small, the amount of heat generated by the heater is smaller than the supplied power. In other words, in this embodiment, the target resistance value RT
By setting DUTYmax to a smaller value as the value decreases, the supply power can be suppressed as the heater generates a larger amount of heat relative to the supplied power.

When the DUTY guard processing is executed as described above, the process moves to the following step 460, and the free running counter CDUTY is incremented by 8. And then step 47
0 (Friend) Compare the size of this CCUTY and the DUTY set above, and if DUTY > CDυ exceeds, turn on the heater port in step 480, otherwise (f
,, In step 490, the heater IO is turned off. Note that CDUTYLt, 2561: is reset to 0 when it is reached. In addition, the process in step 460 (i.e., the heater IO is not energized in step 300 (i.e.,
It is also executed when it is determined that 0FF). Note that the processing of steps 460 to 490 is performed in one predetermined cycle (It, 1 in this embodiment) as shown in FIG. 11(A).
6 m5ec, X (256/8) =512 m5ec
, ) by turning on and off the heater lO.
This is a process for determining the duty ratio according to DUTY.

As explained above, in the heater control processing routine of this embodiment, power control of the heater IO is performed by duty control, and after the start of the control, there is no interruption until the engine warms up.
By suppressing the energization time of heater IO, heater 1
0 is suppressed. Therefore, as in the above embodiment, 1: After the heater IO starts energizing, the temperature of the detection part of the oxygen sensor can be prevented from rising excessively above the target temperature, and the sensor can be prevented from deteriorating due to the temperature rise. can.

[Effects of the Invention] As detailed above, the oxygen sensor heater control device according to the present invention normally controls the energization so that the heater resistance value becomes a predetermined target resistance value. The power supplied to the heater is suppressed only during a predetermined period immediately after the control starts.For this reason, immediately after the start of the heater energization control, the detection part of the sensor rises above the target temperature. This makes it possible to improve the accuracy of air-fuel ratio detection by the oxygen sensor.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the configuration of the present invention. FIG. 2 is an electrical circuit diagram showing the overall configuration of a heater control device according to an embodiment. FIG. 3 is a block diagram showing the configuration of its electronic control unit (ECU). A flowchart representing the heater control processing routine executed by the control unit (ECU), FIG. 5 is a flowchart representing the group calculation routine, FIG. A graph representing a map for determining the correction value ΔRT of the target resistance value RT from the electric power, FIG. 8 is a graph representing a map for determining the heater current from the voltage of the comparison resistor, and FIG. 9 is a graph representing the heater control of FIG. 4. FIG. 10 is a flowchart showing the heater control processing routine of the second embodiment; FIG. 11 is a time chart illustrating the heater energization control of the second embodiment; Figure 12 shows DUTYma based on the target resistance value RT.
FIG. 13, which is a graph representing a map for determining x, is a graph representing the relationship between the temperature (2) of the oxygen sensor and the operating air-fuel ratio A/F. Ml...Electrification condition determining means M2...Heater power suppressing means O3...Oxygen sensor HT, lO...Heater 26...Electronic control unit (ECU)

Claims (1)

[Claims] Detects the resistance value of a heater installed in a sensor that detects the oxygen concentration in the exhaust gas of an internal combustion engine of a vehicle, and supplies the heater so that the resistance value becomes a predetermined target heater resistance value. A control device for an oxygen sensor heater that controls electric power, comprising: an energization condition determining means for determining whether or not to perform energization control to the heater of the oxygen sensor according to a state of the vehicle; a heater power suppressing means for suppressing the power supplied to the heater only during the first predetermined period;