JP2006207424A - Heater control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heater control device with improved reliability of an air/fuel ratio sensor. <P>SOLUTION: This heater control device for the air/fuel ratio sensor with a heater mounted to an exhaust pipe of an internal combustion engine is provided with a heater resistance detecting means for detecting internal resistance of the heater; an exhaust temperature estimating means for estimating exhaust temperature inside the exhaust pipe based on the internal resistance of the heater detected by the heater resistance detecting means; and a heating allowing means allowing heating of the air fuel ratio sensor by the heater when the exhaust temperature estimated by the exhaust temperature estimating means exceeds predetermined temperature. The heater control device for the air fuel ratio sensor with the heater mounted to the exhaust pipe of the internal combustion engine is further provided with a soak time measuring means for measuring soak time of the internal combustion engine; and a heating allowing means for allowing heating of the air fuel ratio sensor by the heater when the soak time measured by the soak time measuring means is below predetermined time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a heater control device for an air-fuel ratio sensor with a heater attached to an exhaust pipe of an internal combustion engine.

  When the temperature in the exhaust pipe is low when the engine is started and water droplets remain in the exhaust pipe or when there is a risk of water droplets in the exhaust pipe, the oxygen sensor heating heater is turned off and the oxygen sensor thermal There is a need to prevent shock. The following proposals have been made as heater control devices for preventing this thermal shock.

  An internal resistance detection means for detecting the internal resistance of the oxygen sensor, an oxygen sensor surface temperature is estimated based on the internal resistance value detected by the internal resistance detection means, an exhaust pipe temperature is estimated based on the oxygen sensor surface temperature, There is known a heater energization control device including a control means for controlling energization start of a heating heater integrated with an oxygen sensor when the exhaust pipe temperature reaches a predetermined temperature (for example, a patent) Reference 1).

Further, exhaust pipe temperature calculating means for calculating the exhaust pipe temperature in the vicinity of the air-fuel ratio sensor based on the engine load and a heater energization control device for controlling heater energization of the air-fuel ratio sensor in accordance with the exhaust pipe temperature are known. (For example, refer to Patent Document 2).
JP 2000-97902 A JP 2002-256949 A

  However, in the heater energization control device shown in Patent Document 1, the internal resistance of the oxygen sensor at a low temperature of 300 ° C. or lower becomes infinite, so it is difficult to measure the internal resistance of the oxygen sensor at a low temperature. is there. On the other hand, by configuring a special circuit, the internal resistance of the oxygen sensor at low temperatures can be measured, but this leads to an increase in cost.

  Further, in the heater control device disclosed in Patent Document 2, even when the cooling water temperature is high, the exhaust pipe temperature may be lowered and water droplets may be generated in the exhaust pipe when the outside air temperature is low.

  The present invention has been made to solve such problems, and its main object is to improve the reliability of an air-fuel ratio sensor.

  One aspect of the present invention for achieving the above object is a heater control device for an air-fuel ratio sensor with a heater attached to an exhaust pipe of an internal combustion engine, a heater resistance detecting means for detecting an internal resistance of the heater, Based on the internal resistance of the heater detected by the heater resistance detection means, exhaust temperature estimation means for estimating the exhaust temperature in the exhaust pipe, and the exhaust temperature estimated by the exhaust temperature estimation means is equal to or higher than a predetermined temperature. And a heating permission unit that allows heating of the air-fuel ratio sensor by the heater.

  According to this aspect, the exhaust temperature in the exhaust pipe is estimated based on the internal resistance of the heater, and the heater is allowed to heat the air-fuel ratio sensor when the exhaust temperature is equal to or higher than a predetermined temperature. . Thereby, the exhaust temperature can be estimated with high accuracy in a wide temperature range regardless of the high temperature side or the low temperature side. Therefore, the occurrence of thermal shock in the air-fuel ratio sensor can be predicted and prevented more reliably. That is, the reliability of the air-fuel ratio sensor can be further improved.

  Further, in this aspect, the exhaust temperature estimation means estimates the exhaust temperature based on a predetermined relationship between the internal resistance of the heater and the exhaust temperature, and detects the intake temperature of the internal combustion engine. And soak time measuring means for measuring the soak time of the internal combustion engine, and when the soak time measured by the soak time measuring means is a predetermined time or more, the intake air temperature detected by the intake air temperature detecting means and the intake air temperature Correction means for correcting the predetermined relationship based on the internal resistance of the heater detected by the heater resistance detection means is further provided. When the soak time is equal to or longer than a predetermined time, the intake air temperature and the heater temperature are approximated. Therefore, by using the intake air temperature as the heater temperature, it is possible to suppress variations in the internal resistance of the heater when calculating a predetermined relationship between the internal resistance of the heater and the exhaust temperature. That is, the exhaust temperature in the exhaust pipe can be estimated with higher accuracy.

  Further, in this aspect, the water temperature detecting means for detecting the water temperature of the internal combustion engine, the water temperature detected by the water temperature detecting means, and the intake air temperature detected by the intake air temperature detecting means are within a predetermined temperature range. Range determining means for determining whether or not the temperature is within the predetermined temperature range, and when the range determining means determines that the water temperature and the intake air temperature are within the predetermined temperature range, Corrections may be made to the relationship.

  In this aspect, the correction means corrects the predetermined relationship based on the water temperature detected by the water temperature detection means and the internal resistance of the heater detected by the heater resistance detection means. You may go.

  One aspect of the present invention for achieving the above object is a heater control device for an air-fuel ratio sensor with a heater attached to an exhaust pipe of an internal combustion engine, the soak time measuring means for measuring the soak time of the internal combustion engine, And a heating permission means for permitting heating of the air-fuel ratio sensor by the heater when the soak time measured by the soak time measuring means is a predetermined time or less. May be.

  Further, in this aspect, the apparatus further includes integrated amount acquisition means for acquiring an integrated amount of intake air to the internal combustion engine until the start of measurement of the soak time, and the heating permission means is acquired by the integrated amount acquisition means. When the integrated amount of the intake air is equal to or greater than a predetermined amount, it is preferable to allow the heater to heat the air-fuel ratio sensor.

  In these embodiments, the soak time of the internal combustion engine refers to the time from when the internal combustion engine was last driven and stopped until the current internal combustion engine is started to be driven.

  According to the present invention, the reliability of the air-fuel ratio sensor can be improved.

Hereinafter, the best mode for carrying out the present invention will be described with reference to the accompanying drawings. The basic concept, main hardware configuration, operating principle, basic control method, and the like of the control device for a vehicle are known to those skilled in the art, and thus detailed description thereof is omitted.
(First embodiment)
FIG. 1 is a schematic diagram of a system configuration showing a heater control apparatus according to first to third embodiments of the present invention. As shown in FIG. 1, an exhaust pipe 5 is connected to an internal combustion engine 3 such as an engine for guiding the burned exhaust gas to the rear of the vehicle. The exhaust pipe 5 is provided with an air-fuel ratio sensor 7 such as an oxygen sensor for detecting the oxygen concentration in the exhaust gas flowing through the exhaust pipe 5. Further, the oxygen sensor 7 is provided with a heater 9 for heating and activating the sensor element.

  A control means 11 such as an ECU for controlling energization and power failure of the heater 9 is connected to the heater 9 via a control circuit 13. An intake manifold 15 of the engine 3 is provided with an intake air temperature sensor 15 such as a thermistor for detecting the intake air temperature of the engine 3, and the intake air temperature sensor 15 is connected to the ECU 11. The ECU 11 is connected to a water temperature sensor 17 such as a thermistor for detecting the temperature of the cooling water of the engine 3. The intake manifold of the engine 3 is provided with an air flow meter 19 that detects the intake air amount of the engine 3, and the air flow meter 19 is connected to the ECU 11. The ECU 11 calculates an integrated amount of intake air based on the intake air amount from the air flow meter 19.

  The oxygen sensor 7 is made of a solid electrolyte such as zirconia and has a limited operating temperature. That is, the oxygen concentration is not detected unless the oxygen sensor 7 is heated to an activation temperature of several hundred degrees Celsius or higher (for example, 700 degrees Celsius) and activated. For this reason, the oxygen sensor 7 is heated by the heater 9 in order to maintain the temperature of the oxygen sensor 7 at a desired activation temperature when the exhaust pipe temperature decreases due to a long idling operation or the like.

  The heater 9 is in close contact with the oxygen sensor 7, and energization and power outage are performed at a predetermined DUTY ratio (ratio between energization time and power outage time) so that the oxygen sensor 7 operates stably at the activation temperature. The oxygen sensor 7 is heated repeatedly. A battery 21 is connected to the heater 9 via the control circuit 13, and power is supplied from the battery 21 to the heater 9. When the control circuit 13 receives the energization signal from the ECU 11, the heater 9 is repeatedly energized and interrupted at a predetermined DUTY ratio to heat the oxygen sensor 7. Further, when receiving a stop signal from the ECU 11, the control circuit 13 stops energization of the heater 9 and stops heating of the oxygen sensor 7. In this way, the oxygen sensor 7 is heated to the activation temperature by the heater 9 and is maintained at the activation temperature.

  The ECU 11 is connected to a voltage sensor 23 that detects an applied voltage to the heater 9 and a current sensor 25 that detects an applied current to the heater 9. The ECU 11 calculates the internal resistance R of the heater 9 by the following equation (1) based on the voltage V from the voltage sensor 23 and the current I from the current sensor 25.

R = V / I (1) The ECU 11 energizes the heater 9 for a predetermined time (for example, about 1 to 5 seconds) when calculating the internal resistance of the heater 9. By energizing for a short time in this way, the internal resistance R due to energization of the heater 9 can be calculated while suppressing the temperature rise of the heater 9.

  The ECU (Electronic Control Unit) 11 is constituted by a microcomputer and has a ROM for storing a control program, a readable / writable RAM for storing calculation results, a timer, a counter, an input interface, and an output interface. is doing. Further, an ignition switch (IGSW) 27 is connected to the ECU 11, and when the ignition switch 27 is turned on, an on signal is transmitted to the ECU 11, and when the ignition switch 27 is turned off, an off signal is transmitted to the ECU 11. The ECU 11 has a built-in soak timer 11a that measures a soak time (engine stop time) after receiving an OFF signal of the ignition switch 27. The soak timer 11a starts measurement when it receives an off signal from the ignition switch 27, and ends the measurement when it receives an on signal.

  A predetermined relationship between the internal resistance of the heater 9 and the temperature of the heater 9 is stored in the ROM of the ECU 11. In this predetermined relationship, the predetermined relationship between the internal resistance of the heater 9 and the temperature in the exhaust pipe 5 is calculated by subtracting the self-heating temperature of the heater 9 from the temperature of the heater 9. A predetermined relationship between the calculated internal resistance of the heater 9 and the temperature in the exhaust pipe 5 is stored in the RAM of the ECU 11. Each predetermined relationship is derived by experimentally measuring the temperature of the heater 9, the resistance of the heater 9, etc., and calculating an approximate line by the least square method or the like. Moreover, each predetermined relationship is a substantially direct proportional relationship.

  By the way, when the temperature of the exhaust pipe is low, such as when the engine 3 is started at a low temperature or during a warm-up process, water droplets may remain in the exhaust pipe 3 or may be generated in the exhaust pipe 3. For example, when energization of the heater 9 of the oxygen sensor 7 is started while water droplets are attached to the oxygen sensor 7, a rapid temperature difference is caused by a temperature drop due to the water drop adhesion of the oxygen sensor 7 and a temperature rise due to heating of the heater 9. And the element of the oxygen sensor 7 is cracked by so-called thermal shock. In order to prevent this thermal shock, when there is a possibility of water droplets adhering to the oxygen sensor 7, the following control processing is performed so as to prohibit heating of the oxygen sensor 7 by the heater 9.

  FIG. 2 is a flowchart of a control routine of the heater control apparatus according to the first embodiment. This control routine and the control routine shown in FIGS. 3 and 5 are repeatedly executed every predetermined minute time, for example, every 64 ms.

  As shown in FIG. 2, when the ECU 11 receives the ON signal from the ignition switch 27 (S100), the heater 9 is energized for a predetermined time via the control circuit 13 (S110). At this time, the ECU 11 calculates the internal resistance R of the heater 9 by the above equation (1) based on the voltage V from the voltage sensor 23 and the current I from the current sensor 25 (S120). The ECU 11 energizes the heater 9 for a predetermined time via the control circuit 13, and then stops energization (S130).

  Next, the ECU 11 estimates the temperature in the exhaust pipe 5 based on the predetermined relationship between the internal resistance of the heater 9 and the temperature in the exhaust pipe 5 stored in the ROM, and the calculated internal resistance of the heater 9 ( S140).

  Thereafter, the ECU 3 determines whether or not the estimated temperature in the exhaust pipe 5 is equal to or higher than a predetermined temperature (for example, 60 ° C. or higher) and there is no possibility that a thermal shock occurs in the oxygen sensor 7 (S150). When the ECU 3 determines that the estimated temperature in the exhaust pipe 5 is equal to or higher than the predetermined temperature and there is no risk of thermal shock occurring in the oxygen sensor 7, the ECU 3 transmits an energization signal to the control circuit 13 (S160). The control circuit 13 that has received the energization signal energizes and interrupts the heater 9 at a predetermined DUTY ratio to heat the oxygen sensor 7 (S170). In this way, the ECU 11 heats the oxygen sensor 7 to the activation temperature and maintains it at the activation temperature.

  On the other hand, when the ECU 11 determines that the estimated temperature in the exhaust pipe 5 is lower than the predetermined temperature and there is a risk of thermal shock occurring in the oxygen sensor 7 (S150), the energization of the heater 9 is stopped (S180). . Thereafter, the ECU 11 determines whether or not a predetermined time has elapsed (S190). When the ECU 11 determines that the predetermined time or more has elapsed, the ECU 11 proceeds to the process of (S110). When the ECU 11 determines that the predetermined time or more has not elapsed, the ECU 11 proceeds to the process of (S180).

  As described above, since the temperature in the exhaust pipe 5 is estimated based on the internal resistance of the heater 9, the temperature in the exhaust pipe 5 can be accurately determined over a wide temperature range regardless of whether the temperature is low or high. Can be estimated. Thereby, it becomes possible to prevent the thermal shock of the oxygen sensor 7 more reliably, and the reliability of the oxygen sensor can be improved. Further, since it is not necessary to attach a temperature sensor for detecting the temperature in the exhaust pipe 5 to the exhaust pipe 5, it is possible to improve the assembly and reduce the cost.

Hereinafter, in the second and third embodiments, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.
(Second Embodiment)
If the temperature in the exhaust pipe 5 becomes high when the engine is driven last time and the driving is stopped in the high temperature state, the temperature in the exhaust pipe 5 can be kept high if the soak time is within a predetermined time. In this case, since there is no possibility that water droplets remain in the exhaust pipe 3 or water droplets are generated in the exhaust pipe 3, even if the oxygen sensor 7 is heated by the heater 9, thermal shock occurs in the oxygen sensor 7. There is no fear. Hereinafter, an example of the control method of the heater control device 1 in such a case will be described.

  FIG. 3 is a flowchart of a control routine of the heater control apparatus 1 according to the second embodiment.

  As shown in FIG. 3, when the ECU 11 receives an ON signal from the ignition switch 27 (S200), the ECU 11 determines whether or not the integrated amount of intake air at the previous driving of the engine is a predetermined amount or more and the engine 3 is sufficiently warmed up. (S210).

  When the ECU 11 determines that the integrated amount of intake air is greater than or equal to a predetermined value, the ECU 11 determines whether or not the soak time measured by the soak timer 11a is greater than or equal to a predetermined time (eg, 2 hours or more) (S220). On the other hand, when the ECU 11 determines that the integrated amount of intake air is less than the predetermined value, the ECU 11 proceeds to the process of (S230).

  Here, the predetermined time is set based on the integrated amount of intake air, and is set large in proportion to the integrated amount of intake air. For example, when the temperature inside the exhaust pipe 5 is 300 ° C, 400 ° C, and 500 ° C, the predetermined time is set to 1 hour, 2 hours, and 3 hours, respectively. Note that the temperature in the exhaust pipe 5 increases substantially in proportion to the integrated amount of intake air. Therefore, when the integrated amount of intake air at the previous driving of the engine is large (for example, running for a long time, the engine 3 is driven at a high speed, etc.), it can be determined that the exhaust pipe 5 is sufficiently hot and the soak time is large. Even when the temperature in the exhaust pipe 5 decreases, it can be determined that the temperature in the exhaust pipe 5 is kept sufficiently high. On the other hand, when the cumulative amount of intake air at the time of the previous engine drive is small (for example, the engine 3 is driven in an idle state for a short time), it can be determined that the exhaust pipe 5 is not sufficiently hot and the soak time is long. And the temperature in the exhaust pipe 5 falls, and the inside of the exhaust pipe 5 becomes a low temperature state. As described above, the optimum relationship between the predetermined time and the integrated amount of intake and intake air is stored in the ROM of the ECU 11.

  When the ECU 11 determines that the soak time measured by the soak timer 11a is equal to or longer than the predetermined time, the ECU 11 energizes the heater 9 for a predetermined time via the control circuit 13 (S230). At this time, the ECU 11 calculates the internal resistance R of the heater 9 by the above equation (1) based on the voltage V from the voltage sensor 23 and the current I from the current sensor 25 (S240). The ECU 11 energizes the heater 9 for a predetermined time via the control circuit 13 and then stops energization (S250).

  On the other hand, when the ECU 11 determines that the soak time measured by the soak timer 11a is less than the predetermined time, the ECU 11 proceeds to the process of (S280).

  Next, the ECU 11 estimates the temperature in the exhaust pipe 5 based on the predetermined relationship between the internal resistance of the heater 9 and the temperature in the exhaust pipe 5 stored in the ROM, and the calculated internal resistance of the heater 9 ( S260).

  Thereafter, the ECU 11 determines whether or not the estimated temperature in the exhaust pipe 5 is equal to or higher than a predetermined temperature (for example, 60 ° C. or higher) (S270). When the ECU 11 determines that the estimated temperature in the exhaust pipe 5 is 60 ° C. or higher and no thermal shock is generated, the ECU 11 transmits an energization signal to the control circuit 13 (S280). Upon receiving the energization signal, the control circuit 13 energizes the heater 9 at a predetermined DUTY ratio and causes a power failure to heat the oxygen sensor 7 (S290).

  On the other hand, when the ECU 11 determines that the estimated temperature in the exhaust pipe 5 is less than 60 ° C. and there is a risk of thermal shock, the ECU 11 stops energization of the heater 9 and stops heating of the oxygen sensor 7 ( S300). Thereafter, the ECU 11 determines whether or not a predetermined time has elapsed (S310). When the ECU 11 determines that the predetermined time or more has elapsed, the ECU 11 proceeds to the process of (S210). When the ECU 11 determines that the predetermined time or more has not elapsed, the ECU 11 proceeds to the process of (S300).

  Next, a modification of the present embodiment will be described.

  In (S210) of the above embodiment, it is determined whether or not the integrated amount of intake air at the time of the previous engine drive is equal to or greater than a predetermined amount and the engine 3 is sufficiently warmed, but the oxygen sensor 7 is activated. It may be determined whether or not it has been performed (whether or not the activation temperature is exceeded). Further, the ECU 11 may determine whether or not the temperature in the exhaust pipe 5 at the previous engine stop is equal to or higher than a predetermined value and the engine 3 is sufficiently warmed up.

  As described above, the heater 9 heats the oxygen sensor 7 when the cumulative amount of intake air at the time of previous engine driving is a predetermined amount or more and the soak time is a predetermined time or more. Thereby, the thermal shock of the oxygen sensor 7 can be reliably prevented while reducing the cost by a simple method, and the reliability of the oxygen sensor 7 can be improved.

Moreover, since the temperature in the exhaust pipe 5 is estimated based on the internal resistance of the heater 9, the temperature in the exhaust pipe 5 can be accurately determined in a wide temperature range regardless of whether the temperature is low or high. Can be estimated. Thereby, it becomes possible to prevent the thermal shock of the oxygen sensor 7 more reliably.
(Third embodiment)
When the soak time is a predetermined time or longer (for example, a long time of 5 hours or longer), the intake air temperature and the water temperature are reduced to near the outside air temperature. Furthermore, it can be estimated that the temperature of the heater 9 also decreases to near the intake air temperature and the water temperature. Therefore, when the soak time is a predetermined time or longer, the intake air temperature from the intake air temperature sensor 15 or the water temperature from the water temperature sensor 17 can be estimated as the temperature of the heater 9.

  Based on the estimated temperature of the heater 9, a predetermined relationship (solid line (a) shown in FIG. 3) between the internal resistance of the heater 9 and the temperature of the heater 9 stored in advance in the ROM of the ECU 11 is corrected. Thereby, when measuring the internal resistance of the heater 9 and the temperature of the heater 9 and calculating the predetermined relationship, the variation of each measured value is suppressed, and the predetermined relationship with higher accuracy (dotted line (b) shown in FIG. 3). Can be derived. That is, by calculating a predetermined relationship between the internal resistance of the heater 9 and the temperature of the heater 9 with higher accuracy, the predetermined relationship between the temperature of the heater 9 and the temperature in the exhaust pipe 5 is calculated based on this predetermined relationship. Thus, it is possible to derive a predetermined relationship between the internal resistance of the heater 9 and the temperature in the exhaust pipe 5 with higher accuracy.

  FIG. 4 is a diagram showing an example of a predetermined relationship between the internal resistance of the heater before and after correction and the temperature of the heater. In FIG. 4, a solid line (a) indicates a predetermined relationship between the internal resistance of the heater 9 and the temperature of the heater 9 before correction, and a dotted line (b) indicates a predetermined relationship between the internal resistance of the heater 9 and the temperature of the heater 9 after correction. Showing the relationship.

  As shown in FIG. 4, for example, if the internal resistance of the heater 9 calculated by the ECU 11 is 13Ω, the temperature of the heater 9 is about 20 ° C. from a predetermined relationship (solid line (a)) stored in the ROM of the ECU 11. At this time, if the water temperature of the water temperature sensor 17 or the intake air temperature from the intake air temperature sensor 15 is about 40 ° C., a predetermined relationship is established so that the temperature of the heater 9 is about 40 degrees when the internal resistance of the heater 9 is 13Ω. Correction is performed by shifting in parallel. The ECU 11 calculates a predetermined relationship between the corrected internal resistance of the heater 9 and the temperature in the exhaust pipe 5 based on the corrected predetermined relationship (dotted line (b)).

  Hereinafter, the correction process of the predetermined relationship between the internal resistance of the heater 9 and the temperature in the exhaust pipe 5 will be described in detail.

  FIG. 5 is a flowchart of a control routine of the heater control apparatus 1 according to the third embodiment.

  As shown in FIG. 5, when the ECU 11 receives an ON signal from the ignition switch 27 (S400), the ECU 11 determines whether or not the soak time measured by the soak timer 11a is a predetermined time or more (for example, 5 hours or more) (S410). ). Here, the predetermined time is set based on the integrated amount of intake air when the engine was driven last time, and is set to be substantially proportional to the integrated amount of intake air.

  Next, the intake air temperature sensor 15 detects the intake air temperature and the water temperature sensor 17 detects the water temperature (S420), and the ECU 11 determines whether or not the detected intake air temperature and water temperature are equal to or lower than a predetermined temperature (S430). . By this determination, when the intake air temperature and the water temperature are high, it can be determined that the temperature is not close to the outside air temperature, and it is determined that the temperature of the heater 9 cannot be approximated.

  Thereafter, when the ECU 11 determines that the intake air temperature and the water temperature are equal to or lower than the predetermined temperature, the ECU 11 determines whether the intake air temperature and the water temperature are within a predetermined temperature range (for example, within ± 1 ° C.) (S440). By this determination, variations in intake air temperature and water temperature can be suppressed, and the accuracy of the control processing can be further improved.

  When the ECU 11 determines that the intake air temperature and the water temperature are within the predetermined temperature range, the ECU 11 energizes the heater 9 for a predetermined time via the control circuit 13 (S450). At this time, the ECU 11 calculates the internal resistance R of the heater 9 by the above equation (1) based on the voltage V from the voltage sensor 23 and the current I from the current sensor 25 (S460). The ECU 11 energizes the heater 9 for a predetermined time via the control circuit 13, and then stops energization (S470).

  Further, the ECU 11 estimates the intake air temperature detected by the intake air temperature sensor 15 as the temperature of the heater 9, and becomes the estimated temperature of the heater 9 when the internal resistance of the heater 9 calculated in (S460). As described above, the predetermined relationship between the temperature of the heater 9 stored in the ROM of the ECU 11 and the internal resistance of the heater 9 is shifted in parallel, and the predetermined relationship is corrected. Further, the ECU 11 corrects the predetermined relationship between the temperature in the exhaust pipe 5 and the internal resistance of the heater 9 based on the predetermined relationship between the corrected temperature of the heater 9 and the internal resistance of the heater 9 (S480). ).

  The ECU 11 is based on the predetermined relationship between the corrected temperature in the exhaust pipe 5 and the internal resistance of the heater 9 (S140) in the first embodiment described above, and (S260) and thereafter in the second embodiment. The control process is performed.

  As described above, by correcting the predetermined relationship between the temperature of the heater 9 and the internal resistance of the heater 9 based on the intake air temperature from the intake air temperature sensor 15 and the water temperature from the water temperature sensor 17, the temperature of the heater 9 and the inside of the heater 9 are corrected. Variations in the internal resistance of the heater 9 when calculating the predetermined relationship with the resistance can be suppressed. Therefore, since the predetermined relationship between the temperature of the heater 9 and the internal resistance of the heater 9 can be calculated with high accuracy, the predetermined relationship between the temperature in the exhaust pipe 5 and the internal resistance of the heater 9 can be calculated with high accuracy. That is, since the temperature in the exhaust pipe 5 can be estimated with high accuracy, the thermal shock of the oxygen sensor 7 can be prevented more reliably, and the reliability of the oxygen sensor 7 can be improved.

  The best mode for carrying out the present invention has been described with reference to the embodiments. However, the present invention is not limited to these embodiments, and has been described above without departing from the gist of the present invention. Various modifications and substitutions can be made to the embodiments.

  The present invention can be used for a heater control device employed in a vehicle air-fuel ratio sensor. The appearance, weight, size, running performance, etc. of the adopted vehicle are not questioned.

It is the schematic of the system configuration | structure which shows the heater control apparatus which concerns on the 1st thru | or 3rd embodiment of this invention. It is a flowchart of the control routine of the heater control apparatus which concerns on 1st Embodiment. It is a flowchart of the control routine of the heater control apparatus which concerns on 2nd Embodiment. It is a figure which shows an example of the predetermined relationship between the internal resistance of the heater before and behind correction | amendment, and the temperature of a heater. It is a flowchart of the control routine of the heater control apparatus 1 which concerns on 3rd Embodiment.

Explanation of symbols

1 Heater control device 3 Engine (internal combustion engine)
5 Exhaust pipe 7 Oxygen sensor (air-fuel ratio sensor)
9 Heater 11 ECU
11a Soak timer 13 Control circuit 15 Intake temperature sensor 17 Water temperature sensor 19 Air flow meter 21 Battery 23 Voltage sensor 25 Current sensor 27 Ignition switch (IGSW)

Claims (5)

A heater control device for an air-fuel ratio sensor with a heater attached to an exhaust pipe of an internal combustion engine,
Heater resistance detection means for detecting the internal resistance of the heater;
Exhaust temperature estimating means for estimating the exhaust temperature in the exhaust pipe based on the internal resistance of the heater detected by the heater resistance detecting means;
A heater control device comprising: a heating permission unit that permits heating of the air-fuel ratio sensor by the heater when the exhaust gas temperature estimated by the exhaust gas temperature estimation unit is equal to or higher than a predetermined temperature. The heater control device according to claim 1,
The exhaust temperature estimating means estimates the exhaust temperature based on a predetermined relationship between the internal resistance of the heater and the exhaust temperature,
An intake air temperature detecting means for detecting an intake air temperature of the internal combustion engine;
Soak time measuring means for measuring the soak time of the internal combustion engine;
Based on the intake air temperature detected by the intake air temperature detecting means and the internal resistance of the heater detected by the heater resistance detecting means when the soak time measured by the soak time measuring means is a predetermined time or more. The heater control device further comprising: correction means for correcting the predetermined relationship. The heater control device according to claim 2,
Water temperature detecting means for detecting the water temperature of the internal combustion engine;
Range determining means for determining whether or not the water temperature detected by the water temperature detecting means and the intake air temperature detected by the intake air temperature detecting means are within a predetermined temperature range;
The heater control device according to claim 1, wherein when the range determination unit determines that the water temperature and the intake air temperature are within the predetermined temperature range, the correction unit corrects the predetermined relationship. A heater control device for an air-fuel ratio sensor with a heater attached to an exhaust pipe of an internal combustion engine,
Soak time measuring means for measuring the soak time of the internal combustion engine;
A heater control device, comprising: a heating permission unit that permits heating of the air-fuel ratio sensor by the heater when the soak time measured by the soak time measuring unit is a predetermined time or less. The heater control device according to claim 4,
An integrated amount acquisition means for acquiring an integrated amount of intake air to the internal combustion engine until the start of measurement of the soak time;
The heater control device, wherein the heating permission unit permits heating of the air-fuel ratio sensor by the heater when the integrated amount of intake air acquired by the integrated amount acquisition unit is a predetermined amount or more.

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