JP2007278802A - Heater controller of exhaust gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To optimize the heating of the heater of an exhaust gas sensor and to prevent the enhancement of a fuel cost due to the suppression of power consumption and the cracking of an element due to the covering of an exhaust pipe with water. <P>SOLUTION: If the electromotive force produced by the theoretical air/fuel ratio detection part of a sensor element or the change quantity of the electromotive force becomes a predetermined value or above during the passage of a warming-up current the passage of a current to the heater is changed over to the activation passage of a current for obtaining a temperature higher than the heating temperature due to the passage of the warming-up current by heating. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heater control device for an exhaust gas sensor, and more particularly to a heater control device that controls energization of a heater for heating a sensor element of an exhaust gas sensor installed in an exhaust system of an internal combustion engine.

In order to reduce harmful components of exhaust gas in gas combustion of an internal combustion engine, it is effective to more precisely control the air-fuel ratio of the combustion gas. For this reason, instead of an oxygen concentration sensor (hereinafter referred to as an O ₂ sensor) that detects only the rich and lean binary values of the air / fuel ratio of the combustion gas, a linear air / fuel ratio sensor (hereinafter referred to as a LAF sensor) capable of linearly measuring the air / fuel ratio. ) Has been adopted by many internal combustion engines.

However, when measuring the air-fuel ratio by the LAF sensor, it is necessary to keep the sensor element at a predetermined high temperature as in the conventional O ₂ sensor in order to increase the amount of oxygen ion movement in the sensor. Moreover, this high temperature state requires a higher temperature state (about 600 ° C. to about 800 ° C.) than a conventional O ₂ sensor (about about 300 ° C.). For this reason, the heater used for the LAF sensor is set to have a larger calorific value than the heater used for the O ₂ sensor.

On the other hand, in the structure of the sensor element and the heater in the LAF sensor, there is one in which the sensor element and the heater are arranged in parallel in a plate state. In such a configuration, heater control is required in consideration of the influence of thermal stress generated in the sensor element when the sensor element is heated up, in addition to the O ₂ sensor.

  Furthermore, moisture generated and adhering in the exhaust pipe is also an obstacle when heating the sensor element (causing the sensor element to crack), and at present, the thermal stress of the LAF sensor is taken into account in order to deal with such a problem. A heater control device technology has been proposed.

  As one of them, the moisture adhering to the inner surface of the exhaust pipe scatters and enters from the hole of the protector cover provided in the linear air-fuel ratio sensor at the start etc., and gets wet to the high temperature sensor element heated by the heater. Focusing on the fact that the sensor element is cracked by this, a technique of a heater control device for preventing this is proposed (for example, Patent Document 1).

  Also, when the engine is started, if liquid moisture exists in the exhaust pipe or inside the sensor, the temperature until the linear air-fuel ratio sensor activates the sensor until a predetermined period of time elapses after the engine is started. There has been proposed a technique of a heater control device that controls a heater with electric power lower than electric power that can raise the temperature and evaporates water in an exhaust pipe so as not to boil (for example, Patent Document 2).

JP 2001-41923 A JP 2004-69644 A

  However, in Patent Document 1, in order to prevent liquid moisture present in the exhaust pipe from entering the protector cover through the hole of the protector cover and directly applied to the sensor element, the energization of the heater is limited. However, sensor element cracking due to moisture is not only the case where water enters the protector cover from the hole in the protector cover, but there are cases where moisture in the exhaust pipe condenses inside the protector cover and moisture adheres to the surface of the sensor element. Yes, this point is not considered.

  For example, when the engine is restarted after being left for a relatively short period of time, such as 10 minutes to 1 hour after the engine is stopped, the cooling water temperature of the internal combustion engine does not drop much, but the temperature of the exhaust pipe is Since it is cooled to the same level as the ambient outside air temperature, water vapor accumulated in the exhaust pipe is condensed, and condensation is also generated inside the linear air-fuel ratio sensor. And dew condensation water adheres to each surface of a sensor element and a heater. In this state, if the heater control is performed so that the temperature of the heater immediately reaches 600 ° C., a large temperature difference occurs between the surface side of the sensor element that receives heat from the heater and the opposite surface side of the surface, An excessive thermal stress is generated in the sensor element, and the sensor element may be damaged.

  In the technique disclosed in Patent Document 2, when liquid moisture is present inside the sensor, the heater is controlled with electric power lower than the electric power that can raise the temperature up to the sensor activation, and the moisture inside the sensor is reduced. Although it is a technology that slowly evaporates without boiling, no proposal has been made to switch the heater to activation energization control when moisture in the sensor body runs out, and moisture present in the exhaust pipe or sensor is measured. It seemed difficult to do so, and there was a big problem in terms of practical use.

  For this reason, as a means for setting the condition for switching to the activation energization control, a period from the temperature change of the exhaust pipe wall surface after the start in the experiment to the time when the moisture is indirectly lost (elapsed time after the start, etc.) It can be measured for each combination of environmental conditions, and in actual operation, a method of switching to activation energization control after a period measured in an experiment according to the operating conditions and environmental conditions is considered.

  However, in this method, what can be measured in the experiment is a combination of limited operating conditions and environmental conditions, so that the heater is not switched to activation energization control while moisture is present in actual operation. In addition, the switching to the activation energization control is performed after the longest period of the worst case or the period obtained by adding the margin to the measured period has elapsed.

  In any of the prior arts, the optimum timing for heating the heater is not taken into consideration, and there is a concern that a wasteful state of energy such as the catalyst being inactive and the LAF sensor being in an active state may occur.

  The present invention has been made in view of the problems described above, and the object of the present invention is to optimize the activation timing of the exhaust gas sensor and improve the fuel consumption without deteriorating the exhaust performance. An object of the present invention is to provide a heater control device for an exhaust gas sensor capable of preventing damage to the sensor element due to the presence of moisture adhering to the sensor element.

  In order to achieve the above object, an exhaust gas sensor heater control apparatus according to the present invention is an exhaust gas sensor heater control apparatus having a sensor element including a theoretical air-fuel ratio detection unit and a heater for heating the sensor element. It has a discriminating means for discriminating whether or not the electromotive force or electromotive force change amount generated by the theoretical air-fuel ratio detection unit of the sensor element has become a predetermined value or more, and is heated at a temperature lower than the sensor activation temperature after the heater energization is started. A first period for performing the first warm-up energization for the heater is set, and in the first period, the energization for the heater is the first warm-up energization, and the first period has elapsed or the first When the determination means makes a positive determination during the period, the heater is energized at a temperature higher than the heating temperature of the first warm-up energization. It switched to the activation energized.

  In order to achieve the above object, a heater control device for an exhaust gas sensor according to the present invention is a heater control device for an exhaust gas sensor having a sensor element including a theoretical air-fuel ratio detector and a heater for heating the sensor element. And determining means for determining whether the electromotive force or the electromotive force change amount generated by the theoretical air-fuel ratio detection unit of the sensor element is equal to or higher than a predetermined value, and a temperature lower than the sensor activation temperature after the heater energization is started. A first period in which a first warm-up energization is performed on the heater, and a second warm-up energization is performed on the heater that is heated at a lower temperature than the first period after the first period has elapsed. A second period is set, the energization to the heater is the first warm-up energization in the first period, and the heater is energized in the first period. Is the second warm-up energization, and when the second period has elapsed, or when the determination means makes an affirmative determination in the first period or the second period, the heater is energized as a heating of the previous first warm-up energization. Switch to activation energization that heats at a temperature higher than the temperature.

  In order to achieve the above object, a heater control device for an exhaust gas sensor according to the present invention is a heater control device for an exhaust gas sensor having a sensor element including a theoretical air-fuel ratio detector and a heater for heating the sensor element. And determining means for determining whether the electromotive force or the amount of change in electromotive force generated by the theoretical air-fuel ratio detection unit of the sensor element has exceeded a predetermined value, and heating is performed at a temperature lower than the sensor activation temperature. A first period in which the first warm-up energization is performed on the heater, and a second period in which a second warm-up energization is performed on the heater in which the heating is performed at a temperature lower than the first period; After the heater energization is started, the first warm-up energization in the first period and the second warm-up energization in the second period are repeated, and the number of repetitions reaches a predetermined value. , Or when the determination means has positive determination in the first period or the second time period, the power supply to the heater, switching to the activation current of performing high temperature heat than the heating temperature of the first warm-up power.

  In the exhaust gas sensor heater control device according to the present invention, preferably, the first heater warm-up energization performed in the first period is such that the temperature of the sensor element rises from 250 ° C to 300 ° C.

  In the exhaust gas sensor heater control device according to the present invention, preferably, in the second heater warm-up energization performed in the second period, the temperature at which the sensor element rises is in the range of 50 ° C to 100 ° C.

  The heater control device for an exhaust gas sensor according to the present invention preferably stores a period from the start of the first period until the determination unit makes an affirmative determination when the determination unit makes an affirmative determination during the first period. A storage unit configured to variably set the first period based on the period information stored in the storage unit.

  The heater control apparatus for an exhaust gas sensor according to the present invention preferably sets the first period to a value within the predetermined range when the period information stored in the storage means is outside the predetermined range.

  The heater control device for an exhaust gas sensor according to the present invention preferably changes the heater energization at the time of heater energization switching gradually by a predetermined amount.

  In the exhaust gas sensor heater control apparatus according to the present invention, preferably, a parameter for determining that the first period or the second period has elapsed is an elapsed time.

  In the heater control apparatus for an exhaust gas sensor according to the present invention, preferably, the parameter for determining that the first period or the second period has elapsed is an integrated value of the intake air amount taken into the internal combustion engine.

  The heater control apparatus for an exhaust gas sensor according to the present invention preferably sets a threshold value for determining whether the first period or the second period has elapsed according to the operating state of the internal combustion engine.

  In the heater control apparatus for an exhaust gas sensor according to the present invention, preferably, the heater is driven by a duty signal and the heater energization is controlled by duty ratio control.

  Optimization of heater heating of the exhaust gas sensor can be achieved, and an effect of improving fuel efficiency by suppressing power consumption and an effect of preventing element cracking due to water covering of the exhaust pipe can be expected.

An embodiment of a heater control device for an exhaust gas sensor according to the present invention will be described with reference to the drawings.
FIG. 1 shows the overall configuration of an internal combustion engine to which a heater control device for an exhaust gas sensor according to the present invention is applied and its control system.

  The internal combustion engine 10 has a plurality of cylinders 11 as a multi-cylinder engine. Each of the cylinders 11 includes a piston 12 and a combustion chamber 13 that reciprocate.

  In the internal combustion engine 10, an ignition plug 15 connected to an ignition coil / power switch means 14 is arranged for each cylinder 11, an intake valve 17 that opens and closes an intake port 16, and an exhaust that opens and closes an exhaust port 18. A valve 19 is provided.

  An intake pipe 20 and an air cleaner 21 are connected to the intake port 16 in this order. The intake pipe 20 is provided with an injector (fuel injection valve) 22 that injects fuel toward the intake port 16, and an air flow sensor 23 and a throttle valve 24 that measure the amount of intake air taken into the combustion chamber 13. A throttle opening sensor 25 for measuring the opening degree of the engine and an idle speed control valve (ISC) 26 for controlling the engine speed at the time of idling to be the target engine speed are arranged at appropriate positions. The injector 22 is arranged for each cylinder 11 and adopts a fuel injection system that is a multi-point injection (MPI) system.

  An exhaust pipe 29, a catalytic converter 30, and a muffler 31 are connected to the exhaust port 18 in this order.

  The internal combustion engine 10 is provided with a coolant temperature sensor 27 for measuring the coolant temperature and a crank angle sensor 28 for measuring the engine speed at appropriate positions.

  Air sucked from an air cleaner 21 provided upstream of the intake pipe 20 is mixed with gasoline injected at a predetermined timing from an injector (fuel injection valve) 22 after the flow rate is adjusted by a throttle valve 24. It is supplied into each combustion chamber 13.

  On the other hand, the fuel from the fuel tank 33 is sucked and pressurized by the fuel pump 34 and then guided to the fuel inlet of the injector 22 through the fuel pipe 36 having the pressure regulator 35, and the excess fuel is removed from the fuel tank. In a manner returned to 33, the fuel is supplied to the injector 22.

  The air-fuel mixture supplied into the combustion chamber 13 is ignited by the spark plug 15, and exhaust gas generated by the combustion of the air-fuel mixture is led to the catalytic converter 30 through the exhaust pipe 29 and purified by the catalytic converter 30, Released into the atmosphere.

  In the exhaust pipe 29, a linear air-fuel ratio sensor 32, which is an aspect of an exhaust gas sensor that outputs an air-fuel ratio signal linear with respect to the exhaust air-fuel ratio (oxygen concentration), is disposed at an appropriate position.

  The output signal indicating the intake air amount obtained from the air flow sensor 23, the output signal from the throttle opening sensor 25, and the output signals from the cooling water temperature sensor 27, the crank angle sensor 28 and the linear air-fuel ratio sensor 32 are the engine control unit. (ECU) 40 is input.

  The ECU 40 is of a computer type and is arranged in the vehicle compartment or engine room, and performs predetermined arithmetic processing based on electrical signals indicating the operating state of the internal combustion engine 10 output from the various sensors described above. In order to perform optimum control in accordance with the operating state, signals for opening / closing the injector 22 for injecting and supplying fuel, driving the spark plug 15 and opening / closing the idle speed control valve 26 are output, and the fuel pump 34 is also provided. Control. Then, the ECU 40 performs control to inject fuel from the injector 22 for each cylinder in accordance with the intake stroke of each cylinder 11 and the fuel injection timing.

  The ECU 40 includes a CPU 41 that performs arithmetic processing, a clock generator 42 that generates a reference time (clock signal), a ROM 43 and a RAM 44 that store a large number of control programs, a timer counter 45, an input / output interface (I / I). O) 46, an output circuit 47, a digital input circuit 48, an A / D (analog / digital) converter 49, and an analog input circuit 50.

  Specifically, the ECU 40 calculates the required fuel amount to be supplied from the injector 22 to each cylinder 11 based on the intake air amount and the set air-fuel ratio, and also calculates the required fuel amount and the injection amount characteristic of the injector 22. The required injection pulse width (the valve opening time of the injector 22) is calculated based on the flow rate gradient and the invalid injection pulse width, and the injector 22 opens the valve for the injection pulse time based on the required fuel injection pulse width. A command signal (drive signal) to be performed is generated. Further, the injection timing of the injector 22 is calculated based on the intake air amount, the engine speed, etc., and synchronized with the intake stroke, and the fuel injection timing during the intake stroke is set to an optimal timing, and the injector is set based on the timing. 22. A drive signal is output to the ignition coil / power switch means 14.

  FIG. 2A shows a configuration example of the linear air-fuel ratio sensor 32. The linear air-fuel ratio sensor 32 includes an exhaust gas sensor element (hereinafter referred to as sensor element) 32S formed of a zirconia solid electrolyte or the like, and a heater 32H that heats the sensor element 32S, both of which are plate-shaped. The sensor element 32S and the heater 32H are arranged in parallel at a predetermined interval.

  The sensor element 32S has an Ip cell part 32S-Ip and a Vs cell part (theoretical air-fuel ratio detection part) 32S-Vs, and a measurement chamber 32A for introducing exhaust gas to both sides of the Vs cell part 32S-Vs. An atmosphere chamber (oxygen reference chamber) 32B for introducing the atmosphere is defined.

  The linear air-fuel ratio sensor 32 detects the amount of residual oxygen contained in the exhaust gas in the exhaust pipe 29, measures the actual air-fuel ratio of the exhaust gas, and outputs an electrical signal corresponding to the oxygen concentration to the ECU 40.

  That is, in the linear air-fuel ratio sensor 32, the air-fuel ratio measurement current Ip flowing through the Ip cell portion 32S-Ip of the sensor element 32S changes with respect to the measured air-fuel ratio, and this air-fuel ratio measurement current Ip is converted into the sensor voltage control unit. (Air-fuel ratio detection unit) A sensor voltage generated at both ends of the measurement resistor is measured through the measurement resistor 401, and the actual air-fuel ratio of the exhaust gas is converted from the sensor voltage. FIG. 2B shows the relationship between the actual air-fuel ratio A / F of the exhaust gas and the air-fuel ratio measurement current Ip.

  On the contrary, the sensor voltage control unit 401 is introduced into the measurement chamber 32A so that oxygen in the measurement chamber 32A is released into the exhaust gas when the exhaust gas introduced into the measurement chamber 32A is thinner than the stoichiometric air-fuel ratio. When the exhaust gas is richer than the stoichiometric air-fuel ratio, the direction and magnitude of the air-fuel ratio measurement current Ip are adjusted so that oxygen is taken into the measurement chamber 32A.

The Vs cell portion 32S-Vs is provided with electrodes on the surface in contact with the measurement chamber 32A and the surface in contact with the atmospheric chamber 32B, and is structurally similar to the conventional O ₂ sensor used as an exhaust gas sensor. The electromotive force Vs having the characteristics shown in FIG. 2C is generated at both ends of the electrode in accordance with the oxygen concentration (air-fuel ratio A / F) of the measurement chamber 32A. It is detected by the electromotive force detection unit 402.

  The electromotive force Vs of the Vs cell unit 32S-Vs depends on the sensor element temperature, and an electromotive force Vs sufficient to discriminate between rich (deep) / lean (thin) is generated around 300 ° C. The lower the electromotive force Vs is, the lower it is (around 100 ° C.). Based on the electromotive force Vs detected by the electromotive force detection unit 402, the sensor voltage control unit 401 determines a rich / lean state in the measurement chamber 32S, and based on this, the polarity of the air-fuel ratio measurement current Ip is determined. (Flow direction) is controlled.

  The heater 32H is configured by a ceramic heater or the like, and the energization state is controlled by the heater energization control unit 403 according to the engine speed and the coolant temperature.

  In the present embodiment, the sensor voltage control unit 401, the electromotive force detection unit 402, and the heater energization control unit 403 are embodied by a computer-type ECU 40.

  3A and 3B show a protector structure for protecting the linear air-fuel ratio sensor 32. FIG. This protector structure has a double structure of an inner protector tube 321 and an outer protector tube 322 so that a hole 323 provided in the inner protector tube 321 and a hole 324 provided in the outer protector tube 322 do not overlap. Alternatively, no hole is provided at the position where the sensor element 32S is disposed.

  Thereby, even if the dew condensation water on the inner wall surface of the exhaust pipe 29 rides on the flow of the exhaust gas and is applied to the outer protector tube 322 and the inner protector tube 321, the dew condensation water from the holes 323 and 324 provided in these protector tubes However, the sensor element 32S is not directly applied.

  However, even if such a structure is adopted, another problem arises if the sensor element 32S itself is below the dew point temperature. This is because water vapor in the exhaust gas is condensed inside the inner protector tube 321.

  In particular, when the engine is started, the intake efficiency is increased and the required air-fuel ratio is maintained at 14.7 or less until the first explosion occurs, so that the rotation is maintained. Here, when the engine water temperature is 10 ° C. or lower, in order to promote warming up of the internal combustion engine 10, the rotational speed is set higher than the normal idle rotational speed to about 1000 to 1500 r / min, and the air-fuel ratio is set. Since it is set slightly darker, more fuel is injected than during normal idling, and water vapor in the exhaust gas is also generated at about 5 to 10 g / min. Further, when the water temperature is 10 ° C. or lower, the temperature of the exhaust pipe 29 in the vicinity of the linear air-fuel ratio sensor 32 corresponds to the outside air temperature, so that the water vapor is cooled and the condensed water adheres to the inside of the linear air-fuel ratio sensor 32 as well. Resulting in.

  4A shows the state of condensed water adhesion of the sensor element 32S of the linear air-fuel ratio sensor 32, and FIGS. 4B and 4C show the temperature change of the sensor element 32S of the linear air-fuel ratio sensor 32. FIG. . As shown in FIG. 4A, the linear air-fuel ratio sensor 32 includes a sensor element 32S and a heater 32H that heats the sensor element 32S arranged in a plate shape at predetermined intervals. 32S has the heater surface 32Sa which faces the heater 32H, and the surface (condensation water adhesion surface) 32Sb far from the heater 32H.

  The exhaust pipe 29 is cooled by the outside air temperature, the internal combustion engine 10 is started in a state where condensed water is present in the sensor element 32S and the heater 32H, and the heater 32H is set to the activation temperature (600 ° C.) of the sensor element 32S ( Hereinafter, as shown in FIG. 4B, the heater surface 32Sa of the sensor element 32S rapidly rises in temperature due to the radiant heat of the heater 32H, and the condensed water evaporates. It becomes substantially the same temperature as the heater 32H.

  On the other hand, on the surface 32Sb far from the heater 32H, the condensed water is not yet evaporated due to the delay in heat transfer, and the time until the condensed water evaporates is maintained at the surface temperature of 100 ° C. which is the boiling point of water. After the evaporation, the activation temperature (600 ° C.) is reached.

  That is, on the surface 32Sb far from the heater 32H, the activation temperature is rapidly reached after the dew condensation water evaporates, so that the rate of temperature increase per unit time is also high as shown in FIG. Therefore, a large thermal stress is generated inside the sensor element 32S, causing damage to the sensor element 32S.

  For this reason, the temperature of the sensor element 32S is kept low, for example, at 100 ° C. until the condensed water evaporates from the surface of the sensor element 32S, and while the condensed water on the element surface is evaporated, the sensor element 32S It is necessary to prevent the sensor element 32S from being damaged by controlling the energization of the heater 32H so that no thermal stress is generated (hereinafter, this energization control is referred to as warm-up energization).

  However, when the sensor element 32S is not activated, air-fuel ratio control that maintains the air-fuel ratio of the exhaust gas at the target value cannot be performed, and there is a problem that the amounts of NOx, HC, and CO components in the exhaust gas increase.

On the other hand, in the heater control apparatus for the exhaust gas sensor of the present embodiment, while preventing such breakage of the sensor element 32S, appropriately determines the time point when all the condensed water attached to the sensor element 32S has evaporated, In order to end the warm-up energization and switch to the activation energization, the Vs cell part (theoretical air-fuel ratio detection part) 32S-Vs of the linear air-fuel ratio sensor 32 has the same structure as the conventional O ₂ sensor, Focusing on the fact that the electromotive force is generated at a temperature lower than the activation temperature (600 ° C.) of the fuel ratio sensor 32 (300 ° C.), the heater control is performed as follows.

  FIG. 5 shows an embodiment of the heater control device (built in the ECU 40). The heater control device determines a determination unit 404, a storage unit 405 that stores a period (time) until the determination unit 404 makes an affirmative determination when the heater is energized last time, and an abnormality in information stored in the storage unit 405. Collation means 406. The determination unit 404 is a determination unit that determines whether or not the electromotive force Vs or the amount of change in electromotive force generated by the Vs cell portion (theoretical air-fuel ratio detection unit) 32S-Vs of the sensor element 32S has become a predetermined value or more. Further, parameters necessary for heater control are obtained by the operating state detection means 407, and the temperature control of the heater 32H is performed by the energization control by the heater energization control unit 403.

  FIG. 6 is a timing chart showing the first embodiment of the present invention. In the first embodiment, when the heater 32H is energized (first warm-up energization) and heated so that the temperature of the sensor element 32S can be increased to 300 ° C., the electromotive force Vs of the Vs cell unit 32S-Vs is started to energize the heater. If there is a change of a predetermined amount later, it can be determined that the temperature of the sensor element 32S has increased because no condensed water has adhered to the surface of the sensor element 32S. In this case, the energization of the heater 32H is switched to the activation energization. .

  On the other hand, when the electromotive force Vs of the Vs cell unit 32S-Vs has not changed from the time when the heater energization is started, the sensor element 32S rises due to the process in which condensed water adheres to the surface of the sensor element 32S and is evaporated. The start of activation energization is delayed until the first period (300 ° C. holding time T1) has elapsed from the time when the heater energization is started by determining that the temperature is not high (the state where the temperature is stagnant at 100 ° C. in FIG. 4B). Thus, the presence or absence of condensed water on the surface of the sensor element 32S is determined.

  The first warm-up energization performed in the first period may be energization in which the temperature at which the sensor element 32S rises is in the range of about 250 ° C to 300 ° C.

The operation of the first embodiment will be described using the flowchart of FIG.
First, in step S701, it is determined from the number of revolutions of the internal combustion engine 10 whether or not it is in a complete explosion state. If it is in a complete explosion state, the process proceeds to step S703, and if step S701 is negative, the heater 32H is turned off in step S702. And exit.

  In step S703, a timer for measuring the 300 ° C. holding time T1 (first period) is initialized, and the 300 ° C. holding time T1 is set.

  Next, in step S704, the heater energization control unit 403 sets the heater target temperature to a first warm-up energization equivalent to 300 ° C. (hereinafter referred to as first heater energization), energizes the heater 32H, The sensor element 32S is heated.

  Next, in step S705, the determination means 404 determines the amount of change of the voltage of the electromotive force detection unit 402 measured from the electromotive force Vs of the Vs cell unit 32S-Vs of the linear air-fuel ratio sensor 32 and the threshold SL1 from the start of energization of the heater. Compare and judge by. In the example of FIG. 6, when the electromotive force Vs is generated, the voltage of the electromotive force detection unit 402 is reduced.

  If step S705 is negative, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process proceeds to step S706, and the first heater energization in step S704 is performed until the 300 ° C. holding time T1 elapses. The determination in step S705 is repeated.

  On the other hand, if step S705 is positive, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process proceeds to step S707. If step S705 is negative even after the 300 ° C. holding time T1 has elapsed (YES at step S706), the process proceeds to step S707.

  In step S707, heater energization (activation energization) corresponding to a heater target temperature of 600 ° C. is performed, and the first warm-up energization is terminated.

  By the above-described control, the temperature of the sensor element 32S is maintained at, for example, 100 ° C. until the condensed water evaporates from the surface of the sensor element 32S, and while the condensed water on the element surface is evaporated, If the first warm-up energization (first heater energization) is performed on the heater 32H so that no thermal stress is generated in the element 32S, and the electromotive force Vs of the Vs cell portion 32S-Vs changes, the dew condensation water on the element surface As a result, the first warm-up energization is immediately terminated and activation energization is started. This prevents damage to the sensor element 32S due to condensed water on the element surface, optimizes the sensor activation time, and improves fuel efficiency without deteriorating the exhaust performance.

  Further, when the preset 300 ° C. holding time T1 has elapsed after the start of energization of the heater due to a failure of the heater function or the like, the electromotive force detection unit voltage change amount> the threshold value SL1 does not hold. In this case, the first warm-up energization is terminated and the transition to activation energization is performed, and then failure diagnosis or the like is performed.

  FIG. 8 is a timing chart showing the second embodiment of the present invention. In the second embodiment, when the condensed water is not attached to the surface of the sensor element 32S, the time until the electromotive force detection unit voltage change amount <SL1 after the first heater energization (first warm-up energization) is started. Is substantially constant (there is no water evaporation, so if the amount of heat generated by the heater 32H is the same, the time for the sensor element 32S to rise to about 300 ° C. is reproducible). Based on the above, a 300 ° C. holding time T1A (first period) is set, and during the 300 ° C. holding time T1A, the first heater is energized. If voltage change amount> threshold value SL1, it is determined from the beginning that condensed water has not adhered to the surface of sensor element 32S, the first warm-up energization is immediately terminated, and activation energization is started.

  The 300 ° C. holding time T1A adds a margin to the time when the electromotive force detection unit voltage change> threshold SL1 when the first heater is energized with no dew condensation attached to the sensor element 32S. And set.

  When condensed water is present on the surface of the sensor element 32S, the condensed water evaporates, so the temperature of the sensor element 32S temporarily stagnates around 100 ° C. Therefore, even if the 300 ° C. holding time T1A elapses, the electromotive force detector If the amount of voltage change is not greater than the threshold value SL1, it can be determined that condensed water has adhered to the surface of the sensor element 32S. In this case, a second warm-up energization equivalent to a heater target temperature of 100.degree. Switching to the heater energization), it is determined that the electromotive force detection unit voltage change amount> threshold value SL1, and if the electromotive force detection unit voltage change amount> threshold value SL1, the second warm-up energization is terminated. Then, activation energization is started.

  As a result, while the condensed water adhering to the surface of the sensor element 32S is evaporating, the heater is energized so that the heater target temperature is lowered to 100 ° C. and no thermal stress is applied to the sensor element 32S.

  Further, if the electromotive force detection unit voltage change> threshold value SL1 is not satisfied even after the second period (100 ° C. holding time T2) has elapsed since the second heater energization is started, the second warm-up energization is performed. And start energization.

  The first warm-up energization performed in the first period is energization when the temperature of the sensor element 32S rises from about 250 ° C. to 300 ° C. The second warm-up energization performed in the second period is performed by the sensor element 32S The energizing temperature may be in the range of about 50 ° C to 100 ° C.

The operation of the second embodiment will be described using the flowchart of FIG.
First, in step S901, it is determined from the rotational speed of the internal combustion engine 10 whether or not a complete explosion has occurred. If it is a complete explosion, the process proceeds to step S903. If step S901 is negative, the heater 32H is turned off in step S902. And exit.

  In step S903, a timer for measuring the 300 ° C. holding time T1A (first period) is initialized, and the 300 ° C. holding time T1A is set.

  In step S904, the heater energization control unit 403 sets the heater target temperature to the first warm-up energization (first heater energization) corresponding to 300 ° C., the first heater energization is performed on the heater 32H, and the sensor element 32S is heated. To do.

  Next, in step S905, the determination unit 404 determines the amount of change of the voltage of the electromotive force detection unit 402 obtained by measuring the electromotive force Vs of the Vs cell unit 32S-Vs of the linear air-fuel ratio sensor 32 and the threshold SL1. Compare and judge by. The example of FIG. 8 also has a detection circuit configuration in which the voltage of the electromotive force detection unit 402 decreases when the electromotive force Vs occurs.

  If step S905 is negative, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process proceeds to step S906, and the first heater energization in step S904 is performed until the 300 ° C. holding time T1A elapses. The determination in step S905 is repeated.

  If step S905 is negative even when the 300 ° C. holding time T1A has elapsed, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process proceeds to step S907.

  On the other hand, if step S905 becomes affirmative during the 300 ° C. holding time T1A, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process immediately proceeds to step S911.

  In step S907, a timer for measuring the 100 ° C. holding time T2 (second period) is initialized, and the 100 ° C. holding time T2 is set.

  Next, in step S908, the heater energization controller 403 sets the heater target temperature to a second warm-up energization equivalent to 100 ° C. (hereinafter referred to as the second heater energization), and the heater 32H is energized with the second heater. The sensor element 32S is heated.

  Next, in step S909, a determination is made that electromotive force detection unit voltage change amount> threshold value SL1, and if affirmative, the process proceeds to step S911, and if negative, the process proceeds to step S910.

  In step S910, the second heater energization in step S908 and the determination in step S909 are repeatedly performed until the 100 ° C. holding time T2 elapses.

  Since the sensor element 32S is always exposed to high-temperature exhaust gas, after all the condensed water on the surface of the sensor element 32S evaporates during the 100 ° C. holding time T2, the sensor element 32S is warmed by receiving heat from the exhaust gas. In this embodiment, the determination in step S909 is performed even while the second heater is energized.

  If step S909 is affirmative within the 100 ° C. holding time T2, or if step S909 is negative even after the 100 ° C. holding time T2 has elapsed, the process proceeds to step S911.

  In step S911, heater energization (activation energization) corresponding to a heater target temperature of 600 ° C. is performed, and the first or second warm-up energization is terminated.

FIG. 10 is a timing chart showing the third embodiment of the present invention.
In the third embodiment, as described with reference to FIG. 4C, when the temperature increase rate of the sensor element 32S is high, a thermal stress is generated inside the sensor element. By gradually changing the value, the temperature of the sensor element 32S is gradually increased, and the heater control is performed while suppressing the thermal stress.

The operation of the third embodiment will be described using the flowchart of FIG.
First, in step S1101, it is determined from the number of revolutions of the internal combustion engine 10 whether or not a complete explosion has occurred. If it is a complete explosion, the process proceeds to step S1103, and if step S1101 is negative, the heater 32H is turned off in step S1102. And exit.

  In step S1103, a timer for measuring the 300 ° C. holding time T1A (first period) is initialized, and the 300 ° C. holding time T1A is set.

  In step S1104, the heater energization control unit 403 sets the heater target temperature to a temperature obtained by adding a predetermined value (for example, 10 ° C.) to the current heater target temperature and does not exceed 300 ° C. The first warm-up energization (first heater energization) according to the heater target temperature is performed to heat the sensor element 32S. Thereby, the heater target temperature does not change rapidly, and the heating temperature of the sensor element 32S gradually increases toward 300 ° C.

  Next, in step S1105, the determination means 404 determines the amount of change in the voltage of the electromotive force detection unit 402 obtained by measuring the electromotive force Vs of the Vs cell unit 32S-Vs of the linear air-fuel ratio sensor 32 and the threshold SL1. Compare and judge by. The example of FIG. 10 also has a detection circuit configuration in which the voltage of the electromotive force detection unit 402 decreases when the electromotive force Vs occurs.

  If step S1105 is negative, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process proceeds to step S1106, and the first heater energization in step S1104 is performed until the 300 ° C. holding time T1A elapses. The determination in step S1105 is repeatedly performed.

  If step S1105 is negative even when the 300 ° C. holding time T1A has elapsed, that is, if the electromotive force detection unit voltage change> threshold value SL1, the process proceeds to step S1107.

  On the other hand, if step S1105 becomes affirmative during the 300 ° C. holding time T1A, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process immediately proceeds to step S1111.

  In step S1107, a timer for measuring 100 ° C. holding time T2 (second period) is initialized, and 100 ° C. holding time T2 is set.

  In step S1108, the heater energization control unit 403 sets the heater target temperature to a value obtained by subtracting a predetermined value (eg, 10 ° C.) from the current heater target temperature, and is set to a temperature higher than 100 ° C. A second warm-up energization (second heater energization) corresponding to the target temperature is performed to heat the sensor element 32S. Thereby, the heater target temperature does not change rapidly, and the heating temperature of the sensor element 32S gradually decreases toward 100 ° C.

  Next, in step S1109, determination is made that electromotive force detection unit voltage change amount> threshold value SL1. If affirmative, the process proceeds to step S1111. If negative, the process proceeds to step S1110.

  In step S1110, the second heater energization in step S1108 and the determination in step S1109 are repeated until the 100 ° C. holding time T2 elapses.

  If step S1109 is affirmative within the 100 ° C. holding time T2, or if step S1109 is negative even after the 100 ° C. holding time T2 has elapsed, the process proceeds to step S1111.

  In step S1111, the heater energization control unit 403 sets the heater target temperature to a temperature obtained by adding a predetermined value (for example, 10 ° C.) to the current heater target temperature and does not exceed 600 ° C. Then, heater energization (activation energization) according to the heater target temperature is performed to heat the sensor element 32S. Accordingly, the first or second warm-up energization ends without the heater target temperature changing rapidly, and the heating temperature of the sensor element 32S gradually increases toward 600 ° C.

  In steps S1104, S1108, and S1111 described above, the heater target temperature is changed by a predetermined value, but the value for gradually changing the heater target temperature may be variably set according to a fixed value, a predetermined ratio, or an operating state. Good.

  FIG. 12 is a timing chart showing the fourth embodiment of the present invention.

The fourth embodiment is the second embodiment described with reference to FIGS. 8 and 9, and even if all the condensed water on the surface of the sensor element 32S evaporates before the 100 ° C. holding time T2 elapses, the temperature of the exhaust gas remains. In a low situation, for example, in a situation where the internal combustion engine 10 is left in an idle state, the temperature of the sensor element 32S does not rise, so that the electromotive force detection unit voltage change amount> the threshold value SL1, and the 100 ° C. holding time T2 has elapsed. It has been improved that it cannot be switched to activation energization until.
It pays attention to the point.

  That is, in the fourth embodiment, the 300 ° C. holding time T1B (first period) for performing the first heater energization (heater target temperature 300 ° C.) is provided a plurality of times after the heater energization is started. In this case, a relatively short 300 ° C. holding time T1B (first period) in which the first heater energization is performed and a relatively short 100 ° C. holding time T2B (second period) in which the second heater energization is performed alternately a plurality of times. Since it repeats, even after all the water on the surface of the sensor element 32S evaporates, the first heater is energized, and even when the temperature of the exhaust gas is low, the temperature of the sensor element 32S rises due to heat received from the heater 32H, and the electromotive force detection unit Voltage change amount> threshold value SL1, and switching to activation energization can be performed.

  FIG. 13 is a flowchart of the heater control apparatus for the exhaust gas sensor, and the operation of the fourth embodiment will be described using the flowchart.

  First, in step S1301, it is determined from the number of revolutions of the internal combustion engine 10 whether or not it is in a complete explosion state. If it is in a complete explosion state, the process proceeds to step S1303, and if step S1301 is negative, the heater 32H is turned off in step S1302. And exit.

  In step S1303, a timer for measuring the 300 ° C. holding time T1B (first period) is initialized, and the 300 ° C. holding time T1B is set.

  In step S1304, the heater energization control unit 403 sets the heater target temperature to the first warm-up energization (first heater energization) corresponding to 300 ° C., the first heater energization is performed on the heater 32H, and the sensor element 32S is heated. To do.

  Next, in step S1305, the determination unit 404 determines the amount of change of the voltage of the electromotive force detection unit 402 obtained by measuring the electromotive force Vs of the Vs cell unit 32S-Vs of the linear air-fuel ratio sensor 32 and the threshold SL1. Compare and judge by. The example of FIG. 12 also has a detection circuit configuration in which the voltage of the electromotive force detection unit 402 decreases when the electromotive force Vs occurs.

  If step S1305 is negative, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process proceeds to step S1306 and the first heater energization in step S1304 is performed until the 300 ° C. holding time T1B elapses. The determination in step S1305 is repeatedly performed.

  If step S1305 is negative even when the 300 ° C. holding time T1B has elapsed, that is, if the electromotive force detection unit voltage change> threshold SL1, the process proceeds to step S1307.

  On the other hand, if step S1305 becomes affirmative during the 300 ° C. holding time T1B, that is, if the electromotive force detection unit voltage change amount> threshold value SL1, the process immediately proceeds to step S1312.

  In step S1307, a timer for measuring 100 ° C. holding time T2B (second period) is initialized, and 100 ° C. holding time T2B is set.

  Next, in step S1308, the heater energization control unit 403 sets the heater target temperature to a second warm-up energization equivalent to 100 ° C. (hereinafter referred to as the second heater energization), and the heater 32H is energized with the second heater. The sensor element 32S is heated.

  Next, in step S1309, a determination is made that electromotive force detection unit voltage variation> threshold value SL1, and if affirmative, the process proceeds to step S1312, and if negative, the process proceeds to step S1310.

  In step S1310, the second heater energization in step S1308 and the determination in step S1309 are repeatedly performed until the 100 ° C. holding time T2B elapses.

  Even if the 100 ° C. holding time T2B has elapsed, if step S1309 is negative, the process proceeds to step S1311.

   In step 1311, if the number of times that steps S1303 to S1310 have been performed is less than KN times, the process returns to step S1303, and steps S1303 to S1310 are repeated. On the other hand, if the number of repetitions is KN, the process proceeds to step S1312.

  In step S1312, heater energization (activation energization) corresponding to a heater target temperature of 600 ° C. is performed, and the first or second warm-up energization is terminated.

  Here, the heater target temperature set in step S1304 may be fixed at 300 ° C. or changed according to the number of repetitions. For example, as shown in FIG. 12, the heater target temperature is set to 300 ° C. for the first time after the heater energization is started, and is set to a temperature lower than 300 ° C. (for example, 250 ° C.) after the second time. This is because the temperature of the sensor element 32S is raised from the cold state for the first time, but the temperature of the sensor element is raised from the state corresponding to 100 ° C. for the second and subsequent times, so the heating value of the heater is set smaller than the first time. An example is shown.

  Hereinafter, another embodiment of the heater control apparatus for the exhaust gas sensor according to the present invention will be described.

(1) The 300 ° C. holding times T1 and T1A for conducting the first heater energization (heater target temperature 300 ° C.) need to set the worst case maximum period in consideration of sensor production variations and variations due to deterioration over time. .

  However, when water has adhered to the sensor element 32S, the period during which the first heater energization (heater target temperature of 300 ° C.) is performed in a state where water has adhered to the sensor element 32S becomes longer, as shown in FIG. Since thermal stress is generated inside the described sensor element 32S, it is desirable to set an appropriate period according to each sensor element.

  Therefore, a time from when the first heater energization is started until the electromotive force detection unit voltage change amount> threshold value SL1 (for example, elapsed time T1BCT) is a non-volatile memory (for example, battery backed up RAM 44). = The storage means 405), and at the next heater energization start, the 300 ° C. holding times T1 and T1A may be set from the elapsed time T1BCT stored in the storage means 405.

  In addition, since the actually measured value is stored in the storage unit 405, the voltage of the electromotive force detection unit is erroneously detected when the storage unit 405 fails or when electrical noise is mixed in the signal line connecting the electromotive force detection unit 402 and the sensor element 32S. Since an affirmative determination may be made that the amount of change> the threshold value SL1, if the elapsed time T1BCT stored in the storage unit 405 is outside the upper and lower limits stored in the ROM 43 in advance (eg, T1BCTMN to T1BCTMX), A predetermined value (for example, T1BCTMX) may be set to the 300 ° C. holding times T1 and T1A.

(2) A parameter for determining that the first period or the second period has elapsed, that is, the period in which the first heater energization or the second heater energization is performed, in addition to the elapsed time from the start of each heater energization, A period from when the internal combustion engine 10 is started until the integrated value of the intake air amount reaches a predetermined value may be used. Since the intake air amount corresponds to the amount of heat generated by the internal combustion engine 10, by setting the period during which the heater 32H is energized using the integrated value of the intake air amount, the sensor element 32S and the exhaust pipe are received by the heat received from the exhaust gas. You can set the period that is in the temperature rise situation. Note that the amount of heat generated by the heater 32H can be obtained by detecting the battery voltage as the power source and the current flowing through the heater, so that the period of time during which the temperature of the sensor element has been raised can be set.

(3) The threshold value for determining that the period (time) for conducting the first heater energization or the second heater energization has elapsed may be obtained from the operating state of the internal combustion engine 10. For example, when the outside air temperature is low, the amount of condensed water generated in the exhaust pipe increases, so the period until all the water attached to the surface of the sensor element evaporates becomes longer. Can be set longer.

(4) As a means for controlling energization of the heater 32H, a duty signal may be used, and the heater target temperature set by the first heater energization, the second heater energization, and the activation energization may be set by a duty value. . That is, heater energization may be controlled by duty ratio control. Since the duty signal can be generated using the clock generator 42 in the control unit 40, the heater energization control unit 403 provided in the control unit 40 can be simplified.

(5) The amount of change in the voltage of the electromotive force detection unit 402 that measures the electromotive force of the Vs cell portion (theoretical air / fuel ratio detection unit) 32S-Vs of the linear air-fuel ratio sensor 32 is compared with the threshold value SL1. When switching to activation energization according to the determination result, a predetermined delay time (for example, 2 seconds) is provided between when the determination result becomes affirmative and switching to activation energization, or when the determination result is affirmative It is good also as a structure switched to activation energization when it continues for predetermined time (for example, 2 second).

  As described with reference to FIG. 4, when all the condensed water on the surface of the sensor element 32S is evaporated, if there is a temperature difference between the heater surface and the condensed water adhering surface, the temperature increase rate becomes high (FIG. 4B). ) And (c)), for example, it is possible to avoid a malfunction in which noise is mixed in the signal line connected to the electromotive force detection unit 402 of the control unit 40 and the determination result is falsely determined.

  The embodiment described above is not limited to the linear air-fuel ratio sensor 32 having the structure described in FIG. 2, but can also be applied to the linear air-fuel ratio sensor 320 having the structure shown in FIG. 14, parts corresponding to those in FIG. 2 are denoted by the same reference numerals as those in FIG. 2, and description thereof is omitted.

  The linear air-fuel ratio sensor 320 has a structure sharing a signal line for detecting the air-fuel ratio measurement current Ip and a signal line for detecting the electromotive force Vs. In the state where the air-fuel ratio measurement current Ip is stopped, only the electromotive force Vs corresponding to the oxygen concentration difference between the atmosphere chamber 32B and the sensor element surface side in contact with the exhaust gas appears on the signal line, so the electromotive force detection unit 402 of the ECU 40 The electromotive force Vs can be detected.

  The heater control described in the above embodiment is a heater control in a state where the sensor is not activated from the start of the engine until the sensor reaches the activation temperature, and the air-fuel ratio measurement current is in a stopped state. Therefore, the present invention can also be applied to the linear air-fuel ratio sensor 320 having the structure shown in FIG.

  As can be understood from the above description, the exhaust gas heater control device according to the present invention can prevent the condensed water from evaporating so that the thermal stress generated in the sensor element does not become excessive when the condensed water adheres to the sensor element. The period during which warm-up energization is performed to prevent damage to the sensor element by setting the heater or sensor element temperature lower than the temperature at which the sensor is activated and energizing the heater. It is possible to accurately determine that condensed water on the surface of the sensor element has evaporated, and switch from warm-up energization to activation energization to raise the temperature to a temperature at which the exhaust gas sensor is activated.

  As a result, the exhaust gas sensor can be activated more reliably and earlier than in the prior art, so that the range in which the exhaust gas can be controlled to the target air-fuel ratio can be expanded. Therefore, it is possible to further reduce the exhaust level while preventing damage to the exhaust gas sensor due to warm-up energization.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various changes can be made in the design without departing from the spirit of the invention described in the claims. Is.

1 is an overall configuration diagram of an engine control system including a heater control device for an exhaust gas sensor according to the present invention. (A) is a block diagram showing one embodiment of a linear air-fuel ratio sensor to which the heater control device according to the present invention is applied, (b) is a graph showing the air-fuel ratio measurement current characteristics of the linear air-fuel ratio sensor, and (c) is a graph. The graph which shows the electromotive force characteristic of a linear air fuel ratio sensor. (A), (b) is explanatory drawing which shows the protector structure of the linear air fuel ratio sensor to which the heater control apparatus by this invention is applied. (A) is explanatory drawing which shows the dew condensation water adhesion of the linear air fuel ratio sensor to which the heater control apparatus by this invention is applied, (b), (c) is a graph which shows the temperature change of a sensor element, and a temperature rise rate. The control block diagram which shows one Embodiment of the heater control apparatus of the exhaust gas sensor by this invention. 1 is a timing chart showing Embodiment 1 of a heater control device for an exhaust gas sensor according to the present invention. The flowchart which shows Embodiment 1 of the heater control apparatus of the exhaust gas sensor by this invention. The timing chart which shows Embodiment 2 of the heater control apparatus of the exhaust gas sensor by this invention. 9 is a flowchart showing Embodiment 2 of the heater control apparatus for an exhaust gas sensor according to the present invention. 6 is a timing chart showing Embodiment 3 of the heater control apparatus for an exhaust gas sensor according to the present invention. 9 is a flowchart showing Embodiment 3 of the heater control apparatus for an exhaust gas sensor according to the present invention. 9 is a timing chart showing Embodiment 4 of the heater control apparatus for an exhaust gas sensor according to the present invention. 9 is a flowchart showing Embodiment 4 of the heater control apparatus for an exhaust gas sensor according to the present invention. The block diagram which shows other embodiment of the linear air fuel ratio sensor with which the heater control apparatus by this invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 11 Cylinder 12 Piston 13 Combustion chamber 14 Ignition coil power switch means 15 Spark plug 16 Intake port 17 Intake valve 18 Exhaust port 19 Exhaust valve 20 Intake pipe 21 Air cleaner 22 Injector 23 Air flow sensor 24 Throttle valve 25 Throttle opening sensor 26 Idle Speed Control Valve (ISC)
27 Cooling water temperature sensor 28 Crank angle sensor 29 Exhaust pipe 30 Catalytic converter 31 Muffler 32 Linear air-fuel ratio sensor 320 Linear air-fuel ratio sensor 32S Sensor element 32H Heater 32S-Ip Ip cell section 32S-Vs Vs cell section (theoretical air-fuel ratio detection section)
321 Inner protector tube 322 Outer protector tube 323, 324 Hole 33 Fuel tank 34 Fuel pump 35 Pressure regulator 36 Fuel tube 40 Control unit (ECU)
401 Sensor voltage control unit 402 Electromotive force detection unit 403 Heater energization control unit 404 Determination unit 405 Storage unit 406 Verification unit 42 Clock generator 43 ROM
44 RAM
45 Timer counter 46 I / O interface (I / O)
47 output circuit 48 digital input circuit 49 A / D (analog / digital) converter 50 analog input circuit

Claims (12)

A heater control device for an exhaust gas sensor having a sensor element including a theoretical air-fuel ratio detection unit and a heater for heating the sensor element,
Determining means for determining whether an electromotive force or an electromotive force change amount generated by the theoretical air-fuel ratio detection unit of the sensor element is equal to or greater than a predetermined value;
A first period in which a first warm-up energization is performed on the heater, which is heated at a temperature lower than the sensor activation temperature after the heater energization is started, and the heater is energized in the first warm-up energization in the first period. When the first period has elapsed or the determination means makes an affirmative determination in the first period, the energization of the heater is switched to activation energization that performs heating at a temperature higher than the heating temperature of the first warm-up energization. A heater control device for an exhaust gas sensor. A heater control device for an exhaust gas sensor having a sensor element including a theoretical air-fuel ratio detection unit and a heater for heating the sensor element,
Determining means for determining whether an electromotive force or an electromotive force change amount generated by the theoretical air-fuel ratio detection unit of the sensor element is equal to or greater than a predetermined value;
A first period in which the heater is energized at a temperature lower than the sensor activation temperature after the heater energization is started, and heating at a temperature lower than the first period after the first period has elapsed. A second period in which the second warm-up energization is performed on the heater is set. In the first period, the energization to the heater is the first warm-up energization, and in the first period, the energization to the heater is the second period. When the warm-up energization is performed and the second period has elapsed, or when the determination means makes an affirmative determination in the first period or the second period, the heater is energized at a temperature higher than the heating temperature of the first warm-up energization. A heater control device for an exhaust gas sensor, wherein switching to activation energization for heating is performed. A heater control device for an exhaust gas sensor having a sensor element including a theoretical air-fuel ratio detection unit and a heater for heating the sensor element,
Determining means for determining whether an electromotive force or an electromotive force change amount generated by the theoretical air-fuel ratio detection unit of the sensor element is equal to or greater than a predetermined value;
A first period in which a first warm-up energization is performed on the heater at a temperature lower than the sensor activation temperature, and a second warm-up energization in the heater is performed at a temperature lower than the first period. A second period is set for the heater, and after the heater energization starts, the first warm-up energization by the first period and the second warm-up energization by the second period are repeated, and the number of repetitions reaches a predetermined value, Alternatively, when the determination means makes an affirmative determination in the first period or the second period, the energization of the heater is switched to activation energization that performs heating higher than the heating temperature of the first warm-up energization. A heater control device for an exhaust gas sensor.   4. The first heater warm-up energization performed in the first period is a temperature at which the sensor element is heated in a range of 250 ° C. to 300 ° C. 4. Exhaust gas sensor heater control device.   5. The second heater warm-up energization performed in the second period is a temperature at which the sensor element is heated in a range of 50 ° C. to 100 ° C. 5. Exhaust gas sensor heater control device.   A storage unit that stores a period from the start of the first period until the determination unit makes an affirmative determination when the determination unit makes an affirmative determination during the first period, and the period stored in the storage unit The heater control device for an exhaust gas sensor according to any one of claims 1 to 5, wherein the first period is variably set based on information.   The heater control device for an exhaust gas sensor according to claim 6, wherein when the period information stored in the storage means is outside a predetermined range, the first period is set to a value within the predetermined range. .   The heater control apparatus for an exhaust gas sensor according to any one of claims 1 to 7, wherein the heater energization at the time of heater energization switching is gradually changed by a predetermined amount.   The heater control apparatus for an exhaust gas sensor according to any one of claims 1 to 8, wherein a parameter for determining that the first period or the second period has elapsed is an elapsed time.   9. The parameter according to claim 1, wherein the parameter for determining that the first period or the second period has elapsed is an integrated value of an intake air amount sucked into the internal combustion engine. Exhaust gas sensor heater control device.   The exhaust gas sensor according to any one of claims 1 to 10, wherein a threshold value for determining whether the first period or the second period has elapsed is set in accordance with an operating state of the internal combustion engine. Heater control device.   The heater control device for an exhaust gas sensor according to any one of claims 1 to 11, wherein the heater is driven by a duty signal, and heater energization is controlled by duty ratio control.

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