JPH09184443A - Heater control device for air-fuel ratio sensor in downstream of catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely prevent an element of an air-fuel ratio sensor provided in an exhaust passage downstream of catalyst and incorporating a heater, from cracking, by accumulating heat values given to the catalyst from the time of starting an engine, and by comparing thus accumulated heat value with a predetermined value so as to inhibit energization to the heater when the accumulated value is the predetermined value or below. SOLUTION: An upstream precatalyst 6 and a downstream main catalyst 7 for control exhaust gas are provided in an exhaust passage 5 of an internal combustion engine 1, and air fuel ration sensors 12, 13 are provided in the upstream of the precatalyst 6 and downstream of the main catalyst 7 in the exhaust passage 5. The air-fuel ratio sensors 12, 13 are incorporated therein with heaters 12a, 13a, respectively, in order to activate their sensor elements. In this case, the heater 13a of the downstream sensor 13a is energized when the engine speed and the engine load are low, and while the battery voltage VB is a predetermined value or below. Further, an accumulated heat value given to the catalyst 7 from the time of starting the engine is obtained, and when the accumulated heat value is below a predetermined value, the energization to the heater 13a is prohibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater control device for an air-fuel ratio sensor provided downstream of a catalyst in an exhaust passage of an internal combustion engine.

[0002]

2. Description of the Related Art When an air-fuel ratio sensor (generally an O ₂ sensor) is provided in an exhaust passage of an internal combustion engine to detect an exhaust air-fuel ratio (rich / lean), a heater is installed to activate the air-fuel ratio sensor. The heater is energized under predetermined operating conditions to heat the air-fuel ratio sensor (sensor element).

However, when an air-fuel ratio sensor is provided downstream of the catalyst in the exhaust passage of the internal combustion engine for diagnosing catalyst deterioration, etc., when the temperature is low immediately after the engine is started, the water content in the exhaust gas condenses when passing through the catalyst inside the container. If the condensed water or the steam resulting from the evaporation of the condensed water is applied to the air-fuel ratio sensor (sensor element) heated by the heater, element cracking may occur.

Therefore, for example, as disclosed in Japanese Patent Publication No. 6-90167, a temperature detecting means for detecting the temperature of the exhaust pipe wall near the air-fuel ratio sensor is provided, and the temperature near the air-fuel ratio sensor is the water in the exhaust pipe. When the value is less than or equal to a predetermined value that is set in consideration of the presence or absence of, the heating of the air-fuel ratio sensor by the heater may be prohibited.

[0005]

However, the temperature in the vicinity of the air-fuel ratio sensor is detected, and when the temperature is below a predetermined value, the heater is not energized. In the method of uniquely determining by the method, the heater energization start temperature must be set to a considerably high temperature in consideration of the margin, and the heating by the heater continues to be prohibited for a while even after the water content is exhausted. Therefore, there is a problem that the start of the catalyst deterioration diagnosis using the catalyst downstream side air-fuel ratio sensor is delayed.

In view of such conventional problems, the present invention further optimizes the energization prohibition control of the heater for heating the catalyst downstream side air-fuel ratio sensor to surely prevent cracking of the sensor element, and An object of the present invention is to provide a heater control device for an air-fuel ratio sensor on the downstream side of a catalyst, which makes it possible to advance the energization start time as early as possible.

[0007]

Therefore, in the invention according to claim 1, a heater for heating the air-fuel ratio sensor provided downstream of the catalyst in the exhaust passage of the internal combustion engine is provided, and the heater is energized under predetermined operating conditions. In the heater control device for the catalyst downstream side air-fuel ratio sensor configured to heat the air-fuel ratio sensor, as shown in FIG. 1, based on the operating state of the engine,
An applied heat amount calculation means for calculating the heat quantity given to the catalyst at every predetermined time, an accumulation means for accumulating the heat quantity given to the catalyst from the time of engine start, and a comparison for comparing the cumulative heat quantity given to the catalyst with a predetermined value. Means and heater energization prohibition means for prohibiting energization to the heater while the accumulated heat quantity is equal to or less than a predetermined value as a result of comparison.

That is, the accumulated heat quantity applied to the catalyst is calculated according to the operation history from the engine start time, and by comparing this with a predetermined value, the water content in the exhaust gas condensed in the catalyst container immediately after the engine start. It is accurately determined whether or not the evaporation is completed, and while the accumulated heat quantity is equal to or less than the predetermined value, it is determined that the evaporation of the water is not completed, and the energization to the heater is prohibited. Claim 2
In the invention according to claim 1, the predetermined value for comparison in the comparison means is a heat quantity necessary for vaporizing the water in the exhaust gas condensed in the catalyst container immediately after the engine is started, and is variable depending on the cooling water temperature at the time of starting the engine. It is characterized by

By setting the required amount of heat of vaporization according to the temperature of the cooling water when the engine is started, it is possible to easily and accurately determine the completion of evaporation of water. In the invention according to claims 3 to 6, it is assumed that the catalyst includes an upstream side pre-catalyst and a downstream side main catalyst. And
In the invention according to claim 3, as shown in FIG. 2, the applied heat amount calculation means, based on the operating state of the engine, a pre-applied heat amount calculation means for calculating the amount of heat given to the pre-catalyst at predetermined time intervals, Pre-accumulation means for accumulating the amount of heat given to the pre-catalyst, pre-comparison means for comparing the cumulative amount of heat given to the pre-catalyst with a predetermined value from the time of engine start, It is configured to include a heat transfer amount calculation means for calculating the amount of heat transferred after the catalyst, based on the amount of heat transferred after the pre-catalyst, to calculate the amount of heat given to the main catalyst To do.

When the pre-catalyst and the main catalyst are provided, the moisture in the exhaust gas is condensed also in the pre-catalyst and the evaporation of the condensed water in the pre-catalyst is completed, and then the heat transfer to the pre-catalyst and thereafter is started. To be done. Therefore, it is determined whether or not the evaporation of the condensed water on the pre-catalyst is completed by calculating the cumulative amount of heat given to the pre-catalyst according to the operation history from the start of the engine and comparing this with a predetermined value. Then, the amount of heat transferred to the pre-catalyst and thereafter is calculated according to this determination result, and the amount of heat given to the main catalyst is calculated based on this amount of heat transfer.

In the invention according to claim 4, the predetermined value for comparison in the pre-comparison means is the amount of heat necessary for vaporizing the moisture in the exhaust gas condensed in the pre-catalyst container immediately after the engine is started, The feature is that it is variable according to the cooling water temperature at the time of engine start. By setting the required amount of heat of vaporization in the pre-catalyst according to the cooling water temperature at the engine start, it is possible to easily and accurately determine the completion of evaporation of water in the pre-catalyst.

In the invention according to claim 5, the applied heat quantity calculating means has a reaction heat quantity calculating means for calculating the reaction heat quantity generated in the precatalyst, and at least with respect to the heat quantity transferred after the precatalyst, The heat quantity applied to the main catalyst is calculated by adding the reaction heat quantity (see FIG. 2). The amount of heat given to the main catalyst can be more accurately determined by considering the amount of heat of reaction generated by the pre-catalyst.

In the invention according to claim 6, the applied heat amount calculation means has a heat radiation amount calculation means for calculating a heat radiation amount in the exhaust passage from the precatalyst to the main catalyst, and the heat is transferred to the precatalyst and thereafter. At least the amount of heat radiation is subtracted from the amount of heat to calculate the amount of heat given to the main catalyst (see FIG. 2). By considering the amount of heat radiation in the exhaust passage from the pre-catalyst to the main catalyst, the amount of heat given to the main catalyst can be obtained more accurately.

[0014]

According to the first aspect of the present invention, the cumulative heat quantity given to the catalyst is obtained from the operation history from the engine start time, and the accumulated heat quantity is compared with a predetermined value, so that the catalyst immediately after the engine start can be obtained. By accurately determining whether or not the evaporation of the condensed water of is completed and prohibiting the energization to the heater before the completion of the evaporation, it is possible to reliably prevent the element breakage of the air-fuel ratio sensor and to set the energization start timing. The effect is that it can be made as soon as possible.

According to the second aspect of the present invention, the required amount of heat of vaporization is set according to the temperature of the cooling water at the time of starting the engine, so that it is possible to easily and accurately determine the completion of evaporation of water. According to the invention of claim 3, when the pre-catalyst and the main catalyst are provided, it is considered that the heat transfer to the pre-catalyst and thereafter is started after the evaporation of the condensed water in the pre-catalyst is completed. By calculating the amount of heat transferred to the pre-catalyst and thereafter, and calculating the amount of heat given to the main catalyst based on this amount of heat transfer, it is possible to improve the estimation accuracy.

According to the fourth aspect of the present invention, the required amount of heat of vaporization in the pre-catalyst is set by the cooling water temperature at the time of starting the engine, so that the completion of the evaporation of water in the pre-catalyst can be determined easily and accurately. The effect is obtained. Claim 5
According to the invention of claim 1, the amount of heat given to the main catalyst can be more accurately obtained by considering the amount of heat of reaction generated in the precatalyst.

According to the invention of claim 6, the amount of heat given to the main catalyst can be obtained more accurately by considering the amount of heat radiation in the exhaust passage from the pre-catalyst to the main catalyst. To be

[0018]

Embodiments of the present invention will be described below. FIG. 3 is a system diagram showing an embodiment of the present invention. A throttle valve 3 is provided in an intake passage 2 of an internal combustion engine 1, and a fuel injection valve 4 for injecting fuel toward an intake port is provided downstream of the throttle valve 3 for each cylinder.
The exhaust passage 5 is provided with an upstream side pre-catalyst (manifold catalyst) 6 and a downstream side main catalyst (underfloor catalyst) 7 as exhaust gas purification catalysts.

The fuel injection valve 4 is an electromagnetic fuel injection valve that is energized by a drive pulse signal from the control unit 8 to open the valve, and is deenergized to close the valve. Injection quantity is controlled,
The air-fuel ratio is controlled by controlling the fuel injection amount. To control the fuel injection amount, signals are input to the control unit 8 from various sensors.

As the various sensors, the intake air flow rate (mass flow rate) GA is provided upstream of the throttle valve 3 in the intake passage 2.
For example, a hot-wire type air flow meter 9 for detecting is provided. Further, a crank angle sensor 10 that outputs a reference crank angle signal and a unit crank angle signal is provided, and the engine speed NE can be calculated from the cycle of the reference crank angle signal.

A water temperature sensor 11 for detecting the cooling water temperature TW of the engine 1 is also provided. Further, an upstream air-fuel ratio sensor 12 is provided upstream of the pre-catalyst 6 in the exhaust passage 5, and a downstream air-fuel ratio sensor 13 is provided downstream of the main catalyst 7. These air-fuel ratio sensors 12, 13 are specifically O ₂ sensors, which generate an electromotive force according to the residual oxygen concentration in the exhaust gas, and especially when the electromotive force suddenly changes at the theoretical air-fuel ratio, It becomes a high level (about 1 V) on the rich side and a low level (about 100 mV) on the lean side of the theoretical air-fuel ratio.
Therefore, rich lean can be detected.

Further, these air-fuel ratio sensors 12, 13 have heaters 12a, 13a built therein for activating the sensor elements, respectively, and these heaters 12a, 13a are energized by signals from the control unit 8, respectively. To be controlled. Besides, a throttle sensor, a vehicle speed sensor, an outside air temperature sensor and the like are provided, but they are not shown.

Here, the control unit 8
The built-in microcomputer controls the fuel injection amount by the fuel injection valve 4 based on the signals from the various sensors to control the air-fuel ratio. That is, the intake air flow rate GA detected based on the signal from the air flow meter 9 and the engine speed NE calculated based on the signal from the crank angle sensor 10 correspond to the amount of air taken into the engine. Basic fuel injection amount TP = K × equivalent to stoichiometric air-fuel ratio
GA / NE (K is a constant) is calculated. Then, the air-fuel ratio feedback correction coefficient α is calculated based on the output signal of the upstream side air-fuel ratio sensor 12, the air-fuel ratio feedback correction is added to the basic fuel injection amount TP, and the final fuel injection amount TI = TP × α × COEF (COEF is various correction coefficients) is calculated. The air-fuel ratio feedback correction coefficient α
In the calculation of, the correction may be performed based on the output signal of the downstream side air-fuel ratio sensor 13.

When the fuel injection amount TI is calculated, a drive pulse signal having a pulse width of this TI is output to the fuel injection valve 4 at a predetermined timing synchronized with the engine rotation, and fuel injection is performed. Further, the control unit 8 performs deterioration diagnosis of the catalyst (pre-catalyst 6 and main catalyst 7) based on the signals from the upstream side air-fuel ratio sensor 12 and the downstream side air-fuel ratio sensor 13, and when it is diagnosed that the catalyst has deteriorated. Turns on the warning light 14.

That is, while measuring the rich / lean inversion period T1 of the output signal of the upstream side air-fuel ratio sensor 12,
The rich / lean inversion period T2 of the output signal of the downstream side air-fuel ratio sensor 13 is measured. If the catalysts 6, 7 are normal, the reversal cycle T2 of the downstream side air-fuel ratio sensor 13 is sufficiently longer than the reversal cycle T1 of the upstream side air-fuel ratio sensor 12, but the catalysts 6, 7
Is deteriorated, the reversal period T2 of the downstream side air-fuel ratio sensor 13 is gradually shortened. Therefore, the inversion cycle T2 of the downstream side air-fuel ratio sensor 13 with respect to the inversion cycle T1 of the upstream side air-fuel ratio sensor 12.
The ratio (T2 / T1) is monitored, and when it falls below a predetermined value (around 1), it is diagnosed that the catalyst is deteriorated and the warning lamp 14 is turned on.

The control unit 8 also controls the heaters of the upstream side air-fuel ratio sensor 12 and the downstream side air-fuel ratio sensor 13, and in particular, the heater control of the downstream side air-fuel ratio sensor 13 will be described in detail below. Downstream air-fuel ratio sensor 13
The heater control is performed according to the heater control routine of FIG. 4, the startup routine of FIG. 5, and the moisture evaporation determination routine of FIG.

First, the heater control routine of FIG. 4 will be described. In step 1 (denoted as S1 in the figure; the same applies hereinafter), it is determined whether the prohibition flag F according to the present invention is set (F = 1). If F = 1, step 6 Proceed to and turn off the heater 13a. If F = 0, go to step 2. The prohibition flag F will be described later with reference to FIGS. 5 and 6.

In step 2, it is determined whether the engine is rotating or not. If the engine is not rotating, the process proceeds to step 6 to turn off the heater 13a. If the engine is rotating, proceed to step 3. In step 3, it is determined whether the engine speed NE is equal to or less than a predetermined value. If the engine speed NE is greater than a predetermined value (at high speed), the process proceeds to step 6 to turn off the heater 13a. When the engine speed NE is equal to or less than the predetermined value (at low speed), the process proceeds to step 4.

In step 4, it is determined whether the engine load (basic fuel injection amount) TP ≦ predetermined value. If the engine load TP> predetermined value (high load), the process proceeds to step 6 and the heater 13
Turn off a. Engine load TP ≤ predetermined value (at low load)
If, then go to step 5. In step 5, it is determined whether or not the battery voltage VB ≦ a predetermined value (for example, 16V). If the battery voltage VB> the predetermined value, the process proceeds to step 6 to turn off the heater 13a. If the battery voltage VB ≦ predetermined value (abnormal high voltage), the process proceeds to step 7 and the heater 13
Turn on a.

That is, on the premise that the prohibition flag F is released (F = 0), the engine speed NE is below a predetermined value (low speed) and the engine load TP is below a predetermined value (low) during engine rotation. When the battery voltage VB is equal to or lower than a predetermined value (for example, 16 V), the heater 13a is energized. It should be noted that the heater at high rotation or high load
The reason why energization to 13a is prohibited is that the exhaust gas temperature is high, so that an excessive temperature rise of the air-fuel ratio sensor 13 may cause burnout, and when the battery voltage VB exceeds 16V, for example. It is because the heater 13a is overheated by an abnormally high voltage that the energization of the heater 13a is prohibited.
This is because burning may occur.

Next, the starting routine of FIG. 5 will be described. In step 11, it is determined whether or not the engine is starting (when the key is ON). Only when starting, proceed to step 12, set the prohibition flag F (F = 1), and step 13
Then, the water temperature TW is detected based on the signal from the water temperature sensor 11, and this is stored and held as the starting water temperature TWst = TW.

Next, the moisture evaporation determination routine of FIG. 6 will be described. Note that this routine takes a predetermined time (for example, 100ms
Every). In step 21, the heat quantity Q0 given to the pre-catalyst 6 by the exhaust of the engine 1 is calculated by the following equation. This portion corresponds to the pre-applied heat amount calculating means. Q0 = GE × Cpg × (T0-343) GE is the exhaust gas mass, the theoretical air-fuel ratio (A / F = 14.6)
Assuming that the intake air flow rate GA, GE = GA ×
It can be calculated by (1 + 1 / 14.6). Cpg is the specific heat of exhaust gas, and from the mass ratio of N ₂ , CO ₂ and H ₂ O,
It is determined in advance (for example, Cpg = 0.274). T0 is the pre-catalyst inlet temperature (° K), the engine speed NE and the load T
It is obtained by referring to the engine total performance map from P. However,
The standard was 343 ° K = 70 ° C.

In step 22, the calorific value Q0 given to the pre-catalyst 6 is accumulated from the engine start-up by the following equation to calculate the pre-cumulative calorific value ΣQ0. This part corresponds to the pre-accumulation means. ΣQ0 = ΣQ0 + Q0 In step 23, refer to the table of FIG. 7 in which the amount of heat Cp required to vaporize the water in the exhaust gas condensed in the container of the pre-catalyst 6 immediately after the engine is started is assigned according to the starting water temperature TWst. Then, the pre-required heat quantity of vaporization Cp is retrieved from the actual starting water temperature TWst.

In step 24, the pre-cumulative heat quantity ΣQ0 is compared with the pre-required vaporization heat quantity Cp. This part corresponds to the pre-comparison means. As a result of the comparison, when ΣQ0 <Cp,
Go to step 25. That is, it is considered that the heat transfer to the pre-catalyst 6 and thereafter is started after the evaporation of the condensed water in the pre-catalyst is completed, and the heat quantity Q1 transferred to the pre-catalyst 6 and thereafter is set to 0 during the vaporization ( Q1 = 0).

On the other hand, when ΣQ0 ≧ Cp, step 26
Proceed to. That is, since the evaporation of the condensed water in the pre-catalyst 6 is completed, the amount of heat Q1 transferred to the pre-catalyst 6 and thereafter is set to Q0 (Q1 = Q0). It is even better considering heat transfer delay. Here, the steps 25 and 26 correspond to the heat transfer amount calculating means. In step 27, the reaction heat quantity QP generated in the pre-catalyst 6 is calculated by the following equation. Here, it is assumed that the temperature difference causes heat generation corresponding to a temperature rise of 50 ° K. This part corresponds to the reaction heat quantity calculating means.

ΔQP = GE × Cpg × 50 (however, when T0 <673 ° K, ΔQP = 0) In step 28, the reaction heat quantity ΔQP is converted into the heat quantity Q1 transferred to the pre-catalyst 6 and thereafter as shown in the following equation. The pre-catalyst outlet side heat quantity Q2 is calculated by adding. Q2 = Q1 + ΔQP In step 29, the heat radiation amount ΔQF in the exhaust passage (front tube) from the precatalyst 6 to the main catalyst 7 is calculated by the following equation. This portion corresponds to the heat radiation amount calculation means.

ΔQF = GE × Kft × Aft × ΔT Kft is the conductivity of the front tube, Aft is the surface area of the front tube, and ΔT is the temperature difference between the precatalyst outlet side temperature and the outside air temperature. In step 30, as shown in the following equation, the heat quantity Q2 from the precatalyst outlet side to the heat radiation quantity ΔQF from the front tube is calculated.
Is subtracted to calculate the heat quantity Q3 applied to the main catalyst 7.

Q3 = Q2-ΔQF In step 31, the heat quantity Q3 given to the main catalyst 7 is accumulated from the engine start-up by the following equation to calculate the main cumulative heat quantity ΣQ3. This part corresponds to the accumulating means. ΣQ3 = ΣQ3 + Q3 In step 32, refer to the table of FIG. 7 in which the amount of heat Cm required to vaporize the water in the exhaust gas condensed in the container of the main catalyst 7 immediately after the engine is started is assigned according to the starting water temperature TWst. Then, the main required vaporization heat quantity Cm is searched from the actual starting water temperature TWst.

At step 33, the main cumulative heat quantity ΣQ3 is compared with the main required heat quantity of vaporization Cm. This part corresponds to the comparison means. As a result of the comparison, when ΣQ3 <Cm,
This routine is terminated as it is (while maintaining the prohibition flag F = 1). That is, assuming that the evaporation of the condensed water in the main catalyst 7 is not completed, the prohibition flag F = 1 is maintained, and the energization to the heater 13a is continuously prohibited. Therefore, this portion corresponds to the heater energization prohibition means.

On the other hand, when ΣQ3 ≧ Cm, the routine proceeds to step 34. That is, it is considered that the evaporation of the condensed water in the main catalyst 7 is completed, and the prohibition flag F is cleared (F
= 0). As a result, as shown in FIG. 4, the heater 13
It is possible to energize a. As described above, by comparing the cumulative amount of heat given to the catalyst with the predetermined value and determining the presence or absence of evaporation of the condensed water, as shown in FIG. 8, the evaporation is completed more accurately than in the case of detecting the temperature. The timing can be detected, and the heater control can be started early.

[Brief description of the drawings]

FIG. 1 is a functional block diagram (1) showing the configuration of the present invention.

FIG. 2 is a functional block diagram (2) showing the configuration of the present invention.

FIG. 3 is a system diagram showing an embodiment of the present invention.

FIG. 4 is a flowchart of a heater control routine.

FIG. 5 is a flowchart of a startup routine.

FIG. 6 is a flowchart of a moisture evaporation determination routine.

FIG. 7 is a diagram showing a required vaporization heat quantity table.

FIG. 8 is a diagram showing characteristics after starting.

[Explanation of symbols]

 1 engine 5 exhaust passage 6 pre-catalyst 7 main catalyst 8 control unit 9 air flow meter 10 crank angle sensor 11 water temperature sensor 12 upstream air-fuel ratio sensor 12a heater 13 downstream air-fuel ratio sensor 13a heater

Claims (6)

[Claims] 1. A catalyst downstream side air comprising a heater for heating an air-fuel ratio sensor provided downstream of the catalyst in an exhaust passage of an internal combustion engine and heating the air-fuel ratio sensor by energizing the heater under predetermined operating conditions. In the heater control device for the fuel ratio sensor, the applied heat amount calculation means for calculating the amount of heat given to the catalyst at predetermined time intervals based on the operating state of the engine, and the accumulating means for accumulating the amount of heat given to the catalyst from the time when the engine is started. A comparison means for comparing the cumulative heat quantity applied to the catalyst with a predetermined value, and a heater energization prohibition means for prohibiting energization of the heater while the cumulative heat quantity is below a predetermined value as a result of the comparison. A heater control device for a catalyst downstream side air-fuel ratio sensor. 2. The predetermined value for comparison in the comparison means is
2. The catalyst downstream side air according to claim 1, wherein the amount of heat required to vaporize the water in the exhaust gas condensed in the catalyst container immediately after the engine is started is variable depending on the cooling water temperature at the time of engine start. Heater control device for fuel ratio sensor. 3. An upstream side pre-catalyst and a downstream side main catalyst are provided as the catalyst, and the applied heat amount calculation means determines the amount of heat given to the pre-catalyst at predetermined time intervals based on the operating state of the engine. Pre-applied heat amount calculation means for calculating, pre-accumulation means for accumulating heat quantity given to the pre-catalyst from engine start, pre-comparison means for comparing the cumulative heat quantity given to the pre-catalyst with a predetermined value, comparison result According to, the heat transfer amount calculation means for calculating the amount of heat transferred to the pre-catalyst after every predetermined time, and based on the amount of heat transferred to the pre-catalyst, the amount of heat given to the main catalyst The heater control device for the catalyst downstream side air-fuel ratio sensor according to claim 1 or 2, which is calculated. 4. The predetermined value for comparison in the pre-comparing means is the amount of heat necessary to vaporize the water in the exhaust gas that condenses in the pre-catalyst container immediately after the engine is started, and is the cooling water temperature at the time of engine starting. The heater control device for the catalyst downstream side air-fuel ratio sensor according to claim 3, wherein the heater control device is variable. 5. The applied heat quantity calculating means has a reaction heat quantity calculating means for calculating the reaction heat quantity generated in the pre-catalyst, and adds at least the reaction heat quantity to the heat quantity transferred after the pre-catalyst. 5. The heater control device for the catalyst downstream side air-fuel ratio sensor according to claim 3 or 4, wherein the amount of heat given to the main catalyst is calculated. 6. The applied heat amount calculation means has a heat release amount calculation means for calculating a heat release amount in an exhaust passage extending from a pre-catalyst to a main catalyst, and at least with respect to a heat amount transferred after the pre-catalyst, The heater of the catalyst downstream side air-fuel ratio sensor according to any one of claims 3 to 5, wherein the heat amount given to the main catalyst is calculated by subtracting the heat radiation amount. Control device.