JP2006118976A - Temperature control system of gas sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature control system of a gas sensor capable of suppressing the rich shift of output. <P>SOLUTION: The temperature control system of the gas sensor is arranged to an exhaust system of an internal combustion engine and constituted so as to control the temperature of the gas sensor for measuring the concentration of the specific gas in a gas to be measured. The gas sensor is internally provided with a gas sensor element 1 which has an oxygen ion conductive solid electrolyte 2, the electrode 31 or the side of the gas to be measured and the electrode 32 on the side of a reference gas both of which are respectively provided to one side and other side of the solid electrolyte 2 and the porous diffusion resistant layer 4 covering the electrode 31 on the side of the gas to be measured to transmit the gas to be measured. Even if the internal combustion engine is stopped, the gas sensor element 1 is heated to 430°C or above. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a gas sensor temperature control system that controls the temperature of a gas sensor that can be used for combustion control of an internal combustion engine such as a vehicle engine.

  A gas sensor such as an A / F sensor is provided in the exhaust system of a vehicle engine, and the air-fuel ratio is detected from the oxygen concentration in the exhaust gas, and the combustion control of the engine may be performed using this (exhaust gas control). Feedback system). In particular, in order to efficiently purify exhaust gas using a three-way catalyst, it is important to control the air-fuel ratio to a specific value in the combustion chamber of the vehicle engine.

The gas sensor incorporates a gas sensor element that detects the oxygen concentration in the exhaust gas. The gas sensor element includes, for example, an oxygen ion conductive solid electrolyte body, a gas side electrode to be measured and a reference gas side electrode provided on one surface and the other surface of the solid electrolyte body, respectively. It has a chamber space facing the measured gas side electrode. The chamber space is covered with a porous diffusion resistance layer and a dense shielding layer. And it is comprised so that to-be-measured gas may be introduce | transduced into chamber space via this porous diffusion resistance layer (refer patent document 1).
In addition to the A / F sensor, the gas sensor used in the exhaust gas feedback system or the like directly detects the oxygen concentration in the exhaust gas or the concentration of NOx that is an air pollutant in the exhaust gas. A NOx sensor to be detected is known.

  The gas sensor used in the exhaust gas feedback system requires performance such as early activation and high detection accuracy. Particularly in early activation, activation and control start early after engine startup can be effective in reducing unburned gas components such as hydrocarbon (HC) discharged in large quantities during engine cold startup.

  By the way, the inventors have found a phenomenon that an A / F sensor element with a built-in gas sensor left in the exhaust pipe of a vehicle causes a rich shift in output within about 10 seconds after the start of the internal combustion engine. . The rich shift is a phenomenon in which the air-fuel ratio in the internal combustion engine obtained based on the detection value of the gas sensor element is richer than the actual air-fuel ratio.

This phenomenon does not always occur. For example, this phenomenon does not occur when the vehicle internal combustion engine is restarted while the engine is stopped for a very short time. Although the shift amount increases depending on the standing time, it is almost saturated when left for about 1-2 days.
This rich shift makes the combustion of the vehicle internal combustion engine extremely unstable.
That is, although the system that has received the rich signal works in the direction of controlling the air-fuel ratio of the vehicle internal combustion engine to the lean side, the actual exhaust gas state is leaner than the indicated value of the air-fuel ratio sensor, so in the worst case, There is also a risk of misfire (engine stop). In addition, since the control point is greatly deviated, the concentration of atmospheric pollutant gas such as NOx may be increased in the exhaust gas.

A detailed investigation of this rich shift phenomenon revealed that the substance that adheres to the gas sensor element and causes the rich shift phenomenon is H ₂ O, that is, water vapor (water), and the adhering moisture is mostly porous diffused. It was found that it adhered to the resistance layer. Of course, the reproduction of the rich shift phenomenon has also been confirmed in the gas sensor element left in a high humidity atmosphere (see Experimental Example 3).

The rich shift is considered to occur to disappear by the following process.
That is, the rich shift occurs after the gas sensor is left in a high-humidity atmosphere such as an exhaust pipe of a vehicle internal combustion engine. Enters and moisture is adsorbed mainly on the porous diffusion resistance layer of the gas sensor element.

This moisture is desorbed and vaporized from the porous diffusion resistance layer by heating the gas sensor element.
Vaporized moisture, that is, water vapor, tends to be expelled to the outside through the porous diffusion resistance layer while expanding in volume, but since the porous diffusion resistance layer has a diffusion resistance that is greater or lesser, the water vapor passes through the porous diffusion resistance layer. It takes some time to pass.

Therefore, the water vapor pressure increases inside the gas sensor element (particularly in the vicinity of the measured gas side electrode), and the oxygen partial pressure relatively decreases. As a result, a rich shift occurs in the output of the gas sensor.
Water vapor gradually escapes to the outside through the porous diffusion resistance layer, and at the same time, exhaust gas around the element starts to be taken into the A / F sensor element. As a result, the rich shift is reduced with the passage of time, and a normal output is obtained.

As described above, it is considered that the rapid volume expansion of water vapor due to the desorption and vaporization of water causes a large rich shift of air-fuel ratio error (ΔA / F) = 1 to 2.
Of course, this problem does not occur if the atmosphere to be left is dry, but the exhaust pipe of the parked vehicle has a high humidity atmosphere due to moisture contained in the exhaust gas as a combustion product, and a rich shift occurs. It is considered an easy environment.

  The rich shift due to the above mechanism occurs in an element using a limiting current type oxygen sensor element such as an A / F sensor element, but also in an element using an oxygen concentration electromotive force type oxygen sensor element. A rich shift phenomenon due to a similar mechanism has been confirmed. Even in the oxygen concentration electromotive force type oxygen sensor element, the gas side electrode to be measured is often covered with a porous body, and the porous body has a diffusion resistance even if the pores are rough. This is because a certain amount of time is required for water vapor to escape from the water.

  In order to suppress the above-described rich shift phenomenon, it is effective to prevent water vapor from adhering to the gas sensor element when the engine is stopped. In particular, in the control system, the temperature of the gas sensor element when the engine is stopped is maintained under moisture adhesion suppression conditions. The method is considered.

JP 2000-65782 A

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a gas sensor temperature control system capable of suppressing a rich shift in output.

The present invention is a gas sensor temperature control system that controls the temperature of a gas sensor that is disposed in an exhaust system of an internal combustion engine and measures a specific gas concentration in a gas to be measured.
The gas sensor includes an oxygen ion conductive solid electrolyte body, a measurement gas side electrode and a reference gas side electrode provided on one surface and the other surface of the solid electrolyte body, and the measurement gas side electrode. A gas sensor element having a porous diffusion resistance layer that covers and allows the gas to be measured to pass therethrough is built-in,
In the gas sensor temperature control system, the gas sensor element is heated at a temperature of 430 ° C. or higher when the internal combustion engine is stopped.

Next, the effects of the present invention will be described.
As described above, it is considered that the main cause of the rich shift of the gas sensor output is the moisture adhering to the gas sensor element, particularly the porous diffusion resistance layer when the internal combustion engine is stopped.
In the gas sensor temperature control system, the gas sensor element is heated at a temperature of 430 ° C. or higher when the internal combustion engine is stopped.

Therefore, when the internal combustion engine is stopped, it is possible to suppress the adhesion of moisture to the gas sensor element.
In addition, moisture adhering to the gas sensor element can be sufficiently removed. That is, as will be described later, the moisture adhering to the gas sensor element includes physically adhering moisture and moisture adhering in a shape changed by a chemical change. This physically attached moisture can be desorbed if heated to about 100 ° C., but chemically attached moisture cannot be desorbed unless heated to about 400 ° C. or higher. Therefore, by chemically heating the gas sensor element at a temperature of 430 ° C. or higher as in the present invention, chemically attached moisture can be desorbed.

As described later, the rich shift amount can be drastically reduced by setting the temperature of the gas sensor element to 430 ° C. or higher.
Therefore, by causing the gas sensor element to be heated at a temperature of 430 ° C. or higher when the internal combustion engine is stopped, the occurrence of a rich shift when starting the internal combustion engine can be suppressed.

  As described above, according to the present invention, it is possible to provide a gas sensor temperature control system capable of suppressing an output rich shift.

In the present invention (Claim 1), as the gas sensor, for example, an air-fuel ratio sensor (A / F sensor) installed in an exhaust pipe of an internal combustion engine for various vehicles such as an automobile engine and used for an exhaust gas feedback system, There are oxygen sensors that measure the oxygen concentration in exhaust gas, and NOx sensors that measure the concentration of air pollutants such as NOx that are used for detecting deterioration of a three-way catalyst installed in an exhaust pipe.
Examples of the gas sensor element include a cup-type gas sensor element in which the solid electrolyte body is formed into a bottomed cylindrical cup-type, and a laminated gas sensor element using a flat-plate-shaped solid electrolyte body.

Moreover, it is preferable to heat the said gas sensor element at the temperature of 500 degrees C or less (Claim 2).
In this case, power consumption required for heating can be reduced.
When the heating temperature exceeds 500 ° C., even if the heating temperature is increased, the effect of suppressing the rich shift is not particularly improved, and power consumption may be wasted.

The gas sensor element is preferably heated intermittently (Claim 3).
Also in this case, power consumption required for heating can be suppressed. That is, since moisture adheres to the gas sensor element after a relatively long time, adsorption of moisture can be sufficiently prevented by heating the element intermittently.

The gas sensor element is preferably heated when the temperature of the gas sensor element is lower than 430 ° C. for a predetermined time.
In this case, it is possible to efficiently prevent moisture from adhering to the gas sensor element and efficiently suppress rich shift.
That is, when the temperature of the gas sensor element is lower than 430 ° C. for a long time, there is a risk of moisture adhesion. Therefore, by controlling the gas sensor element temperature to be less than 430 ° C. within a range in which this moisture adhesion can be sufficiently prevented, the moisture adhesion is suppressed while suppressing power consumption for heating. Can be prevented. As a result, the rich shift can be efficiently suppressed.

The gas sensor element is heated intermittently at a predetermined time interval, and the time interval is preferably determined based on the temperature and humidity of the gas atmosphere to be measured.
Also in this case, the rich shift can be efficiently suppressed.
That is, the moisture adhesion amount per unit time to the gas sensor element can be predicted in detail based on the temperature and humidity of the measured gas atmosphere. For example, based on the temperature and humidity, the number of water molecules (H ₂ O) that collide with the gas sensor element per unit time is derived, and the water per unit time when the adhesion probability at the time of collision is considered to be constant. The amount of molecular adhesion can be predicted.
Therefore, by measuring the temperature and humidity of the gas atmosphere to be measured, the amount of moisture adhesion is estimated, and element heating is performed when the amount of adhesion reaches a predetermined value, thereby enabling finer control. As a result, it is possible to suppress a rich shift while further reducing power consumption.

Preferably, the gas sensor element is integrally provided with a ceramic heater for heating the gas sensor element.
In this case, an accurate sensor output can be obtained earlier from the start of the internal combustion engine.
That is, by integrating the ceramic heater with the gas sensor element, it is possible to activate the gas sensor element at an early stage and to further suppress a rich shift. Since the gas sensor element integrated with the ceramic heater has a high heating effect, it quickly reaches the activation temperature. If the moisture is not sufficiently desorbed when the activation temperature is reached, an accurate sensor output cannot be obtained after all. On the other hand, in the present invention, since the adhesion of moisture is suppressed in advance before the internal combustion engine is started, the high heating effect of the gas sensor can be fully exhibited.

Example 1
The gas sensor temperature control system of the present invention will be described with reference to FIGS.
The gas sensor temperature control system of this example is a system that is disposed in an exhaust system of an internal combustion engine and controls the temperature of a gas sensor that measures a specific gas concentration in a gas to be measured.
As shown in FIGS. 1 and 2, the gas sensor includes an oxygen ion conductive solid electrolyte body 2, a measured gas side electrode 31 provided on one surface and the other surface of the solid electrolyte body 2, and a reference. The gas sensor element 1 which has the gas side electrode 32 and the porous diffusion resistance layer 4 which covers the said to-be-measured gas side electrode and permeate | transmits the to-be-measured gas is incorporated.

  The gas sensor temperature control system intermittently heats the gas sensor element 1 at a temperature of 430 ° C. to 500 ° C. when the internal combustion engine is stopped. For example, heating is performed every 90 minutes for about 1 to 2 minutes, and the temperature of the gas sensor element 1 is set to 430 to 500 ° C. During this intermittent heating, that is, while heating is not being performed, the temperature of the gas sensor element 1 may be less than 430 ° C.

  As shown in FIGS. 1 and 2, the gas sensor element 1 is integrally formed with a ceramic heater 5 for heating the gas sensor element 1. That is, the ceramic heater 5 is laminated on the surface of the solid electrolyte body 2 on which the reference gas side electrode 32 is disposed. The ceramic heater 5 includes a heater substrate 51 and a heating element 52 formed inside the heater substrate 51. The heater substrate 51 includes an inner heater substrate 512 formed with a recess and disposed on the solid electrolyte body 2 side, and a flat outer heater substrate 511. A reference gas chamber 162 for introducing a reference gas is formed between the concave portion of the heater substrate 51 and the solid electrolyte body 2. A reference gas side electrode 32 is formed in the reference gas chamber 162.

A spacer 11 having an opening, a porous diffusion resistance layer 4, and a shielding layer 12 are sequentially laminated on the surface of the solid electrolyte body 2 where the measured gas side electrode 31 is disposed. .
The spacer 11 forms a measured gas chamber 161 for introducing a measured gas between the solid electrolyte body 2 and the porous diffusion resistance layer 4. A measured gas side electrode 31 is disposed in the measured gas chamber 161.

The porous diffusion resistance layer 4 can be introduced into the measured gas chamber 161 by allowing the measured gas entering from the end face 41 to pass therethrough. At this time, the gas to be measured permeates while receiving a predetermined diffusion resistance.
Further, the shielding layer 12 and the spacer 11 are densely formed so as not to transmit the measurement gas.
The spacer 11, the porous diffusion resistance layer 4, the shielding layer 12, and the heater substrate 51 are each formed of alumina ceramic.

  The temperature of the gas sensor element when the internal combustion engine is stopped is controlled by the ceramic heater 5. That is, ON / OFF control of the ceramic heater 5 is performed by a control signal from an ECU (Engine Control Unit) connected to the gas sensor. During operation of the internal combustion engine, the temperature control of the gas sensor element 1 is performed as in the prior art.

Next, the function and effect of this example will be described.
As described above, it is considered that the main cause of the rich shift of the gas sensor output is the moisture adhering to the gas sensor element 1, particularly the porous diffusion resistance layer 4 when the internal combustion engine is stopped.
In the gas sensor temperature control system, the gas sensor element 1 is heated at a temperature of 430 ° C. or higher when the internal combustion engine is stopped.

Therefore, it is possible to suppress the adhesion of moisture to the gas sensor element 1 when the internal combustion engine is stopped.
Moreover, the water | moisture content adhering to the gas sensor element 1 can fully be removed. That is, the moisture adhering to the gas sensor element 1 includes moisture adhering by changing its shape due to a chemical change, in addition to moisture adhering due to physical aggregation. That is, when water vapor in the exhaust pipe penetrates into the porous diffusion resistance layer 4 containing alumina as a main component, alumina (Al ₂ O ₃ ) and water (H ₂ O) undergo hydroxylation through the following chemical reaction. It becomes aluminum (Al (OH) ₃ ) and adheres chemically.
2Al ₂ O ₃ + 3H ₂ O → 2Al (OH) ₃

The physically attached moisture can be desorbed if heated to about 100 ° C., but chemically attached moisture cannot be desorbed unless heated to about 400 ° C. or higher.
Therefore, by chemically heating the gas sensor element 1 at a temperature of 430 ° C. or higher as in the present invention, chemically attached moisture can be desorbed.

As shown in Experimental Example 2, the rich shift amount can be drastically reduced by setting the temperature of the gas sensor element 1 to 430 ° C. or higher.
Therefore, when the internal combustion engine is stopped, the gas sensor element 1 is heated at a temperature of 430 ° C. or higher, so that the occurrence of a rich shift at the start of the internal combustion engine can be suppressed.

Moreover, since the said gas sensor element 1 is heated at the temperature of 500 degrees C or less, the power consumption required for a heating can be reduced. That is, as shown in Experimental Example 2 (FIG. 5) to be described later, even if the heating temperature is increased above 500 ° C., the effect of suppressing the rich shift is not particularly improved.
Moreover, since the gas sensor element 1 is heated intermittently, power consumption required for heating can be suppressed. That is, since moisture adheres to the gas sensor element 1 after a relatively long time, moisture adsorption can be sufficiently prevented by heating the element intermittently. This is considered that when the engine is restarted after stopping the engine for a very short time (for example, less than 90 minutes), a rich shift does not occur, so that it takes a relatively long time for the moisture to adhere. Because.

  As described above, according to this example, it is possible to provide a gas sensor temperature control system that can suppress a rich shift in output.

(Experimental example 1)
In this example, as shown in FIG. 4, the desorption temperature of water adhering to the gas sensor element 1 was examined.
First, moisture was adsorbed to the gas sensor element 1. This moisture adsorption was performed by leaving the gas sensor element 1 in a high humidity atmosphere of 95% for 15 hours.

Next, the gas sensor element 1 was gradually heated in a helium (He) atmosphere to gradually increase the temperature.
Then, in each temperature range, the amount of moisture released from the gas sensor element 1 was detected using a mass analyzer.
The result is shown in FIG.

As shown in the figure, it was confirmed that moisture was desorbed in two temperature regions near 100 ° C. and 400 ° C.
Moisture desorbed in the vicinity of 100 ° C. is considered to be the above-mentioned physically attached moisture, and moisture desorbed in the vicinity of 400 ° C. is considered to be the above-mentioned chemically attached moisture.

(Experimental example 2)
This example is an example in which the relationship between the heating temperature of the gas sensor element 1 and the rich shift amount is investigated as shown in FIG.
The gas sensor element 1, which was once left in a high humidity atmosphere (humidity 95%) for 15 hours to adhere moisture, was left to stand in various constant temperature atmospheres ranging from room temperature to 600 ° C. for about 5 minutes and heated. Then, after cooling at room temperature, the amount of rich shift was measured.
The measurement results are shown in FIG.

As shown in the figure, a temperature region was found in which the rich shift amount suddenly decreased with the heating temperature in the vicinity of 400 to 430 ° C as a boundary.
Therefore, as shown in Example 1, it is understood that the rich shift can be significantly suppressed by heating the gas sensor element 1 at a temperature of 430 ° C. or higher when the internal combustion engine is stopped.

(Experimental example 3)
In this example, as shown in FIG. 6, the time for leaving the gas sensor element 1 in a high humidity atmosphere and the amount of rich shift are investigated.
The high humidity atmosphere is an atmosphere having a humidity of 95%.
As shown in S0 of the figure, it can be seen that the rich shift occurs greatly as the leaving time becomes longer. Further, it was confirmed that the rich shift started to occur after approximately 90 to 120 minutes.

From this result, it is understood that the rich shift can be sufficiently suppressed by heating the gas sensor element 1 at a temperature of 430 ° C. every 90 minutes.
If heating is performed every 3 hours, a slight rich shift may occur as shown by the curve S1 in FIG. 6, but it is significantly higher than when temperature control is not performed (S0). Rich shift can be suppressed.

(Example 2)
In this example, as shown in FIG. 7, the gas sensor element 1 is heated intermittently at a time interval determined based on the temperature and humidity of the measured gas atmosphere when the internal combustion engine is stopped. It is an example.
That is, the moisture adhesion amount per unit time to the gas sensor element 1 can be predicted in detail based on the temperature and humidity of the gas atmosphere to be measured. For example, based on the temperature and humidity, the number of water molecules (H ₂ O) that collide with the gas sensor element per unit time is derived, and the water per unit time when the adhesion probability at the time of collision is considered to be constant. The amount of molecular adhesion can be predicted.
Therefore, the amount of moisture adhesion is estimated by measuring the temperature and humidity of the gas atmosphere to be measured, and element heating is performed when the amount of adhesion reaches a predetermined value.

A specific method for estimating the amount of water adhesion will be described below.
That is, the amount N of water adhering to the gas sensor element 1 is proportional to a value obtained by integrating the product of the water vapor density of the gas atmosphere to be measured and the motion speed of water molecules over time t [minutes]. The water vapor density is proportional to the product of the saturated water vapor pressure P [atm] and the humidity W [%], and the motion speed of water molecules is proportional to the 1/2 power of the absolute temperature T [K]. Therefore, for the moisture adhesion amount N, the following equation (1) is established using the proportionality constant k. In the equation (1), the temperature and humidity of the gas atmosphere to be measured are respectively functions of time t, and thus are represented as T (t) and W (t), respectively, and the saturated water vapor pressure is a function of temperature T, respectively. (T (t)).

Then, the moisture adhesion amount when the gas sensor element 1 is left for 90 minutes at a humidity of 100% and a temperature of 300 K in the measured gas atmosphere is set as the limit moisture adhesion amount (limit moisture adhesion amount) at which rich shift starts to occur. To do. This condition is a condition obtained by checking in advance.
This limit moisture adhesion amount is 6110k from the above equation (1).

  Then, the actual water adhesion amount N is calculated using the above formula (1), and when the calculated value N reaches the reference value 6000 k, the gas sensor element 1 is heated as shown by the curve S2 in FIG. Do. The reference value 6000k is a value set as a value slightly smaller than the limit moisture adhesion amount (6110k).

Note that it is sufficient that the measurement of the temperature (curve S3 in FIG. 7) and humidity (curve S4) of the gas atmosphere to be measured and the calculation process of the amount of adhering water are sequentially performed every few seconds to 1 minute, for example.
Others are the same as in the first embodiment.

Also in this case, the rich shift can be efficiently suppressed. That is, it is possible to suppress a rich shift while further reducing power consumption.
In addition, the same effects as those of the first embodiment are obtained.

(Example 3)
In this example, the gas sensor element 1 is heated when the temperature of the gas sensor element 1 is lower than 430 ° C. for a predetermined time.
That is, the temperature of the gas sensor element 1 is monitored when the internal combustion engine is stopped, and when, for example, 60 minutes have elapsed from the time when the temperature becomes less than 430 ° C., the ceramic heater 5 is energized and heating of the gas sensor element 1 is started. . Then, when the temperature of the gas sensor element 1 reaches, for example, 500 ° C., energization to the ceramic heater 5 is terminated. When 60 minutes have passed after the temperature of the gas sensor element 1 has dropped below 430 ° C., the same operation as described above is repeated.
This predetermined time (the time during which the state of less than 430 ° C. continues) is determined after an examination in advance as a time that does not cause a rich shift.
Others are the same as in the first embodiment.

In this case, it is possible to efficiently prevent moisture from adhering to the gas sensor element 1 and efficiently suppress rich shift.
That is, when the temperature of the gas sensor element 1 is lower than 430 ° C. for a long time, there is a risk of moisture adhesion. Therefore, by controlling the gas sensor element 1 so that the time during which the temperature of the gas sensor element 1 is less than 430 ° C. is shortened within a range in which the adhesion of moisture can be sufficiently prevented, Adhesion can be prevented. As a result, it is possible to efficiently suppress the rich shift.
In addition, the same effects as those of the first embodiment are obtained.

FIG. 3 is a cross-sectional view of a gas sensor element in Example 1. FIG. 3 is a developed perspective view of the gas sensor element in the first embodiment. The diagram which shows the intermittent heating of the gas sensor heating control system in Example 1. FIG. The diagram which shows the temperature dependence of the water | moisture-content desorption amount in Experimental example 1. FIG. The diagram which shows the relationship between the heating temperature of a gas sensor element, and the rich shift amount in Experimental example 2. FIG. The diagram which shows the relationship between the leaving time to the high humidity atmosphere of a gas sensor element, and the rich shift amount in Experimental example 3. FIG. The diagram which shows the intermittent heating performed based on the temperature measurement and humidity measurement which a gas sensor heating control system in Example 2 performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas sensor element 2 Solid electrolyte body 31 Gas side electrode to be measured 32 Reference gas side electrode 4 Porous diffusion resistance layer 5 Ceramic heater

Claims (6)

A gas sensor temperature control system that is disposed in an exhaust system of an internal combustion engine and controls the temperature of a gas sensor that measures a specific gas concentration in a gas to be measured,
The gas sensor includes an oxygen ion conductive solid electrolyte body, a measurement gas side electrode and a reference gas side electrode provided on one surface and the other surface of the solid electrolyte body, and the measurement gas side electrode. A gas sensor element having a porous diffusion resistance layer that covers and allows the gas to be measured to pass therethrough is built-in,
A gas sensor temperature control system, wherein the gas sensor element is heated at a temperature of 430 ° C. or higher when the internal combustion engine is stopped.   The gas sensor temperature control system according to claim 1, wherein the gas sensor element is heated at a temperature of 500 ° C. or less.   3. The gas sensor temperature control system according to claim 1, wherein the gas sensor element is heated intermittently.   4. The gas sensor temperature control system according to claim 3, wherein the gas sensor element is heated when the temperature of the gas sensor element is lower than 430 ° C. for a predetermined time.   4. The gas sensor temperature control according to claim 3, wherein the gas sensor element is heated intermittently at a predetermined time interval, and the time interval is determined based on the temperature and humidity of the gas atmosphere to be measured. system.   The gas sensor temperature control system according to claim 1, wherein the gas sensor element is integrally provided with a ceramic heater for heating the gas sensor element.

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