JPH0643986B2 - Activation detection device for air-fuel ratio sensor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an activation detection device for an air-fuel ratio sensor that detects an air-fuel ratio based on the oxygen concentration in the exhaust gas of various combustion equipment such as an internal combustion engine.

[Prior Art] As one of the air-fuel ratio sensors for detecting the air-fuel ratio of the air-fuel mixture supplied to various combustion equipment such as an internal combustion engine from the oxygen concentration in the exhaust gas, a porous oxygen ion conductive solid electrolyte on both sides of a plate is porous. Two detection elements equipped with electrodes are arranged such that one porous electrode of each detection element is in contact with the measurement gas chamber in which the diffusion of exhaust gas is restricted, and is in contact with the measurement gas chamber of one detection element. An air-fuel ratio sensor has been proposed in which the electrode on the non-contact side is arranged so as to come into contact with an internal reference oxygen source that is in communication with the outside through a leakage resistance portion (Japanese Patent Application No. 137586/60. -296262), Japanese Patent Application No. 60-2140.
04 (JP-A-62-148849).

In this type of air-fuel ratio sensor, the detection element on the side in contact with the internal reference oxygen source is used as the oxygen concentration battery element, and the other detection element is used as the oxygen pump element. Oxygen is generated in the air-fuel ratio, and by controlling the current flowing in the oxygen pump element bidirectionally so that the voltage generated at the electrodes at both ends of the oxygen concentration battery element becomes constant, the air-fuel ratio is continuously changed from the lean region to the rich region. A changing air-fuel ratio signal can be obtained. That is, oxygen in the measurement gas chamber is pumped into the internal reference oxygen source by passing a constant current through the oxygen concentration battery element, and in the oxygen concentration battery element, the oxygen partial pressure of the internal reference oxygen source and the oxygen partial pressure in the measurement gas chamber are Since a voltage is generated according to the ratio of the above, the current flowing through the oxygen pump element is bidirectionally controlled so that this voltage becomes constant, that is, the oxygen partial pressure in the measurement gas chamber becomes constant, and the current value is If detected, a detection signal corresponding to the air-fuel ratio will be obtained.

By the way, in this type of air-fuel ratio sensor, in order to detect the air-fuel ratio satisfactorily, it is necessary that each of the above-mentioned detection elements is above a predetermined temperature and activated. For this reason, conventionally, an air-fuel ratio sensor is provided with an activation detection device for detecting its activation, and thereby the air-fuel ratio is detected after confirming the activation of the sensor.

[Problems to be Solved by the Invention] However, in the conventional activation detection device, the air-fuel ratio sensor is checked by confirming the heat generation state of the heater provided in the air-fuel ratio sensor, the heater current, and the like. Since the activation is judged, there is a problem that the activation of the air-fuel ratio sensor cannot be directly detected and the air-fuel ratio cannot be detected even though the air-fuel ratio sensor is activated.

That is, for example, when the operation of the air-fuel ratio sensor is stopped and then restarted immediately, the air-fuel ratio sensor is naturally activated, but conventionally, the air-fuel ratio sensor is operated,
The activation of the air-fuel ratio sensor is confirmed after the heater has been energized for a predetermined period of time, so the air-fuel ratio cannot be detected until then even though the air-fuel ratio sensor has been activated. However, there is a problem that the air-fuel ratio control of the internal combustion engine or the like cannot be performed well.

Therefore, the present invention has been made for the purpose of providing an activation detection device for an air-fuel ratio sensor that can quickly detect activation of the air-fuel ratio sensor from the operating state of the air-fuel ratio sensor. It took such a structure.

[Means for Solving the Problems] That is, the constitution of the present invention as a means for solving the above-mentioned problems is a structure in which a pair of porous electrodes are provided on both surfaces of an oxygen ion conductive solid electrolyte. Detection element, a measurement gas chamber formed in contact with one porous electrode of each detection element and communicating with a measurement gas atmosphere through a gas diffusion limiting section, and the measurement gas chamber of one detection element Is an activation detection device for an air-fuel ratio sensor, which is formed by being in contact with a porous electrode on the opposite side and which is communicated with the outside through a leakage resistance part, Current supply means for supplying a predetermined current to the detection element formed in contact with the source to generate oxygen in the internal reference oxygen source, and the porous electrode of the detection element supplied with current by the current supply means. Voltage detection to detect the voltage generated between Means for determining whether or not the voltage detected by the voltage detecting means is less than or equal to a preset setting voltage, and detecting activation of the air-fuel ratio sensor when the voltage is less than or equal to the preset setting voltage. When the internal combustion engine is operated in an air-fuel ratio rich region, the air-fuel ratio sensor is activated in the exhaust gas when the air-fuel ratio sensor is actually activated. The activation detection device for an air-fuel ratio sensor is characterized in that the voltage generated between the porous electrodes of the detection element is measured and preset based on the measurement result.

As the oxygen ion conductive solid electrolyte used in the detection element here, a solid solution of zirconia and yttria, or a solid solution of zirconia and calcia is typical, and other cerium dioxide, thorium dioxide, and hafnium dioxide A solid solution, a perovskite type oxide solid solution, and a trivalent metal oxide solid solution can also be used. As the porous electrodes provided on both sides of the solid electrolyte, platinum or rhodium, which has a catalytic action for the oxidation reaction, may be used. A method of mixing powders of the same ceramic material into a paste, printing using thick film technology, and then sintering, or flame spraying, chemical plating,
Examples thereof include a method of forming using a thin film technique such as vapor deposition. In addition, it is preferable that the electrode directly in contact with the exhaust gas and the electrode on the measurement gas chamber side are formed by further forming a porous protective layer of alumina, spinel, zirconia, mullite or the like on the electrode layer by using a thick film technique.

Next, the measurement gas chamber is a chamber in which ambient exhaust gas is introduced in a diffusion-limited manner via a gas diffusion limiting section that limits diffusion of the measurement gas, that is, exhaust gas.
₂ O ₃ , spinel, forsterite, steatite,
It can be formed by sandwiching a hollow spacer made of zirconia or the like, and forming a hole as a gas diffusion limiting portion in a part of the spacer so as to communicate the surrounding measurement gas atmosphere with the measurement gas chamber. The gas diffusion limiting portion is for communicating the ambient exhaust gas atmosphere with the measurement gas chamber in a diffusion limiting manner and is not limited in shape. For example, a part or all of the spacer may be replaced with a porous body, or the spacer ( Holes (including thick film coating), or even on the terminal side of the two detector elements to form a gap between the detector elements, and this gap is integrated with the measurement gas chamber to limit gas diffusion. It can also be provided as a gap. Further, a porous material, which is preferably electrically insulative, may be arranged throughout the measurement gas chamber.

Further, the internal reference oxygen source is a portion that stores oxygen by moving it from the measurement gas chamber by a current flowing through the detection element in contact with the internal reference oxygen source, and corresponds to, for example, the electrode of the detection element on the side opposite to the measurement gas chamber. Al ₂ O ₃ with recesses,
It can be formed by stacking shields made of spinel, forsterite, steatite, zirconia, or the like. Further, this internal reference oxygen source is communicated with the measurement gas chamber via a leakage resistance part so that the internal oxygen can be leaked to the measurement gas chamber side. It can be formed by forming a through hole communicating with the chamber and providing a porous layer between the through hole and the internal reference oxygen source.

It should be noted that this leakage resistance part needs only to be able to gradually move the oxygen in the internal reference oxygen source to the measurement gas chamber or to the outside (for example, the external measurement gas). You may be made to communicate by.
Further, as the internal reference oxygen source, a shield having a recess as described above may be laminated on the detection element, and the recess may be used as the reference oxygen source, but the communication hole itself of the porous electrode itself may be used as the internal reference oxygen source. Alternatively, the flat shield may be directly laminated on the detection element.

In the air-fuel ratio sensor thus configured, the detection element on the side in contact with the internal reference oxygen source is usually used as the oxygen generation and oxygen concentration battery element, and the other detection element is used as the oxygen pump element. That is, in the detection element (oxygen concentration cell element) on the side in contact with the internal reference oxygen source, oxygen in the measurement gas chamber is pumped into the internal reference oxygen source by applying a voltage to the electrodes on both sides of this detection element and passing a constant current. At the same time, a voltage corresponding to the partial pressure of oxygen gas in the measurement gas chamber can be generated based on the partial pressure of oxygen gas in the internal reference oxygen source generated by the pumping, and the other detection element (oxygen pump element) can , By applying a predetermined voltage to the electrodes at both ends and flowing a current in both directions, oxygen in the measurement gas chamber is pumped into the surrounding exhaust gas, or oxygen in the exhaust gas is pumped into the measurement gas chamber, Since the generated voltage of the concentration cell element can be controlled, for example, a constant voltage is applied to the oxygen concentration cell element via a resistor, and the voltage generated across the resistance is constant. So as to control the current flowing through the oxygen pump element, 醸素 concentration in the exhaust by detecting the control current, that is, the air-fuel ratio is detected. The air-fuel ratio may also be detected by applying a constant current to the oxygen pump element to pump out or pump in a predetermined amount of oxygen in the measurement gas chamber and then detect the voltage generated in the oxygen concentration cell element at that time. In this case as well, a constant or almost constant current is passed through the oxygen concentration battery element to make the oxygen gas partial pressure in the internal reference oxygen source constant or substantially constant.

[Operation] The present invention detects activation of the air-fuel ratio sensor configured as described above, and a predetermined current is supplied to the detection element on the internal reference oxygen source side, that is, the oxygen concentration battery element, by the current supply means. Flow at that time, the voltage generated between the porous electrodes of this oxygen concentration battery element is detected by the voltage detection means,
If the detected voltage is equal to or lower than the preset set voltage, the activation determining means determines activation of the air-fuel ratio sensor.

In other words, this is because the internal resistance of the oxygen concentration battery element is large when the air-fuel ratio sensor is not sufficiently activated, and the voltage generated between the porous electrodes at both ends of the oxygen concentration battery element is much larger than usual when a current is applied to the oxygen concentration battery element. Therefore, the activation of the air-fuel ratio sensor itself is judged by detecting the activation of the oxygen concentration battery element using this.

Here, when the oxygen concentration battery element is activated, the voltage generated between the porous electrodes is different depending on the oxygen concentration of the measurement gas, that is, the air-fuel ratio.
It is desirable to set according to the air-fuel ratio until the air-fuel ratio sensor is activated.

On the other hand, in an internal combustion engine in which air-fuel ratio control is executed by using this type of air-fuel ratio sensor, at the time of starting the air-fuel engine in which the air-fuel ratio sensor is started, operation is performed in the air-fuel ratio rich region due to so-called fuel increase at startup. To be done.

Therefore, in the present invention, by operating the air-fuel ratio sensor in the exhaust gas when the internal combustion engine is operated in the air-fuel ratio rich region, the voltage generated between the porous electrodes of the detection element when the air-fuel ratio sensor is actually activated. Is measured, and based on the measurement result, by setting the set voltage used to detect the activation of the air-fuel ratio sensor in the activation determination means, the activation of the air-fuel ratio sensor Accurate detection is possible according to the measurement gas component.

That is, specifically, for example, in the case of an internal combustion engine which is operated in the rich region of the excess air ratio λ = 0.8 at the time of starting by the fuel increase correction, the detection result obtained by operating the air-fuel ratio sensor under this operating condition in advance Is timed to 90% of the activation time, the internal combustion engine is operated under the same operating conditions, and the voltage generated between the porous electrodes of the oxygen concentration battery element is measured at the corresponding time Tw. However, the measured voltage may be set as the set voltage.

Since the air-fuel ratio sensor is provided with a current supply circuit for supplying a current to the oxygen concentration cell element in the detection circuit as described above, the current supply means is conventionally provided in the detection circuit. The current supply circuit that is used may be used as it is.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

First, FIGS. 2 and 3 show the structure of an air-fuel ratio sensor provided with the activation detecting device of this embodiment. FIG. 2 is a partially cutaway perspective view thereof, and FIG. 3 is an exploded perspective view thereof.

As shown in the figure, the air-fuel ratio sensor of this embodiment has an oxygen pump element 4 formed by laminating porous electrodes 2 and 3 on both sides of a solid electrolyte plate 1, and a porous electrode 6 and a porous electrode 6 on both sides of a solid electrolyte plate 5. The oxygen concentration battery element 8 formed by stacking 7 and the detection elements 4 and 8 are stacked between the detection elements 4 and 8, and the hollow portions 9a are formed by the facing porous electrodes 3 and 6 of the detection elements 4 and 8. It is composed of a spacer 9 and a shield 10 laminated on the porous electrode 7 side of the oxygen concentration battery element 8.

First, the spacer 9 is composed of the porous electrode 3 and the porous electrode 6.
Is to form a measurement gas chamber in which the diffusion of the measurement gas is restricted, and the hollow portion 9a is used as the measurement gas chamber. Further, in the spacer 9, notches T as gas diffusion limiting portions are formed at three locations around the hollow portion 9a so that the measurement gas around the hollow portion 9a can be introduced.

Next, the shield 10 is for shielding the porous electrode 7 from the external measurement gas in order to use the porous electrode 7 of the oxygen concentration battery element 8 as an internal reference oxygen source. The porous electrode 7 covered with the shield 10 is made of, for example, alumina or the like so that oxygen generated inside the porous electrode 7 can be leaked into the measurement gas chamber, that is, the hollow portion 9a when used as an internal reference oxygen source. Is connected to the lead portion 6l of the porous electrode 6 via the porous insulator Z and the through hole H.
That is, the porous insulator Z, the through hole H, and the lead portion 6l of the porous electrode 6 are formed as the above-mentioned leakage resistance portion, and the oxygen generated in the porous electrode 7 is hollowed through the leakage resistance portion. It is designed to be able to leak into the portion 9a.

Further, the electrode terminals of the porous electrodes 2, 3, 6, 7 of the oxygen pump element 4 and the oxygen concentration cell element 8 are formed on the outer wall surface of the air-fuel ratio sensor. That is, the oxygen pump element 4
Since the porous electrode 2 of is formed to be exposed to the outside,
In the porous electrode 3 of the oxygen pump element 4 or the porous electrodes 6 and 7 of the oxygen concentration battery element 8 which are laminated inside, the lead portion 2l is directly used as an electrode terminal, and the lead portion 3l or 6l and 7l Formed by electrically connecting the solid electrolyte plate 1 or the electrode terminals 3t or 6t and 7t laminated on the outer wall surface of the shield 10 through through holes 3h or 6h and 7h, respectively. Is there.

The air-fuel ratio sensor of this embodiment configured as described above has the first
As shown in the figure, the fixing portion 1 that seals the porous electrode layer 7 so that oxygen does not leak to the outside and fixes the air-fuel ratio sensor S.
5 is attached to the exhaust pipe 17 of the internal combustion engine through the screw 16 and the activation is detected by the activation detection circuit 20, and then the air-fuel ratio detection circuit 30 operates. In the figure, the lead portion and electrode terminal of each porous electrode are omitted in order to facilitate understanding of the attachment state of the air-fuel ratio sensor 7.

The activation detection circuit 20 supplies a constant current (for example, 22 [μA]) to the oxygen concentration cell element 8 of the air-fuel ratio sensor S to generate oxygen in the porous electrode 7 serving as a reference oxygen source, and is an operational amplifier. Constant current circuit 2 configured using OP1
1 and the porous electrodes 6 at both ends of the oxygen concentration battery element 8 at this time
And a voltage detecting circuit 22 configured by using an operational amplifier OP2 for detecting the voltage generated in the voltage detecting element 7, and a voltage detected by the voltage detecting circuit 22 is a preset voltage E
When it becomes less than or equal to o, the activation determination circuit 23 configured by using the operational amplifier OP3 that detects the activation of the air-fuel ratio sensor S and outputs the activation detection signal, and the activation determination circuit 23 And the analog switches 24 and 25 which are switched by the activation detection signal output from the air-fuel ratio detection circuit 30 and connect the air-fuel ratio detection circuit 30 and the air-fuel ratio sensor S to detect the air-fuel ratio by the air-fuel ratio detection circuit 30. There is.

The constant current circuit 21, the voltage detection circuit 22, and the activation determination circuit 23 correspond to the above-mentioned current supply means, voltage detection means, and activation determination means, respectively. The set voltage Eo used in the activation detection circuit 23 will be described later in detail.

Next, the air-fuel ratio detection circuit 30 detects that the air-fuel ratio sensor S has been activated by the activation detection circuit 20, and the analog switches 24 and 25 are switched in the opposite direction to that shown in FIG. Connected. In the air-fuel ratio detection circuit 30, the partial pressure of oxygen gas generated in the porous electrode 7 of the oxygen concentration battery element 8 by the operation of the constant current circuit 21 and the oxygen gas in the hollow portion 9a serving as the measurement gas chamber. The voltage generated at the electrodes at both ends of the oxygen concentration battery element 8 becomes constant according to the ratio with the partial pressure, that is, the hollow portion 9a.
Oxygen pump element 4 so that the partial pressure of oxygen gas inside is constant
It is configured to bi-directionally control the current flowing through and output the current value as an air-fuel ratio signal.

That is, as shown in FIG. 4, the air-fuel ratio detection circuit 30 detects a voltage generated at the electrodes on both sides of the oxygen concentration battery element 8 and raised by the reference voltage Va (for example, 5 [V]).
Buffer circuit 31 composed of operational amplifier OP4
And a non-inverting amplifier circuit 32 configured by an operational amplifier OP5 for amplifying the detection voltage output from the buffer circuit 31, and the detection voltage amplified by the non-inverting amplifier circuit 32 is compared with a predetermined reference voltage Vc. Then, when the detected voltage is larger than the reference voltage Vc, it gradually decreases with a predetermined integration constant, and in the opposite case, it gradually increases with a predetermined integration constant and outputs a control voltage as shown in FIG. And a comparison / integration circuit 33 configured using the operational amplifier OP6,
The buffer circuit 34 configured by the operational amplifier OP7 that outputs the reference voltage Va and the reference voltage Va from the buffer circuit 34 are applied to the porous electrode 3 on the hollow portion 9a side of the oxygen pump element 4, and the electrode 3 And comparison / integration circuit 33
Current detection resistor Ri for detecting a current flowing between the other porous electrode 2 to which the control voltage from
And an output circuit 35 constituted by an operational amplifier OP8, which outputs the voltage generated in the resistor Ri as an air-fuel ratio signal Vλ. The air-fuel ratio signal obtained by the air-fuel ratio detection circuit 30 is, for example, the sixth
As shown in the figure, it continuously changes from the air-fuel ratio rich region to the lean region.

In the air-fuel ratio detection device configured as described above, activation of the air-fuel ratio sensor S is detected by the activation detection circuit 20, and the operation causes the air-fuel ratio detection circuit 30 to be connected to the air-fuel ratio sensor S. However, a method of setting the set voltage Eo used when the activation detection circuit 20 determines whether the air-fuel ratio sensor S is activated will be described below.

The set voltage Eo is set in the air-fuel ratio rich region when the internal combustion engine is started, because the internal combustion engine is operated in the air-fuel ratio rich region where the fuel is rich when the internal combustion engine is started when the air-fuel ratio sensor S starts operating. The air-fuel ratio detection circuit 30 is operated at that time.
It is set experimentally by measuring the air-fuel ratio signal obtained by

That is, FIG. 7 shows that the air-fuel ratio sensor S having the dimensions shown in the following table is mounted on the exhaust pipe of a 1.5 [] internal combustion engine for 4 cycles, and the internal combustion engine is rotated at a rotation speed of 1200 [rpm],
The air-fuel ratio sensor S is simultaneously operated by the air-fuel ratio detection circuit 30 when operated under the conditions of intake pipe negative pressure -500 [mmHg], exhaust temperature 170 [° C], and air-fuel ratio A / F: 12. The measured data represents the pump current Ip flowing through the oxygen pump element 4 at that time, the voltage Vp generated at both ends thereof, and the voltage Vs generated at both ends of the oxygen concentration cell element 8, respectively. From the measured data, the air-fuel ratio sensor S Takes 90% of time Tw (22 [sec] in this case)
The voltage generated across the oxygen concentration battery element 8 when the air-fuel ratio detection circuit 30 is open corresponding to the time Tw is experimentally obtained, and this value may be set as the set voltage Eo.

FIG. 8 shows the result of the experiment, and in the case of the air-fuel ratio sensor S having the above-mentioned configuration, the oxygen concentration battery corresponding to the time Tw (22 [sec]) of activation up to 90% obtained from the above measurement data. The voltage across the element is approximately 1100 [mV]
Therefore, the set voltage Eo may be set to 1100 [mV]. The current passed through the oxygen concentration battery element 8 by the constant current circuit 21 was 22 [μA], and the sensor was heated by a heater.

In the air-fuel ratio sensor activation detection device of the present embodiment configured as described above, the activation can be directly detected from the operating state of the air-fuel ratio sensor S before the air-fuel ratio detection circuit 30 detects the air-fuel ratio. After the air-fuel ratio sensor is activated, the air-fuel ratio detection circuit 30 can promptly detect the air-fuel ratio. Therefore, even though the air-fuel ratio sensor is activated as in the past, the air-fuel ratio cannot be detected and the air-fuel ratio control of the internal combustion engine or the like cannot be performed satisfactorily. Can be always executed well.

[Effects of the Invention] As described in detail above, in the activation detection device of the air-fuel ratio sensor of the present invention, activation of the air-fuel ratio sensor is performed by energizing the detection element on the internal reference oxygen source side used as the oxygen concentration battery element. It is possible to detect the activation of the air-fuel ratio sensor promptly without a response delay because it is directly detected from the inter-electrode voltage when the air-fuel ratio sensor is activated, and to promptly execute the air-fuel ratio control after the activation of the air-fuel ratio sensor. You can

Further, in the present invention, the air-fuel ratio sensor is operated in the exhaust gas in the air-fuel ratio rich region that is actually activated, and the voltage generated between the porous electrodes when the sensor is actually activated is measured, and the measurement is performed. Since the set voltage for activation determination is set based on the result, activation of the air-fuel ratio sensor can be determined extremely accurately.

Further, as the current supply means, the current supply circuit conventionally provided in the air-fuel ratio sensor can be used as it is, and it is not necessary to provide the current supply circuit for activation detection.

[Brief description of drawings]

1 to 8 show an embodiment of the present invention, FIG. 1 is a configuration diagram showing the overall configuration of an air-fuel ratio sensor and an activation detection circuit of this embodiment, and FIG. 2 is a portion of the air-fuel ratio sensor. Fig. 3 is a broken perspective view, Fig. 3 is an exploded perspective view thereof, Fig. 4 is an electric circuit diagram showing an air-fuel ratio detection circuit, and Fig. 5 is a diagram showing control signals of an oxygen pump element generated in the air-fuel ratio detection circuit. , Sixth
FIG. 7 is a diagram showing an air-fuel ratio signal obtained by the air-fuel ratio detection circuit, FIG. 7 is a diagram showing an activated state when the air-fuel ratio sensor is operated in the exhaust gas in the air-fuel ratio rich region, and FIG. It is a diagram showing the change of the voltage which occurs in the oxygen concentration battery element in the fuel ratio rich region. 1, 5 ... Solid electrolyte plate 2, 3, 6, 7 ... Porous electrode 4 ... Oxygen pump element 8 ... Oxygen concentration battery element 9 ... Spacer 9a ... Hollow part (measurement gas chamber) 20 ... Activation detection circuit 21 ... constant current circuit 22 ... voltage detection circuit 23 ... activation determination circuit 30 ... air-fuel ratio detection circuit

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-60-224051 (JP, A) JP-A-60-86457 (JP, A) JP-A-52-104991 (JP, A) JP-A-56- 22949 (JP, A)

Claims (1)

[Claims] 1. A gas diffusion device which is formed by contacting two detection elements each having a pair of porous electrodes disposed on both surfaces of an oxygen ion conductive solid electrolyte and one porous electrode of each of the detection elements. The measurement gas chamber is communicated with the measurement gas atmosphere through the restriction portion, and is formed in contact with the porous electrode on the opposite side of the one measurement element from the measurement gas chamber, and is communicated with the outside through the leakage resistance portion. An internal reference oxygen source, and an activation detection device for an air-fuel ratio sensor, which supplies a predetermined current to a detection element formed in contact with the internal reference oxygen source, A current supply means for generating oxygen, a voltage detection means for detecting a voltage generated between the porous electrodes of the detection element to which current is supplied by the current supply means, and a voltage detected by the voltage detection means are set in advance. Below the set voltage Activation determining means for determining whether the air-fuel ratio sensor is activated when the voltage is equal to or lower than a preset set voltage, and the set voltage is set in the air-fuel ratio rich region. By operating the air-fuel ratio sensor in the exhaust gas during operation, the voltage generated between the porous electrodes of the detection element when the air-fuel ratio sensor is actually activated is measured, and preset based on the measurement result. An activation detection device for an air-fuel ratio sensor, characterized in that