JP2020165761A - Gas sensor and control method thereof - Google Patents

Abstract

To provide a gas sensor and a control method of the gas sensor, which can suppress both decreases in oxygen concentration of a reference gas around a reference electrode due to a contaminate from the outside and in detection accuracy of gas concentration due to control of pumping in oxygen.SOLUTION: A gas sensor 10 includes a reference gas adjuster 190 for making a control current Ip flow between a reference electrode 102 and a measured gas-side electrode so as to pump oxygen into surroundings of the reference electrode 102. The reference gas adjuster 190 includes: a temperature measurement section 192 for measuring a temperature Ta of a measured gas; and a control current adjustment section 194 for adjusting a value of the control current Ip according to an elevation difference between the temperature Ta of the measured gas and a preset threshold temperature Tth.SELECTED DRAWING: Figure 3

Description

The present invention relates to a gas sensor and a method for controlling a gas sensor.

Usually, the gas sensor is provided with a reference gas adjusting means for applying a voltage between the reference electrode and the electrode to be measured to pass a control current and drawing oxygen around the reference electrode (for example, Patent Document). 1). By pumping oxygen around the reference electrode by this reference gas adjusting means, when the oxygen concentration of the reference gas around the reference electrode temporarily decreases, the decrease in oxygen concentration can be compensated for, and it can be specified. Suppresses the decrease in gas concentration detection accuracy.

JP-A-2015-200643

However, in the control of drawing oxygen into the reference electrode described in Patent Document 1, a voltage drop occurs due to the resistance value of the reference electrode and the flowing current. As a method of reducing the voltage drop due to this oxygen pumping control, there is a method of reducing the control current, but when a substance that reduces the oxygen concentration of the reference gas invades, the oxygen concentration around the reference electrode decreases. There was a risk that it would be easier.

The present invention has been made in view of the above-mentioned problems, and both the decrease in the oxygen concentration of the reference gas around the reference electrode due to an external pollutant and the decrease in the detection accuracy of the gas concentration due to the oxygen pumping control can be achieved. It is an object of the present invention to provide a gas sensor that can be suppressed and a method for controlling the gas sensor.

The gas sensor according to one aspect of the present invention is formed by stacking a plurality of oxygen ion conductive solid electrolyte layers, and detects a specific gas concentration in the measured gas and a measured gas flow section that introduces and distributes the measured gas. A reference gas introduction space for introducing the reference gas that serves as the reference for the above, a laminate provided inside, and
A reference electrode formed inside the laminate and into which the reference gas is introduced through the reference gas introduction space,
The measurement electrodes arranged on the inner peripheral surface of the gas flow section to be measured,
A sensor element having a gas-measured gas-side electrode disposed in a portion of the laminated body exposed to the gas to be measured.
A heater unit that heats and retains the sensor element and a heater unit that plays a role of temperature control.
A detection means for detecting a specific gas concentration in the gas to be measured based on an electromotive force generated between the reference electrode and the measurement electrode.
A reference gas adjusting means for drawing oxygen around the reference electrode by passing a control current between the reference electrode and the electrode to be measured.
With
The reference gas adjusting means is
A temperature measuring means for measuring the temperature of the gas to be measured and
It has a control current adjusting means for adjusting the value of the control current according to the height of the temperature of the gas to be measured and the preset threshold temperature.

The method for controlling the gas sensor according to another aspect of the present invention comprises stacking a plurality of oxygen ion conductive solid electrolyte layers to introduce and circulate the gas to be measured, and to specify the gas to be measured and the gas to be measured. A laminate with a reference gas introduction space for introducing a reference gas, which is a reference for detecting the gas concentration, and a laminate provided inside.
A reference electrode formed inside the laminate and into which the reference gas is introduced through the reference gas introduction space,
The measurement electrodes arranged on the inner peripheral surface of the gas flow section to be measured,
A sensor element having a gas-measured gas-side electrode disposed in a portion of the laminated body exposed to the gas to be measured.
A heater unit that heats and retains the sensor element and a heater unit that plays a role of temperature control.
In a method for controlling a gas sensor having a detection means for detecting a specific gas concentration in the gas to be measured based on an electromotive force generated between the reference electrode and the measurement electrode.
The step of measuring the temperature of the gas to be measured and
A step of passing a control current between the reference electrode and the electrode to be measured to draw oxygen around the reference electrode.
It has a control current adjusting step that adjusts the value of the control current according to the height of the temperature of the gas to be measured and the preset threshold temperature.

According to the present invention, it is possible to suppress both a decrease in the oxygen concentration of the reference gas around the reference electrode due to an external pollutant and a decrease in the detection accuracy of the gas concentration due to the oxygen pumping control.

It is sectional drawing which shows the gas sensor which concerns on this embodiment. It is sectional drawing which showed typically the example of the structure of the sensor element. It is a block diagram which shows the reference gas adjustment part provided in the gas sensor which concerns on this embodiment. It is a flowchart which shows the control method of the gas sensor which concerns on this embodiment. It is sectional drawing which showed typically the example of the structure of the sensor element which concerns on 1st modification. It is sectional drawing which showed typically the example of the structure of the sensor element which concerns on 2nd modification.

The gas sensor and the control method of the gas sensor according to the present invention will be described in detail below with reference to the accompanying drawings, citing suitable embodiments.

As shown in FIG. 1, the gas sensor 10 according to the present embodiment includes a sensor element 12. The sensor element 12 has a long rectangular body shape, the longitudinal direction of the sensor element 12 (horizontal direction in FIG. 2) is the front-rear direction, and the thickness direction of the sensor element 12 (vertical direction in FIG. 2) is the vertical direction. To do. Further, the width direction of the sensor element 12 (direction perpendicular to the front-rear direction and the up-down direction) is defined as the left-right direction.

As shown in FIG. 1, the gas sensor 10 includes a sensor element 12, a protective cover 14 that protects the front end side of the sensor element 12, and a sensor assembly 18 that includes a connector 16 that conducts with the sensor element 12. As shown in the figure, this gas sensor 10 is attached to a pipe 20 such as an exhaust gas pipe of a vehicle, and is used to measure the concentration of a specific gas such as NOx or O ₂ contained in the exhaust gas as a gas to be measured. Be done. The gas sensor 10 of the present embodiment measures the NOx concentration as a specific gas concentration.

The protective cover 14 includes a bottomed tubular inner protective cover 14a that covers the front end of the sensor element 12, and a bottomed tubular outer protective cover 14b that covers the inner protective cover 14a. The inner protective cover 14a and the outer protective cover 14b are formed with a plurality of holes for allowing the gas to be measured to flow into the protective cover 14. The sensor element chamber 22 is formed as a space surrounded by the inner protective cover 14a, and the front end of the sensor element 12 is arranged in the sensor element chamber 22.

The sensor assembly 18 includes an element sealing body 30 that seals and fixes the sensor element 12, a nut 32 attached to the element sealing body 30, an outer cylinder 34, and the surface (upper and lower surfaces) of the rear end of the sensor element 12. A connector 16 is provided which is in contact with and electrically connected to electrodes (not shown) formed in the above.

The element sealing body 30 is enclosed in a tubular main metal fitting 40, a tubular inner cylinder 42 that is welded and fixed coaxially with the main metal fitting 40, and a through hole inside the main metal fitting 40 and the inner cylinder 42. It includes ceramics supporters 44a to 44c, green compacts 46a and 46b, and a metal ring 48. The sensor element 12 is located on the central axis of the element encapsulant 30, and penetrates the element encapsulant 30 in the front-rear direction. The inner cylinder 42 has a reduced diameter portion 42a for pressing the green compact 46b in the central axis direction of the inner cylinder 42, and ceramic supporters 44a to 44c and the green compacts 46a and 46b forward via a metal ring 48. A reduced diameter portion 42b for pressing is formed. The green compacts 46a and 46b are compressed between the main metal fitting 40 and the inner cylinder 42 and the sensor element 12 by the pressing force from the reduced diameter portions 42a and 42b, so that the green compacts 46a and 46b are covered with the protective cover 14. The sensor element chamber 22 inside and the space 50 inside the outer cylinder 34 are sealed, and the sensor element 12 is fixed.

The nut 32 is fixed coaxially with the main metal fitting 40, and a male screw portion is formed on the outer peripheral surface. The male threaded portion of the nut 32 is inserted into the fixing member 52 welded to the pipe 20 and provided with a female threaded portion on the inner peripheral surface. As a result, the gas sensor 10 is fixed to the pipe 20 with the front end of the sensor element 12 and the portion of the protective cover 14 of the gas sensor 10 protruding into the pipe 20.

The outer cylinder 34 covers the periphery of the inner cylinder 42, the sensor element 12, and the connector 16, and a plurality of lead wires 54 connected to the connector 16 are pulled out from the rear end. The lead wire 54 is electrically connected to each electrode (described later) of the sensor element 12 via the connector 16. The gap between the outer cylinder 34 and the lead wire 54 is sealed by a rubber stopper 56. The space 50 in the outer cylinder 34 is filled with a reference gas (atmosphere in this embodiment). The rear end of the sensor element 12 is arranged in this space 50.

As shown in FIG. 2, the sensor element 12 includes a first substrate layer 60, a second substrate layer 62, and a third substrate layer 64, each of which is composed of an oxygen ion conductive solid electrolyte layer such as zirconia (ZrO ₂ ). , The first solid electrolyte layer 66, the spacer layer 68, and the second solid electrolyte layer 70 are six layers, which are laminated in this order from the bottom in the drawing. Further, the solid electrolyte forming these six layers is a dense and airtight one. The sensor element 12 is manufactured, for example, by performing predetermined processing, printing of a circuit pattern, or the like on a ceramic green sheet corresponding to each layer, laminating them, and further firing and integrating them.

A gas inlet 80 and a first diffusion-controlled unit 82 are located between one end of the sensor element 12 (left side in FIG. 2) and the lower surface of the second solid electrolyte layer 70 and the upper surface of the first solid electrolyte layer 66. , The buffer space 84, the second diffusion-controlled unit 86, the first internal space 88, the third diffusion-controlled unit 90, the second internal space 92, the fourth diffusion-controlled unit 94, and the third interior. The vacant space 96 is formed adjacent to each other in this order.

The gas inlet 80, the buffer space 84, the first internal space 88, the second internal space 92, and the third internal space 96 have upper parts provided in a manner in which the spacer layer 68 is hollowed out. The space inside the sensor element 12 is partitioned by the lower surface of the second solid electrolyte layer 70, the lower portion by the upper surface of the first solid electrolyte layer 66, and the side portion by the side surface of the spacer layer 68.

The first diffusion-controlled unit 82, the second diffusion-controlled unit 86, and the third diffusion-controlled unit 90 are all provided as two horizontally long slits (the openings have a longitudinal direction in the direction perpendicular to the drawing). .. Further, the fourth diffusion-controlled unit 94 is provided as one horizontally long slit (the opening has a longitudinal direction in the direction perpendicular to the drawing) formed as a gap with the lower surface of the second solid electrolyte layer 70. The portion from the gas introduction port 80 to the third internal space 96 is also referred to as a gas distribution section to be measured.

Further, at a position far from one end side of the gas flow portion to be measured, between the upper surface of the third substrate layer 64 and the lower surface of the spacer layer 68, the side portion is on the side surface of the first solid electrolyte layer 66. A reference gas introduction space 98 is provided at a position to be partitioned. For example, the atmosphere (the atmosphere in the space 50 of FIG. 1) is introduced into the reference gas introduction space 98 as a reference gas when measuring the NOx concentration.

The atmosphere introduction layer 100 is a layer made of ceramics such as porous alumina and exposed to the reference gas introduction space 98. The reference gas is introduced into the atmosphere introduction layer 100 through the reference gas introduction space 98. Further, the atmosphere introduction layer 100 is formed so as to cover the reference electrode 102. The atmosphere introduction layer 100 introduces the reference gas into the reference electrode 102 while imparting a predetermined diffusion resistance to the reference gas in the reference gas introduction space 98. The atmosphere introduction layer 100 is formed so as to be exposed to the reference gas introduction space 98 only on the rear end side (right side in FIG. 2) of the sensor element 12 with respect to the reference electrode 102. In other words, the reference gas introduction space 98 is not formed up to directly above the reference electrode 102. However, the reference electrode 102 may be formed directly below the reference gas introduction space 98 in FIG. 2.

As in the gas sensor 10A according to the first modification of FIG. 5, the reference gas introduction space 98 may be eliminated and the atmosphere introduction layer 100 may be extended to the rear end of the sensor element 12. In this case, the reference gas is introduced directly into the reference electrode 102 via the atmosphere introduction layer 100.

The reference electrode 102 is an electrode formed so as to be sandwiched between the upper surface of the third substrate layer 64 and the first solid electrolyte layer 66, and as described above, the reference electrode 102 is connected to the reference gas introduction space 98 around the reference electrode 102. An air introduction layer 100 is provided. The reference electrode 102 is formed directly on the upper surface of the third substrate layer 64, and the portion other than the portion in contact with the upper surface of the third substrate layer 64 is covered with the atmosphere introduction layer 100. Further, as will be described later, it is possible to measure the oxygen concentration (oxygen partial pressure) in the first internal space 88, the second internal space 92, and the third internal space 96 using the reference electrode 102. It has become. The reference electrode 102 is formed as a porous cermet electrode (for example, a cermet electrode of Pt and ZrO ₂ ).

In the gas flow section to be measured, the gas introduction port 80 is a portion that is open to the external space, and the gas to be measured is taken into the sensor element 12 from the external space through the gas introduction port. .. The first diffusion-controlled unit 82 is a portion that imparts a predetermined diffusion resistance to the gas to be measured taken in from the gas introduction port 80. The buffer space 84 is a space provided for guiding the gas to be measured introduced from the first diffusion-controlled unit 82 to the second diffusion-controlled unit 86. The second diffusion-controlled unit 86 is a portion that imparts a predetermined diffusion resistance to the gas to be measured introduced from the buffer space 84 into the first internal space 88. When the gas to be measured is introduced from the outside of the sensor element 12 to the inside of the first internal space 88, the pressure fluctuation of the gas to be measured in the external space (if the gas to be measured is the exhaust gas of an automobile, the exhaust pressure The gas to be measured, which is rapidly taken into the sensor element 12 from the gas introduction port 80 by pulsation), is not directly introduced into the first internal space 88, but is not directly introduced into the first internal space 88, but the first diffusion rate-determining unit 82, the buffer space 84, and the first. After the fluctuation in the concentration of the gas to be measured is canceled through the 2 diffusion rate-determining unit 86, the gas is introduced into the first internal space 88. As a result, the concentration fluctuation of the gas to be measured introduced into the first internal space 88 becomes almost negligible. The first internal space 88 is provided as a space for adjusting the oxygen partial pressure in the gas to be measured introduced through the second diffusion-controlled unit 86. The oxygen partial pressure is adjusted by operating the main pump cell 110, which will be described later.

The main pump cell 110 has an outer space (sensor of FIG. 1) in a region corresponding to the inner pump electrode 112 on the upper surface of the inner pump electrode 112 provided on the inner surface of the first internal space 88 and the second solid electrolyte layer 70. It is an electrochemical pump cell composed of an outer pump electrode 114 provided in an aspect exposed to the element chamber 22) and a second solid electrolyte layer 70 sandwiched between these electrodes.

The inner pump electrode 112 is formed across the upper and lower solid electrolyte layers (second solid electrolyte layer 70 and the first solid electrolyte layer 66) that partition the first internal space 88, and the spacer layer 68 that provides the side wall. There is. Specifically, the ceiling electrode portion 112a of the inner pump electrode 112 is formed on the lower surface of the second solid electrolyte layer 70 that provides the ceiling surface of the first internal space 88, and the bottom surface of the first internal space 88 is formed. A bottom electrode portion 112b is directly formed on the upper surface of the first solid electrolyte layer 66 to be provided, and a side electrode portion (not shown) is provided so as to connect the ceiling electrode portion 112a and the bottom electrode portion 112b. 1 It is formed on the side wall surface (inner surface) of the spacer layer 68 that constitutes both side wall portions of the internal space 88, and is arranged as a tunnel-shaped structure at the arrangement portion of the side electrode portion.

The inner pump electrode 112 and the outer pump electrode 114 are formed as a porous cermet electrode (for example, a cermet electrode of Pt containing 1% Au and ZrO ₂ ). The inner pump electrode 112 that comes into contact with the gas to be measured is formed by using a material having a weakened reducing ability for the NOx component in the gas to be measured.

In the main pump cell 110, a desired pump voltage Vp0 is applied between the inner pump electrode 112 and the outer pump electrode 114, and a pump current is applied in the positive or negative direction between the inner pump electrode 112 and the outer pump electrode 114. By flowing Ip0, the oxygen in the first internal space 88 can be pumped into the external space, or the oxygen in the external space can be pumped into the first internal space 88.

Further, in order to detect the oxygen concentration (oxygen partial pressure) in the atmosphere in the first internal space 88, the inner pump electrode 112, the second solid electrolyte layer 70, the spacer layer 68, and the first solid electrolyte layer 66 are used. And the reference electrode 102 constitutes an electrochemical sensor cell, that is, an oxygen partial pressure detection sensor cell 120 for controlling a main pump.

By measuring the electromotive force V0 in the oxygen partial pressure detection sensor cell 120 for controlling the main pump, the oxygen concentration (oxygen partial pressure) in the first internal space 88 can be known. Further, the pump current Ip0 is controlled by feedback-controlling the pump voltage Vp0 of the variable power supply 122 so that the electromotive force V0 becomes constant. As a result, the oxygen concentration in 88 in the first internal space can be maintained at a predetermined constant value.

The third diffusion-controlled unit 90 imparts a predetermined diffusion resistance to the gas to be measured whose oxygen concentration (oxygen partial pressure) is controlled by the operation of the main pump cell 110 in the first internal space 88, and transfers the gas to be measured. It is a part leading to the second internal space 92.

In the second internal space 92, the oxygen concentration (oxygen partial pressure) is adjusted in advance in the first internal space 88, and then the auxiliary pump cell 124 is further applied to the gas to be measured introduced through the third diffusion-controlled unit 90. It is provided as a space for adjusting the oxygen partial pressure. As a result, the oxygen concentration in the second internal space 92 can be kept constant with high accuracy, so that the gas sensor 10 can measure the NOx concentration with high accuracy.

The auxiliary pump cell 124 includes an auxiliary pump electrode 126 provided on the inner surface of the second internal space 92 and an outer pump electrode 114 (not limited to the outer pump electrode 114, but an appropriate electrode outside the sensor element 12). It is an auxiliary electrochemical pump cell composed of the second solid electrolyte layer 70.

The auxiliary pump electrode 126 is arranged in the second internal space 92 in a structure having a tunnel shape similar to that of the inner pump electrode 112 provided in the first internal space 88. That is, the ceiling electrode portion 126a is formed on the second solid electrolyte layer 70 that provides the ceiling surface of the second internal space 92, and the upper surface of the first solid electrolyte layer 66 that provides the bottom surface of the second internal space 92. The bottom electrode portion 126b is directly formed in the surface, and the side electrode portion (not shown) connecting the ceiling electrode portion 126a and the bottom electrode portion 126b provides a side wall of the second internal space 92. It has a tunnel-like structure formed on both wall surfaces of the spacer layer 68. The auxiliary pump electrode 126 is also formed by using a material having a weakened reducing ability for the NOx component in the gas to be measured, similarly to the inner pump electrode 112.

In the auxiliary pump cell 124, by applying a desired voltage Vp1 between the auxiliary pump electrode 126 and the outer pump electrode 114, oxygen in the atmosphere in the second internal space 92 is pumped out to the external space or outside. It is possible to pump from the space into the second internal space 92.

Further, in order to control the oxygen partial pressure in the atmosphere in the second internal space 92, the auxiliary pump electrode 126, the reference electrode 102, the second solid electrolyte layer 70, the spacer layer 68, and the first solid electrolyte The layer 66 constitutes an electrochemical sensor cell, that is, an oxygen partial pressure detection sensor cell 130 for controlling an auxiliary pump.

The auxiliary pump cell 124 pumps at the variable power supply 132 whose voltage is controlled based on the electromotive force V1 detected by the auxiliary pump control oxygen partial pressure detection sensor cell 130. As a result, the partial pressure of oxygen in the atmosphere in the second internal space 92 is controlled to a low partial pressure that does not substantially affect the measurement of NOx.

Along with this, the pump current Ip1 is used to control the electromotive force V0 of the oxygen partial pressure detection sensor cell 120 for controlling the main pump. Specifically, the pump current Ip1 is input to the oxygen partial pressure detection sensor cell 120 for controlling the main pump as a control signal, and the electromotive force V0 is controlled so that the third diffusion rate-determining unit 90 to the second internal space The gradient of the oxygen partial pressure in the gas to be measured introduced into the 92 is controlled to be always constant. When used as a NOx sensor, the oxygen concentration in the second internal space 92 is maintained at a constant value of about 0.001 ppm by the action of the main pump cell 110 and the auxiliary pump cell 124.

The fourth diffusion-controlled unit 94 imparts a predetermined diffusion resistance to the gas to be measured whose oxygen concentration (oxygen partial pressure) is controlled by the operation of the auxiliary pump cell 124 in the second internal space 92, and transfers the gas to be measured. It is a part leading to the third internal space 96. The fourth diffusion-controlled unit 94 plays a role of limiting the amount of NOx flowing into the third internal space 96.

The third internal space 96 is in the gas to be measured with respect to the gas to be measured introduced through the fourth diffusion rate-determining unit 94 after the oxygen concentration (oxygen partial pressure) is adjusted in advance in the second internal space 92. It is provided as a space for performing a process related to the measurement of the nitrogen oxide (NOx) concentration of. The measurement of the NOx concentration is mainly performed by the operation of the measurement pump cell 140 in the third internal space 96.

The measurement pump cell 140 measures the NOx concentration in the gas to be measured in the third internal space 96. The measurement pump cell 140 includes a measurement electrode 134 provided directly on the upper surface of the first solid electrolyte layer 66 facing the third internal space 96, an outer pump electrode 114, a second solid electrolyte layer 70, and a spacer layer. It is an electrochemical pump cell composed of 68 and a first solid electrolyte layer 66. The measuring electrode 134 is a porous cermet electrode. The measurement electrode 134 also functions as a NOx reduction catalyst that reduces NOx existing in the atmosphere in the third internal space 96.

In the measurement pump cell 140, oxygen generated by the decomposition of nitrogen oxides in the atmosphere around the measurement electrode 134 can be pumped out, and the amount of oxygen generated can be detected as the pump current Ip2.

Further, in order to detect the oxygen partial pressure around the measurement electrode 134, the first solid electrolyte layer 66, the measurement electrode 134, and the reference electrode 102 provide an electrochemical sensor cell, that is, an oxygen content for controlling a measurement pump. The pressure detection sensor cell 142 is configured. The variable power supply 144 is controlled based on the electromotive force V2 detected by the oxygen partial pressure detection sensor cell 142 for controlling the measurement pump.

The gas to be measured guided into the second internal space 92 reaches the measurement electrode 134 of the third internal space 96 through the fourth diffusion-controlled unit 94 under the condition that the oxygen partial pressure is controlled. Nitrogen oxides in the gas to be measured around the measurement electrode 134 are reduced (2NO → N ₂ + O ₂ ) to generate oxygen. Then, the generated oxygen is pumped by the measurement pump cell 140, and at that time, a variable power source is used so that the electromotive force V2 detected by the measurement pump control oxygen partial pressure detection sensor cell 142 becomes constant. The voltage Vp2 of 144 is controlled. Since the amount of oxygen generated around the measurement electrode 134 is proportional to the concentration of nitrogen oxides in the gas to be measured, the nitrogen oxides in the gas to be measured are used by using the pump current Ip2 in the measurement pump cell 140. The concentration will be calculated.

Further, the electrochemical sensor cell 146 is composed of the second solid electrolyte layer 70, the spacer layer 68, the first solid electrolyte layer 66, the third substrate layer 64, the outer pump electrode 114, and the reference electrode 102. The electromotive force Vref obtained by the sensor cell 146 makes it possible to detect the oxygen partial pressure in the gas to be measured outside the sensor.

Further, from the second solid electrolyte layer 70, the spacer layer 68, the first solid electrolyte layer 66, the third substrate layer 64, the outer pump electrode 114, and the reference electrode 102, the electrochemical reference gas adjusting pump cell 150 Is configured. The reference gas adjusting pump cell 150 pumps when the control current Ip3 flows by the voltage Vp3 applied by the variable power supply 152 connected between the outer pump electrode 114 and the reference electrode 102. As a result, the reference gas adjusting pump cell 150 draws oxygen from the space around the outer pump electrode 114 (sensor element chamber 22 in FIG. 1) to the space around the reference electrode 102 (atmosphere introduction layer 100). The voltage Vp3 of the variable power supply 152 is predetermined as a DC voltage such that the control current Ip3 becomes a predetermined value (DC current of a constant value).

Further, in the reference gas adjusting pump cell 150, the area of the reference electrode 102, the control current Ip3, so that the average current density of the reference electrode 102 when the control current Ip3 flows is less than 400 μA / mm ^{2 in} excess of 0 μA / mm ² . The voltage Vp3 and the like of the variable power supply 152 are predetermined. Here, the average current density means the current density obtained by dividing the average value of the control current Ip3 by the area S of the reference electrode 102. The area S of the reference electrode 102 is the area of the portion of the reference electrode 102 facing the atmosphere introduction layer 100, and in the present embodiment, is the area of the upper surface of the reference electrode 102 (length in the front-rear direction × width in the left-right direction). Since the vertical thickness of the reference electrode 102 is very small with respect to the length in the front-rear direction and the width in the left-right direction of the reference electrode 102, the area of the side surface (front-back left-right surface) of the reference electrode 102 can be ignored. The average value of the control current Ip3 is a value averaged over time for a sufficiently long predetermined period in which a momentary change in the control current Ip3 can be ignored. The average current density is preferably set to 200 .mu.A / mm ² or less, more preferably, to 170μA / mm ² or less, and even more preferably from 160μA / mm ² or less. The area S of the reference electrode 102 is preferably 5 mm ² or less. Although not particularly limited, the length of the reference electrode 102 in the front-rear direction is, for example, 0.2 to 2 mm, and the width in the left-right direction is, for example, 0.2 to 2.5 mm. The average value of the control current Ip3 is, for example, 1 to 100 μA. The average value of the control current Ip3 is preferably more than 1 μA, more preferably 4 μA or more, further preferably 5 μA or more, and further preferably 8 μA or more.

In the gas sensor 10 having such a configuration, the oxygen partial pressure is always kept at a constant low value (a value that does not substantially affect the measurement of NOx) by operating the main pump cell 110 and the auxiliary pump cell 124. The gas to be measured is supplied to the measurement pump cell 140. Therefore, the NOx concentration in the gas to be measured is determined based on the pump current Ip2 that flows when oxygen generated by the reduction of NOx is pumped out from the measurement pump cell 140 in substantially proportional to the concentration of NOx in the gas to be measured. You can know it.

Further, the sensor element 12 includes a heater unit 160 which plays a role of temperature adjustment for heating and keeping the sensor element 12 warm in order to increase the oxygen ion conductivity of the solid electrolyte. The heater unit 160 includes a heater connector electrode 162, a heater 164, a through hole 166, a heater insulating layer 168, a pressure dissipation hole 170, and a lead wire 172.

The heater connector electrode 162 is an electrode formed so as to be in contact with the lower surface of the first substrate layer 60. By connecting the heater connector electrode 162 to an external power source, power can be supplied to the heater unit 160 from the outside.

The heater 164 is an electric resistor formed by being sandwiched between the second substrate layer 62 and the third substrate layer 64 from above and below. The heater 164 is connected to the heater connector electrode 162 via a lead wire 172 and a through hole 166, and generates heat when power is supplied from the outside through the heater connector electrode 162 to heat the solid electrolyte forming the sensor element 12. And keep warm.

Further, the heater 164 is embedded in the entire area from the first internal space 88 to the third internal space 96, and the entire sensor element 12 can be adjusted to a temperature at which the solid electrolyte is activated. ing.

The heater insulating layer 168 is an insulating layer made of porous alumina formed on the upper and lower surfaces of the heater 164 by an insulator such as alumina. The heater insulating layer 168 is formed for the purpose of obtaining electrical insulation between the second substrate layer 62 and the heater 164 and electrical insulation between the third substrate layer 64 and the heater 164.

The pressure dissipation hole 170 is a portion provided so as to penetrate the third substrate layer 64 and communicate with the reference gas introduction space 98, and for the purpose of alleviating the increase in internal pressure due to the temperature rise in the heater insulating layer 168. It is formed.

The variable power supplies 122, 144, 132, 152 and the like shown in FIG. 2 are actually connected to each electrode via a lead wire (not shown) formed in the sensor element 12 and a connector 16 and a lead wire 54 in FIG. Is connected to.

Next, an example of such a manufacturing method of the gas sensor 10 will be described below. First, six unfired ceramic green sheets containing an oxygen ion conductive solid electrolyte such as zirconia as a ceramic component are prepared. A plurality of sheet holes, necessary through holes, etc. used for positioning during printing and laminating are formed in advance on this green sheet. Further, the green sheet to be the spacer layer 68 is provided with a space to be a gas distribution section to be measured in advance by punching or the like. Then, each of the first substrate layer 60, the second substrate layer 62, the third substrate layer 64, the first solid electrolyte layer 66, the spacer layer 68, and the second solid electrolyte layer 70 correspond to each of them. A pattern printing process and a drying process are performed to form various patterns on the ceramic green sheet. Specifically, the pattern to be formed is, for example, each electrode described above, a lead wire 172 connected to each electrode, an atmosphere introduction layer 100, a heater portion 160, or the like. Pattern printing is performed by applying a pattern forming paste prepared according to the characteristics required for each formation target onto a green sheet using a known screen printing technique. The drying treatment is also carried out using a known drying means. After the pattern printing / drying is completed, the adhesive paste for laminating / bonding the green sheets corresponding to each layer is printed / dried. Then, the green sheets on which the adhesive paste is formed are laminated in a predetermined order while being positioned by the sheet holes, and crimped by applying predetermined temperature and pressure conditions to form a single laminated body. The laminated body thus obtained includes a plurality of sensor elements 12. The laminate is cut and cut into the size of the sensor element 12. Then, the cut laminate is fired at a predetermined firing temperature to obtain the sensor element 12.

When the sensor element 12 is obtained in this way, the gas sensor 10 can be obtained by manufacturing the sensor assembly 18 (see FIG. 1) incorporating the sensor element 12 and attaching the protective cover 14, the rubber stopper 56, and the like. A method for manufacturing such a gas sensor is known and is described in, for example, International Publication No. 2013/005491.

Here, the role played by the reference gas adjusting pump cell 150 will be described in detail. The gas to be measured is introduced from the sensor element chamber 22 shown in FIG. 1 into the gas distribution section to be measured such as the gas introduction port 80 of the sensor element 12. On the other hand, the reference gas (atmosphere) in the space 50 shown in FIG. 1 is introduced into the reference gas introduction space 98 of the sensor element 12. The sensor element chamber 22 and the space 50 are partitioned by a sensor assembly 18 (particularly, powder powders 46a and 46b), and are sealed so that gas does not flow to each other. However, when the pressure on the gas to be measured side temporarily increases, for example, the gas to be measured slightly enters the space 50 due to a gap between the green compacts 46a and 46b and the sensor element 12 and the main metal fitting 40. It may invade. As a result, if the oxygen concentration around the reference electrode 102 temporarily decreases, the reference potential, which is the potential of the reference electrode 102, changes. As a result, the electromotive force based on the reference electrode 102, such as the electromotive force V2 of the oxygen partial pressure detection sensor cell 142 for controlling the measurement pump, changes, and the detection accuracy of the NOx concentration in the measured gas deteriorates. It ends up. The reference gas adjusting pump cell 150 plays a role of suppressing such a decrease in detection accuracy. The reference gas adjusting pump cell 150 draws a constant amount of oxygen from the sensor element chamber 22 into the space 50 by flowing the control current Ip3. As a result, when the gas to be measured temporarily lowers the oxygen concentration around the reference electrode 102 as described above, the reduced oxygen can be supplemented and the decrease in the detection accuracy of the NOx concentration is suppressed. It is. The value of the control current Ip3 (for example, the average value) is how much the oxygen concentration around the reference electrode 102 decreases when the pressure of the measured gas is the maximum expected value (how much oxygen is around the reference electrode 102). It can be determined in advance by an experiment or the like based on (whether it is necessary to pump it into the container).

In the present embodiment, the control current Ip3 is always applied when the gas sensor 10 detects the NOx concentration, regardless of whether or not the gas to be measured has slightly entered the space 50. In this case, even when the oxygen concentration of the reference gas around the reference electrode 102 does not decrease, such as when the pressure of the gas to be measured is relatively low and does not enter the space 50, the reference gas adjustment pump cell 150 Will draw oxygen around the reference electrode 102. However, such excess oxygen is promptly diffused into the reference gas introduction space 98 and the space 50 through the atmosphere introduction layer 100. Therefore, the oxygen concentration around the reference electrode 102 does not increase too much and the detection accuracy of the NOx concentration does not decrease.

Further, when the electromotive force Vref is obtained (measured) by the sensor cell 146 described above and the oxygen partial pressure in the gas to be measured outside the sensor is detected, the sensor cell 146 does not allow the variable power supply 152 to flow the control current Ip3. The operation timing of the reference gas adjusting pump cell 150 and the reference gas adjusting pump cell 150 is adjusted in advance. As a result, the oxygen pumping operation by the reference gas adjusting pump cell 150 does not interfere with the operation of the sensor cell 146.

Then, as shown in FIG. 3, the gas sensor 10 according to the present embodiment has a reference gas adjusting unit 190.

The reference gas adjusting unit 190 passes a control current Ip between the reference electrode 102 and the electrode to be measured (for example, the outer pump electrode 114) to draw oxygen around the reference electrode 102.

The reference gas adjusting unit 190 further sets the value of the control current Ip according to the temperature measuring unit 192 that measures the temperature Ta of the gas to be measured and the height of the temperature Ta of the gas to be measured and the preset threshold temperature Tth. It has a control current adjusting unit 194 for adjusting.

The temperature measuring unit 192 may be, for example, a thermometer installed in the gas to be measured. Of course, a thermocouple may be used instead of the thermometer. Further, the temperature measuring unit 192 may estimate the temperature Ta of the gas to be measured from the engine speed.

The temperature measuring unit 192 may measure the temperature of the gas to be measured based on the resistance value of the heater 164 constituting the heater unit 160. Further, the temperature measuring unit 192 may measure the temperature Ta of the gas to be measured based on the electric power applied to the heater 164 constituting the heater unit 160.

On the other hand, the control current adjusting unit 194 flows a control current Ip having a preset current value when, for example, the temperature Ta of the measured gas is equal to or lower than the threshold temperature Tth, and the temperature Ta of the measured gas exceeds the threshold temperature Tth. If so, the current value of the control current Ip is adjusted. For example, the current value of the control current Ip is increased.

The control current adjusting unit 194 is composed of, for example, one or more electronic circuits having one or a plurality of CPUs (central processing units) and a storage device. The electronic circuit is also a software function unit in which a predetermined function is realized by, for example, the CPU executing a program stored in a storage device. Of course, it may be composed of an integrated circuit such as an FPGA (Field-Programmable Gate Array) in which a plurality of electronic circuits are connected according to the function.

Here, the control method of the gas sensor 10 according to the present embodiment will be described with reference to the flowchart of FIG.

First, in step S1 of FIG. 4, the control current adjusting unit 194 causes a control current Ip to flow between the reference electrode 102 and the gas side electrode to be measured (outer pump electrode 114) to charge oxygen around the reference electrode 102. Pump in.

In step S2, the temperature measuring unit 192 measures the temperature Ta of the gas to be measured. For example, the temperature Ta of the gas to be measured in the sensor element chamber 22 in the protective cover 14 and the space 50 in the outer cylinder 34 is measured.

In step S3, the control current adjusting unit 194 determines whether or not the temperature Ta of the gas to be measured exceeds the preset threshold temperature Tth. If the temperature Ta of the gas to be measured exceeds the threshold temperature Tth (step S3: YES), the process proceeds to step S4, and the control current adjusting unit 194 adjusts the current value of the control current Ip. For example, the current value of the control current Ip is increased. The threshold temperature Tth may be a temperature lower than the temperature at which the inert gas is generated from the rubber stopper 56 by about 1 to 5 ° C.

When the process in step S4 is completed, or when it is determined in step S3 that the temperature Ta of the gas to be measured is equal to or lower than the threshold temperature Tth (step S3: NO), the process after step S1 after a predetermined time has elapsed. repeat.

[Invention obtained from the present embodiment]
The inventions that can be grasped from the above embodiments are described below.

[1] In the present embodiment, a plurality of oxygen ion conductive solid electrolyte layers are laminated, and a measurement gas flow section for introducing and circulating the measurement gas and detection of a specific gas concentration in the measurement gas are detected. A reference gas introduction space 98 for introducing a reference gas as a reference, a laminate provided inside, and a reference electrode formed inside the laminate and the reference gas is introduced through the reference gas introduction space 98. The 102, the measurement electrode 134 arranged on the inner peripheral surface of the gas flow section to be measured, and the gas side electrode to be measured (outer pump electrode 114) arranged in the portion of the laminate exposed to the gas to be measured. ), The heater unit 160 that heats and keeps the sensor element 12 warm, and the electromotive force V2 generated between the reference electrode 102 and the measurement electrode 134. A control current Ip is passed between the detection means (measurement pump cell 140) for detecting the specific gas concentration in the measurement gas and the reference electrode 102 and the electrode to be measured, and oxygen is drawn around the reference electrode 102. The reference gas adjusting unit 190 includes a reference gas adjusting unit 190 for measuring the temperature Ta of the gas to be measured, and the temperature measuring unit 192 for measuring the temperature Ta of the gas to be measured and a preset threshold temperature Tth. It has a control current adjusting unit 194 that adjusts the value of the control current Ip according to the height.

Conventionally, due to the control of oxygen pumping into the reference electrode, the voltage drop is included in the potential difference between the sensor cells, and as a result, the oxygen difference between the sensor cells is reduced, resulting in a decrease in the detection accuracy of the gas concentration. There was a risk.

However, in the present embodiment, the temperature Ta of the gas to be measured is measured, and the control current Ip is adjusted according to the height of the temperature Ta of the gas to be measured and the preset threshold temperature Tth. For example, it is possible to suppress a decrease in oxygen concentration to the reference electrode 102 due to the inert gas generated from the rubber stopper 56, and it is possible to improve the detection accuracy of a predetermined component (for example, NO) in the gas to be measured.

[2] In the present embodiment, when the temperature Ta of the measured gas is equal to or lower than the threshold temperature Tth, the control current adjusting unit 194 passes a control current Ip having a preset current value, and the temperature Ta of the measured gas is changed. When the threshold temperature Tth is exceeded, the current value of the control current Ip is adjusted. When the temperature Ta of the gas to be measured becomes high and, for example, an inert gas is generated from the rubber stopper 56, the reference gas changes to the inert gas, so that a predetermined component (for example, NO) in the gas to be measured The detection accuracy is reduced. Therefore, when the temperature Ta of the gas to be measured exceeds the threshold temperature Tth, the decrease in the detection accuracy of a predetermined component (for example, NO) in the gas to be measured is suppressed by adjusting the current value of the control current Ip. Can be done.

[3] In the present embodiment, it is preferable that the control current adjusting unit 194 increases the current value of the control current Ip when the temperature Ta of the gas to be measured exceeds the threshold temperature Tth. As a result, the oxygen concentration of the reference gas can be increased, and a decrease in the detection accuracy of a predetermined component (for example, NO) in the gas to be measured can be suppressed.

[4] In the present embodiment, the temperature measuring unit 192 may be a thermometer installed in the gas to be measured. If the gas sensor 10 has a space in which a thermometer can be installed, the temperature Ta of the gas to be measured can be easily measured by using the thermometer. A thermocouple may be used as the thermometer.

[5] In the present embodiment, the temperature measuring unit 192 measures the temperature Ta of the gas to be measured based on the resistance value of the heater 164 constituting the heater unit 160. If the heater 164 is made of, for example, platinum, the electrical resistance of the heater 164 increases as the temperature Ta of the gas to be measured increases. Therefore, the temperature Ta of the gas to be measured can be measured based on the resistance value of the heater 164.

[6] In the present embodiment, the temperature measuring unit 192 measures the temperature Ta of the gas to be measured based on the electric power applied to the heater 164 constituting the heater unit 160. For example, when the gas sensor 10 is exposed to a gas to be measured having a high temperature, the power (electric power) applied to the heater 164 is reduced. Therefore, the temperature Ta of the gas to be measured can be measured based on the electric power to the heater 164.

[7] The control method of the gas sensor 10 according to the present embodiment is a method of stacking a plurality of oxygen ion conductive solid electrolyte layers, and introducing and circulating the measured gas in the measured gas flow section and in the measured gas. A reference gas introduction space 98 for introducing a reference gas that serves as a reference for detecting a specific gas concentration is formed inside the laminate and a reference gas introduction space 98 provided inside the laminate. The reference electrode 102 into which the gas is introduced, the measurement electrode 134 arranged on the inner peripheral surface of the gas flow section to be measured, and the gas to be measured arranged in the portion of the laminate exposed to the gas to be measured. Occurrence between the sensor element 12 having the side electrode (outer pump electrode 114), the heater portion 160 that heats and keeps the sensor element 12 warm, and the reference electrode 102 and the measurement electrode 134. In the control method of the gas sensor 10 having a detecting means (measurement pump cell 140) for detecting a specific gas concentration in the gas to be measured based on the electric power V2, a step of measuring the temperature Ta of the gas to be measured and a reference electrode. A step of passing a control current Ip between the 102 and the electrode to be measured to draw oxygen around the reference electrode 102, and the height of the temperature Ta of the gas to be measured and the preset threshold temperature Tth. It has a control current adjustment step for adjusting the value of the control current Ip according to the above.

Conventionally, due to the control of oxygen pumping into the reference electrode 102, the voltage drop is included in the potential difference between the sensor cells, and as a result, the oxygen difference between the sensor cells is reduced, so that the detection accuracy of the gas concentration is lowered. There was a risk of inviting.

However, in the present embodiment, the temperature Ta of the gas to be measured is measured, and the control current Ip is adjusted according to the height of the temperature Ta of the gas to be measured and the preset threshold temperature Tth. For example, it is possible to suppress a decrease in oxygen concentration to the reference electrode 102 due to the inert gas generated from the rubber stopper 56, and it is possible to improve the detection accuracy of a predetermined component (for example, NO) in the gas to be measured.

[8] In the present embodiment, in the control current adjustment step, when the temperature Ta of the measured gas is equal to or less than the threshold temperature Tth, a control current Ip having a preset current value is passed, and the temperature Ta of the measured gas is the threshold. When the temperature Tth is exceeded, the current value of the control current Ip is adjusted. When the temperature Ta of the gas to be measured becomes high and, for example, an inert gas is generated from the rubber stopper 56, the reference gas changes to the inert gas, so that a predetermined component (for example, NO) in the gas to be measured The detection accuracy is reduced. Therefore, when the temperature Ta of the gas to be measured exceeds the threshold temperature Tth, the decrease in the detection accuracy of a predetermined component (for example, NO) in the gas to be measured is suppressed by adjusting the current value of the control current Ip. Can be done.

[9] In the present embodiment, it is preferable that the control current adjusting step increases the current value of the control current Ip when the temperature Ta of the gas to be measured exceeds the threshold temperature Tth. As a result, the oxygen concentration of the reference gas can be increased, and a decrease in the detection accuracy of a predetermined component (for example, NO) in the gas to be measured can be suppressed.

It should be noted that the gas sensor and the control method of the gas sensor according to the present invention are not limited to the above-described embodiment, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

For example, in the above-described embodiment, the reference electrode 102 is formed directly on the upper surface of the third substrate layer 64, but the present invention is not limited to this. For example, it may be formed directly on the lower surface of the first solid electrolyte layer 66.

In the above-described embodiment, the sensor element 12 of the gas sensor 10 includes, but is not limited to, the first internal space 88, the second internal space 92, and the third internal space 96. For example, the third internal space 96 may not be provided. FIG. 6 shows a schematic cross-sectional view of the sensor element 12 of the gas sensor 10B according to the second modification in this case.

As shown in FIG. 6, in the gas sensor 10B, between the lower surface of the second solid electrolyte layer 70 and the upper surface of the first solid electrolyte layer 66, a gas introduction port 80, a first diffusion-controlled unit 82, and a buffer space are provided. The 84, the second diffusion-controlled unit 86, the first internal space 88, the third diffusion-controlled unit 90, and the second internal space 92 are formed adjacent to each other in this order.

The third diffusion-controlled unit 90 of the gas sensor 10B is provided as one horizontally long slit formed as a gap with the lower surface of the second solid electrolyte layer 70, similarly to the fourth diffusion-controlled unit 94 of FIG. ing. Further, the measurement electrode 134 is arranged on the upper surface of the first solid electrolyte layer 66 in the second internal space 92. The measurement electrode 134 is covered with a fifth diffusion-controlled unit 202. The fifth diffusion-controlled unit 202 is a film made of a ceramic porous body such as alumina (Al ₂ O ₃ ). The fifth diffusion-controlled unit 202 plays a role of limiting the amount of NOx flowing into the measurement electrode 134, similarly to the fourth diffusion-controlled unit 94 of the gas sensor 10 described above. The fifth diffusion-controlled unit 202 also functions as a protective film for the measurement electrode 134. The ceiling electrode portion 126a of the auxiliary pump electrode 126 is formed up to directly above the measurement electrode 134.

The gas sensor 10B according to this second modification also has a reference gas adjusting unit 190, a temperature measuring unit 192, and a control current adjusting unit 194 specified in FIG.

Therefore, it is possible to suppress a decrease in oxygen concentration to the reference electrode 102 due to, for example, an inert gas generated from the rubber stopper 56 due to the high temperature of the gas to be measured, and improve the detection accuracy of a predetermined component (for example, NO) in the gas to be measured. be able to.

In the above-described embodiments and modifications, the reference gas is the atmosphere, but the gas is not limited to this as long as it is a reference gas for detecting the concentration of the specific gas in the gas to be measured. For example, a gas adjusted to a predetermined oxygen concentration (> oxygen concentration of the gas to be measured) may be filled in the space 50 (see FIG. 1) as a reference gas.

In the above-described embodiment, the sensor element 12 detects the NOx concentration in the gas to be measured, but the present invention is not limited to this as long as it detects the concentration of the specific gas in the gas to be measured. For example, the oxygen concentration in the gas to be measured may be detected.

In carrying out the present invention, various means for improving reliability as automobile parts may be added as long as the idea of the present invention is not impaired.

10, 10A, 10B ... Gas sensor 12 ... Sensor element 14 ... Protective cover 14a ... Inner protective cover 14b ... Outer protective cover 16 ... Connector 18 ... Sensor assembly 20 ... Piping 22 ... Sensor element room 50 ... Space 56 ... Rubber stopper 80 ... Gas inlet 98 ... Reference gas introduction space 100 ... Atmospheric introduction layer 102 ... Reference electrode 110 ... Main pump cell 112 ... Inner pump electrode 114 ... Outer pump electrode 124 ... Auxiliary pump cell 140 ... Measurement pump cell 150 ... Reference gas adjustment pump cell 160 ... Heater Unit 162 ... Heater connector electrode 164 ... Heater 168 ... Heater insulation layer 190 ... Reference gas adjusting unit 192 ... Temperature measuring unit 194 ... Control current adjusting unit

Claims (9)

A gas flow section to be measured, which is formed by stacking a plurality of oxygen ion conductive solid electrolyte layers and introduces and distributes the gas to be measured, and a reference gas which is a standard for detecting a specific gas concentration in the gas to be measured are introduced. The reference gas introduction space, the laminate provided inside, and
A reference electrode formed inside the laminate and into which the reference gas is introduced through the reference gas introduction space,
The measurement electrodes arranged on the inner peripheral surface of the gas flow section to be measured,
A sensor element having a gas-measured gas-side electrode disposed in a portion of the laminated body exposed to the gas to be measured.
A heater unit that heats and retains the sensor element and a heater unit that plays a role of temperature control.
A detection means for detecting a specific gas concentration in the gas to be measured based on an electromotive force generated between the reference electrode and the measurement electrode.
A reference gas adjusting means for drawing oxygen around the reference electrode by passing a control current between the reference electrode and the electrode to be measured.
With
The reference gas adjusting means is
A temperature measuring means for measuring the temperature of the gas to be measured and
A gas sensor having a control current adjusting means for adjusting a value of the control current according to the height of the temperature of the gas to be measured and a preset threshold temperature. In the gas sensor according to claim 1,
The control current adjusting means is
When the temperature of the gas to be measured is equal to or lower than the threshold temperature, a control current having a preset current value is applied.
A gas sensor that adjusts the current value of the control current when the temperature of the gas to be measured exceeds the threshold temperature. In the gas sensor according to claim 2.
The control current adjusting means is
A gas sensor that increases the current value of the control current when the temperature of the gas to be measured exceeds the threshold temperature. In the gas sensor according to any one of claims 1 to 3.
The temperature measuring means is a gas sensor, which is a thermometer installed in the gas to be measured. In the gas sensor according to any one of claims 1 to 3.
The temperature measuring means is a gas sensor that measures the temperature of the gas to be measured based on the resistance value of the heater constituting the heater unit. In the gas sensor according to any one of claims 1 to 3.
The temperature measuring means is a gas sensor that measures the temperature of the gas to be measured based on the electric power applied to the heater constituting the heater unit. A gas flow section to be measured, which is formed by stacking a plurality of oxygen ion conductive solid electrolyte layers and introduces and distributes the gas to be measured, and a reference gas which is a standard for detecting a specific gas concentration in the gas to be measured are introduced. The reference gas introduction space, the laminate provided inside, and
A reference electrode formed inside the laminate and into which the reference gas is introduced through the reference gas introduction space,
The measurement electrodes arranged on the inner peripheral surface of the gas flow section to be measured,
A sensor element having a gas-measured gas-side electrode disposed in a portion of the laminated body exposed to the gas to be measured.
A heater unit that heats and retains the sensor element and a heater unit that plays a role of temperature control.
In a method for controlling a gas sensor having a detection means for detecting a specific gas concentration in the gas to be measured based on an electromotive force generated between the reference electrode and the measurement electrode.
The step of measuring the temperature of the gas to be measured and
A step of passing a control current between the reference electrode and the electrode to be measured to draw oxygen around the reference electrode.
A method for controlling a gas sensor, which comprises a control current adjusting step for adjusting a value of the control current according to a height of the temperature of the gas to be measured and a preset threshold temperature. In the gas sensor control method according to claim 7,
The control current adjustment step
When the temperature of the gas to be measured is equal to or lower than the threshold temperature, a control current having a preset current value is applied.
A method for controlling a gas sensor, which adjusts the current value of the control current when the temperature of the gas to be measured exceeds the threshold temperature. In the gas sensor control method according to claim 8,
The control current adjustment step
A method for controlling a gas sensor, which increases the current value of the control current when the temperature of the gas to be measured exceeds the threshold temperature.

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