JP2004354400A - Gas sensor and nitrogen oxide sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evade an influence of pulsation in exhaust gas pressure generated in measured gas and hereby enhance measurement precision in a detecting electrode. <P>SOLUTION: The first diffusion rate determining part 26 for imparting a prescribed diffusion resistance to the measured gas introduced into the first chamber 18 is constituted to have a slit 30 wherein an oblong opening part formed in a portion of a front end portion in the second spacer layer 12e to contact with an under face of the second solid electrolyte layer 12f is formed to have the same opening width up to the first chamber 18, and a slit 32 wherein an oblong opening part formed in a portion of a front end portion in the second spacer layer 12e to contact with an upper face of the first solid electrolyte layer 12d is formed to have the same opening width up to the first chamber 18. The slit 30, 32 are formed into the substantially same cross-sectional shape, and have 10μm or less of longitudinal-directional length, and about 2mm of lateral-directional length. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a gas sensor for measuring oxides such as O ₂ , NO, NO ₂ , SO ₂ , CO ₂ , H ₂ O, and flammable gases such as CO and CnHm contained in vehicle exhaust gas and air. And a nitrogen oxide sensor.

  Conventionally, as a method for measuring NOx in a gas to be measured such as a combustion gas, a sensor using a NOx reducing property of Rh and forming a Pt electrode and a Rh electrode on an oxygen ion-conductive solid electrolyte such as zirconia is used. There is known a method of measuring the electromotive force between these two electrodes using the following method.

  However, such a sensor not only has a large change in electromotive force due to a change in the concentration of oxygen contained in the combustion gas that is the gas to be measured, but also has a small change in electromotive force with respect to a change in the concentration of NOx. There is a problem that is easily affected by the.

  In addition, since reducing gas such as CO is indispensable in order to bring out the reducibility of NOx, in general, under the combustion condition of insufficient fuel in which a large amount of NOx is generated, the amount of generated CO is reduced by the amount of generated NOx. As a result, the measurement cannot be performed with the combustion gas formed under such combustion conditions.

In order to solve the above problem, pump electrodes having different NOx decomposing abilities are arranged in a first internal space communicating with the measured gas existing space and a second internal space communicating with the first internal space. The NO 2 sensor and the first pump cell in the first internal space adjust the O ₂ concentration, decompose NO by the decomposition pump disposed in the second internal space, and obtain NOx from the pump current flowing through the decomposition pump. A method for measuring the concentration is disclosed in Patent Document 1, for example.

  Further, Patent Document 2 discloses a sensor element in which an auxiliary pump electrode is arranged in the second internal space so that the oxygen concentration in the second internal space is controlled to be constant even when the oxygen concentration changes suddenly. Has been.

JP-A-8-271476 JP-A-9-113484

  By the way, when the gas sensor is attached to an exhaust system of an internal combustion engine such as an automobile engine to drive the internal combustion engine, normally, as shown by a solid line a in FIG. 32, the sensor output becomes 0 according to a change in oxygen concentration. Although it changes proportionally as a base point, it has been found that the sensor output as a whole shifts up under specific operating conditions, as shown by the solid line b.

  In general, as shown in FIG. 33, the total pressure of the exhaust gas of an automobile engine is composed of a constant static pressure and a dynamic pressure generated by a pulsation of the exhaust pressure, and the fluctuation cycle of the dynamic pressure is synchronized with the explosion cycle of the engine. However, as a result of investigating the cause of the shift up of the sensor output, it was found that the shift up occurs when the pulsation (= dynamic pressure) of the exhaust pressure is larger than the static pressure.

  That is, as shown in FIG. 34, as a result of measuring the shift amount of the sensor output with respect to the ratio between the dynamic pressure and the static pressure (dynamic pressure / static pressure), if the dynamic pressure / static pressure is about 25% or less, the shift Although the amount was almost 0, it was found that the shift amount increased proportionally from the stage where the dynamic pressure / static pressure exceeded about 25%.

  Therefore, when the dynamic pressure increases, the correlation between the oxygen pumping amount of the main pump in the first space and the oxygen concentration in the gas to be measured is inevitably deteriorated, and the disturbance of the oxygen concentration in the first space is There is a possibility that the control of the oxygen concentration in the second space communicating with the one space and the deterioration of the measurement accuracy at the detection electrode serving as the NOx detection unit may be caused.

  The present invention has been made in view of such a problem, and can avoid the influence of pulsation of exhaust pressure generated in a gas to be measured, and can improve measurement accuracy at a detection electrode. It is an object to provide a gas sensor and a nitrogen oxide sensor.

  The gas sensor according to the present invention is a gas sensor that measures an amount of a gas component to be measured in a gas to be measured in an external space, and includes at least a solid electrolyte in contact with the external space and an internal space formed inside the solid electrolyte. Diffusion controlling means formed by a slit for introducing the gas to be measured based on a predetermined diffusion resistance from the external space via a gas inlet, and an inner side formed inside and outside the internal space. A gas sensor having a pump electrode and an outer pump electrode, and a pump means for pumping oxygen contained in the gas to be measured introduced from the external space based on a control voltage applied between the electrodes. In the above, the dimension of one factor forming the cross-sectional shape of the diffusion rate controlling means is set to 10 μm or less.

  The limiting current value Ip in the pump means is approximated by the following limiting current theoretical formula.

Ip ≒ (4F / RT) × D × (S / L) × (POe-POd)
Note that F is a Faraday constant (= 96500 A / sec), R is a gas constant (= 82.05 cm ³ · atm / mol · K), T is an absolute temperature (K), D is a diffusion coefficient (cm ² / sec), S is the cross-sectional area (cm ² ) of the diffusion controlling means, L is the path length of the diffusion controlling means (cm), POe is the oxygen partial pressure (atm) outside the diffusion controlling means, and POd is the oxygen content inside the diffusion controlling means. Indicates pressure (atm).

  The present invention defines a factor for forming the cross-sectional area S of the diffusion-limiting means in the theoretical formula for current-limiting current. In particular, one factor of the dimension for forming the cross-sectional area S is set to 10 μm or less. .

  In this case, the pulsation (= dynamic pressure) of the exhaust pressure is attenuated by the wall resistance in the diffusion control means, and specifically, the ratio between the dynamic pressure and the static pressure (dynamic pressure / static pressure) is reduced to a level of 25% or less. Therefore, the shift-up phenomenon of the sensor output due to the fluctuation of the dynamic pressure can be effectively suppressed.

  In the above-mentioned configuration, when the cross-sectional shape of the diffusion rate controlling means is formed by at least one horizontal slit, the one factor may be a length of the slit in the vertical direction. Further, when the cross-sectional shape of the diffusion rate controlling means is formed by at least one vertical slit, the one factor may be a horizontal length of the slit.

  Further, in the above configuration, a buffer space may be provided between the gas inlet and the diffusion controlling means. Normally, oxygen suddenly enters the sensor element through the gas inlet due to the pulsation of the exhaust pressure in the external space, but oxygen from the external space does not directly enter the processing space but enters the buffer space at the preceding stage. Will be. That is, the rapid change of the oxygen concentration due to the pulsation of the exhaust pressure is canceled by the buffer space, and the effect of the pulsation of the exhaust pressure on the internal space is almost negligible.

  As a result, the correlation between the oxygen pumping amount by the pump means in the processing space and the oxygen concentration in the gas to be measured is improved, and the measurement accuracy is improved by the measuring pump means or the concentration detecting means. In addition, the internal space can be used also as a sensor for obtaining an air-fuel ratio, for example.

  Further, in the above configuration, a clogging prevention portion and a buffer space are provided in series between the gas introduction port and the internal space (processing space), and the gas introduction port is formed at a front opening of the clogging prevention portion. It may be configured such that a diffusion-controlling unit that provides a predetermined diffusion resistance to the gas to be measured is provided between the clogging prevention unit and the buffer space.

  In this case, it is possible to avoid that particles (soot, oil combustion products, etc.) generated in the gas to be measured in the external space are clogged near the entrance of the buffer space, and to measure the predetermined gas component with higher accuracy. It is possible to maintain a high-accuracy state for a long time.

  Further, in the above configuration, the pump means performs a pumping process on oxygen contained in the gas to be measured from the external space introduced into the internal space, thereby reducing an oxygen partial pressure in the internal space (processing space). The predetermined gas component in the measured gas may be controlled to a predetermined value that cannot be decomposed.

  A measuring pump means for decomposing a predetermined gas component contained in the gas to be measured after being pumped by the pump means by catalytic action and / or electrolysis, and pumping oxygen generated by the decomposition; And the predetermined gas component in the gas to be measured may be measured based on a pump current flowing through the measuring pump means by a pumping process of the measuring pump means.

  Alternatively, a predetermined gas component contained in the gas to be measured after being pumped by the pump means is decomposed by a catalytic action, and the difference between the amount of oxygen generated by the decomposition and the amount of oxygen contained in the reference gas is decomposed. Oxygen partial pressure detecting means for generating an electromotive force according to the above, the predetermined gas component in the gas to be measured is measured based on the electromotive force detected by the oxygen partial pressure detecting means Is also good.

  Next, the present invention is a nitrogen oxide sensor for measuring the amount of the nitrogen oxide component in the gas to be measured in the external space, at least, a substrate made of an oxygen ion conductive solid electrolyte in contact with the external space, A first internal space formed in the solid electrolyte and communicating with the external space; and a slit for introducing the gas to be measured into the first internal space under a predetermined diffusion resistance. A first diffusion-controlling means, a first inner pump electrode and a first outer pump electrode formed inside and outside the first internal space, and the measured object introduced from the external space. Oxygen contained in gas is pumped based on a control voltage applied between the electrodes to control the oxygen partial pressure in the first internal space to a predetermined value at which NO can be substantially decomposed. Main pump means and the first pump A second internal cavity communicating with the cavity, and a slit for introducing an atmosphere pumped in the first internal cavity into the second internal cavity under a predetermined diffusion resistance. A second diffusion-controlling means, a second inner pump electrode and a second outer pump electrode formed inside and outside the second internal space, and are introduced from the first internal space. Pump means for decomposing NO contained in the atmosphere by catalytic action and / or electrolysis and pumping oxygen generated by the decomposition, and performing the measurement by the pumping process of the measuring pump means. A nitrogen oxide sensor for measuring an amount of nitrogen oxides in the gas to be measured based on a pump current flowing through a pumping means for use in a sensor, wherein at least one factor forming a cross-sectional shape of one diffusion-controlling means , And configure to 10μm or less.

  As a result, the pulsation (= dynamic pressure) of the exhaust pressure is attenuated by the wall resistance in the diffusion controlling means, and specifically, the ratio of the dynamic pressure to the static pressure (dynamic pressure / static pressure) is reduced to a level of 25% or less. Therefore, the shift-up phenomenon of the sensor output due to the fluctuation of the dynamic pressure can be effectively suppressed.

  Further, the present invention is a nitrogen oxide sensor for measuring the amount of a nitrogen oxide component in a gas to be measured in an external space, at least a substrate made of an oxygen ion conductive solid electrolyte in contact with the external space, A first internal space formed in the solid electrolyte and communicating with the external space, and a slit for introducing the gas to be measured into the first internal space under a predetermined diffusion resistance. A first diffusion-controlling means, a first inner pump electrode and a first outer pump electrode formed inside and outside the first internal space, and the gas to be measured introduced from the external space A pumping process based on a control voltage applied between the electrodes to control oxygen partial pressure in the first internal space to a predetermined value at which substantially no NO can be decomposed. Pump means; A second internal cavity communicating with the cavity, and a slit for introducing an atmosphere pumped in the first internal cavity into the second internal cavity under a predetermined diffusion resistance. A second diffusion-controlling means, a second inner measurement electrode and a second outer measurement electrode formed inside and outside the second internal space, and are introduced from the first internal space. And oxygen partial pressure detecting means for decomposing NO contained in the atmosphere by a catalytic action and generating an electromotive force corresponding to a difference between the amount of oxygen generated by the decomposition and the amount of oxygen contained in the reference gas. A nitrogen oxide sensor for measuring the amount of nitrogen oxides in the gas to be measured based on the electromotive force detected by the oxygen partial pressure detection means, wherein at least one diffusion-controlling means has a cross-sectional shape Reduce the size of one factor to be formed to 10 μm or less Constitute.

  Also in this case, the pulsation (= dynamic pressure) of the exhaust pressure is attenuated by the wall resistance in the diffusion rate controlling means. Specifically, the ratio between the dynamic pressure and the static pressure (dynamic pressure / static pressure) is at a level of 25% or less. Therefore, the shift-up phenomenon of the sensor output due to the fluctuation of the dynamic pressure can be effectively suppressed.

  As described above, according to the gas sensor and the nitrogen oxide sensor according to the present invention, the influence of the pulsation of the exhaust pressure generated in the gas to be measured can be avoided, and the measurement accuracy at the detection electrode is improved. be able to.

Hereinafter, the gas sensor according to the present invention may be used, for example, to measure an exhaust gas of a vehicle or an oxide such as O ₂ , NO, NO ₂ , SO ₂ , CO ₂ , H ₂ O, or a combustible gas such as CO or CnHm contained in the atmosphere. Several embodiments applied to a gas sensor for measurement will be described with reference to FIGS. 1A to 31.

As shown in FIGS. 1A, 1B and 2, the gas sensor 10A according to the first embodiment has, for example, six solid electrolyte layers 12a made of ceramics using an oxygen ion conductive solid electrolyte such as ZrO _2. To 12f are stacked.

  In the sensor element 14, the first and second layers from the bottom are the first and second substrate layers 12a and 12b, and the third and fifth layers from the bottom are the first and second spacer layers 12c and 12c. 12e, and the fourth and sixth layers from the bottom are the first and second solid electrolyte layers 12d and 12f.

  Between the second substrate layer 12b and the first solid electrolyte layer 12d, a space 16 (reference gas introduction space 16) into which a reference gas serving as an oxide measurement reference, for example, the atmosphere, is introduced. The lower surface of the solid electrolyte layer 12d, the upper surface of the second substrate layer 12b, and the side surfaces of the first spacer layer 12c are defined and formed.

  Further, between the lower surface of the second solid electrolyte layer 12f and the upper surface of the first solid electrolyte layer 12d, a first chamber 18 for adjusting the oxygen partial pressure in the gas to be measured, A second chamber 20 for finely adjusting the oxygen partial pressure of the sample and measuring an oxide in the gas to be measured, for example, nitrogen oxide (NOx), is formed.

  In addition, the gas inlet 22 formed at the tip of the sensor element 14 and the first chamber 18 communicate with each other via a first diffusion-controlling part 26, and the first chamber 18 and the second chamber 20 They are communicated via a diffusion control unit 28.

  Here, the first and second diffusion-controlling sections 26 and 28 impart a predetermined diffusion resistance to the gas to be measured introduced into the first chamber 18 and the second chamber 20, respectively. As shown in FIG. 1A, the first diffusion control section 26 is formed by two horizontally long slits 30 and 32. Specifically, the first diffusion-controlling portion 26 has a horizontally elongated opening formed at a front end portion of the second spacer layer 12e and in contact with a lower surface of the second solid electrolyte layer 12f. The first chamber 18 has a slit 30 formed with the same opening width up to 18 and a horizontally long opening formed at the front end portion of the second spacer layer 12e and in contact with the upper surface of the first solid electrolyte layer 12d. Up to the same opening width.

  In the first embodiment, each of the slits 30 and 32 has substantially the same cross-sectional shape, and as shown in FIG. 1A, the vertical length ta is 10 μm or less, and the horizontal length tb is about 2 mm. I have.

The second diffusion control section 28 is also formed by two horizontally long slits 34 and 36 having the same cross-sectional shape as the first diffusion control section 26. A porous body made of ZrO ₂ or the like is filled and arranged in the slits 34 and 36 of the second diffusion-controlling section 28, and the diffusion resistance of the second diffusion-controlling section 28 is equal to that of the first diffusion-controlling section 26. You may make it larger than a diffusion resistance. It is preferable that the diffusion resistance of the second diffusion control part 28 is larger than that of the first diffusion control part 26, but there is no problem if it is small.

  Then, the atmosphere in the first chamber 18 is introduced into the second chamber 20 under a predetermined diffusion resistance through the second diffusion control section 28.

Further, of the lower surface of the second solid electrolyte layer 12f, the entire lower surface to shape the first chamber 18, a flat substantially rectangular porous cermet electrode (for example Pt · ZrO ₂ cermet electrode containing Au1%) Inner pump electrode 40 is formed, and an outer pump electrode 42 is formed in a portion corresponding to the inner pump electrode 40 on the upper surface of the second solid electrolyte layer 12f. An electrochemical pump cell, that is, a main pump cell 44 is constituted by the pump electrode 42 and the second solid electrolyte layer 12f interposed between the electrodes 40 and 42.

  Then, a desired control voltage (pump voltage) Vp1 is applied between the inner pump electrode 40 and the outer pump electrode 42 in the main pump cell 44 through an external variable power supply 46, so that the outer pump electrode 42 and the inner pump electrode 40 are By flowing the pump current Ip1 in the positive direction or the negative direction, oxygen in the atmosphere in the first chamber 18 can be pumped into the external space, or oxygen in the external space can be pumped into the first chamber 18. Has become.

  A reference electrode 48 is formed in a portion of the lower surface of the first solid electrolyte layer 12d exposed to the reference gas introduction space 16, and the inner pump electrode 40, the reference electrode 48, and the second solid electrolyte layer An electrochemical sensor cell, that is, a control oxygen partial pressure detection cell 50 is constituted by 12f, the second spacer layer 12e, and the first solid electrolyte layer 12d.

  The control oxygen partial pressure detection cell 50 is configured to control the inner pump electrode 40 and the reference electrode 48 based on the oxygen concentration difference between the atmosphere in the first chamber 18 and the reference gas (atmosphere) in the reference gas introduction space 16. The oxygen partial pressure of the atmosphere in the first chamber 18 can be detected through an electromotive force V1 generated between the first and second chambers.

  The detected oxygen partial pressure value is used for feedback control of the variable power supply 46. Specifically, the oxygen partial pressure of the atmosphere in the first chamber 18 is controlled by the oxygen partial pressure in the next second chamber 20. The pump operation of the main pump cell 44 is controlled through the main pump feedback control system 52 so that the predetermined value is low enough to perform the following.

  The feedback control system 52 controls the pump voltage between the outer pump electrode 42 and the inner pump electrode 40 so that the difference (detection voltage V1) between the potential of the inner pump electrode 40 and the potential of the reference electrode 48 becomes a predetermined voltage level. It has a circuit configuration for feedback-controlling Vp1. In this case, the inner pump electrode 40 is grounded.

  Therefore, the main pump cell 44 pumps or pumps oxygen out of the gas to be measured introduced into the first chamber 18 by an amount corresponding to the level of the pump voltage Vp1. Then, by repeating the series of operations, the oxygen concentration in the first chamber 18 is feedback-controlled to a predetermined level. In this state, the pump current Ip1 flowing between the outer pump electrode 42 and the inner pump electrode 40 indicates the difference between the oxygen concentration in the gas to be measured and the control oxygen concentration in the first chamber 18, and the oxygen current in the gas to be measured It can be used for measuring the concentration.

The porous cermet electrodes constituting the inner pump electrode 40 and the outer pump electrode 42 are composed of a metal such as Pt and a ceramic such as ZrO _2. For the inner pump electrode 40 disposed in the 18, it is necessary to use a material having reduced or no reduction ability to the NO component in the measurement gas, for example, a compound having a perovskite structure such as La ₃ CuO ₄ , Alternatively, a cermet of a metal having low catalytic activity such as Au and a ceramic, or a cermet of a metal having low catalytic activity such as Au and a Pt group metal and a ceramic is preferable. Further, when an alloy of Au and a Pt group metal is used as the electrode material, the amount of Au added is preferably set to 0.03 to 35 vol% of the entire metal component.

  In the gas sensor 10A according to the first embodiment, the upper surface of the upper surface of the first solid electrolyte layer 12d that forms the second chamber 20, and the upper surface of the second solid electrolyte layer A detection electrode 60 formed of a porous cermet electrode having a substantially rectangular shape in a plane is formed in the separated portion, and an alumina film forming a third diffusion-controlling portion 62 is formed so as to cover the detection electrode 60. . The detection electrode 60, the reference electrode 48, and the first solid electrolyte layer 12d constitute an electrochemical pump cell, that is, a pump cell 64 for measurement.

  The detection electrode 60 is formed of a porous cermet made of a metal capable of reducing NOx as a gas component to be measured and zirconia as a ceramic, and thereby reduces NOx present in the atmosphere in the second chamber 20. In addition to functioning as a NOx reduction catalyst, by applying a constant voltage Vp2 to the reference electrode 48 through a DC power supply 66, oxygen in the atmosphere in the second chamber 20 can be pumped into the reference gas introduction space 16. It has become. The pump current Ip2 flowing by the pump operation of the measuring pump cell 64 is detected by the ammeter 68.

  The constant voltage (direct current) power supply 66 is a voltage having a magnitude that gives a limiting current to pumping of oxygen generated during decomposition by the measurement pump cell 64 under the inflow of NOx restricted by the third diffusion control unit 62. Can be applied.

On the other hand, of the lower surface of the second solid electrolyte layer 12f, the entire surface of the lower surface forming the second chamber 20 is provided with a porous cermet electrode having a substantially rectangular planar shape (for example, a Pt.ZrO ₂ cermet electrode containing Au1%). The auxiliary pump electrode 70 is formed, and the auxiliary pump electrode 70, the second solid electrolyte layer 12f, the second spacer layer 12e, the first solid electrolyte layer 12d, and the reference electrode 48 support the auxiliary pump electrode 70. An electrochemical pump cell, that is, an auxiliary pump cell 72 is formed.

As with the inner pump electrode 40 in the main pump cell 44, the auxiliary pump electrode 70 is made of a material that has reduced or no reduction ability with respect to the NO component in the gas to be measured. In this case, the cermet is composed of a compound having a perovskite structure such as La ₃ CuO ₄ , a cermet of a metal having low catalytic activity such as Au and ceramics, or a cermet of a metal having low catalytic activity such as Au and a Pt group metal and ceramics. Preferably. Further, when an alloy of Au and a Pt group metal is used as the electrode material, the amount of Au added is preferably set to 0.03 to 35 vol% of the entire metal component.

  Then, by applying a desired constant voltage Vp3 between the auxiliary pump electrode 70 and the reference electrode 48 in the auxiliary pump cell 72 through an external DC power supply 74, oxygen in the atmosphere in the second chamber 20 is reduced to the reference gas introduction space. 16 can be pumped out.

  As a result, the oxygen partial pressure of the atmosphere in the second chamber 20 does not substantially reduce or decompose the gas component (NOx) to be measured, and does not substantially affect the measurement of the target component amount. A low oxygen partial pressure value is used. In this case, the change in the amount of oxygen introduced into the second chamber 20 is greatly reduced by the operation of the main pump cell 44 in the first chamber 18 compared to the change in the gas to be measured. The oxygen partial pressure at is precisely and constantly controlled.

  Therefore, in the gas sensor 10 </ b> A according to the first embodiment having the above configuration, the gas to be measured whose oxygen partial pressure is controlled in the second chamber 20 is guided to the detection electrode 60.

  Further, in the gas sensor 10A according to the first embodiment, as shown in FIG. 1, when the gas sensor 10A is sandwiched from above and below by the first and second substrate layers 12a and 12b, heat is generated by external power supply. Heater 80 is embedded. The heater 80 is provided to enhance the conductivity of oxygen ions. On the upper and lower surfaces of the heater 80, in order to obtain electrical insulation from the first and second substrate layers 12a and 12b, An insulating layer 82 of alumina or the like is formed.

  The heater 80 is disposed over the entirety of the first chamber 18 to the second chamber 20, whereby the first chamber 18 and the second chamber 20 are each heated to a predetermined temperature, and the main pump cell 44, The control oxygen partial pressure detection cell 50 and the measurement pump cell 64 are also heated and maintained at a predetermined temperature.

Next, the operation of the gas sensor 10A according to the first embodiment will be described. First, the distal end side of the gas sensor 10A is arranged in the external space, whereby the gas to be measured is introduced into the first chamber 18 under a predetermined diffusion resistance through the first diffusion control part 26 (slits 30 and 32). Is done. The gas to be measured introduced into the first chamber 18 is subjected to an oxygen pumping action caused by application of a predetermined pump voltage Vp1 between the outer pump electrode 42 and the inner pump electrode 40 constituting the main pump cell 44. The oxygen partial pressure is controlled to a predetermined value, for example, 10 ⁻⁷ atm. This control is performed through the feedback control system 52.

  The first diffusion-controlling section 26 narrows down the amount of oxygen in the gas to be measured that diffuses and flows into the measurement space (first chamber 18) when the pump voltage Vp1 is applied to the main pump cell 44, It has the function of suppressing the current flowing through 44.

Further, in the first chamber 18, even under heating by an external gas to be measured and further under a heating environment by a heater 80, a state under an oxygen partial pressure where NOx in the atmosphere is not reduced by the inner pump electrode 40, for example, NO → A situation is established under an oxygen partial pressure at which the reaction of 1 / 2N ₂ + 1 / 2O ₂ does not occur. This is because if NOx in the gas to be measured (atmosphere) is reduced in the first chamber 18, accurate measurement of NOx in the subsequent second chamber 20 cannot be performed. In the first chamber 18, it is necessary to create a situation where NOx cannot be reduced by a component involved in the reduction of NOx (here, the metal component of the inner pump electrode 40). Specifically, as described above, this is achieved by using a material having a low NOx reducing property, for example, an alloy of Au and Pt for the inner pump electrode 40.

  The gas in the first chamber 18 is introduced into the second chamber 20 through the second diffusion-controlling section 28 under a predetermined diffusion resistance. The gas introduced into the second chamber 20 is subjected to an oxygen pumping action caused by application of the voltage Vp3 between the auxiliary pump electrode 70 and the reference electrode 48 constituting the auxiliary pump cell 72, and the oxygen partial pressure is reduced. Fine adjustment is made to a constant low oxygen partial pressure value.

  Similarly to the first diffusion control unit 26, when the voltage Vp3 is applied to the auxiliary pump cell 72, the second diffusion control unit 28 transfers oxygen in the gas to be measured to the measurement space (the second chamber 20). It functions to reduce the amount of diffusion and inflow to suppress the pump current Ip3 flowing through the auxiliary pump cell 72.

  Then, the gas to be measured whose oxygen partial pressure is controlled in the second chamber 20 as described above is guided to the detection electrode 60 through the third diffusion control part 62 under a predetermined diffusion resistance. .

  When the main pump cell 44 is operated to control the oxygen partial pressure of the atmosphere in the first chamber 18 to a low oxygen partial pressure that does not substantially affect the NOx measurement, in other words, the control oxygen partial pressure When the pump voltage Vp1 of the variable power supply 46 is adjusted through the feedback control system 52 so that the voltage V1 detected by the detection cell 50 is constant, the oxygen concentration in the gas to be measured is large, for example, 0 to 20%. When it changes, each oxygen partial pressure of the atmosphere in the second chamber 20 and the atmosphere near the detection electrode 60 usually slightly changes. This is because, when the oxygen concentration in the gas to be measured increases, an oxygen concentration distribution occurs in the width direction and the thickness direction of the first chamber 18, and the oxygen concentration distribution changes according to the oxygen concentration in the gas to be measured. Conceivable.

  However, in the gas sensor 10A according to the first embodiment, the auxiliary pump cell 72 is set in the second chamber 20 so that the oxygen partial pressure of the atmosphere inside the second chamber 20 is always a constant low oxygen partial pressure value. Even if the oxygen partial pressure of the atmosphere introduced from the first chamber 18 to the second chamber 20 changes in accordance with the oxygen concentration of the gas to be measured, the pump operation of the auxiliary pump cell 72 causes The oxygen partial pressure of the atmosphere in the two chambers 20 can always be kept at a constant low value. As a result, the oxygen partial pressure can be controlled to a low oxygen partial pressure value that does not substantially affect the measurement of NOx.

Then, the NOx of the gas to be measured introduced into the detection electrode 60 is reduced or decomposed around the detection electrode 60 to cause, for example, a reaction of NO → １ ／ N ₂ +＋ １O ₂ . At this time, a predetermined voltage Vp2, for example, 430 mV, is applied between the detection electrode 60 and the reference electrode 48 constituting the measurement pump cell 64 in a direction in which oxygen is pumped from the second chamber 20 to the reference gas introduction space 16 side. (700 ° C.).

  Accordingly, the pump current Ip2 flowing through the measurement pump cell 64 is generated by reducing or decomposing NOx in the oxygen concentration in the atmosphere led to the second chamber 20, that is, the oxygen concentration in the second chamber 20 and the detection electrode 60. It is a value proportional to the sum of the calculated oxygen concentration.

  In this case, since the oxygen concentration in the atmosphere in the second chamber 20 is controlled to be constant by the auxiliary pump cell 72, the pump current Ip2 flowing through the measurement pump cell 64 is proportional to the NOx concentration. Become. Further, since the NOx concentration corresponds to the NOx diffusion amount limited by the third diffusion-controlling section 62, even if the oxygen concentration of the gas to be measured greatly changes, the NOx concentration is measured by the measurement pump cell 64. It is possible to accurately measure the NOx concentration through the ammeter 68.

  From this, the pump current value Ip2 in the measurement pump cell 64 almost represents the amount of NOx reduced or decomposed, and therefore does not depend on the oxygen concentration in the gas to be measured.

  By the way, the shift amount usually increases proportionally from the stage where the ratio of dynamic pressure to static pressure (dynamic pressure / static pressure) exceeds about 25% (see FIG. 34). In the gas sensor 10A according to the embodiment, the length ta in the vertical direction, which is one factor forming the cross-sectional shape of the first diffusion-controlling portion 26 (slits 30 and 32), is set to 10 μm or less.

  The limit current value Ip1 in the main pump cell 44 is approximated by the following limit current theoretical formula.

Ip1 ≒ (4F / RT) × D × (S / L) × (POe-POd)
Note that F is a Faraday constant (= 96500 A / sec), R is a gas constant (= 82.05 cm ³ · atm / mol · K), T is an absolute temperature (K), D is a diffusion coefficient (cm ² / sec), S is the cross-sectional area (cm ² ) of the first diffusion control part 26 (slit 30 or 32), L is the path length (cm) of the first diffusion control part 26 (slit 30 or 32), and POe is the external space. The oxygen partial pressure (atm) and POd indicate the oxygen partial pressure (atm) of the first chamber 18.

  The gas sensor 10A according to the first embodiment defines the formation factor of the cross-sectional area S of the first diffusion-controlling portion 26 (slit 30 or 32) in the theoretical formula for limiting current. One factor of the dimension for forming the cross-sectional area S, in this case, the length in the vertical direction is 10 μm or less.

  As a result, the pulsation (= dynamic pressure) of the exhaust pressure is attenuated by the wall resistance in the first diffusion-controlling section 26, and more specifically, the ratio of dynamic pressure to static pressure (dynamic pressure / static pressure) is 25%. Since the level is attenuated to the following level, a shift-up phenomenon of the sensor output (the pump current value Ip2 in the measurement pump cell or the pump current value Ip1 flowing in the main pump cell) due to the fluctuation of the dynamic pressure can be effectively suppressed.

  Here, two experimental examples (referred to as first and second experimental examples for convenience) are shown. The first experimental example is a measurement of how the sensor output changes when the oxygen concentration of the gas to be measured is changed in the example and the comparative example. In the example and the comparative example, how the sensor output changes when the NOx concentration of the gas to be measured is changed is measured.

  The measurement conditions were as follows: a 2.5-liter diesel engine was used as the engine, the number of revolutions was 1,000 to 4,000 rpm, and the engine load was 5 to 20 kgm. Then, the rotation speed, the engine load, and the EGR opening were appropriately changed, and the fluctuation of the sensor output at that time was also measured.

  In the example, similarly to the gas sensor 10A according to the first embodiment, as shown in FIG. 3A, FIG. 3B and FIG. 4, the first diffusion control part 26 is formed by two upper and lower horizontally long slits 30 and 32 ( 5A, 5B and 6 show a comparative example in which the gas sensor 10A according to the first embodiment is configured as shown in FIG. 5A, FIG. 5B and FIG. And the case where the first diffusion-controlling portion 26 is constituted by one slit 100 (length in the horizontal direction 0.2 mm × length in the vertical direction 0.2 mm).

  The experimental results of the first and second experimental examples are shown in FIGS. 7 and 8 (comparative example) and FIGS. 9 and 10 (example). In the comparative example, as shown in FIGS. 7 and 8, the sensor output fluctuates by changing the measurement conditions, and it can be seen that the sensor output fluctuates remarkably especially when the engine load is high.

  This is because, as shown in the waveform diagrams of FIG. 11A and FIG. 11B, the fluctuation of the exhaust pressure near the gas inlet and the fluctuation of the exhaust pressure near the inlet of the first chamber 18 are almost the same, and the measurement conditions change. It is considered that the fluctuation of the exhaust pressure directly affects the sensor output.

  On the other hand, in the embodiment, as shown in FIGS. 9 and 10, the sensor output does not fluctuate even if the measurement conditions are changed, and the sensor output according to the changes in the oxygen concentration and the NOx concentration can be obtained with high accuracy. . This is because the fluctuation of the exhaust pressure near the gas inlet is attenuated by the wall resistance of the first diffusion control part 26 as shown in the waveform diagrams of FIGS. It is considered that the fluctuation of the exhaust pressure of the gas becomes smaller than the fluctuation of the exhaust pressure near the gas inlet.

  As described above, in the gas sensor 10A according to the first embodiment, it is possible to avoid the influence of the pulsation of the exhaust pressure generated in the gas to be measured, and to improve the measurement accuracy of the measurement pump cell 64. Can be.

  Next, some modified examples of the gas sensor 10A according to the first embodiment, that is, modified examples mainly based on the shapes of the first diffusion controlling section 26 and the second diffusion controlling section 28 are shown in FIGS. This will be described with reference to FIG. In FIGS. 13A to 30, illustration of an electric circuit system is omitted to avoid complication of the drawings. Also, components corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description thereof will be omitted.

  First, in the gas sensor 10Aa according to the first modification, as shown in FIGS. 13A, 13B, and 14, the first and second diffusion-controlling units 26 and 28 are respectively formed in one horizontally long slit 110 and 112. It is different in that it is formed.

  Specifically, the first diffusion-controlling portion 26 has a horizontally long opening formed in a front end portion of the second spacer layer 12e and in a portion in contact with the upper surface of the first solid electrolyte layer 12d. The second diffusion-controlling portion 28 is a terminal portion of the first chamber 18 in the second spacer layer 12e and has a first solid electrolyte layer. An opening formed in a portion in contact with the upper surface of 12d has a slit 112 formed with the same opening width up to the second chamber 20. In the first modification, each of the slits 110 and 112 has substantially the same cross-sectional shape, and has a vertical length ta of 10 μm or less and a horizontal length tb of about 2 mm.

  Next, as shown in FIG. 15A, FIG. 15B and FIG. 16, the gas sensor 10Ab according to the second modification has a configuration in which the first and second diffusion-controlling portions 26 and 28 each have one horizontally long wedge-shaped slit 114. And 116.

  Specifically, the first diffusion-controlling portion 26 has an opening width (vertical length) of a horizontally long opening formed at a front end portion of the second spacer layer 12e and at a portion in contact with the upper surface of the first solid electrolyte layer 12d. (Width in the direction) is gradually enlarged toward the first chamber 18 and is formed to have a wedge-shaped slit 114. The second diffusion-controlling part 28 is formed in the first chamber in the second spacer layer 12e. The wedge-shaped slit 116 formed by gradually increasing the opening width of the horizontally long opening formed at the end portion of the portion 18 and the portion in contact with the upper surface of the first solid electrolyte layer 12 d toward the second chamber 20 is formed. It is configured to have.

  In this second modification, the minimum opening at the front end of each of the wedge-shaped slits 114 and 116 has substantially the same cross-sectional shape, a vertical length ta of 10 μm or less, and a horizontal length tb of about 2 mm. It has been.

  Next, in a gas sensor 10Ac according to a third modification, as shown in FIGS. 17A, 17B, and 18, the first diffusion-controlling unit 26 includes three horizontally long slits 118a, 118b, and 118c arranged in parallel. In that the second diffusion-controlling portion 28 is formed by a single horizontally elongated slit 120.

  Specifically, the first diffusion-controlling portion 26 is formed of three horizontally long portions formed in parallel with each other at a front end portion of the second spacer layer 12e and a portion in contact with the upper surface of the first solid electrolyte layer 12d. Are formed to have three slits 118a, 118b, and 118c each having the same opening width up to the first chamber 18, and the second diffusion-controlling portion 28 One slit 120 formed at a terminal end portion of the one chamber 18 and a portion in contact with the upper surface of the first solid electrolyte layer 12 d has the same opening width as the second chamber 20. Is configured. In the third modification, the length ta in the vertical direction of each of the slits 118a, 118b, 118c, and 120 is set to 10 μm or less.

  Next, as shown in FIGS. 19A, 19B, and 20, a gas sensor 10Ad according to a fourth modification includes a space 122 and a buffer space 124 between the gas inlet 22 and the first diffusion-controlling unit 26. Are provided in series, the front opening of the space 122 constitutes the gas inlet 22, and a fourth diffusion resistance is provided between the space 122 and the buffer space 124 for providing a predetermined diffusion resistance to the gas to be measured. In that it has a diffusion-controlling part 126.

  The first diffusion control part 26 and the second diffusion control part 28 are formed by two horizontally long slits 30 and 32 and 34 and 36, respectively, similarly to the gas sensor 10A according to the first embodiment. I have.

  The fourth diffusion-controlling portion 126 has a horizontally elongated opening formed at a terminal portion of the space portion 122 in the second spacer layer 12e and in contact with the lower surface of the second solid electrolyte layer 12f, and is the same as the buffer space 124. And a laterally elongated opening formed at a terminal portion of the space 122 in the second spacer layer 12e and in contact with the upper surface of the first solid electrolyte layer 12d. Up to the same opening width.

  Next, in the gas sensor 10Ae according to the fifth modified example, as shown in FIGS. 21A, 21B, and 22, the first and second diffusion-controlling sections 26 and 28 each have one vertically long slit 132 and The difference is that it is formed at 134.

  Specifically, the first diffusion-controlling portion 26 has a vertically long opening formed at the front end portion of the second spacer layer 12e and substantially at the center in the width direction, and has the same opening width up to the first chamber 18. The second diffusion-controlling portion 28 has a vertically elongated opening formed at the end of the first chamber 18 in the second spacer layer 12e and substantially at the center in the width direction. The second chamber 20 has a slit 134 formed with the same opening width. In the fifth modification, the slits 132 and 134 have substantially the same cross-sectional shape, the vertical length tc is the same as the thickness of the second spacer layer 12e, and the horizontal length td is 10 μm. It is as follows.

  Next, as shown in FIGS. 23A, 23B, and 24, the gas sensor 10Af according to the sixth modified example is such that the first and second diffusion control portions 26 and 28 each have one vertically long wedge-shaped slit 136. And 138.

  Specifically, the first diffusion-controlling portion 26 has a first elongated portion formed at the front end portion of the second spacer layer 12e and substantially at the center in the width direction, and has an opening width (width in the horizontal direction) of the first portion. It has a wedge-shaped slit 136 that is gradually enlarged toward the chamber 18, and the second diffusion-controlling portion 28 is a terminal portion of the first chamber 18 in the second spacer layer 12 e. The opening width (width in the horizontal direction) of the vertically long opening formed substantially at the center in the width direction has a wedge-shaped slit 138 formed so as to gradually increase toward the second chamber 20.

  In the sixth modification, the minimum opening at the front end of each of the wedge-shaped slits 136 and 138 has substantially the same cross-sectional shape, and the vertical length tc is the same as the thickness of the second spacer layer 12e. , The horizontal length td is set to 10 μm or less.

  Next, in a gas sensor 10Ag according to a seventh modification, as shown in FIGS. 25A, 25B, and 26, the first diffusion-controlling portion 26 is formed by one planar, substantially hourglass-shaped slit 140. The difference is that the two diffusion-controlling portions 28 are formed by one vertically elongated slit 142.

  Specifically, the first diffusion-controlling portion 26 is configured such that the opening width (width in the horizontal direction) of the horizontally long opening formed at the front end portion of the second spacer layer 12 e is in the depth direction of the first diffusion-controlling portion 26. The slit 144 is gradually reduced toward the center to form a vertically elongated slit 144, and the opening width (width in the horizontal direction) of the slit 144 is gradually increased toward the first chamber 18. Is provided.

  On the other hand, the second diffusion-controlling portion 28 has a vertically elongated opening formed at the terminal end of the first chamber 18 in the second spacer layer 12e and substantially at the center in the width direction thereof, and has the same opening width up to the second chamber 20. Is formed.

  In the seventh modification, the minimum opening (slit 144) of the hourglass-shaped slit 140 forming the first diffusion-controlling portion 26 and the slit 142 forming the second diffusion-controlling portion 28 have substantially the same cross-sectional shape. The vertical length tc is the same as the thickness of the second spacer layer 12e, and the horizontal length td is 10 μm or less.

  Next, in a gas sensor 10Ah according to an eighth modification, as shown in FIGS. 27A, 27B, and 28, the first diffusion-controlling portion 26 includes five vertically long slits 146a to 146e formed in parallel with each other. And that the second diffusion-controlling portion 28 is formed by one vertically elongated slit 148.

  Specifically, the first diffusion-controlling portion 26 has five vertically long openings formed in parallel at the front end portion of the second spacer layer 12 e with the same opening width up to the first chamber 18. The second diffusion-controlling portion 28 is formed at the terminal end portion of the first chamber 18 in the second spacer layer 12e and substantially at the center in the width direction thereof. The vertically long opening has a single slit 148 formed with the same opening width up to the second chamber 20. In the eighth modification, each of the slits 146a to 146e and 148 has a horizontal length td of 10 μm or less.

  Next, a gas sensor 10Ai according to a ninth modification includes a space 122 and a buffer space 124 between the gas inlet 22 and the first diffusion control part 26, as shown in FIGS. 29A, 29B and 30. Are provided in series, the front opening of the space 122 constitutes the gas inlet 22, and a fourth diffusion resistance is provided between the space 122 and the buffer space 124 for providing a predetermined diffusion resistance to the gas to be measured. In that it has a diffusion-controlling part 126.

  The first diffusion-controlling portion 26 and the second diffusion-controlling portion 28 each have one longitudinal slit 132 and a single longitudinal slit 132, similarly to the gas sensor 10Ae according to the fifth modification (see FIGS. 21A, 21B, and 22). 134.

  The fourth diffusion-controlling portion 126 has a vertically elongated opening substantially at the center of the second spacer layer 12e in the width direction at the terminal portion of the space portion 122e and the same opening width up to the buffer space 124. It has a slit 150.

  In the gas sensors 10Aa to 10Ai according to the first to ninth modified examples, similarly to the gas sensor 10A according to the first embodiment, it is possible to avoid the influence of the pulsation of the exhaust pressure generated in the gas to be measured. Thus, the measurement accuracy of the measurement pump cell 64 can be improved.

  In particular, in the gas sensors 10Ad and 10Ai according to the fourth and ninth modified examples, the buffer space 124 is provided before the first diffusion control part 26. Normally, oxygen rushes into the sensor element 14 through the gas inlet 22 due to the pulsation of the exhaust pressure in the external space. However, the oxygen from the external space does not directly enter the processing space but the buffer space in the preceding stage. 124. That is, the rapid change in the oxygen concentration due to the pulsation of the exhaust pressure is canceled by the buffer space 124, and the influence of the pulsation of the exhaust pressure on the first chamber 18 is almost negligible.

  As a result, the correlation between the oxygen pumping amount in the main pump cell 44 in the first chamber 18 and the oxygen concentration in the gas to be measured is improved, and the measurement accuracy in the measurement pump cell 64 is improved. For example, the first chamber 18 can also be used as a sensor for obtaining an air-fuel ratio.

  In the gas sensors 10Ad and 10Ai according to the fourth and ninth modified examples, the space 122 and the buffer space 124 are provided in series between the gas inlet 22 and the first diffusion-controlling unit 26, The gas inlet 22 is formed by the front opening of the portion 122. The space portion 122 functions as a clogging prevention portion for preventing particulate matter (soot, oil combustion material, etc.) generated in the gas to be measured in the external space from being clogged near the entrance of the buffer space 124. Accordingly, the measurement pump cell 64 can measure the NOx component with higher accuracy, and can maintain a high-accuracy state for a long period of time.

  The gas sensor 10A according to the above-described first embodiment and the gas sensors 10Aa to 10Ad according to the first to fourth modified examples are configured such that the first and second diffusion-controlling portions 26 and 28 are configured by horizontally long slits. In the gas sensors 10Ae to 10Ai according to the ninth to the ninth modified examples, the first and second diffusion control sections 26 and 28 are configured by vertically long slits. For example, the first diffusion control section 26 is formed by a horizontally long slit. And the second diffusion-controlling section 28 may be constituted by a vertically long slit, or the reverse arrangement may be adopted.

  The shape of the first and second diffusion-controlling portions 26 and 28 does not have to be a slit shape, and it is sufficient if one factor constituting the cross-sectional area is 10 μm or less. The same effect can be obtained by forming a cylindrical diffusion-controlling portion of 10 μm or less.

  Next, a gas sensor 10B according to a second embodiment will be described with reference to FIG. Components corresponding to those in FIG. 2 are denoted by the same reference numerals, and redundant description is omitted.

  The gas sensor 10B according to the second embodiment has substantially the same configuration as the gas sensor 10A according to the first embodiment (see FIG. 2) as shown in FIG. The difference is that a measurement oxygen partial pressure detection cell 160 is provided.

  The measurement oxygen partial pressure detection cell 160 includes a detection electrode 162 formed on an upper surface of the first solid electrolyte layer 12d which forms the second chamber 20, and a lower surface of the first solid electrolyte layer 12d. And the first solid electrolyte layer 12d sandwiched between the two electrodes 162 and 48.

  In this case, the oxygen concentration difference between the atmosphere around the detection electrode 162 and the atmosphere around the reference electrode 48 between the detection electrode 162 and the reference electrode 48 in the measurement oxygen partial pressure detection cell 160 is determined. An electromotive force (electromotive force of oxygen concentration cell) V2 is generated.

  Therefore, by measuring the electromotive force (voltage) V2 generated between the detection electrode 162 and the reference electrode 48 with the voltmeter 164, the oxygen partial pressure of the atmosphere around the detection electrode 162, in other words, the measured gas An oxygen partial pressure defined by oxygen generated by reduction or decomposition of the component (NOx) is detected as a voltage value V2.

  Also in the gas sensor 10B according to the second embodiment, the pulsation (= dynamic pressure) of the exhaust pressure is attenuated by the wall resistance in the first diffusion-controlling section 26, and thus the sensor output (measurement The shift-up phenomenon of the pump current value in the pump cell can be effectively suppressed. As a result, the influence of the pulsation of the exhaust pressure generated in the gas to be measured can be avoided, and the measurement accuracy in the measurement oxygen partial pressure detection cell 160 can be improved.

  The configuration of the gas sensors 10Aa to 10Ai according to the first to ninth modifications can also be adopted in the gas sensor 10B according to the second embodiment.

In the gas sensors 10A and 10B (including the respective modifications) according to the first and second embodiments, oxygen and NOx are targeted as the gas components to be measured. Can be effectively applied to the measurement of a bound oxygen-containing gas component other than NOx, such as H ₂ O or CO ₂ , which is affected by the above.

For example the CO ₂ and H ₂ O ₂ to O were generated by electrolysis and gas sensor pumped composed oxygen pump, and H ₂ generated by electrolyzing with H ₂ O using proton ion conductive solid electrolyte pumping The present invention can also be applied to a gas sensor to be processed.

  Note that the gas sensor and the nitrogen oxide sensor according to the present invention are not limited to the above-described embodiment, but may adopt various configurations without departing from the gist of the present invention.

FIG. 1A is a front view showing the configuration of the gas sensor according to the first embodiment, and FIG. 1B is a plan view thereof. It is sectional drawing on the II-II line in FIG. 1B. FIG. 3A is a front view showing the configuration of the embodiment used in the first and second experimental examples, and FIG. 3B is a plan view thereof. FIG. 4 is a perspective view of a configuration of an example used in first and second experimental examples, particularly, a configuration of first and second diffusion-controlling portions. FIG. 5A is a front view showing a configuration of a comparative example used in the first and second experimental examples, and FIG. 5B is a plan view thereof. FIG. 9 is a perspective view illustrating a configuration of a comparative example used in first and second experimental examples, particularly, a configuration of first and second diffusion control units. FIG. 9 is a characteristic diagram illustrating a change in sensor output with respect to oxygen concentration when measurement conditions are changed in a comparative example. FIG. 9 is a characteristic diagram showing a change in sensor output with respect to a NOx concentration when a measurement condition is changed in a comparative example. FIG. 7 is a characteristic diagram illustrating a change in sensor output with respect to an oxygen concentration when a measurement condition is changed in the example. FIG. 9 is a characteristic diagram illustrating a change in sensor output with respect to a NOx concentration when a measurement condition is changed in the example. FIG. 11A is a waveform diagram showing a change in exhaust pressure near the gas inlet in the comparative example, and FIG. 11B is a waveform diagram showing a change in exhaust pressure near the inlet of the first chamber. FIG. 12A is a waveform diagram showing a change in exhaust pressure near the gas inlet in the embodiment, and FIG. 12B is a waveform diagram showing a change in exhaust pressure near the inlet of the first chamber. FIG. 13A is a front view illustrating a configuration of a gas sensor according to a first modification, and FIG. 13B is a plan view thereof. It is sectional drawing on the XIV-XIV line in FIG. 13B. FIG. 15A is a front view illustrating a configuration of a gas sensor according to a second modification, and FIG. 15B is a plan view thereof. It is sectional drawing on the XVI-XVI line in FIG. 15B. FIG. 17A is a front view illustrating a configuration of a gas sensor according to a third modification, and FIG. 17B is a plan view thereof. It is sectional drawing on the XVIII-XVIII line in FIG. 17B. FIG. 19A is a front view illustrating a configuration of a gas sensor according to a fourth modification, and FIG. 19B is a plan view thereof. It is sectional drawing on the XX-XX line in FIG. 19B. FIG. 21A is a front view showing a configuration of a gas sensor according to a fifth modification, and FIG. 21B is a plan view thereof. It is sectional drawing on the XXII-XXII line in FIG. 21B. FIG. 23A is a front view illustrating a configuration of a gas sensor according to a sixth modification, and FIG. 23B is a plan view thereof. It is sectional drawing on the XXIV-XXIV line in FIG. 23B. FIG. 25A is a front view illustrating a configuration of a gas sensor according to a seventh modification, and FIG. 25B is a plan view thereof. It is sectional drawing on the XXVI-XXVI line in FIG. 25B. FIG. 27A is a front view illustrating a configuration of a gas sensor according to an eighth modification, and FIG. 27B is a plan view thereof. FIG. 27 is a sectional view taken along line XXVIII-XXVIII in FIG. 27B. FIG. 29A is a front view illustrating a configuration of a gas sensor according to a ninth modification, and FIG. 29B is a plan view thereof. It is sectional drawing on the XXX-XXX line in FIG. 29B. It is a sectional view showing the composition of the gas sensor concerning a 2nd embodiment. FIG. 10 is a characteristic diagram showing a change in sensor output with respect to an oxygen concentration of a conventional gas sensor. FIG. 2 is an explanatory diagram showing the total pressure of exhaust gas of an automobile engine. FIG. 9 is a characteristic diagram illustrating a shift amount of a sensor output with respect to a ratio between a dynamic pressure and a static pressure (dynamic pressure / static pressure).

Explanation of reference numerals

10A, 10Aa to 10Ai, 10B ... gas sensor 14 ... sensor element 18 ... first chamber 20 ... second chamber 22 ... gas inlet 26 ... first diffusion control part 28 ... second diffusion control part 30, 32, 34, 36A: slit 44: main pump cell 64: measuring pump cell 72: auxiliary pump cell 100, 110, 112: slit 114, 116: wedge-shaped slits 118a to 118c, 120: slit 122: space 124: buffer space 126: fourth Diffusion controlling parts 128, 130, 132, 134: slits 136, 138: wedge-shaped slit 140: hourglass-shaped slits 142, 144, 146a to 146e, 148, 150: slit 160: oxygen partial pressure detection cell for measurement

Claims (10)

A gas sensor for measuring the amount of the gas component to be measured in the gas to be measured in the external space, at least,
A solid electrolyte in contact with the external space,
An internal space formed inside the solid electrolyte,
Diffusion-controlled means formed by a slit for introducing the gas to be measured under a predetermined diffusion resistance from the external space via a gas inlet,
An inner pump electrode and an outer pump electrode formed inside and outside the internal space, and based on a control voltage applied between the electrodes, oxygen contained in the gas to be measured introduced from the external space is applied. And a pump means for performing a pumping process.
A dimension of one factor forming a cross-sectional shape of the diffusion-controlling means is 10 μm or less. The gas sensor according to claim 1,
When the cross-sectional shape of the diffusion control means is formed by at least one horizontal slit, the one factor is a vertical length of the slit. The gas sensor according to claim 1,
When the cross-sectional shape of the diffusion-controlling means is formed by at least one vertical slit, the one factor is a horizontal length of the slit. The gas sensor according to any one of claims 1 to 3,
A gas sensor, wherein a buffer space is provided between the gas inlet and the diffusion control means. The gas sensor according to claim 4,
A clogging prevention part and a buffer space are provided in series between the gas inlet and the internal space,
Constituting the gas inlet with the front opening of the clogging prevention unit,
A gas sensor, characterized in that a diffusion-controlling part for providing a predetermined diffusion resistance to the gas to be measured is provided between the clogging prevention part and the buffer space. The gas sensor according to any one of claims 1 to 5,
The pump means performs a pumping process on oxygen contained in the gas to be measured from the external space introduced into the internal space, and a predetermined gas component in the gas to be measured changes an oxygen partial pressure in the internal space. A gas sensor controlled to a predetermined value that cannot be decomposed. The gas sensor according to claim 6,
A measuring pump means for decomposing a predetermined gas component contained in the gas to be measured after being pumped by the pump means by catalytic action and / or electrolysis, and for pumping oxygen generated by the decomposition; A gas sensor, wherein the predetermined gas component in the gas to be measured is measured based on a pump current flowing through the measuring pump means by a pumping process of the measuring pump means. The gas sensor according to claim 6,
A predetermined gas component contained in the gas to be measured after being subjected to the pumping treatment by the pump means is decomposed by a catalytic action, and according to a difference between the amount of oxygen generated by the decomposition and the amount of oxygen contained in the reference gas. Oxygen pressure detecting means for generating an electromotive force,
A gas sensor, wherein the predetermined gas component in the measured gas is measured based on an electromotive force detected by the oxygen partial pressure detecting means. A nitrogen oxide sensor for measuring the amount of the nitrogen oxide component in the gas to be measured in the external space, at least,
A substrate made of an oxygen ion conductive solid electrolyte in contact with the external space,
A first internal cavity formed in the solid electrolyte and communicating with the external space;
First diffusion limiting means formed by a slit for introducing the gas to be measured into the first internal space under a predetermined diffusion resistance;
A first inner pump electrode and a first outer pump electrode formed inside and outside the first internal space, and oxygen contained in the gas to be measured introduced from the external space is supplied between the electrodes. Main pump means for performing a pumping process based on a control voltage applied to the first internal space to control the oxygen partial pressure in the first internal space to a predetermined value at which NO can be substantially not decomposed;
A second internal space communicating with the first internal space;
A second diffusion-controlling means formed by a slit for introducing an atmosphere pumped in the first internal space into the second internal space under a predetermined diffusion resistance;
It has a second inner pump electrode and a second outer pump electrode formed inside and outside the second internal space, and contains NO contained in the atmosphere introduced from the first internal space. A measuring pump means for decomposing by catalytic action and / or electrolysis and pumping oxygen generated by the decomposition;
In a nitrogen oxide sensor for measuring the amount of nitrogen oxides in the gas to be measured based on a pump current flowing through the pump for measurement by the pumping process of the pump for measurement,
A nitrogen oxide sensor characterized in that at least one dimension forming a cross-sectional shape of one diffusion-controlling means is 10 μm or less. A nitrogen oxide sensor for measuring the amount of the nitrogen oxide component in the gas to be measured in the external space, at least,
A substrate made of an oxygen ion conductive solid electrolyte in contact with the external space,
A first internal cavity formed in the solid electrolyte and communicating with the external space;
First diffusion limiting means formed by a slit for introducing the gas to be measured into the first internal space under a predetermined diffusion resistance;
A first inner pump electrode and a first outer pump electrode formed inside and outside the first internal space, and oxygen contained in the gas to be measured introduced from the external space is supplied between the electrodes. Main pump means for performing a pumping process based on a control voltage applied to the first internal space to control the oxygen partial pressure in the first internal space to a predetermined value at which NO can be substantially not decomposed;
A second internal space communicating with the first internal space;
A second diffusion-controlling means formed by a slit for introducing an atmosphere pumped in the first internal space into the second internal space under a predetermined diffusion resistance;
It has a second inner measurement electrode and a second outer measurement electrode formed inside and outside the second internal space, and includes NO contained in the atmosphere introduced from the first internal space. Comprising oxygen partial pressure detection means for generating an electromotive force in accordance with the difference between the amount of oxygen generated by the decomposition and the amount of oxygen contained in the reference gas,
In a nitrogen oxide sensor that measures the amount of nitrogen oxide in the gas to be measured based on the electromotive force detected by the oxygen partial pressure detection means,
A nitrogen oxide sensor characterized in that at least one dimension forming a cross-sectional shape of one diffusion-controlling means is 10 μm or less.

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