KR20160054707A - A nitrogen oxide sensor - Google Patents

Abstract

A nitrogen oxide sensor is provided. Wherein the nitrogen oxide sensor includes a solid electrolyte layer and a solid electrolyte layer, the solid oxide fuel cell including a solid electrolyte layer and a solid electrolyte layer, the solid oxide electrolyte layer including an inlet surface through which an exhaust gas flows in and a outlet surface through which exhaust gas is discharged, An inner pumping electrode formed in the first cavity, and an outer pumping electrode formed in a position different from the first cavity, the first pumping electrode being connected to the first pumping electrode and the second pumping electrode, A first pumping electrode that controls the voltage between the inner pumping electrode and the outer pumping electrode to remove oxygen in the exhaust gas, a second pumping electrode that communicates with the first cavity to decompose the nitrogen oxide that has passed through the first cavity into nitrogen and oxygen ions A reference electrode formed in a second cavity, a detection electrode formed in the second cavity, and an air duct formed at a position different from the second cavity and having one end communicating with the atmosphere, Also to, and measure the concentration of NOx from the current by controlling the voltage between the detecting electrode and the reference electrode is generated by detecting the movement of oxygen ion electrode.

Description

[0001] The present invention relates to a nitrogen oxide sensor,

The present invention relates to a nitrogen oxide sensor.

The nitrogen oxide gas is indicated as NOx including nitrogen monoxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O) and the like. Among them, nitrogen monoxide occupies about 80% of nitrogen oxides, and nitrogen monoxide and nitrogen dioxide occupy the majority of nitrogen oxide gas.

In order to prevent global warming caused by fossil fuels, there is an increasing demand for suppressing the emission of carbon dioxide, and it is necessary to improve fuel efficiency in response to this. With this demand, researches on nitrogen oxide sensors are increasing.

As a method for measuring the concentration of the conventional nitrogen oxide gas, there are a method using equilibrium potential, a method of measuring an oxygen current by decomposition of NOx gas, and a mixed potential method.

In the method using the equilibrium potential, the electrochemical cell forms a noble metal electrode that forms a solid state nitrate in the solid electrolyte as a sensing electrode and keeps the activity of ions in the solid electrolyte constant as a noble metal electrode, and uses the electromotive force generated in the electrochemical cell To measure the concentration of nitrogen oxides.

The method of measuring the oxygen current by the decomposition of NOx gas is a method of measuring the nitrogen oxide concentration by measuring the current by the oxygen ions obtained by decomposing the NOx gas using the pumping cell.

In the mixed potential method, a sensing electrode is formed of a metal oxide on one surface of a solid electrolyte, and a reference electrode is formed on the other surface of the solid electrolyte to measure a potential difference between the sensing electrode and the reference electrode. At this time, the sensing electrode has reactivity to nitrogen oxide and oxygen, but the reference electrode has reactivity only to oxygen, and a potential difference is generated between the sensing electrode and the reference electrode according to the concentration of nitrogen oxide contained in the gas. By measuring the potential difference, The concentration is measured.

However, the conventional nitrogen oxide sensor has a serious problem in performance when a small amount of harmful substances are introduced from the outside.

JP 2873250 B1

An object of the present invention is to provide an oxide sensor that can prevent the inflow of harmful substances present in the exhaust gas and reduce the non-uniformity of the signal due to the pulsation of the exhaust gas.

According to an aspect of the present invention, there is provided a solid electrolytic capacitor comprising: a solid electrolyte layer; a solid electrolyte layer disposed on one end of the solid electrolyte layer and including an inlet surface through which exhaust gas from the outside flows and a discharge surface through which exhaust gas is discharged; A first cavity communicating with the first diffusion passage and controlling an oxygen partial pressure in exhaust gas passing through the first diffusion passage, an inner pumping electrode formed in the first cavity, and a second cavity formed in the first cavity, A first pumping electrode connected to the first cavity to control the voltage between the inner pumping electrode and the outer pumping electrode to remove oxygen in the exhaust gas, and an outer pumping electrode formed at a position different from the first cavity, A second cavity for decomposing the nitrogen oxide which has passed through the first cavity into nitrogen and oxygen ions, a detection electrode formed in the second cavity, And a reference electrode provided at an other position in the air duct and having one end communicating with the atmospheric air to control the voltage between the detection electrode and the reference electrode to move the oxygen ion from the current generated by the detection electrode A nitrogen oxide sensor for measuring the concentration of nitrogen oxide is provided.

The ratio of the area of the inflow surface to the area of the discharge port may be 5: 1 or more and 50: 1 or less.

Further, the first diffusion passage may have a trumpet shape.

In addition, a reducing agent may be contained in the first diffusion passage to reduce nitrogen dioxide to nitrogen monoxide.

In addition, the heater may include a heater portion disposed inside the solid electrolyte layer.

Further, the first diffusion passage may be made of a porous solid electrolyte.

Also, a second pumping electrode formed in the second cavity may be included to control the voltage between the outer pumping electrode and the second pumping electrode to remove oxygen in the exhaust gas.

The inner pumping electrode may include a first electrode disposed on one side of the first cavity to remove oxygen and a second electrode disposed on the other side of the first cavity and connected to the first electrode, So that the oxygen in the exhaust gas can be removed.

And a second diffusion passage connected to the first cavity at one end and connected to the second cavity to lead the exhaust gas passed through the first cavity to the second cavity under a predetermined diffusion resistance have.

The solid electrolyte layer may be formed of a plurality of substrate layers.

The nitrogen oxide sensor according to an embodiment of the present invention may have a different area between the inlet and outlet sides of the first diffusion path to increase the collection of external harmful substances and reduce the unevenness of the signal due to the pulsation of the exhaust gas .

1 is a plan view of a nitrogen oxide sensor according to an embodiment of the present invention.
2 is a cross-sectional view taken along line AA in Fig.
3 is a cross-sectional view showing a modified example of a cross section taken along line AA in Fig.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In this specification, the terms "comprises" or "having" and the like refer to the presence of stated features, integers, steps, operations, elements, components, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, where a section such as a layer, a film, an area, a plate, or the like is referred to as being "on" another section, it includes not only the case where it is "directly on" another part but also the case where there is another part in between. On the contrary, where a section such as a layer, a film, an area, a plate, etc. is referred to as being "under" another section, this includes not only the case where the section is "directly underneath"

1 and 2, a nitrogen oxide sensor 1 according to an embodiment of the present invention includes a first diffusion passage 5, a first cavity 7, a first pumping electrode 15, a second diffusion The reference electrode 23, the solid electrolyte layer 3, the heater unit 27, the air duct 13, the first cavity 11, the second cavity 11, the second pumping electrode 25, the detection electrode 21, . ≪ / RTI >

The nitrogen oxide sensor 1 according to an embodiment of the present invention increases the amount of impurities in the exhaust gas (hereinafter referred to as poisoning substances) by varying the area of the inlet surface and the exhaust surface of the first diffusion passage 5 It is possible to prevent the entry of poisonous substances.

Referring to FIGS. 1 to 3, the solid electrolyte layer 3 may be formed by stacking one layer or a plurality of substrate layers 3a to 3f in a rectangular shape having a flat plate shape in that order.

The solid electrolyte layer 3 includes a first substrate layer 3a, a second substrate layer 3b, a third substrate layer 3c, a fourth substrate layer 3d, 5 substrate layer 3e, and a sixth substrate layer 3f may be stacked, but the present invention is not limited thereto.

The solid electrolyte layer 3 can be produced by using an oxygen ion conductive solid electrolyte such as zirconium oxide and integrally sintering a stack of solid electrolyte layers.

At this time, oxygen is pumped through the solid electrolyte layer 3 because the electrolyte can be conducted to the oxide ions. Further, the solid electrolyte layer 3 is not shown between the respective layers, but an insulating layer is laminated so that the solid electrolyte layer 3 is not denatured by electricity or heat.

In one embodiment of the present invention, the first diffusion passage 5 is formed at the left end of the solid electrolyte layer through which the exhaust gas first passes, for example, as shown in Fig. 3, a fifth substrate layer 3e But it is not limited thereto.

1 and 2, the first diffusion passage 5 is exposed to the outside where the exhaust gas is introduced at one end and communicated with the first cavity 7 at the other end, and the exhaust gas containing nitrogen oxide The gas can be drawn into the first cavity 7.

At this time, the sensitivity of the nitrogen oxide concentration detection can be adjusted by changing the cross-sectional area, the shape of the cross-section, the length, and the like.

On the other hand, the first diffusion passage 5 is a porous solid electrolyte, which prevents the poisoning substances and the like from being introduced into the nitrogen oxide sensor according to the embodiment of the present invention by the diffusion resistance of the porous body, It is possible to reduce the non-uniformity of the signal caused by the signal.

As shown in FIGS. 1 and 2, the first diffusion passage 5 may have a circular or rectangular shape and a trumpet shape in cross section, but the present invention is not limited thereto. The first diffusion passage 5 may be formed by stacking sheets and includes pores 5c can do.

Therefore, if the diameter of the pores 5c is large, the diffusion rate of the exhaust gas increases. If the diameter of the pores is small, the first diffusion passage 5 reduces the diffusion rate of the exhaust gas, Can be adjusted.

The first diffusion passage 5 has an inlet surface 5a exposed to an exhaust gas outside and an exhaust gas inlet 5b connected to the first cavity 7 to discharge the exhaust gas to the first cavity 7 ).

At this time, the first diffusion passage 5 prevents the poisoning substances and the like from flowing into the nitrogen oxide sensor 1 by making the area of the inlet surface 5a larger than the area of the discharge surface 5b, 1) can be maintained.

The first diffusion passage 5 of the nitrogen oxide sensor 1 according to an embodiment of the present invention may have a ratio of the area of the inflow surface 5a to the area of the discharge surface 5b of 5: But is not limited thereto. Thereby increasing the amount of poisonous substances or the like collected in the first diffusion passage (5).

A reducing agent may be contained in the first diffusion passage 5 to improve the accuracy of the nitrogen oxide concentration measurement. At this time, since the nitrogen dioxide has a molecular weight larger than that of the nitrogen monoxide, the diffusion rate is slow and causes the inaccuracy of the measurement of the nitrogen oxide concentration, so that the reducing agent reduces nitrogen dioxide to nitrogen monoxide. Therefore, the reducing agent contained in the first diffusion passage 5 can improve the measurement sensitivity of the nitrogen oxide concentration.

Referring to FIG. 2, the first cavity 7 is formed to extend rightward from one end of the first diffusion passage 5, which is the direction of diffusion of the exhaust gas, .

The oxygen partial pressure of the first cavity 7 is controlled by controlling the voltage between the inner pumping electrode and the outer pumping electrode 19 so that the voltage between the inner pumping electrode 17 and the reference electrode 23 is a constant value The oxygen partial pressure in the exhaust gas flowing into the second cavity 11 is made constant.

Referring to FIG. 2, in the first cavity 7, the concentration of oxygen remaining in the exhaust gas can be reduced to a certain level or less through the first pumping electrode 15. Wherein the first pumping electrode 15 may include an inner pumping electrode 17 and an outer pumping electrode 19 and controls the voltage for pumping the oxygen component in the exhaust gas.

At this time, the inner pumping electrode 17 and the outer pumping electrode 19 may be connected to each other to form the first pumping electrode 15. The first pumping electrode 15 reduces oxygen partial pressure by removing oxygen from the exhaust gas.

At this time, if the oxygen present in the exhaust gas is not sufficiently removed from the first pumping electrode 15, the oxygen reaches the detection electrode 21 and is ionized to act as noise. Therefore, the concentration of nitrogen oxides can be measured to be larger than actual.

On the other hand, when oxygen existing in the exhaust gas is excessively removed from the first pumping electrode 15, nitrogen oxide is reduced in the inner pumping electrode 17 or the second pumping electrode 25 and decomposed into nitrogen and oxygen to act as noise .

Referring to FIG. 2, in one embodiment of the present invention, the inner pumping electrodes 17 are arranged in pairs on the upper and lower sides of the first cavity 7 through which the exhaust gas flows through the first diffusion passage 5 But not limited thereto, and may be disposed only on one side of the first cavity, for example, on the upper side or the lower side.

2, the inner pumping electrode 17 may include a first electrode 17a provided on the upper side of the first cavity 7 and a second electrode 17b provided on the lower side. Of the porous cermet electrode.

Also, in one embodiment of the present invention, the inner pumping electrode 17 may include a connecting electrode 17c connecting the first electrode 17a and the second electrode 17b. In this case, oxygen may be pumped by the first electrode 17a and current may flow between the second electrode 17b and the outer pumping electrode 19 as an embodiment.

The outer pumping electrode 19 may correspond to the inner pumping electrode 17, that is, the first electrode 17a or the second electrode 17b, and may be disposed in contact with the upper surface of the solid electrolyte layer 3, Shape. At this time, the inner pumping electrode 17 and the outer pumping electrode 19 may be used as a material having a weak or no reducing ability for nitrogen oxides.

At this time, a predetermined voltage is applied from an external variable power source between the inner pumping electrode 17 and the outer pumping electrode 19 to cause a current to flow from the outer pumping electrode 19 to the inner pumping electrode 17, The oxygen in the cavity 7 can be poured into the outer space.

The first pumping electrode 15 is also capable of pumping oxygen present in the exhaust gas of the first cavity 7 by energization between the inner pumping electrode 17 and the outer pumping electrode 19, So as to lower the oxygen partial pressure of the gas inside the first cavity 7.

2, in an embodiment of the present invention, the second diffusion passage 9 is connected to the first cavity at one end to introduce the gas that has passed through the first cavity 7, and the other end is connected to the second cavity 11, And directs the exhaust gas to the second cavity 11 under a predetermined diffusion resistance.

Referring to FIGS. 1 and 2, the second diffusion passage 5 is a porous solid electrolyte, and it is possible to prevent the poisoning substances and the like from flowing into the nitrogen oxide sensor by the diffusion resistance of the porous body.

Meanwhile, the second diffusion passage 9 may have a circular or rectangular cross section, but the present invention is not limited thereto. The second diffusion passage 9 may be formed by stacking sheets and may include pores 9a therein.

Accordingly, if the diameter of the pores 9a is large, the second diffusion passage 9 increases the diffusion speed of the exhaust gas and decreases the diffusion speed of the exhaust gas when the diameter of the pores is small, Can be adjusted.

At this time, the second diffusion passage 9 can control the detection sensitivity of the nitrogen oxide concentration by changing the cross-sectional area, the shape of the cross-section, the length, and the like.

2 and 3, in an embodiment of the present invention, the second cavity 11 may extend in the right direction from the second diffusion passage 9 and may have a rectangular or circular cross section, but not limited thereto Do not. At this time, the second cavity (11) is a space for finely adjusting the oxygen partial pressure with respect to the gas that has passed through the second diffusion passage (9).

The nitrogen oxide sensor 1 according to an exemplary embodiment of the present invention may have a structure in which the voltage between the second pumping electrode 25 and the reference electrode 23 is a constant value between the outer pumping electrode 19 and the inner pumping electrode 17 So that the oxygen partial pressure in the second cavity 11 is constant.

At this time, the oxygen partial pressure can be kept constant by removing oxygen to the extent that the nitrogen oxide is not reduced.

Meanwhile, in one embodiment of the present invention, the detection electrode 21 includes a nitrogen oxide reduction catalyst so that the nitrogen oxide is decomposed into nitrogen and oxygen. At this time, oxygen is ionized and reaches the reference electrode by the voltage caught between the detection electrode 21 and the reference electrode 23.

The concentration of nitrogen oxide can be measured from the current (Ip) generated by the movement of such oxygen ions. At this time, the value of the current Ip changes depending on the concentration of nitrogen oxide.

2, the air duct 13 is located at the right end of the solid electrolyte layer 3, for example, at the right end of the third substrate layer 3c, as shown in Fig. 3, (7) and the second cavity (11). At this time, the air duct 13 is formed to extend in the longitudinal direction, and one end of the air duct 13 can communicate with the atmosphere.

Although the air duct 13 is not shown in the area where it is in contact with the atmosphere, an opening may be formed, and the atmosphere, which is the reference gas, may be introduced into the air duct 13 through the opening.

1 to 3, in an embodiment of the present invention, the detection electrode 21 is formed on the lower surface of the second cavity 11, for example, on the fourth substrate layer 3d, But it is not limited thereto.

The detection electrode 21 may contain a catalyst capable of reducing nitrogen oxides and may be formed of a porous cermet electrode. At this time, cermet is a sintered material composed of a combination of ceramics and metal.

On the other hand, the detection electrode 21 can also function as a reduction catalyst capable of reducing the nitrogen oxide present in the gas of the second cavity 11. Through this, nitrogen oxides are decomposed into nitrogen and oxygen, and then oxygen is generated.

Referring to FIG. 2, in one embodiment of the present invention, the reference electrode 23 serves as a reference for the oxygen concentration partial pressure measurement, and the upper side of the air duct 13, for example, But it is not limited thereto.

Referring to FIG. 2, in an embodiment of the present invention, the second pumping electrode 25 may remove oxygen that has not been removed from the first pumping electrode 15, secondarily. The second pumping electrode 25 is disposed on the upper side of the second cavity 11 so as to be spaced apart from the inner pumping electrode 17 by a predetermined distance to the right as shown in FIG. 2, for example, However, the present invention is not limited thereto.

At this time, the second pumping electrode 25 may be used as a material having a weak or no reducing ability for nitrogen oxides like the inner pumping electrode 17. [

The voltage between the second pumping electrode 25 and the outer pumping electrode 19 is controlled so that the voltage between the second pumping electrode 25 and the reference electrode 23 is a constant value, The oxygen concentration can be appropriately maintained.

Further, the second pumping electrode 25 removes oxygen in the exhaust gas constantly so as to be in a range where the nitrogen oxide of the second cavity 11 is not decomposed, that is, a low oxygen concentration that does not substantially affect the nitrogen oxide measurement.

The heater portion 27 of the nitrogen oxide sensor 1 according to the embodiment of the present invention may be provided on the lower side of the solid electrolyte layer 3, 2 substrate layer 3b and the upper and lower surfaces of the heater portion may be located between the insulating layers 27a to obtain electrical insulation with the solid electrolyte layer.

At this time, the heater unit 27 can raise the temperature to a temperature at which the nitrogen oxide sensor 1 according to the embodiment of the present invention can smoothly operate. This is because when the solid electrolyte layer 3 is stabilized zirconia, the ion conductivity of oxygen is expressed at a temperature of 350 ° C or more. At this time, the heater unit 27 can transmit heat such that the nitrogen oxide sensor is above 350 ° C.

The nitrogen oxide sensor 1 according to the embodiment of the present invention is configured such that the area of the inflow surface 5a of the first diffusion passage 5 is made larger than the area of the discharge surface 5b, And the non-uniformity of the signal due to the pulsation of the exhaust gas can be reduced.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

1: nitrogen oxide sensor 3: solid electrolyte layer
5: first diffusion passage 5a: inflow surface
5b: discharge surface 5c: pore of the first diffusion passage
7: first cavity 9: second diffusion passage
9a: pores of the second diffusion passage 11: second cavity
13: air duct 15: first pumping electrode
17: inner pumping electrode 17a: first electrode
17b: second electrode 17c: connecting electrode
19: outer pumping electrode 21: detection electrode
23: reference electrode 25: second pumping electrode
27: heater portion 27a: insulating layer

Claims (10)

A solid electrolyte layer;
A first diffusion passage located at one end of the solid electrolyte layer and including an inlet surface through which exhaust gas from the outside flows and a discharge surface through which the exhaust gas is discharged, the area of the inlet surface being larger than the area of the outlet;
A first cavity communicating with the first diffusion passage and controlling an oxygen partial pressure in exhaust gas passing through the first diffusion passage;
An inner pumping electrode formed in the first cavity and an outer pumping electrode formed in a different position from the first cavity to control a voltage between the inner pumping electrode and the outer pumping electrode to remove oxygen in the exhaust gas, electrode;
A second cavity communicating with the first cavity to decompose the nitrogen oxide that has passed through the first cavity into nitrogen and oxygen ions;
A sensing electrode formed in the second cavity; And
And a reference electrode which is formed at a position different from the second cavity and is installed inside an air duct whose one end communicates with the atmosphere,
Wherein the concentration of nitrogen oxide is measured from a current generated by controlling a voltage between the detection electrode and the reference electrode and moving the oxygen ion to the detection electrode. The method according to claim 1,
Wherein the ratio of the area of the inlet surface to the area of the outlet is 5: 1 or more and 50: 1 or less. The method according to claim 1,
Wherein the first diffusion path is a trumpet shape. The method according to claim 1,
And a reducing agent is contained in the first diffusion passage to reduce nitrogen dioxide to nitrogen monoxide. The method according to claim 1,
And a heater portion positioned inside the solid electrolyte layer. The method according to claim 1,
Wherein the first diffusion passage is made of a porous solid electrolyte. 7. The method according to any one of claims 1 to 6,
And a second pumping electrode formed in the second cavity to control the voltage between the outer pumping electrode and the second pumping electrode to remove oxygen in the exhaust gas. 8. The method of claim 7,
Wherein the inner pumping electrode includes a first electrode provided on one side of the first cavity to remove oxygen and a second electrode provided on the other side of the first cavity and connected to the first electrode, A nitrogen oxide sensor that controls the voltage between the pumping electrodes to remove oxygen in the exhaust gas. 8. The method of claim 7,
And a second diffusion passage connected to the first cavity at one end and connected to the second cavity for leading the exhaust gas passed through the first cavity to the second cavity under a predetermined diffusion resistance. . 8. The method of claim 7,
Wherein the solid electrolyte layer comprises a plurality of substrate layers.

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