KR20150118069A - NOx SENSOR ELEMENT WITH IMPROVED INSULATION PROPERTY - Google Patents

Abstract

The present invention relates to an NOx sensor element and, more specifically, relates to the NOx sensor element having an improved insulation layer. According to the present invention, the NOx sensor element comprises a measuring cell, and a heating element to heat the measuring cell. A heater of the heating element is insulated by a first insulation layer and a second insulation layer. Here, the first insulation layer and the second insulation layer comprises: 70-95 wt% of Al_2O_3; and 0.1-25 wt% of a mixture of one or two selected from among MgO, CaO, SiO_2, TiO_2, and ZrO_2 (each substance is added by 10 wt% or less.). According to the present invention, the NOx sensor element has excellent insulation property, and prevents an inflow of soot by a porous barrier. In addition, as an insulation substance is included in the support layer, almost no exfoliation between a layer or camber occurs by a difference in a sintering motion of the support layer and the insulation layer.

Description

TECHNICAL FIELD [0001] The present invention relates to a NOx sensor element with improved insulation characteristics,

The present invention relates to a knox sensor element, and more particularly, to a knox sensor element having an improved insulation layer.

FIG. 1 is a plan view of a conventional knock sensor element, and FIG. 2 is a cross-sectional view of the knox sensor element shown in FIG. As shown in FIGS. 1 and 2, a conventional knock sensor element includes an electrochemical measurement cell 112 and a heating element 114. The measurement cell 112 includes a first solid electrolyte layer 121 and a second solid electrolyte layer 122 and a first spacer layer 131 and a second spacer layer 132. A reference gas passage 133 is formed in the first spacer layer 131 and an exhaust gas passage 134 is formed in the second spacer layer 132. A first chamber 135 and a second chamber 136 are formed in the exhaust gas passage 134. A first diffusion portion 137 having a narrow width is formed on the upstream side of the first chamber 135 so as to give a predetermined diffusion resistance to the exhaust gas and a diffusion resistance is provided between the first chamber 135 and the second chamber 136 The second diffusion portion 138 is formed.

The first oxygen pump electrode 123 and the second oxygen pump electrode 124 are formed on the lower surface and the upper surface of the second solid electrolyte layer 122, respectively. When a voltage is applied between the first oxygen pump electrode 123 and the second oxygen pump electrode 124, the oxygen in the first chamber 135 is removed through the electrochemical pumping action, The oxygen can be supplied to the inside of the chamber.

A reference electrode 125 and a measurement electrode 126 are formed on the lower surface and the upper surface of the first solid electrolyte layer 121, respectively. When the reference electrode 125 is connected to the measuring electrode 126, an electrical signal corresponding to the difference in oxygen concentration between the exhaust gas passage 134 and the reference gas passage 133 is output. By using this electric signal, the concentration of the knock in the exhaust gas can be measured.

The heating element 114 serves to heat the measuring cell 112 to a temperature at which the measuring cell 112 can operate. The heating element 114 includes a first supporting layer 141, a first insulating layer 151 coated on the upper surface of the first supporting layer 141, a second supporting layer 142, And a resistance heating body 160 formed between the second insulating layer 152 and the first insulating layer 151 and the second insulating layer 142.

In the conventional knock sensor element described above, the heating element 114 is formed by applying the first insulating layer 151 on the first support layer 141 that is not sintered by the screen printing method, Layer and the second insulating layer 152, and then the second supporting layer 142 is laminated thereon, followed by sintering.

Japanese Patent Application Laid-Open No. 9-113482 Japanese Laid-Open Patent Publication No. 2013-0205316

The conventional knock sensor element has a limitation on the thickness of the insulating layer that can be formed because the insulating layer is formed by using the screen printing method. In addition, since the printing property is problematic, the content of the solid content of the paste used for forming the insulating layer can not be sufficiently increased. Further, in order to improve the printability, a large amount of a solvent, a softening agent, a binder and the like are contained, and the density of the insulating layer is lowered at the time of sintering. These problems have been disadvantageous in that the insulating effect of the insulating layer is deteriorated.

In addition, due to the difference in the content of the solid content and the difference in composition, sintering behavior of the supporting layer and the insulating layer of the heating element during sintering is different, resulting in delamination and camber.

In addition, there is a problem that foreign matter such as soot may be introduced through the exhaust gas passage because the exhaust gas passage is opened, although the first diffusion portion having a narrow width is present.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new method of manufacturing a knock sensor element capable of sufficiently increasing the thickness of an insulating layer.

It is another object of the present invention to provide a knox sensor element which is excellent in insulation characteristics and can prevent soot from entering.

In order to achieve the above object, a knock sensor according to the present invention includes a measuring cell and a heating element for heating the measuring cell, and the heater of the heating element is insulated by the first insulating layer and the second insulating layer. The first insulating layer and the second insulating layer may be formed of a mixture of 70 to 95 parts by weight of Al ₂ O ₃ and 0.1 to 25 parts by weight of a mixture of one or more selected from the group consisting of MgO, CaO, SiO ₂ , TiO ₂ and ZrO ₂ Each component is added in an amount of 10 parts by weight or less).

In the above-described knox sensor element, it is preferable that the first supporting layer and the second supporting layer, which respectively couple to the first insulating layer and the second insulating layer, contain 3 to 10 wt% of the first insulating layer.

In addition, the measurement cell may include a solid electrolyte layer having an exhaust gas passage through which exhaust gas flows, and the solid electrolyte layer may be formed of a porous mullite having an average particle diameter of 5 to 10 μm.

The exhaust gas passage may include a first chamber for controlling the concentration of oxygen and a second chamber for measuring the nitric oxide concentration, and a porous barrier may be formed between the first chamber and the second chamber. In addition, it is preferable that at least one porous barrier is formed on the upstream side of the first chamber.

The knox sensor element according to the present invention has an excellent insulating property and has an advantage of preventing soot from being introduced by a porous barrier. Further, since the support layer contains the insulating layer component, there is an advantage that almost no interlayer peeling or camber is generated due to the difference in sintering behavior between the support layer and the insulating layer.

1 is a plan view of a conventional knock sensor element.
2 is a cross-sectional view of the knox sensor element shown in FIG.
3 is an exploded perspective view of a knock sensor according to an embodiment of the present invention.
4 is a cross-sectional view of the knox sensor element shown in FIG.
5 is a flowchart illustrating a method of manufacturing a knock sensor according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

FIG. 3 is an exploded perspective view of a knock sensor device according to an embodiment of the present invention, and FIG. 4 is a cross-sectional view of the knox sensor device shown in FIG.

As shown in FIGS. 3 and 4, the knock sensor element includes a measuring cell 1 for converting a change in knox concentration into an electric signal, and a heating element 2 for heating the measuring cell 1 to a temperature at which the measuring cell 1 can be operated .

The measurement cell 1 includes a first solid electrolyte layer 10, a second solid electrolyte layer 20, and a third solid electrolyte layer 30.

A reference gas passage 11 is formed long in the first solid electrolyte layer 10. For example, an atmosphere is introduced into the reference gas passage 11 as a reference gas. The upper end of the reference gas passage 11 is covered with the second solid electrolyte layer 20 and the lower end thereof is covered with the heating element 2.

The first solid electrolyte layer 10 may be made of Yttria-stabilized zirconia (YSZ).

A second solid electrolyte layer 20 is laminated on the first solid electrolyte layer 10. An exhaust gas passage (21) is formed in the second solid electrolyte layer (20). An exhaust gas containing a knock is introduced into the exhaust gas passage (21). The upper end of the exhaust gas passage 21 is covered with the third solid electrolyte layer 30 and the lower end thereof is covered with the first solid electrolyte layer 10.

The exhaust gas passage 21 is formed with porous barriers 22a, 22b, and 22c that apply a predetermined diffusion resistance to the exhaust gas. In the exhaust gas passage 21, chambers 23 and 24 divided by the porous barriers 22a, 22b and 22c are formed. A second chamber (24) used for measuring the concentration of the rust gas is formed on the innermost side of the exhaust gas passage (21). A first chamber 23 separated from the second chamber 24 by a third barrier 22c is formed on the side of the second chamber 24. The first chamber 23 is a space for uniformly regulating the concentration of oxygen in the exhaust gas flowing into the exhaust gas passage 21 and the second chamber 24 is a space for measuring the concentration of the oxus gas. The first barrier 22a and the second barrier 22b are spaced apart from each other on the upstream side of the first chamber 23. The exhaust gas is not directly introduced into the second chamber 24 but flows through the barriers 22a, 22b, and 22c. This makes it possible to neglect the change in the concentration of the knock due to the change in exhaust gas pressure. In addition, foreign substances such as soot are prevented from entering the first chamber 23.

Unlike the first solid electrolyte layer 10, the second solid electrolyte layer 20 is preferably made of porous mullite having an average particle diameter of 5 to 10 mu m. This is because the barriers 22a, 22b and 22c must be made of porous ceramics in order for the exhaust gas to flow into the second chamber 24 through the barriers 22a, 22b and 22c. The thickness of the side wall 25 of the exhaust gas passage 21 is larger than the thickness of the barriers 22a, 22b, and 22b of the second solid electrolyte layer 20 so that exhaust gas does not flow through the side wall 25 of the exhaust gas passage 21. [ 22c.

On the second solid electrolyte layer 20, a third solid electrolyte layer 30 is laminated. The third solid electrolyte layer 30 may be made of Yttria-stabilized zirconia (YSZ).

A first oxygen pump electrode 41 and a second oxygen pump electrode 42 constituting a pump cell for controlling the oxygen concentration in the first chamber 23 are formed on the lower surface and the upper surface of the third solid electrolyte layer 30, . A third oxygen pump electrode 43 is also formed on the upper surface of the first solid electrolyte layer 10. The oxygen pump electrodes 41, 42, and 43 may be made of platinum. The first oxygen pump electrode 41 and the third oxygen pump electrode 43 are disposed inside the first chamber 23 and electrically connected to each other to serve as one electrode. The third oxygen pump electrode 43 serves to increase the area of the platinum serving as a catalyst. When a voltage is applied between the first oxygen pump electrode 41 and the second oxygen pump electrode 42, the oxygen is discharged to the outside through the third solid electrolyte layer 30 to reduce the oxygen concentration in the first chamber 23 .

The porous protective layer 50 is laminated on the portion of the third solid electrolyte layer 30 where the second oxygen pump electrode 42 is formed so as to protect the second oxygen pump electrode 42 from the exhaust gas.

A first measuring electrode 45 is formed on the lower surface of the third solid electrolyte layer 30. A second measuring electrode 46 is formed on the upper surface of the first solid electrolyte layer 10. The first measuring electrode 45 and the second measuring electrode 46 are disposed inside the second chamber and are electrically connected to each other. The second measuring electrode 46 serves to increase the area of the platinum serving as a catalyst.

A reference electrode 47 is formed on the lower surface of the first solid electrolyte layer 10. A reference gas introducing layer (15) is formed between the lower surface of the first solid electrolyte layer (10) and the reference electrode (47). The reference gas introducing layer 15 serves to transmit the reference gas introduced through the reference gas passage 11 to the reference electrode 47. The reference gas-introducing layer 15 may be made of porous alumina.

The knock concentration in the second chamber 24 can be measured by measuring the electromotive force between the reference electrode 47 and the first measuring electrode 45.

3 and 4, the heating element 2 includes a first supporting layer 60, a first insulating layer 70 disposed on the first supporting layer 60, a heater 70 formed on the first insulating layer 70, A second insulating layer 71 disposed on the substrate 49 and a heater 49 and a second supporting layer 61 disposed on the second insulating layer 71. [ The upper surface of the second support layer 61 is bonded to the lower surface of the first solid electrolyte layer 10.

The heater 49 is formed in a serpentine shape to increase the heating value.

The first insulating layer 70 and the second insulating layer 71 are made of ceramics containing alumina (Al ₂ O ₃ ) as a main component. The first insulating layer 70 and the second insulating layer 71 may be formed of a mixture of 70 to 95 parts by weight of Al ₂ O ₃ and 0.1 to 25 parts by weight of a mixture of one or more selected from MgO, CaO, SiO ₂ , TiO ₂ and ZrO ₂ (Each component is added in an amount of 10 parts by weight or less).

The second support layer 61 and the first support layer 60 are made of yttria-stabilized zirconia as a main component and contain 3 to 10% by weight of ceramics having the same composition as that of the first insulating layer 70 and the second insulating layer 71 . This is because the first support layer 60, the first insulation layer 70, the second support layer 61, and the second insulation layer 71 help to achieve perfect bonding during sintering.

Hereinafter, a method of manufacturing the above-described sensor element will be described with reference to FIG.

First, green sheets of the first insulating layer 70 and the second insulating layer 71, the first supporting layer 60, and the second supporting layer 61 are manufactured (S1, S2, S3, S4).

The green sheets of the first support layer 60 and the second support layer 61 are prepared by mixing a ceramic powder, an organic solvent, an organic binder and the like to prepare a slurry, aging to remove air bubbles in the slurry, Into a sheet form, and drying the formed sheet. Wherein the ceramic powder comprises 3 to 10% by weight of a ceramic powder having the same composition as the insulating layers and yttria-stabilized zirconia powder.

The green sheet of the first insulating layer 70 and the second insulating layer 71 may contain 70 to 95% by weight of Al ₂ O ₃ and one or a mixture of two or more selected from MgO, CaO, SiO ₂ , TiO ₂ and ZrO ₂ And 0.1 to 10% by weight of a binder, 0.1 to 10% by weight of a solvent, and 0.1 to 10% by weight of a solvent are mixed in a solvent to form a slurry, do.

As the softener, a phthalate plasticizer can be used. As the binder, polyvinyl butyral (PVB) and the like can be used.

The green sheets of the first insulating layer 70 and the second insulating layer 71 can be formed by the same method as the above-described method of manufacturing the green sheets of the support layers.

In the present invention, since the green sheet of the first insulating layer 70 and the second insulating layer 71 has a very high solids content of 70% by weight or more and exhibits an insulating property, The insulating layer 70 and the second insulating layer 71 have high densities and thus have excellent insulating properties.

Next, a platinum heater layer is printed on the green sheet of the first insulation layer by a screen printing method (S5).

Next, a first insulating layer green sheet on which a platinum heater layer is printed on the first supporting layer green sheet, a second insulating layer green sheet and a second supporting layer green sheet are laminated to produce a heating element in an uncured state (S6).

Next, a previously prepared measurement cell S7 of a micro-defect state and a heating element of a micro-defect state are stacked (S8).

Next, the sensor elements in the stacked state are vacuum-packed, compressed by a method such as HIP (Hot Isostatic Press) (S9), cut into unit sensor elements (S10) After the solvent, the binder and the softening agent contained in the unit sensor elements are removed (S11), the unit sensor element is completed through sintering (S12).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the invention as defined by the appended claims. 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 present invention.

1: Measurement cell 2: Heating element
10: first solid electrolyte layer 11: reference gas passage
15: reference gas introducing layer 20: second solid electrolyte layer
21: exhaust gas passage 22: porous barrier
23: first chamber 24: second chamber
30: third solid electrolyte layer 41: first oxygen pump electrode
42: second oxygen pump electrode 43: third oxygen pump electrode
45: first measuring electrode 46: second measuring electrode
47: reference electrode 49: heater
50: protection layer 60: first support layer
61: second supporting layer 70: first insulating layer
71: second insulating layer

Claims (5)

1. A sensor element comprising a measuring cell and a heating element for heating the measuring cell, wherein the heater of the heating element is insulated by a first insulating layer and a second insulating layer,
Wherein the first insulating layer and the second insulating layer are made of a metal,
70 to 95 parts by weight of Al ₂ O ₃ and 0.1 to 25 parts by weight of a mixture of one or more selected from MgO, CaO, SiO ₂ , TiO ₂ and ZrO ₂ (each component is added in an amount of 10 parts by weight or less) And the knox sensor element. The method according to claim 1,
Wherein the measurement cell includes a solid electrolyte layer having an exhaust gas passage through which exhaust gas flows, the solid electrolyte layer being made of porous mullite having an average particle diameter of 5 to 10 占 퐉. 3. The method of claim 2,
Wherein the exhaust gas passage has a first chamber for adjusting the oxygen concentration and a second chamber for measuring the knock concentration, and a porous barrier is formed between the first chamber and the second chamber. The method of claim 3,
Wherein at least one porous barrier is formed on the upstream side of the first chamber. The method according to claim 1,
Wherein the first supporting layer and the second supporting layer, which are respectively coupled to the first insulating layer and the second insulating layer, each comprise 3 to 10 wt% of the first insulating layer.

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