SENSOR ELEMENT AND GAS SENSOR

Abstract

The aim is to provide a sensing element and a gas sensor that reduce the amount of a noble metal catalyst supported on a porous carrier and suppress a decrease in gas response due to excessive presence of the catalyst. The means for the solution comprise a sensor element (100) which contains a plate-shaped element body (300) with a sensing section (130) and a porous protective layer (20) which has two or more layers and surrounds at least the circumference of a front end section of the element body (300) in which the sensing section (130) is located, wherein at least one layer (21) of the porous protective layer (20) is a mixed layer containing a catalyst-supporting region (60) in which a catalyst substance formed from one or more noble metals selected from a group consisting of Pt, Pd, Rh and Au, and a non-catalytic region which does not contain the catalyst substance,the sensor element (100) has a gas inlet opening (113a) for introducing a gas to be measured into the detection section (130), and the catalyst-supporting region (60) of the mixed layer is present in the entirety of an imaginary region R extending from the contour of the gas inlet opening (113a) in a thickness direction of the porous protective layer (20) and reaching the outer surface of the porous protective layer (20).

Description

TECHNICAL FIELD

[0001] The present invention relates to a sensor element used in a gas sensor preferably used for detecting the concentration of a specific gas contained, for example, in combustion gas or exhaust gas discharged from a combustion plant, an internal combustion engine or the like, and the gas sensor. STATE OF THE ART

[0002] As a gas sensor for detecting the oxygen concentration in the exhaust gas of a motor vehicle or the like, a gas sensor is known that includes a sensor element in which a detection electrode and a reference electrode are provided on the surface of a tubular or plate-shaped solid electrolyte. Furthermore, a porous protective layer is formed on the surface of the detection electrode to prevent poisoning of the detection electrode.

[0003] In addition, a technique for improving the accuracy and response of gas detection or stabilizing the sensor output has been developed by forming the porous protective layer of the electrode such that catalyst particles made of a noble metal (e.g., Pt) are carried by the protective layer of the electrode and cause a specific component of the exhaust gas that has passed through the porous protective layer to react with the catalyst particles (Patent Document 1). CITATION LISTPATENT LITERATURE

[0004] Patent document 1: JP 2017 - 083 289 A SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[0005] However, there is a desire to reduce the amount of precious metals used to account for rising precious metal prices and reduce costs. Furthermore, if the electrode protective layer contains more precious metal catalyst particles than necessary, the gas response tends to decrease during periods when exhaust gas is combusted by the catalyst particles and the combusted oxygen is bound to the catalyst particles.

[0006] The present invention therefore aims to provide a sensor element that reduces the amount of a noble metal catalyst supported on a porous carrier and suppresses a decrease in gas response due to an excessive presence of the catalyst, and a gas sensor containing the sensor element. SOLUTION TO THE PROBLEM

[0007] To solve the above-described problem, a sensor element according to a first aspect of the present invention comprises a plate-shaped element body including a sensing portion having a solid electrolyte body and sensing and reference electrodes disposed on the solid electrolyte body; and a porous protective layer having two or more layers and surrounding at least a periphery of a front end portion of the element body where the sensing portion is located.The sensor element is characterized in that at least one layer in the porous protective layer is a mixed layer comprising a catalyst-supporting region in which a catalyst substance formed of one or more noble metals selected from a group consisting of Pt, Pd, Rh, and Au is supported, and a non-catalytic region that does not contain the catalyst substance, and in that the sensor element has a gas inlet port for introducing a gas to be measured into the sensing portion, and in that the catalyst-supporting region of the mixed layer is present in the entirety of an imaginary region extending from a contour of the gas inlet port in a thickness direction of the porous protective layer and reaching an outer surface of the porous protective layer.

[0008] A gas to be measured, e.g. exhaust gas, is introduced from the outer surface of the porous protective layer through the imaginary region along the shortest distance in the thickness direction into the gas inlet opening.

[0009] Therefore, in the case where the catalyst-supporting region is present throughout the imaginary region, the gas to be measured comes into contact with the catalyst substance in the catalyst-supporting region and reacts (combusts). This makes it possible to improve the accuracy and responsiveness of gas detection and stabilize the sensor output.

[0010] Since the catalyst-supporting region is contained only in a portion of at least one layer, including the imaginary region, it is not necessary to form an excessively large catalyst-supporting region (made of a noble metal) in the porous protective layer.

[0011] Therefore, the amount of precious metal catalyst used can be reduced. Furthermore, it is possible to suppress a reduction in gas response that would otherwise be caused by the excessive presence of the catalyst, i.e., the excessively large catalyst-supporting area.

[0012] A sensor element according to a second aspect of the present invention comprises a tubular element body having a sensing portion including a solid electrolyte body and sensing and reference electrodes disposed on the solid electrolyte body; and a porous protective layer having two or more layers and surrounding at least a periphery of a front end portion of the element body where the sensing portion is located.The sensor element is characterized in that the sensing portion is formed continuously in a circumferential direction of the solid electrolyte body, that at least one layer in the porous protective layer is a mixed layer including a catalyst-supporting region in which a catalyst substance formed from one or more noble metals selected from a group consisting of Pt, Pd, Rh, and Au is supported, and a non-catalytic region not containing the catalyst substance, and that the catalyst-supporting region of the mixed layer is present in the entirety of an imaginary region extending from the sensing portion in a thickness direction of the porous protective layer and reaching an outer surface of the porous protective layer.

[0013] A gas to be measured, such as exhaust gas, is introduced from the outer surface of the porous protective layer through the imaginary region along the shortest distance in the thickness direction into the gas inlet opening.

[0014] Therefore, in the case where the catalyst-bearing region is present throughout the imaginary region, the gas to be measured comes into contact with the catalyst substance in the catalyst-bearing region and reacts (combusts). This makes it possible to improve the accuracy and response of gas detection and stabilize the sensor result.

[0015] Since the catalyst-supporting region is contained only in a portion of at least one layer, including the imaginary region, it is not necessary to form an excessively large catalyst-supporting region (made of a noble metal) in the porous protective layer.

[0016] Therefore, the amount of precious metal catalyst used can be reduced. Furthermore, it is possible to suppress a reduction in gas response that would otherwise be caused by the excessive presence of the catalyst, i.e., the excessively large catalyst-supporting area.

[0017] In the sensor element of the present invention, the outermost layer of the porous protective layer may be a layer different from the mixed layer and formed from the non-catalytic region.

[0018] In this sensor element, since the layer having the catalyst-supporting region is covered with the outermost layer in which the catalyst-supporting region is not formed, the catalyst-supporting region does not come into direct contact with water or a poisoning substance, and it is possible to suppress a decrease in the reactivity of the catalyst.

[0019] A gas sensor comprises a sensor element of the present invention for detecting the concentration of a specific gas component in a gas to be measured and a housing body holding the sensor element, characterized in that the sensor element is the sensor element according to claim 1 or 2. ADVANTAGEOUS EFFECT OF THE INVENTION

[0020] According to the invention, a sensor element is obtained which reduces the amount of a noble metal catalyst carried on a porous support and suppresses a decrease in gas response due to an excessive presence of the catalyst. BRIEF DESCRIPTION OF THE CHARACTERS Fig. 1 is a cross-sectional view of a gas sensor (oxygen sensor) according to an embodiment of the present invention, the cross-sectional view being taken in the longitudinal direction of the gas sensor. Fig. 2 is a schematic exploded perspective view of a sensor element. Fig. 3 is an enlarged cross-sectional view of a portion of the sensor element at its front end side. Fig. 4 is a cross-sectional view along line AA of Fig. 3. Fig. 5 is a schematic cross-sectional view showing another example of a porous protective layer. Fig. 6 is a schematic cross-sectional view showing another example of a porous protective layer. Fig. 7 is a schematic cross-sectional view showing another example of a porous protective layer. Fig. 8 is a perspective view of a tubular sensor element according to the embodiment of the present invention. DESCRIPTION OF THE EMBODIMENT

[0021] An embodiment of the present invention will now be described.

[0022] Fig. 1 is a cross-sectional view of a gas sensor (oxygen sensor) 1 according to an embodiment of the present invention, the cross-sectional view being taken in the longitudinal direction (the direction of an axial line L) of the gas sensor 1. Fig. 2 is a schematic exploded perspective view of a sensor element 100. Fig. 3 is an enlarged cross-sectional view of a portion of the sensor element 100 at its front end side. Fig. 4 is a cross-sectional view along line AA of Fig. 3.

[0023] As in Fig. 1, the gas sensor 1 includes the sensor element 100, a case body (metal case) 30 that holds the sensor element 100, etc. therein, a protector 24 attached to a front end portion of the case body 30, etc. The sensor element 100 is arranged to extend in the direction of the axial line L.

[0024] In addition, a porous protective layer 20 is provided on the front end side of the sensor element 100 to cover a detection electrode (see Fig. 2).

[0025] As in Fig. As shown in Figure 2, the sensor element 100 includes an oxygen concentration detection cell (detection section) 130 formed from a solid electrolyte body 105 and a reference electrode 104 and a detection electrode 106 formed on opposite sides of the solid electrolyte body 105. The reference electrode 104 has a reference electrode section 104a and a reference lead section 104L extending from the reference electrode section 104a along the longitudinal direction of the solid electrolyte body 105. The detection electrode 106 has a detection electrode section 106a and a detection lead section 106L extending from the detection electrode section 106a along the longitudinal direction of the solid electrolyte body 105.

[0026] In particular, Fig. 2 the porous protective layer 20 is not shown.

[0027] A protective layer 111 has a porous electrode protecting portion 113a and a reinforcing portion 112. The electrode protecting portion 113a prevents poisoning of the sensing electrode portion 106a by sandwiching the sensing electrode portion 106a between the electrode protecting portion 113a and the solid electrolyte body 105. The reinforcing portion 112 protects the solid electrolyte body 105 and sandwiches the sensing lead portion 106L between the reinforcing portion 112 and the solid electrolyte body 105. Specifically, the sensor element 100 of the present embodiment constitutes a so-called electromotive oxygen concentration gas sensor (λ sensor) capable of detecting the oxygen concentration using the voltage (electromotive force) generated between the electrodes of the oxygen concentration detection cell 130.

[0028] The electrode protection portion 113a corresponds to the “gas inlet opening” in the claims.

[0029] In this context, a lower surface layer 103 and an atmosphere introduction hole layer 107 are stacked on a lower surface of the reference electrode 104, so that the reference electrode 104 is sandwiched between the solid electrolyte body 105 and the lower surface layer 103 and the atmosphere introduction hole layer 107. The atmosphere introduction hole layer 107 has a generally square C-like shape with an opening at its rear end. An internal space surrounded by the solid electrolyte body 105, the atmosphere introduction hole layer 107, and the lower surface layer 103 forms an atmosphere introduction hole 107h. The reference electrode 104 is exposed to the atmosphere (reference gas) introduced into this hole 107h.

[0030] A stack of the lower surface layer 103, the atmosphere introduction hole layer 107, the reference electrode 104, the solid electrolyte body 105, the detection electrode 106, and the protective layer 111 forms an element body 300. In the present embodiment, the element body 300 has a plate-like shape.

[0031] One end of the reference lead portion 104L is electrically connected to a sensing element-side contact surface 121 on the solid electrolyte body 105 via a conductor provided in a through-hole 105a formed in the solid electrolyte body 105. In this connection, the protective layer 111 is shorter in the axial direction L than the end of the sensing lead portion 106L, so that the end of the sensing lead portion 106L protrudes from the rear end of the protective layer 111 and appears on the upper surface. The end of the sensing lead portion 106L is connected to an external terminal (not shown) for connecting an external circuit.

[0032] The solid electrolyte body 105, in particular, has oxygen ion conductivity and can contain, for example, a partially stabilized solid solution of zirconium oxide (YSZ) as a main component, which is prepared by adding yttrium oxide as a stabilizer. The main component is defined here as a component whose amount amounts to more than 50 percent by mass of the solid electrolyte body 3s.

[0033] For example, the reference electrode 104 and the detection electrode 106 are formed mainly of Pt. The term "mainly of Pt" here means that "the component whose amount is more than 50 mass percent of the electrode is Pt."

[0034] Each of the lower surface layer 103, the protective layer 111, and the atmosphere introduction hole layer 107 may be formed of an insulating material such as alumina. The electrode protective portion 113a may be a porous body formed mainly of zirconium oxide. The porous body may be formed, for example, by bonding particles of one or more ceramic materials selected from the group consisting of alumina, spinel, zirconium oxide, mullite, zircon, and cordierite through firing or the like. When a slurry containing these particles is fired, an organic or inorganic binder present in the gaps between the ceramic particles and in the slurry burns and disappears, forming pores in the skeleton of the layer.

[0035] Back to Fig. 1: The housing body 30 is made of SUS430 and has an externally threaded portion 31 for attaching the gas sensor to an exhaust pipe and a hexagonal portion 32 into which a fastening tool engages when attaching the gas sensor to the exhaust pipe. The housing body 30 has a housing-side stepped portion 33 that protrudes radially inward. The housing-side stepped portion 33 supports a metal holder 34 for holding the sensor element 100.

[0036] Inside the metal holder 34, a ceramic holder 35 and talc 36 are arranged in this order from the front end. The talc 36 is formed of a first talc 37 arranged inside the metal holder 34 and a second talc 38 arranged at the rear end of the metal holder 34.

[0037] The first talc 37 is compressed and packed into the metal holder 34, thereby securing the sensor element 100 to the metal holder 34. The second talc 38 is compressed and packed into the housing body 30, thereby forming a seal between the outer surface of the sensor element 100 and the inner surface of the housing body 30.

[0038] A sleeve 39 made of alumina is disposed at the rear end of the second talc 38. This sleeve 39 is formed in a stepped cylindrical shape and has an axial hole 39a extending along the axial line, and the sensor element 100 is inserted into the axial hole 39a. A crimping portion 30a on the rear end of the housing body 30 is bent inward, so that the sleeve 39 is pressed against the front end of the housing body 30 via a ring portion 40 made of stainless steel.

[0039] The protector 24, formed of a metal and having a plurality of gas inlet ports 24a, is welded to the outer periphery of a front end portion of the housing body 30 to cover a front end portion of the sensor element 100 protruding from the front end of the housing body 30. This protector 24 has a dual structure including a cylindrical outer protector 41 with a closed end disposed on the outside and having a uniform outer diameter, and a cylindrical inner protector 42 with a closed end disposed on the inside and formed such that its rear end portion 42a has a larger outer diameter than its front end portion 42b.

[0040] A front end portion of an outer tube 25 formed of SUS430 is fitted into a rear end portion of the housing body 30. A front end portion 25a of the outer tube 25, which is enlarged in diameter on the front end side, is fixed to the housing body 30, for example, by laser welding. A partition member 50 is disposed in a rear end portion of the outer tube 25, and a holding member 51 is provided in the gap between the partition member 50 and the outer tube 25. This holding member 51 engages a projecting portion 50a, described later, of the partition member 50. When the outer tube 25 is crimped, the holding member 51 is fixed by the outer tube 25 and the partition member 50.

[0041] An insertion hole 50b into which connecting wires 11 and 12 (in Fig. 1, the lead wire 12 is not shown because it is hidden behind the lead wire 11) for the sensor element 100 is formed in the separator 50 so as to extend therethrough from the front end to the rear end. Terminals 16 for connecting the lead wires 11 and 12 to the sensing-element-side contact surfaces 121 of the sensor element 100 are housed in the insertion hole 50b. The lead wires 11 and 12 are externally connected to a connector (not shown). Electrical signals are transmitted between the lead wires 11 and 12 and an external device, such as a control device, via the connector (for input and output of the electrical signals). Although not shown in detail, each of the lead wires 11 and 12 has a structure in which a conductive wire is covered with an insulating resin coating.

[0042] On the rear end side of the separator 50, a nearly cylindrical rubber cap 52 is arranged to close a rear opening 25b of the outer tube 25. This rubber cap 52 is inserted into the rear end of the outer tube 25 and fixed to the outer tube 25 by radially crimping the outer circumference of the outer tube 25. Insertion holes 52a are formed in the rubber cap 52, into which the lead wires 11 to 15 are inserted so that they extend from the front end to the rear end.

[0043] Next, the porous protective layer 20 is described. As in Fig. 3 and Fig. 4, the porous protective layer 20 is a porous layer having two or more porous layers and is provided to cover the entire circumference of the detection portion 130 on the front end side of the sensor element 100 (the element body 300).

[0044] The porous protective layer 20 is formed to include a front end surface of the sensor element 100 (the element body 300) and extend along the direction of the axial line L toward the rear end side. As shown in Fig. As shown in Figure 4, the porous protective layer 20 is formed to completely surround the four surfaces (i.e., the front and rear surfaces and the opposite side surfaces) of the sensor element 100 (the element body 300). Viewed in the direction of the axial line L, the porous protective layer 20 covers at least a region of the sensor element 100 (the element body 300) including the reference electrode portion 104a and the detection electrode portion 106a (this region constitutes the detection portion), and extends from this region to the rear end.

[0045] The sensor element 100 may be exposed to a poisonous substance such as silicon and phosphorus contained in the exhaust gas, and water droplets in the exhaust gas may adhere to the sensor element 100. Since the outer surface of the sensor element 100 is covered with the porous protective layer 20, it is possible to trap the poisonous substance and prevent water droplets from coming into direct contact with the sensor element 100.

[0046] The porous protective layer 20 is a porous body formed by bonding ceramic particles by firing.

[0047] In the present example, the porous protective layer 20 is formed of two layers, namely an inner layer 21 and an outer layer 22 covering the inner layer 21, wherein the outer layer 22 extends further toward the rear end side than the inner layer 21.

[0048] The outer layer 22 corresponds to the “outermost layer” in the claims.

[0049] Furthermore, a catalyst-supporting region 60 is provided in a portion of the inner layer 21, in which a catalytic substance consisting of one or more precious metals from the group consisting of Pt, Pd, Rh, and Au is formed. The inner layer 21 is a mixed layer comprising the catalyst-supporting region 60 and a non-catalytic region containing no catalytic substance.

[0050] The catalyst-supporting region 60 is formed on an upper surface of the inner layer 21 to cover the electrode protection portion 113a.

[0051] Specifically, the catalyst-supporting region 60 of the mixed layer (the inner layer 21) is present in the entirety of an imaginary region R extending from a rectangular contour of the electrode protecting portion 113a in the thickness direction of the porous protecting layer 20 and reaching an outer surface of the porous protecting layer 20. The catalyst-supporting region 60 is formed to protrude outside the imaginary region R.

[0052] Of course, the area where the catalyst-supporting region 60 is formed may coincide with the imaginary region R. However, since it is difficult to completely coincide with each other from a manufacturing perspective, the catalyst-supporting region 6 is formed so that the catalyst-supporting region 6 protrudes outside the imaginary region R (form the catalyst-supporting region 6 to include the imaginary region R). This is easy from a manufacturing perspective.

[0053] A gas to be measured, e.g., exhaust gas, is introduced from the outer surface of the porous protective layer 20 through the imaginary region R along the shortest distance in the thickness direction of the porous protective layer 20 into the electrode protection portion 113a (gas inlet port).

[0054] Therefore, when the catalyst-supporting region 60 is present throughout the imaginary region R, the gas to be measured comes into contact with the catalyst substance in the catalyst-supporting region 60 and reacts (burns). In this way, it is possible to improve the accuracy and responsiveness of gas detection and stabilize the sensor output.

[0055] In the present invention, since the catalyst-supporting region 60 is formed in a portion of the inner layer 21 including the imaginary region R, it is not necessary to form an excessively large catalyst-supporting region 60 (made of a noble metal) in the porous protective layer 20.

[0056] Therefore, the amount of precious metal catalyst used can be reduced. Furthermore, it is possible to suppress a reduction in gas response caused by the excessive presence of the catalyst, i.e., the excessively large catalyst-supporting region 60.

[0057] The determination of whether the catalyst-supporting region 60 is present or not can be determined by analysis, ie, by determining whether Pt, Pd, Rh, and Au are detected or not in an EDS (energy dispersive X-ray analysis) image of a cross section of the porous protective layer 20.

[0058] A method for forming the catalyst-supporting region 60 in a portion of the porous protective layer 20 is as follows. After forming a layer in which the catalyst-supporting region 60 is to be formed (in this example, the inner layer 21), a solution containing noble metal ions is added dropwise to a location where the catalyst-supporting region 60 is to be formed, and (after forming an unfired outer layer 22 thereon), the whole is calcined.

[0059] An example of a solution containing precious metal ions is a dinitrodiamine Pt nitrate solution.

[0060] In addition, in the present example, since the inner layer 21 having the catalyst-supporting region 60 is covered with the outer layer 22 (the outermost layer) in which the catalyst-supporting region 60 is not formed, the catalyst-supporting region 60 does not come into direct contact with water or a poisoning substance, and it is possible to suppress a decrease in the reactivity of the catalyst.

[0061] Fig. 5 is a schematic cross-sectional view showing another example of a porous protective layer.

[0062] In the example of Fig. 5, the catalyst-supporting region 60 is formed in a portion of the outer layer 22 to include the imaginary region R.

[0063] Fig. 6 is a schematic cross-sectional view showing another example of a porous protective layer.

[0064] In the example of Fig. 6, the catalyst-supporting region 60 is formed in a portion of the inner layer 21 and a portion of the outer layer 22 to include the imaginary region R.

[0065] In the example of Fig. 6, after the inner layer 21 and the outer layer 22 are formed by firing, the solution containing ions of a noble metal is added dropwise to a portion of the outer layer 22 in an amount determined so that the solution penetrates into the inner layer 21, and the whole is fired, thereby forming the catalyst-supported region 60.

[0066] Fig. 7 is a schematic cross-sectional view showing another example of the porous protective layer.

[0067] In the example of Fig. 7, the catalyst-supporting region 60 is formed in a portion of the inner layer 21 and in the entire outer layer 22 to include the imaginary region R.

[0068] In the example of Fig. 7, after the inner layer 21 is formed by firing, the solution containing ions of a noble metal is added dropwise to a portion of the inner layer 21. Then, a mixture of ceramic particles having a catalyst substance previously supported thereon and combustible particles (carbon, etc.) that form pores is applied as a slurry, which becomes the outer layer 22, to the outer surface of the inner layer 21 by dipping or the like, and the whole is fired.

[0069] Alternatively, after the noble metal ion-containing solution is added dropwise to a portion of the inner layer 21 as described above, the slurry forming the outer layer 22 can be prepared as follows. Namely, a mixture of ceramic particles, combustible particles (carbon, etc.) that form pores, and a noble metal ion-containing solution is applied to the outer surface of the inner layer 21 by dipping or the like, and the whole is fired, thereby forming the catalyst-supporting region 60.

[0070] The present invention is not limited to the above-described embodiment. The sensor element only needs to include a solid electrolyte body, a detection electrode, and a reference electrode and can be applied to the oxygen sensor (oxygen sensor element) of the present embodiment. However, the present invention is not limited to these applications and includes various modifications and equivalents that fall within the spirit and scope of the present invention.

[0071] The present invention can be applied, for example, to a full-range oxygen sensor with an oxygen pumping cell, a NOx sensor (NOx sensor element) for detecting the NOx concentration in a gas to be measured, and an HC sensor (HC sensor element) for detecting the HC concentration. The sensor element can be tubular and can be a binary sensor or a linear sensor.

[0072] The gas sensor can be equipped with a heater that generates heat when energy is supplied.

[0073] As in Fig. As shown in Fig. 8, the present invention can be applied to a tubular sensor element.

[0074] In Fig. 8, a sensor element 100B has a well-known structure, that is, it includes an element body 300B formed of a tubular solid electrolyte body, a detection electrode 106B continuously formed in the circumferential direction on an outer surface of a front end portion of the element body 300B, and a reference electrode (not shown) continuously formed in the circumferential direction on an inner surface of the front end portion of the element body 300B.

[0075] A region where the element body 300B, the detection electrode 106B, and the reference electrode overlap each other serves as a detection section 130B.

[0076] Further, a porous protective layer 20B (formed of two layers in the present example) is provided, which surrounds at least the periphery of the front end portion of the element body 300B where the detection portion 130B is located.

[0077] In the case of Fig. 8, the inner layer (not shown) is a mixed layer in which a catalyst-supporting region 60B and a non-catalytic region are mixedly present.

[0078] Since the detection portion 130B in the tubular sensor element 100B is formed continuously in the circumferential direction of the element body 300B, it is sufficient that the catalyst-supporting region 60B is present in the entirety of an imaginary region R2 extending from the detection portion 130B in the thickness direction of the porous protective layer 20B and reaching the outer surface of the porous protective layer 20B. LIST OF REFERENCE SYMBOLS 1 gas sensor 20, 20B porous protective layer 30 housing bodies 60, 60B catalyst-carrying area 100, 100B sensor element 104 Reference electrode 106, 106B Detection electrode 105, 105B solid electrolyte body 113a Electrode protection section (gas inlet opening) 130, 130B Recording section 300, 300B element body R imaginary area QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2017 - 083 289 A

[0004]

Claims

[1] A sensor element comprising: a plate-shaped element body having a detection portion including a solid electrolyte body and detection and reference electrodes disposed on the solid electrolyte body; and a porous protective layer having two or more layers and surrounding at least a periphery of a front end portion of the element body where the detection portion is disposed, the sensor element characterized by is that at least one layer in the porous protective layer is a mixed layer containing a catalyst-supporting region in which a catalyst substance formed from one or more noble metals selected from a group consisting of Pt, Pd, Rh and Au is supported, and a non-catalytic region which does not contain the catalyst substance, the sensor element has a gas inlet opening for introducing a gas to be measured into the detection section, and the catalyst-supporting region of the mixed layer is present in the entirety of an imaginary region extending from a contour of the gas inlet opening in a thickness direction of the porous protective layer and reaching an outer surface of the porous protective layer. [2] A sensor element comprising: a tubular element body having a detection portion including a solid electrolyte body and detection and reference electrodes disposed on the solid electrolyte body; and a porous protective layer having two or more layers and surrounding at least a periphery of a front end portion of the element body where the detection portion is disposed, the sensor element characterized by is that the detection section is formed continuously in a circumferential direction of the solid electrolyte body, at least one layer in the porous protective layer is a mixed layer containing a catalyst-supporting region in which a catalyst substance formed from one or more noble metals selected from a group consisting of Pt, Pd, Rh and Au is supported, and a non-catalytic region which does not contain the catalyst substance, and the catalyst-supporting region of the mixed layer is present in the entirety of an imaginary region extending from the detection portion in a thickness direction of the porous protective layer and reaching an outer surface of the porous protective layer. [3] The sensor element according to claim 1 or 2, wherein the outermost layer of the porous protective layer is a layer different from the mixed layer and formed from the non-catalytic region. [4] Gas sensor comprising a sensor element for detecting the concentration of a specific gas component in a gas to be measured and a housing body holding the sensor element, characterized by that the sensor element is the sensor element according to claim 1 or 2.

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