JP2015184262A - Gas sensor element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor element capable of easily providing a porous protective layer having approximately constant thickness to be targeted on the surface of a diffusion resistor when the diffusion resistor is provided in a tip portion of the element, and a method for manufacturing the same.SOLUTION: A gas sensor element 1 has a structure formed by laminating a solid electrolyte body 2 having oxygen ion conductivity, an insulator 3 forming a measurement gas space 30 to the solid electrolyte body 2 and a heater 4 for heating the solid electrolyte body 2. A diffusion resistor 5 for introducing a measurement gas G into the measurement gas space 30 under a predetermined diffusion resistance is provided in a tip portion 11 of the gas sensor element 1. In a portion including the diffusion resistor 5 on the tip surface 111 of the tip portion 11 of the element, an inclined surface 112 is formed to be inclined linearly from a state rectangular to the longitudinal direction L of the gas sensor element 1. A porous protective layer 6 having the property of permeating the measurement gas G and an approximately constant thickness is provided on the inclined surface 112.

Description

  The present invention relates to a gas sensor element for measuring a change in oxygen concentration in a gas to be measured and a method for manufacturing the same.

  The gas sensor element includes a measurement electrode that is exposed to a gas to be measured on one surface of a solid electrolyte body having oxygen ion conductivity, and a reference electrode that is exposed to a reference gas on the other surface of the solid electrolyte body. . Further, in a laminated type gas sensor element, a measurement gas space into which a measurement gas is introduced is formed between a solid electrolyte body and an insulator laminated on one surface thereof, and the solid electrolyte body and the other A reference gas space into which a reference gas is introduced is formed between the heater and the heater laminated on the surface.

In addition, a diffusion resistor for introducing the measurement gas under a predetermined diffusion resistance is provided at the introduction port of the measurement gas into the measurement gas space. In addition, the gas sensor element is provided with a porous protective layer for preventing the occurrence of poisoning in the electrode or the like so as to cover the surface of the diffusion resistor. This porous protective layer is formed by immersing the tip of the gas sensor element in the raw slurry as a dipping method.
For example, in the gas sensor element of Patent Document 1 and the manufacturing method thereof, a predetermined range of the sensor part and the heater part of the gas sensor element is immersed in alumina slurry a plurality of times, dried, and heat-treated. It describes that a porous protective layer is formed on the surface.

JP2011-252894A

In general, the introduction port of the gas to be measured and the diffusion resistor are provided on the side surface of the gas sensor element. Therefore, when forming the porous protective layer by the dip method, it is easy to control the thickness of the porous protective layer formed on the side surface of the gas sensor element.
However, the following problems arise when the porous protective layer is formed by the dipping method when the introduction port of the gas to be measured and the diffusion resistor are located on the tip surface of the gas sensor element.
That is, when the front end portion of the gas sensor element is taken out after being immersed in the raw material slurry for forming the porous protective layer, the raw material slurry is largely attached to the front end surface of the gas sensor element due to surface tension. Therefore, there is a possibility that the thickness of the porous protective layer formed on the measurement gas inlet and the surface of the diffusion resistor becomes thicker than the target thickness.

  The present invention has been made in view of such a background, and when a diffusion resistor is provided at the tip of the element, a porous protective layer having a substantially constant target thickness is easily provided on the surface of the diffusion resistor. It was obtained in an attempt to provide a gas sensor element that can be used and a manufacturing method thereof.

In one embodiment of the present invention, a solid electrolyte body having oxygen ion conductivity, an insulator that forms a gas space to be measured between the solid electrolyte body, and a heater that heats the solid electrolyte body are stacked. In the gas sensor element,
A diffusion resistor for introducing the measurement gas into the measurement gas space under a predetermined diffusion resistance is provided at the element tip of the gas sensor element.
An inclined surface that is inclined linearly or arcuately from a state perpendicular to the longitudinal direction of the gas sensor element is formed in a portion including the diffusion resistor in the distal end surface of the element distal end,
In the gas sensor element, a porous protective layer having a property of allowing a gas to be measured to permeate is provided on the inclined surface with a substantially constant thickness.

Another aspect of the present invention is a method for manufacturing the gas sensor element, comprising:
When the element tip portion on which the inclined surface is formed is immersed in the raw material slurry of the porous protective layer stored in the dip tank, and then the element tip portion is taken out from the raw material slurry, In the method of manufacturing a gas sensor element, the material slurry is drained from the most advanced position on the inclined surface.

In the gas sensor element described above, when a diffusion resistor is provided at the tip end of the element, a contrivance is made to form a porous protective layer having a substantially constant thickness at the tip end of the element by dipping.
Specifically, an inclined surface is formed in a portion including the diffusion resistor in the tip surface of the tip portion of the gas sensor element. This inclined surface exhibits an effect when the porous protective layer is formed by the dipping method. In forming the porous protective layer at the tip of the element, the tip of the element is immersed in a raw material slurry constituting the porous protective layer. And when taking out an element front-end | tip part from raw material slurry, raw material slurry flows down from the rear end side in an inclined surface to the front end side, and the raw material slurry is drained in the most advanced position arrange | positioned at the lowest end.

As a result, the raw slurry hardly adheres excessively to the tip surface of the element tip due to surface tension. Therefore, a porous protective layer having a target thickness can be formed on the inclined surface of the tip surface of the element tip. Thus, a target porous protective layer having a substantially constant thickness can be formed on the surface of the diffusion resistor included in the inclined surface.
Therefore, according to the gas sensor element, when a diffusion resistor is provided at the tip of the element, a target porous protective layer having a substantially constant thickness can be easily provided on the surface of the diffusion resistor.

  In the method for manufacturing the gas sensor element, similarly to the gas sensor element, when a diffusion resistor is provided at the tip of the element, a target porous protective layer having a substantially constant thickness can be easily formed on the surface of the diffusion resistor. Can be provided.

Sectional explanatory drawing which shows the element front-end | tip part of the gas sensor element concerning an Example in the state seen from (a) width direction, (b) the state seen from the lamination direction. The figure which shows the element front-end | tip part of the other gas sensor element concerning an Example in the state seen from the width direction, (a) Linear inclined surface, (b) Other linear inclined surface, (c) Still others Cross-sectional explanatory drawing shown about the case where this linear inclined surface and (d) circular-arc-shaped inclined surface are formed. It is a figure which shows the element front-end | tip part of the other gas sensor element concerning an Example in the state seen from the lamination direction, (a) Linear inclined surface, (b) Other linear inclined surface, (c) Still others Cross-sectional explanatory drawing shown about the case where this linear inclined surface and (d) circular-arc-shaped inclined surface are formed. Explanatory drawing which shows the state which immerses the element front-end | tip part of the gas sensor element concerning the Example in the raw material slurry of a porous protective layer. Explanatory drawing which shows the state which moves back and forth the gas sensor element concerning an Example up and down along the longitudinal direction. Explanatory drawing which shows the state which pulls up the gas sensor element concerning an Example from the raw material slurry of a porous protective layer. Explanatory drawing which shows the state which pulled up the gas sensor element concerning background art from the raw material slurry of a porous protective layer.

A preferred embodiment of the above-described gas sensor element and manufacturing method thereof will be described.
In the gas sensor element, an inlet for the gas to be measured is formed in a portion of the insulator located on the tip side of the gas space to be measured, and the diffusion resistor is embedded in the inlet. It may be.
In this case, the structure of the gas sensor element can be simplified.

The inclined surface may be formed in a state of being inclined with respect to at least one of a stacking direction of the gas sensor elements and a width direction orthogonal to the stacking direction and the longitudinal direction.
In this case, it is possible to facilitate draining of the raw material slurry from the most advanced position of the inclined surface at the tip of the element, and to easily form a porous protective layer having a substantially constant thickness on the surface of the diffusion resistor.

Below, the example concerning a gas sensor element and its manufacturing method is described with reference to drawings.
The gas sensor element 1 of this example includes a solid electrolyte body 2 having oxygen ion conductivity, an insulator 3 that forms a measured gas space 30 between the solid electrolyte body 2, and a heater 4 that heats the solid electrolyte body 2. And have a laminated structure. A diffusion resistor 5 for introducing the measurement gas G into the measurement gas space 30 under a predetermined diffusion resistance is provided at the element tip 11 of the gas sensor element 1. An inclined surface 112 that is linearly inclined from a state perpendicular to the longitudinal direction L of the gas sensor element 1 is formed in a portion including the diffusion resistor 5 in the distal end surface 111 of the element distal end portion 11. The inclined surface 112 is provided with a porous protective layer 6 having a property of allowing the measurement gas G to pass therethrough with a substantially constant thickness.

Hereinafter, the gas sensor element 1 of this example and the manufacturing method thereof will be described in detail with reference to FIGS.
The gas sensor element 1 is used in a gas sensor that measures the oxygen concentration in exhaust gas as the gas G to be measured. The gas sensor element 1 is covered with a cover attached to the housing in the gas sensor. The cover is provided with a through hole that guides the gas to be measured to the gas sensor element 1 in the cover. The gas sensor is attached to the exhaust pipe of the vehicle and measures the oxygen concentration in the exhaust gas exhausted from the exhaust pipe.
The gas sensor element 1 utilizes the property of measuring the oxygen concentration, in addition to the oxygen concentration sensor, an A / F (air-fuel ratio) sensor that measures the air-fuel ratio, and a NOx sensor that measures the concentration of NOx (nitrogen oxide). It can be used for an HC sensor for measuring the concentration of HC (hydrocarbon).

  As shown to Fig.1 (a), the solid electrolyte body 2 is comprised from the zirconia etc. which have oxygen ion conductivity. On one surface of the solid electrolyte body 2 on which the insulator 3 is laminated, a measurement electrode 21 that is exposed to an exhaust gas as the measurement gas G is provided. A reference electrode 22 that is exposed to the atmosphere as the reference gas A is provided on the other surface of the solid electrolyte body 2 on which the heater 4 is stacked. In the gas sensor, the oxygen concentration in the exhaust gas is measured by measuring the oxygen ion current flowing between the measurement electrode 21 and the reference electrode 22 via the solid electrolyte body 2.

  The insulator 3 is made of alumina having an insulating property. The insulator 3 is laminated on the solid electrolyte body 2 via a spacer portion 31 facing the periphery of the solid electrolyte body 2 in order to form a measured gas space 30 with a predetermined gap between the insulator 3 and the solid electrolyte body 2. ing. In the spacer portion 31 of the insulator 3, a portion of the spacer portion 31 located on the front end side of the measurement gas space 30 is formed with an introduction port 32 for the measurement gas G in which a part of the spacer portion 31 is notched. The diffused resistor 5 is embedded in the introduction port 32 formed in the spacer portion 31 of the insulator 3. The diffusion resistor 5 has a large number of pores for allowing the measurement gas G to pass therethrough.

  As shown in FIG. 1A, the heater 4 includes an insulating substrate 41 and a conductor layer 42 that is provided inside the substrate 41 and generates heat when energized. The substrate 41 of the heater 4 is laminated on the solid electrolyte body 2 via a spacer portion 411 facing the periphery of the solid electrolyte body 2 in order to form a reference gas space 40 with a predetermined gap between the substrate 41 and the solid electrolyte body 2. Has been.

As shown in FIGS. 1A and 1B, the gas sensor element 1 has a long shape. The inclined surface 112 formed on the distal end surface 111 of the element distal end portion 11 of the gas sensor element 1 is formed so as to be inclined with respect to the stacking direction D in which the insulator 3, the solid electrolyte body 2, and the heater 4 are stacked. . The inclined surface 112 of this example is formed in parallel to the width direction W that is a direction orthogonal to the longitudinal direction L and the stacking direction D.
The inclined surface 112 in the element distal end portion 11 of this example is formed on the entire distal end surface 111. A tip end position 113 is formed on the side surface of the inclined surface 112 on the heater 4 side, and the inclined surface 112 is inclined toward the rear end side from the side surface on the heater 4 side toward the side surface on the insulator 3 side. ing. The angle of the inner angle between the side surface and the inclined surface 112 in the gas sensor element 1 can be 45 ° or more, and can be 60 ° or more.

The inclined surface 112 in the element front end portion 11 can be formed as a shape inclined in the following various directions.
For example, as shown in FIG. 2A, the inclined surface 112 may be inclined toward the rear end side from the side surface on the insulator 3 side toward the side surface on the heater 4 side. In this case, the forefront position 113 is formed on the side surface on the insulator 3 side. Further, as shown in FIG. 2B, the inclined surface 112 can be formed on a part of the tip surface 111. Even in this case, the inclined surface 112 is formed in a portion where the diffused resistor 5 is disposed. In this case, the forefront position 113 is a boundary position between the surface 114 perpendicular to the longitudinal direction L of the sensor element 1 and the inclined surface 112.
Moreover, as shown in FIG.2 (c), the inclined surface 112 may incline with respect to the lamination direction D so that it may become a mountain shape. In this case, the forefront position 113 is the apex position of the mountain-shaped inclined surface 112. In addition, the inclined surface 112 may be inclined not only in a straight line but also in an arc as shown in FIG. In this case, the forefront position 113 is the apex position of the arcuate inclined surface 112.

Further, the inclined surface 112 formed on the distal end surface 111 of the element distal end portion 11 is inclined with respect to the width direction W as shown in FIGS. 3 (a), (b), (c), and (d). It can also be formed. In this case, the inclined surface 112 can be formed in various shapes as in the case of FIG. Even in this case, the forefront position 113 is the same position as in FIG.
The inclined surface 112 may be formed to be inclined with respect to the stacking direction D and the width direction W.

  The porous protective layer 6 is provided in the exposed portion of the gas sensor element 1 that is exposed to the gas G to be measured, including the element tip 11. The porous protective layer 6 is formed with a large number of pores that allow the gas G to be measured to pass through, and is formed on the surface of the exposed portion of the gas sensor element 1 by a dip method.

Next, the manufacturing method of the gas sensor element 1 of this example and an effect are demonstrated.
The gas sensor element 1 is manufactured by laminating and firing a solid electrolyte body 2 provided with electrodes 21 and 22, an insulator 3 and a heater 4. Further, an inclined surface 112 is formed on the distal end surface 111 of the element distal end portion 11 of the gas sensor element 1. The inclined surface 112 may be formed in advance at the position of the tip surface 111 of each of the solid electrolyte body 2, the insulator 3, and the heater 4 so as to become one inclined surface 112 when these are stacked. it can. The inclined surface 112 can also be formed by processing the assembly in which the solid electrolyte body 2, the insulator 3, and the heater 4 are stacked. And the porous protective layer 6 is formed with respect to the gas sensor element 1 by a dip construction method.

In forming the porous protective layer 6, first, a raw material slurry 61 constituting the porous protective layer 6 is made. This raw material slurry 61 includes heat-resistant particles such as alumina, titania, and spinel having a predetermined particle size distribution, an inorganic binder such as silica sol, alumina sol, and titania sol, and an organic binder such as PVB and PVA. It is assumed that it is dispersed in a dispersion medium.
Next, as shown in FIG. 4, the exposed portion including the element tip 11 of the gas sensor element 10 before forming the porous protective layer 6 is immersed in the raw material slurry 61 stored in the dip tank 7. At this time, the gas sensor element 10 is immersed in the raw material slurry 61 in a state substantially perpendicular to the liquid surface of the raw material slurry 61. Then, as shown in FIG. 5, the gas sensor element 10 is moved back and forth along the longitudinal direction L, and then pulled up from the raw slurry 61 as shown in FIG.

  At this time, as shown in the figure, the raw material slurry 61 flows down from the rear end side to the front end side on the inclined surface 112, and the raw material slurry 61 is drained at the frontmost position 113 arranged at the lowermost end. . By forming the inclined surface 112, the raw material slurry 61 can be drained well, and the raw material slurry 61 is less likely to be excessively attached to the tip surface 111 of the element tip portion 11 due to surface tension. And the raw material slurry 61 can be made to adhere to the inclined surface 112 in the front end surface 111 as uniformly as possible. The effect of draining the raw slurry 61 is particularly remarkable when water having a large surface tension is used as a dispersion medium.

  Thereafter, the raw material slurry 61 adhering to the gas sensor element 10 is dried and heat-treated to form the porous protective layer 6. By forming the inclined surface 112, the porous protective layer 6 having a target thickness can be formed on the inclined surface 112 of the distal end surface 111 of the element distal end portion 11. Thereby, the target porous protective layer 6 having a substantially constant thickness can be formed on the surface of the diffusion resistor 5 included in the inclined surface 112.

  Therefore, according to the gas sensor element 1 and the manufacturing method thereof of the present example, when the diffusion resistor 5 is provided at the element distal end portion 11, the target porous body having a substantially constant thickness on the surface of the diffusion resistor 5. The protective layer 6 can be easily provided.

  FIG. 7 shows a state in which the porous protective layer 6 is formed by the dipping method on the conventional gas sensor element 9 in which the distal end surface 911 of the element distal end portion 91 is formed in a state perpendicular to the longitudinal direction L. As shown in the figure, the surface tension of the raw material slurry 61 acts on the tip surface 911 of the element front end portion 91 so that the raw material slurry 61 adheres in an arc shape, and the arc-shaped porous protective layer 6 is formed. The Therefore, in the conventional gas sensor element 9, it is difficult to form the porous protective layer 6 having a substantially constant thickness on the surface of the diffusion resistor 5 located on the tip surface 911 of the element tip portion 91.

DESCRIPTION OF SYMBOLS 1 Gas sensor element 11 Element front-end | tip part 111 End surface 112 Inclined surface 2 Solid electrolyte body 3 Insulator 30 Gas space to be measured 4 Heater 5 Diffusion resistor 6 Porous protective layer G Gas to be measured

Claims (4)

A solid electrolyte body (2) having oxygen ion conductivity, an insulator (3) that forms a measured gas space (30) between the solid electrolyte body (2), and the solid electrolyte body (2) In the gas sensor element (1) in which the heater (4) to be heated is laminated,
A diffusion resistor (5) for introducing the gas to be measured (G) under a predetermined diffusion resistance into the gas space to be measured (30) is provided at the element tip (11) of the gas sensor element (1). And
The portion including the diffusion resistor (5) on the tip surface (111) of the tip portion (11) of the element is linear or arcuate from a state perpendicular to the longitudinal direction (L) of the gas sensor element (1). An inclined surface (112) inclined to
The gas sensor element (1), wherein the inclined surface (112) is provided with a porous protective layer (6) having a property of allowing the measurement gas (G) to pass therethrough with a substantially constant thickness. An inlet (32) for the gas to be measured (G) is formed in a portion of the insulator (3) located on the tip side of the gas to be measured space (30).
The gas sensor element (1) according to claim 1, wherein the diffusion resistor (5) is embedded in the introduction port (32).   The inclined surface (112) is at least one of a stacking direction (D) of the gas sensor element (1) and a width direction (W) orthogonal to the stacking direction (D) and the longitudinal direction (L). The gas sensor element (1) according to claim 1 or 2, wherein the gas sensor element (1) is formed in an inclined state. It is a manufacturing method of the gas sensor element (1) according to any one of claims 1 to 3,
The element tip (11) on which the inclined surface (112) is formed is immersed in the raw material slurry (61) of the porous protective layer (6) stored in the dip tank, and then the element The gas sensor element (1) is characterized in that when the tip (11) is taken out from the raw slurry (61), the raw slurry (61) is drained from the most advanced position on the inclined surface (112). Manufacturing method.

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