JP2001272371A - Multilayered gas sensor element and gas sensor equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayered gas sensor element capable of enhancing the insulating property of a solid electrolyte layer in the vicinity of a reed terminal part, so as to miniaturize the gas sensor itself. SOLUTION: This multilayered gas sensor element A, mainly consisting of zirconia is constructed of lamination of a heater unit 2, having a heater unit second body layer (solid electrolyte layer) 23b, which is provided with a heating resistor 21 arranged on one surface, and an oxygen concentration cell element 1. On the other surface of the heater unit second main body layer 23, a pair of heater unit current carrying terminals 25a, 25b connected to an external terminal for connecting an external circuit and electrically connected to a heating resistor 21 are formed with a heater unit fourth insulating layer (insulating coat film) 24b arranged between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor for detecting a specific component contained in exhaust gas discharged from an internal combustion engine of an automobile or the like, and to a laminated gas sensor element incorporated in the gas sensor.

[0002]

2. Description of the Related Art Conventionally, oxygen sensors, HC sensors, N
As a gas sensor element incorporated in a gas sensor for detecting a specific component in a gas to be measured, such as an Ox sensor, a layer formed of a solid electrolyte having oxygen ion conductivity and having a long shape ( Hereinafter, a stacked gas sensor element (hereinafter, simply referred to as “element”) in which a plurality of “solid electrolyte layers” are stacked is known.

As an example of such an element, Japanese Utility Model No.
No. 54825 is exemplified. This publication discloses an element having a structure in which a detection electrode and a reference electrode are provided on the front and back surfaces of a solid electrolyte layer, and a heating element is provided on the surface of another solid electrolyte layer. Here, for the electrodes and the heating resistor, a lead terminal formed on one surface (outermost surface) of each solid electrolyte layer is electrically connected to an external terminal for connecting an external circuit. (Specifically, via a conductor lead portion). Each lead terminal portion is opposite to the front side of the element that is exposed to the gas to be measured (i.e.,
It is general that it is formed in a paired form on one surface (rear end side).

[0004]

The solid electrolyte layer mainly composed of zirconia has a specific temperature range (2.
At a temperature lower than (approximately 00 ° C.) or lower, the film has sufficient insulating properties. In the conventional devices, the distance (dimension) in the longitudinal direction of the device itself has been formed to be larger than 40 mm. Therefore, even if the temperature on the front side of the device becomes high, the distance to the rear side on which the lead terminal portion is formed is increased. During the heating, the temperature rise of the solid electrolyte layer near the lead terminal was suppressed, and the solid electrolyte layer near the lead terminal was able to maintain insulation. For this reason, the lead terminal portion has been formed directly on the solid electrolyte layer serving as a base.

[0005] However, in recent years, due to the tightening of exhaust gas regulations and the like, it has become necessary to install a gas sensor even in an internal combustion engine having a small displacement, for example, a two-wheeled vehicle, and accordingly, the gas sensor itself has been required to be downsized. For this reason, miniaturization is also required for the stacked gas sensor element,
Specifically, a device having a distance (dimension) in the element longitudinal direction of 40 mm or less is required. However, as the size of the device is reduced, the entire solid electrolyte layer (device) is more likely to be exposed to a high temperature region in an actual use environment, and the entire solid electrolyte layer is activated. This means that when the lead terminal portion is formed directly on the solid electrolyte layer as in the related art,
Leakage current occurs in the solid electrolyte layer near the lead terminal,
There is a possibility that a problem that has not occurred in the related art, such as a short circuit occurring between the lead terminals, may occur. Further, when a large leakage current flows in the solid electrolyte layer near the lead terminal, oxygen of the solid electrolyte (zirconia) is released when the charge is transferred, thereby causing blackening (blackening phenomenon). It also causes deterioration of the durability.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a laminated gas sensor element capable of improving the insulating property of a solid electrolyte layer in the vicinity of a lead terminal portion, whereby the gas sensor can be downsized. With the goal. Still another object is to provide a gas sensor using such a stacked gas sensor element.

[0007]

Means for Solving the Problems and Effects of the Invention
The stacked gas sensor element of the present invention is a stacked gas sensor element mainly composed of zirconia and having a solid electrolyte layer having a conductor layer formed on the surface, and one surface of the solid electrolyte layer is in contact with an external terminal. Further, a pair of lead terminal portions electrically connected to the conductor layer are formed in a form via an insulating film.

[0008] A pair of "lead terminal portions" to be formed on one surface of the solid electrolyte layer is electrically connected to a heating resistor disposed on the other surface of the solid electrolyte layer,
One for applying a voltage to the heating resistor can be mentioned. Further, a pair of lead terminal portions provided on one surface on which the detection electrode is provided in order to extract electrical output from the detection electrode and the reference electrode provided on the front and back surfaces of the solid electrolyte layer can be exemplified.

The one surface of the solid electrolyte layer on which the heating resistor, and the lead terminals electrically connected to the sensing electrode and the reference electrode are formed, corresponds to the outermost surface when the entire device is viewed. This is advantageous in connecting the lead terminal portion to an external terminal for connecting an external circuit. The solid electrolyte layer is mainly composed of zirconia having oxygen ion conductivity, but the `` main component '' described in this specification means that the mass content is the highest, It does not necessarily mean that it occupies 50% by mass or more.

In the present invention, it is noted that the lead terminal portion is not formed directly on one surface of the solid electrolyte layer serving as a base, but is formed in a form via the above-mentioned "insulating film". It should be. Thereby, the insulating property of the solid electrolyte layer in the vicinity of the lead terminal portion can be increased,
Blackening or the like due to the effect of leakage current flowing in the solid electrolyte layer can be effectively suppressed. The composition of the insulating film is not particularly limited, and may be constituted by a composition mainly composed of a material having excellent insulating properties such as alumina, mullite, magnesia / alumina spinel,
As in the fourth invention, it is preferable to mainly use alumina. Alumina has a very high insulating property and furthermore has a higher thermal conductivity than zirconia or the like, and is therefore a material excellent in terms of reducing thermal shock to the element.

Incidentally, as the size of the element is reduced, the area of the lead terminal itself formed on one surface of the solid electrolyte layer may be reduced. As a result, when the external terminal for external circuit connection comes into contact with the lead terminal portion, the external terminal protrudes from the lead terminal portion while being in contact with the external terminal, and a part of the protruding external terminal is on the surface of the solid electrolyte layer. It may be possible to touch again. Therefore, it is desirable that the insulating film is formed not only between the lead terminal portion and the surface of the solid electrolyte layer but also on the surface of the solid electrolyte layer so as to exist around the lead terminal portion. Thereby, the insulating property of the solid electrolyte layer in the vicinity of the lead terminal portion can be ensured.

[0012] As in the first invention, by forming a stacked gas sensor element in which a pair of lead terminal portions is formed on one surface of a solid electrolyte layer with an insulating film interposed therebetween, for example, a temperature of 450 ° C or more ( In addition, when a normal in-vehicle power supply voltage of 14 V is applied to the lead terminal under an environment of 550 ° C. or higher), the solid electrolyte layer near the lead terminal can maintain sufficient insulation. Become.

By the way, in the element (solid electrolyte layer), when one surface on which the lead terminal portion is formed, especially when one surface corresponds to the outermost surface when the whole element is viewed, one surface of the solid electrolyte layer is formed. Chamfers may be formed at both longitudinal edges. The reason for forming the chamfered portion in this manner is to effectively reduce excessive bending stress applied from the outside of the element (solid electrolyte layer), prevent breakage of the element, and improve the strength of the element itself. . In forming the chamfered portion, an unsintered solid electrolyte layer (solid electrolyte sheet) is screened in order with an insulating paste to be baked to form an insulating film and a conductive paste to be baked to become a lead terminal portion. A method is considered in which assemblies are formed by coating by printing or the like, and chamfered portions are formed before firing the assemblies.

However, when the lead terminal portion is formed on one surface of the solid electrolyte layer via an insulating film as in the present invention (first invention), the unsintered solid electrolyte layer is formed before firing as described above. When the chamfered portion is provided, even the insulating film may be chamfered after firing. Then, the solid electrolyte layer is exposed on the surface formed by the chamfering, and when the external terminal for connecting an external circuit is brought into contact with the lead terminal portion, the external terminal extends to the surface where the solid electrolyte layer is exposed by the chamfering. May be approaching. As a result, even though the lead terminal portion is formed in a form via an insulating film, the external terminal comes into contact with the exposed surface of the solid electrolyte due to chamfering, and a leakage current occurs in the solid electrolyte layer, Blackening may be induced.

In view of the above, the laminated gas sensor element in which the chamfered portions are formed on both longitudinal edges of one surface on which the lead terminals are formed via the insulating film of the solid electrolyte layer as described above, As in the invention, it is preferable to form an insulating film on the chamfered portion. By adopting such a configuration, the insulating property of the solid electrolyte layer in the vicinity of the lead terminal portion can be enhanced, and even in the case where the external terminal comes into contact with the chamfered portion, the occurrence of blackening can be reliably suppressed. it can. Further, by forming an insulating film on the chamfered portion, it is possible to play a role of buffering thermal stress applied from the outside of the element (solid electrolyte layer). The chamfered shape of the “chamfered portion” is not particularly limited, and may be any one of a C-chamfered shape that is substantially flush with each other and an R-shaped shape that is formed in a convex shape.

Further, the thickness of the insulating film in the present invention is preferably 1.0 μm or more (more preferably, 5.0 μm or more) as in the fourth invention. If the thickness is less than 1.0 μm, the insulating property may not be sufficiently maintained. In addition, as the upper limit of the thickness of the insulating film, it is preferable that the thickness is large in consideration of insulation properties. However, if the thickness is extremely large, manufacturing and economic waste will occur. A preferable value may be appropriately determined.

Further, the gas sensor according to the fifth aspect of the present invention comprises
The multilayer gas sensor element according to any one of the fourth inventions, characterized by comprising a multilayer gas sensor element in which the solid electrolyte layer in the vicinity of the lead terminal has an enhanced insulating property. The structure and mounting method of the gas sensor are not particularly limited. For example, the element is arranged inside the metal shell, and the mounting screw portion formed on the outer peripheral surface of the metal shell is attached to the exhaust pipe or the like. One that can be mounted and used such that the front side of the element projects into the exhaust pipe or the like can be used.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a stacked gas sensor element of the present invention and a gas sensor incorporating the same will be described in detail with reference to examples. 1. FIG. 1 shows a gas sensor in which a laminated gas sensor element of the present invention is incorporated. The gas sensor is attached to an exhaust pipe of an internal combustion engine.
FIG. 2 is a cross-sectional view showing an example of an oxygen sensor B commonly called a λ-type oxygen sensor used for measuring the oxygen concentration in exhaust gas.

The stacked oxygen sensor element A incorporated in the oxygen sensor B has an insertion hole 3 formed in the metal shell 3 so that the front side projects from the tip of the metal shell 3.
2, and the space between the inner surface of the insertion hole 32 and the outer surface of the element A is sealed by a sealing material layer 41 mainly composed of glass (for example, crystallized zinc silica borate glass). . Metallic double protectors 61 and 62 covering the protruding portion of the element A are fixed to the outer periphery of the distal end portion of the metal shell 3 by laser welding or the like. This protector 6
Reference numerals 1 and 62 denote caps. Exhaust gas flowing through the exhaust pipe is protected at the tip and periphery thereof by protectors 61 and 62.
Ventilation holes 61a and 62a leading to the inside are formed. On the other hand, the rear end portion of the metal shell 3 is inserted inside the front end portion of the outer cylinder 7, and the overlapped portion is joined by laser welding or the like in the circumferential direction. At the outer peripheral portion of the metal shell 3, a mounting screw portion 31 for screwing and mounting the oxygen sensor B (metal shell 3) into the exhaust pipe is screwed.

For the element A, the first connector 51, the elongated metal thin plate 52, the second connector portion 53 and the insulating plate (not shown) (these are collectively referred to as "external terminals")
) And an external circuit (not shown) via a lead wire 9. The four lead wires 9 extend through the grommet 8 located at the rear end side of the outer cylinder 7.

In the longitudinal direction (axial direction) of the element A, at least one side of the sealing material layer 41 is adjacent (in this embodiment, the end face side of the sealing material layer 41 near the detection portion X). A buffer layer 42 made of a porous inorganic substance (for example, a compact formed of an inorganic substance powder of talc talc or a porous calcined body) is formed. This buffer layer 42
Supports the element A projecting in the axial direction from the sealing material layer 41 so as to wrap the element A from the outside, and excessive bending stress and thermal stress
It plays a role in suppressing the participation of the user.

2. Structure of Stacked Gas Sensor Element Next, a stacked gas sensor element which is a main part of the present invention will be described with reference to FIG. FIG. 2 is an exploded perspective view of an element A provided in the oxygen sensor B shown in FIG. 1, and the element A includes an oxygen concentration cell section 1 and a heater section 2.

The oxygen concentration cell section 1 includes an oxygen concentration cell solid electrolyte layer 11 mainly composed of zirconia having oxygen ion conductivity, and one end of the oxygen concentration cell solid electrolyte layer 11 (FIG. 1). The detection electrode 131a and the reference electrode 131b are formed directly on the front and back surfaces (the side protruding from the front end of the metal shell 3 in FIG. 1), and constitute the detection unit X in FIG. The detection electrode 131a and the reference electrode 131
In b, conductor lead portions 132a and 132b extend in the longitudinal direction of the solid electrolyte layer 11 for oxygen concentration cells, respectively. However, each of these conductor leads 132a and 1
Reference numeral 32b is formed on the front and back surfaces of the solid electrolyte body 11 for an oxygen concentration cell via the oxygen concentration cell section first insulating layer 12a and the oxygen concentration cell section second insulation layer 12b. The oxygen-concentration cell part first insulating layer 12a and the oxygen-concentration cell part second insulation layer 12b are both mainly composed of alumina having excellent insulation properties.

The end of the conductor lead portion 132a is connected to an external terminal (not shown) for connection to an external circuit and constitutes a signal extraction terminal 133a electrically connected to the detection electrode 131a. . The lead 132
The terminal of b is connected to an external terminal (see FIG. 1) via an oxygen concentration cell part through hole 15 penetrating through the solid electrolyte layer 11 for oxygen concentration cell, the first insulation layer 12a of oxygen concentration cell part, and the second insulation layer 12b of oxygen concentration cell part. (Not shown) to be connected to a signal extraction terminal 14. Note that the signal extraction terminals 133a and 133 are a pair of lead terminal portions in the present invention, and these lead terminal portions are formed in a form via the oxygen concentration cell portion first insulating layer 12a corresponding to the insulating film of the present invention. I have. The detection electrode 131a and the reference electrode 131b correspond to the conductor layer of the present invention, and the solid electrolyte layer 11 for an oxygen concentration cell corresponds to the solid electrolyte layer of the present invention.

On the other hand, the heater section 2 is provided with a heating resistor 21 made of a high melting point metal (Pt or Pt alloy or the like) or a conductive ceramic, and the heating resistor 21 is mainly made of alumina having excellent insulating properties. It is sandwiched between the heater unit first insulating layer 22a and the heater unit second insulating layer 22b. Further, the heating resistor 21 sandwiched between the insulating layers
Is sandwiched between the heater portion first main body layer 23a and the heater portion second main body layer 23b mainly composed of zirconia, and then has a heater portion third insulating layer 24a and a heater portion It has a multilayer structure sandwiched between the four insulating layers 24b.

The heating resistor 21 includes a heater portion fourth insulating layer 24b, a heater portion second main body layer 23b, and a heater portion third body layer 23b.
Through holes 26a and 26b penetrating insulating layer 22b
Are electrically connected to heater unit energizing terminals 25a and 25b which are connected to external terminals (not shown) for an external circuit. Note that the heater section energizing terminals 25a and 25b are a pair of lead terminal sections in the present invention, and these lead terminal sections are formed in the form of a heater section fourth insulating layer 24b corresponding to an insulating film of the present invention. Further, the heating resistor 21 corresponds to the conductor layer of the present invention, and the heater portion second main body layer 23b corresponds to the solid electrolyte layer of the present invention.

If the thickness of the first insulating layer 12a in the oxygen concentration cell portion and the fourth insulating layer 24b in the heater portion, which are the insulating films of the present invention, is 1.0 μm or more, sufficient insulation can be obtained. There are no problems. Note that, in FIG. 3, the chamfered portions formed on at least one longitudinal edge of the front and back surfaces of the element A are omitted, and the chamfered portions will be described later.

3. Manufacture of stacked gas sensor element Manufacture of first assembly to be oxygen concentration cell section Oxygen concentration using a green body obtained by kneading zirconia powder in which a stabilizer such as yttria or calcia is dissolved together with an organic binder and a solvent. 5 which becomes the solid electrolyte layer 11 for the battery
An unsintered solid electrolyte sheet large enough to cut out individual elements was formed by a doctor blade method. On the front and back surfaces of the sheet excluding the portions where the detection electrodes 131a and the reference electrodes 131b are formed, the oxygen concentration cell part insulating layers 12a and 12b are formed by using an insulating paste mainly composed of alumina for five elements. The coating was printed and dried.
Thereafter, a through hole serving as a through hole 15 for five elements is formed at a predetermined position of the unsintered solid electrolyte sheet on which the coating films are formed, and the inner wall surface and the opening edge of the through hole 15 are covered. The insulating paste was printed and dried.

Further, a conductive paste containing platinum as a main component is provided in a required area on the coating film (including a coating film made of an insulating paste on the through-holes serving as the through holes 15) serving as the oxygen concentration cell part insulating layers 12a and 12b. Is printed in a predetermined pattern
After drying, the detection electrode 131a, the reference electrode 131b, the leads 132a and 132b, the signal extraction terminal 133
Conductor patterns (coatings) to be a and 14 were formed. Thus, a first assembly to be the oxygen concentration cell unit 1 was obtained.

Next, a green solid electrolyte sheet similar to the one described above, which is to be the second main body layer 23b of the heater part, is formed on the front and back surfaces of the second assembly. Print and dry the paste,
Heater part third insulating layer 22b and heater part fourth insulating layer 24
A coating film serving as b was formed. Thereafter, at predetermined positions of the unsintered solid electrolyte sheet on which these coating films are formed, through holes serving as through holes 26a and 26b for five elements are formed, and the inner wall surfaces and opening edges of the through holes 26a and 26b are formed. The insulating paste was printed and dried so as to cover the entire surface.

Further, a coating film (through hole 26) serving as the heater portion third insulating layer 22b and the heater portion fourth insulating layer 24b is formed.
a) and a conductive film similar to the above is printed in a predetermined pattern on a required area on the through-holes a and 26b) and dried.
A conductor pattern (coating film) to be a pair of heater terminals 25a and 25b was formed. Then, a layer serving as the heater unit first insulating layer 22a is printed on the conductor pattern serving as the heating resistor 21, and the same unsintered solid electrolyte sheet as described above serving as the heater unit first body layer 23a is laminated and depressurized. Crimped. Thus, a second assembly to be the heater unit 2 was obtained.

Assembling, Degreasing, and Firing Steps A layer serving as the heater portion third insulating layer 24a was printed on the second assembly, and the first assembly was laminated and pressure-compressed to obtain a laminate. Then, the laminate was cut into the element A, and five unfired element laminates were cut out. Then, C-chamfering is performed on both longitudinal edges of one surface of the unsintered solid electrolyte sheet, which is to be the heater unit second main body layer 23b of each unsintered element laminate, on which the lead terminal portion is formed, and is chamfered. Part was formed. Then, the same insulating paste as described above is printed and dried on the chamfered portion, and the temperature of the unfired element laminate is increased at 20 ° C./hour in an air atmosphere to a maximum temperature of 450 ° C.
Degreasing (binder removal) was performed by keeping at 1 ° C. for 1 hour, followed by baking at 1500 ° C. for 1 hour to obtain an element A.

FIG. 3 shows an element A obtained in the above-described manufacturing process, in which a pair of heater section energizing terminals 25a and 25b formed on the heater section 2 are connected to external terminals for connecting an external circuit (specifically, Are longitudinal metal thin plates 52a, 5
2b) schematically shows the state when connected to the device using a partially enlarged view. The elongated metal plates 52a, 52 shown in FIG.
“b” has such a size as to be in contact with the lead terminal portion and also to contact the surface and the chamfered portion of the solid electrolyte layer around the lead terminal.

Here, in this embodiment (the present invention),
The heater unit energizing terminals (lead terminal units) 25a and 25b are formed with the heater unit fourth insulating layer 24b (insulating film) interposed therebetween, and at the same time, the heater unit energizing terminals 25a and 25b are formed.
An insulating film is formed on the periphery of b and on the chamfered portion 27. As a result, the heater section energizing terminal 25
a, second body layer (solid electrolyte layer) near heater 25b
24b is an element having a sufficient insulating property, and the insulating film can maintain the insulating property even when the whole of the heater unit second main body layer is activated in some cases. In order to make contact between the element A and the long metal thin plates 52a and 52b in a state where the insulation property is completely maintained, a part or the whole of the element end surface 28 on the side where the lead terminals of the element are formed is provided. An insulating film may be formed.

4. Evaluation of Element Performance Using five elements A obtained in the above-described manufacturing process, the presence or absence of occurrence of blackening due to energization of the heater unit 2 was evaluated. In this evaluation, each of the five elements A was incorporated into a gas sensor as shown in FIG. 1, the obtained gas sensor was exposed to a pseudo exhaust gas at 750 ° C., and the heater unit energizing terminals 25 a and 25 b were turned on to energize the heating resistor 21. Was applied and a voltage of 14 V was applied thereto, and then left for 500 hours. Note that the evaluation of the element A is performed on the premise that the solid electrolyte layer constituting the element A is large enough to be activated (length in the longitudinal direction). As a result of the evaluation, the gas sensor was disassembled after 500 hours, and the occurrence of blackening in the heater portion second main body layer (solid electrolyte layer) near the heater portion lead terminals 25a and 25b of the element A was visually observed. However, no blackening occurred in any of the devices A.

In the case of the stacked gas sensor element,
In order to achieve conduction between the front and back surfaces of the solid electrolyte layer, it is general to adopt a structure which is usually performed via through holes as in this embodiment. When conducting through the through-hole in this way, as described in this embodiment, the conduction is performed after the inner wall surface and the opening edge of the through-hole are covered with an insulating film (insulating layer). It is preferable to aim. By applying such a configuration, the insulating property of the solid electrolyte layer near the through hole can be increased,
This leads to further enhancement of the insulation property of the solid electrolyte layer near the lead terminal, and it can be expected that blackening and the like can be more reliably prevented. In the above, the present invention has been described in accordance with the embodiment, but the present invention is not limited to this embodiment, and without departing from the gist thereof,
It goes without saying that the present invention can be applied by changing it appropriately.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a cross section of a gas sensor in which a laminated gas sensor element of the present invention is incorporated.

FIG. 2 is an exploded perspective view showing a laminated gas sensor element of the present invention.

FIG. 3 is an enlarged perspective view of a portion of the laminated gas sensor element according to the present invention in which a heater section energizing terminal (lead terminal section) is formed, showing a state of connection between the element having a chamfered section and an external terminal. FIG.

[Explanation of symbols]

A: oxygen sensor element (laminated gas sensor element), 1; oxygen concentration cell part, 11: solid electrolyte layer for oxygen concentration cell (solid electrolyte layer), 12a; oxygen concentration cell part first insulating layer (insulating film), 12b A second insulating layer of the oxygen concentration cell section, 13
a; detection electrode (conductor layer); 13b; reference electrode (conductor layer); 2; heater section; 21; heating resistor (conductor layer);
2a; heater unit first insulating layer, 22b; heater unit second insulating layer, 23a; heater unit first main body layer, 23b; heater unit second main body layer (solid electrolyte layer), 24a; heater unit third insulating layer, 24b; fourth insulating layer (insulating film) of heater section, 133
a, 14: Signal extraction terminal (lead terminal portion), 25
a, 25b: heater section conducting terminals (lead terminal section), 2
7; chamfer, B; oxygen sensor (gas sensor), 52;
Long metal sheet (external terminal).

Continuation of the front page (72) Inventor Teppei Okawa 14-18 Takatsuji-cho, Mizuho-ku, Nagoya Japan F-term (reference) 2G004 BB04 BF15 BF19 BF27 BJ03 BM07

Claims (5)

[Claims] 1. A stacked gas sensor element mainly composed of zirconia and having a solid electrolyte layer having a conductor layer formed on a surface thereof, wherein one surface of the solid electrolyte layer is in contact with an external terminal and A stacked gas sensor element, wherein a pair of lead terminal portions electrically connected to a conductor layer are formed with an insulating film interposed therebetween. 2. A chamfered portion is formed at both longitudinal edges of one surface of the solid electrolyte layer on which the lead terminal portion is formed, and the insulating film is formed on the chamfered portion. The laminated gas sensor element as described in the above. 3. The laminated gas sensor element according to claim 1, wherein the insulating film is mainly composed of alumina. 4. The multilayer gas sensor element according to claim 1, wherein the thickness of the insulating film is 1.0 μm or more. 5. A gas sensor comprising the multilayer gas sensor element according to claim 1 arranged inside a metal shell.