JP6438877B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor such as an oxygen gas sensor, a NOx gas sensor, or an HC gas sensor for detecting a specific gas concentration in a gas to be measured such as exhaust gas.

  In such a gas sensor (for example, an oxygen sensor), a sensor having a strip shape or a rod shape made of a solid electrolyte having oxygen ion conductivity in which a pair of electrodes (detection electrodes) are provided on the tip side forming the detection portion. Some elements (hereinafter also simply referred to as elements) are used. Such a gas sensor (hereinafter also referred to simply as a sensor) has an insulating material (inside) inside a metal fitting body (main metal fitting) formed in a cylindrical shape with a screw portion attached to an exhaust gas pipe of an engine, for example. A holder made of ceramic (for example, alumina), that is, a member for positioning the element is disposed. Then, the sensor element is made to project forward from the tip of the holder to the through hole provided in the holder so as to penetrate through the tip, and the projecting part including the sensor is measured. It is configured to be exposed to the target gas. Such a gas sensor is fixed to the exhaust pipe through a screw portion of the metal fitting body by screwing, and the tip end side of the element protrudes into the exhaust pipe to be exposed to the exhaust gas, and is generated based on the gas concentration difference. It is used for air-fuel ratio control by outputting an electric signal to an ECU (Engine Control Unit) provided outside via an electric lead connected to an electrode terminal provided near the rear end of the element. The

  By the way, about the sensor element which comprises this kind of gas sensor, noble metals, such as platinum, are used for conductors (conductive layer), such as an electrode provided inside and outside and an electrode for energizing a heater. For this reason, as the front and rear length of the element increases, the amount of use increases and the cost increases. Therefore, there is a demand for shortening the length of the head in order to reduce costs. In addition to the reduction of the amount of precious metals used, not only the demand for energy saving such as the reduction of power consumption, but also the recent shortening or miniaturization has been demanded. As for the shortening of the sensor element, for example, it is conceivable to shorten the protruding amount (protruding length) of the rear end portion protruding behind the holder provided in the metal fitting body, but this naturally has a limit. This is because the rear end portion of this element is formed with an electrode terminal that forms a contact point with a terminal (terminal fitting) provided at the leading end of a lead wire drawn out to the outside. In order to improve reliability, a predetermined front and rear length (dimension) is required on the formation surface. Further, at the contact, it is necessary to avoid the thermal influence received from the tip side of the element. For this purpose, the position of the electrode terminal is desired to be as far as possible from the tip of the element that is at a high temperature. For these reasons, there is a limit to shortening the length dimension of the element on the rear end side of the holder.

  Therefore, the holder is recessed backward from the tip side to form a recess, and a part on the tip side of the sensor element is accommodated in the recess, so that the tip side protruding from the tip of the holder, that is, the measurement target A gas sensor has been developed in which the protruding length of the tip portion exposed to the gas is reduced (see, for example, Patent Document 1).

JP 2014-228313 A

By the way, when manufacturing a ceramic holder having a recess, as shown in FIG. 7, the raw material powder of the holder is placed in the cavity formed by the mold parts 1100, 1300, 1500, 1700, 1900 constituting the mold 1000. (Ceramic powder) RM is filled, male molds (mold parts) 1300, 1500, and 1700 are sequentially pressed upward to press the raw material powder RM in the cavity to form a green compact. Thereafter, the green compact is taken out from the mold and fired to complete the holder.
At this time, the corner portion 300R of the concave portion 350 of the green compact 300 shown in FIG. 8 is formed by the corner portion 1500S on the upper surface side of the male die 1500. In consideration of the above, the corner 1500S is chamfered and has a curved surface as viewed from the cross section.
However, if the corner 1500S is curved as viewed from the cross section, the pressing force of the corner 1500S of the male mold 1500 (the arrow in FIG. 7, force from the corner 1500S obliquely outwardly upward) is dispersed, so that the raw material powder There is a case where the powder is not sufficiently transmitted to the RM and the compaction becomes insufficient. For this reason, as shown in FIG. 8, when the male mold 1500 is punched, cracks may occur in the corners 300 </ b> R of the green compact 300, or cracks may occur in the corners 300 </ b> R due to a shrinkage reaction during firing of the green compact 300. was there.

  This invention is made | formed in view of this present condition, Comprising: It aims at providing the gas sensor which reduced the product defect of the holder which has a recessed part as a holder which penetrates and hold | maintains a sensor element.

In the gas sensor of the present invention, a ceramic holder in which a through-hole penetrating in the axial direction is formed inside a cylindrical metal fitting body, and a detector is provided on the tip side in the through-hole. In a gas sensor in which a sensor element in the form of a band plate or a bar is passed, and the sensor element projects its tip forward from the tip of the holder, the holder is provided in an inner hole of the metal fitting body The front end facing surface that is locked to the rear end facing surface, the front end facing surface, and a pressing member that presses the holder from the rear end side to the metal fitting main body. A recess recessed backward with respect to the region surrounding the through-hole when viewed from the front-facing surface, or a recess recessed forward with respect to the region surrounding the through-hole when viewed from the rear-facing surface. And said When the cross section along the line direction is viewed, the concave portion includes a horizontal portion extending perpendicularly to the axial direction from the through hole, and a first straight portion extending from the edge of the concave portion toward the through hole side, A connecting portion that connects the horizontal portion and the first straight portion to form a corner portion of the concave portion, and is a region that is 70% or more of the total length of the connecting portion and includes the center of the connecting portion. Forms a second straight line portion.
According to this gas sensor, 70% or more of the total length of the connecting portion forming the corner of the recess is linear (second straight portion). In this case, when the holder is manufactured by compacting the ceramic raw material powder or more, when the male mold for forming the corner is viewed in a cross section along the axial direction, it is 70% or more of the total length of the corner. The length is also linear. For this reason, when the raw material powder is pressed with a male mold, the pressing force at the corners is sufficiently transmitted to the raw material powder without being dispersed, and the powder compaction can be sufficiently performed. This prevents cracks from occurring in the corners of the green compact during die cutting of the male mold or cracks in the corners due to the shrinkage reaction during firing of the green compact, reducing or preventing product defects in the holder. can do.
Further, since the region including the center of the connecting portion is linear (second linear portion), for example, the pressing force at the corner of the male mold is more reliably than when only one end side of the connecting portion is linear. Join the raw powder.

When the cross section of the concave portion along the axial direction is viewed, a region connecting both ends of the second straight portion, the horizontal portion, and the first straight portion of the connection portion protrudes outward. It is good to make the curve part.
According to this gas sensor, since 70% or more of the total length of the corner of the male mold is linear when viewed in cross section, the wear of the male mold is prevented because of the chamfering, and the mold can be easily removed. Become.

  According to this invention, the gas sensor which reduced the product defect of the holder which has a recessed part as a holder which penetrates and hold | maintains a sensor element can be obtained.

It is sectional drawing of the gas sensor concerning embodiment of this invention. It is a top view when the recessed part of a holder is seen from the front end side of an axial direction. It is sectional drawing along the axial direction of the holder. FIG. 4 is a partially enlarged view of FIG. 3. It is a figure which shows the manufacturing process of a ceramic holder. It is sectional drawing which shows the modification of the gas sensor concerning embodiment of this invention. It is a figure which shows the manufacturing process of the ceramic holder in the conventional gas sensor. It is sectional drawing of the green compact of the conventional ceramic holder.

The form for implementing the gas sensor of this invention is demonstrated in detail based on FIGS. 1-4. However, the present embodiment embodies an all-range air-fuel ratio gas sensor that detects the oxygen concentration in the exhaust gas. Therefore, first, the overall configuration of the gas sensor 1 will be briefly described, and then the configuration together with each part. Further details will be described.
In FIG. 1, a gas sensor (full-range air-fuel ratio gas sensor) 1 includes a sensor element 21, a holder (ceramic holder) 30 having a through hole 32 that penetrates the sensor element 21 through the axis O direction, and a ceramic holder 30. And a metal shell 11 surrounding the periphery in the radial direction.
Of the sensor element 21, a portion closer to the tip where the detection unit 22 is formed protrudes from the ceramic holder 30 to the tip. The sensor element 21 thus passed through the through-hole 32 is made up of a sealing material 41 (talc in this example) disposed on the rear end face side (the upper side in the figure) of the ceramic holder 30, a sleeve 43 made of an insulating material, and a ring washer. By compressing in the front-rear direction via 45, the airtightness is fixed in the front-rear direction inside the metal shell 11 and fixed. The portion near the rear end 29 including the rear end 29 of the sensor element 21 protrudes rearward from the sleeve 43 and the metal shell 11, and the electrode terminal 24 formed at the portion closer to the rear end 29 passes through the sealing material 85 to the outside. The terminal fittings 75 provided at the tips of the lead wires 71 drawn out are pressed and electrically connected. Further, a portion near the rear end 29 of the sensor element 21 including the electrode terminal 24 is covered with a protective cylinder 81. This will be described in more detail below.
The ceramic holder 30, the metal shell 11, and the sealing material 41 correspond to “holder”, “metal body”, and “pressing member” in the claims, respectively.

The sensor element 21 extends in the direction of the axis O, and includes a detection electrode or the like (not shown) on the tip side (lower side) directed toward the measurement target, and a detection unit 22 that detects a specific gas component in the detected gas. It has a strip shape (plate shape) with The cross section of the sensor element 21 has a rectangular shape (see FIG. 2) of a certain size (see FIG. 2), and is formed as an elongated body mainly made of ceramic (solid electrolyte or the like). The sensor element 21 itself is the same as a conventionally known one, and a pair of detection electrodes forming the detection unit 22 is disposed near the tip of the solid electrolyte (member). The electrode terminal 24 for connecting the lead wire 71 for taking out the detection output is exposed. In this example, a heater (not shown) is provided in the sensor element 21 inside the ceramic material formed in a laminated form on the solid electrolyte (member) in the vicinity of the front end. The electrode terminal 24 for connecting the lead wire 71 for applying a voltage to the heater is exposed. Although not shown, these electrode terminals 24 are formed in a vertically long rectangle. For example, at a portion near the rear end 29 of the sensor element 21, three or two electrode terminals are arranged side by side on the wide surface (both sides) of the strip. It is out.
The detection unit 22 of the sensor element 21 may be covered with a porous protective layer made of alumina or spinel.

The metal shell 11 has a cylindrical shape with concentric and different diameters at the front and back, a small diameter at the tip side, and a cylindrical annular portion (hereinafter also referred to as a cylindrical portion) for externally fitting and fixing protectors 51 and 61 to be described later. 12 and a screw 13 for fixing to the exhaust pipe of the engine having a larger diameter is provided on the outer peripheral surface behind (upward in the figure). In addition, a polygonal portion 14 for screwing the sensor 1 with the screw 13 is provided behind it. Further, behind the polygonal portion 14, a cylindrical portion 15 for externally fitting and welding a protective cylinder (outer cylinder) 81 that covers the back of the gas sensor 1 is provided, and the outer diameter is provided behind it. A small and thin caulking cylindrical portion 16 is provided. The caulking cylindrical portion 16 is bent inward in FIG. 1 after caulking. A gasket 19 for sealing at the time of screwing is attached to the lower surface of the polygonal portion 14.
On the other hand, the metal shell 11 has an inner hole 18 penetrating in the axis O direction. The inner peripheral surface of the inner hole 18 has a tapered step portion tapering radially inward from the rear end side toward the front end side, and this step portion forms a rear end facing surface 17.

A ceramic holder 30 made of an insulating ceramic (for example, alumina) and formed in a substantially short cylindrical shape is disposed inside the metal shell 11. The ceramic holder 30 has a tip-facing surface 30a formed in a tapered shape that tapers toward the tip. Then, the ceramic holder 30 is positioned in the metal shell 11 by pressing the ceramic holder 30 with the sealing material 41 from the rear end side while the portion near the outer periphery of the front end facing surface 30a is locked to the rear end facing surface 17. And a gap fit.
On the other hand, the through-hole 32 is provided at the center of the ceramic holder 30 and is a rectangular opening having substantially the same dimensions as the cross section of the sensor element 21 so that the sensor element 21 passes through with almost no gap.

  As shown in FIG. 2 and FIG. 3, the through hole 32 has a recess at the front end side that is recessed rearward with respect to the region surrounding the through hole 32 when viewed from the front surface, and communicates with the front end of the through hole 32. A recess 35 having a diameter larger than that of the through hole 32 is formed. In this example, the recess 35 is circular with a diameter larger than that of the through hole 32, and the bottom surface (position of the tip of the through hole 32) 35b of the recess 35 is flat. In this example, the inner peripheral surface 35 i of the recess 35 is parallel to the axis O direction. And the site | part which connects between the bottom face 35b of the recessed part 35 and the internal peripheral surface 35i forms the corner part 35c. In addition, the site | part between the internal peripheral surface 35i and the front end surface 30a, and the site | part between the through-hole 32 and the bottom face 35b are each chamfered.

The sensor element 21 is passed through the through-hole 32 of the ceramic holder 30, and the tip of the sensor element 21 protrudes ahead of the ceramic holder 30 and the tip 12 a of the metal shell 11.
On the other hand, the tip portion of the sensor element 21 is covered with bottomed cylindrical protectors (protective covers) 51 and 61 each having a two-layer structure and both having vent holes (holes) 56 and 67 in this embodiment. Yes. Of these, the rear end of the inner protector 51 is externally fitted and welded to the cylindrical portion 12 of the metal shell 11. For example, eight vent holes 56 are provided in the circumferential direction on the rear end side of the protector 51. On the other hand, for example, four discharge holes 53 are provided in the circumferential direction on the tip side of the protector 51. The outer protector 61 is externally fitted to the inner protector 51 and is welded to the cylindrical portion 12 at the same time. The vent holes 67 of the outer protector 61 are provided, for example, at eight locations in the circumferential direction near the tip, and a discharge hole 69 is also provided at the bottom center of the protector 61 tip.

Further, as shown in FIG. 1, each electrode terminal 24 formed near the rear end 29 of the sensor element 21 has each terminal provided at the tip of each lead wire 71 drawn out through a sealing material 85 to the outside. The metal fitting 75 is pressed and electrically connected by its spring property. In the gas sensor 1, each terminal fitting 75 including the pressure contact portion is provided in a terminal fitting holding member 91 made of an insulating material disposed in a protective cylinder (metal cylinder) 81 having a different diameter cylindrical shape. In each accommodating part, it is provided in opposing arrangement, respectively. The terminal fitting holding member 91 is restricted from moving in the radial direction and the distal end side via an annular support member 80 fixed in a protective cylinder (metal cylinder) 81. The rear end of the gas sensor 1 is covered in an airtight manner by fitting the front end portion (large diameter cylindrical portion) 82 of the protective cylinder 81 to the cylindrical portion 15 near the rear end of the metal shell 11 and welding it. ing. The lead wire 71 is drawn out through a sealing material (for example, rubber) 85 disposed inside the small-diameter cylindrical portion 83 at the rear end of the protective cylinder 81, and the small-diameter cylindrical portion 83 is reduced in diameter. By crimping and compressing the sealing material 85, the airtightness of this part is maintained.
Incidentally, this sealing material 85 is arranged in such a manner that the rear end of the terminal fitting holding member 91 is pushed forward, whereby the mounting stability of the terminal fitting holding member 91 and the terminal fitting 75 provided therein is improved. It has been. The terminal fitting holding member 91 has a flange 93 formed on the outer periphery thereof supported on an annular support member 80 fixed to the inside of the protective cylinder 81, and receives the compressive force of the sealing material 85. ing.

Next, with reference to FIG. 4, the structure of the recessed part 35 of the ceramic holder 30 is demonstrated. 4 is a partially enlarged view of the vicinity of the corner 35c of FIG. 3, and is a cross section along the axis O direction of the ceramic holder 30. FIG.
In FIG. 4, the recess 35 includes a horizontal portion (bottom surface) 35 b extending perpendicularly from the through hole 32 in the direction of the axis O, and a first straight portion extending in the direction of the axis O from the leading edge of the recess 35 toward the through hole 32. Inner peripheral surface) 35i and a connecting portion 35c that connects the horizontal portion 35b and the first straight portion 35i to form the corner of the concave portion 35.
In addition, the horizontal part 35b, the 1st linear part 35i, and the connection part 35c represent the outline in the cut surface of the bottom face 35b of the recessed part 35, the internal peripheral surface 35i, and the corner part 35c, and are described with the same code | symbol.
A chamfered portion may be formed between the first straight portion 35i and the tip-facing surface 30a, but a straight line excluding the chamfered portion of the length in the axis O direction from the bottom surface 35b of the recess 35 to the tip edge. This part is defined as a first straight part 35i. Further, the first straight line portion is not necessarily parallel to the direction of the axis O, and may be inclined. Further, the horizontal portion 35b is horizontal enough to allow an in-plane height difference (for example, about 0.05 mm) caused by a shrinkage error during firing.

A region that is 70% or more of the entire length of the connection portion 35c and includes the center Ce of the connection portion 35c forms the second straight portion 35L. Here, the boundary P1 between the connecting portion 35c and the horizontal portion 35b is a point where the contour of the concave portion 35 deviates from the extension line of the horizontal portion 35b. Similarly, the boundary P2 between the connecting portion 35c and the first straight portion 35i is a point where the contour of the concave portion 35 deviates from the extension line of the first straight portion 35i.
In this way, the entire length of the connecting portion 35c is determined by the contour line between the boundaries P1 and P2, and the midpoint thereof is regarded as the center Ce of the connecting portion 35c. And let the straight line which passes along this center Ce be the 2nd linear part 35L.
In the present embodiment, regions 35r1 and 35r2 that connect both ends P3 and P4 of the second straight portion 35L, the horizontal portion 35b, and the first straight portion 35i respectively form convex curved portions toward the outside. Both ends P3 and P4 of the second straight portion 35L are points where the contours of the recesses 35 are deviated from the extended line of the second straight portion 35L. In the present embodiment, the midpoint of P3 and P4 is the center Ce of the connecting portion 35c.

According to such a gas sensor 1, 70% or more of the total length of the connecting portion 35c forming the corner of the recess 35 is linear (second straight portion 35L). In this case, as shown in FIG. 5 below, when the male mold 150 for forming the corner is viewed in a cross section along the direction of the axis O, the length of 70% or more of the entire length of the corner 150S is also a straight line. It becomes a shape. For this reason, the pressing force of the corner portion 150S (the arrow in FIG. 5, a force obliquely upward from the corner portion 150S) when the raw powder (ceramic powder) RM of the ceramic holder 30 is pressed by the male die 150 is dispersed. Without being sufficiently transmitted to the raw material powder RM, the powder compaction can be sufficiently performed. For this reason, it is possible to prevent cracks from occurring in the corners of the green compact when the male mold 150 is die-cut, and cracks from occurring in the corners due to the shrinkage reaction during the firing of the green compact, thereby reducing product defects in the ceramic holder 30. It can be reduced or prevented.
In addition, since the region including the center Ce of the connection portion 35c is linear (second linear portion 35L), for example, compared to a case where only one end side of the connection portion 35c is linear, the corner portion 150S of the male mold 150 is formed. The pressing force is more reliably applied to the raw material powder RM.
Furthermore, in the present embodiment, the regions 35r1 and 35r2 at both ends of the second straight portion 35L form curved portions that protrude outward, and therefore the male mold 150 for forming the corners is arranged in the direction of the axis O. When viewed in a cross section along, the front and rear edges of the corner 150S are curved and chamfered. For this reason, when viewed in a cross section, 70% or more of the entire length of the corner portion 150S is linear, but since the chamfer is chamfered, the wear of the male die 150 is prevented and the die can be easily removed.

Next, the manufacturing process of the ceramic holder 30 will be described with reference to FIG.
First, a cavity is formed so as to be surrounded by the mold parts 110, 130, 150, and 170 constituting the mold 100 so that the upper surface is opened. Then, the raw material powder (ceramic powder) RM of the ceramic holder 30 is supplied into the cavity from above (FIG. 5A).
Next, the upper mold 190 is lowered from above the cavity, and the raw material powder RM is sandwiched between the mold parts 110, 130, 150, 170, and 1900 (FIG. 5B).
Next, the male molds (mold parts) 130, 150, and 170 are raised in order, and the raw material powder RM in the cavity is pressed to produce a green compact (FIG. 5C). At this time, first, the male mold 130 is raised to form a portion corresponding to the tip-facing surface 30a of the ceramic holder 30, then the male mold 150 is raised to form a portion corresponding to the recess 35, and finally the male mold The mold 170 is raised to form a portion corresponding to the through hole 32. At this time, as described above, since 70% or more of the total length of the corner portion 150S of the male mold 150 is linear as viewed from the cross section, the pressing force of the corner portion 150S of the male mold 150 is sufficient for the raw material powder RM. The powder can be fully compressed.
Thereafter, the green compact is removed from the mold and fired to complete the ceramic holder 30.

The gas sensor of the present invention can be embodied by appropriately changing the structure and configuration without departing from the gist of the present invention.
For example, the shape of the ceramic holder and its recess is not limited to the above.
Specifically, as shown in FIG. 6, a ceramic holder 30 having a recess 235 that is recessed forward with respect to a region surrounding the through hole 220 when viewed from the rear end-facing surface can be used. The gas sensor 1B shown in FIG. 6 is substantially the same as the gas sensor 1 except that the shapes of the metal shell 11B, the ceramic holder 30, and the terminal metal fitting holding member 91B are different from those of the gas sensor 1. The detailed description is omitted by attaching “B” to the reference numerals of the components. For example, although the protectors 51B and 61B in FIG. 6 are slightly different from the protectors 51 and 61 of the gas sensor 1, they are similarly double protectors.

In the gas sensor 1B, the metal shell 11B has an inner hole 18B penetrating in the direction of the axis O. The inner peripheral surface of the inner hole 18B has two tapered steps that taper radially inward from the rear end side toward the front end side, and the step portion on the rear end side is the rear end facing surface 17B. Is forming.
On the other hand, the ceramic holder 200 is disposed inside the metal shell 11B. In the vicinity of the center of the ceramic holder 200 in the axis O direction, a step portion whose tip side is reduced in diameter is formed, and this step portion constitutes a tip-facing surface 200a. A cylindrical terminal fitting holding member 91B that opens toward the tip is disposed at the rear end of the ceramic holder 200, and the terminal fitting holding member 91B is covered with a protective cylinder 81.
The ceramic holder 200 is pressed by the terminal fitting holding member 91B from the rear end side while the front end facing surface 200a of the ceramic holder 200 is locked to the rear end facing surface 17B of the metallic shell 11B. The ceramic holder 200 is positioned and fitted with a gap. The terminal fitting holding member 91B corresponds to a “pressing member” in the claims.
On the other hand, the through-hole 220 is provided at the center of the ceramic holder 200, and is a rectangular opening having substantially the same dimensions as the cross-section of the sensor element 21B so that the sensor element 21B passes through with almost no gap.

  Furthermore, the rear end side of the through hole 220 is recessed forward with respect to the region surrounding the through hole 200 when viewed from the rear end-facing surface, and communicates with the rear end of the through hole 220 and has a diameter larger than that of the through hole 220. A large recess 235 is formed. In this example, the recess 235 has a circular shape with a diameter larger than that of the through hole 220, and the bottom surface (position of the rear end of the through hole 32) 235b of the recess 235 has a flat surface. In this example, the inner peripheral surface 235i of the recess 235 is parallel to the axis O direction. And the site | part which connects between the bottom face 235b and the internal peripheral surface 235i of the recessed part 235 forms the corner part 235c. In addition, the site | part between the internal peripheral surface 235i and the rear-end edge of the ceramic holder 200, and the site | part between the through-hole 220 and the bottom face 235b are each chamfered.

  In the example of FIG. 6 as well, 70% or more of the total length of the connecting portion 235c forming the corner of the concave portion 235 is linear. In this case, when the male mold for forming the corner is viewed in the axial section, the length of 70% or more of the total length of the corner is also linear. Therefore, the pressing force at the corners when the raw material powder (ceramic powder) of the ceramic holder is pressed with a male die is sufficiently transmitted to the raw material powder without being dispersed, and the powder compaction can be sufficiently performed. For this reason, cracks in the corners of the green compact during die cutting of the male mold and cracks in the corners due to the shrinkage reaction when the green compact is fired are suppressed, reducing product defects in the ceramic holder. Can be prevented.

  In the above embodiment, the sensor element has a rectangular plate shape with a rectangular cross section. However, the sensor element used in the gas sensor of the present invention may have a square cross section. Other than that. Furthermore, in the above description, the full-range air-fuel ratio gas sensor is embodied, but the gas sensor according to the present invention can be embodied in other gas sensors.

1, 1B gas sensor 11, 11B metal shell (metal body)
17, 17B Rear end-facing surfaces 18 and 18B of the metal shell Inner holes 21 and 21B Sensor element 22 Detector 30 and 200 Holder (ceramic holder)
30a, 200a Front-facing surfaces 32, 220 of the ceramic holder Through holes 35, 235 of the ceramic holder Recess 41, 91B Press member 35b Horizontal portion 35i First straight portion 35c, 235c Connection portion (corner portion of the recess)
35L 2nd straight line part 35r1, 35r2 Curved part Ce Central O axis of connecting part

Claims (2)

A ceramic holder in which a through-hole penetrating in the axial direction is disposed inside the cylindrical metal fitting body, and a strip-like or rod-like shape having a detection portion on the tip side in this through-hole. In the gas sensor in which the sensor element is formed, and the sensor element has its tip protruding forward from the tip of the holder,
The holder has a front end facing surface that is locked to a rear end facing surface provided in an inner hole of the metal fitting body, and the front end facing surface and a pressure that presses the holder from the rear end side to the metal fitting body. Is positioned on the metal fitting body by a member,
The holder is recessed backward with respect to the region surrounding the through hole when viewed from the front surface, or forward with respect to the region surrounding the through hole when viewed from the rear surface. Has a recessed recess,
When the cross section along the axial direction is viewed, the concave portion includes a horizontal portion that extends perpendicularly to the axial direction from the through hole, and a first straight portion that extends from an edge of the concave portion toward the through hole side. A connecting portion that connects the horizontal portion and the first straight portion to form a corner portion of the concave portion, and has a length of 70% or more of the total length of the connecting portion and includes the center of the connecting portion. A gas sensor characterized in that the region forms a second straight portion.   When the cross section of the concave portion along the axial direction is viewed, a region connecting both ends of the second straight portion, the horizontal portion, and the first straight portion of the connection portion protrudes outward. The gas sensor according to claim 1, wherein the gas sensor has a curved portion.

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