WO2022249924A1

WO2022249924A1 - Gas sensor

Info

Publication number: WO2022249924A1
Application number: PCT/JP2022/020451
Authority: WO
Inventors: 伸幸辻
Original assignee: 株式会社デンソー
Priority date: 2021-05-24
Filing date: 2022-05-17
Publication date: 2022-12-01
Also published as: JPWO2022249924A1

Abstract

This gas sensor (1) comprises a sensor element (2), a housing (5) in which the sensor element (2) is held, and tip-side covers (61A, 61B) fitted to a tip-side site (53) positioned on the tip side (L1) of the housing (5) in an axial direction (L). A joined part (711), where opening ends (611A, 611B) of the tip-side covers (61A, 61B) and a tip-side fitting end (532) of the housing (5) are joined on the entire circumference in a circumferential direction (C), is formed in one area in the axial direction (L) of a tip-side fitting site (71) where the opening ends (611A, 611B) are fitted to the tip-side fitting end (532). A gap (712A) having a radius of at least 50 μm is formed in a circumferential-direction site excluding a portion in the circumferential direction (C), the site being the remaining area of the tip-side fitting site (71) in the axial direction (L) excluding the one area.

Description

gas sensor

Cross-reference to related applications

This application is based on Japanese Patent Application No. 2021-86655 filed on May 24, 2021, and the contents thereof are incorporated herein by reference.

The present disclosure relates to gas sensors.

The gas sensor is arranged in an exhaust pipe of an internal combustion engine, and is used to detect the air-fuel ratio of the internal combustion engine based on the detection target gas, which is the exhaust gas flowing through the exhaust pipe, and to detect oxygen or a specific gas contained in the detection target gas. It is used for applications such as A gas sensor includes a sensor element provided with a gas detection portion, a housing holding the sensor element, a cover attached to the housing, and the like. The covers include a front end cover that is placed inside the exhaust pipe and protects the gas detection part of the sensor element from being exposed to water, etc., and a base that is placed outside the exhaust pipe and protects the electrical connection part of the sensor element from being exposed to water and the like. There is an end cover.

In order to ensure airtightness, the attachment part where the open end of the distal end cover or the proximal end cover is attached to the attachment end of the housing is fixed by welding, press fitting, crimping, etc. so as not to create a gap. has been For example, in the gas sensor of Patent Document 1, it is described that the open end of the tip side cover is crimped and welded to be fixed to the housing. In particular, in Patent Document 1, a small diameter portion in the circumferential direction is formed on the tip side cover (outer member) by caulking or the like, and a welded portion in the circumferential direction is formed in the small diameter portion and joined to the housing (inner member). I am trying to By forming the small-diameter portion, the amount of gap between the distal end cover and the housing at the position where the weld is formed is reduced, and the adhesion is enhanced, thereby forming a state in which poor welding is less likely to occur.

JP-A-11-352095

In each region in the axial direction of the mounting portion where the opening end of the distal end cover or the proximal end cover and the mounting end of the housing face each other, in addition to the joint region where the entire circumference is joined by laser welding, laser welding is performed. There are unbonded areas that are not bonded by In this non-bonded region, the open end and the mounting end appear to be in contact with each other, and an unintended minute gap with a width of about 10 μm is formed due to the surface roughness. A liquid such as water may enter this minute gap.

Then, the liquid accumulates in the minute gaps, causing a difference in concentration of dissolved oxygen and ions in the liquid, and a potential difference depending on the concentration difference. If the state in which this potential difference is not eliminated continues, there is a risk that corrosion of the concentration cell will progress at the attachment site forming the minute gap. In this case, the mounting strength of the cover to the housing may be reduced.

In addition, due to the minute gaps formed in the non-bonded areas, inert gas or the like may be involved in the bonded areas when laser welding is performed on the bonded areas. In this case, there is a possibility that the attachment strength of the cover to the housing may be reduced due to blow holes occurring in the joint region.

The present disclosure seeks to provide a gas sensor that can make it difficult for the mounting strength of the cover to the housing to decrease.

One aspect of the present disclosure is
comprising a sensor element, a housing holding the sensor element, and a cover attached to the housing,
The opening end of the cover is attached to the mounting end of the housing in one axial region of the mounting portion, and the opening end and the mounting end are joined to each other along the entire circumference of the housing. is formed and
A gas sensor, wherein a gap is formed in a remaining area of the mounting portion in the axial direction, excluding the one area, in a circumferential portion excluding the entire circumferential circumference or a portion of the circumferential direction. It is in.

Another aspect of the present disclosure is the
a sensor element, a housing holding the sensor element, an inner peripheral side cover attached to the housing, and an outer peripheral side cover attached to the inner peripheral side cover,
In one region in the axial direction of the mounting portion where the inner peripheral side open end portion of the inner peripheral side cover and the outer peripheral side open end portion of the outer peripheral side cover are attached to the mounting end portion of the housing, the outer peripheral side open end A joint portion is formed by joining the portion, the inner peripheral side opening end portion, and the mounting end portion along the entire circumference in the circumferential direction,
Between the inner peripheral side open end portion and the mounting end portion and between the outer peripheral side open end portion and the inner peripheral side open end portion in the remaining area excluding the one area in the axial direction of the attachment portion In the gas sensor, a gap is formed in at least one of the positions between and in the circumferential direction except for the entire circumference or the part in the circumferential direction.

(Gas sensor of one aspect)
In the gas sensor of the above aspect, the gap is intentionally formed in the remaining area except for one area in the axial direction of the mounting portion where the opening end of the cover is mounted on the mounting end of the housing. This gap is formed along the entire circumference, or along a circumferential portion excluding a portion of the circumference. Also, the intentionally formed gap is formed with a width of, for example, 50 μm or more.

With this configuration, even if liquid such as water enters the gap, it is possible to prevent the liquid from accumulating in the gap and to prevent corrosion of the concentration cell. In addition, with this configuration, when the joint is formed in one region of the mounting portion in the axial direction, it is possible to prevent inert gas or the like from being caught in the joint.

Therefore, according to the gas sensor of one aspect, it is possible to make it difficult for the mounting strength of the cover to the housing to decrease.

(Gas sensor of another aspect)
In the gas sensor of the other aspect, the inner peripheral side open end portion of the inner peripheral side cover and the outer peripheral side open end portion of the outer peripheral side cover are attached to the mounting end portion of the housing except for one area in the axial direction of the mounting portion. A gap is intentionally formed in the remaining portion. This gap is at least one between the inner peripheral side open end and the mounting end and between the outer peripheral side open end and the inner peripheral side open end, and is the entire circumference in the circumferential direction, or is formed in a circumferential portion except for a part of the Also, the intentionally formed gap is formed with a width of, for example, 50 μm or more.

Therefore, even with the gas sensor of the other aspect, the mounting strength of the cover to the housing can be made less likely to decrease.

It should be noted that the symbols in parentheses for each component shown in each aspect of the present disclosure indicate the correspondence relationship with the symbols in the drawings in the embodiment, but each component is not limited only to the contents of the embodiment.

Objects, features, advantages, etc. of the present disclosure will become clearer from the following detailed description with reference to the accompanying drawings. Drawings of the present disclosure are provided below.
FIG. 1 is an explanatory diagram showing a gas sensor according to Embodiment 1. FIG. FIG. 2 is an enlarged cross-sectional view showing a periphery of a joint portion of a distal end side attachment end portion of a housing, an inner peripheral distal side cover, and an outer peripheral distal side cover according to the first embodiment. 3 is a view showing the vicinity of the joint portion of the front end side mounting end portion of the housing, the inner peripheral front end cover and the outer peripheral front end cover according to the first embodiment, and is a cross-sectional view taken along line III-III in FIG. 1. FIG. . FIG. 4 is an enlarged cross-sectional view showing a periphery of a joint portion between a base-end mounting end portion of the housing and an inner circumference base-end cover according to the first embodiment; 5 is a cross-sectional view taken along the line VV in FIG. 1, showing the periphery of the joint portion between the base-side mounting end portion of the housing and the inner peripheral base-side cover according to the first embodiment. 6 is another view showing the vicinity of the joining portion of the front end side attachment end portion of the housing, the inner peripheral front end cover, and the outer peripheral front end cover according to the first embodiment, and corresponds to the III-III cross section of FIG. 1; It is a diagram. FIG. 7 is a view showing the vicinity of the joining portion of the tip end side attachment end portion of the housing, the inner peripheral tip side cover, and the outer periphery tip side cover according to the second embodiment, and is a view corresponding to the cross section III-III of FIG. 1; be. FIG. 8 is another view showing the vicinity of the joining portion of the tip side mounting end portion of the housing, the inner periphery tip side cover, and the outer periphery tip side cover, corresponding to the III-III cross section of FIG. 1, according to the second embodiment; It is a diagram. FIG. 9 is a view showing the vicinity of the joining portion between the base-side attachment end portion of the housing and the inner peripheral base-side cover according to the second embodiment, and is a cross-sectional view corresponding to VV in FIG. 10 is another view showing the periphery of the joint portion of the base-side mounting end portion of the housing and the inner peripheral base-side cover according to the second embodiment, and is a cross-sectional view corresponding to the VV of FIG. 1. FIG.

A preferred embodiment of the gas sensor described above will be described with reference to the drawings.
<Embodiment 1>
As shown in FIG. 1, the gas sensor 1 of this embodiment is attached to a sensor element 2, a housing 5 holding the sensor element 2, and a distal end portion 53 positioned on the distal end side L1 of the housing 5 in the axial direction L. and proximal side covers 62A, 62B attached to the proximal side portion 54 positioned on the proximal side L2 in the axial direction L of the housing 5. As shown in FIG.

As shown in FIGS. 2 and 3, the

opening ends

611A and 611B of the front end covers 61A and 61B are located in one region in the axial direction L of the front end mounting portion 71 mounted on the front end mounting end 532 of the housing 5. , the

open end portions

611A and 611B and the tip side mounting end portion 532 are joined in the entire circumference in the circumferential direction C to form a joint portion 711. As shown in FIG. A gap 712A having a radius of 50 μm or more is formed in a circumferential portion excluding a part in the circumferential direction C, which is the remaining region in the axial direction L of the distal end side mounting portion 71 excluding one region.

As shown in FIGS. 4 and 5, the opening end 621A of the base end cover 62A is located in one region in the axial direction L of the base end mounting portion 72 mounted to the base end mounting end 541 of the housing 5. , and the opening end 621A and the base-side mounting end 541 are joined over the entire circumference in the circumferential direction C to form a joint 721. As shown in FIG. A gap 722 having a radius of 50 μm or more is formed in a circumferential portion of the base end mounting portion 72 in the axial direction L, excluding one region, and excluding a portion in the circumferential direction C. As shown in FIG.

The gas sensor 1 of this embodiment will be described in detail below.
(Gas sensor 1)
As shown in FIG. 1, the gas sensor 1 is arranged in an exhaust pipe of an engine of a vehicle, and is used to detect the oxygen concentration and the like in the exhaust gas G flowing through the exhaust pipe as the gas to be detected. The gas sensor 1 of this embodiment is used as an oxygen sensor (also called a λ sensor). The oxygen sensor detects the electromotive force generated between the

electrodes

35 and 36 via the solid electrolyte body 3 to be described later, and the air-fuel ratio of the engine obtained from the composition of the exhaust gas G is lower than the stoichiometric air-fuel ratio. It is determined whether it is on the fuel-rich side where the ratio is high or on the fuel-lean side where the ratio of fuel to air is small compared to the stoichiometric air-fuel ratio. The gas sensor 1 may be used as an air-fuel ratio sensor (A/F sensor) that quantitatively determines the air-fuel ratio in the engine on the lean side and the rich side based on the oxygen concentration or the unburned gas concentration in the exhaust gas G. .

A catalyst for purifying harmful substances in the exhaust gas G is arranged in the exhaust pipe, and the gas sensor 1 is arranged upstream of the catalyst in the flow direction of the exhaust gas G in the exhaust pipe. The gas sensor 1 may be arranged downstream of the catalyst in the flow direction of the exhaust gas G in the exhaust pipe. Further, the gas sensor 1 may be arranged both upstream and downstream of the catalyst in the flow direction of the exhaust gas G in the exhaust pipe. Further, the gas sensor 1 may be arranged in a pipe on the suction side of a turbocharger that uses the exhaust gas G to increase the density of the air that the engine takes in. Further, the piping in which the gas sensor 1 is arranged may be piping in an exhaust gas recirculation mechanism that recirculates part of the exhaust gas G discharged from the engine to the exhaust pipe to the intake pipe of the engine.

(Axial direction L and circumferential direction C)
As shown in FIGS. 1 to 5, in this embodiment, the axial direction L refers to the direction along the central axis O1 of the sensor element 2 and the housing 5. As shown in FIGS. The circumferential direction C is the direction around the center axis O1 of the sensor element 2 and the housing 5 .

(Sensor element 2)
As shown in FIG. 1, the solid electrolyte body 3 of the sensor element 2 has a cylindrical portion 31 and a hemispherical bottom portion 32 that closes the tip end side L1 of the cylindrical portion 31 in the axial direction L. In other words, the solid electrolyte body 3 has a hollow shape in which the front end side L1 in the axial direction L is closed. An opening 33 that allows the reference gas A to flow into the solid electrolyte body 3 is formed at the base end of the solid electrolyte body 3 in the axial direction L. As shown in FIG. The outer diameter of each portion in the axial direction L of the cylindrical portion 31 is appropriately changed in consideration of attachment to the housing 5 .

The solid electrolyte body 3 of the sensor element 2 is mainly composed of zirconia, and is composed of stabilized zirconia or partially stabilized zirconia obtained by partially substituting zirconia with a rare earth metal element or alkaline earth metal element. The solid electrolyte body 3 can be composed of yttria-stabilized zirconia or yttria-partially-stabilized zirconia. The solid electrolyte body 3 has ion conductivity to conduct oxide ions (O ²⁻ ) at a predetermined activation temperature. The detection electrode 35 and the reference electrode 36 contain platinum or the like that exhibits catalytic activity with respect to oxygen.

A detection electrode 35 exposed to the exhaust gas G is provided on the outer surface 311 of the solid electrolyte body 3, and a reference electrode 36 exposed to the reference gas A is provided on the inner surface 312 of the solid electrolyte body 3. . The detection electrode 35, the reference electrode 36, and the portion of the solid electrolyte body 3 sandwiched between the

electrodes

35 and 36 form a detection cell for detecting the gas concentration. An electromotive force generated between the detection electrode 35 and the reference electrode 36 is detected by the sensor control device of the gas sensor 1 .

A protective layer 211 made of a porous body of metal oxide such as alumina is provided on the element tip portion 21 of the sensor element 2 in the axial direction L so as to cover at least the tip side portion of the detection electrode 35 . The protective layer 211 is for preventing the detection electrode 35 from being poisoned or exposed to water.

(Heater element 4)
As shown in FIG. 1, a heater element 4 for heating the detection cells of the sensor element 2 is arranged inside the sensor element 2 . The heater element 4 has a central shaft portion 41 made of an insulating base material, and a sheet portion 42 made of an insulating base material on which a heating element 43 is provided and wound around the outer circumference of the central shaft portion 41 . The heating element 43 is embedded between the central shaft portion 41 and the sheet portion 42 in a state where the sheet portion 42 is wound around the central shaft portion 41 . The heating element 43 is made of a conductive material. The central shaft portion 41 and the sheet portion 42 are made of a ceramic material, particularly a metal oxide such as alumina (aluminum oxide).

An outer terminal fitting 81 electrically connected to the detection electrode 35 is attached to the outer periphery of the base end of the sensor element 2 . An inner terminal fitting 82 for supporting the heater element 4 inside the sensor element 2 and electrically connected to the reference electrode 36 is attached to the inner periphery of the base end portion of the sensor element 2 . A power supply fitting 83 for supplying power to the heating element 43 is attached to the outer periphery of the base end of the heater element 4 .

(Housing 5)
As shown in FIG. 1, an insertion hole 51 is formed in the central position of the housing 5 so as to pass therethrough in the axial direction L for holding the sensor element 2 . The insertion hole 51 has a small-diameter hole portion 511 positioned on the distal end side L1 in the axial direction L and a large-diameter hole portion 512 positioned on the proximal end side L2 in the axial direction L and having a larger diameter than the small-diameter hole portion 511. . The sensor element 2 is inserted into the small-diameter hole portion 511 and the large-diameter hole portion 512 of the insertion hole 51, and a sealing material such as talc powder or a sleeve is placed in the gap between the sensor element 2 and the large-diameter hole portion 512. 84 is retained. By locking the flange portion 34, which is the portion of the sensor element 2 having the largest outer diameter, to the end portion of the small-diameter hole portion 511, the sensor element 2 is prevented from slipping out of the insertion hole 51 toward the tip side L1. .

In addition, the housing 5 has a mounting portion 52 having the largest outer diameter and having a hexagonal outer shape, and a front end side L1 of the mounting portion 52 in the axial direction L and having a diameter smaller than that of the mounting portion 52. It has a distal side portion 53 and a proximal side portion 54 provided on the proximal side L2 of the mounting portion 52 in the axial direction L and having a smaller diameter than the mounting portion 52 . The distal end portion 53 is formed with an externally threaded portion 531 and a distal end mounting end portion 532 located on the distal side L1 of the externally threaded portion 531 having a smaller diameter than the externally threaded portion 531 . ing. The proximal side portion 54 has a proximal side mounting end portion 541 and a crimped portion 542 having a smaller diameter than the proximal side mounting end portion 541 and positioned on the proximal side L2 of the proximal side mounting end portion 541 . formed.

The gas sensor 1 is attached to the exhaust pipe by being rotated by a tool that engages the attachment portion 52 of the housing 5 and tightening the male threaded portion 531 of the housing 5 to the female threaded portion of the attachment hole of the exhaust pipe. By bending the crimped portion 542 inward, the sealing material 84 is compressed in the axial direction L between the crimped portion 542 and the flange portion 34 , and the sensor element 2 is held by the housing 5 . The element tip portion 21 of the sensor element 2 is arranged to protrude from the tip side mounting end portion 532 of the housing 5 toward the tip side L1 in the axial direction L. As shown in FIG.

In this embodiment, the

joints

711, 721 and the

gaps

712A, 712B, 722 are formed between the distal attachment portion 71 between the housing 5 and the

distal covers

61A, 61B and between the housing 5 and the proximal cover 62A. is formed at the proximal side mounting portion 72 of the . The

joints

711 and 721 and the

gaps

712A, 712B and 722 may be formed only in one of the distal attachment portion 71 and the proximal attachment portion 72 .

(Distal side covers 61A, 61B)
As shown in FIG. 1 , tip side covers 61A and 61B are attached to the outer periphery of the tip end mounting end 532 of the housing 5 to cover the element tip 21 of the sensor element 2 and protect the element tip 21 . It is The tip side covers 61A and 61B are arranged inside the exhaust pipe. A gas passage hole 612 for allowing the exhaust gas G to pass is formed in the tip side covers 61A and 61B. Exhaust gas G flowing into the tip side covers 61A and 61B from the gas passage holes 612 of the tip side covers 61A and 61B passes through the protective layer 211 of the sensor element 2 and is guided to the detection electrode 35 . The tip side covers 61A and 61B of this embodiment have a double structure.

As shown in FIGS. 2 and 3, the distal end covers 61A and 61B are composed of an inner peripheral distal end cover (inner peripheral cover) 61A attached to the outer periphery of the distal attachment end 532 of the housing 5, and an inner peripheral distal end cover 61A. It is composed of an outer peripheral tip side cover (outer peripheral side cover) 61B attached to the outer periphery of the side cover 61A. An open end (inner peripheral side open end) 611A of an inner peripheral tip side cover 61A is attached to the outer periphery of the tip side attachment end portion 532 of the housing 5 . A joint portion 711 and a gap 712A are formed in mutually different regions in the axial direction L in the tip-side attachment portion 71 between the tip-side attachment end portion 532 and the opening end portion 611A of the inner peripheral tip-side cover 61A. . A gap 712</b>A is formed in regions on both sides in the axial direction L with respect to the joint portion 711 in the distal end side mounting portion 71 .

The center axis O2 of the opening end portion 611A of the inner peripheral tip side cover 61A and the center axis O1 of the tip side mounting end portion 532 of the housing 5 are offset from each other. In other words, the inner diameter of the opening end portion 611A of the inner peripheral tip end cover 61A of this embodiment is larger than the outer diameter of the tip end mounting end portion 532 of the housing 5 by 50 μm or more. The opening end portion 611A of the peripheral tip side cover 61A is attached eccentrically to the tip side attachment end portion 532 of the housing 5. As shown in FIG. With this configuration, the mounting of the inner peripheral front end cover 61A to the housing 5 is facilitated, and a gap 712A of 50 μm or more is formed between the front end mounting end 532 of the housing 5 and the opening end 611A of the inner peripheral front cover 61A. can be easily formed.

As shown in FIG. 3, in the cross section of the housing 5 in the direction orthogonal to the axial direction L, the width of the gap 712A between the front end mounting end portion 532 and the opening end portion 611A of the inner peripheral front end cover 61A is It is changing toward direction C. Specifically, in the cross section of the distal end mounting portion 71 in the direction orthogonal to the axial direction L, the opening end 611A of the inner peripheral distal end cover 61A and the distal end mounting end 532 of the housing 5 are positioned in the circumferential direction C. They are in contact at the specific site C1. In other words, the gap 712A between the opening end portion 611A of the inner peripheral distal end cover 61A and the distal end mounting end portion 532 of the housing 5 is the smallest at the specific portion C1 in the circumferential direction C and Largest at the site opposite site C1.

The width of the gap 712A at the maximum position in the circumferential direction C is made larger than the height of the unevenness due to the surface roughness of the front end mounting end 532 and the surface roughness of the opening end 611A. For example, the tip side mounting end portion 532 is formed with a surface roughness of 25Z (ten-point average roughness Rz, 25 μm), and the opening end portion 611A is formed with a surface roughness of 6.3Z (ten-point average roughness Rz, 25 μm), for example. 6.3 μm). In this case, since the width of the gap 712A at the maximum position in the circumferential direction C is 50 μm or more, it is possible to prevent liquid such as water from accumulating in the gap 712A. This is due to a gap 712B between an opening end portion 611A of the inner periphery distal end cover 61A and an opening end portion 611B of the outer periphery distal end cover 61B, and a proximal mounting end portion 541 of the housing 5 and the inner periphery proximal end, which will be described later. The same applies to the gap 722 between the side cover 62A and the open end 621A.

In this embodiment, the width of the gap 712A may be the width between the average lines (reference lines) of the 10-point average or arithmetic average of the unevenness of the surfaces of the distal attachment end 532 and the opening end 611A. The same applies to

gaps

712B and 722, which will be described later.

As shown in FIG. 2, the opening end portion 611A of the inner periphery front end side cover 61A and the opening end portion (outer periphery side opening end portion) 611B of the outer periphery front end side cover 61B of the present embodiment are laser-welded to form the housing 5. is joined to the distal mounting end 532 of the . In a state in which the opening end 611A of the inner periphery tip cover 61A and the opening end 611B of the outer periphery tip cover 61B are attached to the tip attachment end 532 of the housing 5, the opening end 611B of the outer periphery tip cover 61B is attached. The laser reaches from the perimeter to the distal attachment end 532 . As a result, the open end 611B of the outer peripheral front end cover 61B, the open end 611A of the inner peripheral front end cover 61A, and the front end mounting end 532 are partially melted and welded to form a joint 711. .

A gap 712A between the mounting end portion 532 on the front end side of the housing 5 and the open end portion 611A of the inner peripheral front end cover 61A has a width of 50 μm or more in terms of radius at the maximum position in the circumferential direction C. , the width of which is equal to or less than 1/2 of the thickness of the opening end portion 611A of the inner circumference tip side cover 61A. If the width of the gap 712A is less than 50 μm, there is a possibility that the welding quality may be deteriorated due to concentration cell corrosion in the tip-side mounting portion 71, entrainment of inert gas in the joint portion 711, or the like. On the other hand, if the gap 712A is larger than half the thickness of the opening end portion 611A of the inner peripheral tip cover 61A, the outer peripheral tip cover 61B and the inner peripheral tip cover 61A will be perforated during welding. may occur.

The front mounting end 532 of the housing 5, the open end 611A of the inner peripheral front cover 61A, and the open end 611B of the outer peripheral front cover

61B form gaps

712A and 712B of appropriate widths to provide appropriate power. By performing the laser welding of (W), they are properly joined. The laser welding power may be determined, for example, within the range of 400-700 (W).

Here, the front end mounting portion 71 is a portion where the front end mounting end portion 532 of the housing 5 and the opening end portion 611A of the inner peripheral front end cover 61A face each other. The front end mounting portion 71 includes a front end mounting end portion 532 and an opening end portion 611A of the inner circumference front end cover 61A.

2 and 3, the gap 712B between the opening end portion 611A of the inner peripheral front end cover 61A and the opening end portion 611B of the outer peripheral front end cover 61B of this embodiment is the maximum in the circumferential direction C. At the position, the radius is formed with a width of 50 μm or more and a width of 1/2 or less of the thickness of the opening end portion 611A of the inner periphery tip side cover 61A. By forming the gap 712B, the exhaust gas G flows between the opening end portion 611A of the inner periphery front end cover 61A and the opening end portion 611B of the outer periphery front end cover 61B, and water is less likely to remain.

Moreover, the gap having a width of 50 μm or more is defined between the front end mounting end 532 of the housing 5 and the opening end 611A of the inner peripheral front cover 61A, or between the opening end 611A of the inner peripheral front cover 61A and the outer periphery. It may be formed only on either side between the tip side cover 61B and the open end 611B.

In particular, the gap having a width of 50 μm or more may be formed only between the open end 611A of the inner peripheral front end cover 61A and the open end 611B of the outer peripheral front end cover 61B for the following reason. In this embodiment, the linear expansion coefficient of the metal material forming the inner peripheral front end cover 61A and the outer peripheral front end cover 61B is larger than the linear expansion coefficient of the metal material forming the housing 5 . In addition, the inner peripheral tip side cover 61A and the outer peripheral tip side cover 61B are made of the same metal material. The housing 5 is made of, for example, SUS430, and the front end covers 61A and 61B are made of, for example, SUS310S, an alloy containing nickel, or the like.

Therefore, when the opening ends 611A and 611B and the tip end side mounting end portion 532 are laser-welded, the tip side mounting end portion 532 of the housing 5 and the opening end portion 611A of the inner periphery tip side cover 61A are separated due to the difference in thermal expansion. The gap 712A between them becomes large, and the liquid hardly accumulates in this gap 712A, and it becomes difficult for inert gas or the like to be involved in the gap 712A. Further, even when the gas sensor 1 is heated during use of the gas sensor 1, the gap 712A between the front end mounting end 532 of the housing 5 and the opening end 611A of the inner peripheral front cover 61A is increased. change to

For this reason, even if only the gap 712B has a width of 50 μm or more, it is possible to suppress the occurrence of concentration cell corrosion and the occurrence of blowholes at the time of joining in the front end mounting portion 71 .

It should be noted that the tip side covers 61A and 61B may have a single-layer structure with only the inner periphery tip side cover 61A. Also in this case, a gap 712A is formed between the front end side mounting end portion 532 of the housing 5 and the opening end portion 611A of the inner peripheral front end side cover 61A, as in the case of the double structure.

(Base end covers 62A, 62B)
As shown in FIG. 1, proximal side covers 62A and 62B are mounted on the outer periphery of the proximal mounting end portion 541 of the housing 5 to cover the wiring portions of the sensor element 2 and the heater element 4, respectively. The proximal side covers 62A, 62B are arranged outside the exhaust pipe. An introduction hole 622 for introducing the atmosphere as the reference gas A into the proximal side covers 62A, 62B is formed in a part of the proximal side covers 62A, 62B. The introduction hole 622 is provided with a filter 623 that blocks liquid but allows gas to pass. The reference gas A introduced into the base end covers 62A, 62B from the introduction hole 622 passes through the gaps in the base end covers 62A, 62B and is guided to the reference electrode 36 of the sensor element 2 . The base end covers 62A and 62B of this embodiment have a double structure with the filter 623 sandwiched therebetween.

As shown in FIGS. 4 and 5, the proximal covers 62A and 62B include an inner peripheral proximal cover (inner peripheral cover) 62A attached to the outer periphery of the proximal attachment end 541 of the housing 5, and an inner peripheral proximal cover 62A. It is composed of an outer peripheral base end cover (outer peripheral cover) 62B attached to the outer periphery of the side cover 62A. An open end portion 621A of an inner circumference proximal side cover 62A is mounted on the outer periphery of the proximal side mounting end portion 541 of the housing 5 . In the proximal mounting portion 72 between the proximal mounting end portion 541 and the opening end portion 621A of the inner peripheral proximal side cover 62A, a joint portion 721 and a gap 722 are formed in mutually different regions in the axial direction L. there is A gap 722 is formed in regions on both sides in the axial direction L with respect to the joint portion 721 in the proximal-side mounting portion 72 .

The central axis O4 of the opening end portion 621A of the inner circumference proximal side cover 62A and the central axis O1 of the proximal side mounting end portion 541 of the housing 5 are offset from each other. In other words, the inner diameter of the open end portion 621A of the inner circumference proximal side cover 62A of this embodiment is larger than the outer diameter of the proximal side attachment end portion 541 of the housing 5 by 50 μm or more. The opening end portion 621A of the circumferential proximal side cover 62A is mounted eccentrically with respect to the proximal side mounting end portion 541 of the housing 5 . This configuration facilitates mounting of the inner circumference proximal side cover 62A to the housing 5, and provides a gap 722 of 50 μm or more between the proximal side mounting end portion 541 of the housing 5 and the opening end portion 621A of the inner circumference proximal side cover 62A. It can be easily formed.

As shown in FIG. 5, in the cross section of the housing 5 in the direction orthogonal to the axial direction L, the width of the gap 722 between the proximal mounting end portion 541 and the opening end portion 621A of the inner circumferential proximal side cover 62A is It is changing toward direction C. Specifically, in the cross section of the proximal side mounting portion 72 in the direction orthogonal to the axial direction L, the opening end portion 621A of the inner circumferential proximal side cover 62A and the proximal side mounting end portion 541 of the housing 5 are aligned in the circumferential direction C are in contact at a specific site C1. In other words, the gap 722 between the opening end portion 621A of the inner peripheral proximal side cover 62A and the proximal side mounting end portion 541 of the housing 5 is the smallest at the specific portion C1 in the circumferential direction C and Largest at the site opposite site C1.

As shown in FIG. 4, the open end portion 621A of the inner circumferential proximal side cover 62A of this embodiment is joined to the proximal side mounting end portion 541 of the housing 5 by performing laser welding. In a state where the open end portion 621A of the inner peripheral proximal side cover 62A is attached to the proximal side mounting end portion 541 of the housing 5, the laser beam is emitted from the outer circumference of the open end portion 621A of the inner peripheral proximal side cover 62A to the proximal side mounting end portion 541. to reach As a result, a joint portion 721 is formed in which the opening end portion 621A of the inner peripheral base end cover 62A and the base end mounting end portion 541 are partially melted and fused.

A gap 722 between the base end mounting end portion 541 of the housing 5 and the opening end portion 621A of the inner peripheral base end cover 62A has a width of 50 μm or more in radius at the maximum position in the circumferential direction C. , the width of which is equal to or less than 1/2 of the thickness of the opening end portion 621A of the inner circumference base end side cover 62A. If the width of the gap 722 is less than 50 μm, there is a possibility that the welding quality may be deteriorated due to concentration cell corrosion at the base end side attachment portion 72, entrainment of inert gas at the joint portion 721, or the like. On the other hand, if the gap 722 is larger than half the thickness of the open end portion 621A of the inner circumference base end side cover 62A, the inner circumference tip side cover 61A may be perforated during welding.

Here, the base end mounting portion 72 is a portion where the base end mounting end portion 541 of the housing 5 and the opening end portion 621A of the inner peripheral base end cover 62A face each other. The proximal side mounting portion 72 includes a portion of the proximal side mounting end portion 541 and a portion of the opening end portion 621A of the inner circumferential proximal side cover 62A.

(other configurations)
As shown in FIG. 1, the detection electrode 35 of the sensor element 2 is electrically connected to an external control device by an outer terminal fitting 81 and a lead wire 85 connected to the outer terminal fitting 81 . The reference electrode 36 of the sensor element 2 is electrically connected to an external control device by an inner terminal fitting 82 and a lead wire 85 connected to the inner terminal fitting 82 . The heating element 43 of the heater element 4 is electrically connected to an external control device by a power supply fitting 83 and a lead wire 85 connected to the power supply fitting 83 . The lead wire 85 is held by a bushing 86 arranged inside the proximal side covers 62A, 62B.

(Another sensor element 2)
In this embodiment, the sensor element 2 using the bottomed cylindrical solid electrolyte body 3 is shown. Alternatively, the sensor element 2 may be of a laminated type having a plate-shaped solid electrolyte body and a heating element laminated on the solid electrolyte body with an insulator interposed therebetween. In this case, sensor element 2 is held in housing 5 via an insulator.

(Effect)
In the gas sensor 1 of this embodiment, the opening end portion 611A of the inner peripheral tip side cover 61A extends over the remaining region of the tip side attachment portion 71 attached to the tip side attachment end portion 532 of the housing 5 except for one region in the axial direction L. , intentionally forms a gap 712A. In addition, the opening end portion 621A of the inner circumferential proximal side cover 62A is intentionally provided with a gap in the remaining region except for one region in the axial direction L of the proximal side mounting portion 72 mounted on the proximal side mounting end portion 541 of the housing 5. 722 is formed. These

gaps

712A and 722 are formed with a width of 50 μm or more in a circumferential portion except for a part in the circumferential direction C. As shown in FIG.

With these configurations, even if liquid such as water enters the

gaps

712A and 722, the liquid is less likely to accumulate in the

gaps

712A and 722, and corrosion of the concentration cell can be less likely to occur. In addition, due to these configurations, when the

joints

711 and 721 are formed in one area of each of the distal side mounting portion 71 and the proximal side mounting portion 72 in the axial direction L, the

joints

711 and 721 are filled with an inert gas or the like. can be made difficult to get caught.

Therefore, according to the gas sensor 1 of this embodiment, it is possible to make it difficult for the mounting strength of the inner peripheral distal end side cover 61A and the inner peripheral proximal end side cover 62A to the housing 5 to decrease.

(Other configurations of

gaps

712A, 712B, 722)
The front end mounting end 532 of the housing 5 and the opening end 611A of the inner peripheral front cover 61A do not have to be in contact with each other in the circumferential direction C. As shown in FIG. A gap 712A between the front end mounting end 532 of the housing 5 and the opening end 611A of the inner peripheral front end cover 61A may be formed along the entire circumference in the circumferential direction C.

The proximal side mounting end portion 541 of the housing 5 and the opening end portion 621A of the inner peripheral proximal side cover 62A do not need to be in contact with each other in a part of the circumferential direction C. A gap 722 between the base end mounting end portion 541 of the housing 5 and the opening end portion 621A of the inner peripheral base end cover 62A may be formed along the entire circumference in the circumferential direction C.

Further, as shown in FIG. 6, the central axis O2 of the opening end 611A of the inner peripheral tip cover 61A and the central axis O3 of the opening end 611B of the outer peripheral tip cover 61B may be offset from each other. In this case, the gap 712B between the opening end 611A of the inner peripheral front end cover 61A and the opening end 611B of the outer peripheral front end cover 61B is 50 μm in radius at the position where the gap 712B becomes maximum in the circumferential direction C. It is sufficient that the width is within the range of 1/2 or less of the thickness of the opening end portion 611B of the outer peripheral tip side cover 61B.

In FIG. 6, the center axis O1 of the front end mounting end 532 of the housing 5 and the center axis O2 of the opening end 611A of the inner circumference front end cover 61A are substantially aligned. In the case of FIG. 6, the central axis O1 of the front end mounting end 532 of the housing 5 and the central axis O2 of the opening end 611A of the inner peripheral front cover 61A may be offset from each other.

<Embodiment 2>
In this embodiment, as shown in FIG. 7, the opening end portion 611A of the inner peripheral front end cover 61A has an oval cross section, and the front mounting end portion 532 of the housing 5 has a circular cross section. show. In this embodiment, when the opening end portion 611A of the inner circumference tip end cover 61A is attached to the tip attachment end portion 532 of the housing 5, the width of the gap 712A in the circumferential direction C is partially different. .

The oval shape may be any shape such as an elliptical shape, an oval shape, and an egg shape. An open end portion 611A of the inner circumference distal end side cover 61A of this embodiment is formed in an elliptical shape. The gap 712A between the front end mounting end 532 of the housing 5 and the opening end 611A of the inner peripheral front cover 61A is the largest at two specific positions in the circumferential direction C that are 180° apart from each other. It is smallest at the orthogonal position where the angle is different by 90° with respect to the two specific positions.

In this embodiment, the width of the gap 712A changes greatly in the circumferential direction C every 90° in the cross section in the direction orthogonal to the axial direction L of the housing 5 . The opening end portion 611A of the inner periphery tip side cover 61A may be formed in an elliptical shape by forming an elliptical cross section of a mold for press molding such as drawing. Also, the opening end portion 611A of the inner periphery front end side cover 61A may be formed into an elliptical shape by deforming after press molding such as drawing is performed.

A gap 712A between the mounting end portion 532 on the front end side of the housing 5 and the position of the long diameter portion of the elliptical shape in the circumferential direction C of the open end portion 611A of the inner peripheral front end cover 61A has a width of 50 μm or more in radius. It is formed within a range of width equal to or less than 1/2 of the thickness of the opening end portion 611A of the inner periphery tip side cover 61A. In addition, the gap 712A between the front end mounting end portion 532 of the housing 5 and the position of the elliptical short diameter portion in the circumferential direction C of the opening end portion 611A of the inner peripheral front end cover 61A is less than 50 μm in radius. width.

In this embodiment, the opening end portion 611A of the inner peripheral front end cover 61A has an oval cross-sectional shape, so that the opening end portion 611A of the inner peripheral front end cover 61A is attached to the front end mounting end portion 532 of the housing 5. It is possible to easily form the gap 712A having a required width while ensuring mountability.

Further, in FIG. 7, since the cross-sectional shape of the opening end portion 611B of the outer peripheral tip side cover 61B is a perfect circle, the opening end portion 611A of the inner peripheral tip side cover 61A and the opening end portion of the outer peripheral tip side cover 61B The gap 712B between the 611B and 611B is the largest at two specific positions in the circumferential direction C that are different from each other by 180°, and is the smallest at orthogonal positions that are different from the two specific positions by 90°. In this case, the gap 712B between the position of the elliptical long diameter portion in the circumferential direction C of the open end 611A of the inner peripheral tip cover 61A and the open end 611B of the outer peripheral tip cover 61B is the smallest. Therefore, the width of the radius may be less than 50 μm. In addition, the gap 712B between the position of the elliptical short diameter portion in the circumferential direction C of the open end portion 611A of the inner peripheral tip side cover 61A and the open end portion 611B of the outer peripheral tip side cover 61B is the largest. It may be formed within a range of a radius of 50 μm or more and a width of 1/2 or less of the thickness of the opening end portion 611B of the outer peripheral tip side cover 61B.

Further, as shown in FIG. 8, the cross-sectional shape of the opening end portion 611A of the inner peripheral tip side cover 61A may be a perfect circle, and the cross-sectional shape of the tip side mounting end portion 532 of the housing 5 may be oval. In this case, the cross-sectional shape of the molding portion of the front mounting end 532 in the mold for molding the housing 5 may be oval, and the cross-sectional shape of the front mounting end 532 of the housing 5 after molding may be oval. , may be formed into an oval shape by cutting or the like. Further, in this case, the cross-sectional shape of the opening end portion 611B of the outer peripheral tip side cover 61B may be an oval shape instead of a perfect circular shape.

Further, as shown in FIG. 9, the cross-sectional shape of the opening end portion 621A of the inner peripheral proximal side cover 62A may be oval, and the cross-sectional shape of the proximal side mounting end portion 541 of the housing 5 may be circular. Further, as shown in FIG. 10, the cross-sectional shape of the opening end portion 621A of the inner circumference proximal side cover 62A may be a perfect circle, and the cross-sectional shape of the proximal side mounting end portion 541 of the housing 5 may be oval. In these cases as well, the width of the gap 722 in the circumferential direction C is partially different, as in the case of the inner peripheral tip cover 61A and the tip end mounting end 532 of the housing 5 . Also, the width of the gap 722 may be the same as the width of the gap 712A.

Other configurations, effects, etc. of the gas sensor 1 of this embodiment are the same as the configuration, effects, etc. of the first embodiment. Also in the present embodiment, constituent elements indicated by the same reference numerals as those in the first embodiment are the same as those in the first embodiment.

The present disclosure is not limited to only each embodiment, and further different embodiments can be configured without departing from the gist thereof. In addition, the present disclosure includes various modifications, modifications within the equivalent range, and the like. Furthermore, the technical idea of the present disclosure includes combinations of various constituent elements, forms, and the like assumed from the present disclosure.

Claims

comprising a sensor element (2), a housing (5) holding the sensor element, and covers (61A, 62A) attached to the housing,
In one region in the axial direction (L) of the mounting portions (71, 72) where the opening ends (611A, 621A) of the cover are mounted to the mounting ends (532, 541) of the housing, the opening end and joint portions (711, 721) are formed in which the mounting end portion is joined along the entire circumference in the circumferential direction (C),
Gaps (712A, 722) are formed in the remaining area of the mounting portion in the axial direction, excluding the one area, in the circumferential direction, excluding the entire circumference or part of the circumferential direction. A gas sensor (1).
the center axis (O2, O4) of the opening end and the center axis (O1) of the mounting end are shifted from each other,
2. The gas sensor according to claim 1, wherein the width of said gap changes in said circumferential direction in a cross section in a direction orthogonal to said axial direction.
One of the opening end and the mounting end is formed in a perfect circle shape, and the other is formed in an oval shape,
2. The gas sensor according to claim 1, wherein the width of said gap changes in said circumferential direction in a cross section in a direction orthogonal to said axial direction.
A sensor element (2), a housing (5) holding the sensor element, inner peripheral side covers (61A, 62A) attached to the housing, outer peripheral side covers (61A, 62A) attached to the inner peripheral side cover ( 61B, 62B),
The inner peripheral side open end (611A, 621A) of the inner peripheral side cover and the outer peripheral side open end (611B) of the outer peripheral side cover are attached to the mounting ends (532, 541) of the housing ( 71, 72) in one region in the axial direction (L), the outer peripheral side open end portion, the inner peripheral side open end portion and the mounting end portion are joined over the entire circumference in the circumferential direction (C). A part (711, 721) is formed,
Between the inner peripheral side open end portion and the mounting end portion and between the outer peripheral side open end portion and the inner peripheral side open end portion in the remaining area excluding the one area in the axial direction of the attachment portion A gas sensor (1) in which gaps (712A, 712B, 722) are formed in at least one of the positions between and in the circumferential direction except for the entire circumference or the part in the circumferential direction.
The central axis (O2, O4) of the inner peripheral side open end and the central axis (O1) of the mounting end, and the central axis (O3) of the outer peripheral side open end and the center of the inner peripheral side open end at least one of the axes (O2, O4) is offset from each other;
5. The gas sensor according to claim 4, wherein the width of said gap changes in said circumferential direction in a cross section in a direction perpendicular to said axial direction.
one or two of the outer peripheral side open end portion, the inner peripheral side open end portion, and the mounting end portion are formed in a perfect circle shape, and the rest are formed in an oval shape,
5. The gas sensor according to claim 4, wherein the width of said gap changes in said circumferential direction in a cross section in a direction perpendicular to said axial direction.