WO2016152621A1

WO2016152621A1 - Gas sensor

Info

Publication number: WO2016152621A1
Application number: PCT/JP2016/057962
Authority: WO
Inventors: 直人小澤; 欣二宝平; 山田　弘一
Original assignee: 株式会社デンソー
Priority date: 2015-03-24
Filing date: 2016-03-14
Publication date: 2016-09-29

Abstract

This gas sensor includes: a sensor element which detects the concentration of a prescribed gas component in gas being measured; an insulator which holds on the inside thereof a metal terminal which is electrically connected to a positive electrode of the sensor element; and a housing which holds, by insertion, the sensor element on the inside thereof, and which is electrically connected to a negative electrode of the sensor element. The housing includes: a screw thread capable of being screwed into a threaded hole formed in an attachment part to which the gas sensor is to be secured; and a sealing part disposed facing a sealed part formed in such a way as to surround an opening edge of the threaded hole. The sealing part includes an annular contacting part which is in localized contact with a section, in the radial direction, of the sealed part, and which is in contact with the sealed part around the entire circumference thereof. By this means, productivity can be improved while improving the electrical conductivity and the sealing properties between the sealing part and the attachment part.

Description

Gas sensor

The present invention relates to a gas sensor.

In an internal combustion engine such as an automobile, a gas sensor that measures the concentration of a predetermined gas component such as oxygen or nitrogen oxide in exhaust gas is used. The gas sensor includes a sensor element that detects the concentration of a predetermined gas component in the exhaust gas (gas to be measured), and a housing that holds the sensor element inside. A screw is formed on the outer peripheral side surface of the housing, and the gas sensor is fixed to the attached portion by screwing the screw into the screw hole of the attached portion. A seal mechanism is formed between the gas sensor and the mounted portion for suppressing leakage of the gas to be measured.

For example, a sealing mechanism is known in which a metal gasket is sandwiched between a gas sensor and a mounted portion.
Patent Document 1 discloses a gas sensor having a bolt for fixing the gas sensor to a mounted portion (boss), and a seal member disposed between the mounted portion and the bolt.

Japanese Patent No. 4726261

However, in the gas sensor disclosed in Patent Document 1, if there is an oxide film or foreign matter between the seal member and the attached portion (boss), it is difficult to ensure electrical conductivity and sealability between the two. There is a risk. Therefore, in order to eliminate the inconvenience, before the gas sensor is attached to the attachment portion, if a step of removing an oxide film or a foreign substance at the contact portion between the seal member and the attachment portion is included, the productivity of the gas sensor decreases. End up.

The present invention has been made in view of the above problems, and intends to provide a gas sensor capable of improving productivity and improving electrical conductivity and sealing performance between a housing and a mounted portion. It is.

One embodiment of the present invention includes a sensor element that detects a concentration of a predetermined gas component in a gas to be measured, an insulator that holds a metal terminal electrically connected to the positive electrode of the sensor element, and the sensor element. A gas sensor having a housing that is inserted and held inside and electrically connected to the negative electrode of the sensor element,
The housing is arranged so as to face a screw portion that can be screwed into a screw hole formed in a mounting portion to which the gas sensor is fixed, and a sealed portion that is formed so as to surround the periphery of the opening edge of the screw hole. And a seal portion to be installed,
The seal portion is a gas sensor that has a contact portion that contacts a part of the sealed portion in a radial direction of the sealed portion and contacts the entire circumference of the sealed portion in an annular shape.

In the gas sensor, by forming the contact portion, the productivity of the gas sensor is improved, and the sealing performance and electrical conductivity between the gas sensor and the attached portion are improved.
Specifically, in order to fix the gas sensor to the attached portion, the contact portion is provided to the sealed portion when the screw of the housing is screwed into the screw hole of the attached portion. The seal part approaches while rotating. When the contact portion and the sealed portion come into contact with each other, an axial force generated by screwing between the screw and the screw hole is applied between the contact portion and the sealed portion. When the axial force is applied, the contact portion rotates with respect to the sealed portion, so that the contact portion and the sealed portion rub against each other. Therefore, the oxide film and foreign matter existing between the contact portion and the sealed portion are removed. Thereby, the process of removing an oxide film and a foreign substance becomes unnecessary, and the productivity of a gas sensor improves.

Further, the axial force can be concentrated on the contact portion by locally contacting the contact portion and the sealed portion. Therefore, one or both of the contact portion and the sealed portion is deformed so that the shape of the contact portion and the shape of the sealed portion are along each other, and the contact portion and the sealed portion are They can be in close contact with each other. Thereby, the electrical conductivity and sealing performance between the shape of the contact portion and the sealed portion can be improved. Even if the processing accuracy of the contact surfaces of the contact portion and the sealed portion is low, reliable contact can be obtained over the entire circumference of the contact portion and the sealed portion.

As described above, according to the present invention, it is possible to provide a gas sensor capable of improving productivity and improving electrical conductivity and sealing performance with a mounted portion.

FIG. 3 is an explanatory diagram showing a gas sensor seal structure according to the first embodiment. FIG. 3 is an explanatory diagram showing a gas sensor in the first embodiment. Sectional drawing of the housing in Example 1 (equivalent to the III-III arrow section of FIG. 1). Explanatory drawing which shows the seal structure of the gas sensor in Example 2. FIG. Sectional drawing of the housing in Example 2 (equivalent to the VV arrow cross section of FIG. 4). Explanatory drawing which shows the seal structure of the gas sensor in Example 3. FIG. Sectional drawing of the housing in Example 3 (equivalent to the VII-VII arrow cross section in FIG. 6). Explanatory drawing which shows the seal structure of the gas sensor in Example 4. FIG. FIG. 9 is an explanatory diagram showing a gas sensor seal structure in a fifth embodiment. Explanatory drawing which shows the seal structure of the gas sensor in Example 6. FIG. Explanatory drawing which shows the seal structure of the gas sensor in Example 7. FIG. Explanatory drawing which shows the seal structure of the gas sensor in Example 8. FIG.

The seal portion of the gas sensor is formed as a tapered surface having a diameter that decreases toward the distal end side in the axial direction of the gas sensor, and the contact portion contacts the opening edge of the screw hole. It is preferable that it is formed as a part of. In this case, the contact area between the contact portion and the sealed portion can be reduced, and the electrical conductivity and sealing performance can be improved. Moreover, the said contact part can be easily formed by making the said housing into a simple shape. Thereby, the productivity of the housing can be improved, and as a result, the productivity of the gas sensor can be improved.

Further, it is preferable that the abutting portion is composed of a seal protrusion protruding from the seal portion toward the sealed portion. In this case, by forming the seal protrusion, the contact area between the seal portion and the sealed portion can be reduced, and the electrical conductivity and the sealing performance can be improved.

(Example 1)
A gas sensor 1 according to a first embodiment will be described with reference to FIGS.
As shown in FIG. 2, the gas sensor 1 includes an insulator that holds a sensor element 2 that detects the concentration of a predetermined gas component in the gas to be measured and a metal terminal 23 that is electrically connected to the positive electrode of the sensor element 2. 25 and a housing 3 that holds the sensor element 2 inside and is electrically connected to the negative electrode of the sensor element 2.

As shown in FIGS. 1 and 2, the housing 3 surrounds the screw hole 51 formed in the attached portion 5 to which the gas sensor 1 is fixed and a screw 332 that can be screwed together, and the periphery of the opening edge of the screw hole 51. And a seal portion 333 disposed opposite to the sealed portion 53 formed on the surface. The seal portion 333 has an abutting portion 334 that abuts locally on a part of the sealed portion 53 and annularly abuts on the entire circumference of the sealed portion 53 in the radial direction of the sealed portion 53.

1 and 2, the gas sensor 1 is an oxygen sensor for detecting the concentration of oxygen contained in the exhaust gas discharged from the internal combustion engine, and is fixed to an exhaust pipe extending from the internal combustion engine. The exhaust pipe has a to-be-attached portion 5 and a boss having a screw hole formed therein, and the boss forms a sealed portion 53 that surrounds the periphery of the opening edge of the screw hole. The sealed portion 53 is formed as an end surface of the boss portion.

The gas sensor 1 includes a sensor element 2 for detecting oxygen. The sensor element 2 includes a bottomed cylindrical solid electrolyte body 21, and a positive electrode and a negative electrode provided on an inner surface and an outer surface of the solid electrolyte body 21. And a pair of electrodes 22. On the base end side of the sensor element 2, a metal terminal 23 electrically connected to the positive electrodes of the pair of electrodes 22 is provided. Further, the negative electrodes of the pair of electrodes 22 are electrically connected to the housing 3. The sensor element 2 is inserted and fixed in the housing 3 and hermetically sealed between the two.

As shown in FIG. 2, a measured gas side cover 41 having a double structure is caulked on the front end side of the housing 3 so as to cover the sensor element 2. The measured gas side cover 41 includes an inner cover 411 positioned near the sensor element 2 and an outer cover 412 positioned outside the inner cover 411. The measured gas is introduced into the inner cover 411 and the outer cover 412. Conductive holes 413 are provided respectively.

An atmosphere side cover 42 is disposed on the base end side of the housing 3, and an insulator 25 is provided inside the atmosphere side cover 42. A metal terminal 23 electrically connected to the positive electrode of the sensor element 2 is provided inside the insulator 25, and a lead wire 24 is connected to the metal terminal 23. An elastic insulating member 27 that seals the base end portion of the atmosphere side cover 42 while the lead wire 24 is inserted is provided at a position on the base end side of the insulator 25 inside the atmosphere side cover 42.

As shown in FIGS. 1 and 2, the housing 3 is made of a substantially cylindrical member made of metal having electrical conductivity. The housing 3 includes an engagement portion 31 formed substantially at the center in the axial direction L of the gas sensor 1, a distal end cylindrical portion 33 protruding from the engagement portion 31 toward the distal end side, and an end surface on the proximal end side of the engagement portion 31. A proximal end cylindrical portion 32 projecting toward the proximal end side of the gas sensor 1. The engaging portion 31, the proximal end cylindrical portion 32, and the distal end cylindrical portion 33 are formed integrally with each other to constitute the housing 3 made of one component. A screw 332 is formed on the outer peripheral surface of the distal end cylindrical portion 33, and the end surface on the distal end side of the engaging portion 31 is a seal portion 333. The engaging portion 31 is formed with a diameter larger than the outer diameter of the screw 332. Accordingly, the screw 332 and the seal portion 333 are integrally configured. Here, the integral structure of the screw 332 and the seal portion 333 is not limited to a structure in which the screw 332 and the seal portion 333 are formed in one component as in this example. For example, in a state before the gas sensor 1 is fixed to the attached portion 5, the component in which the screw 332 is formed and the component in which the seal portion 333 is formed may be assembled with each other.

The sensor element 2 is inserted and fixed inside the housing 3.
The proximal end cylinder part 32 is fixed inside the atmosphere side cover 42.
A screw 332 that can be screwed into the screw hole 51 of the attached portion 5 is formed on the outer peripheral side surface of the distal end tubular portion 33, and the measured gas side cover 41 is caulked on the distal end side surface of the distal end tubular portion 33. A caulking groove 331 for fixing is formed.

As shown in FIG. 3, the engaging portion 31 is formed in a regular hexagon when viewed from the axial direction L of the gas sensor 1, and is formed to be engageable with a tool for fixing the gas sensor 1. The outer shape of the engaging portion 31 is formed larger than the outer shapes of the proximal end cylindrical portion 32 and the distal end cylindrical portion 33. A portion of the housing 3 between the proximal end cylindrical portion 32 and the distal end cylindrical portion 33 and the engaging portion 31 is formed in a step shape.

Further, the end surface on the distal end side of the engaging portion 31 forms a seal portion 333 that faces the sealed portion 53 of the attached portion 5. In this example, the seal portion 333 has a substantially truncated cone shape whose outer diameter is reduced toward the distal end side in the axial direction L of the gas sensor 1, and is formed as a tapered surface 335. The outer diameter of the tapered surface 335 on the distal end side is formed smaller than the inner diameter of the screw hole 51 in the mounted portion 5, and when the gas sensor 1 is fixed to the mounted portion 5, The part is disposed inside the screw hole 51. The contact portion 334 is formed as a part of the tapered surface 335 so as to contact the opening edge 52 of the screw hole 51.

The attachment structure for attaching the gas sensor 1 to the attachment portion 5 is as follows.
Specifically, the screw 332 of the gas sensor 1 is screwed into the screw hole 51 of the attached portion 5. When the gas sensor 1 is rotated and the screw 332 is screwed into the screw hole 51, the abutting portion 334 of the seal portion 333 rotates together with the gas sensor 1 with respect to the sealed portion 53, while partially in the radial direction. It locally contacts the sealed portion 53. In this way, the attachment structure of the gas sensor 1 in which the entire circumference of the contact portion 334 is in close contact with the sealed portion 53 is formed with a change in the circumferential direction between the contact portion 334 and the sealed portion 53.

Hereinafter, the function and effect of this example will be described.
In the gas sensor 1, by having the contact portion 334, the productivity of the gas sensor 1 is improved, and the sealing performance and the electrical conductivity between the gas sensor 1 and the attached portion 5 are improved.

Specifically, when the gas sensor 1 is fixed to the attached portion 5, the screw 332 of the housing 3 is screwed into the screw hole 51 of the attached portion 5. At this time, the entire gas sensor 1 is rotated with respect to the attached portion 5, and the housing 3 is rotated with respect to the attached portion 5. Therefore, the contact portion 334 provided on the seal portion 333 of the housing 3 approaches the sealed portion 53 of the attached portion 5 while rotating. When the contact portion 334 and the sealed portion 53 come into contact with each other, an axial force generated by screwing between the screw 332 and the screw hole 51 is applied between the contact portion 334 and the sealed portion 53. With the axial force applied, the contact portion 334 rotates relative to the sealed portion 53, and the contact portion 334 and the sealed portion 53 rub against each other. Therefore, an oxide film and foreign matter existing between the contact portion 334 and the sealed portion 53 can be removed. Thereby, the process of removing an oxide film and a foreign material becomes unnecessary, and the productivity of the gas sensor 1 is improved.

Also, the axial force concentrates on the contact portion 334 by bringing the contact portion 334 and the sealed portion 53 into contact with each other locally. Therefore, one or both of the contact part 334 and the sealed part 53 are deformed so as to conform to the other shape and are in close contact with each other. Thereby, the electrical conductivity and sealing performance between the shape of the contact part 334 and the sealed part 53 are improved. Even if the processing accuracy of the contact surfaces of the contact part 334 and the sealed part 53 is low, the contact part 334 and the sealed part 53 are reliably in contact with each other on the entire circumference.

Further, the seal portion 333 is formed as a tapered surface 335 whose diameter decreases in the axial direction L of the gas sensor 1 toward the tip side of the gas sensor 1. The contact portion 334 is formed as a part of the tapered surface 335 so as to contact the opening edge 52 of the screw hole 51. Therefore, the contact area between the abutting portion 334 and the sealed portion 53 is reduced, and the electrical conductivity and sealing performance are further improved. Further, the housing 3 has a simple shape, and the contact portion 334 can be easily formed.

As described above, the productivity of the gas sensor 1 of this example is improved, and the electrical conductivity and the sealing performance with the attached portion 5 are improved.

(Example 2)
As shown in FIGS. 4 and 5, the gas sensor 1 of this example differs from the gas sensor 1 of Example 1 in a part of the shape.
The seal portion 333 of the gas sensor 1 of the present example includes a seal surface 336 extending in a direction orthogonal to the axial direction L, and a seal protrusion 337 as a contact portion 334 protruding from the seal surface 336 toward the sealed portion 53. have. The seal protrusion 337 has an annular shape centered on the central axis of the gas sensor 1 and has a substantially semicircular cross section.
Other configurations are the same as those of the first embodiment. Also in this example, the same effects as those of the first embodiment can be obtained. Of the reference numerals used in the drawings relating to the following embodiments and examples, the same reference numerals as those used in the first embodiment denote the same components as in the first embodiment unless otherwise specified.

(Example 3)
As shown in FIGS. 6 and 7, the gas sensor 1 of this example includes a seal protrusion 337 having a shape different from that of the second embodiment.
That is, the seal portion 333 of the gas sensor 1 has a plurality of seal protrusions 337. The seal projection 337 protrudes toward the sealed portion 53 and abuts the entire circumference of the sealed portion 53 to form a plurality of abutting portions 334. As shown in FIG. 7, the seal protrusion 337 is formed by coaxially forming a plurality of grooves on the seal surface 336. In other words, the seal protrusions 337 are annular and are arranged concentrically around the central axis of the gas sensor 1. The longitudinal direction of the seal protrusion 337 in the axial direction of the gas sensor 1 is substantially rectangular.
Other configurations are the same as those of the first embodiment. Also in this example, the same effects as those of the first embodiment are obtained.

Example 4
As shown in FIG. 8, the gas sensor 1 of this example has a shape different from that of the gas sensor 1 of Example 1 in a part thereof.
The sealed portion 53 formed as the end face of the boss portion of the exhaust pipe is formed in a tapered shape that is reduced in diameter toward the distal end side in the axial direction L of the gas sensor 1. The contact portion 334 in the gas sensor 1 contacts the tapered sealed portion 53.
Other configurations are the same as those of the first embodiment. Also in this example, the same effects as those of the first embodiment are obtained.

(Example 5)
As shown in FIG. 9, the gas sensor 1 of this example has a shape different from that of the gas sensor 1 of Example 4 in a part thereof.
In the axial direction L of the gas sensor 1, the seal portion 333 of the gas sensor 1 is loosened as compared with the outer peripheral side taper surface 338 and the outer peripheral side taper surface 338 whose outer diameter is reduced toward the front end side of the gas sensor 1. An inner peripheral tapered surface 339 having a reduced diameter is formed. The inner peripheral taper surface 339 is formed adjacent to the inner peripheral side of the outer peripheral taper surface 338. The contact portion 334 includes a convex portion formed at the boundary between the outer peripheral taper surface 338 and the inner peripheral taper surface 339. Further, the sealed portion 53 of the present example is also formed in a tapered shape as in the fourth embodiment.
Other configurations are the same as those of the first embodiment. Also in this example, it is possible to obtain the same effect as that of the first embodiment.

(Example 6)
As shown in FIG. 10, the gas sensor 1 of this example has a shape different from that of the gas sensor 1 of Example 5 in a part thereof.
The seal portion 333 of the gas sensor 1 is a seal as a contact portion 334 formed at the boundary between the outer peripheral side taper surface 338, the inner peripheral side taper surface 339, and the outer peripheral side taper surface 338 and the inner peripheral side taper surface 339. And a protrusion 337. The seal protrusion 337 is formed so as to protrude from the seal portion 333 toward the sealed portion 53. The seal protrusion 337 has an annular shape centered on the central axis of the gas sensor 1 and has a substantially semicircular cross section. Further, the sealed portion 53 of the present example is also formed in a tapered shape as in the fourth embodiment.
Other configurations are the same as those of the first embodiment. Also in this example, the same effects as those of the first embodiment are obtained.

(Example 7)
As shown in FIG. 11, the gas sensor 1 of this example has a shape different from that of the gas sensor 1 of Example 4 in a part thereof.
The abutting portion 334 of the gas sensor 1 is formed as a corner portion on the outer side of the distal end of the engaging portion 31. Further, the sealed portion 53 is also formed in a tapered shape as in the fourth embodiment. The contact portion 334 of this example contacts the tapered sealed portion 53.
Other configurations are the same as those of the first embodiment. Also in this example, the same effects as those of the first embodiment are obtained.

(Example 8)
As shown in FIG. 12, the gas sensor 1 of this example has a shape different from that of the gas sensor 1 of Example 7 in a part thereof.
The engaging portion 31 of the gas sensor 1 has a distal end portion 311 having a circular outer shape and a proximal end portion 312 having a hexagonal outer shape and a smaller outer shape than the distal end portion 311. The contact portion 334 is formed as a corner portion of the tip portion 311 close to the tip of the gas sensor 1. Further, the sealed portion 53 of the present example is also formed in a tapered shape as in the fourth embodiment. The contact portion 334 of this example contacts the tapered sealed portion 53.
Other configurations are the same as those of the first embodiment. Also in this example, the same effects as those of the first embodiment are obtained.

The present invention is not limited to the above embodiments, and can be applied to various embodiments without departing from the scope of the invention.

Claims

A sensor element (2) for detecting a concentration of a predetermined gas component in the gas to be measured; an insulator (25) for holding a metal terminal (23) electrically connected to the positive electrode of the sensor element; A gas sensor (1) having a housing (3) that holds the sensor element inside and is electrically connected to the negative electrode of the sensor element,
The housing is formed so as to surround a screw hole (51) formed in a mounting portion (5) to which the gas sensor is fixed and a screw (332) that can be screwed together, and an opening edge of the screw hole. A seal part (333) disposed opposite to the sealed part (53),
The seal portion (333) is in contact with a part of the sealed portion (53) in the radial direction of the sealed portion (53) and in contact with the entire circumference of the sealed portion (53) in an annular shape. A gas sensor having a portion (334).
The seal portion is formed as a tapered surface that is reduced in diameter toward the distal end side in the axial direction (L) of the gas sensor,
The gas sensor according to claim 1, wherein the contact portion is formed as a part of the tapered surface so as to contact the opening edge (52) of the screw hole.
The gas sensor according to claim 1, wherein the contact portion includes a seal protrusion (337) protruding from the seal portion toward the sealed portion.
The gas sensor according to claim 3, wherein a plurality of the seal protrusions (337) are concentrically formed.
The gas sensor according to any one of claims 1 to 4, wherein the abutting portion abuts on the sealed portion whose diameter is reduced toward a distal end side in the axial direction of the gas sensor.
The seal portion is formed as an end surface on the distal end side of the engaging portion (31) whose diameter is larger than the outer diameter of the screw,
2. The contact portion according to claim 1, wherein the contact portion is formed as a corner portion on the outer side of the distal end of the engagement portion, and abuts on the sealed portion whose diameter is reduced toward the distal end side in the axial direction of the gas sensor. The gas sensor described.
The engaging portion has a distal end portion having a circular outer shape, and a proximal end portion having a hexagonal outer shape and having a smaller outer shape than the distal end portion,
The gas sensor according to claim 6, wherein the abutting portion is formed as a corner portion outside the distal end of the distal end side portion.
When the screw of the gas sensor is screwed into the screw hole of the attached portion, the contact portion of the seal portion rotates with the gas sensor and comes into contact with the sealed portion. The gas sensor according to any one of claims 1 to 7.