JP5529070B2 - Gas sensor - Google Patents

Description

  The present invention relates to a gas sensor including a gas sensor element that detects the concentration of a gas to be detected.

As a gas sensor for detecting the concentration of a specific gas (for example, oxygen or NO _x ) in exhaust gas of an automobile or the like, one having a gas sensor element using a solid electrolyte is known.
As shown in FIG. 4, this type of gas sensor 1000 is configured by holding the periphery of the gas sensor element 3 extending in the direction of the axis O in the radial direction with the metal shell 20 and attaching an outer cylinder 400 to the rear end side of the metal shell 20. ing. An electrode (not shown) provided on the rear end side of the gas sensor element 3 inside the outer cylinder 400 is electrically connected to the terminal fittings 71, 91, and further lead wires connected to the terminal fittings 71, 91. 141 is inserted through an elastic member (grommet) 131 inserted in the rear end side of the outer cylinder 400 and taken out to the outside.
Further, in order to introduce outside air having a reference oxygen concentration into the gas sensor element 3 inside the outer cylinder 400, a first vent hole 410 is formed on the side surface of the outer cylinder 400, and the first vent hole 410 is formed through the air-permeable filter 50. The protective outer cylinder 600 is further covered from the outside of the filter 50, and the filter 50 is fixed by crimping the protective outer cylinder 600 and the outer cylinder 400 (Patent Document 1). The protective outer cylinder 600 also has a second vent hole 610 communicating with the filter so that the outside air is introduced into the outer cylinder 400 through the filter 50.

JP 2003-114210 A Japanese Patent Laying-Open No. 2006-1445397 (FIG. 2)

By the way, in the case of the gas sensor 1000 described in Patent Document 1, in order to firmly fix the protective outer cylinder 600 to the outer cylinder 400, the protective outer cylinder 600 and the outer cylinder 400 are positioned at the position _S102 of the grommet 131 at the rear end from the filter 50. Is directly caulked. For this reason, the position of the resin filter 50 is closer to the distal end side (lower side in FIG. 3) of the gas sensor 1000 (that is, disposed closer to the distal end side than the position where the grommet 131 is disposed), and a heat source (for example, The filter 50 may creep due to heat received from the exhaust pipe or the exhaust gas), and the air permeability of the filter 50 may be reduced.
Therefore, in order to keep the filter as far as possible from the heat source and maintain the air permeability of the filter, the filter is arranged so as to overlap with the position of the grommet arranged on the rear end side of the gas sensor, and the filter is disposed outside the grommet in the radial direction. A technique for crimping the protective outer cylinder and the outer cylinder has been developed (Patent Document 2). In the case of the gas sensor described in Patent Document 2, the protective outer cylinder and the outer cylinder are directly swaged at a position closer to the tip than the filter to directly form the swaged portion so that the protective outer cylinder is firmly attached to the outer cylinder. It is fixed.

However, in the case of the technique described in Patent Document 2 described above, there is a problem that crevice corrosion occurs when the protective outer cylinder and the outer cylinder are directly caulked at the position on the tip side of the filter to form the direct caulking portion.
This crevice corrosion is protected by the salt tension, etc. that has been applied to the gas sensor being held for a long period of time by the surface tension in the minute gap between the protective outer cylinder and the outer cylinder provided on the tip side of the direct caulking part. A chemical reaction occurs between the outer cylinder and the outer cylinder, and the outer cylinder or the protective outer cylinder is corroded.

  Therefore, the present invention maintains the air permeability of the filter by moving the position of the filter away from the front end side of the gas sensor, and also caulks directly to the front end side of the filter in order to prevent crevice corrosion between the protective outer cylinder and the outer cylinder. An object is to provide a gas sensor in which a protective outer cylinder is firmly fixed to an outer cylinder without forming a portion.

In order to solve the above problems, a gas sensor of the present invention is attached to a gas sensor element extending in an axial direction, a cylindrical metal shell that surrounds the gas sensor element in a radial direction and holds the gas sensor element, and the metal shell. And a cylindrical outer cylinder extending to the rear end side of the metal shell and having a first vent hole for introducing outside air into the metal shell, and inserted into the rear end side of the outer cylinder, An elastic member to be sealed, a resin filter disposed on the outer side in the radial direction of the outer cylinder so as to close the first ventilation hole, and surrounding the filter from the outer side in the radial direction, and surrounding the filter from the outer side in the radial direction A cylindrical protective outer cylinder having a second vent hole that communicates with the gas sensor, wherein the outer cylinder and the protective outer cylinder respectively precede and follow the first vent hole and the second vent hole. In two places, the fill A front end side caulking portion and a rear end side caulking portion that are crimped via the outer cylinder and the protective outer cylinder are not directly caulked, and the rear end side caulking portion is It is located in the area | region of the axial direction of an elastic member, and the said front end side crimping part is deform | transforming so that the said outer cylinder may dent radially inward.

According to this gas sensor, the rear end side caulking portion is located in the axial direction region of the elastic member. As a result, the filter can be disposed so as to overlap the position of the elastic member disposed on the rear end side of the gas sensor, so that the position of the filter can be further away from the front end side of the gas sensor, and from the heat source (exhaust pipe) It is possible to suppress the filter from creeping due to the heat received and reducing the air permeability of the filter.
Further, the outer cylinder and the protective outer cylinder are in direct contact and are not crimped. Thereby, it can prevent that crevice corrosion arises in the direct caulking part of an outer cylinder and a protection outer cylinder.
In addition, the outer cylinder is deformed so as to be recessed inward at the front end side crimping portion. That is, since the outer cylinder is strongly caulked at the distal end side caulking portion until the outer cylinder is deformed inward in the radial direction, the protective outer cylinder can be firmly fixed to the outer cylinder.

  Further, in the gas sensor according to the present invention, the rear end side crimping portion is deformed so that the outer cylinder is recessed radially inward. In the rear end side crimping portion, the elastic member repels due to the elastic force with respect to the caulking which is reduced in diameter inward, so that the protective outer cylinder can be attached even if the outer cylinder of the rear end side crimping portion is not deformed. It is firmly fixed to the outer cylinder. However, in the rear end side caulking portion, too, the outer cylinder is strongly caulked until it is dented inward in the radial direction and deformed. Therefore, the elastic member repels due to elastic force against caulking that is reduced in diameter radially inward. The force can be increased, and the protective outer cylinder can be more firmly fixed to the outer cylinder.

  Further, in the gas sensor according to the present invention, the front end side crimping portion is positioned on a front end side with respect to the front end of the elastic member, and the outer cylinder is located at the front end side crimping portion rather than the rear end side crimping portion. It is greatly deformed. Thereby, the protective outer cylinder can be firmly fixed to the outer cylinder even at the front end side caulking part where the elastic force of the elastic member cannot be used and the caulking force is weaker than that of the rear end side caulking part.

  According to the present invention, the position of the filter is kept away from the front end side of the gas sensor, and the air permeability of the filter is maintained, and the caulking portion is directly closer to the front end side than the filter in order to prevent crevice corrosion between the protective outer cylinder and the corresponding one. The protective outer cylinder can be firmly fixed to the outer cylinder without forming the.

It is sectional drawing which cut | disconnected the gas sensor which concerns on embodiment of this invention by the surface which follows an axial direction. It is sectional drawing which shows the arrangement | positioning state of the outer cylinder before crimping, and a protection outer cylinder. It is a perspective view which shows another embodiment which showed the positional relationship of the 1st ventilation hole of an outer cylinder, and the 2nd ventilation hole of a protection outer cylinder. It is sectional drawing which cut | disconnected the conventional gas sensor in the surface in alignment with an axial direction.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 shows a cross-sectional structure in which a gas sensor 100 according to a first embodiment of the present invention is cut along a plane along an axis O direction (a direction along the rear end from the front end). In this embodiment, the gas sensor 100 is an oxygen sensor that is inserted into an exhaust pipe of an automobile and the tip (the protector 7 side in FIG. 1) is exposed to the exhaust gas to detect the oxygen concentration in the exhaust gas.
The lower side (the protector 7 side) in FIG. 1 is the front end side of the gas sensor 100, and the upper side in FIG.

In the gas sensor 100, the gas sensor element 3 is assembled in a housing (metal shell) 20. This gas sensor element 3 is a known oxygen gas sensor element that constitutes an oxygen concentration cell in which a pair of electrodes is laminated on an oxygen ion conductive solid electrolyte body and outputs a detection value corresponding to the amount of oxygen. Specifically, the gas sensor element 3 includes a bottomed cylindrical solid electrolyte body that is tapered toward the tip, and an inner electrode and an outer electrode formed on the inner and outer peripheral surfaces of the solid electrolyte body ( (Not shown). Then, the internal space of the gas sensor element 3 is set as a reference gas atmosphere, and the gas to be detected is brought into contact with the outer surface of the gas sensor element 3 to detect the gas.
Near the center of the gas sensor element 3, a flange 3 a that protrudes radially outward is provided. On the other hand, on the inner peripheral surface near the tip of the housing 20, a step portion 20e having a diameter reduced inward is provided, and the packing 12 is disposed between the flange portion 3a and the step portion 20e. Then, the gas sensor element 3 is inserted into the inside of the housing 20, and the flange 3 a is applied to the packing 12, so that the flange 3 a of the gas sensor element 3 is indirectly brought into contact with the stepped portion 20 e from the rear end side. Is assembled in the housing 20.

  Further, a cylindrical seal material (talc powder) 6 is filled in a radial gap between the gas sensor element 3 and the housing 20 on the rear end side of the flange 3 a, and a cylindrical shape is further formed on the rear end side of the seal material 6. An insulating member (ceramic sleeve) 31 is disposed. Then, a metal ring (stainless flat washer) 30 is disposed on the rear end side of the insulating member 31 and the rear end portion of the housing 20 is bent inward to form the crimped portion 20a. The insulating material 31 and the sealing material 6 are crimped and fixed while being pressed against the distal end side, and the gap between the gas sensor element 3 and the housing 20 is sealed.

  Further, a metal cylindrical outer cylinder 40 is joined to the rear end of the housing 20 in order to cover the rear end portion of the gas sensor element 3. For the outer cylinder 40, for example, stainless steel such as SUS430, SUS304, SUS304L, SUS310S, SUS316, SUS316L, or the like can be used. The outer cylinder 40 has a front end portion 40a connected to the housing 20 and a rear end portion 40b having a diameter smaller than that of the front end portion 40a. A stepped portion 43 is provided between the front end portion 40a and the rear end portion 40b. Is provided.

  An insulating cylindrical separator 111 is disposed inside the distal end portion 40 a of the outer cylinder 40. Further, the base portions 74 and 94 of the terminal fittings 71 and 91 are inserted into the two insertion holes of the separator 111, respectively. Connection end portions 75 and 95 are formed at the rear ends of the base portions 74 and 94, and lead wires 141 and 141 are caulked and connected to the connection end portions 75 and 95, respectively. In addition, the separator 111 abuts the inner end of the outer cylinder 40 by bringing the front end surface of the separator 111 into contact with the holding metal fitting 45 disposed on the front end side of the separator 111 while bringing the rear end surface of the separator 111 into contact with the stepped portion 43. Retained. The holding metal fitting 45 is disposed on the front end side of the separator 111, and is fixed in the outer cylinder 40 by crimping the front end portion 40 a of the outer cylinder 40.

  A cylindrical grommet (corresponding to an “elastic member” in the claims) 131 is inserted and fixed inside the rear end portion 40b of the outer cylinder 40 by caulking. In the grommet 131, lead wires 141 and 141 are drawn out from the two insertion holes, respectively. As the grommet 131, for example, an elastic member made of silicon rubber, fluorine rubber, or the like can be used. Further, in this embodiment, the rear end side of the grommet 131 is enlarged in a flange shape, and the grommet 131 is easily positioned by placing this enlarged diameter portion on the rear end of the outer cylinder 40.

  The terminal fitting 71 has a cylindrical shape, is fitted inside the gas sensor element 3, and is electrically connected to an inner electrode provided inside the gas sensor element 3. The terminal fitting 91 has a cylindrical shape, is fitted on the outside of the gas sensor element 3, and is electrically connected to an outer electrode provided on the outside of the gas sensor element 3.

  On the other hand, a cylindrical protector 7 made of metal (such as stainless steel) is fixed to the distal end portion 20 f of the housing 20, and the distal end of the gas sensor element 3 protruding from the housing 20 is covered with the protector 7. The protector 7 has a plurality of holes for taking the exhaust gas into the protector 7.

In the vicinity of the center of the housing 20, a polygonal flange portion 20c that protrudes radially outward and engages with a hexagon wrench or the like is provided, and is formed on the outer surface of the housing 20 between the flange portion 20c and the tip portion 20f. Has a male screw portion 20d. Further, a gasket (not shown) for preventing gas escape when attached to the exhaust pipe is fitted into a step portion between the front end surface of the flange portion 20c and the rear end of the male screw portion 20d.
Then, by attaching the male screw portion 20d of the housing 20 to a screw hole such as an exhaust pipe, the tip of the gas sensor element 3 is exposed in the exhaust pipe to detect the detected gas (exhaust gas).

Next, the rear end portion 40b of the outer cylinder 40, the filter 50, and the protective outer cylinder 60, which are features of the present invention, will be described.
In the side surface of the rear end portion 40b of the outer cylinder 40, four first vent holes 41 (only three are shown in FIG. 1) are opened at equal intervals in the circumferential direction at a position closer to the tip than the tip 131a of the grommet 131. The outside air can be introduced into the outer cylinder 40. An outer side of the rear end portion 40b of the outer cylinder 40 is covered with an annular air-permeable filter 50 so as to close the first ventilation hole 41. Further, the filter 50 is formed in a metal cylindrical shape from the outer side in the radial direction. A protective outer cylinder 60 surrounds. For example, stainless steel such as SUS430, SUS304, SUS304L, SUS310S, SUS316, and SUS316L can be used for the protective outer cylinder 60. Four second vent holes 61 (only two are shown in FIG. 1) are opened at equal intervals in the circumferential direction on the side surface of the protective outer cylinder 60, and a part of the outer surface of the filter 50 is exposed from the second vent hole 61. Thus, the second ventilation hole 61 communicates with the filter 50, and the outside air is introduced into the outer cylinder 40 through the filter 50.
The filter 50 is made of, for example, a porous structure made of a resin such as a fluorine resin, and has water repellency. It has become.
The protective outer cylinder 60 is bent radially inward so that the rear end portion is provided on the rear end surface of the grommet 131, and an opening 63 is formed at the center of the rear end portion. 141 are pulled out to the outside.

Here, the outer cylinder 40 (rear end portion 40 b) and the protective outer cylinder 60 were crimped via the filter 50 at two points before and after the first ventilation hole 41 and the second ventilation hole 61. distal side caulking part S ₁ and rear side caulking portion S ₂ is provided. Among these, the rear end side crimping portion S < _b > ₂ is located in the region R of the elastic member 131 in the axis O direction.
When caulking in this manner, the filter 50 can be disposed so as to overlap the position of the grommet 131 disposed on the rear end side of the gas sensor 100, so that the position of the resin filter 50 is changed from the front end side of the gas sensor 100. Further, the filter 50 can be prevented from contracting due to heat received from the heat source (exhaust pipe) and sealing performance can be prevented from being lowered.

  Further, the gas sensor 100 is not crimped because the outer cylinder 40 and the protective outer cylinder 60 are in direct contact with each other. Thereby, the direct crimping part of the outer cylinder 40 and the protection outer cylinder 60, or the clearance at the front end side thereof is not provided, and it is possible to prevent crevice corrosion from occurring between the outer cylinder 40 and the protection outer cylinder 60.

Further, the gas sensor 200, the leading end side crimp portion S _1, it is deformed so that the outer tube 40 is recessed radially inward. That is, since the outer cylinder 40 is strongly crimped at the distal end side crimping portion S ₁ until it is recessed and deformed inward in the radial direction, the crimping is sufficient and the protective outer cylinder 60 can be firmly fixed to the outer cylinder 40.

Further, in the gas sensor 100, the rear side caulking portion S ₂ are deformed as the outer tube 40 is recessed radially inward. That is, the rear side caulking portion S _2, and tighten pressure to the outer tube 40 is deformed recessed radially inward. Thereby, the force which the grommet 131 repels with an elastic force with respect to the caulking which shrinks | diameters radially inward can be enlarged more, and the protection outer cylinder 60 can be firmly fixed to the outer cylinder 40. FIG.

Further, in the gas sensor 100, the leading end side caulking part _{S 1} is located on the distal end side than the distal end 131a of the grommet 131 at the distal end side crimping portion _{S 1} from the rear end side caulking section _{S 2,} the outer cylinder 40 Is greatly deformed. As a result, the protective outer cylinder 60 is firmly fixed to the outer cylinder 40 even at the front end side caulking portion S ₁ where the elastic force of the grommet 131 cannot be used and the caulking force is weaker than the rear end side caulking portion S _2. can do.

Incidentally, the rear side caulking section S ₂ and is located within the region R in the axial O direction of the grommet 131, it refers to the portion of the rear side caulking portion S ₂ is located in the region R.
The outer cylinder 40 and the protective outer cylinder 60 may have a hardness of 100 to 400 Hv and a thickness of 0.2 to 0.8 mm.
Furthermore, it is preferable that the front end side crimped portion S1 and the rear end side crimped portion S2 are crimped so that the hole shapes of the first vent hole 41 and the second vent hole 61 are not deformed. Accordingly, an accurate ventilation amount can be secured by the first ventilation hole 41 and the second ventilation hole 61.

Next, the manufacturing method of the gas sensor 100 of this embodiment is demonstrated. FIG. 2 is a cross-sectional view showing an arrangement state of the outer cylinder 40 and the protective outer cylinder 60 before caulking. First, the separator 111 is disposed inside the outer cylinder 40. At this time, the rear end surface of the separator 111 is brought into contact with the stepped portion 43 of the outer cylinder 40. Next, the holding metal fitting 45 is arranged on the front end side of the separator 111, and the holding metal fitting 45 is fixed by crimping the outer cylinder 40 (the front end portion 40a). Thereby, the separator 111 is fixed in the front end portion 40 a of the outer cylinder 40.
Next, the filter 50 is arranged at the rear end portion 40 b of the outer cylinder 40, and the grommet 131 is arranged so that the grommet 131 is engaged with the rear end of the outer cylinder 40. Then, covered with a protective outer cylinder 60 on the outside of the outer cylinder 40, the crimp through the filter 50 between the outer cylinder 40 and the protective outer cylinder 60, distal end side crimping portion S ₁ and the rear end side crimping portion S ₂ and the outer cylinder 40 and the protective outer cylinder 60 are fixed.

  Thereafter, the gas sen 100 is prepared by a known method. Specifically, the outer cylinder 40 to which the above-described protective outer cylinder 60 is fixed is assembled to the lower assembly formed by the gas sensor element 3, the metal shell 10, the protector 7, etc., and the outer cylinder 40 and the metal shell 10 are assembled. Fix by laser welding or the like.

  It goes without saying that the present invention is not limited to the above-described embodiment, but extends to various modifications and equivalents included in the spirit and scope of the present invention.

In the present embodiment, the rear end side crimp portion S ₂ is the outer cylinder 40 has been deformed, not limited thereto, and may be configured to the outer cylinder 40 is not deformed. Rear side caulking part S _2, since the grommet 131 with respect crimping reduced in diameter radially inwardly is repelled by the elastic force, without deforming the outer tube 40 of the rear side caulking portion S ₂ is, The protective outer cylinder 60 can be firmly fixed to the outer cylinder 40.

Further, FIG. 3 is another embodiment showing the positional relationship between the first ventilation hole 41 of the outer cylinder 40 and the second ventilation hole 61 of the protective outer cylinder 60. The positions of the first vent holes 41 and the second vent holes 61 do not have to coincide with each other, and even if the first vent holes 41 and the second vent holes 61 are alternately arranged in the circumferential direction as shown in FIG. Good. This is because the first ventilation hole 41 and the second ventilation hole 61 communicate with the filter 50, respectively, so that outside air can be introduced into the outer cylinder 40. As described above, when a plurality of the first ventilation holes 41 and the second ventilation holes 61 are provided in the circumferential direction, the first ventilation holes 41 of the outer cylinder 40 and the second ventilation holes 61 of the protective outer cylinder 60 overlap each other. Therefore, productivity is improved.
Further, as viewed in the direction of the axis O, the first vent hole 41, it is necessary to position the tip of the distal end 131a of the grommet 131, there the second vent hole 61 is distal to the rear end side crimp portion S ₂ For example, the grommet 131 may be positioned at the rear end from the front end 131a.

  Further, in the present embodiment, all of the first vent holes 41 are located at the tip of the tip 131a of the grommet 131. However, the present invention is not limited to this, and a part of the first vent hole 41 is more than the tip 131a of the grommet 131. It may be located at the tip (that is, the first vent hole 41 may be located across the tip 131a of the grommet 131).

In the above embodiment, a plurality of the first vent holes 41 and the second vent holes 61 are provided in the circumferential direction. However, the positions and the number of the first vent holes 41 and the second vent holes 61 are not limited to the above. I can't.
Further, in the present embodiment, the filter 50 has an annular shape, but is not limited to this, and the filter 50 is partially in the circumferential direction as long as the first ventilation hole 41 and the second ventilation hole 61 communicate with each other. It may be provided.
Further, as the gas sensor element, in addition to the above-described oxygen sensor element (entire region air-fuel ratio sensor element), a λ sensor element, a NO _x sensor element, and an ammonia sensor element can be used. It may be a type element.

3 gas sensor element 20 metal shell 40 outer cylinder 41 first vent hole 50 filter 60 protective outer cylinder 61 second vent hole 100 gas sensor 131 elastic member 141 lead wire O axial direction S ₁ front end side crimping part S ₂ rear end side crimping Part R Elastic member region

Claims (3)

A gas sensor element extending in the axial direction;
A cylindrical metal shell surrounding the gas sensor element in the radial direction and holding the gas sensor element;
A cylindrical outer cylinder that is attached to the metal shell, extends to the rear end side of the metal shell, and has a first vent hole that introduces outside air into itself,
An elastic member inserted into the rear end side of the outer cylinder and sealing the outer cylinder;
A resin-made filter that is disposed on the outer side in the radial direction of the outer cylinder so as to close the first vent hole, and has air permeability;
A cylindrical protective outer cylinder that surrounds the filter from the outside in the radial direction and has a second vent hole communicating with the filter;
A gas sensor comprising:
The outer cylinder and the protective outer cylinder are a front-end side crimped portion and a rear-end side crimped portion that are crimped via the filter at two locations ahead and behind the first vent hole and the second vent hole, respectively. Part
The outer cylinder and the protective outer cylinder are in direct contact and are not crimped,
The rear end side crimping portion is located in a region in the axial direction of the elastic member;
The front end side crimping portion is a gas sensor that is deformed so that the outer cylinder is recessed inward in the radial direction.   The gas sensor according to claim 1, wherein the rear end side crimping portion is deformed so that the outer cylinder is recessed radially inward. The distal end side crimping portion is located on the distal end side with respect to the distal end of the elastic member,
The gas sensor according to claim 2, wherein the outer cylinder is largely deformed at the front end side caulking portion rather than the rear end side caulking portion.

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