JP2015132493A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor capable of preventing the deformation of a fastener to increase the certainty of separator retention and maintaining the reliability of electrical connection with a sensor element, as well as capable of reducing a mechanical shock to the separator.SOLUTION: Provided is a gas sensor comprising a sensor element, a main metal-fitting, a separator 70 having a flange part 70d, an outer tube covering the separator, and a ring-shaped fastener 80 secured to the outer tube while being in contact with a tip-facing surface 70b of the flange part, where the fastener 80 has a cylindrical circumferential wall part 80a enclosing an outside surface 70c of the separator, a plurality of long pieces 80s extending to a tip side via a fold-back part 80b in which it is folded back inward in the radial direction from the circumferential wall part and coming in contact with the outer surface of the separator, thereby elastically holding the separator, and a plurality of shoulder parts 80e provided in a circumferential direction between the long pieces and being in contact with the tip-facing surface of the flange part, the tip-facing surface 70b of the flange part and the fold-back part 80b being separated.

Description

  The present invention relates to a gas sensor having a configuration in which a rear end of a sensor element is accommodated in a separator and detecting the concentration of a specific gas component.

As gas sensors that improve fuel consumption and control combustion in an internal combustion engine such as an automobile engine, oxygen sensors and air-fuel ratio sensors that detect the oxygen concentration in exhaust gas are known.
As such a gas sensor, a sensor element for detecting the concentration of a specific gas is held by a metal shell, and an electrode extraction portion (electrode pad) arranged on the surface of the rear end side of the sensor element is surrounded by a cylindrical ceramic separator. The structure is generally used. The terminal fittings attached to the separator are electrically connected to the electrode pads of the sensor element, rubber grommets are arranged on the rear end side of the separator, and the separator and grommets are attached to the metal outer cylinder. Covered. Further, a lead wire is connected to the terminal fitting, and the lead wire is drawn out through the through hole of the grommet.
Here, an annular clasp is disposed between the separator and the outer cylinder. The fastener has a cylindrical peripheral wall portion and a plurality of long pieces (spring pieces) folded back radially inward from the peripheral wall portion. It is held elastically in the peripheral wall (Patent Document 1). Then, the front-facing surface of the flange of the separator is locked to the rear-facing surface of the fastener, and the rear-facing surface of the separator is locked to the grommet, so that the front and rear of the separator are fixed in the outer cylinder. Yes.

JP 2012-225737 A

By the way, when assembling the clasp to the outer cylinder, the clasp containing the separator is pressed to the rear end side through a jig and brought into contact with the grommet, and the outer cylinder is crimped and clamped at the position of the clasp. Fix the bracket in the outer cylinder. At this time, in order to securely position the separator and fix it in the fastener, it is necessary to strongly press the fastener toward the rear end side. The long piece may be crushed by being pressed by the collar portion, and the separator may be unstable due to the long piece. As a result, vibration or the like accompanying the driving of the engine is easily transmitted from the outer cylinder to the separator, and there is a risk that the reliability of the electrical connection between the terminal fitting and the electrode pad in the separator may be reduced or the separator may be shocked. .
Accordingly, the present invention provides a gas sensor that can prevent deformation of the fastener, increase the reliability of holding the separator, maintain the reliability of electrical connection with the sensor element, and reduce the impact on the separator. For the purpose of provision.

In order to solve the above-described problems, a gas sensor according to the present invention includes a sensor element that extends in the axial direction and has a detection portion on a distal end side, a cylindrical metal shell that surrounds the periphery of the sensor element, and a flange that projects radially outward. An insulating separator that is disposed on the rear end side of the metal shell and surrounds the rear end side of the sensor element, and a cylindrical shape that is disposed on the rear end side of the metal shell while covering the separator A gas sensor comprising: an outer cylinder; and an annular fastener that is fixed to the outer cylinder while being in contact with a tip-facing surface of the flange, wherein the fastener surrounds an outer surface of the separator. A plurality of long pieces that elastically hold the separator, extending to the distal end side through a folded portion that is folded back radially inward from the peripheral wall portion and contacting the outer surface of the separator. Front along direction Is provided between the long piece has a plurality of shoulders adjacent to the forward-facing surface of the flange portion, forward-facing surface of the flange portion and said folded portion are spaced apart from each other.
When the fastener is assembled to the outer cylinder, the fastener containing the separator is strongly pressed to the rear end side through the jig. Therefore, according to the gas sensor of the present invention, since the tip-facing surface of the flange portion of the separator and the folded portion are separated from each other, the folded portion is suppressed from being pushed and crushed by the flange portion. As a result, the long piece is prevented from spreading outward in the radial direction due to the deformation of the folded portion, and the long piece reliably contacts the outer surface of the separator. Therefore, it is possible to increase the reliability of holding the separator, maintain the reliability of the electrical connection with the sensor element, and reduce the impact on the separator.

The site | part which touches the front end surface of the said collar part among the said shoulder parts may be located in the back end side rather than the said folding | returning part.
According to this gas sensor, even if the shoulder is pushed by the buttocks and deformed to some extent, the tip-facing surface of the buttocks and the folded portion can be reliably separated, and the folded portion is pushed by the buttocks and crushed. Is more reliably suppressed.

The shoulder portion may extend radially inward from the peripheral wall portion and obliquely with respect to the radial direction.
According to this gas sensor, the actual length of the shoulder portion is longer than the length L in the axial direction of the shoulder portion, and the amount of deflection (stroke) of the shoulder portion when an elastic load is applied to the shoulder portion is increased accordingly. Become. Therefore, the vibration and impact in the axial direction of the separator can be absorbed by the elastic force of the shoulder, and the impact on the separator can be further reduced.

The tip-facing surface of the flange may be formed in a tapered shape that narrows toward the tip.
According to this gas sensor, when the tip-facing surface, which is a tapered surface, comes into contact with the shoulder portion, it is easy to be held at the center of the axis, and the separator can be securely held in alignment with the center of the axis.

The tip of the long piece may be in contact with the outer surface of the separator.
According to this gas sensor, the leading end of the long piece is hooked on the outer surface to hold the separator more securely, and suppress the displacement of the separator. In addition, since the length (span) in the axial direction between the shoulder portion and the long piece, which is a part for holding the separator, becomes longer, the axial blur of the separator can be further suppressed.

  According to the present invention, there is provided a gas sensor capable of preventing the deformation of the clasp, improving the reliability of holding the separator, maintaining the reliability of the electrical connection with the sensor element, and reducing the impact on the separator. can get.

It is sectional drawing which follows the axial direction of the gas sensor which concerns on embodiment of this invention. It is a disassembled perspective view of a separator and a fastener. It is sectional drawing which follows the axial direction which shows the engagement state of a separator and a metal fitting. It is a disassembled perspective view of the fastener of a modification. It is sectional drawing which follows the axial direction which shows the engagement state of the separator and fastener in FIG. It is a disassembled perspective view of the fastener of another modification. It is sectional drawing which follows the axial direction which shows the engagement state of the separator and fastener in FIG.

Hereinafter, embodiments of the present invention will be described.
First, a gas sensor (oxygen sensor) 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 is a cross-sectional view of the gas sensor 100 along the direction of the axis O, FIG. 2 is an exploded perspective view of the separator 70 and the fastener 80, and FIG. 3 is a cross-sectional view showing an engaged state of the separator 70 and the fastener 80. The lower side in FIG. 1 (side on which the detection part 10a of the sensor element 10 is located) is referred to as “tip side”, and the upper side (side on which the electrode extraction part (electrode pad) 10e of the sensor element 10 is located) is referred to as “rear side”. It is called “end side”.

The gas sensor 100 is an assembly in which the sensor element 10 is assembled. The gas sensor 100 includes a plate-like sensor element 10 extending in the direction of the axis O (vertical direction in FIG. 1), and a metal shell 2 fixed to the exhaust pipe of the automobile engine. The metal shell 2 has a substantially cylindrical shape, and a threaded portion 24 for fixing to the exhaust pipe is formed on the outer surface, while a shelf portion 2p having an inner hole 25 and projecting radially inward from the inner hole 25. On the tip side. The metal shell 2 accommodates the sensor element 10 in the inner hole 25, and the detection portion 10a provided on the front end side of the sensor element 10 and the electrode pad 10e provided on the rear end side protrude from the metal shell 2, respectively. In this state, the sensor element 10 is held. Further, between the inner peripheral surface of the metal shell 2 and the outer peripheral surface of the sensor element 10, an annular holding member 21 made of ceramic surrounding the outer peripheral surface of the sensor element 10, powder fillers (talc rings) 22, 23, And the ceramic sleeve 30 is laminated | stacked from the detection part 10a side in this order. Then, the rear end portion 2a of the metal shell 2 is swaged and the sleeve 30 is pressed to the front end side, so that the holding member 21 is locked to the shelf portion 2p and the talc rings 22 and 23 are crushed into the inner hole 25. The sensor element 10 is filled and firmly fixed at a predetermined position in the metal shell 2. Examples of the talc rings 22 and 23 include talc (ceramic powder) and glass (silicate compounds such as silicate glass or silicate glass).
The holding member 21 and the talc ring 22 are accommodated in the inner hole 25 of the metal shell 2 via the metal cup 20.

Further, a metal external protector 4 and an internal protector 3 that surround the detection portion 10 a of the sensor element 10 are attached to the outer periphery on the front end side of the metal shell 2.
In this example, the sensor element 10 is an oxygen sensor element having a configuration in which a pair of electrodes are arranged on the surface of the solid electrolyte layer. In addition, a heater for activating the cell and a solid electrolyte layer are protected. Insulating layers (such as alumina) are laminated. Further, the porous protective layer 12 covers the surface of the detection unit 10 a of the sensor element 10.

On the other hand, electrode pads 10e provided on both plate surfaces on the rear end side of the sensor element 10 (four in this example, two on each surface in total) are surrounded by a cylindrical ceramic separator 70. As will be described later, the separator 70 has the insertion hole 70h of the sensor element 10 at the center, and communicates with the insertion hole 70h to accommodate a plurality of terminal fittings 60 (four in this example). As shown in FIG. 2, there are four in this example. The terminal fittings 60 are respectively attached to the partitioned holes 71h while ensuring insulation, and the terminal fittings 60 are electrically connected to the electrode pads 10e of the sensor element 10, respectively.
The separator 70 is provided with a cylindrical outer surface 70c on the front end side, and on the rear end side is provided with a flange portion 70d that protrudes radially outward so as to increase the diameter from the outer surface 70c. And the outer side surface 70c and the collar part 70d are connected by the front end surface 70b (taper surface) which diameter-reduces toward a front end.

A cylindrical rubber seal member (grommet) 50 is disposed at the rear end of the separator 70 so as to be separated from the separator 70, and the separator 70 and the grommet 50 are covered with a metal outer cylinder 90. Near the center of the outer cylinder 90 in the direction of the axis O, an annular fastener 80 that holds the separator 70 is fixed by caulking, and the rear end of the outer cylinder 90 is reduced in diameter toward the rear end side from the caulking portion. Thus, the inner convex portion 90a is formed. As shown in FIG. 2, the fastener 80 is made of metal and has a substantially cylindrical peripheral wall portion 80a, and a folded portion 80b folded back radially inward from the rear end edge of the peripheral wall portion 80a. It has a plurality of long pieces 80s (six in this example) that extend and are arranged at equal intervals in the circumferential direction. A plurality of shoulder portions 80e (six in this example) are provided between the long pieces 80s adjacent in the circumferential direction, extending from the folded portion 80b to the inside in the radial direction and parallel to the radial direction. ing.
The folded portion 80b side of the clasp 80 is fitted into the tip-facing surface 70b of the separator 70, the shoulder 80e abuts on the tip-facing surface 70b of the flange 70d, and the inner convex portion 90a (the tip-facing surface thereof) is the separator. 70 is engaged with the rear end facing surface 70a. As a result, the separator 70 is held apart from the metal shell 2 (rear end portion 2a) in the axis O direction while being sandwiched in the axis O direction at the top and bottom of the front end side and the rear end side. The long piece 80s abuts on the outer surface 70c, and the impact applied to the outer cylinder 90 is not directly transmitted to the separator 70 due to the elastic force of the long piece 80s.

Each terminal fitting 60 held in the separator 70 is folded inward at the tip, and the folded portion is electrically connected to each electrode pad 10 e of the sensor element 10. On the other hand, the rear end side of each terminal fitting 60 is a crimping portion 65 protruding from the rear end of the separator 70. The crimping portion 65 has a lead wire 68 crimped and connected to the inside thereof. Each lead wire 68 is drawn out through a separate lead hole 51 h (see FIG. 2) of the grommet 50.
Further, the rear end side of the outer cylinder 90 is crimped, and the grommet 50 is held in the outer cylinder 90. The outer cylinder 90 that holds the separator 70 and the grommet 50 in this way is fitted to the rear end side of the metal shell 2, and the fitting part is welded on the entire circumference to connect them.

Next, an engaged state between the separator 70 and the fastener 80 will be described with reference to FIG.
As shown in FIG. 3, the front-facing surface 70 b of the flange 70 d of the separator 70 abuts on a shoulder 80 e that protrudes from the rear end of the fastener 80.
At this time, the shoulder portion 80e is flush with the folded portion 80b in the direction of the axis O, but the shoulder portion 80e projects radially inward from the folded portion 80b, so that the positional relationship with the tapered tip-facing surface 70b. Thus, the folded portion 80b is separated from the tip-facing surface 70b. As a result, when the fastener 80 is assembled to the outer cylinder 90, the folded portion 80 b of the fastener 80 can be attached to the separator 70 even if the fastener 80 including the separator 70 is strongly pressed to the rear end side through the jig. It is suppressed that it is pushed and crushed by the tip-facing surface 70b of the collar part 70d. As a result, the long piece 80 s is prevented from spreading outward in the radial direction due to the deformation of the folded portion 80 b, and the long piece 80 s reliably contacts the outer surface 70 c of the separator 70. Therefore, the certainty of holding the separator 70 is improved, the reliability of the electrical connection between the terminal fitting 60 held by the separator 70 and the electrode pad 10e of the sensor element 10 is maintained, and the impact on the separator 70 is reduced. Can do.
However, in the case of the separator 72 shown in FIG. 7 to be described later, since the tip-facing surface 72b is parallel to the radial direction, the folded portion 80b comes into contact with the tip-facing surface 72b when the fastener 80 of this example is used. . Therefore, in the case of the separator 72 shown in FIG. 7, it is necessary to use fasteners 81 and 82 (see FIGS. 4 to 7) whose shoulders protrude from the rear end (folded portion) of the fastener.

In this example, the tip-facing surface 70b of the collar portion 70d is formed in a tapered shape that narrows toward the tip, so that when the tip-facing surface 70b that becomes the taper surface comes into contact with the shoulder 80e, the center of the axis O The separator 70 can be reliably aligned with the center of the axis O and held.
Furthermore, in this example, the tip 80s1 of the long piece 80s is in contact with the outer surface 70c of the separator 70. Thereby, the front-end | tip part 80s1 is hooked on the outer surface 70c, hold | maintains the separator 70 more reliably, and suppresses the position shift of the separator 70. FIG. Further, since the length (span) in the direction of the axis O between the shoulder 80e and the long piece 80s, which are the parts that hold the separator 70, becomes longer, the blur in the direction of the axis O of the separator 70 can be further suppressed.

In this example, a ventilation filter 52 is disposed inside the grommet 50 as shown in FIG. Specifically, a vent hole 50h penetrating in the axis O direction is formed at the center of the grommet 50, and a plurality of (four in this example) leads penetrating in the axis O direction radially outward from the vent hole 50h. A hole 51h is formed along the circumferential direction.
A cylindrical filter clasp 55 and a water-repellent vent filter 52 that covers the outside of the filter clasp 55 are inserted into the vent hole 50h. Thereby, the reference gas (atmosphere) can be introduced into the gas sensor from the outside of the grommet 50. The ventilation filter 52 is made of a fluororesin such as PTFE (polytetrafluoroethylene) and can pass through the atmosphere without passing water droplets.
The filter clasp 55 is made of metal and has a bottomed cylindrical shape with the rear end closed. A center hole 55h is formed in the rear end face of the filter clasp 55, and the reference atmosphere flows into the gas sensor through the vent hole 52 from the center hole 55h. On the other hand, a flange portion 55 f that protrudes radially outward is formed on the tip end side of the filter clasp 55. Further, on the side facing the front end 50a of the grommet 50, the periphery of the vent hole 50h is recessed toward the rear end to form a recess 50a1, and the rear end facing surface 55a of the flange 55f abuts against the recess 50a1 (the recess 50a1 Housed) and prevents the filter clasp 55 from falling off to the rear end side.
The recess 50a1 extends to the outside in the radial direction from the lead hole 51h. And the outer periphery of the ventilation filter 52 accommodated in the recessed part 50a1 protrudes on the radial direction outer side rather than the lead hole 51h.

Next, a modified example of the fastener will be described with reference to FIGS. 4 and 5. 4 is a perspective view of the fastener 81, and FIG. 5 is a cross-sectional view showing an engaged state of the separator 70 and the fastener 81. As shown in FIG.
As shown in FIG. 4, the fastener 81 is made of metal and has a substantially cylindrical peripheral wall portion 81a, and a folded portion 81b that is folded back radially inward from the rear end edge of the peripheral wall portion 81a. It has a plurality of long pieces 81s (six in this example) that extend and are arranged at equal intervals in the circumferential direction. Further, a plurality of shoulder portions 81e (six in this example) projecting toward the rear end side are provided between the long pieces 81s adjacent in the circumferential direction. That is, the fastener 81 has the same configuration as the fastener 80 of FIG. 2 except that the shoulder portion 81e is different. The shoulder portion 81e extends radially inward from the rear end edge of the peripheral wall portion 81a and extends obliquely upward (rear end side) with respect to the radial direction.
As shown in FIG. 5, the tip-facing surface 70b of the flange 70d of the separator 70 contacts the shoulder 81e of the fastener 81, while the folded-back portion 81b is separated from the tip-facing surface 70b. As a result, the folded portion 81b of the clasp 81 is suppressed from being crushed by being pressed by the flange portion 70d of the separator 70.
In this example, since the folded portion 81b is located on the distal end side in the axis O direction from the shoulder portion 81e, the folded portion 81b is reliably separated from the distal-facing surface 70b of the flange portion 70d. In this example, the shoulder portion 81e extends radially inward from the rear end of the peripheral wall portion 81a and extends obliquely with respect to the radial direction. For this reason, the actual length of the shoulder portion 81e is longer than the length L of the shoulder portion 81e in the direction of the axis O, and the amount of deflection (stroke) of the shoulder portion 81e when an elastic load is applied to the shoulder portion 81e. ) Becomes larger. Therefore, the vibration and impact in the direction of the axis O of the separator 70 can be absorbed by the elastic force of the shoulder portion 81e, and the impact on the separator 70 can be further reduced.

Next, another modified example of the fastener will be described with reference to FIGS. FIG. 6 is a perspective view of the fastener 82, and FIG. 7 is a cross-sectional view showing an engaged state of the separator 72 and the fastener 82.
As shown in FIG. 6, the clasp 82 is made of metal and has a substantially cylindrical peripheral wall portion 82 a and a distal end side through a folded portion 82 b that is folded back radially inward from the rear end edge of the peripheral wall portion 82 a. It has a plurality of long pieces 82s (six in this example) that extend and are arranged at equal intervals in the circumferential direction. Further, a plurality of shoulder portions 82e (six in this example) projecting from the folded portion 82b to the rear end side along the axis O direction are provided between the long pieces 82s adjacent in the circumferential direction. Yes. That is, the clasp 82 has the same configuration as the clasp 80 in FIG. 2 except that the shoulder portion 82e is different.
On the other hand, as shown in FIG. 7, the separator 72 is provided with a cylindrical outer surface 72 c on the front end side, and a collar portion 72 d that protrudes from the outer surface 72 c so as to expand its diameter on the rear end side. Yes. And the outer side surface 72c and the collar part 72d are connected by the front end surface 72b (flat surface) parallel to a radial direction.
The front end facing surface 72b of the separator 72 is in contact with the shoulder portion 82e protruding from the rear end (the folded back portion) of the fastener 82, while the folded back portion 82b is separated from the front end facing surface 72b. As a result, the folded-back portion 82b of the clasp 82 is suppressed from being pushed and crushed by the flange portion 72d of the separator 72.

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. For example, the shapes of the separator and the fastener are not limited to the above.
In addition to the oxygen sensor, the sensor can be applied to a gas sensor for measuring a gas concentration such as a NOx sensor, HC, H ₂ or the like.

2 Main metal fitting 10 Sensor element 10a Detection part 70, 72 Separator 70b, 72b Tip end facing surface 70c, 72c Separator outer surface 70d, 72d Separator flange 80-82 Fastener 80a-82a Peripheral wall 80b-82b Portion 80e to 82e Shoulder 80s to 82s Long piece 80s1 Long piece tip 90 Outer cylinder 100 Gas sensor O Axial direction

Claims (5)

A sensor element extending in the axial direction and having a detector on the tip side;
A cylindrical metal shell surrounding the sensor element;
An insulating separator having a flange projecting radially outward, disposed on the rear end side of the metal shell and surrounding the rear end side of the sensor element;
A cylindrical outer cylinder disposed on the rear end side of the metal shell while covering the separator;
An annular fastener that is fixed to the outer cylinder while being in contact with the tip-facing surface of the flange,
A gas sensor comprising:
The fastener extends to the distal end side through a cylindrical peripheral wall portion that surrounds the outer surface of the separator and a folded portion that is folded back radially inward from the peripheral wall portion, and contacts the outer surface of the separator. A plurality of long pieces that elastically hold the separator, and a plurality of shoulder portions that are provided between the long pieces along the circumferential direction and that contact the tip-facing surface of the flange portion,
A gas sensor in which a tip-facing surface of the flange portion is spaced from the folded portion.   2. The gas sensor according to claim 1, wherein a portion of the shoulder portion that is in contact with a front-facing surface of the collar portion is located on a rear end side with respect to the folded portion.   The gas sensor according to claim 1, wherein the shoulder portion extends radially inward from the peripheral wall portion and obliquely with respect to the radial direction.   The gas sensor according to any one of claims 1 to 3, wherein the tip-facing surface of the flange portion is formed in a tapered shape that narrows toward the tip.   The gas sensor according to any one of claims 1 to 4, wherein a tip portion of the long piece is in contact with the outer surface of the separator.

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