JP2019184386A - Gas sensor - Google Patents

Abstract

To provide a gas sensor with improved reliability of an electrical connection between a sensor element and a terminal bracket when having a tip-side separator and a rear end separator to suppress a breakage of the sensor element.SOLUTION: The gas sensor 1 includes a plate-shaped sensor element 10 having an electrode portion 11a; principal metal fittings 138; terminal fittings connected to the electrode portion 20, 30; a tip-side separator 90 for holding terminal fittings; a rear end separator 95 connected to the rear end of the tip-side separator; and an outer cylinder 144, and satisfies D2<D1 when the tip-side separator is elastically held in the outer cylinder, the rear end separator is not held in the outer cylinder, the minimum dimensional difference between the outer peripheral surface of the sensor element and the inner peripheral surface of the tip-side separator is D1 in a first measurement cross-section S1 perpendicular to an axis O direction, and the minimum dimensional difference between the outer peripheral surface of the rear end separator and the inner peripheral surface of the outer cylinder is D2 in a second measurement section S2 along the direction parallel to the first measurement direction M1 in which D1 is measured.SELECTED DRAWING: Figure 7

Description

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

As a gas sensor for detecting the concentration of oxygen or NOx in exhaust gas of an automobile or the like, one having a plate-like sensor element using a solid electrolyte is known.
In such a gas sensor, in order to take out the output of the sensor element according to the concentration of the gas to be detected, the terminal metal fitting is brought into contact with the electrode pad provided on the rear end side of the sensor element to electrically connect them. At the same time, a lead wire is crimped to the rear end side of the terminal fitting. The terminal fitting itself is held by a separator made of an insulating member, and the lead wire is drawn out of the gas sensor from the rear end side of the separator through a grommet that is an elastic member.

And the gas sensor which uses the division | segmentation type separator divided into two in the axial direction as a separator is also known (patent documents 1 and 2). Split-type separators are often employed when the number of terminal fittings held by the separator is large or for the convenience of assembling the terminal fittings to the separator.
As shown in FIG. 10, in this type of gas sensor, the rear end side of the sensor element 10 is surrounded by a front end side separator 202, and the terminal fittings 20 and 30 held by the front end side separator 202 are connected to the rear end side of the sensor element 10. The electrode pad 11a is brought into contact. Then, the front end side separator 202 is elastically held in the outer cylinder 206 by the holding metal fitting 208 so that the front end side separator 202 does not come into contact with the sensor element 10 due to blurring in the radial direction.
On the other hand, the rear end side separator 204 is connected to the rear end side of the front end side separator 202, and the rear end side separator 204 is held so as to be sandwiched between the front end side separator 202 and the grommet 170. Since the rear end side separator 204 is separated from the sensor element 10, it is not particularly held by the outer cylinder 204, and is held by the elastic force of the grommet 170, so that the rear end side separator 204 is not in contact with the outer cylinder 204.

JP 2009-47574 A (FIG. 1) JP 2017-198656 A (FIG. 1)

By the way, since the rear end side separator 204 is not in contact with the outer cylinder 204, when the gas sensor vibrates during traveling of the vehicle, the fixed portion between the front end side separator 202 and the holding metal fitting 208 is used as a fulcrum. The rear end side separator 204 may be blurred in the radial direction T.
Then, the rear end side separator 204 is shaken, so that radial stress is applied to the front end side separator 202 in contact with the rear end side separator 204, and thus the sensor element 10. , 30 may be lost.
On the other hand, if the rear end side separator 204 is held in the outer cylinder 206 by the holding metal fitting 208, the number of parts and the production process increase and the cost increases.

  Therefore, the present invention provides a gas sensor that suppresses breakage of the sensor element and improves the reliability of electrical connection between the sensor element and the terminal fitting when the front end side separator and the rear end side separator are provided. Objective.

  In order to solve the above-mentioned problems, the gas sensor of the present invention has a plate shape extending in the axial direction, has a sensor element having an electrode portion on the outer surface on the rear end side, and surrounds the sensor element to hold the sensor element. A metal shell that is electrically connected to the electrode portion, a cylindrical front end separator that holds the terminal metal and surrounds the rear end side of the sensor element, and a rear end of the front end separator. A rear end side separator that is coaxially disposed on the end side and is directly or indirectly connected to the front end side separator, and is fixed to a rear end side of the metal shell, and surrounds the front end side separator and the rear end side separator. A gas sensor, wherein the front end side separator is elastically held by the outer cylinder, and the rear end side separator is not held by the outer cylinder, and is perpendicular to the axial direction. In the measurement cross section, the minimum dimensional difference between the outer peripheral surface of the sensor element and the inner peripheral surface of the front end side separator is D1, and in the second measurement cross section orthogonal to the axial direction, the D1 is measured. When a minimum dimensional difference between the outer peripheral surface of the rear end side separator and the inner peripheral surface of the outer cylinder is D2 along a direction parallel to the measurement direction 1, D2 <D1 is satisfied. .

When the gas sensor vibrates, since the front end side separator and the rear end side separator are coaxially connected, the rear end side separator blurs in the radial direction with the fixed portion of the front end side separator held by the outer cylinder as a fulcrum. Sometimes.
Therefore, according to this gas sensor, by setting D2 <D1, before the sensor element collides with the front end side separator due to radial blur, the rear end side separator comes into contact with the inner peripheral surface of the outer cylinder and is in the radial direction. Absorbs blurring. As a result, it is possible to prevent the sensor element from being damaged by applying a radial stress to the front end separator connected to the rear end separator, and thus to the sensor element, and to maintain the electrical connection with the terminal fitting. Reliability can be improved.

In the gas sensor of the present invention, in the first measurement cross section, a dimensional difference between the outer peripheral surface of the sensor element and the inner peripheral surface of the tip side separator is D3, and the D3 is measured in the second measurement cross section. When the minimum dimensional difference between the outer peripheral surface of the rear end side separator and the inner peripheral surface of the outer cylinder is D4 along a direction parallel to the second measurement direction, any of the second measurement directions In this case, D4 <D3 may be satisfied.
According to this gas sensor, even if the sensor element approaches the front end side separator in any second measurement direction (that is, all 360 degrees in the radial direction), the rear end side separator is not moved as in the case of D2 <D1. It collides first with the inner peripheral surface of the outer cylinder to absorb the blur in the second measuring direction. Accordingly, the sensor element can be further prevented from being damaged, and the reliability of electrical connection with the terminal fitting can be further improved.
In the figure, D31 and D32 correspond to D3, and D41 and D42 correspond to D4.

In the gas sensor of the present invention, the rear end side separator surrounds the terminal fitting or the second terminal fitting connected to the terminal fitting in the axial direction, and the terminal fitting or the When the maximum distance between the second terminal fitting and the rear end side separator is D5, D5 <D1 may be satisfied.
According to this gas sensor, when D5 <D1, when D1 is contracted, the sensor element approaches the front end side separator, and the rear end side separator is also shaken, the rear end side metal fitting is joined with the rear end side separator. Therefore, damage and deformation of the rear end side terminal fitting can be suppressed. On the other hand, in the case of D5> D1, when D1 contracts, the sensor element approaches the front end side separator, and the rear end side separator also blurs, the rear end side terminal fittings blur in the opposite direction due to inertia in the rear end side separator. As a result, the rear end side terminal fitting may be damaged or deformed.

The gas sensor of this invention WHEREIN: The ventilation | gas_flowing filter which has waterproofness may be arrange | positioned on the outer side of the said outer cylinder facing the said rear end side separator.
As described above, the present invention absorbs the radial blur of the front end side separator even if the rear end side separator is not held by the outer cylinder. For this reason, according to this gas sensor, a member that inhibits the flow of air (for example, a holding metal fitting that holds the rear end side separator on the outer cylinder, or an outer cylinder that is swaged and compressed between the ventilation filter and the outer cylinder). There is no need to interpose a diameter caulking portion, and the introduction of the atmosphere into the gas sensor can be performed stably.

  According to this invention, when a gas sensor has a front end side separator and a rear end side separator, breakage of the sensor element can be suppressed, and the reliability of electrical connection between the sensor element and the terminal fitting can be improved.

It is sectional drawing which follows the axial direction of the gas sensor which concerns on embodiment of this invention. It is a perspective view of a sensor element. It is a perspective view which shows the state which hold | maintained the front end side metal fitting to the front end side separator. It is sectional drawing which shows the state which hold | maintained the front end side metal fitting to the front end side separator. It is a perspective view which shows the state which hold | maintained the rear-end side terminal metal fitting in the rear-end side separator. It is a perspective view which shows the state which connected the rear end side terminal metal fitting to the front end side metal fitting. It is sectional drawing of the front end side separator and rear end side separator which follow the AA line and BB line of FIG. It is sectional drawing of the rear end side separator in the 2nd measurement cross section when the axial center of a front end side separator and a rear end side separator has shifted | deviated largely. It is a fragmentary sectional view which shows the modification of a terminal metal fitting. It is sectional drawing which shows the conventional division type separator.

Hereinafter, embodiments of the present invention will be described.
1 is an overall cross-sectional view of the gas sensor (NOx sensor) 1 according to an embodiment of the present invention along the direction of the axis O, FIG. 2 is a perspective view of the sensor element 10, and FIG. FIG. 4 is a cross-sectional view showing a state where the front end side metal fittings 20 and 30 are held by the front end side separator 90, and FIG. 5 is a rear end side metal fitting 40 attached to the rear end side separator 95. FIG. 6 is a perspective view showing a state in which the rear end side terminal fitting 40 is connected to the front end side terminal fitting 20.
The gas sensor 1 is a NOx sensor that detects the oxygen concentration in the exhaust gas of automobiles and various internal combustion engines.

  In FIG. 1, the gas sensor 1 includes a cylindrical metal shell 138 having a screw portion 139 for fixing to an exhaust pipe formed on the outer surface, and an axis O direction (longitudinal direction of the gas sensor 1: vertical direction in the figure). A sensor element 10 having an extending plate shape, a cylindrical ceramic sleeve 106 arranged so as to surround the periphery of the sensor element 10 in the radial direction, and an internal space on the front end side of the sensor element 10 at the rear end portion of the sensor element 10. The front end side separator 90 made of ceramic and disposed in a state of surrounding the periphery, and the six front end sides inserted and held through the insertion holes 90h (90h1, 90h2) penetrating the front end side separator 90 in the direction of the axis O Terminal fittings 20 and 30 (FIG. 1 shows only the two front end side terminal fittings 20), a ceramic cylindrical rear end side separator 95, and six pieces held by the rear end side separator 95 (In Figure 1, shows only two) rear terminal fitting 40 is provided with a, a.

Further, the rear end side separator 95 is coaxially disposed on the rear end side of the front end side separator 90 and is connected in direct contact with the front end side separator 90.
Here, “coaxial” means that the axial centers of the front end side separator 90 and the rear end side separator 95 coincide with each other within a range of manufacturing tolerances. Specifically, even if a slight deviation occurs in the shaft center due to an error during assembly, and Dmax, which is a dimension difference larger than D2, occurs on the opposite side of D2 across the rear end side separator 95, It is sufficient if Dmax <D1.
The front end side metal fittings 20 and 30 correspond to “terminal metal fittings” in the claims, and the rear end side metal fitting 40 corresponds to “second terminal metal fittings” in the claims.

As shown in FIG. 4, the insertion holes 90h1 and 90h2 of the front end side separator 90 communicate with the internal space on the front end side of the front end side separator 90, and the front ends held by the insertion holes 90h1 and 90h2. The side terminal fittings 20 and 30 face the outer surface on the rear end side of the sensor element 10 and are electrically connected to an electrode pad (electrode part) 11a formed on the outer surface.
In addition, as shown in FIG. 2, three electrode pads 11 a are arranged in the width direction on both surfaces on the rear end side of the sensor element 10. Specifically, one electrode pad 11a is arranged at the center in the width direction on the rear end side of the sensor element 10, and two electrode pads 11a are arranged apart from each other in the width direction on the front end side.
Each electrode pad 11a can be formed as a sintered body mainly composed of Pt, for example.
On the other hand, the gas detector 11 at the tip of the sensor element 10 is covered with a porous protective layer 14 such as alumina.

  The metal shell 138 is made of stainless steel, has a through-hole 154 that penetrates in the axial direction, and has a substantially cylindrical shape that has a shelf 152 that protrudes radially inward of the through-hole 154. The sensor element 10 is disposed in the through hole 154 so that the tip of the sensor element 10 protrudes from the tip of the sensor element 10. Further, the shelf portion 152 is formed as an inwardly tapered surface having an inclination with respect to a plane perpendicular to the axial direction.

In addition, inside the through hole 154 of the metal shell 138, a substantially annular shaped ceramic holder 151 made of alumina surrounding the sensor element 10 in the radial direction, a powder filling layer 153 (hereinafter also referred to as a talc ring 153), And the above-mentioned ceramic sleeve 106 is laminated | stacked from the front end side to the rear end side in this order.
Further, a caulking packing 157 is disposed between the ceramic sleeve 106 and the rear end portion 140 of the metal shell 138. Note that the rear end portion 140 of the metal shell 138 is crimped so as to press the ceramic sleeve 106 toward the distal end side via the crimping packing 157.

  On the other hand, as shown in FIG. 1, a metal (for example, stainless steel) 2 having a plurality of holes and covering the protruding portion of the sensor element 10 on the outer periphery of the front end side (lower side in FIG. 1) of the metal shell 138. An external protector 142 and an internal protector 143, which are heavy protectors, are attached by welding or the like.

An outer cylinder 144 is fixed to the outer periphery on the rear end side of the metal shell 138. Further, a lead wire 146 is connected to the rear end side of the rear end side terminal fitting 40, and the lead wire 146 is drawn out to the rear end side of the rear end side separator 95.
Then, six lead wires 146 (only two are shown in FIG. 1) drawn from the rear end side separator 95 are inserted into the opening on the rear end side (upper side in FIG. 1) of the outer cylinder 144. A grommet 170, which is a rubber elastic member, in which a lead wire insertion hole 170h is formed is disposed.

In addition, on the rear end side (upper side in FIG. 1) of the sensor element 10 that protrudes from the rear end portion 140 of the metal shell 138, a front end side separator 90 is disposed, and a flange portion 90p that protrudes radially outward from the outer surface. Is provided. The front end side separator 90 is held inside the outer cylinder 144 by the flange portion 90p coming into contact with the outer cylinder 144 via the holding member 169. The holding member 169 is crimped together with the outer cylinder 144 at the first crimping portion 144 s 1 of the outer cylinder 144, and is fixed to the outer cylinder 144.
Here, the inner surface of the holding member 169 has a plurality of elastic pieces that bend in the radial direction, and the front end side separator 90 is elastically held inside the outer cylinder 144 by being held by the elastic pieces. .
Further, a rear end side separator 95 is disposed between the grommet 170 and the front end side separator 90, and the rear end side separator 95 presses the front end side separator 90 toward the front end side by the elastic force of the grommet 170. As a result, the flange 90p is pressed against the holding member 169 side, and the front end side separator 90 and the rear end side separator 95 are connected to each other inside the outer cylinder 144 (that is, without being separated in the direction of the axis O). ) Is retained.

Further, a protective outer cylinder 145 is placed on the outer side of the outer cylinder 144 from the rear end of the front end separator 90 to the front end of the grommet 170 in the direction of the axis O, and water-repellent ventilation is provided between the outer cylinder 144 and the protective outer cylinder 145. A filter 180 is arranged.
More specifically, on the side surface of the rear end portion of the outer cylinder 144, four first vent holes 144h (only two are shown in FIG. 1) are opened at equal intervals in the circumferential direction. Outside air can be introduced. An annular ventilation filter 180 is placed on the outer side of the outer cylinder 144 in the radial direction so as to close the first ventilation hole 144h, and the protection outer cylinder 145 surrounds the ventilation filter 180 from the outer side in the radial direction. Six second vent holes 145h (only two are shown in FIG. 2) are opened at equal intervals in the circumferential direction on the side surface of the protective outer cylinder 145, and a part of the outer surface of the vent filter 180 extends from the second vent hole 145h. When exposed, the second ventilation hole 145h communicates with the ventilation filter 180, and the outside air is introduced into the outer cylinder 144 via the ventilation filter 180.

  The ventilation filter 180 has water repellency (waterproofness), and is made of a porous structure such as a fluororesin such as Teflon (registered trademark), and has water repellency (waterproofness). The reference gas (atmosphere) is introduced into the sensor element 10 without passing through.

The outer cylinder 144 and the protective outer cylinder 145 are crimped via the ventilation filter 180 at two positions ahead and behind the first ventilation hole 144h and the second ventilation hole 145h, respectively, and the front-end side crimping portion 144s3 and the rear end Side caulking portions 144s4 are provided.
Further, the distal end of the protective outer cylinder 145 is crimped together with the outer cylinder 144 by the second crimping section 144s2 at the distal end from the distal end side crimping section 144s3, and is fixed to the outer cylinder 144.
The rear end side separator 95 is not in contact with the outer cylinder 144, and the outside air introduced through the ventilation filter 180 flows into the sensor element 10 side from the gap G between the rear end side separator 95 and the outer cylinder 144. To do.

FIG. 3 is a perspective view showing a state in which the distal end side metal fittings 20 and 30 are held by the distal end side separator 90. The lower side of FIG. In this embodiment, a total of six tip end side metal fittings 20 and 30 of two types are used.
As shown in FIG. 4, the four tip side terminal fittings 30 are all symmetrical with each other in the tip side separators 90, and the two tip side terminal fittings 20 are adjacent to each other. In both cases, the tip terminal fittings 20 facing each other in the tip separator 90 have a line-symmetric shape.

The front end side terminal fitting 20 extends in the direction of the axis O as a whole, the connection portion 23 connected to the rear end side terminal fitting 40, the substantially plate-shaped main body portion 21 connected to the front end side of the connection portion 23, and the main body portion 21. And an elastic portion 22 that is folded back toward the sensor element 10 on the distal end side.
The connecting portion 23 has a cylindrical shape with a C-shaped cross section, and a distal end portion 43 (see FIG. 6) of the cylindrical rear end side terminal fitting 40 having a C-shaped distal end is inserted into and connected to the cylinder. . In this case, the front end side terminal fitting 20 is indirectly connected to the lead wire 146 via the rear end side terminal fitting 40.
The elastic part 22 is folded back toward the sensor element 10 from the front end of the main body part 21 and elastically connected to one electrode pad 11a on the rear end side in FIG. The elastic part 22 is elastically bent in the radial direction with respect to the main body part 21.
Further, the main body 21 is formed with holding portions of various shapes that are locked to the inner wall or the like of the front end side separator 90.

Further, the front end side terminal fitting 30 extends in the direction of the axis O as a whole, a connection portion 33 connected to the rear end side terminal fitting 40, a substantially plate-like main body portion 31 connected to the front end side of the connection portion 33, and a main body portion. And an elastic portion 32 that is folded back toward the sensor element 10 on the tip end side of 31.
The connection portion 33 has a cylindrical shape similar to that of the connection portion 23, and, similarly to the connection portion 23, the tip end portion 43 of the rear end side terminal fitting 40 is inserted and connected in its own cylinder.
The elastic part 32 is folded back toward the sensor element 10 from the front end of the main body part 31 and elastically connected to the two electrode pads 11a on the front end side in FIG. The elastic part 32 is elastically bent in the radial direction with respect to the main body part 31.
The main body 31 has an L-shaped cross section, and is formed with holding portions of various shapes that are locked to the inner wall or the like of the front end side separator 90.
The distal-end terminal fittings 20 and 30 can be manufactured by punching out, for example, one metal plate (Inconel (registered trademark), etc.) and then bending it into a predetermined shape. However, the present invention is not limited to this.

As shown in FIG. 4, the front end side separator 90 has insertion holes 90h1 and 90h2. The insertion holes 90h2 are arranged at the four corners of the front end side separator 90, and the insertion holes 90h1 are located between the two insertion holes 90h2 along the width direction of the sensor element 10.
The distal end side terminal fittings 20 and 30 are inserted into the insertion holes 90h1 and 90h2, respectively, and are held in the distal end side separator 90.
And the connection parts 23 and 33 protrude in the rear end side of the front end side separator 90 in the state which the front end side metal fittings 20 and 30 were hold | maintained in the front end side separator 90 (FIG.3 (b)).

On the other hand, as shown in FIG. 6, the rear end side terminal fitting 40 extends in the direction of the axis O as a whole, and is held by the lead wire connecting portion 47 connected to the lead wire 146 and the rear end side separator 95 from the rear end side. A cylindrical central portion 45 having a C-shaped cross section and a cylindrical tip portion 43 having a C-shaped cross section are integrally provided in this order. Further, the distal end portion 43 and the central portion 45 are integrally connected via a distal end side neck portion 49, and the central portion 45 and the lead wire connecting portion 47 are integrally connected via a rear end side neck portion 41. Has been.
The rear end side terminal fitting 40 can be manufactured, for example, by punching out a single metal plate (SUS304 or the like) and then bending it into a predetermined shape, but is not limited thereto.

The lead wire connecting portion 47 has a cylindrical shape (barrel shape by crimping), sandwiches the exposed core wire toward the tip of the lead wire 146, and crimps (clamps) the core wire from outside.
The tip portion 43 has a cylindrical shape and is pointed toward the tip. And the front-end | tip part 43 is inserted in the cylinder of the connection parts 23 and 33, and the rear-end side terminal metal fitting 40 is electrically connected with the front-end | tip side terminal metal fittings 20 and 30. As shown in FIG.
The central portion 45 is larger in diameter than the lead wire connecting portion 47 and the tip portion 43.

As shown in FIG. 5, the rear end side separator 95 has six insertion holes 95h arranged in the circumferential direction. Here, the insertion hole 95h has a large diameter on the tip F side, and is reduced in a step shape near the center in the direction of the axis O, and this step portion forms a tip-facing surface (not shown).
Further, on the outer peripheral side of the surface facing the front end of the rear end side separator 95, two convex portions 95p protruding to the front end side are formed.

  Then, the lead wire 146 is passed through the distal end side of the insertion hole 95 h in advance, and the lead wire 146 is crimped and connected to the lead wire connecting portion 47 of the rear end side terminal fitting 40 on the distal end side of the rear end side separator 95. Next, when a part of the lead wire 146 side of the rear end side terminal fitting 40 is inserted into the insertion hole 95h from the front end F side and the lead wire 146 is pulled out to the rear end side, the central portion 45 of the rear end side terminal fitting 40 is obtained. The rear end facing surface is positioned in contact with the front end facing surface of the rear end side separator 95, and the rear end side terminal fitting 40 is held in the rear end side separator 95.

Here, as shown in FIG. 5, the front end portion 43 of the rear end side terminal fitting 40 protrudes from the front end facing surface of the rear end side separator 95.
Then, the front end side separator 90 shown in FIG. 3 and the rear end side separator 95 shown in FIG. 5 are arranged in contact with the front end side and the rear end side through the convex portions 95p, respectively. Thereby, as shown in FIG. 6, the front-end | tip part 43 of the rear end side terminal metal fitting 40 is inserted by the connection part 23 of the front end side terminal metal fitting 20, and is mutually connected.
The convex portion 95p supports the front end side terminal fitting 20 and the rear end side terminal fitting 40 that protrude from the rear end facing surface of the front end side separator 90 and the front end facing surface of the rear end side separator 95 in the axis O direction. These terminals are prevented from being crushed between the front end side separator 90 and the rear end side separator 95.
Although not shown in the drawings, the front end portion 43 of the rear end side terminal fitting 40 is similarly inserted into the connection portion 33 of the front end side terminal fitting 30 and connected to each other.
That is, in the present embodiment, the rear end side terminal fitting 40 is indirectly electrically connected to the electrode pad 11 a of the sensor element 10 via the front end side terminal fitting 30.

Next, a characteristic part of the present invention will be described with reference to FIG.
FIG. 7 is a cross-sectional view of the front end side separator 90 and the rear end side separator 95 in a cross section taken along the lines AA and BB in FIG. 1, and is a view in which the respective cross sections are arranged in the same direction.
As shown in FIG. 7B, in the first measurement cross section S1 that is a cross section along the line AA (perpendicular to the direction of the axis O), the outer peripheral surface of the sensor element 10 and the inner peripheral surface of the front end side separator 90 And D1 is the smallest dimensional difference (minimum distance). The direction in which D1 is measured (the direction connecting both ends of D1, the left-right direction in FIG. 7) is defined as a first measurement direction M1.
Here, as shown in FIG. 7A, in the second measurement section S2 that is a section along the line BB (perpendicular to the direction of the axis O), the direction is parallel to the first measurement direction M1. The minimum dimensional difference between the outer peripheral surface of the rear end side separator 95 and the inner peripheral surface of the outer cylinder 144 is defined as D2. This D2 is not necessarily the minimum distance between the outer peripheral surface of the rear end side separator 95 and the inner peripheral surface of the outer cylinder 144 as long as it is parallel to the first measurement direction M1. The “outer cylinder” refers to the innermost member when a plurality of outer cylinders (the outer cylinder 144 and the protective outer cylinder 145) are provided.
At this time, it is necessary to satisfy D2 <D1. This is due to the following reason.

As shown in FIG. 1, when the gas sensor 1 vibrates, the front end side separator 90 and the rear end side separator 95 are coaxially connected, so that the front end side separator 90 held by the outer cylinder 144 by the holding metal fitting 169. The rear end side separator 95 may blur in the radial direction T with the fixed part as a fulcrum.
Therefore, if D2 <D1, before the sensor element 10 collides with the front end side separator 90 due to blurring in the radial direction T, the rear end side separator 95 comes into contact with the inner peripheral surface of the outer cylinder 144 and moves in the radial direction T. Absorb blur. As a result, the front end separator 90 connected to the rear end side separator 95 and, in turn, the sensor element 10 can be prevented from being damaged by applying radial stress, and the electrical connection with the terminal fittings 20 and 30 can be prevented. It is possible to maintain and improve the reliability of the electrical connection.

From such a viewpoint, as the first measurement cross section S1, the outer peripheral surface of the sensor element 10 among the cross sections in which the sensor element 10 first collides with the front end separator 90, that is, a plurality of cross sections orthogonal to the axis O direction. 1 is selected from the cross sections along the direction of the axis O in FIG. However, in this example, since the inner hole of the front end side separator 90 is straight in the direction of the axis O, any cross section may be adopted as the first measurement cross section S1. Parts that do not pass are excluded from the target of the first measurement cross section S1.

Similarly, as the second measurement cross section S2, the rear end side separator 95 first collides with the inner peripheral surface of the outer cylinder 144, that is, among the plurality of cross sections orthogonal to the axis O direction, the rear end side separator 95 is The cross section closest to the inner peripheral surface of the outer cylinder 144 is selected from the cross sections along the direction of the axis O in FIG.
In this example, the rear end side separator 95 is straight in the direction of the axis O, but since the rear end side crimping portion 144s4 of the outer cylinder 144 is located on the innermost radial direction, the cross section at the rear end side crimping portion 144s4 is This is adopted for the second measurement section S2.

The reason why D2 is set in the direction parallel to the first measurement direction M1 is that the front-end separator 90 and the rear-end separator 95 are connected, so that the sensor element 10 first collides with the front-end separator 90. By aligning the direction of D1 and the direction of D2, the rear end side separator 95 becomes the inner peripheral surface of the outer cylinder 144 when the sensor element 10 moves close to the inner peripheral surface of the front end side separator 90 in the measurement direction M1. This is because blurring can be absorbed by contact with the tip first.
On the other hand, if D2 is not aligned with measurement direction M1 (for example, a direction perpendicular to M1), D2 is irrelevant if D1 is close to measurement direction M1, and effectively absorbs blurring in measurement direction M1. Can not.

The reason why the front end side separator 90 and the rear end side separator 95 need to be arranged coaxially is as follows.
That is, as shown in FIG. 8, when the axial centers of the front end side separator 90 and the rear end side separator 95 are greatly displaced, the axial centers of the rear end side separator 95 and the outer cylinder 144 are also displaced, and temporarily satisfy D2 <D1. However, on the opposite side of D2 across the rear end side separator 95, a dimensional difference Dmax is generated in which the distance between the separator 95 and the outer cylinder 144 is wide.
Then, when the rear end side separator 95 approaches the outer cylinder 144 in the direction of narrowing D2, blur can be absorbed as described above, but when it approaches the outer cylinder 144 in the direction of narrowing Dmax, Dmax> D1. Therefore, the blur cannot be effectively absorbed, and the sensor element 10 cannot be prevented from colliding with the front end side separator 90 first.

As shown in FIG. 7, in the first measurement cross section S1, the dimensional difference between the outer peripheral surface of the sensor element 10 and the inner peripheral surface of the front end side separator 90 is D3, and in the second measurement cross section S2, D3 is When the minimum dimensional difference between the outer peripheral surface of the rear end side separator 95 and the inner peripheral surface of the outer cylinder 144 is D4 along a direction parallel to the second measurement direction to be measured, any second measurement is performed. Also in the direction, D4 <D3 may be satisfied.
Here, for example, D41 is defined along the direction parallel to the second measurement direction M31 as D4 with respect to D31 measured along the second measurement direction M31 which is the vertical direction of FIG. 7 as D3. . Similarly, D42 is defined along the direction parallel to the second measurement direction M32 as D4 with respect to D32 measured along the second measurement direction M32 which is the oblique direction of FIG. 7 as D3.

  At this time, D41 <D31 and D42 <D32. If this is satisfied in all the second measurement directions in the first measurement cross section S1, the sensor element 10 approaches the leading end separator 90 in any second measurement direction (that is, in all directions of 360 degrees in the radial direction). However, the rear end side separator 95 collides first with the inner peripheral surface of the outer cylinder 144 and absorbs the blur in the second measurement direction. Accordingly, the sensor element 10 can be further prevented from being damaged, and the reliability of electrical connection with the terminal fittings 20 and 30 can be further improved.

In FIG. 7, each insertion hole 95 h of the rear end side separator 95 surrounds the rear end side terminal fitting 40. Here, in the second measurement cross section S2, when the maximum distance between the rear end side metal fitting 40 and the rear end side separator 95 (the insertion hole 95h) is D5, it is preferable to satisfy D5 <D1.
By setting D5 <D1, when D1 contracts, the sensor element 10 approaches the front end side separator 90, and the rear end side separator 95 also blurs, the rear end side terminal fitting 40 is moved together with the rear end side separator 95. Since it moves, damage and deformation of the rear end side terminal fitting 40 can be suppressed. On the other hand, in the case of D5> D1, when D1 contracts, the sensor element 10 approaches the front end side separator 90, and the rear end side separator 95 also blurs, the rear end side metal fitting 40 is inertial in the rear end side separator 95. May cause the rear end side metal fitting 40 to be damaged or deformed.

Further, the present invention is more effective when a waterproof ventilation filter 180 is disposed outside the outer cylinder 144 facing the rear end side separator 95.
As described above, the present invention absorbs the radial blur of the front end side separator 90 even if the rear end side separator 95 is not held by the outer cylinder 144. For this reason, between the ventilation filter 180 and the outer cylinder 144, a member that obstructs the flow of air (for example, a holding metal fitting that holds the rear end side separator 95 on the outer cylinder 144 or a diameter reduction by caulking the outer cylinder 144) It is not necessary to interpose the crimped portion), and the atmosphere can be stably introduced into the gas sensor 1.

  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.

  The rear end side separator may be indirectly connected to the front end side separator. As an example, as shown in FIG. 9, the flange 50f1 is provided at two different locations in the direction of the axis O of one terminal fitting 50. , 50f2 is provided, and the space between the flanges 50f1 and 50f2 is a rigid cylinder. Then, the rear end facing surface of the front end side separator 90 is held by the flange 50f1, the rear end facing surface of the rear end side separator 98 is held by the flange 50f2, and the rear end side separator 98 and the front end side separator 90 are axially connected. There is a form in which a gap is provided in the direction for connection.

The shapes and the like of the rear end side separator and the front end side separator are not limited to the above embodiment. Further, as shown in FIG. 8, one terminal fitting 50 may be disposed on the rear end side separator and the front end side separator.
The terminal fitting surrounded by the rear end side separator does not necessarily have to be held by the rear end side separator, and may be loosely fitted (separated) into the insertion hole of the rear end side separator.
Examples of the gas sensor include an NOx sensor, an oxygen sensor, and a full range gas sensor.

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Sensor element 11a Electrode part (electrode pad)
20, 30 Terminal bracket (tip side terminal bracket)
40 Second terminal fitting (rear terminal fitting)
50 One terminal fitting 90 Front end side separator 95, 98 Rear end side separator 138 Main metal fitting 144 Outer cylinder 180 Ventilation filter S1 First measurement section S2 Second measurement section M1 First measurement direction M2, M3 Second Measuring direction O-axis

Claims (4)

A sensor element having a plate shape extending in the axial direction and having an electrode portion on the outer surface on the rear end side;
A metal shell that surrounds the sensor element and holds the sensor element;
A terminal fitting electrically connected to the electrode portion;
A cylindrical tip side separator that holds the terminal fitting and surrounds the rear end side of the sensor element;
A rear end side separator that is coaxially disposed on the rear end side of the front end side separator and is directly or indirectly connected to the front end side separator;
An outer cylinder fixed to a rear end side of the metal shell and surrounding the front end side separator and the rear end side separator;
A gas sensor comprising:
The front end side separator is elastically held by the outer cylinder, the rear end side separator is not held by the outer cylinder,
In the first measurement cross section orthogonal to the axial direction, the minimum dimensional difference between the outer peripheral surface of the sensor element and the inner peripheral surface of the front end side separator is D1,
In a second measurement cross section orthogonal to the axial direction, along the direction parallel to the first measurement direction in which the D1 is measured, the outer peripheral surface of the rear end side separator and the inner peripheral surface of the outer cylinder When the minimum dimensional difference is D2,
A gas sensor characterized by satisfying D2 <D1. In the first measurement cross section, D3 is a dimensional difference between the outer peripheral surface of the sensor element and the inner peripheral surface of the tip side separator,
In the second measurement cross section, a minimum dimensional difference between the outer peripheral surface of the rear end side separator and the inner peripheral surface of the outer cylinder is along a direction parallel to the second measurement direction in which the D3 is measured. When D4
2. The gas sensor according to claim 1, wherein D4 <D3 is satisfied in any of the second measurement directions. The rear end side separator surrounds the terminal fitting or the second terminal fitting connected to the terminal fitting in the axial direction,
In the second measurement cross section, when the maximum distance between the terminal fitting or the second terminal fitting and the rear end separator is D5,
The gas sensor according to claim 1, wherein D5 <D1 is satisfied.   The gas sensor according to any one of claims 1 to 3, wherein a waterproof ventilation filter is disposed outside the outer cylinder facing the rear-end separator.

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