Gas Sensor

Abstract

To provide a gas sensor that reliably keeps terminal fittings from coming out.SOLUTION: A gas sensor 200 comprises: a sensor element 10 having an electrode pad 11; terminal fittings 21; and a separator 166 that accommodates the terminal fittings in insertion holes 166h. The terminal fitting includes: a body portion 21a having a principal surface 21m; a first locking portion 21d that can retractably protrude to the inside and outside of the principal surface; and a second locking portion 21e that is arranged closer to a tip side than the first locking portion and protrudes in a principal surface direction in the same plane of the principal surface. The separator further includes: a shelf portion 166a that communicates with the insertion holes and has a first rear end facing surface 312; and a first tip end facing surface 314. In the first locking portion, the rear end side is connected to the body portion and the tip side of the first locking portion is not restrained and retractably protrudes to the inside and outside of the principal surface; the tip is opposite the first rear end facing surface; and in the principal surface direction, a maximum opening width W2 of retaining holes 166hs that each retain a single terminal fitting is less than a maximum width W1 of the terminal fittings at a location in which the second locking portion is arranged to satisfy a relation W2<W1.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a gas sensor having a sensor element for detecting the concentration of a target gas. [Background technology]

[0002] 2. Description of the Related Art Gas sensors for detecting the concentrations of oxygen and NOx in exhaust gases from automobiles and the like are known to have a sensor element using a solid electrolyte. This type of gas sensor has an electrode pad provided at the rear end of a plate-shaped sensor element, a separator (insulating member) arranged to surround the radially outer side of the rear end of the sensor element, and a terminal fitting held in an insertion hole of the separator (Patent Documents 1 and 2). The terminal fitting is electrically connected to the electrode pad of the sensor element, and the rear end of the terminal fitting is crimped to a lead wire so that a sensor output signal from the sensor element can be taken out via the lead wire. The lead wire is inserted into a rubber grommet arranged at the rear end of the gas sensor and taken out.

[0003] In the gas sensor of Patent Document 1, a locking portion 21f is provided at the tip of the terminal fitting to prevent it from coming off. When the lead wire drawn out of the gas sensor is pulled toward the rear end during use, the second rear-facing surface 304 of the locking portion abuts against the front-facing surface of the separator, preventing the terminal fitting from coming off toward the rear end. Furthermore, in the gas sensor of Patent Document 2, a cut-and-raised portion 121 is provided near the center of the axial direction of the terminal fitting to prevent it from coming out. This cut-and-raised portion 121 expands in the radial direction inside a shelf portion provided in the insertion hole of the separator and abuts against the shelf portion, preventing the terminal fitting from coming out toward the tip side. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-132407 A (Figs. 3 and 7) [Patent Document 2] Chinese Patent Publication No. CN105467075 (Fig. 12, Fig. 13) Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the gas sensors of Patent Documents 1 and 2, it is difficult to reliably prevent the terminal fitting from coming off both at the front end and the rear end. For example, in the gas sensor of Patent Document 2, the terminal fitting is likely to come off at the rear end. On the other hand, in the gas sensor of Patent Document 1, the terminal fitting is inserted from the rear end side of the separator. Therefore, the locking portion 21f is bent (flexed) in the radial direction to pass through the slit of the insertion hole of the separator, and when the locking portion 21f passes through the slit of the separator, the locking portion 21f elastically returns to its original shape, and the plate surface faces obliquely relative to the insertion hole of the separator. However, excessive bending of the locking portion 21f results in plastic deformation, which limits the amount of bending of the locking portion 21f and the amount of return, causing the locking portion 21f to come close to the notch.As a result, if the terminal fitting becomes loose, the locking portion 21f may slip into the notch and fall out, possibly coming off toward the rear end. If the terminal metal fitting comes off either towards the front end or the rear end of the separator, the contact points between the terminal metal fitting and the electrode pad become misaligned, reducing the reliability of the electrical connection.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a gas sensor that reliably prevents the terminal fittings from coming loose at the front and rear ends, thereby improving the reliability of the electrical connection between the terminal fittings and the electrode pads. [Means for solving the problem]

[0007] In order to solve the above problems, the gas sensor of the present invention includes a sensor element that extends in the axial direction, has a detection unit on the tip side, and has an electrode pad on the outer surface of the rear end side; a terminal fitting that extends in the axial direction and is electrically connected to the electrode pad; and a cylindrical separator that has an insertion hole extending along the axial direction, houses the terminal fitting inside the insertion hole, and surrounds the electrode pad of the sensor element. The terminal fitting includes a plate-shaped main body portion that extends in the axial direction and is supported inside the insertion hole and has a main surface, a first locking portion that can project and retract inside and outside the main surface while being connected to the main body portion, and a second locking portion that is disposed on the tip side of the first locking portion, is connected to the main body portion, and projects in the direction of the main surface of the main body portion flush with the main surface. The separator further includes a shelf portion that communicates with the insertion hole and has a first rear-end-facing surface, and a first tip-facing surface that communicates with the insertion hole and is on the tip side of the first rear-end-facing surface. The first locking portion is connected to the main body portion at the rear end side, the tip side is not restricted, projects and retracts inside and outside the main surface, the tip faces the first rear-end-facing surface, and in the direction of the main surface, the maximum opening width W2 of the holding hole that holds each terminal fitting in the insertion hole satisfies the relationship W2 < W1 with respect to the maximum width W1 of the terminal fitting at the location where the second locking portion is disposed.

[0008] According to this gas sensor, since the tip side of the first locking portion is not restricted, it is pushed by the wall surface of the insertion hole and shrinks inside the main surface, so the terminal fitting can be passed through from the tip side of the separator. Therefore, the second locking portion can be connected flush with the main surface of the main body portion, and for example, it is not necessary to bend the second locking portion in the radial direction as in the case of inserting the terminal fitting from the rear end side of the separator. As a result, the second locking portion is not bent too much and plastically deformed to reduce the maximum width W1, and the relationship W2 < W1 can be reliably satisfied. Then, even if the terminal fitting moves in the main surface direction inside the holding hole, the second locking portion is suppressed from falling off from the first tip-facing surface of the separator and entering the holding hole, and the rear end side of the terminal fitting can be reliably prevented from coming off. Furthermore, because the front end of the first locking portion is a free end that rotates around the rear end and protrudes in and out of the main surface, the amount of movement (rotation) at the front end can be increased, which in turn increases the amount of protrusion of the first locking portion from the main surface in the space around the shelf. This prevents the first locking portion from falling off the shelf and slipping out toward the front end even if the terminal fitting moves inside the separator.

[0009] The gas sensor of the present invention may have a plurality of the terminal fittings, and when viewed in a cross section perpendicular to the axial direction, the first locking portions of the two terminal fittings that face each other across the sensor element may protrude radially outward. With this gas sensor, compared to when each first locking portion protrudes radially inward, each first locking portion faces away from the sensor element in the radial direction, thereby preventing contact between the first locking portions 21d and the crimp terminal portion 21c of the terminal fitting 21.

[0010] The gas sensor of the present invention may include a plurality of the terminal fittings, and the second locking portion may be formed only at one end of the main body in the width direction facing radially outward of the separator. According to this gas sensor, the second locking portions of adjacent terminal fittings are prevented from facing each other and coming close to each other, and the second locking portions are prevented from coming into contact with each other and causing a short circuit. [Effects of the Invention]

[0011] According to the present invention, a gas sensor can be obtained in which the terminal metal fittings are reliably prevented from coming loose at the front and rear ends, and the reliability of the electrical connection between the terminal metal fittings and the electrode pads is improved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view taken along the longitudinal direction of a gas sensor according to an embodiment of the present invention. [Figure 2] FIG. [Figure 3] FIG. [Figure 4]FIG. 2 is a bottom view of the separator as viewed from the tip side. [Figure 5] FIG. 5 is a cross-sectional view of the separator in the axial direction taken along line AA in FIG. 4. [Figure 6] FIG. 2 is a bottom perspective view of the separator as viewed from the tip side. [Figure 7] 10A and 10B are diagrams showing widths of respective portions of a holding hole and a terminal fitting; [Figure 8] FIG. 10 is a perspective view showing a modified example of the terminal fitting. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described. FIG. 1 is an overall cross-sectional view along the longitudinal direction of a gas sensor (oxygen sensor) 200 according to an embodiment of the present invention, FIG. 2 is a perspective view of a sensor element 10, FIG. 3 is a perspective view of a terminal fitting 21, and FIG. 4 is a bottom view of a separator as seen from the tip side. This gas sensor 200 is an oxygen sensor that detects the oxygen concentration in the exhaust gas of an automobile or various internal combustion engines.

[0014] In FIG. 1, the gas sensor 200 includes a cylindrical metal shell 138 having a threaded portion 139 formed on its outer surface for fixing to an exhaust pipe, a plate-shaped sensor element 10 extending in the direction of axis O (the longitudinal direction of the gas sensor 200: the up-down direction in the figure), a cylindrical ceramic sleeve 106 arranged to surround the radial periphery of the sensor element 10, a cylindrical ceramic separator 166 arranged inside the tip side of an insertion hole 166h that penetrates in the axial direction so as to surround the periphery of the rear end of the sensor element 10, and four terminal fittings 21 (only two are shown in FIG. 1) arranged between the sensor element 10 and the separator 166. The gas detection portion 10a at the tip of the sensor element 10 is covered with a porous protective layer 20 made of alumina or the like (see FIG. 2).

[0015] The metal shell 138 is made of stainless steel, has a through hole 154 penetrating in the axial direction, and is configured in a generally cylindrical shape having a shelf portion 152 protruding radially inward from the through hole 154. The sensor element 10 is disposed in this through hole 154 so that the tip portion of the sensor element 10 protrudes beyond the tip of the sensor element 10. Furthermore, the shelf portion 152 is formed as an inward tapered surface that is inclined with respect to a plane perpendicular to the axial direction.

[0016] Inside the through hole 154 of the metal shell 138, an annular alumina ceramic holder 151, a powder-filled layer 156 (hereinafter also referred to as a talc ring), and the above-mentioned ceramic sleeve 106 are layered in this order from the front end to the rear end, surrounding the radial periphery of the sensor element 10. A crimping packing 157 is disposed between the ceramic sleeve 106 and the rear end portion 140 of the metallic shell 138. The rear end portion 140 of the metallic shell 138 is crimped so as to press the ceramic sleeve 106 toward the front end side via the crimping packing 157.

[0017] On the other hand, as shown in FIG. 1, a single-layer protector 143 made of metal (e.g., stainless steel) having a plurality of holes is attached by welding or the like to the outer periphery of the tip side (lower side in FIG. 1) of the metal shell 138, covering the protruding portion of the sensor element 10.

[0018] An outer cylinder 144 is fixed to the outer periphery on the rear end side of the metallic shell 138. A rubber grommet 170 is disposed in an opening on the rear end side (upper side in FIG. 1) of the outer cylinder 144. The rubber grommet 170 has lead wire insertion holes (not shown) through which four lead wires 146 (only two are shown in FIG. 1) electrically connected to the four terminal metal fittings 21 (only two are shown in FIG. 1) of the sensor element 10 are inserted. The grommet 170 is held inside the outer tube 144 by crimping it from the outside of the outer tube 144 .

[0019] A separator 166 is disposed on the rear end side (upper side in FIG. 1) of the sensor element 10 protruding from the rear end portion 140 of the metallic shell 138. The separator 166 is disposed around a total of four electrode pads 11 (only two are shown in FIG. 1) formed on the main surface of the rear end side of the sensor element 10. The separator 166 is formed in a cylindrical shape having an insertion hole 166h penetrating in the axial direction, and is provided with a flange portion 167 protruding radially outward from the outer surface. The separator 166 is held inside the outer cylinder 144 by the flange portion 167 abutting against the outer cylinder 144 via a holding member 169.

[0020] 2, the sensor element 10 has a plate shape extending in the direction of the axis O, and a tip portion 10s serves as a gas detection portion 10a that detects the oxygen concentration, and the gas detection portion 10a is covered with a porous protective layer 20. The sensor element 10 itself has a known configuration, and although not shown, it includes a gas detection portion having an oxygen ion-permeable solid electrolyte body and a pair of electrodes, and a heater portion that heats the gas detection portion and maintains it at a constant temperature. Two electrode pads 11 are arranged in the width W direction at the rear end side of one main surface of the sensor element 10, and a sensor output signal from the gas detection unit 10a is output from these electrode pads 11 via lead portions (not shown). Two more electrode pads 11 are also arranged in the width W direction at the rear end side of the other main surface provided opposite the main surface, and power is supplied to the heater unit via lead portions (not shown). Each electrode pad 11 has a rectangular shape that is long in the direction of the axis O, and can be formed as a sintered body mainly made of Pt, for example.

[0021] Fig. 3 shows a perspective view of the terminal fittings 21. In this embodiment, as will be described later, the gas sensor 200 has four terminal fittings 21, which are arranged at the vertices of a rectangle within the separator 166 as shown in Fig. 4, with adjacent terminal fittings 21 line-symmetrical to each other and terminal fittings 21 on diagonal lines having the same shape. That is, there are two types of terminal fittings: the terminal fitting 21 in Fig. 3 and a terminal fitting line-symmetrical to it to the right of Fig. 3 (corresponding to the terminal fitting 21 on the right side in Fig. 4), and the components of each terminal fitting are substantially the same, so only the terminal fitting 21 in Fig. 3 will be described.

[0022] As shown in Figure 3, the terminal fitting 21 integrally comprises a plate-like main body portion 21a that is approximately plate-shaped and extends in the direction of the axis O, a tip portion 21b that is folded back from the tip edge of the main body portion 21a toward the rear end, a crimp terminal portion 21c that connects to the rear end of the main body portion 21a, a first locking portion 21d, and a second locking portion 21e that is positioned closer to the tip than the first locking portion 21d. In this example, the main body 21a has a main surface 21m that is a folded surface with the tip 21b, and a pair of rib portions 21r1, 21r2 that are bent in an L-shape from both widthwise ends of the main surface 21m toward the tip 21b. Therefore, the cross section of the main body 21a in the radial direction D that intersects with the axis O direction is U-shaped. The tips of the rib portions 21r1, 21r2 elastically expand outward in the widthwise direction to form a pair of pressing portions 21f. However, the ribs 21r1 and 21r2 and the pressing portion 21f are not essential. Furthermore, the main surface 21m refers to the surface that is folded back to meet the tip portion 21b.

[0023] Here, first locking portion 21d is cut and raised from main surface 21m of main body portion 21a toward the side opposite tip portion 21b, and its rear end 21d2 side is connected to main body portion 21a. Then, tip 21d1 side of first locking portion 21d is an unconstrained free end, and can bend elastically so as to rotate around rear end 21d2 side. In this way, the first locking portion 21d can bend in the radial direction D and protrude further outward in the radial direction D (opposite the tip portion 21b) than the main surface 21m. More specifically, the first locking portion 21d protrudes outward in the radial direction D in an unloaded state, and when inserted through the insertion hole 166h of the separator 166, it is pressed by the inner wall of the separator 166 and elastically bends inward in the radial direction D, contracting so as to become approximately flush with the main surface 21m. In addition, a second surface 302 facing the tip end is formed on the tip end 21d1 of the first locking portion 21d.

[0024] The second engaging portion 21e is connected to the main body portion 21a and extends from one widthwise end (left side in Figure 3) of the main body portion 21a, protruding flush with the main surface 21m in the main surface direction D (the direction along the main surface 21m, in this example, the same direction as the radial direction). Further, a second rear-facing surface 304 is formed on the second locking portion 21e.

[0025] The crimp terminal portion 21c has a known cylindrical shape, and the lead wire 146, with the coating facing the exposed conductor, is inserted into this cylinder and crimped, whereby the lead wire 146 is electrically connected. The tip edge of the tip portion 21b is folded back toward the rear end to form a free end. The tip portion 21b is pressed toward the electrode pad 11 by the springiness (elasticity) of the terminal fitting 21 itself, thereby ensuring a reliable electrical connection between the electrode pad 11 and the terminal fitting 21. The terminal fitting 21 can be manufactured by punching out a metal plate (such as Inconel (registered trademark)) and then bending the tip portion 21b, for example, but is not limited to this.

[0026] FIG. 5 shows a cross-sectional view of the separator 166 in the direction of the axis O along the line AA in FIG. 4, and FIG. 6 shows a bottom perspective view of the separator 166 as seen from the tip side. 4, a rectangular insertion hole 166h penetrates the center of the separator 166 in the axial direction. Four rectangular retaining holes 166hs, each retaining one terminal fitting 21, are integrally connected to the insertion hole 166h on the radially outer side of each vertex of the rectangle of the insertion hole 166h, and the insertion hole 166h is formed into a generally H-shape as viewed from the direction of the axis O. The four terminal fittings 21 are inserted into the retaining holes 166hs located at the vertices of the rectangle of the insertion hole 166h.

[0027] As shown in FIG. 5, the separator 166 is formed with a shelf portion 166a that communicates with the insertion hole 166h and has a first rear-facing surface 312. As shown in FIG. 6, the separator 166 is formed with a first front-facing surface 314 that communicates with the insertion hole 166h.

[0028] Next, a description will be given of how the terminal fitting 21 is arranged in the separator 166. In this example, the terminal fitting 21, to which the lead wire 146 has been connected in advance, is passed through the insertion hole 166h from the tip side of the separator 166. At this time, the tip 21d1 side of the first locking portion 21d is pressed by the wall surface of the above-mentioned retaining hole 166hs, so that it protrudes and retracts into and out of the main surface 21m and elastically bends inward in the radial direction D, contracting so as to become approximately flush with the main surface 21m, thereby preventing the tip 21d1 side of the first locking portion 21d from interfering with the insertion. In this example, the tip 21d1 side of the first locking portion 21d elastically bends inward in the radial direction D and retracts into the inside of the main surface 21m.

[0029] Then, as shown in Figure 5, when the terminal fitting 21 is passed through the insertion hole 166h to a predetermined insertion depth, the tip 21d1 of the first locking portion 21d reaches the space around the shelf portion 166a, and the first locking portion 21d enters an unloaded state and protrudes outward in the radial direction D (outward from the main surface 21m). Therefore, when the terminal fitting 21 is pulled toward the tip side and attempts to come out, the second tip-facing surface 302 of the first locking portion 21d abuts against the first rear-facing surface 312 of the separator 166, preventing it from coming out toward the tip side.

[0030] Further, the first locking portion 21d is elastically bent such that the rear end 21d2 side thereof is connected to the main body portion 21a and the front end 21d1 side is a free end. Therefore, it can be applied to the mode of inserting the terminal fitting 21 from the front end side of the separator 166. As a result, the second locking portion 21e described later can surely suppress the detachment of the terminal fitting 21 to the rear end side. Furthermore, since the front end 21d1 side of the first locking portion 21d is a free end and protrudes and retracts inside and outside the main surface 21m so as to rotate around the rear end 21d2 side, the amount of movement (rotation amount) of the front end 21d1 side can be increased, and consequently, the amount of protrusion outside from the main surface 21m of the first locking portion 21d in the space around the shelf portion 166a can be increased. Thereby, even if the terminal fitting 21 shakes inside the separator 166, it is possible to suppress the first locking portion 21d from falling off from the shelf portion 166a and coming out to the front end side.

[0031] Also, as shown in FIG. 6, when the terminal fitting 21 is passed through the insertion hole 166h to a predetermined insertion depth, the second locking portion 21e cannot pass through the above-described holding hole 166hs and is caught by the first front-facing surface 314 of the separator 166. Therefore, when the terminal fitting 21 is pulled toward the rear end side and tries to come out, the second rear-facing surface 304 of the second locking portion 21e abuts against the first front-facing surface 314 of the separator 166 to suppress the detachment to the rear end side. In this example, since the pair of pressing portions 21f elastically expand outward in the width direction inside the above-described holding hole 166hs and abut against the wall surface of the hole, it is possible to suppress the terminal fitting 21 from shaking inside the holding hole 166hs.

[0032] Here, as shown in FIG. 7, in the main surface direction D, the maximum opening width W2 of the holding hole 166hs satisfies the relationship of W2 < W1 with respect to the maximum width W1 of the terminal fitting 21 at the location where the second locking portion 21d is disposed. By doing so, even if the terminal fitting 21 shakes in the main surface direction D inside the holding hole 166hs, it is possible to suppress the second locking portion 21d from falling off from the first front-facing surface 314 of the separator 166 and entering the holding hole 166hs, and surely suppress the detachment of the terminal fitting 21 to the rear end side. Moreover, since it can be applied to the mode of inserting the terminal fitting 21 from the tip side of the separator 166 as described above, the second locking portion 21e can be connected flush with the main surface 21m of the main body portion 21a. Therefore, there is no need to bend the second locking portion 21e in the radial direction as in the case of inserting the terminal fitting 21 from the rear end side of the separator 166. As a result, the second locking portion 21e is not bent too much and plastically deformed to reduce the maximum width W1, and the relationship of W2 < W1 can be surely satisfied, and the disengagement to the rear end side can be surely suppressed.

[0033] As described above, the first locking portion 21d and the second locking portion 21e surely suppress the disengagement of the terminal fitting 21 to the front end side and the rear end side, so that the reliability of the electrical connection between the terminal fitting 21 and the electrode pad 11 can be improved.

[0034] As shown in FIG. 6, in this example, a plurality (four) of terminal fittings 21 are provided, and each second locking portion 21e is formed only at one end in the width direction facing the outside in the radial direction of the separator 166 in the main body portion 21. By doing so, it is possible to avoid the situation where the second locking portions 21e face each other and are close to each other between the adjacent terminal fittings 21, and it is possible to suppress the second locking portions 21e from contacting and short-circuiting.

[0035] The present invention is not limited to the above-described embodiment, and it is needless to say that the present invention extends to various modifications and equivalents included in the spirit and scope of the present invention. For example, the shape and number of the terminal fittings are not limited to the above-described embodiment. The shape of the separator, the shape and number of the insertion holes and shelf portions of the separator are also not limited to the above-described embodiment.

[0036] For example, as shown in FIG. 8, the first locking portion 221d may be raised not from the main surface 221m of the main body portion 221a but from the rib portion 221r2 of the main body portion 221a. In this case, the rear end 221d2 side of the first locking portion 221d is connected to the rib portion 221r2 of the main body portion 21a, and the front end 221d1 side becomes a free end and can elastically bend. In this way, the first locking portion 221d is bent in the radial direction D and can protrude further outward in the radial direction D (in a direction parallel to the main surface 221m) than the rib portion 221r2 of the main body portion 21a.

[0037] In addition, in this example, there are multiple (four) terminal fittings 21, and when viewed in a cross section (radial direction) perpendicular to the axial direction, as shown in Figure 5, the first locking portion 21d of each of the two terminal fittings 21 facing each other across the sensor element 10 protrudes radially outward. If the first locking portions 21d of the two terminal fittings 21 facing each other across the sensor element 10 are made to protrude radially inward, it is necessary to form a step portion for locking the first locking portions 21d by providing a gap on the radial center side of the separator 166. However, in this case, there is a risk that the first locking portions 21d may come into contact with each other or the crimp terminal portions 21c of the terminal fittings 21 may come into contact with each other. Therefore, if the first locking portions 21d of the terminal fittings 21 are made to protrude radially outward, the above-mentioned interference can be suppressed.

[0038] Further, types of gas sensors include oxygen sensors, full-range air-fuel ratio sensors, NOx sensors, and the like. [Explanation of symbols]

[0039] 10 Sensor element 10a Detector 11 Electrode pads 21, 221 Terminal fittings 21a, 221a Main body 21m, 221m main surface 21d, 221d 1st locking part 21d1 Tip of first locking portion 21d2 Rear end of first locking portion 21e 2nd locking part 166 Separator 166a Shelf 166h Insertion hole 166hs holding hole 200 Gas Sensor 312 First rear-facing surface 314 First tip-facing surface 302 Second tip facing surface 304 Second rear-facing surface O axis D Radial direction (main surface direction)

Claims

1. a sensor element extending in the axial direction, having a detection portion at its tip end and an electrode pad on its outer surface at its rear end; a terminal fitting extending in the axial direction and electrically connected to the electrode pad; a cylindrical separator having an insertion hole extending along the axial direction, the insertion hole accommodating the terminal metal fitting inside the insertion hole and surrounding the electrode pad of the sensor element; A gas sensor comprising: The terminal fitting includes a plate-shaped main body portion extending in the axial direction, supported inside the insertion hole, and having a main surface; a first locking portion connected to the main body portion and capable of protruding and retracting inward and outward from the main surface; and a second locking portion disposed distally of the first locking portion, connected to the main body portion, and protruding in the direction of the main surface of the main body portion while being flush with the main surface, the separator further includes a shelf portion communicating with the insertion hole and having a first rear-facing surface, and a first front-facing surface communicating with the insertion hole and located closer to the front end than the first rear-facing surface, The first engaging portion has a rear end connected to the main body portion and a front end that is not constrained and protrudes and retracts inward and outward from the main surface, and a front end that faces the first rear-end-facing surface, a maximum opening width W2 of the retaining holes, which hold the terminal fittings one by one among the insertion holes, in the main surface direction, satisfying the relationship W2 < W1 with respect to a maximum width W1 of the terminal fittings at a location where the second engaging portion is disposed.

2. The terminal fittings are provided in a plurality, 2. The gas sensor according to claim 1, wherein, when viewed in a cross section perpendicular to the axial direction, the first engaging portions of the two terminal fittings facing each other across the sensor element protrude radially outward.

3. The terminal fittings are provided in a plurality, 3. The gas sensor according to claim 1, wherein the second engaging portion is formed only at one end of the main body portion in the width direction facing radially outward of the separator.

Images