Gas sensor

Abstract

To provide a gas sensor which inhibits damage of a terminal metal fitting due to vibration and the like when the gas sensor is used.SOLUTION: A gas sensor 1 comprises: a sensor element 10 which is tabular and extends in an axis O direction, and includes an electrode pad 11a on an external surface of a rear end side; and a terminal metal fitting 20 extending in the axial direction and electrically connected to the electrode pad. The terminal metal fitting integrally includes: a main body part 21; a folding part 24 folded from the main body part toward the electrode pad; and an element contact part 22 connected to the folding part and having a free end side thereof coming into contact with the electrode pad. A first portion 22a of the element contact part connecting to the folding part has a substantially constant first width W1. When total length of the element contact part in the axial direction is denoted by L, a side of the element contact part which is close to the folding part by more than L / 2 is provided with at least one width change part 22b having a substantially constant second width W2 different from the first width W1.SELECTED DRAWING: Figure 2

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 gas from automobiles and the like are known that have a plate-shaped sensor element using a solid electrolyte. A widely used gas sensor of this type has multiple electrode pads on the outer surface of the rear end of a plate-shaped sensor element, and terminal fittings are electrically connected to each of the electrode pads to extract a sensor output signal from the sensor element to the outside or to supply power to a heater stacked on the sensor element (Patent Document 1). This terminal fitting has a main body, a folded-back portion that is folded back from the main body toward the electrode pad, and an element contact portion, a part of which abuts against the electrode pad. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-051770 A (Figure 2) Summary of the Invention [Problem to be solved by the invention]

[0004] However, due to vibrations or the like that occur during use of the gas sensor, the folded-back portion of the terminal metal fitting is frequently bent, causing stress concentration, which may result in fatigue failure.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide a gas sensor which suppresses damage to terminal fittings due to vibrations or the like during use of the gas sensor. [Means for solving the problem]

[0006] In order to solve the above problems, the gas sensor of the present invention includes a sensor element having a plate shape extending in the axial direction and having an electrode pad on the outer surface on the rear end side, and a terminal fitting extending in the axial direction and electrically connected to the electrode pad. The terminal fitting integrally has a main body portion, a folded-back portion folded back from the main body portion toward the electrode pad, and an element contact portion connected to the folded-back portion and having its free end side in contact with the electrode pad. A first portion of the element contact portion that is connected to the folded-back portion has a substantially constant first width W1. When the total length of the element contact portion in the axial direction is L, at least one width change portion having a substantially constant second width W2 different from the first width W1 is provided on a side of the element contact portion closer to the folded-back portion than L / 2.

[0007] In the width change portion, the width rapidly changes from the first portion to form a stepped portion, and stress also concentrates on this stepped portion (notch). Then, the stress on the folded-back portion side is reduced rather than on the width change portion by the amount of stress concentration, and the stress on the folded-back portion is also reduced. Thereby, stress concentration on the folded-back portion of the terminal fitting due to vibration or the like during use of the gas sensor can be alleviated, and breakage of the terminal fitting can be suppressed. However, since the region where the stress decreases occurs only in a relatively narrow range on the folded-back portion side of the width change portion, the position where the width change portion is provided is determined on the side of the element contact portion 22 closer to the folded-back portion than L / 2. Note that "substantially constant" means that when the maximum width of the first portion is the first width W1, the width of all regions of the first portion may be in the range of 0.95 < W1 < 1.05 (a change within 5% from W1). The same applies to "substantially constant" in the following W2 to W4.

[0008] In the gas sensor of the present invention, a third portion including a contact point in contact with the electrode pad of the element contact portion may have a substantially constant third width W3 that is narrower than the electrode pad, and a fourth portion between the contact point and the position of L / 2 of the element contact portion may have a substantially constant fourth width W4 that is wider than the electrode pad. According to this gas sensor, by making the third portion narrow, the contacts do not protrude from the electrode pads, and it is possible to suppress the loss of electrical connection between the contacts and the electrode pads due to vibrations or the like during use of the gas sensor. In addition, by making the fourth portion adjacent to the third portion wide, it is possible to improve the mechanical strength of the element contact portion 22.

[0009] In the gas sensor of the present invention, the width of the third portion may be tapered toward the free end. In this gas sensor, the free end side of the third portion (contact point) that comes into contact with the electrode pad is the narrowest, so the electrode pad can also be made narrower by that amount, and the amount of precious metal used in the electrode pad can be reduced. On the other hand, the third portion can be made wider on the folded-back side than the contact point to increase its strength, and damage to the terminal fittings due to vibrations during use of the gas sensor can be further suppressed.

[0010] In the gas sensor of the present invention, a width between the first portion and the second portion may be tapered toward the second portion. If the shape of the connection between the first section and the width-changing section is a right angle, there is a risk of excessive stress being concentrated on the step. Therefore, by providing a tapered section, stress is appropriately concentrated on the step, making it possible to further suppress damage to the terminal fitting due to vibrations, etc. when the gas sensor is in use. Effect of the Invention

[0011] According to the present invention, a gas sensor can be obtained in which damage to the terminal fittings due to vibrations or the like during use of the gas sensor is suppressed. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view taken along an axial direction of a gas sensor according to an embodiment of the present invention; [Diagram 2] FIG. [Diagram 3] FIG. 11 is a perspective view of another tip terminal fitting. [Figure 4] FIG. [Diagram 5] 11 is a cross-sectional view showing a state in which a front end terminal fitting is held by a front end separator. FIG. [Figure 6] 6A to 6C are process diagrams showing the assembly of the leading-end separator and the trailing-end separator. [Figure 7] 13 is a front view of an element contact portion of a tip terminal fitting at the center in the width direction. FIG. [Figure 8] 13 is a diagram showing the results of a simulation of the stress acting on the surface of each terminal fitting when the terminal fitting of the embodiment and the comparative example are pressed in a radial direction from the sensor element side toward the contact point of the terminal fitting. FIG. [Figure 9] FIG. 9 is a diagram in which stress values ​​at the widthwise center along the entire length L of each terminal fitting are plotted in the stress calculation of FIG. 8. [Figure 10] 13A and 13B are diagrams showing modified examples of the shape of the element contact portion. [Figure 11] 13A and 13B are diagrams showing other modified examples of the shape of the element contact portion. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described. FIG. 1 is an overall cross-sectional view along the axis O of a gas sensor (NOx sensor) 1 according to an embodiment of the present invention, FIG. 2 and FIG. 3 are oblique views of the front end terminal fittings 20, 30, FIG. 4 is an oblique view of the rear end terminal fitting 40, FIG. 5 is a cross-sectional view showing the front end terminal fittings 20, 30 held by the front end separator 90, and FIG. 6 is a process diagram showing the assembly of the front end separator 90 and the rear end separator 95, as viewed from a specified cross section of the front end separator 90 and a specified cross section of the rear end separator 95. The gas sensor 1 is a NOx sensor that detects the oxygen concentration in the exhaust gas from automobiles and various internal combustion engines.

[0014] In FIG. 1, the gas sensor 1 includes a cylindrical metal shell 138 having a screw portion 139 formed on its outer surface for fixing to an exhaust pipe, a plate-like sensor element 10 extending in the direction of axis O (the longitudinal direction of the gas sensor 1: 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 front-end separator 90 arranged in the internal space on the front side of the sleeve 106 so as to surround the periphery of the rear end of the sensor element 10, six front-end terminal fittings 20, 30 (only four are shown in FIG. 1) inserted into and held in insertion holes 90h that pass through the front-end separator 90 in the direction of axis O, a cylindrical ceramic rear-end separator 95, and six rear-end terminal fittings 40 (only two are shown in FIG. 1) held by the rear-end separator 95. As described below, the rear end separator 95 is disposed in contact with the rear end side of the front end separator 90, and the two are connected to each other. The front end terminal fittings 20, 30 and the rear end terminal fitting 40 are disposed on the front end side and the rear end side, respectively, and are connected to each other.

[0015] As shown in FIG. 5, each of the tip terminal fittings 20, 30 held in the insertion hole 90h of the tip separator 90 faces the outer surface of the rear end side of the sensor element 10 and is electrically connected to the electrode pad 11a formed on this outer surface. Three electrode pads 11a are arranged in a line in the width direction on each of both surfaces on the rear end side of the sensor element 10. Each electrode pad 11a can be formed as a sintered body mainly made of Pt, for example. On the other hand, the gas detection portion 11 at the tip of the sensor element 10 is covered with a porous protective layer 14 such as alumina.

[0016] 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 the through hole 154 such 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.

[0017] Inside the through hole 154 of the metal shell 138, a substantially annular alumina ceramic holder 151, a powder packed layer 153 (hereinafter also referred to as the talc ring 153), and the above-mentioned ceramic sleeve 106 are layered in this order from the front end to the rear end in a state surrounding the radial periphery of the sensor element 10. In addition, 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 against the tip side via the crimping packing 157.

[0018] On the other hand, as shown in FIG. 1, an outer periphery of the tip side (lower side in FIG. 1) of the metal shell 138 is provided with an outer protector 142 and an inner protector 143, which are double protectors made of metal (e.g., stainless steel) and have a plurality of holes and cover the protruding portion of the sensor element 10. The outer periphery is attached by welding or the like.

[0019] An outer cylinder 144 is fixed to the outer periphery of the rear end side of the metallic shell 138. Lead wires 146 are connected to the rear ends of the rear end side terminal fittings 40, and the lead wires 146 are drawn out to the rear end side of the rear end side separator 95. A rubber grommet 170 is disposed at the opening on the rear end side (upper side in FIG. 1) of the outer tube 144. The rubber grommet 170 has lead wire insertion holes 170h through which six lead wires 146 (only two are shown in FIG. 1) drawn out from the rear end separator 95 are inserted.

[0020] A front end separator 90 is disposed on the rear end side (upper in FIG. 1) of the sensor element 10 protruding from the rear end portion 140 of the metallic shell 138, and is provided with a flange portion 90p protruding radially outward from the outer surface. The front end separator 90 is held inside the outer cylinder 144 by the flange portion 90p abutting against the outer cylinder 144 via a holding member 169. Furthermore, the rear end separator 95 is disposed between the grommet 170 and the front end separator 90, and the rear end separator 95 presses the front end separator 90 toward the front end side due to the elastic force of the grommet 170. As a result, the flange portion 90p is pressed toward the holding member 169, and the front end separator 90 and the rear end separator 95 are held in a connected state to each other inside the outer tube 144 (i.e., without being separated in the direction of the axis O).

[0021] 2 and 3 are perspective views of the front end terminal fittings 20 and 30. In this embodiment, two types of front end terminal fittings 20 and 30 are used. Here, the front end terminal fitting 20 corresponds to the "terminal fitting" in the claims.

[0022] As shown in FIG. 5, the two tip terminal fittings 20 facing each other within the tip separator 90 have linearly symmetrical shapes, so the following description will be given using one of the tip terminal fittings 20 (the upper position in FIG. 5). 5 is symmetrical to the upper tip terminal fitting 20 with respect to a line along the surface direction of the sensor element 10. The tip terminal fitting 20 is located between the two tip terminal fittings 30 along the width direction of the sensor element 10.

[0023] Furthermore, since all four tip side terminal fittings 30 have linearly symmetrical shapes with adjacent tip side terminal fittings 30 within the tip side separator 90, the following description will be given using one of these tip side terminal fittings 30 (position I in the upper left of Figure 5). Here, the tip terminal fitting 30 at the lower left of position II in Fig. 5 is line-symmetrical to the tip terminal fitting 30 at position I, with a line along the surface direction of the sensor element 10 as an axis. The tip terminal fitting 30 at position III in the lower right of Fig. 5 is line-symmetrical to the tip terminal fitting 30 at position II, with a line perpendicular to the surface direction of the sensor element 10 as an axis. The tip terminal fitting 30 at position IV in the upper right of Fig. 5 is line-symmetrical to the tip terminal fitting 30 at position I, with a line perpendicular to the surface direction of the sensor element 10 as an axis.

[0024] As shown in FIG. 2, the tip terminal fitting 20 extends in the direction of axis O as a whole, and integrally includes a connection portion 23 connected to the rear terminal fitting 40, a substantially plate-shaped main body portion 21 connected to the tip side of the connection portion 23, a folded portion 24 folded back from the tip of the main body portion 21 toward the sensor element 10 (electrode pad 11a), and an element abutment portion 22 connected to the folded portion 24 and whose free end side abuts the electrode pad 11a. The front end terminal fitting 20 can be manufactured, for example, by punching out a metal plate (such as Inconel (registered trademark)) and then bending it into a predetermined shape, but the manufacturing method is not limited to this.

[0025] The connecting portion 23 has a cylindrical shape with a C-shaped cross section, and the rear end terminal fitting 40, which has a cylindrical tip with a C-shaped cross section, is inserted into and connected to the connecting portion 23. In this case, the front end terminal fitting 20 is indirectly connected to the lead wire 146 via the rear end terminal fitting 40.

[0026] The outer sides on both sides in the width direction of the center of the main body 21 in the axis O direction are folded back 90 degrees toward the sensor element 10 side to form a holding portion 27 having a U-shaped cross section. A connecting portion 23 is integrally connected to the rear end side of the main body 21. The main body 21 serves as a base portion of the tip side terminal fittings 20 and ensures the strength of the tip side terminal fittings 20. Meanwhile, a pair of rectangular piece-shaped rear end holding portions 25, 25 that are flush with the main body portion 21 extend outward from both sides in the width direction of the rear end side of the main body portion 21 in the axis O direction. Similarly, a pair of rectangular piece-shaped front end holding portions 29, 29 that are flush with the main body portion 21 extend outward from both sides in the width direction of the front end side of the main body portion 21 in the axis O direction.

[0027] The element contact portion 22 elastically connects to the electrode pad 11a (see FIGS. 1 and 5) at a contact point P1 as a result of bending of the folded portion 24. The element contact portion 22 elastically bends in the radial direction relative to the main body portion 21, generating a pressing force D. Further, as will be described in detail later, the element contact portion 22 integrally includes a first portion 22a, a width varying portion 22b, a third portion 22c, and a fourth portion 22d, each of which has a different width. The third portion 22c includes a contact point P1, and the contact point P1 contacts the electrode pad 11a.

[0028] As shown in FIG. 3, the tip terminal fitting 30 extends in the direction of the axis O as a whole, and integrally includes a connection portion 33 connected to the rear terminal fitting 40, a substantially plate-shaped main body portion 31 connected to the tip side of the connection portion 23, and an element abutment portion 32 folded back at the tip side of the main body portion 31 toward the sensor element 10. The front end terminal fitting 30 can be manufactured, for example, by punching out a metal plate (such as Inconel (registered trademark)) and then bending it into a predetermined shape, but the manufacturing method is not limited to this. The connecting portion 33 has a cylindrical shape similar to the connecting portion 23, and similar to the connecting portion 23, the rear end side terminal fitting 40 is inserted into and connected to the connecting portion 33 itself.

[0029] The main body 31 has an L-shaped cross section, and one widthwise outer side of the main body 31 is folded back 90 degrees toward the sensor element 10 to form a position retaining portion 35. A connecting portion 33 is integrally connected to the rear end side of the main body 31. The main body 31 serves as a base portion of the tip side terminal fittings 30 and ensures the strength of the tip side terminal fittings 30. The element contact portion 32 is folded back from the tip of the main body portion 31 toward the rear end side toward the sensor element 10, and is elastically connected to the electrode pad 11a (see Figs. 1 and 5) at a contact point P2. The element contact portion 32 elastically bends in the radial direction relative to the main body portion 31, generating a pressing force D.

[0030] On the other hand, as shown in FIG. 4 , the rear-end terminal fitting 40 extends in the direction of axis O as a whole, and integrally comprises a crimp terminal portion 47 connected to the lead wire 146, a substantially plate-shaped neck portion 41 connected to the tip side of the crimp terminal portion 47, a cylindrical large diameter portion 45 connected to the tip side of the neck portion 41 and formed by bending a plate into a C-shaped cross section, and a cylindrical tip portion 43 connected to the tip side of the large diameter portion 45 and formed by bending a plate into a C-shaped cross section. The rear end terminal fitting 40 can be manufactured, for example, by punching out a metal plate (such as SUS304) and then bending it into a predetermined shape, but the manufacturing method is not limited to this. The tip portion 43 is cylindrical and pointed toward the tip. The tip portion 43 is inserted into the cylindrical interior of the connecting portions 23, 33, so that the rear end side terminal fitting 40 is electrically connected to the front end side terminal fittings 20, 30. The large diameter portion 45 has a diameter larger than the crimp terminal portion 47 and the tip portion 43 , and a rear-facing surface 45 e of the large diameter portion 45 is exposed radially outward beyond the crimp terminal portion 47 .

[0031] 5, the tip side terminal fittings 20, 30 are assembled to the tip side separator 90. Here, when the tip side terminal fitting 20 is inserted into the insertion hole 90h from the rear end side as shown in FIG 6(a), the tip side holding portion 29 of the tip side terminal fitting 20 abuts against the rear end facing surface 90s of the tip side separator 90 to prevent the tip side terminal fitting 20 from slipping out towards the tip side, and the tip side terminal fitting 20 is held within the tip side separator 90. Similarly, although not shown, when the tip side terminal fitting 30 is inserted into the insertion hole 90h from the rear end side, the tip of the position retaining portion 35 of the tip side terminal fitting 30 abuts against a predetermined rear end facing surface of the tip side separator 90, preventing the tip side terminal fitting 30 from slipping out toward the tip side, and the tip side terminal fitting 30 is retained within the tip side separator 90. In addition, with the front end terminal fittings 20 , 30 held within the front end separator 90 , the connection portions 23 , 33 protrude toward the rear end side of the front end separator 90 .

[0032] 6(a), the rear-end separator 95 has six insertion holes 95h (only two are shown in FIG. 6) arranged in the circumferential direction. The insertion holes 95h have a large diameter at the tip end and are tapered in a step shape near the center in the axis O direction, and this step forms a tip-facing surface 95s. Then, the lead wire 146 is passed through the tip side of the insertion hole 95h in advance, and the lead wire 146 is connected to the rear end terminal fitting 40 at the tip side of the rear end separator 95. Next, when a part of the lead wire 146 side of the rear end terminal fitting 40 is inserted through the insertion hole 95h from the tip side and the lead wire 146 is drawn out to the rear end side, the rear end facing surface 45e (see FIG. 4) of the large diameter portion 45 of the rear end terminal fitting 40 abuts against the tip facing surface 95s, preventing the rear end terminal fitting 40 from slipping out to the rear end side, and the rear end terminal fitting 40 is held within the rear end separator 95. At this time, the tip side of the tip portion 43 of the rear end side terminal fitting 40 (the tip side from the center of the tip portion 43 in the direction of the axis O) protrudes beyond the surface of the rear end side separator 95 facing the tip. The outer diameter of the large diameter portion 45 is slightly smaller than the inner diameter of the insertion hole 95 h, and the large diameter portion 45 engages with the insertion hole 95 h to hold the rear end side terminal fitting 40 within the rear end side separator 95 .

[0033] A recess 90r is formed along the width direction of the sensor element on the rear-facing surface of the front-side separator 90. In addition, two protrusions 95p are formed on the outer periphery of the front-facing surface of the rear-side separator 95, protruding along the width direction of the sensor element. Therefore, as shown in FIG. 6(b), the front end terminal fittings 20, 30 are assembled to the front end separator 90, and the rear end terminal fitting 40 is assembled to the rear end separator 95, and then the front end separator 90 and the rear end separator 95 are connected to each other by engaging the recess 90r with the protrusion 95p. At this time, the tip portion 43 of the rear end terminal fitting 40 protruding toward the tip side of the rear end separator 95 is inserted into the connection portion 23 of the tip end terminal fitting 20 protruding toward the rear end side of the tip end separator 90, and the two terminal fittings are connected. In FIG. 6, for ease of understanding, one of the terminal fittings (front end terminal fittings 20, 30 and rear end terminal fitting 40) facing each other within the separator (front end separator 90 and rear end separator 95) is omitted from the illustration.

[0034] Next, the characteristic features of the present invention will be described with reference to FIGS. FIG. 7 is a front view of the front terminal fitting 20. FIG. As shown in FIG. 7, a first portion 22a of the element contact portion 22 that is connected to the folded-back portion 24 has a substantially constant first width W1. In addition, when the overall length of the element contact portion 22 in the axial direction O is L, at least one width-changing portion 22b having a substantially constant second width W2 different from the first width W1 is provided on the side of the element contact portion 22 closer to the folded portion 24 than L / 2 (below the dashed line in FIG. 7). <W1である。 The "width" of the element contact portion 22 refers to the width extending in a direction perpendicular to the axis O. Moreover, the total length L is not the length of the element contact portion 22 projected onto the axis O, but the actual length from the free end of the element contact portion 22 to the folded-back portion 24 as shown in FIG.

[0035] Next, the effect of the element contact portion 22 having the width-changing portion 22b will be described with reference to FIGS. FIG. 8 shows the results of a simulation (software name: ANSYS) calculating the stress acting on the surface of each terminal fitting when the terminal fitting of the embodiment (FIG. 2) and the terminal fitting of the comparative example (constant width) are pressed radially from the sensor element 10 side toward contact P1. FIG. 9 is a diagram in which the stress values ​​at the widthwise center along the entire length L of each terminal fitting are plotted.

[0036] As shown in FIG. 8, it can be seen that when the width-changing portion 22b is provided, the stress increases in the vicinity of the folded-back portion 24 and the width-changing portion 22b (the gray region in the figure). This is because in the width-changing portion 22b, the width changes suddenly from the first portion 22a to form a step, and stress is concentrated not only in the folded-back portion 24 but also in this step (notch). On the other hand, the stress is small in the third portion 22c on the side of the contact point P1 (black area in the figure).

[0037] 9, when width-changing portion 22b is provided, stress is concentrated (increased) compared to the comparative example (without width-changing portion 22b), but a region SR is generated where the stress is correspondingly reduced on the folded-back portion 24 side from width-changing portion 22b. Then, the reduced stress in region SR has the effect of reducing the stress in folded-back portion 24 compared to the comparative example (without width-changing portion 22b). This reduces the concentration of stress on the folded-back portion 24 of the terminal fitting 20 due to vibrations or the like that occur when the gas sensor is in use, and makes it possible to suppress damage to the terminal fitting 20.

[0038] However, as shown in FIG. 9, the region SR where stress is reduced occurs only in a relatively narrow range from the width changing portion 22b toward the folded portion 24. For example, even if a step portion is provided near the tip of the terminal fitting 20, the region where stress is reduced does not reach the folded portion 24. Therefore, the position where the width-changing portion 22b is provided is determined to be on the side of the element contact portion 22 closer to the folded-back portion 24 than L / 2.

[0039] The reason why the first portion 22a, the width changing portion 22b, the third portion 22c and the fourth portion 22d have "substantially constant" widths W1, W2, W3 and W4, respectively, is that if the width changes smoothly from the first portion 22a to the third portion 22c and the entire element abutment portion 22 is tapered, there will be no step where the width changes suddenly, and the effect of generating stress in the step (notch) described above will not occur.

[0040] Also, as shown in FIG. 7, in this example, a third portion 22c of the element contact portion 22 including the contact point P1 that contacts the electrode pad 11a has a narrower and substantially constant third width W3 than the electrode pad 11a, and a fourth portion 22d of the element contact portion 22 between the contact point P1 and the position L / 2 has a wider and substantially constant fourth width W4 than the electrode pad 11a. According to this gas sensor 1, by making the third portion 22c narrow, the contact point P1 does not protrude from the electrode pad 11a, and it is possible to suppress loss of electrical connection between the contact point P1 and the electrode pad 11a due to vibrations or the like during use of the gas sensor. In addition, by making the fourth portion 22d adjacent to the third portion 22c wide, it is possible to improve the mechanical strength of the element contact portion 22. In this example, the fourth portion 22d has the same width as the width-changing portion 22b (W4=W2), but the two may have different widths.

[0041] As shown in FIG. 7, in this example, the width of the third portion 22c tapers toward the free end to form a tapered portion 22t2. According to this gas sensor 1, the free end side of the third portion 22c (contact point P1) that contacts the electrode pad 11a has the narrowest width, so that the electrode pad 11a can also be made narrower by that amount, and the amount of precious metal used for the electrode pad 11a can be reduced. On the other hand, the third portion 22c can be made wider on the folded portion 24 side than the contact point P1 to increase its strength, and damage to the terminal fittings due to vibrations or the like during use of the gas sensor can be further suppressed.

[0042] As shown in FIG. 7, in this example, the width between the first portion 22a and the width-changing portion 22b tapers toward the width-changing portion 22b to form a tapered portion 22t1. If the shape of the connection between the first portion 22a and the width-changing portion 22b were a right angle, there would be a risk of excessive stress being concentrated on the step portion. By providing the tapered portion 22t1, therefore, it is possible to appropriately concentrate stress on the step portion, and further suppress damage to the terminal fitting due to vibrations or the like when the gas sensor is in use.

[0043] It goes without saying that the present invention is not limited to the above-described embodiment, but covers various modifications and equivalents within the spirit and scope of the present invention. For example, two or more width changing portions may be provided.

[0044] The shape of the element contact portion is not limited to the above embodiment. For example, as shown in FIG. 10, the element contact portion 220 may be cross-shaped, and the widths of the first portion 220a, the width change portion 220b, and the third portion 220c may satisfy the relationship of W2>W1 = W3. In the element contact portion 220, the shape of the connection portion between the width change portion 220b and the third portion 220c constitutes a right-angled stepped portion S.

[0045] Also, for example, as shown in FIG. 11, the element contact portion 221 may be I-shaped, and the widths of the first portion 221a, the width change portion 221b, and the third portion 221c may satisfy the relationship of W2<W1 = W3.

[0046] Further, the terminal fitting may not be divided into two parts, but may have an integral structure that does not separate into a front end side and a rear end side. Also, examples of the gas sensor include an oxygen sensor and an all-region gas sensor in addition to the NOx sensor.

Explanation of Reference Numerals

[0047] 1 Gas sensor 10 Sensor element 11a Electrode pad 20 Terminal fitting (front end side terminal fitting) 21 Body portion 22, 220, 221 Element contact portion 22t1, 22t2 Tapered portion 22a, 220a, 221a First portion 22b, 220b, 221b Width change portion 22c, 220c, 221c Third portion 22d Fourth portion 24, 240, 241 Folded-back portion O Axis

Claims

1. a plate-like sensor element extending in an axial direction and having an electrode pad on an outer surface of a rear end side of the sensor element; a terminal metal fitting extending in the axial direction and electrically connected to the electrode pad; A gas sensor comprising: the terminal fitting integrally includes a main body portion, a folded portion folded back from the main body portion toward the electrode pad, and an element contact portion connected to the folded portion and having a free end side in contact with the electrode pad, a first portion of the element contact portion connected to the folded-back portion has a substantially constant first width W1; a second width W2 that is substantially constant and different from the first width W1, and a second width W3 that is substantially constant and different from the first width W1. The gas sensor is characterized in that, when the total axial length of the element contact portion is L, at least one width changing portion is provided on the side of the element contact portion closer to the folded-back portion than L / 2.

2. a third portion of the element contact portion including a contact point that contacts the electrode pad has a third width W3 that is narrower than the electrode pad and is substantially constant; 2. The gas sensor according to claim 1, wherein a fourth portion of the element contact portion between the contact point and a position of L / 2 has a fourth width W4 that is wider than the electrode pad and is substantially constant.

3. 3. The gas sensor according to claim 1, wherein a width of the third portion tapers toward the free end.

4. 3. The gas sensor according to claim 1, wherein a width between the first portion and the width-changing portion tapers toward the width-changing portion.

Images