Gas sensor

Abstract

To provide a gas sensor capable of preventing a sensor element from being broken.SOLUTION: A gas sensor 1 comprises: a sensor element 21 including electrode pads 25a-25c, 26a, 26b respectively on a first principal surface 21a and a second principal surface 21b; a first terminal metal fitting 75 and a second terminal metal fitting 76 respectively connected to the electrode pad; and a separator 91. On the first terminal metal fitting having a main body part 751a closest to the first principal surface, a straight line including the main body part and parallel to the first principal surface is defined as a first straight line L1. On the second terminal metal fitting having the main body part closest to the second principal surface, a straight line including the main body part and parallel to the second principal surface is defined as a second straight line L2. A straight line equidistant to the L1 and L2 is defined as a center line CL. A total of first weight applied on a bent portion 751b of the first terminal metal fitting is larger than a total of second weight applied on a bent portion of the second terminal metal fitting. Center of gravity G of the sensor element when the first terminal metal fitting and the second terminal metal fitting are removed from the separator slants toward the second straight line from the center line CL.SELECTED DRAWING: Figure 4

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] Oxygen and NO in exhaust gases from automobiles, etc. x 2. Description of the Related Art As a gas sensor for detecting the concentration of a gas, there is known one having a plate-shaped sensor element using a solid electrolyte. A widely used gas sensor of this type has a plate-shaped sensor element with a plurality of electrode pads arranged in the width direction at the rear end sides of the opposing main surfaces of the sensor element, and a terminal metal fitting is electrically connected to each of the electrode pads to extract a sensor output signal from the sensor element to the outside (Patent Document 1). In this case, each terminal has an element contact portion that contacts the electrode pad, and the element contact portion is pressed against the electrode pad by the spring force. The terminals face each other across the main surface of the sensor element, and the spring load of the terminals acts on both sides of the sensor element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-181768 A (Figs. 4 and 6) Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, if the same number of terminal fittings of the same shape are arranged on both sides of the main surface of the sensor element, the spring loads of the terminal fittings acting on both sides of the sensor element will be the same. On the other hand, if the shapes (spring forces) or the number of terminal fittings on both sides of the sensor element are different, the spring loads of the terminal fittings acting on both sides of the sensor element will be different. Since the sensor element is normally held with its center of gravity in the axial direction aligned with the center of gravity of the metal shell, if the spring loads of the terminal fittings on both sides of the sensor element are different, bending stress will be applied to the sensor element with the holding portion of the metal shell as a fulcrum, and there is a risk of the element being damaged. Therefore, an object of the present invention is to provide a gas sensor that reduces the stress applied to the sensor element and suppresses damage to the sensor element when one or more terminal fittings are arranged on each of the two main surfaces of the sensor element. [Means for solving the problem]

[0005] In order to achieve the above object, a gas sensor of the present invention comprises a sensor element extending in an axial direction and having a plate shape with opposing first and second main surfaces, the sensor element having one or more electrode pads on rear end sides of the first and second main surfaces, a metal shell for holding the sensor element, one or more first terminal fittings and one or more second terminal fittings facing the first and second main surfaces, respectively, and connected to the electrode pads, and a separator for holding the first terminal fittings and the second terminal fittings, the first terminal fittings and the second terminal fittings having a main body portion extending in the axial direction, a bent portion bent from one end of the main body portion towards the sensor element, and an element contact portion connected to the bent portion and in contact with the electrode pads, When viewed from the axial direction, the first terminal fitting, of which the main body portion is closest to the first main surface, includes the main body portion and a straight line parallel to the first main surface is defined as a first straight line, the second terminal fitting, of which the main body portion is closest to the second main surface, includes the main body portion and a straight line parallel to the second main surface is defined as a second straight line, and a straight line equidistant from the first straight line and the second straight line is defined as a center line CL, the sum of first loads applied to the folded portions of the first terminal fittings is greater than the sum of second loads applied to the folded portions of the second terminal fittings, and the center of gravity G of the sensor element when the first terminal fittings and the second terminal fittings are removed from the separator is positioned offset toward the second straight line from the center line CL.

[0006] If the sum of the first loads F1 and the sum of the second loads F2 differ in magnitude, a bending stress is applied to the sensor element with the holding portion of the metal shell as a fulcrum, and there is a risk that the element will be damaged. Therefore, when the first terminal fittings and the second terminal fittings are removed from the separator (i.e., when the load of the first terminal fittings and the second terminal fittings is not applied), the center of gravity G of the sensor element is biased toward the second straight line side from the center line CL. As a result, even after the load of the first terminal fitting and the second terminal fitting is applied, the bending stress acting on the sensor element toward the second straight line due to F1>F2 is reduced compared to when the center of gravity G is on the center line CL, and damage to the sensor element can be suppressed. In other words, by shifting the center of gravity G of the first and second terminal fittings toward the second straight line when no load is applied, the first terminal fitting is farther from the first main surface of the sensor element than the second terminal fitting. As a result, the stroke length of the first terminal fitting is longer, and compared to when the center of gravity G is on the center line CL, the spring force of the element contact portion of the first terminal fitting, and therefore F1, is weakened, and the bending stress is reduced.

[0007] In the gas sensor of the present invention, the center of gravity G may be offset from the center line CL by 0.2 mm or more toward the second straight line. According to this gas sensor, the spring force of the element contact portion of the first terminal fitting, and therefore F1, can be further reduced, thereby reducing the bending stress applied to the sensor element.

[0008] In the gas sensor of the present invention, the center of gravity G may be offset from the center line CL by 0.5 mm or more toward the second straight line. According to this gas sensor, the spring force of the element contact portion of the first terminal fitting, and therefore F1, can be further reduced, and the bending stress applied to the sensor element can be further reduced. Effect of the Invention

[0009] According to the present invention, when one or more terminal fittings are provided on each of the two main surfaces of the sensor element, it is possible to obtain a gas sensor in which the stress applied to the sensor element is reduced and damage to the sensor element is suppressed. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view taken along the longitudinal direction of a gas sensor according to a first embodiment of the present invention. [Diagram 2] FIG. [Diagram 3]4 is a perspective view showing a first terminal fitting and a second terminal fitting held in a separator. FIG. [Figure 4] 4 is a plan view showing a first terminal fitting and a second terminal fitting in a separator as viewed from the tip side (axial direction). FIG. [Diagram 5] FIG. 5 is a cross-sectional view taken along the longitudinal direction of a gas sensor according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a plan view showing a first terminal fitting and a second terminal fitting in a separator as viewed from the tip side (axial direction) in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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) 1 according to a first embodiment of the present invention, FIG. 2 is an oblique view of a sensor element 21, FIG. 3 is an oblique view showing a first terminal fitting 75 and a second terminal fitting 76 held in a separator 91, and FIG. 4 is a plan view showing the first terminal fitting 75 and the second terminal fitting 76 in the separator 91 as viewed from the tip side (axis O direction). The gas sensor 1 is an oxygen sensor (full range air-fuel ratio gas sensor) that detects the oxygen concentration in the exhaust gas of an automobile or various internal combustion engines.

[0012] In FIG. 1, the gas sensor 1 includes a sensor element 21, a holder (ceramic holder) 30 having a through hole 32 penetrating in the axial direction O for inserting the sensor element 21 therethrough, a metal shell 11 surrounding the radial periphery of the ceramic holder 30, a ceramic separator 91, and five terminal fittings 75, 76 (only three are shown in FIG. 1) held by the separator 91.

[0013] A portion of the sensor element 21 near the front end where the detection portion 22 is formed protrudes toward the front end from the ceramic holder 30. The sensor element 21 thus passed through the through hole 32 is fixed inside the metallic shell 11 while maintaining airtightness in the front-to-rear direction by compressing a seal material (talc in this example) 41 arranged on the rear end face side (upper side in the figure) of the ceramic holder 30 in the front-to-rear direction via a sleeve 43 and a ring washer 45 made of an insulating material. The portion of the sensor element 21 close to the rear end 29, including the rear end 29, protrudes rearward from the sleeve 43 and the metallic shell 11, and the terminal fittings 75 provided at the ends of the lead wires 71 drawn to the outside through a sealing material 85 are pressed and electrically connected to the electrode pads 24 formed in the portion close to the rear end 29. The portion of the sensor element 21 close to the rear end 29, including the electrode pads 24, is covered by an outer tube 81. This will be described in more detail below.

[0014] The sensor element 21 extends in the direction of the axis O and is in the form of a strip (plate) equipped with a detection section 22 consisting of a detection electrode or the like (not shown) for detecting a specific gas component in a gas to be detected, at the tip side (lower side in the figure) facing the measurement target. The cross section of the sensor element 21 has a rectangular shape of a constant size at the front and rear, and is formed as an elongated object mainly made of ceramic (solid electrolyte, etc.).

[0015] The sensor element 21 itself is the same as that known in the art, and a pair of detection electrodes forming a detection section 22 are arranged near the tip of the solid electrolyte (member), and an electrode pad 24 for connecting a lead wire 71 for extracting detection output is exposed and formed at a portion connected to the detection electrodes near the rear end. In this example, a heater (not shown) is provided inside the portion of the sensor element 21 near the front end of the ceramic material formed in a laminated shape on the solid electrolyte (component), and an electrode pad 24 for connecting a lead wire 71 for applying a voltage to the heater is formed and exposed near the rear end.

[0016] As shown in FIG. 2, these electrode pads 24 are formed in a vertically long rectangle, and three or two electrode terminals are arranged horizontally on the wide surfaces (both surfaces) of the strip plate near the rear end 29 of the sensor element 21, for example. The detection portion 22 of the sensor element 21 is covered with a porous protective layer 23 made of alumina, spinel, or the like.

[0017] The metal shell 11 is tubular and concentric with different diameters at the front and rear, with a cylindrical annular portion (hereinafter also referred to as the cylindrical portion) 12 having a smaller diameter at the front end for fitting and fixing protectors 51, 61 (described later) thereto, and a screw 13 of larger diameter is provided on the outer circumferential surface at the rear of the metal shell 11 (upper part in the figure) for fixing the protectors to the exhaust pipe of the engine. At the rear of the sensor, a polygonal portion 14 is provided for screwing the sensor 1 with the screw 13.

[0018] A cylindrical section 15 is connected to the rear of the polygonal section 14, and a protective tube (outer tube) 81 that covers the rear of the gas sensor 1 is fitted and welded to the cylindrical section 15. A thin-walled cylindrical section 16 for crimping is provided behind the cylindrical section 15. In FIG. 1, the cylindrical section 16 for crimping is bent inward for use after crimping. A gasket 19 for sealing when screwed is attached to the bottom surface of the polygonal section 14. On the other hand, the metallic shell 11 has an inner hole 18 penetrating therethrough in the direction of the axis O. The inner peripheral surface of the inner hole 18 has a tapered step portion 17 that tapers radially inward from the rear end side to the front end side. Furthermore, a rear-facing surface 11e is formed on the rear end side of the cylindrical portion 15 of the metallic shell 11, and a reflecting surface 11r and a tapered surface 11t, which will be described later, are formed on the rear-facing surface 11e.

[0019] A ceramic holder 30 made of insulating ceramic (e.g., alumina) and formed into a roughly short cylindrical shape is disposed inside the metal shell 11. The ceramic holder 30 has a front-facing surface 30a formed in a tapered shape tapering toward the front end. A portion of the front-facing surface 30a near the outer periphery is engaged with the step portion 17, and the ceramic holder 30 is pressed from the rear end side by a seal material 41, whereby the ceramic holder 30 is positioned within the metal shell 11 and is gap-fitted. On the other hand, the through hole 32 is provided in the center of the ceramic holder 30 and is a rectangular opening having substantially the same dimensions as the cross section of the sensor element 21 so that the sensor element 21 can pass through with almost no gap.

[0020] The sensor element 21 is inserted into the through hole 32 of the ceramic holder 30 , and the tip of the sensor element 21 protrudes forward beyond the ceramic holder 30 and the tip 12 a of the metallic shell 11 . Meanwhile, in this embodiment, the tip portion of the sensor element 21 is covered with cylindrical protectors (protective covers) 51, 61, each of which has a two-layer structure and has vent holes (holes) 56, 67, respectively. Of these, the rear end of the inner protector 51 is fitted onto the cylindrical portion 12 of the metal shell 11 and welded. The vent holes 56 are provided, for example, at eight locations in the circumferential direction on the rear end side of the protector 51. Meanwhile, the tip side of the protector 51 is also provided with exhaust holes 53, for example, at four locations in the circumferential direction. The outer protector 61 is fitted onto the inner protector 51 and welded to the cylindrical portion 12 at the same time. The outer protector 61 has ventilation holes 67, for example, eight holes in the circumferential direction near the tip, and also has a drain hole 69 in the center of the bottom of the tip of the protector 61.

[0021] As shown in FIG. 1, each electrode pad 24 formed near the rear end 29 of the sensor element 21 is pressed against and electrically connected to each terminal fitting 75, 76 provided at the tip of each lead wire 71 that is drawn to the outside through a sealing material 85 by the spring properties of the terminal fittings 75, 76. In the gas sensor 1 of this embodiment, the terminal fittings 75, 76 including the pressure-contact portions are disposed opposite each other in respective receiving portions provided in an insulating separator 91 disposed in the outer cylinder 81. The separator 91 is restricted in its radial and tip-side movement by a holding member 82 that is crimped and fixed inside the outer cylinder 81. The tip of the outer cylinder 81 is fitted onto and welded to the cylindrical portion 15 near the rear end of the metallic shell 11, thereby covering the rear of the gas sensor 1 in an airtight manner. The lead wire 71 is passed through a sealing material (e.g., rubber) 85 arranged inside the rear end of the outer tube 81 and led out to the outside. The small-diameter tube portion 83 is crimped to reduce the diameter and compress the sealing material 85, thereby maintaining the airtightness of this portion.

[0022] Incidentally, a step 81d having a larger diameter at the front end side is formed slightly rearward from the center of the outer cylinder 81 in the direction of the axis O, and the inner surface of this step 81d supports the rear end of the separator 91 so as to push it forward. Meanwhile, a flange 93 formed on the outer periphery of the separator 91 is supported on a holding member 82 fixed to the inside of the outer cylinder 81, and the separator 91 is held in the direction of the axis O by the step 81d and the holding member 82.

[0023] 2, the sensor element 21 has a plate shape extending in the direction of the axis O, and a tip portion 21s serves as a detection portion 22 that detects the oxygen concentration, and the detection portion 22 is covered with a protective layer 23. The sensor element 21 itself has a known configuration, and includes a gas detection portion having an oxygen ion-permeable solid electrolyte and a pair of electrodes, and a heater portion that heats the gas detection portion and maintains it at a constant temperature, although these are not shown. Three electrode pads 25a to 25c are arranged in the width W direction on the rear end side of the first main surface 21a of the sensor element 21, and a sensor output signal from the gas detection unit is output from these electrode pads 25a to 25c via a lead portion (not shown). Two electrode pads 26a, 26b are arranged in the width direction on the rear end side of the second main surface 21b provided so as to face the main surface 21a, and power is supplied to the heater unit via the lead portion (not shown).

[0024] Each of the electrode pads 25a to 25c, 26a, and 26b 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. In this embodiment, the electrodes 25a to 25c arranged on each surface of the sensor element 21 and the electrode pads 26a and 26b face each other.

[0025] Next, the terminal fittings 75 and 76 will be described with reference to FIGS. FIG. 3 is a perspective view showing terminal fittings 75, 76 held in separator 91, and FIG. 4 is a plan view showing terminal fittings 75, 76 in separator 91 as viewed from the tip side (axis O direction). In this embodiment, the gas sensor 1 has five terminal fittings 75, 76. Among the terminal fittings 75, 76, three terminal fittings that face the first main surface 21a and are connected to the electrode pads 25a to 25c respectively are referred to as first terminal fittings 75, and two terminal fittings that face the second main surface 21b and are connected to the electrode pads 26a, 26b respectively are referred to as second terminal fittings 76.

[0026] Of the three first terminal fittings 75, the ones at both ends are referred to as first terminal fittings 751 and 752, and the one in the middle is referred to as first terminal fitting 753. The first terminal fittings 751, 752 and the second terminal fitting 76 all have the same shape or are symmetrical with respect to a line along the axis O direction, so the structure will be described using the first terminal fitting 751 as a representative, but the other terminal fittings, the first terminal fitting 752 and the second terminal fitting 76, have the same structure. The first terminal fitting 753 has a slightly different shape from the first terminal fitting 751, but has the same structure.

[0027] 3, the first terminal metal fitting 751 has a main body portion 751a extending in the direction of the axis O, a bent portion 751b that bends from the tip of the main body portion 751a toward the sensor element 21, and an element contact portion 751c (see FIG. 1) that is connected to the bent portion 751b and contacts the electrode pad 25a. Also, a crimp terminal portion 751d into which the lead wire 71 with exposed conductor is inserted and crimped is provided on the rear end side of the main body portion 751a. The terminal fittings 75, 76 can be manufactured, for example, by punching out a single metal plate (such as Inconel (registered trademark)) and then bending it appropriately, but the manufacturing method is not limited to this. The element contact portion 751c is pressed toward the electrode pad 25a by the springiness (elasticity) of the first terminal metal fitting 751 itself, thereby ensuring a reliable electrical connection.

[0028] 4, among the first terminal fittings 75, the first terminal fittings 751 and 752 have body portions 751a that are closest to the first main surface 21a. In this regard, in the first terminal fitting 751, a straight line that includes the body portion 751a and is parallel to the first main surface 21a is defined as a first straight line L1. Similarly, in the second terminal metal fitting 76 whose main body is closest to the second main surface 21b, a straight line that includes the main body and is parallel to the second main surface 21b is defined as a second straight line L2. The main bodies of the two second terminal metal fittings 76 are equidistant from the second main surface 21b.

[0029] Here, when a straight line equidistant from the first straight line L1 and the second straight line L2 is taken as the center line CL, the sum F1 of the first loads applied to the bent portion 751b of the first terminal fitting 75 is greater than the sum F2 of the second loads applied to the bent portion of the second terminal fitting 76. Furthermore, when the first terminal metal fitting 75 and the second terminal metal fitting 76 are removed from the separator 91, the center of gravity G of the sensor element 21 is positioned offset toward the second straight line L2 side from the center line CL.

[0030] Here, in Figure 4, only the bent portion 751b of first terminal fitting 751 is shown as the bent portion of first terminal fitting 75, but it goes without saying that a load (as a reaction force from the electrode pads) is also applied to the bent portions of the other first terminal fittings 752, 753.

[0031] The load acting on the bent portion of each of the terminal fittings 75, 76 is measured as follows: First, an X-ray CT image of a cross section passing through the element contact portion of each of the terminal fittings 75, 76 and perpendicular to the axis O direction is obtained. Next, on this image, the stroke length Sr (see FIG. 4, the distance from the main body of the terminal metal fitting to the element contact part on the image), which is the spring height of the target terminal metal fitting, is measured. Then, the terminal fitting is removed from the separator 91, the main body is grounded to the base, and the element contact part is pressed toward the main body part until the stroke length Sr is reached, and the load at that time is measured. At this time, the element contact part may be pressed via a pressure gauge, for example, to read the pressure value.

[0032] As described above, F1>F2. In this example, since the number of the first terminal fittings 75 is greater than the number of the second terminal fittings 76, in a state where the gas sensor 1 is assembled (i.e., where the terminal fittings 75, 76 are held in the separator 91 and the sensor element 21 is held in the metallic shell 11), the sum F1 of the first loads of the first terminal fittings 75 pressing against the first main surface 21a is greater than the sum F2 of the second loads of the second terminal fittings 76 pressing against the second main surface 21b. In this case, sensor element 21 is usually held with its axis (center of gravity G in the axial direction) aligned with the center of gravity (center) of metallic shell 11. Therefore, if F1 and F2 differ in size, bending stress is applied to sensor element 21 with the holding portion of metallic shell 11 as a fulcrum, which may damage the element.

[0033] Therefore, when the first terminal fittings 75 and the second terminal fittings 76 are removed from the separator 91 (i.e., when the load of the first terminal fittings 75 and the second terminal fittings 76 is not applied), the center of gravity G of the sensor element 21 is biased toward the second straight line L2 from the center line CL. As a result, even after the load of the first terminal fitting 75 and the second terminal fitting 76 is applied, the bending stress acting on the sensor element 21 toward the second straight line L2 due to F1>F2 is reduced compared to when the center of gravity G is on the center line CL, and damage to the sensor element 21 can be suppressed. In other words, by shifting the center of gravity G of the first terminal metal fitting 75 and the second terminal metal fitting 76 toward the second straight line L2 when no load is applied, the first terminal metal fitting 75 becomes farther from the first main surface 21a of the sensor element 21 than the second terminal metal fitting 76. As a result, the stroke length Sr (FIG. 4) of the first terminal metal fitting 75 becomes longer, and the spring force of the element contact portion of the first terminal metal fitting 75, and therefore F1, becomes weaker than when the center of gravity G is on the center line CL, thereby reducing the bending stress.

[0034] FIG. 4 shows the center of gravity G of the sensor element 21 when the load of the first terminal metal fitting 75 and the second terminal metal fitting 76 is applied. 1, in the first embodiment, the sensor element 21 is held so that its axis (center of gravity G in the axial direction) is aligned with the center of gravity (center) of the metallic shell 11. Meanwhile, the first terminal metal fitting 75 and the second terminal metal fitting 76 are held by the separator 91 so that the central hole (hole surrounding the sensor element 21) of the separator 91 is offset toward the second straight line L2 from the center line CL. This allows the center of gravity G to be offset toward the second straight line L2 from the center line CL. Although FIG. 4 shows the position of the center of gravity G when a load is applied to the first terminal metal fitting 75 and the second terminal metal fitting 76, the position of the center of gravity G does not change significantly when no load is applied.

[0035] Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is an overall cross-sectional view along the longitudinal direction of a gas sensor (oxygen sensor) 1B according to a second embodiment of the present invention, and FIG. 6 is a plan view showing a first terminal fitting 75 and a second terminal fitting 76 in a separator 91 as viewed from the tip side (axis O direction). This gas sensor 1A is similar to the first embodiment except that the axial center (center of gravity G in the axial direction) of the sensor element 21 is shifted toward the second straight line L2 from the center of gravity (center) of the metallic shell 11. Therefore, the same components are denoted by the same reference numerals and their descriptions are omitted. As a result, as shown in FIG. 6, even in the second embodiment, the center of gravity G can be biased toward the second straight line L2 when no load is applied to the first terminal fitting 75 and the second terminal fitting 76, thereby reducing the bending stress applied to the sensor element 21 toward the second straight line L2 and suppressing damage to the sensor element 21.

[0036] In the second embodiment, the first terminal metal fitting 75 and the second terminal metal fitting 76 are held by the separator 91 so that the central hole of the separator 91 (a hole surrounding the sensor element 21) is on the center line CL. Meanwhile, as described above, the axis of the sensor element 21 (center of gravity G in the axial direction) is held shifted toward the second straight line L2 side from the center of gravity (center) of the metallic shell 11. This allows the center of gravity G to be biased toward the second straight line L2 side from the center line CL.

[0037] The center of gravity G is preferably positioned offset from the center line CL toward the second straight line L2 by 0.2 mm or more, and more preferably offset by 0.5 mm or more.

[0038] 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, the shapes and numbers of the first terminal fittings and the second terminal fittings are not limited. In the above embodiment, the number of first terminal fittings and the number of second terminal fittings are different, but the number of first terminal fittings and the number of second terminal fittings may be the same (for example, two each). In this case, the material (springiness) or shape of the first terminal fittings and the second terminal fittings may be different. Moreover, examples of the gas sensor include an oxygen sensor, a full range gas sensor, and a NOx sensor. [Explanation of symbols]

[0039] 1. 1A gas sensor 11 Metal fitting 21 Sensor element 21a 1st main surface 21b 2nd principal surface 25a~25c, 26a, 26b Electrode pads 75, 751~753 First terminal fitting 76 Second terminal fitting 91 Separator 751a Main body 751b Bending part 751c Element contact part O axis L1 1st straight line L2 2nd straight line CL center line G center of gravity

Claims

1. a plate-like sensor element extending in an axial direction and having a first main surface and a second main surface opposed to each other, the plate-like sensor element having one or more electrode pads on each of the first main surface and the second main surface on a rear end side thereof; a metal shell for holding the sensor element; one or more first terminal metals and one or more second terminal metals facing the first main surface and the second main surface, respectively, and connected to the electrode pads; a separator that holds the first terminal metal fitting and the second terminal metal fitting, the first terminal metal fitting and the second terminal metal fitting each have a main body portion extending in the axial direction, a bent portion bent from one end of the main body portion toward the sensor element, and an element contact portion connected to the bent portion and in contact with the electrode pad; When viewed from the axial direction, In the first terminal fitting, the main body portion is closest to the first main surface, and a straight line including the main body portion and parallel to the first main surface is defined as a first straight line, In the second terminal fitting, the main body portion of which is closest to the second main surface, a straight line including the main body portion and parallel to the second main surface is defined as a second straight line, When a straight line equidistant from the first straight line and the second straight line is defined as a center line CL, a sum of first loads applied to the bent portions of the first terminal fittings is greater than a sum of second loads applied to the bent portions of the second terminal fittings, a center of gravity G of the sensor element when the first terminal fitting and the second terminal fitting are removed from the separator, the center of gravity G being shifted toward the second straight line side from the center line CL.

2. 2. The gas sensor according to claim 1, wherein the center of gravity G is offset from the center line CL by 0.2 mm or more toward the second straight line.

3. 3. The gas sensor according to claim 2, wherein the center of gravity G is offset from the center line CL by 0.5 mm or more toward the second straight line.

Images