Gas sensor

Abstract

To provide a gas sensor in which fracture of a terminal fitting at a rear end of a separator is suppressed.SOLUTION: A gas sensor 10 includes a plate-shaped sensor element 20 including a plurality of electrode pads 21a, 21b on a main surface 20m1, 20m2 on a rear end side, a plurality of plate-shaped terminal fittings 71 electrically connected to the electrode pads, a separator 50 having an accommodation part 50h to accommodate the rear end side of the sensor element and the terminal fitting, an external cylinder 46, and a grommet 47 made of an elastic member disposed on the rear end side of the separator. An inner surface of the accommodation part includes an enlarged diameter part 50s. The grommet includes a grommet hole 47a to pass a rear end part of the terminal fitting and a lead wire 48. In addition, to an outer periphery on a tip side of the grommet, a reduced diameter member 80, which is obtained by reducing the diameter of the grommet, is fitted in a direction F perpendicular to the main surface. The reduced diameter member is disposed more on a tip side than a caulking part 46c that is formed in the external cylinder and fixes the grommet and in a region overlapping with the terminal fitting in the grommet in an axial line O direction.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gas sensor that is suitably used for detecting the concentration of a specific gas contained in, for example, combustion gas or exhaust gas from a combustor, an internal combustion engine, or the like. [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. One type of gas sensor that has been used is one in which multiple electrode pads are provided on the rear end side of the opposing main surfaces of a plate-shaped sensor element, and terminal fittings are electrically contacted to each of the electrode pads to extract a sensor output signal from the sensor element to the outside (Patent Document 1).

[0003] In the gas sensor of Patent Document 1, each terminal metal fitting is held by a two-part insulating connector (separator). This connector houses each terminal metal fitting in a box-shaped housing of the same shape, and the housings are aligned and fixed with a metal clamp. When the rear end side of the sensor element is inserted into the insertion hole of the connector, the terminal metal fitting inside the connector is in electrical contact with the electrode pad. On the other hand, at the rear end side of the connector, the insertion hole expands radially outwardly toward the rear-facing surface and in a direction perpendicular to the main surface of the sensor element, thereby preventing the terminal fitting drawn out to the rear end side of the connector from interfering with the inner surface of the connector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-209104 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, it has been found that when the rear end of the connector is expanded in diameter, the gap between the terminal fitting and the connector becomes large, and the terminal fitting becomes susceptible to vibration and breakage within the connector due to vibrations, etc. caused during use of the gas sensor. SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a gas sensor in which breakage of the terminal fitting at the rear end side of the separator is suppressed. [Means for solving the problem]

[0006] In order to achieve the above object, a gas sensor of the present invention includes a plate-shaped sensor element extending in an axial direction and having a plurality of electrode pads on a main surface of a rear end side of the sensor element, a plurality of plate-shaped terminal fittings electrically connected to the electrode pads, a separator having a housing portion penetrating in the axial direction and housing a rear end side of the sensor element and the terminal fittings and holding the terminal fittings, an outer cylinder housing the sensor element and the separator, and a grommet made of an elastic member disposed on the rear end side of the separator and closing an opening on the rear end side of the outer cylinder, wherein an inner surface of the housing portion becomes thinner as it approaches a surface facing the rear end of the separator. the grommet has a rear end of the terminal fitting and a grommet hole through which a lead wire connected to the rear end is inserted, the electrode pads and the terminal fittings are arranged at a distance from each other in the width direction of the sensor element, and a diameter reducing member is fitted onto an outer periphery of the tip side of the grommet, which reduces the diameter of the grommet at least in a direction perpendicular to the main surface, and the diameter reducing member is disposed on the tip side of a crimping portion formed on the outer tube for fixing the grommet, and in a region overlapping with the terminal fitting in the grommet in the axial direction.

[0007] The terminal metal fitting is plate-shaped, and its plate surface faces the main surface of the sensor element. Since the plate-shaped terminal metal fitting swings in a direction perpendicular to the plate surface, the terminal metal fitting is prone to swing inward in the radial direction (toward the center of the sensor element) and break when the gas sensor is vibrated during use. According to this gas sensor, the grommet hole around the terminal metal fitting is pressed by the diameter reducing member and contracts radially inward, and the inner wall of the grommet hole comes into contact with or is close to the terminal metal fitting to hold it in place, thereby preventing or reducing the terminal metal fitting from swinging radially inward and thus preventing the terminal metal fitting from breaking.

[0008] In the gas sensor of the present invention, the diameter reducing member may surround the entire periphery of the grommet. According to this gas sensor, the diameter of the grommet can be reliably reduced.

[0009] In the gas sensor of the present invention, a connecting portion to be connected to the lead wire may be provided at a rear end of the terminal fitting, and the diameter reducing member may be disposed on a tip side of the connecting portion. The connection portion is thicker than other portions of the terminal fitting in order to hold the lead wire, so the diameter-reducing member reduces the diameter of the grommet at a position that avoids the connection portion, thereby ensuring that the diameter of the grommet can be reduced.

[0010] In the gas sensor of the present invention, the reduced diameter member may extend further toward a tip side than the grommet. When the tip of the diameter reducing member is disposed rearward of the tip of the grommet, the tip of the grommet may not be sufficiently reduced in diameter. Therefore, by making the diameter reducing member extend forward of the grommet, the tip of the grommet can also be reliably reduced in diameter.

[0011] In the gas sensor of the present invention, the reducing member has on its inner surface a tapered portion that expands in diameter toward the rear end edge, and a straight portion that is further toward the tip side than the tapered portion, and the inner diameter D1 of the straight portion may be smaller than an outer diameter D2 of the grommet when not fitted into the reducing member. According to this gas sensor, the reduced diameter member can be easily fitted into the grommet, and the straight portion, which has a smaller diameter than the grommet, is pressed in by the fitting, so that the grommet hole around the grommet and therefore the terminal fitting can be reliably contracted, thereby improving airtightness. Effect of the Invention

[0012] According to the present invention, a gas sensor is obtained in which breakage of the terminal metal fitting at the rear end side of the separator is suppressed. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view of a gas sensor according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] 13 is a diagram showing a state in which a diameter reducing member is fitted into the tip side of the grommet. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. First, a gas sensor 10 according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view along axis O of a gas sensor (sensor) 10 according to an embodiment of the present invention, FIG. 2 is an oblique view of a separator 50, FIG. 3 is a cross-sectional view along line AA in FIG. 2, FIG. 4 is an oblique view of a connection terminal 71, FIG. 5 is an oblique view of a diameter-reducing member 80, and FIG. 6 is a diagram showing the state in which the diameter-reducing member 80 is fitted from the tip side of a grommet 47. 2 and 3 show a state before the grommet 47 is placed.

[0015] 1, the gas sensor 10 includes a sensor element 20 that measures a specific gas component in a measurement target gas, a protector 30 that protects the tip end of the sensor element 20, and a sensor assembly 40 that includes a separator 50 that houses the rear end side of the sensor element 20. The gas sensor 10 is attached to, for example, an exhaust pipe of a vehicle and is used to measure gas components such as NOx and O2 contained in the measurement target gas (exhaust gas).

[0016] The sensor element 20 is a long, thin plate-like element extending in the direction of the axis O, and is formed by laminating ceramic substrates or the like made of oxygen ion conductive solid electrolyte layers such as zirconia (ZrO2). The end of the sensor element 20 on the protector 30 side is referred to as the front end, and the end on the separator 50 side is referred to as the rear end.

[0017] On main surfaces 20m1 and 20m2 (FIGS. 2 and 3) on the rear end side of the sensor element 20, a plurality of electrode pads 21a and 21b (FIG. 3) are formed. Specifically, as shown in FIG. 3, a plurality of electrode pads 21a are arranged on one main surface 20m1 of the sensor element 20 at a distance in the width direction of the sensor element 20, and similarly, a plurality of electrode pads 21b are arranged on the other main surface 20m2 of the sensor element 20 at a distance in the width direction of the sensor element 20. The electrode pads may be arranged on only one of the main surfaces 20m1 or 20m2 of the sensor element 20. The electrode pads 21a and 21b are used to apply a voltage to the sensor element 20, to output a detection signal of the sensor element 20, and, if the sensor element 20 has a heater, to energize the heater.

[0018] 1, the protector 30 is disposed so as to surround the periphery of the tip of the sensor element 20. The protector 30 includes an inner protector 31 that covers the tip of the sensor element 20, and an outer protector 32 that covers the inner protector 31. The inner protector 31 is formed in a cylindrical shape and includes an inner gas inlet 31a for introducing a gas to be measured into the tip of the sensor element 20. The outer protector 32 is formed in a cylindrical shape with a bottom and includes an outer gas inlet 32a on the side for introducing a gas to be measured. The inner protector 31 and the outer protector 32 are made of a metal such as SUS.

[0019] The sensor assembly 40 includes a metallic main body 41 , a cylindrical inner cylinder 42 and an outer cylinder 46 which are fixed to the metallic main body 41 by welding, and a separator 50 which is connected to the rear end of the sensor element 20 . The metallic shell 41 is attached to, for example, an exhaust pipe of a vehicle by the male thread portion 41a. A plurality of ceramic sleeves 43a to 43c and powder filled layers 44a, 44b of talc or the like filled between the ceramic sleeves 43a, 43b and between the ceramic sleeves 43b, 43c are enclosed inside the inner cylinder 42. These are sandwiched and sealed between a metal ring 45 and the inner wall of the metallic shell 41.

[0020] The outer cylinder 46 covers the inner cylinder 42, the sensor element 20, and the separator 50. A rubber grommet 47 closes an opening on the rear end side of the outer cylinder 46. A lead wire 48 is connected by crimping or the like to a connection portion 71g (FIG. 4) on the rear end side of the terminal fitting 71, and the lead wire 48 passes through a grommet hole 47a that penetrates the grommet 47 in the axial O direction and is drawn out from the rear end of the grommet 47 to the outside. The connecting portion 71g of the terminal fitting 71 and the lead wire 48 are inserted into the grommet hole 47a.

[0021] Next, a description will be given of the separator 50. As shown in Fig. 2, the separator 50 includes a first member 51a and a second member 51b made of ceramics such as sintered alumina, and a metal clamp 90 that clamps and fixes the first member 51a and the second member 51b. A terminal metal fitting 71 is held by the first member 51a or the second member 51b, and the terminal metal fitting 71 is disposed so as to be in contact with the electrode pads 21a, 21b of the sensor element 20 in a one-to-one facing relationship.

[0022] The first member 51a and the second member 51b each hold four terminal fittings 71 arranged in a width direction perpendicular to the longitudinal direction (=axis O direction) of the terminal fittings 71. Since the first member 51a and the second member 51b have the same box-shaped configuration, the same components are denoted by the same reference numerals in the following description. The first member 51a and the second member 51b are collectively referred to as the housing 51. The housing 51 has an accommodating portion 50h penetrating in the direction of the axis O, four locking grooves 52 for locking the tip side of the terminal fitting 71, four insertion holes 53 into which the central upright portion 71d of the terminal fitting 71 is inserted, and locking portions 54 formed within each insertion hole 53 for locking the terminal fitting 71.

[0023] The housing 51 has a protrusion 55 on one side in the width direction across the sensor element 20, and has regulating members 56, 57 on the other side for regulating the distance in the thickness direction between the first member 51a and the second member 51b (see FIG. 2). The protrusion 55 is inserted into a recess between the regulating members 56 and 57 of the opposing housing 51, thereby regulating the relative positions in the thickness direction between the first member 51a and the second member 51b.

[0024] As shown in FIG. 4, terminal fitting 71 is a metal member held by housing 51 at a position facing electrode pads 21a, 21b of sensor element 20 in a one-to-one relationship, and includes a tip portion 71a that is engaged with engagement groove 52 due to its curved shape, a protruding portion 71b that curves and protrudes toward sensor element 20, a contact portion 71c that curves and protrudes toward sensor element 20 to contact electrode pads 21a, 21b, an upright portion 71d that is inserted into insertion hole 53, a curved portion 71f that is pulled out to the outside of separator 50, and a connection portion 71g that crimps and holds multiple core wires 48a of lead wire 48 outside separator 50.

[0025] The protruding portion 71b and the contact portion 71c are arranged along the longitudinal direction of the terminal fitting 71, and the contact portion 71c is arranged closer to the connecting portion 71g than the protruding portion 71b. The protruding portion 71b and the contact portion 71c are both formed to be elastically deformable. The upright portion 71d has a locking portion 71e that is locked to the locking portion 54 by its curved shape. The contact portion 71c of the terminal fitting 71 held by the first member 51a is in contact with the electrode pad 21a of the sensor element 20 in a one-to-one opposing relationship, and the contact portion 71c of the terminal fitting 71 held by the second member 51b is in contact with the electrode pad 21b of the sensor element 20 in a one-to-one opposing relationship (Figure 3). On the other hand, as shown in FIG. 3, the electrode pads 21a and 21b are formed from the rear end of the sensor element 20 to a position between the contact portion 71c and the protruding portion 71b.

[0026] 2, the clamp 90 is made by bending a metal plate, and has an elastic force capable of clamping the first member 51a and the second member 51b and pressing them in a direction toward each other. When the first member 51a and the second member 51b are clamped by this elastic force, the regulating members 56, 57 of the first member 51a come into contact with the second member 51b, and the regulating members 56, 57 of the second member 51b come into contact with the first member 51a. This fixes the distance between the first member 51a and the second member 51b.

[0027] In addition, when the clamp 90 clamps the first member 51a and the second member 51b in a state in which the sensor element 20 and the terminal fitting 71 are sandwiched between the first member 51a and the second member 51b so that the contact portion 71c of the terminal fitting 71 faces the electrode pads 21a, 21b of the sensor element 20, the pressing force from the clamp 90 causes the protrusion portion 71b and the contact portion 71c to elastically deform, thereby clamping and fixing the sensor element 20. At this time, the protrusion 71b and the contact portion 71c elastically deform and press, thereby reliably clamping and fixing the sensor element 20. In addition, because the contact portion 71c elastically deforms, the electrical contact between the contact portion 71c and the electrode pads 21a and 21b can be more reliably maintained.

[0028] Next, the characteristic features of the present invention will be described. First, as shown in FIG. 3, the separator 50 has a receiving portion 50h penetrating in the direction of the axis O, and the receiving portion 50h receives the rear end side of the sensor element 20 and the terminal fitting 71. As shown in FIG. More specifically, the accommodating portion 50h opens in a rectangular shape that is slightly larger than the outer shape of the sensor element 20 at the front end surface of the housing 51, and communicates at its rear end with each insertion hole 53. The accommodating portion 50h may be an insertion hole that opens only at the front and rear ends of the housing 51. In this example, the accommodation portion 50h is formed by recessing a part of each of the opposing surfaces of the first member 51a and the second member 51b.

[0029] Furthermore, the inner surface of the housing portion 50h has an expanding portion 50s whose diameter expands in a direction perpendicular to the two main surfaces 20m1, 20m2 of the sensor element 20 (the vertical direction in FIG. 3) toward the rear-facing surface of the separator 50. Note that "towards a direction perpendicular to the principal surfaces 20m1, 20m2" means that it is sufficient to have a directional component perpendicular to the principal surfaces 20m1, 20m2, and includes those in which the degree of expansion of the expanded diameter portion 50s varies depending on the location. For example, it also includes those in which the expanded diameter portion 50s is not parallel to the principal surfaces 20m1, 20m2, those in which the expanded diameter portion 50s is a curved surface, those in which the expanded diameter portion 50s itself is parallel to the principal surfaces 20m1, 20m2 but the leading edge or trailing edge of the expanded diameter portion 50s is not parallel to the principal surfaces 20m1, 20m2 (those in which the lengths and positions of the line segments when the expanded diameter portion 50s is cut along the principal surfaces 20m1, 20m2 are different), and the like.

[0030] On the other hand, the terminal fitting 71 is plate-shaped, and its plate surface faces the main surfaces 20m1, 20m2 of the sensor element 20. Since the plate-shaped terminal fitting 71 swings in a direction perpendicular to the plate surface, the terminal fitting 71 swings radially inward (toward the center of the sensor element 20, in the IN direction in FIG. 3) and is likely to break due to vibrations during use of the gas sensor 10.

[0031] Therefore, as shown in FIG. 1, a diameter reducing member 80 that reduces the diameter of the grommet 47 in a direction F perpendicular to at least the main surfaces 20m1, 20m2 of the sensor element 20 is fitted onto the outer periphery of the tip end side of the grommet 47. The reduced diameter member 80 is disposed on the tip side of the crimped portion 46c that is formed on the outer tube 46 and fixes the grommet 47, and in a region that overlaps with the terminal fitting 71 inside the grommet 47 in the axis O direction. As a result, grommet hole 47a around terminal fitting 71 is pressed by diameter-reducing member 80 and contracts radially inward, and the inner wall of grommet hole 47a comes into contact with or is close to terminal fitting 71 to hold terminal fitting 71. As a result, swinging of terminal fitting 71 radially inward (IN direction in FIG. 3) is suppressed or reduced, and breakage of terminal fitting 71 can be suppressed.

[0032] 5, the reduced diameter member 80 is made of a metal ring such as SUS304, and has a tapered portion 80t on the inner surface of the rear end side, the diameter of which increases toward the rear end edge. The inner surface of the reduced diameter member 80 on the tip side of the tapered portion 80t is a straight portion 80s.

[0033] Then, as shown in FIG. 6, the reducing member 80 is fitted into the grommet 47 from the tip side of the semi-finished sensor assembly (an assembly in which the grommet 47, the separator 50, the terminal fittings 71 and the lead wires 48 are assembled, but the outer tube 46 has not yet been attached) (FIG. 6(a)). Here, the inner diameter D1 of the straight portion 80s of the diameter-reducing member 80 is smaller than the outer diameter D2 of the grommet 47 in an uncompressed state (a state in which the diameter-reducing member 80 is not fitted).

[0034] The diameter reducing member 80 is fitted into the tip portion 47s of the grommet 47 from the tapered portion 80t side, and then further fitted toward the rear end, whereby the straight portion 80s, which has a smaller diameter than the grommet 47, is pressed in, causing the grommet 47, and ultimately the grommet hole 47a around the terminal fitting 71, to contract radially inward (Figure 6(b)). This assembly is then housed in the outer tube 46, and the outer tube 46 is crimped on the outside of the grommet 47 to form the crimped portion 46c.

[0035] The method for checking whether grommet 47 has been reduced in diameter by the reducing diameter member 80 is to remove outer tube 46 from grommet 47, then remove reducing diameter member 80, and if the outer diameter D2 of grommet 47 near the reducing diameter member 80 is larger than the minimum inner diameter D1 of the reducing diameter member 80 that was in contact with the grommet, it is determined that grommet 47 has been reduced in diameter.

[0036] The diameter reducing member 80 can be made of a metal such as SUS 304. The hardness of the diameter reducing member 80 is preferably 200 Hv or more.

[0037] The diameter reducing member 80 is not limited to being annular, and may be C-shaped, clip-shaped, or the like. However, an annular shape surrounding the entire circumference of the grommet 47 is preferable because it ensures that the diameter of the grommet 47 can be reduced.

[0038] As shown in FIG. 6(b), a connection portion 71g connected to the lead wire 48 may be provided at the rear end of the terminal fitting 71, and the diameter reducing member 80 may be disposed on the tip side of the connection portion 71g. Connection portion 71g is thicker than other portions of terminal fitting 71 in order to hold lead wire 48. Therefore, diameter-reducing member 80 reduces the diameter of grommet 47 at a position that avoids connection portion 71g, thereby ensuring that grommet 47 is reduced in diameter.

[0039] Also, as shown in FIG. 6(b), the diameter reducing member 80 may extend further toward the tip side than the grommet 47. If the tip of diameter reducing member 80 is disposed rearward of the tip of grommet 47, the diameter of the tip of grommet 47 may not be sufficiently reduced. Therefore, by making diameter reducing member 80 extend toward the tip side beyond grommet 47, the diameter of the tip of grommet 47 can also be reliably reduced.

[0040] 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. The diameter reducing member is not limited to the member having the tapered portion described above, and a ring having a diameter larger than the grommet may be fitted into the grommet and then the ring may be reduced in diameter. The separator is not limited to being in the shape of a two-part box, but may be in the shape of a cylinder or the like. Furthermore, the diameter reducing member may reduce the diameter of the grommet at least in a direction perpendicular to the main surface of the sensor element, but the diameter reducing member may be annular, for example, to reduce the diameter of the grommet in a direction other than the main surface. [Explanation of symbols]

[0041] 10 Gas Sensor 20 Sensor element 20m1, 20m2 Main surface of sensor element 21a, 21b Electrode pads 46 Outer cylinder 46c Crimping part 47 Grommet 47a Grommet hole 48 Lead Wire 50 Separator 50h Storage section 50s expanded diameter part 71 Terminal fittings 71g Connection 80 Reducing diameter member 80t tapered section 80s Straight section O axis F Perpendicular to the main surface

Claims

1. a plate-shaped sensor element extending in the axial direction and having a plurality of electrode pads on a main surface on the rear end side; a plurality of plate-shaped terminal fittings electrically connected to the electrode pads, respectively; a separator having an accommodating portion penetrating in the axial direction and accommodating a rear end side of the sensor element and the terminal metal fitting, the separator holding the terminal metal fitting; an outer cylinder that houses the sensor element and the separator; a grommet made of an elastic member disposed on a rear end side of the separator and closing an opening on the rear end side of the outer cylinder; A gas sensor comprising: an inner surface of the housing portion has an expanding portion that expands in diameter in a direction perpendicular to the main surface as it approaches a rear-facing surface of the separator, the grommet has a rear end of the terminal fitting and a grommet hole through which a lead wire connected to the rear end is inserted, the plurality of electrode pads and the plurality of terminal fittings are arranged at intervals in a width direction of the sensor element, Furthermore, a diameter reducing member is fitted to an outer periphery of the tip side of the grommet, the diameter reducing member reducing the diameter of the grommet at least in a direction perpendicular to the main surface, The gas sensor is characterized in that the reduced diameter member is disposed on the tip side of a crimping portion formed on the outer tube and fixing the grommet, and in an area overlapping with the terminal fitting inside the grommet in the axial direction.

2. 2. The gas sensor according to claim 1, wherein the reduced diameter member surrounds the entire periphery of the grommet.

3. A connecting portion is provided at a rear end of the terminal metal fitting to be connected to the lead wire, 3. The gas sensor according to claim 1, wherein the reducing member is disposed closer to a tip end than the connecting portion.

4. 3. The gas sensor according to claim 1, wherein the reduced diameter member extends further toward a tip side than the grommet.

5. the reducing member has an inner surface including a tapered portion that expands in diameter toward a rear end edge and a straight portion that is located toward a tip side of the tapered portion, 3. The gas sensor according to claim 1, wherein an inner diameter D1 of the straight portion is smaller than an outer diameter D2 of the grommet when not fitted into the diameter reducing member.

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