Gas sensor

Abstract

To provide a gas sensor which suppresses fracture of a terminal metal fitting on a rear end side of a separator.SOLUTION: A gas sensor 10 includes: a tabular sensor element 20 which extends in a direction of an axis O and which has electrode pads 21a, 21b on main surfaces 20m1, 20m2 on its rear end side; terminal metal fittings 71 which extend in the axial direction and which are electrically connected to the electrode pads; and a separator 50 which has a storage part 50h for storing a rear end of the sensor element penetrating it in the axial direction and the terminal metal fittings and which holds the terminal metal fittings. The storage part includes a taper surface 50s whose diameter increases in a direction vertical to the main surfaces as it goes toward a rear-end facing surface of a separator. The terminal metal fittings include protrusions 75 protruding toward the taper surface, and the protrusions contact with the taper surface.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a gas sensor suitably used for detecting the gas concentration of a specific gas contained in combustion gas or exhaust gas, such as a combustor or an internal combustion engine.

Background Art

[0002] As a gas sensor for detecting the concentration of oxygen or NO in exhaust gas of an automobile or the like, one having a plate-shaped sensor element using a solid electrolyte is known. x As this type of gas sensor, a plurality of electrode pads are provided on the rear end side of the opposing main surfaces of the plate-shaped sensor element, and a terminal fitting is electrically contacted to each of these electrode pads to extract a sensor output signal from the sensor element to the outside (Patent Document 1).

[0003] Further, in the gas sensor of Patent Document 1, each terminal fitting is held by a two-piece insulating connector (separator). This connector houses each terminal fitting in a box-shaped housing of the same shape, and the respective housings are fixed together with a metal clamp. Then, when the rear end side of the sensor element is inserted into the insertion hole of the connector, the terminal fitting inside the connector comes into electrical contact with the electrode pad. On the other hand, on the rear end side of the connector, the insertion hole faces the rear end-facing surface and expands radially outward in a direction perpendicular to the main surface of the sensor element. Thereby, it is suppressed that the terminal fitting drawn out to the rear end side of the connector interferes with the inner surface of the connector.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, it has been found that if the rear end side of the connector has an enlarged diameter, the distance between the terminal fitting and the connector increases, and the terminal fitting is likely to swing and break within the connector due to vibrations during the use of the gas sensor. Therefore, an object of the present invention is to provide a gas sensor that suppresses breakage of the terminal fitting on the rear end side of the separator.

Means for Solving the Problems

[0006] To solve the above problems, the gas sensor of the present invention includes a plate-shaped sensor element that extends in the axial direction and has an electrode pad on the main surface on the rear end side, a terminal fitting that extends in the axial direction and is electrically connected to the electrode pad, and a separator that has a housing portion that penetrates in the axial direction and houses the rear end side of the sensor element and the terminal fitting, and holds the terminal fitting. The housing portion has a tapered surface that expands in a direction perpendicular to the main surface as it faces the surface of the separator facing the rear end, the terminal fitting has a protrusion that protrudes toward the tapered surface, and the protrusion abuts against the tapered surface.

[0007] The terminal fitting is plate-shaped, and the plate surface faces the main surface of the sensor element. Therefore, due to vibrations during the use of the gas sensor or the like, the plate-shaped terminal fitting is likely to swing and break in a direction perpendicular to the main surface. Therefore, a protrusion that protrudes toward the tapered surface of the separator is provided on the terminal fitting, and the protrusion is brought into contact with the tapered surface. As a result, the terminal fitting is fixed to the separator via the tapered surface, so that the vibration of the terminal fitting is suppressed and the breakage of the terminal fitting can be suppressed.

[0008] In the gas sensor of the present invention, the protrusion may be a tongue piece portion that extends toward the tip side in the axial direction. In this way, when the protrusion is a tongue piece portion that extends toward the tip side in the axial direction, the tip (free end) of the protrusion is likely to contact the tapered surface at an angle, and the tip of the protrusion becomes flat and is likely to be locked to the tapered surface. As a result, the terminal fitting is more securely fixed to the separator via the tapered surface.

[0009] In the gas sensor of the present invention, the terminal fitting has a plate shape, a plate surface faces the tapered surface, and the protrusion may be a plate piece portion folded from at least one side surface of the terminal fitting toward the tapered surface. According to this gas sensor, the protrusion can be easily formed simply by folding the side surface of the plate-shaped terminal fitting.

[0010] In the gas sensor of the present invention, the protrusion may be a bent portion obtained by bending the terminal fitting so as to protrude toward the tapered surface. According to this gas sensor, the protrusion can be easily formed simply by bending the terminal fitting toward the tapered surface.

[0011] In the gas sensor of the present invention, the protrusion may be formed by fixing a separate member to a portion of the terminal fitting facing the tapered surface. According to this gas sensor, the protrusion can be easily formed simply by fixing a separate member to the terminal fitting.

Advantages of the Invention

[0012] According to this invention, a gas sensor that suppresses breakage of the terminal fitting on the rear end side of the separator can be obtained.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view along the axis O direction of a gas sensor (sensor) 10 according to an embodiment of the present invention, FIG. 2 is a perspective view of a separator 50, FIG. 3 is a cross-sectional view along line A-A of FIG. 2, and FIG. 4 is a perspective view of a connection terminal 71.

[0015] As shown in FIG. 1, the gas sensor 10 includes a sensor element 20 that measures a specific gas component in the gas to be measured, a protector 30 that protects the tip 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 used, for example, to measure gas components such as NOx and O2 contained in the gas to be measured (exhaust gas) by being attached to an exhaust pipe of a vehicle.

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

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

[0018] As shown in Fig. 1, the protector 30 is arranged 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 has an inner gas introduction hole 31a for introducing the gas to be measured into the tip of the sensor element 20. The outer protector 32 is formed in a bottomed cylindrical shape and has an outer gas introduction hole 32a for introducing the gas to be measured on the side surface. The inner protector 31 and the outer protector 32 are made of a metal such as SUS, for example.

[0019] The sensor assembly 40 includes a metal main fitting 41, a cylindrical inner cylinder 42 and outer cylinder 46 welded and fixed to the main fitting 41, and a separator 50 connected to the rear end of the sensor element 20. The main fitting 41 is attached to, for example, the exhaust pipe of a vehicle by a male screw portion 41a. Inside the inner cylinder 42, a plurality of ceramic sleeves 43a to 43c and powder filling layers 44a, 44b such as talc filled between the ceramic sleeves 43a, 43b and between the ceramic sleeves 43b, 43c are enclosed, and these are sandwiched and sealed between a metal ring 45 and the inner wall of the main fitting 41.

[0020] The outer cylinder 46 covers the inner cylinder 42, the sensor element 20, and the separator 50. Also, an opening on the rear end side of the outer cylinder 46 is closed by a rubber grommet 47. And a lead wire 48 is connected to a connection portion 71g (Fig. 4) on the rear end side of the terminal fitting 71 by means such as crimping. The lead wire 48 is drawn out to the outside from the rear end of the grommet 47 through a grommet hole 47a that penetrates the grommet 47 in the direction of the axis O. Note that the connection portion 71g of the terminal fitting 71 and the lead wire 48 are inserted into the grommet hole 47a.

[0021] Next, the separator 50 will be described. As shown in FIG. 2, the separator 50 includes a first member 51a and a second member 51b made of ceramics such as an alumina sintered body, and a metal clamp 90 that sandwiches and fixes the first member 51a and the second member 51b. And a terminal fitting 71 is held by the first member 51a or the second member 51b, and the terminal fitting 71 is arranged to face and contact the electrode pads 21a and 21b of the sensor element 20 one-to-one.

[0022] The first member 51a and the second member 51b each hold four terminal fittings 71 arranged side by side in the width direction orthogonal to the longitudinal direction of the terminal fitting 71 (= the direction of the axis O). Since the first member 51a and the second member 51b have the same box shape, the same reference numerals will be used to describe the same components. Also, the first member 51a and the second member 51b are collectively referred to as the housing 51. The housing 51 includes a housing 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 upright portion 71d at the center of the terminal fitting 71 is inserted, and locking portions 54 formed in each insertion hole 53 for locking the terminal fitting 71.

[0023] Further, the housing 51 includes a convex portion 55 on one side surface in the width direction with the sensor element 20 interposed therebetween, and regulating members 56 and 57 for regulating the distance in the thickness direction between the first member 51a and the second member 51b on the other side surface (see FIG. 2). The convex portion 55 is inserted into a recess between the regulating members 56 and 57 of the opposing housing 51, thereby regulating the relative position in the thickness direction between the first member 51a and the second member 51b.

[0024] As shown in FIG. 4, the terminal fitting 71 is a metal member held by the housing 51 at a position facing the electrode pads 21a and 21b of the sensor element 20 one-to-one. It has a tip portion 71a locked in the locking groove 52 due to its curved shape, a protruding portion 71b curved and protruding toward the sensor element 20, a contact portion 71c curved and protruding toward the sensor element 20 to contact the electrode pads 21a and 21b, an upright portion 71d inserted into the insertion hole 53, a curved portion 71f drawn out to the outside of the separator 50, and a connection portion 71g that crimps and holds a plurality of core wires 48a of the lead wire 48 outside the separator 50. Furthermore, although it will be described in detail later, a part of the curved portion 71f has a protruding portion 75 that is cut up and protrudes on the side opposite to the sensor element 20.

[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 at a position closer to the connection portion 71g than the protruding portion 71b. Both the protruding portion 71b and the contact portion 71c are formed to be elastically deformable. The upright portion 71d has a locking portion 71e locked to the locking portion 54 due to its curved shape. Note that the contact portion 71c of the terminal fitting 71 held by the first member 51a contacts the electrode pad 21a of the sensor element 20 one-to-one, and the contact portion 71c of the terminal fitting 71 held by the second member 51b contacts the electrode 21b of the sensor element 20 one-to-one (FIG. 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] As shown in Fig. 2, the clamp 90 is formed by bending a plate-shaped metal and has an elastic force capable of sandwiching the first member 51a and the second member 51b and pressing them in a direction approaching each other. When the first member 51a and the second member 51b are sandwiched by this elastic force, the regulating members 56 and 57 of the first member 51a come into contact with the second member 51b, and the regulating members 56 and 57 of the second member 51b come into contact with the first member 51a. Thereby, the distance between the first member 51a and the second member 51b is fixed.

[0027] Further, when the clamp 90 sandwiches the first member 51a and the second member 51b with the sensor element 20 and the terminal fitting 71 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 and 21b of the sensor element 20, the protruding portions 71b and the contact portion 71c are elastically deformed by the pressing force from the clamp 90 to sandwich and fix the sensor element 20. At this time, by elastically deforming and pressing the protruding portions 71b and the contact portion 71c, the sensor element 20 can be reliably sandwiched and fixed. Further, since the contact portion 71c is elastically deformed, the electrical contact between the contact portion 71c and the electrode pads 21a and 21b can be more reliably maintained.

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

[0029] Furthermore, the accommodating portion 50h has a tapered surface 50s that expands in diameter in a direction (the vertical direction in FIG. 3) perpendicular to the two main surfaces 20m1 and 20m2 of the sensor element 20 as it faces the rear end-facing surface of the separator 50. Note that "in a direction perpendicular to the main surfaces 20m1 and 20m2" means that it only needs to have a direction component perpendicular to the main surfaces 20m1 and 20m2, and includes cases where the degree of diameter expansion of the tapered surface 50s varies depending on the location. For example, cases where the tapered surface 50s is not parallel to the main surfaces 20m1 and 20m2, cases where the tapered surface 50s is a curved surface, cases where the tapered surface 50s itself is parallel to the main surfaces 20m1 and 20m2 but the leading edge or trailing edge of the tapered surface 50s is not parallel to the main surfaces 20m1 and 20m2 (cases where the lengths and positions of the line segments when the tapered surface 50s is cut along the main surfaces 20m1 and 20m2 are different), etc.

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

[0031] Therefore, as described above, a protrusion 75 that protrudes toward the tapered surface 50s (on the side opposite to the sensor element 20) is provided on the terminal fitting 71, and the protrusion 75 is brought into contact with the tapered surface 50s. As a result, the terminal fitting 71 is fixed to the separator 50 via the tapered surface 50s, so the vibration of the terminal fitting 71 is suppressed and the breakage of the terminal fitting 71 can be suppressed.

[0032] As shown in FIG. 4, in this example, the central portion in the width direction on the tip side of the curved portion 71f is cut and raised so that the tip side becomes a free end to form the protrusion 75. The protrusion 75 is substantially rectangular and has a tongue piece portion that extends toward the tip side in the direction of the axis O. Thus, when the protrusion 75 is a tongue piece portion extending toward the tip side in the direction of the axis O, the tip (free end) of the protrusion 75 forms an angle with the tapered surface 50s and is likely to come into contact therewith, and the tip of the protrusion 75 becomes flat and is likely to be locked to the tapered surface 50s. As a result, the terminal fitting 71 is more securely fixed to the separator 50 via the tapered surface 50s. On the other hand, when the protrusion 75 extends toward the rear end side in the direction of the axis O (that is, the rear end side of the protrusion 75 is the free end), the tip (free end) of the protrusion 75 forms an angle that is close to parallel with the tapered surface 50s that widens toward the rear end side, making it difficult for the tip of the protrusion 75 to come into contact with the tapered surface 50s, and the locking state with the tapered surface 50s may be easily disengaged.

[0033] Note that the protrusion 75 may not be parallel to the tapered surface 50s and may extend obliquely with respect to the tapered surface 50s.

[0034] The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention extends to various modifications and equivalents included in the spirit and scope of the present invention. The shape, position of the protrusion, and the number of protrusions that one terminal has are not limited.

[0035] For example, as shown in FIG. 5, the plate surface 71s of the terminal fitting 71 faces the tapered surface 50s, and the protrusion 75B may be a plate piece portion folded back from at least one side surface of the terminal fitting 71 toward the tapered surface 50s. Note that in the example of FIG. 5, the protrusion 75B is a pair of members folded back on both side surfaces of the terminal fitting 71 and from the same position in the direction of the axis O.

[0036] Also, for example, as shown in FIG. 6, the protrusion 75C may be a bent portion obtained by bending the terminal fitting 71 so as to protrude toward the tapered surface 50s. Note that in the example of FIG. 6, the protrusion 75C has a shape that curves convexly toward the tapered surface 50s, but for example, it may have a shape that bends acutely (in a V shape) toward the tapered surface 50s.

[0037] Further, for example, as shown in FIG. 7, the protrusion 75D may be formed by fixing a separate member to a portion facing the tapered surface 50s of the terminal fitting 71. For example, in the example of FIG. 7, the protrusion 75D has a stud shape in which the tip of a round bar of metal such as stainless steel has a small-diameter portion 75p, and this stud (protrusion) 75D is tightly fitted and fixed in a mounting hole 71h opened in the plate surface facing the tapered surface of the terminal fitting 71.

[0038] In the examples of FIGS. 5 to 7, in the vicinity of the protrusions 75B to 75D, the terminal fitting 71 extends straight and the bent portion 71f is not provided.

[0039] The terminal fitting is not limited to a plate shape and may be a rod shape. Further, for example, a plate-shaped protrusion may be attached like a flag to a portion facing the tapered surface of a rod-shaped terminal fitting.

[0040] The separator 50 is not limited to a two-part box shape and may be a cylindrical shape such as a cylinder.

Explanation of Reference Numerals

[0041] 10 Gas sensor 20 Sensor element 20m1, 20m2 Main surfaces of the sensor element 21a, 21b Electrode pads 50 Separator 50h Accommodating portion 50s Tapered surface 71 Terminal fitting 75 Protrusion 75B Protrusion (plate piece portion) 75C Protrusion (bent portion) 75D Protrusion (separate member) O Axis

Claims

1. a plate-shaped sensor element extending in the axial direction and having an electrode pad on a main surface on the rear end side; a terminal metal fitting extending in the axial direction and electrically connected to the electrode pad; 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; A gas sensor comprising: the housing portion has a tapered surface that increases in diameter in a direction perpendicular to the main surface as it approaches a rear-facing surface of the separator, The terminal fitting has a protrusion protruding toward the tapered surface, The gas sensor is characterized in that the protrusion abuts against the tapered surface.

2. 2. The gas sensor according to claim 1, wherein the protrusion is a tongue portion extending toward a tip end in the axial direction.

3. The terminal metal fitting is plate-shaped, and a plate surface of the terminal metal fitting faces the tapered surface.

2. The gas sensor according to claim 1, wherein the protrusion is a plate portion folded back from at least one side surface of the terminal metal fitting toward the tapered surface.

4. 2. The gas sensor according to claim 1, wherein the protrusion is a bent portion of the terminal metal fitting that is bent so as to protrude toward the tapered surface.

5. 2. The gas sensor according to claim 1, wherein the protrusion is formed by fixing a separate member to a portion of the terminal metal fitting facing the tapered surface.

Images