Gas sensor

Abstract

To provide a gas sensor in which breakage of a terminal metal fitting at the back end side of a separator is suppressed.SOLUTION: A gas sensor 10 includes: a plate-like sensor element 20 extending in the direction of an axial line O, the sensor element having electrode pads 21a and 21b in main surfaces 20m1 and 20m2 on a back end side; a terminal metal fitting 71 extending in the axial direction, the terminal metal fitting being electrically connected to the electrode pad; and a separator 50 having a storage part 50h penetrating in the axial direction and storing the back end side of the sensor element and the terminal metal fitting, the separator holding the terminal metal fitting. The storage part has a tapered surface 50s whose diameter becomes larger in a direction perpendicular to the main surface in a site closer to the back end facing surface of the separator. The back end of the sensor element is arranged in the inside of the tapered surface along the axial direction.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 and NO in exhaust gas of automobiles, etc. x There is known one having a plate-shaped sensor element using a solid electrolyte. 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 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 in the radially outer direction 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 electrode pads 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 pads, 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, wherein the housing portion has a tapered surface that expands in a direction perpendicular to the main surface toward the surface of the separator facing the rear end, and along the axial direction, the rear end of the sensor element is disposed inside the tapered surface.

[0007] According to this gas sensor, among the terminal fittings that are likely to swing near the tapered surface, the plate surface facing the sensor element side approaches or contacts the rear end side of the sensor element, so that the swing of the terminal fitting is reduced or suppressed, and the vibration of the terminal fitting is suppressed, thereby suppressing breakage of the terminal fitting.

[0008] In the gas sensor of the present invention, the terminal fitting may have a contact portion that is electrically connected to the electrode pad and a main body portion that extends from the rear end side of the contact portion to the tapered surface. According to this gas sensor, the contact portion and the main body portion are arranged substantially in a line, and the protrusion of the terminal fitting in the radial direction and the width direction is reduced, so that the housing portion 50h, and thus the separator 50, can be reduced in size and weight, and the vibration resistance is improved.

[0009] In the gas sensor of the present invention, the terminal fitting may contact the sensor element in a region that overlaps the tapered surface in the axial direction. According to this gas sensor, among the terminal fittings that are likely to vibrate near the tapered surface, the plate surface facing the sensor element side contacts and is held by the rear end side of the sensor element. Therefore, the vibration of the terminal fitting is further suppressed, and the breakage of the terminal fitting can be more effectively suppressed.

Advantages of the Invention

[0010] According to this invention, a gas sensor that suppresses the breakage of the terminal fitting on the rear end side of the separator can be obtained.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0012] 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 taken along line A-A of FIG. 2, and FIG. 4 is a perspective view of a connection terminal 71.

[0013] 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) when attached to the exhaust pipe of a vehicle.

[0014] The sensor element 20 is an elongated plate-like element extending in the direction of the axis O, and is formed by laminating a ceramic substrate or the like composed 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.

[0015] A plurality of electrode pads 21a, 21b (Fig. 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 spaced apart 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 spaced apart in the width direction of the sensor element 20. 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 the heater when the sensor element 20 has a heater.

[0016] As shown in Fig. 1, the protector 30 is arranged to surround the periphery of the tip of the sensor element 20. This 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 to 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.

[0017] The sensor assembly 40 includes a main metal fitting 41 made of metal, a cylindrical inner cylinder 42 and an outer cylinder 46 welded and fixed to the main metal 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 the metal ring 45 and the inner wall of the main fitting 41.

[0018] 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, and 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 through the grommet hole 47a.

[0019] 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 so as to be in one-to-one opposition and contact with the electrode pads 21a, 21b of the sensor element 20.

[0020] 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 given to the same components for description. Also, the first member 51a and the second member 51b are collectively referred to as a housing 51. The housing 51 includes a housing portion 50h that penetrates 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 a locking portion 54 formed in each insertion hole 53 for locking the terminal fitting 71.

[0021] Further, the housing 51 has a convex portion 55 on one side surface in the width direction with the sensor element 20 interposed therebetween, and restricting members 56 and 57 for restricting 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 depression between the restricting member 56 and the restricting member 57 of the opposing housing 51, thereby restricting the relative position in the thickness direction between the first member 51a and the second member 51b.

[0022] As shown in FIG. 4, the terminal fitting 71 is a metal member held by the housing 51 at positions that face the electrode pads 21a and 21b of the sensor element 20 one-to-one. It has a tip portion 71a locked to the locking groove 52 due to its curved shape, a protruding portion 71b that curves and protrudes toward the sensor element 20, a contact portion 71c that curves and protrudes 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. Also, among the terminal fitting 71, a portion from the rear end side of the contact portion 71c to the front end side of the connection portion 71g along the axis O direction is defined as the main body portion 71m. The main body portion 71m extends to the tapered surface 50s of the separator 50 described later.

[0023] 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 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 pads 21a of the sensor element 20 in a one-to-one correspondence, and the contact portion 71c of the terminal fitting 71 held by the second member 51b contacts the electrodes 21b of the sensor element 20 in a one-to-one correspondence (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.

[0024] 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 restricting members 56 and 57 of the first member 51a contact the second member 51b, and the restricting members 56 and 57 of the second member 51b contact the first member 51a. Thereby, the distance between the first member 51a and the second member 51b is fixed.

[0025] 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.

[0026] Next, the characteristic parts 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 is open 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 through hole that is open only at the front end and the rear end of the housing 51. Also, 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.

[0027] Furthermore, the housing 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 goes toward 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 (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.

[0028] 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 use of the gas sensor 10 or the like, the terminal fitting 71 is likely to swing and break in a direction (the V direction in FIG. 3) perpendicular to the main surfaces 20m1 and 20m2.

[0029] Therefore, as shown in FIG. 3, along the direction of the axis O, the rear end 20e of the sensor element 20 is arranged inside the tapered surface 50s (within the region R). As a result, among the terminal fittings 71 that are likely to swing in the V direction near the tapered surface 50s, the plate surface facing the sensor element 20 side comes close to or contacts the rear end side of the sensor element 20. Thus, the swing of the terminal fitting 71 in the V direction can be reduced or suppressed, and the vibration of the terminal fitting 71 is suppressed, thereby suppressing the breakage of the terminal fitting 71. In addition, when the rear end 20e of the sensor element 20 protrudes rearward of the rear end of the separator 50 (that is, outside the region R), there are problems such as the sensor element 20 itself becoming more likely to swing due to vibration or interference with the rear end 20e of the sensor element 20 when the grommet 47 is disposed on the rear end side of the separator 50.

[0030] In this example, the terminal fitting 71 has a contact portion 71c that is electrically connected to the electrode pads 21a and 21b, and a main body portion 71m that extends from the rear end side of the contact portion 71c to the tapered surface 50s. As a result, the contact portion 71c and the main body portion 71m are arranged substantially in a line, and the protrusion of the terminal fitting 71 in the radial direction and the width direction is reduced. Therefore, the accommodation portion 50h, and thus the separator 50, can be reduced in size and weight, and the vibration resistance is improved.

[0031] Note that the terminal fitting 71 preferably contacts the 20 sensor element in a region overlapping the tapered surface 50s in the direction of the axis O. As a result, among the terminal fittings 71 that are likely to swing in the V direction near the tapered surface 50s, the plate surface facing the sensor element 20 side contacts and is held by the rear end side of the sensor element 20. Therefore, the vibration of the terminal fitting 71 is further suppressed, and the breakage of the terminal fitting 71 can be more effectively suppressed.

[0032] 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 separator 50 is not limited to a two-part box shape, and may be a cylindrical shape such as a cylinder.

Description of Reference Numerals

[0033] 10 Gas sensor 20 Sensor element 20e Rear end of the sensor element 20m1, 20m2 Main surfaces of the sensor element 21a, 21b Electrode pads 50 Separator 50h Accommodation portion 50s Tapered surface 71 Terminal fitting 71c Contact portion 71m Body portion O Axis

Claims

1. A plate-shaped sensor element extending in the axial direction and having electrode pads on the main surface on the rear end side, A terminal fitting extending in the axial direction and electrically connected to the electrode pads, A separator having 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, A gas sensor comprising: The housing portion has a tapered surface that expands in diameter in a direction perpendicular to the main surface as it faces the rear end-facing surface of the separator, A gas sensor, wherein, along the axial direction, the rear end of the sensor element is disposed inside the tapered surface.

2. The gas sensor according to claim 1, wherein the terminal fitting has a contact portion that is electrically connected to the electrode pad and a main body portion that extends from the rear end side of the contact portion to the tapered surface.

3. The gas sensor according to claim 1 or 2, wherein the terminal fitting contacts the sensor element in a region overlapping the tapered surface in the axial direction.

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