JP2024026034A - gas sensor - Google Patents

Abstract

To provide a gas sensor capable of reducing displacement of a sensor element of a terminal metal fitting in a width direction and achieving reliable electrical connection between a terminal metal fitting and an electrode pad of the sensor element.SOLUTION: The gas sensor comprises: a sensor element 21 extending in an axial direction and including an electrode pad 24; a terminal metal fitting 75 connected to the electrode pad via a contact part C1; and a cylindrical separator 91 holding a rear end side of the terminal metal fitting. The terminal metal fitting includes a stopper part 75p extending in a direction intersecting the axial direction. The contact part and the stopper part are stored in the separator. In a pair of one electrode pad 751 and one terminal metal fitting 241 connected to the same, when viewed in the width direction of the sensor element, DA>DB is satisfied, where an end of the electrode pad closest to one inner surface 91si of the separator is defined as pad end, distance between the pad end and the contact part is defined as DA, and distance between one inner surface of the separator and a tip of the stopper part is defined as DB.SELECTED DRAWING: Figure 2

Description

The present invention relates to a gas sensor that includes a sensor element that detects the concentration of a gas to be detected and a terminal fitting.

2. Description of the Related Art Gas sensors that detect the concentration of oxygen and _NOx in exhaust gas from automobiles and the like are known to have a plate-shaped sensor element using a solid electrolyte.
In this type of gas sensor, a plurality of electrode pads (electrode terminal parts) are provided on the rear end side of the opposing main surfaces of a plate-shaped sensor element, and a bar-shaped (wire-shaped) terminal fitting is attached to each of the electrode pads. A device that is brought into contact with a sensor element to extract a sensor output signal from the sensor element to the outside or to supply power to a heater laminated on the sensor element is widely used (Patent Document 1).
This terminal fitting has a spring contact portion that contacts the electrode pad, and a spring holding portion that is folded back from the spring contact portion, and the spring holding portion is held by a separator (insulator).

JP 2017-116273 Publication

By the way, when viewed in the width direction of the sensor element, the spring contact portion of, for example, a rod-shaped terminal fitting is in almost point contact with the electrode pad. Therefore, if the spring contact portion swings in the width direction due to vibrations during assembly or use of the gas sensor, there is a risk that the connection with the electrode pad will be severed, reducing the reliability of the electrical connection.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a gas sensor that can reduce misalignment of a terminal fitting in the width direction of a sensor element and ensure electrical connection between the terminal fitting and an electrode pad of a sensor element. .

In order to solve the above problems, the gas sensor of the present invention includes a sensor element that extends in the axial direction and has an electrode pad on the rear end side outer surface, and a sensor element that extends in the axial direction and connects the electrode pad electrically through a contact portion. A gas sensor comprising a terminal fitting to be connected, and a cylindrical separator extending in the axial direction and holding a rear end side of the terminal fitting, wherein the terminal fitting extends in a direction intersecting the axial direction. The contact portion and the stopper portion are housed inside the separator, and in the pair of one of the electrode pads and one of the terminal fittings connected thereto, the contact portion and the stopper portion extend in the width direction of the sensor element. When viewed along the line, the end of the one electrode pad closest to one inner surface of the separator is defined as a pad end, the distance between the pad end and the contact portion is DA, and the one inner surface of the separator It is characterized in that DA>DB is satisfied, where DB is a distance from the stopper portion.

If the spring contact part swings in the width direction due to vibrations during assembly or use of the gas sensor, the stopper part will come into contact with the inner surface of the separator when the swing reaches its maximum, but the maximum swing width at this time is DB. becomes.
On the other hand, according to this gas sensor, the distance DA between the pad end and the contact portion is larger than DB. In this way, even if the deflection of the spring contact part reaches its maximum and the stopper part comes into contact with the inner surface, the contact part will still be located inside the pad end (in other words, the contact part will not be in contact with the electrode pad). ), it is possible to prevent the connection between the terminal fitting (particularly rod-shaped) and the electrode pad from being disconnected and the reliability of the electrical connection from decreasing.

In the gas sensor of the present invention, the stopper portion may be provided at a different position from the contact portion along the radial direction.
According to this gas sensor, the stopper part can be provided at a position different from the contact part depending on the inner surface shape of the separator, etc., and the degree of freedom in design is increased.

In the gas sensor of the present invention, the terminal fitting may be rod-shaped.
The present invention can be effectively applied to rod-shaped terminal fittings because they tend to shift in the width direction of the sensor element.

According to the present invention, it is possible to obtain a gas sensor that can reduce misalignment of the terminal fitting in the width direction of the sensor element and can reliably electrically connect the terminal fitting and the electrode pad of the sensor element.

FIG. 1 is a cross-sectional view of a gas sensor according to an embodiment of the present invention. 2 is a sectional view taken along line AA in FIG. 1. FIG. It is a perspective view of a terminal metal fitting. FIG. 7 is a perspective view of a modification of the terminal fitting. FIG. 3 is a cross-sectional view showing an example in which a stopper portion of a terminal fitting extends toward an inner surface on a far side among the inner surfaces of a separator in the width direction of a sensor element.

Embodiments of the present invention will be described in detail based on FIGS. 1 to 3. 1 is a sectional view of a gas sensor 1 according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a perspective view of a terminal fitting 75.

In FIG. 1, a gas sensor (NOx sensor) 1 includes a sensor element 21, a holder (ceramic holder) 30 having a through hole 32 extending in the direction of an axis O and through which the sensor element 21 is inserted, and a radial periphery of the ceramic holder 30. A housing 11 that surrounds the housing 11 and a separator 91 are provided.
A portion of the sensor element 21 near the tip where the detection portion 22 is formed protrudes from the ceramic holder 30 toward the tip.
A filling hole 30h that communicates with the through hole 32 is formed on the rear end side of the through hole 32 of the ceramic holder 30, and the sensor element 21 applies a sealing material (talc in this example) 41 to the filling hole 30h. By filling, the through hole 32 of the ceramic holder 30 is held airtight.
A separator 91 that holds a plurality of terminal fittings 75 and 76 is arranged on the rear end side of the ceramic holder 30. The separator 91 has a cylindrical shape with a bottom, and the rear end side is a bottom portion 91e.

As shown in FIG. 2, inside the side wall 91s of the separator 91, a plurality of holding grooves 91r for holding the terminal fittings 75, 76 are formed along the axis O direction.
The terminal fitting 75 has a bent portion 75s that extends outward in the radial direction, and an obliquely facing wall 91p is formed inside the side wall 91s of the separator 91 to engage with the bent portion 75s.
One terminal fitting 75 is arranged at each end of the sensor element 21 in the width direction, and one terminal fitting 76 is arranged at the center of the sensor element 21 in the width direction.

Further, a center hole 91h in which the sensor element 21 is disposed is formed in the center portion of the separator 91, and the plurality of holding grooves 91r communicate with the center hole 91h. The terminal fittings 75 and 76 are in contact with the electrode pad 24 (FIG. 1) of the sensor element 21 via the holding groove 91r and the center hole 91h.
Note that the bottom portion 91e of the separator 91 is formed with insertion holes (not shown) for the terminal fittings 75 and 76.

Returning to FIG. 1, a portion near the rear end of the sensor element 21 protrudes rearward from the ceramic holder 30 and the housing 11, and terminal fittings 75 and 76 are press-contacted to each electrode pad 24 formed at the portion near the rear end. connected.
Note that the terminal fitting 76 is arranged closer to the tip than the terminal fitting 75. Further, the electrode pad 24 that is electrically connected to the terminal fitting 76 via the contact portion C2 is also arranged closer to the tip side than the electrode pad 24 that is electrically connected to the terminal fitting 75 via the contact portion C1. There is.
On the other hand, the rear end sides of the terminal fittings 75 and 76 are connected to a lead wire 71, and the lead wire 71 is drawn out through a sealing material 85.
Further, a portion near the rear end of the sensor element 21 including the electrode pad 24 is covered by an outer cylinder 81. This will be explained in more detail below.

The sensor element 21 extends in the direction of the axis O, and has a detection section 22 on the tip side facing the measurement target (lower side in the figure) that includes a detection electrode or the like (not shown) and detects a specific gas component in the gas to be detected. It has a band-like (plate-like) shape. The cross section of the sensor element 21 has a rectangular shape with a constant size from front to back, and is formed as an elongated object mainly made of ceramic (solid electrolyte, etc.).
This sensor element 21 itself is the same as a conventionally known one, and a pair of detection electrodes constituting the detection part 22 are arranged at a portion near the tip of the solid electrolyte (member), and a pair of detection electrodes constituting the detection section 22 are arranged at a portion near the rear end of the solid electrolyte (member). , an electrode pad 24 for connecting a lead wire 71 for taking out a detection output is exposed.

Furthermore, in this example, a heater (not shown) is provided inside a portion of the sensor element 21 near the tip of the ceramic material laminated on the solid electrolyte (member), and a heater (not shown) is provided inside the portion near the rear end of the ceramic material layered on the solid electrolyte (member). , electrode pads 24 for connecting lead wires 71 for applying voltage to this heater are formed exposed.
Although not shown, these electrode pads 24 are formed in a vertically long rectangular shape, and three or two electrode terminals are arranged horizontally on the wide side (both sides) of the strip, for example, in a region near the rear end of the sensor element 21.
Note that the detection portion 22 of the sensor element 21 is coated with a porous protective layer (not shown) made of alumina, spinel, or the like.

The housing 11 has a cylindrical shape with concentrically different diameters at the front and rear, and has a small diameter at the tip side, and has a cylindrical annular part (hereinafter also referred to as a cylindrical part) 12 for externally fitting and fixing protectors 51 and 61, which will be described later. , and a screw 13 having a larger diameter than that and for fixing to the exhaust pipe of the engine is provided on the outer circumferential surface at the rear (upper side in the figure). A polygonal portion 14 into which the sensor 1 is screwed in is provided at the rear thereof. Further, a cylindrical part 15 is provided at the rear of the polygonal part 14, into which a protective cylinder (outer cylinder) 81 that covers the rear of the gas sensor 1 is fitted and welded. A small and thin cylindrical portion 16 for caulking is provided.
Note that this crimping cylindrical portion 16 is bent inward in FIG. 1 for the purpose of being crimped.

On the other hand, the housing 11 has an inner hole 18 penetrating in the direction of the axis O. The inner circumferential surface of the inner hole 18 has a tapered step 17 that tapers radially inward from the rear end side toward the front end side.

Inside the housing 11, a ceramic holder 30 made of insulating ceramic (for example, alumina) and formed into a generally short cylindrical shape is arranged. The ceramic holder 30 has a flange 31, and while the distal end surface of the flange 31 is locked to the stepped portion 17, the ceramic holder 30 is inserted into the cylindrical portion for caulking from the rear end side via a sealing material 42, a sleeve 43, etc. It is pressed at 16. Thereby, the ceramic holder 30 is positioned within the housing 11 and is fitted with a clearance.

On the other hand, in this embodiment, the tip end portion of the sensor element 21 has a two-layer structure and is covered with bottomed cylindrical protectors (protective covers) 51 and 61, each having a ventilation hole (hole). The rear ends of the protectors 51 and 61 are fitted onto the cylindrical portion 12 of the housing 11 and welded.

Further, as shown in FIG. 1, each electrode pad 24 formed near the rear end of the sensor element 21 has a terminal fitting provided at the tip of each lead wire 71 drawn out through a sealing material 85. 75 and 76 are pressed together due to their spring properties and are electrically connected. In the gas sensor 1 of this example, each of the terminal fittings 75 and 76 including the press-contact portion is provided in each holding groove 91r (FIG. 2) provided in an insulating separator 91 disposed within the outer cylinder 81. It is being Note that the separator 91 is locked to a disc spring 82 disposed inside the outer cylinder 81.

On the other hand, a protective outer cylinder 83 is fitted onto the outer surface of the rear end side of the outer cylinder 81, and a sealing material (for example, rubber) 85 is disposed inside the protective outer cylinder 83. Furthermore, a water-repellent ventilation filter 95 is interposed between the outer cylinder 81 and the protective outer cylinder 83.
Further, the lead wire 71 is passed through a sealing material 85 disposed inside the rear end of the outer cylinder 81 and pulled out to the outside, and the protective outer cylinder 83 is crimped to reduce its diameter to compress this sealing material 85. This keeps this area airtight.

Next, the terminal fitting 75 will be explained with reference to FIGS. 2 and 3.
In this example, the terminal fitting 75 is a polygonal rod-shaped terminal with a circular cross section or an aspect ratio of 1:1.0 to 1:1.2 (in this example, the cross section is circular), and is made of a metal wire. ing. However, the terminal metal fitting 75 is not limited to a rod shape, and may be, for example, a plate shape obtained by cutting out and pressing a metal plate.
Further, the terminal fitting 75 integrally includes a main body portion 75a extending in the direction of the axis O, and a spring contact portion 75b obtained by folding the tip of the main body portion 75a toward the sensor element 21 side. The spring contact portion 75b is brought into contact with the electrode pad 24 by elastically bending the spring contact portion 75b in the radial direction with respect to the main body portion 75a.
On the other hand, the rear end side of the main body portion 75a is connected to the lead wire 71 via a crimp terminal.

Here, as shown in FIGS. 2 and 3, the terminal fitting 75 includes a stopper portion 75p extending in a direction intersecting the axis O direction (in FIG. 2, a direction along the main surface of the sensor element 21). Specifically, the stopper portion 75p is formed by bending the tip portion, which is the open end of the spring contact portion 75b, into an L-shape in the direction along the main surface of the sensor element 21.
The contact portion C1 and the stopper portion 75p of the terminal fitting 75 are housed inside the separator 91.
The reason for specifying that the stopper part 75p "extends in a direction intersecting the axis O direction" is that if the stopper part 75p extends in the axis O direction, the stopper part 75p will extend in the direction crossing the axis O direction, as will be described later. This is because the stopper portion 75p (terminal fitting 75) cannot be prevented from shifting in the width direction of the sensor element 21 because it cannot come into contact with the inner surface 91si.

Here, consider a set of one electrode pad 241 and one terminal fitting 751 connected thereto. The electrode pad 241 is located on the leftmost side of the three electrode pads 24 on one main surface of the sensor element 21 (top surface side in FIG. 2). Further, the terminal fitting 751 is located on the left side of the two terminal fittings 75.
In the pair of electrode pad 241 and terminal fitting 751 described above, when viewed along the width direction of sensor element 21, the end of electrode pad 241 closest to one inner surface 91si of separator 91 (inner surface of side wall 91s) is When the distance between the pad end and the contact portion C1 is DA, and the distance between one inner surface 91si and the stopper portion 751p of the terminal fitting 751 is DB, DA>DB is satisfied. Here, one inner surface 91si is the left inner surface of the two inner surfaces of the separator 91 in the width direction of the sensor element 21, and is the inner surface on the side closer to the electrode pad 241 and the terminal fitting 751.

In this way, when the spring contact portion 75b swings in the width direction due to vibrations during assembly or use of the gas sensor 1, the stopper portion 751p comes into contact with the inner surface 91si when the swing reaches its maximum. The maximum swing width at that time is DB.
On the other hand, the distance DA between the pad end and the contact portion C1 is larger than DB. Therefore, even if the deflection of the spring contact portion 75b becomes maximum and the stopper portion 751p comes into contact with the inner surface 91si, the contact portion C1 is still located inside the pad end (that is, the contact portion C1 is located inside the electrode pad 241). This can prevent the terminal fitting 751 (particularly rod-shaped) from being disconnected from the electrode pad 241 and reducing the reliability of the electrical connection.

In this example, the terminal fitting 75 and the spring contact portion 75b are rod-shaped with a circular cross section, and the spring contact portion 75b makes almost point contact with the electrode pad 24, so the contact portion C1 is determined at one point. On the other hand, when the terminal fitting 75 has a rod shape or a plate shape with a polygonal cross section, the contact portion C1 may have a certain range of area in the direction along the main surface of the sensor element 21 (width direction). In this case, the midpoint of the area in the width direction is regarded as the contact portion C1.
Further, the contact portion C1 is determined by acquiring a CT image of the gas sensor 1 from the direction of the axis O, and viewing an image near the contact point between the spring contact portion 75b and the electrode pad 24 from a cross-sectional view as shown in FIG.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and can be implemented in various forms without departing from the gist of the present invention.

For example, in the above embodiment, the stopper part 75p is formed by bending the tip of the spring contact part 75b into an L shape, so that the stopper part 75p and the contact part C1 are on the same straight line when viewed in the radial direction. It was located.
However, as shown in FIG. 4, for example, the stopper portion 175p may be provided at a different position from the contact portion C1 along the radial direction of the terminal fitting 175. In addition, in the example of FIG. 4, specifically, the stopper part 175p bends the tip part forming the open end of the spring contact part 175b into an L-shape in the direction along the main surface of the sensor element 21, and A distal end portion of the stopper portion 175b is bulged toward the electrode pad 24 side, and this bulged portion is used as a contact portion C1.
Note that the main body portion 75a and the bent portion 75s in FIG. 2 are replaced with the main body portion 175a and the bent portion 175s.

However, the stopper parts 75p, 175p need to be arranged on the tip side (on the spring contact part 75b side) of the terminal fittings 75, 175 than the folded part between the main body part 75a and the spring contact part 75b. . This is because the tip side is more flexible than the folded portion and is more likely to shift in the width direction of the sensor element 21.

Further, in this example, stopper portions 75p are provided for the terminal fittings 75 disposed on both ends of the sensor element 21 in the width direction. This is because the terminal fittings 75 at the ends of the sensor element 21 swing more easily than the terminal fittings 76 at the center. However, the present invention is not limited to this, and a stopper portion may be provided on the terminal fitting 76 at the center of the sensor element 21 in the width direction.

Furthermore, as shown in FIG. 5, the stopper portion 752p of the terminal fitting 752 may extend toward the far side inner surface 91si of the two inner surfaces of the separator 91 in the width direction of the sensor element 21.
Specifically, in FIG. 5, consider a set of one electrode pad 242 and one terminal fitting 752 connected thereto. The electrode pad 242 is located on the rightmost side of the three electrode pads 24 on one main surface of the sensor element 21 (upper surface side in FIG. 2). Furthermore, the terminal fitting 752 is located on the right side of the two terminal fittings 75.
In the pair of electrode pad 242 and terminal fitting 752 described above, when viewed along the width direction of sensor element 21, the end of electrode pad 242 closest to one inner surface 91si of separator 91 (inner surface of side wall 91s) is When the distance between the pad end and the contact portion C1 is DA, and the distance between one inner surface 91si and the stopper portion 752p of the terminal fitting 752 is DB, DA>DB is satisfied. Here, one inner surface 91si is the left inner surface of the two inner surfaces of the separator 91 in the width direction of the sensor element 21, and is the inner surface on the side farthest from the electrode pad 242 and the terminal fitting 752.

In the example of FIG. 5 as well, since the distance DA between the pad end and the contact portion C1 is larger than DB, it is possible to prevent the connection between the terminal fitting 752 and the electrode pad 242 from being disconnected and reducing the reliability of the electrical connection. .
Note that the terminal fitting 752 in FIG. 5 has a stopper portion 752p that extends in the width direction of the sensor element 21 on the rear end side relative to the other terminal fittings 75 and 76.

When the terminal fitting is rod-shaped, it may have a circular or polygonal cross section with an aspect ratio of 1:1.0 to 1:1.2, for example.

Further, the gas sensor to which the present invention is applied is not limited to an oxygen sensor, and may be a gas sensor that detects other types of gas, such as a NOx sensor or a hydrogen sensor, as long as it includes a terminal fitting.
The sensor element is not limited to a plate type, but may be a cylindrical element.
In addition, in this example, the stopper part is integrated with the terminal fitting and is formed by bending a part of the terminal fitting, but for example, a separate plate-shaped stopper part can be welded to a predetermined position of the terminal fitting. A combined form may also be used.

1 Gas sensor 21 Sensor element 24 Electrode pad 241, 242 One electrode pad 75, 175 Terminal fitting 751, 752 One terminal fitting 75p, 175p Stopper portion 91 Separator 91si Inner surface of separator C1 Contact portion O Axis

Claims (3)

a sensor element extending in the axial direction and having an electrode pad on the outer surface on the rear end side;
a terminal fitting extending in the axial direction and electrically connected to the electrode pad via a contact portion;
a cylindrical separator extending in the axial direction and holding the rear end side of the terminal fitting;
A gas sensor comprising:
The terminal fitting includes a stopper portion extending in a direction intersecting the axial direction,
The contact portion and the stopper portion are housed inside the separator,
In a set of one of the electrode pads and one of the terminal metal fittings connected thereto, the end of the one of the electrode pads closest to one inner surface of the separator when viewed along the width direction of the sensor element. is a pad end, the distance between the pad end and the contact portion is DA, and the distance between the one inner surface of the separator and the tip of the stopper portion is DB, then DA>DB is satisfied. gas sensor. The gas sensor according to claim 1, wherein the stopper portion is provided at a different position from the contact portion. The gas sensor according to claim 1 or 2, wherein the terminal fitting is rod-shaped.

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