JP6726604B2 - Gas sensor - Google Patents

Description

The present invention relates to a gas sensor used for measuring a gas concentration of a specific component contained in a gas to be measured.

In recent years, a urea SCR (selective catalytic reduction) system has been attracting attention as a technology for purifying nitrogen oxides (NOx) contained in exhaust gas discharged from an internal combustion engine such as a diesel engine. The urea SCR system purifies nitrogen oxides contained in exhaust gas by chemically reacting ammonia (NH ₃ ) and nitrogen oxides (NOx) to reduce the nitrogen oxides to nitrogen (N ₂ ). System.

In this urea SCR system, when the amount of ammonia supplied to the nitrogen oxides becomes excessive, unreacted ammonia may be released to the outside while being contained in the exhaust gas. In order to suppress such release of ammonia, a multi-gas sensor capable of measuring a plurality of types of gas concentrations including a sensor element that measures the concentration of ammonia contained in exhaust gas is used in a urea SCR system (for example, See Patent Document 1).
Further, a composite sensor element having two or more cells that respectively measure the NOx concentration and the air-fuel ratio is disclosed (for example, see Patent Document 2).
In order to electrically connect these sensor elements to an external circuit, the terminal fitting is elastically connected to the electrode pad arranged at the rear end of the sensor element, and the lead wire is drawn out from the terminal fitting.

JP, 2013-221931, A JP-A-2003-149202 (FIG. 3)

By the way, in the case of the above-mentioned multi (composite) gas sensor, since a plurality of sensor parts (cells) are provided in one sensor element, the number of electrode pads of each sensor part increases (for example, 8 in total), and these electrode pads are increased. It becomes difficult to dispose them at the rear end of the sensor element so as to be separated from each other. Therefore, for example, in the composite sensor element described in Patent Document 2, two stages of electrode pads are arranged apart from each other in the longitudinal direction of the element, and the electrode pads of each stage are arranged in a zigzag pattern in the width direction of the element, The electrode pads are arranged so that they do not overlap in either the longitudinal direction or the width direction.

On the other hand, as shown in FIG. 10, when the sensor element 1000 is downsized, the dimension of the element in the width direction also becomes smaller, so that the electrode pads 1202 and 1204 in each stage must be arranged in the width direction.
However, in this case, when the terminal fitting 1100 is connected to the electrode pad 1204 on the front end side from the rear end side, the folded-back portion 1102 of the terminal fitting 1100 is caught by the electrode pad 1202 on the rear end side, and the terminal fitting 1100 and the electrode pad 1202 are The conductive material may be rubbed and adhered between the electrode pads 1202 and 1204 to form the conductive portion SC. When the electrode pads 1202, 1204 are short-circuited via the conductive portion SC in this way, there arises a problem that the detection signal of the gas concentration from the sensor element 1000 cannot be accurately output or short-circuits.

The present invention has been made in order to solve the above problems, the insulation reliability between the electrode pads that are separated in the axial direction and at least part of which overlaps in the width direction is high, and the measurement accuracy of the gas concentration and An object is to provide a gas sensor having excellent safety.

To solve the above problems, a gas sensor of the present invention, a plate-like shape extending in the axial direction, and the sensor element having two or more electrode pads the axial position on the plate surface of the rear end spaced apart, the In a gas sensor including two or more terminal fittings that are electrically connected to the electrode pads, the two electrode pads that are adjacent to each other without overlapping the axial positions are provided in a width direction perpendicular to the axial direction . The positions are overlapped at least at a part , the terminal fitting is folded back from the front end toward the rear end side, and has a folding back portion elastically connected to the electrode pad at a contact connecting portion, and is adjacent in the axial direction. Of the two electrode pads, when the terminal metal fitting on the tip side that contacts the electrode pad on the tip side is viewed from the width direction, the contour between the contact connection portion and the tip of the folded portion is a first contour, and A second contour is formed by the rear end side of the tip side electrode pad and the plate surface and includes a corner portion on the rear end side of the electrode pad, and the terminal on the tip side is in contact with the corner portion. When the metal fitting is translated, no matter which position of the corner portion the first contour is in contact with, at least a part of the second contour exists on the plate surface side with respect to the first contour , and the axial direction. between two of the electrode pads position of the adjacent convex portions made of a ceramic is provided to protrude from the plate surface, the second contour is characterized Rukoto Do comprising said protrusions.

According to this gas sensor, at least a part of the second contour exists on the plate surface side of the first contour regardless of where the first contour contacts the corner, that is, between the first contour and the second contour. A gap is formed in. If this is done, the folded portion of the terminal fitting is temporarily caught by the electrode pad on the rear end side, the terminal metal and the electrode pad are rubbed, and the conductive material adheres between the electrode pads whose axial positions are separated from each other. Even if is formed, since the terminal fitting does not contact the gap, the conductive portion does not reach the gap. As a result, the conductive portion is divided between the electrode pads, and a short circuit between the electrode pads is prevented.
Therefore, it is possible to accurately output the gas concentration detection signal from the sensor element and suppress a short circuit. As a result, the insulation reliability between the electrodes separated from each other in the axial direction is high, and the gas concentration measurement accuracy and safety can be improved.
Further, according to this gas sensor, the first contour can be further distanced from the second contour by the convex portion, and a gap is surely formed in the portion sandwiched by the convex portion 1 and the electrode pad to thereby short-circuit between the electrodes. It can be prevented further.

The gas sensor of the present invention has a plate-like shape extending in the axial direction, and a sensor element having two or more electrode pads spaced apart from each other in the axial direction on the plate surface on the rear end side and the electrode pad electrically. In a gas sensor including two or more terminal fittings to be connected, the two electrode pads that are adjacent to each other without overlapping their axial positions overlap each other at least partially in their widthwise positions perpendicular to the axial direction. The terminal fitting is folded back from the front end toward the rear end side, and has a folded-back portion that elastically connects to the electrode pad at a contact connection portion, and the two axial positions of the two electrode pads are adjacent to each other. When the terminal fitting on the tip side, which is in contact with the electrode pad on the tip side, is viewed from the width direction, the contour between the contact connecting portion and the tip of the folded portion is defined as a first contour, and the tip-side electrode pad The second end is a contour formed by the rear end side and the plate surface and including the corner on the rear end side of the electrode pad, and the terminal metal fitting on the front end side is moved in parallel so as to be in contact with the corner. At this time, no matter which position of the corner portion the first contour is in contact with, at least a part of the second contour is present on the plate surface side with respect to the first contour , and the positions in the axial direction are adjacent to each other. between two of the electrode pad, the plate surface recess recessed are provided than, the second contour is characterized Rukoto Do comprising said recess.
According to this gas sensor, at least a part of the second contour exists on the plate surface side of the first contour regardless of where the first contour contacts the corner, that is, between the first contour and the second contour. A gap is formed in. If this is done, the folded portion of the terminal fitting is temporarily caught by the electrode pad on the rear end side, the terminal metal and the electrode pad are rubbed, and the conductive material adheres between the electrode pads whose axial positions are separated from each other. Even if is formed, since the terminal fitting does not contact the gap, the conductive portion does not reach the gap. As a result, the conductive portion is divided between the electrode pads, and a short circuit between the electrode pads is prevented.
Therefore, it is possible to accurately output the gas concentration detection signal from the sensor element and suppress a short circuit. As a result, the insulation reliability between the electrodes separated in the axial direction is high, and the measurement accuracy and safety of the gas concentration can be improved.
Further, according to this gas sensor, the first contour can be further distanced from the second contour by the concave portion, and a gap can be surely formed at a portion sandwiched between the concave portion and the electrode pad to further shorten the short circuit between the electrode pads. It can be prevented.

In the gas sensor of the present invention, the sensor element may be a multi-sensor element section having two or more sensor sections that detect different gas components in the gas to be measured.
According to this gas sensor, since the electrode pads are closer to each other in the axial direction, the present invention which prevents a short circuit between the electrode pads is further effective.

In the gas sensor of the present invention, two electrode pads may be arranged in the axial direction and two electrodes may be arranged in the width direction on at least one surface of the plate surface of the sensor element.
According to this gas sensor, at least four electrode pads existing on one surface are closer to each other in the axial direction, so that the present invention for preventing a short circuit between the electrode pads is further effective.

According to the present invention, it is possible to obtain a gas sensor that has high insulation reliability between electrode pads that are separated in the axial direction and at least partially overlap in the width direction, and that has excellent gas concentration measurement accuracy and safety.

It is sectional drawing which follows the axial direction of the multi gas sensor which concerns on embodiment of this invention. It is a block diagram which shows the structure of a multi-gas sensor and a gas sensor control apparatus. It is sectional drawing which follows the width direction of a 1st ammonia sensor part and a 2nd ammonia sensor part. It is the figure seen from the thickness direction of the rear end part of a multi-sensor element part. It is the figure seen from the width direction of the rear end part of a multi-sensor element part. It is a figure which shows the state which translated the 1st outline of a terminal metal fitting, when it sees from the width direction of the rear end part of a multi-sensor element part. It is a figure which shows the state which the electroconductive material of a terminal metal fitting or an electrode pad adhered between electrode pads, and formed the electroconductive part. It is a figure which shows the positional relationship of the 1st outline and 1st outline seen from the width direction of the rear end part of a multi-sensor element part, when a convex part is provided between two electrode pads adjacent to an axial direction. It is a figure which shows the positional relationship of the 1st outline and the 1st outline seen from the width direction of the rear end part of a multi-sensor element part, when a recessed part is provided between two electrode pads adjacent in the axial direction. FIG. 10 is a diagram showing a state in which a conventional gas sensor is short-circuited between electrode pads that are separated in the axial direction and overlap in the width direction.

Hereinafter, a multi-gas sensor according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. 1 is a cross-sectional view of the multi-gas sensor along the direction of the axis O (longitudinal direction), FIG. 2 is a block diagram illustrating the configuration of the multi-gas sensor device, and FIG. 3 is a configuration of the first ammonia sensor unit and the second ammonia sensor unit. It is sectional drawing which follows the width direction shown.
The multi-gas sensor 200A of the present embodiment and the multi-gas sensor device 400 including the same are used in a urea SCR system that purifies nitrogen oxides (NOx) contained in exhaust gas (gas to be measured) discharged from a diesel engine. Is. More specifically, the concentrations of nitric oxide (NO), nitrogen dioxide (NO ₂ ) and ammonia contained in the exhaust gas after reacting NOx contained in the exhaust gas with ammonia (urea) are measured. It is a thing.
The engine to which the multi-gas sensor 200A (multi-gas sensor device 400) of the present embodiment is applied may be the above-described diesel engine or may be applied to a gasoline engine, and the engine type is particularly limited. Not a thing.

As shown in FIG. 1, the multi-gas sensor 200A is an assembly in which a multi-sensor element unit 100A that detects an ammonia concentration and a NOx concentration is assembled. The multi-gas sensor 200A includes a plate-shaped multi-sensor element portion 100A extending in the axial direction, a tubular metal shell 138 having a screw portion 139 for fixing to an exhaust pipe formed on the outer surface, and a multi-sensor element portion 100A. The cylindrical ceramic sleeve 106 arranged so as to surround the radial periphery thereof and the inner wall surface of the contact insertion hole 168 penetrating in the axial direction are arranged so as to surround the periphery of the rear end portion of the multi-sensor element portion 100A. An insulating contact member 166 and a plurality of (only two in FIG. 1) terminal fittings 110 arranged between the multi-sensor element portion 100A and the insulating contact portion 166 are provided.
The multi-gas sensor 200A and the multi-sensor element unit 100A correspond to the "gas sensor" and the "sensor element" in the claims, respectively.

The metallic shell 138 has a through hole 154 penetrating in the direction of the axis O, and is formed in a substantially tubular shape having a shelf portion 152 protruding radially inward of the through hole 154. Further, the metallic shell 138 is arranged such that the front end side of the multi-sensor element portion 100A is arranged outside the front end side of the through hole 154 and the plurality of electrode pads 80 (see FIG. 4) are arranged outside the rear end side of the through hole 154. The multi-sensor element portion 100A is held in the through hole 154. Further, the shelf portion 152 is formed as an inward taper surface having an inclination with respect to a plane perpendicular to the axial direction.
Note that, for simplification, the electrode pads on the front surface and the back surface of the multi-sensor element portion 100A are represented by reference numeral 80 in FIG. 1, but as shown in FIG. 4, the electrode pad 80 is a NOx sensor portion described later. A plurality of electrodes are formed according to the number of electrodes and the like of 30A and the first and second ammonia sensor portions 42x and 42y.

In addition, inside the through hole 154 of the metal shell 138, an annular ceramic holder 151, a powder filling layer 153 (hereinafter, also referred to as a talc ring 153), which surrounds the radial circumference of the multi-sensor element portion 100A, and the above-mentioned. Ceramic sleeves 106 are laminated in this order from the front end side to the rear end side. Further, a caulking packing 157 is arranged between the ceramic sleeve 106 and the rear end portion 140 of the metal shell 138, and a talc ring 153 is provided between the ceramic holder 151 and the shelf portion 152 of the metal shell 138. A metal holder (not shown) for holding the ceramic holder 151 is arranged. The rear end portion 140 of the metal shell 138 is caulked so as to press the ceramic sleeve 106 toward the tip side via the caulking packing 157.

On the other hand, on the outer periphery of the metal shell 138 on the tip side (downward in FIG. 1), a double external protector 142 made of metal (for example, stainless steel) having a plurality of holes while covering the protruding portion of the multi-sensor element portion 100A. The inner protector 143 is attached by welding or the like.

An outer cylinder 144 is fixed to the outer periphery of the metal shell 138 on the rear end side. In addition, a plurality of lead wires 146 (four in FIG. 1) electrically connected to the electrode pads 80 of the multi-sensor element portion 100A are provided in the opening on the rear end side (upper side in FIG. 1) of the outer cylinder 144. Grommet 150 in which a lead wire insertion hole 161 for inserting (only) is formed, and the second insulating contact portion 170 are arranged in this order from the rear end side.

An insulating contact member 166 is disposed on the rear end side (upper side in FIG. 1) of the multi-sensor element portion 100A protruding from the rear end portion 140 of the metal shell 138. The insulating contact member 166 is arranged around the electrode pad 80 formed on the front and back surfaces on the rear end side of the multi-sensor element portion 100A. The insulating contact member 166 is formed in a tubular shape having a contact insertion hole 168 penetrating in the axial direction, and is provided with a flange portion 167 protruding radially outward from the outer surface. The insulating contact member 166 is arranged inside the outer cylinder 144 by the flange 167 contacting the outer cylinder 144 via the holding member 169. Then, the terminal fitting 110 on the insulating contact member 166 side and the electrode pad 80 of the multi-sensor element portion 100A are electrically connected to each other and are electrically connected to the outside by the lead wire 146.

FIG. 2 is a block diagram showing the configuration of the multi-gas sensor device 400 according to the embodiment of the present invention. In FIG. 2, for convenience of description, only the cross section along the axis O direction of the multi-sensor element portion 100A housed in the multi-gas sensor 200A is shown.
The multi-gas sensor device 400 includes a control device (controller) 300 and a multi-gas sensor 200A (multi-sensor element unit 100A) connected to the control device 300. The control device 300 is mounted on a vehicle including an internal combustion engine (engine) not shown, and the control device 300 is electrically connected to the ECU 220. The end of the lead wire 146 extending from the multi-gas sensor 200A is connected to a connector, and this connector is electrically connected to the connector on the control device 300 side.

Next, the configuration of the multi-sensor element unit 100A will be described. The multi-sensor element unit 100A includes a NO _x sensor unit 30A having the same configuration as a known NO _x sensor, a first ammonia sensor unit 42x and a second ammonia sensor unit 42y that are two ammonia sensor units, and As will be described later, the first ammonia sensor portion 42x and the second ammonia sensor portion 42y are formed on the outer surface of the NO _x sensor portion 30A.

First, the NO _x sensor unit 30A includes the insulating layer 23e, the first solid electrolyte body 2a, the insulating layer 23d, the third solid electrolyte body 6a, the insulating layer 23c, the second solid electrolyte body 4a, and the insulating layers 23b and 23a. It has a structure in which layers are sequentially stacked. A first measurement chamber S1 is defined between the first solid electrolyte body 2a and the third solid electrolyte body 6a, and a first diffusion resistor 8a is arranged at the left end (inlet) of the first measurement chamber S1. Exhaust gas is introduced from the outside. A protective layer 9 made of a porous material is arranged outside the first diffusion resistor 8a.
A second diffusion resistor 8b is arranged at an end of the first measurement chamber S1 opposite to the inlet, and communicates with the first measurement chamber S1 on the right side of the first measurement chamber S1 via the second diffusion resistor 8b. A second measurement chamber (corresponding to the “NO _x measurement chamber” of the present invention) S2 is defined. The second measurement chamber S2 is formed between the first solid electrolyte body 2a and the second solid electrolyte body 4a by penetrating the third solid electrolyte body 6a.

A long plate-shaped heat generating resistor 21 extending along the axis O direction of the multi-sensor element portion 100A is embedded between the insulating layers 23b and 23a. The heating resistor 21 is provided with a heating portion on the tip side in the axis O direction, and a pair of lead portions from the heating portion toward the rear end side in the axial direction. This heater is used to raise the temperature of the gas sensor to the activation temperature, enhance the conductivity of oxygen ions in the solid electrolyte body, and stabilize the operation.

The first pumping cell 2 includes a first solid electrolyte body 2a mainly composed of zirconia having oxygen ion conductivity, an inner first pumping electrode 2b arranged so as to sandwich the same, and an outer first pumping electrode serving as a counter electrode. 2c, the inner first pumping electrode 2b faces the first measurement chamber S1. Both the inner first pumping electrode 2b and the outer first pumping electrode 2c are mainly made of platinum, and the surface of the inner first pumping electrode 2b is covered with a protective layer 11 made of a porous body.
Further, the insulating layer 23e corresponding to the upper surface of the outer first pumping electrode 2c is hollowed out and filled with the porous body 13, and the outer first pumping electrode 2c is communicated with the outside so that gas (oxygen) can flow in and out. There is.

The oxygen concentration detection cell 6 includes a third solid electrolyte body 6a mainly composed of zirconia, and a detection electrode 6b and a reference electrode 6c arranged so as to sandwich the third solid electrolyte body 6a. The detection electrode 6b is the inner first pumping electrode 2b. It faces the first measurement chamber S1 on the further downstream side. Both the detection electrode 6b and the reference electrode 6c are mainly made of platinum.
The insulating layer 23c is cut out so that the reference electrode 6c in contact with the third solid electrolyte body 6a is arranged inside, and the cutout portion is filled with a porous body to form the reference oxygen chamber 15. .. Then, the Icp supply circuit 54 is used in the oxygen concentration detection cell 6 to flow a weak constant current in advance to send oxygen from the first measurement chamber S1 into the reference oxygen chamber 15 to be used as the oxygen reference.

The second pumping cell 4 includes a second solid electrolyte body 4a mainly composed of zirconia, an inner second pumping electrode 4b and a counter electrode arranged on the surface of the second solid electrolyte body 4a facing the second measurement chamber S2. And a second pumping counter electrode 4c. The inner second pumping electrode 4b and the second pumping counter electrode 4c are mainly made of platinum.
The second pumping counter electrode 4c is arranged in the cutout portion of the insulating layer 23c on the second solid electrolyte body 4a, and faces the reference oxygen chamber 15 so as to face the reference electrode 6c.
The inner first pumping electrode 2b, the detection electrode 6b, and the inner second pumping electrode 4b are each connected to the reference potential.

Next, the first ammonia sensor unit 42x and the second ammonia sensor unit 42y, which are two ammonia sensor units (cells), will be described.
As shown in FIG. 3, the multi-sensor element portion 100A has a first ammonia sensor portion 42x and a second ammonia sensor portion 42y that are separated from each other in the width direction.

The first ammonia sensor portion 42x and the second ammonia sensor portion 42y are formed on the insulating layer 23a that forms the outer surface (lower surface) of the NO _x sensor portion 30A. More specifically, in the first ammonia sensor section 42x, the first reference electrode 42ax is formed on the insulating layer 23a, and the first solid electrolyte body 42dx is formed on the surface of the first reference electrode 42ax. Further, the first detection electrode 42bx is formed on the surface of the first solid electrolyte body 42dx. Then, the concentration of ammonia in the gas to be measured is detected by a change in electromotive force between the first reference electrode 42ax and the first detection electrode 42bx.
Similarly, in the second ammonia sensor portion 42y, the second reference electrode 42ay is formed on the insulating layer 23a, and the second solid electrolyte body 42dy is formed on the surface of the second reference electrode 42ay. Further, the second detection electrode 42by is formed on the surface of the second solid electrolyte body 42dy.

The first detection electrode 42bx and the second detection electrode 42by can be formed from a material containing Au as a main component (for example, 70 mass% or more) and Pt or Pd. The first reference electrode 42ax and the second reference electrode 42ay can be formed of Pt alone or a material containing Pt as a main component (for example, 70 mass% or more). The first detection electrode 42bx and the second detection electrode 42by are electrodes in which ammonia gas is difficult to burn on the electrode surface. Ammonia reacts with oxygen ions (electrode reaction) at the three-phase interface described below, and the concentration of ammonia is detected.
The first solid electrolyte body 42dx and the second solid electrolyte body 42dy are made of, for example, partially stabilized zirconia (YSZ).

Further, the first ammonia sensor portion 42x and the second ammonia sensor portion 42y are integrally covered with the protective layer 23g made of a porous material.
The protective layer 23g prevents the poisoning substance from adhering to the first sensing electrode 42bx and the second sensing electrode 42by, and protects the measured gas flowing into the first ammonia sensor part 42x and the second ammonia sensor part 42y from the outside. It adjusts the diffusion rate.
The first ammonia sensor part 42x and the second ammonia sensor part 42y may be exposed without providing the protective layer 23g, and there is no particular limitation.

Next, returning to FIG. 2, an example of the configuration of the control device 300 will be described. The control device 300 includes an (analog) control circuit 59 and a microcomputer 60 on a circuit board. The microcomputer 60 controls the entire control device 300, includes a CPU (central processing unit) 61, a RAM 62, a ROM 63, a signal input/output unit 64, an A/D converter 65, and a clock (not shown), and is stored in advance in the ROM or the like. The executed program is executed by the CPU.
The control circuit 59 includes a reference voltage comparison circuit 51, an Ip1 drive circuit 52, a Vs detection circuit 53, an Icp supply circuit 54, an Ip2 detection circuit 55, a Vp2 application circuit 56, a heater drive circuit 57, and a first ammonia sensor, which will be described later in detail. A first electromotive force detection circuit 58a and a second electromotive force detection circuit 58b that detect electromotive force of the portion 42x and the second ammonia sensor portion 42y are provided.
The control circuit 59 controls the NO _x sensor unit 30A, NO _x sensor unit first pumping current flowing through 30A Ip1, and outputs to the microcomputer 60 detects the second pumping current Ip2.
The first electromotive force detection circuit 58a and the second electromotive force detection circuit 58b detect the ammonia concentration output (electromotive force) between the electrodes of the first ammonia sensor unit 42x and the second ammonia sensor unit 42y, and cause the microcomputer 60 to detect it. Output.

Specifically, the outer first pumping electrode 2c of the NO _x sensor unit 30A is connected to the Ip1 drive circuit 52, and the reference electrode 6c is connected in parallel to the Vs detection circuit 53 and the Icp supply circuit 54. The second pumping counter electrode 4c is connected in parallel with the Ip2 detection circuit 55 and the Vp2 application circuit 56. The heater circuit 57 is connected to the heater (specifically, the heating resistor 21).
The pair of electrodes 42ax and 42bx of the first ammonia sensor unit 42x are connected to the first electromotive force detection circuit 58a. Similarly, the pair of electrodes 42ay and 42by of the second ammonia sensor portion 42y are respectively connected to the second electromotive force detection circuit 58b.

Each of the circuits 51 to 57 has the following functions.
The Ip1 drive circuit 52 supplies the first pumping current Ip1 between the inner first pumping electrode 2b and the outer first pumping electrode 2c, and detects the first pumping current Ip1 at that time.
The Vs detection circuit 53 detects the voltage Vs between the detection electrode 6b and the reference electrode 6c, and outputs the detection result to the reference voltage comparison circuit 51.
The reference voltage comparison circuit 51 compares the reference voltage (for example, 425 mV) with the output (voltage Vs) of the Vs detection circuit 53, and outputs the comparison result to the Ip1 drive circuit 52. Then, the Ip1 drive circuit 52 controls the direction and the magnitude of the Ip1 current so that the voltage Vs becomes equal to the reference voltage, and the oxygen concentration in the first measurement chamber S1 is a predetermined value at which NO _x is not decomposed. Adjust to.
The Icp supply circuit 54 causes a weak current Icp to flow between the detection electrode 6b and the reference electrode 6c, sends oxygen from the first measurement chamber S1 into the reference oxygen chamber 15, and causes the reference electrode 6c to have a predetermined oxygen concentration as a reference. Expose to.
The Vp2 applying circuit 56 has a constant voltage Vp2 (for example, 450 mV) between the inner second pumping electrode 4b and the second pumping counter electrode 4c so that the NO _x gas in the measurement gas is decomposed into oxygen and N ₂ gas. Is applied to decompose NO _x into nitrogen and oxygen.

The Ip2 detection circuit 55 causes the second pumping cell 4 to discharge oxygen generated by decomposition of NO _x to the second pumping counter electrode 4c side from the second measurement chamber S2 via the second solid electrolyte body 4a. The flowing second pumping current Ip2 is detected.
At this time, since the second pumping current Ip2 and the NO _x concentration have a linear relationship, the Ip2 detection circuit 55 detects the second pumping current Ip2 to detect the NO _x concentration in the measured gas. You can

The first electromotive force detection circuit 58a detects the ammonia concentration output (electromotive force) between the pair of electrodes 42ax and 42bx, and the second electromotive force detection circuit 58b detects the ammonia concentration output (electromotive force) between the pair of electrodes 42ay and 42by. By detecting (electric power), the ammonia concentration in the gas to be measured can be detected as described later.
The reason for providing the two ammonia sensor parts, that is, the first ammonia sensor part 42x and the second ammonia sensor part 42y, is as follows. That is, since the ammonia sensor unit detects not only ammonia but also NO ₂ , if the NO ₂ gas other than ammonia is contained in the gas to be detected, the detection accuracy of ammonia will decrease. Therefore, if two ammonia sensor parts having different ratios of the sensitivity to ammonia and the sensitivity to NOx are respectively provided, values for two unknown concentrations of the ammonia gas and the NO ₂ gas are obtained from the two ammonia sensor parts with different sensitivities. Since it is detected, the concentrations of ammonia gas and NO ₂ can be calculated.

Next, the characteristic part of the multi-gas sensor of the present invention will be described with reference to FIGS. 4 is a view as seen from the thickness direction of the rear end portion of the multi-sensor element portion 100A, FIG. 5 is a view as seen from the width direction of the rear end portion of the multi-sensor element portion 100A, and FIG. FIG. 7 is a diagram showing a state in which the first contour C1 of the terminal fitting 110 is translated when viewed from the width direction of the end portion. FIG. 7 shows that the conductive material of the terminal fitting 111 or the electrode pad 82 is between the electrode pads 82, 81. It is a figure which shows the state which adhered and formed the conductive part SC.

As shown in FIG. 4 and FIG. 5, four electrode pads 81 and 82 are provided on the front and back plate surfaces 100s on the rear end side of the multi-sensor element portion 100A, respectively, spaced apart from each other in the axis O direction. Of these, the electrode pad 81 on the front end side and the electrode pad 82 on the rear end side are adjacent to each other in the axis O direction and are arranged to overlap each other in the width direction perpendicular to the axis O direction. The two electrode pads 81 and the two electrode pads 82 are arranged side by side in the width direction.

The terminal fitting 111 on the tip side that contacts the electrode pad 81 on the tip side extends in a strip shape in the direction of the axis O, and has a main body portion 111b, a folded-back portion 111a that is folded back from the front end of the main body portion 111b toward the rear end side, and the main body portion. And a crimping terminal portion (not shown) integrally connected to the rear end side of 111b.
The folding|returning part 111a is facing the electrode pad 81 side rather than the main-body part 111b, and the contact connection part 111p which protrudes most to the electrode pad 81 side among itself is elastically connected to the electrode pad 81. The folded-back portion 111a elastically bends in the radial direction to press the electrode pad 81.
Further, the crimp terminal portion is electrically connected to the lead wire by crimping and fixing a lead wire (not shown) from which the core wire is peeled off.

The rear-end-side terminal fitting 112, which is in contact with the rear-end-side electrode pad 82, also extends in the direction of the axis O in a strip shape, and has a main body 112b having a shape similar to that of the terminal fitting 111, and the main body 112b extends from the front end to the rear end. It includes a folded-back portion 112a that is folded back toward itself, and a crimp terminal portion (not shown) integrally connected to the rear end side of the main body portion 112b. The contact connection portion 112p of the folded-back portion 112a, which projects the most toward the electrode pad 82 side, is elastically connected to the electrode pad 82.
In addition, the two terminal fittings 112 on the rear end side are arranged inside the width direction of the multi-sensor element portion 100A, and the two terminal fittings 111 on the front end side are arranged outside each of the terminal fittings 112 on the rear side in the width direction. There is. Therefore, the terminal fitting 111 on the front end side is integrally connected to the body fitting 111b at a position offset outward from the folded-back portion 111a in the width direction so as not to interfere with the terminal fitting 112 on the rear end side.

Here, as shown in FIG. 5, when the terminal fitting 111 on the tip end side is viewed from the width direction, the contour between the contact connecting portion 111p and the tip 111af of the folded portion 111a is defined as a first contour C1, and the tip end side A contour formed by the rear end side of the electrode pad 81 and the plate surface 100s and including a corner 81c on the rear end side of the electrode pad 81 is referred to as a second contour C2.
At this time, as shown in FIG. 6, when the distal end side metal fitting 111 is moved in parallel as indicated by reference numeral 111x so as to be in contact with the corner 81c, the first contour C1 is in contact with any position of the corner 81c. Also, at least a part of the second contour C2 exists closer to the plate surface 100s than the first contour C1. That is, the gap V is formed between the first contour C1 and the second contour C2.

In this way, as shown in FIG. 7, the folded portion 111a of the terminal fitting 111 is tentatively caught by the electrode pad 82 on the rear end side, the terminal fitting 111 and the electrode pad 82 are rubbed, and the conductive material thereof becomes the electrode pads 82, 81. Even if the conductive part SC is formed by adhering between them, the terminal fitting 111 does not contact the gap V, so that the conductive part SC does not reach the gap V. As a result, the conductive portion SC is divided between the electrode pads 82 and 81, and a short circuit between the electrode pads 82 and 81 is prevented.
Therefore, it is possible to accurately output the gas concentration detection signal from the multi-sensor element unit 100A and suppress a short circuit. As a result, the insulation reliability between the electrode pads 82 and 81 separated in the direction of the axis O is high, and the gas concentration measurement accuracy and safety can be improved.
When the terminal fitting 111 on the front end side comes into contact with the electrode pad 81 from the rear end side through the electrode pad 82, a portion on the front end side with respect to the contact point connecting portion 111p rubs against the electrode pads 82 and 81, so that the contact point connecting portion 111p. The contour C1 of the portion closer to the tip side than that is defined.

Further, as shown in FIG. 8, a ceramic convex portion 100p protruding from the plate surface 100s is provided between the electrode pads 82 and 81 adjacent to each other in the direction of the axis O, and the second contour C2 forms the convex portion 100p. May be included.
By doing this, the first contour C1 of the terminal fitting 111 can be further distanced from the second contour C2 by the convex portion 100p, and the gap V is surely formed in the portion sandwiched between the convex portion 100p and the electrode pad 81. It is possible to further prevent a short circuit between the electrode pads 82 and 81.
The convex portion 100p can be formed by printing a paste of a ceramic material such as alumina on the unfired sheet of the multi-sensor element portion 100A and then firing the whole.

Further, as shown in FIG. 9, a recess 100r recessed from the plate surface 100s may be provided between the electrode pads 82 and 81 adjacent to each other in the direction of the axis O, and the second contour C2 may include the recess 100r.
With this configuration, the first contour C1 of the terminal fitting 111 can be further distanced from the second contour C2 by the recess 100r, and the gap V can be reliably formed at the portion sandwiched between the recess 100r and the electrode pad 81, so that the electrode pad can be formed. A short circuit between 82 and 81 can be further prevented.
Note that the recess 100r can be formed, for example, by stacking or printing partially cut sheets and then firing the whole when forming an unfired sheet of the multi-sensor element portion 100A.

It is needless to say that the present invention is not limited to the above-described embodiments and covers various modifications and equivalents included in the concept and scope of the present invention.
For example, the shape of the terminal fitting including the first contour and the shape of the second contour are not limited to the above embodiment. The number and arrangement of the electrode pads are not limited. Further, in the above embodiment, the two electrode pads adjacent to each other in the axial direction are completely overlapped in the width direction, but at least a part may be overlapped in the width direction.
Further, in the above-described embodiment, one convex portion or one concave portion is formed between the electrode pads 82 and 81 adjacent to each other in the axis O direction, but two or more convex portions and concave portions may be formed. Further, in the above embodiment, the front and back plate surfaces on the rear end side of the multi-sensor element portion each have four electrode pads spaced apart in the direction of the axis O, but there are four electrode pads on one surface instead of both surfaces. It may have an electrode pad.
Further, in the above embodiment, the multi-gas sensor is used, but the present invention is not limited to this, and various gas sensors such as a NOx sensor and an oxygen sensor may be used.

80, 81, 82 Electrode pad 81 Tip-side electrode pad 81c Tip-side electrode pad rear-end corners 110, 111, 112 Terminal fittings 111 Tip-side terminal fittings 111a, 112a Folding portion 111af Folding tip 111p , 112p contact connection part 100A sensor element (multi-sensor element part)
100s plate surface of sensor element 100p convex portion 100r concave portion 200A gas sensor (multi-gas sensor)
C1 1st contour C2 2nd contour O axis

Claims (4)

A sensor element having a plate shape extending in the axial direction and having two or more electrode pads on the plate surface on the rear end side with the axial positions being separated from each other;
A gas sensor including two or more terminal fittings electrically connected to the electrode pads, respectively,
Two of the electrode pads adjacent without overlapping the position of the axial direction, the position of the width direction perpendicular to the axial direction overlaps at least a portion,
The terminal metal fitting is folded back from the front end toward the rear end side, and has a folding back portion elastically connected to the electrode pad at a contact connection portion,
Of the two electrode pads adjacent to each other in the axial direction, when viewed from the width direction, the terminal metal fitting on the tip side in contact with the electrode pad on the tip side, the contour between the contact connection portion and the tip of the folded portion. As a first contour, and a contour formed by the rear end side of the electrode pad on the front end side and the plate surface and including a corner portion on the rear end side of the electrode pad is a second contour,
When the terminal metal fitting on the tip side is moved in parallel so as to be in contact with the corner portion, at least a part of the second contour is the first contour regardless of the position of the corner portion where the first contour is in contact. Exists on the plate surface side than
Between two of the electrode pads positioned in the axial direction are adjacent convex portions made of a ceramic is provided to protrude from the plate surface, the second contour and wherein Rukoto Do comprising said protrusions Gas sensor to do. A sensor element having a plate shape extending in the axial direction and having two or more electrode pads on the plate surface on the rear end side with the axial positions being separated from each other;
A gas sensor including two or more terminal fittings electrically connected to the electrode pads, respectively,
The two electrode pads that are adjacent to each other and do not overlap each other in the axial direction at least partially overlap each other in the width direction perpendicular to the axial direction,
The terminal metal fitting is folded back from the front end toward the rear end side, and has a folding back portion elastically connected to the electrode pad at a contact connection portion,
Between the contact connection portion and the tip of the folded portion, when the terminal metal fitting on the tip end side, which is in contact with the tip end side electrode pad, of the two electrode pads adjacent to each other in the axial direction is viewed from the width direction. Is defined as a first contour, and a contour formed by the rear end side of the tip side electrode pad and the plate surface and including a corner on the rear end side of the electrode pad is defined as a second contour,
When the terminal metal fitting on the tip side is moved in parallel so as to be in contact with the corner portion, at least a part of the second contour is the first contour regardless of the position of the corner portion where the first contour is in contact. Exists on the plate surface side than
A gas sensor characterized in that a recessed portion that is recessed from the plate surface is provided between two electrode pads that are adjacent to each other in the axial direction , and the second contour includes the recessed portion . The gas sensor according to claim 1 or 2 , wherein the sensor element is a multi-sensor element unit having two or more sensor units that detect different gas components in the gas to be measured . The gas sensor according to claim 1 , wherein two electrode pads are arranged in the axial direction and two in the width direction on at least one surface of the plate surface of the sensor element .

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