JP6933571B2 - Gas sensor - Google Patents

Description

The present disclosure relates to a gas sensor that detects a specific gas contained in a gas to be measured.

As in Patent Document 1, there is known a gas sensor that can detect the concentration of a specific gas contained in a gas to be measured by being heated to a predetermined activation temperature or higher. Such a gas sensor is provided with a heater so as to be in a state (that is, an activated state) in which a specific gas concentration can be detected at an early stage after the start-up.

Further, the internal resistance of the detection element formed by the solid electrolyte body has a property of changing in a form correlating with the temperature of the detection element. Therefore, the sensor control device that controls the detection element detects this internal resistance and drives the heater based on the temperature calculated using the detected internal resistance so that the detection element reaches the target temperature. Can be controlled to.

Japanese Unexamined Patent Publication No. 2012-18050

However, if the temperature of the detection element deviates from the target temperature due to a temperature change around the gas sensor, the accuracy of detecting the specific gas concentration by the gas sensor may decrease.
An object of the present disclosure is to suppress temperature fluctuations of a detection element.

One aspect of the present disclosure is a gas sensor including a detection element, a metal accommodating member, and a metal protector. The detection element is formed in a long shape and detects a specific gas contained in the gas to be measured. The accommodating member is formed in a tubular shape extending in the axial direction, and accommodates the detection element inside itself.

The protector is fixed to the accommodating member so as to have a vent through which the gas to be measured passes and to cover the tip of the detection element.
Further, the gas sensor of the present disclosure includes a space forming member which is formed in a tubular shape extending in the axial direction and is arranged so as to form an annular or endless annular space extending in the axial direction between the gas sensor and the accommodating member.

The detection element includes a detection cell having an oxygen ion conductive solid electrolyte body and a pair of electrodes formed on the solid electrolyte body, and a heater for heating the detection cell to a predetermined temperature. The detection cell is arranged inside the space. In addition, "arranged inside the space" means that it is arranged inside the space in the radial direction.

In the gas sensor of the present disclosure configured in this way, in the detection cell, the periphery of the detection cell is formed by a portion in which the space forming member, the space, and the metal accommodating member are laminated along the radial direction (hereinafter referred to as the laminated portion). Be covered.

Therefore, one path in which the temperature change around the gas sensor affects the temperature of the detection cell of the gas sensor is a path in which the heat around the gas sensor is conducted through the above-mentioned laminated portion to reach the detection cell.

In the laminated portion, a space is formed between the space forming member and the accommodating member. That is, a gas exists between the space forming member and the metal accommodating member. And gas has a lower thermal conductivity than metal. Therefore, in the gas sensor of the present disclosure, it becomes difficult for the heat around the gas sensor to be conducted to the detection cell through the laminated portion, and the temperature fluctuation of the detection cell can be suppressed. Then, by suppressing the temperature fluctuation of the detection cell, the temperature fluctuation of the detection element can be suppressed.

Further, in one aspect of the present disclosure, the space forming member may be arranged so as to cover at least a part of the outer peripheral surface of the accommodating member in a state where a space is formed between the space forming member and the accommodating member. Further, in one aspect of the present disclosure, the space forming member is arranged inside the accommodating member so as to cover at least a part of the inner peripheral surface of the accommodating member in a state where a space is formed between the space forming member and the accommodating member. You may do it.

Further, in one aspect of the present disclosure, the detection element includes a measurement chamber, a pumping cell, and an oxygen concentration detection cell, the oxygen concentration detection cell is a detection cell, and the pumping cell detects more than the oxygen concentration detection cell. It may be arranged on the tip end side of the element and inside the accommodating member. The gas to be measured is introduced into the measurement room. The pumping cell has an oxygen ion conductive first solid electrolyte body and a pair of pumping electrodes formed on the first solid electrolyte body, and is measured by passing a pumping current between the pair of pumping electrodes. The oxygen in the gas to be measured introduced into the chamber is pumped out or pumped out. The oxygen concentration detection cell has a second solid electrolyte body having oxygen ion conductivity, and a detection electrode and a reference electrode formed on the second solid electrolyte body, and the detection electrode is arranged so as to face the measurement chamber. An electromotive force is generated according to the difference in oxygen concentration between the detection electrode and the reference electrode.

In the gas sensor of the present disclosure configured in this way, since the pumping cell is arranged inside the accommodating member, the radial circumference of the pumping cell is covered with the accommodating member. Therefore, in the gas sensor of the present disclosure, the heat around the gas sensor can be suppressed from reaching the pumping cell by the accommodating member. Thereby, the gas sensor of the present disclosure can further suppress the temperature fluctuation of the detection element.

It is sectional drawing of NOx sensor 1. It is a figure which shows the schematic structure of the element main body part 31 and the sensor control device 170. It is sectional drawing around the detection part 31a in NOx sensor 1. FIG.

(First Embodiment)
Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.
The NOx sensor 1 of the present embodiment is mounted on a vehicle and detects nitrogen oxides (hereinafter referred to as NOx) contained in exhaust gas discharged from an internal combustion engine.

As shown in FIG. 1, the NOx sensor 1 includes a main metal fitting 2, a gas sensor element 3, a holding portion 4, a protector 5, an outer cylinder 6, a plurality of lead wires 7, and a plurality of connection terminals 8. A separation unit 9 and a grommet 10 are provided. In FIG. 1, the lower end side of the NOx sensor 1 is referred to as a front end side FE, and the upper end side of the NOx sensor 1 is referred to as a rear end side BE.

The main metal fitting 2 is a member formed in a tubular shape with a refractory metal such as stainless steel. The main metal fitting 2 includes a main body portion 21 and a mounting portion 22.
The main body 21 is a member formed in a cylindrical shape extending in the direction of the axis O of the NOx sensor 1 (hereinafter, referred to as the axis direction DA). Further, the main body portion 21 is provided with a through hole 21a penetrating along the axial direction DA. A step portion 21b that projects inward in the radial direction is formed on the inner peripheral wall of the through hole 21a.

The mounting portion 22 is a tubular member that surrounds the main body portion 21 so as to be rotatable with respect to the main body portion 21, and includes a hexagonal portion 22a and a screw portion 22b. A cylindrical space 23 extending in the axial direction DA is formed between the outer peripheral surface of the main body 21 and the inner peripheral surface of the mounting portion 22. The space 23 is an ended ring and is a space closed in the radial direction. More specifically, in the cross-sectional view of FIG. 1, the space 23 is uniformly formed with a predetermined thickness in the axial direction and the radial direction, respectively, but the inner peripheral surface of the mounting portion 22 and the outer peripheral surface of the main body portion 21 are different from each other. Some are in contact. Therefore, the space 23 has an endd ring (C-shape).

The hexagonal portion 22a extends outward from the outer circumference of the main body portion 21 along the radial direction, and the outer circumference is formed in a hexagonal plate shape. The hexagonal portion 22a is a portion for fitting a mounting tool such as a hexagonal wrench when the NOx sensor 1 is mounted on the exhaust pipe.

The screw portion 22b is located on the tip side FE from the hexagonal portion 22a, extends outward from the outer circumference of the main body portion 21 along the radial direction, and a male screw is formed on the outer circumference. The male screw has a shape that can be fitted into a mounting screw hole provided in the exhaust pipe for mounting the NOx sensor 1 on the exhaust pipe of the internal combustion engine.

The gas sensor element 3 includes an element main body 31 and a protective layer 32. The element main body 31 is formed in the shape of a long plate extending in the axial direction DA. Then, the detection that detects the concentration of the specific gas (NOx in this embodiment) contained in the gas to be measured (exhaust gas of the internal combustion engine in this embodiment) to which the gas sensor element 3 is exposed to the tip side FE of the element main body 31. Part 31a is formed. The protective layer 32 is made of porous alumina and is arranged on the tip end side FE of the element main body 31 so as to cover at least the detection unit 31a.

The holding portion 4 includes a ceramic holder 41, a talc powder 42, a ceramic sleeve 43, and a packing 44.
The ceramic holder 41 is a member made of alumina formed in a substantially cylindrical shape that can be accommodated in the through hole 21a of the main body 21 while being supported by the stepped portion 21b of the main body 21. The ceramic holder 41 is formed with a through hole penetrating along the axial direction DA, and the gas sensor element 3 is inserted into the through hole.

The talc powder 42 is filled in the through hole 21a of the main body 21 at the rear end side BE of the ceramic holder 41.
The ceramic sleeve 43 is a member made of alumina formed in a substantially cylindrical shape that can be accommodated in the through hole 21a of the main body 21. The ceramic sleeve 43 is formed with a through hole penetrating along the axial direction DA, and the gas sensor element 3 is inserted into the through hole. As a result, the ceramic sleeve 43 is housed in the through hole 21a of the main body 21 at the rear end side BE of the talc powder 42.

The packing 44 is a member formed in an annular shape that can be accommodated in the through hole 21a of the main body 21. The packing 44 is arranged between the ceramic sleeve 43 and the end portion 21c of the rear end side BE in the main body portion 21. The end portion 21c of the main body portion 21 is crimped so as to press the ceramic sleeve 43 against the tip end side FE via the packing 44. As a result, the talc powder 42 is compression-filled, and in the holding portion 4, the front end side FE of the gas sensor element 3 protrudes from the front end side FE of the ceramic holder 41, and the rear end side BE of the gas sensor element 3 is behind the main metal fitting 2. The gas sensor element 3 is held in a state of protruding from the end side BE.

The step portion 21b of the main body portion 21 is arranged on the rear end side BE from the screw portion 22b. Therefore, the holding portion 4 is housed in the through hole 21a of the main body portion 21 at the rear end side BE from the screw portion 22b. As a result, the holding portion 4 holds the gas sensor element 3 in a state where the detecting portion 31a is arranged in the through hole 21a at the tip side FE from the step portion 21b.

Further, in the oxygen concentration detection cell 140 described later provided inside the detection unit 31a, a space 23 exists in the through hole 21a of the main body 21 at the tip side FE from the holding unit 4 along the axial direction DA. It is arranged in the range Rs1. The radial length of the through hole 21a in the range Rs1 (that is, the inner diameter of the through hole 21a) is the radial length of the threaded portion 22b of the main body 21 in the range Rs1 (that is, the thickness of the threaded portion 22b). ) Is larger than.

The protector 5 is a metal member formed in a tubular shape so as to cover the end portion of the FE on the distal end side of the gas sensor element 3 protruding from the main metal fitting 2. A plurality of gas intake holes 5a are formed in the protector 5. The protector 5 is joined to the outer periphery of the FE on the tip end side of the main metal fitting 2 by welding.

The protector 5 has a double structure and includes an outer protector 51 and an inner protector 52. A bottomed cylindrical outer protector 51 is arranged on the outside, and a bottomed cylindrical inner protector 52 is arranged on the inside.

The outer cylinder 6 is a metal member formed in a tubular shape extending in the axial direction DA. The outer cylinder 6 is fixed in a state in which a portion of the main body 21 of the main metal fitting 2 located on the rear end side BE of the main metal fitting 2 is fitted into the opening 6a at the end portion of the front end side FE.

The plurality of lead wires 7 are provided corresponding to each of a plurality of electrode pads (not shown) formed on the rear end side BE of the element body portion 31, and drive and control the element body portion 31 and the gas sensor element 3. It is a lead wire for electrically connecting to the sensor control device 170. Note that FIG. 1 shows two lead wires 7. Further, the sensor control device 170 is not shown in FIG. 1 but is shown in FIG.

The plurality of connection terminals 8 are provided corresponding to each of the plurality of lead wires 7, and are attached to one end of the corresponding lead wires 7.
The separation unit 9 includes a separator 91 and a holding member 92. The separator 91 is a member made of ceramic formed in a cylindrical shape extending in the axial direction DA, and is arranged in the outer cylinder 6. Inside the separator 91, a space capable of accommodating a plurality of connection terminals 8 and a part of the rear end side BE of the element main body 31 is formed. In the separator 91, the rear end side BEs of the plurality of connection terminals 8 are projected from the rear end side BEs of the separator 91, and the plurality of connection terminals 8 are kept in a state of not contacting each other, and the plurality of connection terminals 8 are placed inside. To accommodate. Further, the separator 91 holds a state in which the plurality of connection terminals 8 are in contact with the electrode pads of the element main body 31, respectively. Further, a flange portion 91a extending outward along the radial direction is formed on the outer peripheral surface of the rear end side BE of the separator 91.

The holding member 92 includes a main body portion 92a and a curved portion 92b. The main body portion 92a is a metal member formed in a tubular shape extending in the axial direction DA. The curved portion 92b is a member that extends from the rear end side BE of the main body portion 92a and is bent in a U shape. The holding member 92 is installed so as to be located between the outer cylinder 6 and the separator 91 on the tip side FE of the flange portion 91a. As a result, the main body portion 92a is in contact with the inner peripheral surface of the outer cylinder 6, and the curved portion 92b is in a state of pressing the flange portion 91a of the separator 91 toward the inside thereof. Therefore, the separator 91 is held in the outer cylinder 6 by the holding member 92.

The grommet 10 is an elastic member made of fluororubber formed in a cylindrical shape extending in the axial direction DA. The grommet 10 is formed with a plurality of through holes penetrating along the axial direction DA. The plurality of through holes are provided corresponding to each of the plurality of lead wires 7 described above, and the corresponding lead wires 7 are inserted into the plurality of through holes.

The grommet 10 is arranged inside the opening 6b at the end of the rear end side BE in the outer cylinder 6, and is crimped in the radial direction via the outer cylinder 6. As a result, the opening 6b at the end of the rear end side BE in the outer cylinder 6 is closed.

As shown in FIG. 2, the element main body 31 of the gas sensor element 3 has an insulating layer 113, a ceramic layer 114, an insulating layer 115, a ceramic layer 116, an insulating layer 117, a ceramic layer 118, an insulating layer 119, and an insulating layer 120 in that order. It is constructed by stacking. The insulating layers 113, 115, 117, 119, 120 are formed mainly of alumina.

The element main body 31 includes a first measurement chamber 121 formed between the ceramic layer 114 and the ceramic layer 116. The element main body 31 is exhausted from the outside to the inside of the first measurement chamber 121 via a diffusion resistor 122 arranged between the ceramic layer 114 and the ceramic layer 116 so as to be adjacent to the first measurement chamber 121. Introduce gas. The diffusion resistor 122 is made of a porous material such as alumina.

The element main body 31 includes a first pumping cell 130. The first pumping cell 130 includes a solid electrolyte layer 131 and pumping electrodes 132 and 133.
The solid electrolyte layer 131 is mainly formed of zirconia having oxygen ion conductivity. A part of the ceramic layer 114 in the region in contact with the first measurement chamber 121 has been removed, and the solid electrolyte layer 131 is filled in place of the ceramic layer 114.

The pumping electrodes 132 and 133 are formed mainly of platinum. The pumping electrode 132 is arranged on the surface of the solid electrolyte layer 131 in contact with the first measurement chamber 121. The pumping electrode 133 is arranged on the surface of the solid electrolyte layer 131 on the opposite side of the solid electrolyte layer 131 from the pumping electrode 132. The insulating layer 113 in the region where the pumping electrode 133 is arranged and the region around the pumping electrode 133 is removed, and the porous body 134 is filled in place of the insulating layer 113. The porous body 134 allows gas (for example, oxygen) to enter and exit between the pumping electrode 133 and the outside.

The element main body 31 includes an oxygen concentration detection cell 140. The oxygen concentration detection cell 140 includes a solid electrolyte layer 141, a detection electrode 142, and a reference electrode 143.
The solid electrolyte layer 141 is mainly formed of zirconia having oxygen ion conductivity. A part of the ceramic layer 116 in the region on the rear end side (that is, the right side in FIG. 2) of the solid electrolyte layer 131 is removed, and the solid electrolyte layer 141 is filled in place of the ceramic layer 116.

The detection electrode 142 and the reference electrode 143 are formed mainly of platinum. The detection electrode 142 is arranged on the surface of the solid electrolyte layer 141 in contact with the first measurement chamber 121. The reference electrode 143 is arranged on the surface of the solid electrolyte layer 141 on the side opposite to the detection electrode 142 with the solid electrolyte layer 141 interposed therebetween.

The element main body 31 includes a reference oxygen chamber 146. The reference oxygen chamber 146 is a through hole formed by removing the insulating layer 117 in the region where the reference electrode 143 is arranged and the region around the reference electrode 143.

The element main body 31 includes a second measurement chamber 148. The second measurement chamber 148 is formed so as to penetrate the solid electrolyte layer 141 and the insulating layer 117 on the rear end side of the detection electrode 142 and the reference electrode 143. The element main body 31 introduces the exhaust gas discharged from the first measurement chamber 121 into the inside of the second measurement chamber 148.

The element main body 31 includes a second pumping cell 150. The second pumping cell 150 includes a solid electrolyte layer 151 and pumping electrodes 152 and 153.
The solid electrolyte layer 151 is formed mainly of zirconia having oxygen ion conductivity. The ceramic layer 118 in the region in contact with the reference oxygen chamber 146 and the second measurement chamber 148 and the region around the reference oxygen chamber 146 has been removed, and the solid electrolyte layer 151 is filled in place of the ceramic layer 118.

The pumping electrodes 152 and 153 are formed mainly of platinum. The pumping electrode 152 is arranged on the surface of the solid electrolyte layer 151 in contact with the second measurement chamber 148. The pumping electrode 153 is arranged on the surface of the solid electrolyte layer 151 on the side opposite to the reference electrode 143 with the reference oxygen chamber 146 interposed therebetween. Inside the reference oxygen chamber 146, a porous body 147 is arranged so as to cover the pumping electrode 153.

The element main body 31 includes a heater 160. The heater 160 is a heat generating resistor formed mainly of platinum and generating heat when energized, and is arranged between the insulating layer 119 and the insulating layer 120.

The element main body 31 is connected to the sensor control device 170. The sensor control device 170 controls the element main body 31 and calculates the NOx concentration in the exhaust gas based on the detection result of the element main body 31.

The sensor control device 170 includes a control circuit 180 and a microcomputer 190 (hereinafter referred to as a microcomputer 190).
The control circuit 180 is an analog circuit arranged on a circuit board. The control circuit 180 includes an Ip1 drive circuit 181, a Vs detection circuit 182, a reference voltage comparison circuit 183, an Icp supply circuit 184, an Rpvs detection circuit 185, a Vp2 application circuit 186, an Ip2 detection circuit 187, and a heater drive circuit 188.

Then, the pumping electrode 132, the detection electrode 142, and the pumping electrode 152 are connected to the reference potential. The pumping electrode 133 is connected to the Ip1 drive circuit 181. The reference electrode 143 is connected to the Vs detection circuit 182, the Icp supply circuit 184, and the Rpvs detection circuit 185. The pumping electrode 153 is connected to the Vp2 application circuit 186 and the Ip2 detection circuit 187. The heater 160 is connected to the heater drive circuit 188.

The Ip1 drive circuit 181 applies a voltage Vp1 between the pumping electrode 132 and the pumping electrode 133 to supply the first pumping current Ip1 and detects the supplied first pumping current Ip1.

The Vs detection circuit 182 detects the voltage Vs between the detection electrode 142 and the reference electrode 143, and outputs the detected result to the reference voltage comparison circuit 183.
The reference voltage comparison circuit 183 compares the reference voltage (for example, 425 mV) with the output of the Vs detection circuit 182 (that is, the voltage Vs), and outputs the comparison result to the Ip1 drive circuit 181. Then, the Ip1 drive circuit 181 controls the flow direction of the first pumping current Ip1 and the magnitude of the first pumping current Ip1 so that the voltage Vs becomes equal to the reference voltage, and controls the oxygen concentration in the first measuring chamber 121. , Adjust to a predetermined value so that NOx does not decompose.

The Icp supply circuit 184 causes a weak current Icp to flow between the detection electrode 142 and the reference electrode 143. As a result, oxygen is sent from the first measurement chamber 121 to the reference oxygen chamber 146 via the solid electrolyte layer 141, so that the reference oxygen chamber 146 is set to a predetermined oxygen concentration as a reference.

The Rpvs detection circuit 185 momentarily supplies a current Ir between the detection electrode 142 and the reference electrode 143 of the oxygen concentration detection cell 140, and between the detection electrode 142 and the reference electrode 143 generated by the supplied current Ir. The voltage Vr of is detected. The microcomputer 190 calculates the internal resistance Rpvs of the oxygen concentration detection cell 140 based on the current Ir and the voltage Vr. Since this internal resistance Rpvs corresponds to the temperature of the oxygen concentration detection cell 140, as is well known, the temperature of the oxygen concentration detection cell 140 can be calculated from the internal resistance Rpvs.

The Vp2 application circuit 186 applies a constant voltage Vp2 (for example, 450 mV) between the pumping electrode 152 and the pumping electrode 153. As a result, in the second measurement chamber 148, NOx is dissociated by the catalytic action of the pumping electrodes 152 and 153 constituting the second pumping cell 150. The oxygen ion obtained by this dissociation moves through the solid electrolyte layer 151 between the pumping electrode 152 and the pumping electrode 153, so that the second pumping current Ip2 flows. The Ip2 detection circuit 187 detects the second pumping current Ip2.

The heater drive circuit 188 drives the heater 160 by applying a positive voltage for energizing the heater to one end of the heater 160, which is a heat generating resistor, and applying a negative voltage for energizing the heater to the other end of the heater 160. ..

The microcomputer 190 includes a CPU 191 and a ROM 192, a RAM 193, and a signal input / output unit 194.
The CPU 191 executes a process for controlling the NOx sensor 1 based on the program stored in the ROM 192. The signal input / output unit 194 is connected to the Ip1 drive circuit 181, the Vs detection circuit 182, the Rpvs detection circuit 185, the Ip2 detection circuit 187, and the heater drive circuit 188.

The CPU 191 calculates the NOx concentration in the exhaust gas and the temperature of the oxygen concentration detection cell 140 based on the signals input from the circuits 181, 182, 185, and 187 via the signal input / output unit 194. Further, the CPU 191 controls the heater 160 by outputting a drive signal to the heater drive circuit 188 via the signal input / output unit 194.

Next, an example of the operation of the gas sensor element 3 will be described.
First, when the sensor control device 170 is activated, the sensor control device 170 supplies electric power to the heater 160. The heater 160 heats the first pumping cell 130, the oxygen concentration detection cell 140, and the second pumping cell 150 to the activation temperature.

Then, when each of the cells 130, 140, and 150 is heated to the activation temperature, the sensor control device 170 causes the first pumping current Ip1 to flow through the first pumping cell 130. As a result, the first pumping cell 130 moves oxygen between the pumping electrode 132 and the pumping electrode 133 via the solid electrolyte layer 131, so that the oxygen contained in the exhaust gas flowing into the first measuring chamber 121 Perform pumping and pumping.

The sensor control device 170 sets a first pumping current Ip1 to be passed through the first pumping cell 130 so that the voltage Vs between the detection electrode 142 and the reference electrode 143 of the oxygen concentration detection cell 140 becomes the reference voltage (for example, 425 mV). Control. The voltage Vs of the oxygen concentration detection cell 140 is a value corresponding to the oxygen concentration in the detection electrode 142 with reference to the oxygen concentration in the reference oxygen chamber 146. By this control, the oxygen concentration inside the first measuring chamber 121 is adjusted so that NOx is not decomposed.

The exhaust gas whose oxygen concentration has been adjusted in the first measurement chamber 121 further flows toward the second measurement chamber 148.
The sensor control device 170 applies a constant voltage Vp2 between the pumping electrode 152 and the pumping electrode 153 of the second pumping cell 150. This voltage is set to such a voltage that the NOx gas in the exhaust gas decomposes into oxygen and nitrogen gas. As a result, NOx in the exhaust gas is decomposed into nitrogen and oxygen. A second pumping current Ip2 flows through the second pumping cell 150 so that oxygen generated by the decomposition of NOx is pumped out from the second measuring chamber 148. Since there is a proportional relationship between the second pumping current Ip2 and the NOx concentration, the NOx concentration in the exhaust gas can be detected by detecting the current value of the second pumping current Ip2.

Further, the sensor control device 170 uses the temperature of the oxygen concentration detection cell 140 calculated based on the internal resistance Rpvs to generate a current in the heater 160 via the heater drive circuit 188 so that the gas sensor element 3 reaches the target temperature. Control to supply.

The NOx sensor 1 configured in this way includes a gas sensor element 3, a metal main body 21, and a metal protector 5. The gas sensor element 3 is formed in a long shape and detects NOx contained in the exhaust gas. The main body 21 is formed in a tubular shape extending in the axial direction DA, and houses the gas sensor element 3 inside itself. The protector 5 is fixed to the main body 21 so that a gas intake hole 5a through which the exhaust gas passes is formed and covers the end of the FE on the tip end side of the gas sensor element 3.

Further, the NOx sensor 1 includes a mounting portion 22 which is formed in a tubular shape extending in the axial direction DA and is arranged so as to form an ended annular space 23 extending in the axial direction DA between the NOx sensor 1 and the main body portion 21. The mounting portion 22 is arranged so as to cover at least a part of the outer peripheral surface of the main body portion 21 in a state where a space 23 is formed between the mounting portion 22 and the main body portion 21.

The gas sensor element 3 includes an oxygen concentration detection cell 140 having an oxygen ion conductive solid electrolyte layer 141, a pair of detection electrodes 142 and a reference electrode 143 formed on the solid electrolyte layer 141, and an oxygen concentration detection cell 140. A heater 160 for heating to a predetermined temperature is provided. The oxygen concentration detection cell 140 is arranged inside the space 23.

As described above, in the NOx sensor 1, the oxygen concentration detection cell 140 has an oxygen concentration due to a portion in which the mounting portion 22, the space 23, and the metal main body portion 21 are laminated along the radial direction (hereinafter, the first laminated portion). The periphery of the detection cell 140 is covered.

Therefore, one path in which the temperature change around the NOx sensor 1 affects the temperature of the oxygen concentration detection cell 140 is that the heat around the NOx sensor 1 conducts through the first laminated portion and the oxygen concentration detection cell. This is the route to 140.

In the first laminated portion, a space 23 is formed between the mounting portion 22 and the main body portion 21. That is, gas exists between the mounting portion 22 and the metal main body portion 21. And gas has a lower thermal conductivity than metal. Therefore, in the NOx sensor 1, it becomes difficult for the heat around the NOx sensor 1 to be conducted to the oxygen concentration detection cell 140 via the first laminated portion, and the temperature fluctuation of the oxygen concentration detection cell 140 can be suppressed. Then, by suppressing the temperature fluctuation of the oxygen concentration detection cell 140, the temperature fluctuation of the gas sensor element 3 can be suppressed.

Further, in the NOx sensor 1, the gas sensor element 3 includes a first measurement chamber 121 and a first pumping cell 130, and the first pumping cell 130 is arranged on the tip side FE of the gas sensor element 3 rather than the oxygen concentration detection cell 140. At the same time, it is arranged inside the main body 21.

Exhaust gas is introduced into the first measurement chamber 121. The first pumping cell 130 has an oxygen ion conductive solid electrolyte layer 131 and a pair of pumping electrodes 132 and 133 formed on the solid electrolyte layer 131, and is located between the pair of pumping electrodes 132 and 133. By passing 1 pumping current Ip1, oxygen in the exhaust gas introduced into the first measuring chamber 121 is pumped out or pumped out. The oxygen concentration detection cell 140 has a solid electrolyte layer 141, a detection electrode 142 formed on the solid electrolyte layer 141, and a reference electrode 143, and the detection electrode 142 is arranged so as to face the first measurement chamber 121. An electromotive force is generated according to the difference in oxygen concentration between the detection electrode 142 and the reference electrode 143.

As described above, in the NOx sensor 1, since the first pumping cell 130 is arranged inside the main body 21, the circumference of the first pumping cell 130 in the radial direction is covered by the main body 21. Therefore, in the NOx sensor 1, the main body 21 can suppress the heat around the NOx sensor 1 from reaching the first pumping cell 130. As a result, the NOx sensor 1 can further suppress the temperature fluctuation of the gas sensor element 3.

The NOx sensor 1 corresponds to a gas sensor, the gas sensor element 3 corresponds to a detection element, the main body 21 corresponds to an accommodating member, and the gas intake hole 5a corresponds to a ventilation hole.
Further, the mounting portion 22 corresponds to a space forming member, the space 23 corresponds to an endless annular space, the solid electrolyte layer 141 corresponds to a solid electrolyte body, and the detection electrode 142 and the reference electrode 143 correspond to a pair of electrodes. However, the oxygen concentration detection cell 140 corresponds to the detection cell.

Further, the exhaust gas corresponds to the gas to be measured, and NOx corresponds to the specific gas.
Further, the first measurement chamber 121 corresponds to the measurement chamber, the solid electrolyte layer 131 corresponds to the first solid electrolyte body, the pumping electrodes 132 and 133 correspond to the pumping electrodes, and the first pumping cell 130 corresponds to the pumping cell. However, the solid electrolyte layer 141 corresponds to the second solid electrolyte.

(Second Embodiment)
The second embodiment of the present disclosure will be described below together with the drawings. In the second embodiment, a part different from the first embodiment will be described. The same reference numerals are given to common configurations.

The NOx sensor 1 of the second embodiment is different from the first embodiment in that the configuration of the main metal fitting 2 is changed.
Specifically, as shown in FIG. 3, the main metal fitting 2 includes a main body portion 21, a mounting portion 22, and a space forming member 25.

The space forming member 25 is a metal member formed in a tubular shape extending in the axial direction DA. The space forming member 25 includes a cylindrical portion 25a and a diameter-expanded portion 25b.
The cylindrical portion 25a is formed in a cylindrical shape so that its diameter is smaller than the diameter of the through hole 21a in the tip side FE from the step portion 21b.

The diameter-expanded portion 25b is formed in a shape that extends from the end portion of the rear end side BE of the cylindrical portion 25a and expands in diameter toward the rear end side BE. The diameter-expanded portion 25b is formed so that the diameter of the opening at the rear end side BE is smaller than the diameter of the through hole 21a at the rear end side BE than the step portion 21b.

The space forming member 25 is held in the through hole 21a by sandwiching the enlarged diameter portion 25b between the step portion 21b and the ceramic holder 41. As a result, the cylindrical portion 25a is arranged in the through hole 21a in the tip side FE from the step portion 21b. Then, a cylindrical space 26 extending in the axial direction DA is formed between the outer peripheral surface of the cylindrical portion 25a and the inner peripheral surface of the through hole 21a.

The oxygen concentration detection cell 140 provided inside the detection unit 31a is located in the through hole 21a of the main body 21 at the tip side FE from the holding unit 4 and in the range Rs2 where the space 26 exists along the axial direction DA. Be placed. The radial length of the cylindrical portion 25a in the range Rs2 (that is, the inner diameter of the cylindrical portion 25a) is the radial length of the threaded portion 22b of the main body portion 21 in the range Rs2 (that is, the thickness of the threaded portion 22b). ) Is larger than.

The NOx sensor 1 configured in this way is formed in a tubular shape extending in the axial direction DA, and is arranged so as to form an annular space 26 extending in the axial direction DA between the NOx sensor 1 and the main body 21. 25 is provided. The space forming member 25 is arranged inside the main body 21 so as to cover at least a part of the inner peripheral surface of the main body 21 in a state where the space 26 is formed between the space forming member 25 and the main body 21.

In the oxygen concentration detection cell 140, the space 26 is located on a straight line (hereinafter, radial straight line) passing through the oxygen concentration detection cell 140 along a direction perpendicular to the axial direction DA (hereinafter, radial direction). Be placed.

As described above, in the NOx sensor 1, the oxygen concentration detection cell 140 is a portion in which the metal space forming member 25, the space 26, and the metal main body 21 are laminated along the radial direction (hereinafter, the second laminated portion). ) Covers the periphery of the oxygen concentration detection cell 140.

Therefore, one path in which the temperature change around the NOx sensor 1 affects the temperature of the oxygen concentration detection cell 140 is that the heat around the NOx sensor 1 conducts through the second laminated portion and the oxygen concentration detection cell. This is the route to 140.

In the second laminated portion, a space 26 is formed between the space forming member 25 and the main body portion 21. That is, gas exists between the space forming member 25 and the metal main body 21. And gas has a lower thermal conductivity than metal. Therefore, in the NOx sensor 1, it becomes difficult for the heat around the NOx sensor 1 to be conducted to the oxygen concentration detection cell 140 via the second laminated portion, and the temperature fluctuation of the oxygen concentration detection cell 140 can be suppressed.
The space 26 corresponds to an annular space.

Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment, and can be implemented in various modifications.
For example, in the above embodiment, the space 23 formed by the inner peripheral surface of the mounting portion 22 and the outer peripheral surface of the main body portion 21 is an endd ring, but it may be an annular space.
Further, in the above embodiment, the NOx sensor for detecting the NOx concentration in the exhaust gas has been described as a gas sensor for detecting the concentration of the specific gas contained in the gas to be measured, but the gas sensor of the present disclosure is limited to the NOx sensor. There is no such thing. The gas sensor of the present disclosure may be a gas sensor having a cell to which a detection current is supplied to detect the internal resistance, and examples thereof include an all-region air-fuel ratio sensor.
Further, in the above embodiment, a current is supplied between the detection electrode and the reference electrode of the oxygen concentration detection cell to calculate the internal resistance Rpvs of the oxygen concentration detection cell, but the present invention is not limited to this, and for example, voltage. And the internal resistance may be calculated from the current generated by the supplied voltage. If there is another physical quantity that correlates with the internal resistance of the detection element, the heater may be driven based on the physical quantity instead of the internal resistance of the detection element.

Further, in the above embodiment, the oxygen concentration detection cell 140 is arranged in the range Rs1 or the range Rs2. In this way, in order to arrange the oxygen concentration detection cells 140 in the ranges Rs1 and Rs2, the arrangement of the gas sensor element 3 in the main body 21 may be changed, or the arrangement of the gas sensor element 3 may be changed. Instead, the arrangement of the oxygen concentration detection cell 140 in the gas sensor element 3 may be changed.

The function of one component in each of the above embodiments may be shared by a plurality of components, or the function of the plurality of components may be exerted by one component. Further, a part of the configuration of each of the above embodiments may be omitted. In addition, at least a part of the configuration of each of the above embodiments may be added or replaced with respect to the configuration of the other embodiment. It should be noted that all aspects included in the technical idea specified from the wording described in the claims are embodiments of the present disclosure.

1 ... NOx sensor, 2 ... Main metal fittings, 3 ... Gas sensor element, 5 ... Protector, 5a ... Gas intake hole, 21 ... Main body, 22 ... Mounting part, 23, 26 ... Space, 25 ... Space forming member, 140 ... Oxygen concentration detection cell, 141 ... solid electrolyte layer, 142 ... detection electrode, 143 ... reference electrode, 160 ... heater

Claims (4)

A detection element that is formed in a long shape and detects a specific gas contained in the gas to be measured,
A metal accommodating member formed in a tubular shape extending in the axial direction and accommodating the detection element inside itself, and a metal accommodating member.
A gas sensor having a vent hole through which the gas to be measured passes and a metal protector fixed to the accommodating member so as to cover the tip of the detection element.
A space forming member formed in a tubular shape extending in the axial direction and arranged so as to form an annular or endless annular space extending in the axial direction with the accommodating member.
The detection element includes a detection cell having an oxygen ion conductive solid electrolyte body and a pair of electrodes formed on the solid electrolyte body.
A heater for heating the detection cell to a predetermined temperature is provided.
The detection cell is arranged inside the space and
The detection cell, the housing member and the space forming member and radially apart from disposed Ru gas sensor. The gas sensor according to claim 1.
The space forming member is a gas sensor arranged so as to cover at least a part of an outer peripheral surface of the accommodating member in a state where the space is formed between the accommodating member and the accommodating member. The gas sensor according to claim 1.
The space forming member is a gas sensor arranged inside the accommodating member so as to cover at least a part of the inner peripheral surface of the accommodating member in a state where the space is formed between the accommodating member and the accommodating member. The gas sensor according to any one of claims 1 to 3.
The detection element is
The measurement room into which the gas to be measured is introduced and
The measurement chamber has an oxygen ion conductive first solid electrolyte body and a pair of pumping electrodes formed on the first solid electrolyte body, and a pumping current is passed between the pair of pumping electrodes. A pumping cell for pumping or pumping oxygen in the gas to be measured, which was introduced into the above.
It has an oxygen ion conductive second solid electrolyte body, a detection electrode and a reference electrode formed on the second solid electrolyte body, and the detection electrode is arranged facing the measurement chamber, and the detection electrode It is provided with an oxygen concentration detection cell that generates an electromotive force according to the difference in oxygen concentration between the reference electrode and the reference electrode.
The oxygen concentration detection cell is the detection cell and
The pumping cell is a gas sensor that is arranged closer to the tip of the detection element than the oxygen concentration detection cell and is arranged inside the accommodating member.

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