JP7017425B2 - Gas sensor element, gas sensor and gas detector - Google Patents

Description

The present invention provides a laminated body in which one or more cells having a plate-shaped solid electrolyte body and a pair of electrodes provided on the surface of the solid electrolyte body, and a plate-shaped heater having a heat generating portion are laminated. The present invention relates to a gas sensor element including, a gas sensor including a gas sensor element, and a gas detection device.

As an example of the gas sensor element, the gas sensor element described in Patent Document 1 is known. The gas sensor element described in Patent Document 1 includes a cell having a plate-shaped solid electrolyte body and a pair of electrodes provided on both sides of the solid electrolyte body, and a laminated body of a plate-shaped heater having a heat generating portion. The gas sensor element described in Patent Document 1 activates the pair of electrodes and the solid electrolyte by heating the temperature of the pair of electrodes and the solid electrolyte with the heat of the heat generating portion.

Japanese Unexamined Patent Publication No. 2013-234896

In the gas sensor element described in Patent Document 1, the distance from each of the pair of electrodes to the heat generating portion of the heater is different, and the amount of heat transferred to the electrode on the side closer to the heat generating portion and the amount of heat transferred to the electrode on the side farther from the heat generating portion are different. Makes a big difference. Therefore, the temperature of the electrode near the heat generating portion is higher than that of the electrode far from the heat generating portion, and a temperature difference occurs between the pair of electrodes. As a result, a thermoelectromotive force is generated between the pair of electrodes due to the temperature difference, and the generated thermoelectromotive force becomes a noise component with respect to the sensor output. As described above, there is a problem that the detection accuracy of the gas sensor is lowered due to the addition of a noise component due to the temperature difference between the pair of electrodes to the sensor output.

The present invention has been made in view of these problems, and an object of the present invention is to provide a sensor element capable of suppressing a temperature difference between a pair of electrodes, a gas sensor including the sensor element, and a gas detection device.

The gas sensor element in one aspect of the present invention includes a laminated body in which one or more cells and a plate-shaped heater are laminated. One or more cells have a plate-shaped solid electrolyte and a pair of electrodes provided on the surface of the solid electrolyte. The plate-shaped heater has a heat generating portion that generates heat when energized.

In the cell closest to the heater in the stacking direction among one or more cells, the pair of electrodes are provided on both sides of the solid electrolyte body so as to overlap the heat generating portion, and the first electrode and the heat generating portion on the side closer to the heat generating portion are provided. A second electrode on the far side is provided. The laminated body is continuously formed around the heat insulating portion provided between the first electrode and the heat generating portion and the heat insulating portion when viewed from the stacking direction, and has a higher thermal conductivity than the heat insulating portion. It is equipped with a part.

In this gas sensor element, the laminated body is provided with a heat insulating portion between the first electrode and the heat generating portion on the side close to the heat generating portion of the heater, so that the heat conduction path from the heat generating portion to the pair of electrodes is linear. It is not a simple route, but a route that bypasses the heat insulating part and goes around. As a result, the difference between the amount of heat transferred from the heat generating portion to the first electrode and the amount of heat transferred to the second electrode is suppressed, so that the temperature difference between the pair of electrodes can be suppressed.

Further, the laminated body includes a heat conductive portion continuously formed around the heat insulating portion when viewed from the stacking direction. That is, the heat insulating portion is surrounded by the heat conductive portion when viewed from the stacking direction and is not exposed to the outside of the laminated body. Therefore, since more heat conduction paths are formed as compared with the case where a part of the heat insulating portion is exposed to the outside, heat can be efficiently transferred from the heat generating portion to the pair of electrodes and the solid electrolyte body. .. As a result, it is possible to suppress a decrease in the activation of the pair of electrodes and the solid electrolyte while suppressing the difference in the amount of heat transferred from the heat generating portion to the first electrode and the amount of heat transferred to the second electrode.

Next, in the above-mentioned sensor element, the laminated body has a higher thermal conductivity than the heat insulating portion, and may include a ceramic layer sandwiched between the first electrode and the heat insulating portion.
Since a ceramic layer having a higher thermal conductivity than the heat insulating portion is sandwiched between the first electrode and the heat insulating portion, the pair of electrodes from the heat generating portion and the heat insulating portion are more than when the first electrode and the heat insulating portion are in contact with each other. Heat can be transferred to the solid electrolyte more efficiently.

Next, in the above-mentioned sensor element, the heat insulating portion may be configured so that the area of the surface perpendicular to the stacking direction is equal to or larger than the area of the surface of the first electrode facing the heat generating portion.
According to the experiment, when the area of the surface perpendicular to the stacking direction of the heat insulating portion (hereinafter, the cross-sectional area of the heat insulating portion) is less than the area facing the heat generating portion of the first electrode (hereinafter, the area of the first electrode), the cross-sectional area of the heat insulating portion. It was found that the temperature difference between the pair of electrodes became smaller as the value was increased, and when the cross-sectional area of the heat insulating portion became equal to or larger than the area of the first electrode, the temperature difference between the pair of electrodes was almost unchanged. Therefore, by setting the cross-sectional area of the heat insulating portion to be equal to or larger than the area of the first electrode, the temperature difference between the pair of electrodes can be suitably suppressed.

Next, in the above-mentioned sensor element, the heat insulating portion may be a space.
By providing a space between the heat generating portion and the first electrode, the laminated body suppresses the linear heat conduction from the heat generating portion to the first electrode and suppresses the temperature difference between the pair of electrodes. Can be done.

Next, in the above-mentioned sensor element, the heat insulating portion may be formed of a porous member having a higher porosity than the heat conductive portion.
Even in such a case, the temperature difference between the pair of electrodes can be suppressed as in the case where the heat insulating portion is a space.

Next, in the above-mentioned sensor element, the heat insulating portion may be formed of a dense member having a lower thermal conductivity than the heat conductive portion.
Even in such a case, the temperature difference between the pair of electrodes can be suppressed as in the case where the heat insulating portion is a space.

The gas sensor in another aspect of the present invention includes the gas sensor element described above and a housing for holding the gas sensor element.
By providing such a gas sensor with the above-mentioned gas sensor element, the detection accuracy can be improved.

The gas detection device in another aspect of the present invention includes the above-mentioned gas sensor and a sensor control unit that PWM controls the energization of the heat generating unit. PWM is an abbreviation for Pulse Width Modulation.
When the heat generating portion is PWM-controlled so that the temperature of the gas sensor element becomes constant, noise that fluctuates with respect to the sensor output is added as compared with the case where the heat-generating portion is not PWM-controlled, so that the detection accuracy tends to decrease. By providing the above-mentioned gas sensor, the gas detection device can suppress noise added to the sensor output and improve the detection accuracy even when the heat generating portion is PWM-controlled.

The term "vertical" here is not limited to vertical in a strict sense, and may not be strictly vertical as long as it produces the desired effect.

It is a figure which shows the structure of the gas detection device which includes a gas sensor and a sensor control unit. It is a perspective view which shows the gas sensor element of 1st Embodiment. It is sectional drawing which cut the gas sensor element of 1st Embodiment along the line III-III in FIG. It is sectional drawing which cut the gas sensor element of 1st Embodiment along the IV-IV line in FIG. It is a figure which shows the heat generation resistor pattern of a heater. It is a figure which shows the cross section which cut the conventional gas sensor element in the plane perpendicular to the stacking direction and the axial direction. It is a figure which shows the fluctuation amount of the output generated when the heater of the conventional gas sensor element is PWM controlled. It is a schematic diagram which shows the 1st cell and the heat insulating part in the case where the width of the heat insulating part is made smaller than the width of the 1st electrode. It is a schematic diagram which shows the 1st cell and the heat insulating part in the case where the width of a heat insulating part is made equal to the width of a 1st electrode. It is a schematic diagram which shows the 1st cell and the heat insulating part in the case where the width of a heat insulating part is made larger than the width of a 1st electrode. It is a schematic diagram which shows the heat generating part, the heat insulating part, and the 1st electrode when the cross-sectional area of a heat insulating part is made smaller than the electrode area of a 1st electrode. It is a schematic diagram which shows the heat generating part, the heat insulating part, and the 1st electrode when the cross-sectional area of a heat insulating part is made equal to the electrode area of a 1st electrode. It is a schematic diagram which shows the heat generating part, the heat insulating part, and the 1st electrode when the cross-sectional area of a heat insulating part is made larger than the electrode area of a 1st electrode. It is a figure explaining the relationship between the size of a 1st electrode, the size of a heat insulating part, and a noise reduction rate when a heat insulating part is a space or a porous member. It is sectional drawing corresponding to FIG. 3 of the gas sensor element of another example of 1st Embodiment. It is a perspective view which shows the appearance of the gas sensor element of 2nd Embodiment. It is sectional drawing which cut the gas sensor element of 2nd Embodiment along the XVII-XVII line in FIG. FIG. 5 is a cross-sectional view of the gas sensor element of the second embodiment cut along the line XVIII-XVIII in FIG.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings.
(First Embodiment)
<1. Gas detector>
First, the configuration of the gas detection device 900 of the first embodiment will be described with reference to FIG. The gas detection device 900 includes a gas sensor 1 and a sensor control unit 800 (hereinafter referred to as SCU800). The gas sensor 1 is assumed to be a gas sensor mounted on a vehicle and used, and is, for example, an oxygen sensor that detects an oxygen concentration in an exhaust gas. In FIG. 1, the gas sensor 1 is shown by a cross-sectional view obtained by cutting the gas sensor 1 along the axial direction.

The gas sensor 1 includes a main metal fitting 5, a ceramic sleeve 9, an insulating contact member 13, five connection terminals 15 (only two are shown in FIG. 1), an outer cylinder 57, a grommet 61, and a protector 55. , And a gas sensor element 7.

The main metal fitting 5 has a screw portion 3 on the outer surface for fixing the gas sensor 1 to the exhaust pipe of the engine. Further, the main metal fitting 5 has a tubular shape having a through hole 37 penetrating in the axial direction and a shelf portion 39 protruding inward in the radial direction of the through hole 37. In the main metal fitting 5, the gas introduction portion 94 of the gas sensor element 7, which will be described later, is arranged closer to the tip side than the tip of the through hole 37, and the electrode pads 25, 27, 29, 31, 33 of the gas sensor element 7 are formed in the through hole 37. It is configured to hold the gas sensor element 7 inserted through the through hole 37 in a state of being arranged on the rear end side of the rear end. The axial direction is the longitudinal direction of the gas sensor 1 and is the vertical direction in FIG. The front end side is the lower side in FIG. 1, and the rear end side is the upper side in FIG.

Further, inside the through hole 37 of the main metal fitting 5, an annular ceramic holder 41, a talc ring 43, a talc ring 45, and a ceramic sleeve 9 are tipped in this order while surrounding the radial circumference of the gas sensor element 7. It is laminated from the side to the rear end side.

The ceramic sleeve 9 is formed in a cylindrical shape and is arranged so as to surround the radial circumference of the gas sensor element 7. A crimping packing 49 is arranged between the ceramic sleeve 9 and the rear end portion 47 of the main metal fitting 5. On the other hand, a metal holder 51 for holding the talc ring 43 and the ceramic holder 41 is arranged between the ceramic holder 41 and the shelf portion 39 of the main metal fitting 5. The rear end portion 47 of the main metal fitting 5 is crimped so as to press the ceramic sleeve 9 toward the tip end side via the crimping packing 49.

The protector 55 has a double structure of cylindrical members. Each cylindrical member is a metal (for example, stainless steel) member having a plurality of holes. The protector 55 is fixed to the outer periphery of the tip portion 53 of the main metal fitting 5 by welding or the like so as to cover the protruding portion of the gas sensor element 7 from the main metal fitting 5.

The outer cylinder 57 is formed in a cylindrical shape and is fixed to the outer periphery of the rear end side of the main metal fitting 5. The insulating contact member 13 is formed in a cylindrical shape, and has an insertion hole 11 that penetrates in the axial direction inside. The insulating contact member 13 is arranged inside the outer cylinder 57 so that the inner wall surface of the insertion hole 11 surrounds the periphery of the rear end portion of the gas sensor element 7. A protrusion 63 is formed on the outer periphery of the insulating contact member 13, and the protrusion 63 is fixed to the outer cylinder 57 via the holding member 65.

Each of the five connection terminals 15 is arranged between the gas sensor element 7 and the insulating contact member 13. The five connection terminals 15 are electrically connected to the electrode pads 25, 27, 29, 31, 33 of the gas sensor element 7, respectively, and are also electrically connected to the lead wire 35 disposed inside the gas sensor 1 from the SCU 800. Is connected.

The grommet 61 is arranged in the opening on the rear end side of the outer cylinder 57. The grommet 61 includes an insertion hole 59 through which five lead wires 35 are inserted. The first end of the five lead wires 35 is electrically connected to the electrode pads 25, 27, 29, 31, 33 via the connection terminal 15, and the second end is connected to the SCU 800. FIG. 1 shows three of the five lead wires 35.

The gas sensor element 7 is a plate-shaped element extending in the axial direction. As shown in FIG. 2, the gas sensor element 7 includes a plate-shaped element portion 71 extending in the axial direction, a plate-shaped heater 73 extending in the axial direction, and a protective layer 17 covering the element portion 71 and the tip end side of the heater 73. And prepare. The tip end side of the element unit 71 and the heater 73 is an element body unit 70 directed to the gas to be measured. Further, in the gas sensor element 7, electrode pads 25, 27, 29, 31, 33 are formed on the first main surface 21 and the second main surface 23, which are in a positional relationship between the front and back surfaces of the outer surface on the rear end side. .. Details of the configuration of the gas sensor element 7 will be described later.

The sensor control unit 800 (hereinafter referred to as SCU800) is a control device mainly composed of a microcomputer equipped with a CPU, ROM, RAM and the like. The SCU 800 executes various processes including a concentration detection process of the gas sensor 1 and an energization control of the heater 73.

<2. Gas sensor element>
Next, the configuration of the gas sensor element 7 will be described with reference to FIGS. 2 to 5. The gas sensor element 7 is a long, substantially rectangular parallelepiped plate material including a laminated body 72 in which a plate-shaped element portion 71 and a plate-shaped heater 73 are laminated, and a protective layer 17. A C-chamfered portion 131 is formed on the rear end side (upper side of FIG. 2) of the gas sensor element 7. The C chamfered portion 131 is formed by performing C chamfering on the ridges on all four sides around the rear end surface of the gas sensor element 7. The rear end surface of the gas sensor element is a surface perpendicular to the longitudinal direction of the gas sensor element.

Here, in each figure, the longitudinal direction of the gas sensor element 7 is the Y-axis direction, the stacking direction perpendicular to the longitudinal direction is the Z-axis direction, and the width direction perpendicular to the longitudinal direction and the stacking direction is the X-axis direction. In the gas sensor element 7, the element portion 71 is arranged on one side in the stacking direction, and the heater 73 is arranged on the opposite side of the element portion 71.

The element unit 71 includes two cells, an oxygen concentration detection cell 81 and an oxygen pump cell 89, and an insulating spacer 93 laminated between the two cells to form a hollow gas measuring chamber.

The oxygen concentration detection cell 81 is formed closer to the heater 73 than the oxygen pump cell 89, and includes a first solid electrolyte body 75, and a pair of electrodes, a first electrode 79 and a second electrode 77. The oxygen pump cell 89 includes a second solid electrolyte body 83, and a pair of electrodes, a third electrode 87 and a fourth electrode 85. The first and second solid electrolytes 75 and 83 are formed in a plate shape extending in the longitudinal direction from zirconia in which yttria is dissolved as a stabilizer.

The first electrode 79, the second electrode 77, the third electrode 87, and the fourth electrode 85 are porous electrodes formed mainly of Pt. The first electrode 79 and the second electrode 77 are provided on both sides of the tip portion of the first solid electrolyte body 75, the first electrode 79 is provided on the surface closer to the heater 73, and the second electrode 77 is provided. Is provided on the surface far from the heater 73. Further, the third electrode 87 and the fourth electrode 85 are provided on both surfaces of the second solid electrolyte body 83, the third electrode 87 is provided on the surface closer to the heater 73, and the fourth electrode 85 is provided. It is provided on the surface far from the heater 73.

Further, the insulating spacer 93 forming the gas measuring chamber 91 is mainly formed of alumina, and inside the hollow gas measuring chamber 91, the second electrode 77 of the oxygen concentration detection cell 81 and the oxygen pump cell 89 are formed. The third electrode 87 is arranged so as to be exposed.

Two gas introduction portions 94 serving as exhaust gas intake ports are formed on the side surface of the insulating spacer 93, that is, the side surface of the element portion 71. The gas introduction unit 94 communicates with the gas measurement chamber 91. A diffusion rate control section 95 is formed in each path from the two gas introduction sections 94 to the gas measurement chamber 91. The diffusion rate-determining unit 95 is composed of, for example, a porous body made of alumina or the like, and controls the rate when the gas to be measured flows into the gas measuring chamber 91. The diffusion rate control unit 95 is provided in a state where a part thereof is exposed from the gas introduction unit 94. That is, in the gas sensor element 7, the gas introduction portion 94 is formed in two different directions on the outermost surface of the element main body portion 70, and the diffusion rate controlling portion 95 is exposed in two different directions. ..

An insulating substrate 97 mainly composed of alumina is laminated on the first main surface 21 side of the element portion 71, and the insulating substrate 97 has a ventilation portion made of a porous body, similarly to the diffusion rate controlling portion 95. 99 is formed. The vent 99 is used to pass oxygen that is moved by the drive of the oxygen pump cell 89.

The gas measurement chamber 91 is formed so as to be located at the element main body 70 on the tip side of the element 71, and the oxygen concentration detection cell 81 and the oxygen pump cell 89 face the gas measurement chamber 91 and oxygen. It is provided as a gas detector for detecting.

The protective layer 17 is made of porous alumina and is formed so as to cover the outermost surface of the element main body 70. Specifically, the protective layer 17 is made of a porous material having a diffusion resistance smaller than that of the diffusion rate controlling portion 95. In the gas sensor element 7 having such a configuration, the exhaust gas reaches the gas introduction unit 94 via the protective layer 17 and is introduced from the gas introduction unit 94 to the gas measurement chamber 91 via the diffusion rate control unit 95.

The heater 73 is formed by sandwiching a heat generating resistor pattern 105 mainly composed of Pt between insulating substrates 101 and 103 which are dense layers mainly composed of alumina, and an oxygen concentration detection cell 81 and an oxygen pump cell 89. Is heated to the activation temperature. Since the insulating substrates 101 and 103 surround the heat-generating resistor pattern 105 so as to sandwich the heat-generating resistor pattern 105 above and below, the heat from the heat-generating resistor pattern 105 promptly causes the oxygen concentration detection cell 81 and the oxygen pump cell 89. Is transmitted to.

Further, the heater 73 is energized and controlled by the SCU 800. In the present embodiment, the heater 73 is PWM controlled so that the temperature of the element unit 71 becomes constant. That is, the SCU 80 controls the energization of the heater 73 so that the ratio of the on period to the off period in the predetermined cycle becomes a predetermined duty ratio.

As shown in FIG. 5, the heat generation resistor pattern 105 includes a plurality of straight line portions 105a provided on the front end side, and a heater lead portion extending from the rear end to the rear end side of the plurality of straight line portions 105a. In this embodiment, the heat generation resistor pattern 105 includes four linear portions 105a. Of the heat generation resistor patterns 105, the plurality of linear portions 105a generate heat. The plurality of linear portions 105a are provided in the element main body portion 70 so that the plurality of straight portions 105a, the oxygen concentration detection cell 81, the gas measuring chamber 91, and the oxygen pump cell 89 overlap in this order in the stacking direction.

Further, the laminated body 72 includes a heat insulating portion 18 provided between a plurality of linear portions 105a of the heat generation resistor pattern 105 and the first electrode 79 of the oxygen concentration detection cell 81. The heat insulating portion 18 is formed in a recess provided in a portion of the insulating substrate 101 on the element portion 71 side of the heater 73 so as to overlap with the first electrode 79. That is, the heat insulating portion 18 is not directly in contact with the plurality of straight line portions 105a, and the insulating substrate 101 is sandwiched between the heat insulating portion 18 and the plurality of straight line portions 105a. Further, the heat insulating portion 18 is provided so as to straddle at least two of the plurality of linear portions 105a in the width direction of the gas sensor element 7.

The heat insulating portion 18 may be a space formed in the recess, a porous member embedded in the recess, or a dense member embedded in the recess. When the heat insulating portion 18 is a porous member, the porous member has a porosity higher than that of the insulating substrate 103 around the heat insulating portion 18, for example, a pore diameter of 0.7 μm and a porosity of about 45%. Porous members can be adopted. Further, when the heat insulating portion 18 is a dense member, a dense member having a lower thermal conductivity than the insulating substrate 101 around the heat insulating portion 18 can be adopted as the dense member.

The heat insulating portion 18 is embedded inside the laminated body 72 and is not exposed from the laminated body 72. That is, when viewed from the stacking direction, the insulating substrate 101 is continuously formed around the heat insulating portion 18. The insulating substrate 101 is a member having a higher thermal conductivity than the heat insulating portion 18. Specifically, the insulating substrate 101 may be a member formed of a substance having a higher thermal conductivity than a substance forming a space or a porous member or a dense member which is a heat insulating portion 18, or a porous member which is a heat insulating portion 18. A member having a higher thermal conductivity than the heat insulating portion 18 may be used because the porosity and / or the pore diameter is different from that of the quality member or the dense member.

Therefore, the heat conduction path from the straight section 105a to the oxygen concentration detection cell 81 is not a straight path from the straight section 105a to the oxygen concentration detection cell 81, but a path that bypasses the heat insulating section 18. .. Therefore, the difference between the amount of heat transferred from the linear portion 105a to the first electrode 79 and the amount of heat transferred to the second electrode 77 is suppressed. Further, since the heat insulating portion 18 is not exposed to the outside of the laminated body 72, more heat conduction paths are formed as compared with the case where a part of the heat insulating portion 18 is exposed to the outside. Further, since the heat insulating portion 18 is provided so as to straddle at least two of the plurality of straight portions 105a, heat is transferred from the plurality of heat sources to the oxygen concentration detection cell 81, so that the first electrode is formed from the straight portion 105a. The oxygen concentration detection cell 81 can be heated more effectively while suppressing the difference between the amount of heat transferred to the 79 and the amount of heat transferred to the second electrode 77 and suppressing the generation of thermoelectromotive force.

Further, the laminated body 72 includes a ceramic insulating substrate 102 sandwiched between the heat insulating portion 18 and the first electrode 79. Specifically, the insulating substrate 102 is provided between the insulating substrate 101 and the first solid electrolyte body 75, and the first electrode 79 is embedded in the insulating substrate 102. Therefore, the first electrode 79 is not in direct contact with the heat insulating portion 18, and the insulating substrate 102 is sandwiched between the first electrode 79 and the heat insulating portion 18. The insulating substrate 102 is a member having a higher thermal conductivity than the heat insulating portion 18. In this way, the insulating substrate 102 having a higher thermal conductivity than the heat insulating portion 18 is sandwiched between the first electrode 79 and the heat insulating portion 18, so that the linear portion 105a bypasses the heat insulating portion 18 and is transmitted. The generated heat spreads in the axial direction at the portion of the insulating substrate 102 and is efficiently transferred to the oxygen concentration detection cell 81.

Here, the conventional gas sensor element shown in FIG. 6 includes a heater H11, a first cell C11, and a second cell C12, and does not include a heat insulating portion. The first cell C11 includes an electrode Vs + on the side closer to the heater H11 and an electrode Vs− on the side farther from the heater H11. Since the conventional gas sensor element does not have a heat insulating portion, the difference in the amount of heat transferred between the electrode Vs + and the electrode Vs- becomes larger than that in the case where the heat insulating portion is provided, and the temperature difference between the electrode Vs + and the electrode Vs- Becomes larger. As a result, a thermoelectromotive force is generated between the electrode Vs + and the electrode Vs-due by the Seebeck effect.

As shown in FIG. 7, the thermoelectromotive force generated by the temperature difference between the electrode Vs + and the electrode Vs− is a noise component that contributes to the fluctuation amount ΔVs of the electromotive force Vs. Other noise components with respect to the electromotive force Vs are electromagnetic induction and white noise associated with switching on / off of energization of the heater 73. Among these noise components, the output fluctuation due to the thermoelectromotive force is large and always occurs. Therefore, if the temperature difference between the electrode Vs + and the electrode Vs- is large, the sensor output of the gas sensor may become unstable. On the other hand, since the gas sensor element 7 of the present embodiment includes the heat insulating portion 18, the output fluctuation due to the thermoelectromotive force is suppressed, and the sensor output of the gas sensor 1 is likely to be stable.

<3. Size of heat insulation part>
Next, the size of the heat insulating portion 18 and the noise reducing effect will be described. Here, the thickness in the stacking direction and the length in the axial direction of the heat insulating portion 18, that is, the thickness in the z direction and the length in the y direction of the heat insulating portion 18 are made constant, and the width of the heat insulating portion 18, that is, the length in the x direction is set. The noise reduction effect was compared by changing in three ways.

Specifically, as shown in (i) FIGS. 8 and 11, the width of the heat insulating portion 18 is made smaller than the width of the first electrode 79. (Ii) As shown in FIGS. 9 and 12, the width of the heat insulating portion 18 is made equal to the width of the first electrode 79. (Iii) As shown in FIGS. 10 and 13, the width of the heat insulating portion 18 is made larger than the width of the first electrode 79. In the case of (i), the area of the surface perpendicular to the stacking direction of the heat insulating portion 18 (hereinafter, the cross-sectional area of the heat insulating portion) is the area of the surface facing the straight portion 105a of the heat generating resistor pattern 105 of the first electrode 79 (hereinafter,). , First electrode area), that is, smaller than the area of the surface facing the heat insulating portion 18. In the case of (ii), the cross-sectional area of the heat insulating portion and the area of the first electrode are equal. In the case of (iii), the cross-sectional area of the heat insulating portion is larger than the area of the first electrode.

FIG. 14 shows the presence or absence of noise in the cases of (i) to (iii) in which the heat insulating portion 18 is not provided and the heat insulating portion 18 is used as a space, and in the cases of (i) to (iii) in which the heat insulating portion 18 is used as a porous material. Shows the noise reduction rate. The presence or absence of noise indicates that the noise is less in the order of ×, Δ, ○, and ◎. The noise reduction rate is a numerical value indicating how much the noise is reduced as compared with the case where the heat insulating portion 18 is not used.

As shown in FIG. 14, the noise reduction effect is obtained when the heat insulating portion 18 is made of a space or a porous material as compared with the case where the heat insulating portion 18 is not provided, but the heat insulating portion 18 is made a space. In this case, it can be seen that the noise reduction effect is particularly high. When the heat insulating portion 18 is made of a porous material, the noise reducing effect can be brought closer to the noise reducing effect when the heat insulating portion 18 is used as a space by increasing the pore diameter and / or the porosity. ..

Further, it can be seen that the noise reduction effect can be obtained regardless of the size of the heat insulating portion 18 (i) to (iii) as compared with the case where the heat insulating portion 18 is not provided. It can be seen that the noise reduction effect is higher when the size of the heat insulating portion 18 is set to (i) and when the size is set to (ii) and (iii). Therefore, in order to improve the noise reduction effect, it is desirable that the cross-sectional area of the heat insulating portion is equal to or larger than the first electrode area.

However, the noise reduction effect is substantially the same between the case where the size of the heat insulating portion 18 is set to (ii) and the case where the size is set to (iii), and no significant difference is observed. Further, when the heat insulating portion 18 is made of a space or a porous material, the larger the heat insulating portion 18, the lower the strength of the gas sensor element 7. Therefore, from the viewpoint of noise reduction effect and strength of the gas sensor element 7, it is most desirable that the cross-sectional area of the heat insulating portion is equal to the area of the first electrode.

<4. Effect>
According to the first embodiment described above, the following effects can be obtained.
(1) By providing the heat insulating portion 18, the heat conduction path from the straight section 105a to the oxygen concentration detection cell 81 is not a linear path but a path that bypasses the heat insulating section 18 and goes around. As a result, the difference between the amount of heat transferred from the linear portion 105a to the first electrode 79 and the amount of heat transferred to the second electrode 77 is suppressed, and the temperature difference between the electrodes of the first electrode 79 and the second electrode 77 can be suppressed. .. Further, since the heat insulating portion 18 is not exposed to the outside of the laminated body 72, more heat conduction paths are formed as compared with the case where a part of the heat insulating portion 18 is exposed to the outside. Therefore, heat can be efficiently transferred from the linear portion 105a to the oxygen concentration detection cell 81. As a result, it is possible to suppress a decrease in activation of the oxygen concentration detection cell 81 while suppressing a difference in the amount of heat transferred from the linear portion 105a to the first electrode 79 and the amount of heat transferred to the second electrode 77.

(2) Since the insulating substrate 102 having a higher thermal conductivity than the heat insulating portion 18 is sandwiched between the first electrode 79 and the heat insulating portion 18, the first electrode 79 and the heat insulating portion 18 are in contact with each other. Also, heat can be transferred more efficiently from the linear portion 105a to the oxygen concentration detection cell 81.

(3) By setting the heat insulating cross-sectional area of the heat insulating portion 18 to be equal to or larger than the area of the first electrode of the first electrode 79, the temperature difference between the first electrode 79 and the second electrode 77 can be suitably suppressed. ..
(4) The gas sensor 1 is provided with the gas sensor element 7, so that the detection accuracy can be improved.

(5) By providing the gas sensor element 7 in the gas detection device 900, noise added to the sensor output can be suppressed and the detection accuracy can be improved even when the energization of the heater 73 is PWM-controlled.

<5. Modification example of the first embodiment>
In the first embodiment described above, the laminated body 72 includes an insulating substrate 102 sandwiched between the heat insulating portion 18 and the first electrode 79. From the viewpoint of the efficiency of heat conduction to the oxygen concentration detection cell 81, it is desirable that the laminated body 72 is provided with the insulating substrate 102, but as shown in FIG. 15, the laminated body 72 may not be provided with the insulating substrate 102. .. That is, the first electrode 79 may be in direct contact with the heat insulating portion 18. Even if the first electrode 79 is in direct contact with the heat insulating portion 18, the thermoelectromotive force can be suppressed by providing the heat insulating portion 18, and the output fluctuation can be suppressed.

<6. Correspondence of words>
Here, the correspondence between words will be described.
The first and second solid electrolytes 75 and 83 correspond to plate-shaped solid electrolytes, and the first and second electrodes 79 and 77 and the third and fourth electrodes 87 and 85 correspond to a pair of electrodes. Further, the heater 73, the plurality of linear portions 105a, and the laminated body 72 correspond to the plate-shaped heater, the heat generating portion, and the laminated body, respectively. Further, the oxygen concentration detection cell 81 and the oxygen pump cell 89 correspond to one or more cells, and the oxygen concentration detection cell 81 corresponds to the cell closest to the heater. Further, the first electrode 79, the second electrode 77, the heat insulating portion 18, the insulating substrate 101, and the insulating substrate 102 correspond to the first electrode, the second electrode, the heat insulating portion, the heat conductive portion, and the ceramic layer, respectively. Further, the gas sensor element 7, the gas sensor 1, the SCU 800, and the gas detection device 900 correspond to the gas sensor element, the gas sensor, the control unit, and the gas detection device, respectively. Further, the main metal fitting 5, the outer cylinder 57, and the protector 55 correspond to the housing.

(Second Embodiment)
<1. Differences from the first embodiment>
Since the basic configuration of the second embodiment is the same as that of the first embodiment, the description of the common configuration will be omitted, and the differences will be mainly described. It should be noted that the same reference numerals as those in the first embodiment indicate the same configuration, and the preceding description will be referred to.

In the first embodiment described above, the gas sensor element 7 includes two cells. On the other hand, the second embodiment differs from the first embodiment in that the gas sensor element 204 includes only one cell.

As shown in FIGS. 16 to 18, the gas sensor element 204 has a laminated body 350 in which a shielding layer 312, a diffusion rate controlling unit 315, an oxygen pump cell 500, an insulating substrate 307, and a heater 400 are laminated, and the tip end side of the laminated body 350. A protective layer 330 for covering is provided. The tip end side of the laminated body 350 is an element main body portion 501 directed to the gas to be measured.

Like the heater 73, the heater 400 is formed in a plate shape extending in the axial direction, and is configured such that the heat generating resistor pattern 105 is sandwiched between the insulating substrate 301 and the insulating substrate 303.
Like the oxygen pump cell 89, the oxygen pump cell 500 is formed in a plate shape extending in the axial direction, and includes the solid electrolyte body 309 and the fifth electrode 308 and the sixth electrode 310 formed on both sides of the solid electrolyte body 309. , Equipped with. The fifth electrode 308 and the sixth electrode 310 are provided on both sides of the solid electrolyte body 309 so as to overlap the linear portion 105a of the heater 400. The fifth electrode 308 includes a lead portion (not shown) extending along the longitudinal direction of the solid electrolyte body 309, and this lead portion is electrically connected to the electrode terminal portion 321. In the gas sensor element 204, a minute current is passed between the fifth electrode 308 and the sixth electrode 310, and the fifth electrode 308 is used as a reference potential according to the reference concentration.

Further, the element main body portion 501 includes a gas introduction portion 322 for introducing exhaust gas. The element main body portion 501 includes a gas measuring chamber 316 in which the exhaust gas is introduced via the gas introducing portion 322. The gas measuring chamber 316 is provided on the surface of the solid electrolyte body 309 so as to cover the sixth electrode 310.

The diffusion rate control unit 315 is a porous material made of alumina, and is provided on the surface of the solid electrolyte body 309 so as to cover the gas measuring chamber 316. Further, a shielding layer 312 is laminated on the surface of the diffusion rate controlling portion 315 on the side opposite to the solid electrolyte body 309. Further, the diffusion rate controlling unit 315 has four side surfaces exposed to the outside, which are not in contact with the shielding layer 312 and the solid electrolyte body 309. This exposed portion of the diffusion rate control unit 315 becomes the gas introduction unit 322 for introducing the exhaust gas from the element main body portion 501 of the gas sensor element 204.

The insulating substrate 307 is provided between the heater 400 and the oxygen pump cell 500. The insulating substrate 307 is not particularly limited as long as it is a ceramic sintered body having an insulating property, and for example, an oxide-based ceramic such as alumina or mullite can be adopted.

Further, in the insulating substrate 307, a portion facing the fifth electrode 308 on the side close to the heater 400 is hollowed out, and a heat insulating portion 325 is formed in the hollowed out portion. That is, the heat insulating portion 325 is provided between the linear portion 105a of the heat generation resistor pattern 105 and the fifth electrode 308, and is in direct contact with the fifth electrode 308.

The insulating substrate 307 is a member having a higher thermal conductivity than the heat insulating portion 325, and is continuously formed around the heat insulating portion 325 when viewed from the stacking direction. That is, the heat insulating portion 325 is embedded in the laminated body 350 and is not exposed from the laminated body 350.

Further, the heat insulating portion 325 may be a space, a porous member having a higher porosity than the surrounding insulating substrate 307, or a dense member having a lower thermal conductivity than the insulating substrate 307, as in the heat insulating portion 18. good. Further, the heat insulating portion 325 is provided so as to straddle at least two of the plurality of linear portions 105a in the width direction of the gas sensor element 204, similarly to the heat insulating portion 18.

Further, as for the size of the heat insulating portion 325, it is desirable that the cross-sectional area of the heat insulating portion is equal to or larger than the area facing the straight portion 105a of the fifth electrode 308 (hereinafter referred to as the fifth electrode area), similarly to the heat insulating portion 18. In particular, it is most desirable to make the area of the heat insulating portion step picture of the heat insulating portion 18 equal to the area of the fifth electrode.

Further, the heat insulating portion 325 is in direct contact with the fifth electrode 308, but in order to increase the heat conduction efficiency, as the insulating substrate 102 is provided between the heat insulating portion 18 and the first electrode 79. An insulating substrate having a thermal conductivity higher than that of the heat insulating portion 325 and having a thermal conductivity higher than that of the insulating substrate 307 may be provided between the heat insulating portion 325 and the fifth electrode 308.

The protective layer 330 is made of a porous material, alumina, and is formed so as to cover the outermost surface of the element main body portion 501. Specifically, the protective layer 330 is made of a porous material having a diffusion resistance smaller than that of the diffusion rate controlling unit 315. In the gas sensor element 204 having such a configuration, the exhaust gas reaches the gas introduction unit 322 via the protective layer 330 and is introduced from the gas introduction unit 322 to the gas measurement chamber 316 via the diffusion rate control unit 315.

According to the second embodiment described above, the same effects as those of the above-mentioned effects (1) to (5) of the first embodiment are obtained. However, the oxygen concentration detection cell 81 of the first embodiment corresponds to the oxygen pump cell 500 of the second embodiment.

<2. Correspondence of words>
Here, the correspondence between words will be described.
The solid electrolyte body 309 corresponds to a plate-shaped solid electrolyte body, and the fifth and sixth electrodes 308 and 310 correspond to a pair of electrodes. Further, the heater 400 and the laminated body 350 correspond to the plate-shaped heater and the laminated body, respectively. Also, the oxygen pump cell 500 corresponds to one or more cells and the cell closest to the heater. Further, the gas sensor element 204 corresponds to the gas sensor element. Further, the fifth electrode 308, the sixth electrode 310, the heat insulating portion 325, and the insulating substrate 307 correspond to the first electrode, the second electrode, the heat insulating portion, and the heat conductive portion, respectively.

(Other embodiments)
Although the embodiment for carrying out the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment, and can be variously modified and carried out.

(A) In the above embodiment, the SCU 800 has PWM controlled the energization of the heaters 73 and 400, but the present invention is not limited to the PWM control, and may be continuously turned on, for example. When the SCU 800 does not PWM control the heaters 73 and 400, the sensor output is offset when a thermoelectromotive force is generated.

(B) A plurality of functions possessed by one component in the above embodiment may be realized by a plurality of components, or one function possessed by one component may be realized by a plurality of components. .. Further, a plurality of functions possessed by the plurality of components may be realized by one component, or one function realized by the plurality of components may be realized by one component. Further, a part of the configuration of the above embodiment may be omitted. Further, at least a part of the configuration of the above embodiment may be added or replaced with the configuration of the other above embodiment. It should be noted that all aspects included in the technical idea specified only by the wording described in the claims are embodiments of the present disclosure.

1 ... Gas sensor, 5 ... Main metal fittings, 7,204 ... Gas sensor element, 17,330 ... Protective layer, 18,325 ... Insulation part, 55 ... Protector, 57 ... Outer cylinder, 70,501 ... Element body part, 71 ... Element Part, 72, 350 ... Laminated body, 73, 400 ... Heater, 75 ... First solid electrolyte body, 77 ... Second electrode, 79 ... First electrode, 81 ... Oxygen concentration detection cell, 83 ... Second solid electrolyte body, 85 ... 4th electrode, 87 ... 3rd electrode, 89,500 ... Oxygen pump cell, 91,316 ... Gas measuring chamber, 94,322 ... Gas introduction section, 95,315 ... Diffusion rate control section, 97,101,102,103 , 301, 303, 307 ... Insulated substrate, 105 ... Heat generation resistor pattern, 105a ... Straight part, 308 ... Fifth electrode, 309 ... Solid electrolyte, 310 ... Sixth electrode, 800 ... Sensor control unit, 900 ... Gas detection Device.

Claims (5)

A laminated body in which one or more cells having a plate-shaped solid electrolyte body and a pair of electrodes provided on the surface of the solid electrolyte body, and a plate-shaped heater having a heat generating portion that generates heat by energization are laminated. It is a gas sensor element equipped with
In the cell closest to the heater in the stacking direction among the one or more cells, the pair of electrodes are provided on both sides of the solid electrolyte body so as to overlap the heat generating portion, and the side closer to the heat generating portion. A first electrode and a second electrode on the far side of the heat generating portion are provided.
The laminated body is
A heat insulating portion provided between the first electrode and the heat generating portion,
An insulating substrate that surrounds the entire periphery of the heat insulating portion is provided.
The insulating substrate is
A heat conductive portion that is continuously formed around the heat insulating portion when viewed from the stacking direction and has a higher thermal conductivity than the heat insulating portion.
It has a higher thermal conductivity than the heat insulating portion, and includes a ceramic layer sandwiched between the first electrode and the heat insulating portion.
The heat insulating portion is a space.
Gas sensor element. A laminated body in which one or more cells having a plate-shaped solid electrolyte body and a pair of electrodes provided on the surface of the solid electrolyte body, and a plate-shaped heater having a heat generating portion that generates heat by energization are laminated. It is a gas sensor element equipped with
In the cell closest to the heater in the stacking direction among the one or more cells, the pair of electrodes are provided on both sides of the solid electrolyte body so as to overlap the heat generating portion, and the side closer to the heat generating portion. A first electrode and a second electrode on the far side of the heat generating portion are provided.
The laminated body is
A heat insulating portion provided between the first electrode and the heat generating portion, and a heat conduction portion which is continuously formed around the heat insulating portion when viewed from the stacking direction and has a higher thermal conductivity than the heat insulating portion. Department and
It has a higher thermal conductivity than the heat insulating portion, and includes a ceramic layer sandwiched between the first electrode and the heat insulating portion.
The heat insulating portion is formed of a porous member having a higher porosity than the heat conductive portion.
Gas sensor element. The heat insulating portion is configured such that the area of the surface perpendicular to the stacking direction is equal to or larger than the area of the surface of the first electrode facing the heat generating portion.
The gas sensor element according to claim 1 or 2 . The gas sensor element according to any one of claims 1 to 3 and a housing for holding the gas sensor element are provided.
Gas sensor. The gas sensor according to claim 4 and a sensor control unit that PWM controls the energization of the heat generating unit.
Gas detector.

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