JPH0714879Y2 - Oxygen concentration sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an oxygen concentration sensor.

[Prior Art] Conventionally, oxygen concentration sensors having various structures have been used or proposed. The applicant of the present invention discloses a device body formed by forming a cathode and an anode each having an area corresponding to a corresponding portion on both surfaces of a plate of an oxygen ion permeable solid electrolyte cell, which is described in Japanese Utility Model Publication No. 60-15659. . A heat resistant ceramic plate with a slit provided with an opening having a size corresponding to the area of the cathode and a slit reaching the plate end from the opening, which is laminated on the cathode side surface of the element body,
A heating element printed on the element body or the heat-resistant ceramic plate with a slit, a heat-resistant ceramic plate laminated on the heat-resistant ceramic plate with a slit, and an anode laminated on the surface of the element body on the anode side. We have proposed a limiting current type oxygen concentration sensor equipped with a sensor element consisting of a heat-resistant ceramic plate having an opening of a size corresponding to the area. FIG. 9 is an exploded perspective view showing the structure of an example thereof, showing a heat-resistant ceramic plate 1 for coating, a heat-resistant ceramic sheet 3 with slits 2, a cell 4, and a heat-resistant ceramic plate 5 from the top in the figure. . As shown in the drawing, a cathode 6 is formed on the upper surface of the cell 4, and although not shown, the cathode 6 is formed on the lower surface of the cell 4.
An anode having a corresponding size is formed at a position corresponding to. Reference numeral 7 is a lead portion, and 8 and 9 are openings provided in the respective ceramic plates. Also, 10
Is a heat generating part.

The applicant of the present invention has been described in Japanese Utility Model Publication No. 61-108963.
A sheet-shaped oxygen-ion permeable solid electrolyte having a positive electrode formed on the inner surface and a negative electrode formed on the outer surface is coated on a rod-shaped ceramic heater having at least a porous surface, and further on the negative electrode. We proposed a limiting current type oxygen concentration sensor equipped with a sensor element with a diffusion-controlled layer. 10th
An example is shown in FIGS. In the figure, 11 is a ceramic rod, 12 is a ceramic sheet, 13 is a solid electrode material, 14 is an anode, 15 is a gas diffusion rate controlling layer, 16 is a holder, and 17 is a lead wire. Further, FIG. 11 shows a process of winding a ceramic sheet 12 having a heating portion 10 formed on a ceramic rod 11 in the form of a green sheet, and FIG. 12 shows a ceramic sheet having a cathode 6 and an anode formed on both front and back sides thereof. The process of winding 13 in the form of a green sheet is shown.

The applicant of the present invention is described in Japanese Utility Model Laid-Open No. 61-108964.
A ceramic rod is coated with a sheet-shaped oxygen ion-permeable solid electrolyte in which a heater heating part and a positive electrode are formed on the inner surface and a negative electrode is formed on the outer surface, and a diffusion rate controlling layer is formed on the negative electrode. We proposed a limiting current type oxygen concentration sensor equipped with the above sensor element. An example is shown in FIGS. 13 and 14. In the figure, 18 is a ceramic sheet, 19 is a heat generating part / anode, and 20 is a ceramic cylinder. Further, FIG. 14 shows a step of winding a heating portion / anode 19 around the ceramic cylinder 20 and a ceramic sheet (not shown) having a cathode 6 formed on the back surface thereof.

Further, the present applicant discloses that the ceramic green sheet having the heater and the ceramic green sheet having the sensitive portion and the lead wire described in Japanese Utility Model Laid-Open No. 62-37757 have an opening of a predetermined size on the peripheral side surface. An anti-detection-type oxygen concentration sensor formed by coating each green sheet so that the heater and the sensitive portion are located in the opening, and firing it on the outer periphery of the ceramic cylindrical support provided with . An example is shown in FIGS. 15 to 17. In the figure,
21 is a ceramic cylinder, 22 and 25 are openings, 23 and 24 are ceramic sheets (green sheets), 26 is a protective sheet,
27 is an oxide semiconductor. As shown in FIG. 15, the sensor has a ceramic cylinder 21 and a ceramic sheet 23 shown in FIG.
Then, the ceramic sheet 24 of FIG. 17 is sequentially wound to manufacture.

[Problems to be solved by the device]

The above-mentioned conventional oxygen concentration sensor has some problems. That is, the sensor disclosed in Japanese Utility Model Laid-Open No. 60-15659 has a rectangular cross-sectional shape in a direction orthogonal to the length direction even if it is a plate type, so that it is difficult to assemble the element
In addition, it is necessary to take measures against oxygen leakage from the portions where the ceramic plates are overlapped.

Further, the above-mentioned sensor and the sensor described in Japanese Utility Model Laid-Open No. 62-37757 have a gas intake port to be measured only on one side, so that the responsiveness is deteriorated depending on the mounting position.

The sensors described in Japanese Utility Model Publication Nos. 61-108963 and 61-108964 are cylindrical types and are easy to assemble, but since there is no space on the cathode surface, the gas is only hit in one direction. The detection sensitivity differs depending on whether the gas is hit or not, and although the sensor element is warmed by the heater, it is easily affected by the temperature of the gas to be measured, and the activity of the electrode is deteriorated.

The present invention is to solve the above problems in the prior art, and the purpose thereof is to easily assemble the element, not to be influenced by the assembly position, and to prevent oxygen leakage. Another object of the present invention is to provide an oxygen concentration sensor which is not affected by the direction in which the gas to be measured impinges and its temperature and which has good temperature rising characteristics.

[Means for Solving the Problems]

In order to achieve the above object, the oxygen concentration sensor of the present invention is
A sheet-shaped oxygen ion permeable solid electrolyte in which at least one set of an inner electrode and an outer electrode is formed on a cylindrical surface, and a ceramic sheet wound around the solid electrolyte with a space provided on the outer electrode. And a sheet-shaped ceramic heater wound around the ceramic sheet and having a heat generating portion formed in a portion facing the outer electrode and having a plurality of gas introduction holes provided at substantially equal intervals in the circumferential direction, and a cylinder having the above configuration The sensor element is composed of a ceramic sheet laminated on one end surface of the body.

The sheet-shaped oxygen ion permeable solid electrolyte is, for example, ZnO ₂ or ZrO _{2 in} which Y ₂ O ₃ is dissolved.

The solid electrolyte and the ceramic sheet are in the form of a green sheet, for example, wound around a ceramic rod or a cylinder having a circular cross section, and then calcined, the ceramic rod or the cylinder is pulled out, and then calcined.

The electrodes and the heating portion of the ceramic heater are formed by screen printing platinum, for example.

The size and shape of the space provided on the outer electrode and the size, shape and number of gas introduction holes are selected according to the size of the sensor and required characteristics.

Ceramics may be plasma sprayed on the gas introduction holes to form a gas diffusion rate controlling layer.

[Action]

By providing a space and a ceramic heater on the outer electrode, and providing a plurality of gas introduction holes in the several ceramic heaters at substantially equal intervals in the circumferential direction, the influence of the direction in which the gas to be measured hits, its temperature, and the assembly position are affected. I do not receive it. Further, if the shape is cylindrical, it is easy to assemble the element.

〔Example〕

The invention will be described in more detail in the following examples. The present invention is not limited to the following embodiments.

Embodiment 1 FIGS. 1 to 3 show Embodiment 1 of the oxygen concentration sensor of the present invention. This example is an example of a case where a stoichiometric air-fuel ratio detection type oxygen concentration sensor is configured. This example is the same as Example 2 except that instead of the zirconia sheet 28 in Example 2, a zirconia sheet 38 having an electrode 39 formed on the outer surface and an electrode 40 formed on the inner surface was used. Manufactured.

Embodiment 2 FIG. 4 shows an example of a method of manufacturing the oxygen concentration sensor of the present invention. As shown in FIGS. 7 and 8, the ceramic cylinder 27 has electrodes 29 and 30 on its outer surface and electrodes on its inner surface.
A zirconia sheet 28, which is a sheet-shaped oxygen ion permeable solid electrolyte in which 31 and 32 are formed, is wound, and an electrode 29 and
A space is provided on 30 and further zirconia sheets 33 and 34 are wound, and a heat generating portion 10 is formed on the inner surface as shown in FIG. 5, and gas introduction holes 35 are formed at equal intervals in the circumferential direction. The formed zirconia sheet 36 is wound. A zirconia sheet 37 is laminated on one end face of this cylindrical body, pre-baked at 1000 ° C., the ceramic cylinder 27 is pulled out, and then baked at 1400 ° C. After firing, pinel on the gas inlet hole 35 is about 300-500μ
A gas diffusion rate controlling layer 15 was formed by thermal spray coating with a thickness of m to obtain a sensor element of FIG. Zirconia sheet 28
A pair of electrodes on both inside and outside of the sensor electrode is used as a sensor electrode,
The other set of electrodes is a pump cell electrode.

In the oxygen concentration sensor of the present invention, since the heating portion of the heater is near the gas introduction hole, the temperature of the gas hitting the detection portion can be kept constant by controlling the heat quantity of the heater, and the temperature dependence of the sensor's limiting current value Does not affect sexuality.

[Effect of device]

Since the oxygen concentration sensor of the present invention has the above-mentioned configuration, it has the following effects.

That is, since the sensor element is manufactured from the ceramic green sheet, the sensor element can be downsized and the temperature rise characteristic of the element is improved.

In the conventional laminated oxygen concentration sensor, the heater is arranged inside the detection part (atmosphere inlet side), so that it has a higher temperature rise characteristic than the test tube type sensor element (cylindrical sensor element with one end closed). Although there was only the effect of improving the temperature rising characteristic only by downsizing, in the case of the present invention, the heat generating portion is arranged on the entire outer circumference of the detecting portion, and the element is also heated by using the heat of the gas to be measured. Stable temperature rising characteristics can be obtained without being affected by the temperature variation of the gas to be measured.

Compared to the conventional stacked sensor, the measured gas introduction holes are arranged at equal intervals in the circumferential direction of the cylinder, so there is no directionality for gas contact and the sensor mounting direction can be selected arbitrarily. The degree of freedom has been increased and assembly has become easier.

Since the solid electrolyte is thin, the activation temperature can be lowered by using the laminated type. Therefore, the usable temperature range can be set lower than that of the conventional sensor including the test tube type element.

Since the heater is outside the electrode, impurities attached to the electrode can be reduced as compared with the case where the electrode is exposed. Further, a heater provided with a gas diffusion rate controlling layer is more effective.

In the case where the electrode and the heater are integrated as in the sensor described in Japanese Utility Model Laid-Open No. 61-108964, when the heating portion and the electrode are separately formed on the same surface of the ceramic sheet, the electrode in the portion close to the heating portion is formed. Since the temperature gradually rises from the part, the temperature of the entire electrode varies, the electrode activity deteriorates, and the temperature rise characteristics deteriorate because the low temperature exhaust gas directly hits the engine. Since the heat of the heater is evenly transferred to the entire electrode of the sensor, the temperature is stably raised, and the exhaust gas is also heated by the heater, so that the temperature raising characteristic is further improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a sensor element of an oxygen concentration sensor of the present invention, and FIGS. 2 and 3 are plan views showing an outer surface and an inner surface of a zirconia sheet on which electrodes are formed, FIG. 4 is a perspective view showing a manufacturing process of the sensor element of the present invention, FIG. 5 is a plan view of a zirconia sheet having a heating portion and a gas introduction hole, and FIG. 6 is another embodiment of the sensor element of the present invention. 7 and 8 are plan views showing the outer surface and the inner surface of the zirconia sheet having electrodes formed thereon, and FIG. 9 is an exploded perspective view of an example of a sensor element of a conventional oxygen concentration sensor. Fig. 10, Fig. 10 is a cross-sectional view of another example of a conventional sensor element, Figs. 11 and 12 are perspective views showing a manufacturing process of the sensor element of Fig. 10, and Fig. 13 is a sectional view of a conventional sensor element. Fig. 14 is a sectional view of an example of Fig. 14, Fig. 14 is a perspective view showing the manufacturing process of the sensor element of Fig. 13, FIG. 15 is a perspective view showing a manufacturing process of another example of a conventional sensor element, FIG. 16 is a plan view of a ceramic sheet having a heating portion formed thereon, and FIG. 17 is a plan view of a ceramic sheet having an oxide semiconductor formed thereon. is there. In the figure, 1,3,5 ... ceramic plate, 2 ... slit, 4 ... cell, 6 ... cathode, 7 ... lead part, 8,9,22,25 ... opening part, 10
Heat generating part, 11 ... Ceramic rod, 12,13,18,23,24-ceramic sheet, 14 ... Anode, 15 ... Gas diffusion rate controlling layer, 16 ... Holder, 17 ... Lead wire, 19 ... Heat generating part / anode, 20 , 21, 27 ... Ceramic cylinder, 26 ... Protective sheet, 28, 33, 34, 36, 37 ... Zirconia sheet, 29, 30, 31, 32 ... Electrode, 35 ... Gas introduction hole

Claims (1)

[Scope of utility model registration request] 1. A sheet-shaped oxygen ion permeable solid electrolyte in which at least one set of an inner electrode and an outer electrode is formed in a cylindrical shape and formed on both sides, and a space portion is provided on the outer electrode to provide the solid electrolyte. And a sheet-shaped ceramic heater in which a heating portion is formed in a portion wound around the ceramic sheet and facing the outer electrode, and a plurality of gas introduction holes are provided at substantially equal intervals in the circumferential direction. ,
An oxygen concentration sensor comprising a sensor element comprising a ceramic sheet laminated on one end surface of a cylindrical body having the above structure.