JPS60129661A - Oxygen sensor - Google Patents

Abstract

PURPOSE:To improve the response property of sensor output, by controlling an air-fuel ratio in the vicinity of lambda=1. CONSTITUTION:Now, it is set that the oxygen concn. in exhaust gas is low and rich (lambda<1). When the oxygen concn. in exhaust gas begins to increase at this time, delay is generated between the oxygen concn. in the exhaust gas within a gap part 4 and that in external exhaust gas and, therefore, positive electromotive force is generated between electrodes 2, 3 in a pulse form. As a result, an actuator is changed over from a lean (lambda>1) side to a rich side. Whereupon, oxygen concn. begins to increase now and, when the actuator enters the rich side again at this time, pulse like negative output is generated because of the timewise delay in the concn. difference between the gap part 4 and external exhaust gas. By this operation, the actuator is changed over from the rich side to the lean side. By this method, exhaust gas is automatically controlled in the vicinity of lambda=1. Therefore, good response is obtained even if oxygen concn. changes abruptly.

Description

[Detailed description of the invention] [Technical field,]:) ,, .

Kiba, Akira is concerned with devices for detecting oxygen concentration in gas and other oxygen sensors that utilize solid electrolytes.

[Prior art, prior art] Conventionally, oxygen-permeable electrodes such as Pt were provided on the inner and outer surfaces of a solid electrolyte in a tubular body with one end closed, and air was introduced into the inner surface to serve as a reference electrode, and the outer surface was used as a reference electrode. Oxygen sensors have been provided that are exposed to a gas to be measured and serve as a measurement electrode.

This oxygen sensor has a sensor output that changes suddenly when the oxygen content of the gas to be measured changes suddenly. , But what about the atmosphere? Because it was necessary to introduce the product into the sensor, there was a risk that moisture could enter from the outside, impairing reliability and performance. . 5. Also, in the case of low temperature, it is necessary to wear a heater when using it, and there is a problem that effective efficiency cannot be obtained because there is no method of incorporating it with good thermal efficiency. In addition, there are limits to miniaturization due to the structure, and there are limits to reducing manufacturing costs.
,there were.

[Object of the Invention] The object of the present invention is the above. This was done in view of the points mentioned above.
The aim is to provide an oxygen sensor with a simple structure and improved output response.
And there it is.

[Structure of the Invention] The structure of the present invention for achieving the above object is as follows: -2- A flat first part made of an oxygen ion conductive solid electrolyte, and a first part attached to the inner and outer surfaces of the first member. The device comprises: an electrode that is permeable to oxygen gas; a second member that is disposed across a gap facing the electrode and blocks oxygen gas; and a measuring means that measures the electromotive force between the electrodes. This article focuses on an oxygen sensor with the following characteristics.

[Embodiment 1] Hereinafter, an oxygen sensor according to the present invention will be described by way of an embodiment with reference to the drawings. FIGS. 1 to 3 represent an embodiment of the oxygen sensor. FIG. 1 represents a cross-sectional view of the embodiment. In the figure, 1 is a first electrode made of an oxygen ion conductive solid electrolyte.
It is a flat plate corresponding to a member, and oxygen gas permeable electrodes 2 and 3 are attached to the inner and outer surfaces of the flat plate, respectively. The electrode 2
．． 3 is vertically 7 by printing or plating Pt etc.
It was coated and fired to Ill111 x 2mm width,
Protected by coating (alumina, spinel base material, etc.) as necessary.

Further, a ceramic heater 5 corresponding to a second member is disposed between the electrode 3 and a gap 4 . The flat plate 1 and the heater 5 are fixed to each other by an adhesive layer 6 at a distance of about 0.1 mm.

The adhesive is silica.

An inorganic heat-resistant adhesive such as alumina or zirconia or glass frit is used. At this time, the distance between the flat plate 1 and the heater 5 is paper or aluminum wheel.

It is adjusted to about 0.1 mm using a commercially available product such as tape or a regular feeler gauge. Note that 4a is an opening.

' Electrodes 2 and 3 attached to the inner and outer surfaces of the flat plate 1 are connected to respective terminals A of a voltmeter 8, and a heating wire 7 in the heater 5 is connected to a terminal port of a DC power source 9. The heating wire 7 is provided in the heater 5 by printing PT or W or by embedding the wire. The reference numeral 10 is a stand for fixing the sensor at a desired measurement location.

Next, FIG. 2 shows a cross-sectional view taken along the line X--X in FIG. 1.

-4- Electrodes 2.3 are attached to the inner and outer surfaces of the flat plate 1, respectively, and the heater 5 is fixed to the flat plate 1 by an adhesive layer 6.

FIG. 3 is an enlarged view of the flat plate 1 and the heater 5.

In the figure, the tip of the electrode 2 is made slightly wider, and accordingly, the tip of the heating wire 7 is also shaped into a circumferential shape, roughly serrated. A fixing base 10 is provided at the bottom of the flat plate 1 and the heater 5, and the flat plate 1 has terminals and the heater 5.
is connected to inverter 0.

□Next, the operation of the sensor when this embodiment is applied as an air-fuel ratio sensor for an automobile will be explained. First, use some conventional means to turn the actuator of the fuel control system lean (λ〉1).
) to rich (λ<1)□ or vice versa.

Then, if the air-fuel ratio λ of the exhaust gas changes from rich to lean, the sensor outputs a steep positive pulse voltage as shown in Figure 4 when λ = 1. ,
When changing from lean to rich, a steep negative valve pressure is output at the point when λ-1 is cut. When this positive output or negative output occurs, a signal is given to switch the actuator of the fuel control system, the actuator is switched to the rich side or the lean side, and the process is repeated □ to adjust the air-fuel ratio to λ = It is possible to control the value close to 1.

The operation of this embodiment will be explained in more detail based on FIGS. 1- and 4. In FIG. 4, it is assumed that before time t1, the oxygen concentration in the exhaust gas is low, that is, rich (λ<1).

First, at time t1, when the oxygen concentration in the exhaust gas increases to C, there is a lag between the oxygen concentration in the exhaust gas in the gap 4 and the oxygen concentration in the external exhaust gas, so a positive electromotive force is generated. is electrode 2.
It occurs in a pulsed manner every 3 hours. As a result, the actuator is switched from the lean side to the rich side, but when this happens, the oxygen concentration starts to increase, and when it switches to the rich side again at time t2, the difference in concentration between the gap 4 and the external exhaust gas increases. Because of the time lag, a pulse-like negative output is generated, which switches the actuator from rich to lean. In this manner, the exhaust gas is automatically controlled to be near λ-1.

As described in detail above, the structure of this embodiment allows the structure for introducing atmospheric air to be omitted, and the oxygen sensor can be simplified. Therefore, it is possible to prevent the intrusion of water and the like, improve reliability, improve yield during manufacturing, save resources, and be easy to install and lightweight, contributing to energy saving.

Further, since the heater 5 can be arranged very close to the flat plate 1 and the heat generating part can be provided near the electrode 3, good thermal efficiency can be obtained.

Then, the gas to be measured, for example, oxygen 11 in the exhaust of a car
In the case of rapid fluctuations, an output with good responsiveness can be obtained, and therefore the exhaust λ can be controlled within a range of values that are not too far from λ-1. Moreover, since it is a pulse signal, it can be easily used for digital processing.

[Effects of the Invention] The present invention comprises a flat first member made of an oxygen ion conductive solid electrolyte, an oxygen gas permeable electrode attached to the inner and outer surfaces of the first member, and an oxygen gas permeable electrode attached to the inner and outer surfaces of the first member. The second member is disposed facing each other with a gap in between and blocks oxygen gas, and a measuring means is provided for measuring the electromotive force between the electrodes.

Therefore, it is possible to provide an oxygen sensor with a simple structure for detecting the oxygen concentration of a gas to be measured, and moreover, it is possible to obtain good responsiveness. Then, it can be used as a pulse signal for digital processing.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the oxygen sensor, Figure 2 is X-x in Figure 1.
A cross-sectional view, FIG. 3 is an enlarged view of the flat plate and heater, and FIG. 4 is a graph showing temporal changes in voltage measured by a voltmeter. 1... Flat plate 2.3... Electrode 4... Gap 5... Heater 8-6... Adhesive layer 8... Voltmeter. Agent: Patent attorney Tsutomu Setatetsu and 1 other person -9- Figure 2R Figure 3

Claims (1)

[Claims] . 1. A flat first member made of a solid electrolyte conductive to acids and elementary ions; 2. Electrodes permeable to phosphorus gas attached to the inner and outer surfaces of the first member 5. A second member disposed facing the electrode through a gap, the second member blocking and shielding oxygen gas, and a measuring means for measuring the power l of the N horizontal opening. An oxygen sensor characterized by: ,,2. 2. The oxygen sensor according to claim 1, wherein said second part includes a heater.