JPS6352052A - Lamination type air fuel ratio sensor - Google Patents

Abstract

PURPOSE:To improve the temperature control accuracy of a diffusion hole by arranging an atmospheric chamber layer at an upper part, a diffusion chamber layer below it, and a heater layer further below it. CONSTITUTION:A cell consists of a zirconia solid electrolyte 1 molded in a plate shape, and a reference electrode 2 and a measuring electrode 3 provided on its opposite surface. The electrode 2 faces an atmospheric chamber 4 and air is admitted into the atmospheric chamber 4 through an atmosphere introduction passage; and the electrode 3 faces a diffusion chamber 6 and discharge gas to be measured is admitted into the diffusion chamber 6 from the diffusion hole 7. Here, the diffusion chamber 9 which forms the diffusion chamber 6 and diffusion hole 7 is thinner than the atmospheric chamber layer 8 which forms the atmospheric chamber 4 and atmosphere introduction passage. The heater layer 13 consisting of an electric insulating layer 11 and a heater member 12 is provided closely to the diffusion chamber layer 9. Then, a heater is controlled to constant temperature of, for example, 600-800 deg.C and a voltage is applied, so that the cell is heated by the heater. At this time, the cell is insulated thermally from the discharge gas by the atmospheric chamber layer 8 and heater layer 13, so the cell is held at the constant temperature of 600-800 deg.C regardless of variation in the temperature of the discharge gas.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a device for detecting the mixture ratio of air and fuel in combustion equipment such as an internal combustion engine, and is particularly suitable for detecting the air-fuel ratio of exhaust gas from automobiles. Related to air-fuel ratio sensors.

[Conventional technology]

As described in Japanese Patent Application Laid-Open No. 60-228955, a conventional device has a structure in which a measuring electrode or a reference electrode is in contact with exhaust gas directly through a porous ceramic layer in a laminated element having a heater. Ta. A method of controlling the temperature of a cell to measure the air-fuel ratio is described in Japanese Patent Application Laid-Open No. 57-1928.
As described in Japanese Patent Application No. 52, Japanese Patent Laid-Open No. 59-214756, etc., this has been carried out by detecting the resistance of the cell and controlling the heater through feedback.

(Problems to be Solved by the Invention) In the above conventional technology, since the cell temperature is affected by the temperature of the exhaust gas, in order to keep the cell temperature and resistance constant,
It was necessary to detect the cell temperature and resistance and control the temperature with a heater using feedback control. The purpose of the present invention is to detect cell temperature and cell resistance, and to make it possible to control the cell temperature to a constant temperature by controlling the heater to a constant temperature by making the cell have an element structure that is less susceptible to the influence of exhaust gas temperature. .

The object of the present invention is to provide an air-fuel ratio sensor with an element structure that does not require a signal processing section.

[Means for resolving interstices]

The above purpose is to provide the element with a diffusion chamber layer above the heater layer and a detection electrode on the diffusion chamber side so that the cell and heater have the same temperature. A cell composed of a solid electrolyte having an electrode is provided above the diffusion chamber layer, and an air quality layer that can introduce air into the atmospheric chamber can be constructed by stacking the cell on the reference @ pole side above the diffusion chamber layer. The gas to be measured is introduced into the diffusion chamber by a single hole diffusion or multihole diffusion function. The atmospheric chamber is thicker than the diffusion chamber so that sufficient air can be introduced.

[Effect]

The heater is controlled to maintain a constant temperature, and the cells in close contact with it are also maintained at a constant temperature. At this time.

The diffusion chamber is thinner than the atmospheric chamber, and the cell temperature can be controlled more efficiently by providing a heater on the diffusion chamber side. In addition, the element is exposed to the exhaust gas, which is the gas to be measured, which has a flow rate, and is exposed to temperature changes from the outside temperature to about 8oO℃, but the atmospheric chamber in contact with the cell and the insulating support of the heater layer act as heat insulators. Even if there are temperature changes or disturbances in the exhaust gas, the cell is maintained at approximately the heater temperature.

This makes it possible to control the temperature of the cell by simply keeping the heater at a constant temperature, without having to detect the temperature and resistance of the cell and use feedback to control the temperature of the cell.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. The cell is composed of a zirconia solid electrolyte chamber 1 formed into a plate shape, and a reference electrode 2 and a measurement electrode 3 on opposite surfaces thereof. The reference electrode 2 faces the atmospheric chamber 4 and air is introduced into the atmospheric chamber 4 through an atmospheric air introduction passage 5. The measurement electrode 3 faces a diffusion chamber 6 , and the exhaust gas, which is the gas to be measured, is introduced into the diffusion chamber 6 through the diffusion hole 7 .

However, the size of the diffusion hole 7 is limited in order to control the diffusion rate of unburned components of the combustion gas and oxygen.
~0, 7 m, thickness 0, 1~0, 5 trxr
That's about it.

The atmospheric chamber 4 does not need to be as thin as the diffusion hole 7 and needs to obtain sufficient air, so it is approximately 0.3 to 1.0 m. Therefore, the diffusion chamber layer 9 that forms the diffusion chamber 6 and the diffusion hole 7 is thinner than the atmospheric chamber layer 8 that forms the atmosphere chamber 4 and the air introduction passage 5. Closely to the diffusion chamber layer or through an adhesive layer 1o consisting of at least one layer between them,
Electrical insulation such as alumina M! 111, and a heater layer 13 made of a heater member 12 made of platinum, tungsten, etc. therebetween. As mentioned above, the atmospheric chamber layer 8° cell,
Diffusion chamber layer 9. An element having a structure in which (adhesive layer 10) and heater layer 13 are laminated in this order is exposed to exhaust gas whose temperature changes from 200 to 700°C. Heater for example 600~80
When a voltage is applied while controlling the temperature to a constant temperature of 0° C., the cell is heated by the heater. At this time, the cell has atmospheric chamber layer 8.
Since the cell is insulated from the exhaust gas by the heater layer 13, the cell is maintained at a constant temperature of 600 to 800°C regardless of changes in the temperature of the exhaust gas.

〔Effect of the invention〕

According to the present invention, since the cell temperature can be kept constant by controlling the heater temperature, the cell temperature and resistance are detected,
Since there is no need for temperature control through feedback control, there is no need for a cell temperature or resistance detection section or for processing the detection signals, resulting in a circuit cost reduction of approximately 20%. Furthermore, compared to a case where a heater layer is attached to the atmospheric chamber layer side, since the distance to the cell is closer, the heater power is less and the temperature can be easily maintained at the same temperature. Furthermore, since the diffusion rate of the diffusion arc is also affected by temperature, the temperature control accuracy of the diffusion hole is improved, and the accuracy of air-fuel ratio recognition is further improved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view and circuit diagram of a sensor element according to an embodiment of the present invention, FIG. 2 is an enlarged perspective view of the sensor element of FIG. 1, and FIG. 3 is a longitudinal cross-section of the sensor element of FIG. 1. 4 are cross-sectional views of a sensor element according to another embodiment of the present invention. 1... Zirconia solid electrolyte, 2... Basic electrode, 3
... Measuring electrode, 4... Atmospheric chamber, 6... Diffusion chamber, 7
...Diffusion hole, 1st /Z /---Rirukoni r1 Kik M Hi Kakuki `` 4- Popular! (/-FAN Enoki (//-++ Rikiki I, 2-0-Hee 7th Division Cup 13---74th Z episode

Claims (1)

[Claims] 1. A cell consisting of a solid electrolyte body and a pair of catalytic electrodes facing each other with the solid electrolyte body sandwiched therebetween; an atmospheric chamber layer for introducing atmospheric air as a reference gas into one of the reference electrodes; A diffusion chamber layer that introduces the chamber gas to be measured into the detection electrode, and an air chamber that detects the mixture ratio of air and fuel during combustion in the combustion gas, which has a heater layer surrounding it to maintain the cell at a high temperature. The fuel ratio sensor is a laminated type air-fuel ratio sensor, in which the above atmospheric chamber layer is disposed at the top, a diffusion chamber layer is laminated below the atmospheric chamber layer, and a heater layer is laminated below the atmospheric chamber layer. 2. A laminated air-fuel ratio sensor according to claim 1, in which combustion exhaust gas, which is a gas to be measured, is introduced into the detection electrode into the diffusion chamber of the diffusion chamber layer through a diffusion hole that controls diffusion rate. 3. In claim 2, the heater layer is at least between a heater layer consisting of an electrical insulating layer and a heater provided in contact therebetween, and a diffusion chamber layer consisting of a fixed electrolyte. A laminated air-fuel ratio sensor with a single adhesive layer.