Oxygen gas concentration-detecting apparatus
First Claim
1. An oxygen concentration-detecting apparatus comprising a ceramic substrate for generating an electromotive force between a first surface contacted with a reference gas and a second surface contacted with a gas to be detected according to the ratio of the concentration of oxygen gas O2 between said two gases, a pair of electrode members formed at parts of said first and second surfaces, respectively, of said ceramic substrate, to detect said electromotive force, a first oxidation catalyst layer for promoting mainly oxidation reaction of unburnt components, which is arranged to cover said second surface of said ceramic substrate and an outer surface of the electrode member on the second surface, a laminate comprising a protecting layer of a metal oxide covering the outer surface of said ceramic substrate and a reduction catalyst layer for promoting mainly reduction reaction of nitrogen oxides NOx, and a second oxidation catalyst layer for promoting mainly oxidation reaction of hydrogen gas H2, which is arranged to cover an outer surface of said laminate.
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Accused Products
Abstract
An oxygen gas concentration-detecting apparatus in an internal combustion engine using an alcohol fuel includes a ceramic substrate having one surface falling in contact with a reference gas and the other surface falling in contact with an exhaust gas of the engine and generating an electromotive force according to oxygen gas concentrations of both the gases. A pair of electrode members are arranged on the ceramic substrate to take out the electromotive force. A first oxidation catalyst layer is formed on the outer surface of the ceramic substrate to promote oxidation reaction of unburnt components. A laminate of a protecting layer of a metal oxide and a reduction catalyst layer of promoting reduction reaction of nitrogen oxides is formed on the outer surface of the first oxidation catalyst layer, and a second oxidation catalyst layer is arranged on the outer side face of the laminate to promote oxidation reaction of hydrogen gas. According to this apparatus, hydrogen gas is oxidized in the first oxidation catalyst layer and a bad influences by the differences of the diffusion speed between hydrogen gas and oxygen gas in the protecting layer are eliminated, the time of inversion of the concentration of oxygen gas inclusive of oxygen gas generated by reduction of nitrogen oxides can be precisely detected and discharge of nitrogen oxides is controlled with omission of a so-called EGR control device.
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Citations
14 Claims
- 1. An oxygen concentration-detecting apparatus comprising a ceramic substrate for generating an electromotive force between a first surface contacted with a reference gas and a second surface contacted with a gas to be detected according to the ratio of the concentration of oxygen gas O2 between said two gases, a pair of electrode members formed at parts of said first and second surfaces, respectively, of said ceramic substrate, to detect said electromotive force, a first oxidation catalyst layer for promoting mainly oxidation reaction of unburnt components, which is arranged to cover said second surface of said ceramic substrate and an outer surface of the electrode member on the second surface, a laminate comprising a protecting layer of a metal oxide covering the outer surface of said ceramic substrate and a reduction catalyst layer for promoting mainly reduction reaction of nitrogen oxides NOx, and a second oxidation catalyst layer for promoting mainly oxidation reaction of hydrogen gas H2, which is arranged to cover an outer surface of said laminate.
Specification