Oxygen concentration measuring device
First Claim
1. An oxygen concentration measuring device comprising:
- a limit current type oxygen sensor;
voltage applying means for applying voltage to said oxygen sensor;
current detecting means for detecting current flowing through said oxygen sensor due to said voltage applied to said oxygen sensor;
temperature measuring means for measuring temperature of said oxygen sensor based on the detected current; and
oxygen concentration measuring means for measuring oxygen concentration based on the measured temperature;
wherein said voltage applying means has negative bias means for negatively biasing said oxygen sensor and said oxygen concentration measuring device further comprises current estimating means for estimating a variation termination value of said current flowing through said oxygen sensor negatively biased by said negative bias means at a point of time in a variation process thereof, and for supplying the variation termination value to said temperature measuring means so that said temperature measuring means uses the variation termination value in place of the detected current.
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Accused Products
Abstract
An oxygen concentration measuring device capable of significantly shortening the period of time during which oxygen concentration cannot be measured. When measuring the temperature of a sensor main body, a microcomputer determines the temperature of the sensor main body by estimating a saturation current starting from a current detected by a current detecting circuit in a period of time before current flowing through the sensor main body finishes rising, after the sensor main body has been negatively biased by a bias control circuit. The sensor main body is positively biased by the bias control circuit directly after the period of time has lapsed. The microcomputer determines an air fuel ratio by using current in a period of time before current flowing through the sensor main body due to the positive bias finishes decreasing.
23 Citations
13 Claims
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1. An oxygen concentration measuring device comprising:
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a limit current type oxygen sensor; voltage applying means for applying voltage to said oxygen sensor; current detecting means for detecting current flowing through said oxygen sensor due to said voltage applied to said oxygen sensor; temperature measuring means for measuring temperature of said oxygen sensor based on the detected current; and oxygen concentration measuring means for measuring oxygen concentration based on the measured temperature; wherein said voltage applying means has negative bias means for negatively biasing said oxygen sensor and said oxygen concentration measuring device further comprises current estimating means for estimating a variation termination value of said current flowing through said oxygen sensor negatively biased by said negative bias means at a point of time in a variation process thereof, and for supplying the variation termination value to said temperature measuring means so that said temperature measuring means uses the variation termination value in place of the detected current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An oxygen concentration measuring device comprising:
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voltage applying means for applying voltage to said oxygen sensor; current detecting means for detecting current flowing through said oxygen sensor due to said voltage applied thereto and for obtaining a current level; internal resistance determining means for detecting an internal resistance of said oxygen sensor and determining a resistance range, to which said detected internal resistance of said oxygen sensor belongs, from among a plurality of set resistance ranges; and voltage determining means for determining a voltage to be applied to said oxygen sensor based on said resistance range determined by said internal resistance determining means and said current level obtained by said current detecting means. - View Dependent Claims (12)
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13. An oxygen concentration measuring device comprising:
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a limit current type oxygen sensor; voltage source providing a voltage to said oxygen sensor, said voltage source is used for negatively biasing said oxygen sensor; current monitoring device that detects current flowing through said oxygen sensor due to said voltage applied to said oxygen sensor; temperature monitoring device that measures a temperature of said oxygen sensor based on said detected current; and oxygen concentration measuring device that measures an oxygen concentration based on said measured temperature; and current estimating device that estimates a variation termination value of said current flowing through said oxygen sensor negatively biased by said negative bias means at a point of time in a variation process thereof, and for supplying said variation termination value to said temperature measuring means so that said temperature measuring means uses said variation termination value in place of said detected current.
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Specification