Gas concentration measuring apparatus compensating for error component of output signal
First Claim
1. A gas concentration measuring apparatus comprising:
- a gas concentration sensor including a diffused resistor into which gasses flow, an oxygen pump cell responsive to application of a voltage to discharge oxygen contained in the gasses and produce a first electric current as a function of concentration of the discharged oxygen, an oxygen detecting cell measuring a concentration of the oxygen discharged by the oxygen pump cell, and a specified gas component measuring cell responsive to application of a voltage to produce a second electric current as a function of concentration of a specified gas component contained in the gasses from which the oxygen is discharged by the first cell;
a first current measuring circuit measuring the first electric current flowing through said oxygen pump cell of said gas concentration sensor;
a second current measuring circuit measuring the second electric current flowing through the given gas component measuring cell of said gas concentration sensor; and
a correcting circuit correcting the second electric current measured by said second current measuring circuit based on the first electric current measured by said first current measuring circuit to compensate for an oxygen-caused error component of the second electric current which depends upon the concentration of oxygen in the gasses and provide an error-corrected second electric current.
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Accused Products
Abstract
A gas concentration measuring apparatus is provided which measures the concentration of two kinds of gas components such as O2 and NOx contained in exhaust gasses of an internal combustion engine of automotive vehicles. The apparatus has a gas sensor which includes a first cell responsive to application of a voltage to discharge O2 in the exhaust gasses to the outside and produce an electric current as a function of concentration of the discharged O2 and a second cell responsive to application of a voltage to produce an electric current as a function of concentration of NOx in the exhaust gasses from which the O2 is discharged by the first cell. The apparatus offsets an error component of the electric current produced by the second cell which depends upon O2 contained in the exhaust gasses.
40 Citations
6 Claims
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1. A gas concentration measuring apparatus comprising:
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a gas concentration sensor including a diffused resistor into which gasses flow, an oxygen pump cell responsive to application of a voltage to discharge oxygen contained in the gasses and produce a first electric current as a function of concentration of the discharged oxygen, an oxygen detecting cell measuring a concentration of the oxygen discharged by the oxygen pump cell, and a specified gas component measuring cell responsive to application of a voltage to produce a second electric current as a function of concentration of a specified gas component contained in the gasses from which the oxygen is discharged by the first cell;
a first current measuring circuit measuring the first electric current flowing through said oxygen pump cell of said gas concentration sensor;
a second current measuring circuit measuring the second electric current flowing through the given gas component measuring cell of said gas concentration sensor; and
a correcting circuit correcting the second electric current measured by said second current measuring circuit based on the first electric current measured by said first current measuring circuit to compensate for an oxygen-caused error component of the second electric current which depends upon the concentration of oxygen in the gasses and provide an error-corrected second electric current. - View Dependent Claims (2, 3, 4, 5, 6)
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Isf=Is·
Kb/(Ka·
Ip+Kb)
where Ka is a structural constant defined by a structure of the gas concentration sensor, and Kb is a correction coefficient defined by sensitivity of the second cell.
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3. A gas concentration measuring apparatus as set forth in claim 2, wherein the structural constant Ka is determined by a diffusion coefficient, a shape, and a volume of said diffused resistor, and locations of the first and second cell in the gas concentration sensor.
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4. A gas concentration measuring apparatus as set forth in claim 1, wherein said correcting circuit stores correction data representing a relation between the concentration of oxygen in the gasses and the oxygen-caused error component of the second electric current and monitors the first electric current to determine the error-corrected second electric current based on the correction data.
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5. A gas concentration measuring apparatus as set forth in claim 4, wherein the correction data is so defined that the concentration of the specified gas component indicated by the second electric current is decreased as the concentration of oxygen indicated by the first electric current increases.
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6. A gas concentration measuring apparatus as set forth in claim 1, wherein said correcting circuit controls the application of voltage to said oxygen pump cell to regulate an amount of the oxygen discharged by said oxygen pump cell based on an output of said oxygen detecting cell indicating the concentration of the oxygen discharged by the oxygen pump cell.
Specification