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US 7,582,197 B2Granted
Gas concentration measuring apparatus with failure monitor
AssigneeDenso Corporation
InventorsTomoo Kawase, Eiichi Kurokawa
Life of this patent
Estimating the term…
Abstract
A gas concentration measuring apparatus for use in air-fuel ratio control of motor vehicle engines is provided which is designed to detect and identify a cause of failure in operation of an A/F sensor. The apparatus works to apply the voltage to a sensor element and sweep it to produce a change in electrical current flowing through the sensor element for measuring the impedance of the sensor element. The apparatus samples values of the change in the current, a sensor output indicating an air-fuel ratio of mixture supplied to the engine, etc., before and/or after the sensor element is activated and uses a combination thereof to identify the cause of the failure of the A/F sensor.
Claims19
A gas concentration measuring apparatus comprising:
- a gas concentration sensor equipped with a sensor element which is made of a solid electrolyte body and a pair of electrodes affixed to the solid electrolyte body;
- a sensor control circuit connected to the electrodes of the sensor element through a positive and a negative terminal, when a gas concentration measuring mode is entered, said sensor control circuit applying a voltage across the electrodes of the sensor element to produce a flow of electrical current through the sensor element and sampling the electrical current through a current-measuring resistor to output a sensor current signal as indicating a concentration of a gas to be measured, when an internal resistance measuring mode is entered, said sensor control circuit working to perform one of a voltage sweep mode and a current sweep mode, in the voltage sweep mode, said sensor control circuit applying a voltage to the sensor element and sweeping the applied voltage in an ac form to sample a resulting change in voltage provided by the sensor element, in the current sweep mode, said sensor control circuit supplying a current to the sensor element and sweeping the supplied current in an ac form to sample a resulting change in current provided by the sensor element, said sensor control circuit outputting one of the resulting changes in voltage and current as an internal resistance signal;
- and
- a failure monitor working to sample values of the sensor current signal before and after the sensor element is activated and a value of the internal resistance signal after the sensor element is activated, said failure monitor detecting a failure in said gas concentration sensor based on the sampled values.
1 more element
A gas concentration measuring apparatus comprising:
- a gas concentration sensor equipped with a sensor element which is made of a solid electrolyte body and a pair of electrodes affixed to the solid electrolyte body;
- a sensor control circuit connected to the electrodes of the sensor element through a positive and a negative terminal, when a gas concentration measuring mode is entered, said sensor control circuit applying a voltage across the electrodes of the sensor element to produce a flow of electrical current through the sensor element and sampling the electrical current through a current-measuring resistor connected to one of the positive and negative terminals to output a sensor current signal as indicating a concentration of a gas to be measured, when an internal resistance measuring mode is entered, said sensor control circuit working to perform one of a voltage sweep mode and a current sweep mode, in the voltage sweep mode, said sensor control circuit applying a voltage to the sensor element and sweeping the applied voltage in an ac form to sample a resulting change in voltage provided by the sensor element, in the current sweep mode, said sensor control circuit supplying a current to the sensor element and sweeping the supplied current in an ac form to sample a resulting change in current provided by the sensor element, said sensor control circuit outputting one of the resulting changes in voltage and current as an internal resistance signal;
- and
- a failure monitor working to sample values of voltages appearing at the other of the positive and negative terminals before and after the sensor element is activated and a value of the internal resistance signal after the sensor element is activated, said failure monitor detecting a failure in said gas concentration sensor based on the sampled values.
1 more element
A gas concentration measuring apparatus comprising:
- a gas concentration sensor equipped with a sensor element which includes a first cell and a second cell, the first cell being made of a solid electrolyte material and working to perform an oxygen pumping operation to produce an electrical current as a function of a pumped amount of oxygen, the second cell being made of a solid electrolyte material and working to produce an electromotive force as a function of a concentration of oxygen contained in a gas to be measured;
- a sensor control circuit working to perform a gas concentration measuring mode and an internal resistance measuring mode, when the gas concentration measuring mode is entered, said sensor control circuit applying a voltage to the first cell, controlling the applied voltage as a function of the electromotive force produced by the second cell to produce a flow of an electrical current through the first cell, and sampling the electrical current through a current-measuring resistor to output the sampled electrical current as a sensor current signal as indicating a concentration of a gas to be measured, when the internal resistance measuring mode is entered, said sensor control circuit working to perform one of a voltage sweep mode and a current sweep mode, in the voltage sweep mode, said sensor control circuit applying a voltage to the second cell and sweeping the applied voltage in an ac form to sample a resulting change in voltage provided by the second cell, in the current sweep mode, said sensor control circuit supplying a current to the second cell and sweeping the supplied current in an ac form to sample a resulting change in current provided by the second cell, said sensor control circuit outputting one of the resulting changes in voltage and current as an internal resistance signal;
- and
- a failure monitor working to sample values of the sensor current signal, the internal resistance signal, and voltages appearing at at least one of positive and negative terminals connected to the first cell before and after the sensor element is activated, said failure monitor detecting a failure in said gas concentration sensor based on the sampled values.
1 more element
A gas concentration measuring apparatus comprising:
- a gas concentration sensor equipped with a sensor element which is made of a solid electrolyte body and a pair of electrodes affixed to the solid electrolyte body;
- a sensor control circuit connected to the electrodes of the sensor element through a positive and a negative terminal, when a gas concentration measuring mode is entered, said sensor control circuit applying a voltage across the electrodes of the sensor element within a given applied-voltage control range to produce a flow of electrical current through the sensor element and sampling the electrical current to output a sensor current signal as indicating a concentration of a gas to be measured, said sensor control circuit also sampling voltages appearing at the positive and negative terminals;
- and
- a failure monitor working to monitor a failure in said gas concentration sensor, when the voltages at the positive and negative terminals, as sampled by said sensor control circuit, are identical with each other, one of the voltages at the positive and negative terminals lies within the applied-voltage control range, and the sensor current signal has an unusual value, said failure monitor determining that an electrical short has occurred between the positive and negative terminals.
1 more element
A gas concentration measuring apparatus comprising:
- a gas concentration sensor equipped with a sensor element which is made of a solid electrolyte body and a pair of electrodes affixed to the solid electrolyte body;
- a sensor control circuit connected to the electrodes of the sensor element through a positive and a negative terminal, when a gas concentration measuring mode is entered, said sensor control circuit applying a voltage across the electrodes of the sensor element within a given applied-voltage control range to produce a flow of electrical current through the sensor element and sampling the electrical current to output a sensor current signal as indicating a concentration of a gas to be measured, said sensor control circuit also sampling voltages appearing at the positive and negative terminals;
- and
- a failure monitor working to monitor a failure in said gas concentration sensor, when the voltages at the positive and negative terminals, as sampled by said sensor control circuit before said sensor element is activated, are identical with each other, and the sensor current signal has an unusual value, said failure monitor determining that an electrical short has occurred between the positive and negative terminals.
1 more element
Dependencies are inferred from the claim text.