Wide-range temperature operating system for combustion gas oxygen sensor, and method
First Claim
1. System for determination of the oxygen content in gases, especially the exhaust gases from a combustion process, and particularly from an internal combustion engine, havingan oxygen sensor (1) furnishing a sensed output signal varying between two values in dependence on oxygen content of the gas, and wherein the change in value, with respect to oxygen content, is dependent on operating temperature of the sensor, comprisingthreshold means (8) responding to the level of the sensed output signal of the sensor and providing discrete output signals (3b, 5b) representative of the sensed output signal;
- temperature signal generating means (4, 5, 6, 10, 11,
12) providing a temperature output signal representative of temperature of the sensor;
at least one controllable timing stage (9,
14) connected to receive the discrete output signals from said threshold means (8) and having a variable time constant, said timing stage being further connected to and controlled by said temperature signal of the temperature signal generating means, for varying the time constant thereof in dependence on the temperature of the sensor;
and means (13;
16, 19,
22) for providing a modified output signal (3d), coupled to said timing means, comprisingcombining means (13, 16;
17) combining an output signal (3c, 5c) from the timing stage (9,
14) with the discrete output signals (3b, 5b) to provide said modified output signal (3d, 5d).
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Abstract
To compensate for temperature-dependent shift on the operating characteristics of an oxygen ion conductive sensor which tends to shift the operating characteristics towards the "lean" range (λ>1) at low temperature, and towards the "rich" range (λ<1) at high temperature, the pulses derived from the sensor are delayed or shifted such that the trailing edge of the pulses, representative of shift from lean to rich direction, is transmitted with delay; dependent on temperature, the shift from rich to lean is also transmitted with delay. The delays are obtained by timing circuits (9, 14) which have variable time delays, the time delay being controlled by a temperature signal (9a) derived by sensing a-c resistance of the sensor, split by a high-pass filter and rectified. The pulses are extended by extending the trailing edge of the pulse by a first timing stage (9) or foreshorten, thus delaying, the occurrence of the leading edge of the pulses by a second timing circuit (14), the respective pulses being logically combined in dependence on temperature determined by a comparator (18) with respect to a temperature level of, for example, 300° C.-400° C. set point.
24 Citations
20 Claims
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1. System for determination of the oxygen content in gases, especially the exhaust gases from a combustion process, and particularly from an internal combustion engine, having
an oxygen sensor (1) furnishing a sensed output signal varying between two values in dependence on oxygen content of the gas, and wherein the change in value, with respect to oxygen content, is dependent on operating temperature of the sensor, comprising threshold means (8) responding to the level of the sensed output signal of the sensor and providing discrete output signals (3b, 5b) representative of the sensed output signal; -
temperature signal generating means (4, 5, 6, 10, 11,
12) providing a temperature output signal representative of temperature of the sensor;at least one controllable timing stage (9,
14) connected to receive the discrete output signals from said threshold means (8) and having a variable time constant, said timing stage being further connected to and controlled by said temperature signal of the temperature signal generating means, for varying the time constant thereof in dependence on the temperature of the sensor;and means (13;
16, 19,
22) for providing a modified output signal (3d), coupled to said timing means, comprisingcombining means (13, 16;
17) combining an output signal (3c, 5c) from the timing stage (9,
14) with the discrete output signals (3b, 5b) to provide said modified output signal (3d, 5d). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Method of determining the oxygen content in gases, especially the exhaust gas from a combustion process, and particularly from an internal combustion engine, in which an oxygen sensor (1) is provided, exposed to the exhaust gases, and furnishing a sensed output signal varying between two values in dependence on the oxygen content in the gas, and wherein the change in output signal value, with respect to oxygen content, is dependent on operating temperature of the sensor, comprising the steps of
deriving a temperature signal representative of temperature of the sensor; -
deriving discrete output pulses (3b, 5b) representative of the sensed output signal; and modifying the length of the pulses in dependence on the sensed temperature. - View Dependent Claims (13, 14, 15, 16, 17)
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18. System for determination of the oxygen content in gases, especially the exhaust gases from a combustion process, and particularly from an internal combustion engine, having
an oxygen sensor (1) furnishing a sensed output signal varying between two values in dependence on oxygen content of the gas, and wherein the change in value, with respect to oxygen content, is dependent on operating temperature of the sensor, comprising threshold means (8) responding to the level of the sensed output signal of the sensor and providing discrete output signals (3b, 5b) representative of the sensed output signal; -
temperature signal generating means (4, 5, 6, 10, 11,
12) providing a temperature output signal representative of temperature of the sensor;at least one controllable timing stage (9,
14) connected to receive the discrete output signals from said threshold means (8) and having a variable time constant, said timing stage being further connected to and controlled by said temperature signal of the temperature signal generating means, for varying the time constant thereof in dependence on the temperature of the sensor;and means (13;
16, 19,
22) connected to receive an output from said least one controllable timing stage for providing a modified output signal;wherein the sensor provides output pulses having a first polarity upon sensing a change of composition of gases from a lean to rich composition; and the timing stage provides for extension of pulses to said modified output signal deriving means to delay the shift of the pulses derived from the sensor upon change of gas composition from "lean" to "rich". - View Dependent Claims (19, 20)
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Specification