Temperature correction method and subsystem for automotive evaporative leak detection systems
AssigneeSiemens Canada Limited
InventorsJohn E. Cook, Paul D. Perry
Life of this patent
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Abstract
A method and sensor or sensor subsystem permit improved evaporative leak detection in an automotive fuel system. The sensor or sensor subsystem computes temperature-compensated pressure values, thereby eliminating or reducing false positive or other adverse results triggered by temperature changes in the fuel tank. The temperature-compensated pressure measurement is then available for drawing an inference regarding the existence of a leak with reduced or eliminated false detection arising as a result of temperature fluctuations.
Claims6
A method for making fast temperature-compensated pressure readings in an automotive evaporative leak detection system having a non-stabilized tank with a vapor pressure having a value P1 at a first point in time, comprising the steps of:
- a. measuring a first temperature T1 of the vapor at substantially the first point in time;
- b. measuring a second temperature T2 of the vapor at a second point in time;
- and
- c. computing a temperature-compensated pressure PC=P1(2−T2/T1) wherein it is assumed that there are negligible changes in moles and volume of the tank.
In an automotive evaporative leak detection system, a temperature-compensated pressure sensor comprising:
- a. a pressure sensing element;
- b. a temperature sensing element;
- b. a processor coupled to the pressure sensing element and to the temperature sensing element and receiving, respectively, pressure and temperature signals therefrom;
- and
- c. logic implemented by the processor for computing a temperature-compensated pressure PC=P1(2−T2/T1) wherein P1 is a pressure measured at a first point in time, T1 is a temperature measured at substantially the first point in time, and T2 is a temperature measured at a second point in time, and wherein it is assumed that there are negligible changes in moles and volume of the system.
In an automotive evaporative leak detection system, a sensor subsystem for compensating for the effects on pressure measurement of changes in temperature of fuel tank vapor, the subsystem comprising:
- a. a pressure sensor in fluid communication with the fuel tank vapor;
- b. a temperature sensor in thermal contact with the fuel tank vapor;
- c. a processor in electrical communication with the pressure sensor and with the temperature sensor;
- and
- d. logic implemented by the processor for computing a temperature-compensated pressure Pc=P1(2−T2/T1) wherein P1 is a pressure measured at a first point in time, T1 is a temperature measured at substantially the first point in time, and T2 is a temperature measured at a second point in time, and wherein it is assumed that there are negligible changes in moles and volume of the system.
Dependencies are inferred from the claim text.