Temperature-compensated exhaust gas recirculation system
First Claim
1. An exhaust gas recirculation (EGR) valve (12) of the type that is connected between an engine exhaust manifold (14) and an engine air intake manifold (16) and is electrically actuable to control exhaust gas flow from the exhaust manifold (14) to the air intake manifold (16), said EGR valve (12) characterized by:
- a first inductive coil (48) including a number of turns of an electrical conductor (52), whereby said first coil (48) produces a magnetic field when energized, said electrical conductor (52) having a positive temperature coefficient of resistance;
a ferromagnetic armature (62) disposed adjacent said first coil (48), said ferromagnetic armature (62) being movable under the influence of the magnetic field to regulate the flow rate of the exhaust gas through said EGR valve (12);
a resistive combination of circuit elements (76) connected in series with said first coil (48), said resistive combination of circuit elements (76) including a first resistive element (75) and a second resistive element (72) connected across said first resistive element (75), said first resistive element (75) having a temperature-dependent range of resistance values and a negative temperature coefficient of resistance and said second resistive element (72) having a resistance value,wherein said resistive combination of circuit elements (76) has a resistance that exhibits a preselected negative temperature characteristic whereby the variation in resistance seen across the series connection of said first coil (48) and said resistive combination (76) due to temperature changes is less than the variation in resistance of said first coil (48) alone due to the temperature changes.
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Accused Products
Abstract
A solenoid exhaust gas recirculation (EGR) valve (12) includes a first inductive coil (48) that generates a magnetic field when energized by a signal from a control unit (13). The magnetic field drives a ferromagnetic armature valve (64) open and closed--metering the flow of recovered exhaust gases from an engine exhaust manifold (14) to an engine air intake manifold (16). The exhaust gas flow rate depends upon the amount of current flowing through the first coil (48). The resistance of the first coil (48) is temperature-dependent. Therefore, to reduce changes in coil current and magnetic field strength due to temperature changes, the first coil (48) is connected in series with a thermistor (75) having a temperature coefficient of resistance that is opposite that of the first coil (48). A temperature stable resistor in the form of a second coil (72) is connected across the thermistor (75) to modify the thermistor temperature-response curve to more closely offset that of the first coil (48). The second coil (72) may be disposed adjacent the first coil (48) to generate a magnetic field opposite that of the first coil (48). The opposing field reduces residual magnetism causing the valve (12) to respond to control inputs more positively.
29 Citations
9 Claims
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1. An exhaust gas recirculation (EGR) valve (12) of the type that is connected between an engine exhaust manifold (14) and an engine air intake manifold (16) and is electrically actuable to control exhaust gas flow from the exhaust manifold (14) to the air intake manifold (16), said EGR valve (12) characterized by:
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a first inductive coil (48) including a number of turns of an electrical conductor (52), whereby said first coil (48) produces a magnetic field when energized, said electrical conductor (52) having a positive temperature coefficient of resistance; a ferromagnetic armature (62) disposed adjacent said first coil (48), said ferromagnetic armature (62) being movable under the influence of the magnetic field to regulate the flow rate of the exhaust gas through said EGR valve (12); a resistive combination of circuit elements (76) connected in series with said first coil (48), said resistive combination of circuit elements (76) including a first resistive element (75) and a second resistive element (72) connected across said first resistive element (75), said first resistive element (75) having a temperature-dependent range of resistance values and a negative temperature coefficient of resistance and said second resistive element (72) having a resistance value, wherein said resistive combination of circuit elements (76) has a resistance that exhibits a preselected negative temperature characteristic whereby the variation in resistance seen across the series connection of said first coil (48) and said resistive combination (76) due to temperature changes is less than the variation in resistance of said first coil (48) alone due to the temperature changes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification