Method and system for determining an accumulator pre-charge pressure in a fluid circuit
First Claim
1. A system comprising:
- a hydraulic fluid pump providing hydraulic fluid at line pressure to a fluid pressure powered component;
a piston having a seal;
a hydraulic accumulator in fluid communication with the hydraulic fluid pump and the fluid pressure powered component, and containing the piston and the seal, wherein the hydraulic fluid pump is configured to selectively feed some of the hydraulic fluid to the hydraulic accumulator to thereby charge the hydraulic accumulator;
a pressure sensor positioned with respect to the hydraulic accumulator that measures the line pressure; and
a controller in electrical communication with the pressure sensor, wherein the controller is configured to;
calculate respective slopes of a first set and a second set of measured pressure values as communicated to the controller by the pressure sensor;
calculate a ratio of the respective slopes;
compare the calculated ratio of the respective slopes to a ratio threshold;
record a pre-charge pressure as a pressure value corresponding to a point of intersection of a pair of lines representing the respective slopes when the calculated ratio exceeds the ratio threshold, wherein the recorded pre-charge pressure corresponds to a point of inflection of the piston within the hydraulic accumulator at which drag from the seal is first overcome when none of the hydraulic fluid is contained in the hydraulic accumulator; and
execute a control action with respect to at least one of the hydraulic fluid pump and the hydraulic accumulator when the recorded pre-charge pressure is less than a calibrated minimum threshold.
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Accused Products
Abstract
A system includes a pump, accumulator, a sensor which measures line pressure in a fluid circuit, and a controller. The controller plots and calculates respective slopes of first and second sets of measured pressure values from the sensor, calculates a slope ratio, and compares the slope ratio to a threshold. The controller also records the pre-charge pressure as the point of intersection of lines representing the slopes when the ratio exceeds the threshold. A control action is executed when the pre-charge pressure drops below a calibrated minimum threshold. A method includes measuring the pressure values, calculating the respective slopes and the slope ratio, comparing the slope ratio to a ratio threshold, recording the point of intersection of lines representing the slopes as an interpolated pre-charge pressure value when the ratio exceeds the threshold, and executing the control action.
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Citations
17 Claims
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1. A system comprising:
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a hydraulic fluid pump providing hydraulic fluid at line pressure to a fluid pressure powered component; a piston having a seal; a hydraulic accumulator in fluid communication with the hydraulic fluid pump and the fluid pressure powered component, and containing the piston and the seal, wherein the hydraulic fluid pump is configured to selectively feed some of the hydraulic fluid to the hydraulic accumulator to thereby charge the hydraulic accumulator; a pressure sensor positioned with respect to the hydraulic accumulator that measures the line pressure; and a controller in electrical communication with the pressure sensor, wherein the controller is configured to; calculate respective slopes of a first set and a second set of measured pressure values as communicated to the controller by the pressure sensor; calculate a ratio of the respective slopes; compare the calculated ratio of the respective slopes to a ratio threshold; record a pre-charge pressure as a pressure value corresponding to a point of intersection of a pair of lines representing the respective slopes when the calculated ratio exceeds the ratio threshold, wherein the recorded pre-charge pressure corresponds to a point of inflection of the piston within the hydraulic accumulator at which drag from the seal is first overcome when none of the hydraulic fluid is contained in the hydraulic accumulator; and execute a control action with respect to at least one of the hydraulic fluid pump and the hydraulic accumulator when the recorded pre-charge pressure is less than a calibrated minimum threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method comprising:
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measuring, via a pressure sensor, a first set and a second set of pressure values in a fluid circuit having a hydraulic fluid pump and a hydraulic accumulator, wherein the hydraulic accumulator includes a piston and a seal, and wherein the hydraulic accumulator is selectively charged via an admission of hydraulic fluid circulated via the hydraulic fluid pump; calculating the respective slopes of the first and second sets of pressure values using a controller that is in electrical communication with the pressure sensor; calculating a ratio of the respective slopes; comparing the calculated ratio of the respective slopes to a ratio threshold; recording a point of intersection of a pair of lines representing the slopes as a calculated pre-charge pressure value when the ratio exceeds the threshold, wherein the calculated pre-charge pressure corresponds to a point of inflection of the piston within the hydraulic accumulator at which drag from the seal is first overcome when none of the hydraulic fluid is contained in the hydraulic accumulator; and executing a control action, via the controller, with respect to at least one of the hydraulic fluid pump and the accumulator when the calculated pre-charge pressure drops below a calibrated pressure threshold. - View Dependent Claims (10, 11, 12, 13, 14)
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15. A vehicle comprising:
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a transmission having a fluid pressure powered component; a hydraulic fluid pump in fluid communication with the fluid pressure powered component, and operable to circulate hydraulic fluid; a hydraulic accumulator having an inlet and containing a piston and a seal, wherein the hydraulic accumulator is in fluid communication with the hydraulic fluid pump, wherein the hydraulic fluid pump is configured to selectively feed some of the hydraulic fluid to the hydraulic accumulator to thereby charge the hydraulic accumulator; a pressure sensor positioned configured to measure line pressure in a fluid circuit in proximity to the inlet of the hydraulic accumulator; and a controller in electrical communication with the pressure sensor, wherein the controller; receives measured pressure values from the pressure sensor; records the measured pressure values in a ring buffer having designated partitions corresponding to the most recently recorded and oldest recorded pressure values; calculates the respective slopes of the most recently recorded and oldest recorded pressure values; calculates a ratio of the respective slopes; compares the calculated ratio of the respective slopes to a ratio threshold of greater than about 4;
1;records a calculated pre-charge pressure value as the point of intersection of a pair of lines representing the respective slopes only when the ratio exceeds the ratio threshold, wherein the calculated pre-charge pressure corresponds to a point of inflection of the piston within the hydraulic accumulator at which drag from the seal is first overcome when none of the hydraulic fluid is contained in the hydraulic accumulator; filters the value of the calculated pre-charge pressure as a function of at least one previously calculated pre-charge pressure; and modifies an operating parameter of the pump when the calculated pre-charge pressure drops below a calibrated minimum threshold. - View Dependent Claims (16, 17)
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Specification