Hydraulic accumulator health diagnosis

Patent metadata

Field	Value
Publication number	US-9366269-B2
Application number	US-201213427095-A
Country	US
Kind code	B2
Filing date	Mar 22, 2012
Priority date	Mar 22, 2012
Publication date	Jun 14, 2016
Grant date	Jun 14, 2016

Abstract

A system to diagnose a health of a hydraulic accumulator is provided. The hydraulic accumulator includes a first fluid chamber, a second fluid chamber, and a separator. The hydraulic accumulator has an associated pre-charge pressure. The system further includes a pressure sensor, a fluid source, a data processor, and a comparator. The pressure sensor and the fluid source are connected to the first fluid chamber. The data processor is configured to determine a first and second rate of pressure changes, and a transition pressure between the first and second rates. The approximate pre-charge pressure is determined based on the transition pressure. The comparator is configured to compare at least one of the determined pre charge pressure and the frictional forces with a pre-determined threshold range of pre-charge pressure and the frictional forces associated with the hydraulic accumulator to diagnose the health of the hydraulic accumulator.

First claim

What is claimed is:

1. A system to diagnose a health of a hydraulic accumulator having a first fluid chamber configured to be filled with a working fluid, a second fluid chamber configured to be filled with a compressible fluid, and a separator disposed therebetween, wherein the hydraulic accumulator is capable of an associated pre-charge pressure, the system comprising:
a pressure sensor connected to the first fluid chamber;
a fluid source configured to connect with the first fluid chamber;
a data processor connected to the pressure sensor, the data processor configured to:
determine a first rate of pressure change, a second rate of pressure change different than the first rate, and a transition pressure between the first and second rates; and
determine an approximated pre-charge pressure of the hydraulic accumulator based on the transition pressure; and

a comparator to compare the approximated pre-charge pressure with a pre-determined threshold range of pre-charge pressures associated with the hydraulic accumulator, thereby to diagnose the health of the hydraulic accumulator.

2. The system of claim 1 , wherein the pre-determined threshold range is derived from one or more historical readings of pre-charge pressure determined by the data processor.

3. The system of claim 1 , wherein the comparator is further adapted to notify an operator if the approximated pre-charge pressure is outside the pre-determined threshold range of pre-charge pressures.

4. The system of claim 1 , wherein the approximated pre-charge pressure is calculated by determining a difference of a pressure of fluid within the first fluid chamber during a minimum volume state of the first fluid chamber and the transition pressure.

5. The system of claim 1 , wherein the data processor is configured to co-relate one or more pressure readings of the fluid in the first fluid chamber to determine the approximated pre-charge pressure of the hydraulic accumulator.

6. The system of claim 1 , wherein the data processor is further configured to monitor a rate of change of pressure, with respect to time, of the fluid to determine frictional forces associated with the separator of the hydraulic accumulator.

7. A method of diagnosing a health of a hydraulic accumulator, the method comprising:
reducing a first fluid chamber of a hydraulic accumulator to a minimum volume state, the first fluid chamber configured to be filled with a working fluid and the hydraulic accumulator having a second fluid chamber configured to be filled with a compressible fluid;
providing a pressurized fluid to the first fluid chamber, wherein a pressure of the fluid in the first fluid chamber changes at a first rate and transitions to a second rate at a first transition pressure;
determining a first approximated pre-charge pressure of the hydraulic accumulator based on the first transition pressure;
comparing the first approximated pre-charge pressure of the hydraulic accumulator based on the first transition pressure with a pre-determined threshold range of pre-charge pressures, thereby to diagnose the health of the hydraulic accumulator;
discharging the fluid from the first fluid chamber after the fluid reaches a pre-determined pressure at the second rate, wherein a pressure of the fluid in the first fluid chamber changes at a third rate and transitions to a fourth rate at a second transition pressure;
determining a second approximated pre-charge pressure of the hydraulic accumulator based on the second transition pressure; and
comparing the second approximated pre-charge pressure of the hydraulic accumulator based on the second transition pressure with the pre-determined threshold range of pre-charge pressures, thereby to diagnose the health of the hydraulic accumulator.

8. The method of claim 7 , further comprising notifying an operator when at least one of the first and second approximated pre-charge pressures is outside the pre-determined threshold range of pre-charge pressures.

9. The method of claim 7 further comprising:
monitoring the first rate, the second rate, the third rate, the fourth rate, and the first and second transition pressures; and
determining frictional forces associated with the hydraulic accumulator based on the first, second, third and fourth rates.

10. The method of claim 9 further comprising comparing the determined frictional forces of the hydraulic accumulator with a pre-determined threshold range of frictional forces associated with the hydraulic accumulator.

11. The method of claim 10 further comprising notifying an operator if the determined frictional forces are outside the pre-determined threshold range of the frictional forces associated with the hydraulic accumulator.

12. The method of claim 7 , wherein the first rate is greater than the second rate.

13. The method of claim 12 , wherein the fourth rate is greater than the third rate.

14. The method of claim 7 , wherein determining the first approximated pre-charge pressure comprises calculating an average of the first and second transition pressures.

15. The method of claim 7 , wherein the minimum volume state of the hydraulic accumulator is associated with a minimum volume state of the first fluid chamber and a maximum volume state in the second fluid chamber of the hydraulic accumulator.

16. The method of claim 7 further comprising monitoring a peak pressure of the fluid between the change of pressure rates of the first and second rates, wherein the peak pressure of the fluid is greater than the first transition pressure.

17. The method of claim 16 , wherein the peak pressure of the fluid corresponds to a required pressure of the fluid to initiate a change in the minimum volume state of the hydraulic accumulator.

18. The method of claim 16 further comprising:
comparing the peak pressure with the first transition pressure; and
determining a dynamic response of the hydraulic accumulator based on the comparison.

19. A computer based system comprising:
a communication interface communicating with a memory;
the memory configured to communicate with a processor; and
the processor, in response to executing a computer program, performs operations comprising:
reducing a first fluid chamber of a hydraulic accumulator to a minimum volume state, the first fluid chamber configured to be filled with a working fluid and the hydraulic accumulator having a second fluid chamber configured to be filled with a compressible fluid;
providing a pressurized fluid to the first fluid chamber, wherein a pressure of the fluid in the first fluid chamber changes at a first rate and transitions to a second rate at a transition pressure;
determining an approximated pre-charge pressure of the hydraulic accumulator based on the transition pressure; and
comparing the approximated pre-charge pressure of the hydraulic accumulator based on the transition pressure with a pre-determined threshold range of pre-charge pressures, thereby to diagnose a health of the hydraulic accumulator.

Assignees

• Chen Dayao
• Ma Pengfei
• Shang Tonglin
• Hillman Bryan J
• Caterpillar Inc

Inventors

• Chen Dayao
• Ma Pengfei
• Shang Tonglin
• Hillman Bryan J

Classifications

• F15B1/033 Primary

  with electrical control means · CPC title

• F15B2201/51

  Pressure detection · CPC title

• F15B2201/505

  Testing of accumulators, e.g. for testing tightness · CPC title