Data processing: measuring – calibrating – or testing – Measurement system – Performance or efficiency evaluation
Reexamination Certificate
2002-10-07
2004-11-23
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Performance or efficiency evaluation
C073S046000, C073S118040, C714S026000
Reexamination Certificate
active
06823289
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pump fault diagnostic apparatus for a hydraulic drive system, and more particularly, to a pump fault diagnostic apparatus provided in a hydraulic drive system of a working machine which performs operations by driving a plurality of hydraulic actuators by a plurality of variable displacement hydraulic pumps, for performing a fault diagnosis of each hydraulic pump, and a display unit thereof.
BACKGROUND ART
There are working machines such as a hydraulic excavator that performs required operations by driving a plurality of hydraulic actuators by hydraulic fluids delivered from a plurality of hydraulic pumps. Of such working machines, for example, a large hydraulic excavator requires a large flow rate of hydraulic fluid to drive one hydraulic actuator, and therefore hydraulic fluids delivered from a plurality of hydraulic pumps are combined or joined to drive one hydraulic actuator. For this reason, when an abnormality is found in driving of a given hydraulic actuator, it is necessary to detect which hydraulic pump has trouble.
A conventional pump fault diagnostic apparatus for determining a faulty hydraulic pump is disclosed in JP, A, 10-54371. This pump fault diagnostic apparatus takes note of check valves placed to prevent backflows when hydraulic fluids delivered from a plurality of hydraulic are joined, and provides a differential pressure sensor to measure a differential pressure across these check valves and places a switch to operate the hydraulic pump to take a maximum tilting position. An operator of the working machine or a service man for maintenance of the working machine presses the switch to operate the hydraulic pump to take the maximum tilting position when the working machine is not operated and decides the quality of the hydraulic pump using a measured value of the differential pressure sensor when the hydraulic pump delivery rate is set at the maximum.
DISCLOSURE OF THE INVENTION
However, the above conventional art has the following problems.
The pump fault diagnostic apparatus described in JP, A, 10-54371 is such that the operator or the service man presses the switch to operate the hydraulic pump to take the maximum tilting position and then performs a fault diagnosis of the hydraulic pump as described above. Thus, the fault diagnosis of the hydraulic pump can be performed not when the working machine is actually operated but when the working machine is not operated. Furthermore, the operator or the service man has to press the switch, which is troublesome.
Furthermore, the hydraulic drive system of the working machine is generally designed to perform horsepower limiting control of the hydraulic pump so that the maximum pump delivery rate decreases as the pump delivery pressure increases. In the above pump fault diagnostic apparatus, the hydraulic pump is operated to take the maximum tilting position and the quality of the hydraulic pump is decided according to the delivery rate situation of the hydraulic pump at that time, and therefore, as a fault example of the hydraulic pump, a fault in which the hydraulic pump does not reach the maximum tilting position and the delivery rate of the pump becomes in short can be detected, but a fault when the hydraulic pump has a problem with the horsepower limiting control such that the delivery rate of the hydraulic pump does not reach a value specified by the horsepower limiting control when the delivery pressure of the hydraulic pump increases cannot be detected.
It is a first object of the present invention to provide a pump fault diagnostic apparatus for a hydraulic drive system and a display unit thereof which is capable of automatically making a fault diagnosis of the hydraulic pump during an actual operation of a working machine.
It is a second object of the present invention to provide a pump fault diagnostic apparatus for a hydraulic drive system and a display unit thereof which is capable of detecting a fault when there is a problem with horsepower limiting control of the hydraulic pump.
(1) To attain the above first and second objects, the present invention provides a pump fault diagnostic apparatus for a hydraulic drive system having at least one variable displacement hydraulic pump and horsepower limiting control means for controlling the hydraulic pumps such that a maximum pump delivery rate is reduced as a delivery pressure of the hydraulic pump increases, wherein the apparatus comprises: first sensor means for detecting the delivery rate of the hydraulic pump; second sensor means for detecting the delivery pressure of the hydraulic pump; data collecting means for measuring the pump delivery rate and pump delivery pressure during operation of the hydraulic drive system based on the detected values of the plurality of first sensor means and second sensor means and collecting the measured values as fault diagnostic data; and fault deciding means for calculating a target pump delivery rate of horsepower limiting control corresponding to the pump delivery pressure collected by the data collecting means, comparing the pump delivery rate collected by the data collecting means and the calculated target pump delivery rate and making a fault decision of the hydraulic pump.
By arranging the first and second sensor means, data collecting means and fault deciding means in this way, and collecting data of a pump delivery rate and a pump delivery pressure during the operation of the hydraulic drive system and comparing the target pump delivery rate of horsepower limiting control corresponding to this collected pump delivery rate and the collected pump delivery rate to make a fault decision of the hydraulic pump, it is possible to make a fault diagnosis of the hydraulic pump automatically during an actual operation of a working machine and detect a fault when there is any problem with horsepower limiting control of the hydraulic pump.
(2) To attain the above first and second objects, the present invention further provides a pump fault diagnostic apparatus for a hydraulic drive system having a plurality of variable displacement hydraulic pumps and horsepower limiting control means for controlling the plurality of hydraulic pumps such that respective maximum pump delivery rates are reduced as respective delivery pressures of the hydraulic pumps increase, wherein the apparatus comprises: first sensor means for detecting the respective delivery rates of the plurality of hydraulic pumps; second sensor means for detecting the respective delivery pressures of the plurality of hydraulic pumps; data collecting means for measuring, for each of the hydraulic pump, the pump delivery rate and pump delivery pressure while during operation of the hydraulic drive apparatus based on the detected values of the plurality of first sensor means and second sensor means and collecting the measured values as fault diagnostic data; and fault deciding means for calculating, for each of the hydraulic pump, a target pump delivery rate of horsepower limiting control corresponding to the pump delivery pressure collected by the data collecting means, comparing the pump delivery rate collected by the data collecting means and the calculated target pump delivery rate and making a fault decision of each of the hydraulic pumps.
With such features, as described in (1) above, it is possible to make a fault diagnosis of the hydraulic pump automatically during an actual operation of a working machine and detect a fault when there is any problem with horsepower limiting control of the hydraulic pumps, and further since data collection and fault decision are performed for each hydraulic pump, it is possible to detect a fault of the hydraulic pump while determining which of the plurality of hydraulic pumps has a problem.
(3) In the above (2), preferably, the data collecting means measures, for each of the hydraulic pump, the pump delivery pressure and pump delivery rate when the pump delivery rate reaches a maximum during operation of the hydraulic drive system based on the detected values of the plurality of f
Kasuya Hirotsugu
Ochiai Masami
Watanabe Yutaka
Barlow John
Hitachi Construction Machinery Co. Ltd.
Le John
Mattingly Stanger & Malur, P.C.
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