Hydraulic Pump Leakage Diagnosis by Bleed-Off Pressure Stabilization
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Solution Overview
Problem
The existing hydraulic pump failure diagnosing apparatus using check valves with differential pressure sensors lacks accuracy in measuring small flow rates, leading to energy loss and reduced precision in flow rate calculations due to large variations in flow rate with pressure changes.
Innovation Solution
A construction machine equipped with a pressure sensor, bleed-off adjusting device, and controller that measures the hydraulic pump's pressure while maintaining the flow rate, allowing for precise calculation of leakage flow rates by stabilizing pressure at a predetermined value and adjusting the bleed-off flow rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If check valves with differential pressure sensors are used to measure flow rate, then the device structure is simple, but the measurement precision drops in small flow rate range
Solution Approach 1:
The invention changes the measurement parameter from differential pressure across a check valve to pressure difference between two points in the discharge line. This parameter change enables accurate flow rate measurement in small flow rate ranges while maintaining simple device structure.
Solution Approach 2:
The invention introduces a flow rate calculation unit as an intermediary that calculates flow rate based on pressure difference measurements. This intermediary component enables precise flow rate determination without requiring complex direct measurement devices.
2Measurement precision
If the check valve opening is reduced to improve flow rate conversion accuracy, then the measurement precision improves, but energy loss increases due to large pressure loss during normal operation
Solution Approach 1:
The invention extracts the measurement function from the check valve and places it in the discharge line where pressure difference can be measured without affecting the check valve's normal operation. This separation allows accurate measurement without causing energy loss during operation.
Solution Approach 2:
The invention uses pressure sensors as intermediaries to measure flow rate indirectly by detecting pressure difference in the discharge line. This indirect measurement approach achieves high accuracy without modifying the check valve opening or causing energy loss.
3Device complexity
If differential pressure across check valve is used to determine flow rate, then the device structure is simple, but the reliability of diagnosis decreases due to large variation in flow rate with pressure changes
Solution Approach 1:
The invention changes the measurement location from across the check valve to along the discharge line, where pressure difference more reliably correlates with flow rate. This parameter change improves diagnosis reliability while keeping the apparatus structure simple.
Solution Approach 2:
The invention uses the controller to process pressure difference signals and calculate flow rate, providing a feedback mechanism that improves diagnosis reliability. The controller can compare calculated flow rate with expected values to detect pump abnormalities.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate measurement of minute leakage flow rates in one-sided tilting variable displacement hydraulic pumps, reducing energy loss and improving diagnostic accuracy.
Implementation Method 1
a pressure sensor that detects a pressure of the hydraulic pump
Implementation Method 2
a bleed-off adjusting device that is enabled to adjust a bleed-off flow rate of the hydraulic pump
Implementation Method 3
a one-sided tilting variable displacement hydraulic pump that is driven by the prime mover and that delivers the hydraulic fluid drawn from the tank
Data Source
AI summary
There is provided a construction machine that is capable of measuring a minute leakage flow rate of a one-sided tilting variable displacement hydraulic pump. The construction machine includes a pressure sensor that detects a pressure of a hydraulic pump, a bleed-off adjusting device that is enabled to adjust a bleed-off flow rate of the hydraulic pump, and an input device that gives an instruction for measurement of a leakage flow rate of the hydraulic pump. The controller is configured to measure, when the controller determines that the operation device is in a non-operated state and when a measuring command is inputted from the input device, a pressure of the hydraulic pump while changing a control command value for the bleed-off adjusting device in a state in which a flow rate of the hydraulic pump is maintained, and calculate the leakage flow rate of the hydraulic pump on the basis of the control command value for the bleed-off adjusting device at the time that the pressure of the hydraulic pump is stabilized at a predetermined pressure.