Hydraulic Pump Pressure-Hold Fault Isolation Using Blocked Flow
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Solution Overview
Problem
Conventional hydraulic units cannot distinguish between abnormalities in the hydraulic circuit and the main machine when a change in rotational frequency of the variable speed motor occurs during a pressure holding state, leading to uncertainty about the source of the issue.
Innovation Solution
A hydraulic unit with a control device that monitors the rotational frequency and discharge flow rate of the hydraulic pump, using a valve to block the discharge flow path and a pressure sensor to detect pressure, determines if the hydraulic circuit is abnormal by comparing these parameters to predetermined values, and includes a leakage flow path to improve stability and accuracy of pressure control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a variable speed motor drives the hydraulic pump in a conventional hydraulic unit, then the hydraulic circuit can be controlled to maintain constant discharge pressure, but it becomes impossible to identify whether abnormality occurs in the hydraulic unit or the main machine when rotational frequency changes
Solution Approach 1:
The patent segments the hydraulic system into two independent testable parts: the hydraulic unit (pump, valve, sensor) and the main machine (hydraulic actuator). By using a blocking valve to isolate the discharge flow path to the actuator, the system can perform abnormality determination tests that specifically evaluate the hydraulic unit's components, thereby identifying whether the abnormality originates in the hydraulic unit or the main machine.
Solution Approach 2:
The patent introduces a blocking valve as an intermediary component that can selectively close the discharge flow path. This valve acts as a mediator between the hydraulic pump and the hydraulic actuator, enabling the system to create test conditions where the discharge flow is blocked to evaluate pump performance and identify abnormality sources without affecting the normal operation of the main machine.
2Loss of information
If the discharge flow path is blocked to determine hydraulic circuit abnormality, then the abnormality source can be identified, but the hydraulic pump cannot supply hydraulic oil to the hydraulic actuator
Solution Approach 1:
The blocking valve is designed as a dynamic component that can switch between open and closed states. During normal operation, the valve remains open to allow hydraulic oil flow to the actuator, maintaining productivity. When abnormality determination is needed, the valve closes to block the flow path for testing. This dynamic switching capability resolves the contradiction between identifying abnormality sources and maintaining continuous hydraulic actuator operation.
3Use of energy by moving object
If the hydraulic pump operates at low rotational frequency, then energy consumption is reduced, but drive torque becomes unstable and pressure control deteriorates
Solution Approach 1:
The patent employs a pressure sensor to detect discharge pressure and feeds this information back to the control device. The control device uses this feedback to determine whether the hydraulic unit is abnormal by comparing the detected pressure with expected values during blocked flow conditions. This feedback mechanism enables accurate abnormality determination without requiring the pump to operate continuously at high rotational frequencies, thereby reducing energy consumption while maintaining control stability through intelligent monitoring.
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
The solution effectively identifies abnormalities in the hydraulic circuit by determining changes in rotational frequency and discharge flow rate, allowing for reliable detection of leaks or clogging, and maintains stable pressure control by adjusting the flow rate set value, thereby improving the performance of the hydraulic actuator.
Implementation Method 1
a pressure sensor configured to detect a pressure of the hydraulic oil in a flow path portion, between the valve and the hydraulic pump, of the discharge flow path
Implementation Method 2
a hydraulic pump configured to supply the hydraulic oil to the hydraulic actuator from the hydraulic oil tank
Data Source
Figure 1
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Figure 4
AI summary
A hydraulic unit (1) includes a hydraulic circuit (10) and a control device (20) that controls the hydraulic circuit (10). The hydraulic circuit (10) includes a hydraulic pump (12) that supplies hydraulic oil to a hydraulic actuator (2a), a discharge flow path (14) that connects the hydraulic pump (12) and the hydraulic actuator (2a), a valve (15) that blocks a flow of the hydraulic oil in the discharge flow path (14), and a pressure sensor (16) that detects a pressure of the hydraulic oil in the discharge flow path (14). In a pressure holding state, when the rotational frequency of the hydraulic pump (12) exceeds a predetermined first determination rotational frequency (N1) or when the discharge flow rate of the hydraulic pump (12) exceeds a predetermined first determination discharge flow rate (Ql), the control device (20) determines that the hydraulic circuit (10) is abnormal.