Hydraulic Work Tool Circuit With Pressure-Feedback Pump Control
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Solution Overview
Problem
Hydraulic excavators require large capacity relief valves for work tools, which are expensive and can degrade the operability of other actuators when used simultaneously due to pressure limitations.
Innovation Solution
A hydraulic circuit with a variable capacity pump, control valves, pressure sensors, and a controller that adjusts the hydraulic oil delivery rate and flow rates to reduce pressure and valve capacity, allowing for efficient operation of work tools and actuators with lower relief pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relief valve of large capacity is installed in the work tool circuit to deliver full flow from the pump during relief, then the work tool can operate properly, but the cost increases
Solution Approach 1:
The patent applies dynamics by making the pump delivery rate variable rather than fixed. The controller dynamically adjusts the pump delivery rate based on real-time pressure feedback from the pressure sensor, reducing it when pressure exceeds the predetermined value. This dynamic adjustment allows the system to maintain reliable work tool operation while avoiding the need for a large capacity relief valve, thereby reducing cost.
Solution Approach 2:
The patent implements feedback control by installing a pressure sensor to detect hydraulic oil pressure and a controller that receives this feedback signal. When the pressure sensor detects that pressure exceeds the predetermined value (set to not more than the relief pressure of the tool's relief valve), the controller responds by reducing the pump delivery rate. This closed-loop feedback system eliminates the need for a large capacity relief valve while ensuring reliable work tool operation.
2Adaptability or versatility
If the relief pressure of the work tool is set lower than the relief pressure of the entire circuit, then the work tool can operate with lower pressure requirements, but the operability of other actuators is degraded when used simultaneously
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting the pump delivery rate based on pressure feedback. When the work tool requires lower pressure operation, the system maintains this adaptability while the controller reduces the pump delivery rate when pressure exceeds the predetermined value. This prevents pressure buildup that would otherwise limit other actuators, ensuring both work tool adaptability and overall system operability can coexist.
Solution Approach 2:
The patent applies parameter changes by dynamically modifying the pump delivery rate parameter in response to pressure conditions. The controller changes the delivery rate parameter based on feedback from the pressure sensor, ensuring that when the work tool operates at lower pressure requirements, the overall circuit pressure does not rise excessively, thereby maintaining operability of other actuators.
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 the use of lower capacity relief valves, reducing costs and maintaining operability when multiple actuators are used simultaneously by controlling pressure and flow rates.
Implementation Method 1
a pressure sensor to detect a pressure of hydraulic oil flowing into the work tool
Implementation Method 2
a hydraulic pump of variable capacity
Implementation Method 3
a tool's relief valve to release hydraulic oil flowing between the control valve and the work tool
Data Source
AI summary
Problem to be solved: To provide a hydraulic circuit for the construction machine which enables to use the relief valve of low capacity in the work tool circuit. Solution: The hydraulic circuit 2 for a construction machine has: a hydraulic pump 4 of variable capacity, a work tool 6 operated by hydraulic oil delivered by the hydraulic pump 4, a work tool operating device 10 to output a signal for operating the work tool 6, a control valve 14 allowing the hydraulic pump 4 to supply the hydraulic oil to the work tool 6 based on the signal output from the work tool operating device 10, a tool's relief valve 44 to release the hydraulic oil flowing between the control valve 14 and the work tool 6, a pressure sensor 46 to detect a pressure of hydraulic oil flowing into the work tool 6, and a controller 48 to reduce a delivery rate from the hydraulic pump 4 when the pressure detected by the pressure sensor 46 exceeds a predetermined value.