Hydraulic Actuator Flow Limiting at Low Prime Mover Speed
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Solution Overview
Problem
The existing hydraulic systems in working machines face issues where the delivery flow rate of the pump may be insufficient, leading to a state where hydraulic actuators are controlled based on the rotation speed of the prime mover, potentially resulting in inadequate fluid supply to the actuators.
Innovation Solution
A working machine with a controller that limits the maximum flow rate of hydraulic fluid supplied to the actuators based on the actual rotation speed of the prime mover, using a variable displacement hydraulic pump and control valves, ensuring the flow rate does not exceed a limit flow rate calculated from standard and maximum flow rate characteristic graphs, and incorporating a load sensing system to maintain constant differential pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the delivery flow rate of the pump is increased to ensure sufficient fluid supply to hydraulic actuators, then the fluid supply adequacy is improved, but the prime mover rotation speed requirement increases leading to higher energy consumption
Solution Approach 1:
The pump displacement is made variable rather than fixed, allowing the system to dynamically adjust the delivery flow rate according to actual hydraulic actuator demands and prime mover capabilities. The controller varies pump displacement to maintain adequate fluid supply while optimizing energy consumption based on operating conditions.
Solution Approach 2:
The system changes the pump delivery flow rate parameter dynamically by adjusting pump displacement based on prime mover rotation speed and hydraulic actuator flow demands. This parameter adaptation ensures sufficient fluid supply across varying operating conditions without requiring excessive prime mover power.
2Use of energy by moving object
If the pump delivery flow rate is limited to match prime mover capabilities, then energy consumption is reduced, but the hydraulic actuators may receive insufficient fluid supply
Solution Approach 1:
The controller receives feedback signals from rotation speed detectors monitoring prime mover speed and hydraulic actuators' flow demands. Based on this feedback, the controller adjusts pump displacement in real-time to ensure the delivery flow rate matches both prime mover capabilities and actual hydraulic system requirements, preventing both excess energy consumption and insufficient fluid supply.
3Device complexity
If a fixed displacement pump is used to simplify the hydraulic system, then device complexity is reduced, but the system cannot adapt to varying prime mover rotation speeds and flow demands
Solution Approach 1:
The pump is designed with variable displacement capability, transforming it from a static to a dynamic component that can adapt its delivery flow rate. This dynamic characteristic enables the hydraulic system to respond to varying prime mover rotation speeds and actuator demands while maintaining manageable complexity through electronic control.
4Stability of the object's composition
If the minimum delivery flow rate of the regulator is set to a value more than zero to maintain constant differential pressure, then pressure stability is improved, but the flow rate cannot be reduced further even when prime mover rotation speed is low
Solution Approach 1:
The regulator's minimum delivery flow rate is transformed from a fixed mechanical setting to a dynamically adjustable parameter. The controller varies the regulator's minimum flow rate based on prime mover rotation speed, allowing the system to maintain adequate pressure stability while adapting flow rates to match actual prime mover capabilities across different operating conditions.
Data Source
AI summary
A working machine includes a prime mover to produce power, a variable displacement hydraulic pump to be actuated by power produced by the prime mover to deliver hydraulic fluid, a hydraulic actuator to be actuated by hydraulic fluid delivered by the hydraulic pump, a control valve to adjust hydraulic fluid to actuate the hydraulic actuator, and a controller configured or programmed to control the control valve. The controller is configured or programmed to, based on an actual rotation speed of the prime mover, control the control valve to limit a maximum flow rate of hydraulic fluid supplied from the control valve to the hydraulic actuator such that the maximum flow rate does not exceed a limit flow rate. The limit flow rate corresponding to a rotation speed of the prime mover is not more than a maximum delivery flow rate of the hydraulic pump corresponding to the rotation speed.