Hydraulic Actuator Pressure Control to Prevent Cavitation
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Solution Overview
Problem
Existing hydraulic work machines face issues with cavitation in hydraulic actuators due to insufficient flow rates when operating against gravitational or inertial forces, leading to inconsistent velocity control and potential over-speeding of hydraulic actuators.
Innovation Solution
A work machine with a controller that computes target velocities and pressures for hydraulic actuators, controlling the pump and meter-in/meter-out valves to maintain minimum pressure on the meter-in side, preventing cavitation while achieving accurate velocity control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the opening degree of the control valve is increased to prevent cavitation, then cavitation is prevented, but the velocity control accuracy deteriorates
Solution Approach 1:
The control valve opening degree is dynamically adjusted based on real-time pressure feedback from the actuator. The control device continuously monitors the pressure downstream of the control valve and modifies the opening degree to maintain pressure within a predetermined range, allowing the system to adapt between preventing cavitation and maintaining velocity control accuracy depending on operating conditions
Solution Approach 2:
A pressure sensor is installed downstream of the control valve to provide real-time pressure feedback to the control device. This feedback mechanism enables the control device to detect when pressure drops below the cavitation threshold and automatically adjust the valve opening degree to prevent cavitation while minimizing impact on velocity control
2Reliability
If the meter-in flow rate is increased to maintain pressure, then cavitation is prevented, but the actuator velocity becomes excessive
Solution Approach 1:
The system dynamically balances meter-in flow rate and meter-out flow rate based on real-time pressure conditions. When pressure drops indicate cavitation risk, the meter-in flow rate is increased to maintain pressure. When pressure is sufficient, the meter-in flow rate is reduced to match the meter-out flow rate, preventing excessive velocity while still preventing cavitation when needed
Solution Approach 2:
The control device changes the flow rate parameters of both meter-in and meter-out control valves based on pressure feedback. By adjusting these parameters dynamically, the system maintains pressure above the cavitation threshold while preventing excessive actuator velocity through coordinated control of both flow rates
3Reliability
If the control valve opening is continuously increased to maintain pressure, then cavitation is prevented, but energy consumption increases
Solution Approach 1:
Instead of continuously increasing the control valve opening degree, the system applies partial action by only increasing the opening degree when and to the extent necessary to prevent cavitation. The control device monitors pressure and makes minimal adjustments sufficient to maintain pressure above the cavitation threshold, avoiding excessive energy consumption that would result from continuously maintaining a large valve opening
Solution Approach 2:
The pressure feedback mechanism enables the system to detect actual pressure conditions and adjust the control valve opening degree only when necessary. This feedback-controlled approach prevents cavitation while minimizing energy consumption by avoiding unnecessary valve openings that would increase hydraulic energy loss
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
Prevents cavitation in hydraulic actuators by ensuring sufficient pressure on the meter-in side, allowing for precise velocity control of driven bodies in hydraulic excavators.
Implementation Method 1
a fluid pressure actuator that operates a driven body by being driven by supply and discharge of working fluid
Implementation Method 2
a meter-in control valve capable of controlling a flow rate of the working fluid to be supplied from the pump to the fluid pressure actuator
Implementation Method 3
a meter-out control valve capable of controlling a flow rate of the working fluid to be discharged from the fluid pressure actuator
Implementation Method 4
control a velocity of the fluid pressure actuator by the meter-out control valve on the basis of the operation signal from the operation device and control at least one of the pump and the meter-in control valve such that a pressure on a meter-in side of the fluid pressure actuator is equal to or higher than a predetermined value
Data Source
AI summary
A controller of a work machine computes a target velocity of a fluid pressure actuator according to an operation signal from an operation device, computes target thrust or target torque of the fluid pressure actuator on the basis of a driven state of the fluid pressure actuator, and controls a velocity of the fluid pressure actuator by a meter-out control valve on the basis of the operation signal from the operation device and controls at least one of a pump and a meter-in control valve such that a pressure on a meter-in side of the fluid pressure actuator is equal to or higher than a predetermined value when a positive or negative sign of the target velocity as a computation result is different from a positive or negative sign of the target thrust or the target torque as a computation result.