Hydraulic Arm Lowering Control to Prevent Actuator Cavitation
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Solution Overview
Problem
Double-acting hydraulic actuators in agricultural and work vehicles experience cavitation and uncontrolled load issues during arm lowering, leading to safety hazards due to excessive oil discharge from the lifting chamber into the recovery tank, which existing solutions like counterbalance or overcenter valves attempt to mitigate but at the cost of complexity and expense.
Innovation Solution
A control unit adjusts the signal to the directional control valve to ensure that the oil flow discharged from the lifting chamber never exceeds the proportional flow entering the lowering chamber, using a check valve to compensate for any oil deficiencies, thereby preventing cavitation without the need for auxiliary valves like counterbalance or overcenter valves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a double-acting hydraulic actuator is used for arm lifting and lowering, then the arm can be controlled to lift and lower, but cavitation occurs in the lowering chamber causing uncontrolled load and safety hazards
Solution Approach 1:
The patent replaces the traditional mechanical counterbalance or overcenter valves with an electro-hydraulic control system. A control unit receives signals from the control lever and dynamically adjusts the directional control valve to regulate oil flow to the lowering chamber, preventing cavitation through electronic control rather than mechanical valve mechanisms.
Solution Approach 2:
The control system dynamically adjusts the oil flow parameters to the lowering chamber based on real-time operating conditions. The control unit modifies the directional control valve position to maintain appropriate flow rates, preventing cavitation by adapting flow parameters rather than using fixed mechanical restrictions.
2Reliability
If counterbalance or overcenter valves are used to prevent cavitation, then cavitation and uncontrolled load are reduced, but the hydraulic circuit becomes more complex and expensive
Solution Approach 1:
The patent merges the control functions of multiple valves into a single electro-hydraulic control system. The directional control valve, when dynamically controlled by the control unit, performs both the flow direction control and the flow rate restriction functions that would traditionally require separate counterbalance or overcenter valves, simplifying the overall hydraulic circuit.
Solution Approach 2:
The patent replaces complex mechanical valve systems (counterbalance or overcenter valves) with a simpler electro-hydraulic control system consisting of a standard directional control valve dynamically adjusted by a control unit, reducing device complexity while maintaining cavitation prevention capability.
3Speed
If the lifting chamber discharges more oil than the lowering chamber receives, then the arm can lower quickly, but sudden arm lowering occurs causing danger to people and property
Solution Approach 1:
The control unit continuously monitors the control lever position and dynamically adjusts the directional control valve to regulate oil flow to the lowering chamber. This feedback control ensures that the lowering speed matches the operator's intent while preventing excessive discharge from the lifting chamber, eliminating sudden arm lowering hazards.
Solution Approach 2:
The system transitions from static mechanical flow restrictions to dynamic electronic control. The control unit continuously adjusts the directional control valve position based on real-time operating conditions, enabling the lowering speed to be dynamically adapted to match operational requirements while preventing harmful sudden movements.
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
This approach ensures a controlled lowering speed, avoiding cavitation and reducing the risk of sudden arm movements, while simplifying the hydraulic circuit and eliminating the need for costly auxiliary valves, thus enhancing safety and operational efficiency.
Implementation Method 1
between the recovery tank and the port of the lowering chamber there is a check valve arranged so as to allow a flow of oil from the recovery tank to the lowering chamber
Data Source
Figure 1
Figure 2~3
AI summary
Control method of an actuator of an arm of an agricultural or work vehicle subject to a load, in which the arm (B) comprises at least one element (AR, TL) directly or indirectly hinged to a vehicle frame (F) and a double action actuator (A1, A2) comprising a lifting chamber (CH1) and a lowering chamber (CH2) opposite the lifting chamber and a directional valve (V1, V2), the method comprising a first step (ST1) of calculate a flow value of hydraulic oil directed to the lowering chamber (CH2) from the directional valve and a corresponding first flow value (F1) of hydraulic oil destined to be discharged from the lifting chamber (CH1), a second step (ST2) of detecting a second flow value (F2) of hydraulic oil actually discharged from the lifting chamber due to the load and a third step (ST3) of adjusting the directional valve (V1, V2) so as to force said second value to equate the first flow value, when the second value exceeds the first (CK = Yes).