Hydraulic Accumulator Pressure Control for Stable Swing Motor Braking
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Solution Overview
Problem
The existing engine power assist systems for work machines, such as hydraulic excavators, face instability in the operation of swing motors due to differential pressure changes across sequence valves, which can lead to unstable operation when pressurized fluid is accumulated in hydraulic accumulators.
Innovation Solution
A work machine equipped with a differential pressure control valve, a pressure sensor, and a controller that adjusts the differential pressure across the valve based on the accumulator pressure, ensuring stable operation by maintaining a constant brake pressure on the swing motor and reducing pressure variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a sequence valve is used to connect the swing motor circuit to the accumulator, then energy recovery is enabled, but the swing motor operation becomes unstable when accumulator back pressure changes
Solution Approach 1:
The patent replaces the fixed differential pressure setting of the sequence valve with a variable differential pressure control valve whose setpoint is dynamically adjusted based on real-time accumulator pressure feedback. This parameter change allows the system to adapt to varying back pressure conditions, maintaining stable swing motor operation while enabling energy recovery.
Solution Approach 2:
The patent introduces a feedback control mechanism where a pressure sensor monitors accumulator back pressure and feeds this information to a controller. The controller then adjusts the differential pressure control valve to maintain constant brake pressure on the swing motor, resolving the instability caused by varying back pressure while preserving energy recovery functionality.
2Device complexity
If a fixed differential pressure control valve is used, then the structure is simple, but the brake pressure varies when accumulator pressure changes
Solution Approach 1:
The patent implements a feedback control system where the controller continuously monitors accumulator pressure and adjusts the differential pressure control valve accordingly. This feedback mechanism compensates for accumulator pressure variations, maintaining constant brake pressure on the swing motor without requiring overly complex hardware modifications.
Solution Approach 2:
The patent transitions from a static, fixed differential pressure control valve to a dynamic control system where the differential pressure setting can change in real-time based on operating conditions. This dynamic adjustment capability allows the system to maintain stable brake pressure despite variations in accumulator pressure.
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 configuration allows for stable operation of hydraulic actuators when pressurized fluid is accumulated, reducing pressure loss and maintaining efficient energy recovery, thereby enhancing the stability and efficiency of the work machine's hydraulic system.
Implementation Method 1
a hydraulic pump that is driven by the engine and delivers a pressurized fluid
Implementation Method 2
a hydraulic accumulator device that accumulates the pressurized fluid discharged from the hydraulic actuator
Data Source
AI summary
A work machine includes a hydraulic pump that is driven by an engine and delivers a pressurized fluid, a hydraulic actuator that is operated by the pressurized fluid delivered by the hydraulic pump, a hydraulic accumulator device that accumulates the pressurized fluid discharged from the hydraulic actuator, a differential pressure control valve that is disposed between the hydraulic actuator and the hydraulic accumulator device and generates a differential pressure across the differential pressure control valve between a pressure of the hydraulic actuator and a pressure of the hydraulic accumulator device, a pressure sensor that senses the pressure of the hydraulic accumulator device, and a controller that controls the differential pressure control valve on the basis of a sensing result of the pressure sensor. The controller controls the differential pressure control valve in such a manner that the differential pressure across the differential pressure control valve reduces according to a rise in the pressure of the hydraulic accumulator device sensed by the pressure sensor.