Hydraulic Energy Regeneration with Duty-Ratio Flow Control
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Solution Overview
Problem
Existing energy regeneration devices for hydraulic systems in work machines, such as hydraulic excavators, face challenges in controlling the operation speed of hydraulically-driven actuators and efficiently regenerating energy, leading to a mismatch between the operation lever input and actuator speed, and require larger accumulators to manage pressure variations, increasing size and cost.
Innovation Solution
An energy regeneration device that includes an actuator, inertial fluid container, low-pressure-side and high-pressure-side containers, and opening/closing devices, controlled by a calculation unit to alternately direct the working fluid between these containers based on duty ratios, allowing energy regeneration even when the accumulator pressure is higher than the actuator pressure, and enabling control of the flow rate in accordance with the actuator's movement speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the accumulator capacity is increased to reduce pressure variation, then the pressure stability is improved, but the apparatus size and cost increase
Solution Approach 1:
The invention divides the single accumulator into two separate accumulators (first accumulator and second accumulator) that operate at different pressure levels. The first accumulator operates at high pressure to store energy efficiently, while the second accumulator operates at low pressure to maintain stable supply pressure. This segmentation allows the system to achieve both pressure stability and compact size without requiring a single large accumulator.
2Loss of energy
If the accumulator pressure is set lower than actuator pressure for stable fluid recovery, then the energy regeneration is improved, but the available pressure for work output is reduced
Solution Approach 1:
The system separates the energy storage function (first accumulator at high pressure) from the fluid supply function (second accumulator at low pressure). This allows the first accumulator to operate at high pressure for efficient energy storage without being constrained by the low pressure needed for stable fluid recovery, thus resolving the contradiction between energy regeneration efficiency and available work pressure.
Solution Approach 2:
The second accumulator acts as an intermediary between the high-pressure first accumulator and the actuator. It receives fluid from the first accumulator and provides stable low-pressure supply to the actuator, mediating the pressure transition and enabling both high energy storage pressure and stable low-pressure operation.
3Loss of energy
If the duty ratio is increased to improve energy regeneration, then the energy recovery is improved, but the actuator operation speed control precision deteriorates
Solution Approach 1:
The control system dynamically adjusts the duty ratio of the opening/closing device based on real-time operating conditions, including actuator position, speed requirements, and energy regeneration needs. This dynamic control allows the system to optimize the balance between energy recovery and operation speed control precision for each specific operating condition, rather than using a fixed duty ratio.
Solution Approach 2:
The control unit receives feedback signals from sensors monitoring actuator position and speed, and adjusts the duty ratio accordingly. This feedback mechanism ensures that the actuator operation speed remains precisely controlled while maximizing energy regeneration, as the control system can compensate for any speed deviations caused by duty ratio adjustments.
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 solution allows for stable energy regeneration and control of the actuator's operation speed in response to the operation lever input, reducing the need for large accumulators and maintaining operational efficiency while preventing backflow, thus enhancing the overall performance and compactness of the hydraulic system.
Implementation Method 1
because of flow of a working fluid, an inertial force of fluid is generated in the inertial fluid container. Thereafter, when the low-pressure-side opening/closing device is closed and the high-pressure-side opening/closing device is opened, a working fluid flows into an accumulator due to the inertial force of fluid generated in the inertial fluid container
Data Source
AI summary
Provided are an energy regeneration device which can regenerate energy of a working fluid discharged from an actuator while controlling a flow rate of the working fluid, and a work machine including the foregoing device. The regeneration device (100) includes a boom cylinder (20), an inertial fluid container (102), an oil tank (110), an accumulator (105), a low-pressure-side opening/closing device (103), and a high-pressure-side opening/closing device (104). A calculation unit (151) calculates a duty ratio for opening/closing the low-pressure-side opening/closing device (103) and the high-pressure-side opening/closing device (104) in accordance with a desired flow rate of a working fluid discharged from the boom cylinder (20). A regeneration control unit (153) selects alternately the low-pressure-side opening/closing device (103) and the high-pressure-side opening/closing device (104) as a destination with which the inertial fluid container (102) communicates in accordance with the calculated duty ratio, and supplies a discharged working fluid to an accumulator (105).