Regenerative Hydraulic Motor Control for Swing Operability
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Solution Overview
Problem
Existing energy recovery devices for construction machines, such as hydraulic excavators, lack effective control methods for managing the flow rate of return hydraulic fluid, leading to potential drops in swing braking pressure and deteriorated operability due to response delays and excessive flow rates.
Innovation Solution
A construction machine with a regeneration device, pressure detection, and a control unit that sets a target flow rate for the regenerative hydraulic motor based on detected pressure, ensuring the flow rate matches the discharge flow rate and maintaining hydraulic pressure, while also simulating the override characteristic of overload relief valves to enhance regeneration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the flow rate through the regenerative hydraulic motor is increased to improve energy regeneration efficiency, then the regeneration efficiency is improved, but the swing braking pressure drops and operability deteriorates
Solution Approach 1:
The control unit dynamically adjusts the target flow rate of the regenerative hydraulic motor based on real-time pressure detection. When pressure is high, the target flow rate is set higher to maximize regeneration; when pressure drops below the first set value, the target flow rate is reduced to zero or low level to maintain braking pressure. This dynamic adjustment resolves the contradiction between regeneration efficiency and operability.
Solution Approach 2:
The system implements closed-loop feedback control where the pressure detection device continuously monitors hydraulic pressure and feeds this information to the control unit. The control unit compares detected pressure with the first set value and adjusts the generator/motor revolution speed accordingly to maintain pressure while maximizing regeneration when possible.
2Loss of energy
If the tilting angle control is used to control the recovery flow rate, then the energy recovery function is achieved, but the responsiveness is low causing pressure drops during swing deceleration
Solution Approach 1:
The invention replaces the mechanical tilting angle control system with an electrical control system that directly adjusts the generator/motor revolution speed. This substitution of control mechanism dramatically improves responsiveness, allowing the system to rapidly adjust flow rate in response to pressure changes during swing deceleration, preventing pressure drops while maintaining energy recovery functionality.
3Stress or pressure
If the flow rate through the regenerative hydraulic motor is set to match the discharge flow rate, then the pressure maintenance is improved, but the regeneration efficiency may be reduced when pressure is low
Solution Approach 1:
The control unit changes the target flow rate parameter based on pressure conditions. When detected pressure is below the first set value, the target flow rate is set to zero or low to maintain pressure. When pressure is sufficient, the target flow rate is increased to maximize regeneration efficiency. This parameter adaptation resolves the contradiction between pressure maintenance and regeneration efficiency.
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 maintains excellent operability equivalent to conventional technology by controlling the flow rate through the regenerative hydraulic motor, preventing pressure drops and increasing regeneration efficiency, even in failure scenarios.
Implementation Method 1
a regenerative hydraulic motor (71) connected to the regeneration hydraulic line (16)
Implementation Method 2
a generator/motor (72) that rotates together with the regenerative hydraulic motor (71)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A controller 8 sets a target flow rate of a regenerative hydraulic motor 71 at zero or a low flow rate within an extent in which hydraulic pressure in a regeneration hydraulic line 16 does not become negative pressure when a detected pressure PS detected by a pressure sensor 18 is lower than a first set value P1 previously set by overload relief valves 10 and 12, sets the target flow rate of the regenerative hydraulic motor at a value corresponding to the detected pressure when the detected pressure is higher than or equal to the first set value, and controls the revolution speed of a generator/motor 72 in such a manner that a flow rate through the regenerative hydraulic motor equals the target flow rate. With such features, excellent operability equivalent to that in the conventional technology can be secured.