Hybrid Construction Machine Swing Torque Control
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Solution Overview
Problem
Hybrid construction machines using both hydraulic and electric motors for the upper swing structure face challenges in balancing the torque between the two motors, leading to an unfamiliar operational feel for operators accustomed to hydraulic-only systems, and lack efficient energy regeneration and assistance mechanisms.
Innovation Solution
A hybrid construction machine design that includes a hydraulic circuit system with a directional control valve featuring meter-in and meter-out restrictors, where the opening area of the meter-out restrictor is set larger than conventional systems, and a control device adjusts the torque of the electric motor to match the braking torque of the hydraulic motor, allowing for energy regeneration and assistance, while maintaining an operational feel similar to hydraulic-only systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the opening area of the meter-out restrictor is increased to improve energy regeneration efficiency, then the braking torque balance is disrupted and operational feeling becomes unfamiliar to operators
Solution Approach 1:
The patent changes the parameter of the meter-out restrictor opening area to be larger than conventional values, which increases energy regeneration efficiency. Simultaneously, it adjusts the electric motor braking torque parameter to compensate for the changed hydraulic braking characteristics, thereby maintaining familiar operational feeling despite the parameter change.
Solution Approach 2:
The electric motor acts as an intermediary between the hydraulic system and the swing mechanism. It provides additional braking torque to compensate for the increased opening area of the meter-out restrictor, thereby maintaining the overall braking torque balance and operational characteristics while enabling improved energy regeneration.
2Loss of energy
If the electric motor torque is increased to improve energy regeneration, then the total braking torque exceeds conventional levels and creates excessive braking force
Solution Approach 1:
The control device monitors the actual braking torque from the hydraulic motor and adjusts the electric motor braking torque accordingly. This feedback mechanism ensures that the sum of hydraulic and electric braking torques equals the target braking torque, preventing excessive braking force while maximizing energy regeneration.
Solution Approach 2:
The system dynamically adjusts the electric motor braking torque based on real-time operating conditions. The control device calculates the required electric motor torque as the difference between the target braking torque and the actual hydraulic braking torque, enabling adaptive torque distribution that optimizes both energy regeneration and braking force control.
3Ease of manufacture
If a conventional directional control valve is used to reduce cost, then the opening area cannot be precisely controlled and torque balance is affected
Solution Approach 1:
The electric motor serves as a compensatory intermediary that offsets the imprecision of conventional directional control valves. By dynamically adjusting electric motor braking torque, the system compensates for variations in hydraulic braking torque caused by imprecise restrictor opening area control, thereby achieving torque balance without requiring high-precision valves.
Solution Approach 2:
The patent accepts the parameter variation inherent in conventional directional control valves and compensates for it by adjusting the electric motor torque parameter. This approach allows the use of cost-effective conventional valves while maintaining overall system performance through active torque management.
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
The design enables efficient energy regeneration and assistance to the hydraulic motor, providing a satisfactory operational feel equivalent to hydraulic-only systems, while allowing for cost-effective implementation using conventional operation systems and directional control valves.
Implementation Method 1
the swing electric motor functioning as an electric generator when the swinging of the upper swing structure is decelerating
Implementation Method 2
a meter-in restrictor placed between the hydraulic pump and the swing hydraulic motor and a meter-out restrictor placed between the swing hydraulic motor and the tank
Data Source
AI summary
A hybrid construction machine drives the upper swing structure using a hydraulic motor and an electric motor together and is capable of regenerating the energy of the upper swing structure in deceleration or stopping into electric power and using the regenerated electric power for assisting the hydraulic motor for driving the upper swing structure. The opening area characteristics of a meter-out restrictor and a bleed-off restrictor of a swing directional control valve are set to become larger than for construction machines driving the upper swing structure with the hydraulic motor alone. Torque of the electric motor is controlled so that the total sum of the actual torque occurring in the hydraulic and electric motors in deceleration or acceleration of the hydraulic motor equals the torque occurring when the opening area of the meter-out restrictor or the bleed-off restrictor is set at the prescribed opening area.