Hydraulic Pump Output Control for Swing Torque Balance
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Solution Overview
Problem
Conventional hybrid construction machines face issues with torque imbalance when the electric motor fails, and inefficient energy usage during electric motor-driven operations, leading to suboptimal fuel cost reduction and operability.
Innovation Solution
A construction machine equipped with a variable displacement hydraulic pump, swing hydraulic and electric motors, an electrical storage device, and a control unit that adjusts the hydraulic pump output based on the operation amount and speed of the swing electric motor to ensure efficient energy use and torque balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the swing structure is driven by using both the hydraulic motor and the electric motor, then fuel efficiency is improved and noise level is reduced, but torque balance and operability become difficult to control
Solution Approach 1:
The control unit continuously monitors the operation amount of the swing control lever and the output torque of the electric motor, then adjusts the hydraulic pump delivery capacity in real-time based on this feedback to maintain proper torque balance between the two motors
Solution Approach 2:
The delivery capacity of the hydraulic pump is made dynamically adjustable rather than fixed, allowing the system to adapt the hydraulic motor torque output to match the electric motor torque output based on operating conditions and control lever position
2Use of energy by moving object
If the electric motor is used for power running driving, then fuel consumption is reduced, but the hydraulic pump continues to operate at full capacity causing energy waste
Solution Approach 1:
When the electric motor provides sufficient torque for swing driving, the hydraulic pump delivery capacity is reduced to only the minimum necessary amount, avoiding excessive hydraulic system operation and the associated energy losses
Solution Approach 2:
The delivery capacity parameter of the hydraulic pump is changed based on the operating mode - reduced when electric motor is providing power, and increased when hydraulic motor is the primary driver
3Reliability
If the electric motor fails and cannot output prescribed torque, then the system must rely solely on the hydraulic motor, but torque balance is disrupted and operability deteriorates
Solution Approach 1:
The control system is designed to detect electric motor failure conditions and automatically compensate by adjusting hydraulic pump delivery capacity to maintain proper torque balance, cushioning against the adverse effects of component failure
Solution Approach 2:
The control unit automatically detects failure conditions and self-adjusts the hydraulic system parameters without operator intervention, maintaining system operability through self-diagnosis and self-correction
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 ensures excellent operability and significant fuel cost reduction by optimizing the hydraulic pump output during electric motor-driven operations, securing necessary power for swing driving.
Implementation Method 1
a hydraulic pump (41) of the variable displacement type which is driven by the engine (22); a swing hydraulic motor (27) which drives the swing structure (20) by using hydraulic fluid delivered from the hydraulic pump (41)
Implementation Method 2
a swing hydraulic motor (27) which drives the swing structure (20) by using hydraulic fluid delivered from the hydraulic pump (41)
Implementation Method 3
a swing electric motor (25) which drives the swing structure (20) by using electric power supplied from the electrical storage device (24)
Implementation Method 4
an electrical storage device (24) which stores and supplies electric power
Data Source
Figure 1
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AI summary
Provided is a construction machine capable of securing excellent operability and achieving great fuel reduction effect by efficiently using recovered energy. A construction machine, comprising a hydraulic pump of the variable displacement type which is driven by an engine, a swing hydraulic motor, a swing electric motor, a delivery capacity regulating device which regulates the delivery capacity of the hydraulic pump, and a control unit which controls the driving/braking of the swing structure by using the sum total of torque of the swing hydraulic motor and torque of the swing electric motor when a swing control lever is operated, is configured to comprise an operation amount detection device for detecting the operation amount of the swing control lever and a speed detection device for detecting the speed of the swing electric motor. The control unit includes a hydraulic pump output reduction control unit which takes in an operation amount signal representing the operation amount of the swing control lever detected by the operation amount detection device and a speed signal representing the speed of the swing electric motor detected by the speed detection device and controls the delivery capacity regulating device by calculating a reduction rate of the output of the hydraulic pump based on the detection signals.