Hydraulic Boom Driving System for Hybrid Excavator
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Solution Overview
Problem
The existing boom driving systems for hybrid excavators face challenges in controlling the retraction speed and force of the boom actuator when moving downward, particularly on slopes, leading to insufficient hydraulic fluid pressure and reduced torque, which affects the efficiency of regenerative energy production.
Innovation Solution
The system includes a control method that adjusts the first and second control valves to manage hydraulic fluid flow rates, with the second control valve being maximally opened during regenerative downward movements and reduced or closed during load downward movements to maintain target speed and force, and the boom auxiliary valve is used to supplement hydraulic fluid when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the second control valve is opened to discharge hydraulic fluid during downward boom movement, then the retraction speed of the boom actuator is increased, but the hydraulic fluid pressure and regenerative energy collection are reduced
Solution Approach 1:
The second control valve is designed with dynamically adjustable opening degrees rather than fixed positions. The control unit adjusts the valve opening in real-time based on operating conditions (slope angle, load weight, desired speed), allowing the system to optimize between speed and pressure requirements for different scenarios
Solution Approach 2:
The system changes the flow rate parameter of hydraulic fluid discharged through the second control valve based on operational requirements. By adjusting the valve opening degree, the system modifies the flow rate to achieve target retraction speed while maintaining sufficient pressure for regenerative energy collection
2Speed
If the second control valve is opened to increase boom actuator retraction speed, then the speed is improved, but the torque and force control are reduced
Solution Approach 1:
The control unit adjusts the opening degree of the second control valve to modify hydraulic fluid flow rate, thereby changing the speed parameter while maintaining force parameter within acceptable ranges through coordinated control
3Loss of energy
If the hydraulic pump motor operates at high flow rate, then the regenerative energy collection is improved, but the permissible flow rate limit is exceeded
Solution Approach 1:
The system dynamically adjusts the flow rate parameter of hydraulic fluid discharged through the second control valve to optimize regenerative energy collection while maintaining compliance with the permissible flow rate limit of the hydraulic pump motor
Solution Approach 2:
The control unit monitors the operating conditions and adjusts the second control valve opening degree based on feedback regarding flow rate, slope angle, and load characteristics, ensuring the hydraulic pump motor operates within permissible limits while maximizing energy recovery
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 controlled retraction speed and force of the boom actuator when moving downward, enabling normal electricity production by the electric motor generator and improving regenerative energy collection.
Implementation Method 1
The hydraulic pump motor 120 may serve as both a hydraulic pump and a hydraulic motor... The hydraulic pump motor 120 implements a hydraulic motor function by pressurized oil (hydraulic fluid), and rotates the electric motor 110
Implementation Method 2
the electric motor 110 regenerates electric energy from potential energy of the boom, and the electric energy storage device is charged with electric energy
Implementation Method 3
by control of the boom control valve, the boom is moved upward, stopped, or moved downward... the second control valve 300 is maximally opened during regenerative downward movements and reduced or closed during load downward movements
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
The present disclosure relates to a boom driving system for a hybrid excavator and a control method therefor, and includes: an electric motor which is operated as a motor or a generator; an electric energy storage device which stores electricity produced by the electric motor; a hydraulic pump motor which is operated by the electric motor and supplies a hydraulic fluid to a boom actuator; a boom control valve which configures a closed circuit that selectively connects or disconnects a discharge line and an inlet line of the hydraulic pump motor to/from a head side or a rod side of a boom cylinder; a first control valve which connects the inlet line to a drain tank for draining the hydraulic fluid; a second control valve which connects the discharge line to the drain tank for draining the hydraulic fluid, and of which the opening area is controlled to be changed according to a size of torque that is applied to a boom electric motor when the boom actuator performs a downward operation; and a control unit which controls the electric motor, the hydraulic pump motor, the boom control valve, and the first and second control valves.