Variable-Speed Hydraulic Excavator Drive Circuit
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Solution Overview
Problem
Conventional all-electric drive hydraulic excavators face issues with high energy consumption, throttle loss, and increased costs due to the need for multiple high-pressure ports and differential cylinder gap area compensation, which limits power output and efficiency.
Innovation Solution
A variable-speed volume-control direct-drive all-electric hydraulic excavator system with an open-type control circuit, where each hydraulic cylinder cavity is independently controlled by a dedicated energy source, allowing for adjustable pressure and flow rates through rotational speed and torque control, and featuring a redundant energy source system for efficient energy recovery and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pump-control circuit is used to control the actuator, then the actuator can be controlled, but the pump must have at least two high pressure ports which increases the cost
Solution Approach 1:
The hydraulic system is divided into two independent closed circuits, with each circuit having its own pump and controlling one cavity of the differential cylinder. This segmentation allows each pump to have a simpler single high-pressure port structure while achieving independent control of both cavities.
2Reliability
If differential cylinder gap area compensate circuit is used, then the normal performance of the hydraulic cylinder can be ensured, but the throttle loss increases and the cost increases
Solution Approach 1:
The gap area compensation function is extracted from the main control circuit and implemented through the independent dual-circuit architecture. Each pump independently supplies oil to its controlled cavity, and the natural balance of the two independent circuits compensates for the gap area effects without requiring additional throttle valves or compensation circuits, thereby eliminating the associated energy losses.
3Productivity
If conventional all-electric drive system is used, then the system can operate, but energy consumption is high and throttle loss occurs
Solution Approach 1:
The system implements local energy optimization by having each pump operate independently in its optimal efficiency range. The two pumps can be sized and controlled to match the specific demands of each cavity, allowing each component to operate at its peak efficiency point rather than forcing a single pump to handle variable and potentially inefficient operating conditions.
4Device complexity
If single motor single pump or dual-pump system is used, then the system can be simplified, but the drive motor cannot satisfy big power output requirements
Solution Approach 1:
The system merges two independent pump-motor units into a unified dual-circuit hydraulic system. Each unit contributes to the overall power output, and their combined effect enables the system to deliver high power output while maintaining the simplicity of individual pump-motor pairs. The merging occurs at the hydraulic circuit level where both pumps supply oil to the differential cylinder.
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 system achieves high efficiency by eliminating throttle loss, reducing energy consumption, and ensuring stable performance with redundancy, while maintaining the advantages of closed-circuit systems like low noise and integrated energy recovery.
Implementation Method 1
a motor generator, an inverter
Implementation Method 2
a hydraulic pump...the hydraulic pump driven by the motor generator
Implementation Method 3
a I and II accumulators...the I and II accumulators respectively
Data Source
AI summary
A variable-speed volume-control direct-drive all-electric hydraulic excavator drive and energy recover system the control drive circuit of which includes the A, B, C energy source, boom cylinder control valve group, arm cylinder control valve group, bucket control valve, swing control valve, swing motor control valve group, left travel control valve, right travel control valve, eight 2-position 2-way valve, I and II 2-position 3-way valve, I and II accumulator. The drive control circuit adopts open control independent-cavity variable-speed pump-control volume direct-drive circuit. Each of the cavities of cylinder is controlled by an energy source and the pressure and flow rate of the cavities are adjusted by the rotational speed and torque control of the generator independently. The present invention is four-quadrant running and have advantages of high efficiency, high integrity, low consumption, redundancy energy source, no need for pilot supply, low noise, integrate recovery of kinetic and potential energy.