Hydraulic Regeneration System for Material Handling Vehicles
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Solution Overview
Problem
Material handling vehicles face excessive wear and electrical frequency issues due to high flow rates of exhausting hydraulic fluid, which adversely affect the pump-motor combination during energy recovery processes.
Innovation Solution
A hydraulic system with electrically operated proportional valves and a speed sensor that controls fluid flow paths to manage energy recovery, allowing the pump to operate as a hydraulic motor in multiple modes, including routing fluid through the pump to recover energy without excessive speed, and using logic to select modes based on desired lowering speeds and load conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pump operates as a hydraulic motor during energy recovery, then energy is recovered from the hydraulic system, but excessive wear and electrical frequency issues occur due to high flow rates
Solution Approach 1:
The hydraulic circuit is divided into multiple independent flow paths: a first path through the pump-motor combination for energy recovery, and a second bypass path around the pump-motor. This segmentation allows the system to route fluid through different paths depending on operating conditions, enabling energy recovery when flow rates are appropriate while protecting the pump-motor from damaging high flow rates.
Solution Approach 2:
A control valve assembly acts as an intermediary between the hydraulic cylinder and the pump-motor combination. The valve assembly includes a first valve controlling flow to the pump and a second valve controlling the bypass flow, mediating the fluid distribution to protect the pump-motor while enabling energy recovery when conditions are favorable.
2Speed
If high flow rates are used during lowering operations, then lowering speed is improved, but the pump-motor combination experiences excessive wear and electrical frequency issues
Solution Approach 1:
The system dynamically adjusts the flow path configuration based on real-time operating conditions. The control valve assembly responds to signals from the controller to switch between different flow paths, allowing the system to optimize for speed when the pump-motor is not engaged, and switch to the bypass path when high flow rates would damage the pump-motor.
Solution Approach 2:
The control valve assembly serves as a dynamic intermediary that mediates between the high-speed lowering requirement and the pump-motor protection requirement. By controlling the distribution of hydraulic fluid between the energy recovery path and the bypass path, the valve assembly enables fast lowering when appropriate while protecting the pump-motor from damaging conditions.
3Power
If the pump operates as a hydraulic motor at high speeds, then energy recovery efficiency is improved, but electrical frequency issues adversely affect the excitation system
Solution Approach 1:
The system incorporates a speed sensor that provides feedback about the rotational speed of the pump-motor combination to the controller. This feedback enables the controller to monitor operating conditions and adjust the valve positions accordingly, preventing the pump-motor from operating at speeds that would generate harmful electrical frequencies while still enabling energy recovery at appropriate speeds.
Solution Approach 2:
The system dynamically adjusts the flow paths based on the rotational speed of the pump-motor. When the speed sensor detects that the pump-motor is operating at speeds that would cause electrical frequency issues, the controller automatically redirects flow through the bypass path, preventing harmful electrical effects while maintaining energy recovery capability at safer operating speeds.
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
Enables efficient energy recovery from hydraulic systems at high flow rates without overdriving the pump-motor combination, reducing wear and minimizing adverse electrical effects, thereby extending equipment lifespan and maintaining system stability.
Implementation Method 1
the pump to operate as a hydraulic motor in multiple modes, including routing fluid through the pump to recover energy
Implementation Method 2
driving the pump in that manner also drives the electric motor coupled to the pump causing the electric motor to act as a generator
Implementation Method 3
A first electrically operated, proportional valve selectively controls a first path through which fluid flows between the pump outlet and the cylinder port
Implementation Method 4
A speed sensor is further comprised detecting a speed of the hydraulic motor
Data Source
Figure 1~3
Figure 2
AI summary
A hydraulic system has a cylinder and ram assembly (68) that raises and lowers a load carrying carriage (32) on a material handling vehicle (10). The fluid exhausting from the cylinder, while the carriage is lowering, is controlled to recover energy from that fluid. A first path (73) routes the exhausting fluid to drive the pump (64) as a hydraulic motor. A second path (85) routes the exhausting fluid to a reservoir (66), bypassing the pump. In a first lowering mode, the second path is closed and the first path is opened. In a second lowering mode, both the first and second paths are open and the flow through each one is proportionally controlled. In a third lowering mode, only the second path is opened. The mode to use is selected based on the desired lowering speed of the carriage.