Variable Displacement Pump Energy Recovery for Hydraulic Tools
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Solution Overview
Problem
Conventional hydraulic tools waste potential energy when articulating hydraulic cylinders and often overheat due to energy dissipation, and their control systems struggle to balance stability and bandwidth across a wide range of operations.
Innovation Solution
An energy recovery system utilizing an open circuit variable displacement pump with a swashplate that can articulate between pump and motor modes, coupled with a bias system and solenoid-driven three-way valve, to recover energy from hydraulic fluid during lowering motions and maintain efficiency by preventing overheating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the hydraulic tool uses a conventional hydraulic circuit with linear control methods, then the control stability is maintained within a certain range around an operating point, but the bandwidth of the closed loop pump control system becomes insufficient and the controllability across a wide range of operation is compromised
Solution Approach 1:
The patent replaces the conventional hydro-mechanical control system with an electro-hydraulic control system. The variable displacement pump is controlled by an electronic control unit that receives signals from sensors and actuators, enabling precise control across a wide range of operating conditions. This substitution allows the system to achieve both high stability through feedback control and wide bandwidth through electronic signal processing, resolving the contradiction between stability and adaptability.
Solution Approach 2:
The patent employs a variable displacement pump with a swashplate mechanism that can dynamically adjust its displacement. The swashplate angle is continuously variable, allowing the pump to adapt its flow output to match changing load conditions. This dynamic adjustment capability, combined with electronic control, enables the system to maintain stability across varying operating points while providing wide bandwidth controllability, overcoming the limitations of fixed-parameter hydro-mechanical systems.
2Loss of energy
If the hydraulic cylinders are articulated through potential energy during lowering operations, then the potential energy is wasted and not recovered, but the hydraulic fluid dissipates the potential energy as heat causing overheating of circuit elements
Solution Approach 1:
The patent converts the harmful effect of potential energy dissipation into a beneficial energy recovery process. During lowering operations, instead of allowing the hydraulic fluid to dissipate potential energy as heat, the system uses the variable displacement pump in motor mode to capture this energy and transfer it back to the hydraulic circuit. This approach simultaneously recovers energy that would otherwise be lost and prevents overheating of hydraulic components by eliminating the heat generation mechanism.
Solution Approach 2:
The patent implements an energy recovery system that captures potential energy during lowering operations and stores it for later use. The variable displacement pump operates in motor mode to absorb energy from the descending load, converting it into hydraulic pressure that can be stored in the circuit. This recovered energy is then available to assist with lifting operations, effectively recycling energy that would otherwise be discarded as heat, thereby reducing both energy loss and temperature rise.
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 effectively recovers potential energy, reduces energy wastage, and enhances control system stability by efficiently managing hydraulic fluid flow and pressure, thereby improving the operational efficiency and longevity of hydraulic tools.
Implementation Method 1
an open circuit variable displacement pump configured to circulate the hydraulic fluid from the tank to the cylinders in the pump mode and circulate the hydraulic fluid from the cylinders to the tank in the motor mode
Implementation Method 2
The open circuit variable displacement pump includes a swashplate articulable between a positive position and a negative position. In the positive position, the hydraulic fluid circulates in the pump mode; and in the negative position, the hydraulic fluid circulates in the motor mode
Implementation Method 3
The open circuit variable displacement pump also includes an actuator configured to articulate the swashplate, and a bias system configured to maintain the swashplate in a positive position when the hydraulic fluid is not in circulation
Implementation Method 4
an engine configured to provide energy to the open circuit variable displacement pump in the pump mode and receive energy from the open circuit variable displacement pump in the motor mode
Data Source
AI summary
An energy recovery system includes cylinders that articulate a hydraulic tool in a pump mode to provide potential energy and in a motor mode to recover the potential energy. The energy recovery system includes a tank that stores a hydraulic fluid for the cylinders and an open circuit variable displacement pump that circulates the hydraulic fluid in the pump mode from the tank to the cylinders and in the motor mode from the cylinders to the tank. The open circuit variable displacement pump includes a swashplate articulable between a positive position and a negative position. In the positive position, the hydraulic fluid circulates in the pump mode and in the negative position the hydraulic fluid circulates in the motor mode. The open circuit variable displacement pump includes an actuator that articulates the swashplate and a bias system that maintains the swashplate in a positive position when the hydraulic fluid is not in circulation.