Hydraulic Elevator Pressure Equalization for Smooth Valve Opening
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Solution Overview
Problem
Conventional hydraulic elevators waste energy by heating working fluid unnecessarily, leading to inefficient operation, unpleasant odors, and viscosity changes that affect ride quality due to fixed-speed pumps and control valve mechanisms.
Innovation Solution
Implementing a bidirectional pump with a VVVF drive and a state-space integral controller to maintain equal pressure on both sides of the control valve, reducing energy consumption and minimizing vibrations by adjusting pump-side pressure to match jack-side pressure, allowing seamless transition between closed-loop pressure and flow control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed-speed pump with control valve is used to control working fluid flow, then the elevator car speed and position can be controlled, but the working fluid is heated unnecessarily causing energy waste, unpleasant odors, and viscosity changes
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed-speed pump to a variable-speed pump with VVVF drive. The pump speed dynamically adjusts to match the required flow rate, eliminating the need for control valve throttling. This dynamic operation maintains working fluid temperature by avoiding unnecessary bypass flow and throttling losses, thereby resolving the energy waste issue while preserving speed and position control capabilities.
Solution Approach 2:
The patent changes the operating parameters of the pump system by implementing variable-speed control through VVVF drive. Instead of maintaining constant speed and using valve throttling to control flow, the system varies pump speed to directly control working fluid flow rate. This parameter change eliminates throttling losses and prevents working fluid heating, addressing the energy efficiency problem while maintaining precise control.
2Speed
If control valve is opened when there is significant pressure difference between inlet and outlet, then the elevator car can move, but pressure waves cause undesirable vibrations and degrade ride quality
Solution Approach 1:
The patent applies preliminary action by pre-adjusting the pump speed to match the pressure requirements before opening the control valve. The VVVF drive gradually adjusts pump speed to equalize pressure between inlet and outlet sides of the valve before valve opening. This preliminary pressure equalization prevents sudden pressure waves and vibrations when the valve opens, eliminating the harmful effects while enabling smooth elevator car movement.
Solution Approach 2:
The patent implements preliminary anti-action by using the variable-speed pump to counteract the pressure difference that would otherwise cause harmful pressure waves. Before valve opening, the pump speed is adjusted to create opposing pressure that balances the pressure gradient across the valve. This preliminary counter-action prevents the formation of pressure waves and vibrations, resolving the ride quality issue while maintaining movement capability.
3Speed
If control valve is used to regulate working fluid flow, then elevator car speed can be controlled, but the working fluid viscosity changes due to heating affecting operating characteristics
Solution Approach 1:
The patent extracts the flow control function from the control valve and relocates it to the variable-speed pump. By taking out the throttling function from the valve, the system eliminates the source of energy loss and heating. The pump directly controls working fluid flow rate through speed variation, removing the need for valve throttling and its associated heating effects, thereby maintaining stable working fluid temperature and viscosity.
Solution Approach 2:
The patent replaces the mechanical throttling system (control valve) with an electrical control system (VVVF drive controlling pump speed). This substitution eliminates the mechanical energy dissipation that occurs in valve throttling, preventing working fluid heating. The electrical control system adjusts pump speed to achieve flow control without the energy losses and temperature increases associated with mechanical valve throttling.
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 approach reduces energy waste, minimizes vibrations, and enhances ride quality by efficiently controlling the hydraulic elevator's movement and position, while maintaining energy efficiency and reducing operational inefficiencies.
Implementation Method 1
Hydraulic elevators utilize hydraulic jacks for raising and lowering elevator cars between floors of a building. Put simply, to raise an elevator car, a motor-driven pump supplies pressurized working fluid to a hydraulic jack.
Implementation Method 2
Advances in variable-voltage variable-frequency (VVVF) AC motor controls have made low-cost, variable speed AC motors a viable option.
Implementation Method 3
Implementing a bidirectional pump with a VVVF drive and a state-space integral controller to maintain equal pressure on both sides of the control valve, reducing energy consumption and minimizing vibrations by adjusting pump-side pressure to match jack-side pressure
Data Source
AI summary
A hydraulic elevator may comprise a bidirectional pump that controls up and down motion of an elevator car. A VVVF drive may cause the bidirectional pump to provide working fluid in a controlled manner to a hydraulic jack that supports the elevator car. A control valve may be disposed between the bidirectional pump and the hydraulic jack so that the control valve can be closed when the elevator car needs to be held in place. To avoid pressure waves that propagate when the control valve is opened with disparate pressures on the pump and jack sides of the control valve, the bidirectional pump may adjust the pressure on the pump side of the closed control valve to the pressure on the jack side of the control valve before the control valve is opened.