Electrohydrostatic Pressure Sensing With Orifice Bypass Speed Limiting
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Solution Overview
Problem
Existing electrohydrostatic systems for controlling the setup speed of hydraulic cylinders in presses are cost-intensive and inefficient due to the requirement for complex and power-intensive 'safe limited speed' functions, which also limit the execution of other functions and incur high computing power reserves, and cannot be directly adapted from classic hydraulic systems without significant and economically unviable modifications.
Innovation Solution
An electrohydrostatic system with a hydraulic cylinder, a fluid hydraulic motor pump unit, a motor control device, a safety valve, a fixed orifice plate, and a pressure sensor that detects pressure and provides enabling signals to control the motor pump unit, eliminating the need for the 'safe limited speed' function by using a 'safe torque off' function and protecting the system from pressure buildup through a bypass connection and redundant safety mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a 'safe limited speed' function is implemented in the motor control device to control setup speed, then the setup speed can be controlled, but the system becomes cost-intensive and power-intensive with limited computing capacity for other functions
Solution Approach 1:
The patent extracts the speed control function from the motor control device by implementing a bypass connection with a fixed orifice plate that physically limits the maximum flow rate to the hydraulic cylinder. This mechanical flow restriction removes the need for complex electronic speed monitoring and control algorithms, thereby reducing computing power requirements and system complexity while maintaining controlled setup speed.
Solution Approach 2:
The patent replaces the electronic control system (motor control device with safe limited speed function) with a mechanical flow restriction system (fixed orifice plate in bypass connection). This mechanical substitution inherently limits the setup speed through fluid dynamics principles without requiring active electronic control, sensors, or computing resources.
2Speed
If classic hydraulic system components (safety valves, fixed orifice plates) are adapted to electrohydrostatic system, then setup speed can be controlled, but extensive and economically unviable modifications are required
Solution Approach 1:
The patent makes the fixed orifice plate serve multiple functions: it acts as both a flow restriction element for setup speed control and as a pressure-limiting component for safety. This multi-functionality eliminates the need for separate safety valves and complex adaptation modifications, making the system economically viable while achieving controlled setup speed.
Solution Approach 2:
The patent segments the hydraulic system into a main circuit and a bypass circuit with the fixed orifice plate. This segmentation allows the electrohydrostatic system to maintain its core advantages while incorporating simple mechanical flow restriction in the bypass path, avoiding extensive modifications to the main electrohydrostatic components.
3Reliability
If pressure buildup protection is implemented through safety valves and bypass connections, then the system is protected from pressure buildup, but the setup speed control becomes more complex
Solution Approach 1:
The patent merges the safety valve function and the setup speed control function into a single integrated bypass connection with a fixed orifice plate. This unified component simultaneously protects against pressure buildup and limits setup speed, eliminating the need for separate safety valves and reducing overall system complexity while maintaining both safety and control functions.
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 solution ensures a controlled setup speed without the need for costly and power-intensive 'safe limited speed' functions, reduces energy losses, and allows for efficient operation by using a pressure sensor to manage pressure and prevent excessive speed, thus enhancing system efficiency and safety.
Implementation Method 1
a motor pump unit (15) of the electrohydrostatic system (1) for providing a fluid hydraulic volume flow for moving the hydraulic cylinder (10)
Data Source
AI summary
The present invention relates to an electrohydrostatic system having a hydraulic cylinder comprising a first cylinder chamber and a second cylinder chamber. Furthermore, the electrohydrostatic system has a fluid hydraulic supply device for providing a hydraulic fluid, a fluid hydraulic motor pump unit, designed to provide a fluid hydraulic volume flow in order to move the hydraulic cylinder. A motor control device is designed to provide a rated current for an electrical drive of the fluid hydraulic motor pump unit. Moreover, the electrohydrostatic system has at least one fluid hydraulic safety valve, which on a first valve side is connected to one of the cylinder chambers of the hydraulic cylinder and on a second valve side is connected to the fluid hydraulic motor pump unit. The fluid hydraulic safety valve can be bridged via a bypass connection with a fixed orifice plate, wherein the bypass connection is connected to the first valve side and to the second valve side of the at least one fluid hydraulic safety valve. Moreover, the electrohydrostatic system has a pressure sensor that is connected to one of the cylinder chambers of the hydraulic cylinder. The pressure sensor is designed to detect a fluid hydraulic pressure on one of the cylinder chambers and, according to the detected fluid hydraulic pressure, to provide an enabling signal for the motor control device to provide the rated current for the electrical drive of the fluid hydraulic motor pump unit.