Frequency-Controlled Baling Press Drive Energy Efficiency
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Solution Overview
Problem
Existing electro-hydraulic drive systems for baling presses face issues such as high complexity and cost, noise, energy inefficiency, and pressure surges due to the use of axial piston pumps or constant displacement pumps, which lead to increased equipment and control engineering effort, as well as unnecessary power consumption and maintenance needs.
Innovation Solution
The integration of a constant pump, such as a vane cell or internal gear pump, with a frequency-controlled electric motor, where control signals from a pressure transducer adjust the pump speed according to the hydraulic line's actual state, allowing for optimized energy use and reduced power consumption by delivering only the required oil volume to actuators, and enabling soft start and reduced mechanical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If axial piston pumps are used for electro-hydraulic drive, then control quality and energy efficiency are improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive axial piston pumps with cheaper constant displacement pumps (vane pumps or gear pumps), accepting lower inherent efficiency but compensating through frequency-controlled motor operation that prevents energy waste through circulation and pressure relief valves
Solution Approach 2:
The patent substitutes the mechanically complex variable displacement pump with an electronically controlled system using a frequency converter to regulate motor speed, replacing mechanical complexity with electronic control
2Stress or pressure
If axial piston pumps with proportional valves are used, then pressure and volume flow can be changed without large pressure surges, but high oil quality and cost are required
Solution Approach 1:
The patent eliminates the need for expensive high-quality hydraulic oil by using constant displacement pumps without proportional valves, accepting simpler pump construction that works with standard hydraulic oil
3Productivity
If constant displacement pumps are used with multiple pump stages, then different flow rates can be implemented, but pressure surges occur when pump stages are switched
Solution Approach 1:
The patent uses dynamic speed control of a single pump stage through frequency conversion, replacing the static switching of multiple pump stages, thereby achieving flow rate variability without the pressure surges associated with stage switching
4Reliability
If electric motor runs permanently at nominal speed, then pump can deliver constant flow rate, but no-load current is approx. 60% of nominal current leading to energy losses
Solution Approach 1:
The patent makes the previously static motor speed dynamic by using frequency converters to continuously adjust motor speed according to actual hydraulic demands, eliminating the need to run at constant nominal speed and thereby eliminating the 60% no-load current waste
Solution Approach 2:
The patent implements feedback control where motor speed is continuously adjusted based on actual hydraulic system demands, ensuring the motor only consumes power when and where needed, rather than running permanently at nominal speed
5Productivity
If pump stages are switched on and off via valves, then different flow rates are implemented, but pressure surges occur and flow rate is constantly circulated even for switched-off stages
Solution Approach 1:
The patent replaces the static on/off switching of pump stages with dynamic speed modulation of a single pump, allowing continuous flow rate adjustment without the energy waste of circulating flow through pressure relief valves
Solution Approach 2:
The patent extracts and eliminates the energy-wasting circulation loop by using frequency-controlled motor speed to match pump output exactly to actuator demand, removing the need for pressure relief valves and continuous circulation
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 reduces noise, energy savings, and extends maintenance intervals by dynamically controlling the actuators, eliminating pressure surges, and allowing for redundant drive trains, thus lowering power consumption and heat generation, while enabling flexible control and efficient operation with reduced equipment complexity.
Implementation Method 1
the control signals output by the drive are first fed to a frequency converter coupled to the electric motor
Implementation Method 2
the control signals then generated and output for further control of the electric motor also take into account the signals generated by a pressure transducer about the actual state of a hydraulic line
Data Source
Figure 1
Figure 2~3
Figure 4~6
AI summary
The method involves delivering control signals from a control unit (2) of a baling press (1) for the control of an electric motor (4) of an engine-pump-unit of the electro-hydraulic drive. The control signals are fed to a frequency converter (3) coupled with the electric engine. An independent claim is also included for a device for executing the method for controlling the drive of a baling press.