Secondary Vacuum Pump Speed Control for Rapid Pressure Drop
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Solution Overview
Problem
Current pressure reduction methods in loading and unloading airlocks for substrates, such as flat screen displays and photovoltaic substrates, are limited by low initial pumping speed and high power consumption of secondary vacuum pumps, leading to potential damage and mechanical wear due to pulsating recirculation valve operation and overheating from hot gases.
Innovation Solution
The method involves controlling the rotational speed of the secondary vacuum pump to maintain a flow rate between 1.3 and six times that of the primary vacuum pump during pressure drop, optimizing the flow rate ratio to reduce power consumption and increase overall pumping speed, while protecting the pumps from excess gas flow and thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the secondary vacuum pump operates at high flow rate to increase initial pumping speed, then the pressure drop time is reduced, but the power consumption increases and the pump is exposed to excess gas flow causing mechanical stress
Solution Approach 1:
The patent applies dynamic control by varying the rotational speed of the secondary vacuum pump according to the pressure differential across it. The control unit adjusts the motor speed based on real-time pressure measurements, allowing the pump to operate at high speed when pressure differential is low (reducing pressure drop time) and at lower speed when pressure differential is high (reducing power consumption and mechanical stress). This dynamic adaptation resolves the contradiction between speed and energy consumption.
Solution Approach 2:
The patent changes the operational parameters of the secondary vacuum pump by controlling its rotational speed as a variable parameter rather than operating at constant speed. The control unit modifies the motor speed parameter in response to pressure differential changes, enabling the system to optimize both pressure drop time and power consumption by adapting the speed parameter to operating conditions.
2Loss of time
If the secondary vacuum pump operates at high flow rate to increase initial pumping speed, then the pressure drop time is reduced, but the recirculation valve experiences pulsating operation causing wear and noise
Solution Approach 1:
The dynamic speed control of the secondary vacuum pump stabilizes the operation of the recirculation valve by preventing excessive pressure differential buildup. By adjusting the pump speed in real-time, the system avoids the pulsating flow conditions that cause valve wear and noise, while still achieving rapid pressure drop through optimized speed profiles.
3Speed
If the secondary vacuum pump handles strong gas flow at atmospheric pressure opening, then the initial pumping speed increases, but the discharge pressure becomes too high causing thermal stress and overheating
Solution Approach 1:
The control unit dynamically adjusts the secondary vacuum pump motor speed in response to discharge pressure and temperature conditions. When the airlock opens to atmospheric pressure and strong gas flow occurs, the pump operates at controlled speeds that prevent excessive discharge pressure buildup, thereby avoiding thermal stress and overheating while maintaining effective initial pumping speed.
Solution Approach 2:
The system employs feedback control where the control unit continuously monitors the operating conditions of the secondary vacuum pump and adjusts the motor speed accordingly. This feedback mechanism prevents discharge pressure from becoming too high by reducing pump speed when necessary, thereby preventing thermal stress and overheating while maintaining optimal pumping performance.
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 enhances the initial pumping speed and reduces power consumption, shortening pressure drop time and minimizing wear and noise in the recirculation valve, with a 20-50% increase in pumping speed and 20% reduction in pressure drop time, and reduced overheating of the secondary vacuum pump.
Implementation Method 1
the pressure difference between the suction and the discharge of the secondary vacuum pump becomes too great
Implementation Method 2
allowing the pressure in the enclosure to be lowered until an appropriate low pressure is reached
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a method for lowering the pressure in a lock for loading and unloading a substrate at atmospheric pressure by a pumping unit (1) including a primary vacuum pump (2) and a secondary vacuum pump (3) arranged upstream from said primary vacuum pump (2) in the direction of flow of the gases to be pumped. During the lowering of the pressure until the pressure in the loading and unloading lock reaches a predefined low-pressure threshold, the speed of rotation of the secondary vacuum pump (3) is controlled as a function of an operating parameter of the secondary vacuum pump (3) in order to increase the flow rate generated by the secondary vacuum pump (SoR) so that the flow rate generated by the secondary vacuum pump (SoR) is comprised in a range of which the upper value corresponds to six times the flow rate generated by the primary vacuum pump (Sol) and the low value corresponds to 1.3 times the flow rate generated by the primary vacuum pump (Sol). The invention also relates to a pumping unit for implementing said pressure-lowering method.