Cryopump Control Method for Cooling Time Reduction
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Solution Overview
Problem
Cryopumps face challenges in efficiently cooling down to cryogenic temperatures, requiring a significant amount of time due to the large temperature difference between high and low temperature stages, which results in downtime and increased cooling time.
Innovation Solution
A control method for cryopumps that adjusts the upper limit operating frequency of the cryocooler motor based on the temperature decrease during the cool-down operation, allowing for dynamic frequency adjustment to optimize cooling efficiency and reduce downtime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the cryocooler operates at high frequency during cool-down, then cooling speed is improved, but friction and pressure losses increase reducing efficiency
Solution Approach 1:
The patent applies dynamics by making the operating frequency of the cryocooler motor variable rather than fixed. The control unit dynamically adjusts the operating frequency based on real-time temperature measurements during the cool-down process, allowing the system to optimize between cooling speed and energy efficiency at different temperature stages.
Solution Approach 2:
The patent changes the operating parameter (frequency) of the cryocooler motor based on temperature conditions. By monitoring the temperature of the cryopanel and adjusting the motor frequency accordingly, the system transitions from high-frequency operation at higher temperatures to lower-frequency operation as the cryopanel approaches its setpoint temperature, thereby reducing friction and pressure losses while maintaining effective cooling.
2Loss of time
If the cryocooler operates at high frequency throughout cool-down, then cooling time is reduced, but energy efficiency deteriorates due to increased friction and pressure losses
Solution Approach 1:
The system dynamically adjusts the operating frequency based on the thermal state of the cryopanel. During early cool-down when temperature difference is large, higher frequencies are used to reduce cooling time. As the cryopanel approaches the target temperature, the frequency is reduced to minimize energy consumption and friction losses, achieving an optimal balance between time and energy efficiency.
Solution Approach 2:
The control system implements periodic monitoring and adjustment of the operating frequency based on temperature feedback. This periodic control allows the system to switch between different operating modes (high frequency for rapid cooling, lower frequency for fine-tuning), optimizing both time and energy efficiency throughout the cool-down process.
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 shortens the cooling time of the cryopump by approximately 10% by maintaining cooling efficiency and reducing friction and pressure losses, enabling faster temperature stabilization across both stages.
Implementation Method 1
a cryocooler which is configured to cool the cryopanel
Implementation Method 2
a cooling stage
Data Source
AI summary
A cryopump includes a cryopanel, a cryocooler which is configured to cool the cryopanel, and includes a cryocooler motor configured to drive the cryocooler and a cryocooler inverter configured to control an operating frequency of the cryocooler motor, and a control unit configured to control the cryocooler to perform a cool-down operation by which a temperature of the cryopanel is decreased from room temperature to a standard operating temperature. The control unit includes an operating frequency determination unit configured to determine an operating frequency of the cryocooler motor within an operating frequency range having an upper limit operating frequency and outputs the operating frequency to the cryocooler inverter, and an upper limit adjustment unit configured to decrease the upper limit operating frequency based on a decrease in a temperature of the cryopanel during the cool-down operation.