Scroll Compressor Startup Control for Liquid Refrigerant Discharge
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Solution Overview
Problem
Existing scroll compressors face issues with liquid compression when starting up with liquefied refrigerant, leading to deformation of scroll walls due to applied loads.
Innovation Solution
A startup operation is implemented with a controller that performs reverse and forward rotations of the motor, along with controlled swinging of a bushing on an eccentric shaft to increase the gap between scroll walls, followed by a gradual speed increase to efficiently discharge liquefied refrigerant before normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the scroll compressor starts with liquefied refrigerant in the compression mechanism, then the refrigerant can be discharged, but liquid compression occurs causing high loads on the scroll walls leading to deformation
Solution Approach 1:
The system performs a preliminary reverse rotation operation before normal forward rotation to discharge liquefied refrigerant from the compression mechanism. This preliminary action removes the harmful liquid refrigerant that would otherwise cause high loads and potential deformation during normal compression operation.
Solution Approach 2:
The motor temporarily rotates in reverse direction during startup to create conditions favorable for discharging liquid refrigerant. This inversion of the normal rotation direction allows the orbiting scroll to move in the opposite direction, opening gaps between scroll walls to facilitate liquid discharge before resuming normal forward rotation for compression.
2Speed
If the motor rotates forward with high acceleration to reach operating speed quickly, then productivity improves, but the bushing posture changes causing increased loads on scroll walls
Solution Approach 1:
The motor operation is divided into distinct periodic phases: reverse rotation phase, forward rotation with reduced acceleration phase, and normal high-speed operation phase. This periodic control of rotation direction and acceleration rate allows the bushing to maintain stable posture while still achieving operational speed.
Solution Approach 2:
The controller adjusts the acceleration parameter during forward rotation to be lower than normal operating acceleration. This parameter change allows the bushing to maintain its posture stability while the motor still increases rotational speed, preventing excessive loads on the scroll walls during the transition to operating speed.
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 method effectively discharges liquefied refrigerant while minimizing loads on the scroll walls, preventing deformation and ensuring efficient operation.
Implementation Method 1
an eccentric shaft extending from the rotary shaft at a position eccentric to an axial line of the rotary shaft, the eccentric shaft extending parallel to the axial line of the rotary shaft; and a bushing mounted on the eccentric shaft and swingable about the eccentric shaft, the bushing swinging about the eccentric shaft to change an orbital radius of the orbiting scroll
Implementation Method 2
the motor is driven at the predetermined rotational speed to cause the orbiting scroll to make orbital motion so that the liquefied refrigerant is discharged from the compression mechanism
Data Source
AI summary
A scroll compressor includes a housing, a rotary shaft, a motor, a controller, a compression mechanism including a fixed scroll and an orbiting scroll, an eccentric shaft, and a bushing. An orbital radius of the orbiting scroll changes with swinging of the bushing about the eccentric shaft. The controller performs a startup operation to discharge liquefied refrigerant from the compression mechanism before performing a normal operation. In the startup operation, the controller performs a startup reverse rotation in which the controller rotates the motor in reverse and swings the bushing, a startup forward rotation, after the startup reverse rotation, in which the controller rotates the motor forward while reducing an acceleration in a rotational speed of the motor, a startup liquid discharge in which the controller rotates the motor at the predetermined rotational speed.