Scroll Compressor Axial Back Pressure Passage for Friction Control
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Solution Overview
Problem
In fixed back pressure type variable capacity scroll compressors, the back pressure passage periodically opens and closes, leading to inadequate pressure adaptation in the back pressure chamber, resulting in excessive pressure rise and increased friction between the non-orbiting and orbiting scrolls, especially in power and low-speed operations, which reduces compressor efficiency.
Innovation Solution
The back pressure passage is designed to communicate with the compression chamber through the front end surface of the non-orbiting wrap, allowing quick pressure variation in the back pressure chamber in response to the compression chamber pressure, and is positioned to adapt to different operating modes, minimizing leakage and excessive contact between the scrolls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the back pressure passage penetrates the end plate portion of the non-orbiting scroll, then the structure is simple and easy to manufacture, but the back pressure passage is periodically opened and closed by the orbiting wrap, causing inadequate pressure adaptation and excessive pressure rise in the back pressure chamber
Solution Approach 1:
The back pressure passage is divided into two separate parts: a first back pressure passage formed in the non-orbiting scroll and a second back pressure passage formed in the end plate. This segmentation allows the orbiting wrap to clear both passages simultaneously, preventing periodic opening and closing while maintaining manufacturing simplicity.
Solution Approach 2:
The back pressure passage is relocated from a radial position (penetrating the end plate) to an axial position (formed in the front end surface of the non-orbiting wrap). This dimensional change allows the passage to remain open during orbiting motion, eliminating periodic closure while maintaining structural simplicity.
2Adaptability or versatility
If the back pressure passage is positioned for saving mode, then appropriate back pressure is secured in saving mode, but excessive back pressure rises in power mode causing increased friction and reduced efficiency
Solution Approach 1:
The system uses a movable partition wall that can shift between saving mode and power mode positions. In power mode, the partition wall moves to open the first back pressure passage, providing a larger communication area to reduce back pressure and minimize friction losses. In saving mode, the partition wall closes the first passage and uses the second passage, maintaining appropriate back pressure.
Solution Approach 2:
The back pressure passage configuration changes based on operating mode. The system switches between different passage configurations (first passage for power mode, second passage for saving mode) by moving the partition wall, thereby adapting the back pressure parameters to match the required operating conditions and minimizing energy loss.
3Productivity
If the orbiting scroll rotates at high speed, then compression capacity increases, but the periodic opening and closing of the back pressure passage prevents quick pressure adaptation
Solution Approach 1:
The back pressure passages are pre-positioned and kept open in advance by designing them to be clear of the orbiting wrap throughout the rotation cycle. The movable partition wall is positioned beforehand to ensure continuous communication between the compression chamber and back pressure chamber, enabling quick pressure adaptation without periodic interruption.
Data Source
AI summary
A scroll compressor may include a back pressure passage that provides communication between a compression chamber and a back pressure chamber to guide refrigerant compressed in the compression chamber partially to the back pressure chamber. The back pressure passage may communicate with the compression chamber through a front end surface of a non-orbiting wrap axially facing an orbiting end plate. Accordingly, when an orbiting scroll tilts, the non-orbiting wrap may be spaced apart from the orbiting end plate to open a scroll back pressure hole, such that the compression chamber and the back pressure chamber communicate with each other to quickly vary pressure in the back pressure chamber to be adaptive to the pressure of the compression chamber. This may result in appropriately adjusting back pressure in the back pressure chamber according to an operating mode and/or operating conditions, thereby increasing a sealing power and suppressing or preventing excessive contact.