New Demands on Scroll Compressor Plain Sliding Bushing Bearings: The Advantages of Steel-Backed PTFE Bushings

As scroll compressor manufacturers strive to enhance efficiency while reducing the physical size of their units, the bearings guiding the rotating scrolls face increasingly stringent demands. These bearings must offer superior tribological performance and exceptional wear resistance to ensure reliable and predictable service lives.

Industry Evolution and Technological Challenges

The evolving requirements of industries such as electric vehicles and residential thermal management systems pose new technological challenges. These include enduring high loads, operating at increased speeds, and maintaining performance over the lifespan of the compressor. The trend in compressor motors is to achieve higher efficiency and performance in a compact size, necessitating higher revolutions per minute (rpm) to compensate for reduced volume. This shift towards higher speeds and more compact designs mandates that bearings operate under elevated pressure-velocity (p-v) conditions and at higher temperatures.

Scroll Compressors in the HVAC and Automotive Markets

Scroll compressors are becoming increasingly popular in the heating, ventilation, and air conditioning (HVAC) and automotive markets due to their high volumetric efficiency, quiet operation, and compact size. Typical applications include cabin temperature control in all-electric vehicles (EVs). Historically, roller bearings (ball bearings) were used to support and guide the rotating scrolls. However, with the move towards more compact designs, plain sliding bearings, specifically designed for scroll compressor applications, are now the preferred choice. These sliding bearings, also known as plain bearings, contain no moving parts, thus reducing vibrations and enhancing reliability.

Requirements for Bearings in Scroll Compressor Applications

Engineers look for four key attributes in bearings used within scroll compressor systems:

• High pressure-velocity-temperature (p-v-T) capabilities
• Low friction
• Increased efficiency
• Excellent wear resistance in boundary lubrication conditions

Steel-Backed PTFE Sliding Bearings

The smooth surface structure of PTFE sliding bearing materials facilitates hydrodynamic lubrication at relatively low speeds and provides excellent wear resistance in boundary lubrication conditions. The high-temperature capabilities of the material ensure reliability, long life, and predictable performance, which are crucial for scroll compressor applications. PTFE formulations are inert and resistant to the chemical refrigerants or working fluids typically used in scroll compressors.

Tribological Performance

During startup, hydrodynamic bearings must initially operate in the boundary lubrication regime before achieving full hydrodynamic operation. Ideally, engineers always aim to design a bearing that operates hydrodynamically to minimize wear and reduce friction. However, the conditions necessary to generate a hydrodynamic region are not always possible; lack of lubrication or low speeds may force the bearing system to operate in a boundary lubrication state. A low-friction material with excellent wear rate characteristics is essential under these conditions.

In summary, the advent of steel-backed PTFE bushings for scroll type compressors addresses the new demands for wear resistance and reduced friction, significantly enhancing the efficiency of scroll compressor applications in evolving markets.