Freudenberg Sealing Technologies' elastomer-based sealing solution

Freudenberg Sealing Technologies has developed a new sealing system for busbar sealing in vehicle air-conditioning compressors. The solution is elastomer-based, withstands test pressures of over 100 bar in leak tests, and is an alternative to conventional glass seals. Created for CO2 compressors, it is also suitable for other refrigerants

European regulations on fluorinated greenhouse gases are driving a transformation in the automotive industry: the fluorinated refrigerants R134a and R1234yf are being phased out in favour of alternatives. 

The natural refrigerants R744 and R290 are considered viable for the future; however, using CO2 in refrigerant compressors involves technical challenges. The operating pressures in CO2 air-conditioning compressors are many times higher than those required by conventional refrigerants.

One of the key tasks in this environment is to reliably seal electrical feedthroughs, busbars or pins, in the compressor housing. The tiny CO2 molecules can permeate the elastomer. In the event of a rapid pressure increase, the trapped gas molecules can suddenly expand and destroy the seal from the inside out, a phenomenon known as explosive decompression, resulting in the seals needing to meet the strictest mechanical requirements.

Freudenberg Sealing Technologies' new solution, which uses a range of materials, has been developed to address these challenges. The company specifically developed materials for use in CO2 compressors that resist explosive decompression and offer high media resistance to conventional refrigerants. This involves using elastomer variants with a high comparative tracking index (CTI) to help prevent creep currents from arcing at the busbar feedthrough.

The sealing contour was developed with an integrated development approach that precisely coordinates manufacturability, component design, and functional safety. In leak tests, the sealing system withstood pressures exceeding 100 bar.

Christian Jaschke, product manager at Freudenberg Sealing Technologies, said, “With this change in refrigerants, manufacturers of air-conditioning compressors are facing entirely new sealing requirements. We offer them not just a technical solution to this challenge, but a true development partnership, from the material selection to a sealing contour that is ready for series production.” 

The new solution offers several advantages, including the ability to reduce the cost per sealed busbar/pin by up to 30%, depending on the specific application. With three busbars per compressor, this creates potential savings. The compact design also optimises the installation space. This is a decisive factor in the densely packed compressor environment.

As a development partner, Freudenberg Sealing Technologies can customise the material, sealing contour, and geometry to meet the requirements of the compressor manufacturer, providing high availability and short development cycles. The basis for this is a broad materials portfolio that covers temperatures from –40 °C to more than 200 °C and offers high media resistance to a variety of refrigerants.

Freudenberg Sealing Technologies is currently working on concrete development projects with several vehicle compressor manufacturers, with the first prototypes already validated. The technology is not limited to CO2 refrigerant compressors, which can be transferred to other high-pressure applications with different media, an advantage acquired during the seal development for R744.