Stays tight — even at over 100 bar

Freudenberg Sealing Technologies has developed a novel sealing system for busbar sealing in vehicle air conditioning compressors. This elastomer-based solution withstands test pressures exceeding 100 bar during leak testing and offers a cost-effective alternative to conventional glass seals. Designed for CO₂ compressors (R744), it is also suitable for use with other refrigerants.

European regulations regarding fluorinated greenhouse gases are driving change within the automotive industry: The fluorine-containing refrigerants R134a and R1234yf—which have predominantly been used until now—are being gradually replaced by alternatives. The natural refrigerants R744 (CO₂) and R290 (propane) are considered particularly future-proof. However, the use of CO₂ in refrigerant compressors presents significant technical challenges: Operating pressures in CO₂ air conditioning compressors are many times higher than those required by conventional refrigerants within the compressor unit.

Tiny molecules, enormous pressure

One of the key tasks in this environment is the reliable sealing of electrical feedthroughs—known as busbars or pins—within the compressor housing. Tiny CO₂ molecules can penetrate the elastomer material through permeation. If a rapid drop in pressure subsequently occurs, the trapped gas molecules expand explosively, potentially destroying the seal from the inside out—a phenomenon known as explosive decompression. Furthermore, the seals must meet the most stringent mechanical requirements.

Material and design from a single source

Freudenberg Sealing Technologies addresses these challenges with a new sealing system utilizing a wide variety of materials. In doing so, the company leverages its profound materials expertise: Materials were specifically developed for use in CO₂ compressors that withstand explosive decompression and demonstrate high media resistance to common refrigerants. Furthermore, specific elastomer variants are employed that offer high Comparative Tracking Index (CTI) ratings, thereby reliably preventing creepage current flashover at the busbar feedthrough.

The sealing contour is the result of an integrated development approach that precisely harmonizes manufacturability, component design, and functional safety. Freudenberg Sealing Technologies masters this balancing act across the entire value chain—from the development and processing of sophisticated materials to the design of the appropriate sealing structure. In leak testing, the sealing system reliably withstood test pressures exceeding 100 bar.

"The transition in refrigerants presents manufacturers of air conditioning compressors with entirely new sealing requirements. We offer them not merely a technical solution to this challenge, but a genuine development partnership—from material selection to a sealing contour ready for series production," says Christian Jaschke, Product Manager at Freudenberg Sealing Technologies.

More cost-effective and flexible than glass

Compared to the glass seals that have historically been widely used, the new solution offers several advantages: Costs per sealed busbar or pin can be reduced by up to 30 percent, depending on the specific application. With typically three busbars per compressor, this translates into significant potential for cost savings. Moreover, thanks to its compact design, the solution contributes to the optimization of installation space—a critical factor within the tightly packed environment of a compressor. As a development partner, Freudenberg Sealing Technologies individually tailors material, sealing contour, and geometry to the specific requirements of each compressor manufacturer—ensuring high availability and short development cycles. This approach is underpinned by a broad material portfolio that covers a temperature range from –40 °C to over 200 °C and offers high media resistance against a wide variety of refrigerants.

From development to application

Industry interest is high: Freudenberg Sealing Technologies is currently engaged in concrete development projects with several automotive compressor manufacturers. Initial prototypes have already been validated. This technology is not limited to CO₂ refrigerant compressors; rather, it can be applied to other high-pressure applications involving different media—an advantage derived from the extensive insights gained in sealing the particularly demanding refrigerant R744.