In any internal combustion engine, engine seals make sure that oil stays in the engine. As a result, the intersection between the engine and transmission is an important sealing point; the crankshaft ends with a shaft seal at the crankcase. As essential as the seal is, it produces a substantial amount of friction with every engine rotation, converting valuable torque into heat energy losses.

The Levitex mechanical seal, by contrast, produces almost no friction at all.

At its core, a Levitex seal consists of two interacting rings, one of which is firmly attached to the crankshaft and the other to the crankcase. One of the rings has grooves that are just a few micrometers deep and which taper to a closed tip. When the crankshaft rotates, the air is dragged against the sealing dam that encloses the grooves, generating a very stable gas film in the magnitude of a few micrometers, which also prevents oil leakage. The low viscosity in the gas film leads to a friction close to zero.

Until now, gas-lubricated mechanical face seals were exclusively used in major industrial facilities. The new design, patented by Freudenberg-NOK, and its associated production process that allow the idea to be carried over to the internal combustion engine, where there is little space available for its installation.

Testing demonstrated the functioning of the sealing rings in extreme temperatures, ranging between -40 and +150 degrees C; with fine dust—such as the “Arizona dust” that automakers use for their functional tests; and penetration of water.

At present, no other technology is known that allows the frictionless and secure sealing of the crankshaft. In view of the ambitious CO₂ goals that become effective in 2020, the focus will be on saving every gram. As a result, we are confident that we will succeed in finding other customers for this innovative technology.

—Dr. Eberhard Bock, the head of strategic product development at Freudenberg Sealing Technologies

Freudenberg-NOK has also successfully introduced a family of low friction Simmerring seals into the market. The seals are based on the innovative material “ACM 380”, a rubber compound that not only reduces friction by up to 20% but is also manufactured with an environmentally-friendly vulcanization accelerator.

The “Energy Saving Seal” from this product group makes it possible to reduce friction by up to 40%. In this seal, the elastomer is reinforced with a plastic sleeve. The company also offers a CASCO cassette seal especially for commercial vehicles that reduces crankshaft friction by 60 percent while protecting against dirt with an axially positioned seal lip. In a test under realistic operating conditions, the CASCO seal passed an operating run of 1.6 million kilometers.

Freudenberg-NOK Sealing Technologies is the Americas joint venture between Freudenberg and Co. in Germany and NOK Corp. in Japan. Freudenberg-NOK is a leading producer of advanced sealing technologies for a variety of markets including: aerospace; agriculture; appliance; automotive; construction; diesel engine; energy; food and beverage; heavy industry; and pharmaceutical.

Resources

• Sören Neuberger, Eberhard Bock, Werner Haas, Klaus Lang (2014) “Gas-lubricated mechanical face seals reduce CO₂ emissions”, Sealing Technology, doi: 10.1016/S1350-4789(14)70343-5