Seals and bearings typically do their jobs out of sight and mind. Nevertheless, they are critical components—as anyone knows who has had one or two fail on them. Then it becomes obvious these are critical components in automotive and industrial applications for safety and performance.
This means their durability and reliability should be as good as they can be to prevent failure. At the same time, bearings and seals must be small, lightweight and cost-efficient in keeping with manufacturers’ efforts to remove cost and weight from vehicles without sacrificing performance.
To come up with a bearing that could bring all this to the table—durability, low cost, lightweight and top-notch performance—engineers at Freudenberg Sealing Technologies started two years ago thinking out-of-the-box at the design stage. The main engineering challenge of the project was to minimalize installation space, weight and complexity. The team came up with the integrated bearing (SWIB), which combines a plastic rotating bearing and seal in a single, precisely matched unit. The design offers significant weight, cost and friction advantages over separate bearings and seals, and improves the properties of the mated bearings and seals.
The seal comes with a coat of light lifetime grease, so it should need no future lubrication, but that depends on the application.
The bearing offers significant improvements compared with separate bearings and seals. The rigidity of the plastic bearing is high, so deflection is reduced by nearly 50% when lateral forces are exerted compared to conventional designs. This lowers the induced vibrations which raises driver’s steering comfort.
The seal, on the other hand, creates 35% less friction, which reduces resistance during steering. This is especially important for automated driving. The bearing’s weight was cut as much as 80%, thanks to combining the two components.
Freudenberg designers validated the bearing and seal’s advantages through extensive testing. They checked the performance in temperature extremes of −40 to 257°F (−40 to 125°C) while under mechanical stress. They also turned high-pressure water on it, which it could see when used in automotive steering subsystems during engine washes.
The design team also put the new bearing through its paces inside a sensor housing in an electrical power steering unit in an electric car. The sensor records data, such as steering angle, which is critical to driver-assistance features such as electronic stability control. The seal in the housing protects the sensor from dust, water and other contaminants getting in during the entire service life of the vehicle. The bearing is also critical and must withstand mechanical loads as great as 3,000 N of radial force when a car drives over a curb with its wheels at an extreme angle.
Engineers at Freudenberg are already researching other applications for the new component. In addition to automotive applications, seals with integrated plastic bearings can likely benefit many industrial operations, according to the company. They also want to improve the manufacturing process. One idea is to switch to other materials and a two-component, injection molding process.