In 1962, a car engine equipped with a timing belt was mass-produced for the first time. This groundbreaking invention was a real revolution for the belt drive at the time. Since then, a wide variety of makes and models worldwide have relied on this type of engine timing. With the development of new materials and tooth designs, the service life of timing belts has also increased, as they are more resistant to extreme temperatures and better able to withstand high loads.
Belt Material: No Two are the Same
Over the decades, various materials have been used in the production of belts:
- Chloroprene rubber (CR): The first generation of belts were not subjected to high operating loads or large thermal loads at an operating temperature of 80 °C to 90 °C. These belts had a short service life because the rubber quickly became brittle. This was accelerated when it came into contact with any escaping engine oil.
- Highly saturated nitrile rubber (HSN): Provides improved resistance to stresses and operating temperatures up to 110 °C.
- Hydrogenated acrylonitrile butadiene rubber (HNBR): Offers improved resistance at load and working temperatures up to 110 °C. Used in the latest generation of timing belts, e.g. also for febi timing belts. HNBR is characterised by ideal temperature resistance, low friction, and noise development during operation. It also has an increased service life and complies with EURO 5 and EURO 6 emission standards for timing and combustion values.
- Belt in oil: This timing belt is designed to operate in oil and is resistant to contamination and high engine oil temperature.
Different Tooth Forms
The first timing belts used existing tooth shapes that were already used in industrial applications. Here, each tooth had a trapezoidal shape. With increasing requirements, the belts were to produce less noise and vibration as well as impress with greater durability and load transmission. To achieve this, the use of curved tooth shapes prevailed.
The circular shape enables an even distribution of the forces acting on the tooth and avoids tension peaks on the belt. In addition to single-sided toothed belts, there are some special versions of double-sided toothed belts that allow the belt to be driven on both sides and are ribbed or have teeth on the back for driving engine controls or auxiliary units.