Nylon rocker cover

Citation

(2001), "Nylon rocker cover", Assembly Automation, Vol. 21 No. 1. https://doi.org/10.1108/aa.2001.03321aaf.004

Nylon rocker cover

Nylon rocker cover

Keyword: Thermoplastics

What is claimed to be one of the first thermoplastic rocker covers on a North American vehicle is being fitted on Tritec's 1.6 litre, four-cylinder engine, an optional powertrain for DaimlerChrysler's Neon in North America and the Rover R50 in Europe. The component reduces weight and offers integration possibilities that improve usefulness and reduce costs, according to DuPont Automotive, the Troy, Michigan, company that supplied the material. Tritec, a joint venture of DaimlerChrysler and BMW, manufactures the engine in Brazil. The nylon rocker cover and gasket are produced by Dana Corp. in Porto Alegro, Brazil.

The rocker cover, injection moulded of DuPont Minlon mineral filled nylon 66, includes a series of integrated baffles to separate oil from the positive crankcase ventilation air supply. The rocker cover incorporates the housing for the PCV valve, an emission control device; has a moulded-in air make up nipple; provides heat-staked inserts for mounting the ignition coil; and includes two heat-staked baffle plates.

The cover, which weighs 2.8lb is about 30 per cent lighter than the part it replaced. The rocker cover has a wall thickness of 2.5mm.

Key performance challenges for the rocker cover were the ability to meet thermal and mechanical requirements and to resist warpage. "We have to keep the part as flat as possible to apply uniform forces in assembling the rocker cover to the engine block", said Gian Luigi Molteni, product development manager of DuPont Automotive. The main issue was to avoid leakage, which can jeopardise the function of the engine.

The part, and seal between the rocker cover and engine block, had to be designed to resist stress relaxation due to long-term exposure to underhood temperatures and mechanical forces when the cover is bolted down. The mineral reinforcement of the nylon reduced shrinkage and warpage, Molteni said. DuPont used finite element modelling to optimise the cross section of the silicone seal, which is 4.5mm in diameter and is mounted in a groove along the flange of the rocker cover.

The engine also incorporates an integrated oil pan gasket carrier, made of glass-filled DuPont Zytel nylon 66, which improves sealing efficiency and reduces assembly time by eliminating manufacturing steps, said Molteni.