The next big under-the-hood application for nylon may be oilpans, which are traditionally made from cast aluminum, stamped steel ormetal-plastic-metal hybrid constructions.

New plastic versions cut weight 40 percent or more and alsointegrate functionality. German auto supplier ElringKlinger developed a designfor pickup trucks that integrates significant components of the oil-circulationsystem. 

"Our selection of a particularly high-melt flow grade ofZytel nylon resin meant that we were able to manage the long flow distances ata comparably low injection pressure and despite some very low wallthicknesses," says Ralf Franz, development engineer at ElringKlinger. "This, inturn, reduces cycle times, helps preserve the tool and keeps energy costslow." 

The multifunctional design includes the pan (measuringapproximately 550 mm long, 400 mm wide and 300 mm high), sections of thepipeline for suction of oil from the sump, the fastening flanges for thepressure pipelines to and from the oil filter and the oil filter flange with adirectly encapsulated oil filter thread. 

Separate injection-molded parts include the two-piece coverof the suction pipe, the double pipe for connection with the oil filter and thecover for the oil filter flange. All ofthe individual parts, as well as the polymer-encapsulated metal sieve locatedin the oil intake, are connected to the pan with friction welding.

The nylon 66 from DuPontis reinforced with 35 percent (by weight) glass fibers, creating very stiffcreep- and hydrolysis-resistant components.The compound combines high-impact resistance over a wide temperaturerange with a high resistance to lubricants, road salts and other media commonlypresent in vehicles. The additional heatstabilization enables the long-term usage of the material at temperatures of upto 150C and makes it particularly resistant to heat aging. And as in air intake manifolds, glass-fiber-reinforcednylon provides good mechanical and acoustic attenuation properties.

Franz says the low warpage behavior of the material is alsoimportant because it facilitates a durable and reliable seal along thecircumference of the oil pan. 

"We had to design the new polymer oil pan in such a way thatits connection to the engine was consistent with the metal constructionpreviously used," says Franz. "We werethereby presented with relatively large distances between the connectionpoints. Thanks to the high stiffness ofthe material and the purpose-made application of ribs, we managed to limitdeformation under load to the required rate despite these unfavorableconditions, thus ensuring a constant surface pressure across the wholeperimeter."

Whereas the ribbing located in the upper section of the oilpan principally contributes to dimensional stability in the seal area, the manyhigh ridges in the lower section are designed to absorb external impactscaused, for example, by stones as they are thrown up from the road duringnormal driving. 

More significant impacts may also occur when the dismountedengine is placed heavily on the floor during transportation.

For the production of the seals between the pan and theengine, as well as for the connection of oil circuit elements, ElringKlinger usesa highly heat- and oil-resistant ethylene acrylic elastomer.

At the National Plastics Exposition held June 22-26 in Chicago, BASFalso emphasized that oil pans are a major target of its development activities.

BASF has developed Ultramid B3ZG7 OSI, an "optimizedfor stone impact" grade that equals and exceeds the performance of castaluminum in oil pans, says Phillip E.  Wilson, the new businessdevelopment manager for engineering plastics at BASF.

The OSI material is a 35-percent glass-reinforced andimpact-modified nylon 6. It has survived a battery of experimental data showingOSI initial cracking at 60 mph, whereas aluminum pans crack at an impact ofaround 50 mph under the BASF proprietary 'stone impact' simulation testing.

Wilsonshowed a nylon pan incorporating a windage tray, oil pickup tube and anintegrated oil filter module. Additional benefits include weight and costreduction.

Plastic Oil Pans Present Major Integration Opportunity A