The German automotive supplier ElringKlinger has developed a production-ready, multifunctional car oil pan made of a grade of glass-fiber-reinforced DuPont Zytel nylon resin optimized for use in engine compartments. In addition to the benefits of previous polymer designs, the new pan - designed for use in pick-up trucks - now integrates significant components of the oil-circulation system. This enables a further reduction of vehicle weight as well as manufacturing and assembly costs. Accordingly, the new oil pan is approximately 40 percent lighter than its aluminum counterpart.
When car oil pans made of thermoplastic polymers were first launched, the initial priority was the replacement of considerably heavier components made of diecast or sheet metal. Progressive developments are now seeking to use the high design freedom associated with thermoplastics to fulfill additional functions. Accordingly, the new design from ElringKlinger involves the single-stage production of not just the pan (measuring approximately 550 mm long, 400 mm wide and 300 mm high) but also sections of the pipeline for suction of oil from the sump, the fastening flanges for the pressure pipelines to and from the oil filter and the oil filter flange with a directly encapsulated oil filter thread. Separate injection-molded parts include the two-piece cover of the suction pipe, the double pipe for connection with the oil filter and the cover for the oil filter flange. All of the individual parts, as well as the polymer-encapsulated metal sieve located in the oil intake, are connected to the pan using the cost-efficient friction welding process.
The manufacturer chose Zytel 70G35 HSLRA4 for the production of the highly integrated oil pan. The nylon 66 is reinforced with 35 wt percent glass fibers and, as a result, is very stiff, creep- and hydrolysis-resistant. It combines high-impact resistance over a wide temperature range with a high resistance to lubricants, road salts and other media commonly present in vehicles. The additional heat stabilization enables the long-term usage of the material at temperatures of up to 150°C and makes it particularly resistant to heat aging. Moreover, glass-fiber-reinforced Zytel nylon resin provides good mechanical and acoustic attenuation properties.
"Our selection of a particularly high-melt flow grade of Zytel nylon resin meant that we were able to manage the long flow distances at a comparably low injection pressure and despite some very low wall thicknesses," said Ralf Franz, development engineer at ElringKlinger. "This, in turn, reduces cycle times, helps preserve the tool and keeps energy costs low." In addition, Franz identifies the low warpage behavior of the material as being of decisive benefit to this application, as it facilitates a durable and reliable seal along the circumference of the oil pan. "We had to design the new polymer oil pan in such a way that its connection to the engine was consistent with the metal construction previously used. We were thereby presented with relatively large distances between the connection points. Thanks to the high stiffness of the material and the purpose-made application of ribs, we managed to limit deformation under load to the required rate despite these unfavorable conditions, thus ensuring a constant surface pressure across the whole perimeter."
Whereas the ribbing located in the upper section of the oil pan principally contributes to dimensional stability in the seal area, the many high ridges in the lower section are designed to absorb external impacts caused, for example, by stones as they are thrown up from the road during normal driving. More significant impacts may also occur when the dismounted engine is placed heavily on the floor during transportation. "Work conducted by DuPont at its technical centers in the United States and Europe included the conducting of crash simulations using LS Dyna software, the investigation of specific material data and the verification of specifications using practical high-speed testing - by this means establishing the suitability of the design," said Franz. "Thus, we were able to optimize the number, size and position of the external ribbing used to protect against impacts from stones or rough handling in such a way as to meet, and in some cases significantly surpass, OEM equirements with minimal material usage. Also, our calculations of noise emission, made using the same set of data, confirmed compliance with the guidelines."
For the production of the seals between the pan and the engine, as well as for the connection of oil circuit elements, ElringKlinger also chose a material from DuPont Performance Elastomers -- Vamac -- the highly heat- and oil-resistant ethylene acrylic elastomer that helps ensure that the joints remain leak-free in the long term.