Hitachi Automotive Systems Europe, Ltd., has selected a reinforced Arnite®
polybutylene terephthalate (PBT) blend from DSM Engineering Plastics for
injection moulded mass airflow sensor body destined for Audi engines. Arnite
TV4 261 30% glass reinforced grade PBT provides a combination of properties
important to the application, including excellent flow, long term dimensional
stability, stiffness and strength over a wide temperature range and chemical
resistance. Production requires only moulding – no annealing is required to
relieve internal stresses that could lead to warpage.
"Throughput is excellent with this design," said Andrew Bridge, Procurement &
Design Manager for Hitachi. "The ability to mould the unit in one piece
without annealing saves us two production steps compared to less
sophisticated, two-piece approaches with alternate materials."
The Hitachi body serves both to mount the mass airflow sensor system precisely
and to shape air flow using a moulded-in grid. To control the turbulent
airflow, the grid induces a laminar flow that helps ensure accurate feedback
about engine air intake temperature to the engine control unit. Mass airflow
sensor data help engine control systems maintain an optimum air-fuel balance.
The grid's thin-wall elements and intricate geometry benefit from Arnite's
flow properties, minimising moulded-in stresses and strains that later might
contribute to warpage or unpredictable dimensional change, causing the sensor
to misread airflow.
The design process for the component was a collaboration involving Hitachi,
moulder and toolmaker W.H. Smith & Sons, Ltd., materials and processing expert
DSM Engineering Plastics and design and mold flow specialist DSM/DADC (Design
and Development Centre).
