In contrast, two-shell welded charge air ducts made from PA46 cost half as much as those made from aluminum or silicone. PA46 air ducts are also lighter than aluminum and have several advantages over those made from silicone. The cross section of the PA46 air ducts can take the shape of the space available, whereas, cross sections of silicone rubber ducts can only be round. PA46 is also recyclable while silicone parts are not.

In comparison to other thermoplastics, Stanyl PA46 has better fatigue resistance and thus gives a higher safety factor. Elbows are used for connecting the turbo compressor side to the air ducts. When made of PA46 they offer similar advantages, as mentioned above, compared to aluminum elbows. The part can be fully molded in a single-shell design and directly bolted onto the turbo compressor thanks again to the outstanding heat resistance of PA46.

PA46 TAKES THE HEAT

The actuation of the VTG system is another area that could benefit from PA46. The resin's high heat resistance, stiffness retention at high temperature, and excellent wear and friction properties are key. The end cap of a VTG motor consists of an end bracket, brush holder, and also acts as a base for the gear reduction mechanism. With PA46 it is possible to combine all three features in a single injection-molded part. The PA46 part will withstand high ambient temperature as it sits in close proximity to the turbine side of the turbo charger.

Sensors molded from polyamide 46 resist constant temperatures of 150 to 160°C (300 to 320°F) for up to 5,000 hr and peak temperatures of 180°C (355°F), even in combination with aggressive AFF oils.

During operation, temperatures in the brush holder area of the end cap can rise to 290°C (554°F) briefly. It's important that the holder doesn't deform or melt at this temperature. If so, it could jam the brush and stop the motor. Stanyl PA46 has a heat-distortion temperature (HDT) of up to 290°C and withstands this short-term peak temperature more readily than other thermoplastics.

There is a rotary electric actuator (REA) that adjusts the position of the turbine vanes. It does this by means of a gear train that converts its output to linear motion. The gears operate at high frequencies in temperatures above 150°C (302°F). PA46 retains its stiffness at these elevated temperatures and demonstrates superior wear resistance, contributing to optimum durability and extended life cycles.

The REA executes a closed loop using a feedback set of sensors that monitor the speed of the compressor and the position of the vanes. The ECU manages the motor and the movement of the vanes. Sensors in the system must retain dimensional stability at a peak temperature of 230°C (446°F). The manufacturer must warranty them for life against oil leakage through the threads and resistance to automotive fluids. The sensors, of course, should not break during installation.

Variable-turbine geometry (VTG) technology can make use of high-performance engineering plastics including polyamide 46.

Sensors are also candidates for PA46. Here, the resin's ability to retain stiffness at peak temperatures and its resistance to creep and stress relaxation are key. Additionally, PA46 demonstrates excellent fatigue and chemical resistance at elevated temperatures. Other important advantages in this application include an opportunity to reduce weight by eliminating metal parts and parts consolidation via injection molding.

The ECU uses surface-mounted electronics soldered to a PCB through reflow processes where peak temperatures can exceed 265°C (509°F). Thus, the ECU housing must withstand this temperature. PA46 with its high HDT and outstanding toughness is an ideal candidate for this application. It is economical and can also save space via the use of snap-fit fasteners.

MAKE CONTACT
DSM Engineering Plastics, (812) 435-7539, www.dsmep.com