Tire Pressure Sensors Lighten Up but Withstand Heavy Spin Loads
Canadian Plastics
Aiming at the emerging market for tire pressure monitoring in passenger cars, SmarTire Systems Inc. has developed a new low-cost system using rugged, extremely lightweight sensors made with DuPont Zytel HTN high performance polyamide and Zytel ny...
Aiming at the emerging market for tire pressure monitoring in passenger cars, SmarTire Systems Inc. has developed a new low-cost system using rugged, extremely lightweight sensors made with DuPont Zytel HTN high performance polyamide and Zytel nylon 66.
SmarTire’s new system uses a sensor weighing just 30 grams. Light weight is a crucial advantage for parts inside the tire that must withstand loads produced by centrifugal forces up to 3,000 times gravity. Heavier sensor parts would increase strength requirements, further adding to weight.
“In meeting strength and stiffness targets, we also had to minimize the use of glass fibre reinforcement,” said Kian Bahaie, senior mechanical engineer for SmarTire. Glass fibres would have added to part weight because they have more than double the specific gravity of typical engineering plastics. In addition, glass fibres cause problems with radio-frequency signals, which transmit tire pressure data from inside the tire to a processing unit mounted in the vehicle.
The SmarTire design team achieved their design goals with the use of DuPont engineering plastics containing only 13 to 15% by weight of glass fibre. DuPont Zytel HTN54G15HSL is used for the sensor’s support cradle and housing body component. The housing body’s cover is molded from Zytel 71G13HS1L nylon. Other plastics evaluated by SmarTire required much higher glass content, up to 35%, to meet strength and toughness targets. Their use would have resulted in heavier parts.
SmarTire met its design goals with body and cradle parts with a combined weight of less than 15 grams.
For the sensor cover, which is not subjected to high loads, Zytel 71G13HS1L provides a cost-effective solution. Based on impact-modified nylon 66, it delivers excellent toughness, important for snap-fit assembly of the cover to the housing body.
Molding economy is a key benefit with both materials, according to Bahaie. “They give us excellent molding productivity, and our molders can use water rather than oil to control mold temperature.”
Based in Richmond, British Columbia, SmarTire supplies systems for commercial vehicles, motorcycles and heavy-duty, off-road equipment.
DuPont Canada Inc. 800-268-3943
