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SONCEBOZ USES DUPONT™ ZENITE® LCP FOR COIL BOBBINS AND STATOR OVERMOULDING OF TORQUE MOTOR
These motors are used in electronically controlled exhaust-gas-recirculation valves (EEGR) assembled in automotive diesel engines, to channel the right proportion of exhaust gas back into the combustion chambers. Daniel Sigg, one of the original developers of the torque motors at Sonceboz, explains: “The main reasons for choosing this material were this liquid crystal polymer’s high thermal resistance and extremely good melt-flow characteristics. With Zenite® we can fill the tool cavities completely in spite of the bobbins’ very thin wall thickness of only 0,30 mm, even with short cycle times. The type 6130L we use is 30 percent glass-fibre-reinforced and combines high toughness with a heat-deflection temperature of 260°C.” In joint development with Dolder, a distributor of DuPont Engineering Polymers, Sonceboz also achieved another objective, Sigg reports. “The type of Zenite® we use produces clean weld-lines, so that the thin-walled bobbins can safely withstand the relatively high mechanical stresses during winding.” Sonceboz also uses Zenite® to overmould the ready-wound coils, because the LCP’s low melt-viscosity prevents the windings from being displaced by the melt as it is being injected. Since the overmould functions at the same time as a housing for the stator, Zenite® also serves as a plastic bearing for the rotor shaft. Sigg comments: “This DuPont material has good sliding properties, so that we could use it to replace the original separate bearings of PEEK and bronze.” With response times of less than 50 ms, the torque motors actuate the EEGR valves so as to block the flow of exhaust gas, or to let it flow freely, or to allow just the right proportion to pass through into the combustion chambers. Dr. Marc-Olivier André, Manager of the Business Unit “Engine Controls” at Sonceboz, explains: “Torque motors are particularly well suited for operating such valves, because the gearless design allows short regulation times. Their compact size is an added advantage in view of the high degree of integration of under-the-bonnet systems. Adding the magnetic analogue sensor yields a totally contactless servo-actuator with minimal wear. Sonceboz SA was established more than 70 years ago in Switzerland. It manufactures electrical drives, specialising in the fields of mechatronic systems. In its automotive product line, the company produces stepper motors, linear actuators and torque motors, which are usually designed and specifically developed as modules to meet customers' requirements. Sonceboz has about 600 employees at the parent company location in Switzerland, and at subsidiaries in France and the United States.
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