Torque Sensor Matching Study For Vehicle Electric Power Steering

Torque sensor is the key component of vehicle electric power steering(EPS) system, its performance will directly impact on the characteristic of EPS. The torque sensor is mainly devided into contact and non-contact two types. This paper is forcused on the study of a kind of contact sensor. To optimize current sensor design as follows: using silver base contacting filamentous wiper instead of the original welding wiper, silver base material has stronger electrical conductivity, the added graphite and molybdenum disulfide can increase wiper lubricity, strength and wear resistance. As multipoint contact filamentous wiper, it also has better endurance to shock, lower contacting resistor and better contact stability. Using epoxy resin substrates instead of traditional ceramic substrates and decreasing the thickness of the copper foil at the epoxy substrate copper foil boundaries to reduce the wear of wiper. To increase the ink resistor print efficiency and consistency by layouting four substrates in one board. To adjust the resistor by laser etching, trial run results show that the channel to channel error can be controlled within 1& after etching. By above corrective action can enhance the sensor production efficiency and increase the pass rate.After implementing the corrective actions, filamentous wiper installation time is only 1/27 of the welded wiper. Epoxy board adjusting speed approximately two-thirds of the adjusting time of ceramic substrate. The product yield rate is as high as 93.3%, increased by 16.6% than before. The pass rate without rework is about 98.78%, increased by 5.69% than before. Cycle time of laser etching station is 15 s which reduced 25 s.This article also theoretically discusses how to take place with contact sensor with non-contact Hall principle. This paper presents the preliminary idea that using the magnet to take place of the wiper and using Hall IC to take place of carbon-film resistor.