Expanded application of Hall IC torque sensors on electric
power steering
～Possesses improved reliability, meets 2010 new European safety standards～

JTEKT Corporation has developed and brought to mass-production a Hall IC-type torque sensor for electric power steering (EPS) that possesses two completely independent sensing circuits and features improved reliability. JTEKT intends to expand application of this sensor on future EPS systems.

In the case of EPS, a torque sensor detects torsion bar twisting that occurs when turning effort is applied to the steering wheel and sends a corresponding torque signal to the electronic control unit (ECU). Based on this torque signal and a vehicle speed signal, the ECU calculates and instructs the motor to provide the appropriate assist torque, reducing the amount of turning effort required from the driver.

Improved performance

This newly developed torque sensor utilizes two highly functional Hall ICs, built into each of which are a digital computation function, electronically erasable and programmable read only memory (EEPROM), and a temperature compensation function, enabling not only improved torque detection accuracy but also a 30% reduction of characteristics fluctuation due to temperature change in comparison with the conventional two-bobbin type torque sensor. As a result, a more stable steering feeling even in the case of high engine-room temperatures is achieved.

Improved safety

Two Hall ICs are used in the detection area to achieve a double sensing circuit. The difference between the two mutually independent torque sensor output signals is monitored, which improves detection of failure in the detection area. In addition, the use of ICs reduces the overall number of components and lowers the risk of component failure.

The Hall IC torque sensor possesses a high degree of safety and meets the new European safety standards to be implemented in 2010. JTEKT intends to utilize this sensor on all its EPS systems in the future and thereby contribute to automobile safety.