Patent ID: 7051601

Claim:
A torque sensor for a vehicle steering system, comprising: a power source that supplies power; an oscillator that oscillates by receiving a voltage from said power source; an offset voltage circuit part that generates an offset voltage by using said voltage supplied from said power source; a current amplifier that outputs an alternating current voltage which is in-phase with a voltage outputted from said oscillator; first and second coils that are in series and connected at both ends thereof to output terminals of said current amplifier and said offset voltage circuit part, respectively; first and second resistances that are in series and connected in parallel to said first and second coils; first and second waveform selecting parts that receive an alternating current voltage from a contact part of said first and second resistances and from a contact part of said first and second coils, respectively, and then select and output a half-period of said alternating current voltage; first and second peak detectors that detect a peak value of each output voltage of said first and second waveform selecting parts; a first differential amplifier that executes differential amplification by receiving voltages outputted through said first and second peak detectors; a first voltage-current converter that outputs a torque signal by converting a voltage, which is outputted from said first differential amplifier, into a current; and third and fourth resistances being in series and connected in parallel to said first and second coils; third and fourth waveform selecting parts that receive an alternating current voltage from a contact part of said third and fourth resistances and from a contact part of said first and second coils, respectively, and then select and output a half-period of said alternating current voltage; third and fourth peak detectors that detect a peak value of each output voltage of said third and fourth waveform selecting parts; a second differential amplifier that executes differential amplification by receiving voltages outputted through said third and fourth peak detectors; and a second voltage-current converter that outputs a fail-safe torque signal by converting a voltage, which is outputted from said second differential amplifier, into a current.