Electric power steering apparatus

An electric power steering apparatus for use on a vehicle, comprising:

• a motor for applying an auxiliary torque to a steering system of said vehicle;
• a steering torque sensor for detecting a steering torque of said steering system;
• and
• a control unit having a motor control unit for drive-controlling said motor based on at least a steering torque signal from said steering torque sensor and a failure detecting unit for detecting a failure of said apparatus;
• wherein each of said motor control unit and said failure detecting unit is provided in a couple, one of said two motor control units performs its control operation in a normal control mode when neither of said failure detecting units detects a failure, and the other of said two motor control units performs its control operation in a first failure control mode in which an assist ratio differs from that of the normal control mode when one of said two failure detecting units detects a certain failure.

An electric power steering apparatus for use on a vehicle, comprising:

• a motor for applying an auxiliary torque to a steering system of said vehicle;
• a steering torque sensor for detecting a steering torque of said steering system;
• and
• a control unit having a motor control unit for drive-controlling said motor based on at least a steering torque signal from said steering torque sensor and a failure detecting unit for detecting a failure of said apparatus;
• wherein each of said motor control unit and said failure detecting unit are provided in a couple, one of said two motor control units performs its control operation in a normal control mode when neither of said two failure detecting units detects a failure, and said one of said two motor control units performs its control operation in a first failure control mode in which an assist ratio differs from that of said normal control mode when the other of said two failure detecting units detects a certain failure.