Electric power steering apparatus
AssigneeToyota Jidosha Kabushiki Kaisha
InventorKenichiro Aoki
Life of this patent
Estimating the term…
Abstract
When a current sensor fails, instead of a normal-time motor control section, an abnormal-time motor control section drives and controls a motor. The abnormal-time motor control section detects a timing at which motor current I becomes zero in a state in which all the switching devices are turned off (S11 to S13). Every time the motor current I becomes zero, the abnormal-time motor control section sets an ON time T0 corresponding to steering torque |tr| (S14 to S15), and turns on the switching devices corresponding to the direction of the steering torque for the ON time T0 (S17 to S20). With this operation, an average current Iavg corresponding to the steering torque |tr| flows through the motor 20, whereby deterioration of the followability of steering assist is suppressed.
Claims6
An electric power steering apparatus comprising:
- steering torque detection means for detecting steering torque input from a steering wheel to a steering shaft;
- a motor provided in a steering mechanism and generating steering assist torque;
- a motor drive circuit composed of an H bridge circuit including switching devices for normal rotation which are turned on so as to drive the motor in a normal rotation direction and switching devices for reverse rotation which are turned on so as to drive the motor in a reverse rotation direction;
- motor current detection means for detecting motor current flowing through the motor;
- anomaly detection means for detecting an anomaly of the motor current detection means;
- normal-time motor control means, operable when the anomaly of the motor current detection means is not detected, for controlling the motor drive circuit by current feedback control based on a target current set in accordance with the steering torque detected by the steering torque detection means and the motor current detected by the motor current detection means;
- and
- abnormal-time motor control means, operable when the anomaly of the motor current detection means is detected, for controlling the motor drive circuit on the basis of the steering torque, detected by the steering torque detection means, without use of the current feedback control,
- the electric power steering apparatus being characterized in that the abnormal-time motor control means includes:
- an off-state-voltage detection section which detects voltage between terminals of the motor in a state in which the motor drive circuit is controlled so as not to apply a power supply voltage between the terminals of the motor;
- a current-zero timing detection section which detects a timing at which the current flowing through the motor becomes zero on the basis of the voltage between the terminals of the motor detected by the off-state-voltage detection section;
- an energization time setting section which sets an energization time corresponding to the steering torque detected by the steering torque detection means;
- and
- a switching control section which turns on the switching devices for normal rotation or the switching devices for reverse rotation for the energization time, set by the energization time setting section, every time the current-zero timing detection section detects the timing at which the current flowing through the motor becomes zero.
Dependencies are inferred from the claim text.