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Patexia Research
Issue Date Dec 26, 2019
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Patent Application - VEHICLE STEERING SYSTEM > Claims

  • 1. A vehicle steering system, comprising: a steering actuator including i) a two-system electric motor having a motor rotation shaft, ii) a steering rod connected to a wheel and configured to steer the wheel by a steering amount corresponding to a motion amount thereof, and iii) a motion converting mechanism configured to convert a rotating motion of the motor rotation shaft into a motion of the steering rod in the motion amount corresponding to an amount of the rotating motion;a first motor rotation angle sensor and a second motor rotation angle sensor provided so as to respectively correspond to the two systems of the electric motor and each configured to detect a motor rotation angle that is a rotation angle of the motor rotation shaft;a steering amount sensor configured to detect, as the steering amount of the wheel, the motion amount of the steering rod or a motion amount of a movable member in a case where the steering actuator includes a movable-member moving mechanism configured to move the movable member in the motion amount corresponding to the motion amount of the steering rod; anda controller configured to execute a steering amount control of controlling the steering amount of the wheel by controlling an operation of the electric motor,wherein the controller is configured to perform detection-value inappropriateness determination in which it is determined that any one or two of a detection value of the first motor rotation angle sensor, a detection value of the second motor rotation angle sensor, and a detection value of the steering amount sensor are inappropriate based on comparison among the detection values.
    • 2. The vehicle steering system according to claim 1, wherein the controller is configured to perform the detection-value inappropriateness determination on condition that none of the first motor rotation angle sensor, the second motor rotation angle sensor, and the steering amount sensor themselves are suffering from a failure.
    • 3. The vehicle steering system according to claim 1, wherein the controller is configured to determine, in the detection-value inappropriateness determination, that the detection value of one of the first motor rotation angle sensor and the second motor rotation angle sensor is inappropriate in a case where the detection value of the one of the first motor rotation angle sensor and the second motor rotation angle sensor is inconsistent with the detection value of the steering amount sensor and the detection value of the other of the first motor rotation angle sensor and the second motor rotation angle sensor is consistent with the detection value of the steering amount sensor.
      • 4. The vehicle steering system according to claim 3, wherein each of the first motor rotation angle sensor and the second motor rotation angle sensor includes a stator attached to a housing of the electric motor and a rotor attached to the motor rotation shaft, andwherein the controller is configured to determine that the detection value of the one of the first motor rotation angle sensor and the second motor rotation angle sensor is inappropriate because of a fitting failure of the stator or the rotor of the one of the first motor rotation angle sensor and the second motor rotation angle sensor.
    • 5. The vehicle steering system according to claim 1, wherein the controller is configured to perform, in the detection-value inappropriateness determination, sensor-function-based inappropriateness determination in which it is determined that one of: the detection value of the first motor rotation angle sensor and the detection value of the second motor rotation angle sensor; and the detection value of the steering amount sensor is inappropriate in a case where the detection value of the first motor rotation angle sensor is consistent with the detection value of the second motor rotation angle sensor and the detection values of the first motor rotation angle sensor and the second motor rotation angle sensor are inconsistent with the detection value of the steering amount sensor.
      • 6. The vehicle steering system according to claim 5, wherein the controller is configured to perform the sensor-function-based inappropriateness determination based on the presence or absence of a delay of a decrease in the detection value of the steering amount sensor generated when the electric motor starts to be controlled for decreasing the steering amount that has increased, the controller determining that the detection value of the steering amount sensor is inappropriate in a case where the delay is being generated and determining that the detection values of the first motor rotation angle sensor and the second motor rotation angle sensor are inappropriate in a case where the delay is not being generated.
        • 7. The vehicle steering system according to claim 6, wherein the steering amount sensor includes a stator attached to a housing of the steering actuator and a mover attached to the steering rod or the movable member, andwherein the controller is configured to determine, in the case where the delay is being generated, that the detection value of the steering amount sensor is inappropriate because of a fitting failure of the stator or the mover of the steering amount sensor or looseness in the movable-member moving mechanism.
        • 8. The vehicle steering system according to claim 6, wherein the controller is configured to determine, in the case where the delay is not being generated, that the detection values of the first motor rotation angle sensor and the second motor rotation angle sensor are inappropriate because of looseness in the motion converting mechanism.
    • 9. The vehicle steering system according to claim 1, wherein the controller is capable of executing the steering amount control based on the detection value of the first motor rotation angle sensor, capable of executing the steering amount control based on the detection value of the second motor rotation angle sensor, and capable of executing the steering amount control based on the detection value of the steering amount sensor, andwherein the controller is configured to control the steering amount of the wheel not based on any of the detection value of the first motor rotation angle sensor, the detection value of the second motor rotation angle sensor, and the detection value of the steering amount sensor that are determined to be inappropriate in the detection-value inappropriateness determination.
    • 10. The vehicle steering system according to claim 1, wherein the electric motor is disposed such that the motor rotation shaft is parallel to the steering rod, andwherein the motion converting mechanism includes a screw provided on the steering rod, a nut which is provided with a screw threadedly engaging with the screw of the steering rod and which is fitted over the steering rod, and a transmission belt configured to rotate the nut by the rotating motion of the motor rotation shaft.
    • 11. The vehicle steering system according to claim 1, wherein the movable member is a rotation shaft, andwherein the movable-member moving mechanism includes a pinion provided on the rotation shaft and a rack provided on the steering rod so as to be in mesh with the pinion.
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