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Power steering device

  • US 9,994,252 B2
  • Filed: 06/15/2017
  • Issued: 06/12/2018
  • Est. Priority Date: 03/21/2013
  • Status: Active Grant
First Claim
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1. A power steering apparatus comprising:

  • a steering mechanism formed of an iron-series metallic material and which steers steerable wheels in accordance with a steering operation of a steering wheel;

    an electrically driven motor which provides a steering force for the steering mechanism;

    a speed reduction mechanism formed of the iron-series metallic material, interposed between the steering mechanism and the electrically driven motor, and which transmits a revolution force of the electrically driven motor to the steering mechanism;

    a torque sensor which detects a steering torque generated in the steering mechanism;

    a control unit which calculates a motor command current drivingly controlling the electrically driven motor on a basis of the steering torque and outputs the motor command current to the electrically driven motor;

    a steering load average value calculating circuit installed in the control unit and which calculates an average value of a steering load corresponding value which corresponds to any one of the steering torque within a predetermined interval of time, the motor command current, and a motor actual current actually flowing through the electrically driven motor; and

    an abnormality detection circuit installed in the control unit, which compares the average value of the steering load corresponding value with a specified value stored in the control unit, and detects an abnormality of the apparatus when the average value is larger than the specified value,wherein the steering mechanism includes a rack bar which axially moves due to a revolution of a steering wheel to steer the steerable wheels and the speed reduction mechanism includes a ball-screw mechanism having;

    a rack bar side ball screw groove installed on an outer peripheral side of the rack bar and having a spiral groove shape;

    a nut annularly installed to enclose the rack bar and rotatably installed with respect to the rack bar;

    a nut side ball screw groove installed on an inner peripheral side of the nut, having a spiral groove shape, and constituting a ball circulation groove together with a steering shaft side ball screw;

    a plurality of balls installed within the ball circulation groove; and

    a circulation member installed at an outer side of a radial direction of the nut and connecting one end side of the ball groove and the other side thereof in order for the plurality of balls to enable a circulation from the one end side of the ball circulation groove to the other end side, anda transmission mechanism which transmits the revolution of the electrically driven motor to the nut.

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