Power steering device

Abstract

A power steering apparatus includes: a steering load average value calculating circuit 39 which calculates a steering torque average value Trav which is the average value of steering torque Tr within a predetermined interval of time; and an abnormality detection circuit 40 which compares steering torque average value Trav with a specified steering torque value Trrf and detects the abnormality of the apparatus when steering torque average value Trav is larger than the specified value.

1 . A control unit of a power steering apparatus, the power steering apparatus comprising:
 a steering mechanism which steers steerable wheels in accordance with a steering operation of a steering wheel;   a torque sensor which detects a steering torque generated on the steering mechanism;   an electrically driven motor which provides a steering force for the steering mechanism; and   a transmission mechanism which transmits a rotational force of the electrically driven motor to the steering mechanism,   the control unit comprising:   a steering torque signal receiving section configured to receive the steering torque signal;   a motor command current calculating section configured to calculate a motor command current which drivingly controls the electrically driven motor on a basis of the steering torque; and   an abnormality detection section configured to obtain a signal related to a steering load during the steering operation within a predetermined period of time and to detect an abnormality of the power steering apparatus on a basis of an averaging processed value of the obtained signal.   
     
     
         2 . The control unit of the power steering apparatus as claimed in  claim 1 , wherein the abnormality detection section detects the abnormality of the apparatus on a basis of the averaging processed value of the signal related to the steering load when the steering wheel is steering operated. 
     
     
         3 . The control unit of the power steering apparatus as claimed in  claim 2 , wherein the abnormality detection section determines a state in which the steering wheel is steering operated on a basis of a steering speed, a yaw moment of a vehicle, or a difference of left and right steerable wheel revolution speeds. 
     
     
         4 . The control unit of the power steering apparatus as claimed in  claim 1 , wherein the abnormality detection section stores a newest value of an average value of the signal related to the steering load into a non-volatile memory, when a power supply of the control unit is turned off. 
     
     
         5 . The control unit of the power steering apparatus as claimed in  claim 1 , wherein the abnormality detection section illuminates an alarm light of the vehicle, when the abnormality detection section detects the abnormality of the power steering apparatus. 
     
     
         6 . The control unit of the power steering apparatus as claimed in  claim 5 , wherein the abnormality detection section calculates the motor command current to become smaller than a case where no abnormality is present in the power steering apparatus, when the abnormality detection section detects the abnormality of the power steering apparatus. 
     
     
         7 . The control unit of the power steering apparatus as claimed in  claim 6 , wherein the abnormality detection section calculates the motor command current to become gradually smaller, when the abnormality detection section detects the abnormality of the power steering apparatus. 
     
     
         8 . The control unit of the power steering apparatus as claimed in  claim 7 , wherein the abnormality detection section gradually reduces the motor command current in accordance with the signal related to the steering load, when the abnormality detection section detects the abnormality of the power steering apparatus. 
     
     
         9 . The control unit of the power steering apparatus as claimed in  claim 5 , wherein the abnormality detection section calculates the motor command current in a form of a gradual decrease of the motor command current and, thereafter, the motor command current becomes zero, when the abnormality detection section detects the abnormality of the power steering apparatus. 
     
     
         10 . The control unit of the power steering apparatus as claimed in  claim 1 , wherein the abnormality detection section detects the abnormality of the power steering apparatus on a basis of the averaging processed value related to the steering load when a steering speed is equal to or above a predetermined value. 
     
     
         11 . The control unit of the power steering apparatus as claimed in  claim 1 , wherein the abnormality detection section does not use the signal related to the steering load when the steering wheel is bumped in which a steering angle becomes maximum for a calculation of the averaging process. 
     
     
         12 . The control unit of the power steering apparatus as claimed in  claim 1 , wherein the steering mechanism includes a rack bar which axially moves due to a revolution of the steering wheel to steer the steerable wheels and the transmission mechanism includes a steerable wheel axis 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, and a transmission member which transmits the revolution of the electrically driven motor to the nut.