Apparatus for automatically setting steering center for use in power steering apparatus

Claim 1

In a power steering system for a vehicle which is adapted to control an amount of steering power assistance by means of a steering power assist signal to which a vehicle velocity responsive characteristic and steering angle responsive characteristic are added in response to a vehicle velocity signal from vehicle velocity sensor means and a steering angle signal from steering angle sensor means, an automatic steering center setting apparatus for providing a rotational reference for a steering wheel so as to effect the function of the steering angle responsive characteristic during a running state of the vehicle, said center setting apparatus comprising: steering angle detecting means for setting a presumed position of said steering wheel as a steering center in response to said steering angle signal and for outputting a steering angle position signal which changes about said steering center; static steering motion detecting means for calculating said steering angle position signal during the steering and, when the calculated steering angle position signal indicates a static steering motion state, for outputting a static steering center instruction signal; dynamic steering motion detecting means for calculating the steering angle position signal during the steering and, when the calculated steering angle position signal indicates a dynamic steering motion state, for outputting a dynamic steering center instruction signal, said dynamic steering motion detecting means executing addition or subtraction of said steering angle position signal which is increased or decreased relative to said presumed position which had been set as said steering center, and outputting an average value for every constant sampling period of time as said dynamic steering center instruction signal; and steering center setting means for outputting a steering angle responsive ON signal to start the function of said steering angle responsive characteristic and a steering center set signal to update said steering center set by said steering angle detecting means when the present steering angle position signal during the steering coincides with either the static steering center instruction signal or the dynamic steering center instruction signal.

Claim 5

An apparatus according to claims 1, wherein said static steering motion detecting means and said dynamic steering motion detecting means start operating when the vehicle velocity signal from said vehicle velocity sensor means exceeds a preset value.