Patent ID: 6931313
Filing Date: 2005-08-16
Classification: B60T,B62D

Abstract:
1. A vehicular steering device having steering means, a steering transmission system, a steering system, and a steered wheel, wherein the steering transmission system includes an electric motor and couples the steering means and a steered wheel, the steering system includes the steering means, a suspension, and components therebetween, and the device comprising: change means which is provided in the steering transmission system, and is used for changing a transfer ratio between a steering angle of the steering means and a steered angle of the steered wheel by drive of the electric motor; state quantity detection means for detecting vehicle state quantity which represents a vehicle state; control means for controlling the electric motor and changing the transfer ratio according to the vehicle state quantity; steering index detection means for detecting at least one steering index among steering indices containing a steering torque and a steering force which are applied to the steering system; self-aligning torque estimation means for estimating a self-aligning torque generated in the steered wheel on the basis of the steering index; steered wheel index estimation means for estimating at least one steered wheel index among steered wheel indices including a side force and a steered wheel slip angle to the steered wheel on the basis of the vehicle state quantity; grip factor estimation means for estimating a grip factor at least to the steered wheel on the basis of a change of the self aligning torque to the steered wheel index; and judging means for judging whether the grip factor is less than a first predetermined threshold value, wherein the control means controls the transfer ratio according to the vehicle state when the grip factor is less than the first predetermined threshold value.