Patent ID: 7765085

Claim:
A road gradient estimating system comprising: a first portion for calculating a first physical amount “Ggrad 0 ” corresponding to an estimated gradient value of a road on which a vehicle is currently traveling, based on a difference between an acceleration “A” detected by an acceleration sensor for detecting acceleration of the vehicle in a vehicle longitudinal direction and an acceleration “A′” of the vehicle with respect to the road; a second portion for storing data for relation between vehicle speed and a second physical amount corresponding to a limiting value for rate-of-change of road gradient; a third portion, to which information of vehicle speed is inputted, for calculating a third physical amount (αup, αdown) corresponding to the limiting value for rate-of-change of road gradient at the inputted vehicle speed, based on the relation between the vehicle speed and the second physical amount stored in the second portion; and a fourth portion for comparing rate-of-change of the first physical amount “Ggrad 0 ” corresponding to the estimated gradient value with the third physical amount (αup, αdown) corresponding to the limiting value for the rate-of-change of road gradient calculated at the third portion, wherein the fourth portion corrects the first physical amount “Ggrad 0 ” corresponding to the estimated gradient value, in such a manner that the first physical amount “Ggrad 0 ” corresponding to the estimated gradient value is limited to the limiting value for the rate-of-change of road gradient calculated at the third portion, when the rate-of-change of the first physical amount “Ggrad 0 ” corresponding to the estimated gradient value is larger than the third physical amount (αup, αdown) corresponding to the limiting value for the rate-of-change of road gradient calculated at the third portion.