Patent ID: 8682599

Claim:
A road surface friction coefficient estimating device comprising: a lateral force detecting section that detects a lateral force of a wheel; a slip angle detecting section that detects a slip angle of the wheel; and a road surface friction coefficient estimating section that: stores information about a characteristic curve in a coordinate plane, wherein the coordinate plane has a coordinate axis representing the lateral force and a coordinate axis representing the slip angle, and wherein the characteristic curve represents a relationship between the lateral force and the slip angle under a condition of a reference road surface friction coefficient; finds with reference to the stored information a point in the coordinate plane at which a straight line intersects with the characteristic curve, wherein the straight line passes through an origin point of the coordinate plane and a detected point, and wherein the detected point corresponds to a detected value of the lateral force obtained by the lateral force detecting section and a detected value of the slip angle obtained by the slip angle detecting section; and calculates an estimated value of a road surface friction coefficient, based on a reference value and the detected value of at least one of the lateral force and the slip angle and the reference road surface friction coefficient, wherein the reference value corresponds to the found point.