Patent ID: 7240972

Claim:
A maximum road friction force estimating device comprising: road friction force obtaining means for obtaining, as road friction force, friction force caused between a road surface on which a vehicle runs and a tire of the vehicle; angular acceleration correspondence value obtaining means for obtaining an angular acceleration correspondence value, the angular acceleration correspondence value being a value based upon an angular acceleration of the tire and a value corresponding to a difference between a torque obtained by converting the road friction force into torque exerted on the tire and a brake torque exerted on the tire in order to brake the tire, wherein a slip ratio of the tire changes in accordance with a change of the angular acceleration correspondence value; body deceleration obtaining means for obtaining deceleration exerted on the vehicle in a front-to-rear direction of the vehicle body as a body deceleration; determining means for determining a predetermined reference value that is the angular acceleration correspondence value corresponding to a case where the slip ratio of the tire exceeds a value by which a maximum value of the road friction force is demonstrated, the determining means being configured to increase the predetermined reference value in accordance with an increase in the obtained body deceleration; comparing means for comparing the angular acceleration correspondence value obtained by the angular acceleration correspondence value obtaining means with the predetermined reference value; and estimated maximum road friction force setting means for setting the road friction force obtained by the road friction force obtaining means as estimated maximum road friction force when the comparing means determines that the angular acceleration correspondence value obtained by the angular acceleration correspondence value obtaining means exceeds the predetermined reference value.