Patent ID: 7899651

Claim:
A method for estimating an entrance angle of a V-ribbed belt from a flat pulley to a V-ribbed pulley when at least one of three pulleys includes misalignment in a belt transmission device in which the V-ribbed belt has an inner peripheral face including a plurality of ribs thereon and is wound to at least two V-ribbed pulleys having an outer peripheral face including a plurality of grooves thereon such that the ribs of the V-ribbed belt are engaged with the grooves of the V-ribbed pulleys, and at least one flat pulley arranged between the V-ribbed pulleys having an outer peripheral face formed to be flat, and an outer peripheral face of the V-ribbed belt on which no rib is formed is in contact with the outer peripheral face of the flat pulley, comprising the steps of: obtaining, on the assumption that, due to friction between the outer peripheral face of the V-ribbed belt and the outer peripheral face of the flat pulley, the V-ribbed belt forms a track: which enters linearly at an entrance angle of zero degrees into the flat pulley from one of the pulleys which is located on the entry side of the flat pulley; which is wound on the outer peripheral face of the flat pulley without deviating in the widthwise direction thereof; and which travels linearly to the other pulley on the exit side of the flat pulley from the flat pulley, the track of the V-ribbed belt; and estimating an entrance angle of a belt from the flat pulley to the V-ribbed pulley on the basis of a mathematical relationship between the entrance angle and an angle of inclination formed by an axis of rotation of the flat pulley and an axis of rotation of the V-ribbed pulley.