Patent ID: 7701116

Claim:
A motor driving method for controlling driving of a vibration wave motor including a vibration member which has a first electrode and a second electrode formed on an electro-mechanical energy conversion element and a projection portion thereon, and generates an elliptic motion on the projection portion by combining vibrations of a first vibration mode and a second vibration mode, the vibration of the first vibration mode being generated by applying alternating voltages of which frequencies and phases are the same to the first electrode and the second electrode, the vibration of the second vibration mode being generated by applying alternating voltages of which frequencies are the same but one of which phases is reverse that of the other to the first electrode and the second electrode, and a driven member which is in contact with the projection portion and driven by the projection portion, said method comprising the steps of: detecting a driving speed of the driven member; changing a phase difference between the alternating voltages, each of which is being applied to the first electrode and the second electrode, respectively, in a state that the frequencies are fixed at a constant value, so as to set the driving speed of the driven member to a predetermined speed; and changing the frequencies so as to set the changed phase difference within a predetermined phase difference range, in a case that the changed phase difference which is set to drive the driven member at the predetermined speed is outside the predetermined phase difference range, wherein in the step of changing the phase difference, a ratio of amplitudes of the vibrations of the first vibration mode and the second vibration mode is changed by changing the phase difference so as to drive the driven member at the predetermined speed.