Patent ID: 7161277

Claim:
A driving device comprising: a vibration-generator comprised of a first weight fixed to a predetermined steady surface; a first electromechanical conversion element, one end of which in its expanding or contracting direction is fixed to the first weight; a second weight fixed to the other end of the first electromechanical conversion element in the expanding or contracting direction; a second electromechanical conversion element, one end of which in its expanding or contracting direction is fixed to the second weight; and a rod fixed to the other end of the second electromechanical conversion element in the expanding or contracting direction, a slider which is frictionally engaged with the outer surface of the rod of the vibration-generator, and a degree of the frictional engagement is set, so that the slider can move together with the rod when the rod is moved at a speed lower than a predetermined speed, and a moving amount of the slider becomes smaller than that of the rod when the rod is moved at a speed higher than the predetermined speed, and a drive circuit which applies voltages to the first electromechanical conversion element and the second electromechanical conversion element to cause the rod to vibrate, such that a moving speed of the rod in one direction is lower than the predetermined speed and a moving speed of the rod in the other direction is higher than the predetermined speed, so as to move the slider along the rod in the one direction, characterized in that a second resonance frequency of the vibration-generator is set to be twice a first resonance frequency thereof by satisfying the following equation, where a mass of the first weight is m w1 ; a mass of the first electromechanical conversion element is m p1 ; a spring constant of the first electromechanical conversion element is k p1 ; a mass of the second weight is m w2 ; a mass of the second electromechanical conversion element is m p2 ; a spring constant of the second electromechanical conversion element is k p2 ; and a mass of the rod is m r . 1 K p1 ⁢ K p2 ⁢ ( m w1 + 2 π 2 ⁢ m p1 ) ⁢ ( 2 π 2 ⁢ m p1 + m w2 + 2 π 2 ⁢ m p2 ) ( 2 π 2 ⁢ m p2 + m r ) ⁢ ( m w1 + m w2 + m r + 4 π 2 ⁢ m p1 + 4 π 2 ⁢ m p2 ) ( 1 K p2 ⁢ ( 2 π 2 ⁢ m p1 + m w2 + 2 π 2 ⁢ m p2 ) ⁢ ( 2 π 2 ⁢ m p2 + m r ) + ( 1 K p1 + 1 K p2 ) ⁢ ( m w1 + 2 π 2 ⁢ m p1 ) ⁢ ( 2 π 2 ⁢ m p2 + m r ) + 1 K p1 ⁢ ( m w1 + 2 π 2 ⁢ m p1 ) ⁢ ( 2 π 2 ⁢ m p1 + m w2 + 2 π 2 ⁢ m p2 ) ) 2 = 4 25 [ Equation ]