Driving device and driving method

A driving device comprising:

• an electromechanical transducer that extends and contracts upon application of voltage thereto,
• a support member that is in the form of a rod, that one end of which is fixed to one end in extension and contraction directions of the electromechanical transducer and that slidably supports a movable body,
• a biasing member that biases the movable body toward the support member, and
• a drive circuit that includes an H-bridge circuit which has four switching elements and which applies the voltage to the electromechanical transducer and a control circuit which controls the switching elements so as to apply from the H-bridge circuit to the electromechanical transducer the voltage which increases or decreases from a first voltage to a last voltage in a stepped manner and in which at least three values sequentially circulates, wherein
• the movable body is relatively moved with respect to the support member while repeating a state where the movable body is moved together with the support member through a frictional force to the support member and a state where the movable body slides along the support member through an action of a force which overcomes the frictional force to the support member by making a difference between an extension velocity and a contraction velocity when the electromechanical transducer extends and contracts upon application of the voltage thereto, and
• a period of time for which the first voltage is applied is smoothly changed when the movable body is started and/or stopped.

A driving method of a movable body in a driving device having:

• an electromechanical transducer that extends and contracts upon application of voltage thereto,
• a support member that is in the form of a rod, that one end of which is fixed to one end in extension and contraction directions of the electromechanical transducer and that slidably supports a movable body,
• a biasing member that biases the movable body toward the support member, and
• a drive circuit that includes an H-bridge circuit which has four switching elements and which applies the voltage to the electromechanical transducer and a control circuit which controls the switching elements,
• the driving method comprising the steps of:
• applying from the driving circuit to the electromechanical transducer the voltage which increases or decreases from a first voltage to a last voltage in a stepped manner and in which at least three values sequentially circulates,
• repeating a state where the movable body is moved together with the support member through a frictional force to the support member and a state where the movable body slides along the support member through an action of a force which overcomes the frictional force to the support member by making a difference between an extension velocity and a contraction velocity when the electromechanical transducer extends and contracts upon application of the voltage thereto, and
• changing smoothly a period of time for which the first voltage on occasion of the start and/or the stop of the movable body.