Small piezoelectric or electrostrictive linear motor

Abstract

A piezoelectric/electrostrictive linear motor is provided. A movable shaft is coupled to a unimorph or bimorph, which is made by attaching a piezoelectric or electrostrictive substrate to an elastic body, so that a movable body provided with respect to the movable shaft is linearly moved along the movable shaft by the vibration or movement of the piezoelectric or electrostrictive substrate.

1 . A piezoelectric/electrostrictive linear motor, comprising:
 a piezoelectric or electrostrictive substrate driven by a voltage applied thereto;   an elastic body, to one surface or each of both surfaces of which the piezoelectric or electrostrictive substrate is attached; and   a movable shaft coupled at an end thereof to the elastic body or the piezoelectric or electrostrictive substrate attached to the elastic body, the movable shaft being operated in conjunction with displacement of the piezoelectric or electrostrictive substrate, wherein a movable body provided with respect to the movable shaft is moved with respect to the movable shaft in response to the operation of the movable shaft.   
   
   
       2 . The piezoelectric/electrostrictive linear motor of  claim 1 , wherein the movable shaft is moved in conjunction with bending displacement of the elastic body and the one or more piezoelectric or electrostrictive substrate attached thereto, to move the movable body. 
   
   
       3 . The piezoelectric/electrostrictive linear motor of  claim 2 , wherein a surface area of a largest surface of the elastic body is greater than a surface area of a largest surface of the piezoelectric or electrostrictive substrate. 
   
   
       4 . The piezoelectric/electrostrictive linear motor of  claim 2 , wherein a portion of the elastic body and/or the piezoelectric or electrostrictive substrate is fixed such that the movable shaft is moved in conjunction with bending displacement of the unfixed portion. 
   
   
       5 . The piezoelectric/electrostrictive linear motor of  claim 1 , wherein the movable shaft is moved in conjunction with displacement of the piezoelectric or electrostrictive substrate between a first position and a second position, and the movable body is moved along with a movement of the movable shaft in response to the piezoelectric or electrostrictive substrate being displaced toward the second position and the movable body is not moved back to a position of the movable shaft in response to the piezoelectric or electrostrictive substrate being displaced toward the first position. 
   
   
       6 . The piezoelectric/electrostrictive linear motor of  claim 1 , wherein the piezoelectric or electrostrictive substrate is polarized. 
   
   
       7 . The piezoelectric/electrostrictive linear motor of  claim 1 , wherein the movable body is moved with respect to the movable shaft in response to vibration of the movable shaft. 
   
   
       8 . The piezoelectric/electrostrictive linear motor of  claim 1 , wherein a weight of the movable body and a frictional force between the movable shaft and the movable body are provided so that the movable body is moved with respect to the movable shaft when the movable shaft vibrates in conjunction with the displacement of the piezoelectric or electrostrictive substrate. 
   
   
       9 . The piezoelectric/electrostrictive linear motor of  claim 1 , wherein the movable body comprises: a friction member being in close contact with an outer surface of the movable shaft; a weight provided around an outer surface of the friction member; and an elastic shell fitted over an outer surface of the weight to hold both the friction member and the weight around the movable shaft, wherein the movable body is fitted over the movable shaft. 
   
   
       10 . A method of driving a piezoelectric/electrostrictive linear motor, the motor having an elastic body to which at least one piezoelectric or electrostrictive substrate is attached and a movable shaft coupled to the elastic body or the piezoelectric or electrostrictive substrate attached to the elastic body, wherein a movable body provided with respect to the movable shaft is to be moved with respect the movable shaft, the method comprising:
 the step (a) of applying a voltage, which varies from a first voltage to a second voltage, to the piezoelectric or electrostrictive substrate during a first period; and   the step (b) of applying a voltage, which varies from the second voltage to the first voltage, to the the piezoelectric or electrostrictive substrate during a second period after the step (a), wherein,   the movable body is moved along with a movement of the movable shaft in conjunction with displacement of the piezoelectric or electrostrictive substrate during the step (a) or step (b), to move with respect to the movable shaft.   
   
   
       11 . The method of  claim 10 , wherein the step (a) and step (b) are repeated. 
   
   
       12 . The method of  claim 10 , wherein the movable body is moved along with the movement of the movable shaft during one of the step (a) and step (b), and the movable body is not moved back to a position of the movable shaft during the other one of the step (a) and step (b). 
   
   
       13 . The method of  claim 10 , wherein the movable shaft is moved in conjunction with bending displacement of the elastic body and the piezoelectric or electrostrictive substrate, the piezoelectric or electrostrictive substrate is displaced between a first position and a second position, and the movable body is moved along with the movement of the movable shaft in response to the piezoelectric or electrostrictive substrate being displaced toward the second position and the movable body is not moved back to a position of the movable shaft in response to the piezoelectric or electrostrictive substrate being displaced toward the first position 
   
   
       14 . The method of  claim 10 , wherein the first period is longer than the second period. 
   
   
       15 . The method of  claim 10 , wherein, during the second period, the movable body is moved along with the movement of the movable shaft, so that the movable body is moved along the movable shaft. 
   
   
       16 . The method of  claim 10 , wherein the first period is shorter than the second period. 
   
   
       17 . The method of  claim 10 , wherein, during the first period, the movable body is moved along with the movement of the movable shaft, so that the movable body is moved along the movable shaft.