LINEAR ACTUATOR

PURPOSE:To shorten a full length and to enlarge a displacement stroke by a method wherein the expansions or contractions of magnetostrictive elements of positive and negative characteristics due to a change in temperature are offset by each other and the magnetostriction of each magnetostrictive element is added for output displacement. CONSTITUTION:Due to a change in temperature, NTC magnetostrictive elements 1a, 1b and 1c expand and so operate as to displace an output shaft 3 downward, while the same expansion occurs also in PTC magnetostrictive elements 2a, 2b and 2c on the other side and so acts as to displace the output shaft 3 upward. When a magnet coil 6 is excited, each of the NTC magnetostrictive elements 1a, 1b and 1c is made to contract, while each of the PTC magnetostrictive elements 2a, 2b and 2c are pulled upward. Besides, the PTC magnetostrictive elements 2a and 2b push the NTC magnetostrictive elements 1b and 1b upward respectively, the element 2c is also displaced and thereby the output shaft 3 is pushed upward.