PURPOSE: To abruptly and largely change the length of a compression spring made of a shape memory alloy supported by supporting members by fitting the compression spring between at least two gears meshed with each other.
CONSTITUTION: A driving device is composed of a tension spring 11 made of a shape memory alloy, a compression spring 12, partial gears 13a and 13b, supporting members 14a and 14b, and the shafts 15a and 15b of the gears 13a and 13b. The gears 13a and 13b are meshed with each other and supported by the shafts 15a and 15b so that their rotations can be transmitted. The springs 11 and 12 are respectively supported by the members 14a and 14b in freely expandable states and the members 14a and 14b are rotatably fixed to the gears 13a and 13b. When the constant of the spring 12 is changed, various characteristics of bias forces can be applied to the spring 11 and the bias load applied to the spring 11 becomes larger as the temperature becomes lower. Therefore, the length of the spring 11 can be changed largely and abruptly.
KURATA NOBORU
TOJO MASAAKI
