To provide a circuit changeover switch having a drive device which does not cause breakage of a pump chamber or a seal due to thermal expansion of operation fluid.
The circuit changeover switch 60 including the drive device 10 includes ceramic pumps 18a and 18 b, which alternately pressurize and depressurize the operation fluid 100 within a fluid chamber 13a on opposite sides of an electroconductive movable body 110, to thereby move the movable body 110 within the flow chamber 13a, whereby one of changeover electrodes 62a and 62b is electrically connected to a common electrode 61. When the pressure of the operation fluid is increased and decreased at high speed by the ceramic pumps, micro channels 16a and 16b exhibit a high passage resistance, so that the pressure within the channel does not escape to an internal-pressure buffering chamber 15a, and the movable body moves without fail. When the pressure of the operation fluid increases slowly due to the thermal expansion of the operation fluid, the micro channels exhibit a low passage resistance, so that an expanded portion of the operation fluid is led to the internal-pressure buffering chamber, and the pressure increase of the operation fluid is suppressed.
TAKAHASHI NOBUO
OWADA IWAO
Shinji Kato