Circuit changeover switch

Abstract

A circuit changeover switch 60 , which includes a drive device 10 , includes ceramic pumps 18 a and 18 b , which alternately pressurize and depressurize operation fluid 100 within a fluid chamber 13 a on opposite sides of an electrically conductive movable body 110 , to thereby move the movable body 110 within the flow chamber 13 a , whereby one of changeover electrodes 62 a and 62 b 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 16 a and 16 b exhibit a high passage resistance, so that the pressure within the channel does not escape to an internal-pressure buffering chamber 15 a , and the movable body moves without fail. When the pressure of the operation fluid increases slowly due to 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. A drive device which does not cause breakage of a pump chamber or a seal due to thermal expansion of operation fluid is provided.

1 . A circuit changeover switch comprising: 
 a channel forming portion for forming a channel, the channel accommodating an incompressible operation fluid and a movable body made of a substance different from that of the operation fluid, and being substantially divided into two operation chambers by means of the movable body;    a pair of pumps each including a pump chamber communicating with the corresponding operation chamber and being filled with the operation fluid, an actuator provided for the pump chamber, and a diaphragm deformed by the actuator, the operation fluid within the pump chamber being pressurized or depressurized through deformation of the diaphragm;    an internal-pressure-buffering-chamber-forming portion for forming an internal-pressure buffering chamber which accommodates the operation fluid and a compressible fluid for pressure buffering; and    a micro channel portion for forming a micro channel which connects the channel of the channel forming portion and the internal-pressure buffering chamber of the internal-pressure-buffering-chamber-forming portion, the micro channel exhibiting a high passage resistance against abrupt pressure change of the operation fluid within the channel, to thereby substantially prohibit passage of the operation fluid through the micro channel and exhibiting a low passage resistance against slow pressure change of the operation fluid within the channel, to thereby substantially permit passage of the operation fluid through the micro channel.    
     
     
         2 . A circuit changeover switch according to  claim 1 , wherein the actuator includes a film-type piezoelectric element comprising a piezoelectric/electrostrictive film or an antiferroelectric film and electrodes; and the diaphragm is formed of ceramic.  
     
     
         3 . A circuit changeover switch according to  claim 1  or  2 , wherein 
 each of the diaphragms of the pumps constitutes a portion of the walls of the corresponding pump chamber and has a film surface in a common plane;  
 the channel of the channel forming portion forms a space whose longitudinal axis lies in a plane parallel to the film surfaces of the diaphragms;  
 the micro channel of the micro channel portion extends along a direction parallel to the film surfaces of the diaphragms; and  
 the internal-pressure buffering chamber of the internal-pressure-buffering-chamber-forming portion forms a space whose longitudinal axis lies in a plane parallel to the film surfaces of the diaphragms and is connected with the channel of the channel forming portion via the micro channel of the micro channel portion.