Diaphragm pump

Abstract

A diaphragm pump includes: a volume changing member which changes the volume of a fluid chamber; a diaphragm member fixed in a stretched state and arranged separate from the fluid chamber, the diaphragm member having a pair of electrodes and a stretch film formed of dielectric elastomer, and the diaphragm member driving the volume changing member in a forward movement direction; a return bias member which drives the volume changing member in a backward movement direction; and a connection member which connects the diaphragm member and the volume changing member. In a low voltage state, the diaphragm member and the return bias member have driving force with respect to the volume changing member. The diaphragm member is arranged so as to be elastically protruded in the backward movement direction compared to the stretched state, and an inclination angle of the diaphragm member in the low voltage state with respect to that in the stretched state is set to 45° or greater in a cross section along a reciprocal movement direction.

1 . A diaphragm pump comprising:
 a housing member including a fluid chamber, a suction opening which sucks a fluid into the fluid chamber, and a discharge opening which discharges the fluid from the fluid chamber;   a volume changing member which changes a volume of the fluid chamber;   a diaphragm member which is fixed to the housing member in a stretched state where a periphery of the diaphragm member is extended in a radial direction, and which is arranged separate from the fluid chamber, the diaphragm member including a pair of electrodes and a stretch film formed of dielectric elastomer, which is provided between the pair of electrodes and an extension amount of which increases in a film expansion direction as an applied voltage between the pair of electrodes increases, and the diaphragm member driving the volume changing member in a forward movement direction which intersects with the film expansion direction;   a return bias member which drives the volume changing member in a backward movement direction opposite to the forward movement direction; and   a connection member which connects the diaphragm member and the volume changing member so as to be capable of power transmission;   wherein a low voltage state where the applied voltage between the pair of electrodes is low and a high voltage state where the applied voltage between the pair of electrodes is high can be switched; and   wherein, in the low voltage state, the diaphragm member and the return bias member have an accumulated driving force with respect to the volume changing member, the diaphragm member is arranged so as to be elastically protruded in the backward movement direction compared to the stretched state, and an inclination angle of the diaphragm member in the low voltage state with respect to the diaphragm member in the stretched state is set to 45° or greater in a cross section in a reciprocal movement direction.   
   
   
       2 . The diaphragm pump according to  claim 1 , wherein the volume changing member is a rubber elastic member. 
   
   
       3 . The diaphragm pump according to  claim 2 , wherein the rubber elastic member also serves as the return bias member. 
   
   
       4 . The diaphragm pump according to  claim 2 , wherein a static spring constant of the rubber elastic member is set to be greater than or equal to a static spring constant of the diaphragm member. 
   
   
       5 . The diaphragm pump according to  claim 1 , further comprising:
 a piston member including a piston body which serves as the volume changing member and a rod section which serves as the connection member connected with the piston body.   
   
   
       6 . The diaphragm pump according to  claim 1 , wherein the connection member includes a substantially spherical surface-shaped spherical surface section contacting the diaphragm member. 
   
   
       7 . The diaphragm pump according to  claim 6 , wherein the connection member includes a substantially sphere-shaped sphere member which includes the spherical surface section, and a concave member which contacts the volume changing member and includes a concave section accommodating a part of the sphere member. 
   
   
       8 . The diaphragm pump according to  claim 7 , wherein an accommodating surface of the concave section has a triangular pyramid mold shape which fits a surface of a triangular pyramid so that the sphere member comes into contact with the accommodating surface of the concave section at three points. 
   
   
       9 . The diaphragm pump according to  claim 1 , wherein at least one of a contact surface of the connection member with the diaphragm member and a contact surface of the diaphragm member with the connection member is formed of a low friction material. 
   
   
       10 . The diaphragm pump according to  claim 1 , wherein at least one of a contact surface of the connection member with the diaphragm member and a contact surface of the diaphragm member with the connection member is formed of an insulating material. 
   
   
       11 . The diaphragm pump according to  claim 1 , wherein a surface of the diaphragm member on a side of the fluid chamber is formed of an insulating material. 
   
   
       12 . The diaphragm pump according to  claim 1 , wherein the diaphragm member is formed of a plurality of the stretch films being laminated with the electrode interposed therebetween. 
   
   
       13 . The diaphragm pump according to  claim 1 , wherein the electrode is capable of stretching so as not to restrict stretching of the stretch film. 
   
   
       14 . The diaphragm pump according to  claim 1 , wherein the dielectric elastomer is one or more selected from a group consisting of acrylic rubber, silicone rubber, fluoro-rubber, urethane rubber, nitrile rubber, ethylene propylene rubber, styrene butadiene rubber, and natural rubber.