Ink jet head compact and allowing ink to be discharged with great force by using deformable structure

An ink jet head comprising:

• a container having an ink discharge opening on a wall thereof, the container defining an ink chamber therein;
• a buckling structure comprising at least two pairs of rectangular strips radially projecting from a center thereof, ends of which are fixed to a wall surface opposed to the wall of the container, the rectangular strips being deformable toward the ink discharge opening;
• a diaphragm disposed spaced from the buckling structure and being fixed to an inner wall of the container, the diaphragm forming a liquid-tight enclosure with the ink chamber and partitioning the container into a buckling structure space and the ink chamber, wherein the buckling structure is deformable toward the ink chamber;
• a connection member for connecting the diaphragm and the buckling structure at a center thereof;
• and
• a compression unit, provided in the buckling structure space, that causes the buckling structure to buckle by generating thermal stress therein with supply of electric current, so that ink is discharged from the ink discharge opening,
• wherein assuming that a Young's modulus of each rectangular strip constituting the buckling structure is E;
• a width thereof is b;
• a thickness thereof is h;
• a coefficient of linear expansion thereof is a;
• a length of a pair of rectangular strips is l;
• a total number of pairs of rectangular strips is n;
• a temperature change in the buckling structure at the time of buckling is t;
• and a spring constant of the diaphragm is k, the thickness (h) of the rectangular strip satisfies an equation expressed below to generate a buckling energy:
• 2l(-p) cos (u/3+4.pi./3)<h<2l(-p) cos (u/3)
• where
• p=-.alpha.t/.pi..sup.2, q=3k/nEb.pi..sup.4, u=cos.sup.-1 {q/p(-p).sup.1/2 }, 0.ltoreq.u.ltoreq..pi..

An ink jet head comprising:

• a container having an ink discharge opening on a wall thereof, the container defining an ink chamber therein;
• a buckling structure comprising at least two pairs of rectangular strips radially projecting from a center thereof, ends of which are fixed to a wall surface opposed to the wall of the container, the rectangular strips being deformable toward the ink discharge opening;
• a diaphragm disposed spaced from the buckling structure and being fixed to an inner wall of the container, the diaphragm forming a liquid-tight enclosure with the ink chamber and partitioning the container into a buckling structure space and the ink chamber, wherein the buckling structure is deformable toward the ink chamber;
• a connection member for connecting the diaphragm and the buckling structure at a center thereof;
• and
• a compression unit, provided in the buckling structure space, that causes the buckling structure to buckle by generating thermal stress therein with supply of electric current, so that ink is discharged from the ink discharge opening,
• wherein assuming that Young's modulus of each rectangular strip constituting the buckling structure is E;
• a width thereof is b;
• a thickness thereof is h;
• a coefficient of linear expansion thereof is .alpha.;
• an entire length of a pair of rectangular strips is C;
• an effective length of a pair of rectangular strips excluding the center thereof is l;
• a total number of pairs of rectangular strips is n;
• a temperature change in the buckling structure at the time of buckling is t;
• and a spring constant of the diaphragm is k, the width (b) of the rectangular strip is given by an equation shown below;
• and the effective length (l) satisfies an equation expressed below to generate a buckling energy:
• b=(C-l)/tan {(n-1).pi./2n}(3nEbhl.sup.2 .alpha.t.pi..sup.2 -nEbh.sup.3 .pi..sup.4 -6l.sup.3 k).sup.2 /3nEbhl.sup.3 .pi..sup.4 >0.