Control valve for controlling fluid passage

A control valve for controlling a fluid passage, comprising:

• a case defining a first cylinder;
• a piston mechanism disposed in said first cylinder so as to be movable in the axial direction of said first cylinder;
• a first fluid pressure chamber defined in said first cylinder by said piston mechanism and being filled with fluid;
• a piezoelectric element group inoluding a plurality of laminar piezoelectric elements stacked in layers, said element group being disposed in said first cylinder and adapted to be extended and contracted when voltage is applied to said piezoelectric elements, whereby said piston mechanism is moved to vary the capacity of said first fluid pressure chamber;
• said case also defining a second cylinder communicating with said first fluid pressure chamber, said second cylinder having a cross-sectional area smaller than that of said first cylinder;
• a second fluid pressure chamber defined in said case, to which fluid is supplied and which is continuous with said first fluid pressure chamber via said second cylinder;
• valve member means disposed in said second cylinder for being driven by the fluid pressure in said first fluid pressure chamber, said valve member means having opposite end faces on which the fluid pressures in said first and second fluid pressure chambers respectively act, the end face area of said valve member means exposed to the fluid pressure in said first fluid pressure chamber being equal to the end face area of said valve member means exposed to the fluid pressure in said second fluid pressure chamber, said valve member means further having valve means formed in a central portion thereof for opening and closing said fluid passage;
• and
• an auxiliary fluid passage at least partially defined by said valve member means for connecting said first fluid pressure chamber to said second fluid pressure chamber.