Piezoelectric hydraulic control valve

A piezoelectric hydraulic control valve for controlling a high-pressure fluid, comprising:

• (a) a housing having an axially extending central bore and having an inlet port for receiving a high-pressure fluid and an outlet port for delivering said fluid and a fluid passage communicating said inlet and outlet ports;
• (b) a valve seat in said housing provided across said fluid passage and having an inside passage forming part of said fluid passage;
• (c) a movable valve member disposed upstream of said valve seat and cooperating with said valve seat to make and break communication between said inlet and outlet ports;
• (d) means for biasing said valve member against said valve seat;
• (e) a piezoelectric actuator received coaxially within said bore of said housing and having one end supported by said housing and the other end displaceable in response to energization of said actuator;
• (f) connecting means for transmitting the displacement of said other end of said piezoelectric actuator to said valve member;
• (g) a relief passage for connecting said fluid passage downstream of said valve member to the outside of said housing;
• and
• (h) a relief valve disposed in said relief passage for relieving the fluid in said fluid passage downstream of said valve member at a relief rate which is less than the incoming flow rate at said inlet port so that a substantial fluid pressure is built up at said outlet port as said valve member makes an open communication between said inlet and outlet ports but said fluid pressure at said outlet port is rapidly diminished due to fluid escaping through said relief passage as said valve member breaks said communication.

A piezoelectric hydraulic control valve comprising:

• (a) a housing having an axially-extending, closed-ended central bore and having an inlet and an outlet port;
• (b) a disc-like valve seat closely and fixedly fitted within said bore of said housing to divide said bore into an upper cavity and a lower cavity, said valve seat having at the lower surface thereof an annular groove open into said lower cavity, said valve seat having a central through-aperture;
• (c) a pumping piston slidably and fluid-tightly received in said upper cavity of said bore, said pumping piston having a cylindrical central projection extending fluid-tightly through said central aperture in said valve seat;
• (d) a pumping chamber defined in said upper cavity between said pumping piston and said valve seat;
• (e) a disc-like valve member in contact with said central projection of said pumping piston and received movably within said lower cavity of said bore of said housing for opening and closing said annular groove in said valve seat in response to the displacement of said pumping piston;
• (f) means disposed in said lower cavity of said bore for biasing said valve member into contact with said valve seat and said central projection;
• (g) a first passage in said housing for transmitting pressurized fluid at said inlet port into said lower cavity;
• (h) a second passage in said housing and said valve seat for transmitting pressurized fluid at said annular groove into said outlet port;
• (i) a third passage in said valve seat for communicating said annular groove with said pumping chamber;
• and
• (j) a piezoelectric actuator received coaxially within said upper cavity of said bore of said housing, said actuator being supported at the top thereof by said housing and at the bottom thereof by said pumping piston so that upon energization, said actuator expands axially causing said pumping piston to move downward to lift said valve member off of the associating valve seat against the action of said biasing means as well as to pressurize the fluid in said pumping chamber thereby accelerating the pressure rise at said outlet port, and, upon de-energization, said actuator contracts axially allowing said pumping piston to move upward under the action of said biasing means and the fluid pressure in said pumping chamber thereby allowing the valve member to close said annular groove and accelerating the collapse of fluid pressure at said outlet port.

A piezoelectric transducer for converting electric pulse into linear displacement, comprising:

• a housing having an axially-extending central bore;
• a column of piezoelectric elements received coaxially within said bore;
• means for applying a voltage to said piezoelectric column to induce piezoelectric deformation of said column in response to said voltage;
• output means connected to the lower end of said piezoelectric column for transmitting linear displacement due to piezoelectric deformation to the outside of said transducer;
• a thermally expansible sleeve, mounted within said bore concentrically around said piezoelectric column, having a coefficient of linear expansion equal to that of said piezoelectric column with the lower end of said sleeve beign fixedly supported by said housing and with the other portions thereof being loosely fitted within said bore to permit the upper end of said sleeve to displace axially in response to thermal expansion and contraction of said sleeve due to a variation in the ambient temperature;
• and
• movable supporting means, received movably within said bore of said housing and connected to the upper ends of said sleeve and said column, for compensating for expansion and contraction of said column due to ambient temperature variations by supporting said upper end of said column to displace conjointly with said upper end of said sleeve, whereby the expansion and contraction in one direction of said column due to ambient temperature variation compensates for the expansion and contraction in the opposite direction of said sleeve so that the relative position of said lower end of said column with respect to said housing is kept constant regardless of ambient temperature variations.

A piezoelectric hydraulic control valve, comprising:

• (a) a housing having an axially-extending, closed-ended central bore and having an inlet port for receiving pressurized fluid and an outlet port for delivering said pressurized fluid and a fluid passage communicating said inlet and said outlet port;
• (b) a valve seat in said housing and extending across said passage;
• (c) a movable valve member cooperating with said valve seat;
• (d) a column of piezoelectric material received coaxially within said bore and having an upper and a lower end;
• (e) means for applying a voltage to said piezoelectric column to induce axial expansion of said column;
• (f) connecting means provided between said lower end of said column and said valve member for transmitting axial expansion of said column to said valve member to thereby open and close said fluid passage;
• (g) a thermal expansible sleeve received within said bore and having an upper and a lower end, said lower end of said sleeve being fixedly supported by said housing but other portions of said sleeve being loosely fitted within said bore to permit said upper end of said sleeve to displace axially in response to thermal expansion of said sleeve due to a variation in the ambient temperature;
• and
• (h) movable supporting means received movably within said bore and attached to the upper end of said sleeve for supporting the upper end of said piezoelectric column in such a manner that is displaces together with the upper end of said sleeve, whereby the expansion and contraction in one direction of said sleeve compensates for the expansion and contraction, due to ambient temperature variation, in the opposite direction of said piezoelectric column so that the lower end of said column is maintained at a constant distance with respect to said valve member regardless of the temperature variation, said movable supporting means comprising a piston received fluid-tightly and slidably in said bore of said housing and defining a pressurizing chamber in said bore and wherein said housing is provided with a second fluid passage therein for transmitting the pressurized fluid in said first-mentioned fluid passage to said pressurizing chamber to pressurize said piston against said sleeve and said piezoelectric column to support said sleeve and said column together.