초록 ▼

A proportional valve is disclosed for controlling the outlet pressure of a fluid flowing therethrough. The valve comprises a valve body having an inlet port and an outlet port for the fluid. The valve also has an inner chamber, within which there is formed a valve seat that may be opened and closed

A proportional valve is disclosed for controlling the outlet pressure of a fluid flowing therethrough. The valve comprises a valve body having an inlet port and an outlet port for the fluid. The valve also has an inner chamber, within which there is formed a valve seat that may be opened and closed variably by a shutter axially movable from and towards the valve seat. Movement of the shutter is controlled by a shape memory alloy (SMA) actuating member operating antagonistically to an elastic member, the temperature of the fluid being lower than the transition temperature of the shape memory alloy. The actuating member and the elastic member are connected to the body valve at opposite sides relative to the valve seat. A power control circuit is also provided for circulating an electric current through the actuating member so as to heat the same by Joule effect from a temperature lower than the transition temperature to one that is higher. At least one vent hole is formed in the valve body for putting a portion of the chamber upstream of the valve seat into fluid communication with the outside or a collection network. The actuating member is housed in that portion of chamber corresponding to the inlet port of the fluid, whereby a continuous flow of fluid around the actuating member is ensured for accelerating the cooling process. A closed-loop control circuit for the power control circuit controls the circulating current as a function of a pressure signal generated by fluid pressure sensing means and in such a way as to offset the retarding effect produced by the fluid during heating of the actuating member.

대표청구항 ▼

1. A proportional valve for controlling the outlet pressure of a fluid flowing therethrough, which comprises a valve body having an inlet port and an outlet port for the fluid and an inner chamber, the chamber including a valve seat that is opened and closed variably by a shutter movable axially tow

1. A proportional valve for controlling the outlet pressure of a fluid flowing therethrough, which comprises a valve body having an inlet port and an outlet port for the fluid and an inner chamber, the chamber including a valve seat that is opened and closed variably by a shutter movable axially towards and away from the valve seat, shutter movement being controlled by a shape memory alloy actuating member operating antagonistically to an elastic member, the temperature of the fluid being lower than the transition temperature of the shape memory alloy, the actuating member and the elastic member being connected to the body valve at opposing sides relative to the valve seat, and a power control circuit circulating an electric current through the actuating member so as to heat the same by Joule effect from a temperature generally lower than the transition temperature, wherein the elastic member on the shutter prevails, to a temperature that is generally greater than the transition temperature, wherein the actuating member on the shutter prevails, at least one vent hole is formed in the valve body for putting a portion of the chamber upstream of the valve seat into fluid communication with the outside or a fluid collection network, the actuating member being housed in that portion of chamber corresponding to the inlet port of the fluid, whereby a continuous flow of fluid around the actuating member is ensured for accelerating the cooling process, a closed-loop control power circuit being provided for controlling the circulating current as a function of pressure signal generated by a fluid pressure sensor and in such a way as to offset the retarding effect produced by the fluid during heating of the actuating member.2. The proportional valve set forth in claim 1, wherein the shape memory alloy actuating member has the shape of a coil spring.3. The proportional valve set forth in claim 1, wherein the fluid inlet port is formed by at least two diametrically opposed radial openings in the valve body and flowing into the chamber corresponding to the actuating member.4. The proportional valve set forth in claim 3, wherein the radial openings have an axially extending slot-like shape.5. The proportional valve set forth in claim 1, wherein the vent hole is formed in the valve body near one end thereof.6. The proportional valve set forth in claim 1, wherein the shutter has a conical shape.7. The proportional valve, wherein the control circuit comprises a PID controller.8. The proportional valve set forth in claim 7, wherein the control circuit comprises a threshold electronic switch for discriminating between operation in PID linear zone or under saturation condition in the positive or negative direction to accelerate the attainment of steady state control conditions.9. A method for controlling a proportional valve with a shape memory alloy actuating member, wherein a continuous circulation of fluid to be controlled is maintained upstream of a valve seat to reduce the slope of the operating curve and, thereby, improve controllability by retarding the valve opening and accelerating valve closure, thus linearizing system operation.