Patent Application
20120186657
A control valve is typically used to control the flow of a fluid under pressure. The valve can be “opened” to allow or increase fluid flow, and can also be “closed” to prevent or reduce the flow of fluid. As a result, by controlling the opening and closing of the valve, flow rate of the fluid can be changed. In some applications the fluid may be under high pressure, and the actuation of the valve requires relatively high actuation forces to overcome the pressure and open or close the valve. In some applications, precisely controlling the actuation of the valve, for example, opening or closing the valve by a repeatable and small amount or with minimal backlash, is desirable. Also, it may be desirable in some applications to be able to quickly and accurately adjust the opening or closing of a valve.
An example of a control valve is a motor driven needle valve. Although motor driven needle valves typically consume little power and provide high actuation forces, they may be slow to respond and exhibit behavior that reduces sensitivity and resolution, such as backlash. Another example of a control valve is a solenoid driven valve. Although these valves are fast and provide good resolution, these valves typically consume a large amount of power and provide limited actuation forces.
The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings merely depict several examples in accordance with the disclosure, and therefore, are not to be considered limiting of its scope; the disclosure will be described with additional specificity and detail through use of the accompanying drawings.
The present disclosure further describes a control valve and method of operating a control valve. The control valve may further include a piezoelectric actuator. The piezoelectric actuator may be configured to deform in response to an applied voltage. The control valve may further include a sealing mechanism associated with the piezoelectric actuator. The sealing mechanism may be configured to be in a closed position and an open position. When the sealing mechanism is in the closed position, the sealing mechanism is configured to prevent the fluid from flowing through the valve. The sealing mechanism may be in the open position in response to piezoelectric actuator deforming thereby allowing the fluid to flow through the valve.
The present disclosure describes a method of operating a control valve. The method may include applying a voltage to a piezoelectric actuator thereby causing the piezoelectric actuator to distort. The method may further include a response to the piezoelectric actuator distorting to create an opening thereby allowing pressurized fluid to flow through the valve.
The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.
The following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative examples described in the detailed description, drawings, and claims are not meant to be limiting. Other examples may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are implicitly contemplated herein.
This disclosure is drawn, inter alia, to methods, systems, devices, and/or apparatus generally related to a control valve. In some examples a proportional control valve comprises a piezoelectric actuator substantially immersed in a fluid in a manifold. The control valve may further include a sealing mechanism configured to be in a closed position and an open position. The piezoelectric actuator may be configured to distort in response to applying a voltage to the piezoelectric actuator. The distortion of the piezoelectric actuator causes the sealing mechanism to be in the open position allowing the fluid to flow therethrough. In response to ceasing application of the voltage to the piezoelectric actuator, the piezoelectric actuator returns to its undistorted position thereby causing the sealing mechanism to be in the closed position preventing the fluid to flow therethrough. In some embodiments, the control valve allows fluid flow in proportion to the voltage applied to the piezoelectric actuator.
The piezoelectric actuator 210 and the tube 212 are positioned in a chamber 214. The chamber may contain the fluid to be controlled by the control valve assembly 200. Placing the piezoelectric actuator 210 in the chamber 214 with the fluid to be controlled may eliminate the need for a dynamic seal between the actuator and sealing mechanism. As known, dynamic seals introduce friction and may make it more difficult to precisely control the position of the ball 220 to provide a desired conductance. The first end of the piezoelectric actuator 210 comprises the sealing mechanism. The sealing mechanism may include a seat 222 configured to receive the ball 220 to create a seal. In some embodiments, the seat 222 is configured to receive other types of sealing components, for example, cones, poppets, or other parts may be used to seal against the seat 222. Additionally, other valve configurations can be used in alternative embodiments. When the control valve assembly 200 is in the closed position, the ball 220 is pressed against the seat 222 by a spring 224. For instance, spring 224 may be a compression spring configured to apply a force to the ball 220 forcing the ball into the seat 222. The ball 220 fits into seat 222 in a manner that prevents fluid from being emitted therebetween. The sealing mechanism may include a needle or plunger, or any other device capable of creating a seal with a seat, rather than the ball 220.
To open the control valve assembly 200, a voltage may be applied to the piezoelectric actuator 210. For instance, the power source (not shown) may be configured to apply a voltage to the piezoelectric actuator 210. In response to the applied voltage, the piezoelectric actuator 210 may expand causing the ball 220 to apply a force against the spring 224. The force causing the ball 220 to press against the spring 224 may be greater than the spring force thereby causing the spring 224 to compress. Movement of the ball 220 creates an opening between the ball 220 and the seat 222 allowing the fluid to flow therebetween. In some examples, such as when the fluid is a gas, the piezoelectric actuator 210 may move the ball 220 less than a micrometer. In some examples, the opening between the ball 220 and the seat 222 caused by the piezoelectric actuator 210 allows fluid flow proportional to the voltage applied to the piezoelectric actuator 210. To close the valve assembly 220, the electric field applied to the piezoelectric actuator 210 may be reduced or is no longer applied. As a result, the spring force may become greater than the force being applied to it by the piezoelectric actuator 210, thus closing the opening between the ball 220 and the seat 222 to prevent the fluid from flowing therebetween, or in examples of a proportional control valve, reduce fluid flow therethrough. In another example, the control valve assembly 200 may be designed and configured to remain closed in response to applying a voltage to the piezoelectric actuator 210 and to be opened in response to no longer applying the voltage. In this example, the ball 220 may be located on the opposite surface of the seat 222.
The fluid that flows through the control valve assembly 200 may be a gas or liquid. In some examples, the control valve assembly 200 may be exposed to fluids in the chamber 214 at high pressures, such as 100 MPa. At high pressure, the affects of the hydrostatic fluid pressure on the components of the control valve assembly may affect the operation of the control valve. For instance, the hydrostatic pressure from the fluid in the chamber 214 applies pressure to the outer surfaces of the piezoelectric actuator 210 and the cone 218, which may cause the piezoelectric actuator 210 to contract. As a result the ball 220 may move closer to seat 222 reducing fluid flow or may not be moved off the seat 222, which causes the valve to remain closed. Having the tube 212, piezoelectric actuator 210, and cone 218 together in the chamber 214 may, however, reduce the impact the pressure has on the operation of the control valve 200. That is, the pressure applied to the piezoelectric actuator 210 and cone 218 is also applied to the tube 212, causing it to contract as well. Contraction of the tube increases the distance between the ball 220 and the seat 222. As a result, although the pressure on the piezoelectric actuator 210 and the cone 218 may cause the ball 220 to move closer to seat 222, that may be compensated for by the tendency for the distance between the ball and seat to increase as the tube 212 reacts to the pressure. Thus, the hydrostatic effects on the piezoelectric actuator 210 and cone 218, and the tube 212 may offset one another and prevent hydrostatic pressures within the assembly from affecting operation of the valve.
In some examples, the configuration of the control valve 200 may allow the piezoelectric actuator 210 to deflect (e.g., bend, bow) within the tube 212. For instance, at the first end of the piezoelectric actuator 210, the cone 218 may be configured to rotate relative to the ball 220. At the second end of the piezoelectric actuator 210, the mount 226 may be configured to rotate relative to the ball 228. Allowing the piezoelectric actuator 210 to deflect within the tube 212 at each end may prevent or at least reduce cracking of the piezoelectric actuator 210 due to bending stress. For instance, in the example in which the piezoelectric actuator 210 is a ceramic piezoelectric actuator, the ceramic piezoelectric actuator may be brittle. As voltage is applied to the ceramic piezoelectric actuator and the ceramic piezoelectric actuator expands in response to the voltage, it may bend slightly. The ability for the ceramic piezoelectric actuator to deflect may assist in preventing bending stress fractures therein.
The manifold body 310 may further include one or more an electrical pass through systems 340.
Referring again to
The adjustment assembly 330 may be configured to adjust the position of the piezoelectric actuator 210 relative to the seat 222 and the ball 220 by adjusting the position of the second end of the piezoelectric actuator 210. Adjustment of the piezoelectric actuator 210 may be obtained by rotating the screw 334 and/or nut 332 relative to the manifold body 310 in a first direction to reduce the amount of force applied to the second end of the piezoelectric actuator 210 and in a second direction to increase the amount of force applied to the second end of the piezoelectric actuator 210. Access to the nut 332 and the screw 334 is provided through an opening in the manifold body 310. In some examples, the external thread pitch and the internal thread pitch of the nut 332 are selected to allow less than a micrometer of adjustment per degree of rotation of the screw 334 or nut 332. Coarse adjustment may be obtained by rotating the screw 334 relative to the nut 332 or rotating the screw 334 and the nut 332 together relative to the tube 212. Fine adjustment may be obtained by rotating the nut 332 without rotating the screw 334. In some examples, the pin 338 may be provided through an opening in the tube 212 and the screw 334 to prevent the rotation of the screw 334 relative to tube 212 when rotating the nut 332 for fine adjustment.
A first end of the spring 336 may rest against a step 334a at an end of the screw 334 and a second end of the spring may rest against a step 212a on an inner surface of the tube 212. The spring 336 may be configured to apply a load to the threads of the screw 334 and/or nut 332 to prevent or reduce backlash and/or adjustment due to vibration. In some examples, the spring 336 comprises a stack of conical washers.
While various aspects and examples have been disclosed herein, other aspects and examples will be apparent to those skilled in the art. The various aspects and examples disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.
