WO1986007429A1

WO1986007429A1 - Apparatus for electrical control of rate of fluid flow

Info

Publication number: WO1986007429A1
Application number: PCT/US1986/001220
Authority: WO
Inventors: Willis T. Lawrence
Original assignee: Arthur D. Little, Inc.
Priority date: 1985-06-11
Filing date: 1986-06-05
Publication date: 1986-12-18
Also published as: AU5992286A; JPS63500050A; EP0225379A1; EP0225379A4

Abstract

Flow control valve device (5, 10, 40, 50) wherein the rate of fluid flow through the valve is controlled by controlling the ratio of the duration for which the valve is open to the duration for which it is closed. The flow control signal controls the deflection of a piezoceramic bender element (12) which, under a no control signal condition, is effective to prevent fluid flow. The valve is responsive to an electrical voltage signal which can be generated by manual control or by computer control thereby providing a means to efficiently and effectively control, with an electrical voltage, the rate of fluid flow.

Description

__!_. APPARATUS FOR ELECTRICAL CONTROL OF RATE OF FLUID FLOW

BACKGROUND OF THE INVENTION

This invention generally relates to the control, by electro-mechanical means, of t e rate of fluid flow and more particularly to the control of the rate of flow of a gas, under pressure, through a valve and more specifically to the control by an electrical signal having a predetermined fixed frequency but a variable on to off duty cycle whereby the on portion of the signal is of an amplitude and polarity so as to cause a mechanical deflection of a piezoceramic beam relative to an inlet or an outlet port of a gas valve of a nature to valve a pressured gas into a storage chamber the gas being a combustion fuel for such as a gas burning appliance.

It is proposed -that due to the current trend, in the design of appliances for home and/or commercial applications, toward the use of electronics to control temperature, the use of manual controls to regulate the flow volume of liquid and particularly gas in cook ranges, will soon give gas range cooktop burners (and ovens) the appearance of being antiquated technology. Microprocessor control of microwave ovens, electric cooktops and electric ovens is currently possible, and are currently being sold by manufacturers. The major barrier to the effective, efficient and economic use of these controls for gas appliances is the absence of a relatively low-cost, flow control valve which is reliable, and which is electrically controlled and additionally, which is consistent as to the volume of gas (or fluid) flow as a function of the voltage level of an electrical flow control signal or modulation signal.

There is a valve available which is constructed using a piezoceramic bender element. However, it is not capable, by virtue of its fundamental nature and design, to modulate flow, rather it is tuned to provide oscillating flow at a tuned frequency. This operation is achieved by structuring the valve so -that the bender element is midway between a back up plate and an outlet orifice when no signal or voltage is applied. In use, alternating voltage is applied to drive the bender back and forth between two stops, an on stop and an off stop. It is important to note that when no voltage is applied the valve is not closed. Moreover, the requirement that the valve oscillate at high frequencies makes it necessary to use very small gaps between the bender element and the on and off stops and a very small gap between the outlet orifice and the bender element. Thus the unit could not reliably modulate fluid flow from an inlet to the outlet port because of the high sensi¬ tivity to minor differences in location of the bender and small changes in voltage. The unit, in labora¬ tory testing, performed in a very erratic manner. The rate of flow was not repeatable. That is the rate of flow did not have a one-to-one correspon¬ dence with the level of voltage applied to the unit. The valve referred to is manufactured by The Lee Company and is identified as LEE Minature Ultra- Speed Interface Valve Part No. PVAA 8000120H and is designed for use on clean, dry, non-combustible gases and a maximum pressure of 10 psi (0.7BAR).

In United States Patent No. 4,238,110 to McCabe there is disclosed a fuel metering valve having a solenoid which cyclicly opens and closes an orifice. The invention of McCabe controls a fluid flow rate by, in effect,alternately fully closing and fully opening a pas¬ sage means during a selected span of time. The McCabe oscillator could have a fixed cycle time but variable "off" time and correspondingly variable "on" time. The ratio of the "on" time to the "off" time would determine the rate of fuel flow. It is important to note, in McCabe, the use of a solenoid winding which " upon energizing and deenergizing influence the position of the metering valve member with respect to the metering orifice, the solenoid winding is energized as through related control means re¬ sponsive to and reflective of engine fuel require- ments to thereby reciprocatingly move the metering valve member toward and away from the cooperating metering orifice—. "

The invention disclosed herein does not use such a solenoid winding nor the reciprocation of an armature and a valve member which fully opens or fully closes a passage means. The McCabe fuel metering valve effective¬ ly meters flow by, during a selected period of time, alternately fully opening and fully closing a passage means. The amount of fuel metered is determined by using feedback signal information which effects the position of the solenoid so as to vary, based upon engine conditions, the amount of fuel. The invention herein disclosed achieves the control of fuel or gas or other fluid by altering in one instance the ratio of time the valve is fully opened to the time the valve is fully closed (to/tc) along with providing for a storage volume to effectively smooth out the fluid flow. In a second instance not only is the fluid volume or flow rate controlled by the ratio to/tc but also by varying the effective open area of the orifice being modulated. Thirdly the modulated orifice opening can be controlled as to the size of the opening by applying a con¬ trol voltage to the bender. Either the inlet orifice or the outlet orifice or a combination of the two can be modulated as noted above. The control is . accomplished by the operator of the equipment, such as a gas range, by a control means such as a rotating knob, a push button switch or by programming a control computer. Thus, three modes of control are disclosed herein; 1) the variation of the ratio of full on time/to full off time; 2) the control of the degree to which the modulated orifice is open, i.e., the opened area of the modulated orifice so as to permit a controlled flow of fluid through the modulated orifice, hereinafter referred to as analog modulation; and 3) the combination of varying both the ratio of the on time to the off time and the degree to which the modulated orifice is opened during the on time.

SUMMARY OF THE INVENTION

A primary object of the invention is to provide a low cost, reliable, flow control valve for control¬ ling the flow rate of a fluid under pressure, the control of fluid flow accomplished by the control of the extent to which a modulated orifice (inlet or outlet) is opened or closed upon application of a controllable voltage to a bender element.

It is a further object of the invention to ^■ provide a low cost, reliable, flow control valve for controlling the flow rate of a fluid under pressure by means of an electrical flow control signal of a predetermined frequency and having a predetermined and required voltage amplitude and waveform said voltage amplitude appropriate to cause a bender ele¬ ment to deflect a predetermined amount that pre¬ determined amount being, a fully opened position, and for a predetermined period of time so as to permit full flow of fluid through the valve thereby permitting the full flow of fluid for a predetermined period of time, the mean flow rate being related to and determined by the ratio of the "on" time to the "off" time whereby the "on" time is the time for which the bender element is deflected by the application of the appropriate voltage amplitude so as to permit the flow of fluid from an inlet port to an outlet port.

A still further object of the invention is to provide control of fluid flow by a combination of the ratio of the time open to the time closed, i.e.,

the signal "on" time and "off" time and by control of the effective area of a modulated orifice which may be the same orifice as the one opened and closed on a time varying basis.

Another object of the invention is to provide control of fluid flow by analog modulating of the inlet, and also cause the outlet orifice to reliably shut off fluid flow through the valve when there is no flow control signal present.

It should be noted that whenever a component of cσntrol -consists of controlling the rate of fluid flow by means of control of the ratio of the time the orifice is open (no matter how far or to what degree it is opened) to the time it is closed there will be a pulsating flow of fluid. Where the fluid is a compressible fluid such as gas or air, etc. , it is necessary, if pulsations are undesirable at the location of use of the rate controlled fluid, that a storage means be incorporated into the system. The storage volume must be adequate to minimize or reduce the pulsations to an acceptable level. The storage volume or the size of the reservoir portion of the system depends upon such factors as flow rates, fluid types, and pressures. It is possible that the conduits connecting the controlled valve to the fluid source and to the location of use may contain sufficient volume to satisfy the need for fluid storage in order to reduce the amplitude of the pulsations and in effect smooth them out.

Various other objects and advantages will become apparent when reference is made to the following detailed description of the invention when considered in conjunction with the accompanying drawings which illustrate only several embodiments of the invention and wherein: BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1. is a schematic of a valve wherein the outlet orifice is modulated due to the deflection of the bender element from application, to the bender, of a flow control signal and for the condition of no control signal, the outlet orifice is sealed closed.

Fig. 2. is a schematic of a valve similar to the valve of Fig. 1 except that the bender is cantilever mounted.

Fig-. 3. is a schematic of the electrically controlled valve of Fig. 1 connected to a volume storage means.

Fig. 4. is a schematic a valve wherein the outlet orifice is sealed closed under a no signal condition and the inlet orifice is modulated which can be time on to time off, i.e., ratio modulated, or analog modulated or modulated by a combination of ratio modulation and analog modulation.

Fig. 5. is a schematic of a valve similar to the valve illustrated by Fig. 3 except that the bender element is assembled in the valve as a cantilever beam allowing for a more extensive movement of the modulating seat relative to the modulating orifice.

Fig. 6. is a system schema^*tic illustrating, in block diagram form, the interrelationship of the controlled valve, the control signal, the controlled fluid, the storage volume and the means for using the flow controlled fluid.

Fig. 7. is a waveform representation of the time and amplitude relationship of the flow control signal, a combination of Vcontrol and Vac (7C) and the flow volume for a combination of ratio and analog modulation (7E) , and ratio only modulation (7G) using a sine wave as the AC (7A) signal having a period T. Fig. 7D represents the bender deflection where ratio and analog modula¬ tion is used and Fig. 7F represents both the bender deflection and the flow control voltage for ratio only modulation.

Fig. 8. is a waveform representation as in Fig. 7 except that the AC signal Fig. 8A is a sawtooth illustrating the more linear variation of the time open to time closed (to/tc) as a function of control voltages having effective amplitudes of Vco,, CO2. Vσθ3, and Vco₄. The control voltages, in effect, move the AC signal positively or negatively thereby varying the time the valve is open. Fig. 8F-H illustrate ratio only modulation signals and Fig. 8B-E illus¬ trate ratio plus analog modulation flow control voltage signals.

Fig. 9. is a waveform representation of analog control voltage and a corresponding rate of gas flow.

DETAILED DESCRIPTION OF THE INVENTION

It will be obvious to one skilled in the art that there are many variations of this invention. Some examples of the variations are: (1) modulation by control of the ratio of the time open to the time closed of an orifice of the valve, or modula¬ tion by analog methods of the area of the inlet or the outlet orifice or of both orifices simultaneously; (2) modulation using a combination of both the ratio and the analog techniques; (3) modulation by a bender element positioned in a cantilever or end mounted configuration; and (4) by voltage signals which would open the modulated orifice when relatively positive and close the orifice when relatively negative and visa versa wherein such a dependence upon voltage polarity would be based upon the orifice being modulated and upon the relative positioning of the modulated orifice with respect to a modulating seal. In addition to the above noted variations, various control signal waveforms are possible including a voltage impulse of controlled width and appropriate polarity and of sufficient amplitude to cause the bender element to either partially deflect or maximally deflect for the duration of the impulse voltage. A sine wave having a DC component of voltage controllably added which effects control of the bender for a lesser or longer duration is also possible. Also a sawtooth wave¬ form would provide a more linear control of fluid flow when a D.C. component is controllably added. An impulse voltage signal having a polarity to forceably close the outlet orifice can be additional to all the waveforms noted above. It is also within the scope of the inven¬ tion to provide the inlet and the outlet orifice on the same side of the bender element.

It will also be obvious to those skilled in the art that the valves of this invention can be used in parallel or in series or in series-parallel combinations to achieve a larger volume of flow, to control fluid at higher or lower pressures to provide for fluid flow governed by an analog or digital logic system. So as not to becloud the description of the in¬ vention, the invention will be described with reference to Figs. 4. and 5. wherein the inlet orifice will be modulated when analog only modulated is used. The valve of Fig. 1. or Fig. 2. will be used to describe the in¬ vention when ratio only modulation is used or when a combination of ratio and analog modulation is used. In addition, the fluid discussed will be a compressible gas such as may be used in a gas stove.

With reference to Figs. 1. and 2. gas from a gas supply tank is introduced into the flow controlled valves 5 and 10 by means of inlet conduit 22. The gas flows through the inlet orifice 20 into the valve cavity 27. When there is no signal to the piezoceramic bender 12, the bender 12 and seal 14 in combination with the gas in the cavity 27, which gas has associated therewith a pressure, tightly presses against the outlet orifice seat 16 to effectively prevent gas flow through the outlet conduit 24. When a flow control signal such as illustrated in Figs. 7F, 8F, 8G, or 8H is applied to the bender element 12, the bender 12 will deflect away causing the seal 14 to move away from seat lβ for the time during which the flow control signal is of proper polarity. The flow control signal may cause the bender 12 to move away when the voltage is positive. The polarity of the "on" or open signal may be positive or negative and will depend upon the orientation of the bender 12 and the modulated (opened-closed) outlet orifice 17. The flow control signal amplitude is suf- ficent in amplitude to cause the bender 12 to deflect an amount which allows for maximum flow rate of the gas through the valves 5 or 10. Such deflection by an amount Xmax is also illustrated by Figs. 7F, 8F, 8G or 8H. When the only variable in the flow control signal is the ratio of the time the voltage is of a polarity to cause the valve 5, 10 to, in effect, be fully open to the time the voltage is of a polarity to cause the valve 5, 10 to be fully closed, then the valve 5, 10 is modulated by, what is called herein, ratio modula¬ tion. Emphasis should be placed on the fact that the bender 12 deflects by a predetermined maximum 'amount or it is in the undeflected or closed position. This form of modulation can be used on the valves illus¬ trated in Figs. 1. and 2.

In Fig. 3. there is illustrated a storage volume 32 and a storage volume outlet conduit 34. The size of the storage volume 32 could vary depending upon the volume of gas, the pressures, and other factors which would be obvious to those skilled in the art. It may not be necessary to have a separate storage volume 32 because the inlet conduit 22 and outlet conduit 24, along with gas source and the means for using the rate controlled gase (See Fig. 5.) have sufficient inherent volume to reduce pulsations of the controlled gas to an acceptable level. The damped pulsations which result due to the storage volume, are illustrated by the curves of Fig. 7E and 7G. The curve of Fig. 7F can represent pulsed gas flow, the flow control sig¬ nal voltage waveform and bender deflection X.

In Fig. 4 and 5 the inlet orifice 44 is analog modulated. The seal 14 and seat 16 function only to close outlet orifice 18 when no signal is applied to the bender 12. In Fig. 4, as in Fig. 1, the bender 12 is mounted at both ends of the beam, 28, 30 respectively.

In Fig. 5 the bender 12 is mounted at one end 28 in a cantilever configuration. Application of an appro¬ priate flow control signal such as illustrated by Fig. 9A to the bender 12, so that the outlet orifice 18 is essentially fully opened, causes the flow to reach a maximum value. Further increases in the amplitude of the control signal causes the bender 12 to move the mod¬ ulating seal 42 toward the inlet orifice 44 thereby re¬ ducing and ultimately closing off gas flow through the valve 40, 50. A lesser amplitude of flow control signal will permit a partial flow of gas as is illustrated by the curves of Fig. 9A and 9B. Thus the control signal when varied from a minimum voltage level (Vmin) to a maximum voltage level (Vmax) will vary the flow rate from a maximum flow rate to a minimum flow rate thereby analog modulating the gas flow by modulating the effective size of the inlet orifice 44. Thus the inlet orifice 44 is the analog modulated orifice. When the flow control signal is removed or effectively zero, the valve 40, 50 will close as noted above.

The valves 40, 50 illustrated by Figs. 4 and 5 respectively are typically analog modulated. It is also possible and within the scope of the invention to use, in combination, both analog and ratio modulation. It should also be noted that analog modulation alone could be _. used with the valves of Figs. 1 and 2.

Figs. 7 and 8 are sketches of approximate flow control signal waveforms which, for the piezoceramic bender element 12, illustrated as a beam, are voltage waveforms. In Fig. 7 the alternating signal (AC signal) is represented as a sine wave (7A) . In Fig. 8A the AC signal is a sawtooth. For all wave¬ forms used as the AC signal, which could also include, a ramp wave, a square wave or obviously a cosine wave, the frequency or in other words the period T is essen¬ tially constant. A method for varying the ratio of time the valve is open, (to) to time the valve is closed (tc) and where to + tc = T, is to vary the zero voltage position of the AC signal by superimposing a control signal (7B or in Fig. 8A, Vcol, Vco2 , Vco3, Vco4) which is, relative to Vac, a direct voltage (DC voltage) . The AC signal zero reference then varies as the DC control signal varies (see Figs. 7C. , and the composite curve of Fig. 8A. ) . When a positive excur¬ sion of the composite signal (7C or 8A) exceeds some predetermined value a pulse Figs. 7F, 3F, 8G, 8H is generated by a pulse shaper. The pulses have a magni¬ tude sufficient to deflect the bender 12 by a maximum predetermined amount. The pulse of voltage will be a relatively negative going pulse when the composite ^'signal amplitude decreases to a predetermined value. It is obvious then from the various waveform sketches that while to + tc = T the ratio to/tσ is varied. If the bender 12 moves to open a modulated orifice during time to and during³ time tc the modulated orifice is closed then t /t is the ratio of the time the valve 5, 10 is full "open" to the time the valve 10 is full "closed."

It is thus apparent that where to/tc is small there will be^' a small flow rate and where to/tc is large the flow rate will be large - thus ratio modulation. The gas pulsations are damped by the storage volume 32 as illustrated by the curves of Figs. 7E (ratio and analog modulation) and 7G (ratio modulation) . A similar curve could be but has not been illustrated for the waveforms of Fig. 8.

A combination of ratio and analog modulation can be obtained by not generating the control voltage pulses having a constant and predetermined amplitude so as to fully "open" the valve 5, 10. If the amplitude of the AC signal is held basically constant and the control signal is varied so that not only does the ratio of time "open" to time "closed" vary but so does the "on" voltage amplitude, then not only will the valve be open for a time, say t, , but will open an amount related to the "on" voltage amplitude. This combination of ratio and analog modulation is illustrated in Figs. 7D, and 8B, 8C, 8D and 8E. Note that the deflection X of the bender 12 relates to and is similar to the flow control voltage waveforms applied to the bender 12. Thus those voltage waveforms also approximately represent the bender deflection waveforms, an example of which is illustrated in Fig. 7D.

It should also be noted that the piezoceramic bender element 12 need not necessarily be in a beam configuration mounted at both ends 28 and 30 to the housing means 26. The bender 12 could be configured as a rectangle having dimensions which would allow for the mounting of the four corners to the four surfaces on the housing means 26. Further the bender 12 could be circu¬ lar, elliptical, etc. to match an interior geometry of the housing means 26 and the cavity 27.

Having described the invention, it will be apparent to those skilled in the art to which this invention pertains, that various additional modifications may be made thereto without departing from the spirit and scope of this invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A flow control valve device comprising;

a housing means defining a cavity therein; an inlet conduit means having one end termi¬ nating as an inlet orifice said inlet orifice having a cross sectional area and being at a predetermined loca¬ tion and within said cavity and another end of said inlet conduit means in fluid communication with a fluid supply; an outlet conduit means having one end termi¬ nating as an outlet orifice at a predetermined location within said cavity and said outlet orifice having a predetermined cross sectional area, another end of said outlet conduit means in fluid communication with a means for using fluid from said fluid supply and having, an effective fluid storage volume. a bender element appropriately positioned within said cavity and affixed to said housing means, having a means adapted for providing signal communication between said bender element and a controllable flow control signal, said signal effective to cause said bender element to deflect a controlled amount thereby permitting an amount of said fluid to flow at a controlled flow rate through said valve device; and

A first sealing means affixed to said bender element to effectively seal, during the absence of said flow control signal, said outlet orifice.

2. The flow control device according to claim 1 wherein said bender element is piezoceramic and said flow control signal is an electric voltage of alternating predetermined maximtαm voltage value and predetermined minimum voltage value, having a pre¬ determined period, a predetermined voltage waveform and also having a direct voltage component.

3. The flow control device according to claim 2 wherein said controllable flow control signal is caused to vary with respect to the ratio of time said voltage value is at said predetermined maxi¬ mum value to time said voltage value is at said pre¬ determined minimum value and said maximum and said minimum voltage values appropriate to cause said piezo¬ ceramic bender element to deflect a predetermined maximal deflection and substantially a zero deflection thereby permitting full flow of said fluid when said bender is maximally deflected and preventing said fluid flow through said modulated orifice when said bender is zero deflected, the sum of the period of time said fluid flows and the period of time when said fluid is prevented from flowing being substantially constant and equal to said predetermined period of said flow control signal.

4. The flow control device according to claim 3 wherein said outlet orifice further comprises a seat.

5. The flow control device according to claim 4 wherein said fluid is a gas at least partially compressible.

6. The flow control device according to claim 5 wherein said controllable flow control signal is additionally effective to cause said bender element to deflect by an amount continuously variable between said zero deflection and said predetermined maximal deflection.

7. The flow control device according to claim 6 wherein said piezoceramic bender element is configured as a beam and both ends of said piezoceramic bender beam are affixed to said housing means.

8. The flow control device according to claim 6 wherein said piezoceramic bender element is configured as a beam having two ends one of said two ends affixed to said housing means.

9. The flow control device according to claim 6 further comprising a second sealing means appro¬ priately affixed to and located on said piezoceramic bender element said second sealing means substantially effective to modulate the effective size of said inlet orifice cross sectional area, said modulation of said inlet orifice area and said outlet orifice area combina- torially with said outlet orifice, controlling said fluid flow.

10. The flow control device depending upon claim 9 wherein said controllable flow control signal is additionally effective to cause said bender element to deflect by an amount continuously variable between said zero deflection and said predetermined maximal deflection.

11. The flow control device depending upon claim 10 wherein said piezoceramic bender element is configured as a beam and both ends of said piezoceramic bender beam are affixed to said housing means.

12. The flow control device depending upon

10 wherein said piezoceramic bender element is configured as a beam having two ends one of said two ends affixed to said housing means.

13. The flow control valve device according to claim 1 wherein said bender element is piezoceramic and said flow control signal is an electric voltage having a controllable amplitude substantially constant at said controlled amplitude and said bender deflection amount being related to said signal amplitude.

14. The flow control valve device according to claim 13 wherein said outlet orifice further comprises a seat.

15. The flow control device according to claim 14 wherein said fluid is a gas at least partially compressible.

16. The flow control device according to claim 15 wherein said piezoceramic bender element is configured as a beam and both ends of said beam are affixed to said housing means.

17. The flow control device according to claim 15 wherein said piezoceramic bender element is configured as a beam having two ends one of said two ends affixed to said housing means.

18. The flow control device according to claim 16 further comprising a second sealing means appropriately affixed to and located on said bender element, said second sealing means substantially effective to analog modulate the effective size of said inlet orifice cross sectional area, said analog modulation of said inlet orifice area combinatorially, with said outlet orifice, controlling said fluid flow.

19. The flow control device according to claim 17 further comprising a second sealing means appropriately affixed to and located on said bender element, said second sealing means substantially effective to analog modulate the effective size of said inlet orifice cross sectional area, said analog modulation of said inlet orifice area combinatorially with said outlet orifice, controlling said fluid flow.