The invention was made by John M. Vranish as President of Vranish Innovative Technologies LLC and may be used John M. Vranish and Vranish Innovative Technologies LLC without the payment of any royalties therein or therefore.
The Charge-Driven Electrostatic Induction concept began with a need to actuate flexures in a Tape Motor invention. Permanent magnet electromagnetic drives were too large and cumbersome. Electrostatic drives were too weak and required voltages that were too high. John M. Vranish looked to electrets as an alternative to permanent magnets. But, it soon became apparent that devices that behave like electrets could be produced by trapping and isolating electric charge on capacitor electrodes. In the process of investigating alternatives to electrets, it soon became apparent that new capacitive materials enabled exceptional charge density from modest voltage. But, there were still problems in isolating the charge and in directing the electric flux from the charge. Step by step, the Charge-Driven electrostatic concept began to evolve to this point. It will continue to evolve.
The invention relates generally to Electrostatic Induction and more particularly to working level voltage, electrostatic applications. The invention relates generally to electret applications as an alternative method. The invention relates generally to electromagnetic induction as an electrostatic alternative for electromagnetic induction applications. The invention relates generally to high voltage applications as a working level voltage alternative and more particularly to step up and step down voltage transformers. The invention relates particularly to electrostatic power generation devices, power transfer devices, motor devices and sensors, both static and quasi-static.
Electrostatic Motors, Micromotors, Piezoelectric Travelling Wave Motors and Piezoelectric Inch Worms have, traditionally, performed precision positioning. Charge-Driven Electrostatic Induction, in combination with bending flexures, is presented as an alternative with advantages. (Bending Flexures is presented separately from this patent application.)
Electric Motors, using electromagnetism, constitutes a body of prior art. Charge-Driven Electrostatic Induction introduces an electrostatic alternative with advantages.
Electromagnetic Generators also constitute a body of prior art. Charge-Driven Electrostatic Induction introduces an electrostatic alternative with advantages.
Electret Microphones use elements with permanent polarization to perform functions of converting mechanical oscillating motion to electrical energy and output voltage. Charge-Driven Electrostatic Induction performs the same function without using permanently polarized elements and with the advantage of being able to easily neutralize stray charge. This argument can be extended to energy harvesting and scavenging devices and methods.
Transformers use coils and electromagnetism to step up or step down voltage as per traditional prior art. Charge-Driven Electrostatic Induction presents an alternative with advantages using multiple stacked capacitors rather than multiple coils.
Electromagnetic means, analogous to Electromagnetic Motors, has been used to transfer electric power across a joint with an air or vacuum gap between the moving members. Charge-Driven Electrostatic Induction performs the same function with advantages using electrostatics.
Charge-Driven Electrostatic Induction is a method for using modest voltage to induce large density electric charge across a large insulation gap. Large density equal and opposite charges are first created in a high performance capacitor adjacent said gap. One charge is removed and the electric field of the remaining charge is reflected into the gap where it induces equal and opposite charge on the far side and stores large density electric energy in said gap as per Gauss' Law of Charges and the method of images. With electrode area to gap ratio kept sufficiently large to limit field fringing, Charge-Driven Electrostatic Induction can rival electromagnetic motor performance. In practice, it will be superior. Constructed of layered, thin film components, Charge-Driven Inductance devices will be lighter, more compact and less expensive than their permanent magnet, electromagnetic counter parts. Coils, winding process, ferromagnetic materials, rare earth permanent magnets and large current power sources will be unnecessary and integration of controls and action devices will be more seamless. The multi-step process will permit high operating speeds. The principles behind Charge-Driven Electrostatic Induction are explained and construction of a device using Charge-Driven Electrostatic Induction is illustrated. Applications are presented illustrating use as an electrostatic motor, an electrostatic generator, and an electrostatic device for transferring power across a large air or vacuum gap. Performance enhancing techniques of Electric Field Projection and Charge Compression are introduced.
A more complete appreciation of the invention and many of its attendant advantages will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
a illustrates how equal and opposite charges are created in close proximity to each other and how one of the charges is trapped in place on its electrode.
b illustrates how the second of the charges is displaced from the trapped charge to provide separation and isolation for said trapped first charge.
c illustrates how the separated equal and opposite charges are trapped in place when the voltage source removed.
a. illustrates the charge arrangement before the grounded conductor is introduced.
b. illustrates the charge arrangement after a grounded conductor is introduced nearby and shows energy stored in the insulation gap between the stack of electrodes and the grounded conductor.
a. illustrates the effects of a nearby grounded conductor on initial charge formation and initial charge arrangement after a first charge is trapped.
b. illustrates the effects of a nearby grounded conductor on charge formation and charge arrangement when a second step in charge formation and charge trapping is performed.
a shows the floating outer electrode case.
b shows the grounded outer electrode case.
a illustrates the electric field and charge configuration when electric field is applied in a motor application, where the moving member moves transverse to the electric field.
b illustrates residual effects when the electric field is removed.
a illustrates charge distribution and electric field configuration in a motor application in which the moving member moves along the direction of the field, after the field is applied, but before the moving member has moved.
b illustrates the charge distribution and electric field configuration after limited movement has occurred.
a shows the effects of applying an electric field in a power transfer application across an air/vacuum gap typical of moving joints of machines, motors and generators.
b shows the effects when the electric field is removed.
a illustrates a first position in an apparatus that converts time varying mechanical energy to electrical energy.
b illustrates a second position. A comparison of the two positions and the effect on the electric energy stored in the apparatus insulation gap provides insight into the charge-driven electrostatic energy conversion process.
a illustrates a first position in an apparatus that uses passive electronic components in converting time varying mechanical energy to electrical energy.
b illustrates a second position. A comparison of the two positions and the effect on the electric energy stored in the apparatus insulation gap provides insight into the charge-driven electrostatic energy conversion process using passive electronic components.
In accordance with the present invention, A Charge-Driven Electrostatic Induction System a Charge-Driven Electrostatic Induction System includes a 1). A Charge Creation and Isolation Capacitor System, 2). An Air or Vacuum Gap adjacent to said Charge Creation and Isolation Capacitor, with Remote Electrical Conductor on the Far Side of the Gap, 3). A Housing. The preferred embodiment of A Charge-Driven Electrostatic Induction System is configured according to
Current technology permits stacks with electrodes and dielectric films in the hundreds so a method for rapidly charging said electrodes is presented, whereby multiple electrodes can be charged or discharged simultaneously. This method is illustrated in
The invention will now be described in more detail by way of example with reference to the embodiments shown in the accompanying figures. It should be kept in mind that the following described embodiments are only presented by way of example and should not be construed as necessarily limiting the inventive concept to any particular physical configuration.
The construction of a Charge-Driven Electrostatic Induction System according to
1). Charge Creation and Isolation System. Said Charge Creation and Isolation System, (according to
2). Switch System. Said Switch System comprising a voltage source, a system of electrically conducting wires whereby said voltage source is connected to each of the electrodes described in 1). Charge Creation and Isolation System and a set of computer controlled switches (according to
The switches in 3 service all n+2 electrodes. Each inner electrode in said stack of electrodes (labeled 2) has one switch that connects it to and disconnects it from +VS (labeled S1P, S2P, S3P, etc.) and has one switch that connects it to and disconnects it from −VS (labeled S1N, S2n, S3N, etc.). The outer electrodes are each, independently, serviced by two switches, with one switch (labeled SO1P) and one switch (labeled SO1N) connecting and disconnecting said first outer electrode (labeled 201) to and from +VS and −VS respectively and one switch (labeled SO2P) and another switch (labeled SO2N) connecting and disconnecting said second outer electrode (labeled 202) to and from +VS and −VS respectively. Said electrodes can be connected in groups so that a group of electrodes can be simultaneously serviced by a single switch. In this arrangement, S1P, S1N, S2P, S2N etc, connect groups of electrodes, hard wired together.
The switches in 4 service all n+2 electrodes. Each inner electrode in said stack of electrodes (labeled 2) has one switch that connects it to and disconnects it from ground (labeled S1G, S2G, S3G, etc.). The second outer electrode (202) has a dedicated switch to and from ground (labeled SO2G). A first outer electrode (201) will also require a dedicated switch (labeled SO1G) to and from ground except when the said electrodes are grouped. With grouped electrodes, S1G eliminates the need for SO1G.
3). Target Conductor. Said Target Conductor, labeled 1 in
4). Support Structure. Said Support Structure (labeled 5), houses and fixes the components of the Charge-Driven Electrostatic Induction System. It also provides the common electrical ground for all components therein.
5). Moving Member (labeled 6 in
A Charge-Driven Electrostatic Induction System operates by first charging a stack of capacitors to emulate a series connection of multiple capacitors and, then using the stepped up voltage from said charged multi-electrode capacitor to induce significant charge in a target conductor separated by a thick insulator (typically air or vacuum) from said stack of capacitors. Stack charging is done in a series of steps so as to enable relatively small working level voltages to charge the individual capacitors in such that the stored charge and energy inside the stack of capacitors emulates that a series arrangement. That is, if the attack of capacitors were charged in series with a very large voltage the same arrangement of stored charge and energy would result.
The method by which electrodes of individual capacitors in said stack can be charged so as to create a result similar to series charging with much higher voltage will be illustrated as per
Using stored energy in a series stack of charged capacitors to induce charge across a large insulation gap is distinct from using an equivalent large voltage source. The stack of capacitors transfers electric energy from internal storage to the insulation gap and the fixed charge distribution on the external electrode nearest said gap adjusts accordingly as does the remainder of the charge in said stacked capacitors. An equivalent very large voltage source would have to supply charge according to the basic equation relating charge, voltage and a a stack of multiple capacitors connected in series. These differences and their ramifications will be discussed in more detail, later.
Speed of operation is maintained even though multiple steps are required by charging a multiple capacitor stack as three sets of parallel capacitors and then trapping the charges so as to leave a stored charge and energy arrangement emulating a series charged capacitor. With this method, a stack of 100 or more capacitors can be charged in three steps and high speed ac operations can be conducted. We will also return to this in more detail.
The Charging Method will be discussed in steps. In the step a), the Charging Method will be discussed for the Isolated Three-Electrode case, with no Target Conductor nearby. In step b), a grounded Target Conductor will be positioned nearby the charged Three-Electrode Capacitor of the first step so the reader can see how the trapped charge on the Three-Electrode Capacitor re-arranges itself to induce charge in said grounded Target Conductor and store electrical energy in the air gap that separates said grounded Target Conductor and said three electrode capacitor. This will illustrate differences in electrostatic induction using trapped charge sources and electrostatic induction using voltage sources in the simplest case. We now begin to add some real world complexity, so in step c) we have said grounded Target Conductor present when we charge said three-electrode capacitor. This illustrates charge formation, electrostatic induction and charge arrangement during expected operational circumstances.
a). Isolated Three-Electrode Case (
The resulting charge arrangement is similar to what would occur if the Three-Electrode Capacitor had been charged by +2VS voltage across electrodes E1 and E3 and the energy stored in the dielectric layers between E1, E2 and E3 also matches the series charge arrangement. The positive charge on E1 and the negative charge on E3 match the series charge arrangement. The middle electrode E2 does also, with a negative charge on its surface nearest E1 and a positive charge on its surface nearest E3. This means we have a +2VS potential difference between E1 and E3, even though only +VS has been used to charge the capacitor(s).
b). Grounded Target Conductor introduced after Charging (
These adjustments are reflected in eq. (1).
Q
1
=Q
11
+Q
12 [2] eq. (1)
Where Q1 is the total charge trapped on electrode E1, Q12 is the charge on E1 that capacitively couples by capacitance with E3 (with E2 as an intermediary) and Q11 is the charge on E1 that couples by capacitance with Target Conductor 1 across capacitance C1. C2 is the capacitance between electrodes E1 and E2 and between E2 and E3.
The voltage on E1 is:
Q
11
/C1=Q12/0.5C2 [3] eq. (2)
Which provides information on the charge distribution on E1 as per:
Q
11
/Q
12=2C1/C2 eq. (3)
From equations (1) and (3) we have:
So we can see that some of Q1 is diverted from coupling with E3 to coupling with Target Conductor 1 and we postulate the charge and voltages on E2 and E3 must adjust accordingly. The amount of charge available to couple with E2 and E3 has been reduced so there is less attractive electrostatic force to hold charge on E3 and the charge on E3 disperses back into ground until a new balance is restored at a lower level. E2 responds by reducing the positive charge on one surface and the negative charge on the other surface by allowing limited charge cancellation (or recombination) consistent with the new balance point. The charge neutrality of E2 is unchanged.
If E3 is disconnected from ground before Target Conductor 1 is introduced, it seems Q11=0 because the positive charge on E1 is balanced by a trapped negative charge on E3 and by Gauss' Law of Charge, the electric flux is zero outside the closed system E1, E2, E3. When E3 is grounded, the system seeks the balance just described. Once the balance is reached and Q11 comes into existence, E3 can be connected and disconnected to ground with no effect on Q11.
c). Grounded Target Conductor present during Charging.
When a grounded Target Conductor is present throughout a charging cycle, additional electric energy is stored in C1 during the charge cycle as per
The added extra charge on said first electrode is given as:
ΔQ11=VSC1=ΔQ1, ΔQ2=0 eq. (6)
For a total charge trapped on E1 of:
We note, as per
We note that a Three-Electrode Capacitor, charged to emulate a series capacitor between said first and third electrodes has an approximately 2VS potential on its outer electrodes while a Two-Electrode Capacitor has VS. We can repeat the pattern by adding a fourth electrode E4 and third dielectric film to obtain approximately +3VS between electrodes E1 and E4. In this instance said third electrode would be connected to source voltage VS and capacitance coupled to a grounded fourth electrode. The resulting added positive charge could be trapped on said third electrode and we would have +3VS between said electrodes E1 and E4 with net positive charge on said electrode E1, net negative charge on said electrode E4 and self-cancelling positive and negative charges on electrodes E2 and E3. This process can be continued until one hundred or more capacitors are added to the stack.
For the n capacitors stacked in series, we estimate the effective series capacitance of the stack as:
C
ST
=C
2
/n [4] eq. (9)
Q1 trapped on electrode E1 in a stack of n capacitors in series has two parallel capacitance paths to ground, C1 and CST=C2/n.
This leads to
Which simplifies to:
Q
1
C
1
=Q
11(C1+CST) eq. (9c)
Without using stacked capacitors we could expect an induced charge of:
Q10=VSC1 eq. (11)
Dividing eq. 10 by eq. 11 we find:
Charge-Driven Electrostatic Induction has operating characteristics that differ from Voltage-Driven Electrostatic Induction, particularly when capacitors are used to supply the charge-drive. In some respects a capacitance-based Charge-Drive is analogous to a current source. There is a fixed amount of current available in a current drive and there is a fixed amount of trapped charge available in capacitance-based Charge-Drive. But, capacitance-based Charge-Drive has a unique problem in separating the charge. Charging a capacitor can yield equal and opposite charges in close proximity to each other. Even if the charges are large, if they are in close proximity to each other, their electric fields tend to cancel when we try to perform charge induction across a large insulation gap. Achieving charge separation and isolation is as important as achieving large charges. Electret devices use one method of achieving charge separation so charge-drive can be employed. This Invention uses a method to separate charge by the length of a stack of capacitors as its method. The method used in this invention can completely remove and return charge or can change polarity on command, while electret devices have a fixed polarity.
To obtain proper charge separation using low voltage sources requires capacitive stacks with electrodes numbering in the hundreds. If we charge them one electrode at a time, responding to high frequency signals becomes problematic. We seek a means by which we can charge several at a time but, still obtain a series charge arrangement in the stack. We choose to organize the electrodes in groups of three, with a first, middle and third electrode in each group as illustrated in
We now detail how this charging system will work. In the first step, all first set electrodes (2O1, 2I3, 2I6) are connected to source voltage +VS and all second set electrodes (2I1, 2I4, 2I7) are connected to −VS as per
From eq. (13) above we can determine the effective voltage that can be applied to induce electrostatic charge in the Target Conductor and electric energy in the air/vacuum gap C1.
Performance is measured as increased voltage across an insulation gap. We will assume the gap to be air or vacuum for our performance estimates.
We choose 3M embedded capacitance material C1011 [5] for our dielectric material between electrodes. This material is 0.00043 in thick with dielectric constant of 20. It has a dielectric strength of 3300 volt/mil and is tested to over 100 volts DC. This calculates to 1419 volts dielectric strength for our 0.43 mil thick layers. We assume operating voltages of 400 volts (+/−200 v using push pull operation). The dielectric layer is coated by copper 0.0015 in thick. The actual thickness of a capacitor is 0.00043+0.0015×2=0.00343 in. Of this, only 0.00043 in is used for separating the positive charges, which is critical to electrostatic induction. We expect we can reduce the copper thickness to 0.0005 in without any adverse effects, especially where multi-layer construction is employed as in our case.
For our case, we wish to penetrate an air/vacuum gap of 0.030 in. (typical for motor or noncontact energy transfer between moving joints). This means C2/C1=20(0.030)/0.00043=1395.3488372093
This makes our Gain
We want n as large as possible. We try 200=n. This provides a gain of 174.927113702624 to 1. Using multiple layers means increasing device thickness so we must now address this concern. For n layers of dielectric, we use n+1 electrodes.
(n+1)TL=TD eq. (15)
(200+1)(0.00093 in)=0.18693 in.=TD (total device thickness)
eq. (16)
We choose VS=200 volts, we obtain the electrostatic induction effects of 35 KV. Using VS=±200 volts in a push pull configuration we obtain the electrostatic induction effects of 70 KV. We do not expect electric discharge to be a problem, 70 KV over 0.030 in is equivalent to 2.333 KV per mil. As stated earlier, the C1011 dielectric material has a dielectric strength of 3.3 KV per mil. In the event discharge does become a problem, source voltage can be lowered.
An electrostatic induction system that can produce large electric fields over air or vacuum insulation gaps on the order of 0.030 in, has applications for motors, generators and power transfer units. These applications typically require magnetic induction across a 0.030 in air gap (because these applications involve two objects, moving with respect to each other and involving rolling bearings and the safe clearance allowed in this circumstance is on the order of 0.030 in). An electrostatic induction system that can produce large electric fields over air or vacuum gaps can also be applied where electrets had been previously used, such as electrostatic microphones and oscillating power generators or motors.
A motor application will now be described whereby a moveable, charge neutral conductor moves transverse to the E-Field projected into the air/vacuum gap C1, according to
Energy stored in field reduces as capacitance of moving member increases. We want the amount of energy in an air gap. The force is the rate of change of energy in the air gap. The energy is
dE
G
/dX={right arrow over (F)}
X
=V(dV/dX)(C11+C12)+(½)V2(dC11/dX+dC12/dX) [7] eq. (20)
C
11=ε0A11/d11, C12=ε0A12/d12, A11=WX, A12=W(X0−X)
dC
11
/dX=ε0W/d11, dC12/dX=ε0W(−1)/d12
dV/dX=−Q
1(C11+C12)−2(ε0W)(1/d11−1/d12)
dV/dX=−V
S(C1+C2)(ε0W)−2(1/d11−1/d12)−2(ε0W)(1/d11−1/d12)
Q
1
=V
S(C1+C2)
This simplifies to:
dV/dX=−V
S(C1+C2)(ε0W)−1(1/d11−1/d12)−1
We plug this into eq. 20 resulting in:
{right arrow over (F)}
X
=−VV
S(C1+C2)(ε0W)−1(1/d11−1/d12)−1+0.5 V2(ε0W)(1/d11−1/d12) eq. (21)
We will now examine the rotary motor case.
We now perform steps to determine dF. We begin by determining C.
Substituting the results of eq. (34) into eq. (20) results in:
Substituting the results of eq. (35) into eq. (31) results in:
We know that V is a function of θ so we calculate V for the angle we are considering, using known design parameters and eq. 39. We then substitute the value for V back into eq 38 to calculate torque.
From eq. (33) we have:
This computes to:
We are working with a fixed amount of trapped Charge VSC2 which will distribute itself between C11 and C12 as per:
Thus we can calculate V for any θ using eq. (39) and can substitute that V into eq. (37) to determine {right arrow over (T)}.
A motor application will now be described whereby a moveable, grounded electrical conductor 1 moves to increase or decrease the air/vacuum gap according to
A Power Transfer application, according to
The load is powered by negative charge when S2Ig is opened, S2I is closed to load and S1I is opened and S1Ig is closed. When discharge through ZL is completed, the system can be reconfigured to begin charging again.
With this introduction we will introduce the equations for predicting performance and providing design guidance for specific device applications. We will, first estimate the amount of charge that can be induced across an air/vacuum gap followed by the power that can be transferred across the gap. The power transfer function equations are similar to those used for a motor application where movement is in the direction of the electric field except that there is no motion and the capacitance of the air/vacuum gap is constant and electrostatic force across the air/vacuum gap is not a factor.
With VX set to zero, Q1 disperses and seeks the nearest ground. It has two choices, C1 and C2 and it will prefer C2 by a C2/C1 ratio.
Equation 59 shows Q2L>>Q11 so most of the charge on electrode 1 moves to electrode 2L during dispersion, with multiple pumping steps not needed. This means nearly all the charge is transferred to 1L and 2L during each step and a relatively large current can be supplied to power ZL on a continuous basis.
We start with the energy stored in a capacitor with electrodes 1L and 2L and examine how much power can be supplied to a load with this stored energy. We also examine how fast we can resupply the stored energy and how much sustained power can be delivered.
This capacitor must cycle between being charged and supplying current to ZL and the speed of this cycle determines the rate of energy, or power, transferred.
The cycle sequence uses two steps, but one of the steps requires charging the Stack, which requires three steps. Thus, in effect, we have a four step for each burst of energy that is supplied to the load. We choose a step frequency so we can achieve an ac load frequency of 25% of the step frequency. This suggests we speed up the drive frequency by a factor of four to obtain suitable power transfer frequency. Power transfer frequencies on the order of a ghz seem possible.
Generation of electricity can be achieved in a reverse application of the electrostatic motors described in 1a and 1b above. In the generator application, an electric field is maintained in the air or vacuum gap by a charged stack of capacitors, the field is periodically changed by using mechanical power, induced ac electrical power is induced in the process and that induced electrical power is stored to be used as needed. The charged stack of capacitors maintains the electric field in the air or vacuum gap without external electrical power because it has charge trapped in place so we have a method and device for converting mechanical power to electrical energy or an electrostatic generator.
The charged Stack of Capacitors stores electrical energy in the air or vacuum gap as per eq. 56.
4a). Electrostatic Generators in which the Moving Member moves in a direction transverse to the electric field which stores energy in the air or vacuum gap.
4a1). Rotary Case
For a rotary electrostatic generator, mechanical power can be used to rotate a moving member as through an air or vacuum gap as shown in
4a2). Linear Case
A linear electrostatic generator can use mechanical power to oscillate back and forth through a region where the air or vacuum gap contains stored electric energy. This motion serves to generate induced ac current and stored electrical energy similar to that done by a rotary electrostatic generator. The circumstances and effects of
4b. Electrostatic Generators in which the Moving Member moves in a direction parallel to the electric field which stores energy in the air or vacuum gap.
In this application, a grounded Moving Member is moved by mechanical force in an air or vacuum gap with electric energy stored therein, with the movement parallel to the direction of the electric field supplying the electric energy in the gap. The movement in one direction causes the air or vacuum gap to decrease and the movement in the opposite direction causes the gap to increase as per
The Energy Scavenger application, according to
The Energy Scavenger application (
A Charge-Driven Electrostatic generator can function as a sensor. As shown in 4. GENERATOR APPLICATIONS, a Charge-Driven Electrostatic generator can provide stored electric energy in an insulation gap between an outer electrode on the generator and a grounded conductive moving member, with power off. When the generator moving member moves in response to an external time variable mechanical force, the electric energy stored in the gap is disturbed and the charge on the grounded outer electrode of the generator changes in a time variable manner. When a load is inserted between ground and the outer electrode, time varying electric power is driven through the load or storage device. The time varying electrical power going through the load produces a time varying voltage across the load and current through the load that can be sensed in frequency, phase and amplitude and information about the nature of the mechanical force driving the moving member is provided. The result is a sensor which measures the behavior of the mechanical force acting on the moving member.
When the moving member is a diaphragm being driven by sound, we have a microphone and this microphone is analogous to an electret microphone with some notable advantages. An electret is permanently polarized with a fixed surface charge. This charge attracts foreign elements with opposite charge which tend to degrade performance over time. A Charge-Driven Electrostatic Induction sensor can simply change the charge every so often and clean the offending foreign elements by repulsion. Also, current electret technology provides a limited εR so, the surface charge available is limited, which limits microphone performance as well. Embedded capacitor technology has a much better energy storage capability with an εR=20 and dielectric thicknesses as thin as 0.00043 in. [5]. This means that large amounts of electrical energy can be stored in a stack of capacitors using modest voltage sources. This also means that surface charge trapped on the outer electrode nearest the diaphragm can be large and microphone performance improved as a result. Another advantage for Charge-Driven Electrostatic Induction microphones are in their ability to measure signal at the grounded outer electrode. The charge on the grounded outer electrode changes with diaphragm movement so measurements can be taken by inserting a measuring system between the grounded outer electrode and ground. The electronics in such a measuring system would be relatively stationary and would be in a protected position. Diaphragm requirements for Charge-Driven Electrostatic Induction microphones and electret microphones are similar and are well within the state of the art. A passive sleep mode (as described in section 4c) above) can be used to reduce or eliminate battery requirements for a Charge-Driven Electrostatic Induction microphone. The method as applied to a microphone would be similar to that described in section 4c, but with application specific adjustments.
5a1). Sensing Method
An application is illustrated, according to
5a2). Sensing Method Using Passive Electric Components
An application is illustrated, according to
5a3). Sensing Method Options
There is also the option of using 5a1) and 5a2) in combination whereby the device is operated in sleep mode until sufficient energy is accumulated to operate in active mode.
Any force or energy source which can disturb the electrostatic energy stored in the insulation gap can be sensed and measured, particularly if it is time variable. Some of these energy sources mechanically act on the moveable member. Some of these act on the moveable member indirectly through an intermediate member. Some of these operate on the electric energy stored in the insulation gap without moving the moveable member.
5b1) Sensors Using Mechanical Energy to Move the Moveable Member
In this section we examine the error that attends the assumption of net zero charge on the internal electrodes. We find that there is a slight net charge on each of the internal electrodes and that this net charge progressively increases as we go down the stack of electrodes. On the other hand, we also find that the error is not great and the net charge helps performance so we are left with confidence that our assumption is good to <5% for the applications described.
The argument in this detailed description assumes that when an interior electrode is charged positive, the negative charge on that interior electrode is held in place by the trapped positive charge on the previously charged electrode. This is an approximation and more accurately we can expect that most, but not all of the negative charge will be held in place. (The argument applies for negative charge voltage as well.) With the first set of 3 electrodes (1 outer and 2 inner), we see the first signs of error in our approximation. In charging the 2 inner electrodes, we raise the effective voltage of the outer electrode nearest the target conductor. This results in more trapped positive charge on the outer electrode coupling with the target conductor and less coupling with the nearest inner electrode. At the same time, the other surface of the effected inner electrode receives a full positive charge, so we have a slight net positive charge on the first inner electrode rather than the net zero charge used in our approximation. When we charge the next pair of inner electrodes, we raise the voltage of the outer electrode again and divert more trapped positive charge to couple with the target conductor. Again, less negative charge is held in place and again the net charge on this new inner electrode is slightly positive, this time slightly more so. This continues as the entire stack of electrodes is charged. With each charge sequence, we gather more and more net positive charge.
We begin by examining the loss of negative charge in the first set of 3 electrodes, outer electrode 2O1 and inner electrodes 2I1 and 2I2. We examine the loss of negative charge on 2I1 when 2I1 and 2I2 are charged.
With our initial charge sequence, we apply VS to electrode 2O2 and ground electrode 2I1. With the target conductor also grounded we have positive charge induced on both surface of 2O1. Most of the charge is between 2O1 and 2I1 because C2>>C1.
V
S(C1+C2)=Q2O1, V2O1=VS Charge trapped on 2O1 (eq. 60)
VSC1=Q10 (original charge across air gap) (eq. 61)
VSC2=Q11 (original charge induced between 2O1 and 2I1) (eq. 62)
We trap the positive charge on 2O1 and apply VS to 2I1 with 2I2 grounded. This causes the voltage potential of 2O1 to be raised above VS.
(V2O1−VS)C2+V2O1C1=Q2O1=VS(C1+C2) (eq. 63)
(V2O1−VS)C2=negative charge held in place on 2I1 (eq. 64)
V201C1=charge now induced across air gap to target conductor (eq. 65)
We rearrange eq. 63 to solve for V2O1.
VSC2=(positive charge held in place on 2I1) (eq. 70)
Subtracting (eq. 69) from (eq. 70) yields the net charge on 2I1 when 2I1 is disconnected from ground and the net charge is trapped.
We will apply some expected values to see what these equations tell us. We expect C1 to be part of an air or vacuum gap typically 0.020 in. We expect C2 to be part of a high capacitance material, such as 3M with an insulation gap of 0.00043 in and εR=20.
And results using (eq. 71) might typically be on the order of:
Net charge is positive, but almost zero (0.072% net+) If this trend continues on a linear basis, we have n 0.0007161534234 (net positive charge accumulated in the stack of electrodes. For n=200, we accumulate 0.14323068468% positive charge in the stack which we will neglect. We do not expect the relationship to be linear, preliminary indications are it is a mathematical series. A more proper solution would probably involve an electrostatic simulation. We conclude the approximation in which we assume charge trapped on electrode 2O1 arranges itself according to the relationship between C1 and nC2 is conservative. This assumes no net positive charge on the interior electrodes. The additional positive charge can only help as per Gauss' Law of Charge. Our approximation looks good to <5% for an air gap of 0.030 in and n=200.
Although the invention has been described with reference to certain preferred embodiments, it will be appreciated that many other variations and modifications thereof may be devised in accordance with the principles disclosed herein. The invention, including the described embodiments and all variations and modifications thereof within the scope and spirit of the invention, is defined in the following claims.
The U.S. patent application claims the priority of U.S. Provisional Application No. 61/458,238 filed on Nov. 19, 2010.
The invention is related to an invention shown and described in Provisional Patent, U.S. Ser. No. 61/458,238 entitled “Charge-Driven Electrostatic Induction”, filed in the name of John M. Vranish, the present inventor on Nov. 19, 2010. The above are assigned to the assignee of the present invention. The teachings of this related application is, herein meant to be incorporated by reference. The invention is also related to an invention shown in: Vranish, J. M., Device, System and Method for a Sensing Electric Circuit, U.S. Pat. No. 7,622,907, Nov. 24, 2009. [“Driven Ground”] the rights to which are held by the US Government.
Number | Date | Country | |
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61458238 | Nov 2010 | US |