Patent Application
20110116205
The embodiments of the present invention are related to ion wind fans, and in particular to a collector electrode for an ion wind fan.
It is well known that heat can be a problem in many electronics device environments, and that overheating can lead to failure of components such as integrated circuits (e.g. a central processing unit (CPU) of a computer) and other electronic components. Most electronics devices, from LED lighting to computers and entertainment devices, implements some form of thermal management to remove excess heat.
Heat sinks are a common passive tool used for thermal management. Heat sinks use conduction and convection to dissipate heat and thermally manage the heat-producing component. To increase the heat dissipation of a heat sink, a conventional rotary fan or blower fan has been used to move air across the surface of the heat sink, referred to generally as forced convection. Conventional fans have many disadvantages when used in consumer electronics products, such as noise, weight, size, and reliability caused by the failure of moving parts and bearings.
A solid-state fan using ionic wind to move air addresses the disadvantages of conventional fans. However, providing an ion wind fan that meets the requirements of consumer electronics devices presents numerous challenges not addressed by any currently existing ionic wind device.
Ion wind or corona wind generally refers to the gas flow that is established between two electrodes, one sharp and the other blunt, when a high voltage is applied between the electrodes. The air is partially ionized in the region of high electric field near the sharp electrode. The ions that are attracted to the more distant blunt electrode collide with neutral (uncharged) molecules en route to the collector electrode and create a pumping action resulting in air movement. The high voltage sharp electrode is generally referred to as the emitter electrode or corona electrode, and the grounded blunt electrode is generally referred to as the counter electrode or collector electrode.
The general concept of ion wind—also sometimes referred to as ionic wind and corona wind even though these concepts are not entirely synonymous—has been known for some time. For example, U.S. Pat. No. 4,210,847 to Shannon, et al., dated Jul. 1, 1980, titled “Electric Wind Generator” describes a corona wind device using a needle as the sharp corona electrode and a mesh screen as the blunt collector electrode. Such a prior art configuration disclosed by Shannon, et al. is illustrated by
U.S. Pat. No. 7,122,070 to Krichtafovitch, dated Oct. 17, 2006, describes a wire to bar electrode geometry—illustrated by FIG. 2—where a wire is used as the sharp electrode and a metal bar is used as the blunt electrode. U.S. Pat. No. 4,689,056 to Noguchi et al., which dates back to 1987, also discloses a substantially similar wire to bar configuration, except the bars are referred to as rods.
The bar collector electrodes 206 are also coplanar with each other, and the planes of the emitters and the collectors are parallel with each other, and perpendicular with the planes of the emitter-collector pairs. Thus,
One challenge to the closer spacing of the corona electrode to the collector electrode, is that to create ion wind, it is desirable to have a high electric field strength at the corona electrode and a low electric field strength at the collector electrode. Furthermore, the high voltage emitter can also interfere with each other, making it difficult to space corona wires or emitter electrodes in general in close proximity.
Since electric fields tend to be stronger around sharp points, corona electrodes have been implemented as sharp points, the edges of blades, or thin wires, while collector electrodes have been implemented as mesh screens, larger bars or rods, or solid plates. For example, the electric field around a corona wind device having several wire corona/bar collector electrode pairs—for example the geometry shown in FIG. 2—is now described with reference to
The present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements. Moreover, where certain elements of the present invention can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention. In the present specification, an embodiment showing a singular component should not necessarily be so limited; rather the principles thereof can be extended to other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present invention encompasses present and future known equivalents to the known components referred to herein by way of illustration.
The collector electrode 400 has a number of openings 402 through the electrode 400. In one embodiment, the openings are arranged in distinct rows so that the centers of the openings of one row are substantially aligned with a line parallel to the lengthwise edge of the collector electrode 400. For example, in
In the embodiment illustrated by
In one embodiment, the openings of two distinct rows are separated by each other by some distance (d) over which there are no openings 402 on the collector electrode 400. In
The pitch between openings 402 is defined as the distance from the center of one opening to the center of an adjacent opening in the same row. It is to be noted that the pitch includes the spacing distance s. In one embodiment, the relationship of the pitch to the spacing distance s is that the pitch is approximately five (5) times the spacing distance.
For example, in one embodiment the pitch is 1 mm and the spacing distance is 0.2 mm. This results in the active area of the collector electrode 400 being approximately 80% open. In one embodiment, the pitch and spacing distance is selected to make the percentage opening—the surface area of the collector electrode 400 comprised of openings 402—in the range of 70-90% open. In one embodiment, the row separation distance d is approximately the same as the spacing interval s, although in other embodiments they can be unrelated.
One embodiment of the present invention is now described with reference to
The collector electrode 400 is supported by a support structure 420. Corona wires 424 are supported by a second support structure 422. In one embodiment, the two support structures are joined together or constructed from one piece, so that the same support structure (collectively referred to by the numeral 430) holds the corona wires 424 as well as the collector electrode 400. This support structure 430 is made out of a dielectric material, such as plastic, and will sometimes be referred to herein as the “isolator” 430.
In the embodiment shown in
Corona electrode 424a is similarly positioned by the isolator 430 above openings 402a that are aligned in a row. Thus, the spacing between the corona electrodes 424—represented in
In the embodiment shown in
One advantage of slit shaped openings 402 is that they are simple to manufacture. Another advantage of slit shaped openings 402 is that their rounded edges in the plane of the top surface of the collector electrode 400 (the surface facing the corona electrodes 424) help in lowering the electric field strength at the collector electrode 400, since electric fields tend to focus around sharp objects. As shown in the Figures, the openings 402 are rectangular and have fillet corners. In the Figures, the fillet corners provide a full radius that connects the two lengthwise sides of the rectangular openings. Other fillet corners can be used in other embodiments.
The distance that the corona electrodes 424 are held above the collector electrode 400 is represented by the quantity (g) in
It should be noted that the values in Table 1 are approximate, and apply only to smooth bare wire corona electrodes using DC power for negative corona wind. They are provided here merely as example size ranges, and do not limit any aspects of the inventions disclosed herein to these specific size ranges.
There are numerous possible designs for the isolator 430 element. For simplicity and ease of understanding, only simple isolator designs are described herein, such as a rectangular frame of thickness t, or two dielectric columns attached to either end of the collector 400 across which the corona wires 424 can be stretched. For the purposes of the present Application, the collector 400 and corona electrodes 424 are all attached to the isolator 430, such that the isolator 430 established the geometric relationship between the electrodes.
Similarly,
It can be noted with reference to
Another embodiment of the present invention is now described with reference to
In the embodiment shown in
In one embodiment, the opening 402c is only rounded along the straight or rectangular portion of a slit like opening 402c that is parallel with the width of the collector electrode 400. In another embodiment—as shown in FIG. 7—the entire circumference of the edge of opening 402c is thus rounded.
Such opening as described with reference to
As can be seen from the Noguchi (U.S. Pat. No. 4,689,056) and Krichtafovitch (U.S. Pat. No. 7,122,070) patents mentioned above, as well as the descriptions of
In one embodiment of the present invention, the collector electrode is made up of a number of rods or wires, but the number of the rods that make up the collector electrode is significantly greater than the number of coronal electrodes. In one embodiment, the number of collector electrodes (col) is an integer multiple of the number of coronal electrodes (cor). Mathematically this can be expressed as col=a*cor, where a>=2. For example, an embodiment in which cor=3 and a=3 is now described with reference to
There are three corona electrodes 600a, 600b, 600c. As described above, the corona electrodes ionize the air in their vicinity in response to a high voltage potential. The ions thus generated move towards the collector electrodes 606a-606i along the electric filed lines, some of which as illustrated in
In this embodiment, since there are three corona electrodes 600, and there are three times as many collector electrodes 606, there are nine collector electrodes shown in
For example, the electric field lines from corona electrode 600b to collector electrodes 606c-606g can be seen as being more forward directed than the electric field lines shown in
The collector electrodes 606 are not subject to such spacing limitations, but each collector electrode 606 does obstruct airflow to a certain extent. Therefore, the integer multiple a can be set to not have an excessive number of collector electrodes 606. For some ion wind fan applications, for example, a<5. Other advantages of providing multiple collector electrodes for each corona electrode include lower electric field strength at the collector electrodes that reduces the likelihood of sparks between corona and collector electrodes, and a reduction in the number of corona electrodes 600 that could interfere with one another.
In the embodiment shown in
According to another embodiment, the number of collector electrodes (col) is greater than an integer multiple of the number of coronal electrodes (cor). Mathematically this can be expressed as col>a*cor, where a>=2. By adding additional collector electrodes the performance of the fan may be balanced more evenly.
Yet another embodiment for an ion wind fan electrode geometry is shown in and described with reference to
Since electric field lines cannot cross, in the example shown in
Such a geometry can further reduce the electric field strength around the collector electrodes 608. The number of electrodes for such arc-situated electrodes can vary, and not every arc need contain the same number of collector electrodes 608. In one embodiment, to keep the collector-to-corona ratio even, the number of electrodes can be expressed mathematically as: col=(a*cor)−(cor−1), where a>=3. For example, in
As has been described further above, emitter electrodes (also referred to as corona electrodes) have been conventionally implemented in laboratory environments as pins, wires, or blades. A blade is a substantially triangular-shaped slab of metal with a sharpened edge. However, each of these types of corona electrodes has disadvantages when used in a mass produced ion wind fan, where cost of construction can become an important consideration. For example, wires, especially very thin wires, can be difficult to handle by automated assembly machines. Blades, on the other hand, must be individually machined at some expense and time cost.
One embodiment of the present invention is now described with reference to
The shim electrode 750 can be made of numerous metals, such as copper, nickel, silver, aluminum, tungsten, or other alloys and metal combinations, and other such conductors. One advantage of using shims for emitter electrodes is that various metals are sold in shim form by metal merchant companies, thus making the process of sizing an electrode from a shim simple and cost effective. The electrodes can either be ordered in custom shim sizes, or they can be stamped by a custom die tool from sheets of metal having the desired shim thickness (t).
Since a shim electrode 750 is thin, it needs some form of structural support when used as an emitter electrode in an ion wind fan. One embodiment of such an ion wind fan implementing shim corona electrodes is now described with reference to
Since
As shown in
The distance that a shim corona electrode 750 is buried in the isolator 802 is represented by the quantity (b) in
The spacing between shim corona electrodes 750 is represented by the quantity (s) in
Therefore, one additional advantage of using shim corona electrodes 750 as opposed to using blade-type corona electrodes is that the corona electrodes can be placed closer together, since the bottom of the shims is not substantially wider than the tip of the shims. By being able to place corona electrodes in closer proximity to one another—essentially decreasing the possible value of s—more corona electrodes can be provided in a given space, thus possibly increasing ion production and fan performance.
While keeping the shim support members 810 as thin as possible will increase potential airflow trough the ion wind fan 800, making the shim support members 810 thicker will stiffen the chassis of the ion wind fan 800, will be less prone to damage, and will be easier to manufacture. While the desired thickness of the shim support members 810 will depend on specific implementation factors such as the dielectric material used for the isolator 802 (which includes the shim support members 810) and the thickness of the shim emitter electrodes being supported by the shim support members 810, in one example, the shim support members are approximately 0.5-2 mm thick.
According to one embodiment, the shim support members 810 have an areo-dynamic profile, as can be seen in
Also shown in
In one embodiment, the shim emitter electrodes 750 extend past the active area of the ion wind fan 800 into an attachment area 814. Since these non-active end areas (814) of the ion wind fan 800 do not have the same aerodynamic requirements as the shim support members 810, the shim emitter electrodes 750 can be more robustly supported at each end of the fan 800. Furthermore, electrical connections to the shim emitter electrodes 750 can be arranged in the attachment areas 814 or the ion wind fan 800.
In
As set forth above, mass-producing an ion wind fan using wire corona electrodes has the potential disadvantage of developing automated tools able to handle wires. This has not been a key issue in ion wind devices in the past, as these devices have been relatively large in scale when compared to ion wind fans used for thermal management of consumer electronics devices. Ion wind fans as described in the present application tend to have very thin corona wires, usually within the range of 10-350 microns in diameter. The precise positioning and tensioning of such thin wires is a challenge for many automated tools suitable for the mass production of an ion wind fan according to embodiments of the present invention.
Using shim emitter electrodes, as described with reference to FIGS. 10 and 11A-C above eliminates the need for wire stringing and tensioning. In one embodiment, the shims electrodes are affixed to the isolator element by injection molding the isolator element directly around the shim electrodes. One embodiment of manufacturing such an ion wind fan is now described with reference to
In block 150, an injection molding tool grasps one or multiple shims. The tool grasps the shim at the top edge, where the shim will protrude from the isolator element. The injection molding tool thus forms a cavity containing the non-grasped portion of the shim. In block 152, a molten dielectric substance (such as plastic) is then injected—also referred to as “shot”—into this cavity. After the plastic cools and solidifies, in block 154, the tool releases the grasp around the shim and the cavity, thus releasing the formed isolator element into which the shim has been molded such that it protrudes out forming an emitter electrode, as shown in
As set forth above, the shim emitter electrodes generally only protrude from the isolator element by approximately 0.2-0.8 mm and are only about 1-5 mils (about 25-225 microns) in thickness. Therefore, holding a thin shim steady while grasping less than a 1 mm strip during the injection of high velocity and high viscosity plastic can present a challenge. Thus, according to another embodiment, the isolator element including the embedded shims can be manufactured according to a process described with reference with
In block 160 a shim is grasped by the isolator molding tool in both primary and secondary locations. The primary locations will remain exposed, as discussed with reference to
As can be see in
In one embodiment, as shown in
Furthermore, while two secondary locations 822 are shown in
In block 162, a first shot of molten dielectric material is injected into the a first isolator mold. This shot will embed the shim 750 into the first shot isolator 830 around the areas not grasped by the tool, that is, in outside of the primary 824 and secondary locations 822. In one embodiment, opening 820 are provided through the shim. One purpose of the openings 820 is to reduce the resistance to the flow of molten plastic created by the shim 750 during injection. Since the flow of injected plastic can warp and move the thin shim 750, such openings 820 (shown in dotted lines in
As shown in
In block 164, the shim 750 is released at the secondary locations. At this stage of the process, a first-shot version of the isolator element has been formed. In block 166, the first-shot isolator element is re-grasped by the tool. The portion of the tool grasping the primary locations 824 of the shim continues to grasp the primary portions 824. The tool can grasp the first-shot isolator element at any location where no more plastic material is to be injection molded, such as the center portion or the end portions of the first shot isolator element 830 shown in
In block 168, a second shot of molten dielectric material is shot into a second isolator mold, while the shim 750 is grasped in the primary locations 824, and the first shot isolator element is grasped at another location. This second shot fills in the secondary locations left exposed on the first-shot isolator element 830. Finally, in block 170, the finished isolator element 802 with shim emitter electrodes embedded into the isolator element 802 is released by the tool, and the isolator and shim electrodes can be removed from the mold.
According to one embodiment, blocks 160-164 are repeated for each shim emitter electrode 750 and shim support member 810 for the ion wind fan. Then after the shim electrodes are embedded into the shim support members, with the secondary locations 822 still being exposed, the first-shot shim support members are inserted into a second molding tool to deliver the second plastic injection of blocks 166-170, thus forming the isolator 802 and embedded shim electrodes 750 of the ion wind fan 800. For example, blocks 160-164 would be repeated (or performed in parallel) three times—once for each emitter 750—to produce the ion wind fan 800 shown in
As has been described further above, emitter electrodes have been conventionally been implemented in laboratory environments as pins, wires, or blades. In the laboratory, these emitter geometries are usually suspended above a collector. For example, a blade is generally suspended from the high voltage power supply connection wire that provides the voltage potential difference between the emitter and the collector electrodes.
Several embodiments for embedding a shim electrode into an isolator element of an ion wind fan were described with reference to
While the example ion wind fan described and pictured above are shown as having two emitter electrodes, any number of emitter electrodes can be used, including one, to create one or more-channel ion wind fans. While most electronics cooling applications using a wire emitter will have between 1-10 emitter electrodes, the invention is not limited to any range of emitter electrodes used.
In the descriptions above, various functional modules are given descriptive names, such as “ion wind fan power supply.” The functionality of these modules can be implemented in software, firmware, hardware, or a combination of the above. None of the specific modules or terms—including “power supply” or “ion wind fan”—imply or describe a physical enclosure or separation of the module or component from other system components.
Furthermore, descriptive names such as “emitter electrode,” “collector electrode,” and “isolator,” are merely descriptive and can be implemented in a variety of ways. For example, the “collector electrode,” can be implemented as one piece of metallic structure, but it can also be made of multiple members spaced apart, and connected by wires or other electrical connections to the same voltage potential, such as ground. Similarly, the isolator can be the substantially frame-like component, but it can have various shapes. The electrodes and the isolator are not limited to any particular material; however, the isolator will generally be made of a dielectric material, such as plastic, ceramic, and other known dielectrics.
This application claims the priority benefit of U.S. Provisional Patent Application No. 61/243,965 entitled “EMITTER AND COLLECTOR ELECTRODES FOR ION WIND FAN,” which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61243965 | Sep 2009 | US |
