Patent Application
20110261499
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. One such challenge faced by currently existing ion wind devices is sparking across electrodes and dust accumulation. Sparks can damage electrodes and other electronic components, create a sharp audible noise, and can create electromagnetic interference (EMI). Dust can change the electrostatics of an ion wind fan resulting in degraded performance.
FIGS. 4A(1) and (2) is a simplified cross-sectional view of an ion wind fan according to one embodiment of the present invention;
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.
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, getter 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. The concept of ion wind has been implemented in relatively large-scale air filtration devices, such as the Sharper Image Ionic Breeze.
An electronic device may need thermal management for an integrated circuit—such as a chip or a processor—that produces heat, or some other heat source, such as a light emitting diode (LED). Some example systems that can use an ion wind fan for thermal management include computers, laptops, gaming devices, projectors, television sets, set-top boxes, servers, NAS devices, memory devices, LED lighting devices, LED display devices, smart-phones, music players and other mobile devices, and generally any device having a heat source requiring thermal management.
The electronic device can have a system power supply 16 or can receive power directly from the mains AC via a wall outlet, Edison socket, or other outlet type. For example, in the case of a laptop computer, the laptop will have a system power supply such as a battery that provides electric power to the electronic components of the laptop. In the case of a wall-plug device such as a gaming device, television set, or LED lighting solution (lamp or bulb), the system power supply 16 will receive the 110V mains AC (in the U.S.A, 220V in the EU) current from an electrical outlet or socket.
The system power supply 16 for such a plug or screw-in device will also convert the mains AC into the appropriate voltage and type of current needed by the device (e.g., 20-50V DC for an LED lamp). While the system power supply 16 is shown as separate from the IWFPS 20, in some embodiments, one power supply can provide the appropriate voltage to both an ion wind fan 10 and other components of the electronic device. For example, a single driver can be design to drive the LEDs of and LED lamp and an ion wind fan included in the LED lamp.
The electronic device also includes a heat source (not shown), and may also include a passive thermal management element, such as a heat sink (also not shown). To assist in heat transfer, an ion wind fan 10 is provided in the system to help move air across the surface of the heat source or the heat sink, or just to generally circulate air (or some other gas) inside the device. In prior art systems, conventional rotary fans with rotating fan blades have been used for this purpose.
As discussed above, the ion wind fan 10 operates by creating a high electric field around one or more emitter electrodes 12 resulting in the generation of ions, which are then attracted to a collector electrode 14. In
Similarly, the collector electrode 14 is shown simply as a plate in
To create the high electric field necessary for ion generation, the ion wind fan 10 is connected to an ion wind power supply 20. The ion wind power supply 20 is a high-voltage power supply that can apply a high voltage potential across the emitter electrodes 12 and the collector electrode 14. The ion wind fan power supply 20 (hereinafter sometimes referred to as “IWFPS”) is electrically coupled to and receives electrical power from the system power supply 16. Usually for electronic devices, the system power supply 16 provides low-voltage direct current (DC) power. For example, a laptop computer system power supply would likely output approximately 5-12V DC, while the power supply for an LED light fixture would likely output approximately 20-70V DC.
The high voltage DC generated by the IWFPS 20 is then electrically coupled to the emitter electrodes 12 of the ion wind fan 10 via a lead wire 17. The collector electrode 14 is connected back to the IWFPS 20 via return/ground wire 18, to ground the collector electrode 14 thereby creating a high voltage potential across the emitters 12 and the collector 14 electrodes. The return wire 18 can be connected to a system, local, or absolute high-voltage ground using conventional techniques.
While the system shown in and described with reference to
The IWFPS 20 may include other components. Furthermore, in some embodiments, some of the components listed above may be omitted or replaced by similar or equivalent circuits. For example, the IWFPS 20 is described only as an example. Many different kinds and types of power supplies can be used as the IWFPS 20, including power supplies that do not have a transformers or other components shown in
As described partially above, ion wind is generated by the ion wind fan 10 by applying a high voltage potential across the emitter 12 and collector 14 electrodes. This creates a strong electric field around the emitter electrodes 12, strong enough to ionize the air in the vicinity of the emitter electrodes 12, in effect creating a plasma region. The ions are attracted to collector electrode 12, and as they move in air gap along the electric field lines, the ions bump into neutral air molecules, creating airflow. On a real world collector electrode 14, air passage openings (not shown) allow the airflow to pass through the collector 14 thus creating an ion wind fan.
An example of such an ion wind fan is now described with reference to
The collector electrode 32 and the emitter electrodes 36 are both supported by an isolator 34. The isolator is made of a dielectric material, such as plastic, ceramic, and the like. The “isolator” component is thusly named as it functions to electrically isolate the emitter electrodes 36 from the collector electrode 32, and to physically support these electrodes. As such the isolator also can establish the spatial relationship between the electrodes, sometimes referred to under the rubric of electrode geometry. The isolator 34 can be made from one integral piece—as shown in FIG. 2A—or it can be made of multiple parts and pieces.
In the embodiment shown in
The ion wind fan 30—in the embodiment shown in FIG. 2A—is substantially rectangular in top view. The longitudinal axis of the ion wind fan 30 is denoted with the dotted arrow labeled “A.” The ion wind fan 30 has two ends opposite each other along the longitudinal axis. The emitter electrodes 36 are suspended between the two ends of the ion wind fan 30.
In one embodiment, the emitter electrodes 36 are supported at the ends of the ion wind fan 30 by an emitter support 38 portion of the isolator 34. The emitter support 38a at the left end of the ion wind fan 30 is most visible in
In the embodiment shown in
Thus, while in one embodiment the emitter support 38a is a substantially rectangular solid portion of the isolator 34 that connects the two elongated side portions of the isolator 34, in other embodiments the emitter supports 38 can have many other shapes and orientations. For example, a part of the center portion of the emitter support 38a between the emitter electrodes 36 could be cut away without substantially affecting the function of the emitter support 38a.
The emitter support 38a is shown as extending to the end of the ion wind fan 30. However, in other embodiments, the emitter support 38a can end before the end of the ion wind fan 30. The emitter support 38a is also shown as having a curved section at its outside edge to smooth out the 90 degree bend in the wire emitter electrodes 36. This is an optional feature not related to the embodiments of the present invention described herein.
Indeed, the actual attachment of the emitter electrodes 36 to either the emitter support 38 or some other portion of the isolator 34 is not material to the embodiments of the present invention, and therefore will not be discussed in much detail for simplicity and ease of understanding. The emitter electrodes 36 are shown as extending downward from the left end of the ion wind fan 30 and they are connected to the power supply via some wire or bus, as is the collector electrode 32. The emitter supports 38 need not have any particular shape of contact with the emitter electrodes 36. The emitter supports 38 are the portions of the isolator 34 that define the physical spatial relationship between the emitter electrodes 34 and other components of the ion wind fan 30. How exactly the emitter supports 38 are in contact with the emitter electrodes 36 (grooves, stakes, friction, posts, welding, epoxy) are not germane to the embodiments of the present invention.
Though wire sag and other emitter irregularities will create some variance, in one embodiment the air gap 39 between the emitter electrodes 36 and the bottom plane of the collector electrode 32 is substantially constant (within a 5% variation). In other embodiments, the air gap 39 can be more variable. The size of the air gap 39 is dependent on the spatial relationship between the electrodes established by the emitter supports 38 (which are not visible in
While the collector electrode 32 shown in
For example,
While the ion wind fan 40 shown in
Another ion wind fan 44 having elongated U-shaped members 42a-c for the collector electrode 42 is shown in
The space between the members 46a-c forms both the air passage channel and the air passage opening 47 at the end of the channels. The direction of airflow (AF) is again substantially parallel to the orientation of the collector members 46a-c. While ion directionality is improved by the design in
The dotted circle centered around the left-side emitter electrode 45 illustrates that the surface of the members 46a and 46b closest to the emitter electrode is the curved portion of the U-shape. The dotted line extending from the right-side emitter electrode 45 illustrates the same point. For the large-scale electrostatic precipitator applications contemplated in the '026 and '698 patents that have air gaps in the centimeter range, the location of the “near-point” on such a curved surface is not important. But by working with ion wind fans on a much smaller scale—fans having air gaps of just a few millimeters—the inventors of the present application discovered that having the nearest surface of the collector electrode to an emitter electrode by a convex curve resulted in increased likelihood of sparking between the electrodes. The sharper the curvature of surface of the collector nearest the emitter, the more pronounced the sparking that has been observed.
The ion wind fan 48 shown in
In the discussion of collector electrodes above, and also in the descriptions below, a collector electrode will be referred to in the singular, even when made up of multiple members that may not touch each other or be composed of a monolithic or integral structure. As long as the members are used to accelerate/collect ions (or electrons in the case of negative corona applications) and are held at the same potential—usually ground or the negative terminal of the power supply—the collection of members (such as members 50a, 50b, and 50c in
One embodiment of the present invention is now described with reference to FIGS. 4A(1) and 4A(2). FIG. 4A(1) is a simplified cross-sectional view of an ion wind fan 55. This cross-section is roughly the equivalent of the cross-section taken along the line B-B in
The ion wind fan 55 has a collector electrode 59 having three elongated members 59a-c. Elongated member 59a is substantially a plane surface elongated in the longitudinal direction and slanted about 45 degrees to the right from the direction of desired airflow AF. Similarly, elongated member elongated member 59c is substantially a plane surface elongated in the longitudinal direction and slanted about 45 degrees to the left from the direction of desired airflow AF. In the middle, elongated member 59b is substantially a V-shaped intersection of two planes elongated in the longitudinal direction.
As can be seen in FIG. 4A(1), this collector 59 arrangement creates two elongated openings; one opening between member 59a and the left side of member 59b, and another opening between the right side of member 59b and member 59c. As such, ion wind fan 55 can be said to be a two-channel fan. More channels can be added by inserting more V-shaped members (such as member 59b) and additional emitter electrodes 57.
The emitter electrodes of the ion wind fan 55 are wire emitters held in tension in the longitudinal direction, similar to the emitter wires 36 shown in
The emitter electrodes 57 and the collector electrode 59 have a spatial relation, such that the emitter electrodes are substantially centered between two members of the collector electrode 59 on the upstream side of the collector electrode 59. For example, the left emitter electrode 57a is approximately centered between members 59a and 59b.
FIG. 4A(2) shows the same ion wind fan 55 as FIG. 4A(2), with additional labels and explanations. For example, the dotted circle 58 around the left emitter electrode 57 shows the near-points on members 59a and 59b to the emitter electrode 57a. It should be appreciated, that the “near-point” is actually a line along the surface of the collector electrode member extending in the longitudinal direction and parallel to the emitter electrode 57. However, in cross-section, the term near-point indicates the area of a collector member that is closest to the emitter electrode 57.
As shown by dotted circle 58 that is centered around emitter electrode 57a and by dotted line 56 that extends from emitter electrode 57b and perpendicular to member 59b, the near-point is located—in this embodiment—approximately mid-way along the collector electrode members 59 in the direction of airflow. The distance from the emitter electrodes 57 to the collector electrode 59—which is the length of the dotted line 56 and the radius of the dotted circle 58—is the air gap analogous to the air gap 39 shown in
In FIG. 4A(2), the angle θ represents the angle of the slant of the surface of the collector electrode members 59 from the axis of airflow. In the embodiment shown in
The electrode arrangement shown in
Furthermore, unlike the collector electrodes shown in
However, the collector electrode 59 and the ion wind fan 55 do have a disadvantage. The sharp point at the center of elongated member 59b at the junction of the right and left plates can potentially concentrate the electrical field and become a spark point for the emitter electrodes 57. To address this issue, the collector electrode 61 of ion wind fan 60 shown in
In the embodiment shown in
The center-member 61b has two rounded planar portions (63b, 63c) connected by a rounded portion 64b. The dotted circle 66 illustrates that the rounded portion 64b has a single radius, the length of the radius being the radius of the dotted circle 66. In one embodiment, the curve of the rounded portion 64b is tangential to the both planar portions 63b and 63c, so that the transition from planar to rounded portion is smooth, with no sharp edges. In such an embodiment, the length of the radius is determined by the angle between the planar portions 63b and 63c—which is approximately 90 degrees in FIG. 4B—and by the relative size of the ion wind fan 60.
In one embodiment, the spatial relationship of the emitter electrodes 62 to the collector electrode 61 is such that the planar portions 63 of the collector electrode 61 are nearest to the emitter electrodes 62. For example, dotted line 65 illustrates that the “near-point” from emitter electrode 62a to central-member 61b is along the slanted planar portion 63b. The electrical field will be lower along the planar portion 63b than along the rounded portion 64b. Thus, having the slanted planar portion 63b be nearest the emitter electrode 62a can produce an ion wind fan 60 that is less prone to sparking across the electrodes.
The width of the air passage opening 67—i.e., the distance between the elongated members 61—is dependant on various geometry considerations, such as the air gap 65 and the length of the planar portions 63. However, the with of the air passage openings 67 must be consistent with the design objective of having the “near-point” on the collector electrode 61 to the emitter electrodes 62 be along the planar portions 63 of the collector electrode. For example, if the elongated members are moved too close together, the curved portions 64 will be nearer to the emitter electrodes 62 than the planar portions 63. This sizing requirement applies to all embodiments of the present invention discussed herein, and not only to the embodiment shown in
Another embodiment of the present invention is now described with reference to
In one embodiment, each arc is still tangent to its adjacent planar portion (73b and 73c respectively). In such an embodiment, the tip/middle of the rounded portion 74b will have a sharp feature or edge, as is visible in
As in the embodiment shown in
In the embodiments shown in and described with reference to
In this embodiment, the collector electrode 80 is again includes three elongated members (80a-c) that are basically rods elongated in the longitudinal direction having cross sections as shown in
The left-side-member 80a has a curved surface portion 83a in the upstream direction, that transitions into a slanted planar surface portion 82a further upstream in the direction of airflow AF. Even further upstream, the slanted planar portion 82a joins at an angle with a parallel planar surface portion that is parallel with the direction of airflow AF. The right-side member 80c is a mirror image of the left-side member 80a reflected around the central airflow axis.
The center member 80b is an elongated solid bar having a upstream surface that is essentially the same as the surface of the center member 71b in
Furthermore, while the rounded tip portion 83b is double-radiused in this embodiment, a single radius curved surface can be used in another embodiment to create a rounded tip portion similar to surface 64b described with reference to
As can be seen in
As in other embodiments, the dotted lines 84a and 84b show the closest distance between the left emitter electrode 78a and the left 80a and center 80b members. It can be seen that—once again—the “near point” on the left member 80a is along the slanted planar surface 82a and that the near point of the center member 80b is along the left-side slanted planar surface 82b of the center member 80b.
In the embodiment illustrated in
As can be seen in
In one embodiment, the elongated members 80a-c and the cross-members 89 are made of one integral piece. For example, the entire collector electrode 80 can be machined from one integral piece of metal, or stamped, molded, or injection-molded and coated with a conductive surface layer. In other embodiments, the individual members can be welded or otherwise attached during collector 80 manufacturing.
The line C-C shows the cross-section of the collector electrode 80 that was shown in
As can be seen in
The embodiment shown in
As stated above,
The collector electrode discussed with reference to
However, the shape of the downstream side of the collector electrode—the side facing away from the emitter electrodes—does factor into the aerodynamics and flow resistance of the collector electrode, and thus, the ion wind fan. Thus, the collector electrode 90 shown in
In the descriptions and Figures above, the emitter electrodes have been represented by wire electrodes. However, other embodiments of the present invention can use different emitter geometries, such as shim emitters, bar emitters, pin emitters, and other such emitter electrodes. Furthermore, pairs of emitter electrodes can be provided together to generate dielectric barrier discharge. The embodiments of the present invention are not limited to any particular type of emitter electrode or discharge phenomena.
Furthermore, while the planar portions and surfaces of the collector electrodes described above have been described as flat and planar, it is understood that the “planar” portions may not form perfect planes, but instead be substantially planar. Both manufacturing tolerances and purposeful design may introduce roughness or curvature to the planar portions, without departing from the spirit of the invention. Thus, in one embodiment the planar surface is considered planar is its arc has a chord length to sagitta (sometimes called “segment height”) ratio of at least 10 to 1. In other embodiments this ration can be required to be 20 to 1, or even higher.
Furthermore, the example ion wind fans described and pictured above are shown as having two emitter electrodes. However, 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.
Figures such as
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 (as shown in the
Similarly, the isolator can be the substantially frame-like component shown in
