# Patent

## Title
Heat dissipation structure for an electronic device

## Abstract

A flexible thermal conduit runs from a first housing portion of an electronic device to a second housing portion of the electronic device, to convey heat generated by an electronic component located in the first housing portion to a heat dissipation structure located in the second housing portion, where the second housing portion is flexibly coupled to the first housing portion, for example, by a hinge or other type of joint. The flexible conduit may include a plurality of layers of thin, flat thermally conductive material, which may be arranged to flex independently of each other in the region where the first and second housing portions are coupled.

## Background
This application claims the benefit of U.S. provisional patent application No. 62/105,684, filed on Jan. 20, 2015, which is incorporated herein by reference.


BACKGROUND
Cooling capacity for passively cooled electronic devices is limited by the area of surfaces available for heat transfer via radiation and natural convection, and the orientation of those surfaces. In products that have a housing to isolate electronic components from the environment, there is an inherent limit on heat exchange surface area, which imposes significant design challenges. Heat dissipation is even more of a challenge for compact, low-mass and low-volume consumer product designs.
SUMMARY
Introduced here is an apparatus that includes a housing and an electronic component that generates heat when the electronic component is in operation, where the housing includes a heat dissipation structure to dissipate heat generated by the electronic component. In certain embodiments, the heat dissipation structure can include a hollow channel that has an interior surface from which heat is to be dissipated into air external to the apparatus, where the interior surface of the hollow channel defines at least a portion of an exterior surface of the housing, so as to define an air channel through the housing. Hence, the heat dissipation structure can essentially form a thermal tunnel through the housing of the apparatus, where the entire interior surface area of the tunnel can be used for heat dissipation into the air around the apparatus.
The apparatus can further include a flexible thermal conduit that has a first end coupled to the heat dissipation structure and a second end coupled to the electronic component. The flexible thermal conduit can comprise a plurality of thin, flat layers of thermally conductive material, where each layer can be, for example, a thin sheet of flexible graphite or metal. To facilitate the transfer of heat from the flexible thermal conduit to the heat dissipation structure, one or more layers of the flexible thermal conduit can be coupled to an exterior surface of the heat dissipation structure, where the exterior surface of the heat dissipation structure is internal to the housing of the apparatus. Other aspects of the technique will be apparent from the accompanying figures and detailed description.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.



BRIEF DESCRIPTION OF THE DRAWINGS
One or more embodiments of the present disclosure are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements.
FIG. 1 shows an example of an environment in which an AR-HMD device can be used.
FIG. 2 is a perspective view of an example of an AR-HMD device.
FIG. 3 shows a rear perspective view of the shield enclosure.
FIGS. 4A and 4B show front and left side orthogonal views, respectively, of the front shield of the shield enclosure.
FIGS. 5A, 5B and 5C show top, right side and front orthogonal views of the chassis.
FIG. 6 shows a front perspective view of the chassis, with a printed circuit board (PCB) mounted to it.
FIG. 7 shows a rear perspective view of the display assembly and sensor assembly coupled to each other.
FIG. 8 shows a front perspective view of the display assembly and sensor assembly coupled to the chassis and to flexible thermal conduits.
FIG. 9 shows a perspective view of the coupling between the left side arm and the chassis.
FIG. 10 shows a perspective view of the coupling between the left side arm and the chassis, without the mechanical hinge.
FIG. 11 shows a perspective view of how the flexible thermal conduits can be coupled to the chassis.
FIG. 12 is a perspective view showing how the flexible thermal conduit can be coupled to a thermal tunnel.
FIG. 13 shows a close-up left-side perspective view of the tunnel core installed in the left side arm.
FIG. 14 shows a front-right perspective view of the tunnel core of the left side arm.
FIGS. 15A, 15B and 15C show top, front and left-side orthogonal views, respectively, of the tunnel core of the left side arm.
FIGS. 16 and 17 are perspective views illustrating the flexible thermal conduit and tunnel core of the left side arm.
FIG. 18 is a perspective view illustrating the flexible thermal conduit and wrapping associated with the tunnel core of the left side arm.



DETAILED DESCRIPTION
In this description, references to “an embodiment”, “one embodiment” or the like, mean that the particular feature, function, structure or characteristic being described is included in at least one embodiment of the technique introduced here. Occurrences of such phrases in this specification do not necessarily all refer to the same embodiment. On the other hand, the embodiments referred to also are not necessarily mutually exclusive.
The flexible thermal conduit introduced here is particularly useful in products that have multiple housing portions that are movably coupled to each other, where it is impractical (e.g. to space limitations) to locate the heat dissipation structure in the same housing portion as the heat generating components. One example of such a product, as described further below, is a head mounted display (HMD) device, where the first housing portion is a space- and weight-constrained visor assembly that contains display elements and other heat-generating electronics, and the second housing portion is part of a head fitting assembly that enables the device to be worn on a user's head, where the head fitting assembly is flexibly connected to the visor assembly (e.g., by a hinge). Note, however, that the flexible thermal conduit introduced here can also be incorporated advantageously into many other types of products, such as in laptop computers or flip-top type cell phones (e.g., to transfer heat from the display portion to the main body of the device via a hinge).
An HMD device can be used for augmented reality (AR) and/or virtual reality applications, for example. AR HMD devices (“AR-HMD” devices) include transparent display elements that enable a user to see concurrently both the real world around them and AR content displayed by the device. FIG. 1 schematically shows an example of an environment in which an AR-HMD device such as described herein can be used. In the illustrated example, the AR-HMD device 1 is configured to communicate data to and from an external processing device 2 through a connection 3, which can be a wired connection, a wireless connection, or a combination thereof. In other use cases, however, the AR-HMD device 1 may operate as a standalone device. The connection 3 can be configured to carry any kind of data, such as image data (e.g., still images and/or full-motion video, including 2D and 3D images), audio, multimedia, voice, and/or any other type(s) of data. The processing system 2 may be, for example, a game console, personal computer, tablet computer, smartphone, or other type of processing device. The connection 3 can be, for example, a universal serial bus (USB) connection, Wi-Fi connection, Bluetooth or Bluetooth Low Energy (BLE) connection, Ethernet connection, cable connection, DSL connection, cellular connection (e.g., 3G, LTE/4G or 5G), or the like, or a combination thereof. Additionally, the processing system 2 may communicate with one or more other processing systems via a network 4, which may be or include, for example, a local area network (LAN), a wide area network (WAN), an intranet, a metropolitan area network (MAN), the global Internet, or a combination thereof.
FIG. 2 shows a perspective views of an illustrative AR-HMD device 20 (hereinafter simply “HMD device” or “device” 20) that can incorporate the features introduced here, according to one embodiment. In certain embodiments, the display components, sensors and processing electronics of the HMD device 20 are mounted on a chassis 31, as described in detail below. The chassis 31 is part of a protective sealed visor assembly 22 that contains the sensors, electronics, and display components, including left and right AR displays 23, at least some of which generate heat when in operation. The AR displays 23 are designed to overlay images on the user's view of his real-world environment, e.g., by projecting light into the user's eyes. Right and left side arms 24A and 24B, respectively, are structures that attach to the chassis 31 at the left and right open ends of the chassis 31, respectively, via a flexible or rigid fastening mechanisms (including one or more hinges, clamps, etc.). The HMD device 20 includes an adjustable headband (or other type of head fitting) 21, attached to the side arms 24A and 24B, by which the AR-HMD device 20 can be worn on a user's head.
In addition to the display elements, the visor assembly 22 may enclose various other components, such as: an ambient light sensor (ALS), one or more microphones to input speech from the user (e.g., for use in recognizing voice commands and providing audio effects); one or more visible-spectrum head-tracking tracking cameras for use in capturing images of surrounding surfaces to allow tracking of the user's head position and orientation in real-world space; one or more infrared (IR) spectrum depth cameras for use in determining distances to nearby surfaces (e.g., for use in surface reconstruction to model the user's environment); one or more IR illumination sources for use with the depth camera(s); one or more visible spectrum video cameras for use in capturing standard video of what the user sees. Note that the term “visible” in the context of this description means visible to a typical human being. The visor assembly may also enclose electronic circuitry to control at least some of the aforementioned elements and to perform associated data processing functions. The circuitry may include, for example, one or more processors and one or more memories. The HMD device 20 may also include one or more audio speakers to output sound to the user. Note that in other embodiments the aforementioned components may be located in different locations on the AR-HMD device 20. Additionally, some embodiments may omit some of the aforementioned components and/or may include additional components not mentioned above.
The visor assembly 22 provides the user with a relatively unobstructed view of the user's surrounding real world environment while also providing physical protection of the sensitive display components and sensors. In certain embodiments the visor assembly 22 includes the chassis 31, various display elements, sensors and electronics, and a protective shield enclosure 37. The shield enclosure 37 is further illustrated according to one embodiment in FIGS. 3, 4A and 4B. FIG. 3 shows a rear perspective view of the shield enclosure 37. The shield enclosure 37 includes a rear shield 32 and a front shield 33. FIGS. 4A and 4B show, respectively, front and left side orthogonal views of the front shield 33 of the shield enclosure 37. In this disclosure, the term “rear” generally refers to a part or surface that is closest to the user (wearer) of the HMD, while the term “front” generally refers to a corresponding part or surface that is farthest from the user. In the fully assembled product, the display elements (not shown) are suspended within the visor assembly 22. The optics and sensors are also mounted to the chassis 31 within the shield enclosure 37.
In certain embodiments, heat generated by the components within the visor simply 22 is conveyed by two flexible thermal conduits (not shown in FIG. 2), one on the left side of the visor assembly 22 and one on the right side, to a heat dissipation structure in each of the side arms 24A and 24B. Each side arm 24A or 24B is a curved, elongated member that roughly follows the curvature of the headband 21. Each side arm 24A or 24B has a substantially rectangular cross-section. Each side arm 24A or 24B includes a heat dissipation structure that forms a thermal tunnel 25A or 25B that passes entirely through the side arm 24A or 24B, from the top surface to the bottom surface of the side arm, thereby providing a channel that allows air to low freely vertically through the body of the side arm 24A or 24B. The thermal tunnel 25A or 25B is thereby oriented such that the usual orientation of the device 1, when in use, favors natural rising air flow through the thermal tunnel 25A or 25B.
Before further describing the heat dissipation elements of HMD device 20, it is useful to consider further its basic structure, according to at least one embodiment. As mentioned above, the visor assembly 20 includes the chassis 31 and the shield enclosure 37 (see FIG. 2). The chassis 31 is the structural component by which all of the display elements, optics, sensors and electronics are coupled to the rest of the HMD device 20. FIGS. 5A, 5B and 5C show, respectively, top, front and right-side views of the chassis 31, while FIG. 6 shows a perspective view of the chassis 31. The chassis 31 can be formed of molded plastic or polymer, for example. The front surface 160 of the chassis 31 may include various fixtures (e.g., screw holes, raised flat surfaces, etc.) to which the sensor assembly (not shown) can be attached. For example, the chassis 31 has screw holes (or other similar mounting fixtures) 161 by which a display assembly (described below) can be attached to it. The chassis 31 further has one or more fixtures by which at least one printed circuit board (PCB) 172 bearing the electronic components of the HMD 20 can be mounted, as shown in FIG. 6. FIG. 6 shows a front perspective view of the chassis 31 with a PCB 172 mounted to a top inner surface 176 of the chassis 31 (see FIGS. 5A, 5B and 5C).
Enclosed within the visor assembly 22 and mounted to the chassis 31 are two main assemblies, namely, a sensor assembly 111 and a display assembly 130, which are illustrated in combination and FIG. 7. The sensor assembly 111 includes a sensor frame 210 and various sensors mounted to it (e.g., head-tracking cameras, IR depth camera, visible-spectrum camera, and ambient light sensor) and IR light sources. FIG. 7 shows a rear perspective view of the display assembly 130 (including optics assembly and a display engine 103) and sensor assembly 111, coupled to each other. The sensor frame 210 can attach to the top inner surface 176 of the chassis 31 (see FIGS. 5A, 5B and 5C) via mounting points 184, for example, by screws or other fastening mechanism.
The display assembly 130 includes a transparent waveguide carrier 101, on which are mounted multiple transparent waveguides 102, and a display engine 103. The display engine 103 contains one or more light-emission elements (e.g., light-emitting diodes (LEDs), not shown) for each of the left and right eye of the user. The display engine 103 is mounted to the waveguide carrier 101 at the center tab 51, such that light emitted by the display engine 103 is optically coupled to the waveguides 102, which convey the emitted light toward the user's eyes. In the fully assembled product, the waveguide carrier 101 (with waveguides 102 and display engine 103 mounted to it) is mounted to the inside vertical surface of the chassis 31 through the nose bridge region 110 of the waveguide carrier 101, as further shown in FIG. 8. The sensor assembly 111 is mounted to the waveguide carrier 101 at the nose bridge region 110 and to the chassis 31.
FIG. 8 shows a front perspective view of how the combined sensor assembly 111 and display assembly 130 can be mounted to the chassis 31. Various components in the HMD device 20 generate heat during operation, including the display engine 103 and electronics mounted on the PCB 172. Accordingly, two flexible thermal conduits 82A and 82B conduct heat away from these components to the thermal tunnels 25A and 25B, respectively, in the side arms 24A and 24B, respectively (FIG. 2). FIG. 8 shows a portion of the flexible thermal conduits 82A and 82B and the manner in which they can be thermally coupled to the heat generating components.
Specifically, the display engine 103 includes, or is coupled to, a metallic thermal plate 132, which conducts heat away from the display engine 103. Part of thermal plate 132 lies flat against a thermally conductive bracket 136. This configuration allows heat from the display engine 103 to be conducted onto flexible thermal conduit 82A via thermal bracket 136. An L-shaped thermal spreader 86 has a horizontal portion that is thermally coupled to PCB 172 and vertical portion (hidden by bracket 136) that is thermally coupled to the back of bracket 136.
Brackets 136 and 137 clamp the anterior ends of flexible thermal conduits 82A and 82B, respectively, to the chassis 31; the opposite (posterior) ends of thermal conduits 82A and 82B can be coupled to the thermal tunnels 25A and 25B in side arms 24A and 24B, as discussed further below. Bracket 137 is an L-shaped (right-angle) bracket, having a horizontal upper portion and a vertical lower portion. The horizontal upper portion of bracket 137 lies flat against the PCB 172 on the inner horizontal surface of the chassis 31. More precisely, in the illustrated embodiment the horizontal upper portion of bracket 137 lies against a thin, flat heat spreader 88, which is sandwiched between the upper portion of bracket 137 and PCB 172. This configuration allows heat generated by electronic components on the PCB 172 to be conducted away from those components and onto flexible thermal conduit 82B, via heat spreader 88 and bracket 137.
In the illustrated embodiment, each of the flexible conduits 82A and 82B includes multiple layers of thin, flat, thermally conductive material, such as flexible graphite or very thin metal, stacked on top of each other. For example, one or more of the layers of flexible conduits 82A and 82B may be made of, for example, eGRAF® SPREADERSHIELDTM SS500 Graphite, from GrafTech International. In alternative embodiments, a flexible conduit 82A or 82B may consist of only a single layer. Additionally, in other embodiments, one or more layers of a flexible thermal conduit 82A or 82B can be made of a material other than graphite, such as a substrate loaded with graphene, or a thin layer of metal such as copper. In alternative embodiments, a flexible thermal 82A or 82B can be implemented in the form of a flexible heat pipe or vapor chamber.
Heat generated by the display engine 103 or electronics on PCB 172 is conducted by flexible thermal conduits 82A and 82B away from the visor assembly 22 to the thermal tunnels 25A and 25B in the side arms 24A and 24B, respectively, as discussed further below, where the heat is dissipated into the air.
Each side arm 24A or 24B can be coupled to the chassis 31 via a hinge assembly, as shown by example in FIG. 9, which allows the side arm 24A or 24B to flex relative to the visor assembly 22. FIG. 9 shows the hinge assembly 92 connecting the left side arm 24B to the chassis 31 (the configuration is essentially identical for the right side arm). Note that the sensor assembly 111 and display assembly 130 are not included in the view of FIG. 9. The flexible thermal conduit 82B passes under the hinge assembly 92 and couples to a tunnel core (described further below), which is the heat dissipation component that forms the thermal tunnel 25B (FIG. 2), as described further below.
FIG. 10 shows a view similar to that of FIG. 9, but with hinge assembly 92 removed to provide a better view of thermal conduit 82B in the region of the hinge assembly 92. Note that the layers of thermal conduit 82B are not attached to each other, at least in the region of the hinge assembly 92, which enables them to flex independently of each other when the side arm 24A or 24B is flexed relative to the chassis 31. The ability of the layers to flex independently of each other increases their durability with respect to repeated flexing. It can be seen, therefore, that the flexible thermal conduit 82A or 82B effectively forms a durable, lightweight “thermal hinge.”
FIG. 11 is another perspective view that further illustrates how thermal conduits 82A and 82B can be coupled to the chassis 31. FIG. 12 is a left-side perspective view that further illustrates how the thermal tunnel 25A or 25B can be installed within the side arm 24A or 24B (in this case, the left side arm 24B) and coupled to a flexible thermal conduit 82A or 24B. The hinge 92 is also not included in the view of FIG. 12.
The thermal tunnel 25A or 25B located in each side arm 24A or 24B (see FIG. 2) will now be further described with reference to FIGS. 13 through 15. The thermal tunnel 25A or 25B is formed by a heat dissipation component called the “tunnel core”. FIG. 13 shows a close-up left-side perspective view of the tunnel core 138 installed in the left side arm 24A, according to an embodiment. FIG. 14 shows a front-right perspective view of that same tunnel core 138 alone, and FIGS. 15A, 15B and 15C show top, front and left-side orthogonal views, respectively, of that same tunnel core 138. Note that the tunnel core in the right side arm is simply the mirror image of tunnel core 138 shown in FIGS. 13 through 15.
The tunnel core 138 has a hollow main body 139 with flanges 140 and 141 extending from its top and bottom ends, respectively. The hollow center of the tunnel core 138 is shaped generally as a hollow oval cylinder, with flanges 140 and 141 forming the top and bottom surfaces, respectively. The interior surface 142 of the hollow tunnel core 138 forms part of the exterior surface of side arm 24B when tunnel core 138 is installed in side arm 24B. The interior surface 142 remains exposed to air and the fully assembled product and provides the surface area for dissipating heat into the air. The tunnel core 138 can be made of, for example, plastic, metal, or essentially any other rigid, thermally conductive material. If made of plastic, the tunnel core 138 can be formed by, for example, injection molding.
In alternative embodiments, the tunnel core 138 can be subdivided by ribs or partitions (not shown), that provide additional cooling surface area. These ribs or partitions can be formed as integral parts of the tunnel core 138, or they can be made as separate parts that are subsequently bonded to the tunnel core 138.
As mentioned above, in certain embodiments, at least some of the layers of the flexible thermal conduit 82B are thermally coupled to the tunnel core 138. In some such embodiments, the main body 139 of the tunnel core 138 can be wrapped at least partly (i.e., at least partially encircled) by one or more thicknesses of multi-layer, flexible, thermally conductive material, such as flexible graphite, to a thickness that extends approximately to the edges of the flanges 137 and 138. The layer(s) that is/are wrapped around the tunnel core 138 can be the continuation of one or more corresponding layer(s) of the flexible thermal conduit 82B. Alternatively, the thermally conductive layers wrapped around the tunnel core 138 can be formed separately from thermal conduit 82B and then subsequently thermally coupled to thermal conduit 82B during product assembly (e.g., physically attached to it) in any suitable manner, such as by clamping.
FIGS. 16 through 18 further illustrate how the thermal tunnel can be thermally coupled to the flexible thermal conduit. In particular, FIGS. 16 and 17 are two corresponding perspective views illustrating how the left-side flexible thermal conduit 82B can be coupled to the tunnel core 138. Note that the corresponding components in the right side of the HMD 20 can be the same as (or mirror images of) those shown. FIG. 18 shows a related perspective view, but with the tunnel core 138 omitted to facilitate visualization of the layers of thermally conductive material.
In the illustrated embodiment, the layers of flexible thermal conduit 82B are held together by a clamp 162 next to the anterior end of the tunnel core 138 (note that clamp is not shown in FIGS. 9 through 12). As shown in FIG. 18, the main body 139 of the tunnel core 138 can be wrapped with (i.e., entirely encircled by) one or more layers 182 of flexible thermally conductive material, which may be but is not necessarily the same material as that of the thermal conduit 82B (e.g., flexible graphite). The layers of thermal conduit 82B are then laid in contact with the outboard side of the main body 139 (which has been wrapped with thermally conductive material). A thermally conductive adhesive (not shown) can be used to affix any of these layers to each other at the tunnel core 138 and/or to the main body 139 of the tunnel core 138. Such adhesive can be based on, for example, acrylics, silicones, epoxies, or any of various other thermosets. Optionally, one or more layers of the thermal conduit 82B can be extended to continue posteriorly past the tunnel core 138 toward the rear of the HMD 20, as shown, where additional heat generating components may be installed (e.g., batteries, not shown); these extended layers 166 can act as a thermal pipe to transfer heat away from those additional components, forward to the tunnel core 138.
Various other alternative embodiment are conceivable. For example, in some alternative embodiments, the thermally conductive layers wrapped around the tunnel core 138 may be rigid instead of flexible, such as very thin layers of metal, which are attached to the flexible thermal conduit 82A or 82B.
Examples of Certain Embodiments
Certain embodiments of the technology introduced herein are summarized in the following numbered examples:
1. An apparatus comprising: an electronic component that generates heat during operation; and a housing that includes a heat dissipation structure to dissipate heat generated by the electronic component, the heat dissipation structure having a hollow channel, the hollow channel having an interior surface from which heat is to be dissipated into air external to the apparatus, the interior surface of the hollow channel defining at least a portion of an exterior surface of the housing so as to define an air channel through the housing.
2. An apparatus as recited in example 1, wherein the hollow channel has a plurality of open ends disposed along different exterior surfaces of the housing.
3. An apparatus as recited in example 1 or 2, further comprising a flexible thermal conduit having a first end coupled to the heat dissipation structure and a second end coupled to the electronic component.
4. An apparatus as recited in any of examples 1 through 3, wherein the flexible thermal conduit comprises a plurality of layers of thermally conductive material.
5. An apparatus as recited in example 4, wherein at least one of the layers is a layer of flexible graphite.
6. An apparatus as recited in example 4 or 5, wherein at least one of layers is a layer of metal.
7. A head-mounted display device comprising: a visor assembly containing a component that generates heat during operation, the visor assembly including a display device; and a head fitting assembly, coupled to the visor assembly, by which the display device can be worn on the head of a user, the head fitting assembly having an exterior surface, the head fitting assembly including a hollow heat dissipation structure that has an exterior surface and an interior surface, wherein the exterior surface of the heat dissipation element is internal to the head fitting assembly and an interior surface of the heat dissipation element defining at least a portion of the exterior surface of the head fitting assembly.
8. A head-mounted display device as recited in example 7, wherein said portion of the exterior surface of the head fitting assembly forms a hollow channel through the head fitting assembly.
9. A head-mounted display device as recited in example 7 or 8, wherein the interior surface of the heat dissipation structure has a plurality of open ends disposed along different exterior surfaces of the head fitting assembly.
10. A head-mounted display device as recited in any of examples 7 through 9, further comprising a flexible thermal conduit having a first end coupled to the heat dissipation structure and a second end coupled to the component that generates heat during operation.
11. A head-mounted display device as recited in any of examples 7 through 10, wherein the flexible thermal conduit comprises a plurality of layers of thermally conductive material.
12. A head-mounted display device as recited in example 11, wherein at least one of the layers is a layer of flexible graphite.
13. A head-mounted display device as recited in example 11 or 12, wherein at least one of layers is a layer of metal.
14. A head-mounted display device comprising: a visor assembly containing a plurality of electronic components that generate heat during operation, the visor assembly including a display component a display component to cause an image to be displayed to a user; and a head fitting assembly, coupled to the visor assembly, by which the display device can be worn on the head of the user, the head fitting assembly including a plurality of curved, elongate side arms, each coupled to a different end of the visor assembly, each side arm including a heat dissipation tunnel, the heat dissipation tunnel having an exterior surface and an interior surface, the exterior surface of the heat dissipation tunnel being internal to the side arm, the interior surface of the heat dissipation tunnel defining a first exterior surface of the side arm such that the first exterior surface of the side arm defines an air channel completely through a body of the side arm.
15. A head-mounted display device as recited in example 14, wherein the heat dissipation tunnel has a plurality of open ends disposed along different exterior surfaces of the left side arm or the right side arm.
16. A head-mounted display device as recited in example 14 or 15, further comprising a plurality of multi-layered flexible thermal conduits, each coupled to convey heat generated by at least one of the electronic components to the heat dissipation tunnel in the left side arm or the right side arm.
17. A head-mounted display device as recited in any of examples 14 through 16, wherein each of the flexible thermal conduit comprises a plurality of layers of flexible graphite.
18. A head-mounted display device as recited in any of examples 14 through 17, wherein each of the flexible thermal conduit comprises at least one layer of metal.
Any or all of the features and functions described above can be combined with each other, except to the extent it may be otherwise stated above or to the extent that any such embodiments may be incompatible by virtue of their function or structure, as will be apparent to persons of ordinary skill in the art. Unless contrary to physical possibility, it is envisioned that (i) the methods/steps described herein may be performed in any sequence and/or in any combination, and that (ii) the components of respective embodiments may be combined in any manner.
Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

## Claims

1. An apparatus comprising:
an electronic component that generates heat during operation;
a housing that includes a heat dissipation structure to dissipate heat generated by the electronic component, the heat dissipation structure having a hollow channel, the hollow channel having an interior surface from which heat is to be dissipated into air external to the apparatus, the interior surface of the hollow channel defining at least a portion of an exterior surface of the housing so as to define an air channel through the housing; and
a flexible thermal conduit having a first end coupled to the heat dissipation structure and a second end coupled to the electronic component.

2. An apparatus as recited in claim 1, wherein the hollow channel has a plurality of open ends disposed along different exterior surfaces of the housing.

3. An apparatus as recited in claim 1, wherein the flexible thermal conduit comprises a plurality of layers of thermally conductive material.

4. An apparatus as recited in claim 3, wherein at least one of the layers is a layer of flexible graphite.

5. An apparatus as recited in claim 3, wherein at least one of layers is a layer of metal.

6. A head-mounted display device comprising:
a visor assembly containing a component that generates heat during operation, the visor assembly including a display device; and
a head fitting assembly, coupled to the visor assembly, by which the display device can be worn on the head of a user, the head fitting assembly having an exterior surface, the head fitting assembly including a hollow heat dissipation structure that has an exterior surface and an interior surface, wherein the exterior surface of the heat dissipation element is internal to the head fitting assembly and an interior surface of the heat dissipation element defining at least a portion of the exterior surface of the head fitting assembly.

7. A head-mounted display device as recited in claim 6, wherein said portion of the exterior surface of the head fitting assembly forms a hollow channel through the head fitting assembly.

8. A head-mounted display device as recited in claim 6, wherein the interior surface of the heat dissipation structure has a plurality of open ends disposed along different exterior surfaces of the head fitting assembly.

9. A head-mounted display device as recited in claim 6, further comprising a flexible thermal conduit having a first end coupled to the heat dissipation structure and a second end coupled to the component that generates heat during operation.

10. A head-mounted display device as recited in claim 9, wherein the flexible thermal conduit comprises a plurality of layers of thermally conductive material.

11. A head-mounted display device as recited in claim 10, wherein at least one of the layers is a layer of flexible graphite.

12. A head-mounted display device as recited in claim 10, wherein at least one of layers is a layer of metal.

13. A head-mounted display device comprising:
a visor assembly containing a plurality of electronic components that generate heat during operation, the visor assembly including a display component a display component to cause an image to be displayed to a user; and
a head fitting assembly, coupled to the visor assembly, by which the display device can be worn on the head of the user, the head fitting assembly including a plurality of curved, elongate side arms, each coupled to a different end of the visor assembly, each side arm including a heat dissipation tunnel, the heat dissipation tunnel having an exterior surface and an interior surface, the exterior surface of the heat dissipation tunnel being internal to the side arm, the interior surface of the heat dissipation tunnel defining a first exterior surface of the side arm such that the first exterior surface of the side arm defines an air channel completely through a body of the side arm.

14. A head-mounted display device as recited in claim 13, wherein the heat dissipation tunnel has a plurality of open ends disposed along different exterior surfaces of the left side arm or the right side arm.

15. A head-mounted display device as recited in claim 13, further comprising a plurality of multi-layered flexible thermal conduits, each coupled to convey heat generated by at least one of the electronic components to the heat dissipation tunnel in the left side arm or the right side arm.

16. A head-mounted display device as recited in claim 15, wherein each of the flexible thermal conduit comprises a plurality of layers of flexible graphite.

17. A head-mounted display device as recited in claim 15, wherein each of the flexible thermal conduit comprises at least one layer of metal.