Fan suspension for reduction of noise

[0001] Conventional circuit boards typically include components which generate heat during operation. These components may require enhanced cooling in order to operate properly and avoid damage. For example, microprocessors typically rely on heat sinks disposed within air streams to maintain the microprocessors within predefined optimized temperature ranges.

[0002] One conventional approach to providing an air stream suitable for cooling electronic components is to place a set of fans at an inlet opening of a chassis which houses the components. The set of fans draw ambient air from the front of the chassis, and blow that air through the chassis and over the components. The air then exits out from the outlet opening of the chassis carrying away heat from the components.

[0003] To prevent the fans from inadvertently unfastening from the chassis, hardware (e.g., screws, nuts, etc.) directly secures the fans to the chassis. In particular, such hardware typically inserts through holes in the frames of the fans and then attaches to the chassis through mounting holes of the chassis. If the fans are installed properly, the hardware competently holds the fans in place.

[0009] Unfortunately there are deficiencies to the above-described conventional approaches to securing a fan to a chassis using hardware. For example, with such an approach vibrations of the fan may be transferred to the chassis. This may cause the entire chassis to resonate and amplify the noise of the fan. Computer systems have become increasingly more crowded as designers seek to produce faster and more powerful systems. Since space is limited in computer systems, increased cooling is usually achieved by increased fan speed. As fan speed increases, so too does the acoustic noise from the fan increase. Noise is generated by the turbulence of the airflow resulting from air being forced through the fan. Noise is also generated by vibration of the fan itself, due to the running of the fan motor and the spinning of its fan blades. The fan vibration is transferred from the fan to the chassis to which the fan is affixed. The acoustic noise is amplified when the fan runs at the speed that falls within the system resonance frequency range. This amplification in noise can be a major annoyance for those individuals who must work close to these electronic systems.

[0010] Another deficiency to the above described conventional fan mount is the excess hardware that can come loose from the fan. This hardware can fall into the circuitry to cause physical damage or short circuits. The excess hardware creates a reliability concern. In addition, excess hardware can mean additional complexity. This could result in greater costs associated with manufacture and assembly.

[0011] In contrast to the above-identified conventional approach to securing a fan to a chassis using hardware, an improved fan mounting technique involves isolating vibrations of the fan from the chassis using a suspension assembly structure. Such a suspension assembly structure is capable of significantly reducing the vibration passed onto the chassis from the fan. Additionally, the suspension assembly structure design is capable of being formed by a one-piece fan mount/fastener in combination with a set of chassis flanges extending from a base of the chassis to enable simple and quick installation without using tools. As a result, there is less noise, little or no hardware to pose a reliability issue, and less manufacturing burden.

[0012] One embodiment is directed to an electronic system. The electronic system has a chassis having a base and a set of flanges extending from the base. The electronic system has electronic circuitry housed within the chassis. The electronic system has a fan assembly having a fan arranged to generate an air stream suitable for cooling the electronic circuitry, and a fan mount. The fan mount has an attachment portion arranged for the fan to attach to. The fan mount has a set of chassis interface portions arranged to form a cantilever with the set of flanges relative to the base to vibrationally isolate the fan from the base.

[0013] An improvement to a fan assembly isolates the fan (e.g. 40 mm×40 mm×20 mm fan) from the chassis (e.g. sheet metal bracket) inside a vibration dampening fan mount. Accordingly, this significantly reduces the vibration passed onto the chassis from the fan, thus reducing the acoustic noise.

[0014] FIG. 1 shows an electronic system 20 which includes a set of fan assemblies 22 (i.e., one or more fan assemblies 22) and a metal chassis 24. Each fan assembly 22 includes a fan mount 26 and a fan 28. The fan mount 26 includes a fan housing 30 configured to be an attachment portion to attach to the fan 28 and a set of latches 32 (i.e., one or more latches 32) adapted to act as chassis interface portions which mount the housing 30 to the chassis 24. The chassis 24 includes a set of flanges 34 (i.e., one or more flanges 34) and a chassis bottom 36.

[0015] As shown in FIG. 1, the metal chassis 24 is a support structure designed to house and provide physical framework for various components. Potential components are electronic circuitry, wiring, power supplies, heat sinks, and fans 28. The set of flanges 34 rigidly integrate with the chassis 24. The flanges 34 as shown in the current embodiment are stamped and folded from sheet stock, and thus form as one piece with the rest of the chassis. However, the flanges 34 may attach to the chassis in various other ways to provide a good rigid attachment such as welding, bolting, or gluing. The flanges 34 extend from the chassis 24 in the positive Y direction.

[0016] As shown in FIG. 1, the fan assembly 22 is formed by attaching the fan 28 to the fan mount 26. The fan mount 26 holds the fan 28 firmly in place. The fan 28 as shown in the current embodiment snap fits to the fan mount 26. However, the fan 28 may attach to the fan mount 26 in various other ways including screws, friction fits, and clamps. The fan mount 26 contains the set of latches 32. The latches 32 extend from the fan mount 26 in the positive and negative Z direction. The latches 32 have an opening on the negative Y side.

[0017] As shown in FIG. 1, as the fan assembly 22 lowers onto the chassis 24 in the negative Y direction, the flanges 34 engage the latches 32. Upon engaging the latches 32, the flanges 34 enter the opening of the latches 32. As the flanges 34 enter the opening of the latches 32, the latches 32 are forced to deform towards the X direction for the flanges 34 to enter. Once the flanges 34 have fully entered the latches 32, the latches 32 return to (snap-in) their original shape and the connection between the latches 32 and the flanges 34 are locked in place. When the set of latches 32 has fully engaged the set of flanges 34, there is no contact between fan assembly 22 and the chassis bottom 36. Thus the fan assembly 22 is suspended by a cantilever structure with respect to the chassis bottom 36 via the latches 32 to flanges 34 connection. In other words, a spatial gap 62 exists between fan assembly 22 and the chassis bottom 36. This cantilever formation serves to dampen any vibrations that occur when the fan 28 operates. Thus vibrations of fan 28 are substantially isolated from the chassis 24. Since the chassis 24 cannot be resonant with the vibrations generated by the fan 28, the noise level is substantially lower when compared to the noise produced by the conventional fan mount with a sheet metal bracket.

[0018] FIG. 2 shows the fan assembly 22 in greater detail and from the opposite side than in FIG. 1. The fan assembly 22 includes the fan 28 inserted into the housing 30. The housing 30 includes a mating panel 38 defining a seating surface 40 configured to mate with a fan 28. The housing 30 also includes an inlet vent 42 defining an inlet vent opening 44. The housing 30 also includes a set of walls 46 (i.e., one or more walls 46) connected to the seating surface 40. The set of walls 46 protrude from the seating surface 40 to form a component that defines a fan space 48. The fan 28 inserts into the fan space 48 until the fan contacts the seating surface.

[0019] As shown in FIG. 2, the set of walls 46 extend in the X direction from edges of the seating surface 40 in the XY plane. The set of walls 46 act as a positioning and retaining feature for the fan 28 upon its insertion into the fan mount 26. Though the set of walls 46 are depicted in the XY plane, they would work just as effectively in the XZ plane in addition to or in lieu of the set of walls 46 in the XY plane.

[0020] As shown in FIG. 2, the housing 30 has a set of snap-in couplings 50 (i.e., one or more snap-in couplings 50) attached to the set of walls 46. As the fan 28 inserts into the fan space 48 in the negative X direction, the couplings 50 deflect open. When the fan 28 contacts the seating surface 40, the snap-in couplings 50 return to their original position and the fan 28 locks into place by couplings 50.

[0021] As shown in FIG. 2, the fan 28 fits snuggly into the fan space 48 of the housing 30. This snug fit prevents the fan 28 from jostling around in the fan mount 26 and producing extra noise. The vibrations of the fan 28 are passed onto and shared with the fan mount 26 and are then dampened by the cantilever formation.

[0022] FIG. 3 shows the fan assembly 22 as seen in FIG. 2 but with the fan 28 removed from the assembly 22 to reveal only the fan mount 26. The housing 30 includes a set of posts 52 (i.e. one or more posts 52). When the fan 28 inserts into the fan space 48 as described above, a set of fan holes 54 (i.e. one or more fan holes) as seen in FIG. 2 on the fan 28 line up with the set of posts 52. The posts 52 then insert into the fan holes 54 in the X direction. In conjunction with the snap in couplings 50, the posts 52 aid in the locking of fan 28 into the housing 30.

[0023] As shown in FIG. 3, the set of posts 52 attach to the seating surface 40 of the mating panel 38. The posts 52 are cross shaped and tapered so that the diameter of the post is slightly larger on the side attached to the seating surface 40 of the mating panel 38. This geometry allows the posts 52 to fit snuggly inside the fan holes 54 while still allowing for easy removal of the posts 52. There are other geometries for posts 52 that can act as good stabilizers, such as cylindrical or box shaped.

[0024] In one embodiment, the entire housing 30 and set of latches 32 are made entirely in one piece. This can be done for example by using an injection molded plastic construction. This makes the fan mount 26 easy and inexpensive to produce. By reducing the number of pieces that are affixed together it prevents excess pieces from clattering against each other to produce additional noise. Reducing the number of pieces prevents small pieces from coming loose and falling onto the circuitry. If pieces were to fall onto the circuitry, there is the possibility that short circuits could occur.

[0025] FIG. 4 shows the electronic system 20 from the side which includes a separating structure 56. The fan 28 is connected to a power source 58 on the chassis 24 by a set of wires 60 (i.e., one or more wires).

[0026] The separating structure 56 is an extension of material that creates some separation between the seating surface 40 and the inlet vent 42. As air passes through the inlet vent 42 on its way to the fan 28, the air is subject to turbulent flow. This turbulence creates audible noise. Both turbulence and noise are decreased as the separating structure 56 becomes longer. The length of the separating structure is a compromise between the noise reducing features of longer lengths and practicality of shorter lengths. For exemplary purposes his length turns out to be approximately 0.4 inches and longer.

[0027] As shown in FIG. 4, the bottom of the fan mount 26 does not contact the metal chassis 24. This ensures that the cantilever is formed so that the only rigid point of contact between the chassis 24 and the fan assembly 22 is the latches 32 on flanges 34 connection. The wires 60 are not rigid attachments and do not pass on significant vibration noise.

[0028] While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

[0029] For example, the position of the flanges 34 and the latches 32 could be swapped to achieve the same cantilever formation.