Patent Application
20100142136
1. Field
The present invention generally relates to techniques for isolating vibrations in computer systems. More specifically, the present invention relates to a method and an apparatus that isolates a computer system from vibrations generated by one or more fans inside the computer system.
2. Related Art
Many new computer systems include powerful processors that require powerful fans to cool them. These powerful fans can increase the vibrations generated in the computer system, which can lead to performance problems for components in the computer system. For example, many new higher density disk drives have smaller track sizes and tighter tolerances to increase their storage capacity. However, smaller track sizes and tighter tolerances make these disk drives potentially more sensitive to vibrations during operation of the computer system.
Often, computer system manufacturers try to isolate vibrations generated by fans from the rest of the computer system using elastomeric mounts for the fan. Typically, each fan in the computer system is separately mounted and isolated. However, the elastomeric mounts can undergo stress relaxation over their life cycle due to temperature cycling and flexing which may reduce the ability of the elastomeric mounts to damp vibrations. The loss of damping ability may occur before the computer system has reached the end of its estimated useful life cycle, and may allow vibrations from the fan to be transmitted to the rest of the computer system, including the disk drives. Moreover, since each fan is typically separately isolated, the deterioration of one of the elastomeric mounts on any one of the fans can lead to a failure of isolation and result in vibrations being transmitted to the computer system. This can lead to performance degradation or even failure of the computer system, or can require a reduction in fan speed to reduce the vibrations generated by a fan, thereby limiting the maximum amount of heat that can be safely generated by a processor cooled by the fan, and hence limiting the maximum speed of the processor.
Hence, what is needed is a method and system that isolates a computer system from vibrations generated by one or more fans inside the computer system without the above-described problems.
Some embodiments of the present invention provide an apparatus that isolates a computer system from vibrations generated by one or more fans inside the computer system. The apparatus includes a fan deck upon which the one or more fans are mounted inside the computer system, and three spring assemblies. Each spring assembly includes: a pin that extends through a clearance hole in the fan deck, wherein a first end of the pin is rigidly coupled to the computer system; a lower spring that extends between a first side of the fan deck and a lower spring mount coupled to the pin; and an upper spring that extends between a second side of the fan deck and a upper spring mount coupled to the pin.
In some embodiments, the lower spring mount in each spring assembly is located between the computer system and the first side of the fan deck, and the upper spring mount in each spring assembly is located between the second end of the pin and the second side of the fan deck.
In some embodiments, the lower spring in each spring assembly is preloaded between the first side of the fan deck and the lower spring mount, and the upper spring is preloaded between the second side of the fan deck and the upper spring mount.
In some embodiments, at least one of the lower spring in each spring assembly and the upper spring in each spring assembly includes a cylindrical helical coil spring.
In some embodiments, at least one of the lower spring in each spring assembly and the upper spring in each spring assembly includes a metal spring.
In some embodiments, a spring constant of the lower spring in each spring assembly, a spring constant of the upper spring in each spring assembly, and a mass of the fan deck and the one or more fans are selected so that a ratio of a fundamental vibration frequency generated by the one or more of the fans during operation of the computer system to a resonant vibration frequency of the fan deck is greater than the square root of 2.
In some embodiments, a spring constant of the lower spring in each spring assembly is equal to a spring constant of the upper spring in each spring assembly.
In some embodiments, the computer system includes a molded plastic mount wherein the molded plastic mount includes the lower spring mount in each spring assembly.
In some embodiments, the one or more fans mounted on the fan deck are attached to a stress-relieved power cable.
Some embodiments include as fourth spring assembly.
In some embodiments, all fans in the computer system are mounted on the fan deck.
In some embodiments, the transmission of the vibrations generated by the one or more fans to the computer system is modified by adjusting a mass of the fan deck.
The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
Spring assembly 106A includes spring 108A preloaded between fan deck 102 and upper spring mount 110A, and spring 108B preloaded between fan deck 102 and lower spring mount 10B in mount 112. Furthermore, pin 114A is coupled to mount 112 and extends through clearance hole 116A in fan deck 102 and is coupled to upper spring mount 108A. Additionally, spring assembly 106B includes spring 108C preloaded between fan deck 102 and upper spring mount 110C, and spring 108D preloaded between fan deck 102 and lower spring mount 110D. Furthermore, pin 114B is coupled to mount 112 and extends through clearance hole 116B in fan deck 102 and is coupled to upper spring mount 110C. Note that each of the four spring assemblies includes two springs.
In the embodiment of
In some embodiments, the preload on the springs in a spring assembly can be adjusted by adjusting the top spring mount. For example, the preload on spring 108A and spring 108B can be adjusted by moving upper spring mount 110A with respect to pin 114A. In some embodiments, one or more of upper spring mount 110A, upper spring mount 110C upper spring mount 110E, and upper spring mount 110F include a plate and a nut.
For example, if upper spring mount 110A includes a plate and a nut and pin 114A is threaded, then the preload on spring 108A and spring 108B can be adjusted by threading the nut in spring mount 110A up or down on pin 114A. In other embodiments, spring mount 110A is adjusted on pin 114A and fixed in position using other methods, including but not limited to epoxy, solder, press-fit, interference-fit, or a ratchet and pawl mechanism.
Note that the four clearance holes in fan deck 102, clearance hole 116A, clearance hole 116B and the clearance holes for the 2 spring assemblies not shown in
In some embodiments, mount 112 is the case for computer system 100 or is separately manufactured and attached to the case or some other portion of computer system 100. Additionally, in some embodiments, the four pins, pin 114A, pin 114B and the two pins for the two hidden spring assemblies, are molded or manufactured as part of mount 112. For example, in some embodiments, mount 112 is a plastic molded part that is molded as one piece which includes four pins (pin 114A, pin 114B, and the two hidden pins). Furthermore, lower spring mount 110B and lower spring mount 110D may be molded into mount 112. In some embodiments, a lower spring mount includes a seat for a spring so that the spring is constrained from moving laterally on mount 112 or interfering with the pin inside the spring. For example, referring to
Note that as depicted in the embodiment of
Additionally, spring constants of the eight springs in the four spring assemblies and the mass of fan deck 102 and fans 104 can be selected so that the resonant frequency of fan deck 102 is a predetermined value. In some embodiments, the resonant frequency of fan deck 102 is selected based on the vibration frequencies generated by one or more of fans 104 during operation of computer system 100. For example, a fundamental vibration frequency generated by one or more of fans 104 may be measured during the operation of computer system 100. Then, spring constants of the eight springs and the mass of fan deck 102 may be selected so that the ratio of the measured fundamental vibration frequency to the resonant frequency of fan deck 102 is a predetermined ratio. In some embodiments, the ratio can include but is not limited to 1, the square root of 2, 2 or a value based on the measured transmission of vibrations from fans 104 to computer system 100 during the operation of computer system 100. For example, if it is desired to reduce the vibrations that are transmitted to computer system 100 from fans 104 in one or more predetermined frequency ranges and/or above a predetermined frequency, then the vibrations of computer system 100 can be monitored as the resonant vibration frequency of fan deck 102 is altered by, for example, adjusting the mass of fan deck 102.
Note that although fan deck 102 has a rectangular shape in the embodiment depicted in
Furthermore, although in the embodiments depicted in
The foregoing descriptions of embodiments have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present description to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present description. The scope of the present description is defined by the appended claims.
