US20070119794A1

US20070119794A1 - Vibration damping unit

Info

Publication number: US20070119794A1
Application number: US11/357,122
Authority: US
Inventors: Hiroshi Hidaka; Yasushi Uraki
Original assignee: Fujitsu Ltd
Current assignee: Fujitsu Ltd
Priority date: 2005-11-28
Filing date: 2006-02-21
Publication date: 2007-05-31
Also published as: JP2007148763A; JP4327790B2

Abstract

A vibration damping unit includes a rack-mounted support body removably mounted on a rack. A mass is supported on the support body for movement along an imaginary plane. An elastic member is coupled to the support body and the mass. The support body is removable from the rack. The vibration damping unit can be mounted on an existing rack in a facilitated manner without any change in the design of the rack. Workers can be released from troublesome works, such as moving the rack, even when the vibration damping unit is applied to the rack. The means for preventing sway or vibration can be applied to the rack even when an electronic apparatus, including a disk array apparatus and the like, is in operation inside the rack.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a method of preventing the sway of a rack accommodating a rack-mounted disk array apparatus, for example.
2. Description of the Prior Art
A rack-mounted disk array apparatus is well known. The disk array apparatus is mounted on a rack located on a seismic isolation apparatus. The seismic isolation apparatus serves to reduce the sway of the rack. The disk array apparatus is thus allowed to keep its normal operation without any interruption. Lifting up the rack is required to place the rack on the seismic isolation apparatus.
The rack weighs at least 150 kg. The disk array apparatus or apparatuses mounted in the rack serves to further increase the weight. It is quite difficult to lift up the rack onto the seismic isolation apparatus. What is worse, lifting up the rack should interrupt the operation of the disk array apparatus. In other words, once the disk array apparatus starts operating, the rack cannot normally enjoy the seismic isolation.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a vibration damping unit contributing to prevention of the sway of an existing rack in a facilitated manner.
According to the present invention, there is provided a vibration damping unit comprising: a rack-mounted support body removably mounted on a rack; a mass or weight supported on the support body for movement along an imaginary plane; and an elastic member coupled to the support body and the mass.
The support body of the vibration damping unit is removable from the rack. The vibration damping unit can be mounted on an existing rack in a facilitated manner without any change in the design of the rack. Workers can be released from troublesome works, such as moving the rack, even when the vibration damping unit is applied to the rack. The means for preventing sway or vibration can be applied to the rack even when an electronic apparatus, including a disk array apparatus and the like, is in operation inside the rack.
The mass is supported on the support body for movement along an imaginary plane. The elastic member is interposed between the support body and the mass. The elastic member serves to realize the reciprocation of the mass along the imaginary plane. The reciprocation of the mass contributes to a significant suppression of the sway or vibration of the rack when the rack suffers from an earthquake, for example. The rack is allowed to have a smaller rigidity. The assembling process can be simplified. The simplified process leads to a reduction in the production cost of the rack. A reduction in the rigidity greatly contributes to a significant reduction in the weight of the rack.
The mass may comprise: a tray coupled to the support body for movement along the imaginary plane; and at least one weight member removably mounted on the tray. The amount of mass can be adjusted depending on the number of the weight member. This structure enables adjustment of the amount of the mass in accordance with the resonance frequency of the rack, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiment in conjunction with the accompanying drawings, wherein:
FIG. 1 is a perspective view schematically illustrating the structure of a rack;
FIG. 2 is a perspective view schematically illustrating the structure of a vibration damping unit according to a specific example of the present invention;
FIG. 3 is an exploded view schematically illustrating the structure of the vibration damping unit;
FIG. 4 is a view schematically illustrating a specific model of the vibration damping unit when the rack moves forward;
FIG. 5 is a view schematically illustrating a specific model of the vibration damping unit when the rack moves backward;
FIG. 6 is a view schematically illustrating a model of the rack for a computer software analysis;
FIG. 7 illustrates a table specifying the values of parameters such as the weight f a mass, spring constants and damper constants;
FIG. 8 is a graph illustrating the correlation between the frequency and the acceleration in a comparative example;
FIG. 9 is a graph illustrating the correlation between the frequency and the acceleration in a specific example of the present invention;
FIG. 10 illustrates a table specifying the peak values of the response acceleration of the comparative example and the specific examples of the present invention;
FIG. 11 is a view schematically illustrating another model of the rack for a computer software analysis; and
FIG. 12 illustrates a table specifying the peak values of the response acceleration of the comparative example and the specific examples of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 schematically illustrates a rack 12 containing a rack-mounted disk array apparatus. In this case, a plurality of disk array apparatuses 11 are mounted on the rack 12, for example. The disk array apparatuses 11 are connected to a host or server computer 13 likewise mounted on the rack 12, for example. The disk array apparatuses 11 operate in response to instruction signals supplied from the server computer 13.
As conventionally known, recording disk drives or hard disk drives (HDDs) are mounted in the individual disk array apparatus 11. The hard disk drive may include a recording disk or hard disk (HD) having the rotation axis extending in the vertical direction perpendicular to the floor, for example. In this case, each disk array apparatus 11 holds fifteen hard disk drives. Alternatively, the rotation axis of the hard disk may extend in the horizontal direction in parallel with the floor.
A vibration damping unit 14 is mounted on the rack 12 just below the top plate of the rack 12. The vibration damping unit 14 is capable of sliding on the rack 12 along a horizontal plane. The vibration damping unit 14 can thus be withdrawn from the front side of the rack 12. The vibration damping unit 14 is coupled to the rack 12 when the vibration damping unit 14 is placed inside the rack 12. Screws 15 may be utilized to couple the vibration damping unit 14, for example. The screws 15 may be screwed into support columns of the rack 12, for example.
As shown in FIG. 2, the vibration damping unit 14 includes a rack-mounted support body 21. The support body 21 includes a bottom plate 21 a and a surrounding wall 21 b standing upright from the periphery of the bottom plate 21 a. The support body 21 defines an inner space in the shape of a parallelepiped based on the bottom plate 21 a and the surrounding wall 21 b.
A pair of first rails 22, 22 is located within the inner space of the support body 21. The first rails 22, 22 are designed to extend in a first direction FD. The first direction FD is set along a horizontal plane in the right and left direction of the vibration damping unit 14. The first rails 22, 22 extend in parallel with each other. The first rails 22 may be fixed to the bottom plate 21 a of the support body 21. Screws may be utilized to fix the first rails 22, for example.
Sliders 23 are mounted on the first rails 22, respectively. The sliders 23 are capable of sliding along the first rails 22 in the first direction FD. A second rail 24 is coupled to the sliders 23, 23. The second rail 24 may be fixed to the sliders 23. The second rail 24 is designed to extend in a second direction SD perpendicular to the first direction FD. The second direction SD is set along the horizontal plane in the back and front direction of the vibration damping unit 14. The second rail 24 serves to connect the sliders 23, 23 to each other.
A tray 25 is mounted on the second rail 24. The tray 25 is capable of sliding along the second rail 24 in the second direction SD. At least one weight member 26 is mounted on the tray 25, for example. The weight members 26 are thus coupled to the support body 21 for movement along an imaginary plane defined on the surface of the bottom plate 21 a, for example. The weight members 26 may removably be attached to the tray 25. Screws may be utilized for attachment, for example. Each weight member 26 may weigh 1 kg, for example. The tray 25 and the weight members 26 in combination serve as a mass according to the present invention.
First coil springs 27 and first dampers 28 are incorporated within the inner space of the support body 21. The first coil spring 27 and the first damper 28 are designed to extend in parallel with the corresponding first rail 22. Pairs of tabs 29, 29 are formed on the bottom plate 21 a so as to stand from the bottom plate 21 a. The tabs 29, 29 of each pair are spaced from each other in the first direction FD. The first coil spring 27 and the first damper 28 are located in a space between the pair of tabs 29, 29.
The slider 23 is located in a space between the first coil spring 27 and the first damper 28. The first coil spring 27 is coupled to the slider 23 at one end and to the tab 29 at the other end. The elasticity of the first coil spring 27 serves to drive the slider 23 for reciprocation along the first rail 22 in a set period. The first damper 28 is likewise coupled to the slider 23 at one end and to the tab 29 at the other end. The first damper 28 serves to attenuate the movement of the slider 23.
Likewise, a pair of second coil springs 31, 31 is incorporated within the inner space of the support body 21. The second coil springs 31, 31 are designed to extend in parallel with the second rail 24. The second coil springs 31, 31 are located in series in a space between the sliders 23, 23. A pair of second dampers 32, 32 is incorporated within the inner space of the support body 21. The second dampers 32, 32 are designed to extend in parallel with the second rail 24. The second dampers 32, 32 are located in series in a space between the sliders 23.
The tray 25 is located between the second coil springs 31, 31 as well as between the second dampers 32, 32. Each of the second coil springs 31 is coupled to the slider 23 at one end and to the tray 25 at the other end. The elasticity of the second coil springs 31 serves to drive the tray 25 for reciprocation along the second rail 24 in a set period. Each of the second dampers 32 is likewise coupled to the slider 23 at one end and to the tray 25 at the other end. The second damper 32 serves to attenuate the movement of the tray 25.
As shown in FIG. 3, the first coil springs 27 and the first dampers 28 can be removed from the sliders 23 and the tabs 29. The second coil springs 31 and the second dampers 32 can likewise be removed from the sliders 23 and the tray 25. The weight members 26 can also be removed from the tray 25. Replacement of the first and second coil springs 27, 31, the first and second dampers 28, 32 and the weight members 26 can thus be realized in a facilitated manner.
As shown in FIG. 2, the weight members 26 are located at a standard position when the rack 12 stands still. The tray 25 is positioned at the intermediate position equally spaced from the first rails 22, 22. The slider 23 is simultaneously positioned at the intermediate position equally spaced from both the ends of the first rail 22. No load affects the first and second coil springs 27, 31 and the first and second dampers 28, 32. The first and second coil springs 27, 31 and the first and second dampers 28, 32 are kept in the original lengths.
Now, assume that the rack 12 suffers from a sway in the second direction SD because of an earthquake, for example. As shown in FIGS. 4 and 5, the vibration damping unit 14 allows a relative movement between the tray 25 and the support body 21 along a horizontal plane so that the tray 25 stays where it is. The support body 21 is forced to reciprocate in the second direction SD. This results in shrinkage and elongation of the second coil springs 31, 31. The rack 12 and the support body 21 is thus allowed to enjoy a suppression in the amplitude of the sway or vibration. The energy of the sway is transformed into deformation of the second coil springs 31. The energy of the sway thus stored in the second dampers 32, 32 is then consumed in the second dampers 32. The rack 12 is in this manner allowed to enjoy a suppression of the vibration.
The vibration damping unit 14 is removably mounted on the rack 12 in the same manner as the disk array apparatus 11. The existing rack 12 thus easily receives the vibration damping unit 14 without any change in design. One is released from troublesome works, such as moving the rack 12, even when the vibration damping unit 14 is applied to the rack 12. Moreover, the means for preventing sway or vibration can be applied to the rack 12 even after the disk array apparatus 11 is in operation.
Since the vibration damping unit 14 serves to sufficiently suppress sway or vibration of the rack 12, the rack 12 is allowed to have a smaller rigidity. Welding can be replaced with riveting in the production process of the rack 12. The production process can be simplified. The simplified process leads to a reduction in the production cost of the rack 12. A reduction in the rigidity greatly contributes to a reduction in the weight of the rack 12.
The first and second coil springs 27, 31, the first and second dampers 28, 32 and the weight members 26 can be removed in a facilitated manner. The spring constants of the first and second coil springs 27, 31 can thus be adjusted depending on the resonance frequency of the rack 12 and the vibration damping unit 14. The damper constants of the first and second dampers 28, 32 can likewise be adjusted. The amount of the mass can also be adjusted.
The inventors have observed the effect of the vibration damping unit 14 based on a computer software analysis. As shown in FIG. 6, a model 41 of the rack 12 was defined for the observation. The model 41 included a rack 42 having four support columns 43 and upper and lower frames 44, 44 coupling the support columns 43. The upper frame 44 was located on the upper ends of the support columns 43. The lower frame 44 was located adjacent to the lower ends of the support columns 43.
Here, the height of the individual support columns 43 in the z-axis was set at 1,800 [mm]. The length of the upper and lower frames 44 in the x-axis was set at 600 [mm]. The length of the upper and lower frames 44 in the y-axis was set at 950 [mm]. The bottom surface of the lower frame 44 was located at a height of 50 [mm] from the bottom ends of the support columns 43. The movement of the bottom ends of the support columns 43 was restrained. The weight of the rack 42 was set at 150 kg. The Young's modulus of the rack 42 was set at 193.198 [GPa]. The Poisson's ratio of the rack 42 was set at 0.3.
As is apparent from FIG. 6, the aforementioned vibration damping unit 14 was imaginarily incorporated within the upper frame 44. Four coil springs 45 and four dampers 46 were defined in the upper frame 44. The coil springs 45 and the dampers 46 were designed to extend inward from the upper frame 44. A mass 47 of the vibration damping unit 14 was defined at a joint of the coil springs 45 and the dampers 46. The movement of the mass 47 in the z-axis was restrained in the vibration damping unit 14. The mass 47 was thus allowed to move only along the xy plane.
First to ninth specific examples were prepared for the observation. As shown in FIG. 7, the weight [kg] of the mass 47, the spring constants [N/mm] of the coil spring 45, and the damper constants [Nmm/s] of the damper 46 were set for the first to ninth specific examples, respectively. Three values were employed in each parameter. A comparative example was also prepared. The vibration damping unit 14 was omitted in the comparative example. The rack 42 was subjected to a sway in the x-axis at the acceleration of 1 [G] or 9.8 m/s². The decrement of the sway was set at 1%. A response acceleration was measured at a measuring point 48 set at one of the corners of the upper frame 44.
As shown in FIG. 8, the maximum or peak appears in the response acceleration [G] at the resonance frequency [Hz] of the rack 42 in the comparative example. On the other hand, as shown in FIG. 9, the maximums or peaks appear in the response acceleration [G] at the resonance frequency of the rack 42 and the resonance frequency of the vibration damping unit 14 in the seventh specific example. Two peaks were observed in the other specific examples as well.
As shown in FIG. 10, the response acceleration measured at the measuring point 48 takes the peak at 58.8 [G] in the comparative example. On the other hand, the resonance frequency measured at the measuring point 48 takes the first peak in a range from 27.6 to 38.8 [G], at the resonance frequency of the rack 42, in the first to ninth specific examples. Likewise, the resonance frequency measured at the measuring point 48 takes the second peak in a range from 27.1 to 38.8 [G], at the resonance frequency of the vibration damping unit 14, in the first to ninth specific examples. It has been confirmed that the racks 42 of the first to ninth specific examples are allowed to enjoy a remarkable reduction in the response acceleration as compared with the comparative example. It has been confirmed that the vibration damping unit 14 enables a remarkable suppression of the sway or vibration of the rack 42.
Referring also to FIG. 7, it has been revealed that a larger weight of the mass 47 contributes to a further suppression of sway or vibration of the rack 42. Likewise, it has been revealed that a smaller spring constants contributes to a further suppression of sway or vibration of the rack 42. It has been revealed that the damper constants have little influence on the suppression of sway or vibration of the rack 42. It has been revealed that the attenuation of sway or vibration depends on the weight of the mass 47 and the spring constants of the coil springs 45.
The inventors have also observed the influence of the position of the vibration damping unit 14 in the rack 12. A computer software analysis was used for the observation in the same manner as described above. As shown in FIG. 11, the rack 42 of a model 41 a included first and second middle frames 44 a, 44 b located in a space between the aforementioned upper and lower frames 44. The distance between the upper and lower frames 44 may be equally divided into three by inserting the first and second middle frames 44 a, 44 b. The first middle frame 44 a was located next to the upper frame 44. The second middle frame 44 b was located next to the lower frame 44.
The same values were used for the Young's modulus, the Poisson's ratio and the weight of the rack 42. The same value was also used for the weight of the mass 47. The spring constants of the coil spring 45 in the vibration damping unit 14 were set at 493 [N/mm]. The damper constants of the dampers 46 in the vibration damping unit 14 were set at 300 [Nmm/s]. The movement of the bottom ends of the support columns 43 was restrained. The vibration damping unit 14 was thus allowed to move only along the xy plane.
Specific examples A to C were prepared for the observation. The specific example A had the vibration damping unit 14 imaginarily incorporated within the upper frame 44. The specific example B had the vibration damping unit 14 imaginarily incorporated within the first middle frame 44 a. The specific example C had the vibration damping unit 14 imaginarily incorporated within the second middle frame 44 b. The same comparative example as described above was prepared. The vibration damping unit 14 was omitted in the comparative example.
The rack 42 was subjected to a sway in the x-axis at the acceleration of 1 [G] or 9.8 m/s²in the specific example A to C as well as the comparative example. The decrement of the sway was set at 1%. A response acceleration was measured at a measuring point 48 set at one of the corners of the upper frame 44. The maximum or peak of the response acceleration was observed in the specific example A to C as well as the comparative example, respectively.
As shown in FIG. 12, the response acceleration measured at the measuring point 48 takes the peak at 64.0 [G] in the comparative example. The response acceleration measured at the measuring point 48 takes the peak at 33.0 [G] in the specific example A. The response acceleration measured at the measuring point 48 takes the peak at 33.6 [G] in the specific example B. The response acceleration measured at the measuring point 48 takes the peak at 36.7 [G] in the specific example C. As is apparent from the ratio to the comparative example, it has been confirmed that the vibration damping unit 14 enables a remarkable suppression of the sway or vibration of the rack 42.
As is apparent from the ratio to the specific example A, it has been confirmed that the specific example A exhibits the minimum value of the response acceleration. In other words, it has been confirmed that the maximum response acceleration reduces as the vibration damping unit 14 gets closer to the top of the rack 12. It has thus been revealed that the vibration damping unit 14 is preferably located as close to the top as possible in the rack 12.
The vibration damping unit 14 can be applied to a rack containing two or more server computers 13, other types of electronic apparatus and other types of recording medium drive as well.

Claims

1. A vibration damping unit comprising:

a rack-mounted support body removably mounted on a rack;

a mass supported on the support body for movement along an imaginary plane; and

an elastic member coupled to the support body and the mass.

2. The vibration damping unit according to claim 1, wherein the mass comprises:

a tray coupled to the support body for movement along the imaginary plane; and

at least one weight member removably mounted on the tray.