1. Field of the Invention
The present invention relates to a rack for electronic devices and equipments that generate heat and in particular to a low-cost instrument rack with high warm-air discharge efficiency.
2. Description of the Related Art
Many diverse electronic devices: personal computers, measuring instruments and others have been installed in places ranging from business offices to factories in recent years, and the environmental conditions under which each electronic device is used have become critical as a result. For instance, there are cases in which multiple electronic devices are mounted in vertical arrangements inside a rack for mounting equipment for the purpose of efficient use of room space.
Electronic devices for this type of rack mount are generally equipped with fans that cool each electronic device because when the temperature of each electronic component in the device housing increases too much due to the emission of heat, problems occur in that degradation of the electronic component takes place, and further, its service life is curtailed.
In the past, an instrument rack comprising a rack for mounting devices having two frames (four support columns) arranged parallel to one another in the longitudinal direction at a pre-determined interval and multiple individual electronic devices with fans attached mounted on the frames of this rack lined up in a row in the vertical direction has been used for this type of instrument rack.
The covers (front door, back door, side covers, etc.) that are normally attached to the rack are removed and the heat from the electronic devices inside the rack is released to outside of the rack with this type of instrument rack.
Nevertheless, this type of rack is awkward to look at, foreign matter easily enters the inside of the rack, and the heat generated is uncomfortable to users of equipment near the rack. Moreover, when several racks of this type are lined up close to one another, heat is exchanged between the adjacent racks and this leads to an abnormal increase in temperature of the mounted electronic devices.
Therefore, holes that lead to the inside of the rack are made in the top of racks with a cover and the hot air from the electronic devices rises from the bottom of the rack and flows outside the rack through these holes.
Nevertheless, there are problems with this method in that the rise of air as a result of natural convection is weak and the amount of air that can be discharged to outside the rack is insufficient. In addition, the convection of air is disturbed by agitation of the air inside the rack by the fans of the electronic devices and this also reduces heat discharge efficiency. Furthermore, there is a problem in that if electronic devices that reach a high temperature are placed at the bottom of the rack, the electronic devices at the top inside the rack will be exposed to air that is hotter and therefore, placement of the electronic devices is difficult.
Therefore, additional fans are attached to the holes in the top in order to force the air to rise and the hot air inside the rack is thereby suctioned and discharged under force. By means of this method, the amount of heat that can be discharged increases in proportion to the capability of the additional fans, but electricity is needed to drive the fans, and a problem develops as a result of the noise generated by the fans. Furthermore, if the additional fans break down, the temperature inside the rack will rise and all of the electronic devices mounted inside the rack will be exposed to the risk of breakdown. Furthermore, there is also a problem in that it is difficult, of course, to arrange the electronic devices for an efficient discharge of heat.
Technology wherein the heat that is discharged from one electronic device does not affect the other electronic devices has been developed as a technology that facilitates the placement of electronic devices (for instance, reference to Patent Reference 1). By means of the technology cited in Patent Reference 1, air from each electronic device is discharged by duct 34, which is formed from inside wall 26 of housing 20 and side surface 6 of unit (electronic device) 4 (or, by blind patch 33 placed where there are no electronic devices), and the warm air that has been discharged is forced outside the device by fan 25 placed at the top of housing 20. On the other hand, cold air from intake port 23 at the bottom of housing 20 is introduced to inside unit 4 by fan 7 of unit 4, passes through unit 4, and is discharged through duct 34. Fan 7 is placed on the side of side surface 12 that faces side surface 6.
In addition, technology has been developed in which the electronic devices mounted on a rack are cooled by natural cooling without attaching any additional fans to the rack (for instance, refer to Patent Reference 2). By means of the technology cited in Patent Reference 2, fans of the electronic devices draw air inside the electronic devices through the air inflow port on the front surface of the rack and this air is discharged by the fan to air ducts outside the electronic devices. Air ducts inside the rack are placed at each electronic device so that the fans are enclosed by the sides of the rack and discharge from the fans is directed to the back surface, which is open at the openings in the top of the rack.
By means of this technology, there is no mixing of discharge air and intake air between electronic devices at the top and bottom. Therefore, it is not necessary to place a cover between the electronic devices at the top and those at the bottom and discharge efficiency can be increased. In addition, it is not necessary to form a path for cooling between the electronic devices at the top and those at the bottom, so that the rack dimensions can be reduced in the direction of height and miniaturization of the overall structure can be anticipated. In addition, by applying a sound-absorbing member inside the air duct, it is possible to partially absorb and thereby attenuate some of the noise generated by the exhaust air from the fan. Furthermore, technology is also disclosed in Patent Reference 2 whereby air inflow ports and air outflow ports that open up inside and outside the housing of the electronic devices are set up and in these, the air channel ports of the air ducts communicate with the air inflow ports. In this case, after the exhaust air from the air ducts has flowed from the air inflow port of the housing into the electronic devices, it flows out again from the air outflow ports of the housing to outside the rack and therefore, the distance for which the exhaust air from the fan passes through the rack is increased and the noise from the exhaust air can be more efficiently attenuated.
There are problems with the prior technology cited in Patent Reference 1 in that although there is no mixing of intake air and discharge air, since fans for forced air cooling are installed, the suctioning of air is restricted to the bottom of the housing, and there are restrictions to the size and direction of the electronic devices, and the like.
There are also problems with the instrument rack cited in Patent Reference 2 in which additional fans for forced air cooling of the rack are not installed. That is, air ducts with a relatively complex structure are set up inside the rack and therefore, cost is high, and the space inside the rack that is used for discharge is also limited. Moreover, exhaust air leaks and enters inside the rack from the connecting parts between the air ducts and the electronic devices and it is necessary to design the connecting parts to match the dimensions of the electronic devices.
[Patent Reference 1]
Official gazette of laying open for the Japanese Utility Model Application No. Showa 62(1987)-174,397 (line 2, page 5 through line 16, page 6; FIGS. 1 and 3).
[Patent Reference 2]
Official gazette of Japanese Patent Application laying open No. 2000-277,956 (sections 0015 through 0037, FIGS. 1 and 2)