Abnormal temperature detector for electronic apparatus

Abstract: An abnormal temperature detector for an electronic apparatus includes a plurality of temperature detectors, an abnormality detector, and a power supply controller. The plurality of temperature detectors are arranged at least at one detection point of a rack, of an electronic apparatus, in which a plurality of wiring boards having IC elements mounted thereon are housed, and respectively output detection outputs when a temperature at the detection point becomes a preset temperature or more. The abnormality detector detects that detection outputs are output from all the temperature detectors at the detection point. The power supply controller interrupts a power supply of the apparatus in response to an abnormality detection output from the abnormality detector.

Description: Background of the Invention The present invention relates to an abnormal temperature detector for an electronic apparatus. Electronic equipment such as a data processor is designed such that a plurality of wiring boards having IC elements mounted thereon are housed in a rack. The IC elements are cooled by forced convection of air using cooling fans to prevent a rise in temperature of each element and to maintain reliability. In order to prevent a breakdown of such an apparatus, which is caused by a rise in temperature of the IC elements upon failure of the cooling fans or the like, the following method is employed. A detector is used to detect an atmospheric temperature near the rack. Upon detection of a temperature higher than a predetermined temperature, the detector sends a signal to a power supply circuit to stop the supply of power to the apparatus, thus protecting it. Fig. 3 shows a conventional abnormal temperature detector. Referring to Fig. 3, reference numeral 101 denotes a rack for housing wiring boards having IC elements mounted thereon; 102, a cooling fan; 103, a thermostat designed to open a contact at a preset temperature or more; 104, an abnormality detector; and 105, a power supply controller. When a temperature near the rack 101 is increased to the preset temperature or more upon failure of the cooling fans 102 or the like, the contacts of the thermostats 103 are opened. The abnormality detector 104 detects this state and outputs a signal to the power supply controller 105 to stop the supply of power to the apparatus. According to the above-described conventional abnormal temperature detector for electronic equipment, however, when the contacts are opened upon failure of the thermostats, or cables for connecting the thermostats to the power supply controller are disconnected, an abnormal temperature is erroneously detected to cause the power supply controller 105 to stop the supply of power to the apparatus. Summary of the Invention It is a principal object of the present invention to provide an abnormal temperature detector for an electronic apparatus, which can improve the reliability of the electronic apparatus. It is another object of the present invention to provide an abnormal temperature detector for an electronic apparatus, which is free from operation errors caused by a breakdown of a temperature detecting means. It is still another object of the present invention to provide an abnormal temperature detector for an electronic apparatus, which is free from operation errors caused by disconnection of a wiring system. In order to achieve the above objects, there is provided an abnormal temperature detector for electronic apparatus having a rack in which a plurality of wiring boards having IC elements mounted thereon are housed, the detector comprising: a first set of temperature detecting means to be disposed at respective detection points on or near a rack and connected in series with each other to abnormality detecting means, the temperature detecting means responding to an excessive temperature by breaking the continuity of said series connection and the abnormality detecting means detecting said break; power supply control means for interrupting a power supply to the apparatus in response to an abnormality detection output from said abnormality detecting means; and characterised by a second set of said temperature detecting means each of which is to be disposed at a respective said detection point in a pair with a temperature detecting means of the first set, the second set of temperature detecting means being connected in series with each other to the abnormality detecting means, the two series-connected sets of temperature detecting means being connected to the abnormality detecting means in separate parallel circuits whereby the abnormality detecting means produces an abnormality detection output in response to an excessive temperature at a said detection point only in response to both temperature detecting means at said detection point breaking the continuity of their respective series connections. Brief Description of the Drawings Figs. 1 and 2 are block diagrams respectively showing the first and second embodiments of the present invention; and Fig.3 is a block diagram showing a conventional abnormal temperature detector. Description of the Preferred Embodiments The present invention will be described below with reference to the accompanying drawings. Fig. 1 shows the first embodiment of the present invention. Referring to Fig. 1, reference numeral 1 denotes a rack for housing a plurality of wiring boards having IC elements mounted thereon; 2, a cooling fan; and 3, a thermostat which is arranged near the rack 1 and opens a contact at a preset temperature or more. The thermostats 3 are arranged in pairs at the respective detection points. One thermostat of each thermostat pair at the respective detection points are connected in series, forming a first set. The other thermostats of each pair also are connected in series to form a second set. The two series-connected sets of thermostats 3 are independently connected to an abnormality detector 4 through cables 6 of independent, parallel wiring systems. Reference numeral 5 denotes a power supply controller. Upon reception of a detection output from the abnormality detector 4, the power supply controller 5 stops the supply of power to the apparatus. Assume that the two thermostats of a given pair function properly. In this case, if a temperature near the rack is lower than the preset temperature, the contacts of the two thermostats are closed. When a temperature near the rack is increased to the preset temperature or more upon failure of the cooling fans 2 or the like, the contacts of the two thermostats are opened. The abnormality detector 4 detects this state and supplies a detection output to the power supply controller 5, thus stopping the supply of power to the apparatus. Assume that one of the thermostats is broken down and presents an open circuit at a temperature lower than the preset temperature. In this arrangement, upon detection of an open state of the contact of a given thermostat 3 in one wiring system, the abnormality detector 4 drives an alarm circuit 7 to generate an alarm to inform a failure. The abnormality detector 4 supplies an output to a power supply controller 5 to stop the supply of power to the apparatus only when it detects that the contacts of given thermostats 3 in each of the two sets are open. With this operation, even if the cable 6 between the thermostats 3 and the abnormality detector 4 is disconnected, and if the disconnection occurs in only one of the wiring systems, the abnormality detector 4 does not detect a contact open state at any detection point. Therefore, the supply of power is not erroneously interrupted. Fig. 2 shows a second embodiment of the present invention. The second embodiment is the same as the first embodiment except that the two terminals of one of the two thermostats at each detection point are connected to those of the other thermostat. With this arrangement, only when the two thermostats 3 at one detection point are simultaneously opened, the supply of power to the apparatus is stopped by an output from an abnormality detector 4. Therefore, even if one of each of thermostat pairs at different detection points fails, the power supply is not erroneously interrupted. In each embodiment described above, the abnormality detector 4 and the power supply controller 5 may be integrated into one circuit. According to the present invention, the abnormal temperature detector for an electronic apparatus is designed to prevent erroneous interruption of the supply of power to the apparatus upon failure of a thermostat for detecting abnormality or disconnection of a wiring system of a circuit. The present invention can be effectively applied especially to a system required to process a large amount of data and to be operated without interruption, such as a large data processor. As has been described above, according to the present invention, since a plurality of temperature detecting means, which open contacts at a preset temperature or more, are arranged at each detection point, a power supply is not erroneously interrupted upon failure of some of the temperature detecting means or disconnection of a wiring system. Therefore, the overall apparatus can be improved in reliability.

Claims: An abnormal temperature detector for electronic apparatus having a rack in which a plurality of wiring boards having IC elements mounted thereon are housed, the detector comprising: a first set of temperature detecting means (3) to be disposed at respective detection points on or near a rack and connected in series with each other to abnormality detecting means (4), the temperature detecting means responding to an excessive temperature by breaking the continuity of said series connection and the abnormality detecting means detecting said break; power supply control means (5) for interrupting a power supply to the apparatus in response to an abnormality detection output from said abnormality detecting means; and characterised by a second set of said temperature detecting means (3) each of which is to be disposed at a respective said detection point in a pair with a temperature detecting means of the first set, the second set of temperature detecting means being connected in series with each other to the abnormality detecting means, the two series-connected sets of temperature detecting means being connected to the abnormality detecting means in separate parallel circuits whereby the abnormality detecting means produces an abnormality detection output in response to an excessive temperature at a said detection point only in response to both temperature detecting means at said detection point breaking the continuity of their respective series connections. A detector according to Claim 1, wherein the terminals of each temperature detecting means at a said detection point are connected to the corresponding terminals of the other temperature detecting means at that point. A detector according to Claim 1 or Claim 2, wherein each of said temperature detecting means includes one contact which is opened at a temperature greater than or equal to a preset temperature. A detector according to Claim 1, further comprising alarm means (7) for generating an alarm, said abnormality detecting means driving said alarm means upon detecting the break of continuity in only one of said parallel circuits. A detector according to any one of the preceding claims, wherein said rack in which said plurality of wiring boards are housed is forcibly cooled by cooling fans.

Inventors: UMEZAWA KAZUHIKO C O NEC CORPO, UMEZAWA, KAZUHIKO, C/O NEC CORPORATION
Applicants: NIPPON ELECTRIC CO, NEC CORPORATION
Application year: 1991
Main classification: H02H5
IPC codes: H02H3, G01K1, H05K7, H02H5, G05D23, G01K7