Abstract:
The present invention discloses a self-stabilizing heat exhaust system including at least several rate-variable fans. Each of the rate-variable fans further includes a power-input terminal for inputting power to the rate-variable fans; a grounded terminal for providing the rate-variable fan a lower level; a signal-output terminal coupled to an adjacent rate-variable fan for outputting a speed signal which may be a normal signal or an abnormal signal; a signal-input terminal coupled to another adjacent rate-variable fan for receiving the speed signal; and a control circuit responding to the abnormal signal to make the rate-variable fan rotate at the higher rotation rate and responding to the normal signal to make the rate-variable fan rotate at the lower rotation rate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a heat exhaust system, and more particularly to a self-stabilizing heat exhaust system. 
     2. Description of the Prior Art 
     As the electric device progresses in performance, a heat exhaust system becomes indispensable for dissipating the heat generated by the electric device. The heat generated by the electric device should be properly dissipated, otherwise the performance may be encumbered with the accumulated heat or the worst burns the electric devices. For example, a computer may be equipped with a heat exhaust system including several fans for dissipating the heat generated by a CPU or a power supply. The heat exhaust system is connected to the control port of the computer, and controlled by the control circuit built in the computer. Once some fan is failed, if the other normal fans in the system do not compensate the decreased heat exhaust ability as soon as possible, the result may be terrible. 
     A conventional heat exhaust system shown in FIG. 1 includes a heat-generating device  10 , such as a computer, and several fans  30 , such as a first fan  30   a , a second fan  30   b  and a third fan  30   c . Among these, the heat-generating device  10  further includes a control circuit  20 , such as a logic control circuit. The control circuit  20  has a speed signal input terminal  21 , a speed control terminal  22 . The fan  30  has a power-input terminal  31 , a grounded terminal  32 , a signal-output terminal  33 (O/P) and a signal-input terminal  35 (I/P). 
     Still referring to FIG. 1, each signal-output terminal  33  of the fan  30  is electrically connected to the speed signal input terminal  21  of the control circuit  20 . Therefore, the control circuit  20  can receive a speed signal representing that the rotation rate of the fan  30  is normal or abnormal. In general, if the rotation rate is normal, the speed signal is a high-level signal. On the contrary, if the rotation rate is abnormal, the speed signal is a low-level signal. However, the low-level signal may indicate that the rotation rate is normal, and the high-level signal may indicate that the rotation rate is abnormal. The signal-input terminal  35  of the fan  30  is electrically connected to the speed control terminal  22  of the control circuit  20 . Therefore, the control circuit  20  can send a speed control signal to the fan  30   a-c  to control the speed of the fan. 
     Still referring to FIG. 1, when some fan, such as the first fan  30   a , is failed, the control circuit  20  received an abnormal signal from the failed fan  30   a . Then, the control circuit  20  sends a signal to the second fan  30   b  and the third fan  30   c  to increase the rotation rate of the fans  30   b  and  30   c . In this manner, the decreased heat exhaust ability, caused by the failed first fan  30   a , can be compensated by the higher rotation rate provided by the normal fans. 
     According to the above-mentioned conventional heat exhaust system, it is understood that the heat-generating device  10 , such as the computer, detects which fan is failed and then the external control circuit activates the compensation. That is, the conventional heat exhaust system itself cannot detect and self-control whether the speed of the fan should be increased or not. The conventional heat exhaust system inherently includes several disadvantages as follows. First, the complexity of the heat-generating device is increased due to the addition of the heat exhaust system. An external control circuit, such as a logic control circuit, is required and thus built in the heat-generating device. As increase in the number of fans, the fan-out ability of the logic control circuit should be increased at the same time. As a result, the cost of the logic control circuit is increased. 
     Therefore, there is a need in the art for resolving the above disadvantages. 
     SUMMARY OF THE INVENTION 
     Therefore, the main object of the present invention is to provide a novel heat exhaust system can overcome the aforementioned problems. Besides, the above object of the present invention is achieved by a self-stabilizing heat exhaust system. 
     The present invention disclosed a self-stabilizing heat exhaust system including a plurality of devices for exhausting heat, such as fans. When all the fans are normal, each of the fans rotates at lower rotation rate. Once some fan fails, an adjacent fan will be switched to rotate at a higher rotation rate. For example, the value of the higher rotation rate may be two times of that of the lower rotation rate. Alternatively, the remaining fans start to rotate at the higher rotation rate so as to compensate the decreased exhaust ability. That is, the system of the present invention responds to the failed fan and then increases the exhaust ability of the normal fans. Thus, the inlet airflow and the outlet airflow can be kept steadily. Therefore, the heat-generating device, such as a computer, connected to the present system substantially does not experience problem in heat exhaust. Especially, the present invention does not need to co-operate with an external logic control circuit. That is, the present invention does not need to be connected to any logic control circuit built in the computer via a control port because the fan of the present system is able to detect the condition of each other and then vary the rotation rate by itself. 
     In sum, the present system is independent of the heat-generating device. There is free of any connection between the present system and the heat-generating device. Therefore, the complexity of the heat-generating device can be reduces significantly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 depicts a conventional heat exhaust system associated with a heat-generating device; 
     FIG. 2 depicts the block diagram of an embodiment of the present invention; and 
     FIG. 3 depicts the block diagram of another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention disclosed a self-stabilizing heat exhaust system including a plurality of devices for exhausting heat, such as fans. When all the fans are normal, each of the fans rotates at a lower rotation rate. Once some fan has a failure, an adjacent fan will be switched to rotate at a higher rotation rate. For example, the value of the higher rotation rate may be two times of that of the lower rotation rate. Alternatively, the remaining fans rotate at the higher rotation rate to compensate the decreased exhaust ability. That is, the system of the present invention responds to the failed fan and then increases the exhaust ability of the normal fans. Thus, the inlet airflow and the outlet airflow can be kept steadily. Therefore, the heat-generating device (i.e. a computer) connected to the present system substantially does not experience problem in heat exhaust. 
     Especially, for the present invention, an external logic control circuit for controlling the exhaust system is not required. That is, the present invention does not need to be connected to an external logic control circuit. For example, the present invention does not need to be connected to the logic control circuit, built in the computer, via a control port because the fan of the present system is able to detect, respond to the condition of each other and then vary the rotation rate by itself. 
     The block diagram shown in FIG. 2 depicts the first embodiment of the present invention. As shown in FIG. 2, the self-stabilizing heat exhaust system  50  includes n rate-variable fans  300 , wherein n is a natural number and n≧2. In any case, the rate-variable fan  300  is able to rotate at a higher rotation rate or a lower rotation rate. That is, the fan  300  is at least a dual-rate fan. In the first embodiment of the present invention, the higher rotation rate is the double of the lower rotation rate. However, any suitable multiples also can be used. In the present system, each fan has a power-input terminal (not shown), a grounded terminal (not shown), a m th  signal-output terminal (O/P)  330 , a m th  signal-input terminal  350  and a m th  control circuit  500 , wherein m is from 1 to n, and m is a natural number. 
     Still referring to FIG. 2, the m th  signal-output terminal  330  can output a m th  speed signal. The m th  speed signal may be a m th  normal signal or a m th  abnormal signal. The m th  normal signal indicates that the m th  fan is normal and m th  abnormal signal indicates that the m th  fan is abnormal, respectively. If m is not 1, the m th  signal-input terminal  350  is coupled to the m−1 th  signal-output terminal  330 . Therefore, the m th  signal-input terminal  350  can receive the m−1 th  speed signal. When m is 1, the m th  signal-input terminal  350  is coupled to the n th  signal-output terminal  330 . Therefore, the m th  signal-input terminal  350  can receive the n th  speed signal. 
     Still referring to FIG. 2, when m is not 1, the m th  control circuit  500  responds to the m−1 th  abnormal signal to make m th  rate-variable fan  300  rotate at the higher rotation rate. Additionally, the m th  control circuit  500  responds to the m−1 th  normal signal to make m th  rate-variable fan  300  rotate at the lower rotation rate. When m is 1, the m th  control circuit  500  responds to the n th  abnormal signal to make m th  rate-variable fan  300  rotate at the higher rotation rate. Additionally, the m th  control circuit  500  responds to the m−1 th  normal signal to make m th  rate-variable fan  300  rotate at the lower rotation rate. 
     That is, when all the fans in the system  50  are normal, each of the fans in the system  50  does not receive any abnormal signal. That is, each of the fans in the system  50  receives the normal signal. However, once some fan (i.e. the first rate-variable fan, m=1) is failed, the failed first rate-variable fan outputs a first abnormal signal to the adjacent rate-variable fan (i.e. the second rate-variable fan, (m=2)) via its signal-output terminal  330 . At this time, the control circuit  500  of the second rate-variable fan responds the first abnormal signal to make the second rate-variable fan rotate at the higher rotation rate. In this manner, the decrease in the heat exhaust ability, caused by the failed first rate-variable fan, can be compensated by the higher rotation rate provided by the second rate-variable fan. The value of the higher rotation rate is at least two times of that of the lower rotation rate. 
     Alternatively, when the n th  rate-variable fan (m=n) is failed, the n th  rate-variable fan outputs a n th  abnormal signal to the first rate-variable fan (m=1) via its signal-output terminal  330 . At this time, the control circuit  500  of the first rate-variable fan responds to the n th  abnormal signal to make the first rate-variable fan rotate at the higher rotation rate. In this manner, the decrease in the heat exhaust ability, resulted from the failed n th  rate-variable fan, can be compensated by the higher rotation rate provided by the first rate-variable fan. The value of the higher rotation rate is at least 2 times of that of the lower rotation rate. That is, once any fan in the system  50  is failed, one of the fans electrically connected to the failed fan will rotate at higher rotation rate. 
     The second embodiment of the present invention is illustrated in FIG.  3 . As shown in the FIG. 3, the self-stabilizing heat exhaust system  50  includes a joint  100  and includes at least two rate-variable fans  300 . For example (but not limited) a first rate-variable fan  300   a , a second rate-variable fan  300   b  and a third rate-variable fan  300   c  are included. In any case, the rate-variable fan  300  can rotate at a higher rotation rate or a lower rotation rate. That is, the fan  300  at least includes a dual-rate fan. Each of the fans has a power-input terminal (not shown), a grounded terminal (not shown), a signal-output terminal (O/P)  330 , a signal-input terminal  350  and a control circuit  500 . Because the functions of the foregoing terminals are identical to the description in the first embodiment, unnecessary description is omitted. 
     Still referring to FIG. 3, all signal-output terminals  330  are coupled to the joint  100 . The signal-output terminal  330  outputs a speed signal. The speed signal may be a normal signal or an abnormal signal. The normal signal indicates that the fan outputting such a signal is normal and the abnormal signal indicates that the fan outputting such a signal is abnormal. In addition, all the signal-input terminals  350  are coupled to the joint  100  so that the signal-input terminals  350  can receive the speed signal. Via the signal-input terminals  350 , the control circuit  500  can receive and then respond to the abnormal signal to make the rate-variable fan  300  rotate at the higher rotation rate. Similarly, the control circuit  500  can receive and then respond to the normal signal to make the rate-variable fan  300  rotate at the lower rotation rate. 
     Still referring to FIG. 3, when some fan, such as the first fan  300   a , in the system  50  is failed, the first fan  300   a  outputs an abnormal signal via its signal-output terminal  330 . At this time, the signal-input terminals  350  of the rest of the fan(s), such as the second fan  300   b  and the third fan  300   c , receive the abnormal signal. Then, both of the control circuits  500  of the second fan  300   b  and the third fan  300   c , respond to the abnormal signal to make the second fan  300   b  and the third fan  300   c  rotate at the higher rotation rate. In this manner, the decrease in the heat exhaust ability, caused by the failed first fan  300   a , can be compensated by the higher rotation rate provided by the second fan  300   b  and the third fan  300   c.    
     The system disclosed by the present invention can be electrically independent of the heat-generating device. That is, there is no any electrical connection between the present system and the heat-generating device. Any external control circuit is not required. Therefore, the complexity of the heat-generating device can be reduced. Furthermore, in the present invention, the control circuit  500  controls the corresponding fan so that it is not necessary to increase the fan-out ability of the control circuit  500  if the number of the fan increases. 
     As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrated of the present invention rather than limiting of the present invention. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.