Liquid cooling apparatus with improved leakage detection for electronic devices

A liquid cooling apparatus includes a heat exchanger, a tank, leakage sensors, first and second level sensors, a timer counter, and a control section. The heat exchanger cools a coolant to be supplied to a heat generating portion in an electronic device. The tank temporarily stores the coolant cooled by the heat exchanger before the coolant is supplied to the electronic device. The leakage sensors detect leakage of the coolant in a circulation path for repeatedly performing cooling and heat absorbing operations. The first and second level sensors detect a decrease in amount of the coolant in the tank. The timer counter counts a time interval between the instant at which a leakage detection output is output from one of the leakage sensors and the instant at which a coolant decrease detection output is output from one of the first and second level sensors. The control section stops an operation of the electronic device when a value of the timer counter is a predetermined value or less.

BACKGROUND OF THE INVENTION 
The present invention relates to a liquid cooling apparatus and, more 
particularly, to a treatment for leakage caused in a liquid cooling 
apparatus. 
In a conventional cooling apparatus, as shown in FIG. 3, a coolant 3 cooled 
by a heat exchanger 51 of a cooling apparatus 5 is stored in a tank 52 
through a pipe 4a. The coolant 3 stored in this tank 52 is supplied to a 
heat generating portion 62 in an electronic device 6 by a pump 54. The 
heat generating portion 62 is then cooled by the coolant 3. 
The coolant 3 which is heated upon cooling the heat generating portion 62 
is returned to the heat exchanger 51 through a pipe 4b. The coolant 3 is 
cooled by the heat exchanger 51 again and is supplied to the heat 
generating portion 62 through the pipe 4a, the tank 52, and the pump 54. 
In the cooling apparatus 5, a decrease in amount of the coolant 3 stored in 
the tank 52 is detected by a level switch 53, and the detection result is 
input to a control section 50 through a signal line 111. The heat 
exchanger 51 and the pump 54 are controlled by the control section 50 
through signal lines 113 and 112. 
In the electronic device 6, power V is supplied from a power supply 61 
controlled by a control section 60 to the heat generating portion 62. The 
heat generating portion 62 is driven by this power V. The control section 
60 and the power supply 61 are connected to the control section 50 of the 
cooling apparatus 5 through a signal line 114. 
If an abnormality occurs in the cooling apparatus 5 while the cooling 
apparatus 5 and the electronic device 6 are operated, the control section 
50 of the cooling apparatus 5 turns off the power supply 61 of the 
electronic device 6 to prevent the heat generating portion 62 from being 
heated to a high temperature. 
In such a conventional liquid cooling apparatus, in order to prevent the 
heat generating portion 62 from being heated to a high temperature when 
the amount of the coolant 3 circulating through the pipes 4a and 4b is 
reduced, only when a decrease in amount of the coolant in the tank is 
detected by the level switch 53, the power supply 61 of the electronic 
device 6 is turned off under the control of the control section 50. For 
this reason, even if the amount of coolant is gradually decreased and the 
power supply 61 need not be turned off, the power supply 61 may be turned 
off. 
In addition, assume that only a small amount of the coolant 3 leaks and is 
stored in drain pans 55 and 63 of the cooling apparatus 5 and the 
electronic device 6 so as not to leak outside, and hence an operation can 
be continued. Even in such a case, the power supply 61 of the electronic 
device 6 is immediately turned off under the control of the control 
section 50. Therefore, the above-described control poses a problem in a 
computer system and the like which are greatly influenced by the 
interruption of an operation. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a liquid cooling 
apparatus which allows an electronic device to be continuously operated 
when a coolant gradually leaks or a coolant amount is gradually decreased 
and no urgent treatment is required. 
It is another object of the present invention to provide a liquid cooling 
apparatus most suitable for a computer system which is greatly influenced 
by the interruption of an operation. 
In order to achieve the above objects, according to the present invention, 
there is provided a liquid cooling apparatus characterized by comprising a 
heat exchanger for cooling a coolant to be supplied to a heat generating 
portion in an electronic device, a tank for temporarily storing the 
coolant cooled by the heat exchanger before the coolant is supplied to the 
electronic device, leakage detecting means for detecting leakage of the 
coolant in a circulation path for repeatedly performing cooling and heat 
absorbing operations, coolant detecting means for detecting a decrease in 
amount of the coolant in the tank, timer counter means for counting a time 
interval between an instant at which a leakage detection output is output 
from the leakage detecting means and an instant at which a coolant 
decrease detection output is output from the coolant detecting means, and 
control means for stopping an operation of the electronic device when a 
value of the timer counter means is a predetermined value or less.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the present invention will be described below with 
reference to the accompanying drawings. 
FIG. 1 shows an arrangement of an embodiment of the present invention. 
Referring to FIG. 1, a coolant 3 cooled by a heat exchanger 11 of a 
cooling apparatus 1 is stored in a tank 12 through a pipe 4a. The coolant 
3 stored in this tank 12 is supplied to a heat generating portion 22 in an 
electronic device 2 by a pump 14. The heat generating portion 22 is cooled 
by the coolant 3. 
The coolant 3 used to cool the heat generating portion 22 is returned to 
the heat exchanger 11 through a pipe 4b. The coolant 3 is cooled by the 
heat exchanger 11 again and is supplied to the heat generating portion 22 
through the pipe 4a, the tank 12, and the pump 14. 
In the cooling apparatus 1, a decrease in amount of the coolant 3 stored in 
the tank 12 is detected by first and second level sensors 13a and 13b. The 
first level sensor 13a monitors whether the level of the coolant 3 is at a 
predetermined level or higher from the bottom of the tank 12, and outputs 
a first detection signal if the level is below the predetermined level. 
The second level sensor 13b monitors whether the level of the coolant 3 is 
at the predetermined level or lower and higher than a predetermined level 
near the bottom of the tank 12, and outputs a second detection signal if 
the level is below the predetermined level near the bottom. These first 
and second detection signals are input to a control section 10 through 
signal lines 101a and 101b. The heat exchanger 11 and the pump 14 are 
controlled by the control section 10 through signal lines 103 and 102. 
In the electronic device 2, power V is supplied from a power supply 21 
controlled by a control section 20 to the heat generating portion 22. The 
heat generating portion 22 is driven by this power V. The control section 
20 and the power supply 21 are connected to the control section 10 of the 
cooling apparatus 1 through a signal line 105. 
A portion of the coolant 3 which leaks out of a circulation path for 
allowing the coolant 3 to circulate through the cooling apparatus 1 and 
the electronic device while repeatedly performing cooling and heat 
absorbing operations is stored in drain pans 15 and 23 of the cooling 
apparatus 1 and the electronic device 2. These drain pans 15 and 23 
respectively include leakage sensors 16 and 24 for detecting leakage of 
the coolant 3. Each of the sensors 16 and 24 has a detecting circuit in 
which two conductive lines connected to each other through a resistor 
having a high resistance are held in a state wherein they are close to 
each other but are not electrically connected. With this arrangement, when 
a coolant leaks, the resistance between the two lines is decreased, and 
the leakage is detected. The detection outputs are input to the control 
section 10 through signal lines 104 and 105. 
An operation of this embodiment will be described next with reference to 
FIGS. 1 and 2. 
In the control section 10, a leakage continuation flag ON/OFF-controlled by 
signals from the leakage sensors 16 and 24 is turned off (step 30 in FIG. 
2). 
Subsequently, the control section 10 receives leakage detection signals 
from the leakage sensors 16 and 24 through the signal lines 104 and 105 
(step 31 in FIG. 2). On the basis of these leakage detection signals, the 
control section 10 checks whether leakage of the coolant 3 occurred in the 
cooling apparatus 1 and the electronic device 2 (step 32 in FIG. 2). 
The control section 10 has a timer counter constituted by a software 
interrupt counter. If no leakage of the coolant 3 is detected form leakage 
detection signals form the leakage sensors 16 and 24, the timer is reset 
(step 33 in FIG. 2). 
The amount of the coolant 3 in the tank 12 is detected by the second level 
sensor 13b to check whether the minimum amount of the coolant 3 remains 
(step 40 in FIG. 2). If a sufficient amount of the coolant 3 is still 
left, the control section 10 receives leakage detection signals from the 
leakage sensors 16 and 24 again (step 31 in FIG. 2). 
If leakage of the coolant 3 is detected from the leakage detection signals 
from the sensors 16 and 24, the control section 10 checks whether the 
leakage continuation flag is ON, i.e., the leakage is continuously 
detected (step 34 in FIG. 2). 
If leakage of the coolant 3 is detected for the first time, the control 
section 10 starts the timer and turns on the leakage continuation flag 
(step 35 in FIG. 2). 
If the leakage of the coolant 3 is continuously detected, and the timer is 
started, the control section 10 receives a coolant amount detection signal 
from the first level sensor 13a in the tank 12 (step 36 in FIG. 2). 
Subsequently, a decrease in amount of the coolant 3 in the tank 12 is 
checked on the basis of the coolant amount detection signal from the first 
level sensor 13a (step 37 in FIG. 2). 
If the control section 10 determines from the detection signal from the 
first level sensor 13a that the amount of the coolant 3 in the tank 12 is 
not decreased, it checks whether the minimum amount of the coolant 3 
remains (step 40 in FIG. 2). If a sufficient amount of the coolant 3 is 
still left, the control section 10 receives leakage detection signals from 
the leakage sensors 16 and 24 again (step 31 in FIG. 2). 
If the control section 10 determines from the detection signal from the 
first level sensor 13a that the amount of the coolant 3 in the tank 12 is 
decreased, it checks whether the value of the timer corresponds to a 
predetermined period of time or less (step 38 in FIG. 2). 
If the value of the timer corresponds to the predetermined period of time 
or more, i.e., if the time interval between the detection of leakage of 
the coolant 3 and the detection of a decrease in amount of the coolant 3 
in the tank 12 is long, it is determined that the operation need not be 
immediately stopped. In this case, the cooling apparatus 1 and the 
electronic device 2 are continuously driven, and the leakage of the 
coolant 3 and the decrease in coolant amount are notified to the control 
section 20 of the electronic device 2, thus causing an operator to 
recognize them. 
It is checked by the second level sensor 13b whether the coolant 3 is 
decreased to the minimum amount (step 40 in FIG. 2). If a sufficient 
amount of the coolant 3 is still left, the control section 10 receives 
leakage detection signals from the leakage sensors 16 and 24 again (step 
31 in FIG. 2). 
If the value of the timer corresponds to the predetermined period of time 
or less, i.e., the time interval between the detection of leakage of the 
coolant 3 and the detection of a decrease in coolant amount, it is 
determined that a large amount of the coolant 3 leaked in the circulation 
path, the operation of the cooling apparatus 1 is immediately stopped, and 
a stop command is output to the control section 20 of the electronic 
device 2 through the signal line 102. 
With this operation, the control section 20 of the electronic device 2 
turns off the power supply 21 to prevent the heat generating portion 22 
from being heated to a high temperature (step 39 in FIG. 2). 
Note that if it is determined from the detection signal from the second 
level sensor 13b that the coolant 3 is decreased to the minimum amount, 
the cooling apparatus 1 and the electronic device 2 are stopped in the 
same manner as described above (step 40 in FIG. 2). 
As has been described above, according to the present invention, if a 
coolant gradually leaks or a coolant amount is gradually decreased, i.e., 
no urgent treatment is required, an electronic device can be continuously 
operated.