US20090301692A1

US20090301692A1 - Electronic Apparatus Cooling Device

Info

Publication number: US20090301692A1
Application number: US12/421,749
Authority: US
Inventors: Hironori Oikawa
Original assignee: Hitachi Ltd
Current assignee: Hitachi Ltd
Priority date: 2008-06-06
Filing date: 2009-04-10
Publication date: 2009-12-10
Also published as: CN101600326A; US20120160460A1; JP5117287B2; CN101600326B; JP2009295869A

Abstract

A compact, low-cost electronic apparatus cooling device which provides a high heat receiving performance with less transfer of the heat of an exothermic body to a pump. In the device, a heat receiving part has fins in a given area of a plate-like base and the height of the fins is almost equal to the thickness of the base which surrounds them. A pressure member with an opening covers part of the top of the fins and part of the base. Refrigerant flows in from part of the top of the fins in contact with the opening of the pressure member and flow out from part of the top of the fins not covered by the pressure member.

Description

CLAIM OF PRIORITY

The present application claims priority from Japanese patent application serial no. JP 2008-149469, filed on Jun. 6, 2008, the content of which is hereby incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to cooling devices for electronic apparatuses incorporating semiconductor integrated circuits and more particularly to a cooling device which efficiently cools the semiconductor integrated circuit of an electronic apparatus.
2. Description of the Related Art
Recent electronic apparatuses incorporate high performance semiconductor integrated circuits as typified by CPUs used in personal computers. Mainly because of the demand for higher performance in electronic apparatuses, there is a rapidly growing tendency that such semiconductor ICs are higher in speed and more integrated than former ones and generate more heat. However, if the temperature exceeds a given level, semiconductor ICs not only may fail to maintain their inherent performance but also may break down due to excessive heat. For this reason, it is necessary to cool the semiconductor ICs in electronic apparatuses by some kind of means.
A general method for cooling a semiconductor IC of an electronic apparatus is an air-cooling system in which the semiconductor IC is thermally connected with a heat sink and the heat sink is cooled by a fan which blows air to the sink. In this air cooling system, however, in order to increase the cooling performance in response to rise in the temperature of an exothermic body, a large high-speed fan must be installed to increase the air flow rate. On the other hand, as the uses of electronic apparatuses are more diversified, portable compact cooling device models have been developed at an accelerated pace. This means that the semiconductor IC cooling device of an electronic apparatus must feature compactness and high performance and thus an air cooling type device may not meet these requirements. For this reason, the liquid cooling system which provides a higher cooling performance by heat transfer of liquid refrigerant is drawing attention.
However, the problem with this liquid cooling system is to reduce the device size and lower the cost because it uses more components than the air cooling system.
One approach toward a smaller and less costly liquid cooling device may be integration of various parts. For example, JP-A No. 2005-142191 and JP-A No. 2007-35901 disclose techniques to integrate a heat receiving part and a pump. The former document describes a cooling device which does not use heat radiating fins. The latter document describes a cooling device which uses heat radiating microfins.

SUMMARY OF THE INVENTION

For the heat receiving components of the heat exchanger in the liquid cooling system, the above technical problem with the related art must be solved in order to achieve compactness and cost reduction.
In the cooling device disclosed in JP-A No. 2005-142191, part of the casing is made of a metal with a high thermal conductivity and this part is in contact with an exothermic body to receive heat. However, from the viewpoint of the ability to receive heat, this heat receiving structure may be lower in heat receiving performance than a heat receiving structure dedicated to heat reception, such as an elaborate finned structure. Besides, another problem is that heat is easily transferred from the exothermic body to the pump and the service life of the pump is unfavorably affected.
On the other hand, the cooling device disclosed in JP-A No. 2007-35901 uses microfins for the heat receiving part. In this case, since the flow channel resistance between fins is high, if fitting or contact with the casing is inadequate, refrigerant may flow not between fins but flow in gaps in the fitting or contact area, resulting in a considerable deterioration in the heat receiving performance. Also, when the fins are smaller, the distance between the exothermic body and the fin top is shorter, so there is a problem that the heat of the exothermic body is easily transferred to the pump through the fins. However, the technique does not suggest any concrete means to solve these problems.
An object of the present invention is to solve the above problems and provide a compact electronic apparatus cooling device which has a high heat receiving performance and hardly causes heat transfer from the exothermic body to the pump.
In order to achieve the above object, according to one aspect of the present invention, an electronic apparatus cooling device which cools an exothermic body by heat transfer of refrigerant, includes a heat receiving part which has a base for receiving heat generated by the exothermic body, a pressure member with an opening, covering part of the base and being located opposite to the exothermic body, and a flow channel allowing the refrigerant to flow therein. The device also includes a heat radiator for radiating heat absorbed by the refrigerant, and a pump for circulating the refrigerant between the heat receiving part and the heat radiator. In the flow channel of the heat receiving part, the refrigerant flows in through the opening of the pressure member and flows out from the periphery of the pressure member in places other than the opening.
According to another aspect of the invention, an electronic apparatus cooling device includes a heat receiving part which has a plate-like base for receiving heat generated by the exothermic body, fins with a height almost equal to the height of the surrounding base, located in an area of the base, opposite to the exothermic body, a pressure member with an opening, covering part of the top of the fins and part of the base, and a flow channel allowing the refrigerant to flow therein. The device also includes a heat radiator for radiating heat absorbed by the refrigerant and a pump for circulating the refrigerant between the heat receiving part and the heat radiator. In the flow channel of the heat receiving part, the refrigerant flows in from the top of the fins in the opening of the pressure member and flows out from the top of the fins on the periphery of the pressure member in places other than the opening.
According to the present invention, it is possible to prevent deterioration in the heat receiving performance attributable to compactness. The invention also produces an advantageous effect that the heat of the exothermic body is hardly transferred to the pump. Consequently, a compact high-performance electronic apparatus cooling device can be offered, contributing to improvement in the performance of an electronic apparatus such as a small personal computer.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, objects and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings wherein:

FIGS. 1A and 1B show the heat receiving part and pump of a cooling device according to an embodiment of the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a sectional view;

FIG. 2 is a perspective view of the heat receiving part according to the embodiment;

FIG. 3 is sectional view of another embodiment of the present invention;

FIG. 4 shows an example of the configuration of an electronic apparatus incorporating a cooling device according to the present invention;

FIGS. 5A and 5B are perspective views of a pressure member of a heat receiving part according to an embodiment of the invention, in which FIGS. 5A is one example thereof and FIG. 5B is another example thereof;

FIGS. 6A and 6B show the heat receiving part and pump of a cooling device according to another embodiment, in which FIG. 6A is a perspective view and FIG. 6B is a sectional view; and

FIGS. 7A and 7B show the heat receiving part and pump of a cooling device according to a further embodiment, in which FIG. 7A is a perspective view and FIG. 7B is a sectional view.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Next, the preferred embodiments of the present invention will be described referring to the accompanying drawings.
FIG. 4 shows an example of the configuration of an electronic apparatus incorporating a cooling device according to the present invention.
The electronic apparatus 401 includes a circuit board 402, a power supply 410, and an HDD 411. The circuit board 402 has an exothermic body 403 such as a semiconductor device.
The cooling device 404 for the exothermic body 403 includes the following components. A heat receiving part 405 is thermally connected with the exothermic body 403 and the refrigerant which flows inside it absorbs the heat by heat transfer. A heat radiator 408 radiates the heat absorbed by the refrigerant to the outside of the electronic apparatus 401 by cooling air flowing through core tubes, radiating fins or the like. A pump 406, integral with the heat receiving part 405, circulates the refrigerant between the heat receiving part 405 and the heat radiator 408. A tank 409 stores the refrigerant for the cooling device 404 and piping 407 connects the pump 406 and the heat radiator 408 to enable the refrigerant to circulate between them.
The electronic apparatus 401 is not a specific type of apparatus and this embodiment assumes that the exothermic body 403 is a semiconductor device. However, the exothermic body is not limited to a semiconductor device but the cooling device 404 may cool an HDD or the like. In this embodiment, although the tank 409 is a separate unit, instead it may be integral with the heat radiator 408.
The heat receiving part 405 and pump 406 of the cooling device 404 according to the present invention are described below in detail. FIGS. 1A and 1B show the heat receiving part and pump of the cooling device according to an embodiment of the present invention. FIG. 1A is a perspective view of the device as seen from the pump side. FIG. 1B is a sectional view taken along the line A-A′ of FIG. 1A. In FIG. 1A, part of the fins 202 which is hidden behind a pressure member 203 is represented by broken lines.
The pump 406 in this embodiment is a vortex pump which has a first suction port 101 for sucking refrigerant and a first discharge port 102 for discharging refrigerant. These communicate with the piping 407. It also includes a second discharge port 104 and a second suction port 105 which are characteristic of the present invention. The openings of these ports face the heat receiving part 405. Partitions 103 and 106 are located between the first suction and discharge ports and between the second suction and discharge ports respectively. Due to these partitions, the suction and discharge ports perform their respective functions. A magnetized impeller 107 is rotated by a coil 109 and a driver board 110; as the impeller 107 rotates, its blade 108 moves the refrigerant and generates a liquid flow. In the pump 406, the refrigerant which has flown in through the first suction port 101 flows out through the second discharge port 104, passes on the heat receiving part 405, and again flows in through the second suction port 105 and flows out through the first discharge port 102.
The heat receiving part 405 joined to the pump 406 is described below. FIG. 2 is a perspective view of the heat receiving part 405. Arrows 206 and 208 denote directions of refrigerant flows. 207 represents the central top of the fins 202. Part of the fins 202 which is hidden by the pressure member 203 or located inside the heat receiving part 405 is represented by broken lines.
The heat receiving part 405 includes a base 201, fins 202, and a pressure member 203. The top of the fins 202 is almost flush with the upper surface of the base 201. More specifically, the height difference between the top of the fins 202 and the upper surface of the base 201 which is produced in the process of making the fins 202 is so small that it is absorbed by the pressure member 203.
The bottom 205 of the fins 202 is thinner than the base 201. The pressure member 203 lies over the base 201 and the fins 202 and has an opening 204. The pressure member 203 is intended to eliminate the gap between the pump and the fins even if the fins 202 are not uniform in size (height, etc) and ensure that refrigerant flows to the fins smoothly. Therefore, the pressure member 203 is made of a flexible material with a sufficient heat resistance to withstand the heat of the fins. One example of the material is a gel sheet which remains flexible in a wide temperature range. If the exothermic body 403 is a semiconductor device, it is desirable that the material retains its flexibility in a temperature range from −20° C. to 100° C., an ambient temperature range in which normal operation of the device is guaranteed. Consequently the height difference between the top of the fins 202 and the upper surface of the base 201 can be absorbed by the pressure member 203 in a desired temperature range.
How refrigerant flows in the heat receiving part 405 is explained below. The refrigerant 206 flowing out through the second discharge port 104 of the pump 406 flows along the opening 204 of the pressure member 203 into the central top 207 of the fins 202. The refrigerant which has flowed into the fins 202 springs out from the periphery of the pressure member 203. The refrigerant 208 which has sprung out is forced to flow into the second suction port 105 of the pump 406 because the periphery is sealed by an O ring 111. As explained above, even if the refrigerant inflow and outflow ports of the heat receiving part 405 are located not over the fins but over the base, the refrigerant can flow in and out in over the fins, contributing to compactness. According to the present invention, the heat receiving part 405 can easily cope with any change in the position of the second discharge port 104. For example, as shown in FIGS. 5A and 5B, even if the second discharge port 104 is not in the position shown in FIG. 5A but in the position shown in FIG. 5B, the shape of the pressure member 203 can be modified as shown in FIG. 5B to cope with this change.
Therefore, the second discharge port 104 can be located in a position convenient for the pump. Also, the second suction port 105 may be in any position unless the pressure member 203 overlaps it. This permits wider design latitude and the pump and the heat receiving part can be integrated in the most compact manner possible.
As described earlier, the absence of gaps between the pump and the fins helps solve the problem that refrigerant may flow in places other than the fins and cause deterioration in the heat receiving performance.
Also as described earlier, the second discharge port 104 further increases the cooling effect as it faces the heat receiving part 405.
In this embodiment, the thickness of the base 201 is 1.5 mm and that of the pressure member 203 is 0.5 mm. Since the second discharge port 104 and second suction port 105 of the pump 406 are simple openings, the overall pump thickness is the same as the thickness of the pump as a single unit. Hence, the thickness of the combination of the single pump unit and heat receiving part is only 2 mm larger than the thickness of the single pump unit.
In the conventional techniques, there is a possibility that the heat of the exothermic body is easily transferred to the pump side through the fins and particularly when the pump shaft 112 is located near the fins, the shaft and its surroundings may deteriorate quickly and the service life of the pump maybe shortened. On the other hand, in this embodiment, the pressure member 203 is made of a material with a lower thermal conductivity than metal, such as a gel sheet as described earlier and it has an opening 204 in the center. Since refrigerant flows in the opening 204, the heat of the heat receiving part is not directly transferred to the pump. Therefore, the embodiment provides a solution to the problem that the heat of the exothermic body may be transferred to the pump. In practice, the pump temperature is 3 to 6 degrees lower than when the pressure member 203 is not employed.
In the above embodiment, the fins 202 are like a plate; however the fins are not limited thereto. For example, an array of pin-like fins may be used instead. Also the pump is not limited to the vortex pump as mentioned above but it may be a centrifugal pump or gear pump.
FIG. 3 shows an embodiment which uses a gear pump. In the figure, 301 represents internal gear and 302 represent external gear. The other elements which may be identical to those shown in FIGS. 1A and 1B are designated by the same reference numerals. In the gear pump shown in FIG. 3, the internal gear 301 and the external gear 302 engage with each other while rotating to move the liquid. As in the foregoing embodiment, this pump has a second discharge port 104 and a second suction port 105 for connection with the heat receiving part in addition to a first suction port (not shown) and a first discharge port 102 for connection with the outside. The top of the fins 202 is almost flush with the base 201 and the pressure member 203 lies between the fins 202 and the second discharge port 104. As in the foregoing embodiment, this structure ensures that refrigerant flows to the microfins and prevents deterioration in the heat receiving performance, curbs transfer of the heat of the fins to the pump and permits contact with the heat receiving part with virtually no size increase from the size of the single pump unit.
Although the above explanation assumes that many fins are provided at short intervals as illustrated in FIGS. 1A and 1B, this is not a restrictive condition. Other embodiments are illustrated in FIGS. 6A, 6B, 7A and 7B. These are perspective views and sectional views taken in the same way as FIGS. 1A and 1B. The same elements are designated by the same reference numerals.
FIGS. 6A and 6B show that the device has three fins 202. Even when a small number of fins are provided at long intervals as in this example, the present invention can be applied and produces a similar effect. If the fins are thicker than those in FIGS. 1A and 1B, the heat radiation effect will be larger.
FIGS. 7A and 7B show that the device has no fins. In this example, a gap is more easily generated between the pressure member 203 and the pump than in the device shown in FIGS. 1A and 1B. If this is a problem, it can be solved by using an adhesive agent. Refrigerant flows out through the second discharge port 104 into the opening 204 of the pressure member and particularly cools the bottom 205 of the base before flowing out from the periphery of the pressure member 203 and being sucked into the pump through the second suction port 105. As in FIGS. 1A and 1B, the present invention can be applied to this structure and a similar effect can be produced.
Directions in which refrigerant flows are indicated by arrows 206 and 208 in FIG. 2. However, even when refrigerant flows in directions opposite to them, a cooling effect can be produced. In order to reduce temperature rise in the pump 406 including the pump shaft 112, it is recommended that refrigerant should flow in the directions as shown in FIG. 2.
As explained so far, according to the present invention, the positions of the refrigerant suction and discharge ports of a small high-performance heat receiving part can be freely determined, so the heat receiving part and the pump can be easily integrated and in integration of the pump and the heat receiving part with microfins, a gap between the microfins and the pump, which could lower the heat receiving performance, can be easily eliminated. Transfer of the heat of the fins to the pump is curbed, and the service life of the pump is not shortened. In addition, since the size of the combination of the pump and heat receiving part is virtually no larger than the pump itself, a high-performance compact liquid cooling device can be realized at low cost.
While we have shown and described several embodiments in accordance with our invention, it should be understood that disclosed embodiments are susceptible of changes and modifications without departing from the scope of the invention. Therefore, we do not intend to be bound by the details shown and described herein but intend to cover all such changes and modifications that fall within the ambit of the appended claims.

Claims

1. An electronic apparatus cooling device which cools an exothermic body by heat transfer of refrigerant, comprising:

a heat receiving part including:

a base for receiving heat generated by the exothermic body;

a pressure member with an opening, covering part of the base and being located opposite to the exothermic body; and

a flow channel allowing the refrigerant to flow therein;

a heat radiator for radiating heat absorbed by the refrigerant; and

a pump for circulating the refrigerant between the heat receiving part and the heat radiator,

wherein in the flow channel of the heat receiving part, the refrigerant flows in through the opening of the pressure member and flow out from the periphery of the pressure member in places other than the opening.

2. An electronic apparatus cooling device which cools an exothermic body by heat transfer of refrigerant, comprising:

a heat receiving part including:

a plate-like base for receiving heat generated by the exothermic body;

fins with a height almost equal to the height of the surrounding base, located in an area of the base, opposite to the exothermic body;

a pressure member with an opening, covering part of the top of the fins and part of the base; and

a flow channel allowing the refrigerant to flow therein;

a heat radiator for radiating heat absorbed by the refrigerant; and

wherein in the flow channel of the heat receiving part, the refrigerant flows in from the top of the fins in the opening of the pressure member and flows out from the top of the fins on the periphery of the pressure member in places other than the opening.

3. The electronic apparatus cooling device according to claim 2,

wherein the heat receiving part and the pump are integrated by joining them vertically through the pressure member in a water-tight manner; and

wherein the pump includes a first suction port to suck the refrigerant into the pump, a first discharge port to discharge the refrigerant to the outside of the pump, a second suction port to suck in the refrigerant from the heat receiving part, and a second discharge port with an end face opposite to the heat receiving part to discharge the refrigerant to the heat receiving part.

4. The electronic apparatus cooling device according to claim 3, further comprising:

a partition for partitioning a pump chamber for circulation of refrigerant in the pump,

wherein the first suction port and the second discharge port are located in a first area partitioned by the partition; and

wherein the second suction port and the first discharge port are located in a second area partitioned by the partition.

5. The electronic apparatus cooling device according to claim 2, wherein the pressure member uses a gel sheet which remains flexible in an ambient temperature range in which normal operation of the exothermic body is guaranteed.