Pump, cooling system, and electronic apparatus

Abstract

A cooling pump includes a rotor including a rotation axis, a disc fixed with the rotation axis, an impeller fixed with the disc for pressurizing a liquid coolant, and a plurality of permanent magnets arrayed to be fixed with the disc in a ring shape; a case including a pump chamber holding the rotor rotatably, the pump chamber having an inlet and an outlet for the liquid coolant, wherein a part of the bottom wall forming the pump chamber is a heat-receiving portion; a cover including a recess, the cover sealing the case, i.e., pump housing, liquid-tightly; and a circular stator disposed in the recess, the stator generating a rotating magnetic field with a plurality of electromagnets to provide the rotor with torque around the rotation axis, wherein a hydrophilic surface is disposed on the inner surface of the pump chamber.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of Japanese Patent Application No. 2004-134426, filed Apr. 28, 2004, the entire contents of which are incorporated herein by reference.

BACKGROUND

1. Field

The present invention relates to a pump, a cooling system, and electronic apparatus, and in particular, to a pump used in a liquid cooling system for cooling a heat generating unit, the cooling system, and electronic apparatus including the same.

2. Description of the Related Art

Recently, the data processing speed of electronic apparatus such as a personal computer has been significantly improved. In order to achieve this, the clock frequency for processing a central processing unit (CPU) or peripheral semiconductor devices has also become significantly higher than that in the known devices.

Accordingly, the heating value from the CPU and other semiconductor devices has also been increased. In a known method, a heat sink is thermally connected to a heat generating unit such as a CPU and the heat sink is air-cooled. However, some recent semiconductor devices cannot be cooled by such a method.

Meanwhile, a technology to apply a liquid cooling system to compact electronic apparatus such as a personal computer has been developed. The liquid cooling system can achieve higher cooling efficiency because a liquid having a specific heat higher than that of air is used as a coolant.

For example, Japanese Patent Nos. 3,431,024 and 3,452,059 disclose cooling systems including a closed circulation path for circulating a coolant, a radiator that dissipates the heat from the coolant, and a contact heat exchange pump. The pump is used for pressuring the coolant in order that the coolant circulates in the closed circulation path and is thermally brought into contact with a heating semiconductor. Thus, the heating semiconductor is cooled by heat exchange of the coolant. In addition, Jpn Pat. Publication No. 2003-172286 discloses a technology to reduce the thickness of the contact heat exchange pump.

In such a liquid cooling method, it is important to increase the thermal conductivity from a heat-receiving face for receiving the heat from a heat generating unit to a face being in contact with a flow path of a liquid coolant. Jpn Pat. Publication No. 2003-68317 discloses a technology relating to a surface treatment of a cooling flow path for cooling a separator of a fuel cell. According to this technology, the surface of the cooling flow path is roughened so as to increase the heat transfer area. As a result, the thermal conductivity is increased. Although the above patent document also describes the application of a hydrophilic coating material, the hydrophilic coating material is applied in order to prevent the freezing of the coolant. Therefore, the application of the hydrophilic coating material does not directly affect the improvement in the cooling efficiency.

In order to cool a heat generating unit such as a CPU at a high cooling efficiency by circulating a coolant, it is extremely important to increase the flow rate of the coolant to increase the flow volume of the coolant per unit of time.

In particular, in a pump for circulating a coolant by pressurizing, the increase in the flow rate of the coolant to increase the flow volume significantly improves the cooling efficiency.

For example, in the above-cited Jpn Pat. Publication No. 2003-172286 disclosing a contact heat exchange pump having a very small thickness, a surface treatment on the inner surface of the pump chamber is not described.

However, when the pump has an inner surface formed by, for example, pressing, injection molding, or die casting, a satisfactory heat transfer performance from a pump housing, which is a heat receiver, to a coolant is not necessarily achieved.

According to the surface treatment technology of a flow path disclosed in the above-cited Jpn Pat. Publication No. 2003-68317, the rough face has the maximum arithmetic mean roughness (Ra) of 3.5 μm. Furthermore, the technical field of the above patent document relates to a fuel cell, which is different from the technical field of the present invention. The present invention relates to the cooling of a heating semiconductor such as a CPU. A sufficient cooling performance cannot be expected with the above-cited technology.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention.

FIG. 1 is a first view showing the appearance of electronic apparatus according to an embodiment of the present invention;

FIG. 2 is a second view showing the appearance of the electronic apparatus according to the embodiment of the present invention;

FIG. 3 is a cross-sectional view showing an example of a mounting state of a cooling pump according to the present invention;

FIG. 4 is a view showing the structure of a cooling system provided in electronic apparatus according to an embodiment of the present invention;

FIG. 5 is a view showing the structure of a radiator of the cooling system;

FIG. 6 is a first view showing the structure of a cooling pump according to an embodiment of the present invention;

FIG. 7 is a second view showing the structure of the cooling pump according to the embodiment of the present invention;

FIG. 8 is a cross-sectional view showing the structure of the cooling pump according to the present invention; and

FIG. 9A, FIG. 9B, and the graph disposed thereunder show an advantage of a surface-treated portion provided on the cooling pump according to the present invention.

DETAILED DESCRIPTION

Embodiments of a cooling pump (pump), a cooling system, and electronic apparatus according to the present invention will now be described with reference to the attached drawings.

FIGS. 1 and 2 are views showing the appearance of a personal computer 1 that is an embodiment of electronic apparatus according to the present invention.

The personal computer 1 includes a main unit 2 and a panel unit 3.

The main unit 2 of the personal computer 1 includes a main unit casing 4 having a thin box-shape. The main unit casing 4 includes a bottom wall 4a, a top wall 4b, a front wall 4c, side walls 4d disposed at the right and the left, and a back wall 4e.

A plurality of outlets 6 for releasing cooling air is provided at the back wall 4e.

The top wall 4b of the main unit casing 4 holds a keyboard 5.

The panel unit 3 includes a panel unit casing 8 and a display unit 9. The display unit 9 is held with the panel unit casing 8 and includes a display panel 9a. The display panel 9a is exposed from an opening 10 disposed at the front face of the panel unit casing 8.

The panel unit casing 8 is supported so as to be opened or closed freely with a hinge provided at the back end of the main unit casing 4.

FIG. 1 shows the appearance when the panel unit 3 is opened, whereas FIG. 2 shows the appearance when the panel unit 3 is closed.

FIG. 3 is a cross-sectional view of a printed circuit board 12 provided in the main unit casing 4, a semiconductor device such as a CPU 13 that is a heat generating unit mounted on the printed circuit board 12, and a cooling pump 17 that is thermally connected to the CPU 13.

The printed circuit board 12 is disposed, for example, in the direction parallel to the bottom wall 4a of the main unit casing 4. The CPU 13 is mounted on a surface, for example, the top surface, of the printed circuit board 12.

The CPU 13 includes a base substrate 14 and an IC chip 15 provided at the center of the top surface of the base substrate 14. In order to maintain the operation of the CPU 13, it is essential to cool the IC chip 15 efficiently.

The outer surface of a bottom wall 25 of the cooling pump 17 forms a heat-receiving face 26. The heat-receiving face 26 is thermally connected to the surface of the IC chip 15 with, for example, heat-transfer grease or a heat-transfer sheet therebetween.

FIG. 4 shows an example of the structure of a cooling system 16 provided in the main unit 2 of the personal computer 1.

The cooling system 16 includes the cooling pump 17, a radiator 18, a circulation path 19, and an electric fan 20.

The cooling pump 17 is disposed so as to cover the CPU 13 mounted on the printed circuit board 12. Four corners of the cooling pump 17 are pierced with screws 47. The screws 47 further pierce the printed circuit board 12 to screw with four bosses 46 fixed on the bottom wall 4a of the main unit casing 4.

Thus, the cooling pump 17 is fixed with the printed circuit board 12 and the bottom wall 4a of the main unit casing 4 and is thermally connected to the CPU 13.

The cooling pump 17 includes an inlet tube 32 for sucking a liquid coolant and an outlet tube 33 for discharging the liquid coolant. The cooling pump 17, the inlet tube 32, and the outlet tube 33 are formed as a single component.

The radiator 18 includes a first passage 50, a second passage 51, and a third passage 52 through which the liquid coolant flows.

FIG. 5 is a perspective view showing the structure of the radiator 18 in detail. Referring to FIG. 5, the first passage 50 and the second passage 51 include pipes 53 and 54 having a flat cross-section, respectively. The pipes 53 and 54 are disposed such that the longitudinal direction of each cross-section is parallel to the bottom wall 4a of the main unit casing 4.

The pipe 53 has a circular cross-section at the upstream end of the first passage 50 to form a coolant inlet 56 through which the liquid coolant is entered. On the other hand, the pipe 53 has the flat cross-section at the downstream end of the first passage 50. The downstream end of the first passage 50 is connected to the upstream end of the third passage 52.

The pipe 54 has a circular cross-section at the downstream end of the second passage 51 to form a coolant outlet 57 through which the liquid coolant is discharged. On the other hand, the pipe 54 has the flat cross-section at the upstream end of the second passage 51. The upstream end of the second passage 51 is connected to the downstream end of the third passage 52.

A plurality of cooling fins 63 are provided between a back face 53a of the pipe 53 and a back face 54a the pipe 54. The cooling fins 63 are fixed on the back faces 53a and 54a by, for example, soldering. Thus, the cooling fins 63 are thermally connected to the pipes 53 and 54.

Spaces between the cooling fins 63 form a plurality of cooling air passages 62.

As shown in FIG. 4, the circulation path 19 includes an upstream tube portion 70 and a downstream tube portion 71.

One end of the upstream tube portion 70 is connected to the outlet tube 33 of the cooling pump 17 and another end of the upstream tube portion 70 is connected to the coolant inlet 56 of the first passage 50.

On the other hand, one end of the downstream tube portion 71 is connected to the inlet tube 32 of the cooling pump 17 and another end of the downstream tube portion 71 is connected to the coolant outlet 57 of the second passage 51.

The electric fan 20 sends cooling air to the radiator 18.

The electric fan 20 includes a fan casing 73 and an impeller 74 of the fan provided in the fan casing 73.

The fan casing 73 includes a cooling air outlet 75 that discharges the cooling air and a duct 76 that guides the discharged cooling air to the radiator 18.

The structure of the cooling pump 17 will now be described in detail.

FIGS. 6 and 7 are views showing the structure of the cooling pump 17 according to an embodiment of the present invention.

The cooling pump 17 includes a pump housing 21 serving as a heat-receiving portion. The pump housing 21 includes a case 22 and a cover 23.

The case 22 is composed of a metal having a high thermal conductivity, for example, copper or aluminum. The cover 23 is composed of a resin. The case 22 and the cover 23 are combined with an O-ring 22a disposed therebetween. The case 22 includes a recess 24 opening in the upward direction in FIG. 7. The bottom wall 25 of the recess 24 faces the CPU 13. The under surface of the bottom wall 25 forms the heat-receiving face 26 that is thermally connected to the CPU 13.

The recess 24 is separated with a partition wall 27 to form a pump chamber 28 and a reserve chamber 29. The reserve chamber 29 stores the liquid coolant.

The partition wall 27 includes an inlet 30 and an outlet 31. The inlet 30 is connected to the inlet tube 32 through which the liquid coolant is sucked in the pump chamber 28. The outlet 31 is connected to the outlet tube 33 through which the liquid coolant is discharged from the pump chamber 28.

A rotor 39 is provided in the pump chamber 28.

The rotor 39 has a disc shape and includes a rotation axis 36 fixed at the center thereof. One end of the rotation axis 36 is rotatably supported at the center of the pump chamber 28 and another end of the rotation axis 36 is rotatably supported at the center of the cover 23.

The rotor 39 includes an impeller 35 that pressurizes the liquid coolant. A plurality of permanent magnets is embedded in an annular side wall 41 of the rotor 39. The impeller 35 and the plurality of permanent magnets are rotated around the rotation axis 36 as a single united component.

The cover 23 liquid-tightly seals the pump chamber 28 including the rotor 39, and the reserve chamber 29.

A stator 38 is disposed in a recess 23a formed on the upper surface of the cover 23 in FIG. 7. The stator 38 includes a plurality of electromagnets 40.

A predetermined current is applied to the plurality of electromagnets 40. As a result, the stator 38 generates a rotating magnetic field. A repulsive force caused by this rotating magnetic field of the stator 38 and a magnetic field of the permanent magnets provided in the rotor 39 generates torque to rotate the rotor 39. Consequently, the impeller 35 provided on the rotor 39 pressurizes to circulate the liquid coolant.

A control circuit board 42 is also disposed in the cover 23. The control circuit board 42 controls the current applied to the electromagnets 40.

A lid 44 covers and protects the stator 38 and the control circuit board 42. The lid 44 is fixed on the pump housing 21 with screws 43.

FIG. 8 is a schematic cross-sectional view of the cooling pump 17.

The case 22 and the cover 23 form the pump chamber 28. In order to increase the flow rate of the liquid coolant and to improve the cooling performance, a surface-treated portion 60 for improving hydrophilicity is provided on the inner surface of the pump chamber 28.

In a first embodiment of the hydrophilic surface 60 for improving hydrophilicity, a silicon oxide film, for example, a silicon dioxide (SiO₂) film is formed on the inner surface of the pump chamber 28 (i.e., a bottom face 25a facing the heat-receiving face 26 and a side face 25b continuous to the a bottom face 25a), an inner surface 32a of the inlet tube 32, and an inner surface 33a of the outlet tube 33. In order to form the silicon dioxide (SiO₂) film, for example, the case 22 is immersed in a solution of silicon dioxide (SiO₂) and is then dried.

In terms of the cooling performance, the thickness of the silicon dioxide (SiO₂) film is, for example, 0.1 to 0.6 μm.

In a second embodiment of the hydrophilic surface 60 for improving hydrophilicity, a titanium oxide film, for example, a titanium dioxide (TiO₂) film is formed on the inner surface of the pump chamber 28, the inner surface 32a of the inlet tube 32, and the inner surface 33a of the outlet tube 33. In order to form the titanium dioxide (TiO₂) film, for example, the case 22 is immersed in a solution of titanium dioxide (TiO₂) and is then dried, as in the first embodiment.

In terms of the cooling performance, the thickness of the titanium dioxide (TiO₂) film is, for example, 0.1 to 0.6 μm.

In a third embodiment of the hydrophilic surface 60 for improving hydrophilicity, a treatment forming a rough face is performed on the inner surface of the pump chamber 28, the inner surface 32a of the inlet tube 32, and the inner surface 33a of the outlet tube 33. In terms of the cooling performance, for example, the inner surface has an arithmetic mean roughness (Ra) of 0.5 to 100 μm.

A method for forming the rough face is not particularly limited. For example, the rough face can be formed by honing.

FIG. 9A, FIG. 9B, and the graph disposed thereunder qualitatively explain an advantage of the hydrophilic surface 60 for improving hydrophilicity provided on the inner surface of the cooling pump 17.

FIG. 9A shows the case wherein the hydrophilic surface 60 for improving hydrophilicity is not provided. When a surface has a low hydrophilicity, for example, a water droplet does not spread out on the surface. In such a case, the liquid coolant flowing in the pump chamber 28 receives a resistance from the inner surface of the pump chamber 28. As a result, the flow rate and the flow volume of the liquid coolant are restricted.

In contrast, FIG. 9B shows the case wherein the hydrophilic surface 60 according to the present invention for improving hydrophilicity is provided on the inner surface of the pump chamber 28. When a surface has a high hydrophilicity, for example, a water droplet can spread out on the surface. In such a case, the resistance of the inner surface of the pump chamber 28 is decreased. As a result, the flow rate and the flow volume of the liquid coolant can be increased, compared with the case wherein the hydrophilic surface 60 for improving hydrophilicity is not provided.

As shown in the graph disposed under FIGS. 9A and 9B, the quantity of heat removed from the heat-receiving face 26 generally has a positive correlation with the flow rate or the flow volume of fluid flowing on the heat-receiving face or a face thermally connected to the heat-receiving face. Therefore, when the hydrophilic surface 60 for improving hydrophilicity is provided on the inner surface of the pump chamber 28, the quantity of heat removed from the heat-receiving face 26 is increased to improve the cooling performance.

The operation of the cooling system 16 including the cooling pump 17 according to the present invention will now be described with reference to FIGS. 4 and 8.

The CPU 13, which is a heat generating unit, is thermally connected to the heat-receiving face 26 of the case 22 shown in FIG. 8 with heat-transfer grease or a heat-transfer sheet (not shown) disposed therebetween.

The heat generated from the CPU 13 is conducted from the heat-receiving face 26 to the inner surface of the pump chamber 28 on which the hydrophilic surface 60 is provided through the bottom wall 25 of the case 22.

A cooled liquid coolant flows in the pump chamber 28 from the inlet tube 32 through the inlet 30. The heat from the CPU 13 conducted to the inner surface of the pump chamber 28 is conducted to the cooled liquid coolant. As a result, the liquid coolant receives the heat.

Meanwhile, in the pump chamber 28, the rotor 39 is rotated by receiving torque due to the rotating magnetic field generated from the stator 38. The liquid coolant that has received the heat is pressurized by the rotation of the impeller 35 provided on the rotor 39. The liquid coolant is discharged from the outlet tube 33 through the outlet 31.

The hydrophilic surface 60 for improving hydrophilicity is provided on the inner surface of the pump chamber 28. Therefore, the liquid coolant circulating in the pump chamber 28 receives less resistance, compared with the case wherein the hydrophilic surface 60 is not provided.

As a result, the flow rate of the liquid coolant circulating in the pump chamber 28 is increased and the flow volume of the liquid coolant per unit of time is also increased.

The increase in the flow rate or the flow volume of the liquid coolant circulating in the pump chamber 28 increases the quantity of heat removed from the CPU to improve the cooling performance.

Furthermore, when the hydrophilic surface 60 in the pump chamber 28 is a rough face described in the third embodiment, the heat-receiving area on the inner surface of the pump chamber 28 is increased. Thus, the cooling performance can be further improved.

As shown in FIG. 4, the liquid coolant that has received the heat is pressurized with the cooling pump 17 and is then discharged from the outlet tube 33. Subsequently, the liquid coolant passes through the upstream tube portion 70 of the circulation path 19 and flows into the radiator 18.

In the radiator 18, the liquid coolant circulates in the first passage 50, the third passage 52, and the second passage 51. During this circulation, the heat from the liquid coolant is transferred to the first passage 50, the second passage 51, and the cooling fins 63, which are thermally connected to the first passage 50 and the second passage 51.

The cooling air generated by the rotation of the impeller 74 of the electric fan 20 blows on the first passage 50, the second passage 51, and the cooling fins 63 to remove the heat from these components. The cooling air is then released from the plurality of outlets 6 provided at the back wall 4e of the main unit casing 4.

As described above, the liquid coolant that has received the heat is cooled during circulating in the radiator 18. The cooled liquid coolant passes through the downstream tube portion 71 of the circulation path 19 and then returns to the pump chamber 28 through the inlet tube 32 of the cooling pump 17.

Repeating this cycle allows the heat generated from the CPU 13 to be released to the outside of the main unit casing 4 continuously with the cooling air generated from the electric fan 20.

The present invention is not limited to the above embodiments. The present invention may be embodied by modifying the components without departing from the spirit and the scope of the present invention. For example, the hydrophilic surface 60 may be provided on the entire inner surface of the recess 24 including the reserve chamber 29. This structure can further improve the heat-receiving efficiency of the cooling pump 17 as a whole. In the above embodiments, the pump includes the heat-receiving portion that is thermally connected to the CPU. Alternatively, the heat-receiving portion that is thermally connected to the CPU and the pump may be separate components, and the pump may be disposed at a halfway position of the circulation path.

Claims

1. A pump comprising:

a housing including a pump chamber;

an impeller disposed in the pump chamber; and

a stator for rotating the impeller,

wherein an inner surface of the pump chamber includes a hydrophilic surface.

2. The pump according to claim 1, wherein the hydrophilic surface is a film mainly composed of a silicon oxide.

3. The pump according to claim 1, wherein the hydrophilic surface is a film mainly composed of a titanium oxide.

4. The pump according to claim 1, wherein the hydrophilic surface comprises a rough face.

5. The pump according to claim 1, wherein the pump housing comprises a metal case and a resin cover to be combined with the metal case, and the hydrophilic surface is provided on the inner surface of the metal case.

6. The pump according to claim 5, wherein the metal case comprises an outlet tube for discharging the liquid coolant and an inlet tube for sucking the liquid coolant, and the hydrophilic surface is provided on the inner surfaces of the outlet tube and the inlet tube.

7. The pump according to claim 6, wherein the metal case comprises the pump chamber and a reserve chamber, and the hydrophilic surface is provided on the inner surface of the reserve chamber.

8. An electronic apparatus comprising:

a casing;

a substrate disposed in the casing;

a heat generating unit mounted on the substrate; and

a cooling system thermally connected to the heat generating unit, the cooling system including a radiator for dissipating the heat from the heat generating unit, a circulation path for circulating a liquid coolant to the radiator, and a pump for forcibly circulating the liquid coolant through the circulation path, the pump including a housing including a pump chamber, an impeller disposed in the pump chamber, and a stator for rotating the impeller,

wherein an inner surface of the pump chamber includes a hydrophilic surface.

9. The electronic apparatus according to claim 8, wherein the hydrophilic surface is a film mainly composed of a silicon oxide.

10. The electronic apparatus according to claim 8, wherein the hydrophilic surface is a film mainly composed of a titanium oxide.

11. The electronic apparatus according to claim 8, wherein the hydrophilic surface comprises a rough face.

12. The electronic apparatus according to claim 8, wherein the housing comprises a metal case and a resin cover to be combined with the metal case, and the hydrophilic surface is provided on the inner surface of the metal case.

13. The electronic apparatus according to claim 12, wherein the metal case comprises an outlet tube for discharging the liquid coolant to the circulation path and an inlet tube for sucking the liquid coolant from the circulation path, and the hydrophilic surface is provided on the inner surfaces of the outlet tube and the inlet tube.

14. The electronic apparatus according to claim 13, wherein the metal case comprises the pump chamber and a reserve chamber, and the hydrophilic surface is provided on the inner surface of the reserve chamber.

15. A cooling system thermally connected to a heat generating unit, the cooling system comprising:

a radiator for dissipating the heat from the heat generating unit;

a circulation path for circulating a liquid coolant to the radiator; and

a pump for forcibly circulating the liquid coolant through the circulation path, the pump including a housing including a pump chamber, an impeller disposed in the pump chamber, and a stator for rotating the impeller,

wherein an inner surface of the pump chamber includes a hydrophilic surface.

16. The cooling system according to claim 15, wherein the hydrophilic surface is a film mainly composed of a silicon oxide.

17. The cooling system according to claim 15, wherein the hydrophilic surface is a film mainly composed of a titanium oxide.

18. The cooling system according to claim 15, wherein the hydrophilic surface comprises a rough face.

19. The cooling system according to claim 15, wherein the housing comprises a metal case and a resin cover to be combined with the metal case, and the hydrophilic surface is provided on the inner surface of the metal case.

20. The cooling system according to claim 19, wherein the metal case comprises an outlet tube for discharging the liquid coolant to the circulation path and an inlet tube for sucking the liquid coolant from the circulation path, and the hydrophilic surface is provided on the inner surfaces of the outlet tube and the inlet tube.