JP5181874B2 - Loop heat pipe and electronic equipment - Google Patents

Description

  The present invention relates to a loop heat pipe that transports heat of a heating element by moving a working fluid, and an electronic device that includes a heat generating electronic component that generates heat by operation.

  In today's society, a wide variety of electronic devices have been developed with the progress of industrial technology, and there are many electronic devices having a complicated configuration. Particularly in recent years, with the progress of the information society, technologies related to electronic devices that perform information processing, such as computers, are rapidly developing, and high-performance electronic devices having complicated configurations are being developed one after another.

  Electronic devices generally have a complicated electronic circuit inside the electronic device, and when operating as an electronic device, such an electronic circuit often generates heat. For example, in a computer, a CPU that plays a central role in computer operation control generates heat as the computer operates. When an electronic circuit generates heat, the heat may cause problems in the electronic circuit and other electronic components around it, so there is a heat transport mechanism for releasing the generated heat from the electronic circuit to other locations. It is often necessary.

  Conventionally, a heat transport device called a loop heat pipe is known as a heat transport mechanism. The loop heat pipe has a configuration in which a working fluid is sealed inside a container such as a pipe, and heat is transported by moving the working fluid that has absorbed heat in the heat pipe. Here, the configuration and operating principle of the loop heat pipe will be described.

  FIG. 1 is a schematic configuration diagram showing the configuration and operating principle of a loop heat pipe.

  The loop heat pipe shown in FIG. 1 includes an evaporator 101 in which the liquid-phase working fluid 100 absorbs heat from a heating element (not shown) and vaporizes, and the gas-phase working fluid 100 releases heat and liquefies. And a condenser 105. In this loop heat pipe, the working fluid 100 vaporized in the evaporator 101 moves through the vapor pipe 104 in the upward arrow direction in the figure and is liquefied in the condenser 105, and the liquefied working fluid 100 is in the liquid pipe 102. It moves in the downward arrow direction through the figure and returns to the evaporator 101. Heat is transported by such movement of the working fluid 100. Here, a wick 1003 made of a porous material is provided inside the evaporator 101, and the liquid-phase working fluid 100 that has returned to the evaporator 101 penetrates into the wick 103 by capillary force. The vaporized working fluid 100 is vaporized by receiving heat from the surroundings, and travels to the condenser 105 via the vapor pipe 104.

  FIG. 2 is a diagram schematically showing how the working fluid 100 changes through the wick 103 and changes from the liquid phase to the gas phase.

Actually, the passages (cavities) in the wick 3 ′ through which the liquid-phase working fluid 100 permeates are winding and complicated, but in this figure, the plurality of passages in the wick 3 ′ are left and right. It is schematically represented as a cylindrical passage that extends parallel to the direction. In this figure, the liquid-phase working fluid 100 proceeds to the right in the wick 103 by capillary force, and is vaporized by receiving heat from the surroundings. Here, the boundary surface between the side in which the working fluid 100 is in a liquid phase (liquid side) and the side in which the working fluid 100 is in a gas phase (steam side), as shown in FIG. The shape is convex toward the liquid side, and the capillary force ΔPc is expressed by the following equation.
ΔPc = (2 × ρ × cos θc) / rc (1)
In the above (1), “ρ” is the surface tension of the working fluid 100, and “θc” is the contact angle between the wall surface of the cylindrical passage and the boundary surface (see FIG. 2), “rc”. Is the radius of the cylindrical passage.
US Pat. No. 4,765,396

  In general, in the loop heat pipe, the capillary force due to the wick in the evaporator tends to decrease as the amount of heat supplied from the heating element to the evaporator decreases, and the circulation speed of the working fluid tends to decrease.

  FIG. 3 is a diagram showing the state of the boundary surface between the liquid side and the vapor side according to the heat generation amount of the heating element.

  Here, part (a) of FIG. 3 shows the state of the boundary surface between the liquid side and the vapor side of the working fluid in a situation where the heat generation amount of the heating element is large. Further, part (b) of FIG. 3 shows the state of the boundary surface between the liquid side and the vapor side of the working fluid in a situation where the heat generation amount of the heating element is small.

  The contact angle θc formed between the wall surface of the cylindrical passage and the boundary surface is supplied from the heating element to the evaporator in the situation of part (b) of FIG. 3 where the amount of heat supplied from the heating element to the evaporator is small. The amount of heat is large compared to the situation in part (a) of FIG. 3, and the capillary force ΔPc is small. In this way, when the capillary force ΔPc is small, the circulation speed of the working fluid is reduced, so that even if the amount of heat generation is small, the temperature around the heating element gradually rises, and there is a risk of causing problems in the electronic components around the heating element. is there. In particular, in a situation where the circulation speed of the working fluid has become completely zero, the working fluid supplied to the evaporator is insufficient, so-called dryout occurs, and the temperature rise around the heating element becomes serious. .

  In view of the above circumstances, there are provided a loop heat pipe and an electronic device capable of suppressing a decrease in the circulation speed of a working fluid even under a situation where a heat generation amount of a heating element or a heat generating electronic component is small.

The basic form of a loop heat pipe that achieves the above objective is:
A plurality of evaporation tubes each having a wick made of a porous material and thermally coupled to a common heating element, wherein the heating element is a liquid-phase working fluid passing through each wick. An evaporator having a plurality of evaporator tubes that evaporate by heat received from;
A condenser that releases heat of the gas-phase working fluid to condense the working fluid;
A vapor pipe that connects the evaporator and the condenser, and moves a vapor-phase working fluid evaporated in the evaporator from the evaporator to the condenser;
A liquid pipe that connects the evaporator and the condenser, and moves the liquid-phase working fluid condensed in the condenser from the condenser to the evaporator;
One or more valves provided corresponding to each of one or more of the plurality of evaporation tubes, and opening and closing the corresponding evaporation tubes;
A valve control unit that controls opening and closing of each of the one or more valves.

  According to the basic form of the loop heat pipe, the number of evaporation pipes through which the working fluid can move can be adjusted by controlling the opening and closing of the valve. ΔPc can be maintained at an appropriate value. As a result, in this basic form of the loop heat pipe, it is possible to avoid a decrease in the circulation speed of the working fluid in the entire loop heat pipe.

The basic form of an electronic device that achieves the above object is
An electronic device provided with a heat generating electronic component that generates heat by operation,
A plurality of evaporation tubes each having a wick made of a porous material and thermally coupled to the heat generating electronic component, wherein the liquid phase working fluid passing through each wick is transferred to the heat generating electronic component; An evaporator having a plurality of evaporator tubes that evaporate by heat received from the part;
A condenser that releases heat of the gas-phase working fluid to condense the working fluid;
A vapor pipe that connects the evaporator and the condenser, and moves a vapor-phase working fluid evaporated in the evaporator from the evaporator to the condenser;
A liquid pipe that connects the evaporator and the condenser, and moves the liquid-phase working fluid condensed in the condenser from the condenser to the evaporator;
One or more valves provided corresponding to each of one or more of the plurality of evaporation tubes, and opening and closing the corresponding evaporation tubes;
A valve control unit that controls opening and closing of each of the one or more valves.

  Since the basic form of the electronic device includes the basic form of the loop heat pipe described above, it is possible to avoid a decrease in the circulation speed of the working fluid, and a preferable operating state is maintained.

  As described above, according to the basic form of the loop heat pipe and the electronic device, it is possible to suppress a decrease in the circulation speed of the working fluid even under a situation where the heat generation amount of the heating element and the heat generating electronic component is small.

  Hereinafter, specific embodiments for the loop heat pipe and the electronic device described above for the basic mode will be described. The embodiment of the electronic device described here is a computer having a CPU, and the computer includes a loop heat pipe for cooling the CPU that generates heat as the computer operates. This loop heat pipe corresponds to one embodiment of the loop heat pipe described above for the basic form.

  FIG. 4 is a diagram illustrating a computer 1000 that is an embodiment of an electronic device, and a loop heat pipe 200 provided in the computer 1000.

  The computer 1000 includes a power source 24 that stores electric power, a hard disk device (HDD) 22 that stores information, and a substrate 21 having various electronic circuits. For example, the board 21 is provided with a memory 23 that temporarily stores information and a CPU 20 that plays a central role in the operation of the computer 1000. The computer 1000 operates under the control of the CPU 20, and the CPU 20 generates heat as the computer 1000 operates. The CPU 20 has a square shape with a side length of 50 mm, and the heat generation amount of the CPU 20 is between 10W and 120W.

  The loop heat pipe 200 serves to cool the CPU 20 by absorbing heat from the CPU 20 and transporting the heat to the outside of the CPU 20. The loop heat pipe 200 has the evaporator 1 in contact with the CPU 20, and the heat of the CPU 20 that has generated heat is conducted to the evaporator 1, and the liquid-phase working fluid 100 in the evaporator 1 is caused by this heat. Vaporize. Here, the evaporator 1 has a shape close to a 50 mm × 50 mm × 15 mm rectangular parallelepiped, and specifically, water is adopted as the working fluid 100.

  The evaporator 1 is connected to a loop-shaped copper tube that is a hollow tube and returns to the evaporator 1 from the evaporator 1, so that the inside of the tube is connected to the heat transport material. The structure which can move the working fluid 100 is realized. The middle part of the tube has a meandering shape as indicated by the dotted line, and copper radiating fins 6a are in contact with this part. The heat of the gas-phase working fluid 100 that has moved through the pipe in the direction of the solid arrow in the figure is conducted to the heat radiating fins 6a at the portion where the heat radiating fins 6a are in contact. Thereby, the gaseous working fluid 100 is cooled and liquefied. Here, the torsion-shaped tube with which the radiation fins 6 a are in contact is the condenser 5, and the tube through which the gas-phase working fluid 100 moves from the evaporator 1 to the condenser 5 is the vapor tube 4. It is. Further, the distance between the evaporator 1 and the condenser 5 is about 300 mm, the inner diameter of the steam pipe 4 is φ3 mm, and the total length of the winding pipe that becomes the condenser 5 is about 250 mm.

  Two fans 6 for exhausting the air inside the computer 1000 to the outside are provided near the heat radiating fins 6 a, and hot air around the heat radiating fins 6 a is released outside the computer 1000 by the exhaust of these fans 6. Is done. As a result, the heat of the CPU 20 is finally released to the outside of the computer 1000. Here, the size of the fan 6 is φ60 mm.

  On the other hand, the liquefied working fluid 100 moves through the pipe along the dotted arrow in the figure and returns to the evaporator 1. The pipe through which the working fluid 100 liquefied at this time moves from the condenser 5 to the evaporator 1 is the liquid pipe 2. The inner diameter of the liquid pipe 2 is φ2 mm.

  Next, the evaporator 1 will be described in detail.

  FIG. 5 is a schematic diagram showing the configuration of the evaporator 1 of FIG.

  The evaporator 1 includes a vapor outlet part 14, a liquid inlet part 11, a wick 3, a heat insulating member 13, and a main body part 12. The liquid inlet part 11 is connected to the main body part 12 through the wick 3. The steam outlet portion 14 is connected to the main body portion 12 on the side opposite to the portion where the liquid inlet portion 11 is connected.

  The liquid inlet 11 has an inlet pipe 11a connected to the liquid pipe 2 (not shown in FIG. 5) of FIG. 4, and the steam outlet 14 is connected to the steam pipe 4 of FIG. 4 (not shown in FIG. 5). It has an outlet pipe 14a connected to the figure.

  The heat insulating member 13 is in contact with the surface of the main body 12 facing upward in FIG. 5 and plays a role of preventing the heat of the main body 12 from escaping to the outside.

  The wick 3 is formed of a porous stainless sintered material, and includes three arms 3a having a cylindrical shape with a bottom surface. Here, each bottom surface of the arm 3a is not shown because it faces the back side of this figure, and a cylindrical opening portion that faces the front side of this figure is shown for each of the three arms 3a. ing.

  The main body portion 12 is provided with three metal tubes, a first metal tube 121, a second metal tube 122, and a third metal tube 123, which are indicated by dotted lines in this figure. The three arms 3a of the wick 3 are respectively inserted. Here, the inner diameter of the three metal tubes is 10 mm on average, and a plurality of protrusions parallel to each other are provided on the inner wall of the three metal tubes along the extending direction of the three metal tubes. It has been. Here, a gap 12a is formed between adjacent ridges. Due to the presence of the groove 12a, when the arm 3a of the wick 3 is fitted in each metal tube, the arm 3a of the wick 3 and each metal tube A gap is formed between the two.

  Here, in the wick 3, based on the average hole radius of the surface of the stainless sintered material that is the material of the wick 3, the aperture ratio of the surface of the stainless sintered material, and the amount of latent heat of vaporization of water, Each arm 3a of the wick 3 in each metal tube has the smallest contact angle θ (see FIG. 2) in each metal tube and the largest capillary force ΔP when the calorific value of the CPU 20 supplied to the metal tube is 40 W. The surface area is adjusted.

  The three metal tubes are connected to the steam outlet 14. Here, in the steam outlet part 14, the first valve 141 and the second valve 141 are provided in the vicinity of the opening on the steam outlet part 14 side of the first metal pipe 121 on the right side and the second metal pipe 122 on the left side in the drawing. The first valve 141 and the second valve 141 close and open the first metal pipe 121 and the second metal pipe 122, respectively. This closing / opening mechanism will be described later. On the other hand, such a valve is not provided for the third metal pipe 123 in the middle of the figure, and this third metal pipe 123 is always open toward the steam outlet portion 14.

  Here, the loop heat pipe 200 is provided with a wattmeter 20a that detects the amount of heat generated by the CPU 20, and a control circuit 20b that controls the closing and opening of the first metal pipe 121 and the second metal pipe 122. These are arranged on the substrate 21 of FIG. The watt meter 20a is an electronic circuit that obtains the voltage supplied to the CPU 20 and the number of clocks of the CPU 20 during operation, and obtains the heat generation amount (unit: W (watts)) of the CPU 20 based on such information. Closing / opening of the first metal pipe 121 and the second metal pipe 122 by the first valve 141 and the second valve 141 described above causes the actuator, which will be described later, to drive the first valve 141 and the second valve 141, and the control circuit 20b. It is realized by controlling. In this control, the control circuit 20b closes / opens the first metal tube 121 and the second metal tube 122 according to the detection result of the wattmeter 20a. Control of closing / opening of the first metal tube 121 and the second metal tube 122 will be described in detail later.

  6 is a cross-sectional view of the evaporator 1 in a plane perpendicular to the first metal tube 121 of FIG. 5, and FIG. 7 is a cross-sectional view of the evaporator 1 in a plane along the first metal tube 121 of FIG. is there.

  In FIG. 6, the first metal tube 121, the second metal tube 122, and the third metal tube 123 included in the main body 12 together with the wick 3 in each metal tube and members provided around each metal tube. It is shown in the figure. The inner wall of each metal tube is uneven as shown in FIG. 6 due to the presence of the groove 12a. Here, although the convex portion (the above-mentioned protrusion) is in contact with the wick 3, there is a gap between the concave portion (the groove portion 12 a) and the wick 3, and the gas-phase working fluid 100. Large enough to pass through.

  As shown in FIG. 6, a heat conductive member 12b having high heat conductivity is provided around each metal tube, and the heat conductive member 12b is covered with a copper case 12c. The CPU 20 is in contact with the case 12c from the lower side of FIG. 6, and the heat insulating member 13 is in contact with the upper side of FIG. With such a configuration, the heat of the CPU 20 is easily transferred to the working fluid 100 through the copper case 12c, the heat conducting member 12b, and each metal tube, and the heat insulating member 13 is present, thereby providing the heat conducting member. The heat is less likely to be transferred from 12 to the electronic elements and electronic circuits around the CPU 20.

  FIG. 7 shows a cross-sectional view of the evaporator 1 in a state where the first metal pipe 121 is not closed (ie, opened) by the first valve 141, and the inlet pipe 11a and the outlet pipe 14a of FIG. Is indicated by a dotted line in FIG. In a state where the first metal pipe 121 is opened, a part of the liquid-phase working fluid 100 flowing into the liquid inlet 11 from the liquid pipe 2 (not shown in FIG. 7) via the inlet pipe 11a is the first. It flows into the metal pipe 121 and passes through the wick 3 in the first metal pipe 121 toward the vapor outlet portion 14 as indicated by the arrow in FIG. During the permeation of the wick 3, the liquid-phase working fluid 100 is vaporized by receiving heat from the surroundings while penetrating into the wick 3. The vaporized working fluid 100 flows out from the steam outlet 14 through the outlet pipe 14 to the steam pipe 4 in FIG.

  Although the working fluid 100 passing through the first metal pipe 121 has been described above, the working fluid 100 passing through the third metal pipe 123 and the second valve 142 in FIG. 5 are not closed (that is, opened). Similarly, the working fluid 100 passing through the second metal pipe 122 is inflowed in the liquid phase and outflowed in the gas phase. In addition, since the working fluid 100 cannot move in the first metal pipe 121 closed by the first valve 141 and the second metal pipe 122 closed by the second valve 142, the liquid phase as described above can be used. Inflow of the working fluid 100 and outflow of the working fluid 100 in the gas phase are not performed.

  Here, the first metal tube 121, the second metal tube 122, and the third metal tube 123 correspond to an example of a plurality of evaporation tubes in the loop heat pipe and the electronic device described above in the basic form, and the first metal tube 121. The second metal tube 122 corresponds to an example of one or more evaporation tubes in the loop heat pipe and the electronic device described above in the basic form. The control circuit 20b corresponds to an example of a valve control unit in the loop heat pipe and the electronic device described above in the basic form.

  In the rope heat pipe 200 of the present embodiment, the first metal pipe 121 and the second metal pipe 122 are closed by the first valve 141 and the second valve 142 being moved by driving of the actuator. And closing the opening of the second metal pipe 122 on the steam outlet 14 side. FIG. 7 shows a state in which two actuators 140 that are responsible for the movement of the first valve 141 are located beside the first valve 141. Although not shown in FIG. 7, the same two actuators 140 as the two actuators 140 responsible for the movement of the first valve 141 are provided beside the second valve 142 (not shown in FIG. 7). This actuator 140 is a type of actuator called a bimorph type among piezo actuators that generate force using a piezo element.

  Hereinafter, the actuator 140 will be described.

  FIG. 8 is a diagram showing the actuator 140 of FIG. 7 together with its displacement.

  The actuator 140 has a configuration in which the upper and lower ends of the metallic thin plate 140a are sandwiched between two piezoelectric elements 140b. Here, the two piezoelectric elements 140b sandwiching the upper end portion of the thin plate 140a and the two piezoelectric elements 140b sandwiching the lower end portion of the thin plate 140a are electrically connected (wired) to the control circuit 20b. With this wiring, the control circuit 20b can apply different voltages to the two upper piezo elements 140b by using the upper end of the thin plate 140a as an electrode for the two upper piezo elements 140b in the drawing. . Further, the control circuit 20b can apply different voltages to the two lower piezoelectric elements 140b by using the lower end portion of the thin plate 140a as an electrode for the lower two piezoelectric elements 140b. .

  In general, a piezo element has a property of expanding and contracting according to the magnitude of an applied voltage when a voltage is applied. A bimorph type piezoelectric actuator has a configuration in which an end of a metallic thin plate is sandwiched between two piezoelectric elements. When voltages of different magnitudes are applied to the two piezoelectric elements, these piezoelectric elements The thin plate warps due to the difference in the degree of expansion and contraction, and in the bimorph type piezo actuator, the force accompanying the change in the shape of the thin plate at this time is used as power.

  The upper two piezoelectric elements 140b in the drawing are partially fixed to the upper fixing portion 140c, and when a voltage is applied, the remaining portions that are not fixed to the fixing portion 140c expand and contract. Similarly, two piezo elements 140b on the lower side of the figure are partially fixed to the lower fixing portion 140c, and when a voltage is applied, the remaining portions that are not fixed to the fixing portion 140c. Expands and contracts. Here, in the actuator 140 of FIG. 8, the right piezo element 140b of the upper two piezo elements 140b is applied to the right piezo element 140b of the lower two piezo elements 140b. A voltage having the same magnitude as the voltage is applied, and the left piezo element 140b of the upper two piezo elements 140b is applied to the left piezo element 140b of the two lower piezo elements 140b. A voltage having the same magnitude as the applied voltage is applied. At this time, the control circuit 20b controls the difference between the voltages applied to the upper two piezoelectric elements 140b (that is, the difference between the voltages applied to the lower two piezoelectric elements 140b). Control the direction of warping. For example, in a situation where a voltage is applied to the upper two piezo elements 140b and the lower two piezo elements 140b and the thin plate 140a is warped to the right as shown by the solid line in the figure, the upper left and right piezo elements 140b. By switching the voltage applied to the element 140b and further switching the voltages applied to the two left and right piezo elements 140b, the arrangement of the thin plate 140a is a thin plate indicated by a solid line as shown by the arrows in the figure. The arrangement can be changed from the arrangement of 140a (arrangement warped to the right) to the arrangement of thin plates 140a (arrangement warped to the left) indicated by a dotted line.

  FIG. 9 is a diagram illustrating a state in which the first valve closes / opens the first metal pipe by the two actuators 140 in FIG. 7.

  In part (a) of FIG. 9, of the thin plates 140a of the two actuators 140, the arrangement of the thin plate 140a of the right actuator 140 is shown by the solid line as shown by the right-pointing arrow of part (a) of FIG. A state of changing from (arranged in a leftward direction) to an arrangement indicated by a dotted line (arranged in a rightward direction) is shown. When the warp of the right thin plate 140 a is changed, the right thin plate 140 a contacts the front surface 141 a of the first valve 141 and pushes the first valve 141 toward the first metal tube 121. Here, the movement of the part (a) in FIG. 9 in the vertical direction is suppressed by the guide 1410, but the first valve 141 can move in the horizontal direction. For this reason, the first valve 141 pushed by the right thin plate 140a moves to the right in part (a) of FIG. 9 and closes the opening of the first metal tube 121. Thereby, the 1st metal pipe 121 will be closed. The first valve 141 at this time is the first valve 141 in a closed state.

  In part (b) of FIG. 9, among the thin plates 140a of the two actuators 140, the arrangement of the thin plate 140a of the left actuator 140 is the arrangement shown by the solid line as shown by the left-pointing arrow of part (b) of FIG. A state of changing from (arranged to the right) to an arrangement indicated by a dotted line (arranged to the left) is shown. When the warpage of the left thin plate 140 a is changed, the left thin plate 140 a contacts the rear surface 141 b of the first valve 141 and pushes the first valve 141 away from the first metal tube 121. For this reason, the first valve 141 pushed by the left thin plate 140 a moves to the left in the part (b) of FIG. 9 and moves away from the opening of the first metal tube 121. As a result, the first metal tube 121 is opened. The first valve 141 at this time is the first valve 141 in an open state.

  When the first valve 141 shifts from the closed state to the open state, the thin plate 140a of the right actuator 140 out of the thin plates 140a of the two actuators 140 is warped to the left (FIG. 9). Next, the thin plate 140a of the left actuator 140 moves to the left-curved arrangement (the arrangement of the dotted line in part (b) of FIG. 9).

  Conversely, when the first valve 141 shifts from the open state to the closed state, the thin plate 140a of the left actuator 140 out of the thin plates 140a of the two actuators 140 is warped to the right (see FIG. Then, the thin plate 140a of the right actuator 140 moves to the right-side arrangement (the arrangement of the dotted line in part (a) in FIG. 9).

  The opening and closing of the first metal pipe 121 by the first valve 141 (opening and closing of the first valve 141) has been described above. However, the second metal pipe 122 by the second valve 142 of FIG. The second valve 142 is moved by the two actuators 140 provided near the valve 142 to open and close the second metal pipe 122 (opening and closing the second valve 142).

  The control circuit 20b of FIG. 5 includes two actuators 140 provided beside the first valve 141 and two actuators provided beside the second valve 142 in accordance with the detection result of the wattmeter 20a. By controlling 140, the opening and closing of the first valve 141 and the second valve 142 are controlled.

  FIG. 10 is a flowchart showing a control method for opening and closing the first valve 141 and the second valve 142 performed by the control circuit 20b.

  When the power of the computer 100 in FIG. 4 is turned on by the user's operation and the CPU 20 starts to generate heat (step S1), the control circuit 20b in FIG. 5 starts monitoring the amount of heat generated by the CPU 20 detected by the wattmeter 20a. (Step S2). Next, the control circuit 20b controls the two actuators 140 provided near the first valve 141 and the two actuators 140 provided near the second valve 142, and the first valve 141 and The second valve 142 is closed (step S3). While the heat generation amount of the CPU 20 is 1/3 or less of the maximum heat generation amount of the CPU 20 (step S4; No), the closed state of the first valve 141 and the second valve 142 is maintained. As described above, the maximum heat generation amount of the CPU 20 is 120 W. Therefore, while the heat generation amount of the CPU 20 is 40 W or less, the first valve 141 and the second valve 142 are kept closed.

  FIG. 11 is a schematic diagram showing a state in which the first valve 141 and the second valve 142 are closed.

  As shown in this figure, the first valve 141 located on the uppermost side of the figure is attached to the thin plate 140a of the right actuator 140 out of the two actuators 140 provided near the first valve 141. The opening of the first metal tube 121 is blocked by being pushed. Similarly, the second valve 142 located at the lowermost side in the drawing is pushed by the thin plate 140a of the right actuator 140 out of the two actuators 140 provided near the second valve 141. The opening of the second metal tube 122 is blocked. In this way, a state in which the first metal tube 121 and the second metal tube 122 are closed is realized. In this state, the working fluid 100 can only pass through the third metal pipe 123, and only the wick 3 in the third metal pipe 123 is used in the phase change of the working fluid 100 from the gas phase to the liquid phase. Will be.

  FIG. 12 is a diagram schematically showing how the working fluid 100 advances through the wick 3 and changes from the liquid phase to the gas phase under the state where the first valve 141 and the second valve 142 are closed.

  In this figure, for each of the first metal pipe 121, the second metal pipe 122, and the third metal pipe 123, the passage of the working fluid 100 in a part of the wick 3 in each metal pipe is schematically shown. ing. Actually, the passages (cavities) in the wick 3 through which the liquid-phase working fluid 100 permeates are winding and complicated, but in this figure, the plurality of passages in the wick 3 are in the left-right direction. It is schematically represented as a cylindrical passage that extends parallel to each other. That is, in FIG. 12, the same way of expression on the drawing as in FIGS. 2 and 3 is used for the wick. In this figure, the liquid-phase working fluid 100 proceeds to the right in the wick 103 by capillary force, and is vaporized by receiving heat from the surroundings. Here, the relationship of the above-described equation (1) is established between the capillary force ΔPc and the contact angle θ formed by the wall surface of the cylindrical passage and the boundary surface.

  In a situation where the heat generation amount of the CPU 20 is small, which is 1/3 or less of the maximum heat generation amount of the CPU 20, the working fluid 100 flows only in the third metal tube 123, and the working fluid 100 flows in the wick 3 in the third metal tube 123. Changes from the liquid phase to the gas phase. On the other hand, the first metal tube 121 and the second metal tube 122 are unused, and the wick 3 in these metal tubes is not used. In the state of FIG. 12, compared with the state where the wick 3 of another metal tube is used in addition to the wick 3 in the third metal tube 123 under such a small amount of heat generation from the CPU 20. In the wick 3 in the third metal tube 123, as shown in FIG. 12, a state where the contact angle θ is small and the capillary force ΔPc is large is realized.

  Returning to FIG.

  When the heat generation amount of the CPU 20 exceeds 1/3 of the maximum heat generation amount of the CPU 20 (step S4; Yes), the control circuit 20b controls the two actuators 140 provided beside the first valve 141 to change the first heat generation amount. One valve 141 is opened (step S5).

  FIG. 13 is a schematic diagram showing a state in which the first valve 141 is open and the second valve 142 is closed.

  Of the thin films 149a of the two actuators 140 provided beside the first valve 141, the control circuit 20b first warps the right thin film 149a that warps rightward in FIG. The left thin film 149a warped rightward is bent leftward. Thereby, as shown in FIG. 13, the thin films 149a of the two actuators 140 provided near the first valve 141 are both warped leftward. When the left thin film 149a is warped to the left, the first valve 141 moves to the left and leaves the opening of the first metal tube 121, thereby opening the first metal tube. In this way, a state in which the first metal tube 121 is opened and the second metal tube 122 is closed is realized. In this state, the working fluid 100 can pass through the first metal tube 121 and the third metal tube 123, and the wick 3 in the first metal tube 121 and the third metal tube 123 is connected to the working fluid 100. It will be used in the phase change from the gas phase to the liquid phase.

  Returning to FIG.

  While the heat generation amount of the CPU 20 is 2/3 or less of the maximum heat generation amount of the CPU 20 (step S6; No), the state where the second valve 122 is closed is maintained (step S7). Here, as described above, the maximum heat generation amount of the CPU 20 is 120 W. Therefore, the second valve 122 is kept closed while the heat generation amount of the CPU 20 is 80 W or less. As long as the heat generation amount of the CPU 20 is 2/3 or less of the maximum heat generation amount of the CPU 20 but exceeds 1/3 of the maximum heat generation amount, the above-described steps S4, S5, S6, and step S7 are performed. The process is repeated. If the heat generation amount of the CPU 20 decreases halfway and becomes less than 1/3 of the maximum heat generation amount of the CPU 20, No is selected again in step S4, and the first valve 141 and the second valve 142 are closed. Is realized.

  When the heat generation amount of the CPU 20 exceeds 2/3 of the maximum heat generation amount of the CPU 20 (step S6; Yes), the control circuit 20b controls the two actuators 140 provided beside the second valve 142 to control the first heat generation amount. The two valve 142 is opened (step S8).

  FIG. 14 is a schematic diagram showing a state in which the first valve 141 and the second valve 142 are open.

  Of the thin films 149a of the two actuators 140 provided beside the second valve 142, the control circuit 20b first warps the right thin film 149a that warps rightward in FIG. The left thin film 149a warped rightward is bent leftward. Thereby, as shown in FIG. 14, the thin films 149a of the two actuators 140 provided near the second valve 142 are both warped leftward. When the left thin film 149a is warped leftward, the second valve 142 moves to the left and leaves the opening of the second metal tube 122, thereby opening the second metal tube. Thus, the state where both the first metal tube 121 and the second metal tube 122 are opened is realized. In this state, the working fluid 100 can pass through the first metal tube 121, the second metal tube 122, and the third metal tube 123, and the wick 3 in all the metal tubes is connected to the working fluid 100. It will be used in the phase change from the gas phase to the liquid phase.

  FIG. 15 is a diagram schematically showing a state in which the working fluid 100 progresses through the wick 3 and changes from the liquid phase to the gas phase with the first valve 141 and the second valve 142 closed.

  In this figure, as in FIG. 12, for each of the first metal pipe 121, the second metal pipe 122, and the third metal pipe 123, the passage of the working fluid 100 in a part of the wick 3 in each metal pipe. Is schematically shown.

  In a situation where the heat generation amount of the CPU 20 is large, which exceeds 2/3 of the maximum heat generation amount of the CPU 20, the working fluid flows in all the metal tubes of the first metal tube 121, the second metal tube 122, and the third metal tube 123. 100 flows, and the working fluid 100 changes from the liquid phase to the gas phase at the wick 3 in each metal tube. Thus, in the state of FIG. 15, the wicks 3 in all the metal tubes are used corresponding to the situation where the amount of heat generated from the CPU 20 is large. As shown in FIG. 15, a state in which the contact angle θ is small and the capillary force ΔPc is large is realized.

  Returning to FIG.

  While the computer 100 in FIG. 4 is turned on (step S9; No), as long as 2/3 of the maximum heat generation amount of the CPU 20 is exceeded, the above-described steps S4, S5, S6, S8, and Step S9 is repeated, and the state where the first valve 121 and the second valve 122 are opened is maintained. If the heat generation amount of the CPU 20 decreases halfway and exceeds 1/3 of the maximum heat generation amount of the CPU 20, but becomes 2/3 or less of the maximum heat generation amount, No is again selected in step S6 and the second. A state where the two-valve 142 is closed is realized. Then, step S4, step S5, step S6, and step S7 described above are repeated. Further, when the heat generation amount of the CPU 20 decreases and becomes 1/3 or less of the maximum heat generation amount of the CPU 20, No is selected again in step S4, and the first valve 141 and the second valve 142 are closed. To do.

  When the power of the computer 100 of FIG. 4 is turned off by the user's operation (step S9; Yes), the control of opening and closing of the first valve 141 and the second valve 142 performed by the control circuit 20b ends.

  As described above, in the loop heat pipe 200 of the present embodiment, the first valve 141 and the first valve 141 are arranged so that the number of metal tubes through which the working fluid 100 flows in the evaporator 1 decreases as the heat generation amount of the CPU 20 decreases. The opening and closing of the two-valve 142 is controlled.

  Assuming that a small amount of heat generated from the CPU 20 is distributed to all of the first metal tube 121, the first metal tube 122, and the third metal tube 123, the wick 3 in these metal tubes has a large contact angle θ. The capillary force ΔPc becomes small, and the working fluid 100 hardly moves in the vicinity of the wick 3 and the circulation speed of the working fluid 100 decreases. In such a state, even if the heat generation amount of the CPU 20 is small, the temperature around the CPU 20 gradually increases, and there is a possibility that a malfunction may occur in the electronic components around the CPU 20. In particular, in a situation where the circulation speed of the working fluid 100 is completely zero in all the metal pipes, a so-called dryout occurs in which the working fluid 100 supplied to each metal pipe is insufficient, and the temperature around the CPU 20 The rise will be serious.

  In the loop heat pipe 200 of the present embodiment, in a situation where the heat generation amount of the CPU 20 is small, the number of metal pipes through which the working fluid 100 flows in the evaporator 1 is reduced, so that the metal pipe through which the working fluid 100 flows is transferred from the CPU 20. A small calorific value can be concentrated. As a result, in the metal pipe, a decrease in the mobility of the working fluid 100 in the vicinity of the wick 3 is avoided, and a decrease in the circulating speed of the working fluid is suppressed. As a result, the loop heat pipe 200 as a whole can be prevented from lowering the circulation speed of the working fluid.

  Further, in the loop heat pipe 200 of the present embodiment, the opening and closing of the first valve 141 and the second valve 142 can be quickly switched by using the actuator 140 using the responsive piezoelectric element 140b.

  Here, in the loop heat pipe 200 of this embodiment, it demonstrates using a specific graph that high capillary force (DELTA) P is maintained even when the emitted-heat amount of CPU200 is small.

  FIG. 16 is a diagram illustrating a change in the capillary force ΔP accompanying an increase in the amount of heat generated by the CPU 20 in the loop heat pipe 200 of the present embodiment.

  In this figure, the state of the change in the capillary force ΔP accompanying the increase in the amount of heat generated by the CPU 20 in the third metal tube 123 of the loop heat pipe 200 of the present embodiment is shown by a solid line graph. Further, in this figure, the configuration is the same as that of the loop heat pipe 200 of the present embodiment except that the first valve 141 and the second valve 142 are always kept open regardless of the heat generation amount of the CPU 20. Taking a loop heat pipe as a comparative example, the state of the change in capillary force ΔP in the third metal tube 123 of the loop heat pipe of the comparative example is shown by a dotted line graph.

  In this figure, the heat generation amount area of the CPU 20 is divided into three areas: an area of 40 [W] or less, an area greater than 40 [W] and 80 [W] or less, and an area greater than 80 [W]. Is shown. Here, in the loop heat pipe 200 of the present embodiment, as described above, in the region of 40 [W] or less, both the first valve 141 and the second valve 142 are closed and larger than 40 [W] and 80 [W]. In the following region, the first valve 141 is opened but the second valve 142 is closed, and in the region larger than 80 [W], both the first valve 141 and the second valve 142 are opened.

  The loop heat pipe 200 of this embodiment and the loop heat pipe of the comparative example are common in that both the first valve 141 and the second valve 142 are opened. Therefore, as shown in FIG. In a region larger than W], the solid line graph and the dotted line graph match. However, at 80 [W] or less, as can be seen from the fact that the solid line graph is located above the dotted line graph, the loop heat pipe 200 of this embodiment has the same heat generation amount as the comparative example, even though the heat generation amount of the CPU 20 is the same. Compared to the higher capillary force.

  As described above, in the loop heat pipe 200 of the present embodiment, it is understood that the high capillary force ΔP is maintained even when the heat generation amount of the CPU 200 is small by the opening / closing control of the first valve 141 and the second valve 142.

  Next, the cooling effect by the loop heat pipe 200 of the present embodiment described above will be described based on specific experimental results.

In this experiment, using the loop heat pipe 200 described above, the rate of increase in the temperature of the evaporator 1 (thermal resistance) relative to the increase in the amount of heat generated by the CPU 20 was measured. In this experiment,
A loop heat pipe having the same configuration as that of the loop heat pipe 200 of the present embodiment, except that the first valve 141 and the second valve 142 are always kept open regardless of the amount of heat generated by the CPU 20. As for the loop heat pipe of the comparative example, the rate (thermal resistance) of the temperature rise of the evaporator 1 with respect to the increase in the heat generation amount of the CPU 20 was measured.

  FIG. 17 is a diagram illustrating experimental results.

  In this figure, in the loop heat pipe 200 of the present embodiment, the state of change in the thermal resistance of the evaporator 1 with the increase in the amount of heat generated by the CPU 20 is shown by a solid line graph. Moreover, in this figure, the state of the change of the thermal resistance of the evaporator 1 accompanying the increase in the emitted-heat amount of CPU20 in the loop heat pipe of a comparative example is shown with the dotted line graph.

  As shown in this figure, in the loop heat pipe 200 of the present embodiment, although there is a slight increase in the value of the thermal resistance when the first valve 141 and the second valve 142 are switched, the overall CPU 20 Even if the amount of heat generated increases, the value of the thermal resistance is maintained at a low value of about the same level. On the other hand, in the loop heat pipe of the comparative example, when the heat generation amount of the CPU 20 is 80 W or less, the value of the thermal resistance increases rapidly. This rapid increase in thermal resistance corresponds to the occurrence of dryout in the evaporator 1 of the loop heat pipe of the comparative example. From this experimental result, when the heat generation amount of the CPU 20 is low, the area of the wick through which the working fluid effectively passes is reduced by closing the first valve 141 and the second valve 142 as in the loop heat pipe 200 of the present embodiment. It can be seen that dryout is avoided.

  The above is the description of the embodiment.

  In the above description, the loop heat pipe provided with three metal tubes has been described, but the loop heat pipe and electronic device described above in the basic form are a loop heat pipe and electronic device provided with two metal tubes, It may be a loop heat pipe and an electronic device provided with four or more metal tubes.

It is a schematic block diagram showing the structure and operating principle of a loop heat pipe. It is the figure which represented typically a mode that a working fluid progressed in a wick and changed from a liquid phase to a gaseous phase. It is a figure showing the mode of the boundary surface of the liquid side and the vapor | steam side according to the emitted-heat amount of a heat generating body. It is a figure which shows the computer which is embodiment of an electronic device, and the loop heat pipe with which this computer is equipped. It is the schematic diagram showing the structure of the evaporator of FIG. It is sectional drawing of the evaporator 1 in a plane perpendicular | vertical to the 1st metal tube of FIG. It is sectional drawing of the evaporator 1 in the plane along the 1st metal tube of FIG. It is the figure which represented the actuator of FIG. 7 with the mode of the displacement. It is a figure showing a mode that a 1st valve closes and open | releases a 1st metal pipe by two actuators of FIG. It is a flowchart showing the control system of opening and closing of a 1st valve and a 2nd valve performed by a control circuit. It is the schematic diagram showing a mode that the 1st valve and the 2nd valve were closed. It is the figure which represented typically a mode that working fluid progressed in the wick and changed from a liquid phase to a gaseous phase under the state where the 1st valve and the 2nd valve were closed. It is the schematic diagram showing a mode that the 1st valve opened and the 2nd valve closed. It is the schematic diagram showing a mode that the 1st valve | bulb and the 2nd valve | bulb were open. It is the figure which represented typically a mode that working fluid progressed in the wick and changed from a liquid phase to a gaseous phase under the state where the 1st valve and the 2nd valve were closed. It is a figure showing the mode of change of capillary force (DELTA) P with the increase in the emitted-heat amount of CPU in the loop heat pipe of this embodiment. It is a figure showing an experimental result.

Explanation of symbols

101, 1 Evaporator 102, 2 Liquid pipe 103, 3 Wick 3a Arm 104, 4 Steam pipe
105,5 Condenser 6 Fan 11 Liquid inlet 11a Inlet pipe 12 Main body 12a Groove 12b Conductive member 12c Case 121 First metal pipe 122 Second metal pipe 123 Third metal pipe 13 Heat insulating member 14 Steam outlet 14a Outlet pipe 140 Actuator 140a Thin plate 140b Piezo element 140c Fixed portion 141 First valve 141a Front surface 141b Rear surface 142 Second valve 20 CPU
20a Wattmeter 20b Control circuit 21 Substrate 22 HDD
23 memory 24 power supply 200 loop heat pipe 1000 computer

Claims (3)

A plurality of evaporation tubes each having a wick composed of a porous material and thermally coupled to a common heating element,
An evaporator having a plurality of evaporating tubes for evaporating liquid phase working fluid passing through each wick by heat received from the heating element;
A condenser that releases heat of the gas-phase working fluid to condense the working fluid;
A vapor pipe that connects the evaporator and the condenser and moves a vapor-phase working fluid evaporated in the evaporator from the evaporator to the condenser;
A liquid pipe that connects the evaporator and the condenser, and moves a liquid-phase working fluid condensed in the condenser from the condenser to the evaporator;
One or more valves provided corresponding to each of one or more of the plurality of evaporation tubes, and opening and closing the corresponding evaporation tubes;
A calorific value detection means for detecting the calorific value of the heating element;
A valve control unit that controls opening and closing of each of the one or more valves, and reduces the number of evaporation pipes that open the valve as the amount of heat generated by the heat generation amount detection unit decreases. Loop heat pipe. 2. The loop heat according to claim 1 , wherein the valve control unit controls a voltage applied to the piezo element, and opens and closes the valve by displacement of the piezo element according to the applied voltage. pipe. An electronic device provided with a heat generating electronic component that generates heat by operation,
A plurality of evaporation tubes each having a wick composed of a porous material and thermally coupled to the heat generating electronic component, wherein the liquid phase working fluid passing through each wick is transferred to the heat generating electron An evaporator having a plurality of evaporator tubes that evaporate by heat received from the part;
A condenser that releases heat of the gas-phase working fluid to condense the working fluid;
A vapor pipe that connects the evaporator and the condenser and moves a vapor-phase working fluid evaporated in the evaporator from the evaporator to the condenser;
A liquid pipe that connects the evaporator and the condenser, and moves a liquid-phase working fluid condensed in the condenser from the condenser to the evaporator;
One or more valves provided corresponding to each of one or more of the plurality of evaporation tubes, and opening and closing the corresponding evaporation tubes;
A calorific value detection means for detecting the calorific value of the heating element;
A valve control unit that controls opening and closing of each of the one or more valves, and reduces the number of evaporation pipes that open the valve as the amount of heat generated by the heat generation amount detection unit decreases. And electronic equipment .

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