JP5287638B2 - Loop heat pipe and electronic equipment - Google Patents

Description

  The present invention relates to a loop heat pipe and an electronic apparatus including the same.

2. Description of the Related Art Conventionally, a heat pipe is known as a device for cooling a heating element (for example, a heating element such as a CPU) of an electronic device. The heat pipe is a heat transfer device that transports heat by utilizing the phase change of the working fluid sealed inside.

  As one type of heat pipe, there is a loop heat pipe (LHP) formed by enclosing a working fluid in a circular flow path formed in an annular shape. As the loop type heat pipe, an evaporating unit that receives heat from the outside (for example, a heating element) and evaporates the liquid-phase working fluid (working fluid) to change the phase to a gas-phase working fluid (vapor); A condensing unit that condenses a gas-phase working fluid (vapor) by heat radiation to the atmosphere (for example, the atmosphere) and changes the phase into a liquid-phase working fluid (working fluid) connects the evaporation unit and the condensing unit to form a gas phase An annular flow path is formed by a steam pipe that guides the working fluid from the evaporation section to the condensation section, and a liquid return pipe that connects the condensation section and the evaporation section to guide the liquid-phase working fluid from the condensation section to the evaporation section. Examples of such communication are illustrated.

  Further, a loop heat pipe is known in which a wick having a capillary structure is accommodated in the evaporation portion. In this type of loop heat pipe, the liquid-phase working fluid supplied via the liquid return pipe is guided to the inner surface of the evaporation section by the capillary force of the wick. The liquid-phase working fluid led to the inner surface of the evaporation section is heated by the heat transferred from the heating element to the evaporation section, and the latent heat is absorbed when the liquid-phase working fluid evaporates.

  The working fluid that has become vapor in the evaporation section moves to the condensation section through the vapor pipe. The working fluid vapor introduced into the condensing unit is cooled by heat radiation from the condensing unit, and latent heat is released when the working fluid vapor condenses. Thereafter, the liquid-phase working fluid is supplied to the evaporation section via the liquid return pipe and evaporated. In this way, the working fluid circulates in the annular flow path while repeating the phase change, so that the heat of the heating element is continuously transported between the evaporation part and the condensation part in the form of latent heat, and the heating element is cooled. The

  In recent years, a liquid reservoir (sometimes referred to as a “compensation chamber”) that temporarily stores liquid-phase working fluid supplied to the evaporator via a liquid return pipe before the evaporator is disposed. A looped heat pipe has also been proposed. For example, if the liquid reservoir is not installed, and the amount of heat received by the evaporator rapidly increases when the working fluid is normally circulated through the annular channel (hereinafter referred to as “normal operation”), The supply amount of the dynamic fluid to the part tends to be insufficient. By disposing the liquid reservoir portion adjacent to the evaporation portion, the working fluid temporarily stored in the liquid reservoir portion can be supplied to the evaporation portion, and the working fluid is depleted in the evaporation portion (so-called dryout). Can be suppressed.

  However, there is a case where the loop heat pipe is used in a so-called top heat state in which heat from the heating element is input to the evaporation unit arranged at a position higher than the condensing unit. When the loop heat pipe is used in a top heat state, for example, when the heat input to the evaporation unit is stopped by turning off the power of the electronic device, the working fluid is also circulated (in the annular flow path). Stop. If it does so, the recirculation | reflux amount of the working fluid of the liquid phase to a liquid reservoir part may become inadequate. In addition, there is a situation in which during the period in which the circulation of the working fluid is stopped, the liquid-phase working fluid leaks downward due to the action of gravity from the liquid reservoir or the evaporation unit.

  In accordance with the above situation, the working fluid to be supplied to the evaporation section at the time of starting to start the circulation of the working fluid in the annular flow path (hereinafter also referred to as “start-up”), that is, at the time of starting the loop heat pipe, There is no guarantee that exists. If the working fluid in the evaporation section is depleted at the start-up, a new working fluid is not supplied from the liquid reservoir to the evaporation section even if there is some working fluid in the evaporation section. The start of circulation will be hindered. If it does so, even if heat_generation | fever of a heat generating body is started, there exists a possibility that the malfunction that the cooling of the heat generating body by heat transport may be inhibited arises.

  Conventionally, in a loop heat pipe used in a top heat state, a technique for suppressing dryout in an evaporation section has been proposed (see, for example, Patent Documents 1 and 2). As a first conventional example, there has been proposed one in which a pump is provided on the downstream side of the condensing unit and a check valve is arranged in order to reliably generate a circulating flow of the working fluid. As a second conventional example, a check valve is provided in the middle of a pipeline, and a buffer tank is provided in order to avoid dryout due to lack of working fluid.

JP-A-4-28998 JP-A-6-257969

  However, the advantage of the heat pipe is that it automatically operates due to a temperature difference or a thermal energy difference between the evaporation part and the condensation part, thereby enabling heat transport. On the other hand, if a pump is provided as in the first conventional example, energy (external power) for driving the pump is required, and the advantage of automatic operation is impaired. Therefore, in this conventional example, there is room for further improvement from the viewpoint of saving energy and reducing running costs. Furthermore, if a check valve or the like is provided in order to cause the working fluid to flow stably in one direction, it will become a resistance that hinders normal circulation of the working fluid during normal operation, and the heat transport capacity may be reduced. Concerned.

  This case was made in view of the above situation, and in a loop heat pipe used in a top heat state, it has excellent heat transport capability during normal operation and automatically starts circulation of working fluid at start-up. It aims at providing the technology which can be done.

  According to one aspect of the present invention, the loop heat pipe is configured to evaporate the liquid-phase working fluid by receiving heat from the outside, and to condense the gas-phase working fluid by dissipating heat by being disposed at a position lower than the evaporation portion. A condensing part is a loop heat pipe communicated so as to form an annular flow path by a steam pipe and a liquid return pipe, and is provided at a position higher than the evaporation part, and passes through the liquid return pipe A liquid reservoir for storing a liquid-phase working fluid supplied to the evaporation section, a first storage region including an outlet for the working fluid flowing out from the liquid reservoir, and the outlet. A partition wall that is separated from a second storage region that is not included, an opening portion that opens to the partition wall, and a valve mechanism that opens and closes the opening portion in conjunction with the temperature of the first storage region. In a normal operation in which the working fluid circulates in the annular flow path, the valve mechanism shuts off the opening so that the working fluid is stored in the second storage region, and the working fluid starts to circulate. Sometimes, when the temperature of the first storage region reaches a specified temperature, the valve mechanism opens the opening, so that the working fluid stored in the second storage region during normal operation is stored in the first storage region. It is characterized by being released into the area.

  According to this case, in the loop heat pipe used in the top heat state, the heat transport capability during normal operation is excellent, and the circulation of the working fluid can be automatically started at start-up.

1 is a diagram illustrating a schematic configuration of a loop heat pipe according to Embodiment 1. FIG. It is the figure which showed the detailed structure of the container which concerns on Example 1. FIG. It is AA arrow sectional drawing in FIG. It is a BB arrow sectional view in FIG. It is the figure which showed the valve mechanism in a valve closing state. It is the figure which showed the valve mechanism in a valve opening state. It is explanatory drawing for demonstrating each operation state of the loop type heat pipe (LHP) which concerns on Example 1. FIG. (A) is the figure which showed the state of LHP at the time of normal operation | movement. (B) is the figure which showed the state of LHP in a heat receiving stop period. (C) is the figure which showed the state of LHP after predetermined time passed, after CPU9 started an operation | movement from the state which the heat input to an evaporation part has stopped. (D) is the figure after the predetermined time passed from the state of (C). It is the figure which showed the relationship between CPU calorific value and 1st storage area | region atmosphere temperature THch concerning Example 1. FIG. FIG. 6 is a view for explaining a modification of the partition wall provided in the liquid reservoir according to the first embodiment. FIG. 10 is an explanatory diagram for explaining a liquid reservoir according to the second embodiment. It is CC sectional view taken on the line in FIG. FIG. 10 is an explanatory diagram for explaining a liquid reservoir according to the second embodiment. It is DD sectional view taken on the line in FIG. It is the figure which showed typically the electronic device carrying LHP.

  Hereinafter, a loop heat pipe according to an embodiment for carrying out the invention will be described with reference to the drawings. Here, an example will be described in which a loop heat pipe is incorporated in a computer as an example of an electronic device, and the CPU of a heating element that generates heat in the operating state of the computer is cooled.

<Example 1>
FIG. 1 is a diagram illustrating a schematic configuration of a loop heat pipe (hereinafter referred to as “LHP”) 1 according to the first embodiment. The LHP 1 generally includes an evaporation unit 2 that evaporates a liquid-phase working fluid by receiving heat from the outside, and a condensing unit 3 that is disposed at a position lower than the evaporation unit 2 and condenses the gas-phase working fluid by heat dissipation. The tube 4 and the liquid return tube 5 communicate with each other so as to form an annular channel (annular channel) CD.

  The white arrow illustrated in FIG. 1 illustrates the height relationship of each member in the LHP 1. As shown in this figure, the LHP 1 is used in a top heat state in which heat from the CPU 9 that is a heating element is input to the evaporation unit 2 located higher than the condensing unit 3.

The annular conduit CD is filled with a working fluid in a state where the inside thereof is depressurized compared to the atmospheric pressure. As will be described in detail later, the working fluid is supplied to the evaporation section 2 in a liquid state via the liquid return pipe 5. When the CPU 9 is in a heat generation state due to operation, it is heated by the heat of the CPU 9 to evaporate. The vapor of the working fluid flowing out from the evaporation unit 2 to the vapor pipe 4 is condensed by being radiated by the condensing unit 3. As a result of the working fluid circulating in the annular conduit CD while repeating the phase change, the heat of the CPU 9 is transported between the evaporation section 2 and the condensation section 3 in the form of latent heat.
Is continuously cooled.

  In the present embodiment, the working fluid enclosed in the annular conduit CD is water. However, the working fluid is not limited to water, and may be other fluids that change between a gas phase and a liquid phase, such as ethanol, methanol, propanol, ethyl ether, ethylene glycol, fluorinate, ammonia, and the like. Moreover, although the material of the vapor | steam pipe | tube 4 and the liquid return pipe | tube 5 has employ | adopted copper, it is not limited to this, For example, you may use the other material excellent in thermal conductivity.

  A liquid reservoir 6 is provided integrally with the evaporator 2 at the upper end of the evaporator 2. The liquid reservoir 6 has a function of temporarily storing the liquid-phase working fluid supplied to the evaporator 2 via the liquid return pipe 5 before the evaporator 2 and then supplying the working fluid to the evaporator 2. . Reference numeral 7 shown in FIG. 1 is a metal container that houses the evaporation section 2 and the liquid reservoir section 6.

  With reference to FIGS. 2-4, the detailed structure inside the container 7 is demonstrated. FIG. 2 is a diagram illustrating a detailed configuration of the container 7, and represents a longitudinal section (vertical section) of the container 7. FIG. 3 is a cross-sectional view taken along the line AA in FIG. FIG. 4 is a cross-sectional view taken along the line BB in FIG.

  The container 7 is formed in a cylindrical shape. The liquid reservoir 6 and the evaporator 2 accommodated in the container 7 are partitioned by a partition wall 7A provided horizontally. A circular communication port 7B opens at a substantially central portion in the in-plane direction of the partition wall 7A. The communication port 7B passes through the partition wall 7A, and the liquid reservoir 6 and the evaporation unit 2 communicate with each other through the communication port 7B.

  The liquid reservoir 6 is provided with a partition wall 8 extending upward from the partition wall 7A. The partition wall 8 includes a first storage region 6A including the communication port 7B and a second storage region 6B that does not include the communication port 7B (corresponding to a region other than the first storage region 6A). It is separated from the storage area 6B. In the example shown in FIG. 3, the partition wall 8 is provided substantially corresponding to the tangential position of the edge portion of the communication port 7B, but the present invention is not limited to this.

  The partition wall 8 is provided such that its upper end is lower than the ceiling surface of the liquid reservoir 6. Therefore, the first storage area 6A and the second storage area 6B in the liquid reservoir 6 communicate with each other above the partition wall 8, and are not completely partitioned. Furthermore, a through hole 8A is formed in a portion of the partition wall 8 near the lower end in the height direction, and the first storage area 6A and the second storage area 6B are communicated with each other through the through hole 8A.

  The through-hole 8A is provided with a valve mechanism 10 that opens and closes the through-hole 8A in conjunction with the temperature of the first storage region 6A (hereinafter referred to as “first storage region atmospheric temperature”) THch. “In conjunction with the first storage region atmosphere temperature THch” means that the valve mechanism 10 is automatically opened or closed according to the first storage region atmosphere temperature THch. The relationship between the opening / closing operation of the valve mechanism 10 and the first storage region atmospheric temperature THch will be described later.

  A hydraulic fluid inlet 6C to which the liquid return pipe 5 is connected is opened on the inner peripheral surface of the liquid reservoir 6. Further, the hydraulic fluid inlet 6C is also included in the first storage region 6A. Accordingly, the liquid-phase working fluid flowing through the liquid return pipe 5 is introduced into the first storage region 6 </ b> A of the liquid reservoir 6. Here, since the first storage region 6A includes the communication port 7B, the liquid-phase working fluid is temporarily stored in the first storage region 6A and then supplied to the evaporation unit 2 through the communication port 7B. Is done.

Next, a detailed configuration of the evaporation unit 2 and a mechanism for evaporating the liquid-phase working fluid supplied to the evaporation unit 2 will be described. A heat receiving block 11 is provided on a portion of the outer peripheral surface of the container 7 corresponding to the evaporation unit 2. The CPU 9 is in thermal contact with the heat receiving block 11. That is, the container 7 is in thermal contact with the CPU 9 via the heat receiving block 11.
The heat of the CPU 9 is transmitted to the evaporation unit 2 accommodated therein.

  The evaporation unit 2 accommodates a wick 12 having a capillary structure. The wick 12 is a porous member made of, for example, a sintered metal or a sintered ceramic. In this embodiment, for example, copper powder is sintered to form the wick 12, but other materials can also be used.

  The wick 12 is formed in a bottomed cylindrical shape having one end opened and the other end closed. The open end of the wick 12 faces the communication port 7 </ b> B, and the closed end of the wick 12 faces the bottom surface side of the evaporation unit 2. A gap 2 </ b> A is formed between the closed end of the wick 12 and the bottom surface of the evaporation unit 2. Further, a steam outlet 2B to which the steam pipe 4 is connected is opened on the bottom surface of the evaporation unit 2. The gap 2A is used as a flow path for guiding the working fluid to the vapor outlet 2B. In addition, since the wick 12 is a porous member, the inner peripheral surface and the outer peripheral surface thereof are communicated with each other through a fine hole.

  A hollow flow path portion 12 </ b> A that is a hollow space is formed on the central axis side of the wick 12. The hollow flow path portion 12A is provided at a position facing the communication port 7B. Therefore, the liquid-phase working fluid supplied from the communication port 7B to the evaporation unit 2 is first guided to the hollow flow path unit 12A. Further, a groove channel portion 12 </ b> B that is a plurality of grooves is formed on the outer peripheral surface of the wick 12 along the axial direction of the wick 12. The recessed channel portion 12B functions to increase the outer peripheral surface area of the wick 12 and is used as a working fluid channel.

  In the vicinity of the opening end of the wick 12, the groove channel portion 12B is not formed. As a result, each groove channel portion 12 </ b> B communicates with the hollow channel portion 12 </ b> A at its lower end, while its upper end is blocked by the wick 12. In addition, a portion of the outer peripheral surface of the wick 12 where the groove channel portion 12B is not formed (hereinafter referred to as “general outer peripheral portion”) is formed so that its outer shape is substantially equal to the inner diameter of the container 7. ing. The wick 12 is in contact with the inner peripheral surface of the container 7 at the general outer peripheral portion.

  Next, the operation of the liquid reservoir 6 and the evaporator 2 will be described. When the liquid-phase working fluid is guided from the first storage region 6 </ b> A of the liquid reservoir 6 to the hollow flow path 12 </ b> A, the working fluid permeates into the micropores of the wick 12 by the capillary force generated by the wick 12. Thereafter, the working fluid oozes out to the general outer periphery of the wick 12 through fine light, and is heated and evaporated by the heat of the CPU 9 transmitted by the heat receiving block 11. Since the latent heat is absorbed when the working fluid evaporates, the CPU 9 is cooled. Then, the working fluid that has become steam passes through the groove channel portion 12B and the gap 2A in order, and then flows out from the steam outlet 2B to the steam pipe 4.

  Although the groove channel portion 12B in the present embodiment is formed along the axial direction of the wick 12, other forms may be adopted as long as the working fluid can be guided to the gap 2A. For example, a spiral shape may be used. Moreover, you may form the flow path corresponding to the ditch | groove channel part 12B in the inner peripheral surface side of the container 7 instead of making it form in the outer peripheral surface side of the wick 12. FIG. In the present embodiment, the communication port 7B corresponds to an example of the outlet in the present case.

  Returning to FIG. 1, the condensing unit 3 will be described. The condensing part 3 has a structure in which a plurality of radiating fins 3A are soldered to the outer surface of the annular conduit CD. A blower fan (not shown) for blowing air toward the heat radiating fins 3A is provided in the vicinity of the heat radiating fins 3A. By the ventilation from the blower fan, the heat of the gas phase working fluid flowing through the condensing unit 3 is dissipated into the air. In this way, the gas-phase working fluid is cooled while passing through the condensing unit 3 to be condensed, and the heat of the CPU 9 absorbed as latent heat is released. Thereafter, the liquid-phase working fluid is introduced into the liquid reservoir 6 through the liquid return pipe 5, temporarily stored, and then supplied to the evaporator 2.

  Next, the detailed configuration of the valve mechanism 10 and the opening / closing operation thereof will be described. FIG. 5A is a view showing the valve mechanism 10 in a closed state. FIG. 5B is a diagram showing the valve mechanism 10 in a valve open state. 5A and 5B show a vertical cross section around the valve mechanism 10 in the liquid reservoir 6.

  The valve mechanism 10 is driven using the shape recovery force of the shape memory alloy that transforms at a predetermined temperature, and opens and closes the through hole 8A. The valve mechanism 10 includes a valve body 100 that blocks (shields) the through-hole 8A by being fitted to the through-hole 8A, and opens the through-hole 8A by being released from the fitting. The valve body 100 includes a valve portion 100A having a shape complementary to the through-hole 8A, and a flange-like flange portion 100B formed on one end surface of the valve portion 100A on the first storage region 6A side. In this example, the through hole 8A is a circular hole, the valve portion 100A is a cylindrical member having an outer diameter substantially equal to the inner diameter of the through hole 8A, and the flange portion 100B is larger in diameter than the valve portion 100A. It is a cylindrical member. For convenience, in the drawing, the outer diameter of the valve portion 100A is drawn smaller than the inner diameter of the through hole 8A.

  The valve mechanism 10 includes a bias spring 101 that biases the valve body 100 (valve portion 100A) from the first storage region 6A side to the second storage region 6B side, that is, in a valve closing direction with a predetermined elastic force. . One end of the bias spring 101 is attached to the other end surface of the valve portion 100A, and the other end of the bias spring 101 is attached to the inner peripheral surface of the container 7 facing the second storage region 6B.

Further, the valve mechanism 10 has a spring (hereinafter referred to as “SMA spring”) 102 made of shape memory alloy (SMA). Shape memory alloy (SMA) is an alloy that has the property that even if it is deformed at a temperature lower than its transformation point, it is restored to its original shape by its shape recovery force when heated to a temperature above that transformation point. Is generally called the shape memory effect (SME). In the valve mechanism 10 of the present embodiment, the SMA spring 102 is used as an actuator that is driven by a change in ambient temperature.

  The SMA spring 102 is disposed between the flange portion 100B and the partition wall 8 so as to surround the outer periphery of the valve portion 100A. The SMA spring 102 biases the valve body 100 (the flange portion 100B) from the second storage region 6B side toward the first storage region 6A side, that is, in the valve opening direction.

Here, the spring constant of the bias spring 101 (hereinafter referred to as “bias spring constant”) is represented by the symbol Kb. The spring constant is a proportional constant obtained by dividing the load when a load is applied to the spring by the elongation amount (deformation amount). The larger this value, the higher the elongation rigidity of the spring. By the way, the shape memory alloy has the shape memory effect (SME) described above, and the spring constant changes at the transformation point. here,
The spring constant of the SMA spring 102 when the temperature is lower than the transformation point (hereinafter referred to as “low temperature SMA spring constant”) is represented by the symbol Ksam, and the spring constant when the temperature is equal to or higher than the transformation point (hereinafter “high temperature”). (Referred to as “SMA spring constant”) is represented by the symbol Ksamh.

  The bias spring constant Kb is larger (higher) than the low temperature SMA spring constant Ksaml and smaller (lower) than the high temperature SMA spring constant Ksamh, that is, a relationship of Ksam <Kb <Ksamh is established. Is set to

  When the temperature of the SMA spring 102 (which can be regarded as a temperature substantially equal to the first storage region atmosphere temperature THch) is lower than the transformation point, the biasing force (hereinafter referred to as “bias biasing force”) by the bias spring 101 is generated. Therefore, the SMA spring 102 contracts due to the urging force of the SMA spring 102 (hereinafter referred to as “SMA urging force”). As a result, the valve body 100 (valve portion 100A) is fitted into the through hole 8A, and the through hole 8A is blocked by the valve body 100 (FIG. 5A).

A heat-resistant O-ring (sealing member) 103 is disposed on the end surface of the flange portion 100B facing the partition wall 8. The O-ring 103 is deformed by being pressed against each other between the partition wall 8 and the flange portion 100B (for example, deformed from O-shape to D-shape or 0-shape). Thereby, the contact surface pressure of the O-ring 103 increases, and the sealed space can be reliably sealed. Therefore, even if the working fluid stored in the second storage region 6B slightly leaks from the clearance between the valve portion 100A and the through-hole 8A in the closed state of the valve mechanism 10, the first storage region 6A And the airtightness of the 2nd storage area | region 6B is ensured by the O-ring 103, and the working fluid of the 2nd storage area | region 6B does not leak into the 1st storage area | region 6A.

  On the other hand, when the temperature of the SMA spring 102 becomes a temperature equal to or higher than the transformation point, the SMA spring 102 generates a shape restoring force for restoring (returning) to the stored shape. Here, the shape stored in the SMA spring 102 is a shape in which the length of the spring is longer than that in the state shown in FIG. 5A, as shown in FIG. 5B. More specifically, the shape is stored in the SMA spring 102 so that the distance between the partition wall 8 and the flange portion 100B is secured as much as necessary to release the fitting of the valve portion 100A to the through hole 8A. It was decided.

  Thereby, when the temperature of the SMA spring 102 becomes equal to or higher than the transformation point, the SMA biasing force is larger than the bias biasing force due to the shape recovery force of the SMA spring 102. Then, the SMA spring 102 extends to a length corresponding to the memorized shape against the bias urging force. As a result, the fitting of the valve body 100 (valve part 100A) to the through hole 8A is released (the valve part 100A comes out of the through hole 8A), and the through hole 8A is opened (FIG. 5B).

  As described above, the valve mechanism 10 is driven to open and close in conjunction with the first storage region atmospheric temperature THch. In this embodiment, the valve opening temperature THop when the valve mechanism 10 is opened is set. Further, when the first storage region atmosphere temperature THch is lower than the valve opening temperature THop, the valve mechanism 10 is closed (see FIG. 5A), and when the first storage region atmosphere temperature THch reaches the valve opening temperature THop or more. Thus, the transformation point of the SMA spring 102 is adjusted so that the valve mechanism 10 is opened (see FIG. 5B). For example, a shape memory alloy having physical properties in which the temperature near the opening / closing drive temperature THac becomes the transformation point may be used for the SMA spring 102.

  Next, setting of the valve opening temperature THop according to the present embodiment will be described. The valve opening temperature THop is set to be higher than the normal upper limit temperature THn and lower than the depletion lower limit temperature THs. The normal upper limit temperature THn is the upper limit temperature of the first storage region ambient temperature when heat input from the CPU 9 to the evaporation unit 2 is performed in a state where dryout does not occur in the first storage region 6A.

  The depletion-time lower limit temperature THs is a lower limit temperature of the first storage region atmospheric temperature when heat is input from the CPU 9 to the evaporation unit 2 in the dry storage state of the first storage region 6A. The normal upper limit temperature THn and the depletion lower limit temperature THs can be obtained in advance based on empirical rules such as experiments.

  Next, each operation state of the LHP 1 will be described with reference to FIGS. 6 and 7. (A) shows the state of the LHP 1 when the working fluid sealed in the annular conduit CD circulates with a phase change (hereinafter referred to as “normal operation”). (B) shows the state of LHP1 during a period in which heat reception in the evaporation unit 2 (that is, heat input to the evaporation unit 2) is stopped (this is referred to as a “heat reception stop period”). (C) shows a state after a predetermined time has elapsed after the CPU 9 starts operating from the state where the heat input to the evaporation unit 2 is stopped. (D) shows a state after a predetermined time has passed since the state of (C). Of the working fluid sealed in the annular conduit CD, a portion existing in the gas phase (steam) is indicated by white, and a portion existing in the liquid phase (water) is indicated by hatching.

  FIG. 7 is a diagram showing the relationship between the heat generation amount Qh of the CPU (there is a correlation with the amount of heat received by the evaporation unit 2) Qh and the first storage region atmosphere temperature THch. (A) to (D) in FIG. 7 correspond to the states in FIGS. 6 (A) to (D).

  FIG. 7A shows the relationship between the CPU heat generation amount Qh corresponding to the normal operation and the first storage region atmosphere temperature THch. Of course, even during normal operation, the CPU heat generation amount Qh is not always constant, and changes every moment depending on the load condition. For example, when the CPU 9 is operating (operating) with the maximum load, the CPU heat generation amount Qh becomes maximum, and the first storage region atmospheric temperature THch at that time coincides with the normal upper limit temperature THn. In this embodiment, since the valve opening temperature THop at which the valve mechanism 10 is opened is set higher than the normal upper limit temperature THn, the valve mechanism 10 is maintained in the closed state during the normal operation of the LHP1. The

  During normal operation, the working fluid sealed in the annular pipe CD is circulated while repeating the phase change as described above, so that heat is transported between the evaporation unit 2 and the condensation unit 3. Therefore, the CPU 9 can be continuously cooled.

  Further, for example, the amount of working fluid enclosed in the LHP 1 is adjusted so that the liquid level of the working fluid in the first storage region 6A of the liquid reservoir 6 is higher than the upper end of the partition wall 8 during normal operation. . During normal operation, the valve mechanism 10 is always kept closed. As described above, during normal operation, the liquid-phase working fluid is automatically guided to the second storage region 6B of the liquid reservoir 6, and can be stored in the second storage region 6B.

  Thereafter, when the power to the computer is turned off and the heat generation of the CPU 9 stops (see FIG. 7B), the LHP1 enters the heat receiving stop period (see FIG. 6B). In the heat receiving stop period, since the circulation of the working fluid in the annular pipe CD stops, a sufficient amount of working fluid is not recirculated to the first storage region 6A to the liquid reservoir 6, and due to the action of gravity, The working fluid present in the first storage region 6A and the hollow flow path portion 12A of the liquid reservoir 6 also falls out to the condensing unit 3 below. As a result, as shown in the drawing, the first storage region 6A and the hollow flow path portion 12A cause dryout.

  During the heat receiving stop period, the circulation of the working fluid stops as described above, and thus the CPU 9 is not cooled. However, since the CPU heat generation amount Qh is zero, the first storage region ambient temperature is increased due to heat dissipation to the surroundings. THch decreases with time. In this way, during the heat receiving stop period, the first storage region atmospheric temperature THch is lower than before the CPU 9 stops, and thus the valve mechanism 10 is still maintained in the closed state. Therefore, in the heat receiving stop period, the second storage region 6B is maintained in a state where the liquid-phase working fluid is stored, and the second storage region 6B is not depleted (see FIG. 6B).

  In FIG. 6B, the liquid level of the working fluid in the steam pipe 4 is higher than that in the liquid return pipe 5, and a part of the evaporation section 2 (in the example shown, the wick 12 in addition to the gap 2A). The working fluid remains in the fine holes or in a part of the recessed channel portion 12B). This is because the liquid-phase working fluid is sucked upward by the capillary force of the wick 12. However, whether or not the liquid levels of the steam pipe 4 and the liquid return pipe 5 are different during the heat receiving stop period is not an essential matter of the present case, and does not affect the technical scope at all.

As shown in FIG. 7C, when the operation of the CPU 9 is started, the evaporation unit 2 starts to be heated by the heat of the CPU 9 (see FIG. 6C). Here, when the evaporation unit 2 is completely depleted during the heat receiving stop period, there is no liquid-phase working fluid to be evaporated even if the evaporation unit 2 is heated, so that no vapor of the working fluid is generated. 6B and 6C, a liquid-phase working fluid is present in a part of the evaporation section 2 (the gap 2A, the minute hole of the wick 12, and the concave groove section 12B). In this case, the working fluid is evaporated by being heated.

  Since there is no liquid-phase working fluid in the hollow flow path portion 12A, a part of the vapor generated in the evaporation section 2 passes through the hollow flow path portion 12A through the fine holes of the wick 12 and from the communication port 7B to the liquid storage section 6. May flow back to the side. Such a vapor reverse flow phenomenon is one of the factors that tend to hinder the formation of a working fluid circulation during startup. Further, at the time of start-up, since the first storage area 6A of the liquid reservoir 6 is depleted, no new liquid-phase working fluid is subsequently supplied to the evaporator 2. For this reason, the liquid phase working fluid remaining in the evaporating section 2 evaporates, so that even if some steam is generated, the absolute amount becomes insufficient, and the circulation of the working fluid is formed in the annular conduit CD. I can't.

  As described above, when the CPU 9 starts the operation, if the dryout occurs in the first storage region 6A of the liquid reservoir 6, the working fluid does not circulate in the annular conduit CD. That is, the LHP 1 is not activated and heat transport between the evaporation unit 2 and the condensation unit 3 is not performed. As a result, the inside of the evaporation unit 2 becomes high temperature with heat input to the CPU 6, and the heat is transmitted to the liquid storage unit 6, thereby increasing the first storage region ambient temperature THch ((C) in FIG. 7). reference).

  If the CPU 9 is maintained in the operating state, the first storage region atmosphere temperature THch increases with time, and finally reaches, for example, the depletion lower limit temperature THs. On the other hand, the valve opening temperature THop is set to a temperature lower than the exhaustion lower limit temperature THs. Therefore, actually, the valve mechanism 10 is opened when the first storage region atmospheric temperature THch reaches the valve opening temperature THop before the exhaustion lower limit temperature THs is reached (FIG. 6D and FIG. 7 (D)).

  As a result, the through-hole 8A of the partition wall 8 is opened, and the liquid-phase working fluid stored in the second storage region 6B of the liquid reservoir 6 is released and introduced into the first storage region 6A. The liquid-phase working fluid is supplied to the evaporation unit 2 through the communication port 7B and then evaporated by being heated.

  At the time when the liquid-phase working fluid stored in the second storage region 6B evaporates in the evaporation section 2, the hollow flow path portion 12A is also filled with the liquid-phase working fluid. Absent. That is, the steam generated in the evaporation section 2 flows out to the steam pipe 4 through the steam outlet 2B, and pushes down the liquid-phase working fluid in the steam pipe 4 downward (condensing section 3 side). Along with this, the liquid-phase working fluid in the liquid return pipe 5 is pushed upward (toward the liquid reservoir 6 side), so that the liquid-phase working fluid accumulated in the liquid return pipe 5 is retained in the liquid reservoir 6. It is introduced into the first storage area 6A.

  The liquid-phase working fluid introduced into the first storage region 6A is supplied to the evaporation unit 2, becomes vapor in the evaporation unit 2, and thereafter circulates in the circulation line CD with phase change. As a result, the LHP 1 is activated, heat transport between the evaporation unit 2 and the condensation unit 3 is started, and the temperature of the first storage region 6A gradually decreases. Then, when the first storage region atmosphere temperature THch becomes lower than the valve opening temperature THop, the valve mechanism 10 is closed again. Then, from the time when the liquid level of the first storage area 6A becomes higher than the upper end of the partition wall 8, the liquid-phase working fluid is also guided to the second storage area 6B, and the liquid is supplied to the second storage area 6B. Storage is started (see FIG. 6A).

  As described above, the LHP 1 according to the present embodiment can reliably start the circulation of the working fluid at the time of start-up. That is, when the operation of the CPU 9 in the stopped state is started, the LHP 1 can be activated quickly and stably even under the top heat condition, and the cooling of the CPU 9 can be started.

Further, according to the valve mechanism 10 according to the present embodiment, the opening / closing drive is automatically performed according to a change in the ambient temperature by using the shape recovery force of the shape memory alloy without applying power from the outside. Can do. Therefore, it is possible to enjoy the advantages of a heat pipe that automatically operates together with heat input to the evaporation section 2 to perform heat transport, which is advantageous from the viewpoint of energy saving and reduction of running costs. Further, since there is no resistance in the annular line CD that prevents the normal flow of the working fluid, the heat transport capability of the LHP 1 does not decrease during normal operation. Therefore, even when LHP1 is used in a top heat state, it has excellent heat transport capacity during normal operation, and automatically circulates the working fluid at startup even when external power is not applied. The CPU 9 can be smoothly cooled.

  Further, since the valve mechanism 10 is closed during normal operation by setting the valve opening temperature THop higher than the normal upper limit temperature THn, the liquid-phase working fluid is automatically stored in the second storage region 6B. Can do. Then, by setting the valve opening temperature THop lower than the depletion lower limit temperature THs, the valve mechanism 10 is automatically opened at start-up, and the working fluid stored in the second storage region 6B is evaporated. Can be supplied to.

  Here, if the valve opening temperature THop is set to a value that is excessively close to one of the normal upper limit temperature THn and the exhaustion lower limit temperature THs, malfunction of the valve mechanism 10 is likely to occur. The malfunction here means that the valve mechanism 10 is opened during normal operation, or the valve mechanism 10 is not opened during start-up and is maintained in a closed state. Therefore, the valve opening temperature THop may be set to a temperature that is a predetermined margin temperature X, Y away from the normal upper limit temperature THn and the exhaustion lower limit temperature THs ((THn + X) ≦ THop ≦ (THs−Y)). For example, the valve opening temperature THop can be set as a temperature in the vicinity of an intermediate value between the normal upper limit temperature THn and the exhaustion lower limit temperature THs. In the present embodiment, the valve opening temperature THop can be cited as an example of the specified temperature.

<Modification>
The valve mechanism 10 according to the present embodiment is driven to open and close by utilizing the shape recovery force of the shape memory alloy that transforms at the transformation point. However, the valve mechanism 10 penetrates the partition wall 8 in conjunction with the first storage region atmospheric temperature THch. If it can open and close the hole 8A, it will not be restricted to this. For example, the valve mechanism 10 may be driven to open and close using a bimetallic shape deformation force. Bimetal is a laminate of two metal materials having different coefficients of thermal expansion.

  As a modification of the valve mechanism 10, a bimetal spring (hereinafter referred to as “bimetal spring”) is disposed instead of the SMA spring 102. The material, dimensions, and shape used for the bimetal spring are such that, during normal operation (when the first storage region atmosphere temperature THch is low), the valve body 100 contracts until it is fitted into the through hole 8A. It is good to adjust etc. Further, at start-up (when the first storage region atmospheric temperature THch is high), the spring is extended due to the difference in thermal expansion coefficient between the two metal materials, and the fitting of the valve body 100 to the through hole 8A is released. The material, dimensions, shape, etc. used for the bimetal spring may be adjusted so that the through hole 8A is opened.

  As a further modification of the valve mechanism 10, a bimetallic leaf spring may be employed as a valve body that opens and closes the through hole 8A in conjunction with the first storage region ambient temperature THch. For example, a bimetallic leaf spring is arranged so as to cover the through hole 8A from the first storage region 6A side. In this case, it is preferable that the coefficient of thermal expansion of the metal disposed on the inner side (the metal on the side facing the partition wall 8) is larger than the coefficient of thermal expansion of the metal disposed on the outer side. When the first storage region atmospheric temperature THch is maintained at a relatively low temperature during normal operation, the leaf spring blocks the through-hole 8A, so that the liquid-phase working fluid can be stored in the second storage region 6B. . In addition, when the first storage region atmospheric temperature THch becomes high during startup, the through hole 8A is opened due to warping of the leaf spring due to the difference in thermal expansion coefficient between the two metal materials, so that the second storage region 6B The stored liquid-phase working fluid can be supplied to the evaporation unit 2.

  FIG. 8 is a view for explaining a modification of the partition wall provided in the liquid reservoir 6 according to the first embodiment. 9 is a cross-sectional view taken along the line CC in FIG. The partition wall 80 according to this modification is provided in a cylindrical shape along the edge of the communication port 7B. In this configuration, the inner region (the region to which the communication port 7B belongs) of the partition wall (hereinafter referred to as “tubular partition wall”) 80 corresponds to the first storage region 6A, and the outer region of the cylindrical partition wall 80 is the first region. 2 corresponds to the storage area 6B. In addition, the point that the through hole 8A is formed at a position near the lower end in the height direction of the cylindrical partition wall 80, and the point that the valve mechanism 10 for opening and closing the through hole 8A is provided are according to the first embodiment. Common with the partition wall 8. In the example of FIG. 8, the edges of the cylindrical partition wall 80 and the communication port 7B coincide with each other. However, the present invention is not limited to this. For example, the cylindrical partition wall 80 is formed so as to have a larger diameter than the through hole 8A. It may be arranged.

  In addition, in the partition wall 10 according to the first embodiment, the upper end of the partition wall 6 is configured to introduce a liquid-phase working fluid from the first storage region 6A of the liquid reservoir 6 into the second storage region 6B during normal operation. Although it is installed to be lower than the ceiling surface, other forms can be adopted if the above functions can be exhibited. That is, like the cylindrical partition wall 80 ′ shown in FIG. 10, the upper end may be extended so as to reach the ceiling surface of the liquid reservoir 6. The second through hole 80'A may be opened at a position above the through hole 8A in the height direction of the cylindrical partition wall 80 '. The second through-hole 80'A is provided for introducing a liquid-phase working fluid from the first storage region 6A to the second storage region 6B during normal operation. A plurality of second through-holes 80'A may be provided so that the working fluid is more smoothly introduced into the second storage region 6B.

<Example 2>
Example 2 will be described. The second embodiment is different from the first embodiment in the configuration of the liquid reservoir. FIG. 11 is an explanatory diagram for explaining the liquid reservoir according to the second embodiment. 12 is a cross-sectional view taken along the line DD in FIG. In the liquid reservoir 60 according to the present embodiment, the second storage region 6B is covered with a heat insulating material. Specifically, each surface of the partition wall 8 facing the second storage region 6B, the partition wall 7A, and the inner peripheral surface of the container 7 is covered with the heat insulating material AD. The broken lines shown in FIG. 11 represent the coverage in the vertical direction of the heat insulating material AD provided on the inner peripheral surfaces of the partition wall 8 and the container 7. The grid-shaped hatching shown in FIG. 12 represents the horizontal coverage of the heat insulating material AD provided on the partition wall 7A.

  In this way, by covering the second storage region 6B with the heat insulating material, from the first storage region 6A in the evaporation unit 2 and the liquid storage unit 60 to the liquid-phase working fluid stored in the second storage region 6B. Heat transfer is suppressed. As a result, evaporation of the working fluid stored in the second storage region 6B can be more reliably suppressed during normal operation or during a heat receiving stop period. Therefore, at the time of start-up in the top heat state, the liquid-phase working fluid can be supplied more reliably from the second storage region 6B to the evaporation unit 2.

<Application examples to electronic devices>
As described above, the embodiment of the LHP 1 according to the present embodiment has been described with reference to the first and second embodiments. However, the LHP 1 of the present embodiment can be applied (mounted) to various electronic devices. FIG. 13 is a diagram schematically showing an electronic device on which the LHP 1 is mounted. The electronic device shown in this figure is a so-called desktop personal computer (hereinafter referred to as “desktop PC”). In addition, the code | symbol attached | subjected in the figure respond | corresponds to each member demonstrated in the above-mentioned Example. Moreover, the relative magnitude relationship between the members is different from the actual one.

The desktop PC shown in FIG. 13 is generally called a so-called vertical type (tower type). For example, the direction of gravity when placed on a desk is indicated by an arrow. Reference numeral 15 represents a housing of a desktop PC on which the LHP 1 is mounted. In FIG. 13, only a part of the internal structure housed in the housing 15 is illustrated, and for example, illustration of a hard disk drive, a DVD drive, and the like is omitted. Inside the casing 15, a printed circuit board 16 is accommodated along the longitudinal sectional direction of the casing 15, and the CPU 9 is mounted on the printed circuit board 16. The LHP 1 is mounted on the printed circuit board 16 in order to cool the CPU 9 via the heat receiving block 11.

  In this application example, LHP1 is used in a top heat state. Therefore, when the desktop PC in the power-off state is turned on, the operation of the CPU 9 may be started from the state where the liquid reservoir 6 is dried out. According to the LHP 1 according to the present embodiment, even when starting up under such top heat conditions, the LHP 1 can be started stably and promptly, and cooling of the CPU 9 can be started.

  Next, application of LHP1 to a notebook personal computer (sometimes referred to as a laptop personal computer, hereinafter abbreviated as “notebook PC”) will be described. In a notebook PC, a main unit that accommodates a printed circuit board, a CPU, and the like and a display unit having a display are hingedly connected to each other. For example, a printed circuit board is disposed inside the main unit, and a CPU is mounted on the printed circuit board.

  When a loop heat pipe is mounted on a notebook PC, a layout is often employed in which an evaporation unit is disposed immediately above a CPU mounted on a printed circuit board. In a so-called space-saving electronic device such as a notebook PC, it is required to make the main unit as thin as possible. For this reason, the loop heat pipe may be used in a top heat state even in a notebook PC due to restrictions on the mounting space. Therefore, it is preferable to apply the LHP 1 according to the present embodiment to a notebook PC in order to stably start the CPU cooling when the notebook PC is activated.

  Furthermore, the LHP 1 according to the present embodiment is excellent in heat transport capability during normal operation, and can automatically start the circulation of the working fluid at start-up even when external power is not applied. Therefore, in an electronic device equipped with this LHP1, it is possible to obtain excellent CPU cooling efficiency while reducing energy consumption. In addition, LHP1 which concerns on this embodiment can be mounted in another electronic device in the range which does not deviate from this point.

1 Loop heat pipe (LHP)
DESCRIPTION OF SYMBOLS 2 Evaporating part 3 Condensing part 4 Steam pipe 5 Liquid return pipe 6 Liquid storage part 6A 1st storage area 6B 2nd storage area 7 Container 7A Partition wall 7B Communication port 8 Partition 8A Through-hole 9 CPU (heating element)
DESCRIPTION OF SYMBOLS 10 Valve mechanism 11 Heat receiving block 12 Wick 12A Hollow flow path part 12B Groove flow path part 100 Valve body 101 Bias spring 102 SMA spring

Claims (5)

An evaporation section that evaporates the liquid-phase working fluid by receiving heat from the outside, and a condensing section that is disposed at a position lower than the evaporation section and condenses the gas-phase working fluid by heat dissipation are formed by a steam pipe and a liquid return pipe. A loop heat pipe communicated to form an annular flow path,
A liquid reservoir that is provided at a position higher than the evaporation section, and stores a liquid-phase working fluid supplied to the evaporation section via the liquid return pipe;
A partition that separates the liquid reservoir into a first storage area that includes an outlet for the working fluid flowing out of the liquid reservoir and a second storage area that does not include the outlet;
An opening opening in the partition;
A valve mechanism that opens and closes the opening in conjunction with the temperature of the first storage region;
With
During normal operation in which the working fluid circulates through the annular flow path, the working fluid is stored in the second storage region by the valve mechanism blocking the opening,
When the temperature of the first storage region reaches a specified temperature during start-up to start the circulation of the working fluid, the second storage region stored during normal operation is opened by the valve mechanism opening the opening. The loop type heat pipe is characterized in that the working fluid is discharged into the first storage region.   The loop heat pipe according to claim 1, wherein the valve mechanism is driven to open and close by using a shape recovery force of a shape memory alloy.   The loop heat pipe according to claim 1, wherein the valve mechanism is driven to open and close by using a bimetallic shape deformation force.   The loop heat pipe according to any one of claims 1 to 3, wherein the second storage region in the liquid reservoir is covered with a heat insulating material.   The electronic device provided with the loop type heat pipe of any one of Claims 1-4.

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