JP4773260B2 - COOLING DEVICE AND ELECTRONIC DEVICE USING THE SAME - Google Patents

Description

  The present invention relates to a cooling device for a high heating element mounted on an electronic device, and provides a small and efficient cooling device and an electronic device using the same, utilizing the phase change of vaporization / condensation of a refrigerant. is there.

  Recent electronic devices include a semiconductor integrated circuit represented by a CPU. This semiconductor integrated circuit is rapidly becoming highly integrated in order to cope with an increase in processing speed, and the amount of heat generated therewith is also increasing. However, a semiconductor integrated circuit not only fails to exhibit the performance possessed by the semiconductor when the temperature exceeds a predetermined temperature, but also breaks down. In other words, it is an indispensable requirement to cool the heat generated in a semiconductor integrated circuit or the like in an electronic device.

  For cooling a semiconductor integrated circuit or the like in a conventional electronic device, for example, an air cooling method is generally performed in which a heat sink is fixed to a semiconductor integrated circuit that is a heating element, and cooling is performed by ventilation with a fan. However, according to this air cooling method, it is necessary to install a large fan in order to cope with the high heat generation of electronic devices. However, as electronic devices are mounted with higher density, the peripheral space where semiconductor integrated circuits are mounted is increased. Due to the downsizing, it is difficult to mount a large fan that can cool a high heating element. Therefore, although cooling is performed with a small fan that can be mounted, in this case, since the fan is rotated at a high speed in order to increase the air volume, there is a problem that noise accompanying the high-speed rotation of the fan increases.

  In order to solve the problem of noise in the air cooling system, in recent years, a water cooling system using a liquid refrigerant has attracted attention as a new cooling system. For example, Patent Document 1 discloses an example of a water-cooling type cooling device mounted on a thin electronic device such as a notebook PC. In this cooling device, the heat of the heat generating portion is received by the refrigerant liquid by the heat receiving header. The received refrigerant liquid is transferred through a flow path connected by a pipe, and is radiated from the refrigerant liquid by a heat radiation header installed on a wall of a housing such as the back surface of the display device and connected to the pipe. In this configuration, the radiated refrigerant liquid is circulated to the heat receiving header by a pump. In the water-cooling method, the refrigerant liquid is circulated between the heat receiving part and the heat radiating part connected by flexible piping, etc., and is cooled by heat transfer, so the arrangement relationship between the heat receiving part and the heat radiating part can be set relatively freely. In addition, there are relatively few restrictions on the shape and size of the heat radiating part, and it is easy to improve the cooling performance. Further, the fan can be downsized by devising the cooling structure of the heat radiating section, and noise during cooling can be reduced.

  Furthermore, as a cooling method having a cooling capacity superior to that of a water cooling method by heat transfer, there is a method using latent heat due to phase change (vaporization and condensation) of refrigerant (hereinafter, latent heat method). Discloses a cooling device using the same. This cooling device receives heat generated by a semiconductor element or the like by a cooling plate, vaporizes the refrigerant in a flow path in the cooling plate, and cools the heating element by the heat of vaporization. The refrigerant that has undergone volume expansion by vaporization is transferred to the condenser by piping, condensed (liquefied), and dissipated. The liquefied refrigerant is configured to be transferred to the cooling plate by piping through a pump. In Patent Document 2, the pipe diameter from the cooling plate to the condenser portion is increased to mitigate pressure loss in the pipe. In Patent Document 3, two refrigerant pumps are provided so that even if one of the pumps fails, the other pump can continue to transfer the refrigerant.

JP-A-7-142886 JP 2005-5366 A Japanese Patent Laid-Open No. 2005-19907

The conventional cooling method described above has the following technical problems.
The amount of heat generated by the heating element mounted on the electronic device is still increasing. In order to improve the cooling performance of the water cooling method by heat transfer described in Patent Document 1, the casing in which the flow rate of the refrigerant liquid is increased to increase the amount of heat received by the refrigerant and the heat radiating unit is installed. It is necessary to increase the heat radiation amount by configuring the wall surface with a large area metal material having good heat dissipation. Alternatively, it is necessary to configure the heat radiating header as a large radiator and to promote ventilation to the heat radiating header by adding a fan. However, these measures increase the size and complexity of component parts compared to the air-cooling method and increase the cost, and are an obstacle to reducing the size and weight of portable electronic devices.

  Further, in a normal water cooling system, it is assumed that the phase state of the refrigerant after receiving heat at the heat receiving portion is not a complete liquid state but transferred as a two-phase flow of gas-liquid mixing (the ratio of gas-liquid mixing is Depending on the amount of heat of the heating element). In this case, when it is configured with piping having poor airtightness such as a flexible tube, the vaporized refrigerant may leak to the outside. In order to prevent this, in the water cooling system, a large-capacity pump is mounted to circulate a large amount of refrigerant liquid so as to suppress vaporization of the refrigerant in the heat receiving part. This also hinders downsizing and weight reduction of electronic devices.

  On the other hand, the latent heat method using the phase change of the refrigerant described in Patent Documents 2 and 3 can be expected to have a large amount of heat absorption by the heat of vaporization, and is effective for cooling a high-temperature heating element. For this purpose, the flowing refrigerant must be completely vaporized. However, due to volume expansion and pressure increase due to vaporization of the refrigerant, the constituent members of the circulation flow path are required to have sufficient mechanical strength and airtightness against refrigerant leakage. For example, measures as described in Patent Documents 2 and 3 Cost. As a result, it is difficult to simplify the structure of the cooling device.

  Further, in the latent heat system by vaporization of the refrigerant, the cooling temperature obtained by vaporization has a limit at the boiling point temperature. Therefore, when obtaining a general semiconductor cooling specification temperature of 60 ° C. to 70 ° C., a refrigerant liquid having a low boiling point is selected instead of pure water, or the pressure in the circulation channel is used to lower the boiling point. It is necessary to take measures such as reducing the pressure below atmospheric pressure to promote vaporization. Even when the flow path is decompressed, a structure that maintains airtightness is required.

  Here, in order to completely evaporate the refrigerant and improve the cooling efficiency in the latent heat method, various devices are required. This is because the phase state of the refrigerant received from the heating element is determined by the heat transfer state depending on the heat generation temperature of the heating element, the evaporation temperature of the refrigerant, the flow rate of the refrigerant, and the like. That is, the flowing refrigerant receives heat from the contact surface portion with the heat receiving portion, receives heat, and conducts heat to the central portion of the refrigerant, so that it is separated from the contact surface portion with the heat receiving portion of the flowing refrigerant. The amount of heat received is different from the central part. In addition, since heat transfer varies depending on the flow rate of the refrigerant, the amount of vaporization of the refrigerant depends on the flow rate.

  Therefore, even in the latent heat system, the flowing refrigerant may not be sufficiently vaporized depending on the temperature rise condition of the heating element and the heat receiving condition of the refrigerant, and the refrigerant is transferred in a gas-liquid mixed state or liquid state and circulated. It is necessary to configure the cooling device in consideration of the above. As a countermeasure, a condenser that condenses and liquefies the vaporized refrigerant is configured as a heat radiating unit having a water cooling type heat radiating function. However, in this case, the cooling performance is lowered. Therefore, in the latent heat type cooling device, it is important to set the cooling conditions in consideration of the cooling conditions such as the flow rate of the refrigerant so that the refrigerant is completely vaporized.

  On the other hand, in a situation where the temperature of the heating element is severely increased, vaporization of the refrigerant is activated, and a structure that absorbs volume expansion and pressure increase inside the circulation channel is required. If this is not sufficient, the vaporized refrigerant flows into the pump and the pump cannot circulate the refrigerant normally. As a result, a new refrigerant is not supplied in the heat receiving section, causing a problem that the temperature of the heating element rises. As a countermeasure against this, Japanese Patent Laid-Open No. 2004-228561 addresses this problem by providing redundancy such as mounting two pumps, but this is not a fundamental solution. In order to cope with these problems, in a cooling device using latent heat, it is considered to be a practical method such as bundling a plurality of heat pipes.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the conventional cooling method, and an object of the present invention is to provide a small cooling device that can efficiently perform cooling even in an electronic device that generates a large amount of heat, and an electronic device using the same. And

  In the present invention, when cooling a high heating element mounted on an electronic device, a cooling device with good cooling efficiency and an electronic device using the same are realized by using both a latent heat cooling method and a water cooling method.

  The cooling device of the present invention includes a heat receiving portion that receives heat generated by a heating element to be cooled by a refrigerant, a heat radiating portion that radiates heat received by the refrigerant to the outside, and a refrigerant between the heat receiving portion and the heat radiating portion. A pipe for circulating the refrigerant, a tank for storing the refrigerant, a pump for driving the refrigerant, and a control unit for controlling the flow rate of the refrigerant driven by the pump. The heat receiving part can be in two cooling modes, a latent heat cooling mode that uses the heat of vaporization when the refrigerant is vaporized, and a water cooling mode in which the refrigerant transfers heat in a liquid state, and the heat radiating part is a heat receiving part. It has a heat radiating function for condensing and liquefying the vaporized refrigerant, and a heat radiating function for radiating heat from the liquid refrigerant received by the heat receiving part. The said control part sets it as the structure which switches the cooling mode in a heat receiving part by controlling the flow volume of the refrigerant | coolant which a pump drives.

  At that time, the control unit switches the cooling mode to the latent heat cooling mode by reducing the flow rate of the refrigerant driven by the pump, and switches to the water cooling cooling mode by increasing the flow rate of the refrigerant.

  Furthermore, in the present invention, among the pipes, the circulation flow path from the heat receiving portion to the heat radiating portion is at least a metal pipe having high sealing performance. The tank has a volume larger than the refrigerant flow volume of the circulation channel from the heat receiving unit to the heat dissipation unit, stores an air layer together with the refrigerant, and increases the pressure in the circulation channel due to the vaporization of the refrigerant by the air layer. A structure that relaxes.

  Further, in the present invention, the pump has two pumps, the first pump drives a refrigerant having a flow rate for operating in the latent heat cooling mode in the heat receiving portion, and the second pump is in the heat receiving portion. A refrigerant having a flow rate for operating in the water cooling mode is driven. The control unit drives either one of the first pump and the second pump, or drives both at the same time.

  The electronic device according to the present invention includes a heat receiving unit that receives heat generated by a built-in heating element by a refrigerant, a heat radiating unit that radiates heat received by the refrigerant to the outside, and the refrigerant between the heat receiving unit and the heat radiating unit. A pipe for circulating the refrigerant, a tank for storing the refrigerant, a pump for driving the refrigerant, a control unit for controlling the flow rate of the refrigerant driven by the pump, and a temperature for detecting the temperature of the heating element or the temperature of the refrigerant in the heat receiving unit A detector. The heat receiving part can be in two cooling modes, a latent heat cooling mode that uses the heat of vaporization when the refrigerant is vaporized, and a water cooling mode in which the refrigerant transfers heat in a liquid state, and the heat radiating part is a heat receiving part. It has a heat radiating function for condensing and liquefying the vaporized refrigerant, and a heat radiating function for radiating heat from the liquid refrigerant received by the heat receiving part. The said control part switches the cooling mode in a heat receiving part by controlling the flow volume of the refrigerant | coolant which a pump drives based on the temperature which the said temperature detection part detected.

  ADVANTAGE OF THE INVENTION According to this invention, even if the emitted-heat amount of an electronic device increases, the small cooling device which can cool this efficiently can be provided, and it contributes to size reduction of an electronic device.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a conceptual block diagram showing an embodiment of an electronic device equipped with a cooling device of the present invention. The electronic device 10 includes a circuit board 9 and a heating element (heating unit) 1 thereof, which are to be cooled. The cooling device has the following configuration. The heat receiving unit 2 is thermally connected to the heating element 1 and absorbs and receives heat by the refrigerant flowing through the heat receiving unit 2. It is assumed that pure water (that is, boiling point 100 ° C.) is used as the refrigerant in this embodiment, and the temperature of the heating element 1 is cooled from 130 ° C. to 70 ° C., for example. The heat radiating section 3 radiates the heat absorbed by the refrigerant through the heat radiating pipe, and at that time, the air is blown by a fan to promote the heat radiation. The tank 4 stores the refrigerant and air, and the volume thereof is larger than the refrigerant flow volume of the circulation flow path from the heat receiving part 2 toward the heat radiating part 3. The pump 5 drives the refrigerant in the tank 4 to circulate to the heat receiving unit 2. The pipe 6 is connected so that the refrigerant circulates between the members. Among them, the pipe 61 is a circulation flow path from the heat receiving part 2 to the heat radiating part 3 and is constituted by a metal pipe having high airtightness. The pipe 62 is a circulation channel from the heat radiating unit 3 toward the heat receiving unit 2. The temperature detection unit 7 detects the temperature of the refrigerant in the heating element 1 or the heat receiving unit 2, and the control unit 8 controls the flow rate of the refrigerant driven by the pump 5 based on the temperature detected by the temperature detection unit 7.

  Here, the electronic device 10 is not limited to a specific device, and the heating element 1 to be cooled is not limited to a specific circuit board 9. Needless to say, the refrigerant is not limited to pure water and can be changed as appropriate.

  The cooling device of the present embodiment transfers the refrigerant in the closed circulation channel, and absorbs the heat generated in the heating element 1 by the refrigerant flowing through the heat receiving unit 2. When absorbing heat from the heating element 1, it is possible to transfer heat in a liquid state or to change the phase of the refrigerant from a liquid to a gas and absorb the heat as vaporization heat. It is characterized by an increase. That is, in the heat receiving unit 2, a water cooling cooling mode (water cooling method, water cooling mode) that absorbs heat when the refrigerant rises in a liquid state and a latent heat cooling mode (latent heat method, latent heat) that absorbs heat when the refrigerant evaporates. Two cooling modes are possible. Similarly, in the heat radiating unit 3, there are two modes: a mode for radiating a high-temperature liquid refrigerant and a mode for condensing and liquefying the vaporized refrigerant. These modes are switched between the water cooling mode and the latent heat mode by controlling the flow rate of the refrigerant supplied from the pump 5 to the heat receiving unit 2. Specifically, the cooling mode is switched to the latent heat mode by decreasing the refrigerant flow rate, and the water cooling mode is switched by increasing the refrigerant flow rate. Furthermore, by controlling the flow rate of the refrigerant according to the temperature of the heating element 1 (or refrigerant) detected by the temperature detector 7, an efficient cooling mode is selected according to the temperature.

  That is, the cooling method of the present embodiment is not fixed to only one of the conventional water cooling method and the latent heat method, but is desired by switching both methods in accordance with the temperature condition of the heating element in the same device. The cooling specification temperature is achieved. At that time, normal refrigerant (pure water) can be used in a state close to normal pressure without lowering the pressure in the closed circulation channel or using a special refrigerant with a low boiling point temperature. It realizes a good cooling device.

  Hereinafter, the operation of the cooling device of the present embodiment will be described in detail.

  FIG. 2 is a diagram showing a relationship (endothermic characteristic) between the flow rate of the refrigerant flowing in the heat receiving unit 2 and the endothermic amount. The two cooling modes in the heat receiving unit 2 are compared. The curve (A) indicates the heat absorption amount due to the vaporization of the refrigerant (latent heat mode), and the curve (B) indicates the heat absorption amount due to the heat transfer to the refrigerant (water cooling mode). Is conceptually shown. In both cases, the endothermic amount W by the refrigerant is proportional to the refrigerant flow rate Q, but the latent heat mode curve (A) has a steeper slope than the water-cooled mode curve (B), and the endothermic amount per flow rate is large. This difference in gradient is based on the difference between the physical properties of the specific heat and the heat of vaporization of the refrigerant (however, the gradients of the two curves shown in the figure do not have a quantitative meaning).

Theoretically, if the density of the refrigerant is ρ, the specific heat is C, the heat of vaporization is V, the temperature change at the time of receiving heat in the refrigerant is ΔT, and the flow rate of the refrigerant to be received is Q, the endothermic amount W in the heat receiving unit 2 is It is shown in the following formula.
W (latent heat mode) = ρ · V · Q (1)
W (water cooling mode) = ρ · C · ΔT · Q (2)
First, the cooling operation of the water cooling method and its problems will be described.
When the temperature T1 of the heating element 1 is cooled to the desired specification cooling temperature T2, the amount of heat to be absorbed is W1. W1 is proportional to the temperature difference (T1-T2). According to the curve (b), the flow rate Q1 of the refrigerant from which the endothermic amount W1 is obtained can be obtained and passed through this to cool the heating element 1 (the operating point is indicated by symbol A). Here, when the heating element is a high heating element 1 ′ that generates heat at a temperature T1 ′ higher than T1, in order to cool the heating element to the specified cooling temperature T2, the amount of heat to be absorbed increases to W1 ′. W1 ′ is proportional to the temperature difference (T1′−T2). In this case, the flow rate of the refrigerant must be increased to Q2 according to the curve (b) (the operating point is indicated by A ′). For this purpose, it is necessary to increase the capacity of the pump that drives the refrigerant, which increases the size of the cooling device.

  Furthermore, since the water cooling method is based on heat transfer that dissipates the heat once received by the refrigerant according to the outside air temperature, the amount of heat that can be transferred depends on the boiling temperature of the refrigerant liquid (100 ° C for pure water) and the outside air temperature for heat dissipation ( For example, 20 ° C.). In other words, since the temperature rise ΔT at the time of heat reception of the refrigerant naturally has a limit (ΔT decreases), even if the flow rate Q is increased, the saturated cooling state in which heat cannot be absorbed in proportion to this (the operating point is indicated by Asat) ) Exists. This means that there is a limit value (lower limit value) for the specification cooling temperature T2 in cooling the heating element mounted on the electronic device.

  On the other hand, the latent heat method uses heat of vaporization and has excellent endothermic characteristics as shown by curve (A). However, since the coolable temperature is restricted by the boiling point of the refrigerant, the cooling temperature cannot be freely changed. In addition, as described later, it is difficult to completely vaporize a large amount of refrigerant, and volume expansion and pressure increase are accompanied by vaporization of the refrigerant. . Therefore, it is difficult to reduce the size of the apparatus by the cooling method using only the latent heat method.

  On the other hand, the cooling operation using the latent heat method and the water cooling method in the present embodiment will be described. In the combined system of the present embodiment, the latent heat that is absorbed by the heat of vaporization is generated by evaporating the flow rate Q3 of a part of the refrigerant by increasing the heat generation amount of the high heating element 1 ′ (temperature T1 ′) while setting the maximum flow rate of the refrigerant to Q1. Use the method. Then, the endothermic characteristic shifts to the curve (A), and the endothermic amount increases up to the B point. Then, the remaining endotherm is absorbed from point B to point C by increasing the flow rate to Q1 in accordance with the endothermic characteristics of the curve (b), which is a water cooling system. As a result, the desired endothermic amount W1 'can be efficiently achieved as a total. In this case, if the heat absorption amount by the latent heat method is less than the point B, the necessary heat absorption amount W1 'cannot be obtained only by the refrigerant flow rate Q1, and it cannot be cooled to the specified cooling temperature T2. Therefore, it is important to accurately distribute the amount of heat absorbed by the latent heat method and the amount of heat absorbed by the water cooling method. In this example, the distribution of both is optimized by controlling the flow rate of the refrigerant, and efficient cooling is achieved. It realizes the characteristics.

  In the combined cooling system of this embodiment, the flow of the vaporized refrigerant and the liquid refrigerant (after receiving heat) is constituted by one cooling device, and control is performed to intentionally switch between the latent heat system and the water cooling system depending on the refrigerant flow rate. . The capacity (flow capacity) of the pump 5 that drives the refrigerant can be reduced in capacity and size by using both methods. In other words, even if the capacity of the pump 5 is constant, a larger cooling performance can be obtained. Further, even if the heat generation amount of the heating element fluctuates, it can be dealt with by controlling the flow distribution of the latent heat method while keeping the maximum flow rate of the pump 5 constant.

  Here, even in the conventional cooling device, the refrigerant may be driven in a gas-liquid mixed state, but it will be described that it is basically different from the operation of the present embodiment. For example, when a part of the refrigerant is vaporized due to the heat generated by the heating element while being a water-cooled apparatus, or conversely, while being a latent heat apparatus, a part of the refrigerant remains liquid without being vaporized. May be driven. These are used in a gas-liquid mixed state as a phenomenon, but none of them are intended and undesirable. This is because when the refrigerant is transported in a gas-liquid mixed state, problems such as inability to drive the pump due to mixed gas and refrigerant leakage from the circulation channel occur in the water cooling system. On the other hand, in the latent heat system, there arises a problem that the cooling capacity is lowered due to the back flow of the liquid or the insufficient amount of vaporization. Therefore, in order to maintain the normal cooling operation and prevent the cooling capacity from being lowered, a contrivance is required to eliminate the occurrence of the gas-liquid mixed state of the refrigerant as much as possible in each method.

  In contrast, in this embodiment, since both the latent heat method and the water cooling method are used, the refrigerant can be circulated and driven in two phases of gas and liquid in a normal pressure environment. The problem is avoided. Therefore, as will be described later, the structures of the pipe 6 and the tank 4 which are refrigerant flow paths are devised.

  In this embodiment, by using the two cooling methods in combination, not only the cooling performance is improved, but also the cooling temperature of the heating element can be set freely. For example, when pure water is used as a refrigerant in an atmospheric pressure environment, the boiling point of the refrigerant is about 100 ° C. Therefore, in the case of the latent heat method using the boiling point, the cooling temperature does not fall below the boiling point (about 100 ° C.). If the specification cooling temperature required for general electronic equipment is about 70 ° C., this requirement cannot be realized. By using a combined method with the water cooling method, it is possible to further cool from the boiling point (about 100 ° C.) to the required cooling temperature (about 70 ° C.). That is, since the required cooling temperature can be realized without changing to a refrigerant having a low boiling point or reducing the pressure in the flow path below atmospheric pressure, the usability is greatly improved.

  In the combined system of this embodiment, the latent heat system and the water cooling system are switched by controlling the flow rate of the refrigerant. Therefore, the relationship between the refrigerant flow rate and the heat absorption operation (vaporization operation) in the heat receiving unit 2 will be described.

The heat absorption amount of the refrigerant is performed by heat transfer from the heating element 1. The amount of heat M to be transferred is expressed by equation (3), where h is the heat transfer coefficient and Δt is the temperature difference between the substances.
M = h (Q) · Δt (3)
Here, the heat transfer coefficient h is not a physical property value but a value determined by the surface shape, flow rate, pressure, and the like. The heat receiving unit 2 is configured with a fine flow path so as to increase the contact area with the refrigerant so that the heat from the heating element 1 is transmitted to the refrigerant to facilitate vaporization of the refrigerant. It is getting bigger.

  The heat transfer coefficient h is also affected by the flow rate Q of the refrigerant. As described in FIG. 2, when the flow rate Q is increased, the endothermic amount W increases, which is basically preferable for improving the cooling capacity. However, when the flow rate Q is large, the flow rate of the refrigerant and the cross-sectional area of the flow path are increased. Therefore, when the flow rate Q is excessively large, the heat from the heating element 1 cannot be sufficiently transferred to the inside of the refrigerant, and the inside of the refrigerant cannot be vaporized in the latent heat cooling method. As a result, although the flow rate Q is increased, the cooling capacity corresponding to the flow rate Q cannot be obtained. That is, in order to vaporize the refrigerant flowing more actively, the heat contact area between the heat receiving surface from the heat generating element 1 and the refrigerant is maximized in the heat receiving section 2 so as to spray water on the road in midsummer. It is important.

  As described above, the cooling device of the present embodiment realizes small and efficient cooling without changing the pump performance of the cooling device, etc., even if a semiconductor circuit or the like that increases the heat generation amount of the heating element is mounted on the electronic device. can do. This can easily cope with the diversification of models according to the demands of customers of electronic devices, and contributes to the improvement of productivity.

  FIG. 3 is a diagram for conceptually explaining the cooling operation (heat reception and heat dissipation) in the cooling device of the present embodiment. In FIG. 3, the conventional water cooling method and the cooling combined method of the present embodiment are compared.

  The heating element 1 of the electronic device has a heat generation temperature T1, and the cooling device cools it to the specified cooling temperature T2. In order to realize this, the cooling device receives the amount of heat W1 from the heating element to the refrigerant in the heat receiving portion, and the amount of received heat radiates the amount of heat W2 from the refrigerant to the outside in the heat radiating portion. At this time, the heat amount W1 at the time of heat reception is equal to the heat amount W2 at the time of heat release, and at the time of heat release, it is necessary to lower the temperature of the refrigerant from the temperature T2 at the time of heat reception to the temperature T3 at the time of heat release.

  In the conventional water cooling system, as shown on the left side of FIG. 3, when the heating temperature T1 of the heating element is a higher temperature T1 ′, in order to obtain the same specification cooling temperature T2, heat is received by the heat receiving unit. The amount of heat to be increased increases to W1 ′. Similarly, the amount of heat to be dissipated in the heat dissipating part increases to W2 ', and the temperature at the time of heat dissipating must be further lowered to T3'. In order to increase the flow rate of the refrigerant from Q1 (Q2) to Q1 ′ (Q2 ′), this is equipped with a pump with a large driving force. It is necessary to use a heat dissipation part.

  On the other hand, the cooling operation in the combined system of the latent heat system and the water cooling system of the present embodiment will be described. As shown on the right side of FIG. 3, the heat generation temperature T1 ′ of the high-temperature heat generator 1 is received and cooled by the evaporation (vaporization) heat to lower the refrigerant to the boiling point temperature (T4 = 100 ° C.). (Latent heat method). Further, the temperature of the heating element 1 once lowered to the boiling point is received by the liquid refrigerant and lowered to the specified cooling temperature T2 (water cooling method). In this case, the heat receiving temperature difference due to the water cooling method is narrowed to (T4-T2), so that both the heat radiation temperature difference and (T2-T5) can be narrowed. As a result, a water cooling device having a small heat receiving portion 2 and a small heat radiating portion 3 may be used. On the other hand, in order to condense and liquefy the vaporized refrigerant, it is possible to liquefy and dissipate heat by lowering the temperature to some extent at the boundary of the boiling point. At that time, in order to increase the liquefaction rate, it is effective to have a structure in which a part of the heat radiating pipe of the heat radiating section 3 is thermally connected to the refrigerant liquid in the tank 4 as shown in FIG.

  By using the combined method as described above, it is possible to improve the cooling efficiency for the high-temperature heating element and to reduce the size of the apparatus. Further, in the cooling device equipped with the pump 5 that drives a predetermined flow rate, even when the high heating element 1 ′ is installed, the latent heat cooling is performed optimally without increasing the drive flow rate of the pump 5, Desired cooling characteristics can be realized.

  That is, in an electronic device equipped with a cooling device in which the flow rate (maximum capacity) of the pump 5 is set to a predetermined flow rate Q1, when a product in which the semiconductor circuit A is replaced with a semiconductor circuit B with high heat generation is used, a conventional water cooling device It was necessary to change the specifications of to higher performance (large flow rate). In the cooling device of this embodiment, the maximum flow rate Q1 of the pump is not changed, and the flow rate is optimally switched based on the heat generation temperature T1 'of the heating element and the specified cooling temperature T2. First, the heat amount W1 'to be absorbed is determined from the temperature difference (T1'-T2), and the operating point C at which the heat absorption amount W1' is obtained in the endothermic characteristic (combination method) of FIG. 2 is determined. The operating point at which the water cooling method and the latent heat method should be switched is set as B point, and the flow rate of the refrigerant in the pump in the latent heat method is set as Q3 corresponding to the B point. First, the flow rate Q3 is supplied to vaporize the entire amount Q3, and then the flow rate is switched to Q1 to absorb the remaining heat. Thus, by controlling the drive flow rate of the pump 5 to switch between Q1 and Q3, it is possible to cool to the desired temperature T2.

  The control unit 8 of the present embodiment shown in FIG. 1 performs control for switching the flow rate of the pump 5 between Q1 and Q3. If a constant flow rate (for example, Q1) is passed without switching the flow rate, a part of the refrigerant is vaporized due to an increase in the heat generation amount of the heating element, but the target flow rate Q3 is sufficiently vaporized. Can't do it. Therefore, the operation of the present embodiment as described above cannot be realized. Further, the value of the switching flow rate Q3 is set to be different depending on the heat generation amount W1 of the heating element. The flow rate is switched based on the temperature detection result by the temperature detection unit 7 for the heating element 1 or the heat receiving unit 2.

  FIG. 4 is a conceptual block diagram showing another embodiment of the cooling device according to the present invention. In this embodiment, a dedicated pump for supplying an optimum flow rate for both cooling systems is provided to switch the driving of the refrigerant. This is effective when there is a large difference in the flow rate of refrigerant between the latent heat method and the water cooling method. That is, a pump 51 that supplies a small-capacity refrigerant flow rate Q3 for cooling latent heat and a pump 52 that supplies a large-capacity refrigerant flow rate Q1 for water-cooling cooling are provided as dedicated pumps. At that time, as will be described later, the heat receiving section 2 is configured so that the flow path for latent heat cooling and the flow path for water cooling cooling are arranged vertically or in parallel, and the refrigerant flow Q1, Q3 is performed simultaneously. Thus, the cooling performance can be further improved. Of course, even in this configuration, if the flow rate Q3 is changed in accordance with the temperature detection result by the temperature detector 7, more precise cooling control can be performed.

  FIG. 5 is a perspective view illustrating a schematic configuration of the heat receiving unit 2 in the cooling device of FIG. 4. In this example, in order to simultaneously perform latent heat cooling by vaporization and water cooling by heat transfer, two channels of the heat receiving unit 2 are provided. First, the flow path 21 for vaporizing the refrigerant is formed on the heating element side, and the flow path 22 for heat transfer with the liquid refrigerant is separated at the upper part or the adjacent part. Thereby, latent heat cooling and water cooling cooling can be performed simultaneously independently.

  Furthermore, in the cooling device of the present embodiment, the refrigerant circulates in a vaporized state, a liquid state, or a mixture of both. In order to circulate such a refrigerant stably, the following configuration is adopted in FIG. 1 or FIG.

  Looking at the volume V of the flowed refrigerant, the volume V1 of the refrigerant as the liquid flowing through the heat receiving section 2 is a volume V2 that is vaporized in the heat receiving section 2 and instantaneously expands several to ten times. And transferred to the pipe 61. Therefore, the pipe 61 needs to have a strength that can cope with an increase in pressure due to expansion of the refrigerant, and is composed of a metal pipe or the like. The vaporized refrigerant that has flowed through the pipe 61 is transferred to the heat radiating unit 3, and is cooled, for example, by a fan or the like to be condensed and liquefied. The liquefied refrigerant flows out to the tank 4 that stores a large-capacity air layer connected to the heat radiating unit 3. The tank 4 has an accumulator structure that can store an air layer volume V4 that is several to ten times the pipe volume V3 occupied by the refrigerant vaporized in the section from the heat receiving unit 2 to the heat radiating unit 3. Therefore, even if the pressure is instantaneously increased by the volume expansion V <b> 2 in the pipe 61, the pressure is dispersed by the stored air layer volume V <b> 4 and the pressure of the entire flow path is relieved. As a result, the pressure in all the channels of the cooling device can be maintained in a pressure state close to normal pressure. The accumulator that stores the air layer may be provided in the portion of the pipe 61 in front of the heat radiating unit 3.

  Further, the refrigerant condensed in the heat radiating unit 3 is configured to flow into the tank 4 as a liquid refrigerant lower than the boiling point temperature T4 even though there is a slight temperature difference due to the heat radiating capability of the heat radiating unit 3. Here, the refrigerant amount of the liquid stored in the tank 4 stores a refrigerant amount that is several to several tens of times larger than the refrigerant amount V <b> 1 passed through the heat receiving unit 2. Therefore, the slightly high-temperature liquid refrigerant just liquefied flowing into the tank 4 is further cooled by the liquid refrigerant in the tank 4. Thereafter, the liquid refrigerant in the tank 4 is circulated and driven from the outlet to the heat receiving unit 2 by the pump 5.

  At this time, the pump 5 controls the amount of refrigerant flowing through the heat receiving unit 2. That is, as described with reference to FIG. 2, the refrigerant flow rate Q is switched between the flow rate Q3 suitable for the latent heat method and the flow rate Q1 suitable for the water cooling method. Alternatively, as described in FIG. 4, the two pumps 51 and 52 each supply a flow rate Q3 suitable for the latent heat method and a flow rate Q1 suitable for the water cooling method.

  As described above, according to this embodiment, although the refrigerant is circulated and driven in two phases, the pressure in all the flow paths of the cooling device can be maintained in a pressure state close to normal pressure. Therefore, there is no problem such as inability to drive the pump or leakage of the refrigerant from the circulation channel, and normal cooling operation can be stably maintained.

It is a conceptual block diagram which shows one Example of the electronic device carrying the cooling device of this invention. It is a figure which shows the relationship (endothermic characteristic) of the flow volume and heat-absorption amount of the refrigerant | coolant which flow in the heat receiving part. It is a figure which illustrates notionally the cooling operation (heat reception and heat dissipation) in the cooling device of a present Example. It is a conceptual block diagram which shows the other Example of the cooling device by this invention. It is a perspective view which shows schematic structure of the heat receiving part 2 in the cooling device of FIG.

Explanation of symbols

1 ... heating element,
2 ... heat receiving part,
3 ... Radiating part,
4 ... Tank,
5, 51, 52 ... pump,
6, 61, 62 ... piping,
7 ... temperature detector,
8 ... control unit,
10: Electronic equipment.

Claims (5)

A heat receiving part that receives heat generated by a heating element to be cooled by a refrigerant;
A heat radiating part for radiating the heat received by the refrigerant to the outside;
Piping for circulating the refrigerant between the heat receiving portion and the heat radiating portion;
A tank for storing the refrigerant;
A pump for driving the refrigerant;
A cooling device comprising a control unit for controlling the flow rate of the refrigerant driven by the pump,
The heat receiving unit is capable of two cooling modes, a latent heat cooling mode using heat of vaporization when the refrigerant is vaporized, and a water cooling cooling mode in which the refrigerant is thermally transferred in a liquid state,
The heat dissipating part has a heat dissipating function for condensing and liquefying the refrigerant vaporized in the heat receiving part, and a heat dissipating function for dissipating heat from the liquid refrigerant received by the heat receiving part,
The control unit switches the cooling mode in the heat receiving unit by controlling the flow rate of the refrigerant driven by the pump , and the cooling mode is changed to the latent heat cooling mode by reducing the flow rate of the refrigerant. A cooling device characterized by switching . The cooling device according to claim 1, wherein
Wherein, by increasing the flow rate of the refrigerant for driving the front SL pump, cooling device and switches the cooling mode to the water-cooled mode. The cooling device according to claim 1 or 2,
Among the pipes, the circulation flow path from the heat receiving part to the heat radiating part is at least a metal pipe with high hermeticity,
The tank has a volume larger than a refrigerant flow volume of a circulation channel from the heat receiving unit to the heat dissipation unit, stores an air layer together with the refrigerant, and increases a pressure in the circulation channel due to vaporization of the refrigerant. A cooling device characterized by having a structure that relaxes by the air layer. The cooling device according to any one of claims 1 to 3,
The pump has two pumps,
The first pump drives a refrigerant having a flow rate for operating in the latent heat cooling mode in the heat receiving unit, and the second pump drives a refrigerant having a flow rate for operating in the water cooling cooling mode in the heat receiving unit. To do,
The control unit drives one of the first pump and the second pump, or drives both at the same time. In an electronic device having a function of cooling a built-in heating element,
A heat receiving part for receiving heat generated by the heating element in the refrigerant;
A heat radiating part for radiating the heat received by the refrigerant to the outside;
Piping for circulating the refrigerant between the heat receiving portion and the heat radiating portion;
A tank for storing the refrigerant;
A pump for driving the refrigerant;
A control unit for controlling the flow rate of the refrigerant driven by the pump;
A temperature detection unit that detects the temperature of the heating element or the temperature of the refrigerant in the heat receiving unit;
The heat receiving unit is capable of two cooling modes, a latent heat cooling mode using heat of vaporization when the refrigerant is vaporized, and a water cooling cooling mode in which the refrigerant is thermally transferred in a liquid state,
The heat dissipating part has a heat dissipating function for condensing and liquefying the refrigerant vaporized in the heat receiving part, and a heat dissipating function for dissipating heat from the liquid refrigerant received by the heat receiving part,
The control unit switches the cooling mode in the heat receiving unit by controlling the flow rate of the refrigerant driven by the pump based on the temperature detected by the temperature detection unit, and reduces the flow rate of the refrigerant. The electronic device is characterized in that the cooling mode is switched to the latent heat cooling mode .

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