COOLING STRUCTURE OF ELECTRONIC EQUIPMENT

[0001] The present application claims priority from Japanese patent application JP 2009-227561 filed on Sep. 30, 2009, the content of which is hereby incorporated by reference into this application.

[0002] 1. Field of the Invention

[0003] The present invention relates to a cooling structure of an electronic equipment, and particularly to a cooling structure of an electronic equipment in which in the electronic equipment installed outdoors, when a temperature difference occurs in the electronic equipment due to external factors such as solar insolation or temperature difference in atmospheric temperature, or when a temperature difference occurs in the electronic equipment due to heat of another device installed in the neighborhood, the influence of the heat energy from the outside is reduced, and the temperature of the equipment is stabilized within an allowable temperature range.

[0004] 2. Description of the Related Art

[0005] In recent years, with an improvement in function and an increase in density of an electronic equipment, management of heat generated from the equipment becomes a serious problem. Particularly, in a precision equipment, an allowable temperature range at the time of operation is often limited, and a requirement relating to the management of heat is a severe design condition.

[0006] When such an equipment is installed especially outdoors, since a temperature difference occurs between a portion which receives solar insolation and a portion which does not receive solar insolation, it is difficult to keep the temperature of the entire equipment within the allowable temperature range.

[0007] FIG. 2 is a conceptual view showing an electronic equipment installed outdoors. In this electronic equipment, a printed board 21 is contained in a housing 20. An electronic component 22 is mounted on the printed board 21, and in order to dissipate the heat of the electronic component 22, a housing inner wall and the electronic component 22 are thermally connected to each other. The phrase “thermally connected” means “thermally joined”, and for example, the heat generated from the electronic component 22 is connected using a heat sink or the like and is conducted to the housing outer wall. The generated heat is released from the housing outer wall to the atmosphere, and temperature rise in the housing is suppressed.

[0008] However, when the electronic equipment receives solar insolation, since the amount of insolation is about 1 KW/m² in summary, the temperature of the housing outer wall receiving the insolation can be 80° C. or higher. At this time, the temperature of the electronic component 22 becomes higher than the temperature of the housing inner wall by its own heat generation, and therefore, it is difficult to use the electronic equipment 22 under the use environment condition (temperature, humidity, etc.).

[0009] Thus, in the electronic equipment installed outdoors, there is a case where a light shielding plate for shielding solar insolation is attached. As shown in FIG. 3, a light shielding plate 24 is attached so as to a cover a portion receiving solar insolation. Thus, in order to install the light shielding plate 24, it is necessary to previously grasp the direction of solar insolation. When the direction of solar insolation can not be specified, the light shielding plate is generally attached to five surfaces except the equipment bottom surface. However, in this method, there is a problem that the electronic equipment becomes large.

[0010] As an example of a case where consideration is given to the reduction of the temperature rise caused by solar insolation and the miniaturization of an electronic equipment, there is a technique disclosed in JP-A-2001-57485 (patent document 1).

[0011] FIG. 4 is a structure conceptual view showing the electronic equipment disclosed in the above publication. In FIG. 4, the electronic equipment includes, in a metal closed housing 40, a printed board 41, an electronic component 42, directional heat conduction members 43, and a low heat resistance member 44. In this electronic equipment, in order to cool the electronic component 42, the electronic component 42 is connected to the closed housing 40 through the plural directional heat conduction members 43 and the low heat resistance member 44. By this, heat generated from the electronic component 42 is transported to the closed housing outer wall through the directional heat conduction members 43 and the low heat resistance member 44, and is released to the atmosphere. Incidentally, the directional heat conduction members 43 are disposed so as to conduct heat only in the direction from the electronic component 42 to the housing outside. Thus, when the electronic equipment receives solar insolation, heat of the housing outer wall surface whose temperature rises by receiving the insolation is not conducted to the electronic component 42 in the housing through the directional heat conduction members 43.

[0012] [Patent document 1] JP-A-2001-57485

[0013] However, when it is considered to keep the temperature of the electronic equipment within an allowable temperature range, the technique disclosed in the publication has following problems.

[0014] In the technique disclosed in the publication, a heat pipe is used as the directional heat transmission member. When a temperature difference occurs between a heat absorption portion and a heat dissipation portion, the heat pipe immediately transports heat from the heat absorption side to the heat dissipation side. At this time, the operation temperature of the heat pipe is passively determined by the temperature of the heat absorption portion and the heat dissipation portion.

[0015] Thus, in the structure of the electronic equipment in which the heat absorption portion of the heat pipe is connected to the electronic component and the heat dissipation portion is connected to the housing inner wall, when the temperature of the housing inner wall (heat dissipation portion) is changed by solar insolation, the temperature of the electronic component (heat absorption portion) is also passively changed, and this can not be kept at a specified temperature.

[0016] Besides, since a metal pipe is used as the heat pipe, heat conduction efficiency as expected can not be obtained, heat energy from the external environment such as the solar insolation is transported into the equipment, and it is liable to be influenced by external environmental factors such as the solar insolation. In other words, in the electronic equipment structure, it can not be expected that the influence of the external environmental factors is greatly reduced.

[0017] The present invention is made in view of the above circumstances, and in an environment in which an influence of heat energy from the outside is received, for example, when a large temperature difference occurs in an electronic equipment by external factors such as solar insolation or when a temperature difference occurs in the electronic equipment by heat of another device installed in the neighborhood, the influence of the external environment is reduced and the temperature of the equipment is stabilized within an allowable temperature range.

[0018] In order to solve the problem, according to an aspect of the invention, an electronic equipment has a structure in which an electronic component contained in a housing is thermally connected to a housing inner wall through plural heat conduction members and a heat conduction control member, and the amount of heat transported from the electronic component to the housing inner wall is controlled by using the heat conduction member, and is characterized in that

[0019] the amount of heat to be transported is decreased for a housing surface whose temperature rises by influence of an external environment, the amount of heat to be transported is increased for a housing surface which is not influenced by the external environment, and temperature of the electronic component is stabilized within an allowable temperature range.

[0020] More specifically, the electronic equipment according to an aspect of the invention includes, for example, as shown in FIG. 5, a printed board 3, an electronic component 4, a heat conduction member 5, a heat conduction control member 6, a control circuit section 12, and a temperature sensor 13 in a housing 1, and

[0021] one of features is a structure in which in order to cool the electronic component 4 mounted on the printed board 3, an upper surface of the electronic component 4 is connected to the heat conduction member 5, and further, the heat conduction member 5 is connected to plural housing inner walls through the heat conduction control member 6.

[0022] Besides, the heat conduction control member 6 is a member capable of controlling the amount of heat to be transported from the electronic component 4 to the housing inner wall, and the control thereof is performed by the control circuit section 12 mounted on the printed board 3.

[0023] Incidentally, the control circuit section 12 receives the temperature of the electronic component 4 and information of the temperature sensor 13 attached to the housing 1, and controls the amount of heat to be transported from the electronic component 4 to the respective housing inner walls so as to stabilize the temperature of the electronic component 4 within the allowable temperature range.

[0024] According to the first solving means of the present invention, there is provided a cooling structure of an electronic equipment in which an electronic component is disposed in a housing and heat is dissipated from a first surface and a second surface of the housing, comprising:

[0025] a first heat conduction control member to control an amount of heat transmitted from the electronic component to the first surface of the housing;

[0026] a second heat conduction control member to control an amount of heat transmitted from the electronic component to the second surface of the housing;

[0027] a first temperature sensor to measure temperature of the first surface of the housing;

[0028] a second temperature sensor to measure temperature of the second surface of the housing; and

[0029] a control circuit to increase the amount of heat transmitted to a lower temperature one of the first and the second surfaces by controlling to decrease a heat resistance of the corresponding first or second heat conduction control member based on the respective temperatures measured by the first temperature senor and the second temperature sensor.

[0030] According to the second solving means of the present invention, there is provided a cooling structure of an electronic equipment in which an electronic component is disposed in a housing and heat is dissipated from a first surface and a second surface of the housing, comprising:

[0031] a first heat conduction control member to control an amount of heat transmitted from the electronic component to the first surface of the housing;

[0032] a second heat conduction control member to control an amount of heat transmitted from the electronic component to the second surface of the housing;

[0033] a first optical sensor to measure light amount of the first surface of the housing;

[0034] a second optical sensor to measure light amount of the second surface of the housing; and

[0035] a control circuit to increase the amount of heat transmitted to a lower light amount one of the first and the second surfaces by controlling to decrease a heat resistance of the corresponding first or second heat conduction control member based on the respective light amounts measured by the first light amount senor and the second optical sensor.

[0036] According to the third solving means of the present invention, there is provided a cooling structure of an electronic equipment in which an electronic component is disposed in a housing and heat is dissipated from a first surface and a second surface of the housing, comprising:

[0037] a first heat conduction control member to control an amount of heat transmitted from the electronic component to the first surface of the housing;

[0038] a second heat conduction control member to control an amount of heat transmitted from the electronic component to the second surface of the housing;

[0039] a first temperature sensor, arranged to the first surface of the housing, to measure outside temperature of the first surface;

[0040] a second temperature sensor, arranged to the second surface of the housing, to measure outside temperature of the second surface; and

[0041] a control circuit to increase the amount of heat transmitted to a lower outside temperature one of the first and the second surfaces by controlling to decrease a heat resistance of the corresponding first or second heat conduction control member based on the respective temperatures measured by the first temperature senor and the second temperature sensor.

[0042] According to the present invention, in an environment in which an influence of heat energy from the outside is received, for example, when a large temperature difference occurs in an electronic equipment by external factors such as solar insolation or when a temperature difference occurs in the electronic equipment by heat of another device installed in the neighborhood, the influence of the external environment can be reduced and the temperature of the equipment can be stabilized within an allowable temperature range.

[0043] According to the present invention, since a light shielding plate is eliminated in the environment in which solar insolation is received, the electronic equipment can be miniaturized.

[0058] Hereinafter, embodiments of the invention will be described with reference to the drawings.

[0059] FIG. 1 is a perspective view showing an electronic equipment of an embodiment.

[0060] The electronic equipment includes a housing 1, a heat sink 2, a printed board 3, a heat conduction member A 5a, a heat conduction member B 5b, a rubber packing 9, a heat pipe 7, a Peltier element (heat conduction control member) 8, a not-shown electronic component 4, a control circuit section 12 and a temperature sensor 13.

[0061] FIG. 6 is a sectional side view showing the electronic equipment of the embodiment.

[0062] The electronic equipment includes a housing A 1a and a housing B 1b, and the heat sink 2 is formed on respective housing surfaces (first surface, second surface) and enables heat dissipation to the atmosphere. The housing A 1a and the housing B 1b respectively have sufficient cooling performance, and have structures with substantially equal heat resistances. Incidentally, the rubber packing 9 serving also as a waterproof measure is nipped between the housing A 1a and the housing B 1b in order to reduce the temperature influence by mutual heat conduction.

[0063] On the other hand, in the equipment, in order to cool the electronic component 4 mounted on the printed board 3, the electronic component 4 is connected to the heat conduction member A 5a. At this time, in order to efficiently transport the heat of the electronic component 4, the heat conduction member A 5a is made of, for example, high heat conduction metal, such as copper or aluminum, or a plate-like heat pipe. Incidentally, the number of the electronic components 4 connected to the heat conduction member A 5a may be one or two or more.

[0064] Besides, the heat conduction member A 5a is connected to the heat conduction member B 5b through the heat pipes 7 attached to the upper and lower surfaces thereof. Similarly to the heat conduction member A 5a, in order to efficiently transport the heat of the electronic component 4, the heat conduction member B 5b can also be made of, for example, high heat conduction metal, such as copper or aluminum, or a plate-like heat pipe. The number of the heat pipes 7 to connect the heat conduction member A 5a and the heat conduction member B 5b is suitably adjusted according to the amount of heat to be transported.

[0065] The back surface of the heat conduction member B 5b is connected to the inner walls of the housing A 1a and the housing B 1b through the Peltier element 8 as the heat conduction control member. By this, heat generated from the electronic component 4 is finally transported to the housing inner wall. Here, the Peltier element is a semiconductor element capable of controlling a heat transport amount (heat generation, heat absorption) by the magnitude of a voltage applied to the element. Incidentally, surfaces for heat dissipation are not limited to the two surfaces as shown in the drawing, and heat dissipation may be performed from three or more surfaces.

[0066] FIG. 7 is an exploded view showing the electronic equipment of the embodiment.

[0067] In the electronic equipment, the control circuit section 12 to control the Peltier element 8 is mounted on the printed board 3. Besides, temperature sensors (a first temperature sensor, a second temperature) 13 are buried in the inner walls of the housing A 1a and the housing B 1b, and the temperature information of the housing inner wall is transmitted to the control circuit section 12. In this embodiment, it is assumed that the temperature distribution of the housing inner wall becomes irregular, and the plural temperature sensors 13 are mounted.

[0068] Hereinafter, the control behavior of the Peltier element 8 at the time of operation of the electronic equipment will be described.

[0069] First, as shown in FIG. 8, it is assumed that the electronic equipment is operated in an environment in which solar insolation is not received (in an environment in which influence of heat energy from the outside is not received). At this time, since a large temperature difference does not occur in the electronic equipment, temperature T1 of the housing A 1a and temperature T2 of the housing B 1b become almost equal to each other (T1≈T2). Thus, it is sufficient if the heat is equally transported to the housing A 1a and the housing B 1b to dissipate the heat of the electronic component 4. Then, the control circuit section 12 controls so that heat resistances θ_A and θ_B of the Peltier element A 8a and the Peltier element B 8b become θ_A≈θ_B. Then, since the housing A 1a and the housing B 1b have the equal heat resistances, the amount Q_A of heat dissipated from the housing A 1a to the outside becomes equal to the amount Q_B of heat dissipated from the housing B 1b to the outside. When the total amount of heat which must be dissipated to the outside in order to keep the temperature of the electronic equipment 4 at a target temperature (electronic component control target temperature) is ΔQ, a relation of ΔQ/2=Q_A=Q_B is established.

[0070] Next, as shown in FIG. 9, it is assumed that the electronic equipment is installed outdoors, and at time t1, the housing A 1a side receives a large amount of insolation. At this time, the temperature of the housing A 1a receiving the solar insolation rises, and T1>T2 is established. Thus, the amount Q_A of heat dissipated from the housing A 1a to the outside becomes small as compared with the case where the solar insolation is not received, and cooling efficiency becomes worse. Then, the control circuit section 12 controls the heat resistances of the Peltier element A 8a and the Peltier element B 8b so that θ_A becomes large and θ_B becomes small. Then, the amount Q_A of heat dissipation becomes small as compared with the case where solar insolation is not received. Although the cooling efficiency remains poor, since the heat resistance becomes large, the influence of solar insolation becomes small. On the other hand, in the housing B 1b, since the heat resistance of the Peltier element B 8b becomes small, the amount Q_B of heat dissipation is increased as compared with the case where solar insolation is not received. Besides, when the amount ΔQ of heat to be dissipated to the outside in order to keep the temperature of the electronic equipment 4 at the electronic component control target temperature in total is ΔQ, when Q_A and Q_B are controlled so that a relation of ΔQ=Q_A+Q_B is established, the temperature of the electronic equipment is kept constant or within the desired temperature range.

[0071] Finally, as shown in FIG. 10, it is assumed that the housing B 1b side receives a large amount of insolation at different time t2 when the insolation direction is changed. Contrary to the case at time t1, since the temperature of the housing B 1b receiving the insolation rises, T1<T2 is established. Thus, the amount Q_B of heat dissipated from the housing B 1b becomes small as compared with the case where insolation is not received, and the cooling efficiency becomes worse. Then, contrary to the case at time t1, the control circuit section 12 controls the Peltier element A 8a and the Peltier element B 8b so that θ_A becomes small and θ_B becomes large. Then, as compared with the case where insolation is not received, the amount Q_A of heat dissipated from the housing A 1a is increased, while the amount Q_B of heat dissipated from the housing B 1b is decreased. Similarly to the case at time t1, when a relation of ΔQ=Q_A+Q_B is satisfied in total, the temperature of the electronic component 4 is kept constant or within the desired temperature range.

[0072] Incidentally, in the electronic equipment of the embodiment, it is needless to say that the same effect is obtained not only in the case where insolation is received, but also in the case where a different device is installed near one of the housing A 1a and the housing B 1b and the influence of unbalance heat energy is received.

[0073] FIG. 11 shows an example of the control circuit section 12 of the Peltier element 8.

[0074] The control circuit section 12 includes a main control section and a balancer section.

[0075] First, at point A in the drawing, the main control section obtains a difference ΔT between electronic component temperature T_PV monitored by the electronic component temperature sensor and target temperature (electronic component control target temperature T_trg) of the electronic component. Incidentally, since an electronic component temperature sensor (third temperature sensor) is often mounted in the electronic component, it is not shown in FIG. 5 to FIG. 10. Incidentally, in addition to the mounting in the electronic component, the temperature sensor may be mounted on the outside. Besides, the electronic component control target temperature T_trg can be set in advance.

[0076] Next, from the temperature difference ΔT, the main control section uses a filter 1 to determine the amount ΔQ of heat which must be dissipated to the outside in order to cause the electronic component temperature T_PV to become the electronic component control target temperature T_trg. In the filter 1, in order to convert ΔT to ΔQ, it is necessary to previously obtain a relation between both by heat simulation or a real machine test. For example, based on data obtained by the heat simulation or the real machine test, the correspondence relation between the value of ΔT and the value of ΔQ may be previously stored in a table, or an expression for obtaining ΔQ from ΔT may be previously obtained and set. In addition to this, ΔT may be converted to ΔQ by an appropriate method.

[0077] Then, at point B in the drawing, ΔQ obtained by the filter 1 is divided into the heat amounts Q_A and Q_B which must be dissipated by the respective housing surfaces. In this embodiment, for simplification, the case where the control is performed for two systems of the housing A side and the housing B side is described. At point B in the drawing, in order to equate the amount Q_A of heat dissipated from the housing A 1a to the amount Q_B of heat dissipated from the housing B 1b, division into two equal parts is performed so that Q_A=Q_B=ΔQ/2 is established. Incidentally, the heat dissipation amount may be divided at a previously determined ratio. For example, the heat dissipation amount may be divided according to the area of each surface for heat dissipation, the number of Peltier elements of each surface, or heat dissipation power.

[0078] On the other hand, when a large temperature difference occurs in the electronic equipment by solar insolation, the balancer section adjusts Q_A and Q_B. At point C in the drawing, the balancer section obtains a difference ΔT_S between the electronic equipment side surface temperatures T1 and T2 monitored by housing temperature sensors 1 and 2. Then, the filter 2 is used to obtain a difference ΔQ_S between the amounts of dissipation heat to be given to the Peltier element A and the Peltier element B in order to cause the temperature difference ΔT_S between both to become 0. In this filter 2, similarly to the case of the filter 1, in order to convert ΔT_S to ΔQ_S, it is necessary to previously obtain the relation of both by simulation or the like. Incidentally, the process by the balancer section may be performed when a large temperature difference occurs in the electronic equipment (for example, when the difference ΔT_S between T1 and T2 is larger than a previously determined threshold value), or the difference ΔT_S between the electronic component temperature T_PV measured by the electronic component temperature sensor and the electronic component control target temperature T_trg is larger than a previously determined threshold value.

[0079] Then, in order to eliminate the temperature difference ΔT_S between T1 and T2 and to cause the electronic component temperature T_PV to approach the electronic component control target temperature T_trg, ΔQ_S has only to be added and subtracted. Thus, the amounts of heat to be dissipated by the respective Peltier elements, Q_A=ΔQ/2−ΔQ_S and Q_B=ΔQ/2+ΔQ_S, are obtained. The thus determined Q_A and Q_B are transmitted to the Peltier elements 8 through drivers mounted in the main control section. The Peltier element 8 controls the heat transport amount by turning on/off all of or part of power sources, or by changing the magnitude of voltage supplied to the elements. Incidentally, the control circuit section 12 may control only the heat resistance of a lower temperature one of the housings A 1a and B 1b and may not control the higher temperature one.

[0080] As described above, according to the embodiment, in an environment in which the influence of heat energy from the outside is received, for example, when a large temperature difference occurs in the electronic equipment by external factors such as solar insolation, or when a temperature difference occurs in the electronic equipment by heat of a different device installed in the neighborhood, the influence of the external environment can be reduced and the temperature of the equipment can be stabilized within the allowable temperature range.

[0081] FIG. 12 is a structural view of an electronic equipment when an optical sensor is used.

[0082] As another unit configured to quickly sense the influence of solar insolation, an optical sensor 14 as shown in FIG. 12 may be used. By this sensor 14, a surface receiving solar insolation is quickly sensed, and temperature control with sufficient time can be performed. Besides, the optical sensor 14 is desirably mounted on each of, for example, a front surface, a side surface and a ceiling surface of a housing 1, which receive the influence of solar insolation. Incidentally, in this electronic equipment, the balancer section shown in FIG. 11 obtains a difference between light amounts measured by the optical sensors 14 instead of obtaining the temperature difference by the temperature sensors.

[0083] FIG. 13 is a structural view of an electronic equipment in a case where a high insolation absorption coefficient temperature sensor is used.

[0084] As another unit configured to quickly sense the influence of solar insolation, a high insolation absorption coefficient temperature sensor 15 as shown in FIG. 13 may be used. As shown in FIG. 14, the sensor 15 has such a structure that a thermistor 51 is attached to a metal plate 52 coated with, for example, black paint, the metal plate is fixed to a housing 1 by a hollow post 50, and a thermistor cable passes through a hollow portion of the post 50 and is fed into the inside of the housing. Since the black paint coated on the metal plate 52 has a high insolation absorption coefficient, temperature rise is sensitive to the reception of insolation, and the direction of the insolation, so-called insolation influence surface can be quickly sensed. Incidentally, for the purpose of accurately sensing the influence of insolation, it is desirable that the black coated metal plate 52 is mounted while a distance from the heating housing surface is secured by the post or the like to a certain degree. Besides, in order to raise the temperature sensitivity, that is, in order to decrease the thermal time constant, it is appropriate that the metal plate is made as thin as possible. Besides, the sensor 15 is desirably mounted on each of, for example, a front surface, a side surface and a ceiling surface of the housing which receives the influence of solar insolation. Further, as the external environment change other than the solar insolation, also in the case where the outside air temperature is changed or a heat generating body exists in the neighborhood, the influence can be quickly sensed.

[0085] In one of cooling structures of the electronic equipment of the embodiment, in an environment in which influence of heat energy from the outside is received, for example, when a large temperature difference occurs in the electronic equipment by external factors such as solar insolation, or when a temperature difference occurs in the electronic equipment by heat of a different device installed in the neighborhood, the amount of heat to be transported is decreased for the housing surface whose temperature rises by the influence of the external environment, and the amount of heat to be transported is increased for the housing surface which is not influenced by the external environment, and the temperature of the electronic component is stabilized within the allowable temperature range.

[0086] In the electronic equipment, the electronic component contained in the housing is thermally connected to the housing inner wall through the plural heat conduction members and the heat conduction control member, and the heat is transported from the electronic component to the housing inner wall.

[0087] Besides, one of the electronic equipment devices of the embodiment is, for example, an electronic equipment device including a metal housing, which includes

[0088] a heat conduction member connected to an electronic component in the electronic equipment device,

[0089] a heat conduction control member to connect the heat conduction member and the housing,

[0090] a control unit to control the heat conduction member, and

[0091] a temperature sensor to measure temperature change of the housing, and in which

[0092] the control unit controls the heat conduction control member based on a measurement result of the temperature sensor, and thermally connects the heat conduction member and the housing.

[0093] The invention can be used for, for example, the industry relating to the electronic equipment.