FR2880192A1 - Thermal control system for e.g. board, has thermal actuator to respectively control passage of system from active to inactive configuration and vice-versa, when actuator temperature is lower and higher than respective threshold values - Google Patents

Abstract

The system has a radiator (5) in contact with and separated from an electronic device (2), during active and inactive configurations of the system, respectively. A thermal actuator (7) controls the passage of the system from active to inactive configuration, when the actuator temperature is lower than a preset threshold value and from inactive to active configuration when the temperature is higher than another preset threshold value.

Description

Two-state system for the thermal regulation of a

  The invention relates to the thermal regulation of electronic devices.

  It is known to provide an electronic device with a cooling device. Such a device can be of two types: active (such as a fan, which generates a stream of air intended to evacuate at least part of the thermal energy generated by the device), or passive (such as a radiator, which increases the surface in contact with the ambient air to facilitate heat dissipation).

  Examples of electronic devices provided with cooling devices are in particular provided by documents WO-93/17536 and US-6,801,431.

  The purpose of any cooling device is to maintain the temperature of the electronic device at a value below a predetermined high critical value (generally provided by the device manufacturer) beyond which the operation of the device may be impaired.

  However, it may be necessary, under certain temperature conditions, to keep the temperature of the electronic device higher than a critical low value, also predetermined, below which the operation of the device can also be altered.

  The fan, when energized, ensures the cooling of the electronic device to prevent its internal temperature from reaching or exceeding the high critical value, while, when it is de-energized, it allows the clean heating of the device. device so that its temperature does not reach or falls below the low critical value.

  But the main disadvantage of the fan is that it requires a power supply and a control circuit of its start or stop depending on the temperature. This results in increased energy consumption and the need to fine tune the control circuit according to the critical temperatures. In addition, given the wear of the internal parts of the fan, including its bearings and bearings, it must be replaced regularly to avoid the risk of failure of its control electronics are added to the risk of failure mechanical.

  As for the radiator, if its passivity is an asset in terms of energy savings, its main disadvantage is to ensure a permanent heat dissipation, including when it would be necessary, however, to ensure proper operation of the device, to allow the latter to warm up to compensate for an excessive drop in temperature.

  The invention aims in particular to solve the aforementioned drawbacks by proposing a solution for achieving effective thermal dissipation of the electronic device at high temperature, while allowing a warming of the device at low temperature.

  For this purpose, the invention proposes a system comprising an electronic device generating thermal energy as well as a radiator, which system can adopt an active configuration in which the radiator is in contact with the electronic device, and an inactive configuration in which the radiator is moved away from the electronic device, the system further comprising a thermal actuator able to control the transition from the active configuration to the inactive configuration when the value of the temperature in the vicinity of the device becomes lower than a first predetermined threshold value, and the inactive configuration to the active configuration when the value of the temperature in the vicinity of the device becomes greater than a second predetermined threshold value.

  In this way, it is possible to ensure both a heat dissipation of the electronic device when the temperature is high, and its own heating when the temperature is low. Thus, it is possible to maintain the electronic device within its prescribed range of temperature operation.

  According to one embodiment, the actuator comprises a shape memory alloy element, for example a nickel-titanium alloy (NiTi), or a nickel-titanium alloy (NiTiCu).

  This element may be of the double-acting type, in which case, irrespective of the configuration of the electronic device, it exerts on it a force, or of the simple effect type, in which case the reaction opposed to the force exerted on the electronic device by the shape memory alloy element may result from the gravity (concretely, the weight of the device or the radiator), or the presence of a return spring coupled to the shape memory alloy element.

  An interface made of a phase change thermal contact material may be interposed between the radiator and the electronic device to increase thermal conduction between these elements when the system is in its active configuration.

  The system can be realized in several ways.

  The electronic device comprises, for example, a support bearing, on the radiator side, an electronic component generating thermal energy, the radiator being mounted on the support at the right of the component, being movable relative to the support between an active position (corresponding to the active configuration of the system) in which it is pressed against the electronic component, and an inactive position (corresponding to the inactive configuration of the system) in which it is removed from said component.

  In a variant, the electronic device comprises a support bearing, on the radiator side, an electronic component generating thermal energy, the support being mounted on the radiator with the electronic component in line with the latter, being mobile with respect to the radiator between an active position (corresponding to the active configuration of the system) in which the electronic component is pressed against the radiator, and an inactive position (corresponding to the inactive configuration of the system) in which the electronic component is moved away from the radiator.

  According to another variant, the electronic device comprises a support carrying, on the opposite side to the radiator, an electronic component generating thermal energy, the radiator being mounted on the support to the right of the component, being movable relative to the support between a position active (corresponding to the active configuration of the system) in which it is pressed against the support, and an inactive position (corresponding to the inactive configuration of the system) in which it is separated from said support.

  According to yet another variant, the electronic device comprises a support carrying, on the opposite side to the radiator, an electronic component generating thermal energy, the support being mounted on the radiator with the electronic component to the right thereof, being mobile relative to the radiator between an active position (corresponding to the active configuration of the system) in which the support is pressed against the radiator, and an inactive position (corresponding to the inactive configuration of the system) in which the support is removed from the radiator.

  In the latter two cases, the support preferably comprises thermal drainage wells arranged in line with the electronic component, for example in the form of metal inserts passing through the support. According to another embodiment, the electronic device is an electronic box containing the minus an electronic component generating thermal energy.

  In this case, the radiator is for example mounted directly on the housing being movable relative thereto between an active position in which it is in contact with the electronic unit, and an inactive position in which it is spaced from said housing.

  Alternatively, the housing is mounted on a frame on which the radiator is also mounted, in line with the housing, being movable relative to the chassis between an active position in which it is in contact with the electronic unit, and an inactive position in which is spaced from said housing.

  Other objects and advantages of the invention will emerge in the light of the description given hereinafter with reference to the appended drawings in which: FIG. 1 is a diagrammatic sectional view illustrating a system according to the invention, according to a first embodiment, in an active configuration; - Figure 2 is a schematic sectional view of the system of Figure 1, in an inactive configuration; FIG. 3 is a view similar to FIG. 1, according to a second embodiment; Figure 4 is a view similar to Figure 2, according to a second embodiment; - Figure 5 is a view similar to Figures 1 and 3, according to a third embodiment; - Figure 6 is a view similar to Figures 2 and 4, according to a third embodiment; Figure 7 is a diagram illustrating the vacuum elongation of a shape memory alloy spring used in the embodiment of an actuator for a system according to the invention. 20

  In the figures is represented a system 1 comprising an electronic device 2 which, in the case of Figures 1 to 4, is an electronic card comprising a support or substrate 3 in the form of a plate of insulating material, carrying electronic components 4.

  One of these components is shown in Figures 1 to 4. It is an electronic power component, which in operation is generating thermal energy.

  As is also shown in the figures, the system 1 also comprises a radiator 5, provided to promote the evacuation of the energy generated by the electronic device 2 in operation.

  By radiator is meant a passive element, that is to say non-powered electrical energy, made of a thermally conductive material, such as an aluminum alloy, and having a large surface given its volume. In the examples shown, the radiator 5 has a plurality of fins 6, which promote the heat exchange between the radiator 5 and the ambient air.

  As can be seen in the figures, the system 1 can adopt two distinct configurations, namely: a first configuration, called active (FIGS. 1, 3, 5), in which the radiator 5 is in contact with the electronic device 2 to facilitate the dissipation of the thermal energy released by the latter, and a second configuration, said inactive (Figures 2, 4, 6), wherein the radiator 5 is removed from the electronic device 2 to, instead, promote the clean warming of the device 2 (that is to say, in the cases illustrated in FIGS. 1 to 4, the increase in the internal temperature of component 4, generated by its own thermal energy).

  The system 1 further comprises a thermal actuator 7 placed in the vicinity of the device 2 arranged to control the passage of the system 1 from the active configuration to its inactive configuration when the value of the temperature of this actuator 7 (equal to the ambient temperature in the vicinity of the electronic device 2) becomes smaller than a first predetermined threshold value T1, and from its inactive configuration to its active configuration when the value of the temperature of the actuator 7 becomes greater than a second predetermined threshold value T2.

  It should be noted that the terms active and passive refer not to the active or passive nature of the actuator - which is in fact passive, that is to say that it is not powered - but reference to favored character (in the active position) or not (in the inactive position) of the heat dissipation.

  Several embodiments are proposed to achieve the functionality mentioned above.

  A first embodiment is described with reference to FIGS. 1 and 2.

  As can be seen in FIGS. 1 and 2, the component 4 is in the form of a parallelepipedal element having an internal electronics that will not be described, fixed on an upper face 8 of the support 3 and itself having a face 9 substantially plane plane by which emerges most of the thermal energy it produces in operation.

  The radiator 5 has meanwhile a substantially parallelepipedal body 10 having a substantially flat bottom face 11, and an upper face 12 whose fins 6 project.

  The radiator 5 is mounted on the support 3 on the component side 4, at the right thereof, its lower face 11 facing the upper face 9 of the component 4. The radiator 5 is fixed on the support 3 by means of screws 13 which pass through the body 10 of the radiator 5 and the support 3, and which, on the side of a lower face 14 thereof, are caught in nuts 15.

  As can be seen in FIG. 1, each screw 13 has an upper portion 13a protruding from the body 10 of the radiator 5 opposite the support 3, to a screw head 16, and an intermediate portion 13b which extends between the radiator 5 and the support 3.

  The radiator 5 is mounted movably relative to the support 3 between an active position (corresponding to the active configuration of the system 1), represented in FIG. 1, in which its lower face 11 is in contact with the upper face 9 of the component 4, and an inactive position (corresponding to the inactive configuration of the system 1), represented in FIG. 2, in which the radiator 5 is separated from the component 4, a gap 17 appearing between the lower face 11 of the radiator 5 and the upper face 9 of the component 4.

  The actuator 7 mentioned above controls the passage of the active position of the radiator 5 to its inactive position, and vice versa, depending on its temperature. In practice, several actuators 7 are provided here, grouped around each screw 13.

  Each actuator comprises a shape memory alloy element (AMF) 18, in the form of a compression spring mounted on the upper portion 13a of the screw 13, and interposed by being compressed between the screw head 16 (via a first washer 19) and the radiator 5 (via a second washer 20).

  The spring 18 is for example made of a nickel-titanium alloy (NiTi), or a nickel-titanium alloy (NiTiCu); it is here of the simple effect type, that is to say that it only works in compression.

  The profile of the vacuum elongation of the spring 18 as a function of its temperature is given by the diagram of FIG. 7: it is a hysteresis profile, the spring 18 exhibiting a minimum empty length L1 when the temperature of the spring 18 is smaller than a first predetermined threshold value Ti (for example of the order of 20 C), associated with a low stiffness, and a maximum empty length L2 when the temperature of the spring 18 is greater than a second threshold value T2 predetermined (for example of the order of 80 C), associated with high stiffness.

  The actuator 7 further comprises a return spring 21 ordinary, that is to say a constant length and constant stiffness, operating in compression, mounted on the intermediate portion 13b of the screw 13 and interposed by being compressed between the body 10 of the radiator 5 and the support 3.

  The return spring 21 is chosen so that, when the temperature of the spring 18 AMF (corresponding, as indicated above, the ambient temperature in the vicinity of the component 4) exceeds the second threshold value T2, the force exerted by the return spring 21 on the radiator 5 is less than that exerted by the spring 18 AMF which pushes the radiator 5 in its active position where, pressed against the component 4, it promotes the dissipation of the thermal energy released by it this.

  On the other hand, when the temperature of the AMF spring 18 passes below the first threshold value T1, the force exerted by the AMF spring 18 on the radiator is less than that exerted by the return spring 21, which then pushes the radiator 5 its inactive position against the spring 18 AMF position where, once the balance of forces reached, the radiator 5 allows the component to heat up under the effect of its own thermal energy.

  It is not necessary for a person skilled in the art to make himself the spring 18 AMF. Specialized companies offer springs of this type on the market. As an example, for the completeness of the present description and not for advertising purposes, the company AMT, based in Belgium, from which the skilled person can provide himself, after having defined his specifications according to the temperature thresholds retained for the modification of the state of the spring 18 in AMF.

  Although in the embodiment which has just been described component 4 is mounted on the support 3 on the radiator 5 side, it may be located on the side of the support opposite the radiator, the structure of the system being otherwise unchanged.

  A second embodiment will now be described with reference to FIGS. 3 and 4.

  This embodiment is similar to the first described above (the common elements have the same references), but the reciprocal mounting of the support 3 and the radiator 5 is achieved in reverse: it is indeed the support 3 which is mounted on the radiator 5 (which is on the side of the lower face 14 of the support 3, that is to say the side opposite the component 4, which is fixed on the upper face 8 of the support 3 to the right of the radiator 5 ), being movable relative to the radiator 5 between: an active position in which the support 3 is in contact, on the side of its lower face 14, with the radiator 5 whose fins 6 are turned on the opposite side to the lower face 14 , so as to facilitate the dissipation of the thermal energy generated by the component 4, and an inactive position in which the support 3 is spaced from the radiator 5 to promote the clean heating of the component 4.

  As can be seen in FIGS. 3 and 4, the radiator 5 has bosses 22 whose ends 23 jointly form an upper face 11 'of the radiator 5, with which the lower face 14 of the support 3 comes into contact in the active position.

  Moreover, in order to promote the thermal conduction through the support 3, thermal drainage wells may be made therein, in the form of metal inserts included in the support 3 to the right of the component 4, inserts 23 which extend in the thickness of the support 3, from one face to the other of the latter.

  The actuators 7 have the same structure as that described in the first embodiment, with the difference that the spring 18 AMF is interposed by being compressed between the screw head 16 and the upper face 8 of the support 3, while the return spring 21 is interposed between the radiator 5 and the lower face 14 of the support 3.

  Thus, when the temperature of the spring 18 AMF exceeds the second threshold value T2, the force exerted by the return spring 21 on the support 3 is less than that exerted by the spring 18 AMF which pushes the support 3 in its active position where, pressed against the radiator 5, it allows the dissipation of the thermal energy released by the component 4, where appropriate via the inserts 23.

  On the other hand, when the temperature of the AMF spring 18 passes below the first threshold value T1, the force exerted by the AMF spring 18 on the support 3 is less than that exerted by the return spring 21, which then pushes the support 3 in its inactive position against the spring 18 AMF position where the support 3, away from the radiator 5, allows the component 4 to heat up under the effect of its own thermal energy.

  Although in the embodiment which has just been described component 4 is mounted on the support 3 on the side opposite the radiator 5, it can be located on the side thereof, the structure of the system being otherwise unchanged.

  A third embodiment will now be described with reference to FIGS. 5 and 6.

  In this embodiment, the operating mode of the system 1 is globally identical to the first embodiment. Numeric references are retained for common elements.

  Here, the electronic device 2 is an electronic box containing at least one electronic component generating thermal energy, mounted on a frame 3 '.

  As can be seen in FIGS. 5 and 6, the radiator 5 is also mounted on the chassis 3 'between an inactive position (FIG. 6) in which it is separated from the housing 2 to allow its own heating up, and an active position (Figure 5) in which it is in contact with the housing 2 to allow the dissipation of thermal energy emanating therefrom.

  The chassis 3 'on which the housing 2 is mounted is optional: the radiator 5 can indeed be mounted directly on the housing 2.

  In any of the embodiments that have just been described, the return spring 21 is optional. It is possible to suppress it provided that a balance of forces applied to the electronic device 2 is restored.

  This equilibrium can, according to a first variant embodiment, be ensured by the gravity, the weight of the support or the radiator acting as an opposing restoring force, in active (or inactive) configuration, all depending on the embodiment. retained), the force exerted on the support or the radiator by the AMF element.

  According to a second variant, the spring AMF spring / common return spring is replaced by a single spring AMF, double-acting type, that is to say, can work in compression or traction, depending on its temperature.

  In this case, the spring AMF is hooked, according to the embodiment retained at the screw head 16 on the one hand and the radiator 5 on the other hand, or the screw head 16 on the one hand and the support 3 (or 3 ') on the other hand, or the support 3 (or 3') on the one hand and the radiator 5 on the other hand, or the housing 2 on the one hand and the radiator 5 on the other hand go.

  To achieve a spring of AMF type double effect, the skilled person can get a spring AMF from the company indicated above. An education of spring is however necessary to achieve the features just described. This education can be carried out by AMF specialists according to the specifications defined by the person skilled in the art taking into account the temperature criteria selected.

  Thus, whatever the embodiment chosen among those which have just been described, or among others not described to which the invention would apply, it is possible to extend the range of normal operating temperatures. that is to say without overheating, or on the contrary without a malfunction due to the cold) of an electronic component generating thermal energy, in a simple and reliable manner by means of a passive actuator, that is to say whose operating energy is provided by its own elasticity and by the temperature variations of the spring 18 in AMF.

  This results in substantial energy savings compared to an active cooling system, especially the fan type, the disadvantages have already been presented in the introduction.

  Moreover, whatever the embodiment chosen, it is also conceivable to interpose between the radiator and the component (or the support) a buffer (not shown) in a phase change thermal contact material, which performs a interface facilitating between them the thermal conduction.

  To achieve such an interface, the skilled person may in particular refer to the document US-2002/096614.

Claims (15)

  1. System (1) comprising an electronic device (2) generating thermal energy and a radiator (5), this system (1) being able to adopt an active configuration in which the radiator (5) is in contact with the device electronics (2), and an inactive configuration in which the radiator (5) is spaced from the electronic device (2), the system further comprising a thermal actuator (7) adapted to control the passage of the system from its active configuration to its configuration inactive when the value of the temperature in the vicinity of the device (2) becomes lower than a first predetermined threshold value, and from its inactive configuration to its active configuration when the value of the temperature in the vicinity of the device (2) becomes greater than one second predetermined threshold value.   2. System (1) according to claim 1, wherein the actuator (7) comprises a member (18) of shape memory alloy.   The system (1) of claim 2, wherein said shape memory alloy member (18) is of the double-acting type.   The system (1) of claim 2, wherein said shape memory alloy member (18) is of the single-acting type.   5. System (1) according to claim 4, wherein the actuator (7) further comprises a return spring (21) coupled to the element (18) shape memory alloy.   6. System (1) according to one of claims 2 to   5, wherein said shape memory alloy member (18) is made of a nickel-titanium alloy, optionally comprising copper.   7. System (1) according to one of claims 1 to   6, which further comprises an interface made of a phase change thermal contact material interposed between the radiator and the electronic device.   8. System (1) according to one of claims 1 to   7, wherein the electronic device (2) comprises a support (3) carrying, on the radiator (3) side, an electronic component (4) generating thermal energy, and wherein the radiator (5) is mounted on the support (3) to the right of the component (4), being movable relative to the support (3) between an active position in which it is in contact with the electronic component (4), and an inactive position in which it is removed from said component (4).   9. System according to one of claims 1 to 7, wherein the electronic device comprises a support carrying, on the radiator side, an electronic component generating thermal energy, and wherein the support is mounted on the radiator with the component. electronic to the right thereof, being movable relative to the radiator between an active position in which the electronic component is in contact with the radiator, and an inactive position in which the electronic component is removed from the radiator.   10. System (1) according to one of claims 1 to 7, wherein the electronic device comprises a support carrying, on the opposite side to the radiator, an electronic component generating thermal energy, and wherein the radiator is mounted on the support to the component right, being movable relative to the support between an active position in which it is in contact with the support, and an inactive position in which it is spaced apart from said support.   11. System (1) according to one of claims 1 to 7, wherein the electronic device comprises a support (3) carrying, on the side opposite the radiator (5), an electronic component (4) generating thermal energy, and wherein the support (3) is mounted on the radiator (5) with the electronic component (4) at the right thereof, being movable relative to the radiator (5) between an active position in which the carrier (3) ) is in contact with the radiator (5), and an inactive position in which the support (3) is spaced from the radiator (5).   12. System according to claim 10 or 11, wherein the support (3) comprises thermal drainage wells (23) arranged in line with the electronic component (4).   13. System according to one of claims 1 to 7,   in which the electronic device (2) is an electronic box containing at least one electronic component generating thermal energy.   14. The system of claim 13, wherein the radiator (5) is mounted on the housing (2) being movable relative thereto between an active position in which it is in contact with the electronic housing (2), and an inactive position in which it is spaced from said housing (2).   15. The system of claim 13, wherein the housing (2) is mounted on a frame (3 ') on which the radiator is mounted to the right of the housing (2), being movable relative to the frame (3') between an active position-in which it is in contact with the electronic box (2), and an inactive position in which it is spaced from said housing (4 ').