JP7673438B2 - Heat Flow Switching Device - Google Patents

Description

The present invention relates to a heat flow switching device that can actively control heat flow by changing the thermal conductivity of a heat flow control element in response to temperature changes in an object to be controlled.

As a conventional thermal switch that changes thermal conductivity, for example, Patent Document 1 describes a thermal diode in which two thermal conductors with different thermal expansion coefficients are lightly brought into contact with each other, and the way heat flows varies depending on the direction of the temperature gradient. Patent Document 2 also describes a heat dissipation device that is a thermal switch that uses physical thermal contact due to thermal expansion.

Furthermore, Patent Document 3 describes a variable thermal conductivity device in which the thermal conductivity changes due to a reversible oxidation-reduction reaction that occurs when a voltage is applied to a compound.
Furthermore, Non-Patent Document 1 proposes a heat flow switching device in which a polyimide tape is sandwiched between two sheets of Ag ₂ S _0.6 Se _0.4 and an electric field is applied to change the thermal conductivity.

Patent No. 2781892 Patent No. 5402346 JP 2016-216688 A

Takuya Matsunaga and 4 others, "Fabrication of a heat flow switching element operated by bias voltage," 15th Annual Meeting of the Thermoelectric Society of Japan, September 13, 2018

The above conventional techniques still have the following problems.
In the techniques described in the above patent documents and non-patent documents, thermal conductivity is changed by physical thermal contact due to thermal expansion, by a redox reaction which is a chemical reaction, or by generating a thermally conductive charge at a material interface.
For elements that can change the thermal conductivity in this way, there is a demand for controlling thermal conduction in response to temperature changes in the controlled object, and actively controlling heat transport from the high temperature side to the low temperature side.

The present invention was made in consideration of the above-mentioned problems, and aims to provide a heat flow switching device that can change the thermal conductivity in response to changes in the temperature of the controlled object.

The present invention employs the following configuration to solve the above problems. That is, the heat flow switching device according to the first invention is characterized by comprising a heat flow control element section that controls heat flow by changing thermal conductivity, a temperature sensor section that detects the temperature of a controlled object or the heat flow control element section, and a control section that controls the heat flow control element section in response to the output of the temperature sensor section.

This heat flow switching device is equipped with a control unit that controls the heat flow control element unit in accordance with the output of a temperature sensor that detects a change in the temperature of the controlled object or the heat flow control element unit. Therefore, the temperature of the controlled object or the heat flow control element unit is directly monitored by the temperature sensor, while the control unit changes the thermal conductivity of the heat flow control element unit in accordance with the temperature detected by the temperature sensor, thereby actively controlling the heat flow and enabling temperature adjustments such as heat dissipation and insulation to be performed with high precision.
In addition, since the heat flow control element unit is used by being joined or contacted to the controlled object directly or via other members, when the temperature sensor unit detects the temperature of the heat flow control element unit, it also indirectly detects the temperature of the controlled object as the temperature of the heat flow control element unit, and therefore detects a temperature that reflects the state of the controlled object and the heat flow control element unit.

The heat flow switching device according to the second invention is characterized in that, in the first invention, the heat flow control element portion comprises an N-type semiconductor layer, an insulator layer stacked on the N-type semiconductor layer, and a P-type semiconductor layer stacked on the insulator layer.
That is, in this heat flow switching device, the heat flow control element part includes an N-type semiconductor layer, an insulator layer laminated on the N-type semiconductor layer, and a P-type semiconductor layer laminated on the insulator layer, so that when a voltage is applied to the P-type semiconductor layer and the N-type semiconductor layer, charges are induced mainly at the interface between the P-type semiconductor layer and the N-type semiconductor layer and the insulator layer, and the thermal conductivity changes as the charges carry heat, so that it is possible to electrically change the thermal conductivity of the heat flow control element part. In particular, charges induced by an external voltage (input voltage to the heat flow control element part) are generated both at the interface between the N-type semiconductor layer and the insulator layer and its vicinity, and at the interface between the P-type semiconductor layer and the insulator layer and its vicinity, so that a large amount of charges is generated, and a large change in thermal conductivity and high thermal responsiveness can be obtained. In addition, since it is a mechanism that changes thermal conductivity electrically and physically without using a chemical reaction mechanism, it is possible to immediately transition to a state where thermal conductivity has changed, and good thermal responsiveness can be obtained.
In addition, since the amount of charge induced at the interface changes depending on the magnitude of the external voltage (input voltage to the heat flow control element unit), it is possible to adjust the thermal conductivity by adjusting the external voltage (input voltage to the heat flow control element unit), making it possible to actively control the heat flow via the heat flow control element unit.
In addition, since the insulator layer is an insulator and no current is generated when a voltage is applied, no Joule heat is generated, making it possible to actively control the heat flow without self-heating.

A heat flow switching device according to a third invention is the heat flow switching device according to the first or second invention, characterized in that the temperature sensing element portion is an NTC thermistor.
That is, in this heat flow switching device, since the temperature sensing element is an NTC thermistor, it exhibits negative temperature characteristics and the electrical resistance value decreases continuously with an increase in temperature, so that in an electric circuit incorporating an NTC thermistor element and a resistor element for resistance division, the output voltage gradually decreases as the temperature increases as a characteristic of the NTC thermistor, so that the control unit can adjust the input voltage to the heat flow control element in response to this output change, gradually increasing or decreasing the thermal conductivity. Since the voltage output from the NTC thermistor changes continuously with temperature, the input voltage to the heat flow control element can also change continuously with temperature, enabling highly accurate thermal conduction tuning and enabling the temperature of the controlled object to be adjusted with high accuracy.

A fourth aspect of the present invention is the heat flow switching device according to the first or second aspect of the present invention, characterized in that the temperature sensitive element portion is a PTC thermistor.
That is, in this heat flow switching device, the temperature-sensitive element is a PTC thermistor, which exhibits a positive temperature characteristic, and when the temperature falls below a certain temperature, the electrical resistance value increases rapidly as the temperature rises, and in an electric circuit incorporating a PTC thermistor element and a resistor element for resistance division, the output voltage drops rapidly when the temperature falls below a certain temperature as a characteristic of the PTC thermistor, so that the control unit can rapidly change the thermal conductivity of the heat flow control element in response to this rapid change in output. Since the voltage output from the PTC thermistor changes rapidly with respect to temperature at a certain temperature, the input voltage to the heat flow control element can also be rapidly changed, and the thermal conductivity can be rapidly changed. Therefore, the state of heat transport flowing from the high temperature side to the low temperature side is rapidly changed at a certain temperature, making it possible to function as a heat flow switch.

A heat flow switching device according to a fifth aspect of the present invention is the heat flow switching device according to the first or second aspect of the present invention, characterized in that the temperature sensing element portion is a CTR thermistor.
That is, in this heat flow switching device, since the temperature-sensitive element is a CTR thermistor, when a certain temperature is exceeded, the electrical resistance value decreases rapidly as the temperature rises, and therefore, in an electric circuit incorporating a CTR thermistor element and a resistor element for resistance division, the output voltage drops rapidly when the temperature exceeds a certain temperature as a characteristic of the CTR thermistor, and the control unit can rapidly increase the thermal conductivity of the heat flow control element in response to this rapid change in output. Since the voltage output from the CTR thermistor changes rapidly with respect to temperature at a certain temperature, the input voltage to the heat flow control element can also be rapidly changed, and the thermal conductivity can be rapidly changed. Therefore, the state of heat transport flowing from the high temperature side to the low temperature side is rapidly changed at a certain temperature, making it possible to function as a heat flow switch.

The heat flow switching device of the sixth invention is characterized in that, in any of the first to fifth inventions, the temperature sensing element portion comprises a thin film thermistor portion formed of a thermistor material and a pair of opposing electrodes formed opposite at least one of the top and bottom of the thin film thermistor portion, and the thin film thermistor portion is laminated on the heat flow control element portion.
That is, in this heat flow switching device, the thin-film thermistor portion is laminated on the heat flow control element portion, and as the thin-film thermistor portion comes into surface contact with the heat flow control element portion, the thermal resistance is reduced, making it possible to detect temperature with high accuracy while also achieving a thin device.

The heat flow switching device of the seventh invention, in any of the first to sixth inventions, is characterized in that it is provided with a heat flow sensor unit joined to the heat flow control element unit and capable of detecting at least one of the direction of heat flow and heat flux, and the control unit controls the heat flow control element unit in accordance with at least one of the direction of heat flow and heat flux detected by the heat flow sensor unit.
That is, in this heat flow switching device, a heat flow sensor unit is attached to the heat flow control element unit and capable of detecting the direction of heat flow and heat flux (heat flow density) as an output voltage, and the control unit controls the heat flow control element unit according to the direction of heat flow and heat flux detected by the heat flow sensor unit, so that the thermal conductivity can be controlled while checking the direction of heat flow and heat flux by the heat flow sensor unit. The heat flow sensor can detect the direction of heat flow based on the sign of the output voltage. Since the voltage output from the heat flow sensor changes continuously with respect to the heat flow, the input voltage to the heat flow control element unit can also change continuously with respect to the heat flow, making it possible to continuously control the heat flow. Therefore, even if the direction of the heat flux and heat flow input/output from an object in thermal contact with the heat flow switching device changes over time, heat flow switching with extremely high thermal responsiveness is possible according to the state of heat conduction at each time, and it becomes possible to adjust the heat transport state of the controlled object with high precision.

The heat flow switching device according to an eighth invention is any of the first to seventh inventions, characterized in that the temperature sensing element portion and the heat flow control element portion are joined to each other and integrated.
In other words, in this heat flow switching device, the temperature sensing element section and the heat flow control element section are joined together and integrated, thereby increasing the time response of the temperature sensing element section to detect the temperature of the heat flow control element section, making it possible to reduce the overall size and facilitating installation work on the object to be controlled.

According to the present invention, the following effects are obtained.
In other words, the heat flow switching device of the present invention is equipped with a control unit that controls the heat flow control element unit in accordance with the output of the temperature sensing element unit that detects a temperature change in the controlled object or the heat flow control element unit, and therefore, by directly monitoring the temperature of the controlled object or the heat flow control element unit using the temperature sensing element unit while changing the thermal conductivity of the heat flow control element unit in accordance with the temperature detected by the temperature sensing element unit using the control unit, it is possible to perform temperature adjustments such as heat dissipation and insulation with high precision.
Therefore, the heat flow switching device of the present invention makes it possible to perform more precise temperature adjustment by controlling the surrounding thermal environment, and to appropriately switch between insulation and heat dissipation in an environment that changes from moment to moment, such as an environment where heat builds up and cannot be discharged.

1 is a schematic perspective view showing a first embodiment of a thermal flow switching device according to the present invention; 1 is a cross-sectional view showing a heat flow switching device in a first embodiment. FIG. 2 is a plan view showing a temperature sensing element unit in the first embodiment. 4 is a conceptual diagram for explaining the principle of a heat flow control element portion in the first embodiment. FIG. FIG. 2 is an explanatory diagram showing an electric circuit and a thermal circuit of the heat flow switching device in the first embodiment. Graph (a) shows the relationship between temperature and output voltage of a temperature-sensing element unit that employs an NTC thermistor in the first embodiment, and graph (b) shows the relationship between the input voltage to the heat flow control element unit and the thermal conductivity of the heat flow control element unit, as an example of this case. In the first embodiment, graph (a) shows the relationship between temperature and output voltage of a temperature-sensing element unit that uses a CTR thermistor, graph (b) shows the relationship between temperature and output voltage of a temperature-sensing element unit that uses a PTC thermistor, and, as an example of these cases, graph (c) shows the relationship between the input voltage to the heat flow control element unit and the thermal conductivity of the heat flow control element unit. FIG. 4 is a cross-sectional view showing a second embodiment of a thermal flow switching device according to the present invention. FIG. 11 is a plan view showing a heat flow sensor unit with a protective film on the upper surface removed in the second embodiment. 10 is a graph showing an output voltage according to a heat flux of a heat flow sensor unit in the second embodiment.

The first embodiment of the heat flow switching device according to the present invention will be described below with reference to Figures 1 to 7. Note that in the drawings used in the following description, the scale has been appropriately changed as necessary to make each part recognizable or easily recognizable.

As shown in Figures 1 and 2, the heat flow switching device 1 of this embodiment comprises a heat flow control element unit 10 that controls heat flow by changing thermal conductivity, a temperature sensing element unit 11A that detects the temperature of the controlled object or the heat flow control element unit 10, and a control unit C that controls the heat flow control element unit 10 in accordance with the output of the temperature sensing element unit 11A.
The heat flow control element section 10 includes an N-type semiconductor layer 3 , an insulator layer 4 laminated on the N-type semiconductor layer 3 , and a P-type semiconductor layer 5 laminated on the insulator layer 4 .
The temperature sensitive element section 11A and the heat flow control element section 10 are joined together and integrated.

The temperature sensitive element 11A is an NTC thermistor, a PTC thermistor or a CTR thermistor.
2 and 3, the temperature sensing element 11A includes a thin film thermistor portion 11a made of a thermistor material, and a pair of counter electrodes 11b formed opposite at least one of the upper and lower portions of the thin film thermistor portion 11a. An insulating protective film 11c is laminated on the thin film thermistor portion 11a and the counter electrodes 11b.
In this embodiment, a pair of counter electrodes 11b are disposed on the thin film thermistor portion 11a so as to face each other, as shown in Fig. 3. A pair of lead wires 8a are connected to the pair of counter electrodes 11b.

The thin film thermistor section 11 a is laminated on the lower part of the heat flow control element section 10 .
In this embodiment, the temperature sensitive element portion 11A is provided on the low temperature side of the heat flow control element portion 10.
That is, in this embodiment, the heat flow direction is set to the stacking direction, and the temperature sensing element section 11A is provided below the heat flow control element section 10.

As shown in FIG. 2 , the heat flow switching device 1 of this embodiment includes an upper high thermal conductivity section 18 provided at the top of the heat flow control element section 10, a lower high thermal conductivity section 2 (substrate) provided at the bottom of the heat flow control element section 10, and a peripheral insulation section 19 provided to cover the peripheral edges of the N-type semiconductor layer 3, the insulator layer 4, and the P-type semiconductor layer 5.
The upper highly thermally conductive portion 18 and the lower highly thermally conductive portion 2 are formed of a material having a higher thermal conductivity than the peripheral insulation portion 19 .
The temperature-sensing element portion 11A is formed on the lower high thermal conductivity portion 2, and the heat flow control element portion 10 is formed on the temperature-sensing element portion 11A with a protective film 11c in between, so that the temperature-sensing element portion 11A is joined to the heat flow control element portion 10 via the protective film 11c.

Furthermore, the heat flow switching device 1 of this embodiment includes an N-side electrode 6 connected to the N-type semiconductor layer 3 , and a P-side electrode 7 connected to the P-type semiconductor layer 5 .
As the film formation method, various film formation techniques such as a sputtering method, a molecular beam epitaxy method (MBE method) and the like are adopted.
When a voltage can be applied directly to the N-type semiconductor layer 3 and the P-type semiconductor layer 5, the N-side electrode 6 and the P-side electrode 7 are not necessary.

Further, lead wires 6a and 7a are connected to the N-side electrode 6 and the P-side electrode 7, respectively.
An external power source (not shown) in the control unit C is connected to the N-side electrode 6 and the P-side electrode 7 , and a voltage is applied to the heat flow control element unit 10 .
The above-mentioned lower highly thermally conductive portion 2 is an insulating base material, and the lower temperature sensitive element portion 11A and the heat flow control element portion 10 are laminated in this order on this base material (lower highly thermally conductive portion 2).

The upper highly thermally conductive portion 18 is formed from a highly thermally conductive material such as silicon-based resin (silicone), and the lower highly thermally conductive portion 2, which is the base material, is a highly thermally conductive substrate formed from, for example, alumina.
The outer peripheral heat insulating portion 19 is made of a low thermal conductive material such as epoxy resin.
The peripheral insulation section 19 covers the periphery of the uppermost insulating layer 4 while leaving the uppermost insulating layer 4 exposed, and the upper high thermal conductivity section 18 is formed on the upper part so as to contact the exposed uppermost insulating layer 4.
The peripheral heat insulating portion 19 is also formed to cover the N-side electrode 6 and the P-side electrode 7 which are disposed on the outer periphery of each layer and connected to the lead wires 6a and 7a.

The heat flow control element section 10 is formed by stacking a plurality of N-type semiconductor layers 3 and P-type semiconductor layers 5 alternately with an insulating layer 4 interposed therebetween.
That is, an insulator layer 4 is first formed on the lower thermosensitive element portion 11A, and then N-type semiconductor layers 3 and P-type semiconductor layers 5 are repeatedly laminated on top of the insulator layer 4 in this order with the insulator layer 4 interposed therebetween to form a laminate of three N-type semiconductor layers 3, three P-type semiconductor layers 5, and seven insulator layers 4.

Each N-type semiconductor layer 3 is connected to an N-side connector 3a provided at the base end, and an N-side electrode 6 is formed on a part of the N-side connector 3a. Each P-type semiconductor layer 5 is connected to a P-side connector 5a provided at the base end, and a P-side electrode 7 is formed on a part of the P-side connector 5a.
Each of the above layers is patterned using a metal mask. The N-type semiconductor layer 3, the P-type semiconductor layer 5, and the insulating layer 4 are laminated in multiple layers by forming the layers while shifting the position of the metal mask.

The N-type semiconductor layer 3 and the P-type semiconductor layer 5 are formed as thin films with a thickness of less than 1 μm. In particular, the charge e generated at the interface with the insulator layer 4 and in its vicinity mainly accumulates in a thickness range of 5 to 10 nm, so it is more preferable that the N-type semiconductor layer 3 and the P-type semiconductor layer 5 are formed with a film thickness of 100 nm or less. It is preferable that the N-type semiconductor layer 3 and the P-type semiconductor layer 5 have a film thickness of 5 nm or more.

The insulator layer 4 is preferably 40 nm or more thick, and is set to a thickness that does not cause dielectric breakdown. If the insulator layer 4 is too thick, it becomes difficult to transport the charge e, so it is preferable that the thickness is less than 1 μm. In FIG. 4, the type of charge e generated at the interface between the N-type semiconductor layer 3 and the insulator layer 4 and in the vicinity thereof is an electron, and is represented by a white circle. The type of charge e generated at the interface between the P-type semiconductor layer 5 and the insulator layer 4 and in the vicinity thereof is a hole, and is represented by a black circle (a hole is a hole created by a shortage of electrons in the valence band of a semiconductor, and appears to have a relatively positive charge).

The N-type semiconductor layer 3 and the P-type semiconductor layer 5 are preferably made of a degenerate semiconductor material having low lattice thermal conductivity, and examples of the material that can be used include a thermoelectric material such as SiGe, a nitride semiconductor such as CrN, and an oxide semiconductor such as _VO2 . The N-type and P-type electrical conductivity are set by adding N-type and P-type dopants to the semiconductor material, for example.

The insulator layer 4 is preferably an insulating material with low thermal conductivity, and may be an insulator such as _SiO2 , a dielectric such as _HfO2 or _BiFeO3 , or an organic material such as polyimide (PI). In particular, a dielectric material with a high dielectric constant is preferable.
The N-side electrode 6 and the P-side electrode 7 are made of a metal such as Mo or Al.

As shown in FIG. 4, in the heat flow switching device 1 of this embodiment, by applying an electric field (voltage) to the heat flow control element section 10, thermally conductive charges e are generated at the interface between the N-type semiconductor layer 3 and the insulator layer 4 and in the vicinity thereof, and the generated charges e carry heat and change the thermal conductivity.
The thermal conductivity is calculated using the following formula:
Thermal conductivity = lattice thermal conductivity + electronic thermal conductivity

Of these two types of thermal conductivity, it is the electronic thermal conductivity that changes according to the amount of charge generated by the application of an electric field (voltage). Therefore, in this embodiment, a material with a small lattice thermal conductivity is suitable for achieving a larger change in thermal conductivity. Therefore, for all of the N-type semiconductor layer 3, the insulator layer 4, and the P-type semiconductor layer 5, a material with a small lattice thermal conductivity, i.e., a small thermal conductivity, is selected.

The thermal conductivity of the material constituting each layer of this embodiment is preferably low, 5 W/mK or less, and more preferably 1 W/mK or less, and the materials described above can be used.
Moreover, the electronic thermal conductivity increases according to the amount of electric charge e generated in response to an applied external electric field (voltage).
In addition, since electric charge e is generated at the interfaces between the N-type semiconductor layer 3 and the P-type semiconductor layer 5 and the insulator layer 4, the amount of electric charge e generated can be increased by increasing the total area of the interfaces.

The thermal conductivity is measured, for example, by the pulsed light heating thermoreflectance method, which involves instantaneously heating a thin film sample formed on a substrate with a pulsed laser and measuring the rate at which the surface temperature drops or rises due to thermal diffusion into the thin film to determine the thermal diffusivity or thermal effusivity of the thin film in the thickness direction. Among the pulsed light heating thermoreflectance methods, the method of directly measuring thermal diffusivity (rear heating/surface temperature measurement (RF) method) requires the use of a transparent substrate through which the pulsed laser can pass. If the substrate is not transparent, the thermal conductivity is measured by the surface heating/temperature measurement (FF) method, which measures the thermal effusivity and converts it into thermal conductivity. Note that a metal film is required for this measurement, and Mo, Al, etc. are used.

As shown in Figure 3, the temperature sensing element unit 11A has a pair of opposing electrodes 11b each having a comb shape with a plurality of comb portions 11d protruding in opposing directions, and the comb portions 11d of one opposing electrode 11b and the comb portions 11d of the other opposing electrode 11b are arranged alternately.
The counter electrode 11b may be made of various metal films, such as a single layer of Cr film or a laminated metal film of Cr film and Au film.

For the thin-film thermistor section 11a, an NTC thermistor (an element that exhibits negative temperature characteristics and whose electrical resistance decreases exponentially with increasing temperature) is generally used, but in order to quickly detect abnormal temperatures, a PTC thermistor (an element that exhibits positive temperature characteristics and whose electrical resistance increases with increasing temperature, or an element that exhibits positive temperature characteristics and whose electrical resistance increases rapidly with increasing temperature above a certain temperature) or a CTR thermistor (similar to an NTC thermistor in that it has a negative temperature coefficient, but whose electrical resistance decreases rapidly above a certain temperature range) is used.

As the NTC thermistor material, oxide materials are generally known, such as (Mn,Co,Ni _{)3O4 having} a spinel crystal structure and (La,Ca)(Cr,Mn) _O3 having a perovskite crystal structure. However, as the thin film thermistor portion 11a in this embodiment, a material made of a metal _nitride having a hexagonal wurtzite type single phase and represented by the general formula: _MxAyNz (wherein M is at least one of Ti, V, _Cr , Mn, Fe, Co, Ni and Cu, and A is Al or (Al and Si), 0.70≦y/(x+y)≦0.98, 0.4≦z≦0.5, x+y+z=1) is preferred. In this embodiment, the thin-film thermistor portion 11a is made of a metal nitride having a hexagonal wurtzite single phase and represented by the general formula Ti _x Al _y N _z (where 0.70≦y/(x+y)≦0.98, 0.4≦z≦0.5, and x+y+z=1).
In the case of Ti--Al--N, the thin film thermistor portion 11a is formed by reactive sputtering in a nitrogen-containing atmosphere using a Ti--Al alloy sputtering target.

The wurtzite crystal structure is in the hexagonal space group _P63mc (No. 186), with M and A belonging to the same atomic site (M represents at least one of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, and A represents Al or (Al and Si)), and is in a so-called solid solution state. The wurtzite structure has a vertex-connected structure of an (M,A) _N4 tetrahedron, with N (nitrogen) being the nearest site to the (M,A) site, and (M,A) having nitrogen 4 coordination.

In addition to Ti, V (vanadium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt), Ni (nickel), and Cu (copper) can also exist at the same atomic site as Ti in the above crystal structure, and can be the element M. The effective ionic radius is a physical property value that is often used to grasp the distance between atoms, and when using the literature value of the particularly well-known Shannon ionic radius, it can be theoretically inferred that a wurtzite type M _x A _y N _z (wherein M represents at least one of Ti, V, Cr, Mn, Fe, Co, Ni, and Cu, and A represents Al or (Al and Si)) can be obtained.
The effective ionic radii of each ion species of Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Si are shown in Table 1 below (see RD Shannon, Acta Crystallogr., Sect. A, 32, 751 (1976)).

In addition, Ti-Al-N is a nitride insulator having a wurtzite crystal structure, and the Al site of Al-N is partially substituted with Ti to perform carrier doping, thereby increasing electrical conductivity, thereby obtaining thermistor characteristics. However, since V, Cr, Mn, Fe, Co, Ni and Cu belong to the same 3d transition metal element as Ti, it is possible to obtain thermistor characteristics in the wurtzite M _x A _y N _z (wherein M represents at least one of Ti, V, Cr, Mn, Fe, Co, Ni and Cu, and A represents Al or (Al and Si)).

As described above, an NTC thermistor, a PTC thermistor, a CTR thermistor or various thermistor materials are applied to the thin film thermistor portion 11a, and generally, an NTC thermistor that shows a negative temperature characteristic and whose electrical resistance value decreases continuously with an increase in temperature is adopted. Note that, if a PTC thermistor whose electrical resistance value increases rapidly with an increase in temperature when a certain temperature is exceeded or a CTR thermistor whose electrical resistance value decreases rapidly with an increase in temperature when a certain temperature is exceeded is used as the thin film thermistor portion 11a, it becomes possible to more quickly detect an abnormal temperature of the controlled object.
The PTC thermistor material used is one that exhibits positive temperature characteristics and whose electrical resistance increases rapidly as the temperature rises above a certain temperature. Examples of such materials include _BaTiO3 , _SrTiO3 , and materials in which trace amounts of metallic elements such as Pb are substituted into these materials, as well as conductive polymers (polymers in which conductive particles are dispersed; when the polymer melts, the conductive powder is no longer in contact and the electrical resistance increases).
As the CTR thermistor material, a metal-insulator transition material is used, whose electrical resistance value decreases rapidly as the temperature increases above a certain temperature. For example, _VO2 and systems in which this material is partially substituted with trace amounts of metal elements are used.
Thin films made of the above PTC thermistor material and CTR thermistor material can be produced by various film-forming techniques such as sputtering, sol-gel method, and printing method.

In this embodiment, for example as shown in Fig. 5, when the heat flow control element unit 10 is arranged in contact with a high-temperature object H and the temperature sensing element unit 11A is arranged in contact with a low-temperature object L, a temperature difference occurs between the high-temperature object H and the low-temperature object L, and a heat flow occurs from the high-temperature object H to the low-temperature object L. At this time, the control unit C changes the thermal conductivity of the heat flow control element unit 10 according to the temperature detected by the temperature sensing element unit 11A. Note that when the purpose is to cool the high-temperature object H, the high-temperature object H becomes the controlled object, and when the purpose is to heat the low-temperature object L, the low-temperature object L becomes the controlled object. There are also cases where both become controlled objects, such as when the main purpose is heat exchange.
The control unit C converts the output voltage Vout from the temperature sensing element unit 11A to an input voltage Vin based on the output voltage Vout from the temperature sensing element unit 11A using a converter C1 in order to control the heat flow control element unit 10, and applies this to the heat flow control element unit 10 to change the thermal conductivity of the heat flow control element unit 10. In other words, it is possible to change the thermal conductivity of the heat flow control element unit 10 according to the output voltage Vout from the temperature sensing element unit 11A. In this case, the thermal circuit HC transfers heat from the high-temperature object H, which is a heat source, to the temperature sensing element unit 11A and the low-temperature object L through a variable thermal resistor R1 according to the thermal conductivity of the heat flow control element unit 10.

At this time, the temperature in the temperature sensor unit 11A changes, and this temperature change is input again to the control unit C as an output voltage Vout according to the changed resistance R2 in the temperature sensor unit 11A, and is output again to the heat flow control element unit 10 via the converter C1 as a control input voltage Vin according to the output voltage Vout. In this way, the control unit C repeatedly adjusts the thermal conductivity of the heat flow control element unit 10 according to the detected temperature of the temperature sensor unit 11A. That is, the temperature sensor unit 11A outputs a voltage according to the input heat, and in response to this, a control voltage is input to the heat flow control element unit 10 via the control unit C, and heat is output to the low-temperature object L with a thermal conductivity according to this input voltage.

When the temperature sensing element 11A is an NTC thermistor, the output voltage of the temperature sensing element 11A has a characteristic of gradually decreasing with increasing temperature, as shown in Fig. 6(a). In this case, the control unit C sets the input voltage of the heat flow control element 10 to increase with decreasing output voltage of the temperature sensing element 11A, as shown in Fig. 6(b).
Since the output voltage from the NTC thermistor changes continuously with temperature, the input voltage to the heat flow control element section 10 can also change continuously with temperature, and it is possible to continuously increase or decrease the thermal conductivity of the heat flow control element section 10. Furthermore, by finely adjusting the output voltage of the temperature sensing element section 11A, highly accurate thermal conductivity tuning is possible, making it possible to adjust the temperature of the controlled object with high accuracy.

When the temperature sensor 11A is a CTR thermistor, the output voltage of the temperature sensor 11A drops suddenly when the temperature exceeds a certain level, as shown in Fig. 7(a). In this case, the control unit C sets the input voltage of the heat flow control element 10 to rise suddenly, as shown in Fig. 7(c), in response to the sudden drop in the output voltage of the temperature sensor 11A.
Since the output voltage from the CTR thermistor changes rapidly with temperature above a certain temperature, the input voltage to the heat flow control element section 10 can also be changed rapidly, and the thermal conductivity can be changed rapidly. Therefore, the thermal conductivity of the heat flow control element section 10 can be increased or decreased rapidly above a certain temperature. For example, the thermal conductivity of the heat flow control element section 10 can be increased rapidly above a certain temperature, allowing it to function as a heat dissipation switch.

Furthermore, when the temperature sensing element 11A is a PTC thermistor, the output voltage of the temperature sensing element 11A has the characteristic of dropping rapidly below a certain temperature, as shown in Fig. 7(b). In this case, the control unit C sets the input voltage of the heat flow control element 10 to drop rapidly, for example, as shown in Fig. 7(c), in response to the sudden drop in the output voltage of the temperature sensing element 11A.
Since the output voltage from the PTC thermistor changes rapidly with temperature above a certain temperature, the input voltage to the heat flow control element section 10 can also be changed rapidly, and the thermal conductivity can be changed rapidly. Therefore, the thermal conductivity of the heat flow control element section 10 can be increased or decreased rapidly above a certain temperature. For example, it becomes possible to rapidly decrease the thermal conductivity of the heat flow control element section 10 below a certain temperature, and have it function as a thermal insulation switch.

In this way, the heat flow switching device 1 of this embodiment is equipped with a control unit C that controls the heat flow control element unit 10 in response to the output of the temperature sensing element unit 11A, so that the heat flow can be actively controlled by directly monitoring the temperature with the temperature sensing element unit 11A while the control unit C changes the thermal conductivity of the heat flow control element unit 10 in response to the temperature detected by the temperature sensing element unit 11A, thereby enabling highly accurate temperature adjustment such as heat dissipation and insulation. In other words, in the heat flow switching device 1 of this embodiment, the control unit C controls the heat flow control element unit 10 using a signal obtained by amplifying or inverting and amplifying the output of the temperature sensing element unit 11A.

In addition, since the heat flow control element unit 10 includes an N-type semiconductor layer 3, an insulator layer 4 laminated on the N-type semiconductor layer 3, and a P-type semiconductor layer 5 laminated on the insulator layer 4, when a voltage is applied to the P-type semiconductor layer 5 and the N-type semiconductor layer 3, an electric charge e is induced mainly at the interface between the P-type semiconductor layer 5 and the N-type semiconductor layer 3 and the insulator layer 4, and this electric charge e carries heat, causing a change in thermal conductivity.

In particular, since electric charge e induced by an external voltage (input voltage to the heat flow control element section 10) is generated both at and near the interface between the N-type semiconductor layer 3 and the insulator layer 4, and at and near the interface between the P-type semiconductor layer 5 and the insulator layer 4, a large amount of electric charge is generated, and a large change in thermal conductivity and high thermal responsiveness can be obtained. In addition, since this is a mechanism that physically changes the thermal conductivity without using a chemical reaction mechanism, it is possible to immediately transition to a state where the thermal conductivity has changed, and good thermal responsiveness can be obtained.
In addition, since the amount of charge induced at the interface changes depending on the magnitude of the external voltage (input voltage to the heat flow control element unit 10), it is possible to adjust the thermal conductivity by adjusting the external voltage (input voltage), making it possible to actively control the heat flow via the heat flow control element unit 10.

Furthermore, since the N-type semiconductor layers 3 and the P-type semiconductor layers 5 are alternately stacked with the insulator layer 4 in between, multiple interfaces are formed between the N-type semiconductor layers 3 and the P-type semiconductor layers 5 and the insulator layer 4, and a large number of electric charges e are induced, thereby making it possible to greatly change the thermal conductivity.
In addition, since the highly thermally conductive lower portion 2, which is the base material, is an insulator and no current is generated when a voltage is applied, no Joule heat is generated. Therefore, it is possible to actively control the heat flow without self-heating.

In addition, since the thin-film thermistor section 11a is laminated on the heat flow control element section 10, the thin-film thermistor section 11a comes into surface contact with the heat flow control element section 10, lowering the thermal resistance, enabling highly accurate temperature detection while also enabling a thinner device.

Furthermore, when the temperature-sensing element unit 11A is an NTC thermistor, a characteristic of an NTC thermistor is that the output voltage gradually decreases as the temperature increases, and therefore the control unit C can adjust the input voltage to the heat flow control element unit 10 in response to this change in output, gradually increasing or decreasing the thermal conductivity, enabling high-precision thermal conductivity tuning and making it possible to adjust the temperature of the controlled object with high precision.
Furthermore, if the temperature-sensing element 11A is a PTC thermistor, the output voltage drops suddenly when the temperature falls below a certain level, and the control unit C responds to this sudden drop in output by suddenly decreasing the thermal conductivity of the heat flow control element 10, causing a sudden change in the state of heat transport from the high temperature side to the low temperature side at a certain temperature, thereby enabling the element to function as a heat flow switch. For example, the element can function as an insulating switch above a certain temperature.
Furthermore, when the temperature-sensing element 11A is a CTR thermistor, the output voltage drops suddenly when the temperature exceeds a certain level, and the control unit C responds to this sudden drop in output by suddenly increasing the thermal conductivity of the heat flow control element 10, causing a sudden change in the state of heat transport from the high temperature side to the low temperature side at a certain temperature, thereby enabling the element to function as a heat flow switch. For example, the element can function as a heat dissipation switch at a certain temperature or higher.
Furthermore, since the temperature-sensing element section 11A and the heat flow control element section 10 are joined together and integrated, the time response of the temperature-sensing element section 11A to detect the temperature of the heat flow control element section 10 is faster, the overall size can be reduced, and installation work on the object to be controlled is made easier.

Thermosensitive element unit 11A may be provided on both the high temperature side and the low temperature side of the heat flow control element unit 10. In this case, the heat flow can be adjusted by the heat flow control element unit 10 using an external voltage (input voltage) that corresponds to the temperatures detected on both the high temperature side and the low temperature side. Therefore, even if the temperature of the object in thermal contact with the heat flow switching device 1 changes over time, heat flow switching with extremely high thermal responsiveness is possible according to the state of thermal conduction at each time.

Next, a second embodiment of the heat flow switching device according to the present invention will be described below with reference to Figures 8 to 10. In the following description of the embodiment, the same components as those described in the above embodiment are given the same reference numerals, and the description thereof will be omitted.

The difference between the second embodiment and the first embodiment is that in the first embodiment, only an upper high thermal conductivity section 18 is formed on the upper part of the heat flow control element section 10, whereas in the heat flow switching device 21 of the second embodiment, as shown in Figures 8 and 9, a heat flow sensor section 22 capable of detecting at least one of the direction of heat flow and heat flux (heat flow density) is provided on the heat flow control element section 10.
That is, the heat flow switching device 21 of the second embodiment is provided with a heat flow sensor unit 22 joined to the heat flow control element unit 10 and capable of detecting at least one of the direction of heat flow and heat flux, and a control unit C controls the heat flow control element unit 10 in accordance with at least one of the direction of heat flow and heat flux detected by the heat flow sensor unit 22.

The heat flow sensor section 22 includes a plurality of anomalous Nernst material films 22a that provide the anomalous Nernst effect and that extend in the same direction and are arranged parallel to each other in the planar direction of the heat flow control element section 10, and connection wiring 22b that electrically connects the plurality of anomalous Nernst material films 22a in series.
Electrode wiring 22c is connected to both ends of the series-connected anomalous Nernst material films 22a.
The connection wiring 22b and the electrode wiring 22c are preferably made of an Au film having a small electromotive force, but a laminated metal film of a Cr film and an Au film may also be used.

The anomalous Nernst material film 22 a is laminated on the heat flow control element section 10 .
That is, an anomalous Nernst material film 22 a , a connection wiring 22 b and an electrode wiring 22 c are formed on an upper high thermal conductive portion 18 formed on an upper portion of the heat flow control element portion 10 .
As shown in FIG. 9, the plurality of anomalous Nernst material films 22a are formed in strip or line shapes arranged parallel to one another in the direction of a voltage generated in response to a heat flow in the thickness direction.
It should be noted that the obtainable voltage can be increased by increasing the number and length of the anomalous Nernst material films 22a connected in series.

The anomalous Nernst material film 22a can be made of materials such as Fe--Al, Fe--Pt, Co--Pt, ferromagnetic materials with large spontaneous magnetization such as Heusler alloy materials such as _Co2MnGa , _Co2MnAl , _Co2MnSi , and antiferromagnetic materials such as _Mn2Sn .
In the anomalous Nernst material film forming step, for example, an Fe--Al alloy sputtering target is used to perform sputtering to form the anomalous Nernst material film 22a.

In the second embodiment, as shown in FIG. 8, the control unit C and the heat flow sensor unit 22 are connected. The control unit C controls the input voltage to the heat flow control element unit 10 according to the output voltage from the heat flow sensor unit 22 as well as the temperature sensor unit 11A. That is, as shown in FIG. 10, the heat flow sensor unit 22 has a characteristic in which the sign of the output voltage is inverted between positive and negative depending on the heat flow direction. For example, when the output voltage of the heat flow sensor unit 22 is positive, the control unit C applies an input voltage to the heat flow control element unit 10 to increase the thermal conductivity, but when the output voltage of the heat flow sensor unit 22 is negative, it determines that the heat flow direction has been reversed, and performs control not to apply an input voltage to the heat flow control element unit 10 and to maintain a low thermal conductivity.

In this way, the heat flow switching device 21 of the second embodiment is equipped with a heat flow sensor unit 22 that is joined to the heat flow control element unit 10 and can detect at least one of the heat flow direction and heat flux, so that the thermal conductivity can be controlled while checking at least one of the heat flow direction and heat flux using the heat flow sensor unit 22. Therefore, even if the heat flux input/output from an object in thermal contact with the heat flow switching device 21 changes over time, heat flow switching with extremely high thermal responsiveness is possible according to the state of thermal conduction at each time.

In addition, since the anomalous Nernst material film 22a is laminated on the heat flow control element section 10, the anomalous Nernst material film 22a comes into surface contact with the heat flow control element section 10, thereby reducing the thermal resistance, making it possible to detect the direction of heat flow with high accuracy and achieving a thinner device.
In particular, by arranging a plurality of anomalous Nernst material films 22a in a planar direction, in which a voltage is generated in a direction perpendicular to the direction of heat flow, and electrically connecting them in series, the voltage can be amplified without increasing the thickness by arranging the anomalous Nernst material films 22a with a large number of wirings.

The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

For example, it is preferable to employ a temperature-sensing element having a thin-film thermistor portion to reduce thermal resistance, but a temperature-sensing element having a thermocouple, a resistance temperature detector, a chip thermistor, or the like may also be employed. In addition, various metal oxide materials and various metal nitride materials can be employed as the thin-film thermistor portion. In addition, the temperature-sensing element may be in non-contact with the controlled object or the heat flow control element portion, and may detect the temperature using an infrared sensor or the like.

Furthermore, the heat flow control element may be of any other known type, provided that the thermal conductivity is variable.
For example, a heat flow control element unit whose thermal conductivity changes according to a magnetic field may be used. That is, a heat flow control element unit using a magnetocaloric material whose temperature changes when a magnetic field is applied and removed (for example, a magnetocaloric material such as an FeRh alloy, Co-Mn-Si-Ge, or Ni-Mn-Sn alloy as described in Japanese Patent No. 5966740) may be used. In this case, the thermal conductivity can be controlled by changing the magnetic field applied to the magnetocaloric material of the heat flow control element unit by the control unit according to the output of the temperature sensing element unit.

In addition, a heat flow control element whose thermal conductivity changes due to a chemical reaction may be used. In this case, the control unit can promote the chemical reaction of the heat flow control element in response to the output of the temperature sensing element to control the thermal conductivity.
Also, a heat flow control element part whose thermal conductivity changes due to mechanical thermal contact such as thermal expansion may be used. In this case, the thermal conductivity can be controlled by controlling the degree of mechanical thermal contact of the heat flow control element part by the control part according to the output of the temperature sensing element part.

1, 21...heat flow switching device, 3...n-type semiconductor layer, 4...insulator layer, 5...p-type semiconductor layer, 6...n-side electrode, 7...p-side electrode, 10...heat flow control element section, 11A...temperature sensing element section, 22...heat flow sensor section, C...control section

Claims (8)

a heat flow control element unit that controls a heat flow by changing a thermal conductivity by changing an amount of induced electric charge by adjusting an input voltage ;
A temperature sensor unit for detecting a temperature of a controlled object or the heat flow control element unit;
a control unit for controlling the heat flow control element unit in response to an output from the temperature sensing element unit. 2. The thermal flow switching device of claim 1,
The heat flow control element portion includes an N-type semiconductor layer,
an insulator layer laminated on the N-type semiconductor layer;
a P-type semiconductor layer laminated on the insulator layer ,
A heat flow switching device, comprising : a first insulating layer and a second insulating layer, the first insulating layer being electrically connected to the first insulating layer and the second insulating layer being electrically connected to the first insulating layer . 3. The thermal flow switching device according to claim 1,
13. A heat flow switching device, wherein the temperature sensitive element is an NTC thermistor. 3. The thermal flow switching device according to claim 1,
13. A heat flow switching device, wherein the temperature sensitive element is a PTC thermistor. 3. The thermal flow switching device according to claim 1,
13. A heat flow switching device, wherein the temperature sensitive element is a CTR thermistor. 6. The thermal flow switching device according to claim 1,
The temperature sensitive element portion is a thin film thermistor portion formed of a thermistor material;
a pair of counter electrodes formed opposite to each other on at least one of the upper and lower sides of the thin film thermistor portion,
A heat flow switching device, wherein the thin film thermistor portion is laminated on the heat flow control element portion. 7. The thermal flow switching device according to claim 1,
a heat flow sensor unit joined to the heat flow control element unit and capable of detecting at least one of a direction of a heat flow and a heat flux;
A heat flow switching device, characterized in that the control unit controls the heat flow control element unit in response to at least one of the direction of heat flow and the heat flux detected by the heat flow sensor unit. 8. The thermal flow switching device according to claim 1,
A heat flow switching device, characterized in that the temperature sensing element portion and the heat flow control element portion are joined together and integrated.

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