WO2024080080A1

WO2024080080A1 - Multi-stage electronic temperature controller

Info

Publication number: WO2024080080A1
Application number: PCT/JP2023/033765
Authority: WO
Inventors: 克博都能
Original assignee: Ｍｐｓデザイン株式会社
Priority date: 2022-10-14
Filing date: 2023-09-15
Publication date: 2024-04-18

Abstract

The present invention provides a multi-stage electronic temperature controller which can cope with from elevated temperatures to ultralow freezing-range temperatures, can be operated so as to have a large temperature difference, and can perform cooling/heating control under good cooling-efficiency conditions. This multi-stage electronic temperature controller, which is for cooling a heat-insulated vessel, comprises: a stack of a plurality of thermoelectric conversion elements having substantially the same specifications; a cooling-side heat conductor disposed on a cooling surface of the stack; a radiation-side heat conductor disposed on a radiating surface of the stack; and a control board for separately supplying electric power to the plurality of thermoelectric conversion elements. The multi-stage electronic temperature controller is characterized in that the electric power to be supplied to each of the thermoelectric conversion elements is determined on the basis of a ratio of temperature allocation to the thermoelectric conversion elements calculated from the heat-insulating performance of the vessel, the heat-conducting performance of the interior of the vessel or the heat-conducting performance of the cooling-side portion of the stack, the radiation performance of the stack, measured data on ambient temperatures, a target temperature of the vessel or measured data on interior temperatures of the vessel, and measured data on radiation temperatures of the stack, so that the cooling efficiency of the stack is within a given range.

Description

Multi-stage electronic temperature control device

The present invention relates to a multi-stage electronic temperature control device for controlling the temperature of an object such as an insulating container. Here, an insulating container is given as an example of an object to be temperature controlled, but the present invention is not limited to this.

When using a thermoelectric conversion element (hereafter simply referred to as element) to absorb heat while maintaining a large temperature difference, if the temperature difference between the two sides of the element becomes large, the amount of heat absorbed by the element decreases, and the cooling efficiency of the element, COP = Qab/P, also deteriorates, so that a single element may not be able to maintain an appropriate temperature difference. To address this issue, a multi-stage electronic temperature control device has been proposed in which multiple elements are stacked and the temperature difference that one element is responsible for is reduced, allowing operation while maintaining a large amount of heat absorption.

A more specific explanation will now be given.
FIG. 1 shows the structure of a typical thermoelectric conversion element 100 .
The element 100 is a substantially flat-plate element in which multiple semiconductor chips 101 are arranged on a plane, connected in series with electrodes 102, and insulating substrates 103a, b are attached to both ends. When a direct current is passed through lead wires 104 connected to the terminals of the electrodes 102, heat is absorbed on one side of the element 100 and heat is generated on the opposite side, resulting in a temperature difference.

The amount of heat absorption Qab generated on the cooling surface of the element 100 is calculated by the following formula (1).
Qab=S×Tcp×I−0.5×I ² ×RK×ΔTp (1) where ΔTp is the temperature difference between both ends of the semiconductor constituting element 100 (Thp−Tcp).
Further, S, R, and K are values determined by the physical properties of the semiconductor (α: Seebeck coefficient, σ: electrical conductivity, κ: thermal conductivity), the element size, and the number of mounted elements, and are determined by selecting the element to be used.
S: Seebeck electromotive force of element (V/℃)
R: Internal resistance of element (Ω)
K: Heat return rate of the element (W/℃)
Therefore, once the elements are selected (i.e., S, R, and K are determined), the amount of heat absorption Qab can be calculated from equation (1) using the current I flowing through the element and the temperature difference ΔT between both ends of the element.

Moreover, the power P applied to the element 100 is determined by the voltage V and current I applied to the element 100 .
P = V x I = (R x I + S x ΔT) x I (2)

Therefore, the coefficient of performance (COP), which indicates the cooling efficiency of the element 100, is calculated by the following formula (3).
COP=Qab/P (3) That is, the cooling efficiency COP is calculated by dividing the amount of heat absorbed by the element 100, Qab, by the power P applied to the element 100. The greater this value, the higher the efficiency.

As shown in FIG. 3, when the current I flowing through the element 100 is increased, the amount of heat absorbed Qab by the element 100 increases, and the temperature difference ΔTp=Thp−Tcp (see FIG. 2) across the element 100 also increases.
However, the Joule heat generated inside the element 100 in formula (2) increases in proportion to the square of the current, and the sum of the reflux heat Qr that returns to the cooling side due to the temperature difference of the element 100 and the Joule heat generation exceeds the heat absorption Qab, and the heat absorption decreases under conditions where the current value (maximum current Imax) is greater. Also, there is a relationship in which the heat absorption Qab decreases as the temperature difference ΔTp increases (see FIG. 4).

FIG. 4 shows the relationship between the current I flowing through the element 100, the temperature difference ΔTp occurring across both ends of the element 100, and the heat absorption capacity Qab.
As can be seen from this figure, even if the maximum current Imax of the element 100 is applied, the amount of heat absorption obtained varies depending on the temperature difference ΔTp between both ends of the element 100. For example, to obtain a heat absorption amount of 20 W, the temperature difference ΔTp occurring between both ends of the element 100 must be 50° C.
Since there are heat transfer materials and contact interfaces on both sides of the element 100, which act as thermal resistance, a temperature difference larger than this temperature difference ΔTp is actually required. Therefore, if the temperature difference required to obtain the required amount of heat absorption exceeds the maximum current Imax, no greater temperature difference can be obtained.

The top characteristic line in Figure 4 shows the relationship between temperature difference and amount of heat absorption when a current Imax flows that does not increase the amount of heat absorption any more. The temperature difference when the amount of heat absorption becomes zero is called the maximum temperature difference ΔTmax. As shown by the dashed line in Figure 4, it can be seen that in order to perform a certain amount of heat absorption work Qab, the temperature difference of element 100 must be lower than the maximum temperature difference ΔTmax.

Therefore, since there is a limit to the temperature difference ΔTp that can be obtained while maintaining the heat absorption Qab with a single element (stage), in applications that require a large temperature difference and heat absorption capacity, such as low-temperature refrigeration, a large amount of heat absorption can be maintained by stacking multiple elements and operating them with a small temperature difference generated between each element.
A multi-stage electronic temperature control device has been developed that can achieve a large temperature difference by adding up the temperature differences of each element (stage). For example, there are the following patents.

Japanese Patent No. 3164862 Japanese Patent No. 3613251 JP 2019-049378 A

Conventional multi-stage electronic temperature regulators employ a structure in which the elements closer to the heat dissipation side become larger in size, as in Patent Document 1 (Patent No. 3164862), for example.
However, in this type of element configuration, it is necessary to dissipate heat horizontally (in a direction perpendicular to the stacking direction of the elements) from the element on the cooling side to the element on the heat dissipation side, and the thermal conductance from the element on the cooling side to the element on the next stage gradually deteriorates.In addition, there is a problem that the cooling efficiency is further deteriorated because heat leaks from the surroundings into the gaps where no chips are mounted.
Furthermore, since multiple elements are fabricated into a single circuit, the manufacturing cost of the device increases.

In Patent Document 2 (JP Patent No. 3613251), in order to improve the thermal conductance from the cooling side element to the heat dissipation side element, elements with the same board size, the same number of mounted semiconductor chips, and the same chip cross-sectional area are stacked, so that the thermal conductance between the elements is the same. Furthermore, the current-carrying circuits of the elements in each stage are divided, and the circuit is formed so that the current flowing toward the heat dissipation side is larger, and the elements are connected in parallel to one power supply voltage, so that the current flowing through the elements is larger from the cooling side element to the heat dissipation side element.
However, with this method, the ratio of currents that can be passed through the elements of each stage is fixed, and although efficient cooling can be performed under certain conditions, when temperature control is performed under other conditions, the cooling efficiency has to be operated under poor conditions. For example, when the set cooling temperature is changed or the outside air conditions change significantly, the cooling efficiency will deviate significantly from the optimal efficiency.
In addition, in this multistage electronic temperature regulator, when the polarity of the power supply voltage is switched and control is performed in heating mode, a large current always flows in the element circuit on the heat dissipation side, so the cooling capacity of the next stage element cannot absorb the heat, and the temperature rises at the interface. Basically, proper heating operation is impossible in a device that performs cooling control of the multistage electronic temperature regulator with the same power supply voltage.
Furthermore, each of the three stages is an element of a different pattern circuit, and the device is a specially designed multi-stage electronic temperature control device, which results in a high cost.

Patent Document 3 (JP 2019-049378 A) discloses a multi-stage electronic temperature control device that uses two stacked elements and controls current by applying individual voltages to each element.
In this patent, the device comprises a cooling side element 1 attached to the object to be cooled, a heat dissipation side element 2 attached to the heat dissipation side of element 1, a temperature sensor 1 that measures the cooling side temperature Tc1 of element 1, and a temperature sensor 2 that measures the heat dissipation side temperature Th1 of element 1, and element 2 is controlled to keep the heat dissipation side of element 1 below a target temperature so that element 2 can maintain the amount of heat absorption and temperature difference required by element 1.
However, this method does not specify any operating conditions for element 2, and the condition is that any amount of power can be used on element 2 in order to maintain the target temperature, and the cooling efficiency of the device including element 2 is ignored.
In addition, it is necessary to detect the temperatures Tc1 and Th1 on both sides of the element 1, and therefore a temperature sensor is required on both sides of the element. Therefore, as the number of stages increases, the number of temperature sensors also increases, and it becomes extremely complicated to determine the operating conditions for optimal cooling efficiency. Naturally, the cost of the device also increases.
Also, with regard to the heating operation, it is difficult to operate it under optimal operating conditions.
Moreover, this patent proposes to place a heat storage material between the elements to store heat and stabilize the element against sudden temperature changes. To achieve this, the patent chose to sandwich a material with high heat storage capacity, high specific heat and density, such as stainless steel, which has low thermal conductivity as a metal, between the elements.
However, if a material with poor thermal conductivity is placed between the elements, it will create a large thermal resistance, resulting in a large temperature difference. As a result, the operating temperature of the elements will have to be increased, further reducing the cooling efficiency. As such, no consideration has been given to optimizing the cooling efficiency of the thermoelectric conversion device.

As described above, there is no multistage electronic temperature regulator that takes into consideration proper cooling efficiency with minimum or nearly minimum power consumption and that can control both cooling and heating with a simple control mechanism.
As mentioned above, control using the same power supply voltage has problems such as the cooling conditions being fixed, making it impossible to control cooling with good efficiency, and not being able to heat. In addition, in a multi-stage electronic temperature control device that controls the voltage of each element individually, it is necessary to detect the temperatures at both ends of the element, and a multi-stage configuration requires many temperature sensors, which makes temperature control complicated, increases costs, and reduces reliability.

As a result of extensive research, the inventors came to the realization that, although a multi-stage electronic temperature control device needs to have a large number of stages in an apparatus that requires a large temperature difference, such as an ultra-low temperature freezer, it is important to be able to efficiently and optimally control this with a simple control mechanism, and thus developed the present invention.
Therefore, an object of the present invention is to provide a multi-stage electronic temperature control device that can handle temperatures ranging from heating to ultra-low temperature freezing, can operate with large temperature differences, and can control cooling and heating under conditions that provide good cooling efficiency.

The present invention provides an electronic temperature control device for cooling an insulating container, comprising:
A stack of a plurality of thermoelectric conversion elements having substantially the same specifications;
A cooling-side heat conductor provided on a cooling surface of the laminate;
A heat dissipation side thermal conductor provided on the heat dissipation surface of the laminate;
a control board that supplies power to each of the plurality of thermoelectric conversion elements individually;
power to be supplied to each thermoelectric conversion element is determined based on a temperature division ratio to each thermoelectric conversion element, which is calculated so that the cooling efficiency of the stack falls within a predetermined range using the insulation performance of the container, the heat transfer performance inside the container or the heat transfer performance on the cooling side of the stack, the heat dissipation performance of the stack, measurement data of the outside air temperature, measurement data of the target temperature of the container or the temperature inside the container, and measurement data of the heat dissipation temperature of the stack;
The present invention provides a multi-stage electronic temperature control device characterized by the above.

In the multi-stage electronic temperature control device of the present invention, it is preferable that the laminate is composed of, in order from the cooling surface side, a first thermoelectric conversion element, a second thermoelectric conversion element, ..., and an nth thermoelectric conversion element, and that the temperature differences in the first thermoelectric conversion element, the second thermoelectric conversion element, ..., and the nth thermoelectric conversion element are ΔTp1, ΔTp2, ..., and ΔTpn, and the temperature division ratio is determined to satisfy ΔTp1≦ΔTp2≦...<ΔTpn.
For example, when three elements are stacked, the stack is composed of, in order from the cooling surface side, a first thermoelectric conversion element, a second thermoelectric conversion element, and a third thermoelectric conversion element, and the temperature differences in the first thermoelectric conversion element, the second thermoelectric conversion element, and the third thermoelectric conversion element are ΔTp1, ΔTp2, and ΔTp3, respectively, and the temperature division ratio may be determined to satisfy ΔTp1≦ΔTp2<ΔTp3.

In addition, it is preferable that the multi-stage electronic temperature control device of the present invention further comprises a thermally conductive spacer block that is disposed between adjacent thermoelectric conversion elements and separates the cooling surface and the heat dissipation surface by a predetermined distance.

In addition, it is preferable that the multi-stage electronic temperature control device of the present invention further comprises a frame that covers and integrates the cooling side heat conductor, the heat dissipation side heat conductor, and the laminate.

The present invention also provides an electronic temperature control device for heating an insulating container, comprising:
A stack of a plurality of thermoelectric conversion elements having substantially the same specifications;
A cooling-side heat conductor provided on the heating surface of the laminate;
A heat dissipation side thermal conductor provided on a heat absorption surface of the laminate;
a control board that supplies power to each of the plurality of thermoelectric conversion elements individually;
power to be supplied to each thermoelectric conversion element is determined based on a temperature division ratio to each thermoelectric conversion element, the ratio being calculated so that the heating efficiency of the stack falls within a predetermined range using the heat insulating performance of the container, the heat transfer performance inside the container, the heat dissipation performance of the stack, measurement data of the outside air temperature, and the target temperature of the container or the measurement data of the temperature inside the container;
The present invention also provides a multi-stage electronic temperature control device, characterized in that

The present invention provides a multi-stage electronic temperature control device that can handle temperatures ranging from heating to ultra-low temperature freezing, can operate with large temperature differences, and can control cooling and heating under conditions that provide good cooling efficiency.

1 is a schematic diagram showing the structure of a general thermoelectric conversion element 100. FIG. 1 is a diagram showing the relationship between the input power P, the amount of heat absorption Qab, and the amount of heat exhaust Qd, as well as the relationship between the cooling side temperature Tcp, the heat dissipation side temperature Thp, and the temperature difference ΔTp in a typical thermoelectric conversion element 100. FIG. 1 is a graph showing the relationship between a current I flowing through a general thermoelectric conversion element 100 and the amount of heat absorption Qab and power consumption P. 1 is a graph showing the relationship between the temperature difference ΔTp and the amount of heat absorption Qab according to the supply current I in a typical thermoelectric conversion element 100. 1 is a schematic diagram showing an example of a freezer 1 incorporating a multistage electronic temperature regulator 10 according to the present embodiment. 1 is a schematic diagram of a multi-stage electronic temperature regulator 10. FIG. 11 is a diagram showing an example of a method for determining a temperature difference (ratio) corresponding to good cooling efficiency of a thermoelectric conversion element 12. FIG. FIG. 4 is an explanatory diagram of a temperature division ratio RΔTp. 3 is an explanatory diagram of heat reflux from a high temperature side to a low temperature side in the multistage electronic temperature regulator 10. FIG. 4 is an explanatory diagram of spacer blocks 51 and 52. FIG. 1 is a schematic diagram of a multistage electronic temperature regulator 10 in which a spacer block 51 on the cooling side is thicker than a spacer block 52 on the heat dissipation side. 1 is an explanatory diagram of a cold/hot temperature boundary line in a multistage electronic temperature regulator 10 having a frame 60. FIG.

Below, a representative embodiment of the multi-stage electronic temperature control device according to the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto. Note that the drawings are intended to conceptually explain the present invention, and therefore dimensions, ratios, or numbers may be exaggerated or simplified for ease of understanding.

This embodiment discloses a multistage electronic temperature control device 10 (hereinafter, sometimes referred to as device 10) that uses a laminate 11 having multiple thermoelectric conversion elements 12 (hereinafter, sometimes referred to as elements 12) stacked on top of each other to control the temperature of an object such as an insulating container 2 (see Figure 5).
The multi-stage electronic temperature regulator 10 is used to cool or heat an object. Therefore, the multi-stage electronic temperature regulator 10 may be called a multi-stage electronic cooling device or a multi-stage electronic heating device.
The thermoelectric conversion element 12 is also called an electronic cooling element. In this embodiment, the element 12 is assumed to be a commercially available electronic cooling element having a size of 4 cm square, a thickness of 3.8 mm, 254 semiconductor chips, a Seebeck coefficient S of 0.014 V/°C, an internal resistance R of 2.114 Ω, and a heat reflux rate K of 0.143 W/°C, but the present invention is not limited to this.

The following explanation assumes cooling of a container 2 unless otherwise specified. For ease of explanation, the explanation will be given using the example of a freezer 1 incorporating the device 10 as shown in FIG. 5, and the laminate 11 in the device 10 is composed of three stages of thermoelectric conversion elements 12 as shown in FIG. 6. However, the present invention is not limited to this configuration, and can be applied to objects other than freezers.

First, the freezer 1 will be outlined.
The freezer 1 described here incorporating the multistage electronic temperature regulator in which the elements 12 are stacked in three stages is assumed to be capable of handling freezer temperatures down to about −25° C. This freezer 1 is also capable of heating.
As shown in Figure 5, the freezer 1 includes a container 2 having excellent heat conductivity, a thermal insulation material 3 surrounding the container 2, a multi-stage electronic temperature control device 10 that cools the container 2, and an electric fan 4 that cools the heat dissipation portion of the multi-stage electronic temperature control device 10.
The container 2 is made of a material with excellent thermal conductivity, such as aluminum. The insulating material 3 is made of a material with excellent insulating performance, such as urethane foam. The insulating performance of the container 2 (insulating material 3), the heat transfer performance inside the container 2, and the heat dissipation performance of the multistage electronic temperature regulator 10 are determined by the specifications.

Next, the multistage electronic temperature regulator 10 will be described.
The device 10 has a laminate 11 formed by stacking thermoelectric conversion elements 12 having substantially the same specifications, mounted between a cooling-side thermal conductor 21 and a heat-dissipation-side thermal conductor 22 .
Here, thermoelectric conversion elements of substantially the same specifications refer to elements of substantially the same substrate size, in which substantially the same number of semiconductor chips of substantially the same size and substantially the same characteristics are mounted. Semiconductors of substantially the same characteristics refer to elements of the same specifications that are generally available, with equivalent Seebeck coefficient α, electrical conductivity σ, and thermal conductivity κ. Naturally, variations are permitted within the range of the manufacturing lot.
The cooling side refers to the container 2 side, and the heat dissipation side refers to the electric fan 4 side. Therefore, the cooling side thermal conductor 21 is a thermal conductor interposed between the laminate 11 and the container 2, and the heat dissipation side thermal conductor 22 is a thermal conductor interposed between the laminate 11 and the heat dissipation fin (heat exchanger).
The cooling-side thermal conductor 21 and the heat-dissipation-side thermal conductor 22 are made of a material having high thermal conductivity, such as a metal such as aluminum. The thicknesses of the cooling-side thermal conductor 21 and the heat-dissipation-side thermal conductor 22 will be described later.

The device 10 is equipped with

several temperature sensors

41, 42.
That is, there is provided a temperature sensor 41 that measures the cooling-side temperature Tcp of the device 10. This temperature sensor 41 is disposed on the cooling-side thermal conductor 21 of the device 10 or in its vicinity.
Also provided is a temperature sensor 42 for measuring the heat radiation side temperature Thp of the device 10. This temperature sensor 42 is disposed on the heat radiation side thermal conductor 22 of the device 10 or in its vicinity.
Here, the term "vicinity" refers to a range or a portion having a temperature that can be evaluated as being equivalent to the temperature of the cooling-side thermal conductor 21 or the heat-radiation-side thermal conductor 22 .
In addition, a temperature sensor 5 that measures a temperature equivalent to the temperature Tc of the object to be cooled (or the inside of the container 2) and a temperature sensor 6 that measures the outside air temperature Ta are provided. These temperature sensors 5 and 6 are not installed in the device 10 but in the product (freezer 1, etc.) in which they are incorporated and whose temperature is to be regulated (see FIG. 5).

The device 10 includes a control board 30 that applies the required power (including voltage or current) to each element 12 of the device 10 based on the output signals of the

temperature sensors

5, 6, 41, and 42 and the input setting values. This control board 30 may also operate the electric fan 4 for heat dissipation and control the battery.

Below, we will explain how to allocate voltage (or current) to each element 12. Here, we will explain the device 10 as being composed of three stages (sheets) of elements 12 as shown in Figures 5 and 6, but it goes without saying that the device 10 may be composed of two stages of elements 12, or may be composed of four or more stages of elements 12.
Here, the three elements 12 having the same specifications will be referred to as element 1, element 2, and element 3, in that order from the cooling side (the side closest to the temperature control target).

In other words, the required maximum operating temperature difference ΔTp of device 10 is calculated based on the temperature difference ΔT (= Ta - Tct) calculated from the measured values of the internal set temperature Tct and the outside air temperature Ta. Using this temperature difference ΔTp, the operating temperature differences ΔTp1, ΔTp2, ΔTp3 of

elements

1, 2, and 3 are divided according to the temperature division ratio RΔTp that provides the previously calculated cooling efficiency COP of device 10 for the most efficient condition, and the individual operating voltages (or operating currents) of

elements

1, 2, and 3 are determined. Note that, as will be described later, the ratio of the temperature division ratio RΔTp that is in the range where the COP can be said to be optimal or appropriate is called the optimal temperature division ratio QΔTp.

More specifically, the temperature difference ΔTp between both ends of the device 10 is expressed by the following equation using the cooling side temperature Tcp and the heat dissipation side temperature Thp.
ΔTp=Thp−Tcp
If the temperature differences between the cooling side and heat dissipation side of element 1, element 2, and element 3 are ΔTp1, ΔTp2, and ΔTp3, respectively, the temperature difference ΔTp1 of element 1 is expressed as follows using the cooling side temperature Tcp1 and the heat dissipation side temperature Thp1.
ΔTp1=Thp1−Tcp1
Similarly, the temperature difference ΔTp2 of the element 2 is expressed by the following equation using the cooling-side temperature Tcp2 and the heat-dissipation-side temperature Thp2.
ΔTp2=Thp2−Tcp2
Further, the temperature difference ΔTp3 of the element 3 is expressed by the following equation using the cooling side temperature Tcp3 and the heat radiation side temperature Thp3.
ΔTp3=Thp3−Tcp3

In addition, the thermal resistance between adjacent elements is small enough that Tcp ≒ Tcp1
Thp1 ≒ Tcp2
Thp2 ≒ Tcp3
Thp3 ≒ Thp
If the thermal resistance cannot be ignored, it can be corrected by actual measurement.

Therefore, the temperature difference ΔTp across the device 10 can also be expressed as follows using the temperature differences ΔTp1, ΔTp2 and ΔTp3 between the

elements

1, 2 and 3:
ΔTp=ΔTp1+ΔTp2+ΔTp3
However, at the initial stage or when operation starts, the temperature difference ΔTp is set as ΔTpt=Ta-Tct using the internal temperature setting Tct and the outside air temperature Ta.

The temperature difference ΔTp is divided into temperatures for element 1, element 2, and element 3.
The temperature division ratio is a division ratio QΔTp=ΔTp1:ΔTp2:ΔTp3 that is determined in advance and that maximizes or optimizes the cooling efficiency. For example, QΔTp=0.2:0.3:0.5 is used here, but the present invention is not limited to this.
Then, the initial temperature difference ΔTpt determines temperature differences ΔTp1, ΔTp2, ΔTp3 assigned to element 1, element 2, element 3. Next, cooling side temperatures Tcp1, Tcp2, Tcp3 of element 1, element 2, element 3 and heat radiation side temperature Thp3 of element 3 are determined.

Next, freezer 1 will be considered.
The following values are determined from the specifications of the freezer 1. That is, the insulation specifications of the freezer 1 determine the leakage heat conductance KL, which indicates how easily heat leaks from the outside into the freezer. Also, the cooling side heat conductance KC, which indicates how well heat is transferred from the container 2 to the multistage electronic temperature control device 10, is determined. Also, the heat dissipation side heat conductance KH is determined by the specifications of the heat dissipation heat exchanger (both are expressed in units of W/°C or W/K).
By determining these thermal conductances KL, KC, and KH, the required heat absorption amount Qab and cooling side temperature Tcp of the multistage electronic temperature regulator 10 are determined.

More specifically, the amount of heat QL leaking into the heat-insulating freezer from the outside is expressed by the following equation using the measured data of the outside air temperature Ta and the freezer 1 internal temperature Tc (however, in the initial cooling mode applied when the power is turned on or after the lid is closed, the internal temperature setting Tct can be used instead of the internal temperature Tc. When the actual internal temperature Tc reaches the internal temperature setting Tct, the system transitions to the constant temperature control mode and the actual internal temperature Tc is used).
QL = KL × (Ta - Tc)
That is, the multistage electronic temperature regulator 10 must absorb this amount of heat QL while maintaining the temperature inside the refrigerator at Tc. Note that there is a relationship between the amount of heat QL and the amount of heat absorption Qab required by the multistage electronic temperature regulator 10, QL ≧ Qab, but for the sake of convenience, the following description will be given assuming QL = Qab.

When the leakage heat amount QL, i.e., the required heat absorption amount Qab, is absorbed from the inner container 2 on the cooling surface of the multistage electronic temperature control device 10, the leakage heat amount QL, i.e., the required heat absorption amount Qab, is calculated using the cooling-side thermal conductance KC as follows:
QL = Qab = KC × (Tc - Tcp)
Therefore, the cooling side temperature Tcp of the multistage electronic temperature regulator 10 can be expressed as follows:
Tcp = Tc - Qab / KC
Thus, the cooling side temperature Tcp and the required heat absorption amount Qab of the multistage electronic temperature regulator 10 are determined.
In this way, when the specifications of the object (here, the freezer 1) into which the multistage electronic temperature regulator 10 is to be incorporated are given, the cooling side temperature Tcp and the required heat absorption amount Qab of the multistage electronic temperature regulator 10 are determined.

In the multistage electronic temperature regulator 10 shown in FIGS. 5 and 6, which performs cooling operation by stacking three elements, the heat absorption amount Qab, input power P, and heat dissipation amount Qd of each element can be calculated by the following formula.
- Regarding element 1, heat absorption amount: Qab1 = S x Tcp1 x I1 - 0.5 x I1^2 x R1 - K x ΔTp1
Input power: m
Heat dissipation: Qd1 = Qab1 + P1
- Regarding element 2, heat absorption amount: Qab2 = S x Tcp2 x I2 - 0.5 x I2^2 x R2 - K x ΔTp2
Input power: P2 = (S x ΔTp2 + R2 x I2) x I2
Heat dissipation: Qd2 = Qab1 + P1 + P2
- Regarding element 3, heat absorption amount: Qab3 = S x Tcp3 x I3 - 0.5 x I3^2 x R3 - K x ΔTp3
Input power: P3 = (S x ΔTp3 + R3 x I3) x I3
Heat dissipation: Qd3 = Qab1 + P1 + P2 + P3
where S is the Seebeck electromotive force of the element (V/°C)
R: Internal resistance of element (Ω)
K: Heat return rate of the element (W/°C)
Therefore, the cooling efficiency COP can be calculated using the following formula.
COP=Qab1/P=Qab1/(P1+P2+P3)

As described above, the coefficients S, R, and K are determined by determining the specifications of the element 12, and Qab1 and Tcp1 are determined by determining the specifications of the freezer 1.
However, the temperature difference ΔTp occurring in the device 10 depends on the operating temperature differences ΔTp1, ..., ΔTpn (n: number of element stages) of each element 12, and since the temperature difference of the elements 12 can take any value, it is difficult to determine under what conditions the COP will be maximum or appropriate.
Therefore, a prototype freezer 1 incorporating the device 10 was manufactured, and the cooling efficiency was examined while changing various operating conditions of each element 12. The details are described below.

The prototype multi-stage electronic temperature regulator is a stack of three thermoelectric conversion elements, each 4 cm×4 cm square and 3.8 mm thick, with the element characteristics S, R, and K being as follows:
S = 0.051 (V / K),
R = 2.114 (Ω),
K = 0.417 (W/K)

For the freezer, a 10 cm x 10 cm x 8 cm aluminum container was covered with urethane insulation, and the above-mentioned multi-stage electronic temperature control device was attached to this container, and an electric fan was installed to forcibly cool the heat dissipation side of the device.
The specifications of the freezer are as follows:
Leakage thermal conductance: KL = 0.120 (W/K)
Thermal conductance on the cooling side inside the chamber: KC = 0.200 (W/K)
Heat dissipation side thermal conductance: KH = 5.000 (W/K)

This device was equipped with temperature sensors for measuring the outside air temperature Ta, the inside temperature Tc, the cooling side temperature Tcp, the heat dissipation side temperature Thp, and the intermediate temperatures Tcp2 and Tcp3 of each element.
Then, in an environment with an outside air temperature of 25°C, the electric fan was operated under constant conditions (i.e., KH = constant) and the cooling efficiency COP of the multi-stage electronic temperature control device 10 was investigated when arbitrary currents I1, I2, and I3 were passed through

elements

1, 2, and 3 to set the temperature inside the cabinet to -25°C.
The measurement results are shown in Table 1 below.

From Table 1, it was found that when the temperature differences ΔTp1, ΔTp2, and ΔTp3 of the

elements

1, 2, and 3 are divided by a certain ratio with respect to the temperature difference ΔTp of the device 10, there exists a temperature division ratio QΔTp that maximizes the COP among the temperature division ratios RΔTp.
RΔTp=ΔTp1:ΔTp2:ΔTp3
RΔTp1=ΔTp1/ΔTp
RΔTp2=ΔTp2/ΔTp
RΔTp3=ΔTp3/ΔTp
Then, in this freezer, the appropriate temperature division ratio in the cooling operation is ΔTp1≦ΔTp2<ΔTp3, and further the optimal condition is approximately ΔTp1:ΔTp2:ΔTp3=0.23:0.33:0.44.

7A shows the relationship between the COP and ΔTp3/ΔTp of the element 3. From this figure, it can be seen that the maximum value of COP is near RΔTp3=ΔTp3/ΔTp=0.44.
7B shows the relationship between COP and ΔTp1/ΔTp for element 1. From this figure, it can be seen that the maximum value of COP is near RΔTp1=ΔTp1/ΔTp=0.23.
Therefore, RΔTp2=ΔTp2/ΔTp=0.33.
Therefore, the temperature division ratio in this example is QΔTp=0.23:0.33:0.44.

FIG. 8 shows an example of the temperature distribution in the multistage electronic temperature regulator 10 having a three-element configuration.
The solid line in Fig. 8 corresponds to data (3) in Table 1 and is an approximately straight line. This indicates that the temperature difference ΔTp is approximately equally divided among

elements

1, 2, and 3. From Table 1, the COP under these conditions is 0.279.
The dashed line in Fig. 8 corresponds to data (5) in Table 1 and is located below the solid line (i.e., the dashed line is downwardly convex). This shows that the temperature difference ΔTp is divided such that ΔTp1 ≦ ΔTp2 < ΔTp3 for element 1, element 2, and element 3. From Table 1, it can be seen that the COP under these conditions is 0.305, which is more efficient than data (3). Data (4), (6), and (7) in Table 1 also show the same tendency as data (3).
In contrast, the dashed line in FIG. 8 corresponds to data (1) in Table 1 and is located above the solid line (i.e., the dashed line is upwardly convex). This shows that the temperature difference ΔTp is divided such that ΔTp1>ΔTp2≧ΔTp3 for element 1, element 2, and element 3. From Table 1, the COP under these conditions is 0.235, which is inferior in efficiency to data (3) to (7). Data (2) in Table 1 also shows the same tendency as data (1).
In this regard, the temperature split ratio at which this COP becomes optimal hardly changes even when the internal temperature setting Tct, the internal temperature Tc, or the outside air temperature Ta is changed.
As a result of careful consideration by the inventors, it was found that the optimal temperature division ratio QΔTp at which the COP of the device 10 can be said to be appropriate (within a range of ±20% from the optimal value) is roughly in the range of ΔTp1:ΔTp2:ΔTp3 = 0.16-0.24: 0.24-0.36: 0.40-0.55 (however, within the range of ΔTp1≦ΔTp2<ΔTp3).

Therefore, once the specifications of element 12 and freezer 1 are determined, there exists a temperature division ratio QΔTp for which the COP is optimal or appropriate for the temperature difference ΔTp that occurs in multi-stage electronic temperature control device 10, and it has been found that by using the optimal temperature division ratio QΔTp, it is possible to operate multi-stage electronic temperature control device 10 under appropriate COP conditions regardless of changes in temperature conditions, i.e., it is possible to control temperature with sufficiently small energy consumption.

In summary, once the specifications of the element 12 and the freezer 1 are determined, and the optimal temperature division ratio QΔTp is determined,
The temperatures Tcp1, Tcp2, Tcp3, and Thp are measured by temperature sensors.
- In the initial cooling mode, the operating temperature difference ΔT = Ta - Tct is set as the initial temperature difference ΔTp of the multi-stage electronic temperature control device 10 based on the internal temperature setting (target temperature) Tct and the measured outside air temperature Ta, and the optimal temperature division ratio QΔTp is applied to determine the temperature differences ΔTp1, ΔTp2, and ΔTp3 of each element 12.
The heat absorption amount Qab1 and temperature Tcp1 are determined from the specifications of the freezer 1.
- A current value I1 that allows element 1 to absorb the amount of heat Qab1 absorbed under the condition of a temperature difference ΔTp1 is applied to element 1. [Here, Qab1 = S x Tcp1 x I1 - 0.5 x I1^2 x R1 - K x ΔTp1, which is a quadratic function of current I, so the current value I1 that results in the amount of heat absorption Qab1 can be found by solving the quadratic function. The same applies below.] At this time, the amount of heat dissipation Qd1 of element 1 = Qab + P1, so this amount of heat dissipation becomes the amount of heat absorption Qab2 required for element 2.
Similarly, a current I2 that allows the heat absorption amount Qab2 of element 2 to absorb heat under the condition of a temperature difference ΔTp2 is applied to element 2. At this time, the heat dissipation amount Qd2 of element 2 = Qab1 + P2, so this heat dissipation amount becomes the required heat absorption amount Qab3 of element 3.
Similarly, a current I3 is applied to element 3 such that the amount of heat absorbed by element 3, Qab3, is sufficient to absorb heat under the condition of a temperature difference ΔTp3.
The amount of heat radiation Qd3=Qab2+P3 of element 3 is the amount of heat radiation QD that needs to be treated by the heat radiation side heat exchanger.
The amount of heat dissipation QD is calculated as Thp=QD/KH+Ta based on the heat dissipation-side thermal conductance KH, the required temperature difference ΔTh=Thp-Ta, and the relational equation QD=KH×(Th-Ta).
Therefore, Thp>Ta.
Therefore, the difference between the inside temperatures Tc and Thp is updated as a new temperature difference ΔTp, and is divided by the optimum temperature division ratio QΔTp.
The temperature division operation is repeated until the measured internal temperature Tc reaches the internal set temperature Tct, and Thp settles at a condition where it is in equilibrium with the heat radiation capacity of the heat radiation side heat exchanger.
When the measured internal temperature Tc reaches the internal set temperature Tct, the mode switches to constant temperature control mode, and the same control as above is performed using the measured data of the internal temperature Tc instead of the internal set temperature Tct.
In this way, the temperature of the device 10 can be controlled under conditions that are considered to be the maximum COP.

By using this method, it is only necessary to know the cooling side temperature Tcp and the heat dissipation side temperature Thp of the device 10, so there is no need to measure intermediate temperatures regardless of the number of stages of the elements 12, and a very simple device structure can be used.
Even when elements 12 of different specifications are not used, that is, when elements of different specifications are stacked, the temperature can be controlled in the same manner as above, although the calculations become more complex.

Next, consider the case where the polarity of the power to element 12 of device 10 is reversed to heat the interior of container 2.
In general, in a multi-stage electronic temperature control device applied to a freezer, the heat exchanger on the heat dissipation side is designed to have a higher heat dissipation capacity than the heat conductor on the heat absorption side in order to cool the device to the freezing temperature. In other words, KC<KH. Therefore, when trying to control such a multi-stage electronic temperature control device in a heating mode, the balance is different from that of the cooling mode, so appropriate control cannot be achieved with the same current density ratio. In addition, the temperature division ratio suitable for heating is also different.
As a result of extensive research by the inventors, it was found that an optimal temperature split ratio Q'ΔTp for heating does exist. However, it was also found that the optimal temperature split ratio Q'ΔTp for heating is a temperature split ratio different from that for cooling.

That is, in the freezer and multistage electronic temperature regulator prototyped by the inventors, the appropriate temperature division ratio in the heating operation was ΔTp1>ΔTp2≧ΔTp3, and optimally Q′ΔTp=0.4:0.3:0.3.
According to the inventor's investigation, the temperature division ratio Q'ΔTp corresponding to the appropriate efficiency of the device 10 during heating operation is generally in the range of ΔTp1:ΔTp2:ΔTp3=0.2-0.5:0.2-0.4:0.1-0.3.

Therefore, when controlling temperature by heating, this temperature division ratio Q'ΔTp is used to individually control the current or voltage of each element 12, making it possible to efficiently control temperatures higher than room temperature and also to rapidly change the temperature.

Returning now to the explanation of the cooling operation, a method for suppressing the reflux of heat from the heat dissipation side to the cooling side of the device 10 will be described.
In other words, from the viewpoint of suppressing heat reflux, it is preferable to insert spacer blocks 51, 52 with high thermal conductivity between adjacent elements 12 and increase the insulating creepage distance L of the insulating material 3 around the device 10 (see Figure 10).
It is also preferable that the spacer blocks 51, 52 are thicker on the cooling side (see FIG. 11).

9, the thickness of the device 10 is determined by the thickness of the element 12. The lowest temperature is the cooling surface of the cooling side element 12, and the highest temperature is the heat dissipation surface of the heat dissipation side element 12. When a large temperature difference occurs between the cooling side element 12 and the heat dissipation side element 12, heat flows back from the high temperature side to the cooling part (low temperature side) through the surrounding insulation material 3, etc.
Therefore, if the distance L between the cooling surface of the cooling side element 12 and the heat radiation surface of the heat radiation side element 12 is short, the amount of heat circulating through the surrounding heat insulating material 3 increases, reducing the cooling efficiency.
10, in order to increase the distance L between the cold source (cooling side) and the heat source (heat dissipation side) of the thermoelectric conversion element 12, it is advisable to install spacer blocks 51 and 52 with high thermal conductivity between adjacent elements 12. This improves the thermal insulation of the surrounding insulation material 3, and reduces the effect of reflux heat on the cooling efficiency of the device 10.
Since the spacer blocks 51 and 52 act as thermal resistance components between the elements 12, it is preferable to use a material with high thermal conductivity, such as aluminum or copper.

However, since the spacer blocks 51 and 52 have thermal resistance, if the thickness is increased, the temperature difference occurring in the spacer blocks 51 and 52 increases, and the cooling efficiency decreases.
In order to alleviate this, it is advisable to make the spacer block 51 on the cooling side thicker (see FIG. 11). This is because the amount of heat passing through the spacer block 51 on the cooling side is small, so it is easy to reduce the temperature difference with respect to the spacer block 51.

That is, if the shape ratio of the spacer block is Asb (=Ssb/Tsb), the cross-sectional area is Sab, the thickness is Tsb, the thermal conductivity is λ, the heat return rate is Ksb (=Asb×λ), and the amount of heat passing through is Qab, then the temperature difference ΔTsb is expressed by the following equation.
ΔTsb=Qab/Ksb
= Q ab / ( Asb × λ)
= Qab / ((Ssb / Tsb) × λ)
As a result, when the amount of heat passed Qab is small, the temperature difference ΔTsb is small, so even if the thickness Tsb is increased, an increase in the temperature difference ΔTsb can be suppressed.
In addition, under the heating conditions, the heating efficiency is high, so that the temperature difference between the spacer blocks 51 and 52 due to the difference in thickness between the spacer blocks 51 and 52 can be ignored.

Alternatively, the outer periphery of the cooling side thermal conductor 21 and the heat dissipation side thermal conductor 22 of the device 10 and the element 12 stacked between them may be covered with a frame body 60, and the frame body 60 may be integrated with the cooling side and heat dissipation side

thermal conductors

21, 22 to seal the element 12 (see Figure 12).
In this case, in the element 12 on the heat dissipation side, the cooling surface is lower than the outside air temperature and the heat dissipation surface is higher than the outside air temperature, so that a cold/hot temperature boundary line M is formed between the two surfaces, where the temperature is equal to the outside air temperature. The area below (outside) this boundary line M becomes the heat dissipation zone.
In contrast, the cold/hot temperature boundary line N of the frame 60 is on the heat dissipation side of the cold/hot temperature boundary line M of the element 12. Therefore, it is preferable to provide a step 61 on the high temperature side of the cold/hot temperature boundary line N of the frame 60, and to position the step 61 exactly inside the thermal insulation material 3 when attaching the device 10 and the frame 60 to the thermal insulation material 3.
That is, by assembling the frame 60 so that the portion that becomes hotter than the environmental temperature, such as room temperature, is disposed outside the heat insulating material 3, an installation with good cooling efficiency can be ensured.

Although a representative embodiment of the present invention has been described above, the present invention is not limited to this, and various design modifications are possible, and all such design modifications are included in the technical scope of the present invention.
In the multistage electronic temperature regulator of the present invention, the laminate may be composed of, in order from the cooling surface side (the side closer to the temperature control target), a first thermoelectric conversion element, a second thermoelectric conversion element, ..., and an nth thermoelectric conversion element (n >= 2). It is preferable that the temperature differences in the first thermoelectric conversion element, the second thermoelectric conversion element, ..., and the nth thermoelectric conversion element are ΔTp1, ΔTp2, ..., and ΔTpn, and the temperature division ratio is determined so as to satisfy ΔTp1≦ΔTp2≦ ...<ΔTpn.
For example, a multistage electronic temperature regulator used in an ultra-low temperature freezer capable of handling temperatures in the ultra-low temperature freezing range up to about -80°C may use a six-stage stacked thermoelectric conversion element in order to operate with a large temperature difference. In this case, the temperature difference ΔTp required for the multistage electronic temperature regulator may be temperature-divided for the six stages of thermoelectric conversion elements so as to satisfy ΔTp1≦ΔTp2≦ΔTp3≦ΔTp4≦ΔTp5<ΔTp6. Furthermore, by using a temperature division ratio QΔTp that provides an optimal or appropriate COP, the multistage electronic temperature regulator can be operated with reduced energy regardless of changes in temperature conditions.

Reference Signs List 1 Freezer 2 Container 3 Insulation material 4 Electric fan 5, 6 Temperature sensor 10 Multi-stage electronic temperature control device 11 Laminated body 12 Thermoelectric conversion element 21 Cooling side heat conductor 22 Heat dissipation side heat conductor 30

Control board

41, 42

Temperature sensor

51, 52 Spacer block 60 Frame

Claims

1. An electronic temperature control device for cooling an insulating container, comprising:
A stack of a plurality of thermoelectric conversion elements having substantially the same specifications;
A cooling-side heat conductor provided on a cooling surface of the laminate;
A heat dissipation side thermal conductor provided on the heat dissipation surface of the laminate;
a control board that supplies power to each of the plurality of thermoelectric conversion elements individually;
power to be supplied to each thermoelectric conversion element is determined based on a temperature division ratio to each thermoelectric conversion element, which is calculated so that the cooling efficiency of the stack falls within a predetermined range using the insulation performance of the container, the heat transfer performance inside the container or the heat transfer performance on the cooling side of the stack, the heat dissipation performance of the stack, measurement data of the outside air temperature, measurement data of the target temperature of the container or the temperature inside the container, and measurement data of the heat dissipation temperature of the stack;
A multi-stage electronic temperature control device characterized by:
the laminate is composed of, in order from the cooling surface side, a first thermoelectric conversion element, a second thermoelectric conversion element, ..., and an n-th thermoelectric conversion element,
where temperature differences in the first thermoelectric conversion element, the second thermoelectric conversion element, ..., and the nth thermoelectric conversion element are ΔTp1, ΔTp2, ..., and ΔTpn, and the temperature division ratio is determined so as to satisfy ΔTp1≦ΔTp2≦ ... <ΔTpn;
2. The multi-stage electronic temperature regulator according to claim 1 .
Further comprising a thermally conductive spacer block disposed between adjacent thermoelectric conversion elements to separate the cooling surface and the heat dissipation surface by a predetermined distance;
2. The multi-stage electronic temperature regulator according to claim 1 .
Further comprising a frame that covers and integrates the cooling side thermal conductor, the heat dissipation side thermal conductor, and the laminate;
2. The multi-stage electronic temperature regulator according to claim 1 .
An electronic temperature control device for heating an insulating container, comprising:
A stack of a plurality of thermoelectric conversion elements having substantially the same specifications;
A cooling-side heat conductor provided on the heating surface of the laminate;
A heat dissipation side thermal conductor provided on a heat absorption surface of the laminate;
a control board that supplies power to each of the plurality of thermoelectric conversion elements individually;
power to be supplied to each thermoelectric conversion element is determined based on a temperature division ratio to each thermoelectric conversion element, the ratio being calculated so that the heating efficiency of the stack falls within a predetermined range using the heat insulating performance of the container, the heat transfer performance inside the container, the heat dissipation performance of the stack, measurement data of the outside air temperature, and the target temperature of the container or the measurement data of the temperature inside the container;
A multi-stage electronic temperature control device characterized by: