JP2000356454A - Method for controlling temperature in deep freezer and refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost control method that is improved in energy efficiency and be suitable for saving of energy, in a method for controlling temperature in a deep freezer and a refrigerator employing electronic cooling element, such as a Peltier element. SOLUTION: A current flowing to an electronic cooling element 1 is decreased at a speed slower than the thermal response speed of a radiator connected to the heat generation side of the electronic cooling element 1. When a refrigerator temperature is increased to a value higher than a set temperature, control is executed such that a current flowing through the element 1 is adjusted at a stroke to a specified allowable current. Further, the lower limit value of a current value to keep the surface temperature of a cooler 4 at a value lower than a refrigerator temperature is determined and control to not only gradually lower a current but also set a lower limit value is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the temperature inside a refrigerator or refrigerator using an electronic cooling element such as a Peltier element, and more particularly to a technique for improving energy efficiency and suitable for energy saving.

[0002]

2. Description of the Related Art First, a refrigerator and a refrigerator using a Peltier element as a cooling means will be described. In the past, the use of Peltier devices, which can be cooled simply by passing current due to the recent rise in environmental issues, has been attracting attention from various directions as a clean cooling means that does not use Freon, and it is said that DC current is passed through the device. Because it can be cooled with a relatively simple structure. It has begun to be used as small refrigerators and refrigerators in camper vans. First, the temperature control method conventionally performed is that, after the sensor for detecting the temperature in the refrigerator detects that the temperature has become lower than the set temperature, the circuit that is energized to the element is opened, the cooling operation is stopped, and the temperature in the refrigerator is returned again. The on-off control of restarting the energization when the temperature rises has been the mainstream. In applications that require more detailed temperature control, a PWM that varies the on / off time width is used.
(Pulse Wided Modulatio
n) A control method is used, in which the energization time and the stop time are alternately repeated at short time intervals, and as a result, the internal temperature is controlled to be constant by increasing or decreasing the average current flowing through the element.

[0003]

The conventional problems will be described below with reference to a conventional temperature control method and an embodiment of the present invention. As described above, the temperature control method that has been conventionally performed is to open and cool the circuit that has been energized to the element after the inside temperature detection means for detecting the inside temperature has detected that the temperature has fallen below the set temperature as described above. The on-off control of stopping the operation and restarting the energization when the inside temperature rises again is the mainstream. Further, in an application in which fine temperature control needs to be performed, a PWM (Pu) that varies an on / off time width is used.
1st Wide Modulation) control method has been used. A method has been adopted in which the energization time and the stop time are alternately repeated at short time intervals, and as a result, the average current is increased or decreased, thereby controlling the temperature in the refrigerator to be constant. However, as a result of a detailed study of the conventional control method, the inventors found that there was a contradiction in the relationship between the amount of electricity and the cooling capacity, and as a result of repeating the experiment,
It has been found that there is a large difference in cooling efficiency between the case where control is performed using a PWM waveform in which an energizing current is intermittent and the case in which a continuous current waveform without intermittent operation is used even though the amount of energized electricity is the same. It was found that when constant temperature control was performed, the cooling efficiency was significantly different depending on how the control was applied. Further research results show that PWM control is more efficient than on-off control, and that PWM control has a higher carrier frequency.
It has been found that the efficiency of the WM control is higher, and that the efficiency of the energization control by a continuous current without intermittent current is higher. In particular, the smaller the change in the current flowing through the element, the better, the smaller the temperature difference between the heating side and the cooling side of the Peltier element, the higher the efficiency, the maximum efficiency when there is no temperature difference between the heating side and the cooling side, etc. Was found. As a result of the research conducted by the inventors, the inventors found that the cause of the reduction in efficiency in relation to the conduction current and the cooling efficiency was due to the reverse flow of thermal energy from the radiation fins on the heating side of the Peltier element. Was. This is similar to a car climbing up a hill and stopping at a specified height. If you do not run the brakes when you stop, you will lose your height by retreating uphill on the contrary. In order to maintain the specified height, the specified height can be maintained only when the forward driving force and gravity are balanced. As in this case, the same phenomenon occurs in cooling by the Peltier element. A cooling body and a radiation fin having a relatively large specific heat amount are connected to the side cooled by energization and the heat generation side. Therefore, on the heat radiation side, heat is dissipated until immediately before the energization is stopped. Therefore, the temperature is considerably higher than the internal temperature. In addition, the cooling body in the refrigerator is cooled to a temperature lower than the refrigerator temperature in order to cool the refrigerator. When the temperature inside the refrigerator reaches the specified temperature, if the power supply is reduced to zero at a stretch, as explained in the example of the car earlier, the high-temperature heat on the heat generation side will cause It has been found that a phenomenon occurs in which the heat flows back toward the cooling body at once, and a heat backflow phenomenon occurs in which the temperature of the cooling body in the refrigerator is raised to a temperature higher than the temperature in the refrigerator. It has been found that since the heat backflow phenomenon occurs every time the current is interrupted, the energy efficiency is deteriorated in the conventional on / off control.

[0004]

In the conventional temperature control method, a heat backflow phenomenon occurs and the energy efficiency required for cooling is reduced, so that the heat backflow phenomenon does not occur. It has been found that it is necessary to control the value of the current flowing through the element. Therefore, the inventor has an in-compartment temperature detecting means for detecting the in-compartment temperature of the freezer and the refrigerator and an in-compartment temperature setting means for setting the temperature to a specified temperature. When detecting that the temperature has dropped below the temperature set by the internal temperature setting means, the current flowing through the electronic cooling element is slower than the heat response speed of the radiator connected to the heat generation side of the electronic cooling element,
That is, it was found that the control method of gradually lowering the current instead of interrupting the current flowing through the element at once was the most efficient, and that the internal temperature rose to or above the set temperature by the internal temperature detecting means. On the other hand, when is detected, on the contrary, the current flowing through the element is controlled so as to flow to the specified allowable current at a stretch. In addition, in addition to the internal temperature detecting means for detecting the internal temperature, a cooler temperature detecting means for detecting the surface temperature of the cooler for cooling the internal space, the surface temperature of the cooler is always below the internal temperature. It has been found that the current value to be kept is defined as the lower limit value, and that the efficiency is further improved by performing control not only to gradually lower the current but also to set the lower limit value. This is devised as a countermeasure against a rise in the temperature of the cooler due to the above-mentioned heat backflow from the heat generation side. And since we have found that it is more efficient to control so that the current flowing through the thermoelectric cooler always keeps a continuous state rather than intermittently, it is better to control the average current by intermitting the current. Instead, the current applied to the element is controlled by linearly controlling the voltage applied to the element.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention is shown in FIGS.
This will be described with reference to 2 and 3. FIG. 1 is a block diagram showing the functions of a refrigerator or a refrigerator based on the temperature control method of the present invention in principle. 1 is a Peltier device, 2 is a radiating fin for dissipating heat on the heat-generating side of the device to the outside, 3 is a fan forcibly cooling air for the purpose of further improving heat radiation, and 4 is cooling the inside of the refrigerator Cooler,
5 is a temperature sensor for detecting the temperature in the refrigerator, 6 is a control circuit for controlling the current flowing through the element, and 7 is a freezer or a refrigerator. FIG. 2 is a more detailed block diagram showing the inside of the control circuit described in FIG. 1 is the Peltier element shown in FIG. Reference numeral 5 denotes an internal temperature sensor shown in FIG. 1, 61 denotes a switch for turning on the power, 62 denotes a voltage control circuit, and 63 denotes an element applied voltage detector. The operation of the control circuit will be described with reference to FIG. 3. First, FIG. 3 is a graph showing the transition between the inside temperature and the energized current, in which the horizontal axis represents the elapsed time, the vertical axis represents the inside temperature, and This represents the applied voltage to the Peltier element. At time 31, the power is turned on and the voltage shown at 41 is applied to the Peltier device 1. The internal temperature at time 31 was the temperature indicated by 50 in the internal temperature graph. The temperature in the refrigerator decreases as time elapses, and decreases to a temperature indicated by 51 at time 32. At this time, assuming that the prescribed temperature is set to 51, the control circuit 62 in FIG. 2 detects the internal temperature based on the data from the internal temperature sensor 5 and determines that the internal temperature has become 51 or less. Upon detection, the control circuit 62 gradually decreases the voltage from the voltages shown in FIGS. As the applied voltage decreases, the internal temperature stops decreasing and then gradually starts increasing. At the point of time 33 when the temperature in the refrigerator exceeds the temperature indicated by 52, an operation of increasing the gradually lowered voltage to a specified value at once is performed. The temperature inside the refrigerator starts to fall again, time 3
The cycle of dropping to the same temperature as 2 is repeated.

FIG. 4 shows a preferred embodiment of the control circuit 6 as a more specific circuit. The Peltier element 11 is connected in series with the DC power supply 12 and the transistor TR1. The temperature switch S1 is a temperature sensor of a type in which a circuit is opened when the temperature is equal to or lower than a specified temperature, and has a structure in which the circuit is closed when the temperature in the refrigerator is high. When the internal temperature is high and the temperature switch is closed, the base current of the transistor TR1 almost passes through R1. At this time, the resistor R1 is selected to be small so that a current that saturates TR1 flows. In such a case, the power supply 12
Voltage is applied almost directly to the Peltier element and acts to lower the internal temperature. The internal temperature decreases and the temperature switch S1
Is opened, the base current flowing through R1 is cut off, and the current charging the capacitor C1 becomes the base current of the transistor through R2. At this time, the current for charging the capacitor C1, ie, the base current of the transistor, gradually decreases as the voltage across C1 increases, and finally the current flowing through R2 becomes zero, and the base current of the transistor TR1 becomes the final current. Specifically, the current gradually decreases to a value having the current value determined by R3 as a lower limit. For this reason, the transistor TR1 operating in the saturation region by appropriately selecting the base current determined by R3 enters the non-saturation region, and the voltage applied to the Peltier element changes to the capacitor C1 and the base resistors R1, R2, and R3. Can be gradually reduced from the power supply voltage to a constant value by selecting an appropriate value for. Also, on the contrary,
When the internal temperature rises and the temperature switch S1 closes, the base current of the transistor TR1 flows through R1 and reaches the saturation region at a stretch, and the voltage applied to the Peltier element becomes substantially equal to the power supply voltage.

[0007]

As described above, according to the method for controlling the temperature in a refrigerator and a refrigerator according to the present invention, a phenomenon occurs in which at least high-temperature heat on the heat-generating side flows back toward the cooling body in the refrigerator at once. Since it is possible to prevent the occurrence of a heat backflow phenomenon, in which the temperature of the cooling body in the refrigerator is raised to a temperature higher than the temperature in the refrigerator, the energy efficiency for cooling can be greatly improved.

[0008]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of a refrigerator using a method for controlling the temperature in a refrigerator according to the present invention.

FIG. 2 is a diagram illustrating the principle of the internal temperature control circuit of the present invention.

FIG. 3 is a temperature control graph using the internal temperature control of the present invention.

FIG. 4 is a preferred control circuit diagram of the present invention.

[Explanation of symbols]

 1 is a Peltier element 2 is a radiation fin 3 is a fan 4 is a cooler 5 is a temperature sensor 6 is a control circuit 7 is a freezer or a refrigerator 8 is a power supply 11 is a Peltier element 12 is a DC power supply 31 is a start time 32 is a time when the temperature first falls below the specified temperature 33 is a time when the price is fixed below the specified temperature 41 is an applied voltage at the start 42 is an applied voltage at the time 33 The switch 62 is a voltage control circuit 63 is an applied voltage detector S1 is a temperature detection switch R1, 3, 3 is a resistor C1, a capacitor TR1 is a transistor

Claims (3)

[Claims] 1. A temperature control method for controlling an internal temperature of a refrigerator and a refrigerator using an electronic cooling element such as a Peltier element, wherein the temperature of the refrigerator is controlled to a set temperature. It comprises a temperature detecting means and an in-compartment temperature setting means for setting a specified temperature, and when it is detected by the in-compartment temperature detecting means that the in-compartment temperature has fallen below the temperature set by the in-compartment temperature setting means, The current flowing through the electronic cooling element is reduced at a slower speed than the thermal response speed of the radiator connected to the heat generation side of the electronic cooling element, and the current flowing through the electronic cooling element is reduced. When detecting that the temperature has risen to the set temperature or more, the electronic cooling device controls the current flowing through the electronic cooling device to flow at a stretch to the specified allowable current of the electronic cooling device. Temperature control method for refrigerators and refrigerators using cooling elements. 2. An internal temperature detecting means for detecting an internal temperature of the refrigerator, and a cooler temperature detecting means for detecting a surface temperature of a cooler for cooling the internal space, wherein the surface temperature of the cooler is determined by the internal temperature. 2. The method according to claim 1, wherein the current value kept below is controlled to a lower limit value. 3. The electronic cooling element according to claim 1, wherein the applied voltage of the element is controlled such that the current flowing through the electronic cooling element such as a Peltier element is always kept in a continuous state. The method of controlling the temperature inside the refrigerator and the refrigerator used.