Refrigerator

Abstract

To provide a refrigerator capable of defrosting an evaporator efficiently.SOLUTION: A refrigerator comprises: a freezer chamber; an evaporator that vaporizes a refrigerant to cool the freezer chamber; a compressor that compresses the refrigerant having flowed through the evaporator and sends it back to the evaporator; a heater that heats the evaporator; a first temperature sensor that detects a temperature of the freezer chamber; and a control unit. The control unit controls a cooling capacity of the evaporator to cool the freezer chamber based on a detection result of the first temperature sensor, and when it determines that the cooling capacity has exceeded a first threshold value indicating a cooling capacity higher than the cooling capacity during steady operation and then fallen below the first threshold value, controls the heater to heat the evaporator and perform a defrosting process to melt frost that has adhered to the evaporator.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a refrigerator.

Background Art

[0002] Patent Document 1 discloses a refrigerator equipped with a heater that defrosts an evaporator by turning on the heater. In the refrigerator disclosed in Patent Document 1, when the temperature of the evaporator becomes sufficiently higher than the frost melting temperature, the heater is turned off.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the refrigerator disclosed in Patent Document 1, the appropriate timing for operating the heater when defrosting the evaporator has not been studied, and there is a problem that the defrosting of the evaporator cannot be performed efficiently.

[0005] An object of the present disclosure is to provide a refrigerator capable of efficiently defrosting an evaporator.

Means for Solving the Problems

[0006] A refrigerator according to one aspect of the present disclosure includes a freezer compartment, an evaporator that vaporizes a refrigerant to cool the freezer compartment, a compressor that compresses the refrigerant that has flowed through the evaporator and sends it back to the evaporator, a heater that heats the evaporator, a first temperature sensor that detects the temperature of the freezer compartment, and a control unit. The control unit controls the cooling capacity for cooling the freezer compartment by the evaporator based on the detection result by the first temperature sensor, and when it is determined that the cooling capacity has fallen below a first threshold value that indicates a cooling capacity higher than the cooling capacity during steady operation, the control unit controls to execute a defrosting process of heating the evaporator by the heater to melt the frost adhering to the evaporator.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments and modified examples of the present disclosure will be described with reference to the drawings. In the following, the same or corresponding elements are denoted by the same reference numerals throughout all the drawings, and the overlapping descriptions thereof are omitted. In addition, the embodiments and modified examples described below are merely examples of the present disclosure, and the present disclosure is not limited to the embodiments and modified examples. Even outside these embodiments and modified examples, various changes can be made according to the design and the like as long as the technical idea of the present disclosure is not deviated from.

[0009] (First Embodiment) With reference to FIGS. 1 and 2, the configuration of the refrigerator 100 according to the first embodiment of the present disclosure will be described. FIG. 1 is a front view showing the main part configuration of the refrigerator 100 according to the first embodiment of the present disclosure. FIG. 2 is a sectional view taken along line II-II in the refrigerator 100 shown in FIG. 1. In FIG. 2, an example of the main part configuration of the refrigerator 100 is schematically shown.

[0010] In the refrigerator 100, the left and right sides of the refrigerator 100 are defined based on the view from the front side. In the refrigerator 100, the bottom side is defined as the lower side and the opposite side is defined as the upper side, respectively.

[0011] The refrigerator 100 according to the first embodiment is composed of two boxes 10a and 10b. The boxes 10a and 10b have an inner wall surface that forms a storage space for storing food and the like, and an outer wall surface that serves as the outer wall of the refrigerator 100. A heat insulating material is filled between the inner wall surface and the outer wall surface. With these boxes 10a and 10b, the refrigerator 100 can separate the outside and the inside of the refrigerator. In the refrigerator 100, the upper box 10a is a refrigerating chamber 2, and the lower box 10b is a freezing chamber 3.

[0012] In the refrigerator 100, the fronts of the refrigerating chamber 2 and the freezing chamber 3 are open, and the opening of the refrigerating chamber 2 is opened and closed by the refrigerating chamber door 20, and the opening of the freezing chamber 3 is opened and closed by the freezing chamber door 30. That is, door hinges (not shown) are provided at the upper and lower parts of the right side of the box 10a forming the refrigerating chamber 2, and the refrigerating chamber door 20 is attached to the box 10a via these door hinges so as to be openable and closable. Similarly, door hinges (not shown) are provided at the upper and lower parts of the right side of the box 10b forming the freezing chamber 3, and the freezing chamber door 30 is attached to the box 10b via these door hinges so as to be openable and closable.

[0013] Also, on the inner surface of the refrigerating chamber door 20, a plurality of door pockets 22 having a bottomed rectangular tube shape with an open upper surface are provided. Therefore, in the refrigerator 100, small items, eggs, plastic bottles, etc. can be stored in the door pockets 22 in the refrigerating chamber 2.

[0014] Also, the refrigerating chamber 2 is vertically divided inside, and a plurality of refrigerating chamber cases 24 are stored in the lower region of the refrigerating chamber 2. In the refrigerator 100 of the present disclosure, two types of refrigerating chamber cases 24, namely a chilled case and a vegetable storage case, are stored in the lower region of the refrigerating chamber 2. On the other hand, the upper region of the refrigerating chamber 2 is partitioned into three storage spaces by a plurality of trays 25 which are flat plates made of glass.

[0015] A control board 9 is provided on the back wall of the refrigerator compartment 2. The control board 9 performs various controls on each part of the refrigerator 100. The control board 9 includes a control unit 90 that can be realized by a CPU or the like, a storage unit 91 that can be realized by semiconductor memories such as a ROM and a RAM, and an interface circuit (not shown) and the like. And, for example, when the control unit 90 is a CPU, the CPU can read the program stored in the ROM into the RAM and execute it to perform various controls on each part.

[0016] As shown in FIG. 3, the control unit 90 is connected to a DF temperature sensor 43 (evaporator temperature sensor), an F temperature sensor 44 (freezer compartment temperature sensor), and an R temperature sensor 45 (refrigerator compartment temperature sensor). And based on the temperatures detected by these temperature sensors, the operations of the compressor 6, the cooling fan 42, and the heater 41 can be controlled respectively. FIG. 3 is a block diagram showing an example of the main part configuration of the refrigerator 100 according to the first embodiment of the present disclosure. Note that the DF temperature sensor 43 is a temperature sensor that detects the temperature in the vicinity of the evaporator 40 housed in the evaporator chamber 4. The F temperature sensor 44 is a temperature sensor that detects the temperature of the freezer compartment 3 and is the first temperature sensor of the present disclosure. The R temperature sensor 45 is a temperature sensor that detects the temperature of the refrigerator compartment 2 and is the third temperature sensor of the present disclosure.

[0017] In the freezer compartment 3, three bottomed rectangular tube-shaped freezer cases 32 with open tops are housed so as to overlap in the vertical direction, and frozen foods and the like can be classified and housed in the freezer cases 32 according to types. Further, in the freezer compartment 3, an ice storage case equipped with an ice tray (not shown) is detachably provided.

[0018] An evaporator chamber 4 is provided on the back side of the freezer compartment 3. The evaporator 40 is housed in the evaporator chamber 4. A heater 41 is provided below the evaporator 40, and a cooling fan 42 is provided above it respectively. Also, directly below the heater 41, in the space at the lower back side of the box body 10b, an evaporation tray 5 is provided, and a compressor 6 is provided below the evaporation tray 5 respectively.

[0019] As shown in FIG. 2, an air passage 8 through which cold air sent from a cooling fan 42 flows is formed in a wall surface that partitions the freezer compartment 3 and the refrigerator compartment 2. A damper 7 is provided in this air passage 8, and the control unit 90 can control the flow of cold air into the refrigerator compartment 2 by opening and closing the damper 7, thereby controlling the temperature inside the refrigerator compartment 2. The control unit 90 executes the opening and closing of the damper 7 based on the temperature detected by the R temperature sensor 45.

[0020] That is, when the damper 7 is in the open state, cold air is sent to the freezer compartment 3 by the cooling fan 42 and also sent to the refrigerator compartment 2 through the air passage 8. The cold air sent to the refrigerator compartment 2 flows from the back side to the front side of the refrigerator compartment 2. Then, the cold air returns to the evaporator chamber 4 through a return air passage (not shown) provided at the back of the freezer compartment 3 from the bottom of the refrigerator compartment 2.

[0021] As described above, in the refrigerator 100, the control unit 90 is configured to be able to cool each of the refrigerator compartment 2 and the freezer compartment 3 by controlling the cooling fan 42 to send cold air into the freezer compartment 3 and the refrigerator compartment 2.

[0022] In the refrigerator 100, the control unit 90 controls the cooling capacity of the refrigerator 100 obtained by the following refrigeration cycle. That is, the control unit 90 compresses the refrigerant flowing through the refrigeration cycle with the compressor 6 to change it into a high-temperature and high-pressure gas, and dissipates heat with a condenser (not shown) to change its state to a liquid. The liquefied refrigerant is vaporized in the evaporator 40 to change its state to a gas. Since the refrigerant absorbs heat from the surroundings when changing to a gas state, the evaporator 40 can generate extremely low-temperature cold air to cool the freezer compartment 3. The refrigerant vaporized in the evaporator 40 returns to the compressor 6 again. In the refrigerator 100, the control unit 90 can calculate the cooling capacity based on the rotation speed and operation rate of the compressor 6. Then, by controlling the operation of the compressor 6 by the control unit 90, the cooling capacity for cooling the freezer compartment 3 by the evaporator 40 can be controlled.

[0023] The control unit 90 operates the cooling fan 42 to send the cold air generated in the evaporator 40 from the upper part of the evaporator chamber 4 to the freezer compartment 3. In the freezer compartment 3, the cold air moves from the upper part of the freezer compartment 3 toward the bottom of the freezer compartment 3. The cold air that has circulated in the freezer compartment 3 returns into the evaporator chamber 4 from the lower part of the evaporator chamber 4.

[0024] Incidentally, every time the refrigerator door 20 or the freezer door 30 is opened or closed, moisture from the outside air enters the interior of the refrigerator 100. Also, when storing foods with a lot of moisture in the refrigerator compartment 2 or the freezer compartment 3, moisture is released from the foods. Thus, when moisture is contained in the interior of the refrigerator, frost is generated in the evaporator 40 and within the evaporator chamber 4. When a large amount of frost is generated in the evaporator 40 and within the evaporator chamber 4, heat exchange in the evaporator 40 is inhibited by the frost, and the cooling efficiency decreases. Therefore, the refrigerator 100 is configured to perform a defrosting process of heating the evaporator 40 and the interior of the evaporator chamber 4 with the heater 41 to remove the frost. Then, the frost removed by this defrosting process becomes water and accumulates in the evaporation tray 5.

[0025] (Defrosting Process) Hereinafter, the defrosting process executed in the refrigerator 100 will be described with reference to FIGS. 4 to 6. First, with reference to FIGS. 4 and 5, an example of the cold air flow path and temperature distribution in the freezer compartment 3 will be described. FIGS. 4 and 5 are diagrams schematically showing an example of the cold air flow path and temperature distribution in the freezer compartment 3 of the refrigerator 100 shown in FIG. 2. FIG. 4 shows an example of the temperature distribution in the steady operation state, and FIG. 5 shows an example of the temperature distribution when a new frozen food 50b is newly introduced as a heat load to the freezer case 32 of the freezer compartment 3. Note that the steady operation state is an operation state when the heat load input from the outside is sufficiently cooled, and is a state in which the refrigerator 100 is operating with a cooling capacity sufficient to maintain the indoor temperature.

[0026] As shown in FIGS. 4 and 5, the cold air generated by the evaporator 40 is sent from the back side to the front side of the freezer compartment 3 by the cooling fan 42. The cold air sent by the cooling fan 42 flows toward the freezer door 30 through the spaces between the plurality of freezer compartment cases 32. Then, it flows along the bottom of the freezer compartment 3 and returns to the evaporator chamber 4 through the lower opening in the evaporator chamber 4.

[0027] In the steady operation state, the temperature distribution in the freezer compartment 3 is, for example, the temperature of the cold air around the evaporator 40 is -30°C, the temperature of the cold air around the cooling fan 42 is -23°C, the temperature of the frozen food 50a stored in the freezer compartment case 32 is -20°C, and the temperature of the cold air circulating in the freezer compartment 3 and returning to the evaporator chamber 4 is -20°C. That is, the -23°C cold air sent by the cooling fan 42 in the freezer compartment 3 rises in temperature when flowing through the freezer compartment 3 to maintain the temperature, and returns to the evaporator chamber 4 at -20°C.

[0028] On the other hand, when a new frozen food 50b is loaded into the freezer compartment case 32 of the freezer compartment 3 as a heat load, the temperature distribution in the freezer compartment 3 becomes as shown in FIG. 5. That is, the temperature in the freezer compartment 3 rises when the new frozen food 50b is loaded. For this reason, the temperature of the cold air flowing through the freezer compartment 3 and returning to the evaporator chamber 4 rises to -15°C. Since the temperature of the return cold air supplied to the evaporator 40 has risen, even if it is cooled in the evaporator 40, the temperature only drops to about -25°C. Therefore, the temperature rises to -20°C by the time it is sent out from the cooling fan 42.

[0029] As described above, when a heat load such as a new frozen food 50b is loaded into the freezer compartment 3, the temperature of the cold air returning to the evaporator chamber 4 becomes higher compared to the steady operation. Therefore, in the refrigerator 100, it is configured to be able to perform defrosting efficiently by starting the defrosting process at the timing when the temperature of the evaporator 40 and the evaporator chamber 4 rises due to the cold air with increased temperature returning to the evaporator chamber 4. In the present disclosure, the start timing of the defrosting process is the timing to operate the heater 41 to heat the evaporator 40 and the evaporator chamber 4.

[0030] Specifically, the defrosting process is started as follows. In the refrigerator 100, in advance, when in a steady state, the cooling capacity at that time is set as the reference cooling capacity, and a cooling capacity higher than the reference cooling capacity, for example, a cooling capacity that is 25% higher than the reference cooling capacity, is set as the first threshold value. And this first threshold value is stored in the storage unit 91 in advance.

[0031] Note that the reference cooling capacity can be obtained as an average value by obtaining the cooling capacity of the refrigerator 100 several times in a steady operation state where there is no input of a new heat load or opening and closing of the freezer door 30 for a certain period and the refrigerator 100 is operating stably.

[0032] Also, the first threshold value is not limited to a value indicating a cooling capacity that is 25% higher than the reference cooling capacity, and can be set as appropriate in consideration of the temperature distribution in the freezer compartment 3 and the time-series change of the temperature distribution, etc.

[0033] As shown in FIG. 6, in the refrigerator 100 according to the first embodiment, the ON / OFF operation cycle of the compressor 6 is taken as one cycle, and the control unit 90 calculates the cooling capacity for each cycle. FIG. 6 is a diagram showing an example of the time-series changes of the ON / OFF and rotational speed of the compressor 6, the DF temperature (evaporator temperature), the F temperature (freezer compartment temperature), and the cooling capacity in the refrigerator 100 according to the first embodiment of the present disclosure. Note that the DF temperature is the temperature detected by the DF temperature sensor 43, and the F temperature is the temperature detected by the F temperature sensor 44. FIG. 6 shows, for example, the operation state of the refrigerator 100 before and after a heat load is input to the freezer compartment 3.

[0034] In FIG. 6, the time-series changes in the ON / OFF and rotational speed of the compressor 6 are indicated by the height of the graph. For convenience of explanation in FIG. 6, the periods of the first to seventeenth cycles are illustrated, and it is assumed that a heat load is applied in the fifth cycle. As shown in FIG. 6, the length of the ON / OFF of the compressor 6 varies according to the detection result of the F temperature sensor 44. For example, when the temperature detected by the F temperature sensor 44 exceeds the temperature detected by the F temperature sensor 44 during steady operation, the period for turning on and driving the compressor 6 becomes longer, and the cooling capacity increases. In the fifth and sixth cycles, when the ON time of the compressor 6 exceeds a predetermined time, the driving rotational speed of the compressor 6 is increased. Thereby, when the ON time of the compressor 6 becomes long, it is determined that the heat load is large, and the cooling capacity per unit time is also increased.

[0035] In the refrigerator 100, the control unit 90 calculates the cooling capacity based on the rotational speed and operation rate of the compressor 6 for each cycle, and stores the log of the calculation result in the storage unit 91. For example, the operation rate is calculated as ON time / (ON time + OFF time) in one cycle in which the ON / OFF of the compressor 6 is repeated. Also, for the rotational speed of the compressor 6, the time average of the rotational speed while the compressor 6 is ON is calculated. It may be the maximum value or the simple average value instead of the time average. Then, the cooling capacity can be calculated from the product of the calculated rotational speed and operation rate of the compressor 6. Note that the calculation of the cooling capacity is not limited to each cycle, and it may be calculated over a plurality of cycles, or may be calculated based on the rotational speed and operation rate of the compressor 6 every predetermined time (for example, 2 hours).

[0036] When the cooling capacity exceeds the first threshold here, the control unit 90 determines that an event has occurred in which the temperature of the cold air returning into the evaporator chamber 4, such as the introduction of a new heat load, has risen. Then, when the cooling capacity of the refrigerator 100 falls below the first threshold, the control unit 90 determines that sufficient heat exchange has been performed between the heat load and the cold air. At this time, the temperature in the evaporator chamber 4 is still higher than the temperature during steady operation. Therefore, when the cooling capacity of the refrigerator 100 falls below the first threshold, the control unit 90 turns on the heater 41 and starts executing the defrosting process. Then, when the temperature detected by the DF temperature sensor 43 satisfies a predetermined condition, such as rising to a predetermined temperature, the control unit 90 stops the execution of the defrosting process.

[0037] In this way, in the refrigerator 100, cold air whose temperature has risen due to heat exchange with the introduced heat load flows into the evaporator chamber 4, and when the temperature in the evaporator chamber 4 is higher than that during steady operation, the defrosting process is started. Since the temperature in the evaporator chamber 4 is rising, the surface temperature of the frost adhering to the evaporator 40 rises and it becomes a state where it is easy to melt. By starting the defrosting process at that time, the energy for the heater 41 to melt the frost can be reduced. That is, in the refrigerator 100, the heat obtained by heat exchange with the heat load can be used for the initial defrosting, and the defrosting of the evaporator 40 can be efficiently performed.

[0038] Note that the defrosting process executed in the refrigerator 100 is not only started when the cooling capacity falls below the first threshold after exceeding the first threshold as described above, but is also configured to be started periodically based on, for example, the cumulative operation time of the refrigerator 100 or the compressor 6. Since it is configured in such a way that the defrosting process can be started periodically in this way, the refrigerator 100 can remove the frost that adheres to the evaporator 40 or the evaporator chamber 4 even when there is no variation in the cooling capacity.

[0039] In addition, the defrosting process using the heater 41 implemented in the refrigerator 100 according to the first embodiment of the present disclosure is suitable for a refrigerator configured to suppress the influence of the temperature rise caused by the heating of the heater 41 on frozen foods in the freezer compartment 3 where the freezer case 32 is provided.

[0040] (Modification example) In the refrigerator 100 according to the first embodiment, the cooling capacity of the refrigerator 100 exceeds the first threshold value, and then the defrosting process is started when it falls below the first threshold value. On the other hand, in the refrigerator 100 according to the modification example of the first embodiment, a second threshold value indicating a cooling capacity even lower than the first threshold value is preset and stored in advance in the storage unit 91. For example, the second threshold value can be set to a value that is 12% higher than the reference cooling capacity. The refrigerator 100 according to the modification example of the first embodiment is different from the refrigerator 100 according to the first embodiment in that the defrosting process is started when the cooling capacity exceeds the first threshold value and then falls below the second threshold value.

[0041] That is, in the refrigerator 100 according to the first modification example of the first embodiment, the start of the defrosting process is waited until the cooling capacity becomes closer to the cooling capacity in the steady state than that of the refrigerator 100 according to the first embodiment. Therefore, in the refrigerator 100 according to the first modification example of the first embodiment, the defrosting process can be started in a state where sufficient heat exchange is performed between the heat load and the cold air and the temperature of the heat load has sufficiently decreased compared to the refrigerator 100 according to the first embodiment. Therefore, it is possible to suppress the cooling from being interrupted in a state where the heat load is not sufficiently cooled.

[0042] It is assumed that the start timing of the regular defrosting process may come while the cooling capacity of the refrigerator 100 exceeds the first threshold value and before it falls below the first or second threshold value. In such a case, the execution of the regular defrosting process may be configured to be postponed until the cooling capacity falls below the first or second threshold value.

[0043] In addition, for the defrosting process, when the temperature detected by the DF temperature sensor 43 rises to a predetermined temperature, the execution of the defrosting process is stopped. However, a plurality of defrosting processes with different predetermined temperatures (defrost stop temperatures) may be switched and executed. For example, it may have a first defrosting process with a lower defrost stop temperature (e.g., 4°C) and a second defrosting process with a slightly higher defrost stop temperature (e.g., 7°C). And in this embodiment, for the regular defrosting process (other defrosting processes), it is set to perform the first defrosting process. When performing the defrosting process using the cold air whose temperature has risen due to heat exchange with the heat load (when the cooling capacity of the refrigerator 100 exceeds the first threshold and then falls below the first threshold or the second threshold), it may be set to execute the second defrosting process. When there is a large amount of heat exchange with the heat load, the amount of frost adhering to the evaporator 40 often increases. Therefore, when it is determined that the heat exchange with the heat load is greater as the cooling capacity of the refrigerator 100 exceeds the first threshold, by executing the defrosting process with the second defrosting process with a higher defrost stop temperature, frost adhering to a position far from the DF temperature sensor 43 and other frost adhering widely to the evaporator 40 can be more reliably removed.

[0044] Also, as described above, in this embodiment, since the defrosting process is executed when the cooling capacity of the refrigerator 100 falls below the first threshold or the second threshold, the surface temperature of the frost adhering to the evaporator 40 rises and is in a state where it is easy to melt. Therefore, even if the second defrosting process is executed, the defrosting time is not likely to become long, and the influence of the temperature rise due to the heating of the heater 41 on the frozen food can be suppressed.

[0045] Further, in the refrigerator 100, the control unit 90 may be configured to extend the processing period of each of the first defrosting process and the second defrosting process based on the temperature change of the evaporator 40 detected by the DF temperature sensor 43. Note that the defrosting process performed by extending the processing period in the first defrosting process or the second defrosting process is referred to as an extended defrosting process. Since there is a large amount of frost adhering to the evaporator 40, when the temperature of the evaporator 40 detected by the DF temperature sensor 43 does not rise to a predetermined defrost stop temperature within a predetermined period, the process shifts from the first defrosting process or the second defrosting process to the extended defrosting process. Then, the extended defrosting process ends when the temperature of the evaporator 40 detected by the DF temperature sensor 43 rises to the predetermined defrost stop temperature + 3°C.

[0046] (Second Embodiment) In the refrigerator 100 according to the first embodiment, it was the defrosting process when a heat load was applied to the freezer compartment 3. In contrast, the refrigerator 200 according to the second embodiment will explain the defrosting process when a heat load is applied to the refrigerator compartment 2. Note that since the configuration of the refrigerator 200 according to the second embodiment is the same as the configuration of the refrigerator 100 according to the first embodiment shown in FIG. 2, the same members are denoted by the same reference numerals and the description thereof is omitted.

[0047] (Defrosting Process) Referring to FIG. 7, the defrosting process in the refrigerator 200 according to the second embodiment will be described. FIG. 7 is a diagram showing an example of the time-series changes of the ON / OFF and rotation speed of the compressor 6, the opening / closing of the damper 7, the DF temperature (evaporator temperature), the F temperature (freezer compartment temperature), the R temperature (refrigerator compartment temperature), and the cooling capacity in the refrigerator 200 according to the second embodiment of the present disclosure. Note that the DF temperature is the temperature detected by the DF temperature sensor 43, the F temperature is the temperature detected by the F temperature sensor 44, and the R temperature is the temperature detected by the R temperature sensor 45. In FIG. 7, for example, the operating state of the refrigerator 200 before and after food is placed in the refrigerator compartment 2 as a heat load is shown.

[0048] As shown in FIG. 7, the time-series changes in the ON / OFF and rotational speed of the compressor 6 are indicated by the height of the graph. The time-series changes in the opening and closing of the damper can also be indicated by the height of the graph. In the refrigerator 100 according to the second embodiment, in the operation cycle of the ON / OFF of the compressor 6, a cycle including the period during which the damper 7 is in the open state is defined as one cycle in the operation cycle of the refrigerator 200. For the sake of convenience of explanation in FIG. 7, the first to ninth cycles are illustrated, and it is assumed that a heat load is input in the fifth cycle.

[0049] Before the heat load is input to the refrigerating chamber 2, that is, until the first to fourth cycles, it is in a steady state where the length of each cycle is substantially constant. Here, when a heat load is input to the refrigerating chamber 2, in order to suppress the temperature rise of the refrigerating chamber 2 and cool the input heat load, the period during which the damper 7 is in the open state becomes longer. Similarly, the period during which the compressor 6 is ON also becomes longer. As a result, the length of the fifth cycle of the refrigerator 200 becomes longer than each of the first to fourth cycles. After the sixth cycle, the length of each cycle repeats a shorter period and a longer period so as to bring the operation state of the refrigerator 200 closer to the steady state.

[0050] In the example shown in FIG. 7, the cooling capacity of the refrigerator 200 exceeds the first threshold value in the sixth cycle. At this time, the control unit 90 determines that an event in which the temperature in the evaporator chamber 4 rises, that is, a heat load is input. Then, when it falls below the first threshold value after the seventh cycle, it is determined that heat exchange has occurred between the heat load and the cold air flowing through the refrigerating chamber 2, and the temperature in the evaporator chamber 4 has risen due to the heat obtained from the heat load. In the refrigerator 200 according to the second embodiment, the control unit 90 controls to operate the heater 41 to execute a defrosting process after the end of the seventh cycle.

[0051] In the refrigerator 200 according to the second embodiment, when the cooling capacity is below the first threshold value and the defrosting process is executed, the control unit 90 calculates the ratio of the opening time of the damper 7 to the ON time of the compressor in the cycle when it is determined that the cooling capacity is below the first threshold value. Then, if the ratio of the opening time of the damper 7 is equal to or greater than a predetermined threshold value, the control unit 90 determines that a heat load has been applied to the refrigerating chamber 2, and if it is less than the predetermined threshold value, the control unit 90 determines that a heat load has been applied to the freezing chamber 3.

[0052] When the control unit 90 determines that a heat load has been applied to the refrigerating chamber 2, the defrost stop temperature of the defrosting process may be set higher than when it is determined that a heat load has been applied to the freezing chamber 3 as in the first embodiment. That is, when a heat load is applied to the refrigerating chamber 2, warmer return cold air enters the evaporator chamber 4, so the surface of the frost adhering to the evaporator 40 is in a state where it is more likely to melt. In addition, since more humid return cold air enters the evaporator chamber 4, there is a possibility that more new frost will adhere to the evaporator 40.

[0053] Therefore, when the control unit 90 determines that a heat load has been applied to the refrigerating chamber 2, by setting the defrost stop temperature of the defrosting process higher than when it is determined that a heat load has been applied to the freezing chamber 3, more frost can be reliably defrosted.

[0054] As described above, in the refrigerator 100 according to the second embodiment, the operation cycle of the refrigerator 100 is defined from the operation cycle of the compressor 6, and the start timing of the defrosting process can be determined based on the change in the cooling capacity in each cycle. Specifically, when the cooling capacity of each cycle exceeds the first threshold value and then falls below the first threshold value, the control unit 90 can operate the heater 41 to start the defrosting process.

[0055] Therefore, the refrigerator 200 according to the second embodiment can efficiently execute the defrosting process by using the heat obtained by heat exchange with the heat load. Therefore, the refrigerator 200 can efficiently defrost the evaporator 40.

[0056] Note that, in the refrigerator 200 according to the second embodiment, the control unit 90 executes a defrosting process when the temperature falls below the first threshold value. However, similar to the refrigerator 100 according to the modified example of the first embodiment, the refrigerator 200 according to the second embodiment may be configured such that the control unit 90 starts a defrosting process when the value of the cooling capacity is lower than a second threshold value which is lower than the first threshold value.

[0057] (Third Embodiment) The refrigerator 100 according to the first embodiment operates under conditions where the temperature change of the ambient temperature around the refrigerator 100 is small, such as when it is installed indoors, or the ambient temperature is constant. In contrast, the refrigerator 300 according to the third embodiment is configured to operate in an environment where the ambient temperature changes.

[0058] Normally, even if the temperature inside the refrigerator is the same, the cooling capacity required for the refrigerator is higher when the ambient temperature around the refrigerator is high than when it is low. Therefore, the refrigerator 300 according to the third embodiment is further provided with a peripheral temperature sensor 46 as shown in FIG. 8, and is configured such that the control unit 90 can use a first threshold value and a second threshold value according to the peripheral temperature detected by the peripheral temperature sensor 46, which is different from the refrigerator 100 according to the first embodiment. Since the other configurations are the same as those of the refrigerator 100 according to the first embodiment, the same members are denoted by the same reference numerals and the description thereof is omitted.

[0059] FIG. 8 is a block diagram showing an example of the main configuration of the refrigerator 300 according to the third embodiment of the present disclosure. The peripheral temperature sensor 46 is a temperature sensor that detects the peripheral temperature around the refrigerator 100 and is the second temperature sensor of the present disclosure.

[0060] Specifically, as shown in FIG. 9, the storage unit 91 stores in advance a model function representing a model curve with the ambient temperature as a variable. FIG. 9 is a graph showing an example of a model curve represented by a model function indicating the correspondence between the ambient temperature and the cooling capacity in the refrigerator 300 according to the third embodiment of the present disclosure. In FIG. 9, the relationship between the points indicating the correspondence between the ambient temperature and the cooling capacity and the model curve derived from this set of points is shown. In FIG. 9, the horizontal axis represents the ambient temperature, and the vertical axis represents the value indicating the cooling capacity.

[0061] This model function can be obtained based on the log of the information indicating the correspondence between the ambient temperature and the cooling capacity during the steady operation of the refrigerator 300. For example, region determination may be performed using the histogram method or the like between the part with the log and the part without the log, and a function representing the curve along the lower limit of the region with the log may be obtained as the model function. Alternatively, the model function may be a predefined mathematical formula.

[0062] Furthermore, as shown in FIG. 10 with the model curve obtained by the model function as the reference cooling capacity, the curve obtained by shifting upward from the model curve by a predetermined value is used as the information indicating the first threshold value and the information indicating the second threshold value according to the ambient temperature. Specifically, the curve shifted so as to be 25% more than the value of the model curve may be used as the information indicating the first threshold value according to the ambient temperature, and the curve shifted so as to be 12% more than the value of the model curve may be used as the information indicating the second threshold value according to the ambient temperature. The information indicating the first threshold value according to the ambient temperature is referred to as the first threshold value information. Also, the information indicating the second threshold value according to the ambient temperature is referred to as the second threshold value information. The first threshold value information and the second threshold value information may be the model function indicating the above-described model curve, or may be table information indicating the correspondence between the ambient temperature and the first threshold value and the second threshold value.

[0063] FIG. 10 is a graph showing the relationship between the model curve and the first threshold value and the second threshold value derived from the model curve in the refrigerator 300 according to the third embodiment of the present disclosure. In FIG. 10, the horizontal axis represents the ambient temperature, and the vertical axis represents the cooling capacity.

[0064] For the refrigerator 300 according to the third embodiment, as described above, the first threshold value information and the second threshold value information are stored in the storage unit 91 in advance. The control unit 90 calculates the cooling capacity based on the rotation speed and the operation rate of the compressor 6 for each cycle, and stores the log of the calculation result in the storage unit 91. Further, the control unit 90 acquires the information on the ambient temperature detected by the ambient temperature sensor 46, and refers to the first threshold value information and the second threshold value information to set the first threshold value and the second threshold value respectively.

[0065] When the cooling capacity of the refrigerator 100 exceeds the first threshold value set according to the ambient temperature, the control unit 90 determines that an event has occurred in which the temperature of the cold air returning into the evaporator chamber 4, such as the input of an external heat load, has risen. After that, when it is determined that the cooling capacity of the refrigerator 100 has fallen below the first threshold value or the second threshold value set according to the ambient temperature, it is determined that sufficient heat exchange has been performed between the heat load and the cold air. Then, the control unit 90 turns on the heater 41 to start the defrosting process.

[0066] As described above, even when the ambient temperature around the refrigerator 300 changes, the refrigerator 300 according to the third embodiment can obtain the timing for starting the defrosting process according to the changed ambient temperature.

[0067] Note that, in the refrigerator 300 according to the third embodiment, the configuration is such that the timing for starting the defrosting process is obtained using the first threshold value and the second threshold value, but a configuration may also be adopted in which the timing for starting the defrosting process is obtained using only the first threshold value.

Explanation of Reference Numerals

[0068] 2 Refrigerator compartment 3 Freezer compartment 4 Evaporator chamber 6 Compressor 7 Damper 8 Ventilation path 9 Control board 10a Cabinet 10b Cabinet 20 Refrigerator compartment door 24 Refrigerator compartment case 30 Freezer Door 32 Freezer Case 40 Evaporator 41 Heater 42 Cooling Fan 43 DF Temperature Sensor 44 F Temperature Sensor 45 R Temperature Sensor 46 Ambient Temperature Sensor 90 Control Unit 91 Memory Unit 100 Refrigerator 200 Refrigerator 300 Refrigerator

Claims

1. A freezer compartment, an evaporator that vaporizes a refrigerant to cool the freezer compartment, a compressor that compresses the refrigerant that has flowed through the evaporator and sends it back to the evaporator, a heater that heats the evaporator, a first temperature sensor that detects the temperature of the freezer compartment, and a control unit, wherein the control unit controls the cooling capacity for cooling the freezer compartment by the evaporator based on the detection result by the first temperature sensor, and when it is determined that the cooling capacity has fallen below a first threshold value that indicates a cooling capacity higher than the cooling capacity during steady operation, controls to execute a defrosting process of heating the evaporator by the heater to melt frost adhering to the evaporator.

2. The refrigerator according to claim 1, wherein the control unit controls to execute the defrosting process when it is determined that the value indicating the cooling capacity has fallen below a second threshold value that indicates a cooling capacity lower than the first threshold value after exceeding the first threshold value.

3. a second temperature sensor that detects the ambient temperature around the refrigerator, and a storage unit that stores first threshold value information indicating the first threshold value corresponding to the ambient temperature, wherein the control unit sets the first threshold value based on the ambient temperature detected by the second temperature sensor and the first threshold value information.

4. a second temperature sensor that detects the ambient temperature around the refrigerator, and a storage unit that stores first threshold value information indicating the first threshold value corresponding to the ambient temperature and second threshold value information indicating the second threshold value corresponding to the ambient temperature, wherein the control unit sets the first threshold value and the second threshold value based on the ambient temperature detected by the second temperature sensor, the first threshold value information, and the second threshold value information.

5. The refrigerator according to claim 1, wherein the control unit is capable of executing another defrosting process that is periodically executed separately from the defrosting process, and sets the temperature at which the execution of the defrosting process stops to be higher than the temperature at which the execution of the other defrosting process stops.

6. a freezer compartment, a third temperature sensor that detects the temperature of the freezer compartment, a ventilation passage that circulates air cooled by the evaporator to the freezer compartment, and a damper that opens and closes the ventilation passage based on the temperature detected by the third temperature sensor. When taking the operation cycle of the compressor including the period during which the damper is in the open state as one cycle, the control unit obtains the cooling capacity for each cycle. When it is determined that the cooling capacity has fallen below the first threshold value after exceeding the first threshold value indicating a cooling capacity higher than the cooling capacity during steady operation, if the ratio of the opening time of the damper to the ON time of the compressor in the cycle is equal to or higher than a predetermined threshold value, it is determined that a heat load has been applied to the refrigerating chamber, and if it is less than the predetermined threshold value, it is determined that the heat load has been applied to the freezing chamber. The refrigerator according to any one of claims 1 to 5.

7. When the control unit determines that the heat load has been applied to the refrigerating chamber, it is set so that the temperature at which the defrosting process is stopped is higher than when it is determined that the heat load has been applied to the freezing chamber. The refrigerator according to claim 6.

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