storage

Abstract

Provided is a storage box for cooling a stored object in one temperature zone, the storage box comprising: a body having a storage chamber and a cooler chamber; a door that is provided to a front surface of the storage chamber; a cooler that is disposed in the cooler chamber and that generates cold air by heat exchange with a refrigerant; a blower that sends the cold air to the storage chamber; a compressor that sends the refrigerant to the cooler; an in-chamber temperature sensor that measures an in-chamber temperature which is the temperature of the storage chamber; a cooler chamber temperature sensor that measures a cooler chamber temperature which is the temperature of the cooler chamber; an opening / closing sensor that detects opening / closing of the door; and a control device that controls the compressor and the blower. The control device determines a use frequency rank for each time zone on the basis of the number of times that the door is opened / closed, and if the current time zone is a non-use time zone in which the use frequency rank is the lowest, the control device determines whether a temperature difference between the in-chamber temperature and the cooler chamber temperature is equal to or greater than a threshold temperature. If the temperature difference is equal to or greater than the threshold temperature, the control device executes a suppression operation in which the blower is operated and the compressor is stopped.

Description

Technical Field

[0001] The present disclosure relates to a storage refrigerator for cooling and storing stored items such as food.

Background Art

[0002] Conventionally, refrigerators with improved energy-saving performance have been proposed. For example, in Patent Document 1, it is proposed to improve the energy-saving performance by devising the air duct configuration from the cooler chamber to the freezer chamber of the refrigerator. Specifically, in Patent Document 1, the upper outlet of the freezer chamber has the largest opening area among the outlets of the freezer chamber, the outlet opening of the cold air duct is provided above the blower, and the upper outlet of the freezer chamber is provided above the outlet opening of the cold air duct. Thereby, the flow of cold air from the cooler chamber to the freezer chamber becomes smooth, the fan power when sending the required air volume is suppressed, and the energy-saving performance is improved.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, due to changes in lifestyle such as the increase in dual-income households and single-person households, and the spread of infectious diseases caused by the coronavirus, there has been a strong tendency to buy a large amount of food at once and store it in the refrigerator. In addition, it is also common to freeze a large amount of cooked food at once and use it regularly, and to use a service that provides frozen food at a fixed monthly amount. As a result, the capacity of refrigerators is increasing, and the number of users who purchase a freezer as a second storage refrigerator in addition to the refrigerator is also increasing.

[0005] With the increased frequency of freezer use, the number of times the freezer door is opened and closed has increased compared to before, leading to increased power consumption of the freezer. Therefore, there has been a desire to improve the energy-saving performance of freezers. In this regard, energy-saving performance can also be improved by adopting an airflow configuration such as that described in Patent Document 1 in a freezer. However, unlike refrigerators that cool at multiple temperature zones, as in Patent Document 1, when cooling at a single temperature zone, there is room to further improve the energy-saving performance of the cooling mechanism's operation control.

[0006] This disclosure aims to solve the above-mentioned problems and improve the energy-saving performance of storage facilities that cool stored items within a single temperature range. [Means for solving the problem]

[0007] The storage facility according to this disclosure is a storage facility that cools stored items in a single temperature range and comprises a main body having a storage room and a cooler room, a door provided on the front of the storage room, a cooler located in the cooler room that generates cold air by heat exchange with a refrigerant, a blower that sends cold air to the storage room, a compressor that sends refrigerant to the cooler, an internal temperature sensor that measures the internal temperature of the storage room, a cooler room temperature sensor that measures the temperature of the cooler room, an open / close sensor that detects the opening and closing of the door, and a control device that controls the compressor and the blower. The control device determines the usage frequency rank for each time period based on the number of times the door is opened and closed, and if the current time period is an unused time period with the lowest usage frequency rank, it determines whether the temperature difference between the internal temperature and the cooler room temperature is above a threshold temperature, and if the temperature difference is above the threshold temperature, it performs a suppression operation that operates the blower and stops the compressor. [Effects of the Invention]

[0008] According to the storage facility described herein, energy-saving performance can be improved by implementing a suppression operation during periods of non-use, in which the blower is operated and the compressor is stopped when the temperature difference between the internal temperature of the storage facility and the temperature of the cooling chamber exceeds a threshold temperature. [Brief explanation of the drawing]

[0009] [Figure 1] This is a front view of the freezer according to Embodiment 1. [Figure 2] This is a schematic cross-sectional view of a freezer according to Embodiment 1. [Figure 3] This is a schematic diagram of the cooling mechanism of a freezer according to Embodiment 1. [Figure 4] This is a schematic diagram showing the structure of the cooling chamber of the freezer according to Embodiment 1. [Figure 5] This is a control block diagram of a freezer according to Embodiment 1. [Figure 6] This figure illustrates an example of the hardware configuration of a control device for a freezer according to Embodiment 1. [Figure 7] This figure illustrates another example of the hardware configuration of the control device for the freezer according to Embodiment 1. [Figure 8] This is a flowchart showing the operation of the freezer according to Embodiment 1. [Figure 9] This figure illustrates the change in internal temperature Tf when the freezer door is opened and closed in Embodiment 1. [Figure 10] This is a flowchart showing the method for calculating the adjustment coefficient α in Embodiment 1. [Figure 11] This flowchart shows the method for measuring the temperature rise and recovery time when opening and closing a door in Embodiment 1. [Figure 12] This is a flowchart showing the method for measuring the return time when opening and closing a door in Embodiment 1. [Figure 13] This diagram illustrates the suppressed operation of a freezer according to Embodiment 1. [Figure 14] This flowchart shows the normal operation flow of the freezer according to Embodiment 1. [Figure 15] This is a flowchart showing the flow of the suppression operation in the freezer according to Embodiment 1. [Figure 16] This is a pH diagram showing the effects obtained by performing a suppression operation in the freezer according to Embodiment 1. [Figure 17] It is a flowchart showing the operation of the refrigerator according to Embodiment 2. [Figure 18] It is an example of a graph showing the number of times the freezer door of the refrigerator according to Embodiment 2 is opened and closed, the usage frequency rank, and the change in the set temperature Tfs of the freezer. [Figure 19] It is a flowchart showing the operation of the refrigerator according to Embodiment 3. [Figure 20] It is an example of a table showing the setting rank according to the usage frequency rank and the outside air rank of the refrigerator according to Embodiment 3. [Figure 21] It is an example of a graph showing the number of times the freezer door of the refrigerator according to Embodiment 3 is opened and closed, the usage frequency rank, and the setting rank. [Figure 22] It is a flowchart showing the operation of the refrigerator according to Embodiment 4. [Figure 23] It is a flowchart showing the flow of the special defrost operation of the refrigerator according to Embodiment 4. [Figure 24] It is a diagram for explaining the electric input and the cooler chamber temperature during the defrost operation at low outside air temperature in a conventional refrigerator. [Figure 25] It is a diagram for explaining the electric input and the cooler chamber temperature during the defrost operation at low outside air temperature in the refrigerator according to Embodiment 4. [Figure 26] It is a diagram for comparing the lengths of the heater energization times between a conventional refrigerator and the refrigerator according to Embodiment 4. [Figure 27] It is a front view of the refrigerator according to Modification 1. [Figure 28] It is a schematic cross-sectional view of the refrigerator according to Modification 1.

Embodiments for Carrying Out the Invention

[0010] The embodiments of the storage facility described herein will be explained below with reference to the drawings. In each drawing, components with the same reference numerals are the same or equivalent components, and this is common throughout the entire specification. In addition, other steps that can be performed between each step of the flowchart of this disclosure may be included. Note that the relative dimensions or shapes of the components in each drawing may differ from those of the actual components.

[0011] Embodiment 1. <Configuration of Freezer 1> Embodiment 1 describes a freezer 1 that stores goods by cooling them at freezing temperatures, as an example of a storage facility. Figure 1 is a front view of the freezer 1 according to Embodiment 1. Figure 2 is a schematic cross-sectional view of the freezer 1 according to Embodiment 1. Figure 2 shows the freezer 1 shown in Figure 1 cut along line segment AA and viewed from the direction of the arrow. In the following description, terms indicating direction, such as "up," "down," "right," "left," "front," "front," "back," and "rear," will be used as appropriate to facilitate understanding, but these are for illustrative purposes only and do not limit the embodiments. In the embodiments, "up," "down," "right," "left," "front," "front," "back," and "rear" will be used to describe the freezer 1 in use when viewed from the front.

[0012] As shown in Figures 1 and 2, the freezer 1 comprises a main body 2 with an open front and a storage compartment inside. The main body 2 has a steel outer casing 21, a resin inner casing 22, and an insulating material 23 filled in the space between the outer casing 21 and the inner casing 22. The outer casing 21 is made of a metal such as steel and has an opening on its front. The inner casing 22 is made of resin and is fitted into the outer casing 21 through the opening. The insulating material 23 is made of, for example, foamed urethane or vacuum insulation material and is filled in the space between the outer casing 21 and the inner casing 22.

[0013] The storage compartment located within the main body 2 is the freezer compartment 10. The freezer compartment 10 consists of an upper freezer compartment 11 and a lower freezer compartment 12. However, there is no partition between the upper freezer compartment 11 and the lower freezer compartment 12, and the upper freezer compartment 11 and the lower freezer compartment 12 are a single space set to the same temperature range. By not providing a partition within the freezer compartment 10, it is possible to increase the internal volume of the freezer compartment 1 compared to a conventional freezer that is divided into upper and lower freezer compartments by a partition. In this embodiment, the space supplied with cold air from outlets 51a to 51c located above the blower 35 (described later) is called the upper freezer compartment 11, and the space supplied with cold air from outlets 52a to 52c located below the blower 35 is called the lower freezer compartment 12. In other words, the space supplied with cold air blown from the blower 35 in the opposite direction to gravity is referred to as the upper freezer compartment 11, and the space supplied with cold air blown from the blower 35 in the direction of gravity is referred to as the lower freezer compartment 12.

[0014] The freezer compartment 10 is provided with a plurality of shelves 13 for placing food and other stored items, and a plurality of storage containers 14 for storing the stored items inside. More specifically, the upper freezer compartment 11 is provided with two shelves 13 and one storage container 14, and the lower freezer compartment 12 is provided with three storage containers 14. The shelves 13 are, for example, glass shelves. The storage containers 14 are, for example, sliding cases that can be pulled out forward. The storage containers 14 are supported by case frames (not shown) provided on the left and right inner walls of the upper freezer compartment 11 and the lower freezer compartment 12, and are configured to slide in the front-back direction independently of the opening and closing of the freezer compartment door 15.

[0015] By designating the top two shelves 13 in the upper freezer compartment 11, items to be used in the short term and frequently used items can be easily retrieved, improving convenience. Furthermore, items to be stored for long-term storage can be stored in the storage containers 14 in the lower freezer compartment 12, thereby minimizing the effects of temperature changes caused by opening and closing the freezer door 15.

[0016] The upper freezer compartment 11 and the lower freezer compartment 12 are set to the freezing temperature range. The freezing temperature range is a temperature range below 0°C, which is significantly lower than the refrigeration temperature range. For example, the freezing temperature range is between -20°C and -18°C.

[0017] An opening formed on the front of the freezer compartment 10 is provided with a single-leaf freezer door 15 that opens and closes the opening. The freezer door 15 is divided into an upper door 15a, which is provided on the front of the upper freezer compartment 11, and a lower door 15b, which is provided on the front of the lower freezer compartment 12. The upper door 15a and the lower door 15b are attached to the main body 2 via hinges provided on the main body 2 and are opened and closed individually. Note that the configuration of the freezer door 15 is not limited to the examples in Figures 1 and 2. For example, the upper door 15a and the lower door 15b may each be double-leaf or drawer-type doors.

[0018] A door partition 16 is provided between the upper door 15a and the lower door 15b to separate them. As shown in Figure 2, the door partition 16 is provided only on the front side of the freezer compartment 10 and does not separate the upper freezer compartment 11 and the lower freezer compartment 12. The door partition 16 is equipped with an opening / closing sensor 17 that detects the opening and closing of the upper door 15a and the lower door 15b, respectively.

[0019] The opening / closing sensor 17 consists of an operating unit provided on the rear side of the upper door 15a and the lower door 15b, and a detection unit provided on the door partition 16. The detection unit is a magnetic sensor such as a reed switch or a low-voltage Hall IC that operates at 48V or less. The operating unit activates the detection unit when it is brought close to it, and is such as a magnet. The opening / closing sensor 17 may also be composed of a single unit such as a push-button switch. By configuring the detection unit of the opening / closing sensor 17 as a parallel circuit, it becomes possible to recognize whether the upper door 15a or the lower door 15b is open, or whether both are open. In this embodiment, when at least one of the upper door 15a or the lower door 15b is opened, the opening / closing sensor 17 transmits an open signal to the control device 6 indicating that the freezer door 15 is in an open state. In other words, in this embodiment, the state in which at least one of the upper door 15a and the lower door 15b is open is defined as the open state, and the state in which both the upper door 15a and the lower door 15b are closed is defined as the closed state.

[0020] An operation display unit 18 is provided on the outer surface of the upper door 15a. The operation display unit 18 comprises an operation unit 18a that receives operations from the user, and a display unit 18b that displays temperature information of the freezer compartment 10, inventory information, and notifications to the user. The operation unit 18a has multiple operation buttons, and the user can set the temperature of the freezer compartment 10 by operating the operation unit 18a. The display unit 18b is, for example, a liquid crystal display. The operation display unit 18 may also be configured as a touch panel in which the operation unit 18a is integrally formed on the display unit 18b.

[0021] Inside the operation display unit 18, there is an outside air temperature sensor 19 that measures the outside air temperature Ta, which is the temperature of the space outside the freezer compartment 10 separated from the freezer compartment by the freezer door 15. The outside air temperature sensor 19 is, for example, a thermistor. The outside air temperature Ta measured by the outside air temperature sensor 19 is output to the control device 6.

[0022] A control device 6 for controlling various parts of the freezer 1 is provided on the rear side of the upper part of the freezer 1. Based on input from the operation unit 18a and output from each sensor, the control device 6 controls the cooling mechanism and each heater, which will be described later, to perform a cooling operation to cool the freezer compartment 10 and a defrosting operation to defrost the evaporator 34. The configuration and control of the control device 6 will be described in detail later.

[0023] A cooling mechanism for supplying cold air is provided on the rear side of the freezer compartment 10. Figure 3 is a schematic diagram of the cooling mechanism of the freezer 1 according to Embodiment 1. As shown in Figure 3, the freezer 1 includes a compressor 31, a condenser 32, a pressure reducing device 33, a cooler 34, and a blower 35 as a cooling mechanism for supplying cold air. The compressor 31, condenser 32, pressure reducing device 33, and cooler 34 are connected by refrigerant pipes to form a refrigerant circuit. The solid arrows in Figure 3 indicate the direction in which the refrigerant circulates in the refrigerant circuit.

[0024] The compressor 31 compresses the refrigerant into a high-temperature and high-pressure gaseous state. As shown in Figure 2, the compressor 31 is located in a machine room 30 below the cooler room 3 on the rear side of the main body 2 of the freezer 1. The high-temperature and high-pressure refrigerant flowing out of the compressor 31 flows into the condenser 32. The condenser 32 dissipates the heat from the refrigerant flowing in from the compressor 31, causing it to condense. The condenser 32 is, for example, a fin-and-tube type heat exchanger.

[0025] The refrigerant condensed in the condenser 32 flows into the pressure reducing device 33. The pressure reducing device 33 reduces the pressure of the refrigerant flowing in from the condenser 32, converting it into a two-phase liquid and gaseous state. The pressure reducing device 33 is, for example, a capillary tube. The two-phase liquid and gaseous refrigerant flowing out of the pressure reducing device 33 flows into the cooler 34. In other words, the compressor 31 sends the refrigerant to the cooler 34 via the condenser 32 and the pressure reducing device 33.

[0026] The cooler 34 evaporates the two-phase refrigerant, which has been depressurized by the depressurization device 33, and cools the air around the cooler 34 through the endothermic effect of the refrigerant evaporation. In other words, the cooler 34 functions as an evaporator in the refrigerant circuit. The cooler 34 is, for example, a fin-and-tube type heat exchanger. The refrigerant that flows out of the cooler 34 returns to the compressor 31. By repeating this cycle, the cooler 34 generates cold air.

[0027] The cold air generated by the cooler 34 is sent to the freezer chamber 10 by the blower 35. The blower 35 is, for example, an axial fan. The rotational speed of the blower 35 is controlled by the control device 6.

[0028] Figure 4 is a schematic diagram showing the structure inside the cooler chamber 3 of the freezer 1 according to Embodiment 1. The dashed arrows in Figure 4 indicate the direction of airflow D1 in the cooler chamber 3. The cooler 34, located inside the cooler chamber 3, generates cold air through heat exchange with the refrigerant. The cooler 34 has a plurality of heat transfer tubes 342, each having a smooth surface and a plurality of thin, plate-shaped fins 341, and a plurality of U-shaped connecting tubes 343. The heat transfer tubes 342 are arranged in the vertical direction. For example, six heat transfer tubes 342 are arranged along the vertical direction. Two vertically adjacent heat transfer tubes 342 are connected at one end in the left-right direction by a connecting tube 343. This forms a continuous refrigerant pipe.

[0029] The refrigerant circulating in the refrigerant pipes of the cooler 34 flows from the inlet 34a, which is connected to the lowest heat transfer tube 342, to the outlet 34b, which is connected to the uppermost heat transfer tube 342. The air inside the cooler chamber 3 is blown by a fan 35 located at the top of the cooler chamber 3 in a direction D1, from the bottom to the top of the cooler 34. Therefore, the lowest heat transfer tube 342 is positioned on the upstream side of the multiple heat transfer tubes 342 with respect to the airflow direction D1. Also, the uppermost heat transfer tube 342 is positioned on the downstream side of the multiple heat transfer tubes 342 with respect to the airflow direction D1.

[0030] The low-temperature gaseous-liquid two-phase refrigerant flowing in from the pressure reducing device 33 flows from the inlet 34a of the cooler 34 through the upstream heat transfer tube 342 relative to the airflow direction D1, gradually flowing through the downstream heat transfer tubes 342 to the outlet 34b of the cooler 34. As the two-phase refrigerant flowing through the cooler 34 moves from the inlet 34a to the outlet 34b, it exchanges heat with the air flowing outside the heat transfer tubes 342. As a result, the liquid phase of the two-phase refrigerant evaporates as it flows through the heat transfer tubes 342. Normally, the temperature of the refrigerant at the inlet 34a of the cooler 34 is lower than the temperature of the refrigerant at the outlet 34b.

[0031] A return air passage 54 for cold air from the freezer chamber 10 is provided in the lower region of the cooler chamber 3. As a result, the return air from the freezer chamber 10 passes from the inlet 34a to the outlet 34b of the cooler 34, that is, from the upstream end to the downstream end of the cooler 34 in the airflow direction D1. Therefore, the heat exchange distance between the return air from the freezer chamber 10 and the cooler 34 is maximized. This allows the return air from the freezer chamber 10 to cover the entire volume of the cooler 34, enabling cooling using the entire cooler 34 and improving the heat exchange capacity with the refrigerant in the cooler 34.

[0032] Furthermore, the cooler chamber 3 is equipped with a cooler chamber temperature sensor 36 that measures the cooler chamber temperature Te, which is the temperature of the air in the cooler chamber 3. The cooler chamber temperature sensor 36 is, for example, a thermistor. The cooler chamber temperature Te measured by the cooler chamber temperature sensor 36 is output to the control device 6.

[0033] Returning to Figure 2, the freezer 1 includes a defrost heater 41 installed in the cooler chamber 3, a drain pipe 42 and drain heater 43 installed between the cooler chamber 3 and the machine room 30, and a drain pan 44 installed in the machine room 30. The defrost heater 41 is a heater that generates heat when energized and melts the frost that has accumulated on the cooler 34.

[0034] The drain pipe 42 discharges the melted water generated by the melting of frost attached to the cooler 34 into the drain pan 44. The drain heater 43 generates heat when energized, thawing the frozen drain pipe 42. The drain heater 43 also melts any ice in the remaining water that has dripped from the cooler 34, guiding it to the drain pipe 42 and then to the drain pan 44. By providing the drain heater 43, it is possible to prevent some of the melted water from remaining in the cooler chamber 3 as ice, solidifying again, and blocking the drain pipe 42.

[0035] The melted frost water guided to the drain pan 44 is stored in the drain pan 44 and evaporates over a certain period of time in the machine room 30, which is heated to a high temperature by the heat generated by the compressor 31. The volume of the drain pan 44 is larger than the volume of the cooler 34, for example, about 1.5 to 2.0 L. By making the volume of the drain pan 44 larger than the volume of the cooler 34, it is possible to prevent the water in the drain pan 44 from overflowing and spilling into the machine room 30.

[0036] The defrost heater 41 and the drain heater 43 are operated synchronously by the control device 6 during defrosting operation. In Figure 2, the drain heater 43 is located adjacent to the drain pipe 42, but the shape and arrangement of the drain heater 43 are not limited to the example in Figure 2. For example, the drain heater 43 may be made of aluminum foil or the like and wrapped around the drain pipe 42.

[0037] The main body 2 of the freezer 1 is provided with an upper air passage 51 for supplying cold air generated by the cooler 34 to the upper freezer compartment 11, and a lower air passage 52 for supplying cold air to the lower freezer compartment 12. The cold air in the cooler compartment 3 is flowed by the blower 35 in the airflow direction D1 from below the cooler 34 upwards. In this embodiment, the blower 35 is controlled to supply an appropriate amount of cold air to the upper air passage 51 and the lower air passage 52, respectively.

[0038] The upper air passage 51 is provided with outlets 51a to 51c that connect the upper freezer compartment 11 and the cooler compartment 3. Outlet 51a blows cold air into the first area A1, which is the storage space on the top shelf 13 of the freezer compartment 10. Outlet 51b blows cold air into the second area A2, which is the storage space on the second shelf 13 from the top of the freezer compartment 10. Outlet 51c blows cold air into the third area A3, which is the storage space inside the storage container 14, which is the third storage space from the top of the freezer compartment 10.

[0039] The lower air passage 52 is provided with outlets 52a to 52c that connect the lower freezer compartment 12 and the cooler compartment 3. Outlet 52a blows cold air into the fourth area A4, which is the storage space in the storage container 14 located fourth from the top in the freezer compartment 10. Outlet 52b blows cold air into the fifth area A5, which is the storage space in the storage container 14 located fifth from the top in the freezer compartment 10. Outlet 52c blows cold air into the sixth area A6, which is the storage space in the storage container 14 located sixth from the top in the freezer compartment 10, or in other words, the storage space at the very bottom of the freezer compartment 10.

[0040] The upper air passage 51 and the lower air passage 52 are not equipped with dampers to adjust the amount of cold air blown out to the upper freezer compartment 11 and the lower freezer compartment 12. This is because the freezer compartment 10 is controlled to maintain the same set temperature range, and the area of ​​each outlet is designed in advance to ensure that the temperature inside the freezer compartment 10 is nearly uniform, in accordance with the insulation specifications of the freezer 1, the specifications of the evaporator 34, and the specifications of the compressor 31. As a result, the freezer 1 can be controlled to the target set temperature without using any extra parts. This reduces the number of parts used, allowing for an increase in the internal volume of the freezer 1.

[0041] An internal temperature sensor 53 is provided near the center of the freezer compartment 10, which is an intermediate area between the upper freezer compartment 11 and the lower freezer compartment 12, for measuring the internal temperature Tf of the freezer compartment 10. The internal temperature sensor 53 is, for example, a thermistor. In the example shown in Figure 2, the internal temperature sensor 53 is provided on the back wall surface 520 of the fourth area A4 of the lower freezer compartment 12, but the position of the internal temperature sensor 53 is not limited to this. Alternatively, multiple internal temperature sensors 53 may be provided in the freezer compartment 10, and the average of these measured values ​​may be taken as the internal temperature Tf of the freezer compartment 10. The internal temperature Tf measured by the internal temperature sensor 53 is output to the control device 6.

[0042] Furthermore, a return air passage 54 is provided on the rear side of the sixth area A6 of the lower freezer compartment 12. The return air passage 54 is an air passage for guiding the air that has passed through the upper freezer compartment 11 and the lower freezer compartment 12 to the cooler room 3. The air that has passed through the upper freezer compartment 11 and the lower freezer compartment 12 flows into the cooler room 3 through the return air passage 54a from its inlet 54a. The inlet 54a of the return air passage 54 is provided away from the outlets of the upper air passage 51 and the lower air passage 52. In Figure 2, the inlet 54a is provided at the bottom of the freezer compartment 10, but the inlet 54a is not limited to the position shown in Figure 2 and can be provided on the wall surface inside the freezer compartment 10.

[0043] Next, the configuration of the airflow path in the freezer 1 according to this embodiment will be described. In the freezer 1, the cooling of the freezer compartment 10 is mainly carried out by indirect cooling using cooling air. In this embodiment, the airflow path is configured such that the amount of cold air (the amount of cooling capacity for objects in each area) Q1 to Q6 blown out to the first area A1 to the sixth area A6 in the freezer compartment 10 is in the relationship Q1>Q2>Q3>Q4>Q5>Q6. In other words, the airflow path is configured such that the amount of cold air in the upper area is greater than the amount of cold air in the lower area.

[0044] Furthermore, the amount of cold air Q can be estimated using the following equation (1). Here, M is the mass [kg], C is the specific heat [J / (kg·K)], and ΔT is the temperature difference of the cold air relative to the object being cooled [K]. Q ≈ M × C × ΔT ... (1)

[0045] In the case of cooling air in freezer 1, the amount of cold air Q can be estimated using the following equation (2). Here, ρ air is the density of air [kg / m³] 3 ], Fn is the flow rate in each area [m 3 / s] Q≒ρ air ×Fn×C×ΔT ···(2)

[0046] In other words, the airflow configuration of the freezer 1 is determined such that, given that the discharge flow rates from each outlet are F1 to F6, the discharge temperatures are T1 to T6, and the discharge areas are ss1 to ss6, the relationship |(F1×T1×ss1)|>|(F2×T2×ss2)|>|(F3×T3×ss3)|>|(F4×T4×ss4)|>|(F5×T5×ss5)|>|(F6×T6×ss6)| holds true. As a result, the amount of cold air per unit time flowing in from outlets 51a to 51c and 52a to 52c is greater in the upper part of the freezer compartment 10 and smaller towards the lower part.

[0047] To maintain the above relationship of cold air volume, the larger the airflow rate at each outlet, the lower the outlet temperature, and the larger the outlet area, the greater the amount of cold air. Therefore, the freezer compartment 10 is basically configured so that the airflow rate, outlet temperature, and outlet area decrease as you move from the top to the bottom.

[0048] As described above, by adjusting the amount of cold air from the outlets 51a-51c and 52a-52c in the freezer 1, it is possible to cool the inside of the freezer compartment 10 more efficiently. Colder air sinks due to gravity, so the cold air circulates in the freezer compartment 10 by falling from top to bottom. Therefore, by increasing the amount of cold air in the upper part of the freezer compartment 10, the cold air can be circulated from top to bottom, improving cooling efficiency and energy saving performance.

[0049] Furthermore, in the freezer 1, the cross-sectional area of ​​the upper air passage 51 is larger than the cross-sectional area of ​​the lower air passage 52. Also, the back wall of the lower air passage 52 is inclined, and the cross-sectional area of ​​the lower air passage 52 decreases towards the bottom. As a result, the pressure loss in the upper air passage 51 is smaller than the pressure loss in the lower air passage 52, and the amount of cold air flowing through the upper air passage 51 can be greater than the amount of cold air flowing through the lower air passage 52.

[0050] Furthermore, the insulation thickness of the wall 510 separating the upper air passage 51 and the upper freezer compartment 11 is greater than the insulation thickness of the wall 520 separating the lower air passage 52 and the lower freezer compartment 12. As a result, the insulation capacity of the upper freezer compartment 11 is greater than that of the lower freezer compartment 12. Alternatively, the specifications of the insulation material for walls 510 and 520 may be adjusted so that the insulation capacity of the upper freezer compartment 11 is greater than that of the lower freezer compartment 12.

[0051] As you move towards the top of the freezer compartment 10, the distance from the cooler 34 increases, and the temperature difference between the cold air and the storage space tends to gradually decrease while the cold air is being supplied. In response to this, by making the insulation thickness of the wall surface 510 of the upper air passage 51 greater than that of the wall surface 520 of the lower air passage 52, as described above, the decrease in the cooling effect at the top of the freezer compartment 10 can be suppressed. As a result, the decrease in the temperature (absolute value) of the cold air supplied to the upper freezer compartment 11 can be suppressed, and the amount of cold air in the upper freezer compartment 11 can be increased. In the case of temperature control of the freezer 1, the cold air is in the negative temperature range, and by using the above insulation structure, the cold air in the negative temperature range can be supplied to the upper freezer compartment 11 while remaining as cold as possible.

[0052] Furthermore, the freezer compartment 10 is subjected to heat intrusion from outside air through the ceiling of the main unit 2, and from the condenser 32 installed inside the main unit 2. Also, the upper door 15a, which opens and closes the upper freezer compartment 11, tends to be used more frequently by users than the lower door 15b, and the upper freezer compartment 11 experiences greater heat intrusion from the outside than the lower freezer compartment 12. Therefore, by making the insulation capacity of the upper freezer compartment 11 greater than that of the lower freezer compartment 12, the temperature difference between the upper freezer compartment 11 and the lower freezer compartment 12 can be reduced, and temperature unevenness within the freezer compartment 10 can be suppressed.

[0053] Furthermore, the blower 35 is positioned to blow out cold air at an oblique upward direction relative to the direction of gravity. The angle of the blower 35 relative to the direction of gravity is, for example, 35 to 40 degrees. In addition, the shape of the front wall surface 520 of the blower 35 is designed to guide the cold air blown out from the blower 35 so that the flow rate at the top is greater than the flow rate at the bottom.

[0054] <Operation of Freezer 1> Next, the operation of the freezer 1 will be described. Figure 5 is a control block diagram of the freezer 1 according to Embodiment 1. As shown in Figure 5, the control device 6 of the freezer 1 includes a storage unit 61, a cooling control unit 62, a heater control unit 63, an adjustment coefficient calculation unit 64, a rank determination unit 65, and a determination unit 66.

[0055] The memory unit 61 stores programs executed by the control device 6 and information used in those programs. For example, the memory unit 61 stores setting information input via the operation display unit 18, programs and parameters such as thresholds used for cooling and defrosting operations, and programs and parameters such as thresholds used for calculating adjustment coefficients and determining ranks, which will be described later. The memory unit 61 also stores the number of times the freezer door 15 has been opened and closed in the past, and the time the freezer door 15 was opened, along with date and time information. The memory unit 61 may be provided separately from the control device 6.

[0056] The cooling control unit 62 cools the freezer compartment 10 based on the measurement results of each sensor in the freezer compartment 1, the setting information input via the operation display unit 18, and the determination result of the determination unit 66. Specifically, the cooling control unit 62 controls the rotation speed of the compressor 31 and the rotation speed of the blower 35 so that the internal temperature Tf measured by the internal temperature sensor 53 becomes a preset temperature Tfs. The cooling control unit 62 also performs either normal operation or suppressed operation based on the determination result of the determination unit 66.

[0057] The heater control unit 63 controls the energization status of the defrost heater 41 and the drain heater 43. Specifically, when performing defrosting, the heater control unit 63 energizes the defrost heater 41 and the drain heater 43 in a synchronous manner. Defrosting is performed when the defrosting conditions are met during cooling operation.

[0058] The adjustment coefficient calculation unit 64 calculates an adjustment coefficient α used by the rank determination unit 65 to determine the usage frequency rank. The adjustment coefficient α is a value between 0 and 1 that indicates the proportion of load (storage) placed in the freezer compartment 10 when the freezer door 15 is opened or closed. Based on the temperature rise value ΔTf and recovery time tf of the internal temperature Tf when the freezer door 15 is opened or closed, and the temperature rise value ΔTe and recovery time te of the evaporator temperature Te, the adjustment coefficient calculation unit 64 determines whether or not a load was placed during each opening and closing in a past preset calculation period and calculates the adjustment coefficient α.

[0059] Initially, when the freezer 1 is first used, the adjustment coefficient calculation unit 64 may set the calculated adjustment coefficient α to an initial value of 0.5. Then, as described later, as the user's usage period of the freezer 1 progresses, an adjustment coefficient α suitable for the user is calculated and reflected in the usage frequency rank. Note that the adjustment coefficient calculation unit 64 is not mandatory, and the adjustment coefficient α may be set to 1 when determining the usage frequency rank.

[0060] The rank determination unit 65 determines the usage frequency rank of the freezer 1 for each time period. The time period is, for example, every hour based on 0:00. The rank determination unit 65 calculates the discrimination parameter X by multiplying the average number of times the freezer door 15 is opened and closed during the same time period over a preset calculation period, the average opening time, and the adjustment coefficient α calculated by the adjustment coefficient calculation unit 64. The preset calculation period is, for example, the most recent week excluding the current day. As an example, the discrimination parameter X for the time period from 7:00 to 8:00 today is the product of the average number of times the freezer door 15 is opened and closed during 7:00 to 8:00 for the week prior to yesterday, the average opening time, and the adjustment coefficient α. If the average number of times the door is opened and closed during 7:00 to 8:00 for the week prior to yesterday is 5, the average opening time is 5 minutes, and the adjustment coefficient α is 0.5, then the discrimination parameter X will be 12.5.

[0061] The rank determination unit 65 compares the obtained discrimination parameter X with a preset threshold to determine the usage frequency rank. As an example, the rank determination unit 65 classifies the usage frequency rank for each time period into five stages, FR1 to FR5, according to the discrimination parameter X. Note that the thresholds compared with the discrimination parameter X below are for when the adjustment coefficient α is 0.5; if the adjustment coefficient α is 1, each threshold will be doubled. Specifically, the threshold for usage frequency rank FR1 is "X ≤ 20". 1) Frequency of use rank FR1: X≦10 2) Frequency of use rank FR2: 10 <X≦50 3) Frequency of use rank FR3: 50 <X≦100 4) Frequency of use rank FR4: 100 <X≦150 5) Frequency of use rank FR5: 150 <X

[0062] Usage frequency rank FR1 represents the lowest usage frequency, and usage frequency rank FR5 represents the highest usage frequency. Usage frequency rank FR1 corresponds to periods of no usage, usage frequency ranks FR2 and FR3 correspond to periods of low usage frequency, and usage frequency ranks FR4 and FR5 correspond to periods of high usage frequency. Note that the number of usage frequency rank levels is not limited to 5 levels; it is possible to classify into any number of levels, two or more.

[0063] The number of times the freezer door 15 is opened and closed at different times of the day varies from user to user, with some users opening and closing it approximately 80 times per day. The duration for which the freezer door 15 is open also varies from user to user; some users close it within an average of 30 seconds, while others leave it open for several minutes on average to search for food. The threshold for usage frequency rank FR1 (≤10) assumes that the number of times the door is opened and closed is less than 10, and the time period in this case is considered an unused period.

[0064] The determination unit 66 determines whether to perform normal operation or reduced operation during cooling operation based on the usage frequency rank determined by the rank determination unit 65. Specifically, the determination unit 66 determines to perform reduced operation if the usage frequency rank for the current time period is the lowest rank FR1, i.e., it is a non-usage period, and determines to perform normal operation if the usage frequency rank for the current time period is anything other than FR1. The determination result of the determination unit 66 is transmitted to the cooling control unit 62.

[0065] Here, the hardware configuration of the control device 6 of the freezer 1 in this embodiment will be described. Figure 6 is a diagram illustrating an example of the hardware configuration of the control device 6 of the freezer 1 according to Embodiment 1. When the cooling control unit 62, heater control unit 63, adjustment coefficient calculation unit 64, rank determination unit 65, and determination unit 66 of the control device 6 are implemented in hardware, the control device 6 is composed of a processing circuit 600. The processing circuit 600 can be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. The cooling control unit 62, heater control unit 63, adjustment coefficient calculation unit 64, rank determination unit 65, and determination unit 66 may each be implemented in separate processing circuits 600, or each part may be implemented in a single processing circuit 600.

[0066] Figure 7 illustrates another example of the hardware configuration of the control device 6 of the freezer 1 according to Embodiment 1. When the cooling control unit 62, heater control unit 63, adjustment coefficient calculation unit 64, rank determination unit 65, and determination unit 66 of the control device 6 are implemented in software, the control device 6 has a processor 601 such as a CPU or GPU and a memory 602. The processor 601 and the memory 602 are connected to each other so as to be able to communicate via a bus 603. In addition, the control device 6 may have multiple processors 601 and multiple memories 602, which may work together to implement the cooling control unit 62, heater control unit 63, adjustment coefficient calculation unit 64, rank determination unit 65, and determination unit 66.

[0067] The cooling control unit 62, heater control unit 63, adjustment coefficient calculation unit 64, rank determination unit 65, and determination unit 66 are implemented by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in memory 602. The processor 601 implements each part by reading and executing the programs stored in memory 602. Memory 602 constitutes the storage unit 61 and is, for example, a non-volatile semiconductor memory such as ROM or flash memory, a volatile semiconductor memory such as RAM, or a recording medium such as HDD or SSD.

[0068] Figure 8 is a flowchart illustrating the operation of the freezer 1 according to Embodiment 1. The operation in Figure 8 is started at 0:00 and ended at 24:00 every day by the control device 6. First, the rank determination unit 65 of the control device 6 calculates the adjustment coefficient α (S1). Then, the rank determination unit 65 determines the usage frequency rank for each time period of the day (S2). The usage frequency rank is determined based on the discrimination parameter X, which is obtained by multiplying the adjustment coefficient α by the average number of times the freezer door 15 was opened and closed over the past week and the average opening time.

[0069] The determination unit 66 determines whether the usage frequency rank for the current time period corresponds to an unused time period (S3). If the usage frequency rank is the lowest rank, FR1, the determination unit 66 determines that it is an unused time period. If the usage frequency rank does not correspond to an unused time period (S3:NO), the determination unit 66 determines that normal operation should be performed, and the cooling control unit 62 performs normal operation (S4).

[0070] If the usage frequency rank corresponds to a period of non-use (S3:YES), that is, if the usage frequency rank is FR1, the determination unit 66 decides to perform suppressed operation, and the cooling control unit 62 performs suppressed operation (S5). After that, the process returns to step S3, and either suppressed operation or normal operation is performed for each time period.

[0071] Next, the method for calculating the adjustment coefficient α, which is performed in step S1 of Figure 8, will be explained. Figure 9 is a diagram illustrating the change in the internal temperature Tf when the freezer door 15 is opened and closed in Embodiment 1. Figure 9 shows the time change of power [W], the operation (ON) and stop (OFF) of the compressor 31 and blower 35, and the time change of the internal temperature Tf measured by the internal temperature sensor 53.

[0072] The cooling control unit 62 of the freezer 1, in the cooling operation to cool the inside of the freezer compartment 10, synchronizes the operation and stopping of the compressor 31 and the blower 35 so that the internal temperature Tf stays within the allowable range of Tfs ± dθf, with the set temperature Tfs as the target value. The allowable range dθf varies depending on the insulation specifications of the freezer 1 and the specifications of the evaporator 34, but is for example 2 to 4 [K].

[0073] This controls the temperature and flow rate of the cold air blown into the freezer compartment 10, and maintains the average internal temperature Tf of the freezer compartment 10 of the freezer 1 at the set temperature Tfs. In other words, the operation or stoppage of the compressor 31 and the blower 35 is synchronized with the internal temperature Tf of the freezer compartment 10. When the compressor 31 is operating, the freezer compartment 10 is cooled, and when the compressor 31 is stopped, cooling is temporarily suspended, and the internal temperature Tf tends to rise.

[0074] The change in the internal temperature Tf when the freezer door 15 is opened and closed during normal operation will be explained. In Figure 9, the solid line after the freezer door 15 is opened shows the temperature change of the internal temperature Tf when no load is applied to the freezer 10 when the freezer door 15 is opened and closed, and the dashed line shows the temperature change of the internal temperature Tf when a load is applied to the freezer 10 when the door is opened and closed. When the freezer door 15 is opened and closed, the temperature rise of the internal temperature Tf is greater when a load is applied to the freezer 10 (dashed line in Figure 9) than when no load is applied to the freezer 10 (solid line in Figure 9). In addition, when a load is applied to the freezer 10, the recovery time tf_load for the internal temperature Tf to return to the temperature just before the freezer door 15 was opened is longer than the recovery time tf_unload when no load is applied.

[0075] This is because the heat load on the freezer 1 increases when a new load is introduced into the freezer compartment 10. When only the door is opened and closed, the internal temperature Tf only rises as the cold air from the freezer compartment 10 leaks out. However, when a new load is introduced into the freezer compartment 10, in addition to the temperature rise due to the cold air leak, it becomes necessary to cool the load, which has a certain amount of heat, in addition to the temperature rise. In other words, the additional heat load from the load is placed on the freezer 1 (cooler 34), and it takes time to cool it down.

[0076] Thus, the temperature rise Tf inside the freezer compartment Tf differs depending on whether or not a load is applied to the freezer compartment Tf when the freezer door 15 of the freezer 1 is opened or closed, and the required cooling capacity of the freezer 1 also differs. The evaporator compartment temperature Te also changes in the same way as the internal temperature Tf. That is, when a load is applied to the freezer compartment Tf when the freezer door 15 is opened or closed, the temperature rise Te in the evaporator compartment is greater than when no load is applied to the freezer compartment Tf. Also, when a load is applied to the freezer compartment Tf, the time it takes for the evaporator compartment temperature Te to return to the temperature just before the freezer door 15 was opened is longer than the time it takes when no load is applied.

[0077] Therefore, the adjustment coefficient calculation unit 64 measures (1) the temperature rise of the internal temperature Tf and the evaporator temperature Te when the freezer door 15 is opened and closed, and (2) the recovery time of the internal temperature Tf and the evaporator temperature Te. The adjustment coefficient calculation unit 64 then compares the temperature rise of the internal temperature Tf and the evaporator temperature Te with a threshold (Tup1 in Figure 9), and (2) the recovery time with a threshold time (tr in Figure 9) to determine whether or not a load is being applied. The adjustment coefficient calculation unit 64 determines whether or not a load is being applied when the freezer door 15 is opened and closed every time during the calculation period, thereby obtaining an adjustment coefficient α that represents the load application ratio during the calculation period.

[0078] Depending on each user's lifestyle, the frequency of applying load when opening and closing the door, or the frequency of checking the inventory in the freezer compartment 10 without applying load, varies greatly. Therefore, by estimating the proportion of load applied to the freezer compartment 10 and using this as a coefficient for the usage frequency rank, it is possible to estimate the usage frequency for each user, i.e., the magnitude of the heat load on the freezer compartment 1. Then, by performing cooling control appropriate to the estimated heat load, energy saving performance can be improved, and user convenience can be enhanced.

[0079] Figure 10 is a flowchart showing the method for calculating the adjustment coefficient α in Embodiment 1. This process is performed by the adjustment coefficient calculation unit 64 of the control device 6. First, the adjustment coefficient calculation unit 64 resets the count C1, which indicates the number of times a load has been applied, and the count C2, which indicates the number of times a load has not been applied (S101). That is, the count C1, which indicates the number of times a load has been applied, and the count C2, which indicates the number of times a load has not been applied, are set to 0.

[0080] Next, the adjustment coefficient calculation unit 64 determines whether the temperature rise value ΔTf of the internal temperature Tf when the freezer door 15 is opened and closed is greater than or equal to the first threshold Tup1, and whether the temperature rise value ΔTe of the evaporator room temperature Te when the same opening and closing occurs is greater than or equal to the second threshold Tup2 (S102). The temperature rise value ΔTf of the internal temperature Tf and the temperature rise value ΔTe of the evaporator room temperature Te when the freezer door 15 is opened and closed are measured each time the freezer door 15 is opened and closed and stored in the storage unit 61. The first threshold Tup1 is, for example, 10 to 12K, and the second threshold Tup2 is smaller than the first threshold Tup1, for example, 8 to 10K. The first threshold Tup1 and the second threshold Tup2 are examples and are set appropriately according to the insulation specifications of the freezer 1 and the specifications of the evaporator 34.

[0081] The first threshold Tup1 and the second threshold Tup2 may be set multiple times for each ambient temperature Ta measured by the ambient temperature sensor 19. For example, the temperature rise when the freezer door 15 is opened when the ambient temperature Ta is high will be greater than the temperature rise when the freezer door 15 is opened when the ambient temperature Ta is low. Therefore, by setting the first threshold Tup1 and the second threshold Tup2 according to the ambient temperature Ta, the accuracy of load application detection can be improved.

[0082] If at least one of the temperature rise value ΔTf of the internal temperature Tf and the temperature rise value ΔTe of the cooler room temperature Te is below a threshold (S102: NO), the adjustment coefficient calculation unit 64 determines that no load was applied during the opening and closing and increments the count C2 for no load application (S103). That is, if the temperature rise value ΔTf is less than the first threshold Tup1 and the temperature rise value ΔTe is less than the second threshold Tup2, if the temperature rise value ΔTf is greater than or equal to the first threshold Tup1 but the temperature rise value ΔTe is less than the second threshold Tup2, or if the temperature rise value ΔTe is greater than or equal to the second threshold Tup2 but the temperature rise value ΔTf is less than the first threshold Tup1, it is determined that no load was applied.

[0083] On the other hand, if the temperature rise value ΔTf of the internal temperature Tf is greater than or equal to the first threshold Tup1, and the temperature rise value ΔTe of the cooler room temperature Te during the same opening and closing is greater than or equal to the second threshold Tup2 (S102: YES), the adjustment coefficient calculation unit 64 determines whether the recovery time tf of the internal temperature Tf and the recovery time te of the cooler room temperature Te during the opening and closing of the freezer door 15 are both greater than or equal to a preset threshold time tr (S104). The threshold time tr is, for example, 240 minutes to 300 minutes. The threshold time tr is just an example and is set appropriately according to the insulation specifications of the freezer 1 and the specifications of the cooler 34.

[0084] If at least one of the recovery time tf for the internal temperature Tf and the recovery time te for the cooler room temperature Te is less than a preset threshold time tr (S104: NO), the adjustment coefficient calculation unit 64 determines that no load was applied during the opening and closing and increments the count C2 for no load application (S103). That is, if the recovery time tf is less than the threshold time tr and the recovery time te is less than the threshold time tr, if the recovery time tf is greater than or equal to the threshold time tr but the recovery time te is less than the threshold time tr, or if the recovery time te is greater than or equal to the threshold time tr but the recovery time tf is less than the threshold time tr, it is determined that no load was applied.

[0085] On the other hand, if the recovery time tf for the internal temperature Tf and the recovery time te for the cooler room temperature Te are both greater than or equal to the threshold time tr (S104: YES), the adjustment coefficient calculation unit 64 determines that a load was applied during the opening and closing and increments the load application count C1 (S105).

[0086] In step S104, the recovery time tf for the internal temperature Tf and the recovery time te for the evaporator room temperature Te are compared with the threshold time tr, but the system is not limited to this. For example, the time tfu [min / K] required for the internal temperature Tf to drop by 1 [K] after closing the freezer door 15 and the time teu [min / K] required for the evaporator room temperature Te to drop by 1 [K] may be compared with a reference time tru [min / K]. The adjustment coefficient calculation unit 64 may then determine that a load was applied during the opening and closing of the door if both time tfu and time teu are greater than or equal to time tru, and may increment the load application count C1. This allows for the determination of load application regardless of the length of time the freezer door 15 is open.

[0087] The adjustment coefficient calculation unit 64 then determines whether the sum of count C1 and count C2 is equal to or greater than the total number N of times the freezer door 15 is opened and closed during the calculation period (the most recent week) (S106). If the sum of counts C1 and C2 is less than the total number N (S106: NO), the unit returns to step S102 to determine whether or not a load is applied during the next door opening and closing in the calculation period.

[0088] If the sum of counts C1 and C2 is equal to or greater than the total number N (S106: YES), that is, if it is determined whether or not a load was applied during all door opening and closings during the calculation period, the adjustment coefficient calculation unit 64 calculates the adjustment coefficient α from the following formula (3) (S107). α = C1 / (C1 + C2) ... (3)

[0089] This allows us to determine the adjustment coefficient α, which represents the proportion of load applied when the door is opened and closed over the past week. In the above calculation method, both the internal temperature Tf and the evaporator temperature Te are used as criteria for determining whether or not a load is applied, thereby improving the accuracy of the estimation of whether or not a load is applied. Basically, the internal temperature Tf and the evaporator temperature Te in freezer 1 move in an almost linearly proportional relationship while maintaining a certain temperature difference ΔT(Tf-Te). Therefore, if the temperature rise and recovery time of the internal temperature Tf and the evaporator temperature Te are synchronized, it is considered that freezer 1 is operating normally. On the other hand, if the temperature rise and recovery time of the internal temperature Tf and the evaporator temperature Te are asynchronous, it is presumed that some kind of abnormality or irregularity such as a power outage has occurred due to external factors. Therefore, if the temperature rise and recovery time of the internal temperature Tf and the evaporator temperature Te are asynchronous, it is determined that there is no load applied.

[0090] Note that the determination based on the temperature rise value ΔTe of the cooler chamber temperature Te and the recovery time te is not mandatory and may be omitted. In this case, only the temperature rise value ΔTf of the internal temperature Tf and the recovery time tf are compared with each threshold value to determine whether or not a load is applied.

[0091] Next, the measurement of the temperature rise value and recovery time during door opening and closing, which are necessary for calculating the adjustment coefficient α, will be explained. Figure 11 is a flowchart showing the method for measuring the temperature rise value and recovery time during door opening and closing in Embodiment 1. This process is carried out by the adjustment coefficient calculation unit 64 of the control device 6. First, it is determined whether or not the freezer door 15 has been opened (S111). If the freezer door 15 has not been opened (S111:NO), the device waits until it is opened.

[0092] If the freezer door 15 is opened (S111: YES), the adjustment coefficient calculation unit 64 acquires the internal temperature Tf and the cooler room temperature Te as the initial internal temperature Tfo and initial cooler room temperature Teo (S112). The initial internal temperature Tfo and initial cooler room temperature Teo are the internal temperature Tf and cooler room temperature Te at the time when the opening of the freezer door 15 is detected by the opening / closing sensor 17 and an open signal is received, and are approximately the same as the internal temperature Tf and cooler room temperature Te immediately before the freezer door 15 is opened. Then, the measurement of the temperature rise time tup of the internal temperature Tf and cooler room temperature Te is started (S113).

[0093] Next, it is determined whether or not the freezer door 15 is closed (S114). If the freezer door 15 is not closed (S114: NO), the system waits until it is closed. Then, when the freezer door 15 is closed (S114: YES), the adjustment coefficient calculation unit 64 obtains the internal temperature Tf1 and the evaporator temperature Te1 at time t1 (S115).

[0094] The adjustment coefficient calculation unit 64 waits for a time Δt1 (S116) and obtains the internal temperature Tf2 and the cooler room temperature Te2 at time t+Δt1 (S117). Then, the adjustment coefficient calculation unit 64 calculates the temperature slope Sf of the internal temperature Tf and the temperature slope Se of the cooler room temperature Te from the following equations (4) and (5) (S118). Sf = (Tf2 - Tf1) / Δt1 ... (4) Se = (Te² - Te¹) / Δt¹ ... (5)

[0095] The adjustment coefficient calculation unit 64 then simultaneously checks the temperature rise changes of the internal temperature Tf and the evaporator room temperature Te. First, let's explain the internal temperature Tf. The adjustment coefficient calculation unit 64 determines whether the temperature slope Sf of the internal temperature Tf is greater than 0 and whether the freezer door 15 is closed (S119). If the temperature slope Sf of the internal temperature Tf is greater than 0 and the freezer door 15 is closed (S119: YES), it is determined that the rise in the internal temperature Tf has not yet finished and the upward trend will continue, so the unit returns to step S115 and repeats the process from steps S115 to S118 to calculate the most recent temperature slope Sf.

[0096] On the other hand, if the temperature gradient Sf of the internal temperature Tf is 0 or less, or if the freezer door 15 is opened again (S119: NO), it is determined that the rise in the internal temperature Tf has reached its peak value, and this internal temperature Tf is obtained as the peak internal temperature Tfmax (S120). Then, the initial internal temperature Tfo obtained in step S112 is subtracted from the peak internal temperature Tfmax obtained in step S120 to calculate the temperature rise value ΔTf of the internal temperature Tf (S121).

[0097] Next, the cooler room temperature Te will be explained. The adjustment coefficient calculation unit 64 determines whether the temperature slope Se of the cooler room temperature Te is greater than 0 and whether the freezer door 15 is closed (S122). If the temperature slope Sf of the cooler room temperature Te is greater than 0 and the freezer door 15 is closed (S122: YES), it is determined that the rise in the cooler room temperature Te has not yet finished and the upward trend will continue, so the unit returns to step S115 and repeats the process from steps S115 to S118 to calculate the most recent temperature slope Se.

[0098] On the other hand, if the temperature slope Se of the cooler room temperature Te is 0 or less, or if the freezer door 15 is opened again (S122: NO), it is determined that the rise in the cooler room temperature Te has reached its peak value, and this cooler room temperature Te is obtained as the peak cooler room temperature Temax (S123). Then, the initial cooler room temperature Teo obtained in step S112 is subtracted from the peak cooler room temperature Temax obtained in step S123 to calculate the temperature rise value ΔTe of the cooler room temperature Te (S124).

[0099] This makes it possible to determine the temperature rise ΔTf of the internal temperature Tf and the temperature rise ΔTe of the evaporator temperature Te each time the freezer door 15 is opened and closed. The determined temperature rise ΔTf of the internal temperature Tf and the temperature rise ΔTe of the evaporator temperature Te are stored in the storage unit 61 along with the date and time.

[0100] Next, the method for measuring the recovery time when the door is opened and closed will be explained. Figure 12 is a flowchart showing the method for measuring the recovery time when the door is opened and closed in Embodiment 1. This process is performed in parallel with the calculation of the temperature rise value by the adjustment coefficient calculation unit 64 of the control device 6. First, it is determined whether or not the freezer door 15 has been opened (S131). If the freezer door 15 has not been opened (S131: NO), it waits until it is opened. If the freezer door 15 has been opened (S131: YES), it is determined whether or not the freezer door 15 has been closed (S132). If the freezer door 15 has not been closed (S132: NO), it waits until it is closed.

[0101] If the freezer door 15 is closed (S132:NO), the adjustment coefficient calculation unit 64 starts measuring the recovery times tf and te (S133). After that, it waits for a time Δt2 (S134) and obtains the internal temperature Tf and the cooler room temperature Te (S135). Then, it checks whether the internal temperature Tf and the cooler room temperature Te have returned to the initial internal temperature Tfo and the initial cooler room temperature Teo, respectively.

[0102] First, let's explain the internal temperature Tf. The adjustment coefficient calculation unit 64 determines whether the internal temperature Tf is less than or equal to the initial internal temperature Tfo (S136). If the internal temperature Tf is higher than the initial internal temperature Tfo (S136: NO), the unit returns to step S134, obtains the internal temperature Tf at intervals of time Δt2, and determines whether it has returned to the initial internal temperature Tfo. If the internal temperature Tf becomes less than or equal to the initial internal temperature Tfo (S136: YES), the adjustment coefficient calculation unit 64 determines that the internal temperature Tf has returned to the temperature before the freezer door 15 was opened, and obtains this time as the return time tf (S137).

[0103] Next, the cooler room temperature Te will be explained. The adjustment coefficient calculation unit 64 determines whether the cooler room temperature Te is less than or equal to the initial cooler room temperature Teo (S138). If the cooler room temperature Te is higher than the initial cooler room temperature Teo (S138: NO), the unit returns to step S134, obtains the cooler room temperature Te at time intervals Δt2, and determines whether it has returned to the initial cooler room temperature Teo. If the cooler room temperature Te becomes less than or equal to the initial cooler room temperature Teo (S138: YES), the adjustment coefficient calculation unit 64 determines that the cooler room temperature Te has returned to its original state and obtains this time as the return time te (S139).

[0104] This makes it possible to determine the recovery time tf for the internal temperature Tf and the recovery time te for the evaporator temperature Te each time the freezer door 15 is opened and closed. The determined recovery time tf for the internal temperature Tf and the recovery time te for the evaporator temperature Te are stored in the storage unit 61 along with the date and time.

[0105] Next, the normal operation and suppressed operation performed in steps S4 and S5 of Figure 8 will be described. Figure 13 is a diagram illustrating the suppressed operation of the freezer 1 according to Embodiment 1. Figure 13 shows the time change of power [W], the operation (ON) and stop (OFF) of the compressor 31 and blower 35, the time change of the internal temperature Tf and the evaporator room temperature Te, and the time change of the temperature difference ΔT between the internal temperature Tf and the evaporator room temperature Te.

[0106] As shown in Figure 13, during normal operation, the compressor 31 and the blower 35 are operated or stopped in sync, so the waveforms of the compressor 31, the blower 35, and the power become square waves that operate or stop in sync. The synchronous operation of the compressor 31 and the blower 35 controls the temperature inside the freezer chamber 10 so that the internal temperature Tf is within the allowable range of the set temperature Tfs.

[0107] The specific control of the internal temperature Tf is the same as described based on Figure 9. The control of the evaporator room temperature Te is the same as the control of the internal temperature Tf. In normal operation, the cooling control unit 62 synchronizes the operation and stopping of the compressor 31 and blower 35 so that the evaporator room temperature Te stays within the allowable range of Tes ± dθe, with the set temperature Tes as the target value. The allowable range dθe varies depending on the insulation specifications of the freezer 1 or the specifications of the evaporator 34, but is, for example, 2 to 4 [K]. This maintains the average value of the evaporator room temperature Te at the set temperature Tes. In reality, as the evaporator 34 cools, cold air circulates within the freezer room 10, so although there is a slight time difference, the temperature change in the evaporator room 3 occurs first, followed by the temperature change in the freezer room 10.

[0108] As described above, the internal temperature Tf and the evaporator temperature Te are controlled, so the freezer compartment 10 and the evaporator compartment 3 basically maintain a constant temperature difference ΔT = Tf - Te. This temperature difference ΔT between the freezer compartment 10 and the evaporator compartment 3 varies depending on the insulation specifications of the freezer compartment 1 or the specifications of the evaporator 34, but is often in the range of approximately 3 to 5 [K].

[0109] Next, let's explain the controlled operation. As described above, a certain temperature difference ΔT occurs between the internal temperature Tf and the evaporator room temperature Te during normal operation. In other words, from the perspective of the freezer room 10, the evaporator room 3 is relatively colder, so by using the residual cold air in the evaporator room 3, it is possible to cool for a certain period of time without having to drive the compressor 31 to cool the evaporator 34 again.

[0110] Therefore, in the freezer 1 of this embodiment, as a suppression operation, the compressor 31 is stopped and only the blower 35 is operated, and the inside of the freezer 10 is cooled using the residual cold air from the evaporator chamber 3. In normal operation, cooling the freezer 10 requires power to drive both the compressor 31 and the blower 35, and power is needed to operate both the compressor 31 and the blower 35, but by performing a suppression operation, the power required to operate the compressor 31 can be temporarily suppressed. In Figure 13, the amount of power that can be suppressed is shown as the hatched area AR.

[0111] When suppression operation is performed, if the temperature difference ΔT between the evaporator chamber 3 and the freezer chamber 10 is not above a certain value, the residual cold air in the evaporator chamber 3 cannot be used to cool the freezer chamber 10. Therefore, when the temperature difference ΔT = Te - Tf between the evaporator chamber 3 and the freezer chamber 10 falls below the threshold Tth, the cooling control unit 62 terminates the suppression operation and drives both the compressor 31 and the blower 35 to cool the freezer chamber 10. The threshold Tth for determining the termination of suppression operation varies depending on the insulation specifications of the freezer 1 and the specifications of the evaporator 34 and the compressor 31, but as an example, it is 1.0 [K].

[0112] Furthermore, the cooling control unit 62 determines whether or not to perform suppression operation only during periods of non-use, i.e., when the usage frequency rank for the current time period is the lowest, FR1. This is because, during periods of non-use, it can be determined that there are few external factors caused by the user that affect the temperature change of the freezer compartment 10. In other words, during periods of non-use, the frequency of opening and closing the freezer compartment door 15 and the application of load to the freezer compartment 10 is low, so it is considered sufficient to consider only the heat load of the stored items already stored in the freezer compartment 10.

[0113] Figure 14 is a flowchart showing the normal operation flow of the freezer 1 according to Embodiment 1. This process is carried out by the cooling control unit 62 of the control device 6. At the start of this process, the compressor 31 and the blower 35 are assumed to be stopped. The cooling control unit 62 determines whether the internal temperature Tf is less than the lower limit of the allowable range of the set temperature Tfs (Tfs-dθf) (S41).

[0114] If the internal temperature Tf is greater than or equal to the lower limit of the allowable range of the set temperature Tfs (Tfs-dθf) (S41:NO), the cooling control unit 62 determines that the internal temperature Tf is within the allowable range of the set temperature Tfs and operates the compressor 31 and the blower 35 (S42). Then, the process returns to step S41. On the other hand, if the internal temperature Tf is less than the lower limit of the allowable range of the set temperature Tfs (Tfs-dθf) (S41:YES), the cooling control unit 62 determines that the freezer compartment 10 has been cooled to a temperature range above the target temperature range and stops the compressor 31 and the blower 35 (S43), temporarily suspending the cooling of the freezer compartment 10.

[0115] The cooling control unit 62 then determines whether the internal temperature Tf is higher than the upper limit of the allowable range of the set temperature Tfs (Tfs + dθf) (S44). If the internal temperature Tf is less than or equal to the upper limit of the allowable range of the set temperature Tfs (Tfs + dθf) (S44: NO), the cooling control unit 62 determines that the internal temperature Tf is within the allowable range of the set temperature Tfs and continues to temporarily suspend cooling while keeping the compressor 31 and blower 35 stopped.

[0116] On the other hand, if the internal temperature Tf is higher than the upper limit of the allowable range of the set temperature Tfs (Tfs + dθf) (S44: YES), the cooling control unit 62 determines that the temperature of the freezer 10 is higher than the target temperature range and operates the compressor 31 and the blower 35 (S45) to restart cooling of the freezer 10. After that, the process returns to step S41 and the subsequent processing is repeated. In this way, the control device 6 can control the compressor 31 and the blower 35 so that the average internal temperature Tf is near the target set temperature Tfs.

[0117] Figure 15 is a flowchart showing the flow of the suppression operation in the freezer 1 according to Embodiment 1. This process is carried out by the cooling control unit 62 of the control device 6. At the start of this process, the compressor 31 and the blower 35 are assumed to be stopped. First, the cooling control unit 62 determines whether the temperature difference ΔT between the internal temperature Tf and the evaporator room temperature Te is greater than or equal to the threshold Tth (S51). If the temperature difference ΔT between the internal temperature Tf and the evaporator room temperature Te is less than the threshold Tth (S51: NO), the cooling control unit 62 determines that the temperature difference between the evaporator room 3 and the freezer compartment 10 is small, and therefore the residual cold air in the evaporator room 3 cannot continue to cool the freezer compartment 10, and terminates the suppression operation and switches to normal operation.

[0118] On the other hand, if the temperature difference ΔT between the internal temperature Tf and the cooler room temperature Te is greater than or equal to the threshold Tth (S51: YES), the cooling control unit 62 determines whether the internal temperature Tf is higher than the upper limit of the allowable range of the set temperature Tfs (Tfs + dθf) (S52). If the internal temperature Tf is less than or equal to the upper limit of the allowable range of the set temperature Tfs (Tfs + dθf) (S52: NO), the cooling control unit 62 determines that the internal temperature Tf is within the allowable range of the set temperature Tfs and remains in standby mode with the compressor 31 and blower 35 stopped.

[0119] On the other hand, if the internal temperature Tf is higher than the upper limit of the allowable range of the set temperature Tfs (Tfs + dθf) (S52: YES), the cooling control unit 62 determines that the temperature of the freezer compartment 10 is higher than the target temperature range, and operates only the blower 35 while keeping the compressor 31 stopped (S53). At this time, the rotation speed of the blower 35 is set to the minimum rotation speed. As a result, the cold air from the evaporator compartment 3 is sent to the freezer compartment 10 by the blower 35, and the freezer compartment 10 is cooled.

[0120] The cooling control unit 62 acquires the internal temperature Tf1 at time t (S54). Then, it waits for time Δt3 (S55) and acquires the internal temperature Tf2 at time t+Δt3 (S56). The cooling control unit 62 then determines whether the temperature difference ΔT between the internal temperature Tf and the cooler room temperature Te is greater than or equal to the threshold Tth (S57). If the temperature difference ΔT between the internal temperature Tf and the cooler room temperature Te is less than the threshold Tth (S57: NO), the cooling control unit 62 determines that the temperature difference between the cooler room 3 and the freezer room 10 is small and therefore the residual cold air in the cooler room 3 cannot continue to cool the freezer room 10, terminates the suppression operation, and switches to normal operation. On the other hand, if the temperature difference ΔT between the internal temperature Tf and the cooler room temperature Te is greater than or equal to the threshold Tth (S57: YES), the cooling control unit 62 calculates the absolute value of the temperature slope Sf of the internal temperature Tf from the following equation (6) (S58). |Sf|=(Tf2-Tf1) / Δt3 ···(6)

[0121] Next, the cooling control unit 62 determines whether the absolute value of the temperature gradient |Sf| is greater than or equal to the absolute value of the previous temperature gradient |Sf| (S59). If the temperature gradient |Sf| is greater than or equal to the previous temperature gradient |Sf| (S59: YES), the process returns to step S54 and repeats. Note that if the temperature gradient |Sf| is calculated for the first time, there is no previous temperature gradient |Sf|, so the process returns to step S54 after determining YES in step S58. On the other hand, if the temperature gradient |Sf| is less than the previous temperature gradient |Sf| (S59: NO), the cooling control unit 62 increases the rotation speed of the blower 35 (S60).

[0122] The cooling control unit 62 then determines whether the internal temperature Tf is less than the lower limit of the allowable range of the set temperature Tfs (Tfs-dθf) (S61). If the internal temperature Tf is equal to or greater than the lower limit of the allowable range of the set temperature Tfs (Tfs-dθf) (S61: NO), the cooling control unit 62 determines that the internal temperature Tf is within the allowable range of the set temperature Tfs and continues operating the blower 35. After that, the process returns to step S52 and the subsequent processing is repeated.

[0123] On the other hand, if the internal temperature Tf is less than the lower limit of the allowable range of the set temperature Tfs (Tfs-dθf) (S61:YES), the cooling control unit 62 determines that the freezer compartment 10 has been cooled to above the target temperature range, stops the blower 35 (S62), and temporarily suspends the cooling of the freezer compartment 10. After that, the process returns to step S51 and the subsequent processing is repeated.

[0124] If the current temperature gradient |Sf| is less than the temperature gradient |Sf| confirmed at the previous timing, it is considered that the efficiency of heat exchange between the residual cold air in the cooler chamber 3 and the freezer chamber 10 has decreased. Therefore, the cooling control unit 62 further promotes heat exchange between the cooler chamber 3 and the freezer chamber 10 by increasing the rotation speed of the blower 35. Here, the increase in rotation speed is, for example, around 200 to 300 rpm. In addition, the blower 35 in this embodiment can be set in the range of approximately 1200 rpm to 2300 rpm.

[0125] During suppression operation, the initial rotation speed of the blower 35 is set to the lowest speed to start operation of the blower 35. Then, based on the internal temperature Tf, the temperature gradient |Sf| of the internal temperature Tf is repeatedly calculated at regular time intervals (Δt3), and the rotation speed of the blower 35 is increased each time the latest temperature gradient |Sf| falls below the previous temperature gradient |Sf|. In this way, the rotation speed of the blower 35 is controlled in stages from low to high speeds.

[0126] Generally, if the blower 35 is operated at its maximum rotational speed from the start, the convection within the cooler chamber 3 increases, preventing maximum efficiency in heat exchange between the air in the cooler chamber 3 and the freezer chamber 10. This is because the high velocity of the convection air also increases the velocity of the air along the walls of the cooler chamber 3, thereby promoting heat exchange between the walls of the cooler chamber 3 and the air. In contrast, as described above, by controlling the rotational speed of the blower 35 in controlled operation, gradually increasing it from a low rotational speed, the decrease in heat exchange efficiency can be suppressed, and the power consumption of the blower 35 can be reduced.

[0127] Furthermore, if the blower 35 is operated at a high rotational speed when cooling the freezer compartment 10, a sudden noise may be emitted from the freezer 1, potentially causing discomfort to the user. In contrast, by gradually increasing the rotational speed of the blower 35 at regular time intervals, as described above, it is less likely for the user to perceive a sudden increase in the operating noise of the blower 35, thereby suppressing any potential discomfort.

[0128] As described above, in the freezer 1 of this embodiment, when the temperature difference ΔT between the evaporator chamber 3 and the freezer chamber 10 is greater than or equal to the threshold Tth during periods of non-use, the operation of the compressor 31 is temporarily stopped and only the blower 35 is operated. This allows the freezer chamber 10 to be cooled using the residual cold air remaining in the evaporator chamber 3, thereby reducing the power consumption of the compressor 31 during suppression operation.

[0129] Figure 16 is a pH diagram showing the effects obtained by performing a suppressed operation in the freezer 1 according to Embodiment 1. In Figure 16, the dashed line shows the refrigeration cycle during normal operation, and the solid line shows the refrigeration cycle during suppressed operation. In the freezer 1 of this embodiment, by performing a suppressed operation, the inside of the freezer chamber 10 is cooled with residual cold air in the cooler chamber 3 before the compressor 31 is driven to perform cooling. Therefore, the heat load on the compressor 31 and the cooler 34 can be reduced compared to when the suppressed operation is not performed.

[0130] As a result, as shown in Figure 16, the amount of work Wcomp generated in the compressor 31 during the compression process for compressing the refrigerant is reduced, and the amount of work of the compressor 31 can be reduced by ΔWcomp. Consequently, the power consumption required to operate the compressor 31 can be suppressed, and energy-saving performance can be improved.

[0131] Embodiment 2. Embodiment 2 will now be described. Embodiment 2 differs from Embodiment 1 in that the set temperature Tfs of the freezer 1 is varied according to the usage frequency rank. The configuration of the freezer 1 in Embodiment 2 is the same as in Embodiment 1, and the differences will be described below.

[0132] Figure 17 is a flowchart showing the operation of the freezer 1 according to Embodiment 2. First, the rank determination unit 65 of the control device 6 calculates the adjustment coefficient α (S201). The method for calculating the adjustment coefficient α is the same as in Embodiment 1. Then, the rank determination unit 65 determines the usage frequency rank for each time period of the day (S202). The usage frequency rank is determined, as in Embodiment 1, based on a discrimination parameter X obtained by multiplying the adjustment coefficient α by the average number of door openings and closings in the past week and the average door open time.

[0133] The cooling control unit 62 then sets the set temperature Tfs of the internal temperature Tf of the freezer 1 according to the usage frequency rank of the current time period (S203). First, when the usage frequency rank is FR1 (S203:FR1), that is, when it corresponds to a period of non-use, the cooling control unit 62 sets the set temperature Tfs to the first reference temperature T1 (S204). The first reference temperature T1 is, for example, -18°C.

[0134] If the usage frequency rank is FR2 or FR3 (S203: FR2 or FR3), that is, if it corresponds to a time period with low usage frequency, the cooling control unit 62 sets the set temperature Tfs to the second reference temperature T2 (S205). The second reference temperature T2 is lower than the first reference temperature T1, for example, -19°C.

[0135] If the usage frequency rank is FR4 or FR5 (S203: FR4 or FR5), that is, if it corresponds to a time period with high usage frequency, the cooling control unit 62 sets the set temperature Tfs to the third reference temperature T3 (S206). The third reference temperature T3 is lower than the second reference temperature T2, for example, -20°C. The subsequent steps S207 to S209 are the same as steps S3 to S5 in Embodiment 1. After S209, the process returns to step S203, and the processing of steps S203 to S209 is repeated for each time period.

[0136] Figure 18 is an example of a graph showing the number of times the freezer door 15 is opened and closed, the usage frequency rank, and the change in the set temperature Tfs of the freezer compartment 10 in the freezer 1 according to Embodiment 2. The first row from the top of Figure 18 shows the results of detecting whether the freezer door 15 is open or closed on the day, and the second row from the top shows the trend in the number of times the freezer door 15 is opened and closed in each time period (1 hour), averaged over the past week excluding the day. The third row from the top shows the usage frequency rank obtained from the discrimination parameter X (= adjustment coefficient α × number of times the door is opened and closed × door open time) for each time period. The fourth row from the top shows the trend in the set temperature Tfs of the freezer compartment 10 when each time period is classified into three categories: unused, low usage frequency, and high usage frequency, based on the usage frequency rank.

[0137] By classifying usage frequency into three categories—none, infrequently used, and frequently used—the time periods and magnitudes of heat load on the freezer compartment 10 can be classified into three types. Then, by varying the set temperature Tfs of the freezer compartment 10 according to the usage frequency, the freezer compartment 10 can be set to cool down during periods of high user usage, thereby suppressing the temperature rise of stored items inside the freezer compartment 10. Furthermore, during periods of low user usage, excessive cooling can be suppressed, reducing the workload of the compressor 31 and lowering power consumption. This further improves the energy-saving performance of the freezer 1.

[0138] Embodiment 3. Embodiment 3 will now be described. Embodiment 3 differs from Embodiment 1 in that it uses a usage frequency rank and an outside air rank to vary the settings of the compressor 31 and blower 35 of the freezer 1. The configuration of the freezer 1 in Embodiment 3 is the same as in Embodiment 1, and the differences will be described below.

[0139] Figure 19 is a flowchart illustrating the operation of the freezer 1 according to Embodiment 3. First, the rank determination unit 65 of the control device 6 calculates the adjustment coefficient α (S301). The method for calculating the adjustment coefficient α is the same as in Embodiment 1. Then, the rank determination unit 65 determines the usage frequency rank for each time period of the day (S302). The usage frequency rank is determined, as in Embodiment 1, based on the adjustment coefficient α and the discrimination parameter X, which is the product of the average number of times the freezer door 15 was opened and closed over the past week and the average opening time.

[0140] Then, the rank determination unit 65 determines the outdoor air rank for the current time period based on the outdoor air temperature Ta measured by the outdoor air temperature sensor 19 (S303). As an example, the rank determination unit 65 classifies the outdoor air rank for each time period into six stages, AR1 to AR6, as shown below, according to the outdoor air temperature Ta. 1) Outdoor temperature rank AR1: Ta < 12℃ 2) Outdoor temperature rank AR2: 12℃≦Ta<18℃ 3) Outdoor temperature rank AR3: 18℃≦Ta<22℃ 4) Outdoor temperature rank AR4: 22℃≦Ta<28℃ 5) Outdoor temperature rank AR5: 28℃≦Ta<36℃ 6) Outdoor temperature rank AR6: 36℃≦Ta

[0141] Next, the rank determination unit 65 determines the setting rank based on the usage frequency rank and the outside air rank for the current time period (S304). Figure 20 is an example of a table showing the setting ranks according to the usage frequency rank and outside air rank of the freezer 1 according to Embodiment 3. The table in Figure 20 is stored in the storage unit 61 of the freezer 1. As shown in Figure 20, five setting ranks from SR1 to SR5 are determined according to the usage frequency rank and the outside air rank.

[0142] As shown in Figure 20, the rank determination unit 65 basically determines that the higher the outside air rank, the greater the external heat load, and sets the setting rank higher. Similarly, the rank determination unit 65 determines that the higher the usage frequency rank, the greater the input heat load, and sets the setting rank higher. This makes it possible to increase the refrigeration capacity when the outside air rank and usage frequency rank are high.

[0143] Note that while Figure 20 uses a five-level setting rank, the classification of ranks is not limited to this. For example, the setting ranks could be further subdivided into 30 levels from 1 to 30. Similarly, the usage frequency rank and outside air rank are not limited to the example in Figure 20; they could be subdivided into 30 levels from 1 to 30, or coarser into 3 levels from 1 to 3. Regarding rank classification, since a finer division of ranks requires more memory space, it is advisable to perform rank classification according to the amount of memory space being used.

[0144] Returning to Figure 19, once the rank determination unit 65 determines the set rank, the cooling control unit 62 sets the basic rotational speeds of the compressor 31 and blower 35 based on the determined set rank (S305). The cooling control unit 62 sets the basic rotational speeds of the compressor 31 and blower 35 according to the set rank such that the rotational speeds of the compressor 31 and blower 35 are smallest when the set rank is SR1, and largest when the set rank is SR1. Note that only the rotational speed of the compressor 31 may be set according to the set rank, and the rotational speed of the blower 35 may be kept constant. The subsequent steps S306 to S308 are the same as steps S3 to S5 in Embodiment 1. After step S308, the process returns to step S303, and the processing of steps S303 to S308 is repeated for each time period.

[0145] Figure 21 is an example of a graph showing the number of times the freezer door 15 is opened and closed, the usage frequency rank, and the setting rank in the freezer 1 according to Embodiment 3. The first, second, and third rows from the top of Figure 21 are the same as Figure 18 of Embodiment 2. The fourth row from the top of Figure 21 is the setting rank, which is determined based on the usage frequency rank and the outside air rank. The setting rank corresponds to the change in the rotational speed of the compressor 31 when the compressor 31 is operating with a refrigeration capacity suitable for the usage frequency rank.

[0146] By classifying usage frequency into three categories—none, infrequently used, and frequently used—the time periods and magnitudes of heat load on the freezer compartment 10 can be classified into three types. Then, the basic rotation speeds of the compressor 31 and blower 35 can be set to suit each usage frequency, thereby enabling operation that is appropriate for the expected heat load.

[0147] Furthermore, the setting rank is determined not only by the frequency of use but also by the ambient temperature Ta, which is the temperature of the space in which the freezer 1 is installed, and the rotation speed of the compressor 31 and blower 35 is varied accordingly. This optimizes the workload of the compressor 31 and blower 35 according to the usage status of the freezer 1, allowing for cooling of the freezer compartment 10 while suppressing power consumption.

[0148] The heat load on the cooler 34 of the freezer 1 is a combination of the external heat load resulting from heat intrusion from the outside space outside the freezer 1, and the input heat load generated by the intrusion of outside air through the freezer door 15 due to the user opening and closing the door, as well as the load of stored items. Therefore, in the cooling operation of the freezer 1, it is necessary to calculate the load amounts of the external heat load and the input heat load, and to perform cooling with a cooling capacity that matches the load expected to be applied to the cooler 34. When a load is applied, the internal temperature Tf rises, so the cooler 34 also bears a load to counteract the temperature rise.

[0149] In this embodiment, the freezer 1 determines the degree of external heat load from the outside air rank and the degree of input heat load from the usage frequency rank to estimate how much cooling capacity the freezer 10 should have during normal operation. The final cooling capacity is determined by a combination of the freezer 1's insulation specifications, the specifications of the cooler 34, and the specifications of the compressor 31. Specifically, the insulation specifications greatly affect the external heat load, the specifications of the cooler 34 are determined by the total amount of heat load from the heat entering from the outside air and the food placed in the freezer 10, and the specifications of the compressor 31 affect the maximum cooling capacity. In other words, since the insulation specifications, the specifications of the cooler 34, and the specifications of the compressor 31 are determined during the design of the freezer 1, the target cooling capacity for each outside air rank and usage frequency rank can be determined in advance through experiments, etc., and stored in the memory unit 61. This further improves the energy-saving performance of the freezer 1.

[0150] Embodiment 4. Embodiment 4 will now be described. Embodiment 4 differs from Embodiment 1 in that it performs defrosting during periods of non-use. The configuration of the freezer 1 in Embodiment 4 is the same as in Embodiment 1, and the differences will be described below.

[0151] First, let's explain the general defrosting operation in the freezer 1. The cooling control unit 62 switches from normal operation to defrosting operation when the compressor 31 has been continuously operating for a period of time equal to or greater than the first determination time, or when the cumulative operating time since the end of the previous defrosting operation of the compressor 31 reaches the second determination time. The first determination time is a predetermined time determined by experiments, etc., and is the time during which frost is considered highly likely to have formed on the evaporator 34. Similarly, the second determination time is a predetermined time determined by experiments, etc., and is the time during which frost is considered highly likely to have formed on the evaporator 34. These determination times vary depending on the insulation specifications of the freezer 1 and the specifications of the evaporator 34, but for example, the first determination time is 12 to 24 hours, and the second determination time is 24 to 72 hours.

[0152] Next, the special defrosting operation of this embodiment will be described. Generally, when opening the freezer door 15 of the freezer 1, more force is required than when opening the refrigerator door of the refrigerator compartment. This is because the temperature inside the freezer compartment 10 is much lower than the temperature of the space outside the freezer 1, so from the perspective of the space outside the freezer 1, the inside of the freezer compartment 10 is under negative pressure.

[0153] Generally, if the pressure of a gas is P, its volume is V, the amount of substance is n, and its temperature is T, then the following equation (7) holds true. PV=nRT ···(7)

[0154] Here, R is a proportionality constant called the gas constant, and its value changes depending on the unit of volume or pressure. From equation (7) above, P = nRT / V, and the smaller the temperature T (the colder it is), the smaller the gas pressure.

[0155] Another reason why the freezer compartment 10 experiences a large negative pressure relative to the space outside the freezer 1 is that the freezer compartment 10 is well-sealed, making it impossible to eliminate the pressure difference with the outside. The freezer 1 in this embodiment has a gas path (not shown) that connects the freezer compartment 10 to the space outside the freezer 1, and is configured to balance the pressure with the outside space through a drain pipe 42 so that the freezer compartment 10 does not become airtight. However, if the drain pipe 42 is blocked, the pressure balance between the freezer compartment 10 and the space outside the freezer 1 cannot be achieved, and the relative negative pressure value inside the freezer compartment 10 cannot be reduced.

[0156] Therefore, in this embodiment, the freezer 1 performs a special defrosting operation before the user is likely to open or close the door, and operates the drain heater 43. This suppresses the closure of the drain pipe 42 and balances the pressure between the freezer compartment 10 and the space outside the freezer 1. As a result, the relative negative pressure value inside the freezer compartment 10 is reduced, making it possible to reduce the force required to open and close the door of the freezer 1.

[0157] Figure 22 is a flowchart showing the operation of the freezer 1 according to Embodiment 4. First, the rank determination unit 65 of the control device 6 calculates the adjustment coefficient α (S401). Then, the rank determination unit 65 determines the usage frequency rank for each time period of the day (S402). The method for calculating the adjustment coefficient α and the method for determining the usage frequency rank are the same as in Embodiment 1.

[0158] The determination unit 66 determines whether the usage frequency rank for the current time period corresponds to an unused time period (S403). If the usage frequency rank for the current time period is the lowest rank FR1, the determination unit 66 determines that it is an unused time period. If the usage frequency rank does not correspond to an unused time period (S403: NO), the determination unit 66 determines that special defrosting operation will not be performed and normal operation will be performed (S404).

[0159] On the other hand, if the usage frequency rank corresponds to a non-used time period (S403:YES), that is, if the usage frequency rank is FR1, the determination unit 66 determines that a special defrosting operation should be performed, and the special defrosting operation is performed (S405). After that, the process returns to step S403, and either normal operation or special defrosting operation is performed for each time period.

[0160] In the special defrosting operation of this embodiment, the termination threshold temperature T_end is varied by referring to the outside air temperature Ta, and the defrosting heater 41 and the drain heater 43 are operated in synchronous manner. Figure 23 is a flowchart showing the flow of the special defrosting operation of the freezer 1 according to Embodiment 4. This process is carried out by the heater control unit 63. First, the heater control unit 63 checks the remaining time tz of the unused period (S501) and determines whether the remaining time tz of the unused period is less than or equal to the termination threshold time t_end (S502). The remaining time tz of the unused period can be determined by the current time and the end time of the unused period that is continuous with the current period. The termination threshold time t_end is the time for performing the special defrosting operation, and is, for example, 5 to 10 minutes.

[0161] If the remaining time tz of the unused period is greater than the termination threshold time t_end (S502: NO), the process returns to step S501 and repeats the determination of whether the remaining time tz of the unused period becomes less than or equal to the termination threshold time t_end. If the remaining time tz of the unused period becomes less than or equal to the termination threshold time t_end (S502: YES), the ambient temperature Ta measured by the ambient temperature sensor 19 is obtained (S503).

[0162] The heater control unit 63 then determines whether the outside air temperature Ta is less than the termination threshold temperature T_end (step S504). If the outside air temperature Ta is less than the termination threshold temperature T_end (S504: YES), the heater control unit 63 sets the outside air temperature Ta to the termination threshold temperature T_end (S505). Then, the heater control unit 63 energizes and operates the defrost heater 41 and the drain heater 43 in sync (S506). On the other hand, if the outside air temperature Ta is greater than or equal to the termination threshold temperature T_end (S504: NO), the heater control unit 63 operates the defrost heater 41 and the drain heater 43 without changing the termination threshold temperature T_end (S506).

[0163] The heater control unit 63 then obtains the cooler room temperature Te at time t (S507). The heater control unit 63 then waits for time Δt4 (S508) and determines whether the cooler room temperature Te is equal to or greater than the termination threshold temperature T_end (S509). The number of determinations in step S509 may be counted. By counting the number of determinations, the defrosting operation time with the defrost heater 41 energized can be determined.

[0164] If the cooler room temperature Te is lower than the termination threshold temperature T_end (S509: NO), the heater control unit 63 returns to step S507 and repeats the subsequent processing. On the other hand, if the cooler room temperature Te is equal to or greater than the termination threshold temperature T_end (S509: YES), the defrost heater 41 and drain heater 43 are stopped (S510), and the special defrost operation is terminated.

[0165] The time Δt4 is set to the shortest possible time, approximately 1 to 5 seconds. By setting the time Δt4 to the shortest possible time, the time during which the defrost heater 41 is energized can be reduced, thereby reducing power consumption. In other words, although the amount of heat from the defrost heater 41 causes the cooler chamber temperature Te to rise, it is desirable that the amount by which the cooler chamber temperature Te exceeds the termination threshold temperature T_end be kept as small as possible. That is, it is desirable to suppress the state in which the cooler chamber temperature Te becomes significantly higher than the termination threshold temperature T_end.

[0166] Next, using Figures 24 to 26, we will compare and explain the case in which the defrosting operation termination threshold temperature T_end in Embodiment 4 is not varied in reference to the outside air temperature Ta, and the case in which it is varied. Figure 24 is a diagram illustrating the electrical input and evaporator room temperature during defrosting operation at low outside temperatures in a conventional freezer. Figure 25 is a diagram illustrating the electrical input and evaporator room temperature during defrosting operation at low outside temperatures in the freezer 1 according to Embodiment 4. Figure 26 is a diagram comparing the length of heater energization time between a conventional freezer and the freezer 1 according to Embodiment 4.

[0167] In the conventional example shown in Figure 24, the ambient temperature is 10°C and the termination threshold temperature is fixed at 16°C. As shown in Figure 24, during the heater energization period, the slope of the rise in the cooler room temperature Te becomes drastically gradual during the period when the cooler room temperature Te is around 0°C and the period when the ambient temperature Ta is around 10°C. During these periods, the slope of the cooler room temperature Te is almost flat, and there is almost no temperature rise.

[0168] The reason the rise in the cooler room temperature Te becomes gentler around 0°C is that the time required to melt the frost is increasing. In other words, since frost absorbs a very large amount of heat during the phase change at 0°C, around 0°C, the heat generated by the defrost heater 41 is being used to melt the frost, and the heat from the defrost heater 41 is not contributing to the rise in the cooler room temperature Te. That is, almost all of the heat from the defrost heater 41 is being used to melt the frost.

[0169] Furthermore, the reason why the rise in the cooler room temperature Te is gradual at around 10°C is that a thermal equilibrium balance is maintained between the amount of heat entering the freezer 1, i.e., the cooler room 3, from the outside air (amount of cold air entering) and the amount of heat generated by the defrost heater 41. If the termination threshold temperature T_end is set higher than the outside air temperature Ta, it is necessary to raise the temperature inside the cooler room 3 above the outside air temperature Ta. If the temperature is raised above the outside air temperature Ta, the amount of heat generated by the defrost heater 41 is absorbed by the outside air, meaning that some of the heat generated by the defrost heater 41 leaks out of the freezer 1, making it difficult for the cooler room temperature Te to rise.

[0170] In heat conduction, heat moves and diffuses from areas with more heat to areas with less heat, always striving to achieve a uniform temperature. Therefore, when the heat from the defrost heater 41 raises the temperature inside the cooler chamber 3 to the ambient temperature Ta, thermal equilibrium is reached between the cooler chamber 3 and the ambient air. In this state, attempting to further increase the temperature inside the cooler chamber 3 would disrupt the thermal equilibrium balance with the ambient air, requiring even more heat, resulting in an inefficient use of the heat generated by energizing the defrost heater 41. Consequently, in conventional freezers where the termination threshold temperature T_end is fixed, energy-saving performance may deteriorate depending on the ambient temperature.

[0171] In contrast, in Figure 25, the termination threshold temperature T_end is changed by referring to the ambient temperature Ta. As a result, as shown in Figure 25, the temperature rise becomes drastically gradual and almost flat only when the cooler chamber temperature Te is around 0°C during the heater energization period. As mentioned above, the reason why the temperature rise slope becomes gradual when the cooler chamber temperature Te is around 0°C is that a very large amount of heat is absorbed during the phase change of frost. In other words, this indicates that the amount of heat generated from the defrost heater 41 is being absorbed not by the rise in the cooler chamber temperature Te, but by the melting of frost, and that defrosting is progressing.

[0172] On the other hand, as shown in Figure 25, except when thermal equilibrium balance does not occur and the cooler chamber temperature Te is around 0°C, there is no region where the slope becomes sharply gentle. Therefore, compared to the conventional example in Figure 24, it can be seen that the amount of heat supplied from the defrost heater 41 is less likely to leak to the outside air.

[0173] Figure 26 shows the waveforms of the cooler chamber temperature Te in Figures 24 and 25, aligned with the timing at which power is supplied to the defrost heater 41. As shown in Figure 26, in the conventional example, when the cooler chamber temperature exceeds the ambient temperature, the temperature rise slope becomes drastically gradual, and the heat generated by the defrost heater 41 is not effectively utilized. For this reason, the heater power supply period in the conventional example is longer than that in Embodiment 4. On the other hand, in Embodiment 4, the termination threshold temperature T_end is variable according to the ambient temperature Ta, so the heat generated by the defrost heater 41 is effectively used for defrosting the cooler 34. For this reason, the heater power supply period in Embodiment 4 is shorter than that in the conventional example.

[0174] As described above, according to Embodiment 4, by performing a special defrosting operation before the end of the unused period, blockage of the drain pipe 42 is resolved, and the pressure balance between the inside of the freezer compartment 10 and the space outside the freezer compartment 1 is restored, making it easier to open the freezer compartment door 15.

[0175] Furthermore, since the termination threshold temperature T_end is variable to match the actual outside air temperature Ta during operation of the freezer 1, the power supply time of the defrost heater 41 can be shortened, reducing power consumption and improving energy-saving performance.

[0176] Furthermore, by synchronizing the energization of the defrost heater 41 and the drain heater 43, the heat generation density in the cooler chamber 3 can be increased compared to when only the defrost heater 41 is energized, thereby promoting the melting of frost accumulated on the cooler 34. Since the heated air is guided to the upper part of the cooler chamber 3, the heat generated by both the defrost heater 41 and the drain heater 43, which are located at the bottom of the cooler 34, can be effectively utilized. This shortens the defrosting operation time compared to when only the defrost heater 41 is energized, improving energy-saving performance during defrosting.

[0177] In the freezer 1 of Embodiment 4, a configuration was described in which the termination threshold temperature T_end is changed according to the ambient temperature Ta. However, the freezer 1 of Embodiment 4 is basically assumed to be used indoors. For example, if the freezer 1 is used at low temperatures such as when the ambient temperature is below 2°C, it is not necessary to change the termination threshold temperature T_end according to the ambient temperature Ta. This is because, even when the ambient temperature is close to 0°C, if the termination threshold temperature T_end is changed according to the ambient temperature Ta, the defrosting operation may be completed at 0°C, which is the frost melting temperature, and some frost may not melt completely, resulting in residual frost. Conversely, if the ambient temperature Ta is somewhat higher than 0°C and the amount of heat supplied from the defrosting heater 41 can be used effectively, it is possible to completely melt the frost, thus improving energy-saving performance.

[0178] Specifically, the termination threshold temperature T_end may be changed in accordance with the ambient temperature Ta only when the ambient temperature Ta is, for example, 2°C or higher. However, the specific ambient temperature Ta at which the termination threshold temperature T_end is changed in accordance with the ambient temperature Ta may be determined by considering the configuration of the freezer 1 and the user's usage conditions, and the ambient temperature may be set at, for example, 5°C instead of 2°C as the reference.

[0179] Furthermore, if the insulation performance of the freezer 1 itself is low, the thermal equilibrium balance described in the conventional example in Figure 24 is likely to occur. This is because if the insulation capacity of the freezer 1 is high, the leakage of heat from the defrost heater 41, which generates heat inside the freezer 1, to the outside air is suppressed. In other words, the thermal equilibrium balance is less likely to occur in a freezer 1 that uses high-performance insulation materials such as vacuum insulation materials with high insulation capacity, but is more likely to occur in an inexpensive freezer 1 that does not use vacuum insulation materials. For this reason, in Embodiment 4, vacuum insulation material may be used for the insulation member 23 of the freezer 1.

[0180] In the above embodiment 4, a special defrosting operation was performed when the usage frequency rank corresponds to a non-used period, but this is not the only limitation. For example, when the usage frequency rank corresponds to a non-used period, the defrosting heater 41 may not be energized, and only the drain heater 43 may be energized. In this case as well, the closure of the drain pipe 42 is suppressed, making it possible to reduce the force required to open and close the door of the freezer 1.

[0181] Furthermore, the freezer 1 may perform both the special defrosting operation of Embodiment 4 and the suppression operation of Embodiment 1. For example, if the current time period is an unused time period, the suppression operation of Embodiment 1 may be performed, and the special defrosting operation may be performed when the remaining time tz of the unused time period becomes less than or equal to the termination threshold time t_end.

[0182] The above describes the embodiments, but this disclosure is not limited to the embodiments described below, and can be modified in various ways without departing from the spirit of this disclosure. Furthermore, this disclosure includes all possible combinations of the configurations shown in the embodiments and their modified examples below. For example, the configuration and control of the freezer 1 in the above embodiment can also be applied to storage facilities that cool stored items other than the freezer 1 to a single temperature range. In this case, threshold values ​​for each rank and discrimination are set appropriately according to the temperature range of the storage room.

[0183] Furthermore, although the above embodiment described the stored items in the freezer compartment 10 as food, it is not limited to this. For example, the stored items may be things collected from nature, such as the raw meat of small animals that are not meant to be eaten, or they may be the raw meat of experimental animals such as cloned animals.

[0184] Furthermore, in the above embodiment, the freezer door 15 is configured to consist of two doors, an upper door 15a and a lower door 15b, but it is not limited to this configuration. Figure 27 is a front view of the freezer 1A according to Modification 1. Figure 28 is a schematic cross-sectional view of the freezer 1A according to Modification 1. Figure 28 is a view of the freezer 1A shown in Figure 27 when it is cut along line segment AA and viewed from the direction of the arrow. As shown in Figures 27 and 28, the freezer door 15 may be a single door.

[0185] In this case, the opening / closing sensor 17 is provided on the front of the top or bottom surface of the main body 2. Furthermore, if the main body 2 is the same size, using a two-door freezer 1, as in the above embodiment, rather than a single-door freezer 1, can suppress cold air leakage during a single opening and closing.

[0186] Furthermore, as in the embodiment, if the freezer compartment 10 is opened and closed by two doors, the opening and closing of the upper door 15a and the lower door 15b may be detected individually, and adjustment coefficients α1 for when the upper door 15a is opened and α2 for when the lower door 15b is opened may be set individually.Then, the product of the average number of times the upper door 15a is opened and the average opening time and adjustment coefficient α1 during the calculation period, and the product of the average number of times the lower door 15b is opened and adjustment coefficient α2 may be averaged to obtain a discrimination parameter X, and the usage frequency rank may be determined. [Explanation of Symbols]

[0187] 1, 1A Freezer, 2 Main unit, 3 Cooler compartment, 6 Control unit, 10 Freezer compartment, 11 Upper freezer compartment, 12 Lower freezer compartment, 13 Shelf, 14 Storage container, 15 Freezer compartment door, 15a Upper door, 15b Lower door, 16 Door partition, 17 Open / close sensor, 18 Operation display unit, 18a Operation unit, 18b Display unit, 19 Outside air temperature sensor, 21 Outer casing, 22 Inner casing, 23 Insulation material, 30 Machine room, 31 Compressor, 32 Condenser, 33 Pressure reducing device, 34 Cooler, 34a Inlet, 34b Outlet, 35 Blower, 36 Cooler compartment temperature sensor, 41 Defrost heater, 42 Drain pipe, 43 Drain heater, 44 Drain pan, 51 Upper air passages, 51a, 51b, 51c; outlets, 52; Lower air passages, 52a, 52b, 52c; outlets, 53; internal temperature sensor, 54; return air passage, 54a; inlet, 61; memory unit, 62; cooling control unit, 63; heater control unit, 64; adjustment coefficient calculation unit, 65; rank determination unit, 66; judgment unit, 341; fins, 342; heat transfer tubes, 343; connecting tubes, 510, 520; wall surfaces, 600; processing circuit, 601; processor, 602; memory, 603; bus.

Claims

1. A storage facility that cools stored items within a single temperature range, A main body having a storage room and a cooler room, A door is provided on the front of the aforementioned storage room, A cooler is placed in the aforementioned cooler chamber and generates cold air by heat exchange with a refrigerant, A blower that sends the aforementioned cold air to the storage room, A compressor that sends the refrigerant to the cooler, A storage chamber temperature sensor that measures the internal temperature, which is the temperature inside the storage chamber, A cooling chamber temperature sensor measures the cooling chamber temperature, which is the temperature of the aforementioned cooling chamber. An opening / closing sensor for detecting the opening and closing of the aforementioned door, The system includes a control device for controlling the compressor and the blower, The control device is Based on the number of times the aforementioned door is opened and closed, the usage frequency rank for each time period is determined. If the current time period is the least used time period according to the usage frequency ranking, it is determined whether the temperature difference between the internal temperature and the cooling chamber temperature is above the threshold temperature. A storage facility that, when the temperature difference is greater than or equal to the threshold temperature, performs a suppression operation in which the blower is operated and the compressor is stopped.

2. The storage facility according to claim 1, wherein the usage frequency rank is determined by the product of the number of times the door is opened and closed for each time period and the duration the door is open.

3. The storage facility according to claim 1, wherein the usage frequency rank is determined by the product of an adjustment coefficient indicating the proportion of stored items placed in the storage room when the door is opened and closed, the number of times the door is opened and closed for each time period, and the duration the door is open.

4. The control device is The temperature rise value of the internal temperature when the door is opened and closed, Determine the recovery time required for the internal temperature to return to the temperature before the door was opened after the door has been opened. If the temperature rise value is greater than or equal to the threshold value and the recovery time is greater than or equal to the threshold time, it is determined that the stored items were placed into the storage chamber when the door was opened or closed. The storage facility according to claim 3, wherein the adjustment coefficient is calculated by dividing the number of times the door was opened and closed in a predetermined calculation period in which the stored items were determined to have been put in by the total number of times the door was opened and closed in the calculation period.

5. The control device is The temperature rise value of the internal temperature and the temperature rise value of the cooling chamber when the door is opened and closed, When the door is opened or closed, the recovery time required for the internal temperature to return to the temperature before the door was opened, and the recovery time required for the cooling chamber temperature to return to the temperature before the door was opened are determined. If the temperature rise values ​​of both the internal temperature and the cooler temperature are above a threshold, and the recovery time of both the internal temperature and the cooler temperature is above a threshold, then it is determined that the stored items were placed into the storage chamber when the door was opened or closed. The storage facility according to claim 3, wherein the adjustment coefficient is calculated by dividing the number of times the door was opened and closed in a predetermined calculation period in which the stored items were determined to have been put in by the total number of times the door was opened and closed in the calculation period.

6. In the suppression operation, the control device The operation of the blower is started by setting the rotation speed of the blower to the minimum rotation speed. The temperature gradient of the internal temperature is repeatedly calculated at predetermined time intervals. A storage unit according to any one of claims 1 to 5, wherein the rotation speed of the blower is increased when the latest temperature gradient falls below the previous temperature gradient.

7. The storage cabinet according to any one of claims 1 to 5, wherein the control device varies the set temperature of the internal temperature of the cabinet based on the usage frequency rank.

8. The system includes an outside air temperature sensor that measures the outside air temperature, which is the temperature of the space outside the storage room separated from the storage room by the aforementioned door. The control device is Based on the aforementioned outside air temperature, the outside air rank for each time period is determined. A storage facility according to any one of claims 1 to 5, wherein the rotational speed of the compressor, or the rotational speeds of the compressor and the blower, are varied based on the usage frequency rank and the outside air rank.

9. A defrost heater that melts frost that has accumulated on the cooler during defrosting operation, A drain pipe for discharging the melted water from the frost, The storage unit according to any one of claims 1 to 5, further comprising a drain heater for unfreezing the drain pipe.

10. The storage unit according to claim 9, wherein the control device operates the defrost heater and the drain heater in a synchronous manner.

11. The storage unit according to claim 9, wherein the control device performs the defrosting operation when the current time period is the unused time period.

12. The control device is The defrosting operation is terminated by comparing the temperature of the cooler chamber with the termination threshold temperature. The storage facility according to claim 9, wherein if the ambient temperature is below the termination threshold temperature, the termination threshold temperature is changed to the ambient temperature.

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