Refrigerator

Abstract

Provided is a refrigerator that, in a period from when a defrosting operation was last performed until a subsequent defrosting operation is started, obtains a first door open state time, which is a time during which a first door is in an open state, on the basis of a first signal input from a first door open / close sensor; obtains a second door open state time, which is a time during which a second door is in an open state, on the basis of a second signal input from a second door open / close sensor; obtains a first energization time, which is an energization time of a first heater, on the basis of the first door open state time; and obtains a second energization time, which is an energization time of a second heater, on the basis of the second door open state time. When the subsequent defrosting operation is started, the energization of the first heater and the second heater is started; if the first energization time is shorter than the second energization time, the first heater is energized for the first energization time, and the second heater is energized until the temperature of a cooler reaches a threshold temperature; and if the second energization time is shorter than the first energization time, the second heater is energized for the second energization time, and the first heater is energized until the temperature of the cooler reaches the threshold temperature.

Description

refrigerator

[0001] The present disclosure relates to a refrigerator having a storage compartment for storing items to be cooled.

[0002] Conventionally, refrigerators have a cooler, a heat exchanger that cools air, installed in a cooler compartment on the rear side of the main body. Return air, which flows from the storage compartment through the return air duct into the cooler compartment, is cooled by heat exchange in the cooler with refrigerant sent to the cooler by the operation of the compressor, and is then blown into each storage compartment by a fan installed above the cooler compartment to cool food. After cooling each storage compartment, the air returns to the cooler compartment again through the return air duct.

[0003] When a user opens and closes the doors of each storage compartment to take food in or out, outside air from the interior space in which the refrigerator is installed flows into the storage compartment. When high-temperature and high-humidity outside air passes through the storage compartment and enters the cooler compartment, the water vapor contained in the outside air forms frost on the surface of the cooler. As the amount of frost increases, it becomes more difficult for the air circulating inside the refrigerator to flow between the multiple fins of the cooler, reducing the efficiency of heat exchange and causing a decrease in the refrigerator's cooling performance.

[0004] To prevent such performance degradation, refrigerators are equipped with a defrosting heater in the cooler, and periodically perform a defrosting operation in which electricity is applied to the heater to melt and remove frost that has adhered to the cooler. Some coolers with a fin-tube heat exchanger having multiple rows of flat fins arranged vertically are equipped with two types of defrosting heaters. The first defrosting heater is a pipe heater for melting frost that has adhered to the middle or upper fins of the cooler. The second defrosting heater is a glass tube heater for melting frost that has adhered to the lower fins of the cooler. A conventional refrigerator that combines two defrosting heaters to melt frost on the cooler is known.

[0005] During defrosting operation, conventional refrigerators supply power to the two defrost heaters and stop powering the two heaters when the temperature sensor attached to the top of the cooler detects a predetermined threshold temperature. Here, if the amount of frost varies depending on the location of the cooler, the following problem occurs. For example, when the defrosting operation is completed, the frost on the lower fins of the cooler may have melted, but frost may still remain on the middle or upper fins of the cooler. In this case, the frost on the middle or upper fins of the cooler prevents the temperature sensor from detecting the threshold temperature. Therefore, conventional refrigerators continue to power the defrost heater for the lower fin of the cooler. This results in an unnecessarily long power-on time and increased power consumption. Furthermore, if the heaters are powered for a long time, the internal temperature of the refrigerator increases excessively after the defrosting operation is completed. This increases the thermal load on the cooler when the refrigerator resumes operation after the defrosting operation, further increasing power consumption. To solve these problems, a technology was needed to efficiently melt the frost in each part of the cooler in a refrigerator.

[0006] Conventionally, a refrigerator-freezer has been known that includes a defrost heater provided below the cooler and a heater tube that is bent multiple times and fixed to the cooler as a defrost heater for melting frost on the cooler (see, for example, Patent Document 1). The refrigerator-freezer disclosed in Patent Document 1 includes a control means that controls the timing for starting and ending energization of the defrost heater and the heater tube based on detection results from a door opening / closing detection means. If the control means of this refrigerator-freezer determines that the number of door openings and closings is large during the defrosting operation time interval between the previous defrosting operation and the next defrosting operation, it simultaneously starts energizing the defrost heater and the heater tube and simultaneously ends energization of the defrost heater and the heater tube. Furthermore, if the control means determines that the number of door openings and closings is small during the defrosting operation time interval, it first starts energizing the heater tube and then starts energizing the defrost heater.

[0007] International Publication No. 2017 / 017850

[0008] The longer the refrigerator door is open, the more frost tends to form on the cooler. Since the number of times the door is opened and closed is not necessarily proportional to the time the door is open, in the refrigerator-freezer disclosed in Patent Document 1, if heater power supply control is performed based on the number of times the door is opened and closed, there is a risk that the amount of heater power supply will be excessive or insufficient relative to the amount of frost formed on the cooler. In the refrigerator disclosed in Patent Document 1, if the number of times the door is opened and closed is high, excessive heater power supply time may be set to ensure that the frost on the cooler is melted, resulting in increased power consumption.

[0009] The present disclosure has been made to solve the above-described problems, and provides a refrigerator that can reduce power consumption.

[0010] A refrigerator according to the present disclosure includes a first storage compartment set to a first temperature zone, a second storage compartment set to a second temperature zone that is lower than the first temperature zone, a first door for opening and closing the first storage compartment, a second door for opening and closing the second storage compartment, a first door opening / closing sensor that detects opening and closing of the first door and outputs a first signal indicating an open state or a closed state of the first door, a second door opening / closing sensor that detects opening and closing of the second door and outputs a second signal indicating an open state or a closed state of the second door, and a power supply that receives the first signal from the first door opening / closing sensor and opens and closes the second door. a control device to which the second signal is input from the sensor; a cooler chamber provided with a cooler that cools air; a cooler temperature sensor that detects the temperature of the cooler; a blower that sends the air cooled by the cooler to the first storage chamber and the second storage chamber; a first return air duct having a first return port that opens into the cooler chamber and that guides the air in the first storage chamber to the cooler chamber; a second return air duct having a second return port that opens into the cooler chamber and that guides the air in the second storage chamber to the cooler chamber; and a second heater that melts frost on the cooler by air flowing into the cooler chamber from the second return air duct, and the control device determines a first door open state time that is a time during which the first door is open based on the first signal, determines a second door open state time that is a time during which the second door is open based on the second signal, and determines a first energization time that is a time during which the first heater is energized based on the first door open state time, during a reference time from when a defrosting operation for melting frost on the cooler was last performed to when a next defrosting operation is started. calculates a time, calculates a second power supply time that is a power supply time of the second heater based on the second door open state time, starts power supply to the first heater and the second heater when starting the next defrosting operation, and if the first power supply time is shorter than the second power supply time, powers the first heater for the first power supply time and powers the second heater until a temperature detected by the cooler temperature sensor reaches a predetermined threshold temperature, and if the second power supply time is shorter than the first power supply time, powers the second heater for the second power supply time;The first heater is energized until the temperature detected by the cooler temperature sensor reaches the threshold temperature.

[0011] According to the present disclosure, the energization time of each of the glass tube heater and the pipe heater is calculated based on the door open time of the first storage chamber and the second storage chamber, and during defrosting operation, the energization of the heater with the shorter energization time of the two energization times is stopped early. Since the energization of the heater in the cooler that has completed defrosting is stopped early during the defrosting operation, the amount of power consumed by the heaters can be reduced.

[0012] 1 is a front view of a refrigerator 100 according to a first embodiment. It is a schematic cross-sectional view taken along line A-A in FIG. 1. It is an enlarged perspective view of a portion of the front surface of the left door 7a1 of the refrigerator compartment 1 shown in FIG. 1. It is a plan view of the insulating partition wall 6a shown in FIG. 2 when viewed from above. It is an enlarged view of the lower part of the cooler compartment 80 formed between the fan grill 16 and the inner box 17a. It is a perspective view showing an example of the configuration of the cooler 18 and the pipe heater 65 in the refrigerator 100 according to the first embodiment. It is a perspective view showing the pipe heater 65 alone shown in FIG. 6. It is a perspective view showing an example of the configuration of the glass tube heater 19 attached to the lower part of the cooler 18 shown in FIG. 6. It is a perspective view showing the positional relationship between the cooler 18 to which the pipe heater 65 is attached and the glass tube heater 19. It is a block diagram for explaining the control performed by the control device 12 for the refrigerator 100 according to the first embodiment. It is an enlarged view of the configuration including the cooler 18 shown in FIG. 5. It is a table showing an example of the results of an investigation into the door-open time of each storage compartment per day for each of the summer and winter seasons in a refrigerator. 11 is a graph showing the relationship between the time tave that the refrigerator compartment door 7a and the freezer compartment door 7d are open and the amount of frost formed on the cooler 18. FIG. 12 is a graph showing the relationship between the amount of frost formed on the cooler 18 and the heater energization time required to melt the frost formed on the cooler 18. FIG. 13 is a hardware configuration diagram showing an example configuration of the control device 12 shown in FIG. 10. FIG. 14 is a hardware configuration diagram showing another example configuration of the control device 12 shown in FIG. 10. FIG. 15 is a flowchart showing the operation procedure in the defrosting operation of the refrigerator according to the first embodiment. FIG. 16 is a flowchart showing the operation procedure in the defrosting operation of the refrigerator according to the first embodiment. FIG. 17 is a timing chart for explaining the effect of the defrosting operation performed by the refrigerator 100 according to the first embodiment. FIG. 18 is a graph showing the relationship between the time tave that the refrigerator compartment door 7a is open and the amount of frost formed on the cooler 18 in the refrigerator 100 according to the first embodiment, when the outside air humidity is different. 10 is a graph showing the relationship between the time tave that the refrigerator compartment door 7a, the freezer compartment door 7d, and the vegetable compartment door 7e are open and the amount of frost that forms on the cooler 18 in the refrigerator 100 according to the second embodiment.

[0013] An embodiment of a refrigerator according to the present disclosure will be described with reference to the drawings. For ease of explanation, some of the drawings show three axes, namely, an X axis, a Y axis, and a Z axis, which define directions in a three-dimensional space. The direction of the Y axis arrow indicates the front side of the refrigerator, and the direction opposite the Y axis arrow indicates the rear side of the refrigerator. The direction opposite the Z axis arrow indicates the direction of gravity.

[0014] Embodiment 1 A refrigerator according to Embodiment 1 will be described with reference to the drawings. Fig. 1 is a front view of a refrigerator 100 according to Embodiment 1. Fig. 2 is a schematic cross-sectional view taken along line AA shown in Fig. 1.

[0015] Refrigerator 100 includes refrigerator body 101, which is a box-like structure having multiple storage compartments therein for storing items to be cooled. The refrigerator body 101 is provided with multiple storage compartments, consisting of, in order from the top, refrigerator compartment 1, ice-making compartment 2, switchable compartment 3, freezer compartment 4, and vegetable compartment 5. Refrigerator compartment 1 corresponds to the first storage compartment, freezer compartment 4 corresponds to the second storage compartment, and vegetable compartment 5 corresponds to the third storage compartment. Ice-making compartment 2 is located below refrigerator compartment 1 on the left, and switchable compartment 3 is located below refrigerator compartment 1 on the right. Ice-making compartment 2 and switchable compartment 3 are located adjacent to each other horizontally. Ice-making compartment 2 may be equipped with an automatic ice maker (not shown).

[0016] The arrangement of the multiple storage compartments is not limited to the arrangement shown in Figures 1 and 2. The arrangement of two storage compartments located vertically or horizontally can be interchanged. Refrigerator 100 has ice-making compartment 2, switchable compartment 3, and vegetable compartment 5 in addition to refrigerator compartment 1 and freezer compartment 4, but it does not have to have ice-making compartment 2, switchable compartment 3, and vegetable compartment 5. For example, refrigerator 100 may be configured so that refrigerator body 101 has only refrigerator compartment 1 and freezer compartment 4, or may have only refrigerator compartment 1 or freezer compartment 4. Refrigerator body 101 may also be configured so that it has multiple freezer compartments 4.

[0017] Of the multiple storage compartments in refrigerator 100, two vertically adjacent storage compartments are separated from each other by heat-insulating partition walls 6a to 6c. Heat-insulating partition wall 6a separates refrigerator compartment 1 from ice-making compartment 2 and switchable compartment 3. Heat-insulating partition wall 6b separates ice-making compartment 2 and switchable compartment 3 from freezer compartment 4. Heat-insulating partition wall 6c separates freezer compartment 4 from vegetable compartment 5. In refrigerator 100 of the first embodiment, the positions of freezer compartment 4 and vegetable compartment 5 can be interchanged.

[0018] Refrigerator 100 is provided with a plurality of doors on the front side of refrigerator body 101 for opening and closing each of a plurality of storage compartments. The doors are refrigerator compartment door 7a, ice making compartment door 7b, switchable compartment door 7c, freezer compartment door 7d, and vegetable compartment door 7e. Refrigerator compartment door 7a corresponds to the first door, freezer compartment door 7d corresponds to the second door, and vegetable compartment door 7e corresponds to the third door. Refrigerator compartment door 7a opens and closes refrigerator compartment 1. Ice making compartment door 7b opens and closes ice making compartment 2. Switchable compartment door 7c opens and closes switchable compartment 3. Freezer compartment door 7d opens and closes freezer compartment 4. Vegetable compartment door 7e opens and closes vegetable compartment 5.

[0019] In the first embodiment, the refrigerator compartment door 7a is a rotating door that rotates around a hinge 11. As shown in Fig. 1, the refrigerator compartment door 7a is a double door consisting of a pair of doors, a left door 7a1 and a right door 7a2, but is not limited to the configuration shown in Fig. 1. The refrigerator compartment door 7a may be a single door or a door other than a double door.

[0020] Ice-making compartment door 7b is a drawer-type door. An ice-making compartment frame is attached to the back of ice-making compartment door 7b, and ice-making compartment case 14 is installed on the ice-making compartment frame. The ice-making compartment frame is attached to ice-making compartment rails on the left and right sides of ice-making compartment 2 and slides on the ice-making compartment rails. When ice-making compartment door 7b closes ice-making compartment 2, ice-making compartment case 14 is stored in ice-making compartment 2.

[0021] The selectable compartment door 7c is a drawer-type door. A selectable compartment frame is attached to the back of the selectable compartment door 7c, and the selectable compartment case 15 is installed on the selectable compartment frame. The selectable compartment frame is attached to selectable compartment rails provided on the left and right sides of the selectable compartment 3, and slides on the selectable compartment rails. When the selectable compartment door 7c closes the selectable compartment 3, the selectable compartment case 15 is stored in the selectable compartment 3.

[0022] The freezer compartment door 7d is a drawer-type door. A freezer compartment frame is attached to the backside of the freezer compartment door 7d, and the lower storage case 22 is installed on the freezer compartment frame. The lower storage case 22 is a storage case designed for long-term storage of approximately one month. A shallow upper storage case 23 is placed on top of the lower storage case 22. When the freezer compartment door 7d closes the freezer compartment 4, the lower storage case 22 and the lower storage case 23 are stored in the freezer compartment 4.

[0023] The vegetable compartment door 7e is a drawer-type door. A vegetable compartment frame is attached to the back of the vegetable compartment door 7e, and a lower storage case 29 is installed on the vegetable compartment frame. The lower storage case 29 is a case for storing larger vegetables. An upper storage case 30, which is shallower than the lower storage case 29 and is convenient for storing leafy vegetables and small vegetables, is placed on top of the lower storage case 29. When the vegetable compartment door 7e closes the vegetable compartment 5, the lower storage case 29 and the upper storage case 30 are stored in the vegetable compartment 5.

[0024] As shown in Fig. 2, the control device 12 is housed in the upper rear portion of the refrigerator body 101. The control device 12 controls the operation of the refrigerator 100. The control device 12 controls various electrical devices related to the cooling operation based on signals received from various sensors provided in the refrigerator 100 and setting information set by the user. The control device 12 will be described in detail later.

[0025] As shown in FIG. 1 , refrigerator compartment 1 is provided with refrigerator compartment temperature sensor 51a for detecting the temperature of refrigerator compartment 1. Ice-making compartment 2 is provided with ice-making compartment temperature sensor 51b for detecting the temperature of ice-making compartment 2. Switchable compartment 3 is provided with switchable compartment temperature sensor 51c for detecting the temperature of switchable compartment 3. Freezer compartment 4 is provided with freezer compartment temperature sensor 51d for detecting the temperature of freezer compartment 4. Vegetable compartment 5 is provided with vegetable compartment temperature sensor 51e for detecting the temperature of vegetable compartment 5. These temperature sensors are, for example, thermistors. Refrigerator compartment temperature sensor 51a, ice-making compartment temperature sensor 51b, switchable compartment temperature sensor 51c, freezer compartment temperature sensor 51d, and vegetable compartment temperature sensor 51e are each connected to control device 12 for communication via signal lines (not shown).

[0026] FIG. 3 is an enlarged perspective view of a portion of the front of the left door 7a1 of the refrigerator compartment 1 shown in FIG. 1 . An operation panel 8 is provided on the front of the left door 7a1 of the refrigerator compartment 1, allowing the user to adjust the temperature of each storage compartment. The operation panel 8 is communicatively connected to the control device 12 via a signal line (not shown). The operation panel 8 includes a panel main body 8a and a circuit board 9. The circuit board 9 is installed on the rear side of the panel main body 8a so as to be covered by the panel main body 8a. The circuit board 9 is provided with an outside air temperature sensor 10 for detecting the outside air temperature. The outside air temperature sensor 10 is, for example, a thermistor. The panel main body 8a is provided with a temperature adjustment button 54 for inputting the set temperature of the storage compartment and a selection button 55 for selecting one of the multiple storage compartments.

[0027] In refrigerator 100, operation panel 8 is provided on refrigerator compartment door 7a on the front side, but when design is prioritized, operation panel 8 may be installed inside refrigerator compartment 1 rather than on the surface of refrigerator body 101, including doors such as refrigerator compartment door 7a. In this case, outside air temperature sensor 10 may be installed, for example, inside hinge 11 that rotates refrigerator compartment door 7a while supported by refrigerator body 101.

[0028] The temperature setting for each storage compartment is determined by the user pressing a selection button 55 on the operation panel 8 to select the storage compartment to be temperature-adjusted, and then the user presses the temperature adjustment button 54 to set the cooling strength, such as low, medium, or high, for the selected storage compartment. For example, the temperature setting for refrigerator compartment 1 is determined by the user pressing the temperature adjustment button 54 to select low (approximately 6°C), medium (approximately 3°C), or high (approximately 1°C). For example, the temperature range (first temperature range) for refrigerator compartment 1 is set to 1°C to 6°C, which is the refrigeration temperature range. The temperature setting for freezer compartment 4 is determined by the user pressing the temperature adjustment button 54 to select low (approximately -16°C), medium (approximately -18°C), or high (approximately -20°C). As an example, the temperature range (second temperature range) for freezer compartment 4 is set to -16°C to -20°C, which is the freezing temperature range. By pressing the temperature adjustment button 54, the user can select one of two temperatures for the switching compartment 3: weak freezing of approximately -7°C, which is suitable for frozen storage for about two weeks, and normal freezing of approximately -18°C, which is suitable for frozen storage for about one month.

[0029] The internal structure of refrigerator 100 will be described with reference to Figures 1 and 2. As shown in Figure 2, a refrigerator door sensor 90a that detects the opening and closing of refrigerator door 7a, an ice-making door sensor 90b that detects the opening and closing of ice-making door 7b, and a switching compartment door sensor 90c that detects the opening and closing of switching compartment door 7c are provided on the front side of insulating partition wall 6a. Refrigerator door sensor 90a corresponds to the first door sensor. A freezer door sensor 90d that detects the opening and closing of freezer door 7d is provided on the front side of insulating partition wall 6b. The freezer door sensor 90d corresponds to the second door sensor. A vegetable door sensor 90e that detects the opening and closing of vegetable door 7e is provided on the front side of insulating partition wall 6c. The vegetable door sensor 90e corresponds to the third door sensor.

[0030] The control device 12 is communicatively connected to each of the refrigerator door open / close sensor 90a, ice making door open / close sensor 90b, switchable compartment door open / close sensor 90c, freezer door open / close sensor 90d, and vegetable compartment door open / close sensor 90e via signal lines (not shown). Each of the refrigerator door open / close sensor 90a, ice making door open / close sensor 90b, switchable compartment door open / close sensor 90c, freezer door open / close sensor 90d, and vegetable compartment door open / close sensor 90e transmits a door status signal indicating the open or closed state of the corresponding door to the control device 12. The door status signal transmitted by the refrigerator door open / close sensor 90a corresponds to a first signal. The door status signal transmitted by the freezer door open / close sensor 90d corresponds to a second signal. The door status signal transmitted by the vegetable compartment door open / close sensor 90e corresponds to a third signal.

[0031] As shown in FIG. 2 , fan grill 16 is installed at the back of freezer compartment 4. Fan grill 16 forms the back surface of ice-making compartment 2, selectable compartment 3, and freezer compartment 4, and is equipped with blower 24, refrigerator compartment damper device 26, and selectable compartment damper device 27 inside. Compressor 25 is installed at the bottom of the rear side of refrigerator body 101. Compressor 25, a radiator (not shown), a pressure-reducing device (not shown) such as a capillary tube, and cooler 18 are connected via refrigerant piping 63 (see FIG. 6 ) to form a refrigerant circuit (not shown) through which the refrigerant circulates. Fan 24, refrigerator compartment damper device 26, selectable compartment damper device 27, and compressor 25 are each connected to control device 12 via signal lines (not shown). Freezer compartment temperature sensor 51d shown in FIG. 1 detects freezer compartment temperature Tf, which is used to determine whether to operate or stop compressor 25. The freezer compartment temperature sensor 51 d is installed at the rear side of the freezer compartment 4 and in front of the fan grill 16 .

[0032] As shown in Figure 2, the refrigerator compartment 1 is divided by multiple shelves 43-45 made of resin or glass. While Figure 2 shows a case with three shelves, the number of shelves is not limited to three. A small item storage case 46 is installed below the lowest shelf 45. The temperature of the small item storage case 46 is 1 to 2°C lower than that of the upper shelves 44 and 45. This is because low-temperature cold air has less buoyancy than room-temperature air and therefore tends to stagnate downward, resulting in a lower temperature in the lower part of the refrigerator compartment 1 compared to the upper part.

[0033] A plurality of pockets 57 are attached to the left door 7a1 of the refrigerator compartment door 7a. Although not shown in Fig. 2, a plurality of pockets 57 are also attached to the right door 7a2 shown in Fig. 1. When a refrigerator is installed in a location where the rotation space for the refrigerator compartment door 7a is narrow, the refrigerator is often installed with two doors, a left door 7a1 and a right door 7a2, as shown in Fig. 1. On the other hand, when the width of the refrigerator (the length in the X-axis direction shown in Fig. 1) is relatively small, for example, less than 60 cm, a refrigerator is often installed with a single door for the refrigerator compartment 1.

[0034] 1 and 2, a control panel 47 is installed at the back of the refrigerator compartment 1 to distribute the cold air supplied from the cooler compartment 80 to each shelf. The decorative surface side of the control panel 47 is made up of a resin part 48, and the back side is made up of a duct part 49 made of polystyrene foam. The duct part 49 and the inner box 17a form a refrigerator compartment outlet air duct 50.

[0035] A plurality of air duct holes 56 are provided on the control panel 47. The plurality of air duct holes 56 serve to blow out onto each shelf the cold air that flows from the cooler compartment 80 into the refrigerator compartment outlet air duct 50 via the refrigerator compartment damper device 26. The refrigerator compartment temperature sensor 51a is installed at the center in the vertical direction on the back of the refrigerator compartment 1, and detects the average temperature of the air inside the refrigerator compartment 1.

[0036] A heat insulating material 28 such as a urethane foam material is filled between inner box 17a and outer box 17b of refrigerator body 101. Furthermore, vacuum heat insulating materials 13 are provided on both side surfaces (not shown), the back surface, the ceiling surface, and the inside of the door of refrigerator body 101 as members for reinforcing heat insulation. Vacuum heat insulating materials 13 are provided inside heat insulating materials 28 so as to surround each storage compartment in order to suppress heat leakage from each storage compartment.

[0037] 1 and 2 , refrigerator body 101 includes refrigerator compartment return air duct 31, which is a first return air duct, freezer compartment return air duct 32, which is a second return air duct, and vegetable compartment return air duct 33, which is a third return air duct. Refrigerator compartment return air duct 31 is an air duct for guiding air in refrigerator compartment 1 to cooler compartment 80. Freezer compartment return air duct 32 is an air duct for guiding air in freezer compartment 4 to cooler compartment 80. Vegetable compartment return air duct 33 is an air duct for guiding air in vegetable compartment 5 to cooler compartment 80. Refrigerator compartment return air duct 31, freezer compartment return air duct 32, and vegetable compartment return air duct 33 are provided independently of one another.

[0038] FIG. 4 is a plan view of the insulating partition wall 6a shown in FIG. 2 when viewed from above. A refrigerator compartment return air duct inlet 81 opening into the refrigerator compartment 1 is provided at the rear side of the insulating partition wall 6a. The refrigerator compartment return air duct inlet 81 constitutes one end of the refrigerator compartment return air duct 31 shown in FIG. 1. As shown in FIG. 1, the refrigerator compartment return air duct 31 has, at its other end, a refrigerator compartment return air duct outlet 82 opening into the cooler compartment 80. The refrigerator compartment return air duct outlet 82 corresponds to the first return port. The refrigerator compartment return air duct inlet 81 is provided away from the refrigerator compartment return air duct outlet 82 in the refrigerator compartment 1. In FIG. 1, the dotted arrow indicates the direction D1 of air flow in the refrigerator compartment return air duct 31. In the refrigerator 100 of the first embodiment, the refrigerator compartment return air duct outlet 82 is provided upstream of the cooler 18 with respect to the direction D1 of air flow in the cooler compartment 80. The refrigerator compartment return air duct outlet 82 is provided below the cooler 18. The position of the refrigerator compartment return air duct outlet 82 is not limited to that shown in Figure 1. The position of the refrigerator compartment return air duct outlet 82 may be any position upstream of the cooler 18. The returning cold air from the refrigerator compartment 1 flows from the refrigerator compartment return air duct inlet 81 into the refrigerator compartment return air duct 31, circulates through the refrigerator compartment return air duct 31, and then flows from the refrigerator compartment return air duct outlet 82 into the cooler compartment 80.

[0039] FIG. 5 is an enlarged view showing the lower part of the cooler chamber 80 formed between the fan grill 16 and the inner box 17a. The freezer chamber return air duct 32, which connects the freezer chamber 4 and the cooler chamber 80, is provided in the insulating wall portion 92 that constitutes the rear portion 4a of the freezer chamber 4 and the front portion 80a of the cooler chamber 80. A freezer chamber return air duct inlet 83 is provided in the rear portion 4a of the freezer chamber 4. The freezer chamber return air duct inlet 83 constitutes one end of the freezer chamber return air duct 32. The freezer chamber return air duct 32 has, at its other end, a freezer chamber return air duct outlet 84 that opens into the cooler chamber 80. The freezer chamber return air duct outlet 84 corresponds to a second return port. The freezer chamber return air duct inlet 83 is provided away from the freezer chamber return air duct outlet 84 in the freezer chamber 4. The direction D1 in the cooler chamber 80 in which air flows when the blower 24 is driven is indicated by an arrow in FIG. 5 . Air flows from below to above cooler 18. As shown in FIG. 1 , freezer compartment return air duct outlet 84 is provided downstream of refrigerator compartment return air duct outlet 82 with respect to air flow direction D1 in cooler compartment 80. In Embodiment 1, freezer compartment return air duct outlet 84 is formed in front surface 80a of cooler compartment 80. Freezer compartment return air duct outlet 84 is provided at a position overlapping with cooler 18 in the depth direction (the opposite direction of the Y-axis arrow) when refrigerator body 101 is viewed from the front side. Returning cool air from freezer compartment 4 flows from freezer compartment return air duct inlet 83 into freezer compartment return air duct 32, flows through freezer compartment return air duct 32, and then flows into cooler compartment 80 from freezer compartment return air duct outlet 84.

[0040] The vegetable compartment 5, located at the bottom of the refrigerator body 101, is slightly warmer than the refrigerator compartment 1. The vegetable compartment 5 is maintained at a refrigeration temperature range of, for example, +3°C to +10°C. The vegetable compartment 5 is cooled using the refrigerator compartment return air duct 31. As described with reference to Figures 1 and 4, the refrigerator compartment return air duct 31 extends downward via the right rear rear of the switchable compartment 3 to the right rear rear of the freezer compartment 4, and further extends from the right rear of the vegetable compartment 5 to the center rear of the vegetable compartment 5, connecting to the bottom of the cooler compartment 80. A portion of the cold air flowing through the refrigerator compartment return air duct 31 is supplied to the vegetable compartment 5. Because the cold air flowing through the refrigerator compartment return air duct 31 is in the refrigeration temperature range, no thermal insulation is required between the refrigerator compartment return air duct 31 and the vegetable compartment 5. Meanwhile, a thermal insulation structure (not shown) is provided between the refrigerator compartment return air duct 31 and the cooler 18 to prevent air duct blockage due to frost formation.

[0041] As shown in FIG. 5 , a vegetable compartment return air duct inlet 85 is provided on the underside 6c1 of the insulating partition wall 6c that separates the freezer compartment 4 and the vegetable compartment 5, which forms the ceiling of the vegetable compartment 5. The rear side 6c2 of the insulating partition wall 6c forms part of the underside of the cooler compartment 80. A vegetable compartment return air duct outlet 86 is provided on the rear side 6c2 of the insulating partition wall 6c. The vegetable compartment return air duct outlet 86 is provided below the cooler 18 on the rear side 6c2 of the insulating partition wall 6c. The vegetable compartment return air duct outlet 86 is provided upstream of the cooler 18 with respect to the direction D1 of air flow in the cooler compartment 80. The vegetable compartment return air duct outlet 86 is provided upstream of the freezer compartment return air duct outlet 84 with respect to the direction D1 of air flow in the cooler compartment 80.

[0042] As shown in Figure 5, vegetable compartment return air duct 33 is provided within insulating partition wall 6c from underside 6c1 to rear side surface 6c2. A portion of the cold air flowing through refrigerator compartment return air duct 31 is blown into vegetable compartment 5 from a vegetable compartment outlet air duct outlet (not shown) provided on underside 6c1 of insulating partition wall 6c, cooling vegetable compartment 5. After cooling vegetable compartment 5, the returning cold air flows from vegetable compartment return air duct inlet 85 into vegetable compartment return air duct 33, passes through vegetable compartment return air duct 33, and then flows into cooler compartment 80 from vegetable compartment return air duct outlet 86.

[0043] As shown in FIG. 5 , the cooler 18 is provided in the cooler chamber 80. A glass tube heater 19, which is a first heater, is provided below the cooler 18. A heater roof 58 is installed between the cooler 18 and the glass tube heater 19. The heater roof 58 serves to protect the glass tube heater 19 from defrost water generated when the cooler 18 is defrosted. A drain tray 59 is provided below the glass tube heater 19. The drain tray 59 forms part of the side surface of the lower part of the cooler chamber 80. A drain pipe 60 is attached to the drain outlet of the drain tray 59 by deforming metal below the drain tray 59. The defrost water flows down the drain pipe 60 into the drain hole 20 and is then discharged into the evaporator dish 21, which is provided below the drain pipe 60 and installed above the compressor 25.

[0044] The configuration of the cooler 18 will be described in detail later. As shown in FIG. 5 , the cooler 18 includes a refrigerant pipe 63 and a plurality of fins 62. In the cross-sectional view of FIG. 5 , the cooler 18 is configured such that multiple tiers, each combining two horizontal rows of refrigerant pipes 63 and fins 62, are stacked vertically (along the Z axis). Hereinafter, each tier, each combining two horizontal rows of refrigerant pipes 63 and fins 62, will be referred to as a "cooler tier." The lowest tier will be referred to as the "lower tier." The first four tiers, from the lower tier to the upper tier, will be referred to as the "middle tier." While FIG. 5 illustrates a case in which the freezer compartment return air duct outlet 84 is provided on a surface corresponding to the middle tier of the cooler, the number of tiers of the freezer compartment return air duct outlets 84 in the vertical direction is not limited to four.

[0045] FIG. 6 is a perspective view showing a configuration example of cooler 18 and pipe heater 65 in refrigerator 100 according to the first embodiment.

[0046] As shown in Fig. 6, the cooler 18 has a plurality of thin, smooth-surfaced fins 62 and refrigerant piping 63. The fins 62 are aluminum fins with a thickness of 0.1 to 0.2 mm. The refrigerant piping 63 in the cooler 18 is aluminum or copper piping with a thickness of 0.5 to 1.3 mm. A cooler temperature sensor 71 is provided on the refrigerant piping 63 to detect the temperature Tkr of the refrigerant piping 63 of the cooler 18. The cooler temperature sensor 71 is, for example, a thermistor.

[0047] The refrigerant pipes 63 are arranged in the vertical direction (Z-axis) with their extension direction folded back by multiple U-shaped connecting pipes 88. The refrigerant pipes 63 are arranged in, for example, eight rows of straight sections extending in the left-right direction (Y-axis). Two adjacent rows of refrigerant pipes 63 are connected at their left-right ends by connecting pipes 88. This allows each refrigerant pipe 63 to travel back and forth in parallel in the left-right direction multiple times while changing height. The refrigerant flowing through the refrigerant pipes 63 of the cooler 18 flows from a cooler inlet 89a connected to the lowest refrigerant pipe 89 to a cooler outlet 89b connected to the highest refrigerant pipe 63. As shown in FIG. 5 , the air flow direction D1 is from below to above the cooler 18. Therefore, the lowest refrigerant pipe 89 is located at the most upstream of the straight sections of the refrigerant pipes 63 arranged in the air flow direction D1. The uppermost refrigerant pipe 63 is disposed on the most downstream side of the plurality of refrigerant pipes 63 with respect to the air flow direction D1.

[0048] The low-temperature refrigerant in a gas-liquid two-phase state that flows into the cooler 18 from a pressure reducing device (not shown) flows from the cooler inlet 89a through the refrigerant pipe 63 on the most upstream side in the air flow direction D1, and then flows through the refrigerant pipes 63 on the gradually downstream side to reach the cooler outlet 89b. As the refrigerant in a gas-liquid two-phase state flowing through the cooler 18 travels from the cooler inlet 89a to the cooler outlet 89b of the refrigerant pipe 89, it exchanges heat with the air flowing outside the refrigerant pipe 63. As a result, the liquid phase of the refrigerant evaporates as it flows through the refrigerant pipe 63. Normally, the temperature of the refrigerant at the cooler inlet 89a is lower than the temperature of the refrigerant at the cooler outlet 89b.

[0049] FIG. 7 is a perspective view showing a single pipe heater 65 shown in FIG. 6 . As shown in FIG. 6 , the pipe heater 65 is provided on a side of the cooler 18 parallel to the YZ plane. The pipe heater 65 corresponds to a second heater. As shown in FIG. 7 , the pipe heater 65 includes an aluminum pipe 91 into which a cord heater 64, each of which has a resistance wire 68 covered with an insulator 69, is inserted. The resistance wire 68 is, for example, a nichrome wire. The insulator 69 is, for example, polyvinyl chloride. The pipe heater 65 is configured such that a plurality of pipes 91 extending in the left-right direction are deformed at positions where they contact the left and right fixing plates 66 of the cooler 18 shown in FIG. 6 to change their extension direction, and are arranged vertically. The pipe heaters 65 are fixed to the left and right fixing plates 66 shown in FIG. 6 .

[0050] The arrangement of the pipe 91 from one end to the other end relative to the cooler 18 will be described in detail with reference to FIGS. 6 and 7 . The pipe 91 extends from the top of one of two side surfaces of the cooler 18 parallel to the YZ plane, turns back multiple times along the side surface, and reaches the bottom of the side surface. After reaching the bottom of one side surface of the cooler 18, the pipe 91 exits the other side surface of the cooler 18 via a pipe 91a. The pipe 91 then turns back multiple times from the bottom of the other side surface of the cooler 18 along the side surface and reaches the top of the side surface. As shown in FIG. 6 , the pipe heater 65 is disposed between two vertically adjacent fins 62. The pipe heater 65 is disposed in contact with or close to the side surface of the cooler 18. Close to the side surface means within a distance sufficient for heat generated by the pipe heater 65 to be sufficiently transmitted to the cooler 18, e.g., 1 to 3 mm.

[0051] FIG. 8 is a perspective view showing an example of the configuration of the glass tube heater 19 attached to the lower part of the cooler 18 shown in FIG. 6 . FIG. 9 is a perspective view showing the positional relationship between the cooler 18 to which the pipe heater 65 is attached and the glass tube heater 19. As shown in FIG. 8 , the glass tube heater 19 is configured such that a resistance wire 68 is provided inside a glass tube 67, and both ends of the glass tube 67 are sealed with rubber caps 70 or the like. In FIG. 8 , a portion of the glass tube 67 is omitted so that the interior of the glass tube 67 can be seen. Also, in FIG. 8 , a portion of the resistance wire 68 is omitted to show that the resistance wire 68 is formed in a spiral shape. A heater roof 58 is disposed above the glass tube 67. The heater roof 58 serves to prevent defrost water dripping from the cooler 18 from breaking the glass tube 67 during defrosting operation. As shown in FIG. 9 , the pipe heater 65 is disposed on the side of the cooler 18, weaving between adjacent fins 62 on the top and bottom. The glass tube heater 19 is disposed below the cooler 18 .

[0052] Next, the configuration of control device 12 will be described. FIG. 10 is a block diagram for explaining the control performed by control device 12 on refrigerator 100 according to the first embodiment. Control device 12 is, for example, a microcomputer. Operation modes performed by refrigerator 100 include, for example, a cooling operation for cooling each storage compartment and a defrosting operation for melting frost adhering to the surface of cooler 18. Control device 12 controls compressor 25, blower 24, and damper devices 26 and 27 in accordance with the operation mode. Control device 12 also has a timer (not shown) function for measuring time to control these devices.

[0053] First, the control by the control device 12 when the refrigerator 100 is in the cooling operation mode will be described. The control device 12 processes signals received from temperature sensors installed in each storage compartment to convert them into temperature values. The control device 12 adjusts the flow rate of cool air flowing from the cooler compartment 80 to each storage compartment by controlling the rotation speeds of the compressor 25 and the blower 24 and the opening and closing of baffles (not shown) of the damper devices 26 and 27 so that the temperature of each storage compartment matches the set temperature of the corresponding storage compartment. In this way, the control device 12 controls the compressor 25, the blower 24, and the damper devices 26 and 27 so that the temperature of each storage compartment matches the set temperature. For example, the control device 12 controls the operation or stop of the compressor 25 and the rotation speed of the compressor 25 so that the freezer compartment temperature Tf detected by the freezer compartment temperature sensor 51d matches the set temperature of the freezer compartment 4. In addition, the control device 12 controls the opening and closing of a baffle (not shown) of the damper device 27 for the switchable compartment 3 so that the switchable compartment temperature Ts detected by the switchable compartment temperature sensor 51c matches the set temperature of the switchable compartment 3.

[0054] Next, before describing in detail the control performed by the control device 12 when the operation mode performed by the refrigerator 100 is the defrosting operation, the generation of frost in the cooler 18 and the selection of a heater in relation to the location of frost generation will be described.

[0055] Fig. 11 is an enlarged view of the configuration including the cooler 18 shown in Fig. 5. In Fig. 11, arrows indicate the flow of air returning from the refrigerator compartment 1, the freezer compartment 4, and the vegetable compartment 5. In this first embodiment, a more appropriate method of energizing the two heaters to prevent frost formation due to the return air from the refrigerator compartment 1 and the return cold air from the freezer compartment 4 will be described. Note that control of frost formation due to the return cold air from the vegetable compartment 5 in addition to the return cold air from the refrigerator compartment 1 and the freezer compartment 4 will be described in the second embodiment described below.

[0056] When a user opens one of the doors of refrigerator 100, air flows into the storage compartment from the external space that was separated from the storage compartment by the door. The external air then flows into cooler compartment 80 via the return air duct of the storage compartment. Cooler 18 cools the air, and water vapor contained in the air freezes on the surface of cooler 18, causing frost to form on cooler 18. For example, when refrigerator compartment door 7a is opened or closed, air flows into refrigerator compartment 1 from the external space. The air that flows into refrigerator compartment 1 flows into cooler compartment 80 via refrigerator compartment return air duct 31 (see FIG. 1 ). The air that flows into cooler compartment 80 flows through cooler compartment 80 in the direction of arrow 72 in FIG. 11 and is cooled by cooler 18. This cools the water vapor contained in the air, causing frost to form in a first region 74 below the lower cooler section of cooler 18. The first region 74 is located near the refrigerator compartment return air duct outlet 82 shown in FIG.

[0057] Furthermore, when the freezer compartment door 7d is opened or closed, air flows into the freezer compartment 4 from the outside. The air that flows into the freezer compartment 4 flows into the cooler compartment 80 via the freezer compartment return air duct 32 (see FIG. 2). The air that flows into the cooler compartment 80 flows through the cooler compartment 80 in the direction of arrow 73 in FIG. 11 and is cooled by the cooler 18. This cools the water vapor contained in the air, and frost forms in a second region 75 near the freezer compartment return air duct outlet 84 and in front of the middle section of the cooler. The middle section of the cooler is located downstream of the lower section of the cooler in the flow direction of the cool air. The second region 75 is located downstream of the first region 74 in the air flow direction D1. Thus, the location of frost formation in the cooler 18 varies depending on the type of door that is opened or closed.

[0058] As described with reference to FIGS. 6 and 9 , the glass tube heater 19 and the pipe heater 65 are attached at different positions in the cooler 18. Specifically, the glass tube heater 19 is attached to the lower part of the cooler 18 with a gap therebetween, and the pipe heater 65 is attached to the main body of the cooler 18. Since the two heaters are attached at different positions relative to the cooler 18, the heat generated by each heater acts on different positions on the cooler 18. The heat generated by the glass tube heater 19 mainly acts on a first region 74 below the lower tier of the cooler, where frost forms due to air returning from the refrigerator compartment 1. The heat generated by the pipe heater 65 mainly acts on a second region 75 in front of the middle tier of the cooler, where frost forms due to air returning from the freezer compartment 4. Note that the second region 75, where the heat generated by the pipe heater 65 acts, is not limited to the range from the lowest tier of the cooler 18 to the four tiers above.

[0059] Here, it will be explained where the glass tube heater 19 and the pipe heater 65 should be installed in accordance with the position where frost grows on the cooler 18.

[0060] Because return air from the refrigerator compartment 1 hits the first region 74 below the lower tier of the cooler 18, frost grows downward from the cooler 18 and away from the cooler 18. If heat is applied to the inside of the cooler 18 or the front or rear side of the cooler 18 to melt the frost, the frost on the first region 74 will peel off in its solid form, which may clog the drain pipe 60. Therefore, it is appropriate to install a glass tube heater 19 below the first region 74 and melt the frost from below the cooler 18 using the radiant heat of the glass tube heater 19.

[0061] Furthermore, by providing freezer compartment return air duct outlet 84 at a position overlapping with second region 75 in front of the middle stage of the cooler in the front-to-rear direction of refrigerator body 101, return air from freezer compartment 4 flows into cooler compartment 80 before the middle stage of the cooler. Generally, the number of times the door of freezer compartment 4 is opened and closed per unit period is less than the number of times the door of refrigerator compartment 1 is opened and closed per unit period, so the amount of frost that forms in second region 75 is less than the amount of frost that forms in first region 74. This will be explained with reference to FIG. 12 . FIG. 12 is a table showing an example of the results of an investigation into the amount of time the doors of each storage compartment are open per day for each of the summer and winter seasons for refrigerators.

[0062] The door open time is the product of the average number of times the door is opened per day (times) and the average time the door remains open (seconds) when opened and closed. The values ​​for each door in the table shown in FIG. 12 are the sum of the door open time (seconds) over a predetermined period. Referring to the table shown in FIG. 12, it can be seen that the door open time for the refrigerator compartment is overwhelmingly longer than that for the other storage compartments, regardless of the season. Based on the survey results shown in FIG. 12, it is assumed that frost formation in the cooler 18 is greater due to return air from the refrigerator compartment than from return air from the freezer compartment. Therefore, in FIG. 11, frost growth in the second region 75 of the middle section of the cooler, which is exposed to return air from the freezer compartment 4, is slower than in the first region 74 of the lower section of the cooler, making it more efficient to heat the frost from within the cooler 18 via heat conduction. For this reason, in this embodiment 1, a pipe heater 65 is installed in the middle section of the cooler, which is exposed to return air from the freezer compartment 4.

[0063] Based on the above, the control of the control device 12 during the defrosting operation will be described. The control device 12 executes the next defrosting operation when a first reference time determined in advance for the time elapsed since the end of the last defrosting operation or a second reference time determined in advance for the cumulative operating time of the compressor 25 is reached. In the first embodiment, the reference time from the end of the last defrosting operation to the start of the next defrosting operation is referred to as the interval time tref.

[0064] When starting the defrosting operation, the control device 12 starts energizing the two heaters, stops the blower 24 and the compressor 25, and closes the damper devices 26 and 27 of each storage compartment. This prevents warm air generated in the cooler compartment 80 during the defrosting operation from flowing into each storage compartment. Furthermore, by stopping the blower 24 during the defrosting operation, the control device 12 can suppress adhesion of moisture to the baffles (not shown) of the damper devices 26 and 27, preventing freezing of the moving parts.

[0065] In the first embodiment, when a defrosting operation is performed, the control device 12 controls the energization time of each heater based on the time that the refrigerator compartment door 7a and the freezer compartment door 7d are open during the interval time tref before the defrosting operation. For each storage compartment, the time that the door is open during the interval time tref is denoted as tave. The energization control of the two heaters will be described in detail below.

[0066] Fig. 13 is a graph showing the relationship between the time tave that the refrigerator compartment door 7a and the freezer compartment door 7d are open and the amount of frost formed on the cooler 18. The horizontal axis of Fig. 13 represents the time tave [seconds] that the doors are open, and the vertical axis represents the amount of frost formed [cc]. The solid line represents the graph for refrigerator compartment 1, and the dashed line represents the graph for freezer compartment 4.

[0067] Before describing FIG. 13 , it will be explained that the control device 12 determines the door open time tave for each storage compartment based on the door status signal received from the door open / close sensor for each storage compartment. For example, for the refrigerator compartment door 7a, the control device 12 starts measuring time t when it receives a door status signal indicating an open state from the refrigerator compartment door open / close sensor 90a. Thereafter, when the control device 12 receives a door status signal indicating a closed state from the refrigerator compartment door open / close sensor 90a, it counts one opening and closing and records the time t from the start of measurement as the open time. The control device 12 records the number of openings and closings and the open time for the refrigerator compartment door 7a in the interval time tref. Based on the recorded information, the control device 12 then calculates the product of the average number of times the refrigerator compartment door 7a is opened per day and the average time the refrigerator compartment door 7a is open when opened and closed, and determines the calculated result as the door open time tave.

[0068] Consider a case where the door-open time tave of refrigerator compartment 1 is 50 seconds and the door-open time tave of freezer compartment 4 is 20 seconds. In this case, the amount of frost that forms on the lower level of the cooler when refrigerator compartment 1 is open is 300 cc, and the amount of frost that forms on the middle level of the cooler when freezer compartment 4 is open is 80 cc. By measuring the amount of frost for each of refrigerator compartment 1 and freezer compartment 4 each time the door-open time tave is changed, a graph such as that shown in Figure 13 can be obtained, which shows the relationship between the door-open time tave of refrigerator compartment 1 and freezer compartment 4 and the amount of frost that forms depending on the door-open time tave.

[0069] Furthermore, from the graph shown in Fig. 13, it is possible to derive a relational expression between the door-open time tave and the amount of frost for each of refrigerator compartment 1 and freezer compartment 4. In Fig. 13, the relationship between the door-open time tave and the amount of frost for refrigerator compartment 1 is approximated by a linear function. The relationship between the door-open time tave and the amount of frost for freezer compartment 4 is also approximated by a linear function. Comparing the two relational expressions, it can be seen that the slope for refrigerator compartment 1 is steeper than that for freezer compartment 4.

[0070] In the first embodiment, for convenience, the relationship between the door open state time tave and the amount of frost formation has been described as being approximated by a linear function, but the actual relationship is not limited to a linear function. For example, the relationship may be a multi-order relationship that includes, as variables, at least one of the ventilation volume associated with the opening and closing of the storage compartment door, the rotation speed nc of the compressor 25, the rotation speed nf of the blower 24, the outside air temperature Tout, and the outside air humidity Hout, in addition to the door open state time tave.

[0071] Fig. 14 is a graph showing the relationship between the amount of frost formed on the cooler 18 and the heater energization time required to melt the frost formed on the cooler 18. The horizontal axis of Fig. 14 represents the amount of frost [cc], and the vertical axis represents the heater energization time [sec]. The solid line represents the graph for the glass tube heater 19, and the dashed line represents the graph for the pipe heater 65.

[0072] 14 shows an example of the results of an investigation into how much frost can be melted when the heater energization time is changed for each of the two heaters. Similar to the relationship between the door open time tave and the amount of frost in each storage compartment, the relationship between the amount of frost and the heater energization time can be clarified by measuring the amount of frost that can be melted each time the heater energization time is changed.

[0073] As shown in Fig. 14, the relationship between the amount of frost and the heater energization time is approximated by a graph of a linear function. From the graph shown in Fig. 14, it can be seen that, for example, in order to melt 300 cc of frost formed in the first region 74 below the lower tier of the cooler by the return air from the refrigerator compartment, it is necessary to energize the glass tube heater 19 for 290 seconds. It can also be seen that in order to melt 80 cc of frost formed in the second region 75 in front of the middle tier of the cooler by the return air from the freezer compartment, it is necessary to energize the pipe heater 65 for 100 seconds.

[0074] In this way, through experiments, the relationship between the door open time tave and the amount of frost for each storage compartment is determined from the graph shown in Figure 13, and the relationship between the amount of frost and the heater power supply time is determined from the graph shown in Figure 14. These relationship formulas are expressed as follows:

[0075] When the amount of frost formed on the lower side of the lower cooler is Afr1, the time tave during which the door of the refrigerator compartment 1 is open is R, and the coefficients are Ra and Rb, the amount of frost formed Afr1 is expressed by the following formula (1): Afr1=R×Ra+Rb (1)

[0076] When the amount of frost formed on the front side of the middle stage of the cooler is Afr2, the time tave during which the door of the freezer compartment 4 is open is F, and the coefficients are Fa and Fb, the amount of frost formed Afr2 is expressed by the following equation (2): Afr2=F×Fa+Fb (2)

[0077] When the energization time of the glass tube heater 19 is tp1, the amount of frost formed by the glass tube heater 19 is G, and the coefficients are Ga and Gb, the energization time tp1 is expressed by the following equation (3): tp1=G×Ga+Gb (3)

[0078] When the energization time of the pipe heater 65 is tp2, the amount of frost formed by the pipe heater 65 is P, and the coefficients are Pa and Pb, the energization time tp2 is expressed by the following equation (4): tp2=P×Pa+Pb (4)

[0079] The above formulas (1) to (4) and the coefficients of each formula as parameters are stored in advance in the control device 12. This allows the control device 12 to control the defrosting operation using the above formulas (1) to (4) during the defrosting operation. Formulas (1) and (2) correspond to a first relational expression. Formulas (3) and (4) correspond to a second relational expression. A calculation formula for determining the energization time tp1 of the glass tube heater 19 based on the door-open time tave of the refrigerator compartment 1 may be determined in advance from formulas (1) and (3). A calculation formula for determining the energization time tp2 of the pipe heater 65 based on the door-open time tave of the freezer compartment 4 may be determined in advance from formulas (2) and (4). These calculation formulas may be stored in the control device 12.

[0080] In addition, in the first embodiment, the formulas are described as linear functions, but they are simply expressed for convenience of explanation, and may be multi-order functions such as quadratic functions. Furthermore, the coefficients of each formula may be different depending on the model of the defrost heater installed in the refrigerator.

[0081] The control device 12 calculates the amount of frost at each position of the cooler 18 from the door-open time tave of each storage compartment, and calculates the power-on time of the glass tube heater 19 and the pipe heater 65 required to melt the frost from the calculated amount of frost. The control device 12 then compares the power-on time of the glass tube heater 19 with the power-on time of the pipe heater 65. When starting a defrosting operation, the control device 12 starts energizing the two defrosting heaters, the glass tube heater 19 and the pipe heater 65, but stops energizing the heater with the shorter power-on time after the power-on time has elapsed. Meanwhile, the control device 12 stops energizing the other heater when the temperature Tkr detected by the cooler temperature sensor 71 reaches a predetermined threshold temperature. According to the first embodiment, during a defrosting operation, the heater with the shorter power-on time of the two calculated power-on times can be stopped earlier than the other heater. Therefore, by performing a defrosting operation according to the amount of frost formed on each portion of the cooler 18, the amount of power consumption required to energize the heater can be reduced more than in the past.

[0082] Here, we will explain how to find equations (1) and (2). This method will be referred to as the first method. In the first method, we assume that frost formation on the cooler 18 depends on the inflow of outside air caused by the opening and closing of the door, and open and close only the door whose coefficient we want to examine. After the moisture contained in the inflowing outside air forms frost on the cooler 18, we examine the amount of frost. We will now explain the specific test flow for the first method.

[0083] (Step 1-1) Open and close the door of one of the multiple storage compartments 10, 20, and 50 times. While specific numbers such as 10, 20, and 50 are mentioned here, these numbers are not particularly significant. It is sufficient to allocate multiple numbers of openings and closings at appropriate intervals. The door open time is calculated using the formula (door open time per opening and closing) x number of openings and closings. The door open time per opening and closing is not limited. (Step 1-2) After opening and closing the door, wait for the outside air that has flowed into the storage compartment to circulate throughout the refrigerator, and then check the amount of frost on the cooler 18. The time for waiting for the outside air that has flowed into the refrigerator to circulate throughout the refrigerator can be a predetermined time. (Step 1-3) Execute the above steps (Step 1-1) and (Step 1-2) for each door, and plot a graph showing the relationship between the door open time and the amount of frost.

[0084] Next, a method for determining equations (3) and (4) will be described. This method will be referred to as the second method. In the second method, frost is formed on a portion where it is thought that the frost can be melted by the heat generated by each heater, and then only the heater whose coefficient is to be checked is energized to check the amount of melted frost. A specific test flow for the second method will be described.

[0085] (Step 2-1) Power on only the heater whose coefficient you want to check. At this time, the distance between the cooler 18 and the heater is considered to be related to the amount of frost melted, so it should be the same as when the refrigerator was first sold. (Step 2-2) As an example, assign 10, 20, and 50 seconds as the power-on time for the heater whose coefficient you want to check, and power on the heater. Here, specific times of 10, 20, and 50 seconds are mentioned, but these times have no particular meaning. It is sufficient to assign multiple times at appropriate intervals. (Step 2-3) For each heater, perform the above steps (Step 2-1) to (Step 2-2), check the amount of frost that has melted after powering on, and plot a graph showing the relationship between the amount of frost melted and the power-on time.

[0086] Next, an example of hardware of the control device 12 will be described. Fig. 15 is a hardware configuration diagram showing an example of the configuration of the control device 12 shown in Fig. 10. When the various functions of the control device 12 are executed by hardware, the control device 12 shown in Fig. 10 is configured by a processing circuit 150 shown in Fig. 15.

[0087] When the functions of the controller 12 are performed in hardware, the processing circuitry 150 may 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.

[0088] Next, another example of hardware of the control device 12 will be described. Fig. 16 is a hardware configuration diagram showing another example of the configuration of the control device 12 shown in Fig. 10. When the various functions of the control device 12 are executed by software, the control device 12 is configured with a processor 151 such as a CPU and a memory 152, as shown in Fig. 16. The various functions of the control device 12 are realized by the processor 151 and the memory 152. Fig. 16 shows that the processor 151 and the memory 152 are communicably connected to each other via a bus 153.

[0089] When the various functions of the control device 12 are executed by software, the various functions of the control device 12 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 152. The processor 151 realizes the various functions of the control device 12 by reading and executing the programs stored in the memory 152.

[0090] The memory 152 may be a non-volatile semiconductor memory such as a read-only memory (ROM), a flash memory, an erasable and programmable ROM (EPROM), or an electrically erasable and programmable ROM (EEPROM). Alternatively, the memory 152 may be a volatile semiconductor memory such as a random access memory (RAM). Alternatively, the memory 152 may be a removable recording medium such as a magnetic disk, a flexible disk, an optical disk, a compact disc (CD), a mini disc (MD), or a digital versatile disc (DVD).

[0091] Next, the operation of the defrosting operation of the refrigerator 100 according to the first embodiment will be described. Figures 17 to 20 are flowcharts showing the operation procedure of the defrosting operation of the refrigerator according to the first embodiment. Here, the case where the storage compartments are the refrigerator compartment 1 and the freezer compartment 4 will be described. Also, the case where frost forms in the lower and middle stages of the cooler 18 will be described.

[0092] After performing a defrosting operation, the control device 12 starts measuring the time tpst. After the last defrosting operation, the control device 12 tallies the number of times the door was opened and closed and the time it was open for each type of door that was opened and closed (step S1). The control device 12 determines whether the measured time tpst is equal to or longer than the interval time tref (step S2). If the time tpst is shorter than the interval time tref (step S2: No), the control device 12 returns to step S1. If the time tpst is equal to or longer than the interval time tref (step S2: Yes), the control device 12 proceeds to the process of step S3 and starts the defrosting operation.

[0093] In step S3, the control device 12 calculates the door-open time tave of each storage compartment. Specifically, the control device 12 calculates the door-open time tave of refrigerator compartment 1 and the door-open time tave of freezer compartment 4 using the information compiled in step S1 for refrigerator compartment 1 and freezer compartment 4. In step S4, the control device 12 calculates the amount of frost formed at each position of the cooler 18. Specifically, the control device 12 substitutes the door-open time tave of refrigerator compartment 1 into equation (1) to calculate the amount of frost that has adhered to the first region 74 of the lower level of the cooler. The control device 12 also substitutes the door-open time tave of freezer compartment 4 into equation (2) to calculate the amount of frost that has adhered to the second region 75 of the middle level of the cooler.

[0094] In step S5, the control device 12 calculates the heater conduction time tp required to melt the frost at each position of the cooler 18. Specifically, the control device 12 calculates the conduction time tp1 of the glass tube heater 19 by substituting the amount of frost adhering to the first region 74 calculated in step S4 into equation (3). The control device 12 also calculates the conduction time tp2 of the pipe heater 65 by substituting the amount of frost adhering to the second region 75 calculated in step S4 into equation (4). The control device 12 then determines whether the heater conduction time tp1 and the heater conduction time tp2 are equal (step S6).

[0095] If the heater energization time tp1 and the heater energization time tp2 are equal as a result of the determination in step S6 (step S6: Yes), the control device 12 starts energizing the two defrost heaters (step S8). In step S9, the control device 12 determines whether the temperature Tkr detected by the cooler temperature sensor 71 is equal to or greater than the threshold temperature Tth. If the temperature Tkr is less than the threshold temperature Tth (step S8: No), the control device 12 returns to the processing of step S8. On the other hand, if the temperature Tkr is equal to or greater than the threshold temperature Tth (step S8: Yes), the control device 12 stops energizing the two defrost heaters (step S10) and ends the defrosting operation.

[0096] On the other hand, if the heater conduction time tp1 and the heater conduction time tp2 are not equal as a result of the determination in step S6 (step S6: No), the control device 12 determines whether the heater conduction time tp1 is shorter than the heater conduction time tp2 (step S7). If the heater conduction time tp1 is shorter than the heater conduction time tp2 (step S7: Yes), the control device 12 starts energizing the two defrost heaters (step S11). The control device 12 monitors the elapsed time tpv from the start of energizing the two defrost heaters. In step S12, the control device 12 determines whether the elapsed time tpv is equal to or longer than the heater conduction time tp1. If the elapsed time tpv is shorter than the heater conduction time tp1 (step S12: No), the control device 12 continues energizing the two defrost heaters and repeats the determination in step S12.

[0097] On the other hand, if the elapsed time tpv reaches the heater power supply time tp1 (step S12: Yes), the control device 12 stops the power supply to the glass tube heater 19 (step S13) and continues the power supply to the pipe heater 65 (step S14). In step S15, the control device 12 determines whether the temperature Tkr detected by the cooler temperature sensor 71 is equal to or higher than the threshold temperature Tth. If the temperature Tkr is lower than the threshold temperature Tth (step S15: No), the control device 12 returns to the processing of step S14. On the other hand, if the temperature Tkr is equal to or higher than the threshold temperature Tth (step S15: Yes), the control device 12 stops the power supply to the pipe heater 65 (step S16) and ends the defrosting operation.

[0098] If the determination result in step S7 is that the heater energization time tp2 is shorter than the heater energization time tp1 (step S7: No), the control device 12 starts energizing the two defrost heaters (step S17). The control device 12 monitors the elapsed time tpv from the start of energizing the two defrost heaters. In step S18, the control device 12 determines whether the elapsed time tpv is equal to or greater than the heater energization time tp2. If the elapsed time tpv is shorter than the heater energization time tp2 (step S18: No), the control device 12 continues energizing the two defrost heaters and repeats the determination in step S18.

[0099] On the other hand, if the elapsed time tpv reaches the heater power supply time tp2 (step S18: Yes), the control device 12 stops the power supply to the pipe heater 65 (step S19) and continues the power supply to the glass tube heater 19 (step S20). In step S21, the control device 12 determines whether the temperature Tkr detected by the cooler temperature sensor 71 is equal to or higher than the threshold temperature Tth. If the temperature Tkr is lower than the threshold temperature Tth (step S21: No), the control device 12 returns to the processing of step S20. On the other hand, if the temperature Tkr is equal to or higher than the threshold temperature Tth (step S21: Yes), the control device 12 stops the power supply to the glass tube heater 19 (step S22) and ends the defrosting operation.

[0100] As described above, if the heater conduction time tp1 is shorter than the heater conduction time tp2 (step S7: Yes), when the elapsed time tpv from the start of energization of the two defrost heaters reaches the heater conduction time tp1, energization to the glass tube heater 19 is stopped. Also, if the heater conduction time tp2 is shorter than the heater conduction time tp1 (step S7: No), when the elapsed time tpv from the start of energization of the two defrost heaters reaches the heater conduction time tp2, energization to the pipe heater 65 is stopped. During the period from the start of the defrosting operation until the temperature Tkr reaches the threshold temperature Tth, energization to one of the two defrost heaters is stopped midway. This not only reduces the power consumption of the defrost heaters, but also prevents the temperature in the cooler chamber 80 from rising more than necessary.

[0101] Next, a description will be given of the effect of the defrosting operation performed by refrigerator 100 according to Embodiment 1. Fig. 21 is a timing chart for describing the effect of the defrosting operation performed by refrigerator 100 according to Embodiment 1. Fig. 21 shows the operation of each device including the compressor during the defrosting operation, and time-series changes in temperature Tkr of cooler 18, refrigerator compartment temperature, and freezer room temperature associated with the operation of each device.

[0102] In the top graph of Figure 21, the solid line indicates the time series change in temperature Tkr detected by cooler temperature sensor 71. The dashed-dotted line indicates the time series change in temperature detected by refrigerator compartment temperature sensor 51a. The dashed line indicates the time series change in temperature detected by freezer compartment temperature sensor 51d. The defrosting operation time is denoted by tfr.

[0103] As shown in Figure 21, during defrosting operation, the control device 12 stops not only the compressor 25 but also the blower 24. This prevents water vapor generated by defrosting from adhering to the opening and closing portions of the baffles (not shown) of the damper devices 26 and 27, thereby preventing condensation and icing on the opening and closing portions of the baffles. The control device 12 also turns off the damper devices 26 and 27 to close the baffles (not shown). This prevents heat from the defrost heater from diffusing into the refrigerator compartment 1 and the selectable compartment 3.

[0104] For example, assume that the door-open time tave of refrigerator compartment 1 is 50 seconds and the door-open time tave of freezer compartment 4 is 20 seconds. In this case, from the relational expressions shown in Figures 13 and 14, the heater energization time tp1, which is the energization time of glass tube heater 19, is calculated to be 290 seconds, and the heater energization time tp2, which is the energization time of pipe heater 65, is calculated to be 100 seconds. The heater energization times tp1 and tp2 have the relationship tp1 > tp2.

[0105] When the control device 12 starts the defrosting operation, it starts supplying current to the pipe heater 65 and the glass tube heater 19, and when 100 seconds have passed since the start of power supply, it stops supplying current to the pipe heater 65 and then continues supplying current to the glass tube heater 19. When the temperature Tkr detected by the cooler temperature sensor 71 reaches the threshold temperature Tth, the control device 12 stops supplying current to the glass tube heater 19 and ends the defrosting operation.

[0106] As shown in FIG. 21 , when heater conduction time tp2 has elapsed since the start of the defrosting operation, power supply to the pipe heater 65 is stopped. If the reduced power supply time for the pipe heater 65 is Dtp, Dtp = tfr - tp2. Conventionally, power supply to the glass tube heater 19 and power supply to the pipe heater 65 have been performed during the defrosting operation time trf. In contrast, in the first embodiment, power supply to the pipe heater 65 is shortened to 100 seconds. Therefore, the refrigerator 100 can improve energy conservation by shortening the power supply time while securing a heat source necessary for defrosting. While the case where the relationship between the heater conduction time tp1 and the heater conduction time tp2 is tp1 > tp2 has been described with reference to FIG. 21 , a similar effect can be obtained when tp2 > tp1.

[0107] In the first embodiment, for the graph described with reference to FIG. 13 , control device 12 may store multiple relational expressions corresponding to the outside air humidity Hu. A humidity sensor (not shown) that detects the outside air humidity is provided, for example, in hinge 11 shown in FIG. 2. FIG. 22 is a graph showing the relationship between the door open time tave of refrigerator compartment door 7a and the amount of frost formed on cooler 18 in refrigerator 100 according to the first embodiment, for different outside air humidities. The horizontal axis of FIG. 22 represents the door open time tave [seconds] of refrigerator compartment 1, and the vertical axis represents the amount of frost formed [cc]. The solid line represents the graph for humidity Hu1, and the dashed line represents the graph for humidity Hu2. The relationship between humidity Hu1 and humidity Hu2 is Hu1<Hu2.

[0108] As shown in FIG. 22 , the higher the humidity Hu, the more moisture there is in the air, resulting in a greater amount of frost. Therefore, the slope indicating the rate of change in the amount of frost with respect to the door-open time is greater for higher humidity Hu. For example, humidity Hu1 represents the winter humidity, and humidity Hu2 represents the summer humidity. The control device 12 stores a relational expression between the door-open time tave of the refrigerator compartment 1 and the amount of frost, corresponding to multiple humidities Hu. The control device 12 uses a relational expression corresponding to the humidity Hu detected by a humidity sensor (not shown) from the multiple relational expressions. This allows the relationship between the door-open time tave of the refrigerator compartment 1 and the amount of frost to be appropriately selected depending on the season. As a result, the accuracy of the heater power-on time calculated based on the amount of frost is improved. Here, estimating the amount of frost by taking humidity into account has been described using the refrigerator compartment 1 as an example, but it may also be applied to the freezer compartment 4.

[0109] The refrigerator 100 of the first embodiment includes a first storage compartment set to a first temperature zone, a second storage compartment set to a second temperature zone that is lower than the first temperature zone, a first door for opening and closing the first storage compartment, a second door for opening and closing the second storage compartment, a first door opening / closing sensor that outputs a first signal indicative of an open state or a closed state of the first door, a second door opening / closing sensor that outputs a second signal indicative of an open state or a closed state of the second door, a control device 12 that receives the first signal from the first door opening / closing sensor and the second signal from the second door opening / closing sensor, and a cooling compartment 8 in which a cooling device 18 that cools air is provided. 0, a cooler temperature sensor 71 that detects the temperature Tkr of the cooler 18, a blower 24 that sends air cooled by the cooler 18 to the first storage chamber and the second storage chamber, a first return air duct having a first return port that opens into the cooler chamber 80 and that guides air in the first storage chamber to the cooler chamber 80, a second return air duct having a second return port that opens into the cooler chamber 80 and that guides air in the second storage chamber to the cooler chamber 80, a first heater that melts frost formed by air flowing into the cooler chamber 80 from the first return air duct, and a second heater that melts frost formed by air flowing into the cooler chamber 80 from the second return air duct.

[0110] The control device 12 calculates a first door open state time, which is the time the first door is open, based on the first signal, during the reference time from the last defrosting operation to melt the frost on the cooler 18 to the start of the next defrosting operation, calculates a second door open state time, which is the time the second door is open, based on the second signal, calculates a first power-on time tp1, which is the time the first heater is powered on, based on the first door open state time, and calculates a second power-on time tp2, which is the time the second heater is powered on, based on the second door open state time. Then, when starting the next defrosting operation, the control device 12 starts energizing the first heater and the second heater. If the first energization time tp1 is shorter than the second energization time tp2, the control device 12 energizes the first heater for the first energization time tp1 and continues energizing the second heater until the temperature Tkr reaches the threshold temperature Tth. If the second energization time tp2 is shorter than the first energization time tp1, the control device 12 energizes the second heater for the second energization time tp2 and continues energizing the first heater until the temperature Tkr reaches the threshold temperature Tth. In the first embodiment, for example, the first storage compartment is the refrigerator compartment 1 and the second storage compartment is the freezer compartment 4. The first heater is a glass tube heater 19 and the second heater is a pipe heater 65.

[0111] According to the first embodiment, the energization times of the glass tube heater 19 and the pipe heater 65 are calculated based on the door-open time tave of the first storage chamber and the second storage chamber, and the heater with the shorter energization time is stopped during the defrosting operation. For example, if the first energization time tp1 of the glass tube heater 19 is shorter than the second energization time tp2 of the pipe heater 65, energization to the glass tube heater 19 is stopped when the elapsed time from the start of energization reaches the first energization time tp1. Since the heater that has completed defrosting in the cooler 18 is stopped early during the defrosting operation, the amount of power consumed by the heater can be reduced. Even if the amount of frost varies depending on the position in the cooler 18, the heater between the glass tube heater 19 and the pipe heater 65 that is estimated to have the least amount of frost is stopped early, thereby reducing power consumption. Furthermore, since the temperature of the cooler 18 can be prevented from becoming excessively high, the amount of power consumed by the compressor 25 for cooling the cooler 18 after the defrosting operation can be reduced.

[0112] Furthermore, according to the first embodiment, the two defrost heaters defrost at different positions relative to the air flow in the cooler 18, and the amount of frost formed at the positions where each heater defrosts the cooler 18 is estimated based on the duration of time the doors of the first storage compartment and the second storage compartment are open. The duration of time for which each heater is energized is then determined based on the estimated amount of frost. This reduces the amount of power consumed, which would have been consumed by excessively energizing the heaters in the past. As a result, it is possible to reduce the amount of power consumed by the heaters during defrosting operation and the amount of power consumed by the compressor 25 for cooling the cooler 18 after defrosting operation.

[0113] Furthermore, in the first embodiment, refrigerator 100 stops blower 24 during defrosting operation. Therefore, compared to conventional refrigerators in which the blower is rotated during defrosting operation and the cool air in the refrigerator compartment is used to defrost the cooler, water vapor generated by defrosting is prevented from adhering to the opening and closing portions of the baffles (not shown) of damper devices 26 and 27, thereby preventing condensation and icing on the opening and closing portions of the baffles. Therefore, there is no need to provide a heating means such as an anti-icing heater on the opening and closing portions of the baffles (not shown) of damper devices 26 and 27. As a result, the manufacturing cost of refrigerator 100 is reduced and energy saving is improved.

[0114] Embodiment 2 In this embodiment 2, the defrosting operation is controlled to melt the frost on the cooler 18 by using the return air from the vegetable compartment 5 as well as the refrigerator compartment 1. In this embodiment 2, the same components as those described in the embodiment 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. In addition, in this embodiment 2, the description will be centered on the differences between the configuration and operation described in the embodiment 1.

[0115] The overall configuration of the refrigerator 100 according to the second embodiment is the same as that described in the first embodiment, and therefore the description thereof will be omitted. The operation of the refrigerator 100 according to the second embodiment will be described with reference to FIG.

[0116] Fig. 23 is a graph showing the relationship between the time tave that refrigerator compartment door 7a, freezer compartment door 7d, and vegetable compartment door 7e are open and the amount of frost formed on cooler 18 in refrigerator 100 according to Embodiment 2. The horizontal axis of Fig. 23 represents the time tave [seconds] that refrigerator compartment 1 is open, and the vertical axis represents the amount of frost formed [cc]. The solid line represents the graph for refrigerator compartment 1, the dashed line represents the graph for freezer compartment 4, and the two-dot chain line represents the graph for vegetable compartment 5. Vegetable compartment 5 is set to a third temperature zone that is higher than the first temperature zone.

[0117] Referring to the table shown in FIG. 12, vegetable compartment 5 is the storage compartment with the second longest door-open time per day after refrigerator compartment 1. Therefore, in the second embodiment, control device 12 calculates the amount of frost formed by water vapor contained in the vegetable compartment return air. Specifically, control device 12 calculates the amount of frost formed by the cool air returning from vegetable compartment 5 using the following formula (5). If the amount of frost formed on the lower stage of the cooler is Afr3, the open door time tave of vegetable compartment 5 is V, and coefficients are Va and Vb, the amount of frost formed Afr3 can be expressed by formula (5). Afr3=V×Va+Vb (5)

[0118] The control device 12 calculates the total amount of frost (Arf1 + Afr3), which is the total amount of frost on the lower shelf of the cooler, by adding the amount of frost Afr1 due to the air from the refrigerator compartment 1 based on equation (1) and the amount of frost Afr3 due to the air from the vegetable compartment 5 based on equation (5). The control device 12 then calculates the heater conduction time tp3 of the glass tube heater 19 required to melt the frost of the total amount of frost (Arf1 + Afr3) using the relational expression represented by the solid line in the graph shown in Figure 14. The heater conduction time tp3 corresponds to the third conduction time.

[0119] According to the second embodiment, the control device 12 can determine the amount of frost formed on the lower stage of the cooler in more detail than in the first embodiment. Other processes performed by the control device 12 are similar to those described in the first embodiment, and therefore detailed description thereof will be omitted. The first method described in the first embodiment can be applied to determine the formula (5).

[0120] Although the second embodiment has been described with reference to the vegetable compartment 5, the control device 12 may calculate the door-open time tave for all storage compartments, not just the vegetable compartment 5, and calculate the amount of frost that forms on each part of the cooler 18 from the relationship between the door-open time tave and the amount of frost. The control device 12 may then calculate the total amount of frost that forms on each part, and based on the calculated total amount, calculate the energization times of the two defrosting heaters, the glass tube heater 19 and the pipe heater 65, to perform defrosting operation control.

[0121] 1 Refrigerator compartment, 2 Ice making compartment, 3 Switching compartment, 4 Freezer compartment, 4a Rear portion, 5 Vegetable compartment, 6a to 6c Heat insulating partition wall, 6c1 Bottom surface, 6c2 Rear side, 7a Refrigerator compartment door, 7a1 Left door, 7a2 Right door, 7b Ice making compartment door, 7c Switching compartment door, 7d Freezer compartment door, 7e Vegetable compartment door, 8 Operation panel, 8a Panel body, 9 Board, 10 Outdoor air temperature sensor, 11 Hinge, 12 Control device, 13 Vacuum insulation material, 14 Ice making compartment case, 15 Switching compartment case, 16 Fan grill, 17a Inner box, 17b Outer box, 18 Cooler, 19 Glass tube heater, 20 Drainage hole, 21 Evaporation dish, 22 Lower storage case, 23 Upper storage case, 24 Blower, 25 Compressor, 26, 27 Damper device, 28: Heat insulating material, 29: Lower storage case, 30: Upper storage case, 31: Refrigerator compartment return air duct, 32: Freezer compartment return air duct, 33: Vegetable compartment return air duct, 43-45: Shelf, 46: Small item storage case, 47: Control panel, 48: Resin parts, 49: Duct parts, 50: Refrigerator compartment outlet air duct, 51a: Refrigerator compartment temperature sensor, 51b: Ice making compartment temperature sensor, 51c: Switching compartment temperature sensor, 51d: Freezer compartment temperature sensor, 51e: Vegetable compartment temperature sensor, 54: Temperature adjustment button, 55: Selection button, 56: Air duct hole, 57: Pocket, 58: Heater roof, 59: Drain tray, 60: Drain pipe, 62: Fin, 63: Refrigerant piping, 64: Cord heater, 65: Pipe heater, 66: Fixing plate, 67: Glass tube, 68: Resistance wire, 69: Insulator, 70: Cap, 71 Cooler temperature sensor, 72, 73 arrows, 74 first area, 75 second area, 80 cooler compartment, 80a front portion, 81 refrigerator compartment return air duct inlet, 82 refrigerator compartment return air duct outlet, 83 freezer compartment return air duct inlet, 84 freezer compartment return air duct outlet, 85 vegetable compartment return air duct inlet, 86 vegetable compartment return air duct outlet, 88 connecting pipe, 89 refrigerant piping, 89a cooler inlet, 89b cooler outlet, 90a refrigerator compartment door opening / closing sensor, 90b ice maker compartment door opening / closing sensor, 90c switchable compartment door opening / closing sensor, 90d freezer compartment door opening / closing sensor, 90e vegetable compartment door opening / closing sensor, 91, 91a pipe, 92 insulating wall portion, 100 refrigerator, 101 refrigerator body, 150 processing circuit, 151 processor, 152 memory, 153 bus.

Claims

1. A first storage chamber set to a first temperature zone; a second storage chamber set to a second temperature zone that is lower than the first temperature zone; a first door for opening and closing the first storage chamber; a second door for opening and closing the second storage chamber; a first door opening and closing sensor that detects the opening and closing of the first door and outputs a first signal indicative of an open or closed state of the first door; a second door opening and closing sensor that detects the opening and closing of the second door and outputs a second signal indicative of an open or closed state of the second door; a control device to which the first signal is input from the first door opening and closing sensor and to which the second signal is input from the second door opening and closing sensor; a cooler chamber provided with a cooler that cools air; a cooler temperature sensor that detects the temperature of the cooler; and a blower that sends air cooled by the cooler to the first storage chamber and the second storage chamber. a first return air duct having a first return port opening into the cooler chamber and guiding air in the first storage chamber to the cooler chamber; a second return air duct having a second return port opening into the cooler chamber and guiding air in the second storage chamber to the cooler chamber; a first heater melting frost on the cooler by air flowing into the cooler chamber from the first return air duct; and a second heater melting frost on the cooler by air flowing into the cooler chamber from the second return air duct, and the control device a first door open state time which is a time during which the first door is open is calculated based on the first signal, a second door open state time which is a time during which the second door is open is calculated based on the second signal, a first energization time which is a time during which the first heater is energized is calculated based on the first door open state time, and a second energization time which is a time during which the second heater is energized is calculated based on the second door open state time, during a reference time from when the last defrosting operation for melting frost on the cooler is performed to when the next defrosting operation is started;a refrigerator which starts energizing the first heater and the second heater when starting the next defrosting operation, and when the first energization time is shorter than the second energization time, energizes the first heater for the first energization time and energizes the second heater until a temperature detected by the cooler temperature sensor reaches a predetermined threshold temperature, and when the second energization time is shorter than the first energization time, energizes the second heater for the second energization time and energizes the first heater until a temperature detected by the cooler temperature sensor reaches the threshold temperature.

2. The refrigerator according to claim 1, wherein the control device calculates a first amount of frost in the cooler based on the first door open time and a first relational equation stored in advance, calculates a second amount of frost in the cooler based on the second door open time and the first relational equation, determines the first power supply time based on the first amount of frost and a second relational equation stored in advance, and determines the second power supply time based on the second amount of frost and the second relational equation.

3. The refrigerator according to claim 1 or 2, wherein the first door open time is the product of the average number of times the first door is opened per day and the average time the first door is open when opened and closed, and the second door open time is the product of the average number of times the second door is opened per day and the average time the second door is open when opened and closed.

4. A refrigerator as described in any one of claims 1 to 3, further comprising a compressor connected to the cooling unit, and wherein the reference time is a first reference time predetermined based on the elapsed time since the end of the last defrosting operation, or a second reference time predetermined based on the accumulated operating time of the compressor.

5. The refrigerator according to claim 2, comprising: a third storage compartment set to a third temperature zone that is higher in temperature than the first temperature zone; a third door that opens and closes the third storage compartment; and a third door opening / closing sensor that detects opening and closing of the third door and outputs a third signal indicative of the open or closed state of the third door to the control device, wherein the control device determines a third door open state time that is a time that the third door is open at the reference time, calculates a third amount of frost on the cooler using the determined third door open state time and the first relational equation, and determines the first power supply time based on the sum of the first amount of frost and the third amount of frost.

6. The refrigerator according to claim 5, wherein the third door open time is a product of an average number of times the third door is opened per day and an average time the third door is open when opened and closed.

7. The refrigerator according to any one of claims 1 to 6, wherein the first heater is a glass tube heater, and the second heater is a pipe heater.

8. A refrigerator as claimed in any one of claims 1 to 7, wherein the first return port opens at a position in the cooler chamber upstream of the cooler in the air flow direction, and the second return port opens at a position in the cooler chamber downstream of the first return port and facing the cooler in the air flow direction.

9. The refrigerator according to any one of claims 1 to 8, wherein the first heater is provided below the cooler, and the second heater is arranged in contact with the cooler or within a predetermined distance from the cooler.

Images