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

Technical Field

[0001] The present disclosure relates to a refrigerator having a storage chamber for storing an object to be cooled.

Background Art

[0002] Conventionally, in a refrigerator, a cooler, which is a heat exchanger for cooling air, is installed in a cooler chamber on the back side of the main body. Return air, which is air flowing from the storage chamber through a return air duct into the cooler chamber, is cooled by exchanging heat with a refrigerant sent to the cooler by the operation of a compressor in the cooler, and is blown into each storage chamber by a blower installed at the upper part of the cooler chamber to cool food. The air that has cooled each storage chamber returns to the cooler chamber again as return air through the return air duct.

[0003] When a user opens and closes the door of each storage chamber when taking in and out food, outside air such as the indoor space where the refrigerator is installed flows into the storage chamber. When high-temperature and high-humidity outside air enters the cooler chamber via the storage chamber, water vapor contained in the outside air adheres to the surface of the cooler as frost. When the amount of frost increases, it becomes difficult for the air circulating inside the refrigerator to flow between the plurality of fins of the cooler, the efficiency of heat exchange decreases, and the cooling performance of the refrigerator deteriorates.

[0004] To prevent such performance degradation, the refrigerator is equipped with a defrosting heater on the cooler, and a defrosting operation is periodically performed by energizing the heater to melt the frost adhering to the cooler and remove the frost. Some coolers of fin-tube type heat exchangers having a plurality of flat fins arranged in a plurality of upper and lower stages include two types of defrosting heaters. The first defrosting heater is a pipe heater for melting the frost attached to the fins in the middle stage or the upper stage of the cooler. The second defrosting heater is a glass tube heater for melting the frost attached to the fins in the lower stage of the cooler. As a conventional refrigerator, one known example is a combination of two defrosting heaters to melt the frost on the cooler.

[0005] Conventional refrigerators, during defrosting, supply power to the two defrost heaters mentioned above, and when the temperature sensor mounted on the top of the cooler reaches a predetermined threshold temperature, power to the two heaters is cut off. However, if there is an uneven distribution of frost depending on the location of the cooler, the following problems arise. 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. In this case, the frost on the middle or upper fins of the cooler prevents the temperature sensor from reaching the threshold temperature. Therefore, conventional refrigerators continue to supply power to the defrost heater for the lower cooler as well. This results in an unnecessarily long power supply time and an increase in power consumption. Furthermore, a longer power supply time to the heaters leads to an excessively large rise in the internal temperature of the refrigerator after the defrosting operation is completed. As a result, when the refrigerator performs a recovery operation after defrosting, the heat load on the cooler increases, further increasing power consumption. To solve these problems, there was a need for technology that could efficiently melt frost from each part of the cooling unit in a refrigerator.

[0006] Conventionally, a refrigerator-freezer is known that includes a defrost heater located below the cooler and a heater tube that is bent multiple times and fixed to the cooler, as a defrost heater for melting frost that accumulates 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 of starting to energize the defrost heater and heater tube, and the timing of ending to energize the defrost heater and heater tube, based on the detection result of a door opening / closing detection means. If the control means of this refrigerator-freezer determines that the number of times the door has been opened and closed has been high during the defrosting operation time interval between the previous defrosting operation and the next defrosting operation, it simultaneously starts energizing the defrost heater and heater tube and simultaneously ends the energizing of the defrost heater and heater tube. Furthermore, if the control means determines that the number of times the door has been opened and closed has been low during the defrosting operation time interval, it first starts energizing the heater tube, and then starts energizing the defrost heater. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2017 / 017850 [Overview of the project] [Problems that the invention aims to solve]

[0008] The longer the refrigerator door is left open, the more frost tends to accumulate on the evaporator. Since the number of times the door is opened and closed does not necessarily correlate with the time the door is open, if the heater power supply is controlled based on the number of times the door is opened and closed in the refrigerator described in Patent Document 1, there is a risk that the amount of power supplied to the heater will be excessive or insufficient in relation to the amount of frost on the evaporator. In the refrigerator described in Patent Document 1, if the number of times the door is opened and closed is high, setting the heater power supply time excessively in order to reliably melt the frost on the evaporator will increase power consumption.

[0009] This disclosure was made to solve the above-mentioned problems and provides a refrigerator that can reduce power consumption. [Means for solving the problem]

[0010] The refrigerator according to this disclosure includes: a first storage compartment set to a first temperature zone; a second storage compartment set to a second temperature zone 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 the opening and closing of the first door and outputs a first signal indicating the open or closed state of the first door; a second door opening / closing sensor that detects the opening and closing of the second door and outputs a second signal indicating the open or closed state of the second door; and a sensor that receives the first signal from the first door opening / closing sensor and controls the opening and closing of the second door. A control device to which the second signal is input from a sensor; a cooler chamber provided with a cooler for cooling air; a cooler temperature sensor for detecting the temperature of the cooler; a blower for sending the air cooled by the cooler to the first storage chamber and the second storage chamber; a first return air passage having a first return port opening into the cooler chamber and guiding the air in the first storage chamber to the cooler chamber; a second return air passage having a second return port opening into the cooler chamber and guiding the air in the second storage chamber to the cooler chamber; and the cooling by the air flowing into the cooler chamber from the first return air passage. The control device comprises a first heater for melting frost on the cooler and a second heater for melting frost on the cooler using air flowing into the cooler chamber from the second return air passage, and the control device determines a first door open state time, which is the time the first door is open, based on the first signal, during a reference time from the time the last defrosting operation to start the next defrosting operation to start the next defrosting operation, determines a second door open state time, which is the time the second door is open, based on the second signal, and determines a first energization time, which is the energization time of the first heater, based on the first door open state time. The time is determined, and based on the second door open state time, a second energizing time is determined, which is the energizing time of the second heater. When the next defrosting operation is started, the first heater and the second heater are energized. If the first energizing time is shorter than the second energizing time, the first heater is energized for the first energizing time. The second heater is energized until the temperature detected by the cooler temperature sensor reaches a predetermined threshold temperature. If the second energizing time is shorter than the first energizing time, the second heater is energized for the second energizing time.The first heater is energized until the temperature detected by the cooler temperature sensor reaches the threshold temperature. [Effects of the Invention]

[0011] According to this disclosure, the energizing time for each of the glass tube heaters and pipe heaters is determined based on the door open time of the first and second storage chambers, and during defrosting, the power supply to the heater with the shorter energizing time is stopped midway through the operation. Since the power supply to the heaters that have completed defrosting in the cooler is stopped first during the defrosting operation, the power consumption of the heaters can be reduced. [Brief explanation of the drawing]

[0012] [Figure 1] This is a front view of the refrigerator 100 according to Embodiment 1. [Figure 2] This is a schematic cross-sectional view along line AA shown in Figure 1. [Figure 3] Figure 1 is an enlarged perspective view of a portion of the front of the left door 7a1 of the refrigerator compartment 1 shown in Figure 1. [Figure 4] Figure 2 is a plan view of the insulated partition wall 6a as seen from above. [Figure 5] This is an enlarged view showing the lower part of the cooler chamber 80 formed between the fan grill 16 and the inner box 17a. [Figure 6] This is a perspective view showing one example configuration of the cooler 18 and pipe heater 65 in the refrigerator 100 according to Embodiment 1. [Figure 7] Figure 6 is a perspective view showing the pipe heater 65 as a single unit. [Figure 8] This is a perspective view showing one example configuration of a glass tube heater 19 attached to the lower part of the cooler 18 shown in Figure 6. [Figure 9] This 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. [Figure 10] This is a block diagram illustrating the control performed by the control device 12 on the refrigerator 100 according to Embodiment 1. [Figure 11] It is an enlarged view of a configuration including the cooler 18 shown in FIG. 5. [Figure 12] It is a table showing an example of the result of investigating the door opening state time of each storage compartment per day for each of the summer and winter seasons for a refrigerator. [Figure 13] It is a graph showing the relationship between the door opening state time tave of the refrigerator door 7a and the freezer door 7d and the amount of frost formation on the cooler 18. [Figure 14] It is a graph showing the relationship between the amount of frost formation on the cooler 18 and the heater energization time required to melt the frost attached to the cooler 18. [Figure 15] It is a hardware configuration diagram showing an example of a configuration of the control device 12 shown in FIG. 10. [Figure 16] It is a hardware configuration diagram showing another example of a configuration of the control device 12 shown in FIG. 10. [Figure 17] It is a flowchart showing the operation procedure in the defrosting operation of the refrigerator according to Embodiment 1. [Figure 18] It is a flowchart showing the operation procedure in the defrosting operation of the refrigerator according to Embodiment 1. [Figure 19] It is a flowchart showing the operation procedure in the defrosting operation of the refrigerator according to Embodiment 1. [Figure 20] It is a flowchart showing the operation procedure in the defrosting operation of the refrigerator according to Embodiment 1. [Figure 21] It is a timing chart for explaining the effect of the defrosting operation performed by the refrigerator 100 according to Embodiment 1. [Figure 22] It is a graph showing the relationship between the door opening state time tave of the refrigerator door 7a and the amount of frost formation on the cooler 18 when the humidity of the outside air is different in the refrigerator 100 according to Embodiment 1. [Figure 23] It is a graph showing the relationship between the door opening state time tave of the refrigerator door 7a, the freezer door 7d, and the vegetable compartment door 7e and the amount of frost formation on the cooler 18 in the refrigerator 100 according to Embodiment 2.

MODE FOR CARRYING OUT THE INVENTION

[0013] Embodiments of the refrigerator described herein will be explained with reference to the drawings. For the sake of explanation, some parts of the drawings show three axes, the X, Y, and Z axes, which define directions in three-dimensional space. The direction of the Y-axis arrow is the front of the refrigerator, and the direction opposite to the Y-axis arrow is the back of the refrigerator. The direction opposite to the Z-axis arrow is the direction of gravity.

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

[0015] The refrigerator 100 comprises a box-shaped refrigerator body 101 having multiple storage compartments inside for storing items to be cooled. Inside the refrigerator body 101, starting from the top, are multiple storage compartments consisting of a refrigerator compartment 1, an ice-making compartment 2 and a switching compartment 3, a freezer compartment 4, and a vegetable compartment 5. The refrigerator compartment 1 corresponds to the first storage compartment, the freezer compartment 4 to the second storage compartment, and the vegetable compartment 5 to the third storage compartment. The ice-making compartment 2 is located below and to the left of the refrigerator compartment 1, and the switching compartment 3 is located below and to the right of the refrigerator compartment 1. The ice-making compartment 2 and the switching compartment 3 are located adjacent to each other horizontally. The ice-making compartment 2 may include an automatic ice maker, which is not shown in the figure.

[0016] The arrangement of the multiple storage compartments is not limited to the arrangements shown in Figures 1 and 2. The arrangement of two storage compartments located vertically or horizontally can be swapped. The refrigerator 100 has an ice-making compartment 2, a switching compartment 3, and a vegetable compartment 5 in addition to the refrigerator compartment 1 and the freezer compartment 4, but it does not have to have the ice-making compartment 2, the switching compartment 3, and the vegetable compartment 5. For example, the refrigerator 100 may have a configuration in which the refrigerator body 101 has only the refrigerator compartment 1 and the freezer compartment 4, or a configuration in which it has only the refrigerator compartment 1 or the freezer compartment 4. Also, the refrigerator body 101 may have a configuration in which it has multiple freezer compartments 4.

[0017] In the refrigerator 100, two storage compartments adjacent to each other in the vertical direction are separated from each other by insulated partition walls 6a to 6c. Insulated partition wall 6a separates the refrigerator compartment 1 from the ice-making compartment 2 and the switching compartment 3. Insulated partition wall 6b separates the ice-making compartment 2 and the switching compartment 3 from the freezer compartment 4. Insulated partition wall 6c separates the freezer compartment 4 from the vegetable compartment 5. In this embodiment 1 of the refrigerator 100, the positions of the freezer compartment 4 and the vegetable compartment 5 can be swapped.

[0018] The refrigerator 100 has multiple doors on the front side of the refrigerator body 101, which open and close each of the multiple storage compartments. The multiple doors are a refrigerator compartment door 7a, an ice maker door 7b, a convertible compartment door 7c, a freezer compartment door 7d, and a vegetable compartment door 7e. The refrigerator compartment door 7a corresponds to the first door, the freezer compartment door 7d corresponds to the second door, and the vegetable compartment door 7e corresponds to the third door. The refrigerator compartment door 7a opens and closes refrigerator compartment 1. The ice maker door 7b opens and closes ice maker compartment 2. The convertible compartment door 7c opens and closes convertible compartment 3. The freezer compartment door 7d opens and closes freezer compartment 4. The vegetable compartment door 7e opens and closes vegetable compartment 5.

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

[0020] The ice-making compartment door 7b is a pull-out door. An ice-making compartment frame is attached to the back of the ice-making compartment door 7b, and the 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 provided on the left and right sides of the ice-making compartment 2, and slides along the ice-making compartment rails. When the ice-making compartment door 7b closes the ice-making compartment 2, the ice-making compartment case 14 is stored inside the ice-making compartment 2.

[0021] The switching chamber door 7c is a retractable door. A switching chamber frame is attached to the back of the switching chamber door 7c, and the switching chamber case 15 is installed on the switching chamber frame. The switching chamber frame is attached to switching chamber rails provided on the left and right sides of the switching chamber 3, and slides along the switching chamber rails. When the switching chamber door 7c closes the switching chamber 3, the switching chamber case 15 is stored inside the switching chamber 3.

[0022] The freezer door 7d is a pull-out door. The freezer frame is attached to the back of the freezer door 7d, and the lower storage case 22 is installed on the freezer frame. The lower storage case 22 is a storage case intended for long-term storage of about one month. A shallow upper storage case 23 is placed on top of the lower storage case 22. When the freezer door 7d closes the freezer compartment 4, the lower storage case 22 and the lower storage case 23 are stored inside the freezer compartment 4.

[0023] The vegetable compartment door 7e is a pull-out door. A vegetable compartment frame is attached to the back of the vegetable compartment door 7e, and the 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 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 inside the vegetable compartment 5.

[0024] As shown in Figure 2, a control device 12 is housed in the upper rear of the refrigerator unit 101. The control device 12 controls the operation of the refrigerator 100. Based on signals received from various sensors installed in the refrigerator 100 and user-defined settings, the control device 12 controls various electrical equipment related to the cooling operation. The control device 12 will be described in detail later.

[0025] As shown in Figure 1, a refrigerator compartment temperature sensor 51a is provided inside the refrigerator compartment 1 to detect the temperature of the refrigerator compartment 1. An ice maker compartment temperature sensor 51b is provided inside the ice maker compartment 2 to detect the temperature of the ice maker compartment 2. A switching compartment temperature sensor 51c is provided inside the switching compartment 3 to detect the temperature of the switching compartment 3. A freezer compartment temperature sensor 51d is provided inside the freezer compartment 4 to detect the temperature of the freezer compartment 4. A vegetable compartment temperature sensor 51e is provided inside the vegetable compartment 5 to detect the temperature of the vegetable compartment 5. These temperature sensors are, for example, thermistors. Each of the refrigerator compartment temperature sensor 51a, ice maker compartment temperature sensor 51b, switching compartment temperature sensor 51c, freezer compartment temperature sensor 51d, and vegetable compartment temperature sensor 51e is connected to the control device 12 via a signal line (not shown).

[0026] Figure 3 is an enlarged perspective view of a portion of the front of the left door 7a1 of the refrigerator compartment 1 shown in Figure 1. An operation panel 8 for the user to adjust the temperature of each storage compartment is provided on the front of the left door 7a1 of the refrigerator compartment 1. The operation panel 8 is communicated with the control device 12 via signal lines (not shown). The operation panel 8 has a panel body 8a and a circuit board 9. The circuit board 9 is installed on the back side of the panel body 8a so as to be covered by the panel body 8a. The circuit board 9 is equipped with an ambient temperature sensor 10 for detecting the ambient temperature. The ambient temperature sensor 10 is, for example, a thermistor. The panel body 8a is equipped with temperature adjustment buttons 54 for inputting the set temperature of a storage compartment and selection buttons 55 used when selecting one storage compartment from a plurality of storage compartments.

[0027] In the refrigerator 100, an operation panel 8 is provided on the front refrigerator door 7a. However, if aesthetics are prioritized, the operation panel 8 may not be installed on the surface of the refrigerator body 101, including the door 7a, but rather inside the refrigerator compartment 1. In this case, the outside air temperature sensor 10 can be installed, for example, inside the hinge 11 that rotates the refrigerator door 7a while it is supported by the refrigerator body 101.

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

[0029] The internal structure of the refrigerator 100 will be described with reference to Figures 1 and 2. As shown in Figure 2, a refrigerator door open / close sensor 90a for detecting the opening and closing of the refrigerator door 7a, an ice maker door open / close sensor 90b for detecting the opening and closing of the ice maker door 7b, and a switch door open / close sensor 90c for detecting the opening and closing of the switch door 7c are provided on the front side of the insulated partition wall 6a. The refrigerator door open / close sensor 90a corresponds to the first door open / close sensor. A freezer door open / close sensor 90d for detecting the opening and closing of the freezer door 7d is provided on the front side of the insulated partition wall 6b. The freezer door open / close sensor 90d corresponds to the second door open / close sensor. A vegetable compartment door open / close sensor 90e for detecting the opening and closing of the vegetable compartment door 7e is provided on the front side of the insulated partition wall 6c. The vegetable compartment door open / close sensor 90e corresponds to the third door open / close sensor.

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

[0031] As shown in Figure 2, a fan grill 16 is installed at the back of the freezer compartment 4. The fan grill 16 forms the back of the ice-making compartment 2, the switching compartment 3, and the freezer compartment 4, and contains a blower 24, a damper device 26 for the refrigerator compartment, and a damper device 27 for the switching compartment. A compressor 25 is installed at the lower rear of the refrigerator body 101. The compressor 25, a heat sink (not shown), a pressure reducing device such as a capillary tube (not shown), and a cooler 18 are connected via refrigerant piping 63 (see Figure 6), forming a refrigerant circuit (not shown) through which the refrigerant circulates. The blower 24, the damper device 26 for the refrigerator compartment, the damper device 27 for the switching compartment, and the compressor 25 are each communicated with the control device 12 via signal lines (not shown). The freezer compartment temperature sensor 51d shown in Figure 1 detects the freezer compartment temperature Tf, which is used to determine the operation and stopping of the compressor 25. The freezer compartment temperature sensor 51d is located at the back of the freezer compartment 4 and is installed in front of the fan grill 16.

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

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

[0034] As shown in Figures 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 cooling unit 80 to each shelf. The control panel 47 is composed of resin parts 48 on the design side and polystyrene foam duct parts 49 on the back side. The duct parts 49 and the inner box 17a form the refrigerator compartment air outlet passage 50.

[0035] The control panel 47 is equipped with multiple air vents 56. These multiple air vents 56 serve to blow the cold air that flows from the cooling chamber 80 through the damper device 26 for the refrigerator chamber into the refrigerator chamber air vent 50 to each shelf. The refrigerator chamber temperature sensor 51a is installed in the center of the vertical direction on the back of the refrigerator chamber 1 and detects the average temperature of the air inside the refrigerator chamber 1.

[0036] An insulating material 28, such as polyurethane foam, is filled between the inner box 17a and the outer box 17b of the refrigerator body 101. Furthermore, vacuum insulation material 13 is provided on both sides (not shown), the back, the top, and inside the door of the refrigerator body 101 as a member to reinforce the insulating properties. The vacuum insulation material 13 is installed inside the insulating material 28 so as to surround each storage compartment in order to suppress heat leakage from each storage compartment.

[0037] As shown in Figures 1 and 2, the refrigerator body 101 is equipped with a first return air passage, the refrigerator compartment return air passage 31, a second return air passage, the freezer compartment return air passage 32, and a third return air passage, the vegetable compartment return air passage 33. The refrigerator compartment return air passage 31 is an air passage for guiding the air in the refrigerator compartment 1 to the cooler compartment 80. The freezer compartment return air passage 32 is an air passage for guiding the air in the freezer compartment 4 to the cooler compartment 80. The vegetable compartment return air passage 33 is an air passage for guiding the air in the vegetable compartment 5 to the cooler compartment 80. The refrigerator compartment return air passage 31, the freezer compartment return air passage 32, and the vegetable compartment return air passage 33 are provided independently of each other.

[0038] Figure 4 is a plan view of the insulated partition wall 6a shown in Figure 2, viewed from above. A refrigerator return air passage inlet 81, which opens into the refrigerator compartment 1, is provided at the rear of the insulated partition wall 6a. The refrigerator return air passage inlet 81 constitutes one end of the refrigerator return air passage 31 shown in Figure 1. As shown in Figure 1, the refrigerator return air passage 31 has a refrigerator return air passage outlet 82 at its other end, which opens into the cooler compartment 80. The refrigerator return air passage outlet 82 corresponds to the first return opening. The refrigerator return air passage inlet 81 is provided in the refrigerator compartment 1, separated from the refrigerator return air passage outlet 82. In Figure 1, the direction D1 in which air flows in the refrigerator return air passage 31 is indicated by a dotted arrow. In the refrigerator 100 of this embodiment 1, the refrigerator return air passage outlet 82 is provided upstream of the cooler 18 with respect to the direction D1 in which air flows in the cooler compartment 80. The refrigerator compartment return air outlet 82 is located below the cooler 18. The location of the refrigerator compartment return air outlet 82 is not limited to the case shown in Figure 1. The location of the refrigerator compartment return air outlet 82 is sufficient as long as it is upstream of the cooler 18. The cold air returning from the refrigerator compartment 1 flows into the refrigerator compartment return air passage 31 from the refrigerator compartment return air passage inlet 81, circulates within the refrigerator compartment return air passage 31, and then flows into the cooler compartment 80 from the refrigerator compartment return air passage outlet 82.

[0039] Figure 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. A freezer chamber return air passage 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 passage inlet 83 is provided on the rear portion 4a of the freezer chamber 4. The freezer chamber return air passage inlet 83 constitutes one end of the freezer chamber return air passage 32. The freezer chamber return air passage 32 has a freezer chamber return air passage outlet 84 at the other end, which opens into the cooler chamber 80. The freezer chamber return air passage outlet 84 corresponds to a second return outlet. The freezer chamber return air passage inlet 83 is provided in the freezer chamber 4, separated from the freezer chamber return air passage outlet 84. In the cooler chamber 80, the direction D1 in which air flows due to the drive of the blower 24 is indicated by an arrow in Figure 5. Air flows from the bottom to the top of the cooler 18. As shown in Figure 1, the freezer compartment return air outlet 84 is located downstream of the refrigerator compartment return air outlet 82 with respect to the direction of airflow D1 in the cooler compartment 80. In this embodiment 1, the freezer compartment return air outlet 84 is formed in the front part 80a of the cooler compartment 80. The freezer compartment return air outlet 84 is located in a position that overlaps with the cooler 18 in the depth direction (opposite direction of the Y-axis arrow) when viewing the refrigerator body 101 from the front. The cold air returning from the freezer compartment 4 flows into the freezer compartment return air outlet 32 ​​from the freezer compartment return air outlet 83, circulates through the freezer compartment return air outlet 32, and then flows into the cooler compartment 80 from the freezer compartment return air outlet 84.

[0040] The vegetable compartment 5, located at the very bottom of the refrigerator body 101, is at a slightly higher temperature than the refrigerator compartment 1. The vegetable compartment 5 is maintained in the refrigerator temperature range, for example, +3°C to +10°C. Cooling of the vegetable compartment 5 utilizes the refrigerator compartment return air passage 31. As explained with reference to Figures 1 and 4, the refrigerator compartment return air passage 31 extends from the rear right rear of the switching compartment 3 to the lower rear right rear of the freezer compartment 4, and further extends from the rear right rear of the vegetable compartment 5 to the center rear of the vegetable compartment 5, connecting to the bottom of the condenser compartment 80. A portion of the cold air flowing through the refrigerator compartment return air passage 31 is supplied to the vegetable compartment 5. Since the cold air flowing through the refrigerator compartment return air passage 31 is in the refrigerator temperature range, no insulation is required between the refrigerator compartment return air passage 31 and the vegetable compartment 5. On the other hand, an insulation structure (not shown) is provided between the refrigerator compartment return air passage 31 and the condenser 18 to prevent air passage blockage due to frost formation.

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

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

[0043] As shown in Figure 5, a 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 during the defrosting of the cooler 18. A drain tray 59 is provided below the glass tube heater 19. The drain tray 59 forms part of the lower side surface of the cooler chamber 80. Below the drain tray 59, a drain pipe 60 is attached to the drain port of the drain tray 59 by deforming metal. The defrost water flows through the drain pipe 60 into the drain hole 20 and is then discharged to an evaporation tray 21 located below the drain pipe 60 and installed on top of the compressor 25.

[0044] The configuration of the cooler 18 will be explained in detail later, but as shown in Figure 5, the cooler 18 has refrigerant piping 63 and a number of fins 62. In the schematic cross-sectional view shown in Figure 5, the cooler 18 has a configuration in which multiple stages, each consisting of refrigerant piping 63 and fins 62 arranged in two horizontal rows, are stacked vertically (Z-axis). Hereinafter, the stages consisting of refrigerant piping 63 and fins 62 arranged in two horizontal rows will be referred to as cooler sub-stages. The cooler sub-stage located at the bottom will be referred to as the lower cooler stage. Furthermore, the stages from the lower cooler stage upwards to the fourth stage will be referred to as the middle cooler stage. Figure 5 shows the case where the freezer return air duct outlet 84 is located on the surface corresponding to the middle cooler stage, but the number of stages in the vertical direction of the freezer return air duct outlet 84 is not limited to four stages.

[0045] Figure 6 is a perspective view showing one example configuration of the cooler 18 and pipe heater 65 in the refrigerator 100 according to Embodiment 1.

[0046] As shown in Figure 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 made of aluminum or copper with a wall thickness of 0.5 to 1.3 mm. A cooler temperature sensor 71 is provided in the refrigerant piping 63 to detect the temperature Tkr of the cooler 18. The cooler temperature sensor 71 is, for example, a thermistor.

[0047] The refrigerant piping 63 is folded back in its extension direction by a plurality of U-shaped connecting pipes 88 and is arranged in the vertical direction (Z-axis). The straight sections of the refrigerant piping 63 that extend along the left-right direction (Y-axis) are arranged in the vertical direction, for example, in 8 rows. Two adjacent rows of refrigerant piping 63 are connected at one end in the left-right direction by a connecting pipe 88. As a result, a single refrigerant piping 63 is formed to reciprocate many times in parallel in the left-right direction while changing height. The refrigerant flowing through the refrigerant piping 63 of the cooler 18 flows from the cooler inlet 89a, which is connected to the lowest refrigerant piping 89, to the cooler outlet 89b, which is connected to the uppermost refrigerant piping 63. The direction of airflow D1 is from the bottom to the top of the cooler 18, as shown in Figure 5. Therefore, the lowest refrigerant piping 89 is located on the upstream side of the straight sections of the multiple refrigerant piping 63 arranged in relation to the direction of airflow D1. Furthermore, the uppermost refrigerant pipe 63 is positioned on the downstream side of the multiple refrigerant pipes 63 with respect to the airflow direction D1.

[0048] The low-temperature gaseous two-phase refrigerant flowing from the pressure reducing device (not shown) into the cooler 18 flows from the cooler inlet 89a through the upstream refrigerant piping 63 relative to the direction of airflow D1, and gradually flows through the downstream refrigerant piping 63 to the cooler outlet 89b. As the gaseous two-phase refrigerant flowing through the cooler 18 moves from the cooler inlet 89a to the cooler outlet 89b, it exchanges heat with the air flowing on the outside of the refrigerant piping 63. As a result, the gaseous two-phase refrigerant flows through the refrigerant piping 63 while the liquid phase within the refrigerant evaporates. 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] Figure 7 is a perspective view showing the pipe heater 65 shown in Figure 6. As shown in Figure 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 the second heater. As shown in Figure 7, the pipe heater 65 comprises an aluminum pipe 91 into which a cord heater 64, in which a resistance wire 68 is 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 pipe 91 extending in the left-right direction is deformed at a position where it contacts the left and right fixing plates 66 of the cooler 18 shown in Figure 6 to change its direction of extension, and multiple pipe heaters are arranged in the vertical direction. The pipe heater 65 is fixed to the left and right fixing plates 66 shown in Figure 6.

[0050] The arrangement of the pipe 91 from one end to the other with respect to the cooler 18 will be described in detail with reference to Figures 6 and 7. The pipe 91 starts from the top of one of the two sides of the cooler 18 parallel to the YZ plane shown in Figure 6, and folds back multiple times along the side to the bottom of the side. When the pipe 91 reaches the bottom of one side of the cooler 18, it exits to the other side of the cooler 18 via pipe 91a. Then, the pipe 91 starts from the bottom of the other side of the cooler 18 and folds back multiple times along the side to the top of the side. The pipe heater 65 is positioned so as to pass between two vertically adjacent fins 62, as shown in Figure 6. The pipe heater 65 is positioned in contact with or close to the side of the cooler 18. Close to means within a distance where the heat generated from the pipe heater 65 is sufficiently transferred to the cooler 18, for example, 1 to 3 mm.

[0051] Figure 8 is a perspective view showing one example configuration of a glass tube heater 19 attached to the lower part of the cooler 18 shown in Figure 6. Figure 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 Figure 8, the glass tube heater 19 has a glass tube 67 with a resistance wire 68 inside, and both ends of the glass tube 67 are sealed with rubber caps 70 or the like. In Figure 8, a part of the glass tube 67 is omitted so that the inside of the glass tube 67 can be seen. Also in Figure 8, a part 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 positioned above the glass tube 67. The heater roof 58 serves to prevent defrost water dripping from the cooler 18 during defrosting operation from cracking the glass tube 67. As shown in Figure 9, the pipe heater 65 is positioned on the side of the cooler 18 so as to weave between the vertically adjacent fins 62. The glass tube heater 19 is located at the bottom of the cooler 18.

[0052] Next, the configuration of the control device 12 will be described. Figure 10 is a block diagram illustrating the control performed by the control device 12 on the refrigerator 100 according to Embodiment 1. The control device 12 is, for example, a microcomputer. The operating modes of the refrigerator 100 include, for example, a cooling operation that cools each storage compartment and a defrosting operation that melts the frost adhering to the surface of the cooler 18. The control device 12 controls the compressor 25, the blower 24, and the damper devices 26 and 27 in accordance with the operating mode. The control device 12 is equipped with a timer (not shown) function for measuring time in order to control these devices.

[0053] First, we will explain the control by the control device 12 when the refrigerator 100 is operating in cooling mode. The control device 12 processes the signals received from temperature sensors installed in each storage compartment and converts them into temperature values. The control device 12 adjusts the flow rate of cold air flowing from the cooler compartment 80 to each storage compartment by controlling the rotation speed of the compressor 25 and blower 24, and the opening and closing of the 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, blower 24, and 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 stopping 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. Furthermore, the control device 12 controls the opening and closing of the baffle (not shown) of the damper device 27 for the switching chamber 3 so that the switching chamber temperature Ts detected by the switching chamber temperature sensor 51c matches the set temperature of the switching chamber 3.

[0054] Next, before explaining in detail the control performed by the control device 12 when the refrigerator 100 is operating in defrost mode, we will explain the generation of frost in the evaporator 18 and the selection of heaters based on the location of frost generation.

[0055] Figure 11 is an enlarged view of the configuration including the cooler 18 shown in Figure 5. In Figure 11, the airflow returning from the refrigerator compartment 1, the freezer compartment 4, and the vegetable compartment 5 is indicated by arrows. In this embodiment 1, 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 embodiment 2 below.

[0056] In the refrigerator 100, when a user opens one of the multiple doors, air flows into the storage compartment from the external space separated from the storage compartment by the door. The external air then flows into the condenser compartment 80 via the return air passage of the storage compartment, where it is cooled by the condenser 18. The water vapor contained in the air freezes on the surface of the condenser 18, causing frost to form on the condenser 18. For example, when the refrigerator door 7a is opened or closed, air flows into the refrigerator compartment 1 from the external space. The air that flows into the refrigerator compartment 1 flows into the condenser compartment 80 via the refrigerator compartment return air passage 31 (see Figure 1). The air that flows into the condenser compartment 80 flows in the direction of arrow 72 in Figure 11 and is cooled by the condenser 18. As a result, the water vapor contained in the air is cooled, and frost forms on the first region 74 on the lower side of the lower part of the condenser 18. The first region 74 is located near the refrigerator return air outlet 82 shown in Figure 1.

[0057] Furthermore, when the freezer door 7d is opened or closed, air flows into the freezer compartment 4 from the outside space. The air that flows into the freezer compartment 4 passes through the freezer compartment return air passage 32 (see Figure 2) and flows into the condenser compartment 80. The air that flows into the condenser compartment 80 flows in the direction of arrow 73 in Figure 11 and is cooled by the condenser 18. As a result, the water vapor contained in the air is cooled, and frost forms in the second region 75, which is near the outlet 84 of the freezer compartment return air passage and in front of the middle section of the condenser. The middle section of the condenser is located downstream of the lower section of the condenser in the direction of cold air flow. The second region 75 is located downstream of the first region 74 in the direction of airflow D1. Thus, the location of frost formation in the condenser 18 differs depending on the type of door that is opened or closed.

[0058] As explained with reference to Figures 6 and 9, the mounting positions of the glass tube heater 19 and the pipe heater 65 are different in the cooler 18. Specifically, the glass tube heater 19 is installed at a distance from the cooler 18 and at the bottom of the cooler 18, while the pipe heater 65 is installed on the main body of the cooler 18. Because the two heaters are installed at different positions relative to the cooler 18, the areas on which the heat generated by each heater acts on the cooler 18 are also different. The heat generated by the glass tube heater 19 mainly acts on the first area 74 at the bottom of the lower section 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 the second area 75 at the front of the middle section of the cooler, where frost forms due to air returning from the freezer compartment 4. Note that the second area 75 on which the heat generated by the pipe heater 65 acts is not limited to the range from the bottom section of the cooler 18 to the top four sections.

[0059] Here, we will explain where the glass tube heater 19 and pipe heater 65 should be installed, corresponding to the location where frost grows on the cooler 18.

[0060] Because the return air from the refrigerator compartment 1 hits the first region 74 at the bottom of the lower section of the cooler, frost grows downward from the cooler 18 and away from the cooler 18. If the cooler 18 is heated from the inside or from the front and rear sides to melt this frost, the frost attached to the first region 74 will peel off as a solid, and the peeled-off frost may block the drain pipe 60. Therefore, it is appropriate to install a glass tube heater 19 below the first region 74 so that the frost is melted from below the cooler 18 by the radiant heat of the glass tube heater 19.

[0061] Furthermore, by positioning the freezer compartment return air outlet 84 in the front-to-back direction of the refrigerator body 101, overlapping with the second area 75 in front of the middle section of the cooler, the return air from the freezer compartment 4 flows into the cooler compartment 80 in front of the middle section of the cooler. Generally, the number of times the door of the freezer compartment 4 is opened per unit period is less than the number of times the door of the refrigerator compartment 1 is opened per unit period, so the amount of frost that accumulates in the second area 75 is less than the amount of frost that accumulates in the first area 74. This will be explained with reference to Figure 12. Figure 12 is a table showing an example of the results of investigating the daily door-open time of each storage compartment for each season, summer and winter, for a refrigerator.

[0062] The door open time is the product of the average number of times the door was opened per day [times] and the average duration [seconds] the door was open when it was opened and closed. The values ​​for each door in the table shown in Figure 12 are the sum of the door open time [seconds] over a predetermined period. Referring to the table shown in Figure 12, it can be seen that the door open time for the refrigerator compartment is overwhelmingly longer than the door open time for other storage compartments, regardless of the season. From the survey results shown in Figure 12, it can be assumed that in the cooler 18, there is a lot of frost formation due to the return air from the refrigerator compartment and little frost formation due to the return air from the freezer compartment. Therefore, in Figure 11, in the second region 75 in the middle of the cooler, where the return air from the freezer compartment 4 hits, frost growth is slower than in the first region 74 in the lower part of the cooler, and it is efficient to heat the frost by heat conduction from inside the cooler 18. For this reason, in this embodiment 1, a pipe heater 65 is installed in the middle of the cooler where the return air from the freezer compartment 4 hits.

[0063] Based on the above, the control of the control device 12 during defrosting operation will now be explained. The control device 12 executes the next defrosting operation when it reaches a predetermined first reference time based on the elapsed time since the end of the last defrosting operation, or a predetermined second reference time based on the cumulative operating time of the compressor 25. In this embodiment 1, the reference time from the end of the last defrosting operation until the start of the next defrosting operation is referred to as the interval time tref.

[0064] When the defrosting operation begins, the control device 12 starts energizing the two heaters, stops the blower 24 and compressor 25, and closes the damper devices 26 and 27 in each storage chamber. This prevents the warm air generated in the cooler chamber 80 during the defrosting operation from flowing into each storage chamber. In addition, by stopping the blower 24 during the defrosting operation, the control device 12 suppresses the accumulation of moisture on the baffles (not shown) of the damper devices 26 and 27, preventing freezing of the movable parts.

[0065] In this embodiment 1, when performing defrosting, the control device 12 controls the energizing time of each heater based on the time that the refrigerator door 7a and the freezer door 7d are open during the interval time tref before the defrosting operation. In each storage compartment, the time that the doors are open during the interval time tref is denoted as tave. The energizing control of the two heaters will be described in detail below.

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

[0067] Before explaining Figure 13, let's explain how the control device 12 can determine the door open state time tave for each storage compartment based on the door status signals received from the door open / close sensors of each storage compartment. For example, for the refrigerator compartment door 7a, when the control device 12 receives a door status signal indicating the open state from the refrigerator compartment door open / close sensor 90a, it starts measuring time t. Subsequently, when the control device 12 receives a door status signal indicating the closed state from the refrigerator compartment door open / close sensor 90a, it counts the number of openings and closings as one and records the time t from the start of measurement as the open state time. For the refrigerator compartment door 7a, the control device 12 records the number of openings and closings and the open state time in the interval time tref. Then, based on the recorded information, the control device 12 calculates the product of the average number of times the refrigerator compartment door 7a was opened per day and the average amount of time the refrigerator compartment door 7a was open when it was opened and closed, and obtains the calculated result as the door open state time tave.

[0068] Consider the case where the door open time tave for refrigerator compartment 1 is 50 seconds and the door open time tave for freezer compartment 4 is 20 seconds. In this case, the amount of frost that accumulates on the lower part of the evaporator when refrigerator compartment 1 is open is 300cc, and the amount of frost that accumulates on the middle part of the evaporator when freezer compartment 4 is open is 80cc. By measuring the amount of frost each time the door open time tave is changed for both refrigerator compartment 1 and freezer compartment 4, a graph showing the relationship between the door open time tave and the amount of frost associated with the door open time tave for refrigerator compartment 1 and freezer compartment 4 can be obtained, as shown in Figure 13.

[0069] Furthermore, from the graph shown in Figure 13, we can derive the relationship between the door open time (tave) and the amount of frost for both refrigerator compartment 1 and freezer compartment 4. Figure 13 shows that the relationship between the door open time (tave) and the amount of frost for refrigerator compartment 1 is approximated by a linear function. Similarly, 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 relationship equations, it can be seen that the slope is steeper for refrigerator compartment 1 than for freezer compartment 4.

[0070] In this embodiment 1, for convenience, the relationship between the door open time tave and the amount of frost was 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, in addition to the door open time tave, at least one of the following variables: the ventilation rate associated with opening and closing the storage room door, the rotational speed nc of the compressor 25, the rotational speed nf of the blower 24, the outside air temperature Tout, and the outside air humidity Hout.

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

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

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

[0074] In this way, through experiments, the relationship between the door open time (tave) of each storage chamber and the amount of frost was determined from the graph shown in Figure 13, and the relationship between the amount of frost and the heater power-on time was determined from the graph shown in Figure 14. These relationships are expressed as follows.

[0075] Let Afr1 be the amount of frost on the lower part of the lower cooler, let R be the time the door of refrigerator compartment 1 is open, and let Ra and Rb be the coefficients. Then the amount of frost Afr1 is expressed by equation (1). Afr1 = R × Ra + Rb ... (1)

[0076] Let Afr2 be the amount of frost on the front of the middle section of the cooler, let F be the time the door of the freezer compartment 4 is open, and let Fa and Fb be the coefficients. Then the amount of frost Afr2 is expressed by equation (2). Afr2 = F × Fa + Fb ... (2)

[0077] If the energizing time of the glass tube heater 19 is denoted as tp1, the amount of frost formed by the glass tube heater 19 is denoted as G, and the coefficients are Ga and Gb, then the energizing time tp1 is expressed by equation (3). tp1 = G × Ga + Gb ... (3)

[0078] If the energizing time of the pipe heater 65 is tp2, the amount of frost that the pipe heater 65 acts on is P, and the coefficients are Pa and Pb, then the energizing time tp2 is expressed by equation (4). tp² = P × Pa + Pb ... (4)

[0079] The above equations (1) to (4) and the coefficients of each equation as parameters are stored in the control device 12 in advance. This allows the control device 12 to perform defrost operation control using the above equations (1) to (4) during defrost operation. Equations (1) and (2) correspond to the first relational equations. Equations (3) and (4) correspond to the second relational equations. In addition, a calculation formula for determining the energizing time tp1 of the glass tube heater 19 based on the time tave when the door of the refrigerator compartment 1 is open may be determined in advance from equations (1) and (3). Similarly, a calculation formula for determining the energizing time tp2 of the pipe heater 65 based on the time tave when the door of the freezer compartment 4 is open may be determined in advance from equations (2) and (4). These calculation formulas may be stored in the control device 12.

[0080] Furthermore, although the first embodiment of this invention explains each formula as a linear function, this is a simplified representation for the sake of explanation, and it may also be a quadratic function or other multi-degree function. In addition, the coefficients of each formula may differ depending on the model of the defrosting heater installed in the refrigerator.

[0081] The control device 12 determines the amount of frost at each position of the cooler 18 from the time the doors of each storage chamber are open (tave), and determines the energizing time for the glass tube heater 19 and the pipe heater 65 to melt the determined amount of frost. The control device 12 then compares the energizing time of the glass tube heater 19 with the energizing time of the pipe heater 65. When the defrosting operation starts, the control device 12 starts energizing the two defrosting heaters, the glass tube heater 19 and the pipe heater 65. However, for the heater with the shorter energizing time, the control device 12 stops the energizing time once that time has elapsed. On the other hand, for the other heater, the control device 12 stops the energizing when the temperature Tkr detected by the cooler temperature sensor 71 reaches a predetermined threshold temperature. According to this embodiment 1, during the defrosting operation, the energizing of the heater with the shorter energizing time can be stopped earlier than that of the other heater. Therefore, by performing defrosting operations according to the amount of frost accumulation in each part of the cooler 18, the amount of power required to power the heater can be reduced compared to conventional methods.

[0082] Here, we will explain how to derive equations (1) and (2). This method will be referred to as the first method. The first method assumes that frost formation on the cooler 18 depends on the inflow of outside air due to the opening and closing of the door. The method involves opening and closing only the door for which the coefficient to be investigated, and after the moisture contained in the incoming outside air frosts onto the cooler 18, the amount of frost is measured. The specific test procedure for the first method will now be explained.

[0083] (Procedure 1-1) Open and close the door of one of the storage rooms 10, 20, and 50 times. The specific numbers 10, 20, and 50 are given here, but these numbers do not have any particular significance. You can allocate multiple types of opening and closing counts with appropriate intervals. The time the door is open is determined by the formula (time the door is open per opening × number of openings and closings). There is no limit to the time the door is open per opening. (Procedure 1-2) After opening and closing the door, wait for the outside air that has entered the storage compartment to circulate throughout the refrigerator, and then check the amount of frost on the evaporator 18. The time to wait for the outside air that has entered the compartment to circulate throughout the refrigerator can be a predetermined amount of time. (Steps 1-3) For each door, perform steps (1-1) to (1-2) above, and plot the relationship between the door open time and the amount of frost on a graph.

[0084] Next, we will explain how to derive equations (3) and (4). This method will be referred to as the second method. The second method involves allowing frost to form on areas where it is thought that the frost can be melted by the heat generated by each heater, then energizing only the heater whose coefficient we want to investigate, and checking the amount of frost that has melted. We will now explain the specific test procedure for the second method.

[0085] (Procedure 2-1) Power is supplied only to the heater whose coefficient is to be investigated. At this time, the distance relationship between the cooler 18 and the heater is thought to be related to the amount of frost that melts, so it should be the same as when the refrigerator was sold. (Procedure 2-2) For the heater whose coefficient you want to investigate, assign energizing times of 10, 20, and 50 seconds as an example, and energize the heater. Here, specific times of 10, 20, and 50 are mentioned, but these times do not have any particular significance. You can assign multiple types of times at appropriate intervals. (Step 2-3) For each heater, perform steps (2-1) to (2-2) above, check the amount of frost that has melted after power is turned on, and plot the relationship between the amount of melted frost and the power-on time on a graph.

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

[0087] When the various functions of the control device 12 are executed in hardware, the processing circuit 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, we will describe another example of the hardware of the control device 12. Figure 16 is a hardware configuration diagram showing another example of the configuration of the control device 12 shown in Figure 10. When the various functions of the control device 12 are executed by software, the control device 12 consists of a processor 151 such as a CPU and memory 152, as shown in Figure 16. The various functions of the control device 12 are realized by the processor 151 and memory 152. Figure 16 shows that the processor 151 and memory 152 are connected to each other so as to be able to communicate with each other via a bus 153.

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

[0090] As memory 152, non-volatile semiconductor memory such as ROM (Read Only Memory), flash memory, EPROM (Erasable and Programmable ROM), and EEPROM (Electrically Erasable and Programmable ROM) may be used. Alternatively, volatile semiconductor memory such as RAM (Random Access Memory) may be used as memory 152. Furthermore, removable recording media such as magnetic disks, flexible disks, optical disks, CDs (Compact Discs), MDs (Mini Discs), and DVDs (Digital Versatile Discs) may be used as memory 152.

[0091] Next, the operation of the refrigerator 100 in this embodiment 1 during defrosting will be described. Figures 17 to 20 are flowcharts showing the operation procedure during defrosting of the refrigerator according to embodiment 1. Here, the case where the storage compartments are refrigerator compartment 1 and freezer compartment 4 will be described. Furthermore, the case where the frost accumulation position in the evaporator 18 is at the bottom and middle of the evaporator will be described.

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

[0093] In step S3, the control device 12 determines the door open time tave for each storage compartment. Specifically, the control device 12 uses the information compiled in step S1 to determine the door open time tave for refrigerator compartment 1 and the door open time tave for freezer compartment 4. In step S4, the control device 12 determines the amount of frost at each position of the cooler 18. Specifically, the control device 12 substitutes the door open time tave for refrigerator compartment 1 into equation (1) to determine the amount of frost attached to the first area 74 in the lower part of the cooler. The control device 12 also substitutes the door open time tave for freezer compartment 4 into equation (2) to determine the amount of frost attached to the second area 75 in the middle part of the cooler.

[0094] In step S5, the control device 12 determines the heater energizing time tp for melting frost at each position of the cooler 18. Specifically, the control device 12 substitutes the amount of frost attached to the first region 74, which was determined in step S4, into equation (3) to determine the energizing time tp1 for the glass tube heater 19. The control device 12 also substitutes the amount of frost attached to the second region 75, which was determined in step S4, into equation (4) to determine the energizing time tp2 for the pipe heater 65. Then, the control device 12 determines whether the heater energizing time tp1 and the heater energizing time tp2 are equal (step S6).

[0095] If, as a result of the determination in step S6, the heater energizing time tp1 and the heater energizing time tp2 are equal (step S6: Yes), the control device 12 starts energizing the two defrosting 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 process in 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 defrosting heaters (step S10) and ends the defrosting operation.

[0096] On the other hand, if the result of the determination in step S6 is that the heater energization time tp1 and the heater energization time tp2 are not equal (step S6: No), the control device 12 determines whether the heater energization time tp1 is shorter than the heater energization time tp2 (step S7). If the heater energization time tp1 is shorter than the heater energization 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 since the start of energizing the two defrost heaters. In step S12, the control device 12 determines whether the elapsed time tpv is greater than or equal to the heater energization time tp1. If the elapsed time tpv is less than the heater energization time tp1 (step S12: No), the control device 12 continues to energize the two defrost heaters and repeats the determination in step S12.

[0097] On the other hand, when the elapsed time tpv reaches the heater energizing time tp1 (step S12: Yes), the control device 12 stops energizing the glass tube heater 19 (step S13) and continues energizing 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 greater than the threshold temperature Tth. If the temperature Tkr is less than the threshold temperature Tth (step S15: No), the control device 12 returns to the process in step S14. On the other hand, if the temperature Tkr is equal to or greater than the threshold temperature Tth (step S15: Yes), the control device 12 stops energizing the pipe heater 65 (step S16) and terminates the defrosting operation.

[0098] If the result of the determination 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 since 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 less than the heater energization time tp2 (step S18: No), the control device 12 continues to energize the two defrost heaters and repeats the determination in step S18.

[0099] On the other hand, when the elapsed time tpv reaches the heater energizing time tp2 (step S18: Yes), the control device 12 stops energizing the pipe heater 65 (step S19) and continues energizing 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 greater than the threshold temperature Tth. If the temperature Tkr is less than the threshold temperature Tth (step S21: No), the control device 12 returns to the process in step S20. On the other hand, if the temperature Tkr is equal to or greater than the threshold temperature Tth (step S21: Yes), the control device 12 stops energizing the glass tube heater 19 (step S22) and terminates the defrosting operation.

[0100] As described above, if the heater energizing time tp1 is shorter than the heater energizing time tp2 (step S7: Yes), when the elapsed time tpv from the start of energizing the two defrost heaters reaches the heater energizing time tp1, the power supply to the glass tube heater 19 is stopped. Also, if the heater energizing time tp2 is shorter than the heater energizing time tp1 (step S7: No), when the elapsed time tpv from the start of energizing the two defrost heaters reaches the heater energizing time tp2, the power supply to the pipe heater 65 is stopped. During the period from the start of defrosting operation until the temperature Tkr reaches the threshold temperature Tth, the power supply to one of the two defrost heaters is stopped midway. Therefore, not only can the power consumption of the defrost heaters be suppressed, but the temperature of the condenser room 80 can also be prevented from becoming unnecessarily high.

[0101] Next, the effect of the defrosting operation performed by the refrigerator 100 of this embodiment 1 will be explained. Figure 21 is a timing chart for explaining the effect of the defrosting operation performed by the refrigerator 100 according to embodiment 1. Figure 21 shows the operation of each component, including the compressor, and the time-series changes in the temperature Tkr of the evaporator 18, the refrigerator compartment temperature, and the freezer room temperature during the defrosting operation.

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

[0103] As shown in Figure 21, the control device 12 stops not only the compressor 25 but also the blower 24 during defrosting operation. This prevents water vapor generated by defrosting from adhering to the opening and closing parts of the baffles (not shown) of the damper devices 26 and 27, thereby suppressing condensation and freezing of the baffle openings and closing parts. In addition, the control device 12 turns off the damper devices 26 and 27 and closes the baffles (not shown). This prevents the heat from the defrosting heater from diffusing into the refrigerator compartment 1 and the switching compartment 3.

[0104] For example, let's assume that the door open time tave for refrigerator compartment 1 is 50 seconds and the door open time tave for freezer compartment 4 is 20 seconds. In this case, from the relational equations shown in Figure 13 and Figure 14, the heater energization time tp1, which is the energization time of the glass tube heater 19, can be determined to be 290 seconds, and the heater energization time tp2, which is the energization time of the pipe heater 65, can be determined to be 100 seconds. The relationship between heater energization time tp1 and heater energization time tp2 is tp1 > tp2.

[0105] When the defrosting operation begins, the control device 12 starts supplying power to the pipe heater 65 and the glass tube heater 19. After 100 seconds have elapsed since the start of power supply, it stops supplying power to the pipe heater 65, and then continues supplying power 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 power to the glass tube heater 19 and terminates the defrosting operation.

[0106] As shown in Figure 21, when the heater energizing time tp2 has elapsed from the start of the defrosting operation, the power supply to the pipe heater 65 is stopped. If the reduced energizing time for the pipe heater 65 is Dtp, then Dtp = tfr - tp2. Conventionally, not only the glass tube heater 19 but also the pipe heater 65 was energized during the defrosting operation time trf. In contrast, in this embodiment 1, the energizing of the pipe heater 65 is shortened to 100 seconds. Therefore, the refrigerator 100 can improve energy efficiency by shortening the energizing time while securing the heat source necessary for defrosting. Referring to Figure 21, the case where the relationship between heater energizing time tp1 and heater energizing time tp2 is tp1 > tp2 has been explained, but a similar effect can be obtained in the case where tp2 > tp1.

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

[0108] As shown in FIG. 22, since there is more moisture contained in the air when the humidity Hu is higher, the amount of frost formation increases. Therefore, the slope indicating the rate of change of the amount of frost formation with respect to the door open state time is larger when the humidity Hu is higher. For example, humidity Hu1 is the humidity in winter, and humidity Hu2 is the humidity in summer. The control device 12 stores relational expressions between the door open state time tave of the refrigerator compartment 1 and the amount of frost formation corresponding to a plurality of humidities Hu. The control device 12 uses the relational expression corresponding to the humidity Hu detected by a humidity sensor (not shown) from the plurality of relational expressions. Thereby, the relational expression between the door open state time tave of the refrigerator compartment 1 and the amount of frost formation is appropriately selected corresponding to the season. As a result, the accuracy of the energization time of the heater obtained based on the amount of frost formation is improved. Here, the case of the refrigerator compartment 1 has been described as an example of estimating the amount of frost formation in consideration of humidity, but it may also be applied to the freezer compartment 4.

[0109] The refrigerator 100 of this embodiment 1 includes a first storage compartment set to a first temperature zone, a second storage compartment set to a second temperature zone 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 indicating the open or closed state of the first door, a second door opening / closing sensor that outputs a second signal indicating the open or closed state of the second door, a control device 12 that receives a first signal from the first door opening / closing sensor and a second signal from the second door opening / closing sensor, and a cooling compartment 8 provided with a cooler 18 for cooling the air. The system comprises: 0; a cooler temperature sensor 71 for detecting the temperature Tkr of the cooler 18; a blower 24 for sending air cooled by the cooler 18 to the first storage chamber and the second storage chamber; a first return air passage having a first return port opening to the cooler chamber 80 and guiding the air in the first storage chamber to the cooler chamber 80; a second return air passage having a second return port opening to the cooler chamber 80 and guiding the air in the second storage chamber to the cooler chamber 80; a first heater for melting frost caused by air flowing into the cooler chamber 80 from the first return air passage; and a second heater for melting frost caused by air flowing into the cooler chamber 80 from the second return air passage.

[0110] The control device 12 determines, based on the first signal, the first door open state time, which is the time the first door is open, based on the second signal, the second door open state time, which is the time the second door is open, based on the first door open state time, the first energization time tp1, which is the time the first heater is energized, based on the first door open state time, and the second energization time tp2, which is the time the second heater is energized, based on the second door open state time. Then, when the next defrosting operation is started, the control device 12 starts energizing the first heater and the second heater. If the first energizing time tp1 is shorter than the second energizing time tp2, the first heater is energized for the first energizing time tp1, and the second heater is energized until the temperature Tkr reaches the threshold temperature Tth. If the second energizing time tp2 is shorter than the first energizing time tp1, the second heater is energized for the second energizing time tp2, and the first heater is energized until the temperature Tkr reaches the threshold temperature Tth. In this embodiment 1, for example, the first storage room is a refrigerator room 1, and the second storage room is a freezer room 4. The first heater is a glass tube heater 19, and the second heater is a pipe heater 65.

[0111] According to this embodiment 1, the energizing time for the glass tube heater 19 and the pipe heater 65 is determined based on the door open time tave of the first and second storage chambers, and during defrosting operation, the power supply to the heater with the shorter energizing time is stopped midway. For example, if the first energizing time tp1 of the glass tube heater 19 is shorter than the second energizing time tp2 of the pipe heater 65, the power supply to the glass tube heater 19 is stopped when the elapsed time from the start of energizing reaches the first energizing time tp1. Since the power supply to the heater that has completed defrosting in the cooler 18 is stopped earlier during the defrosting operation, the power consumption of the heater can be reduced. In the cooler 18, even if there is an uneven distribution of frost depending on the location, the power supply to the heater on the side where the amount of frost is estimated to be less is stopped earlier than the power supply to the glass tube heater 19 and the pipe heater 65, thus reducing power consumption. Furthermore, since it is possible to suppress the excessive rise in temperature of the cooler 18, the power consumption of the compressor 25 used to cool the cooler 18 after the defrosting operation can be reduced.

[0112] Furthermore, according to this embodiment 1, in the two defrosting heaters that defrost at different positions relative to the airflow in the cooler 18, the amount of frost at the position where each heater in the cooler 18 defrosts is estimated based on the time the doors of the first and second storage chambers are open. Then, the energizing time for each heater is determined based on the estimated amount of frost. As a result, the amount of power consumed, which was previously caused by excessive power being supplied to the heaters, can be reduced. Consequently, the power consumption of the heaters during defrosting operation and the power consumption of the compressor 25 for cooling the cooler 18 after defrosting operation can be reduced.

[0113] Furthermore, in this embodiment 1, the refrigerator 100 stops the blower 24 during defrosting. Therefore, compared to conventional refrigerators that rotate the blower during defrosting and use the cold air from the refrigerator compartment to defrost the condenser, the adhesion of water vapor generated by defrosting to the opening and closing parts of the baffles (not shown) of the damper devices 26 and 27 is suppressed, and condensation and freezing of the baffle opening and closing parts are suppressed. Therefore, there is no need to provide heating means such as an anti-freezing heater to the opening and closing parts of the baffles (not shown) of the damper devices 26 and 27. As a result, the manufacturing cost of the refrigerator 100 is reduced and energy efficiency is improved.

[0114] Embodiment 2. This second embodiment takes into account not only the refrigerator compartment 1 but also the vegetable compartment 5, and controls the defrosting operation to melt the frost accumulating on the cooler 18 using the return air from these storage compartments. In this second embodiment, the same reference numerals are used for the same components as in the first embodiment, and their detailed descriptions are omitted. Furthermore, this second embodiment will focus on the differences between the configuration and operation described in the first embodiment.

[0115] The overall configuration of the refrigerator 100 in this second embodiment is the same as that described in the first embodiment, so its description will be omitted. The operation of the refrigerator 100 in this second embodiment will be described with reference to Figure 23.

[0116] Figure 23 is a graph showing the relationship between the door open time (tave) of the refrigerator door 7a, freezer door 7d, and vegetable door 7e and the amount of frost on the evaporator 18 in a refrigerator 100 according to Embodiment 2. The horizontal axis of Figure 23 represents the door open time (tave) of the refrigerator door 1 [seconds], and the vertical axis represents the amount of frost [cc]. The solid line is the graph for the refrigerator door 1, the dashed line is the graph for the freezer door 4, and the dotted line is the graph for the vegetable door 5. The vegetable door 5 is set to a third temperature zone, which is higher than the first temperature zone.

[0117] Referring to the table shown in Figure 12, the vegetable compartment 5 is the storage compartment with the second longest daily door-open time after the refrigerator compartment 1. Therefore, in this embodiment 2, the control device 12 determines the amount of frost due to water vapor contained in the return air from the vegetable compartment. Specifically, the control device 12 determines the amount of frost due to the return cold air from the vegetable compartment 5 using the following equation (5). If the amount of frost on the lower part of the cooler is Afr3, the time the door of the vegetable compartment 5 is open tave is V, and the coefficients are Va and Vb, then the amount of frost Afr3 is expressed by equation (5). Afr3 = V × Va + Vb ... (5)

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

[0119] According to this second embodiment, the control device 12 can determine the amount of frost on the lower stage of the cooler in more detail than in the first embodiment. Other processes performed by the control device 12 are the same as those described in the first embodiment, so a detailed explanation is omitted. The first method described in the first embodiment can be applied to determine equation (5).

[0120] In this embodiment 2, the case of the vegetable compartment 5 was described, but the control device 12 may determine the door open time tave for all storage compartments, not just the vegetable compartment 5, and determine the amount of frost 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 determine the total amount of frost on each part, and based on the determined total amount, determine the energizing time for the two defrosting heaters, the glass tube heater 19 and the pipe heater 65, and perform defrosting operation control. [Explanation of Symbols]

[0121] 1 Refrigerator compartment, 2 Ice maker compartment, 3 Switching compartment, 4 Freezer compartment, 4a Rear section, 5 Vegetable compartment, 6a~6c Insulated partition wall, 6c1 Bottom, 6c2 Rear side, 7a Refrigerator door, 7a1 Left door, 7a2 Right door, 7b Ice maker door, 7c Switching compartment door, 7d Freezer compartment door, 7e Vegetable compartment door, 8 Control panel, 8a Panel body, 9 Circuit board, 10 Outside air temperature sensor, 11 Hinge, 12 Control device, 13 Vacuum insulation material, 14 Ice maker case, 15 Switching compartment case, 16 Fan grill, 17a Inner box, 17b Outer box, 18 Cooler, 19 Glass tube heater, 20 Drain hole, 21 Evaporation tray, 22 Lower storage case, 23 Upper storage case, 24 Blower, 25 Compressor, 26, 27 1. Damper device, 28. Insulation material, 29. Lower storage case, 30. Upper storage case, 31. Refrigerator compartment return air passage, 32. Freezer compartment return air passage, 33. Vegetable compartment return air passage, 43-45. Shelves, 46. Small item storage case, 47. Control panel, 48. Resin parts, 49. Duct parts, 50. Refrigerator compartment outlet air passage, 51a. Refrigerator compartment temperature sensor, 51b. Ice maker 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 passage hole, 57. Pocket, 58. Heater roof, 59. Drain tray, 60. Drain pipe, 62. Fins, 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 arrow, 74 first area, 75 second area, 80 cooler compartment, 80a front section, 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 open / close sensor, 90b ice maker compartment door open / close sensor, 90c switching compartment door open / close sensor, 90d freezer compartment door open / close sensor, 90e vegetable compartment door open / close sensor, 91, 91a pipe, 92 insulated wall section, 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 range that is lower than the first temperature range, A first door for opening and closing the first storage room, A second door for opening and closing the second storage room, A first door opening / closing sensor detects the opening and closing of the first door and outputs a first signal indicating whether the first door is open or closed, A second door opening / closing sensor detects the opening and closing of the second door and outputs a second signal indicating whether the second door is open or closed, A control device that receives a first signal from the first door opening / closing sensor and a second signal from the second door opening / closing sensor, A cooling chamber equipped with a cooler for cooling the air, A cooler temperature sensor for detecting 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 passage has a first return port that opens into the cooler chamber and guides the air in the first storage chamber to the cooler chamber, A second return air passage has a second return port that opens into the cooler chamber and guides the air from the second storage chamber into the cooler chamber, A first heater that melts frost on the cooler with air flowing into the cooler chamber from the first return air passage, The system includes a second heater that melts frost on the cooler with air flowing into the cooler chamber from the second return air passage, The control device is In the reference time from the last defrosting operation to melt the frost on the cooler until the next defrosting operation to begin, a first door open state time is determined based on the first signal, a second door open state time is determined based on the second signal, a first energization time is determined based on the first door open state time, a second energization time is determined based on the second door open state time, a second energization time is determined based on the second door open state time, When starting the next defrosting operation, the first heater and the second heater are energized, and if the energizing time of the first heater is shorter than the energizing time of the second heater, the first heater is energized for the first energizing time, and the second heater is energized until the temperature detected by the cooler temperature sensor reaches a predetermined threshold temperature, and if the energizing time of the second heater is shorter than the energizing time of the first heater, the second heater is energized for the second energizing time, and the first heater is energized until the temperature detected by the cooler temperature sensor reaches the threshold temperature. refrigerator.

2. The control device is Based on the first door open time and a pre-stored first relational expression, the first amount of frost on the cooler is calculated; based on the second door open time and the first relational expression, the second amount of frost on the cooler is calculated; based on the first amount of frost and a pre-stored second relational expression, the first energizing time is determined; and based on the second amount of frost and the second relational expression, the second energizing time is determined. The refrigerator according to claim 1.

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

4. It has a compressor connected to the aforementioned cooler, The aforementioned reference time is either a first reference time predetermined based on the elapsed time since the completion of the last defrosting operation, or a second reference time predetermined based on the cumulative operating time of the compressor. The refrigerator according to claim 1 or 2.

5. A third storage chamber set to a third temperature range that is higher than the first temperature range, A third door for opening and closing the third storage room, The system includes a third door opening / closing sensor that detects the opening and closing of the third door and outputs a third signal to the control device indicating whether the third door is open or closed, The control device determines the third door open state time, which is the time the third door is open during the reference time, calculates the third frost amount on the cooler using the determined third door open state time and the first relational expression, and determines the first energizing time based on the sum of the first frost amount and the third frost amount. The refrigerator according to claim 2.

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

7. The first heater is a glass tube heater, The second heater is a pipe heater. The refrigerator according to claim 1 or 2.

8. The first return port opens in the cooler chamber at a position upstream of the cooler with respect to the direction of airflow, The second return port opens in the cooler chamber downstream of the first return port with respect to the airflow direction and facing the cooler. The refrigerator according to claim 1 or 2.

9. The first heater is located below the cooler. The second heater is positioned in contact with the cooler, or within a predetermined distance from the cooler. The refrigerator according to claim 1 or 2.

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