JPH07239168A - Defrosting device for refrigerator - Google Patents

Abstract

PURPOSE:To perform defrosting of a cooler at a proper timing as power saving operation is effected by a method wherein when there is no need for defrosting operation at a preset defrosting timing, a defrost-starting timing is extended by a specified time. CONSTITUTION:A control device (a defrosting control means, a door release memory means, a forced operation memory means, an outside air temperature determining means) 11 is caused to execute first extension operation, through which a defrost-starting timing is extended by a specified time, when a condition to need no defrosting operation is established in a case a preset cooler 15 defrost timing comes. The control device 11 is caused to execute second extension operation, through which the defrost starting timing is further extended by a specified time, the specified number of times. This constitution performs defrosting of the cooler 15 at a proper timing as power saving operation is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting device for a refrigerator for performing a defrosting operation on a cooler at a preset defrosting start timing.

[0002]

2. Description of the Related Art Conventionally, in a refrigerator, when a large amount of frost adheres to a cooler, the cooling efficiency decreases, so when the preset defrost start timing comes, the defrost heater is energized. The defrosting operation is executed by heating the cooler.

In this case, the conditions for the defrosting start timing include those set as follows.

(1) When a predetermined time has passed since the last defrosting operation.

(2) When the accumulated operation time of the compressor of the refrigeration cycle device has reached a predetermined value since the previous defrosting operation (see FIG. 9 for the control flowchart).

(3) The optimum defrosting start timing is estimated from the outside air temperature, the number of doors opened and closed, and the operation rate of the compressor.

[0007]

[Problems to be Solved by the Invention] However, (1)
Under these conditions, the defrosting start timing is generally determined based on the worst operating condition with a lot of frost, so in reality the defrosting operation is performed with a small amount of frost. , Energy efficiency is extremely poor.

Further, under the condition (2), the defrosting start timing can be set according to the load state of the cooler, but the integrated judgment value in this case is premised on the entrance and exit of food and the like. , If the user is absent for a long period of time, or if the user has left the vehicle open without opening and closing the door,
Even if the amount of frost formed is smaller than usual, defrosting is performed more than necessary, and energy efficiency deteriorates.

Further, under the condition (3), while the optimum defrosting start timing can be set, the amount of calculation for calculating the defrosting start timing becomes large, and high-speed calculation and high calculation accuracy are achieved as a control device for a refrigerator. It has the disadvantage that it requires functions and the controller is complicated and expensive.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a defrosting device for a refrigerator capable of defrosting a cooler at an appropriate timing while achieving labor-saving operation with a simple structure. Especially.

[0011]

A defrosting apparatus for a refrigerator according to the present invention is provided with defrosting control means for executing a defrosting operation of a cooler at a preset defrosting start timing, and at least a previous defrosting operation is performed. A forced operation memory is provided which is provided with a door opening storage means for storing the fact that the refrigerator door is opened later, and at least stores that the forced continuous operation of the compressor for the cooler has been executed after the last defrosting operation. Means for providing the outside temperature determination means for detecting or estimating the ambient temperature of the refrigerator, and the defrost control means is configured to control the door opening storage means and the forced operation storage at the defrost start timing. When the means is in a non-memory state and the temperature detected by the outside air temperature determination means or the estimated temperature is within a predetermined temperature range, the defrosting start timing is postponed for a certain period of time. When the door opening storage means and the forced operation storage means are in the non-storage state at the defrosting start timing at the end of the first extension operation, the defrosting start timing is further limited to a certain time. The second extension operation to be postponed is configured to be executed a specified number of times.

In this case, when the defrosting start timing comes, the defrosting control means does not store the door opening storage means and the forced operation storage means, and detects or estimates the temperature detected by the outside air temperature determination means. When the temperature is within the predetermined temperature range, the first extension operation of forwarding the defrost start timing until the integrated operating time of the compressor reaches a certain time is executed, and the defrost at the end of the first extension operation is performed. When the door opening storage means and the forced operation storage means are in a non-stored state at the start timing, a second extension operation of further advancing the defrost start timing until the cumulative operating time of the compressor reaches a certain time It may be configured to execute a specified number of times.

Further, the outside air temperature determining means may be configured to estimate the outside air temperature based on the operating rate of the compressor.

Further, the defrosting control means is constituted by a defrosting control device for executing an extension operation for advancing the defrosting start timing, and detects the temperature of a predetermined storage space in which the defrosting control device is stored. After providing the temperature sensor, the outside air temperature determination means may be configured to estimate the outside air temperature based on the temperature detected by the temperature sensor.

Further, the defrosting control means may be configured such that, when the forced operation is performed during execution of the extended operation, the time measurement of the extended operation is interrupted until the forced operation is completed.

[0016]

In the defrosting apparatus for a refrigerator according to claim 1, when the preset defrosting start timing is reached, the defrosting control means is such that the door opening storage means and the forced operation storage means are in a non-stored state and the outside air temperature is It is determined whether the determination temperature by the determination means is within a predetermined temperature range. At this time, when the door is not opened and the forced operation is not executed after the previous defrosting operation, and the outside air temperature is within the predetermined temperature range, the defrosting control unit does not need to perform the defrosting operation. It is determined that the defrosting start timing is advanced by a predetermined time and the first extension operation is executed, and the door opening storage means and the forced operation storage means are in the non-stored state at the defrosting start timing at the end of the first extension operation. If it is, it is determined that the defrosting operation is necessary, and the second extension operation of forwarding the defrosting start timing by a further fixed time is executed.

In this case, the defrost control means is configured to execute the second extension operation a prescribed number of times. Therefore, when the condition in which the defrosting operation is not necessary continues, the first extension operation is performed once and the second extension operation is performed the specified number of times, and when the execution of the second extension operation of the specified number of times is completed. The defrosting operation is executed at.

When the defrosting condition is satisfied at the defrosting start timing, the defrosting control means determines that the defrosting operation is necessary and executes the defrosting operation at the end of the extension operation. To do. Accordingly, the defrosting operation can be executed at an appropriate timing while performing the labor-saving operation.

In the case of the refrigerator defroster according to claim 2,
When performing the extension operation, the defrosting control unit delays the defrosting start timing until the cumulative operating time of the compressor reaches a certain time. Thereby, the defrosting start timing can be set accurately.

In the case of the defroster for a refrigerator according to claim 3,
Since the outside air temperature determination means estimates the outside air temperature based on the operating rate of the compressor, a special temperature sensor for detecting the outside air temperature can be omitted.

In the case of the defroster for a refrigerator according to claim 4,
Since the outside air temperature determination means estimates the outside air temperature based on the temperature detected by the temperature sensor that detects the temperature of the predetermined storage space in which the defrost control device as the defrost control means is stored, in order to detect the outside air temperature. It is not necessary to lead the temperature sensor lead wire out of the storage space.

In the case of the defroster for a refrigerator according to claim 5,
When the forced operation is performed during the extension operation, the defrost control means suspends the time measurement of the extended operation until the forced operation ends, so the defrosting operation is performed on the cooler that has been rapidly cooled by the forced operation. It is possible to avoid the problem of heating.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 2 schematically shows the wiring between various electric components provided in the refrigerator and the control device. In FIG. 2, the refrigerator main body 1 is formed with a freezing compartment 2, a refrigerating compartment 3 and a vegetable compartment 4 from above, and each compartment 2, 3,
Doors 5, 6 and 7 for closing 4 are provided. Further, door switches 8, 9 and 10 which are turned on when the doors 5, 6 and 7 are opened are attached to each of the chambers 2, 3 and 4, and the defrost control means and the door open in the ON state. Control device 11 as storage means, forced operation storage means, and outside air temperature determination means
ON signal is output to. A forced operation button 12 and a monitor lamp 13 are arranged on the front surface of the door 5 of the freezer compartment 2. The forced operation command is given to the control device 11 when the forced operation button 12 is on, and the control device is operated during the forced operation. The monitor lamp 13 is turned on by 11.

A cooler chamber 14 is formed at the back of the freezing chamber 2, and a cooler 15 and a defrost heater 16 are arranged in the cooler chamber 14. The defrost heater 16 is the control device 1
The cooler 15 is heated according to the energization by 1. A fan motor 17 is arranged above the cooler chamber 14, and when the fan motor 17 is driven by the control device 11, the air purified in the cooler chamber 14 is blown to the freezing chamber 2. The freezing chamber 2 is provided with a freezing temperature sensor 18, and the temperature detected by the freezing temperature sensor 18 (freezing temperature) is given to the control device 11.

A motor damper 20 is arranged at the cold air outlet 19 to the refrigerating compartment 3, and the motor damper 20 closes the cold air outlet 19 and the open position where the cold air outlet 19 is opened in response to the drive by the controller 11. Controlled to the closed position. The refrigerating chamber 3 is provided with a refrigerating temperature sensor 21, and the temperature detected by the refrigerating temperature sensor 21 (refrigerating temperature) is given to the controller 11.

A compressor 23 is arranged in the machine room 22, and a coolant is supplied to the cooler 15 to cool the cooler 15 while the compressor 23 is driven by the controller 11.

The control device 11 is housed in a closed space (not shown) and has a temperature sensor for detecting the temperature of the closed space, and executes the following control.

(1) When the temperature of the freezing compartment 2 detected by the freezing temperature sensor 18 becomes -20 ° C or higher, the compressor 23 and the fan motor 17 are driven, and when the temperature becomes -24 ° C or lower, the compressor 23 and the fan motor 17 are stopped. To do.

(2) When the temperature of the refrigerating compartment 3 detected by the refrigerating temperature sensor 21 exceeds 5 ° C., the motor damper 20 is controlled to the open position, and when the temperature falls below 3 ° C., the motor damper 20 is controlled to the closed position.

(3) The operating time of the compressor 23 is integrated, and when the integrated operating time reaches a predetermined time, the defrosting heater 16 is energized to basically heat the cooler 15. To run.

(4) When the forced operation button 12 is turned on,
The compressor 23 is forcibly driven to execute the forced operation until a certain time (for example, 90 minutes) elapses or the forced operation button 12 is turned on again, and the monitor lamp 13 is turned on during the forced operation.

(5) When the predetermined condition is satisfied at the defrosting start timing in (3) above, an extension operation is carried out to advance the defrosting start timing by a fixed time.

Next, the operation of the above configuration will be described. FIG. 1 shows a flowchart of the operation of the control device 11. In this case, FIG. 1 shows only the control related to the present invention, and the normal refrigerator cooling control (compressor and damper control) regarding the above (1) to (4) is omitted. That is,
In FIG. 3, the control device 11 first clears the door open flag and the forced operation flag (step S1), and then clears the integration timer (step S2). Then, in the normal cooling control (not shown), when it is determined that the door is opened based on the door switches 8 to 10, the door open flag is set (step S3), and the forced operation button 12 is pressed to perform the forced operation. When executed, set the forced operation flag. Further, while the compressor 23 is on, the integration timer is driven (steps S7, S
8) During the off period, the operation timer of the compressor 23 is calculated by stopping the integration timer (steps S7 and S9). Then, when the integrated timer value reaches, for example, 10 hours (step S10), it is determined that the defrosting start timing has come, and the first extension operation of advancing the defrosting start timing by a certain time is executed by the following control. Determine whether or not.

When the door open flag is in the reset state during the normal cooling control, that is, the doors 5 to 7 are kept closed, the amount of frost deposited on the cooler 15 is small and the defrosting operation is postponed. However, it does not cause any trouble. However,
When the doors 5 to 7 are opened, a large amount of outside air enters the refrigerator and a large amount of frost adheres to the cooler 15.
In this case, the postponement of the defrosting operation will be hindered. Similarly, when the forced operation is executed during the normal cooling control, the amount of heat exchange in the cooler 15 increases and the frost deposition rate increases, so that the defrosting operation is postponed.

Therefore, in the control device 11, the integration timer is set to 1
When 0 hours has elapsed, it is determined whether the door open flag or the forced operation flag is set (step S
11) If any of the flags is set, it is determined that a condition that requires the defrosting operation has occurred, the flag is cleared, and then the defrosting operation is executed (steps S23 and S24). ).

If neither flag is set, the outside air temperature is estimated based on the temperature detected by a temperature sensor (not shown), and the estimated outside air temperature is within a predetermined temperature range (for example, 20 ° C to 30 ° C). It is determined whether or not (step S12). At this time, when the estimated outside air temperature is out of the predetermined temperature range, the flag is cleared and then the defrosting operation is executed (steps S23 and S24) (see FIG. 3). This is because when the outside air temperature is lower than the predetermined temperature range, the operation rate of the refrigerator is reduced and defrosting is not performed for a long period of time, so when food containing a lot of water is stored, the cooler is used. This is because the frost adhering to 15 solidifies to form ice that is difficult to melt, the cooling performance deteriorates, and it is difficult to extend the defrosting operation. On the other hand, when the outside air temperature is higher than the predetermined temperature range, the operating rate of the compressor 23 increases, the amount of heat exchange (cooling amount) in the cooler 15 increases, and frost easily adheres to the cooler 15. Even in this case, extending the defrosting operation causes a trouble.

Here, the estimation of the outside air temperature as described above is performed as follows.
The temperature can be obtained based on a temperature sensor (not shown) provided in the control device 11 and the temperature of the storage space in which the control device 11 is stored and the outside air temperature that has been examined in advance. In other words, the temperature of such a storage space is affected by the outside air temperature and relatively fluctuates.

Now, in the normal cooling control, the doors 5 to 7
When the closed state and the non-operating state of the forced operation button 12 continue and the estimated outside air temperature is within the predetermined temperature range,
The control device 11 determines that the defrosting operation is not necessary, clears the counter, and starts the real-time timer (steps S13 and S14), and then a predetermined time (for example, 10).
The first extension operation is executed by continuing the cooling operation for 0 minutes (step S19).

During execution of the first extension operation, the control device 11 sets the door open flag when the doors 5 to 7 are opened (steps S15 and S16), and the forced operation button 12 is pressed. At this time, the forced operation flag is set (steps S17 and S18). When the first extension operation is finished, the defrosting start timing is reached.
The control device 11 determines whether or not either the door open flag or the forced operation flag is set (step S
20) If the flag is set, it is determined that the condition that requires the defrosting operation has occurred, and the defrosting operation is executed (step S24). Here, the outside air temperature is not estimated at the defrosting start timing at the end of the first extension operation. This is because the room temperature cannot change suddenly by several tens of degrees Celsius in a general household environment, so it is sufficient to estimate the outside air temperature at the first defrosting start timing after the defrosting operation ends. .

Then, when the defrosting condition is not satisfied at the defrosting start timing at the end of the first extension operation, the control device 11 advances the defrosting start timing by a predetermined time (100 minutes) to the second extension. While performing the operation, when the defrosting condition is not satisfied at the defrosting start timing at the end of the second extension operation, such a second extension operation is repeatedly performed (step S2).
2). At this time, when the control device 11 determines that the defrosting operation is necessary based on the door open flag and the forced operation flag at the defrosting start timing at the end of the second extension operation (step S20), the defrosting operation is performed. Is executed (see FIG. 4).

Now, the control device 11 repeats the second extension operation, and when the counter value, that is, the second extension operation has reached the specified number of times (steps S21 and S2).
2) Then, it is determined that the defrosting condition is satisfied, and the defrosting operation is executed (see FIG. 5). In this case, as the prescribed number of times of the second extension operation, when the refrigerator is left in the closed state of the doors 5 to 7 and the non-execution state of the forced operation, the maximum effect is obtained in both cooling performance and power saving. It can be obtained from the defrosting operation interval that can be exhibited. That is, when the defrosting operation interval is set to, for example, 24 hours, the accumulated operation time of the compressor 23 during the normal cooling operation is 10
It is possible to set the defrosting operation interval to 24 hours or more by executing the extension operation time of 100 minutes each subsequent time three times (the first extension operation once and the second extension operation twice). Therefore, the prescribed number of executions of the second extension operation in this case is two. Further, in order to convert the accumulated operation time of the compressor 23 into a real time, the accumulated operation time of 10 hours is calculated from the operation rate of the compressor 23 under the condition that the outside air temperature is 20 ° C. to 30 ° C., which is the condition for forwarding the defrosting start timing. The real time corresponding to can be calculated.

In this embodiment, whether or not to defer the defrosting start timing is made at the end of the extension operation. This is because in a configuration in which the doors 5 to 7 are opened during the extension operation or the defrosting operation is immediately performed by operating the forced operation button 12, the doors 5 to 7 are opened to cool and store food during the extension operation. Then, the defrosting operation is immediately performed, and unless the defrosting operation is completed, the food cannot be cooled and stored. Similarly, if the forced operation button 12 is operated in an attempt to execute the forced operation during the extension operation, the defrosting operation is immediately executed, and the forced operation cannot be executed.

Further, in this embodiment, the flag used for determining whether to defer the defrosting start timing at the end of the extension operation is cleared at the time of executing the defrosting operation. This is because when the doors 5 to 7 are opened and food is taken in and out during the defrosting operation, a large amount of air containing moisture flows into the refrigerator and a large amount of frost is accumulated in the cooler 15 in the subsequent cooling operation. This is because it is necessary to check the opening and closing of the doors 5 to 7 even during defrosting because there is a risk that they will adhere to the.

According to the above configuration, when the condition that does not require the defrosting operation of the cooler 15 continues until the preset defrosting start timing, the defrosting start timing is advanced by a predetermined time. When the operation is performed and the condition that does not require the defrosting operation continues until the defrosting start timing at the end of the extension operation, the second extension operation that further executes the extension operation up to the specified number of times is executed. Therefore, when the condition that does not require the defrosting operation continues, power saving can be achieved by delaying the defrosting operation with large power consumption as much as possible, and the condition that requires the defrosting operation occurs once. If so, the defrosting operation can be executed at the end timing of the normal cooling operation or the extension operation, so that the cooling performance of the cooler 15 can be maintained. Therefore, unlike the conventional example in which the defrosting operation is performed when a predetermined time has passed from the previous defrosting operation or when the accumulated operation time of the compressor reaches a predetermined value, the defrosting operation should be executed at an appropriate timing. Can improve energy efficiency. Further, unlike the one that estimates the defrosting start timing, the control device 11 is not required to have a high-speed calculation function and a high calculation accuracy function as a function of the control device 11.
Is not complicated and expensive.

As a concrete numerical value of the power saving effect according to the present embodiment, in the case of a refrigerator of 400 liter class, if the defrosting interval is set to 24 hours or more in real time, it is 2 per month.
The amount of electric power of KW is reduced, and when the defrosting interval is set to 72 hours or more in real time, the amount of electric power of 4 to 5 KW can be reduced per month.

FIG. 6 shows a flowchart of the control device 11 in the second embodiment of the present invention. The difference between the second embodiment and the first embodiment is that the forward feed time when the extension operation is executed is determined by the cumulative operating time of the compressor 23.

That is, when it is determined that the defrosting operation is not executed based on the flag when the defrosting timing has come (steps S11 and S12), the control device 11 counts up the counter (step S13), When the count value is 1, it is determined that it is the defrosting start timing at the end of the normal cooling control operation, and it is determined whether to extend the defrosting start timing based on the estimated outside air temperature (steps S14 and S15). . When the count value is 2 or more, it is determined that it is the defrosting start timing at the end of the extension operation, and it is determined whether the defrosting start timing is extended by only the door open flag and the forced operation flag. (Steps S14 and S16). In this case, step S1
The constant value for comparison with the integration timer value at 1 is set to different values when the counter is 0 (normal cooling control) and when the counter is 1 or more (extension operation). That is, when the counter is 0, the fixed value is 10 hours, and when the counter is 1 or more, it is 100 minutes.

With such a configuration, the operation of the integration timer of the compressor 23 and the defrosting condition necessary for determining whether to defer the defrosting start timing at the defrosting start timing at the end of execution of the extension operation Since the determination can be combined with the normal cooling control, the configuration of the control device 11 can be simplified and the development period can be shortened and the cost can be reduced while achieving the same effects as the first embodiment. be able to.

FIG. 7 shows a flow chart of the control device in the third embodiment of the present invention. The third embodiment is different from the first embodiment in that when the forced operation is executed during the extension operation, the time counting of the extension operation is interrupted during the forced operation (step S17, S
18, S19, S20).

With such a configuration, when the forced operation is executed during the extension operation, the end timing of the extension operation and the end timing of the forced operation can be shifted without fail as shown in FIG. It is possible to prevent the problem that the defrosting operation is immediately executed at the timing of ending the forced operation.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows.

The defrost control means may be composed of a device for executing a normal cooling operation, a device for performing the first extension operation, and a device for performing the second extension operation.

The door opening storage means may be constructed so that the temperature in the refrigerator fluctuates when the door is opened, and the temperature is estimated based on the fluctuation.

The outside air temperature determining means may be configured to estimate the outside air temperature based on the operating rate of the compressor 23 because the operating rate of the compressor 23 changes according to the outside air temperature.

[0055]

As is apparent from the above description, the defrosting device for a refrigerator according to the present invention has the following effects.

According to the first aspect of the present invention, the defrosting control means, when the preset defrosting start timing is reached and the condition that the defrosting operation is not required is established,
The first to defer the defrost start timing by a fixed time
When the extension operation is executed and the condition that does not require the defrosting operation is satisfied at the defrosting start timing at the end of the first extension operation, the defrosting start timing is further postponed by a certain period of time. Since the extension operation is executed a prescribed number of times, it is possible to defrost the cooler at an appropriate timing while achieving labor-saving operation with a simple configuration.

According to the second aspect of the present invention, when the condition that does not require defrosting is satisfied at the defrosting start timing at the end of the extension operation, the defrosting start timing is set to the integrated operating time of the compressor. Since it is postponed until the fixed time is reached, the defrosting start timing can be set accurately.

According to the third aspect of the present invention, since the outside air temperature determining means estimates the outside air temperature based on the operating rate of the compressor, a special temperature sensor for detecting the outside air temperature can be omitted. .

According to the fourth aspect, the outside air temperature determining means is based on the temperature detected by the temperature sensor for detecting the temperature of the predetermined storage space in which the defrost control device as the defrost control means is stored. Since the outside air temperature is estimated, it is not necessary to lead the lead wire of the temperature sensor for detecting the outside air temperature from the closed space.

According to the fifth aspect of the present invention, the defrost control means suspends the time measurement of the extension operation until the forced operation is completed when the forced operation is performed during the extension operation. It is possible to avoid the problem that the cooler that has been rapidly cooled by the forced operation is heated by the defrosting operation.

[Brief description of drawings]

FIG. 1 is a flowchart of a control device showing a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing an electrical configuration of a refrigerator.

FIG. 3 is a timing chart when the extension operation is not executed.

FIG. 4 is a diagram corresponding to FIG. 3 when the extension operation is executed twice.

FIG. 5 is a diagram corresponding to FIG. 3 when the extension operation is executed a prescribed number of times.

FIG. 6 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 7 is a view corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 8 is a timing chart when the extension operation is executed once.

FIG. 9 is a view corresponding to FIG. 1 showing a conventional example.

[Explanation of symbols]

2 is a freezing room, 3 is a refrigerating room, 4 is a vegetable room, 5 to 7 are doors, 8
10 is a door switch, 11 is a control device (defrost control means,
Door opening storage means, forced operation storage means, outside air temperature determination means), 12 is a forced operation button, 15 is a cooler, 21 is a refrigerating temperature sensor, and 23 is a compressor.

Claims (5)

[Claims] 1. A defrost control means for performing a defrosting operation of a cooler at a preset defrosting start timing, and a door opening for storing that a refrigerator door has been opened since at least a previous defrosting operation. Storage means, at least a forced operation storage means for storing that the forced continuous operation of the compressor for the cooler has been executed since the last defrosting operation, and an outside air temperature determination means for detecting or estimating the ambient temperature of the refrigerator The defrost control means, when the defrost start timing is reached, the door open storage means and the forced operation storage means are in a non-stored state, and the detected temperature or estimated temperature by the outside air temperature determination means is When the temperature is within the predetermined temperature range, the defrosting start timing is deferred for a fixed time, and the first extension operation is performed. When the door opening storage means and the forced operation storage means are in the non-memorized state during minging, the second extension operation for advancing the defrosting start timing by a predetermined time is executed a prescribed number of times. The defrosting device for the refrigerator, which is characterized in that 2. A defrost control means for executing a defrosting operation of a cooler at a preset defrosting start timing, and a door opening for storing that at least a refrigerator door has been opened since the last defrosting operation. Storage means, at least a forced operation storage means for storing that the forced continuous operation of the compressor for the cooler has been executed since the last defrosting operation, and an outside air temperature determination means for detecting or estimating the ambient temperature of the refrigerator The defrost control means, when the defrost start timing is reached, the door open storage means and the forced operation storage means are in a non-stored state, and the detected temperature or estimated temperature by the outside air temperature determination means is When the temperature is within the predetermined temperature range, the first extension operation of advancing the defrosting start timing until the accumulated operating time of the compressor reaches a certain time is performed. When the door opening storage means and the forced operation storage means are in a non-memorized state at the defrosting start timing at the end of the first extension operation, the defrosting start timing is further set to the constant operating time of the compressor. A defrosting device for a refrigerator, characterized in that the defrosting device is configured to perform a second extension operation that is postponed until the time is reached a specified number of times. 3. The defroster for a refrigerator according to claim 1, wherein the outside air temperature determination means is configured to estimate the outside air temperature based on the operating rate of the compressor. 4. The defrost control means is composed of a defrost control device that executes an extension operation to postpone the defrost start timing, and controls the temperature of a predetermined storage space in which the defrost control device is stored. The defrosting device for a refrigerator according to claim 1 or 2, further comprising: a temperature sensor for detecting, wherein the outside air temperature determining means is configured to estimate the outside air temperature based on the temperature detected by the temperature sensor. . 5. The defrosting control means is configured to, when a forced operation is performed during execution of the extended operation, suspend time measurement of the extended operation until the forced operation is completed. The defrosting device for a refrigerator according to claim 1 or 2.