JP2018091494A - Controller of cooling box, cooling box and control method of cooling box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller of a cooling box capable of preventing liquid from backflowing, with change of an in-box temperature suppressed, and also provide a cooling box and a control method of a cooling box.SOLUTION: By executing overheating degree control based on an overheating degree SH detected by overheating degree detection means 7, change of the overheating degree SH can be quickly sensed, thereby preventing liquid from backflowing. In the overheating degree control, using an in-box temperature Tr detected during execution of in-box temperature control and a target overheating degree SH1 acquired based on the overheating degree SH, the in-box temperature Tr can be kept close to a target temperature Ts even in control based on the overheating degree SH, thereby suppressing change of the in-box temperature Tr.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a refrigerator control device, a refrigerator, and a refrigerator control method. An example of the refrigerator is a showcase.

  Generally, a refrigerator such as a refrigerated showcase or a refrigerated showcase includes an expansion valve that lowers the pressure of the refrigerant condensed in the condenser, and an evaporator that changes the state of the refrigerant from a liquid to a gas. The opening degree of the expansion valve is controlled so that the set temperature is reached.

  As a method for controlling the opening degree of the expansion valve in this way, the degree of superheat of the evaporator and the temperature inside the refrigerator are detected, and at the time of pull-down cooling (cooling after defrosting or cooling from room temperature) Has proposed a method of controlling the valve opening based on the degree of superheat and controlling the valve opening based on the internal temperature during constant temperature cooling (see, for example, Patent Document 1). In the method described in Patent Document 1, cooling is quickly performed by control based on the degree of superheat during pull-down cooling, and then the interior temperature is kept constant by control based on the interior temperature.

Japanese Patent Laid-Open No. 2006-80304

  However, the control method described in Patent Document 1 may not be able to appropriately cope with the case where the degree of superheat varies during constant temperature cooling. In other words, there is a time lag from when the degree of superheat changes until the inside temperature changes, and if the valve opening is controlled based on the inside temperature, the inside temperature changes after the degree of superheat changes. In such a case, there is a possibility that the degree of superheat changes greatly before the valve opening is adjusted according to the internal temperature. In a state where the degree of superheat is too small, excessive refrigerant is supplied to the evaporator, which may cause liquid back.

  Therefore, in order to suppress the liquid back, a method of suppressing the liquid back by monitoring the degree of superheat while carrying out constant temperature control of the interior, and reducing the valve opening when the degree of superheat becomes too small. Can be considered. However, in such a method, when the valve opening is reduced in order to suppress the liquid back, the inside temperature temporarily increases.

  An object of the present invention is to provide a cooler control device, a cooler, and a cooler control method capable of making liquid back difficult to occur while suppressing a change in the internal temperature and controlling more stably. There is.

  The control apparatus for the refrigerator of the present invention includes an expansion valve that reduces the pressure of the refrigerant condensed in the condenser, an evaporator that changes the state of the refrigerant from a liquid to a gas, and a superheat degree that detects the superheat degree of the evaporator. In the refrigerator provided with the detection means and the internal temperature detection means for detecting the internal temperature, it is a control device for the cooler that controls the valve opening degree of the expansion valve, and the valve opening control method Switching means for switching between, and acquisition means for acquiring the target superheat degree of the evaporator, the internal temperature becomes a predetermined target temperature based on the internal temperature detected by the internal temperature detection means In this way, the internal temperature control for controlling the valve opening is performed, and the internal temperature detected by the internal temperature detection means during the execution of the internal temperature control, and the superheat detected by the superheat degree detection means Based on the relationship between the degree and the acquisition means. Gets the target degree of superheat Te, then by the switching means, the degree of superheat, characterized in that the switching in the practice of the superheat degree control for controlling the valve opening so that the target degree of superheat.

  According to the present invention as described above, by performing superheat degree control based on the detected superheat degree, it is possible to quickly cope with a change in the superheat degree, and to make it difficult for liquid back to occur. In such superheat control, the value obtained based on the relationship between the internal temperature detected during the execution of the internal temperature control and the superheat degree is used as the target superheat degree. However, the internal temperature can be easily maintained in the vicinity of the target temperature, and the change in the internal temperature can be suppressed and more stable control can be performed. In addition, what is necessary is just to acquire target superheat degree at the appropriate timing in internal temperature control. For example, as will be described later, the target superheat degree may be acquired after the internal temperature becomes stable, or the internal temperature and superheat degree change pattern in the internal temperature control before the internal temperature is stabilized. Based on the above, it is possible to estimate the degree of superheat such that the internal temperature stabilizes near the target temperature, and obtain this degree of superheat as the target degree of superheat.

  At this time, the control device for the refrigerator of the present invention further includes a determination unit that determines whether or not the internal temperature is in a stable state, and that the internal temperature has been stabilized by the determination unit. After the determination, it is preferable to acquire the target superheat degree by the acquisition means.

  According to such a configuration, the target superheat degree is acquired after determining that the internal temperature is in a stable state. That is, an appropriate target superheat degree can be obtained by acquiring the target superheat degree after the inside temperature is stabilized near the target temperature. Therefore, it is possible to easily keep the internal temperature near the target temperature during superheat control. Note that whether or not the internal temperature has become stable may be determined based on, for example, whether the maximum value of the difference between the internal temperature and the target temperature in a predetermined time range is smaller than a predetermined value. Alternatively, the determination may be made based on the elapsed time from the start of the internal temperature control, or may be determined by combining the evaluation of the maximum value of the temperature difference and the evaluation of the elapsed time.

  Moreover, in the control apparatus for the refrigerator of the present invention, the acquisition unit sets the degree of superheat in a predetermined time range before the time when the determination unit determines that the internal temperature has become stable as the target degree of superheat. It is preferable to acquire the internal temperature stable superheat degree based on. According to such a configuration, the internal temperature stable superheat degree based on the superheat degree in a predetermined time range (for example, the average value of the superheat degree in this time range) is set as the target superheat degree, and the overheat detected at a temporary point is detected. Compared with the configuration in which the degree is the target superheat degree, the influence of the detection error can be reduced and the target superheat degree can be made more appropriate.

  Moreover, in the control apparatus for a refrigerator according to the present invention, the acquisition unit is an internal temperature stable overheat that is a degree of superheat when the determination unit determines that the internal temperature is in a stable state as the target superheat degree. You may get the degree. According to such a configuration, it is not necessary to calculate an average value or the like as compared with the configuration in which the target superheat degree is acquired based on the superheat degree in a predetermined time range as described above, and the target superheat degree can be easily obtained. Can be acquired.

  Further, the refrigerator of the present invention includes an expansion valve that reduces the pressure of the refrigerant condensed in the condenser, an evaporator that changes the state of the refrigerant from liquid to gas, and superheat detection that detects the superheat of the evaporator. It is characterized by comprising a means, an internal temperature detecting means for detecting the internal temperature, and the control device for the cooling compartment described above.

  According to the present invention as described above, it is possible to prevent the occurrence of liquid back while suppressing the change in the internal temperature as described above and performing more stable control.

  Further, the control method of the refrigerator of the present invention includes an expansion valve for reducing the pressure of the refrigerant condensed in the condenser, an evaporator for changing the state of the refrigerant from a liquid to a gas, and detecting the degree of superheat of the evaporator. In a refrigerator having a superheat degree detection means and an internal temperature detection means for detecting an internal temperature, a control method of the refrigerator for controlling the valve opening degree of the expansion valve, the internal temperature detection Based on the internal temperature detected by the means, the internal temperature control is performed to control the valve opening degree so that the internal temperature becomes a predetermined target temperature, and during the execution of the internal temperature control, The target superheat degree is acquired based on the relationship between the internal temperature detected by the internal temperature detection means and the superheat degree detected by the superheat degree detection means, and then the superheat degree becomes the target superheat degree. In order to control the degree of valve opening, And wherein the frog.

  According to the present invention as described above, it is possible to prevent the occurrence of liquid back while suppressing the change in the internal temperature as described above and performing more stable control.

  According to the cooler control device of the present invention, after acquiring the target superheat degree based on the relationship between the internal temperature detected during the execution of the internal temperature control and the superheat degree, switching to the superheat degree control is performed. Thus, it is possible to make it difficult for the liquid back to occur while suppressing the change in the internal temperature and performing more stable control.

It is sectional drawing which shows the refrigerator which concerns on embodiment of this invention. It is a flowchart which shows an example of the cooling process which the control apparatus of the said cooler performs. It is a graph which shows an example of the change of the internal temperature when the said control apparatus performs the said cooling process.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The refrigerator 1 according to the present embodiment is a showcase that is installed in a store such as a supermarket or a convenience store and that stores refrigerated or frozen foods such as fresh foods. As shown in FIG. , A defrosting heater 3, a refrigeration cycle internal unit 4, a fan 5, a control device 6, a superheat degree detection means 7, and an internal temperature detection means 8.

  The case main body 2 forms an accommodation space 2A for accommodating a product. The case body 2 includes a display shelf 21 provided in the accommodation space 2 </ b> A on which products are placed, and an electrical box 22 that accommodates the control device 6. In the present embodiment, the electrical box 22 is provided on the lower side of the accommodation space 2A, but the electrical box may be provided on the upper side of the accommodation space. An interior lamp for illuminating the accommodation space 2 </ b> A is provided on the lower surface of the display shelf 21.

  The internal unit 4 includes a pipe 41 through which a refrigerant flows, an expansion valve 42 provided in the pipe 41, and an evaporator 43, and is connected to an outdoor refrigerator. The refrigerant that has been condensed into a liquid by the condenser of the outdoor refrigerator is reduced in pressure by being reduced in pressure by the expansion valve 42, and the state of the low-temperature and liquid refrigerant is changed to a gas by the evaporator 43. . By sending the air in the accommodation space 2 </ b> A toward the evaporator 43 by the fan 5, the air is cooled by the evaporator 43. The air returns to the accommodation space 2A again, whereby the accommodation space 2A is cooled. The refrigerant that has passed through the evaporator 43 flows into the outdoor refrigerator, is condensed again, and is sent to the internal unit 4.

  In such an in-compartment unit 4, by adjusting the valve opening degree of the expansion valve 42, the amount of refrigerant flowing into the evaporator 43 increases or decreases, and the cooling capacity changes. That is, by increasing the valve opening, the storage space 2A is further cooled and the internal temperature is lowered, and by reducing the valve opening, the storage space 2A is hardly cooled and the internal temperature is increased.

  The showcase 1 of the present embodiment is a so-called separate type showcase in which the compressor and the condenser of the refrigeration cycle are installed outside (outdoors etc.), but the compressor and the condenser are built in. A so-called built-in showcase may be used.

  The control device 6 receives signals from the superheat degree detection means 7 and the internal temperature detection means 8 and controls the valve opening of the expansion valve 42 as will be described later, and includes an acquisition means, a switching means, And determination means. The control device 6 includes a control unit such as a CPU (Central Processing Unit) and a storage unit, and the control unit may function as an acquisition unit, a switching unit, and a determination unit. Further, the control means 6 may control not only the expansion valve 42 but also other control objects such as the defrost heater 3, the fan 5, and the interior lamp.

  The superheat degree detection means 7 detects the superheat degree of the evaporator 43, and includes an inlet pipe temperature sensor 71 that detects the refrigerant temperature (evaporation temperature) on the inlet side of the evaporator 43, and an outlet of the evaporator 43. And an outlet pipe temperature sensor 72 for detecting the refrigerant temperature (return pipe temperature) on the side. By subtracting the evaporation temperature from the return pipe temperature, the degree of superheat of the evaporator 43 is calculated. The superheat degree detecting means may detect the superheat degree based on the pressure of the refrigerant. That is, instead of the inlet pipe temperature sensor 71, a pressure sensor that detects the pressure of the refrigerant may be provided, and the degree of superheat of the evaporator 43 may be calculated using the value obtained by converting the detected low-pressure pressure as a saturation temperature as the evaporation temperature. The superheat degree detection means 7 transmits the detected superheat degree to the control device 6 as a signal.

  The internal temperature detection means 8 detects the internal temperature (temperature of the accommodating space 2A), and is provided at the outlet 23 to the accommodating space 2A in the case body 2 to detect the outlet temperature. The sensor 81 and the suction port temperature sensor 82 that is provided in the suction port 24 from the accommodation space 2A to the evaporator 43 side in the case body 2 and detects the suction temperature are configured. For example, the average temperature of the blowing temperature and the suction temperature may be set as the internal temperature. Note that the internal temperature may be calculated by adding an offset to one of the blowing temperature and the suction temperature according to the shape and size of the accommodation space 2A. Moreover, the inside temperature detection means may be configured by only one of the outlet temperature sensor and the inlet temperature sensor. The internal temperature detection means 8 transmits the detected internal temperature to the control device 6 as a signal.

  Here, an example of a method for adjusting the internal temperature by controlling the valve opening degree of the expansion valve 42 by the control unit of the control device 6 will be described. In the following, the control unit of the control device 6 performs feedback control for a predetermined parameter, but at this time, for example, appropriate control such as PID control may be performed.

  When the cooling is started after the defrosting by the defrosting heater 3 or when the inside temperature is at room temperature, the control unit of the control device 6 starts the cooling process as shown in the flowchart of FIG. In the cooling process, the control unit of the control device 6 first opens the expansion valve 42 at a predetermined valve opening for a predetermined time (step S1). The valve opening degree at this time should just be more than predetermined value, and may be 100% and may be less than 100%. When the predetermined time has elapsed, the control unit of the control device 6 controls the valve opening based on the superheat degree SH detected by the superheat degree detection means 7 (step S2). That is, the valve opening degree is controlled so that the superheat degree SH becomes the pull-down superheat degree SH0. As a result, the internal temperature is rapidly lowered so that the evaporator 43 is efficiently cooled.

  The control unit of the control device 6 determines whether or not the internal temperature Tr detected by the internal temperature detection means 8 has become equal to or lower than the target temperature Ts (step S3). The target temperature Ts is a set temperature of the internal temperature, and a predetermined numerical value may be stored in the control device 6 or may be input by the user. The control unit of the control device 6 performs pull-down cooling in such steps S1 to S3.

  When the internal temperature Tr becomes equal to or lower than the target temperature Ts (Y in step S3), the control unit of the control device 6 sets the internal temperature Tr to the target based on the internal temperature Tr detected by the internal temperature detection means 8. The internal temperature control for controlling the valve opening so as to be the temperature Ts is performed (step S4). On the other hand, when the internal temperature Tr is higher than the target temperature Ts (N in step S3), the control unit of the control device 6 returns to step S2 and continues the control based on the degree of superheat, and the internal temperature again in step S3. Judge about Tr.

  After step S4, the control unit of the control device 6 determines whether or not the internal temperature Tr is in a stable state (step S5). That is, the control unit of the control device 6 functions as a determination unit. Specifically, the maximum value of the difference between the internal temperature and the target temperature in the predetermined time range is stored in the storage unit, and when the maximum value is smaller than the predetermined value, the internal temperature Tr is in a stable state. If it is less than a predetermined value, it is determined that the stable state has not been reached. It should be noted that the internal temperature Tr may be determined to be stable when a predetermined time has elapsed since the internal temperature control was started. Further, when the maximum value of the difference between the internal temperature and the target temperature in the predetermined time range is smaller than the predetermined value and the predetermined time has elapsed since the internal temperature control was started, the internal temperature Tr May be determined to be in a stable state.

  When the internal temperature Tr is in a stable state (Y in Step S5), the control unit of the control device 6 acquires the target superheat degree SH1 (Step S6). That is, the control unit of the control device 6 functions as an acquisition unit. At this time, the average value of the superheat degree SH in a predetermined time range before the time when it is determined that the internal temperature Tr is in a stable state is set as the internal stable superheat degree, and the internal stable superheat degree is acquired as the target superheat degree SH1. To do. Note that the degree of superheat SH at the time when it is determined that the internal temperature Tr is in a stable state may be used as the internal stable superheat degree, and this internal stable superheat degree may be acquired as the target superheat degree SH1. On the other hand, when the internal temperature Tr is not in a stable state, the control device 6 returns to step S4 and continues the internal temperature control, and again determines the internal temperature Tr in step S5.

  After step S6, the control unit of the control device 6 performs superheat degree control for controlling the valve opening degree so that the superheat degree SH becomes the target superheat degree SH1 based on the superheat degree SH detected by the superheat degree detection means 7. (Step S7). That is, the control unit of the control device 6 switches the valve opening control method from the internal temperature control to the superheat degree control, and functions as a switching means.

  After step S7, the control device 6 determines whether or not it is necessary to reset the target superheat degree SH1 (step S8). For example, when a predetermined time has elapsed since the start of superheat control, or when the difference between the internal temperature Tr and the target temperature Ts exceeds a predetermined value, the target superheat SH1 needs to be reset. What is necessary is just to determine that there exists. When it is necessary to reset the target superheat degree SH1 (Y in step S8), the control device 6 returns to step S4 and performs the internal temperature control. On the other hand, when the resetting of the target superheat degree SH1 is unnecessary (N in step S8), the control device 6 returns to step S7 and continues the superheat degree control, and the resetting of the target superheat degree SH1 again in step S8. judge. The controller of the control device 6 performs constant temperature cooling in such steps S4 to S8.

  In the above cooling process, the internal temperature control is performed to reset the target superheat degree SH1, but the target superheat degree SH1 may be corrected while continuing the superheat degree control. That is, when the internal temperature Tr is higher than the target temperature Ts, the target superheat degree SH1 is reduced according to the temperature difference, and when the internal temperature Tr is lower than the target temperature Ts, these temperatures are set. What is necessary is just to enlarge target superheat degree SH1 according to a difference. Further, when the temperature difference between the internal temperature Tr and the target temperature Ts is larger than the first threshold value and smaller than the second threshold value, the target superheat degree SH1 is corrected while continuing the superheat degree control. When the temperature difference between the internal temperature Tr and the target temperature Ts is larger than the second threshold, the internal temperature control may be performed to reset the target superheat degree SH1.

  An example of the temporal change of the internal temperature, the degree of superheat, and the valve opening when the control device 6 performs the cooling process as described above will be described with reference to FIG. In FIG. 3, the change of each parameter when the control of the present embodiment is performed is shown by a solid line, and when the control of the prior art is performed (after the control based on the degree of superheat during pull-down cooling, the internal temperature control is performed). The change of each parameter in the case of (when performed) is indicated by a broken line.

  The start time of the cooling process of the present embodiment (that is, when pull-down cooling starts) is set to t0. First, the valve opening is set to 100%, and the superheat control is started when a predetermined time has elapsed. When the degree of superheat begins to decrease, the valve opening is reduced accordingly, and cooling is performed until the internal temperature Tr reaches the target temperature Ts. A time point when the internal temperature Tr becomes equal to the target temperature Ts is defined as t1. The period t0 to t1 corresponds to the control in step S2. The valve opening at the start of cooling does not have to be 100%, and may be opened at a predetermined valve opening or more.

  Next, the inside temperature control is performed, and it waits until the inside temperature Tr becomes a stable state. A time point when the internal temperature Tr is in a stable state is defined as t2. The period t1 to t2 corresponds to the control in step S4. An average value of the superheat degree SH in a predetermined time range before the time point t2 is set as the target superheat degree SH1.

  Next, superheat degree control is implemented. The time after time t2 corresponds to step S7. Note that step S8 is omitted in the graph of FIG.

  In the control of this embodiment, since the superheat control is performed after time t2, even if the superheat SH is about to change due to some factor, the superheat SH is kept substantially constant by adjusting the valve opening. Be drunk. Further, since the target superheat degree SH1 corresponds to the target temperature Ts, by controlling the valve opening so that the superheat degree SH becomes the target superheat degree SH1, the internal temperature Tr becomes close to the target temperature Ts. Kept.

  In the control of the prior art, as in the control of the present embodiment, the control based on the superheat degree SH is performed in the period t0 to t1, and the internal temperature control is performed in the period t1 to t2, but after the time t2 Unlike the control of this embodiment, the internal temperature control is continued.

  In such conventional control, it is assumed that the degree of superheat SH starts to decrease from time t3. There is a time lag from when the superheat degree SH starts to decrease until the internal temperature Tr starts to decrease (time point t4). Since the internal temperature control is performed, the valve opening is decreased from time t4 in order to keep the internal temperature Tr constant. As the valve opening is reduced in this way, the superheat degree SH increases and exceeds the value corresponding to the target superheat degree SH1 (time point t5). Although the internal temperature Tr tends to increase after the time t5 and the valve opening degree is increased to prevent this, the internal temperature Tr may not be prevented from increasing.

  Since the internal temperature Tr changes after the change in the degree of superheat SH, when the control based on the internal temperature is performed, it is necessary to repeatedly increase and decrease the valve opening until the internal temperature Tr becomes stable. Further, in the control based on the internal temperature, it is difficult to keep the degree of superheat that changes before the internal temperature Tr constant.

  According to this embodiment, there are the following effects. That is, by performing the superheat degree control based on the superheat degree SH detected by the superheat degree detection means 7, it is possible to quickly cope with a change in the superheat degree SH and to prevent the occurrence of liquid back. In such superheat degree control, even when the control is based on the superheat degree SH by using the target superheat degree SH1 acquired based on the internal temperature Tr and the superheat degree SH detected during the execution of the internal temperature control. The inside temperature Tr can be easily maintained in the vicinity of the target temperature Ts, and the change in the inside temperature Tr can be suppressed.

  In addition, this invention is not limited to the said embodiment, Including other structures etc. which can achieve the objective of this invention, the deformation | transformation etc. which are shown below are also contained in this invention.

  For example, in the above-described embodiment, the target superheat degree SH1 is acquired after the internal temperature Tr becomes stable, but the target superheat degree SH1 is based on the relationship between the detected internal temperature Tr and the superheat degree SH. The target superheat degree SH1 may be acquired before the internal temperature Tr becomes stable. For example, based on the temporal change pattern of the internal temperature Tr and the superheat degree SH during the execution of the internal temperature control, the superheat degree SH is estimated such that the internal temperature Tr is stabilized near the target temperature Ts. May be acquired as the target superheat degree SH1.

  Moreover, in the said embodiment, it is judged whether the reset of target superheat degree SH1 is required based on the elapsed time after starting superheat degree control, and the difference of internal temperature Tr and target temperature Ts. However, the target superheat degree SH1 may be reset when the setting of the refrigerator is changed. In the refrigerator, for example, the set value of the low pressure of the refrigerant may be changed according to various purposes such as seasonal setting, demand control, energy saving, etc. At this time, the evaporation temperature changes and the internal temperature Tr becomes stable The degree of superheat (stable superheat degree in the cabinet) that changes to the state changes.

  In such a case, it is possible to determine whether or not the setting of the refrigerator has been changed by detecting the evaporation temperature using the inlet pipe temperature sensor 71 or the pressure sensor. Regardless of the elapsed time from the start of superheat control or the difference between the internal temperature Tr and the target temperature Ts, if it is determined that the setting of the cooling chamber has been changed, the target superheat SH1 is reset. A change in the setting of the refrigerator can be quickly handled, and the responsiveness can be improved.

  Further, when the setting of the refrigerator is changed and the target superheat degree SH1 is reset, it may be reset based on the past history without waiting for the in-chamber temperature Tr to be in a stable state. In other words, the relationship between the degree of stable superheat in the storage when the storage temperature Tr actually becomes stable and the evaporation temperature at that time is stored, and the setting of the cooling store is changed to change the evaporation temperature. In this case, the internal stable superheat degree corresponding to the changed evaporation temperature may be read out and used as the target superheat degree SH1. In this way, if the target superheat degree SH1 is reset without waiting for the in-chamber temperature Tr to be in a stable state, a change in the setting of the cooler can be handled promptly.

  In addition, the best configuration, method and the like for carrying out the present invention have been disclosed in the above description, but the present invention is not limited to this. That is, although the present invention has been illustrated and described primarily with respect to particular embodiments, control over the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in the methods and procedures, quantities, and other detailed configurations. Therefore, the description limiting the control method and procedure disclosed above is exemplary for easy understanding of the present invention, and does not limit the present invention. Descriptions excluding some or all of the limitations of the procedure and the like are included in the present invention.

1 Showcase (cooling room)
42 Expansion valve 43 Evaporator 6 Control device 7 Superheat degree detection means 8 Internal temperature detection means

Claims (6)

An expansion valve that lowers the pressure of the refrigerant condensed in the condenser, an evaporator that changes the state of the refrigerant from a liquid to a gas, a superheat detection means that detects the degree of superheat of the evaporator, and an internal temperature In a refrigerator having a chamber temperature detection means, a control device for the refrigerator that controls the valve opening degree of the expansion valve,
Switching means for switching the valve opening control method;
Obtaining means for obtaining a target superheat degree of the evaporator,
Based on the internal temperature detected by the internal temperature detection means, the internal temperature control for controlling the valve opening so that the internal temperature becomes a predetermined target temperature,
During the execution of the internal temperature control, the acquisition means acquires the target superheat degree based on the relationship between the internal temperature detected by the internal temperature detection means and the superheat degree detected by the superheat degree detection means. And then
A control device for a refrigerator, wherein the switching means switches to performing superheat degree control for controlling the valve opening so that the superheat degree becomes the target superheat degree. A judgment means for judging whether or not the internal temperature is in a stable state;
The controller for a refrigerator according to claim 1, wherein the target superheat degree is acquired by the acquisition unit after the determination unit determines that the internal temperature is in a stable state.   The acquisition means acquires, as the target superheat degree, an internal temperature stable superheat degree based on the superheat degree in a predetermined time range before the time point when the determination means determines that the internal temperature has become stable. The control apparatus of the refrigerator of Claim 2 characterized by the above-mentioned.   The said acquisition means acquires the internal temperature stable superheat degree which is a superheat degree at the time of judging that the said internal temperature became the stable state by the said judgment means as the said target superheat degree. Control device for the refrigerator as described in 1.   An expansion valve that lowers the pressure of the refrigerant condensed in the condenser, an evaporator that changes the state of the refrigerant from a liquid to a gas, a superheat detection means that detects the degree of superheat of the evaporator, and an internal temperature A refrigerator comprising: the internal temperature detection means; and the refrigerator control device according to any one of claims 1 to 4. An expansion valve that lowers the pressure of the refrigerant condensed in the condenser, an evaporator that changes the state of the refrigerant from a liquid to a gas, a superheat detection means that detects the degree of superheat of the evaporator, and an internal temperature In the refrigerator having the internal temperature detection means, a control method of the refrigerator for controlling the valve opening degree of the expansion valve,
Based on the internal temperature detected by the internal temperature detection means, the internal temperature control for controlling the valve opening so that the internal temperature becomes a predetermined target temperature,
During the execution of the internal temperature control, a target superheat degree is acquired based on the relationship between the internal temperature detected by the internal temperature detection means and the superheat degree detected by the superheat degree detection means, and then
Switching to superheat degree control for controlling the valve opening degree so that the superheat degree becomes the target superheat degree.

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