JP6180396B2 - Control device and control method for refrigerator - Google Patents

Description

  The present invention relates to a refrigerator control device capable of suppressing frost formation in an evaporator of a refrigerator and preventing a cooling capacity from being lowered in a refrigerator such as a freezer showcase or a refrigerated showcase installed in a store or the like, and It relates to a control method.

  For example, in stores such as supermarkets and convenience stores, showcases such as frozen showcases and refrigerated showcases for displaying products in a frozen or refrigerated state are used.

  As shown in FIG. 1, such a showcase 30 circulates in the showcase 30 by displaying a display shelf 32 for displaying commodities, a blow-out port 34 for blowing cool air to the display shelf, and sucking in air from the display shelf. And a suction port 36 having a fan 38 to be operated.

  In the showcase 30, a general refrigeration cycle is used, and the expansion of the pipe 12 through which the refrigerant flows and the liquid refrigerant provided on the pipe 12 and condensed by the condenser into low-temperature and low-pressure liquid refrigerant. A valve 14 and an evaporator 16 that absorbs and cools the heat of the circulating air by changing the state of the refrigerant from liquid to gas.

  When such a showcase is installed in a store, although not shown, the compressor compresses the gas refrigerant discharged from the evaporator into a high-temperature / high-pressure gas refrigerant, and is discharged from the compressor. A refrigerator equipped with a condenser that releases heat from a high-temperature and high-pressure gas refrigerant to form a liquid refrigerant is installed outdoors, and multiple showcases are connected to a single refrigerator. There are many. However, there may be a case where only one showcase is connected to one refrigerator.

  A showcase in which a refrigerator is separately installed outdoors is called a separate showcase. On the other hand, there is a showcase in which refrigerator parts such as a compressor and a condenser are integrated, and such a showcase is called a refrigerator built-in type showcase or a built-in type showcase.

  The cooler such as the showcase 30 has a control device 22, and the control device 22 provides illumination 26, a fan 38, a defrost heater 24, a dew-proof heater, and an expansion valve 14 (temperature control valve) included in the showcase. Etc. are controlled.

  When a mechanical expansion valve that automatically adjusts the degree of superheat with the temperature sensing cylinder and the pressure inside the pipe is used as the expansion valve 14 of the showcase 30, the liquid is supplied before the expansion valve 14 (on the refrigerator side). An electromagnetic valve is provided, and the controller 22 switches between thermo-on and thermo-off, and adjusts the internal temperature.

  Further, the control device 22 is provided with valve opening control output means for controlling the valve opening of the expansion valve 14, and a high durability electromagnetic valve or an electronic expansion valve is used as the expansion valve 14. Some are configured to control the valve opening.

  Even when a highly durable electromagnetic valve or an electronic expansion valve is used as the expansion valve 14, a liquid supply electromagnetic valve is provided in front of the expansion valve 14 (on the refrigerator side), and the liquid supply electromagnetic valve is controlled by the control device 22. The control device 22 adjusts the valve opening of the expansion valve 14 while the thermo-ON is on by controlling the degree of superheat or controlling the internal temperature at a constant temperature while switching the thermo-ON and thermo-OFF with However, when a highly durable solenoid valve or an electronic expansion valve having a valve closing function is used as the expansion valve 14, the expansion valve 14 performs the role of the supply solenoid valve, and the supply solenoid valve Is often omitted.

  The control device 22 serves as superheat degree detection means for detecting the superheat degree in the evaporator 16, an inlet pipe temperature sensor 18 for detecting the temperature of the refrigerant on the inlet side of the evaporator, and the temperature of the refrigerant on the outlet side of the evaporator. And an outlet pipe temperature sensor 20 for detecting the temperature of the outlet, and a temperature sensor 40 for detecting the temperature of the outlet 34 and a temperature of the inlet 36 as the temperature detecting means for detecting the inside temperature. A suction port temperature sensor.

  Note that the control device 22 uses both the outlet temperature detected by the outlet temperature sensor 40 and the inlet temperature detected by the inlet temperature sensor 42, and treats an intermediate temperature as the internal temperature. Alternatively, only one of the temperature sensors may be used, and a value obtained by adding an offset to the temperature detected by the temperature sensor may be handled as the internal temperature.

  Furthermore, using only one of the temperature sensors, the temperature detected by the outlet temperature sensor can be used as the inside temperature, or the temperature detected by the suction port temperature sensor can be used as the inside temperature. When the inside temperature is obtained using only one of these temperature sensors, it is not necessary to provide both the outlet temperature sensor and the inlet temperature sensor, only the temperature sensor on the side to be used is provided. Just do it.

  The showcase 30 configured as described above is disclosed in ON / OFF control for switching and controlling a thermo-on state in which the refrigerant flows through the evaporator 16 and a thermo-off state in which the refrigerant is not flown, and Patent Documents 1 and 2 and the like. Thus, the method of controlling the cooling capacity by adjusting the opening degree of the expansion valve 14 by the control device 22 and changing the flow rate of the refrigerant is used, and the inside temperature of the showcase 30 is adjusted.

  As a cooling control method for adjusting the valve opening degree of the expansion valve 14, a method of controlling based on the degree of superheat (superheat degree control) and a method of controlling based on the inside temperature (constant inside temperature control) are known. ing.

  Note that the superheat degree control and the constant internal temperature control are performed by PID control by a microcomputer mounted on the control device 22. Such PID control includes position type PID control and speed type PID control. In this specification, the case of speed type PID control will be described.

In the superheat degree control, the valve opening degree of the expansion valve 14 is adjusted so that the superheat degree approaches a predetermined superheat degree set value.
When superheat control is performed with speed-type PID control, the proportional component of the control output is an output that decreases the valve opening when the superheat is decreasing (the change in the superheat is negative). When the degree of superheat increases (the amount of change in the degree of superheat is positive), the output increases the valve opening.

  As the degree of superheat, a value obtained by subtracting the refrigerant temperature (evaporation temperature) on the inlet side of the evaporator 16 from the refrigerant temperature (return pipe temperature) on the outlet side of the evaporator 16 is used. The controller 22 is configured to calculate the detected evaporation temperature and the return pipe temperature detected by the outlet pipe temperature sensor 20.

  In the case where a pressure sensor (not shown) for detecting the pressure of the refrigerant in the pipe 12 is provided instead of the inlet pipe temperature sensor 18 so that the low pressure can be detected, the low pressure is set to the saturation temperature. The value obtained by subtracting the evaporation temperature from the return pipe temperature detected by the outlet pipe temperature sensor 20 can also be used as the degree of superheat, with the converted value as the evaporation temperature.

Further, in the constant chamber temperature control, the opening degree of the expansion valve 14 is adjusted so that the chamber temperature approaches a predetermined chamber temperature set value.
When the internal temperature constant control is also performed by speed-type PID control, as in the superheat control, the proportional component of the control output is when the internal temperature decreases (the amount of change in the internal temperature is negative). ), The valve opening is reduced, and when the internal temperature is increasing (the amount of change in the internal temperature is positive), the valve opening is increased.

  The control method used in the control device employs PID control using an electronic expansion valve or a high durability electromagnetic valve as in the cited document 1, but is not an electronic expansion valve or a high durability electromagnetic valve, but a mechanical type. In the control device attached to the cooler using the expansion valve, the internal temperature is adjusted by turning on / off the liquid supply electromagnetic valve attached on the upstream side of the mechanical expansion valve.

JP 59-185948 A JP 2008-209016 A

  By the way, there are two stages in cooling the inside of the showcase 30. One is when the cooling of the showcase is started for the first time or when the cooling is started after the defrosting is completed. Pull-down cooling that cools from a warmed state to the internal temperature setting value, and the other is constant temperature cooling that maintains the internal temperature at a predetermined temperature.

  In particular, the showcase 30 installed in a store or the like performs constant temperature cooling for a long time. At this time, since the refrigerant flows through the evaporator 16 and the evaporator 16 is at 0 ° C. or less, frost is generated when moisture in the atmosphere adheres to the evaporator 16.

  If frost adheres to the evaporator 16, it will lead to a decrease in cooling capacity. Further, since such frost continues to grow, the evaporator 16 will eventually be unable to vent, and the inside of the refrigerator cannot be cooled. The internal temperature may rise. When frost formation is severe, it may be necessary to stop cooling, take out the products arranged in the showcase, and manually remove the frost adhering to the evaporator 16.

  For this reason, the evaporator 16 is provided with a defrost heater 24 for removing the generated frost. By periodically turning on the power of the defrost heater 24, the frost is melted and defrosted (defrosted). )doing. Such defrosting is called heater defrost.

  On the other hand, in a showcase in which the evaporator 16 is not provided with the defrosting heater 24 and the set temperature is relatively high, defrosting (defrosting) is performed so that no refrigerant flows through the evaporator 16. Such defrosting is called off-cycle defrost.

  In the ON / OFF control that switches between the thermo-on state in which the refrigerant flows to the evaporator 16 and the thermo-off state in which the refrigerant is not flown, the internal temperature is controlled without flowing / flowing the refrigerant. The inside temperature fluctuates by the difference between the point and the OFF point (differential).

  On the other hand, the method of adjusting the internal temperature by PID control of the expansion valve, as in the control of the cited document 1, is not a binary control of ON / OFF, but is controlled to an intermediate valve opening. The change in the internal temperature can be reduced compared to the / OFF control.

  However, since the refrigerant does not flow, the effect of off-cycle defrost is lost and frost formation on the evaporator 16 is promoted.

  For this reason, in the system in which the expansion valve is PID-controlled and the internal temperature is adjusted, the time interval (defrost cycle time) at which defrosting must be performed is short, and the frequency at which defrosting must be performed is high. End up. If defrosting is performed at the same time interval as in the ON / OFF control, the evaporator 16 may be unable to vent and fall into a cooling failure. In the case of a showcase used in a store such as a supermarket or a convenience store, it becomes a big problem if the showcase falls into a poor cooling during business hours.

  In the present invention, in view of such a current situation, it is possible to keep the internal temperature constant by performing constant temperature control by PID control at the time of constant temperature cooling, while preventing the growth of frost in the evaporator, defrosting It is an object of the present invention to provide a control device and a control method for a refrigerator that can reduce the frequency that must be performed and increase the defrost cycle time.

The control device and control method for a refrigerator of the present invention uses a highly durable electromagnetic valve or an electronic expansion valve as an expansion valve, and controls the valve opening degree by the control device.
Specifically, the control device for the refrigerator of the present invention is:
Piping through which refrigerant flows;
An expansion valve that is provided on the pipe and condensed by a condenser with a low-temperature and low-pressure liquid refrigerant;
An evaporator that absorbs and cools the heat of the circulating air by changing the state of the refrigerant from liquid to gas;
A control device for controlling the valve opening of the expansion valve in a refrigerator having at least
The control device stores a predetermined thermo-on time during which the refrigerant flows into the evaporator and a predetermined thermo-off time during which the refrigerant does not flow into the evaporator,
A thermo-on process in which the expansion valve is opened for the thermo-on time and the thermo-on state is set during the thermo-on temperature constant control, and a thermo-off process in which the expansion valve is closed and the thermo-off state is set for the thermo-off time alternately. Repeatedly ,
In the thermo-on step, the opening degree of the expansion valve is adjusted so that the internal temperature of the cooling chamber approaches a predetermined internal temperature setting value .

In this case, the control device stores a preset switching determination time,
When the switching determination time has elapsed from the start of cooling, it is determined that the frosting amount of the evaporator has exceeded a predetermined threshold, and the thermo-on time and the thermo-off time stored in the control device are set to predetermined values. May be configured to change,
It is preferable that the ratio of the thermo-off time to the thermo-on time is greater after the switching determination time has elapsed than before the switching determination time has elapsed.

Moreover, the control method of the refrigerator of the present invention is:
Piping through which refrigerant flows;
An expansion valve that is provided on the pipe and condensed by a condenser with a low-temperature and low-pressure liquid refrigerant;
An evaporator that absorbs and cools the heat of the circulating air by changing the state of the refrigerant from liquid to gas;
In a refrigerator having at least a control method for controlling the valve opening of the expansion valve,
A thermo-on process of the thermo-on state during inside temperature constant control predetermined thermo time by the valve opening of the expansion valve, a thermo-off process of the thermo-off state to the valve closed the expansion valve by a predetermined thermo-off time, the While repeating it alternately ,
In the thermo-on step, the opening degree of the expansion valve is adjusted so that the internal temperature of the cooling chamber approaches a predetermined internal temperature setting value .

In this case, when the switching determination time set in advance from the cooling start has elapsed, it is determined that the frost quantity of the evaporator exceeds a predetermined threshold value, the pre-Symbol thermo time and the thermo-off time to a predetermined value Can be changed.
Moreover, it is preferable that the ratio of the thermo-off time to the thermo-on time is greater after the switching determination time has elapsed than before the switching determination time has elapsed.

  According to the present invention, frosting on the evaporator can be suppressed by forcing the thermo-off during the constant temperature control, and the internal temperature is stabilized by the constant temperature control. The defrost cycle can be lengthened while maintaining the same, and even when defrosting is performed at the same time interval as during ON / OFF control, cooling does not occur due to frost formation and reliable cooling is achieved. A vault can be provided.

FIG. 1 is a schematic configuration diagram for explaining a structure of a showcase provided with a control device. FIG. 2 is a schematic configuration diagram for explaining the configuration of the control device of the present embodiment. FIG. 3 is a flowchart for explaining the flow of the thermo-off control in the control device of the present embodiment.

Hereinafter, embodiments (examples) of the present invention will be described in more detail with reference to the drawings.
In addition, the structure of the showcase 30 provided with the control apparatus 22 in a present Example is a structure similar to the conventional showcase 30 mentioned above fundamentally.

FIG. 2 is a schematic configuration diagram for explaining the configuration of the control device 22 of the present embodiment.
The control device 22 includes a microcomputer 50 that performs PID control calculation processing, a power input terminal 52 for receiving operating power, and a temperature for inputting temperature signals from the temperature sensors 18, 20, 40, 42. A sensor input terminal 54 and a control output terminal 56 for outputting a control signal to the expansion valve 14, the fan 38, the defrost heater 24, and the illumination 26 are provided.

  In addition, for example, the communication terminal 58 for communicating with a host control device (not shown) that controls a plurality of showcases 30 and refrigerators in an integrated manner, and the temperature sensors 18, 20, 40, 42. A display means 60 for displaying the detected temperature and the state of the expansion valve 14 can also be provided.

  The control device 22 of this embodiment controls the expansion valve 14 by constant temperature control during constant-temperature cooling, and opens the expansion valve 14 for a predetermined thermo-on time during the constant temperature control. The thermo-on process and the thermo-off process in which the expansion valve 14 is closed for a predetermined thermo-off time to place the thermo-off state are alternately repeated.

  In order to set the thermo-off state by the control device 22, the valve opening degree of the expansion valve 14 is set to 0%, or when an expansion valve that does not close the valve is used, in addition to the expansion valve that does not close the valve. For example, a valve that can be closed (not shown) such as a liquid supply electromagnetic valve may be provided in the pipe 12 and the valve that can be closed by the control device 22 may be closed.

  In this way, by repeating the thermo-on process and the thermo-off process alternately during the internal temperature constant control, the defrost cycle can be lengthened while maintaining the internal temperature stably, and ON / OFF Even when the defrosting is performed at the same time interval as that at the time of control, the cooling failure due to frost formation does not occur. In the present specification, the time during which the thermo-on process and the thermo-off process are alternately repeated is referred to as a defrost cycle time.

  As will be described later, based on the frosting tendency according to the type and size of the showcase 30, it is estimated that the frosting amount will exceed a predetermined threshold when the predetermined switching determination time has elapsed, and the thermo-on time. The thermo-off time may be changed to a predetermined value.

  In this embodiment, the frost formation amount of the evaporator 16 is estimated based on the switching determination time. However, the frost formation amount of the evaporator 16 is determined by using an optical sensor such as an optical sensor or a digital camera, for example. For example, in order to detect the amount of air flowing through the evaporator 16, an air amount sensor is installed before and after the evaporator 16 to ventilate the evaporator 16. When the air volume becomes smaller than the specified air volume value, it may be estimated that the frost amount of the evaporator 16 exceeds a predetermined threshold value.

  Further, since the superheat degree of the evaporator 16 is substantially constant during the internal temperature control, when the superheat degree of the evaporator 16 is monitored and the superheat degree becomes smaller than the specified superheat degree, the evaporator 16 is monitored. It can also be configured to estimate that the frosting amount of 16 has exceeded a predetermined threshold.

Hereinafter, the thermo-off control in the control device 22 of the present embodiment will be described based on the flowchart shown in FIG.
In the present embodiment, when the cooling of the showcase 30 is started, thermo-off control is executed at predetermined intervals by the control device 22 (S10).

  First, it is determined whether the control device 22 is under superheat degree control or constant temperature control (S20). If it is determined that the superheat degree control is being performed, the thermo-off control is terminated as it is (S110).

  On the other hand, when it is determined that the internal temperature control is being performed, it is determined whether or not the switching determination time A set in advance from the start of cooling has elapsed (S30), and then according to the elapsed time. Set the thermo-on time and thermo-off time.

If the switching determination time A has not elapsed, the thermo-on time is set to the set value b, and the thermo-off time is set to the set value c (S40).
On the other hand, when the switching determination time A has elapsed, the thermo-on time is set to the set value d and the thermo-off time is set to the set value e (S50).

  The switching determination time A is a setting value used to determine the first half and the second half of the defrost cycle, and the defrost cycle time set in advance according to the type and size of the showcase 30, For example, although it is good also as a half, it can change suitably in defrost cycle time.

Further, it is desirable that the set value c and the set value e, which are the thermo-off time, be short times such that the internal temperature does not increase so much.
On the other hand, it is desirable that the set value b and the set value d, which are the thermo-on time, be longer than the set value c and the set value e for cooling the inside of the cabinet.

  In addition, compared with the first half of the defrost cycle, the latter half of the defrost cycle tends to be frosted on the evaporator 16. For this reason, it is desirable to set so that the ratio of the thermo-off time to the thermo-on time is larger in the second half of the defrost cycle than in the first half of the defrost cycle.

  Specifically, the set value c and the set value e, which are the thermo-off time, are set constant, and the set value d, which is the thermo-on time, is set shorter than the set value b. It is desirable to set the set value d constant and set the set value e longer than the set value c for the thermo-off time.

  Next, it is determined whether or not the thermo is on (S60). If it is determined that the thermo-ON is being performed, it is determined whether the thermo-ON time has elapsed (S70). If the thermo-on time has not elapsed, the thermo-off control is terminated as it is (S110).

On the other hand, when the thermo-ON time has elapsed, the expansion valve 14 is closed by the control device 22, the cooling device 10 is thermo-off (S80), and the thermo-off control is ended (S110).
If it is determined in S60 that the thermo-off is in progress, it is determined whether the thermo-off time has elapsed (S90). If the thermo-off time has not elapsed, the thermo-off control is terminated as it is (S110).

On the other hand, when the thermo-off time has passed, the expansion valve 14 is opened by the control device 22, the cooling device 10 is thermo-on (S100), and the thermo-off control is ended (S110).
In this way, by switching between the thermo-on state and the thermo-off state at a predetermined thermo-on time and thermo-off time during the constant temperature control in the refrigerator, a defrost effect can be obtained during the thermo-off, so that frost growth in the evaporator 16 can be achieved. Hinder and lengthen the defrost cycle time.

  In addition, during the thermo-on, the internal temperature of the showcase is kept constant by controlling the internal temperature, and even if the thermo-off state is set for a short time, the internal temperature does not increase so much. During the operation of the control device 22 of the present embodiment, the internal temperature is stably maintained.

In this embodiment, the thermo-on time and the thermo-off time are changed in the first half and the second half of the defrost cycle for the reasons described above. However, the same thermo-on time and thermo-off time may always be used.
Also, instead of setting only one switching judgment time and switching in the first half and the latter half of the defrost cycle, multiple switching judgment times are provided to divide the defrost cycle more finely, with different thermo-on times and thermo-off times. Time may be set.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to this, In the said Example, although demonstrated using the multistage showcase installed in a store etc. as an example of a refrigerator. For example, various modifications are possible without departing from the object of the present invention, such as being applicable to a flat showcase, a prefabricated refrigerator, a prefabricated freezer, and the like.

DESCRIPTION OF SYMBOLS 12 Piping 14 Expansion valve 16 Evaporator 18 Inlet piping temperature sensor 20 Outlet piping temperature sensor 22 Control device 24 Defrost heater 30 Showcase 32 Display shelf 34 Outlet 36 Inlet port 38 Inlet fan 40 Outlet temperature sensor 42 Inlet temperature sensor 50 microcomputer 52 power input terminal 54 temperature sensor input terminal 56 control output terminal 58 communication terminal 60 display means

Claims (6)

Piping through which refrigerant flows;
An expansion valve that is provided on the pipe and condensed by a condenser with a low-temperature and low-pressure liquid refrigerant;
An evaporator that absorbs and cools the heat of the circulating air by changing the state of the refrigerant from liquid to gas;
A control device for controlling the valve opening of the expansion valve in a refrigerator having at least
The control device stores a predetermined thermo-on time during which the refrigerant flows into the evaporator and a predetermined thermo-off time during which the refrigerant does not flow into the evaporator,
A thermo-on process in which the expansion valve is opened for the thermo-on time and the thermo-on state is set during the thermo-on temperature constant control, and a thermo-off process in which the expansion valve is closed and the thermo-off state is set for the thermo-off time alternately. Repeatedly ,
In the thermo-on process, the opening degree of the expansion valve is adjusted so that the inside temperature of the cooling room approaches a predetermined inside temperature setting value . The control device stores a preset switching determination time,
When the switching determination time has elapsed from the start of cooling, it is determined that the frosting amount of the evaporator has exceeded a predetermined threshold, and the thermo-on time and the thermo-off time stored in the control device are set to predetermined values. control device for refrigerator according to claim 1, characterized in that it is configured to change. Than before the switching determination time has elapsed, the controller of the refrigerator according to claim 2, who after the switching determination time has elapsed, characterized in that the ratio of the thermo-off time is increased for the thermo-on time. Piping through which refrigerant flows;
An expansion valve that is provided on the pipe and condensed by a condenser with a low-temperature and low-pressure liquid refrigerant;
A control method for controlling the valve opening of the expansion valve in a refrigerator having at least an evaporator that absorbs and cools the heat of circulating air by changing the state of the refrigerant from liquid to gas. And
A thermo-on process of the thermo-on state during inside temperature constant control predetermined thermo time by the valve opening of the expansion valve, a thermo-off process of the thermo-off state to the valve closed the expansion valve by a predetermined thermo-off time, the While repeating it alternately ,
Wherein in the thermo process, the control method of the refrigerator, characterized in that the inside temperature of the refrigerator to regulating the valve opening degree of the expansion valve so as to approach the predetermined inside temperature setpoint. When the switching determination time set in advance from the cooling start has elapsed, the frost quantity of the evaporator is determined to have exceeded a predetermined threshold value, changes the pre-Symbol thermo time and the thermo-off time to a predetermined value control method for refrigerator according to claim 4, characterized in. Than before the switching determination time has elapsed, the control method of the refrigerator according to claim 5 in which the later of the switching determination time has elapsed, characterized in that the ratio of the thermo-off time is increased for the thermo-on time.

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