JP2016080304A - Control device and control method of cooling box - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control device and control method of a cooling device, capable of quickly cooling the inside of a box by overheat degree control in pull-down cooling, and keeping an in-box temperature constant by in-box temperature constant control in constant-temperature cooling.SOLUTION: A control device of a cooling box performs overheat degree control for controlling valve opening of an expansion valve on the basis of an overheat degree in pull-down cooling, and performs in-box temperature constant control for controlling valve opening of the expansion valve on the basis of an in-box temperature in constant-temperature cooling.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a refrigerator control device capable of quickly pulling down in a refrigerator such as a freezer showcase or a refrigerated showcase installed in a store or the like, and capable of performing stable temperature control even after pulldown. 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 are cases 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.

  Reference numeral 24 denotes a defrost heater for removing frost generated in the evaporator 16. When frost is generated in the evaporator 16, the frost is removed by turning on the power of the defrost heater 24. Melted and defrosted.

  In the showcase 30 configured as described above, as disclosed in Patent Documents 1 and 2 and the like, the cooling capacity is adjusted by changing the flow rate of the refrigerant by adjusting the valve opening degree of the expansion valve 14 by the control device 22. Is controlled to adjust the internal temperature of the showcase 30.

  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.

  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.

  When the superheat is higher than the superheat setting value, the integral component of the control output is an output that increases the valve opening as the superheat value is higher, while the superheat is set to the superheat setting value. If the value is lower than the value, the lower the superheat setting value, the smaller the valve opening, but the control output is divided by the integration time and output gradually. As long as it is not deviated from the superheat setting value, the output for each control cycle is smaller than the control output of the proportional component.

  The differential component of the control output is output in response to the change in the amount of change in superheat, and becomes a component that decreases to 0 over a differentiation time. However, in superheat control, the output itself of the differential component is due to the characteristics of the controlled object. The differential component is not output so that it becomes a disturbance and does not cause hunting.

  The control output of superheat degree control in PID control is a control output that adds the proportional component and integral component for each control cycle, and gradually sets the integral component while reducing the change gradient of the superheat degree with the proportional component. The output is adjusted so that the difference in value is reduced and the superheat degree approaches the superheat degree set value.

  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.

  When the internal temperature is higher than the internal temperature set value, the integral component of the control output is an output that increases the valve opening as the internal temperature is higher than the internal temperature set value. When the temperature is lower than the internal temperature setting value, the lower the internal temperature setting value, the smaller the valve opening becomes, but the control output is divided by the integration time and output gradually. As long as the internal temperature is not far from the internal temperature set value, the output for each control cycle is smaller than the output of the proportional component.

  The differential component of the control output is output in response to the change in the amount of change in the internal temperature, and becomes a component that decreases to 0 over the differential time. However, because the change in the internal temperature is gradual, the output of the differential component is small compared to the proportional component and integral component, and the ratio to the overall output is also low, so the internal temperature control has an effect of the differential component of the control output. Need not be considered.

  The control output of the internal temperature constant control in PID control is a control output that adds all of these proportional, integral and differential components at every control cycle, and the proportional component reduces the change in internal temperature. On the other hand, the difference from the internal temperature setting value is gradually reduced by the integral component, and the output is adjusted so that the internal temperature approaches the internal temperature setting value.

  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 the warmed state to the internal temperature setting value, and the other is constant temperature cooling that maintains the internal temperature at a temperature near the internal temperature setting value after pull-down cooling.

For such control of the inside cooling, as disclosed in Patent Document 1, control based on both the degree of superheat of cooling and the inside temperature is also performed.
In the temperature control method disclosed in Patent Document 1, an output signal having a smaller valve opening degree among a valve opening degree (output signal) based on the degree of superheat and a valve opening degree (output signal) based on the internal temperature. The valve opening degree of the expansion valve 14 is controlled based on the above.

JP 59-185948 A JP 2008-209016 A

When such a temperature control method is used for temperature control of a showcase using speed-type PID control, the internal temperature of the showcase 30 changes as shown in FIG.
First, when pull-down cooling is started, the valve opening degree of the expansion valve 14 that was 0% before the start is set to 100% for a predetermined time. Thereby, a refrigerant | coolant flows into the evaporator 16 and cooling is started. In addition, the predetermined time which makes a valve opening degree 100% may be arbitrary time, and may be 0 second. When this predetermined time has elapsed, the control device 22 starts internal temperature control by PID control.

  At the start of pull-down cooling, the refrigerant begins to flow into the evaporator 16 that has been almost free of refrigerant, so the degree of superheat rises at once. At this time, in the superheat control, the control output increases the valve opening according to the increasing superheat, but in the internal temperature control, the valve opening decreases proportionally to the internal temperature at which cooling is first reduced. The output is the sum of the output and the integral output that gradually increases the valve opening in accordance with the internal temperature that is significantly higher than the internal temperature set value, resulting in an output that decreases the valve opening.

In this case, the internal temperature control is an output that reduces the valve opening, so the internal temperature control is adopted as the control output, and the output is an output that decreases the valve opening.
Although the valve opening becomes small, the expansion valve 14 is not completely closed, so that the refrigerant immediately reaches the evaporator 16. And if a refrigerant | coolant spreads in the evaporator 16, the superheat degree once raised will become small rapidly.

In response to this suddenly small change in superheat, the control device 22 outputs a signal for rapidly reducing the valve opening of the expansion valve 14 as an output signal for superheat control.
On the other hand, as the output of the internal temperature constant control, since the internal temperature gradually decreases and approaches the internal temperature set value, an output that reduces the valve opening of the expansion valve 14 with a proportional component, and integration This is an output obtained by adding the output of the expansion valve 14 gradually increased by the component, that is, the output of decreasing the valve opening of the expansion valve 14.

  In this case, the output signal of the superheat degree control is an output that makes the valve opening smaller than the output of the constant chamber temperature control, and the output signal of the superheat degree control is adopted to open the expansion valve 14. Decrease the degree rapidly.

  When the valve opening degree of the expansion valve 14 suddenly decreases, the degree of superheat increases greatly again. At that time, the output of the superheat degree control becomes an output that increases the valve opening degree, but on the other hand, since the internal temperature gradually decreases toward the internal temperature setting value, The output is an output obtained by adding the output of the proportional component that decreases the valve opening and the integral component that increases the valve opening. Therefore, the output of the internal temperature constant control, which is the control output with the smaller valve opening, is employed.

  When the temperature control method disclosed in Patent Document 1 is performed by speed-type PID control, expansion is performed by using the valve opening degree based on the degree of superheat and the valve opening degree based on the internal temperature, which has a smaller valve opening degree. Since the valve opening degree of the valve 14 is adjusted, the output signal of the internal temperature constant control is adopted, and the degree of superheat that is greatly increased cannot be suppressed.

  After that, since the superheat degree does not decrease and maintains a value higher than the superheat degree set value, a signal for increasing the valve opening degree of the expansion valve 14 is continuously output as an output signal for the superheat degree control. Since the internal temperature is close to the internal temperature set value, the output signal of the internal temperature constant control becomes a signal for reducing the valve opening, and the output signal of the internal temperature constant control is continuously adopted.

As described above, when the temperature control method disclosed in Patent Document 1 is performed by speed-type PID control, the opening degree of the expansion valve 14 cannot be increased in accordance with the increase in the degree of superheat, and the evaporator 16 However, there is a problem that the cooling capacity is reduced without returning while the superheat degree is increased, and the pull-down cooling time is lengthened. In FIG. 6, the pull-down cooling is completed is the time t _2.

  In addition, during constant temperature cooling after pull-down cooling, work such as when the refrigerator is temporarily stopped by the control of the refrigerator connected to the showcase 30 or when products are replaced in the showcase 30 occurs. When a disturbance occurs, the internal temperature may increase.

  When the temperature control method disclosed in Patent Document 1 is performed by speed-type PID control, the valve opening degree of the valve opening degree (output signal) based on the degree of superheat and the valve opening degree (output signal) based on the internal temperature is opened. Since the opening degree of the expansion valve 14 is controlled based on the output signal with the smaller degree, as shown in FIG. 7, when a disturbance occurs at time T, the internal temperature and the degree of superheat increase. The valve opening temporarily increases, but if the degree of superheat decreases by increasing the valve opening, the internal temperature is kept high, and the constant opening temperature control increases the valve opening. Even though the signal is output, the amount of change in superheat is negative, so an output signal that reduces the valve opening of the superheat control is adopted, and the valve opening is adjusted to be small. End up.

  And even if the degree of superheat rises again by reducing the valve opening, the output signal that increases the degree of valve opening of the superheat degree control that is output according to the rise in the degree of superheat is not adopted, and the temperature change is small. An output signal that slightly increases the valve opening with an integral component of constant internal temperature control is employed.

  In this way, if the degree of superheat repeatedly rises and falls, the amount of change in the degree of superheat expands every time the amount of change in the degree of superheat becomes negative, even though the inside temperature remains higher than the inside temperature setting value. When an output signal for reducing the valve opening degree of the valve 14 is employed, and when the amount of change in the superheat degree is positive, the amount by which the valve opening degree is increased despite the increase in the superheat degree. Since a slight output of constant internal temperature control is adopted, the valve opening is gradually reduced.

  For this reason, the degree of superheat that has become high due to the disturbance is not easily lowered, and the cooling capacity of the evaporator 16 becomes low. Therefore, the internal temperature that has also increased due to the external disturbance returns to a temperature near the internal temperature setting value. The time may be very long.

  In the present invention, in view of such a current situation, the cooler can quickly cool the interior by superheat degree control during pull-down cooling, and can keep the interior temperature constant by constant temperature control during constant temperature cooling. An object of the present invention is to provide a control device and a control method.

  Further, in the present invention, even when a disturbance occurs during constant temperature cooling and the internal temperature rises, the internal temperature can be quickly increased by increasing the valve opening of the expansion valve according to the increased internal temperature. An object of the present invention is to provide a control device and a control method for a refrigerator that can return the temperature to a temperature in the vicinity of the internal temperature set value.

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 provided on the pipe, the liquid refrigerant condensed by the condenser is a low-temperature, 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
Superheat degree detecting means for detecting the superheat degree of the evaporator;
An internal temperature detecting means for detecting the internal temperature of the cooling chamber;
With
The control device performs superheat control for controlling the valve opening degree of the expansion valve based on the degree of superheat detected by the superheat degree detection means during pull-down cooling, and the internal temperature detection means during constant temperature cooling. It is configured to perform constant internal temperature control for controlling the valve opening degree of the expansion valve based on the internal temperature detected by the above.

In this case, the superheat degree detection means includes an inlet pipe temperature sensor that detects the temperature of the refrigerant on the inlet side of the evaporator, and an outlet pipe temperature sensor that detects the temperature of the refrigerant on the outlet side of the evaporator, Have
The control device can be configured to calculate a degree of superheat based on an inlet pipe temperature detected by the inlet pipe temperature sensor and a return pipe temperature detected by the outlet pipe temperature sensor.

In addition, the control device stores a pre-set chamber temperature set value,
When the internal temperature of the cooling chamber becomes lower than the internal temperature set value, it is possible to switch from superheat control to constant internal temperature control.

Further, the control device stores a preset internal temperature set value and a predetermined correction value set for the internal temperature set value,
When the internal temperature of the cooling chamber becomes lower than the internal temperature set value + correction value, the superheat degree control can be switched to the internal temperature constant control.

Further, the control device stores a preset internal temperature set value and a predetermined correction value set for the internal temperature set value,
When the internal temperature of the cooling chamber becomes lower than the internal temperature set value−correction value, the superheat degree control can be switched to the internal temperature constant control.

The refrigerator is a compressor that compresses the gas refrigerant from the evaporator to form a high-temperature, high-pressure gas refrigerant;
A condenser that discharges heat from the high-temperature and high-pressure gas refrigerant discharged from the compressor to form a liquid refrigerant;
Can be further provided.

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,
During pull-down cooling, superheat control is performed to control the valve opening of the expansion valve based on the degree of superheat, and during constant temperature cooling, the internal temperature is constant to control the valve opening of the expansion valve based on the internal temperature. Control is performed.

In this case, when the internal temperature of the refrigerator becomes lower than the preset internal temperature setting value, the superheat degree control can be switched to the constant internal temperature control.
In addition, a predetermined internal temperature setting value and a predetermined correction value set for the internal temperature setting value are set in advance,
When the internal temperature of the refrigerator becomes lower than the internal temperature set value + the correction value, the superheat degree control can be switched to the internal temperature constant control.

In addition, a predetermined internal temperature setting value and a predetermined correction value set for the internal temperature setting value are set in advance,
When the internal temperature of the refrigerator becomes lower than the internal temperature set value−the correction value, the superheat degree control can be switched to the internal temperature constant control.

  According to the present invention, the interior temperature can be quickly cooled by superheat control during pull-down cooling, and the interior temperature can be kept constant by constant interior temperature control during constant temperature cooling.

FIG. 1 is a schematic configuration diagram for explaining the structure of a showcase provided with the control device of this embodiment. 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 control of the expansion valve by the control device. FIG. 4 is a graph for explaining a change in the internal temperature, a change in the degree of superheat, and a change in the valve opening degree of the showcase provided with the control device of this embodiment. FIG. 5 is a graph for explaining a change in the internal temperature, a change in the degree of superheat, and a change in the valve opening when a disturbance occurs in the showcase including the control device of the present embodiment. FIG. 6 is a graph for explaining a change in the interior temperature, a change in superheat degree, and a change in valve opening of a conventional showcase. FIG. 7 is a graph for explaining changes in the internal temperature, changes in the degree of superheat, and changes in the valve opening when disturbance occurs in the conventional showcase.

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 for performing PID control arithmetic processing, a power input terminal 52 for receiving operating power, and a temperature for inputting a temperature signal from each of 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 of the expansion valve 14 by the control device 22 configured as described above will be described based on the flowchart shown in FIG.
When the cooling of the showcase 30 is started, the control device 22 controls the expansion valve 14 at a predetermined control cycle. When the showcase 30 is activated, the control mode of the control device 22 is superheat control.

  Further, the control of the valve opening degree of the expansion valve 14 by the control device 22 depends on the type of the expansion valve 14. For example, when the expansion valve 14 is an electronic expansion valve or a highly durable electromagnetic valve, the PID control is used. It can be carried out.

When the control of the expansion valve 14 is started (S10), it is first determined whether the current control mode is superheat control or constant temperature control in the cabinet (S20).
When it is determined that the control mode is constant control of the internal temperature, the expansion valve is based on the internal temperature detected by the internal temperature detection means such as the outlet temperature sensor 40 or the inlet temperature sensor 42. 14 is adjusted (S60).

  On the other hand, when it is determined that the control mode is superheat degree control, the superheat calculated from the inlet pipe temperature detected by the inlet pipe temperature sensor 18 and the return pipe temperature detected by the outlet pipe temperature sensor 20. The valve opening degree of the expansion valve 14 is adjusted based on the degree (S30).

  Next, it is determined whether the internal temperature is lower than a predetermined internal temperature set value (S40). When the internal temperature is higher than the internal temperature set value, the control of the expansion valve 14 is finished as it is (S70), and when the internal temperature is lower than the internal temperature set value, the control mode is the superheat degree. The control is switched to the constant internal temperature control (S50), and the control of the expansion valve 14 ends (S70).

  Thus, at the time of pull-down cooling from when the control device 22 is activated until the internal temperature reaches the internal temperature setting value, the expansion valve 14 is controlled by superheat degree control, and the internal temperature is the internal temperature setting value. During constant temperature cooling, the expansion valve 14 is controlled by constant control of the internal temperature, so that the internal storage can be quickly cooled during pull-down cooling, and the internal storage can be stably maintained during constant temperature cooling. It becomes possible to maintain a constant temperature.

FIG. 4 is a graph for explaining a change in the internal temperature, a change in the degree of superheat, and a change in the valve opening degree of the showcase 30 provided with the control device 22 of the present embodiment.
First, when pull-down cooling is started, the valve opening degree of the expansion valve 14 that was 0% before the start is set to 100% for a predetermined time. In addition, the predetermined time which makes a valve opening degree 100% may be arbitrary time, and may be 0 second.

Thereby, a refrigerant | coolant flows into the evaporator 16 and cooling is started. And when predetermined time passes, the control apparatus 22 will start the internal temperature control by PID control.
At the start of pull-down cooling, the refrigerant begins to flow into the evaporator 16 that has been almost free of refrigerant, so the degree of superheat rises at once. At this time, the control mode of the control device 22 is superheat control, and the control output of the superheat control is an output that increases the valve opening of the expansion valve 14 in accordance with the increasing superheat, but the valve opening is already Since it is 100%, the valve opening remains 100%.

And if a refrigerant | coolant spreads in the evaporator 16 immediately, a superheat degree will become small rapidly.
At this time, since the control mode of the control device 22 is superheat degree control, a signal for abruptly reducing the valve opening degree of the expansion valve 14 is output in accordance with the superheat degree change that rapidly decreases.

  When the valve opening degree of the expansion valve 14 suddenly decreases, the degree of superheat increases greatly again. And since the control mode of the control apparatus 22 is superheat degree control, the control apparatus 22 outputs the signal which enlarges a valve opening according to the superheat degree which raised greatly.

  Thus, during pull-down cooling, the control mode of the control device 22 is superheat control, so that a signal for adjusting the valve opening according to the change in superheat is output, the superheat does not become too high, and evaporation occurs. The vessel 16 exhibits an appropriate cooling capacity and can quickly cool the interior of the showcase 30.

Then, at time t ₁ , after the internal temperature becomes lower than the internal temperature set value, the control mode of the control device 22 is switched to constant internal temperature control, and the valve opening is adjusted according to the internal temperature. Thus, the internal temperature can be kept stable and constant.

  In addition, as a timing which switches the control mode of the control apparatus 22, when a predetermined | prescribed correction value is set with respect to the internal temperature setting value and the internal temperature becomes below the internal temperature setting value + correction value, It does not matter if the temperature falls below the internal temperature set value minus the correction value.

Further, by controlling the expansion valve 14 as in the present embodiment, even when a disturbance occurs, the degree of superheat can be quickly reduced and the internal temperature can be restored.
FIG. 5 is a graph for explaining a change in the internal temperature, a change in the degree of superheat, and a change in the valve opening when a disturbance occurs at time T in the showcase 30 including the control device 22 of the present embodiment. It is.

In addition, the graph shown in FIG. 5 shows an example in which the internal temperature is lowered to the internal temperature set value and a disturbance occurs when the showcase 30 is performing constant temperature cooling.
As shown in FIG. 5, the internal temperature rises due to the occurrence of the disturbance. In the control device 22 of the present embodiment, during the constant temperature cooling, the control mode is switched to perform constant control of the internal temperature, so that the opening degree of the expansion valve 14 increases as the internal temperature increases. To be controlled.

By increasing the valve opening of the expansion valve 14 in the constant chamber temperature control, the degree of superheat increased as the chamber temperature increases, but the control mode of the control device 22 is the constant chamber temperature control. The valve opening is not reduced according to the decrease in the degree of superheat, but the valve opening is controlled according to the change in the internal temperature, so the valve opening is increased according to the increased internal temperature. Then, control is performed so that the internal temperature becomes the internal temperature set value.
For this reason, in the control apparatus 22 of a present Example, when the internal temperature rises by disturbance during constant temperature cooling, the internal temperature can be quickly returned to the temperature near the original set value.

  Even if a disturbance occurs during pull-down cooling, the control device 22 of this embodiment always controls the valve opening degree of the expansion valve 14 by superheat control during pull-down cooling. The valve opening increases in accordance with the degree of superheat increased by the disturbance, and the superheat change and the internal temperature change due to the disturbance can be quickly converged.

  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.

12 piping 14 expansion valve 16 evaporator 18 inlet piping temperature sensor 20 outlet piping temperature sensor 22 control device 24 defrost heater 26 lighting 30 showcase 32 display shelf 34 outlet 36 inlet 38 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 (10)

Piping through which refrigerant flows;
An expansion valve provided on the pipe, the liquid refrigerant condensed by the condenser is a low-temperature, 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
Superheat degree detecting means for detecting the superheat degree of the evaporator;
An internal temperature detecting means for detecting the internal temperature of the refrigerator,
The control device performs superheat control for controlling the valve opening degree of the expansion valve based on the degree of superheat detected by the superheat degree detection means during pull-down cooling, and the internal temperature detection means during constant temperature cooling. A control device for a refrigerator, which is configured to perform constant internal temperature control for controlling the valve opening degree of the expansion valve based on the internal temperature detected by. The superheat degree detecting means includes an inlet pipe temperature sensor that detects the temperature of the refrigerant on the inlet side of the evaporator, and an outlet pipe temperature sensor that detects the temperature of the refrigerant on the outlet side of the evaporator. ,
The control device is configured to calculate a superheat degree based on an inlet pipe temperature detected by the inlet pipe temperature sensor and a return pipe temperature detected by the outlet pipe temperature sensor. The control apparatus of the refrigerator of Claim 1 to do. The control device stores a pre-set internal temperature setting value,
3. The apparatus according to claim 1, wherein when the inside temperature of the cooling compartment becomes lower than the inside temperature setting value, the superheat degree control is switched to the constant inside temperature control. 4. The refrigerator control device described. The control device stores a preset internal temperature setting value and a predetermined correction value set for the internal temperature setting value,
2. The apparatus according to claim 1, wherein when the inside temperature of the cooling compartment becomes lower than the inside temperature setting value + correction value, the superheat degree control is switched to the inside temperature constant control. Or the control apparatus of the refrigerator of 2. The control device stores a preset internal temperature setting value and a predetermined correction value set for the internal temperature setting value,
2. The apparatus according to claim 1, wherein when the internal temperature of the cooling chamber becomes lower than the internal temperature set value−correction value, the superheat degree control is switched to the internal temperature constant control. Or the control apparatus of the refrigerator of 2. The refrigerator is
A compressor that compresses the gas refrigerant from the evaporator into a high-temperature, high-pressure gas refrigerant;
A condenser that discharges heat from a high-temperature, high-pressure gas refrigerant discharged from the compressor to form a liquid refrigerant;
The control device for a refrigerator according to any one of claims 1 to 5, further comprising: 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,
During pull-down cooling, superheat control is performed to control the valve opening of the expansion valve based on the degree of superheat, and during constant temperature cooling, the internal temperature is constant to control the valve opening of the expansion valve based on the internal temperature. A control method for a refrigerator, wherein control is performed.   8. The cooling according to claim 7, wherein when the internal temperature of the cooling chamber becomes lower than a preset internal temperature setting value, the superheat degree control is switched to the constant internal temperature control. How to control the warehouse. A predetermined internal temperature setting value and a predetermined correction value set for the internal temperature setting value are set in advance,
8. The cooling according to claim 7, wherein when the inside temperature of the cooling compartment becomes lower than the inside temperature setting value + the correction value, the superheat degree control is switched to the inside temperature constant control. How to control the warehouse. A predetermined internal temperature setting value and a predetermined correction value set for the internal temperature setting value are set in advance,
8. The cooling according to claim 7, wherein when the inside temperature of the cooling compartment becomes lower than the inside temperature setting value−the correction value, the superheat degree control is switched to the constant inside temperature control. 9. How to control the warehouse.

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