JP5458656B2 - Cooling system - Google Patents

Description

  The present invention relates to a cooling device, and more specifically, by adjusting the opening of an electronic expansion valve and controlling the supply of refrigerant to an evaporator disposed in the storage device, the storage device of the storage device is desired. The present invention relates to a cooling device in a temperature state.

  For example, in a showcase that displays and sells products in a cooled state, an evaporator and an electronic expansion valve are provided inside, and a compressor and a condenser are provided outside thereof, and these evaporator, compressor, The storage of the showcase is maintained at a desired temperature state by circulating the refrigerant in a refrigeration cycle constituted by sequentially connecting a condenser and an electronic expansion valve.

  Specifically, the refrigerant outlet temperature at the outlet of the evaporator and the refrigerant inlet temperature at the inlet of the evaporator are detected, and the superheat degree in the evaporator is calculated by subtracting the inlet temperature from the outlet temperature. The refrigerant supply control is performed on the evaporator by adjusting the opening of the electronic expansion valve based on the deviation between the calculated degree of superheat and a predetermined set degree of superheat. In addition to the refrigerant supply control, the internal temperature of the storage is detected, and the opening degree of the electronic expansion valve is adjusted based on the deviation between the detected internal temperature and a preset temperature.

  In order to prevent the compressor from sucking the liquid refrigerant at the start of driving of the compressor, when the drive start information of the compressor is given, the opening of the electronic expansion valve is reduced from the lower limit value. Refrigerant supply control is performed by adjusting the distance between the lower limit value and the upper limit value to approximately 70% (see, for example, Patent Document 1).

JP 2006-71263 A

  The above-described cooling device adjusts the opening of the electronic expansion valve to a predetermined size at the start of driving of the compressor because the operation of the compressor or the compression due to showcase factors such as the internal temperature of the container It is known to be effective when the machines are individually installed in the same showcase and operating information of the compressor is available.

  However, when the compressor is stopped due to compressor factors such as refrigerating machine oil return control, the stop of the compressor cannot be detected, causing the following problems.

  That is, when the compressor is stopped, the deviation between the internal temperature of the storage and the set temperature increases, and the opening of the electronic expansion valve is increased. As a result, the liquid refrigerant flows from the high-pressure portion to the low-pressure portion in the refrigeration cycle, so that a so-called liquid back is generated in which the compressor sucks the liquid refrigerant at the start of driving of the compressor.

  In addition, when the compressor is stopped, the superheat degree in the evaporator becomes smaller than the set superheat degree, and the opening degree of the electronic expansion valve is reduced. However, if the electronic expansion valve is fully closed, the degree of superheat in the evaporator cannot be calculated, so that the full expansion is avoided and the opening of the electronic expansion valve is set to a preset minimum opening. As a result, the liquid refrigerant flows from the high-pressure portion of the refrigeration cycle into the low-pressure portion, and a liquid back is generated when the compressor starts to be driven.

  In view of the above circumstances, the present invention provides cooling that can prevent liquid refrigerant from being sucked when a compressor that has stopped driving due to a compressor factor, such as refrigeration oil return control, starts to drive again. An object is to provide an apparatus.

To achieve the above object, the cooling device according to the present invention, by adjusting the opening degree of the electronic expansion valve, by controlling the supply of refrigerant for the evaporator which is arranged in the housing unit accommodating chamber of the housing unit In the cooling device in a desired temperature state, the superheat degree calculation for calculating the superheat degree in the evaporator by subtracting the refrigerant inlet temperature in the inlet part of the evaporator from the refrigerant outlet temperature in the outlet part of the evaporator And the superheat degree calculated by the superheat degree calculation means is less than a predetermined threshold value and the outlet temperature is equal to or higher than a predetermined reference temperature, the refrigerant discharged from the evaporator is While determining that the compressor to be compressed is stopped, the electronic expansion valve is fully closed, while the superheat degree calculated by the superheat degree calculation means is less than the threshold value and the outlet temperature is the reference Warm Less than a when it is, and control means for the compressor performs control to reduce the opening of it is determined that results in sucking the liquid refrigerant the electronic expansion valve, said control means, said electronic expansion valve When the superheat degree calculated by the superheat degree calculating means is equal to or higher than the threshold value or the outlet temperature is lower than the reference temperature, the opening degree of the electronic expansion valve is reduced to the compression degree. Control is performed to expand the size of the electronic expansion valve to 55 to 75% of the opening when it is determined that the machine is stopped .

  According to the present invention, when the superheat degree calculated by the superheat degree calculation means is less than a predetermined threshold value and the outlet temperature is equal to or higher than the predetermined reference temperature, the control means discharges from the evaporator. The electronic expansion valve is fully closed by determining that the compressor for compressing the generated refrigerant is stopped, while the superheat degree calculated by the superheat degree calculating means is less than the threshold value and the outlet temperature is the reference temperature. If it is less than that, it is determined that the compressor sucks the liquid refrigerant and control is performed to reduce the opening of the electronic expansion valve. Therefore, the compressor is caused by factors of the compressor itself, such as refrigeration oil return control. Can be detected well. Then, since the electronic expansion valve is fully closed, there is no possibility that the compressor sucks the liquid refrigerant when the compressor starts to drive again thereafter. Therefore, there is an effect that it is possible to prevent the liquid refrigerant from being sucked when the compressor whose driving is stopped due to the compressor causes the driving to start again like the refrigerating machine oil return control.

FIG. 1 is a conceptual diagram conceptually showing the configuration of a cooling device according to an embodiment of the present invention. FIG. 2 is a chart showing an example of the relationship between the degree of superheat in the evaporator, the outlet temperature, the operating state determined by the state determining unit, and the opening of the electronic expansion valve set by the valve opening setting unit. FIG. 3 is a flowchart showing the contents of the expansion valve opening degree control process performed by the valve opening degree adjusting means shown in FIG. FIG. 4 is a chart showing the results of a feel test of the expansion valve opening degree control process of the valve opening degree adjusting means shown in FIG. 3, wherein (a) shows the time variation of the inlet temperature, outlet temperature, and superheat degree. ) Shows the change in the valve opening in the same time change as in (a), and the operating state of the compressor.

  Hereinafter, preferred embodiments of a cooling device according to the present invention will be described in detail with reference to the accompanying drawings as appropriate.

  FIG. 1 is a conceptual diagram conceptually showing the configuration of a cooling device according to an embodiment of the present invention. The cooling device exemplified here is applied to an open showcase (accommodating device) 11 that displays and sells products stored in the storage 10 in a cooled state, and each of the open showcases 11 has an evaporator 12. In addition, the electronic expansion valve 13 is individually provided, while the open showcase 11 is provided with one condenser 14 and one compressor 15 constituting a refrigerator.

  The electronic expansion valve 13 is for adiabatically expanding the liquid refrigerant discharged from the condenser 14 and supplying it to the evaporator 12. In the present embodiment, overheating defined as the difference between the refrigerant temperature at the outlet of the evaporator 12 (hereinafter also referred to as outlet temperature) and the refrigerant temperature at the inlet of the evaporator 12 (hereinafter also referred to as inlet temperature). Based on the degree, the opening degree is changed, and the one that can adjust the flow rate of the refrigerant passing therethrough is applied. More specifically, the electronic expansion valve 13 expands the opening when the degree of superheat is large, and reduces the opening when the degree of superheat is small.

  The compressor 15 compresses the low-temperature and low-pressure gas refrigerant discharged from the evaporator 12 and supplies it to the condenser 14 as a high-temperature and high-pressure gas refrigerant. In the present embodiment, when a pressure value setting command is given, an inverter compressor that can change the suction pressure according to the pressure value setting command is applied.

  In this cooling device, an evaporator 12 and an electronic expansion valve 13 provided in each open showcase 11 are connected in parallel to the condenser 14 and the compressor 15 to constitute a refrigeration cycle. That is, the high-temperature and high-pressure gas refrigerant discharged from the compressor 15 dissipates heat in the condenser 14 and becomes a high-temperature and high-pressure liquid refrigerant. This high-temperature and high-pressure liquid refrigerant is branched and supplied to the electronic expansion valve 13 of each open showcase 11 and is adiabatically expanded to be supplied to the evaporator 12 as a low-temperature and low-pressure gas-liquid two-phase refrigerant. The low-temperature low-pressure gas-liquid two-phase refrigerant supplied to the evaporator 12 exchanges heat with the internal atmosphere of the storage 10 supplied by the blower fan 16 and absorbs heat to become a low-temperature low-pressure gas refrigerant. Cool down. The low-temperature and low-pressure gas refrigerant that has passed through the evaporator 12 joins outside the open showcase 11 and is sucked into the compressor 15.

  In each open showcase 11, an inlet refrigerant temperature sensor 20 and an outlet refrigerant temperature sensor 21 are provided in the refrigerant supply pipe 17 connected to the inlet and outlet of the evaporator 12, respectively. Further, although not shown in the figure, an internal temperature sensor is provided inside the storage 10. The inlet refrigerant temperature sensor 20 and the outlet refrigerant temperature sensor 21 detect the temperature of the refrigerant passing through the respective refrigerant supply pipes 17. The internal temperature sensor detects the internal temperature of the container 10. In this Embodiment, what detects the temperature of the air after passing each evaporator 12 in the inside of the storage 10 as an internal temperature of the storage 10 is applied as an internal temperature sensor.

  Further, the cooling device includes a valve opening degree adjusting means 30 as its control system. As is clear from FIG. 1, in the present embodiment, each open showcase 11 is provided with individual valve opening degree adjusting means 30.

  The valve opening degree adjusting means 30 adjusts the opening degree of the electronic expansion valve 13 based on the refrigerant temperatures detected by the inlet portion refrigerant temperature sensor 20 and the outlet portion refrigerant temperature sensor 21, and includes a setting storage unit 31 and a superheat degree calculation. A part (superheat degree calculation means) 32, a state determination part 33, and a valve opening degree setting part (control means) 34.

  The setting storage unit 31 presets and stores a determination value of the refrigerant superheat degree target value in the evaporator 12 and the refrigerant temperature detected by the outlet refrigerant temperature sensor 21 (hereinafter also referred to as outlet temperature). It is. In the present embodiment, an upper limit value (for example, 5 ° C.) and a lower limit value (threshold value: for example, 2 ° C.) are set as the superheat degree target value, and a reference temperature (for example, 0 ° C.) is set as the determination value. Is set.

  The superheat degree calculation unit 32 subtracts the refrigerant temperature detected by the inlet refrigerant temperature sensor 20 (hereinafter also referred to as inlet temperature) from the outlet temperature detected by the outlet refrigerant temperature sensor 21 to obtain the degree of superheat in the evaporator 12. Is to be calculated.

  The state determination unit 33 determines the operating state of the open showcase 11 based on the degree of superheat calculated by the degree of superheat calculation unit 32 and the outlet temperature detected by the outlet refrigerant temperature sensor 21.

  The valve opening setting unit 34 sets the opening of the electronic expansion valve 13 according to the determination result of the state determination unit 33. More specifically, the valve opening setting unit 34 increases the opening of the electronic expansion valve 13 by a predetermined size (for example, about 10 pulses) when the opening of the electronic expansion valve 13 is increased. In the case of reduction, it is reduced by a predetermined size (for example, about 10 pulses). Further, when the opening degree of the electronic expansion valve 13 is fully closed, the valve opening degree setting unit 34 sets the opening degree of the electronic expansion valve 13 after a preset time (for example, 60 seconds) has elapsed. Then, the size is set to about 70% of the opening degree of the electronic expansion valve 13 when the state determination unit 33 determines that the compressor 15 is stopped. FIG. 2 shows an example of the relationship between the degree of superheat in the evaporator 12, the outlet temperature, the operating state determined by the state determining unit 33, and the opening of the electronic expansion valve 13 set by the valve opening setting unit 34. It is a thing.

  FIG. 3 is a flowchart showing the contents of the expansion valve opening degree control process performed by the valve opening degree adjusting means 30 shown in FIG. Hereinafter, the operation of the cooling device will be described with reference to FIG.

  In the expansion valve opening control process shown in FIG. 3, the valve opening adjusting means 30 detects the refrigerant temperature through the inlet refrigerant temperature sensor 20 and the outlet refrigerant temperature sensor 21 (step S101), and through the superheat calculator 32. Then, the degree of superheat in the evaporator 12 is calculated by subtracting the inlet temperature from the detected outlet temperature (step S102).

  The valve opening degree adjusting means 30 that has calculated the degree of superheat in the evaporator 12 determines whether or not the degree of superheat exceeds the upper limit value (for example, 5 ° C.) of the superheat degree target value stored in the setting storage unit 31. (Step S103).

  When the calculated superheat degree exceeds the upper limit value of the superheat degree target value (step S103: Yes), the valve opening degree adjusting means 30 determines that the superheat degree is excessive through the state determination unit 33, and sets the valve opening degree. The opening of the electronic expansion valve 13 is enlarged through the unit 34, that is, set to an opening obtained by adding a predetermined size (step S104), and then the procedure is returned. As a result, the supply of refrigerant to the evaporator 12 is increased, and the degree of superheat in the evaporator 12 is lowered.

  When the calculated degree of superheat is less than or equal to the upper limit value of the superheat degree target value (step S103: No), the valve opening degree adjusting means 30 is less than the lower limit value (for example, 2 ° C.) of the superheat degree target value. It is determined whether or not (step S105).

  When the calculated superheat degree is below the lower limit value of the superheat degree target value (step S105: Yes), the valve opening degree adjusting means 30 determines the outlet temperature detected in step S101 stored in the setting storage unit 31. It is determined whether the temperature is lower than the reference temperature (for example, 0 ° C.) (step S106).

  When the outlet temperature is lower than the reference temperature (step S106: Yes), the valve opening degree adjusting means 30 causes the compressor 15 to suck the liquid refrigerant through the state determination unit 33, that is, the liquid back is generated. The opening degree of the electronic expansion valve 13 is reduced through the valve opening degree setting unit 34, that is, set to an opening degree reduced by a predetermined size (step S107), and then the procedure is returned. As a result, the supply of the refrigerant to the evaporator 12 is reduced, and the superheat degree in the evaporator 12 is increased.

  On the other hand, when the outlet temperature is equal to or higher than the reference temperature (step S106: No), the valve opening degree adjusting means 30 determines that the compressor 15 is stopped through the state determining unit 33 and the valve opening degree setting unit 34. The electronic expansion valve 13 is fully closed through (step S108), and then the procedure is returned. As a result, there is no possibility that the liquid refrigerant flows from the high pressure portion (region extending from the compressor 15 to the electronic expansion valve 13) into the low pressure portion (region extending from the electronic expansion valve 13 to the compressor 15) of the refrigeration cycle.

  Thereafter, the valve opening degree adjusting means 30 determines the opening degree of the electronic expansion valve 13 through the valve opening degree setting unit 34 after the elapse of a preset set time (for example, 60 seconds) by the state determination unit 33 and the compressor 15. Is set to about 70% of the opening degree of the electronic expansion valve 13 at the time when it is determined that is stopped.

  By the way, when the degree of superheat calculated in step S102 is greater than or equal to the lower limit value of the superheat degree target value and less than or equal to the upper limit value (step S103: No, step S105: No), the valve opening degree adjuster 30 performs overheat through the state determination unit 33. It is determined that the degree is appropriate, the opening degree of the electronic expansion valve 13 is maintained (step S109), and then the procedure is returned.

  FIG. 4 is a chart showing the results of a feel test of the expansion valve opening degree control process of the valve opening degree adjusting means 30 shown in FIG. 3, (a) shows changes over time in inlet temperature, outlet temperature, and superheat degree, b) shows the change of the valve opening in the same time change as (a), and the operating state of the compressor 15. Here, the lower limit value of the superheat degree target value is 2 ° C., the reference temperature of the determination value is 0 ° C., and the expansion valve opening degree control process is performed.

  As shown in FIG. 4, at time t1, the degree of superheat falls below the lower limit (2 ° C.) of the superheat degree target value, and the outlet temperature is equal to or higher than the reference temperature (0 ° C.). 30 makes the electronic expansion valve 13 fully closed. At time t1, the compressor 15 is actually stopped. At time t2 after elapse of a predetermined time (for example, 60 seconds) from time t1, the valve opening degree adjusting means 30 changes the opening degree of the electronic expansion valve 13 to the opening degree at time t1 (that is, the compressor 15 is stopped driving). The degree of opening is adjusted to about 70% of the opening degree at the time when it is determined to be.

  At times t3 and t4, the degree of superheat falls below the lower limit value of the superheat degree target value, but since the outlet temperature is equal to or higher than the reference temperature, the valve opening degree adjusting means 30 sets the opening degree of the electronic expansion valve 13 to 10 pulses, for example. It is set small.

  As shown in the feel test of FIG. 4, at time t1 when the valve opening degree adjusting means 30 determines that the compressor 15 has stopped driving, the compressor 15 has actually stopped driving. It will be understood that the expansion valve opening degree control process was able to satisfactorily determine whether the compressor 15 was stopped.

  As described above, according to the cooling device according to the embodiment of the present invention, the degree of superheat in which the valve opening degree adjusting unit 30 stores the superheat degree calculated by the superheat degree calculation unit 32 in the setting storage unit 31. When it is less than the lower limit value of the target value and the outlet temperature is equal to or higher than the reference temperature of the determination value stored in the setting storage unit 31, it is determined that the compressor 15 constituting the refrigerator is stopped. While the electronic expansion valve 13 is fully closed, when the degree of superheat calculated by the superheat degree calculation unit 32 is less than the lower limit value and the outlet temperature is less than the reference temperature, the compressor 15 sucks the liquid refrigerant. Since it is determined that the opening of the electronic expansion valve 13 is reduced, it is possible to detect well that the compressor 15 has stopped driving due to the factor of the compressor 15 itself, such as refrigeration oil return control. Can do. And since the electronic expansion valve 13 is made into a fully-closed state, when the compressor 15 starts a drive again after that, there is no possibility that this compressor 15 may attract | suck a liquid refrigerant. Therefore, it is possible to prevent the liquid refrigerant from being sucked when the compressor 15 whose driving has been stopped due to the factor of the compressor 15 starts to drive again like the refrigerating machine oil return control.

  Particularly, according to the cooling device, the valve opening degree adjusting means 30 is such that the compressor 15 stops the opening degree of the electronic expansion valve 13 after a predetermined time has elapsed since the electronic expansion valve 13 is fully closed. Is set to about 70% of the opening degree of the electronic expansion valve 13 at the time when it is determined that the evaporating temperature of the refrigerant in the evaporator 12 when the compressor 15 starts to drive again can be set. It is possible to reliably avoid occurrence of a situation in which the liquid 15 sucks the liquid refrigerant.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made.

  In the above-described embodiment, when the opening degree of the electronic expansion valve 13 is fully closed, the valve opening degree adjusting unit 30 is configured so that the electronic expansion valve after a preset time (for example, 60 seconds) elapses. The opening degree of 13 is set to about 70% of the opening degree of the electronic expansion valve 13 at the time when the state determination unit 33 determines that the compressor 15 is stopped. The size may be set to 55 to 75%, and is not necessarily limited to 70%.

  Further, in the above-described embodiment, the valve opening degree adjusting means 30 is configured such that, when the opening degree of the electronic expansion valve 13 is fully closed, the electronic opening valve 13 is electronically set after a preset time (for example, 60 seconds) has elapsed. Although the opening degree of the expansion valve 13 is set to about 70% of the opening degree of the electronic expansion valve 13 at the time when the state determination unit 33 determines that the compressor 15 is stopped, The invention is not limited to this, and after the electronic expansion valve is fully closed, the superheat degree calculated by the superheat degree calculation unit (superheat degree calculation means) is equal to or higher than the lower limit value (threshold value) of the superheat degree target value, or the outlet When the temperature is lower than the reference temperature of the determination value, the opening degree of the electronic expansion valve is set to 55 to 75% of the opening degree of the electronic expansion valve when it is determined that the compressor is stopped. May be set. That is, the return condition of the electronic expansion valve that is once fully closed may be the elapse of a predetermined time or may be when the determination that the compressor is stopped is released.

  Moreover, in the above-described embodiment, the expansion valve opening degree control process based on the deviation between the superheat degree and the superheat degree target value has been described, but in the present invention, in parallel with the expansion valve opening degree control process, You may perform control which adjusts the opening degree of an electronic expansion valve based on the deviation of the internal temperature of a storage and preset temperature.

  As described above, the cooling device according to the present invention is useful for cooling the open showcase container.

DESCRIPTION OF SYMBOLS 10 Container 11 Open showcase 12 Evaporator 13 Electronic expansion valve 14 Condenser 15 Compressor 20 Inlet part refrigerant | coolant temperature sensor 21 Outlet part refrigerant | coolant temperature sensor 30 Valve opening degree adjustment means 31 Setting memory | storage part 32 Superheat degree calculation part 33 State judgment Part 34 Valve opening setting part

Claims (1)

In the cooling device that adjusts the opening of the electronic expansion valve and controls the supply of the refrigerant to the evaporator disposed in the storage device to bring the storage of the storage device into a desired temperature state,
A superheat degree calculating means for subtracting the refrigerant inlet temperature at the inlet of the evaporator from the refrigerant outlet temperature at the outlet of the evaporator to calculate the degree of superheat in the evaporator;
Compression that compresses the refrigerant discharged from the evaporator when the superheat calculated by the superheat calculating means is less than a predetermined threshold and the outlet temperature is equal to or higher than a predetermined reference temperature. It is determined that the machine is stopped and the electronic expansion valve is fully closed, while the superheat calculated by the superheat calculation means is less than the threshold and the outlet temperature is less than the reference temperature. In some cases, the controller includes a control unit that performs control to reduce the opening of the electronic expansion valve by determining that the compressor sucks the liquid refrigerant ,
After the electronic expansion valve is fully closed, the control means, when the superheat degree calculated by the superheat degree calculation means is equal to or higher than the threshold value, or the outlet temperature is lower than the reference temperature. A cooling device that performs control to increase the opening degree of the expansion valve to 55 to 75% of the opening degree of the electronic expansion valve when it is determined that the compressor is stopped .

Images