JP6179333B2 - Refrigerator and showcase - Google Patents

Description

  The present invention relates to a cooling device and a showcase, and more particularly to a cooling device and a showcase provided with a compressor capable of controlling the rotation speed.

  Conventionally, a cooling device including a compressor capable of controlling the rotation speed by inverter control or the like is known. In this cooling device, when the rotational speed of the compressor is near the lower limit, it is difficult to accurately control the cooling temperature because the rotational speed cannot be further reduced. Therefore, various techniques have been proposed in order to accurately control the cooling temperature even when the rotational speed of the compressor is close to the lower limit (see, for example, Patent Document 1).

  Patent Document 1 includes a compressor, a condenser, an expansion valve, and an evaporator that can control the rotation speed, and includes a refrigeration cycle that circulates refrigerant and a control unit that controls the rotation speed of the compressor. An apparatus is disclosed. In the cooling device of Patent Document 1, when the cooling temperature is equal to or lower than a low load temperature that is lower than a preset temperature by a predetermined temperature, the control unit is configured to control the rotation speed of the compressor. The compressor is configured to shift to a mode in which the rotation speed of the compressor is fixed to a lower limit value and the opening degree of the expansion valve is controlled. Thereby, even when the rotational speed of the compressor is near the lower limit, the cooling temperature is accurately controlled by the opening degree control of the expansion valve.

Japanese Patent No. 4970199

  However, in the cooling device described in Patent Document 1, the control unit controls the rotation speed of the compressor when the cooling temperature is equal to or lower than a low load temperature that is lower than a preset temperature by a predetermined temperature. It is configured to shift from the control mode to a mode in which the rotation speed of the compressor is fixed to the lower limit value and the opening degree of the expansion valve is controlled, so even when the cooling temperature is lower than the set temperature, it is always It is necessary to drive the compressor, and there is a problem that it is difficult to save energy of the apparatus.

  Conventionally, as a general configuration other than Patent Document 1, when the cooling temperature falls below the lower limit temperature of a predetermined temperature range centered on a preset temperature, the driving of the compressor is stopped and stopped. There is known a cooling device configured to restart the compressor when an upper limit temperature in a predetermined temperature range is exceeded. In this cooling device, when the compressor is driven at the lower limit speed, when the cooling temperature changes between the preset temperature and the lower limit temperature at which the drive is stopped (within the predetermined temperature range), The cooling temperature is always lower than the cooling target temperature without stopping the machine. In this case, there is a problem that cooling becomes excessive and energy consumption increases correspondingly. In this case, it is difficult to bring the cooling temperature close to the cooling target temperature with high accuracy.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to accurately control the cooling temperature even when the rotational speed of the compressor is near the lower limit. An object of the present invention is to provide a cooling device and a showcase that can save energy.

  A cooling device according to a first aspect of the present invention includes a compressor, a condenser, an expansion valve, and an evaporator that are capable of controlling the rotation speed, and controls the refrigerating cycle for circulating the refrigerant and the rotation speed of the compressor. A control unit that integrates the difference between the cooling target temperature value and the measured temperature value to obtain a temperature difference integrated amount that takes into account a positive or negative sign, and the acquired temperature difference integrated amount is negative. The compressor is configured to stop when it becomes less than the amount.

  In the cooling device according to the first aspect of the present invention, as described above, the control unit integrates the difference between the cooling target temperature value and the measured temperature value, and acquires the temperature difference integration amount considering the positive and negative signs, When the measured temperature difference is lower than the cooling target temperature by configuring the compressor to stop when the acquired temperature difference integrated amount is less than the negative first integrated amount, the compressor Since the drive is stopped, energy can be saved by the amount that the compressor is stopped. In addition, since the compressor is stopped when the temperature difference integrated amount becomes less than the negative first integrated amount, the compressor is not stopped when the compressor rotational speed is close to the lower limit. Unlike the case where the temperature is always lower than the cooling target temperature, it is possible to suppress the cooling average temperature from always being lower than the cooling target temperature. Thereby, excessive cooling is suppressed, and even when the rotation speed of the compressor becomes near the lower limit, the cooling temperature can be controlled accurately and energy can be saved.

  In the cooling device according to the first aspect, preferably, the control unit continuously accumulates the difference between the cooling target temperature value and the measured temperature value after stopping the compressor, and the temperature difference accumulated amount is the second accumulated amount. It is configured to restart the compressor when it exceeds the quantity. By configuring in this way, the difference between the cooling target temperature value and the measured temperature value is continuously accumulated, and unlike when resetting the accumulated temperature difference when the compressor is stopped, the compressor is stopped. Therefore, the cooling average temperature can be brought close to the cooling target temperature with high accuracy by stopping and restarting the compressor.

  In the cooling device according to the first aspect, preferably, the control unit is configured such that when the absolute value of the difference between the cooling target temperature value and the measured temperature value is smaller than a predetermined value, the difference between the cooling target temperature value and the measured temperature value. It is comprised so that accumulation | storage of this may not be performed. With this configuration, when the absolute value of the difference between the cooling temperature and the cooling target temperature is small as in the case where the cooling temperature is substantially the same as the cooling target temperature, the difference between the cooling target temperature value and the measured temperature value. It is possible to prevent the compressor from being stopped when the temperature difference integration amount becomes less than the first integration amount.

  In the cooling device according to the first aspect, preferably, the control unit does not accumulate the difference between the cooling target temperature value and the measured temperature value when the rotation speed of the compressor is higher than a predetermined speed, or the temperature The difference integrated amount is configured to be reset. Here, when the rotational speed of the compressor is larger than a predetermined speed, the cooling temperature can be accurately adjusted only by controlling the rotational speed of the compressor. In such a case, integration is performed. It is possible to prevent the compressor from being stopped due to accumulation of the difference between the cooling target temperature value and the measured temperature value by resetting the accumulated amount or not.

  In the cooling device according to the first aspect, preferably, the control unit integrates the difference between the cooling target temperature value and the measured temperature value, and the normal operation is performed when the temperature difference integrated amount becomes less than the third integrated amount. The mode is changed to the low load mode in which the compressor is driven at a constant rotational speed or less, and the compressor is stopped when the temperature difference integrated amount becomes less than the negative first integrated amount in the low load mode. ing. If comprised in this way, in the low load mode, by controlling to drive the compressor at the lower limit rotational speed and controlling to stop the compressor, the cooling temperature is brought close to the cooling target temperature accurately while saving energy. be able to.

  A showcase according to a second aspect of the present invention includes an accommodating portion that accommodates an article, a compressor, a condenser, an expansion valve, and an evaporator that can control the rotation speed, and circulates a refrigerant to cool the accommodating portion. And a control unit that controls the rotational speed of the compressor, and the control unit integrates the difference between the cooling target temperature value and the measured temperature value and takes into account the positive and negative signs. When the acquired temperature difference integrated amount becomes less than the negative first integrated amount, the compressor is stopped.

  In the showcase according to the second aspect of the present invention, as described above, the controller obtains a temperature difference integrated amount that takes into account the positive and negative signs by integrating the difference between the cooling target temperature value and the measured temperature value, When the measured temperature difference is lower than the cooling target temperature by configuring the compressor to stop when the acquired temperature difference integrated amount is less than the negative first integrated amount, the compressor Since the drive is stopped, energy can be saved by the amount that the compressor is stopped. In addition, since the compressor is stopped when the temperature difference integrated amount becomes less than the negative first integrated amount, the compressor is not stopped when the compressor rotational speed is close to the lower limit. Unlike the case where the temperature is always lower than the cooling target temperature, it is possible to suppress the cooling average temperature from always being lower than the cooling target temperature. Thereby, it is possible to provide a showcase capable of suppressing energy consumption while suppressing excessive cooling and accurately controlling the cooling temperature even when the rotational speed of the compressor is close to the lower limit. .

  According to the present invention, as described above, there is provided a cooling device and a showcase capable of achieving energy saving while accurately controlling the cooling temperature even when the rotational speed of the compressor is near the lower limit. be able to.

1 is a block diagram showing a schematic overall configuration of a showcase according to an embodiment of the present invention. It is the figure which showed the temperature control process of the showcase by one Embodiment of this invention. It is the flowchart which showed the control processing at the time of the normal operation mode of the showcase by one Embodiment of this invention. It is the flowchart which showed the control processing at the time of the inverter stop in the low load mode of the showcase by one Embodiment of this invention. It is the flowchart which showed the control processing at the time of the inverter starting in the low load mode of the showcase by one Embodiment of this invention. It is the figure which showed an example of the temperature transition of the showcase by one Embodiment of this invention. It is the figure which showed the temperature transition of the showcase by the state 1 of a comparative example. It is the figure which showed the temperature transition of the showcase by the state 2 of a comparative example.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

  First, with reference to FIG. 1 and FIG. 2, the structure of the showcase 100 by one Embodiment of this invention is demonstrated. The showcase 100 is an example of the “cooling device” in the present invention.

  As shown in FIG. 1, the showcase 100 according to the present embodiment includes a storage unit 1, a refrigeration cycle 2, a control unit 3, a drive unit 4, an AC power source 5, and a sensor 6. The refrigeration cycle 2 includes a compressor 21, a condenser 22, an expansion valve 23, and an evaporator 24.

  The accommodating part 1 is comprised so that articles | goods (not shown), such as goods, may be accommodated. In addition, the storage unit 1 is configured to be cooled by cold air blown from the evaporator 24 of the refrigeration cycle 2.

The refrigeration cycle 2 is configured to circulate a refrigerant such as carbon dioxide (CO ₂ ) through the compressor 21, the condenser 22, the expansion valve 23, and the evaporator 24 to cool the housing unit 1.

  The compressor 21 is configured to be rotationally driven by a drive unit 4 that is driven by AC power supplied from an AC power supply 5. The compressor 21 has a role of compressing the gas refrigerant sucked from the low pressure side in the refrigeration cycle 2 and discharging it to the high pressure side. The compressor 21 is an inverter-controlled compressor that can control the refrigerant discharge amount by changing the rotation speed (operation frequency).

  The condenser 22 has a function of cooling the superheated gas refrigerant flowing through the inside using external air. The refrigerant condensed (liquefied) in the condenser 22 flows into the expansion valve 23.

  The expansion valve 23 has a role of expanding and reducing (depressurizing) the refrigerant cooled (liquefied) by the condenser 22 and supplying it to the evaporator 24. The expansion valve 23 is configured to open and close the valve mechanism using the driving force of a stepping motor driven by pulse control. Further, the liquid refrigerant expanded and contracted by the expansion valve 23 flows into the evaporator 24 in a gas-liquid two-phase state composed of a gas phase and a liquid phase.

  The evaporator 24 is provided with a blower (not shown), and is configured so that air (cool air) for cooling the article is circulated between the evaporator 24 and the housing portion 1 by the blower. . Further, the evaporator 24 cools the circulating air by taking heat from the circulating air when the circulating refrigerant evaporates (vaporizes). Further, the refrigerant after evaporation in the evaporator 24 is returned to the compressor 21 in a gas state containing a large amount of gas phase. As described above, in the refrigeration cycle 2, the refrigerant discharged from the compressor 21 flows in the order of the condenser 22, the expansion valve 23, and the evaporator 24 and is returned to the compressor 21.

  The control unit 3 is configured to control the entire showcase 100. The control unit 3 is configured to control the rotation speed of the compressor 21. Specifically, the control unit 3 is configured to control the rotation speed of the compressor 21 by transmitting a rotation speed command and an ON / OFF command to the drive unit 4. Further, the control unit 3 is configured to control the rotational speed of the compressor 21 by inverter control that controls the frequency of AC power supplied from the AC power supply 5 and by converting the power.

  Further, as shown in FIG. 2, the control unit 3 measures the temperature (measured temperature) of the cool air blown from the controlled object (refrigeration cycle 2) to the storage unit 1, and compares the measured temperature with the cooling target temperature. The rotation speed of the compressor 21 is calculated by the unit, and the control target (refrigeration cycle 2) is feedback-controlled. For example, when the blowing temperature is higher than the cooling target temperature, the control unit 3 performs control so as to increase the rotational speed of the compressor 21. When the blowout temperature is lower than the cooling target temperature, the control unit 3 performs control so that the rotation speed of the compressor 21 is lowered. Thereby, it is possible to make blowing temperature close to cooling target temperature. Further, it is possible to keep the blowing temperature in the vicinity of the cooling target temperature.

  Here, in the present embodiment, the control unit 3 integrates the difference between the cooling target temperature value and the measured temperature value (the value obtained by subtracting the cooling target temperature value from the measured temperature value), and takes into account the positive / negative sign. The integrated amount I is acquired, and the compressor 21 is stopped when the acquired temperature difference integrated amount I becomes less than the negative first integrated amount Ia (time t1 and time t3 in FIG. 6). Yes. Specifically, the control unit 3 obtains the blowing temperature (measured temperature) of the cold air (circulated air) blown from the evaporator 24 detected by the sensor 6, and is a value obtained by subtracting the cooling target temperature value from the measured temperature value. Is integrated to calculate the temperature difference integrated amount I. The control unit 3 is configured to calculate the difference between the cooling target temperature value and the measured temperature value at predetermined time intervals (for example, 10 seconds). In addition, the 1st integration amount Ia is set to the value of the state which continued the state which fell 1 to 2 degreeC from cooling target temperature for about 10 minutes, for example. For example, the first integrated amount Ia is set to −100 ° C.

  The control unit 3 is configured not to integrate the difference between the cooling target temperature value and the measured temperature value when the absolute value of the difference between the cooling target temperature value and the measured temperature value is smaller than a predetermined value. Yes. For example, when the difference between the cooling target temperature value and the measured temperature value is larger than −0.5 ° C. and smaller than + 0.5 ° C., the control unit 3 does not integrate the difference between the cooling target temperature value and the measured temperature value. It is configured as follows. That is, the control unit 3 is configured not to integrate the difference between the cooling target temperature value and the measured temperature value when it can be considered that the blowout temperature (measured temperature) substantially matches the cooling target temperature. In addition, when the difference between the cooling target temperature value and the measured temperature value is −0.5 ° C. or less or + 0.5 ° C. or more, the control unit 3 determines that the dead zone temperature (substantially coincides with the difference between the cooling target temperature and the measured temperature. The difference between the cooling target temperature value and the measured temperature value is integrated by subtracting (for example, 0.5 ° C.).

  Further, when the rotational speed of the compressor 21 is higher than the predetermined speed, the control unit 3 does not accumulate the difference between the cooling target temperature value and the measured temperature value, and resets the temperature difference accumulated amount Ia (= 0). To be configured). That is, the control unit 3 is configured not to integrate the difference between the cooling target temperature value and the measured temperature value when the temperature can be increased by lowering the rotation speed of the compressor 21. .

  Further, the control unit 3 integrates the difference between the cooling target temperature value and the measured temperature value, and when the temperature difference integrated amount I becomes less than the third integrated amount (time t1 in FIG. 6), the normal operation mode is started. The compressor 21 is shifted to a low load mode in which the compressor 21 is driven at a constant rotational speed or less, and the compressor 21 is stopped when the temperature difference integrated amount I becomes less than the negative first integrated amount in the low load mode. Has been. The low load mode is a mode in which the cooling temperature is controlled by rotating the compressor 21 at the lower limit rotation speed or stopping the rotation. Further, the lower limit rotational speed includes a mechanically lower limit rotational speed of the compressor 21 and a rotational speed that allows for a safety factor in the lower limit rotational speed. The third integrated amount is set to a value in a state where, for example, a state where the temperature is lowered by 1 ° C. to 2 ° C. from the cooling target temperature continues for about 10 minutes. For example, it is set to −100 ° C. That is, the same value is set for the first integrated amount and the third integrated amount. Thus, when the normal operation mode is shifted to the low load mode, the compressor 21 (inverter) is immediately stopped (time t1 in FIG. 6). When the compressor 21 is rotationally driven in the low load mode, the compressor 21 is stopped (time t3 in FIG. 6) when the temperature difference integrated amount I is less than the first integrated amount.

  Further, after the compressor 21 is stopped, the control unit 3 continues to integrate the difference between the cooling target temperature value and the measured temperature value, and the temperature difference integrated amount I becomes larger than the second integrated amount (for example, 0). In such a case (time t2 in FIG. 6), the compressor 21 is restarted. That is, when the temperature difference integrated amount I becomes a positive value, the compressor 21 is restarted. This indicates that, as shown in FIG. 6, the area of the region where the blowing temperature (measured temperature) is lower than the cooling target temperature is equal to the area of the region where the blowing temperature (measured temperature) is higher than the cooling target temperature. This means that the average of the blowing temperature (measured temperature) after the temperature difference integrated amount I starts to be integrated becomes the cooling target temperature.

  Further, the controller 3 is configured to rotate and drive at the lower limit rotation speed when the compressor 21 is started. As a result, by increasing the rotation speed when the compressor 21 is started up, it is possible to suppress an increase in the fluctuation of the cooling temperature due to repeated rapid stopping of the temperature immediately after the temperature suddenly drops. Is possible. Further, it is possible to prevent the compressor 21 from being damaged by suppressing the stop and start of the compressor 21 from being repeated in a short time.

  In addition, after shifting to the low load mode, the control unit 3 continuously accumulates the difference between the cooling target temperature value and the measured temperature value, the temperature difference integrated amount I becomes larger than 0, and the low load mode is set. When a certain period of time has elapsed since the transition (for example, 10 minutes depending on the size of the housing portion 1), the transition is made from the low-load mode to the normal operation mode.

  The drive unit 4 is configured to drive the compressor 21 based on the rotational speed and the ON / OFF command received from the control unit 3. The drive unit 4 is configured to drive the compressor 21 with AC power from the AC power supply 5.

  The sensor 6 is configured to detect the blowing temperature (cooling temperature) of the air blown into the housing unit 1. The sensor 6 is connected to the control unit 3 and configured to transmit the detected blowing temperature to the control unit 3.

  Next, with reference to FIG. 3, the control process in the normal operation mode by the control unit 3 of the showcase 100 of the present embodiment will be described.

  In step S <b> 1 of FIG. 3, the control unit 3 acquires the blowing temperature Tb detected by the sensor 6. In step S <b> 2, the control unit 3 transmits a rotational speed command for rotationally driving the compressor 21 to the drive unit 4 based on the acquired blowing temperature (cooling temperature) Tb and the cooling target temperature Tb <b> 0. In step S3, the control unit 3 determines whether or not the rotational speed F of the compressor 21 is equal to or lower than a predetermined rotational speed FA. If F is less than or equal to FA, the process proceeds to step S4, and if F is greater than FA, the process proceeds to step S7. The predetermined rotation speed FA is set based on the rotation speed of the compressor 21 that can control the cooling temperature by controlling the rotation speed of the compressor 21.

  In step S4, the control unit 3 determines whether or not the blowing temperature Tb is equal to or higher than the cooling target temperature Tb0. If Tb is equal to or greater than Tb0, the process proceeds to step S5. If Tb is less than Tb0, the process proceeds to step S8. In step S5, the control unit 3 determines whether or not the blowout temperature Tb is larger than a value obtained by adding the dead zone temperature Tb1 (for example, 0.5 ° C.) to the cooling target temperature Tb0. That is, the control unit 3 determines whether or not the blowing temperature Tb is substantially the same as the cooling target temperature Tb0 in consideration of the measurement error. If Tb is larger than Tb0 + Tb1, the process proceeds to step S6. If Tb is equal to or less than Tb0 + Tb1, the process is terminated. That is, when Tb is equal to or less than Tb0 + Tb1, the difference between the cooling target temperature Tb0 and the blowing temperature (measured temperature) Tb is not integrated.

  In step S6, the control unit 3 updates the temperature difference integrated amount I as I = I + (Tb−Tb0−Tb1). That is, the control unit 3 integrates the temperature difference integrated amount I by subtracting the dead zone temperature Tb1 from the difference between the blowing temperature (measured temperature) Tb and the cooling target temperature Tb0.

  When it is determined in step S3 that F is larger than FA, in step S7, the control unit 3 sets I = 0 and resets the temperature difference integrated amount I. In this case, the difference between the cooling target temperature Tb0 and the discharge temperature (measured temperature) Tb is not integrated. Thereafter, the process is terminated.

  When it is determined in step S4 that Tb is smaller than Tb0, in step S8, the control unit 3 determines that the blowout temperature Tb is a value obtained by subtracting the dead zone temperature Tb2 (for example, 0.5 ° C.) from the cooling target temperature Tb0. Judge whether it is small or not. That is, the control unit 3 determines whether or not the blowing temperature Tb is substantially the same as the cooling target temperature Tb0 in consideration of the measurement error. If Tb is smaller than Tb0-Tb2, the process proceeds to step S9. If Tb is equal to or greater than Tb0-Tb2, the process proceeds to step S10. That is, when Tb is equal to or higher than Tb0−Tb2, the difference between the cooling target temperature Tb0 and the blowing temperature (measured temperature) Tb is not integrated.

  In step S9, the control unit 3 updates the temperature difference integrated amount I as I = I− (Tb0−Tb2−Tb) (I = I + (Tb−Tb0 + Tb2)). That is, the control unit 3 adds the dead zone temperature Tb2 to the difference between the blowing temperature (measured temperature) Tb and the cooling target temperature Tb0, and integrates the temperature difference integrated amount I. Then, it progresses to step S10.

  In step S10, the control unit 3 determines whether or not the temperature difference integrated amount I is less than the first integrated amount Ia. If I is less than Ia, the process proceeds to step S11. If I is greater than or equal to Ia, the process ends. In step S11, the control unit 3 shifts to the low load mode and ends the process. In the normal operation mode, the blowing temperature Tb is measured every 10 seconds, and the processes of steps S1 to S11 are repeated.

  Next, with reference to FIG. 4, the control process at the time of the inverter (compressor) stop by the control part 3 of the showcase 100 of this embodiment in the low load mode is demonstrated.

  In this process, the compressor 21 starts from a state where the rotation is stopped. In step S <b> 21 of FIG. 4, the control unit 3 acquires the blowing temperature Tb detected by the sensor 6. In step S22, the control unit 3 determines whether or not the blowing temperature Tb is equal to or higher than the cooling target temperature Tb0. If Tb is equal to or greater than Tb0, the process proceeds to step S23, and if Tb is less than Tb0, the process proceeds to step S27.

  In step S23, the control unit 3 determines whether or not the blowing temperature Tb is larger than a value obtained by adding the dead zone temperature Tb1 (for example, 0.5 ° C.) to the cooling target temperature Tb0. That is, the control unit 3 determines whether or not the blowing temperature Tb is substantially the same as the cooling target temperature Tb0 in consideration of the measurement error. When Tb is larger than Tb0 + Tb1, the process proceeds to step S24, and when Tb is equal to or less than Tb0 + Tb1, the process proceeds to step S25. That is, when Tb is equal to or less than Tb0 + Tb1, the difference between the cooling target temperature Tb0 and the blowing temperature (measured temperature) Tb is not integrated.

  In step S24, the control unit 3 updates the temperature difference integrated amount I as I = I + (Tb−Tb0−Tb1). That is, the control unit 3 integrates the temperature difference integrated amount I by subtracting the dead zone temperature Tb1 from the difference between the blowing temperature (measured temperature) Tb and the cooling target temperature Tb0. Thereafter, the process proceeds to step S25. In step S25, the control unit 3 determines whether or not the temperature difference integrated amount I is larger than zero. If I is greater than 0 (if positive), the process proceeds to step S26, and if I is 0 or less, the process ends. In step S26, the control unit 3 drives the compressor 21 at the lower limit rotational speed. Thereafter, the process ends.

  When it is determined in step S22 that Tb is smaller than Tb0, in step S27, the control unit 3 determines that the blowout temperature Tb is a value obtained by subtracting the dead zone temperature Tb2 (for example, 0.5 ° C.) from the cooling target temperature Tb0. Judge whether it is small or not. That is, the control unit 3 determines whether or not the blowing temperature Tb is substantially the same as the cooling target temperature Tb0 in consideration of the measurement error. When Tb is smaller than Tb0-Tb2, the process proceeds to step S28, and when Tb is equal to or greater than Tb0-Tb2, the process ends. That is, when Tb is equal to or higher than Tb0−Tb2, the difference between the cooling target temperature Tb0 and the blowing temperature (measured temperature) Tb is not integrated.

  In step S28, the control unit 3 updates the temperature difference integrated amount I as I = I− (Tb0−Tb2−Tb). That is, the control unit 3 adds the dead zone temperature Tb2 to the difference between the blowing temperature (measured temperature) Tb and the cooling target temperature Tb0, and integrates the temperature difference integrated amount I. Thereafter, the process ends. When the compressor 21 is stopped in the low load mode, the blowing temperature Tb is measured every 10 seconds, and the processes of steps S21 to S28 are repeated.

  Next, with reference to FIG. 5, the control process at the time of starting the inverter (compressor) in the low load mode by the control unit 3 of the showcase 100 of the present embodiment will be described.

  In this process, the compressor 21 starts from a state where it is driven at the lower limit rotational speed. In step S <b> 31 of FIG. 5, the control unit 3 acquires the blowing temperature Tb detected by the sensor 6. In step S32, the control unit 3 determines whether or not the blowing temperature Tb is equal to or higher than the cooling target temperature Tb0. If Tb is equal to or greater than Tb0, the process proceeds to step S33, and if Tb is less than Tb0, the process proceeds to step S37.

  In step S33, the control unit 3 determines whether or not the blowing temperature Tb is larger than a value obtained by adding the dead zone temperature Tb1 (for example, 0.5 ° C.) to the cooling target temperature Tb0. That is, the control unit 3 determines whether or not the blowing temperature Tb is substantially the same as the cooling target temperature Tb0 in consideration of the measurement error. When Tb is larger than Tb0 + Tb1, the process proceeds to step S34, and when Tb is equal to or less than Tb0 + Tb1, the process proceeds to step S35. That is, when Tb is equal to or less than Tb0 + Tb1, the difference between the cooling target temperature Tb0 and the blowing temperature (measured temperature) Tb is not integrated.

  In step S34, the control unit 3 updates the temperature difference integrated amount I as I = I + (Tb−Tb0−Tb1). That is, the control unit 3 integrates the temperature difference integrated amount I by subtracting the dead zone temperature Tb1 from the difference between the blowing temperature (measured temperature) Tb and the cooling target temperature Tb0. Thereafter, the process proceeds to step S35. In step S35, the control unit 3 determines whether or not the temperature difference integrated amount I is greater than 0 and the release timer S is equal to or greater than Sa. The release timer S starts counting after shifting to the low load mode. That is, the control unit 3 determines whether or not the temperature difference integrated amount I is greater than 0 and whether a certain time Sa has elapsed after shifting to the low load mode. If I is greater than 0 (positive) and S is greater than or equal to Sa, the process proceeds to step S36, and if I is less than or equal to 0 or S is less than Sa, the process ends. In step S36, the control unit 3 cancels the low load mode and shifts to the normal operation mode.

  When it is determined in step S32 that Tb is smaller than Tb0, in step S37, the control unit 3 determines that the blowout temperature Tb is a value obtained by subtracting the dead zone temperature Tb2 (for example, 0.5 ° C.) from the cooling target temperature Tb0. Judge whether it is small or not. That is, the control unit 3 determines whether or not the blowing temperature Tb is substantially the same as the cooling target temperature Tb0 in consideration of the measurement error. When Tb is smaller than Tb0-Tb2, the process proceeds to step S38, and when Tb is equal to or greater than Tb0-Tb2, the process proceeds to step S39. That is, when Tb is equal to or higher than Tb0−Tb2, the difference between the cooling target temperature Tb0 and the blowing temperature (measured temperature) Tb is not integrated.

  In step S38, the control unit 3 updates the temperature difference integrated amount I as I = I− (Tb0−Tb2−Tb). That is, the control unit 3 adds the dead zone temperature Tb2 to the difference between the blowing temperature (measured temperature) Tb and the cooling target temperature Tb0, and integrates the temperature difference integrated amount I. In step S39, the control unit 3 determines whether or not the temperature difference integrated amount I is less than the first integrated amount Ia. If I is less than Ia, the process proceeds to step S40, and if I is greater than or equal to Ia, the process ends. In step S40, the control unit 3 stops the rotational drive of the compressor 21 and ends the process. When the compressor 21 is activated (driven) in the low load mode, the blowing temperature Tb is measured every 10 seconds, and the processes of steps S31 to S40 are repeated.

  Next, with reference to FIGS. 6-8, an example of the temperature transition in the showcase 100 of this embodiment and a comparative example is demonstrated.

  As shown in FIG. 6, the showcase 100 of the present embodiment is operated in the normal operation mode in which the blowout temperature (cooling temperature) is controlled by controlling the rotational speed of the compressor 21 during the period up to time t1. ing. Further, in the normal operation mode, when the temperature difference integrated amount I obtained by integrating the difference between the cooling target temperature value and the measured temperature value becomes less than the negative first integrated amount Ia (time t1), the mode shifts to the low load mode. At the same time, the compressor 21 is stopped. Thereafter, the difference between the cooling target temperature value and the measured temperature value is continuously accumulated without resetting the temperature difference accumulated amount I, and the temperature difference accumulated amount I becomes larger than the second accumulated amount (for example, 0). At (time t2), the compressor 21 is restarted. Thereafter, the difference between the cooling target temperature value and the measured temperature value is continuously accumulated without resetting the temperature difference accumulated amount I, and the temperature difference accumulated amount I becomes less than the negative first accumulated amount Ia ( At time t3), the compressor 21 is stopped.

  In the comparative example shown in FIG. 7 and FIG. 8, when the blowing temperature (cooling temperature) reaches an OFF temperature that is lower than the cooling target temperature by a predetermined amount or more, the compressor is stopped, and after the compressor is stopped, the blowing temperature (cooling temperature). ) Reaches the ON temperature that is higher than the cooling target temperature by a predetermined amount or more, the compressor is restarted.

  In the state 1 of the comparative example shown in FIG. 7, the compressor is stopped because the blowing temperature (cooling temperature) has reached the OFF temperature at time t11 (t13). In addition, after the compressor is stopped, the compressor is restarted because the discharge temperature (cooling temperature) reaches the ON temperature at time t12 (t14). In this case, the blowing temperature (cooling temperature) changes so as to rise and fall around the cooling target temperature.

  In the state 2 of the comparative example shown in FIG. 8, when the compressor is driven at the lower limit rotational speed, the blowing temperature (cooling temperature) stably changes between the cooling target temperature and the OFF temperature. . In this case, since the blowing temperature (cooling temperature) does not reach the OFF temperature, the compressor is not stopped and driving at the lower limit rotational speed is continued. For this reason, the average temperature becomes lower than the cooling target temperature. In this case, the cooling is wasted and energy consumption increases.

  In the present embodiment, the following effects can be obtained.

  In the present embodiment, as described above, the controller 3 acquires the temperature difference integration amount I taking into account the positive and negative signs by integrating the difference between the cooling target temperature value and the measured temperature value, and the acquired temperature difference integration. When the measured temperature (blowing temperature) is lower than the cooling target temperature by configuring the compressor 21 to stop when the amount I becomes less than the negative first integrated amount Ia. Since the drive of the compressor 21 is stopped, energy saving can be achieved as the compressor 21 is stopped. Further, since the compressor 21 is stopped when the temperature difference integrated amount I becomes less than the negative first integrated amount Ia, the rotational speed of the compressor becomes close to the lower limit as in the comparative example of FIG. In this case, unlike the case where the cooling temperature is always lower than the cooling target temperature without stopping the driving of the compressor, it is possible to suppress the cooling average temperature from always becoming lower than the cooling target temperature. Thereby, excessive cooling is suppressed, and even when the rotation speed of the compressor 21 is close to the lower limit, it is possible to save energy while accurately controlling the cooling temperature (blowing temperature).

  In the present embodiment, after the compressor 21 is stopped, the control unit 3 continues to integrate the difference between the cooling target temperature value and the measured temperature (blowing temperature) value, and the temperature difference integrated amount I is the second. The compressor 21 is configured to be restarted when it becomes larger than the integrated amount (= 0). Thus, unlike the case where the temperature difference integrated amount I is reset when the compressor 21 is stopped by continuously integrating the difference between the cooling target temperature value and the measured temperature value, the compressor 21 is stopped. Since the temperature transition before and after can be taken into consideration, the cooling average temperature (average of the blowing temperature) can be brought close to the cooling target temperature with high accuracy by stopping and restarting the compressor 21.

  Moreover, in this embodiment, when the absolute value of the difference between the cooling target temperature value and the measured temperature (blowing temperature) value is smaller than the predetermined value, the control unit 3 determines the difference between the cooling target temperature value and the measured temperature value. It is configured not to perform integration. Thus, when the absolute value of the difference between the cooling temperature and the cooling target temperature is small as in the case where the cooling temperature (blow-out temperature) is substantially the same as the cooling target temperature, the difference between the cooling target temperature value and the measured temperature value. When the temperature difference integrated amount I becomes less than the first integrated amount Ia, the compressor 21 can be prevented from being stopped.

  Further, in the present embodiment, when the rotational speed of the compressor 21 is greater than a predetermined speed, the control unit 3 does not perform the integration of the difference between the cooling target temperature value and the measured temperature (blowing temperature) value, and the temperature difference The integrated amount I is configured to be reset. Here, when the rotational speed of the compressor 21 is higher than a predetermined speed, the cooling temperature (blowing temperature) can be accurately adjusted only by controlling the rotational speed of the compressor 21. In addition, the integration is not performed, and the integration amount is reset, whereby the difference between the cooling target temperature value and the measured temperature value can be integrated to prevent the compressor 21 from being stopped.

  In the present embodiment, the control unit 3 integrates the difference between the cooling target temperature value and the measured temperature (blowing temperature) value, and when the temperature difference integrated amount I becomes less than the third integrated amount Ia, The operation mode is shifted to a low load mode in which the compressor 21 is driven at a constant rotational speed or less, and the compressor 21 is stopped when the temperature difference integrated amount I becomes less than the negative first integrated amount Ia in the low load mode. To be configured. Thereby, in the low load mode, the control for driving the compressor 21 at the lower limit rotational speed and the control for stopping the compressor 21 are performed, so that the cooling temperature (blowing temperature) is accurately set to the cooling target temperature while saving energy. Can be approached.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  For example, in the said embodiment, although the example which applied this invention to the showcase as a cooling device was shown, this invention is not limited to this. The present invention may be applied to a cooling device other than a showcase. For example, the present invention may be applied to a refrigerator, a freezer, an air conditioner, a water cooler, a freezer, a vending machine, or the like as a cooling device.

  Moreover, in the said embodiment, although the example of the structure which controls the rotational speed of a compressor by inverter control (frequency control) was shown, this invention is not limited to this. In the present invention, the rotational speed of the compressor may be controlled by means other than inverter control. For example, the compressor may include a DC motor and the rotation speed may be controlled by controlling the current value.

  Moreover, although the said embodiment showed the example of the structure which adds and subtracts a dead zone temperature from the difference of a cooling target temperature value and a measured temperature value, and integrates a temperature difference integrated amount, this invention is not limited to this. In the present invention, the difference between the cooling target temperature value and the measured temperature value may be integrated as the temperature difference integrated amount without adjusting the dead zone temperature.

  Moreover, although the example which performs control which stops a compressor when the temperature difference integrated amount became less than a negative 1st integrated amount was shown in the said embodiment, this invention is not limited to this. In the present invention, when the temperature difference integrated amount becomes less than the negative first integrated amount, the compressor is stopped, and when the measured temperature becomes less than a predetermined threshold value, the compressor is stopped. You may perform together with control. As a result, the separation between the measured temperature and the cooling target temperature can be suppressed on both long-term and short-term sides, so that stable and efficient cooling is possible.

  Moreover, although the example which performs control which restarts a compressor when the temperature difference integrated amount became larger than the 2nd integrated amount was shown in the said embodiment, this invention is not limited to this. In the present invention, when the temperature difference integrated amount becomes larger than the negative second accumulated amount, the compressor is restarted, and when the measured temperature becomes larger than a predetermined threshold value, the compressor is restarted. You may perform together with the control to start.

  Further, in the above embodiment, when the rotation speed of the compressor is higher than a predetermined speed, the difference between the cooling target temperature value and the measured temperature value is not integrated, and the control for resetting the temperature difference integrated amount is performed. Although an example is shown, the present invention is not limited to this. In the present invention, when the rotational speed of the compressor is larger than a predetermined speed, either the control that does not integrate the difference between the cooling target temperature value and the measured temperature value or the control that resets the temperature difference integrated amount is performed. The structure to perform may be sufficient.

  In the above embodiment, the first integrated amount that is the temperature difference integrated amount that stops the compressor and the third integrated amount that is the temperature difference integrated amount that shifts from the normal operation mode to the low load mode are set to the same value. However, the present invention is not limited to this. In the present invention, the first integrated amount and the third integrated amount may be different values.

In the above embodiment, an example of a configuration using a carbon dioxide (CO ₂₎ as a refrigerant, the present invention is not limited thereto. In the present invention, a refrigerant other than carbon dioxide may be used as the refrigerant. For example, a natural refrigerant other than carbon dioxide may be used, or an alternative chlorofluorocarbon refrigerant having an ozone layer depletion coefficient of zero may be used.

  Moreover, in the said embodiment, although the process of the control part was demonstrated using the flow drive type flowchart which processes in order along a process flow for convenience of explanation, this invention is not limited to this. In the present invention, the processing of the control unit may be performed by event-driven (event-driven) processing that executes processing in units of events. In this case, it may be performed by a complete event drive type or a combination of event drive and flow drive.

DESCRIPTION OF SYMBOLS 1 Storage part 2 Refrigeration cycle 3 Control part 21 Compressor 22 Condenser 23 Expansion valve 24 Evaporator 100 Showcase (cooling device)

Claims (6)

A refrigeration cycle including a compressor, a condenser, an expansion valve, and an evaporator capable of controlling the rotation speed, and circulating the refrigerant;
A controller for controlling the rotational speed of the compressor,
The control unit integrates the difference between the cooling target temperature value and the measured temperature value to acquire a temperature difference integrated amount in consideration of a positive / negative sign, and the acquired temperature difference integrated amount is less than the negative first integrated amount. A cooling device configured to stop the compressor when it becomes.   The controller continuously accumulates the difference between the cooling target temperature value and the measured temperature value after stopping the compressor, and the compression is performed when the temperature difference accumulated amount becomes larger than the second accumulated amount. The cooling device of claim 1, wherein the cooling device is configured to restart the machine.   The control unit is configured not to integrate the difference between the cooling target temperature value and the measured temperature value when the absolute value of the difference between the cooling target temperature value and the measured temperature value is smaller than a predetermined value. The cooling device according to claim 1 or 2.   The controller is configured not to integrate the difference between the cooling target temperature value and the measured temperature value or to reset the temperature difference integrated amount when the rotational speed of the compressor is greater than a predetermined speed. The cooling device according to any one of claims 1 to 3.   The control unit integrates the difference between the cooling target temperature value and the measured temperature value, and when the temperature difference integrated amount becomes less than the third integrated amount, the control unit starts the compressor from a normal operation mode at a constant rotational speed or less. It shifts to the low load mode to drive, and is constituted so that the compressor may be stopped when the temperature difference integrated amount becomes less than the negative first integrated amount in the low load mode. 5. The cooling device according to any one of 4 above. A storage section for storing articles;
A refrigeration cycle for cooling the storage unit by circulating a refrigerant, including a compressor, a condenser, an expansion valve, and an evaporator, the rotation speed of which can be controlled;
A controller for controlling the rotational speed of the compressor,
The control unit integrates the difference between the cooling target temperature value and the measured temperature value to acquire a temperature difference integrated amount in consideration of a positive / negative sign, and the acquired temperature difference integrated amount is less than the negative first integrated amount. A showcase configured to stop the compressor when it becomes.

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