JP5392678B2 - Showcase temperature control method - Google Patents

Description

  The present invention relates to a temperature control method for a showcase, and more particularly to a temperature control method for a showcase for cooling a refrigerated / refrigerated showcase provided in a supermarket or a convenience store.

  As a control method when a cooling target device such as a refrigeration / refrigeration showcase provided in a supermarket or a convenience store is cooled with a refrigerator, the temperature in the showcase chamber (or the showcase outlet temperature) is measured, When the measured temperature exceeds the preset upper limit temperature, the refrigerant flow rate is increased (or refrigerant supply to the cooler is started), and the measured temperature falls below the preset lower limit temperature. In addition, a control method for reducing the refrigerant flow rate of the cooler (or stopping the supply of the refrigerant) is well known. Regarding defrosting operation, power consumption is leveled by operating the timing of defrosting operation in a plurality of showcases (see, for example, Patent Document 1).

JP-A-9-189474

  However, in the conventional temperature control, the internal temperature rises (overshoot) after the refrigerant flow rate is increased (or the refrigerant supply is started), or the internal temperature after the refrigerant flow rate is reduced (or the refrigerant supply is stopped). May drop (undershoot), and the internal temperature may become unstable. Further, in the defrosting operation, the method described in Patent Document 1 is effective for a plurality of showcases, but in each showcase, the refrigerant supply amount of the cooler before the start of the defrosting operation. If the cooling operation is increased (or stopped), the defrosting operation time will be longer because the cooler temperature is lower, and the power of the defrosting heater will be increased. There has been a problem that the amount of consumption increases and the cooling operation before the start of the defrosting operation is wasted.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a temperature control method for a showcase that can save energy while suppressing the occurrence of overshoot and undershoot and keeping the inside temperature constant.

To achieve the above object, the showcase temperature control method of the present invention is a showcase temperature control method for cooling a freezing / refrigerated showcase. When performs temperature control to increase or decrease the flow rate of refrigerant of the cooler based on the upper limit temperature and the lower limit temperature set beforehand, have lines of time control to increase or decrease the flow rate of refrigerant of the cooler cycle preset time, the The time control is an increase operation in which the refrigerant flow rate of the cooler is increased by turning on the electromagnetic valve within a preset cycle time, and a decrease operation in which the refrigerant flow rate of the cooler is decreased by turning off the electromagnetic valve. Are alternately performed at a preset time ratio, and when the internal temperature is equal to or higher than the preset temperature, To increase the percentage of time the increment operation in the cycle time, when the inside temperature reaches a temperature below a preset is characterized in that to reduce the time rate of the increment operation within the cycle time.

Also, the when performing the time control, when the inside temperature rises above temperature difference preset the upper limit temperature, increases the flow rate of refrigerant of the condenser by the temperature control to interrupt the time control When the internal temperature is cooled to a preset temperature, the time control is resumed.

  Furthermore, as the pattern of the cycle time and the time ratio within the cycle time, a plurality of patterns are set in advance, and one pattern can be selected according to the state of the showcase.

  In addition, when performing the defrosting operation of the cooler at a preset time interval, when the internal temperature is lower than the preset temperature within the preset time before starting the defrosting operation, the cooler Reduce the refrigerant flow rate.

  According to the temperature control method of the showcase of the present invention, the refrigerant flow rate to the cooler is increased or decreased within a preset cycle time while continuing temperature control similar to the conventional one based on the preset upper limit temperature and lower limit temperature. Since the time control is performed, during normal operation, the flow rate of the refrigerant is increased or decreased by the time control, that is, the solenoid valve is turned on / off, so that the mechanical life of the controller including the solenoid valve can be reduced. It can be set from time to time to ensure stable mechanical operation.

  In the time control, the increase / decrease of the refrigerant flow rate is alternately increased and decreased within a predetermined cycle time at a predetermined time ratio. The cycle time is determined in advance in consideration of the installation condition of the showcase. A plurality of patterns can be set, and the cycle time can be switched according to conditions such as seasons and time zones. Furthermore, by automatically switching the time ratio of the increase operation in one cycle based on the internal temperature, the optimal increase / decrease time ratio can be set according to the internal temperature fluctuation, and overshoot and undershoot Can be suppressed. On the other hand, when the internal temperature rises for some reason, normal temperature control functions, so the internal temperature does not rise abnormally.

  Also, by reducing the refrigerant flow before the start of the defrosting operation, the temperature of the cooler at the start of the defrosting operation can be kept near the upper limit temperature, so that the defrosting time can be shortened and While the energization time of the frost heater can be shortened and the load on the refrigerator can be reduced, energy saving can be achieved.

It is explanatory drawing which compares and shows the change state of the chamber temperature when the temperature control method of the showcase of this invention is applied, and the change state of the chamber temperature at the time of only the conventional temperature control. It is a flowchart which shows one control example of the temperature control method of the showcase of this invention. It is a flowchart which shows one control example before the defrost operation start in the temperature control method of the showcase of this invention. It is explanatory drawing which shows the change state of the internal temperature before the defrost operation start in the temperature control method of the showcase of this invention, and the state of a defrost heater.

  First, the subject of implementation of the method of the present invention is a freezing / refrigeration showcase (hereinafter simply referred to as a showcase) having various general structures installed in a supermarket or a convenience store. The internal temperature is controlled to a preset temperature by a refrigerator equipped with devices such as a solenoid valve, an expansion valve, and a temperature sensor.

  In the present invention, the internal temperature control is performed in addition to the temperature control based on the preset set value, the upper limit temperature and the lower limit temperature, that is, the On / Off control having a normal differential performed conventionally. In addition, time control for increasing or decreasing the refrigerant flow rate of the cooler at predetermined time intervals is performed.

  The time control alternately performs an increase operation for increasing the refrigerant flow rate of the cooler and a decrease operation for decreasing the refrigerant flow rate of the cooler within a preset time (cycle time) at a preset time ratio. For example, as shown in FIG. 1A, when the cycle time T1 is set to 10 minutes, the increase operation time T2 in one cycle is set to 5 minutes, and the decrease operation time T3 is set to 5 minutes. Is performed by alternately repeating a 5-minute increase operation and a 5-minute decrease operation, controlling a thermo output for opening and closing the solenoid valve to open and close the solenoid valve, and performing a predetermined increase operation and a predetermined decrease operation. Alternately.

  In the time control, the cycle time is basically constant, but multiple operation patterns with different cycle times are set. For example, the season when the load fluctuation is small and the time zone when the night cover is attached. Then, a long pattern can be selected as the cycle time. The pattern selection based on the load variation may be performed by a command from the central control device through communication, or the pattern change may be performed when the temperature change in the storage becomes smaller than a preset temperature change. Thereby, the frequency | count of ON and OFF can further be reduced.

  Furthermore, the time ratio between the increase operation and the decrease operation can be automatically adjusted according to the inside temperature measured by the temperature sensor. For example, as described above, when the increase operation for 5 minutes is performed within the cycle time of 10 minutes, when the temperature measured by the temperature sensor becomes equal to or higher than the preset temperature, the increase operation time is set to 5.5. Minutes, the time for reducing operation is 4.5 minutes, the time for supplying the refrigerant to the cooler is lengthened, and when the measured temperature of the temperature sensor falls below the preset temperature, the time for increasing operation is 4.5 minutes, By performing the control to shorten the time for supplying the refrigerant to the cooler by reducing the time for the weight reduction operation to 5.5 minutes, the inside of the refrigerator can be reliably maintained in the predetermined temperature range. In addition, by setting the time ratio in consideration of cooling by the low-temperature refrigerant remaining in the cooler after the completion of the increase operation and the temperature rise until the cooler is cooled by the low-temperature refrigerant increased at the start of the increase operation. The occurrence of undershoot and overshoot can be suppressed.

  In this way, by setting the time ratio between the increase operation and the decrease operation with a constant cycle time according to the conditions, for example, the number of opening and closing operations of the solenoid valve provided in the path for supplying the refrigerant to the cooler ( ON / OFF count) can be set at the time of design, so that the mechanical life can be set reliably, and stable operation can be ensured over a long period of time. Also, since the temperature rise in the cabinet becomes moderate during the night when the night cover is attached, select a pattern with a long cycle time. For example, the above-mentioned 10-minute cycle time in normal time is basically set at a 5-minute interval. By selecting a pattern such that the cycle time is 12 minutes, the increase operation is 4 minutes, and the decrease operation is 8 minutes, the internal temperature is stabilized and the energy is saved when the night cover is attached. Can do. In this case, since the cycle time becomes longer, the number of opening / closing operations of the solenoid valve is reduced, and the life set at the time of design is not shortened.

  On the other hand, in the case of conventional temperature control, as shown in FIG. 1B, the solenoid valve opens and closes in response to fluctuations in the internal temperature. Is repeated in a short time, and it is impossible to set the mechanical life of the solenoid valve at the time of design, and the solenoid valve may reach the mechanical life at an unexpected time. Therefore, by employing the time control, maintenance work such as component replacement can be performed accurately.

  Further, since not only the time control but also the temperature control is operated in parallel, when the internal temperature rises or falls abnormally, the time control is temporarily suspended to control the internal temperature. Return to the specified temperature range. For example, as shown in FIG. 2, after selecting a cycle time pattern in step 11, the difference between the internal temperature and the set value in one cycle is calculated in step 12, and the temperature with the set value is calculated in step 13. If it is determined that the difference is large (Y), the routine proceeds to step 14 where the time control is interrupted and temperature control for opening and closing the solenoid valve is started by a thermo output that operates according to the internal temperature. As a result, even if the internal temperature greatly deviates from the set value for some reason, even if the internal temperature rises abnormally by performing conventional normal temperature control, the predetermined temperature range is quickly reached. The inside temperature can be controlled inside.

  Steps 12 to 14 are repeated until the internal temperature returns to the predetermined range, and if it is determined (N) that the temperature difference calculated in Step 12 has become smaller (no longer larger) in Step 13, Step 15 Then, the time control is resumed.

  When operating under time control, it is determined in step 15 whether the operation state is in progress, that is, during the increase operation time or during the decrease operation time. When it is determined that the operation is during the increase operation time (Y), the process proceeds to step 16. When the solenoid valve is opened and the refrigerant is supplied to the cooler or is increased, and when it is determined that the increase operation time is not in progress (during the decrease operation time) (N), the routine proceeds to step 17 where the solenoid valve is closed. After the refrigerant supply to the cooler is stopped or reduced, the process proceeds to step 18 to recalculate the time ratio between the increase operation time and the decrease operation time according to the relationship between the set value and the internal temperature. Then return to Step 11.

  As described above, when the difference between the internal temperature and the set value is large, the temperature control is performed. When the difference between the internal temperature and the set value is small, the time control based on the selected pattern is performed, and the state of the internal temperature. The internal temperature can be reliably controlled within a predetermined temperature range by recalculating the increase / decrease time ratio accordingly. This eliminates unnecessary cooling and temperature rise, thus saving energy, reducing the amount of frost on the cooler, maintaining high heat exchange efficiency, and maintaining product freshness. It is valid.

  Further, in this embodiment, when performing the defrosting operation of the cooler at a preset time interval, within the preset time before the start of the defrosting operation, when the internal temperature is lower than the preset temperature, Control is performed to reduce the refrigerant flow rate of the cooler. That is, as shown in FIG. 3, the time immediately before defrosting is calculated from one cycle time at step 21, and not within the time set in advance with respect to the defrosting operation start time at step 22, that is, within the time immediately before defrosting. When it is determined that there is no (N), the routine proceeds to step 23 where time control or temperature control is continued and the routine returns to step 21.

  Moreover, when it determines with it being in the predetermined time range before the defrost operation start time in step 22 (Y), it progresses to step 24, and the internal temperature tends to fall or the internal temperature is below a preset value. If both are determined and it is determined that both are satisfied (Y), the process proceeds to step 25 to close the solenoid valve, the refrigerant flow to the cooler is reduced or stopped, and the process proceeds to step 26 to perform the defrosting operation. Hold that state and wait until it starts. On the other hand, when it is determined in step 24 that both are not satisfied (N), the routine proceeds to step 27 where time control is continued and the routine returns to step 21.

  As described above, when the internal temperature is lowered when the internal temperature is within the predetermined time range before the defrosting operation start time and the internal temperature is equal to or lower than the set value, the refrigerant is supplied to the cooler. By reducing the temperature so that the temperature of the cooler does not decrease excessively, the temperature of the cooler at the start of the defrosting operation can be set to a temperature suitable for the defrosting operation.

  For example, as shown to Fig.4 (a), with respect to the defrost operation start time A, the internal temperature tends to fall before the preset time, and the internal temperature becomes below a set value. If so, the increase operation in the time control is stopped at that time and the standby state is set. As a result, the internal temperature gradually rises, but before the temperature rises excessively, the defrosting operation starts, and the defrosting heater is activated to heat the cooler and defrost the cooler.

  Specifically, when the set value is 0 ° C., the differential is set to 1 ° C., and the defrosting operation end temperature is set to 12 ° C., the increase operation is continued as shown in FIG. When the defrosting operation is started when the temperature is −1 ° C. and when the temperature is + 1 ° C. as shown in FIG. Since the temperature difference at the start of the defrosting operation is 2 ° C., the time difference C between the two is several minutes, for example, about 3 minutes until the end of the defrosting operation when the temperature of the cooler rises to 12 ° C. Will occur.

  In this way, the load on the refrigerator can be reduced by reducing or stopping the supply of refrigerant to the cooler when the internal temperature satisfies the predetermined condition before the start of the defrosting operation. The frost operation time can be shortened, and the energization time of the defrost heater can be shortened to reduce the power consumption. Furthermore, since the rise time of the internal temperature is shortened by shortening the defrosting time, the influence on the product is reduced, and high freshness can be maintained.

  If the internal temperature does not tend to decrease or the internal temperature is not lower than the set value, normal time control or temperature control is continued. The inside temperature can be kept in a predetermined cooling state.

  The start of the defrosting operation can be performed by the showcase control device if the showcase control device itself has a built-in defrost timer, and defrosting can be performed from the centralized controller in relation to other showcases. You may make it perform in response to a signal.

Claims (4)

In the temperature control method of the showcase for cooling the freezer / refrigerated showcase,
The inside temperature of the showcase is measured, temperature control is performed to increase / decrease the refrigerant flow rate of the cooler based on the measured inside temperature and preset upper limit temperature and lower limit temperature, and within a preset cycle time the have line time control to increase or decrease the flow rate of refrigerant of the cooler,
The time control includes an increase operation in which the refrigerant flow rate of the cooler is increased by turning on the electromagnetic valve within a preset cycle time, and a decrease amount in which the refrigerant flow rate of the cooler is decreased by turning off the electromagnetic valve. When the chamber temperature is equal to or higher than the preset temperature, the time ratio of the increase operation within the cycle time is increased and the cabinet temperature is set to a preset temperature. A temperature control method for a showcase, wherein the time ratio of the increase operation within the cycle time is reduced when When performing the time control operation, when the inside temperature rises above temperature difference set in advance the upper temperature limit, to increase the flow rate of refrigerant of the condenser by the temperature control to interrupt the time control It was carried out, when the inside temperature is cooled to a temperature set in advance, the temperature control method according to claim 1, wherein the showcase, characterized in that to resume the time control. The pattern of the said cycle time and the said time ratio in the said cycle time has preset several patterns, and selects one pattern according to the state of a showcase, The Claim 1 or 2 characterized by the above-mentioned. temperature control method of the showcase. When performing the defrosting operation of the cooler at a preset time interval, when the internal temperature is lower than the preset temperature within the preset time before the start of the defrosting operation, the refrigerant flow rate of the cooler temperature control method according to claim 1 to 3 set forth in any one showcase is characterized by reducing.

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