JP2019184110A - refrigerator - Google Patents

Abstract

To perform a fast elimination of a differential pressure between a suction side and a discharging side of a compressor after detection of an operation of a protection device of a compressor and perform a re-starting operation of the compressor fast without applying a high load.SOLUTION: This invention comprises a cooling controller 28 for opening or closing a feeder circuit 27 for a compressor 12, a protection device 29 for blocking electric supply to the compressor 12 at the time of overload, an evaporator temperature sensor 24 for detecting a temperature of an evaporator 7, a pressure equalizing circuit 20 for bypassing a suction side and a discharging side of the compressor 12, a pressure equalizing solenoid valve 22 for opening or closing the pressure equalizing circuit 20, and a control part 30 for controlling the cooling controller 28 and the pressure equalizing solenoid valve 22. The control part 30 changes over the cooling controller 28 to open the feeder circuit 27 under an assumption that the protection device 29 is being operated irrespective of the fact that an evaporator temperature E detected by an evaporator temperature sensor 24 fulfills a predetermined high temperature condition to change-over the cooling controller 28 to open the feeder circuit 27 and at the same time to release the pressure equalizing solenoid valve 22.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a refrigerator provided with a compressor protection device constituting a refrigeration cycle. The refrigerator in the present invention includes a refrigerated showcase for display in addition to a refrigerator for storing food and the like.

  Many refrigerators equipped with a refrigeration cycle are provided with a protective device for protecting the compressor. The protection device operates when the refrigeration cycle is overloaded, and protects the compressor by cutting off the power supply to the compressor. For example, Patent Document 1 describes a quick cooler provided with a protection device, in which a conventionally known protection device having a bimetal is employed. This bimetal is heated and deformed when the refrigeration cycle is overloaded, that is, when an overcurrent flows through the compressor, and stops the compressor by opening a power supply circuit to the compressor. Some time after the compressor stops, the bimetal cools and returns to its original form, and the power supply circuit to the compressor is closed again.

  Moreover, in patent document 1, the operating state of a protective device is judged based on the internal temperature detected by the internal temperature sensor. Specifically, the internal temperature is taken in every predetermined time, and when the temperature does not drop by a predetermined value within the predetermined time, it is determined that the protection device is operated and the compressor is stopped. After this determination, the notification lamp is turned on to notify the user that the protective device is operating, that is, the refrigeration cycle is overloaded, and the compressor drive system is disconnected. When the predetermined cutting time elapses, the control unit releases the cutting state of the drive system, and resumes power feeding to the compressor, that is, cooling of the interior.

JP 2014-59090 A

  When the compressor is driven in the refrigeration cycle, a differential pressure is generated between the suction side and the discharge side. If the stopped compressor is restarted without eliminating the differential pressure, a heavy burden is placed on the compressor. Therefore, it is preferable to eliminate the differential pressure during the stop. In the quick cooler of Patent Document 1, the drive system of the compressor is disconnected for a predetermined cutting time after it is determined that the protection device is operating, and the differential pressure is gradually eliminated during this cutting time. Is done. However, if a sufficient cutting time is set for eliminating the differential pressure, the inside temperature may rise greatly during that time, and the object to be cooled such as food may be damaged. Conversely, if the cutting time is set short, an increase in the internal temperature can be suppressed, but this time, the differential pressure is not sufficiently eliminated, and the load at the time of starting the compressor may be increased.

  Further, in Patent Document 1, when the internal temperature does not drop by a predetermined value within a predetermined time, it is determined that the protection device is operated and the compressor is stopped. Therefore, it is not necessary to directly monitor the state of the protection device, and the control circuit can be simplified accordingly. However, in the refrigerator that is the subject of the present invention, the temperature sensor may get wet with condensed water and the condensed water may melt or freeze. Since the temperature of water does not change much at the melting point, that is, around 0 ° C., when the temperature is reached, the temperature gradually decreases even if the compressor is operating normally. That is, if the determination method of Patent Document 1 is applied to the refrigerator as it is, it may be determined that the compressor is erroneously stopped even though it is driven.

  The present invention, in a refrigerator equipped with a compressor protection device, quickly detects the pressure difference between the suction side and the discharge side of the compressor after detecting that the protection device has been operated, thereby prematurely burdening the compressor. The purpose is to accurately determine the driving state of the compressor without directly monitoring the state of the compressor and the protection device.

  The refrigerator according to the present invention is a refrigerator in which the inside R is cooled by a refrigeration cycle including the compressor 12 and the evaporator 7, and includes a cooling controller 28 that opens and closes a power supply circuit 27 to the compressor 12, and an overload A protective device 29 that cuts off power supply to the compressor 12, an evaporator temperature sensor 24 that detects the temperature of the evaporator 7, a pressure equalization circuit 20 that bypasses the suction side and the discharge side of the compressor 12, and a pressure equalization circuit 20 is provided with a pressure equalizing solenoid valve 22 that opens and closes 20 and a controller 30 that controls the cooling controller 28 and the pressure equalizing solenoid valve 22. The control unit 30 protects the protective device 29 when the evaporator temperature E detected by the evaporator temperature sensor 24 satisfies a predetermined high temperature condition even though the power supply circuit 27 is closed via the cooling controller 28. The cooling controller 28 is switched to open the power feeding circuit 27 and the pressure equalizing solenoid valve 22 is opened.

  The control unit 30 determines that the high temperature condition is satisfied when the evaporator temperature E does not show a downward trend for a predetermined analysis time T3 after the evaporator temperature E rises to the predetermined analysis start temperature E1. Can do.

  Specifically, a first rise reference for detecting a sudden rise in the evaporator temperature E in a relatively short time, and a first drop reference for detecting a sudden drop in the evaporator temperature E in a relatively short time, A second rise reference for detecting a gradual rise in the evaporator temperature E over a relatively long time and a second fall reference for detecting a gradual drop in the evaporator temperature E over a relatively long time are set. To do. The control unit 30 includes a determination unit 34 that determines whether or not the evaporator temperature E corresponds to each reference every predetermined processing time T2, and the determination unit 34 includes the first increase reference or the second increase reference. When the rising standard is met, the evaporator temperature E is determined to be rising, and when the first falling reference or the second falling reference is satisfied, the evaporator temperature E is determined to be decreasing. If it does not fall under the above criteria, it is determined that the evaporator temperature E has the same tendency as before.

  More specifically, a predetermined wide temperature width XW and a short time width TS are set for the first increase reference and the first decrease reference, respectively, and the second increase reference and the second decrease reference are narrower than the wide temperature width XW. A narrow temperature width XN and a long time width TL longer than the short time width TS are set. The control unit 30 includes a storage unit 35 that stores a history of the evaporator temperature E detected by the evaporator temperature sensor 24. The determination unit 34 extracts the current evaporator temperature E as the reference temperature X0 every processing time T2, and at the same time, the evaporator temperature E at the first reference time and the first reference time before the short time width TS from the current time. The evaporator temperature E at the second reference time point just before the short time width TS from the current time point, the evaporator temperature E at the third reference time point before the long time width TL from the current time point, and the long time width TL before the third reference time point. Are extracted from the storage unit 35 as the first reference temperature X1, the second reference temperature X2, the third reference temperature X3, and the fourth reference temperature X4, respectively. When both the inequality (X0−X1 ≧ XW) and the inequality (X1−X2 ≧ XW) are satisfied, it is determined that the first increase criterion is satisfied, and the inequality (X1−X0 ≧ XW) and the inequality (X2−X1) are determined. If both satisfy ≧ XW), it is determined that the first descending criterion is met, and if both the inequality (X0−X3 ≧ XN) and the inequality (X3−X4 ≧ XN) are both met, the second ascending criterion is met. Then, when both the inequality (X3−X0 ≧ XN) and the inequality (X4−X3 ≧ XN) are satisfied, it is determined that the second descent criterion is satisfied.

  In the present invention, the protective device 29 of the compressor 12 is considered to be operating when the evaporator temperature E satisfies a predetermined high temperature condition even though the power supply circuit 27 to the compressor 12 is closed. Thus, the power feeding circuit 27 is opened to open the pressure equalizing solenoid valve 22. Accordingly, it is possible to quickly eliminate the differential pressure via the pressure equalization circuit 20 that bypasses the suction side and the discharge side while prohibiting restart until the pressure difference between the suction side and the discharge side of the compressor 12 is eliminated. After the cancellation, the compressor 12 can be restarted without imposing a heavy burden. In the present invention, since the operating state of the protection device 29, that is, the driving state of the compressor 12, is determined based on the evaporator temperature E detected by the evaporator temperature sensor 24, the compressor 12 and the protection device 29 are directly monitored. Therefore, it is possible to simplify the control circuit, that is, to reduce the cost.

  It can be determined that the high temperature condition is satisfied when the evaporator temperature E does not show a downward trend over the analysis time T3 after the evaporator temperature E rises to the analysis start temperature E1. In other words, if the evaporator temperature E shows a downward trend even once during the analysis time T3, it can be determined that the high temperature condition is not satisfied. As described above, the detected temperature (evaporator temperature E) of the evaporator temperature sensor 24 in a state wetted with condensed water does not change much near the melting point of water, that is, around 0 ° C., and the compressor 12 is normally driven. However, the evaporator temperature E falls only slowly. Therefore, in the present invention, if the evaporator temperature E decreases regardless of the speed, it is determined that the high temperature condition is not satisfied, that is, the compressor 12 is driven. According to this, even when the evaporator temperature E reaches a temperature range where it changes slowly, the driving state of the compressor 12 can be accurately determined.

  Moreover, when the analysis start temperature E1 is set as a threshold value and the judgment on the high temperature condition is started only after the evaporator temperature E rises to the analysis start temperature E1, it is clear that the compressor 12 is driven. In this state, it can be prevented that the compressor 12 is erroneously determined to be stopped. Furthermore, when the analysis time T3 is set and it is determined that the high temperature condition is satisfied only when the state where the evaporator temperature E does not show a downward trend is maintained over the time T3, the compressor 12 is driven. If the temperature E rises temporarily even though the evaporator temperature E has fallen as a whole, it is erroneously determined that the compressor 12 has stopped for this rise. Can be prevented.

  A first increase reference and a first decrease reference for detecting a sudden change in the evaporator temperature E in a relatively short time, and a second increase in order to detect a gentle change in the evaporator temperature E in a relatively long time When the reference and the second lowering reference are set, regardless of the temperature zone where the evaporator temperature E is located, the tendency of the change (up or down) can always be accurately determined. According to the first ascending standard and the first descending standard, the tendency of the change can be accurately determined in a temperature zone where the change in the evaporator temperature E is severe, such as immediately after the compressor 12 is started or stopped. According to the 2 ascending standard and the 2nd descending standard, the tendency of the change can be accurately determined in a temperature range where the change is gentle, such as when the evaporator temperature E is around 0 ° C. Further, in a temperature range where the change in the evaporator temperature E is moderate, all four criteria may not be met. However, the compressor 12 does not change from rising to falling or falling to rising in this temperature range. Since it is unlikely to start or stop, it is possible to accurately determine the tendency of change by determining that the tendency is the same as immediately before.

  A reference temperature X0 that is the current evaporator temperature E, a first reference temperature X1 that is a short time width TS ahead of the current time, and a second reference temperature X2 that is a short time width TS before the current time are extracted, and an inequality (X0 -X1 ≧ XW) and the inequality (X1-X2 ≧ XW) are both satisfied, it can be determined that the first rise criterion is met. In other words, if at least one of the two inequalities is not satisfied, it can be determined that the first ascent criterion is not met. The same determination can be made for the first lowering reference, the second rising reference, and the second lowering reference. According to this, even if one of the three temperatures X0, X1, and X2 in the inequality becomes a value far apart due to the influence of external noise, an erroneous determination can be prevented.

  For example, when the actual evaporator temperature E is gradually decreasing (X2> X1> X0), but only the reference temperature X0 is significantly increased due to the external noise (X0 >> X2> X1). Will be described. In this case, one inequality (X0−X1 ≧ XW) related to the first ascent criterion is satisfied, but the other inequality (X1−X2 ≧ XW) is not satisfied, and therefore it is determined that the first ascent criterion is not met. Is done. Similarly, it is determined that neither the first descent standard, the second ascent standard, or the second descent standard is applicable. That is, since it does not correspond to all the criteria and the evaporator temperature E is determined to have the same tendency as immediately before, it is not erroneously determined. Here, if there is only one inequality (X0−X1 ≧ XW) related to the first ascending criterion and only one inequality (X1−X0 ≧ XW) relating to the first descending criterion, Thus, when (X0 >> X1) is mistakenly established, the evaporator temperature E is erroneously determined to be an upward trend rather than a downward trend.

  Further, water droplets may adhere to the evaporator temperature sensor 24 and the water droplets may be supercooled. The temperature of the supercooled water droplets decreases to a minus temperature without freezing, and when freezing progresses at once, the temperature temporarily rises due to the influence of the latent heat. However, if two inequalities are set for each criterion as in the present invention, even if one of the inequalities is affected by the temperature rise during subcooling while the evaporator temperature E is decreasing, the other inequalities are affected by this effect. Thus, it is possible to prevent erroneous determination that the evaporator temperature E is increasing.

  Furthermore, in the present invention, for example, the third reference temperature X3 is shared by the two inequalities for the second rising standard, so that the reference temperatures used in the two inequalities are three (X0, X3, X4). In this way, if three reference temperatures are used in each standard, it is more affected by external noise than when two reference temperatures are not shared by two inequalities, that is, when four reference temperatures are used in both inequalities. The risk of extracting the evaporator temperature E can be reduced.

  As a comparison target of the second ascent criterion according to the present invention, a criterion consisting of an inequality (X0−X3 ≧ XN) and an inequality (X1−X5 ≧ XN) is assumed, and an inequality (X3- Assume a standard composed of X0 ≧ XN) and an inequality (X5−X1 ≧ XN). The fifth reference temperature X5 is the evaporator temperature E at the fifth reference time point that is a long time width TL before the first reference time point. When the respective time points are arranged in order from the current time point, the first reference time point, the third reference time point, the fifth reference time point, and the fourth reference time point are obtained.

  When the evaporator temperature E changes upwardly with the third reference time as the center, that is, the evaporator temperature E increases from the fourth reference time to the third reference time (X4 <X5 <X3). 3 Verify that the evaporator temperature E drops from the reference time point to the present time point (X3> X1> X0) (the temperature change range is relatively narrow and does not correspond to the first rising reference and the first decreasing reference) ). In this case, it does not correspond to the 2nd rise standard and the 2nd fall standard concerning the present invention, and it is judged that evaporator temperature E has the same tendency as the last time. On the other hand, according to the standard to be compared, when the fifth reference temperature X5 becomes higher than the first reference temperature X1, the two inequalities related to the descent standard may be satisfied, and it may be determined that there is a downward trend. . Further, when the evaporator temperature E has a downwardly convex temperature change (X4> X5> X3, X3 <X1 <X0), it does not correspond to the second rising reference and the second decreasing reference according to the present invention. According to the target standard, when the fifth reference temperature X5 becomes lower than the first reference temperature X1, the two inequalities related to the increase standard may be satisfied, and it may be determined that there is an upward trend.

  That is, when the evaporator temperature E is small for each long time width TL and repeatedly moves up and down, the determination of the upward tendency and the downward tendency may be alternately repeated according to the reference to be compared. When vertical movement of the evaporator temperature E occurs during the operation of the protective device 29, according to the comparison target, the evaporator temperature E decreases before the analysis time T3 elapses after the evaporator temperature E rises to the analysis start temperature E1. There is a possibility that the determination of the tendency will reset the timekeeping, and as a result, the detection of the operation of the protection device 29 may be delayed. On the other hand, according to the present invention, even if the evaporator temperature E repeatedly moves up and down every long time width TL, it does not correspond to the second descending reference, so there is a possibility that the time measurement is reset during the analysis time T3. Therefore, the operation of the protection device 29 can be detected early.

It is a refrigeration cycle diagram of a refrigerated showcase to which the present invention is applied. It is a vertical side view which shows schematic structure of a refrigerated showcase. It is a block diagram of the control system of a refrigerated showcase. It is a timing chart which shows transition of internal temperature and the drive state of each part. It is a flowchart which concerns on operation | movement judgment of a protection apparatus. It is a timing chart at the time of operation judgment of a protection device. It is a flowchart which concerns on the tendency determination of evaporator temperature. It is a figure for demonstrating the reference time and reference temperature in a tendency determination.

(Example) FIG. 1 thru | or FIG. 8 shows the Example which applied this invention to the reach-in type refrigerated showcase. In FIG. 2, the refrigerated showcase includes a case main body 1 made of a heat insulating box having an opening on the front, and a door 2 that opens and closes the opening of the case main body 1. The interior R enclosed by the case body 1 and the door 2 is partitioned into a display chamber 4 and a ventilation duct 5 by a partition plate 3, and food to be displayed is placed in the display chamber 4 facing the door 2. The shelf board 6 for this is installed in the upper and lower multistage shape. In the ventilation duct 5 along the inner wall surface of the case body 1, an evaporator 7 constituting a refrigeration cycle and a circulation fan 8 for circulating the air in the warehouse R are arranged.

  In the machine room 11 partitioned on the lower side of the case body 1, a compressor 12 and a condenser 13 that constitute a refrigeration cycle together with the evaporator 7 and a cooling fan 14 for cooling them are arranged. As shown in FIG. 1, the refrigeration cycle is configured by connecting a compressor 12, a condenser 13, a dryer 15, an expansion valve 16, an evaporator 7, and the like in a loop shape with a refrigerant pipe 17. The suction side (low pressure side) and the discharge side (high pressure side) of the compressor 12 are bypassed by a pressure equalization circuit 20, and a capillary tube 21 and a pressure equalization solenoid valve 22 are arranged in the circuit 20. An evaporator temperature sensor 24 for detecting the temperature is provided at the inlet portion of the evaporator 7, and an internal temperature sensor 25 for detecting the temperature is also provided in the internal space R.

  As shown in FIG. 3, a cooling controller 28 and an overload relay (protector: hereinafter referred to as OLR) 29 are arranged in series in a power feeding circuit 27 that connects the compressor 12 and a commercial power source. The cooling controller 28 is on / off controlled based on the internal temperature D detected by the internal temperature sensor 25 by the control unit 30 that controls the entire refrigerated showcase. As a result, the power supply circuit 27 is controlled to open and close (the compressor 12 is controlled to be turned on / off), and the internal temperature D is maintained within the target temperature range. The OLR 29 has a conventionally known configuration having a bimetal, and operates (opens) when the load applied to the refrigeration cycle increases, that is, when an overcurrent flows in the power supply circuit 27, and supplies power to the compressor 12. By shutting off, the compressor 12 is protected. The control unit 30 according to the present embodiment does not directly monitor the operation states of the compressor 12 and the OLR 29, thereby simplifying the control circuit, that is, reducing the cost.

  As shown in FIG. 4, the control unit 30 sets a target temperature zone of (D0 ± α) ° C. centering on the target temperature D 0, and drives the compressor 12 with the upper threshold of the temperature zone, ie, (D 0 + α) ° C. Is set as a cooling start temperature Don, and the lower threshold of the temperature range, that is, (D0−α) ° C., is set as a cooling stop temperature Doff at which the driving of the compressor 12 is stopped. When the internal temperature D rises to the cooling start temperature Don, the control unit 30 switches the cooling controller 28 to the ON state and drives the compressor 12 (time point t1).

  When the inside R is cooled by driving the compressor 12 and the inside temperature D is lowered to the cooling stop temperature Doff, the control unit 30 switches the cooling controller 28 to the off state to stop the compressor 12 and simultaneously equalizes the pressure. The electromagnetic valve 22 is opened (time t2). The pressure equalizing solenoid valve 22 is maintained in an open state for a predetermined pressure equalizing time T1, thereby eliminating the pressure difference between the high pressure side and the low pressure side of the compressor 12 via the pressure equalizing circuit 20 (time points t2 to t3). ). In this embodiment, the pressure equalizing solenoid valve 22 is closed at the time t3 when the pressure equalizing time T1 has elapsed after the pressure equalizing solenoid valve 22 is opened. The pressure electromagnetic valve 22 can be maintained in an open state.

  In this embodiment, the pressure equalization time T1 is set to 5 minutes, which is the same as the stop protection time of the compressor 12 (the lower limit time for maintaining the stopped state). When the internal temperature D rises to the cooling start temperature Don before the pressure equalizing time T1 elapses after the pressure equalizing solenoid valve 22 is opened as at the next time t5, the control unit 30 at this time The cooling controller 28 is maintained in the off state, and at time t6 when the pressure equalizing time T1 has elapsed, the cooling controller 28 is switched on and the compressor 12 is started.

  At the next time t7, the OLR 29 is opened and the compressor 12 is stopped due to the overcurrent flowing through the power supply circuit 27 to the compressor 12. As described above, since the controller 30 cannot directly detect that the OLR 29 is opened or the compressor 12 is stopped, the cooling controller 28 remains on at this time, and the pressure equalizing solenoid valve 22 is also turned on. Not yet released. In this embodiment, as will be described next with reference to the flowchart of FIG. 5, it is detected based on the evaporator temperature E detected by the evaporator temperature sensor 24 that the OLR 29 is opened and the compressor 12 is stopped. Is detected, the cooling controller 28 is switched to the OFF state and the pressure equalizing solenoid valve 22 is opened.

  When the OLR 29 is opened and the compressor 12 is stopped, the evaporator temperature E turns from rising to falling. Control is performed when the evaporator temperature E rises to a predetermined analysis start temperature E1 (-1 ° C. in the present embodiment) (YES in step S2) despite the cooling controller 28 being in the ON state (YES in step S1). The unit 30 determines that the OLR 29 may be open, and starts analysis to determine this.

  Specifically, the control unit 30 starts measuring time by the timer 33 (step S3), and the tendency of the change in the evaporator temperature E by the determination unit 34 every predetermined processing time T2 (10 seconds in this embodiment) ( Ascending or descending) is determined (steps S4 to S7). Details of the tendency determination (step S6) will be described later. If the evaporator temperature E shows a downward trend even once (NO in step S8) by the time T reaches the predetermined analysis time T3 (4 minutes in the present embodiment), the controller 30 indicates that the OLR 29 is operating. It is determined that there is no compressor (the compressor 12 is driven), and the process returns to step S1. On the other hand, if the analysis time T3 has elapsed since the time was started while the evaporator temperature E continued to show an upward trend (YES in step S9), the control unit 30 opens the OLR 29 and the compressor 12 stops. Therefore, the analysis on the state of the compressor 12 and the OLR 29 is finished. In the present embodiment, when the evaporator temperature E satisfies the predetermined high temperature condition, the evaporator temperature E continues to show an upward trend over the analysis time T3 (not showing a downward trend) after the evaporator temperature E rises to the analysis start temperature E1. It is. The tendency determination of the evaporator temperature E (step S6) is always performed regardless of whether the evaporator temperature E rises to the analysis start temperature E1.

  The timing chart of FIG. 6 shows a case where it is determined that the OLR 29 is open and the compressor 12 is stopped according to the flowchart of FIG. At the first time point t7, the compressor 12 is stopped due to the opening of the OLR 29, and the internal temperature D and the evaporator temperature E have started to rise. At the next time point t8, the evaporator temperature E becomes the analysis start temperature. Ascending to E1, the time measurement by the timer 33 is started. At the next time point t9, while the evaporator temperature E continues to show an upward trend, the analysis time T3 has elapsed from the time point t8. Here, the control unit 30 opens the OLR 29 and the compressor 12 is stopped. Therefore, the cooling controller 28 is switched to the OFF state and the pressure equalizing solenoid valve 22 is opened. Thereby, the differential pressure between the suction side and the discharge side of the compressor 12 is quickly eliminated via the pressure equalization circuit 20.

  When the pressure equalizing time T1 elapses after the pressure equalizing electromagnetic valve 22 is opened (time t10), the control unit 30 closes the valve 22, and the internal temperature D is equal to or higher than the cooling start temperature Don. The cooling controller 28 is switched on. In this chart, since the OLR 29 is already closed before the pressure equalization time T1 elapses, the compressor 12 is started simultaneously with the switching of the cooling controller 28, and the interior R is cooled again. As in this embodiment, before starting the compressor 12, if the pressure equalizing solenoid valve 22 is opened over the pressure equalizing time T1 to eliminate the differential pressure between the high pressure side and the low pressure side of the compressor 12, The compressor 12 can be restarted without imposing a heavy burden.

  The flowchart of FIG. 7 shows the procedure for determining the tendency of the evaporator temperature E (step S6) in the flowchart of FIG. For this determination, an ascending criterion and a descending criterion set in advance by two are used. The first rising reference and the first decreasing reference are for detecting a sudden change in the evaporator temperature E in a relatively short time, and the second rising reference and the second falling reference are gentle for a relatively long time. The temperature change of the evaporator temperature E is detected. Details of these standards will be described later.

  The determination unit 34 (see FIG. 3) of the control unit 30 determines whether or not the evaporator temperature E satisfies the reference in the order of the first increase reference, the first decrease reference, the second increase reference, and the second decrease reference. (Steps S11 to S14). If the first ascent criterion or the second ascent criterion is satisfied (YES in step S11 or step S13), an “upward trend” is output as a determination result (step S15), and if the first descending criterion or the second descending criterion is satisfied (step S15) “YES” in step S12 or step S14), “decreasing tendency” is output as the determination result (step S16). If all the criteria are not satisfied (NO in steps S11 to S14), the determination result immediately before is maintained and output (step S17).

  Next, details of each criterion will be described. The control unit 30 includes a storage unit 35 (see FIG. 3) that stores the history of the evaporator temperature E detected by the evaporator temperature sensor 24. When determining the tendency, the control unit 30 is a reference that is the current evaporator temperature E. In addition to the temperature X0, the evaporator temperature E at the first to fourth reference time points stored in the storage unit 35 is extracted as the first to fourth reference temperatures X1 to X4. As shown in FIG. 8, the first reference time point related to the first reference temperature X1 is a short time width TS (10 seconds in this embodiment) before the current time point, and the second reference time point related to the second reference temperature X2 is set. The time point is the short time width TS before the first reference time point (in this embodiment, 20 seconds before the present time). The third reference time point related to the third reference temperature X3 is a long time span TL (30 seconds in this embodiment) before the current time point, and the fourth reference time point related to the fourth reference temperature X4 is 3 is the long time width TL before the reference time (in this embodiment, 60 seconds before the present time).

In the determination relating to the first increase criterion (step S11), it is determined whether or not the following two inequalities are satisfied with respect to the reference temperature X0, the first reference temperature X1, and the second reference temperature X2.
(Formula 1-1) X0-X1 ≧ XW
(Formula 1-2) X1-X2 ≧ XW
The wide temperature range XW in both formulas is a preset constant, which is set to 0.5 ° C. in this embodiment. The determination unit 34 determines that the first increase criterion is satisfied when both inequalities hold (YES in step S11), and does not satisfy the first increase criterion (NO in step S11) when one of the inequalities does not hold. judge.

In the determination relating to the first descent criterion (step S12), it is determined whether or not the following two inequalities are satisfied with respect to the reference temperature X0, the first reference temperature X1, and the second reference temperature X2.
(Formula 1-3) X1-X0 ≧ XW
(Formula 1-4) X2-X1 ≧ XW
The determination unit 34 determines that the first descending criterion is satisfied when both inequalities hold (YES in step S12), and does not satisfy the first descending criterion when the inequality does not hold either (NO in step S12). judge.

In the determination relating to the second increase criterion (step S13), it is determined whether or not the following two inequalities are satisfied with respect to the reference temperature X0, the third reference temperature X3, and the fourth reference temperature X4.
(Formula 2-1) X0-X3 ≧ XN
(Formula 2-2) X3-X4 ≧ XN
The narrow temperature width XN in both formulas is a constant set in advance, and in this embodiment, this is set to 0.2 ° C. which is narrower than the wide temperature width XW (XW> XN). The determination unit 34 determines that the second increase criterion is satisfied when both inequalities hold (YES in step S13), and does not satisfy the second increase criterion (NO in step S13) when one of the inequalities does not hold. judge.

In the determination relating to the second descent standard (step S14), it is determined whether or not the following two inequalities are satisfied with respect to the reference temperature X0, the third reference temperature X3, and the fourth reference temperature X4.
(Formula 2-3) X3-X0 ≧ XN
(Formula 2-4) X4-X3 ≧ XN
The determination unit 34 determines that the second descending criterion is satisfied when both inequalities hold (YES in step S14), and does not satisfy the second descending criterion (NO in step S14) when neither of the inequalities holds. judge.

  According to the first ascending standard and the first descending standard, the tendency of the change can be accurately determined in a temperature zone where the change in the evaporator temperature E is severe, such as immediately after the compressor 12 is started or stopped. According to the 2 ascending standard and the 2nd descending standard, the tendency of the change can be accurately determined in a temperature range where the change is gentle, such as when the evaporator temperature E is around 0 ° C. Further, in a temperature range where the change of the evaporator temperature E is moderate, all four criteria may not be satisfied (NO in steps S11 to S14), but in this temperature range, from rising to falling, or from falling to rising. Since it is unlikely that the compressor 12 starts or stops without turning, it is possible to accurately determine the tendency of change by determining that the tendency is the same as that immediately before (step S17).

  In the above embodiment, the present invention is applied to a reach-in type refrigerated showcase. However, in addition to this, the present invention is also applied to a refrigerated open showcase in which the front opening is always opened, a refrigerator for storing food at a low temperature, and the like. The invention can be applied. In refrigerated showcases and refrigerators, the evaporator temperature E passes through a temperature range near 0 ° C. where the temperature change is gentle every time the thermo control is performed, so that the application of the present invention is effective.

7 Evaporator 12 Compressor 20 Pressure equalizing circuit 22 Pressure equalizing solenoid valve 24 Evaporator temperature sensor 28 Cooling controller 29 Protection device (overload relay)
30 Control part R

Claims (4)

A refrigerator in which the inside (R) is cooled by a refrigeration cycle including a compressor (12) and an evaporator (7),
A cooling controller (28) for opening and closing a power supply circuit (27) to the compressor (12);
A protective device (29) for cutting off the power supply to the compressor (12) in the event of an overload;
An evaporator temperature sensor (24) for detecting the temperature of the evaporator (7);
A pressure equalization circuit (20) bypassing the suction side and the discharge side of the compressor (12);
A pressure equalizing solenoid valve (22) for opening and closing the pressure equalizing circuit (20);
A controller (30) for controlling the cooling controller (28) and the pressure equalizing solenoid valve (22),
Although the control unit (30) closes the power supply circuit (27) via the cooling controller (28), the evaporator temperature (E) detected by the evaporator temperature sensor (24) is a predetermined high temperature. When the condition is satisfied, the protection device (29) is regarded as operating, and the cooling controller (28) is switched to open the power feeding circuit (27) and open the pressure equalizing solenoid valve (22). Features a refrigerator.   When the evaporator temperature (E) does not show a downward trend for a predetermined analysis time (T3) after the evaporator temperature (E) has increased to the predetermined analysis start temperature (E1). Furthermore, the refrigerator of Claim 1 which judges that high temperature conditions were satisfy | filled. A first rise criterion for detecting a sudden rise in evaporator temperature (E) in a relatively short time;
A first descent criterion for detecting a sudden evaporator temperature (E) descent in a relatively short time;
A second rise criterion for detecting a gradual rise in evaporator temperature (E) over a relatively long period of time;
A second descent standard for detecting a moderate evaporator temperature (E) descent in a relatively long time period is set;
The control unit (30) includes a determination unit (34) that determines whether or not the evaporator temperature (E) meets each reference every predetermined processing time (T2). )
When the first rising standard or the second rising standard is met, it is determined that the evaporator temperature (E) is increasing,
When the first descent standard or the second descent standard is satisfied, it is determined that the evaporator temperature (E) has a downward trend,
The refrigerator according to claim 2, wherein the evaporator temperature (E) is determined to have the same tendency as immediately before when not satisfying all the criteria. A predetermined wide temperature width (XW) and a short time width (TS) are set for the first rising reference and the first falling reference,
With respect to the second rising reference and the second decreasing reference, a narrow temperature width (XN) narrower than the wide temperature width (XW) and a long time width (TL) longer than the short time width (TS) are set, respectively.
The control unit (30) includes a storage unit (35) for storing the history of the evaporator temperature (E) detected by the evaporator temperature sensor (24).
The determination unit (34) extracts the current evaporator temperature (E) as the reference temperature (X0) every processing time (T2),
At the same time, the evaporator temperature (E) at the first reference time point just before the short time width (TS) from the current time point and the evaporator temperature (E) at the second reference time point just before the short time width (TS) from the first reference time point. ), The evaporator temperature (E) at the third reference time point that is a long time width (TL) before the current time point, and the evaporator temperature (E) at the fourth reference time point that is a long time width (TL) before the third reference time point. E) are extracted from the storage unit (35) as the first reference temperature (X1), the second reference temperature (X2), the third reference temperature (X3), and the fourth reference temperature (X4), respectively.
When both the inequality (X0−X1 ≧ XW) and the inequality (X1−X2 ≧ XW) are satisfied, it is determined that the first increase criterion is satisfied,
When both the inequality (X1-X0 ≧ XW) and the inequality (X2-X1 ≧ XW) are satisfied, it is determined that the first descent criterion is satisfied,
When both the inequality (X0−X3 ≧ XN) and the inequality (X3−X4 ≧ XN) are satisfied, it is determined that the second increase criterion is satisfied,
The refrigerator according to claim 3, wherein when the inequality (X3-X0 ≧ XN) and the inequality (X4-X3 ≧ XN) are both satisfied, it is determined that the second descent criterion is satisfied.

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