JP2012026590A - Refrigerating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an internal temperature control that is appropriate as a backup operation, by controlling a compressor based on the temperature of an evaporator detected by a defrost sensor, even when an internal temperature sensor is failed.SOLUTION: In a refrigerating apparatus 10, a control device 9 controls the compressor 18 based on the temperature PT detected by the internal temperature sensor 31 in a normal state. When the internal temperature sensor 31 is abnormal, the temperature PT is substituted by a temperature obtained by adding a predetermined offset value OV to a temperature ET of the evaporator 11 detected by a defrost sensor 28, and by changing the offset value OV based on an external temperature AT, thus controlling the compressor 18.

Description

  The present invention relates to a refrigeration apparatus that controls equipment with an internal temperature sensor, and particularly to control when the internal temperature sensor is abnormal.

  Conventionally, this kind of refrigeration apparatus has a refrigeration cycle composed of a compression means, a condenser (gas cooler), a throttle means, an evaporator, etc., and the refrigerant compressed by the compression means radiates heat in the condenser (gas cooler), and the throttle means Then, the refrigerant is evaporated by an evaporator, and the surrounding air is cooled by evaporation of the refrigerant at this time.

  At this time, the internal temperature sensor that detects the current temperature of the space to be cooled controls the operation frequency of the compressor so that the temperature in the space to be cooled becomes the cooling target temperature. At this time, if the current temperature of the space to be cooled detected by the internal temperature sensor reaches a predetermined lower limit temperature lower than the target cooling temperature, the compressor is stopped (thermo-off), and the predetermined temperature is lower than the target cooling temperature. When a high predetermined upper limit temperature is reached, thermocycle control is performed in which the compressor is restarted (thermo-on).

  When the internal temperature sensor has a failure such as a disconnection or a short circuit, it is impossible to execute such control of the compressor. In this case, since the influence on the articles stored in the space to be cooled becomes very large, conventionally, as a backup operation at the time of sensor failure, for example, a cooling operation from a normal defrosting operation to the next defrosting operation Control based on the operation rate of the compressor in the inside (see, for example, Patent Document 1 and Patent Document 2) and compressor control using a defrosting sensor used for defrosting control of the cooler are performed.

Japanese Patent Laid-Open No. 11-14207 JP 2004-116862 A

  However, the control based on the operation rate of the compressor at the normal time cannot deal with the actual opening / closing state of the door and the change in the outside air temperature, and cannot realize the highly accurate inside temperature control.

  Moreover, in the backup operation using the defrost sensor, in addition to the compressor control that substitutes the cooler temperature detected by the defrost sensor as the internal temperature, it is detected by the internal temperature sensor and the defrost sensor. Compared to compressor control in which the cooling target temperature, which is an index of control, is reduced by a predetermined temperature in consideration of the temperature difference, and when the predetermined upper and lower limit temperatures are controlled by the temperature detected by the internal temperature sensor in the thermocycle. Thus, control is performed using the upper and lower temperature limits for a small temperature difference.

  In this case, the relationship between the temperature detected by the internal temperature sensor and the temperature detected by the defrost sensor differs depending on the refrigeration capacity of each device, the cooling target temperature, the load condition such as the outside air temperature at that time, It is not constant. Therefore, in the backup operation using the defrosting sensor, it is difficult to realize highly accurate internal temperature control.

  The present invention has been made to solve the conventional technical problem, and aims to realize more appropriate internal temperature control as a backup operation even when the internal temperature sensor has failed. .

  In order to solve the above problems, a refrigeration apparatus of the present invention cools a space to be cooled by an evaporator constituting a refrigerant circuit and melts and removes frost on the evaporator by a predetermined defrosting means. A cooled space temperature detecting means for detecting the temperature PT of the cooled space, a defrosting end temperature detecting means provided in the evaporator so as to detect the temperature ET of the evaporator, and an outside air temperature AT. And a control means for controlling the compression means and defrosting means constituting the refrigerant circuit, the control means based on the temperature PT of the cooled space detected by the cooled space temperature detecting means, The compression means is controlled so that the space to be cooled reaches a predetermined set temperature ST, and when the evaporator is defrosted by the defrosting means, the predetermined defrosting end temperature DET of the evaporator detected by the defrosting end temperature detection means is set. Finish defrosting In both cases, when the temperature of the cooled space temperature detecting means is abnormal, a temperature obtained by adding a predetermined offset value OV to the evaporator temperature ET detected by the defrosting end temperature detecting means is used as the temperature PT, and based on the outside air temperature AT. The offset value OV is changed.

  The invention of claim 2 is characterized in that, in the above-mentioned invention, the control means changes the offset value OV in a direction of increasing as the outside air temperature AT is higher.

  The invention of claim 3 is characterized in that, in each of the above inventions, the control means changes the offset value OV in such a direction that the lower the set temperature ST, the smaller the set value ST.

  According to the invention of claim 4, in each of the above inventions, the control means switches the offset value OV in a direction in which the other state is larger than the stable cooling state in which the space to be cooled is stably cooled. Features.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the control means includes a temperature PT of the cooled space detected by the cooled space temperature detecting means and a defrosting end temperature detecting means of the evaporator detected in the normal state. It has a database constructed by calculating a difference e from the temperature ET and storing the difference e as an offset value OV for each outside air temperature AT. When the cooled space temperature detecting means is abnormal, the outside air temperature detecting means The offset value OV is changed by reading the offset value OV corresponding to the detected outside air temperature AT from the database.

  According to a sixth aspect of the present invention, in each of the above-mentioned inventions, the control means is a predetermined upper limit temperature HST set above and below the set temperature based on the temperature PT of the cooled space detected by the cooled space temperature detecting means during normal operation. The compression means is started at, and a thermocycle is executed to stop at the lower limit temperature LST. When the cooled space temperature detection means is abnormal, the compression means is stopped when the substitute temperature PT falls to the lower limit temperature LST. Thereafter, when a predetermined OFF time t1 has elapsed, control for starting the compression means is executed.

  According to a seventh aspect of the present invention, in the above invention, the control means performs compression means start / stop short cycle prevention control that prohibits the compression means from stopping until a predetermined forced ON time t2 has elapsed after the compression means is activated. This is characterized in that the OFF time t1 is lengthened when the period in which the substitute temperature PT is lower than the set temperature ST continues for a certain time or longer.

  In the invention of claim 8, in the above invention, after the OFF time t1 is lengthened, the control means further lengthens the OFF time t1 when the substitute temperature PT is lower than the set temperature ST for a certain time or longer. It is characterized by.

  The invention of claim 9 includes, in each of the above-described inventions, at least one temperature detecting means for detecting a temperature that can be substituted for the temperature PT of the cooled space other than the defrosting end temperature detecting means, and the control means includes the temperature detecting means. If the difference between the temperature detected by the means and the temperature detected by the defrosting end temperature detecting means and the temperature detected by the cooled space temperature detecting means increases to a predetermined value or more, the cooled space temperature detecting means is abnormal. It is characterized by judging that it became.

  The invention of claim 10 is characterized in that, in each of the above inventions, the control means comprises an alarm means for notifying abnormality of the cooled space temperature detection means.

  According to the first aspect of the present invention, when the cooled space temperature detecting means is abnormal, the control means sets the temperature PT obtained by adding the predetermined offset value OV to the evaporator temperature ET detected by the defrosting end temperature detecting means. And the compression means is controlled by changing the offset value OV based on the outside air temperature AT so that the room to be cooled has a predetermined set temperature ST. Therefore, the actual space to be cooled affected by the outside air temperature AT. The temperature PT is estimated by a temperature obtained by adding an offset value OV considering the outside air temperature AT to the temperature ET of the evaporator detected by the defrosting end temperature detecting means, and the accuracy is obtained even when the cooling space temperature detecting means is abnormal. It is possible to realize temperature control of the cooling space with a high temperature.

  In particular, as in the second aspect of the invention, the control means changes the offset value OV in such a direction that the higher the outside air temperature AT, the higher the outside air temperature AT, the higher the cooled space temperature PT. Nevertheless, the offset value OV can be changed in consideration of the difference from the evaporator temperature ET detected by the defrosting end temperature detecting means which is not easily affected by the increase in the outside air temperature AT. As a result, appropriate backup control can be realized until the cooling space temperature detecting means is repaired or replaced.

  According to the invention of claim 3, in the above invention, the control means detects the temperature of the space to be cooled in a situation where the set temperature ST is lower by changing the offset value OV in a direction that becomes smaller as the set temperature ST is lower. The offset value OV can be changed in consideration of the fact that the temperature detected by the means and the temperature ET of the evaporator that detects the defrosting end temperature are closer to each other. Thereby, more accurate backup control according to the set temperature ST can be realized.

  According to the invention of claim 4, in each of the above inventions, the control means switches the offset value OV in a direction in which the other state becomes larger than the stable cooling state in which the space to be cooled is stably cooled. Thus, the temperature ET of the evaporator that detects the defrosting end temperature is in a state other than the stable cooling state, for example, at the time of pull-down or immediately after the start of the compression means, etc. The offset value OV can be changed in view of the fact that the evaporator temperature ET is cooled in advance. Thereby, more accurate backup control according to the cooling state can be realized.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the control means is configured such that the cooling means detects the temperature PT of the cooled space detected by the cooled space temperature detecting means and the evaporation detected by the defrosting end temperature detecting means. It has a database constructed by calculating the difference e from the temperature ET of the vessel and storing the difference e as an offset value OV for each outside air temperature AT. When the cooled space temperature detecting means is abnormal, the outside air temperature is detected. By reading the offset value OV corresponding to the outside air temperature AT detected by the means from the database, the offset value OV is changed, and based on the database constructed at the normal time of the cooled space temperature detecting means, The offset value OV to be used can be changed.

  Therefore, it becomes possible to realize temperature control of the cooled space with high accuracy, and appropriate backup control can be realized until the repaired / replacement work of the cooled space temperature detecting means.

  According to the invention of claim 6, in each of the above inventions, the control means is a predetermined upper limit set above and below the set temperature based on the temperature PT of the cooled space detected by the cooled space temperature detecting means in the normal state. The compression unit is started at the temperature HST and the thermocycle is stopped at the lower limit temperature LST. When the temperature of the cooled space temperature detection unit is abnormal, the compression unit is activated when the substitute temperature PT falls to the lower limit temperature LST. By stopping, the compression means can be stopped by the temperature PT substituted based on the evaporator temperature ET and the outside air temperature AT detected by the defrosting end temperature detection means, and the temperature of the space to be cooled is lower than the lower limit temperature LST. Can be avoided.

  Further, when starting the compression means, after the compression means is stopped, the control for starting the compression means is executed when a predetermined OFF time t1 has elapsed, so without using the substitute temperature PT, The compression means can be activated. That is, as the substitute temperature PT, the temperature ET of the evaporator is used, but when the compression means is stopped, the temperature ET of the evaporator is the temperature of the space to be cooled due to the opening and closing of the door. It is difficult to follow the change in PT, and due to the structure, a high temperature refrigerant flows into the evaporator when the compression means is stopped, resulting in a disadvantage that the temperature rises regardless of the temperature of the cooled space PT. is there. Therefore, smooth cooling is performed while preventing the inconvenience caused by frequent start and stop of the compression means by starting the compression means when the predetermined OFF time t1 has elapsed without using the substitute temperature PT. Driving can be realized.

  According to the invention of claim 7, in addition to the above-mentioned invention, the control means generates the compression means for prohibiting the stop of the compression means until the predetermined forced ON time t2 elapses after the compression means is activated. When the stop short cycle prevention control is executed and the period in which the substitute temperature PT is lower than the set temperature ST continues for a certain time or longer, the substitute temperature PT reaches the predetermined lower limit temperature LST by increasing the OFF time t1. In spite of this, when the compression means is further operated for the above-mentioned compression means start / stop short cycle prevention control, the time when the substitute temperature PT is lower than the set temperature ST has continued for a certain time or more. In addition, by making the next OFF time t1 longer, it is possible to escape from a cycle that is excessively cooled. Thereby, it becomes possible to realize temperature control of the cooled space with high accuracy.

  According to the invention of claim 8, in addition to the above-mentioned invention, the control means increases the OFF time t1, and then when the period in which the substitute temperature PT is lower than the set temperature ST continues for a certain time or longer, the OFF time By further increasing t1, it is possible to escape from a cycle that is more efficiently excessively cooled, and it is possible to realize more accurate temperature control of the space to be cooled.

  According to the invention of claim 9, in addition to each of the above inventions, at least one temperature detecting means for detecting a temperature that can be substituted for the temperature PT of the cooled space other than the defrosting end temperature detecting means is provided, and the control means comprises When the difference between the temperature detected by the temperature detecting means and the temperature detected by the defrosting end temperature detecting means and the temperature detected by the cooled space temperature detecting means increases to a predetermined value or more, the cooled space temperature detection By determining that the means has become abnormal, even if an abnormality other than the cause such as disconnection or short circuit of the cooled space temperature detecting means has occurred, a temperature that can be substituted for the temperature PT of the cooled space is set. It is possible to determine the abnormality of the cooled space temperature detecting means based on the detected temperatures of the plurality of temperature detecting means to be detected.

  As a result, it is possible to determine the abnormality of the space temperature detecting means at an early stage, to realize appropriate backup control, and to promptly perform repair / replacement work and the like.

  According to the invention of claim 10, in addition to each of the above inventions, the control means includes an alarm means for notifying the abnormality of the cooled space temperature detecting means, so that the user can detect an abnormality in the cooled space temperature detecting means. It is possible to notify the fact that there has been, and to promptly perform maintenance work such as repair and replacement.

It is a vertical side view of the freezer as an example which applies the present invention. It is a schematic perspective view of the freezing apparatus of this invention. It is a refrigerant circuit figure of the freezing apparatus of this invention. It is an electrical block diagram of a control apparatus. It is a related figure of the offset value with respect to the thermo setting for every outside temperature. It is a related figure of the offset value with respect to the thermo setting for every cooling preset temperature. It is a graph which shows the timing of an offset value change. It is a figure which shows the extension control of OFF time t1.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a longitudinal side view of a commercial freezer (low temperature storage) R as an embodiment to which a refrigeration apparatus 10 of the present invention is applied, FIG. 2 is a schematic perspective view of a refrigerator side unit of the refrigeration apparatus 10, and FIG. 3 is a refrigeration apparatus. 10 refrigerant circuit diagrams are respectively shown. The freezer R according to the embodiment is installed in a kitchen of a hotel or a restaurant, for example, and a main body is constituted by a heat insulating box 1 whose front opening 22 is closed by a door 6 so as to be freely opened and closed. A storage room (cooled space) 5 is configured in the heat insulating box 1.

  In addition, a cooling chamber 14 to which the evaporator 11 of the refrigeration apparatus 10 according to the present invention and the blower 12 for circulating cold air are attached is partitioned by a partition plate 13 in the upper portion of the storage chamber 5. The cold air sucked into the cooling chamber 14 from the storage chamber 5 by the cool air circulation blower 12 is exchanged with the evaporator 11 and then discharged from the opening at the rear of the cooling chamber 14 so that the inside of the storage chamber 5 has a predetermined temperature. To be cooled.

  On the other hand, a machine room 17 is defined by a panel such as a front panel 16 on the top surface of the heat insulation box 1, and an opening 1A formed on the top surface of the heat insulation box 1 is a unit plate constituted by a heat insulation plate. It is closed at 21. On the upper surface of the unit plate 21, a compressor 18, a gas cooler 19, and a gas cooler blower 20 that cools the gas cooler 19 are located in the machine room 17 and constitute a known refrigeration cycle of the refrigeration apparatus 10 together with the evaporator 11. The electrical box 25 and the like are installed. On the lower surface of the unit plate 21, the evaporator 11 located in the cooling chamber 14 in the upper part of the storage chamber 5 is provided. The evaporator 11 is provided with defrosting means for thawing and removing frost attached to the evaporator 11. In the present embodiment, the defrosting means is constituted by a defrost heater (heating heater) 15. In addition, a defrosting means is not limited to this, It is good also as a structure which flows in the hot gas in a refrigerant circuit.

  Here, the refrigerant circuit 7 of the refrigeration apparatus 10 in the present embodiment will be described with reference to the refrigerant circuit diagrams of FIGS. 2 and 3. In the refrigeration cycle of the refrigeration apparatus 10 in the present embodiment, carbon dioxide is enclosed as a refrigerant, and a split cycle (two-stage compression one stage) in which the refrigerant pressure (high pressure) on the high pressure side is equal to or higher than the critical pressure (supercritical). Adopt expansion intercooling cycle).

  The refrigerating apparatus 10 of the present embodiment includes a low-stage compression element 18A that constitutes a compressor (compression means) 18, a high-stage compression element 18B that also constitutes a compression means, a gas cooler 19, and a flow divider 37. , The merger 38, the auxiliary expansion valve (auxiliary throttle means) 39, the intermediate heat exchanger 40, the internal heat exchanger 41, the expansion valve (main throttle means) 8, and the evaporator 11. Is configured.

  The gas cooler 19 dissipates heat from the high-temperature and high-pressure refrigerant discharged from the high-stage compression element 18B, thereby cooling the refrigerant discharged from the high-stage compression element 18B. The flow divider 37 divides the refrigerant from the gas cooler 19 into a first refrigerant flow and a second refrigerant flow, flows the first refrigerant flow to the sub circuit 42, and sends the second refrigerant flow to the main circuit 43. Shed.

  In the main circuit 43 through which the second refrigerant flow flows, the refrigerant diverted by the flow divider 37 includes an inner pipe (second flow path) 40B of the intermediate heat exchanger 40, an inner pipe 41B of the internal heat exchanger 41, The low-stage compression means is constructed by sequentially passing through the strainer 44, the expansion valve 8, the evaporator 11, the outer pipe 41A of the internal heat exchanger 41, the refrigerant introduction pipe 23 provided with the check valve 45, and the strainer 46. It connects so that it may be supplied to the suction side (low pressure part) of 18 A of compression elements.

  In the sub-circuit 42 through which the first refrigerant flow flows, the refrigerant diverted by the flow divider 37 sequentially passes through the strainer 47, the auxiliary expansion valve 39, and the outer pipe (first flow path) 40A of the intermediate heat exchanger 40. And connected so as to be supplied to the suction side (intermediate pressure part) of the compression element 18B constituting the high-stage compression means.

  Next, the control device (control means) 9 of the refrigeration apparatus 10 in the present embodiment will be described with reference to FIG. The control device 9 is composed of a general-purpose microcomputer and incorporates a timer 32 as a time limit means, an arithmetic processing unit 33, and a memory 34 as a storage means.

  A control panel 35 having various setting switches and a display unit is connected to the control device 9. The various setting switches include an LCD panel (setting means) 36 that can arbitrarily set each setting value as will be described in detail later.

  Further, on the input side of the control device 9, an internal temperature sensor (cooled space temperature detecting means) 31 for detecting the temperature (internal temperature) PT in the storage chamber 5 (cooled space), the evaporator 11 A defrosting sensor (defrosting end temperature detecting means) 28 provided in the evaporator 11 for detecting the temperature ET and an outside air temperature sensor (outside air temperature detecting means) 48 for detecting the outside air temperature AT are connected. Yes. In the present embodiment, the internal temperature sensor 31 detects the temperature of the cold air sucked from the storage chamber 5 into the cooling chamber 14 as the temperature PT in the storage chamber 5 (cooled space), so that the cold air suction side of the cooling chamber 14 Is provided. Further, the defrosting sensor 28 is a temperature sensor for detecting the defrosting end temperature in the evaporator 11, so that the temperature at a location where the frosting is likely to occur in the evaporator 11 can be detected, for example, the evaporator 11. The cooling air inlet side and the refrigerant inlet side temperature of the evaporator 11 can be detected. The outside air temperature sensor 48 is disposed on the outer surface of the electrical box 25 disposed in the machine room 17.

  In addition to this, an evaporator inlet side temperature sensor 29 for detecting the refrigerant inlet side temperature of the evaporator 11 and an evaporator for detecting the refrigerant outlet side temperature of the evaporator 11 are provided on the input side of the control device 9. Outlet temperature sensor 30, inlet side temperature sensor 49 for detecting the inlet side temperature of the outer tube 40A of the intermediate heat exchanger 40, outlet for detecting the outlet side temperature of the outer tube 40A of the intermediate heat exchanger 40 A side temperature sensor 50, a gas cooler outlet side temperature sensor 51 for detecting the refrigerant outlet side temperature of the gas cooler 19, a discharge gas temperature sensor 52 for detecting the discharge gas temperature of the high-stage compression element 18B, and the like are connected.

  On the other hand, on the output side of the control device 9, a compressor motor (DC motor) 18M that drives the compressor 18, a blower motor 12M that drives the blower 12 for circulating cold air, a blower motor 20M that drives the blower 20 for gas cooler, The expansion valve 8, the auxiliary expansion valve 39, and a warning lamp 53 are connected as warning means. The compressor motor 18M is connected via the inverter device 25, and the operating frequency of the compressor motor 18M can be arbitrarily changed. Further, the alarm means may employ a buzzer in addition to the alarm lamp 53, and may display the alarm content on the display unit of the control panel 35.

  With the above configuration, when the refrigeration apparatus 10 is operated by the control device 9, the refrigerant taken into the suction side (low pressure portion) of the low-stage compression element 18A of the compressor 18 is increased to the intermediate pressure here. . The refrigerant compressed by the low-stage compression element 18A is discharged into a sealed container through a communication pipe (not shown).

  The refrigerant introduction pipe whose one end is opened in the closed container is provided on the suction side of the high-stage compression element 18B, and the refrigerant whose pressure has been increased to the intermediate pressure by the low-stage compression element 18A The refrigerant mixed with the intermediate pressure refrigerant from the circuit 42 flows into the high-stage compression element 18B (intermediate pressure portion) from the refrigerant introduction pipe, and is further pressurized to a predetermined high pressure.

  At this time, the pressure of the refrigerant compressed by the high-stage compression element 18B (high-pressure side pressure HP) is set to a supercritical pressure, and the refrigerant in the supercritical state is passed through the refrigerant discharge pipe 24 to the gas cooler 19. Is flowed into.

  The refrigerant that has exited the gas cooler 19 is cooled in the process of passing, and then enters the flow divider 37 and is divided into the sub circuit 42 through which the first refrigerant flow flows and the main circuit 43 through which the second refrigerant flow flows. The first refrigerant flow that has flowed into the sub-circuit 42 reaches the intermediate pressure (that is, the discharge pressure of the low-stage compression element 18A and substantially the same pressure as the suction pressure of the high-stage compression element 18B) at the auxiliary expansion valve 39. Depressurized.

  Then, in the process of passing through the outer pipe (first flow path) 40A of the intermediate heat exchanger 40 and passing through the outer pipe (first flow path) 40A, the flow divider 37 passes through the inner pipe 40B. Evaporates by exchanging heat with the second refrigerant flow, which is the other refrigerant flow after being divided in step (b). After that, the merger 38 joins the second refrigerant flow after being compressed by the low-stage compression element 18A, and is sucked into the high-stage compression element 18B (intermediate pressure part).

  On the other hand, the second refrigerant flow flowing into the main circuit 43 passes through the inner pipe (second flow path) 40B of the intermediate heat exchanger 40, and the first refrigerant is decompressed by the auxiliary expansion valve 39. After being cooled by exchanging heat with the flow, it passes through the inner pipe (second flow path) 41B of the internal heat exchanger 41. In the process of passing through the inner pipe (second flow path) 41B, the refrigerant is cooled by exchanging heat with the refrigerant discharged from the evaporator 11 flowing in the outer pipe (first flow path) 41A.

  The first refrigerant flow that has flowed out of the internal heat exchanger 41 is decompressed to the evaporation pressure by the expansion valve 8, and then flows into the evaporator 11 and uses the inside of the storage chamber 5 (cooled space) as a heat source. It evaporates and is sucked into the lower stage compression element 18 (low pressure part) through the outer tube 41A of the internal heat exchanger 41. Here, the refrigerant flowing into the expansion valve 8 is heat-exchanged with the low-temperature refrigerant flowing out from the evaporator 11 by the internal heat exchanger 41.

  As described above, when the refrigeration apparatus 10 is operated, the cold air exchanged with the evaporator 11 in the cooling chamber 14 is discharged to the storage chamber 5 by the cool air circulation blower 12 and circulated in the storage chamber 5. Thereafter, circulation is performed to return to the cooling chamber 14 by the blower 12 again.

  Here, the control of the compressor when the internal temperature sensor 31 is normal will be described. The controller 9 controls the operating frequency of the compressor motor 18M so that the temperature PT in the storage chamber 5 detected by the internal temperature sensor 31 is set to a predetermined set temperature ST. That is, when the temperature PT is lower than the set temperature ST, the operating frequency of the compressor motor 18M is decreased, and when it is higher, the operating frequency is increased.

  Further, in addition to the frequency control of the compressor 18, the controller 9 reaches the predetermined upper limit temperature HST at which the temperature PT in the storage chamber 5 detected by the internal temperature sensor 31 is set above the set temperature ST. In such a case, the compressor motor 18M is started, and when a predetermined lower limit temperature LST set below the set temperature ST is reached, a thermocycle for stopping the compressor motor 18M is executed, and the temperature in the storage chamber 5 is increased. PT is controlled to set temperature ST.

  By performing the cooling operation, the evaporator 11 is frosted. The memory 34 of the control device 9 stores a defrosting operation start cycle (for example, a 6-hour cycle) and a defrosting end temperature DET (for example, + 8 ° C.) preset by the LCD panel 36 or the like. Therefore, the control device 9 stops the thermocycle of the compressor 18 and starts the defrosting operation for energizing the defrost heater 15 provided in the evaporator 11 when the start time comes based on a predetermined defrosting cycle. .

  When the evaporator 11 is heated by the defrosting operation, the frost is melted, and the temperature of the evaporator 11 increases as the defrosting operation proceeds. When the detection temperature of the defrosting sensor 28 that detects the temperature ET of the evaporator 11 rises to a predetermined defrosting end temperature DET, the control device 9 determines that the frosting of the evaporator 11 has been sufficiently melted and removed. Then, the defrost heater 15 is deenergized and the defrosting operation is terminated. Thereafter, the control device 9 restarts the cooling operation.

  Next, the control in the case where an abnormality occurs due to a failure or the like in the internal temperature sensor 31 used for controlling the compressor 18 in the cooling operation will be described.

(1) Determination of abnormality of the internal temperature sensor 31 Whether the internal temperature sensor 31 is abnormal is determined by the control device 9 when the resistance value of the internal temperature sensor 31 is abnormal at a predetermined sampling period. Whether it is (under or over) is determined by judgment.

  In addition to this, the control device 9 includes the temperature ET of the evaporator 11 detected by the defrost sensor 28, the refrigerant inlet-side temperature ETI of the evaporator 11 detected by the evaporator inlet-side temperature sensor 29, and the internal temperature sensor 31. When the difference between each of the detected temperatures and the temperature detected is increased to a predetermined value, for example, 30 deg or more as a temperature that can be clearly determined as abnormal, and each temperature difference is equal to or larger than the predetermined value May determine that an abnormality has occurred in the internal temperature sensor 31.

  At this time, the temperature ET of the evaporator 11 detected by the defrost sensor 28 and the evaporator detected by the evaporator inlet side temperature sensor 29 are detected as the temperature of the temperature sensor that determines the difference from the temperature detected by the internal temperature sensor 31. 11 is an example of the refrigerant inlet side temperature ETI, but is not limited to this. The temperature ET of the evaporator 11 detected by the defrost sensor 28 and other temperature sensors (temperature detecting means) are not limited thereto. And if it is a temperature sensor which detects the temperature which can substitute for temperature PT in the storage chamber 5 (space to be cooled), it is not limited to this. That is, the temperature ET of the evaporator 11 detected by the defrost sensor 28 and the temperature detected by the second defrost sensor provided in the vicinity of the defrost sensor 28 may be used. In this case, the temperature detected by the defrosting sensor 28 and the temperature detected by the others are compared with the temperature detected by the internal temperature sensor 31, but the temperature to be compared is determined. However, the temperature is not limited to these two, and a temperature detected by a temperature sensor that detects a temperature that can be substituted for the temperature PT of the space to be cooled is further adopted. When the difference from the temperature detected by is greater than or equal to a predetermined value, it may be determined that an abnormality has occurred in the internal temperature sensor 31.

  As a result, even if an abnormality other than the cause such as disconnection or short circuit of the internal temperature sensor 31 occurs, the detected temperature of the plurality of temperature sensors that detect the temperature that can be substituted for the temperature PT in the storage chamber 5 is used. Based on this, it is possible to determine the abnormality of the internal temperature sensor 31.

(2) Offset value OV used for backup control
When the controller 9 determines that an abnormality has occurred in the internal temperature sensor 31, the internal temperature of the internal temperature sensor 31 is detected by the alarm lamp 53 or the display unit of the control panel 35 when the abnormality of the internal temperature sensor 31 is detected. The sensor 31 is notified that there is an abnormality, and prompts maintenance work such as repair and replacement at an early stage. Further, the control device 9 substitutes a temperature obtained by adding a predetermined offset value OV to the evaporator temperature ET detected by the defrost sensor 28 as the temperature PT in the storage chamber 5, and executes the backup control of the compressor 18. .

  At this time, the predetermined offset value OV is changed based on the outside air temperature AT detected by the outside air temperature sensor 48 and other thermosettings. That is, the offset value OV is changed according to the outside air temperature AT or the like detected at a predetermined sampling cycle (including rewriting in the same manner as the previous time). Hereinafter, the offset value OV to be changed will be described with reference to FIGS. FIG. 5 shows a relationship diagram of the offset value OV with respect to the thermosetting for each outside air temperature AT, and FIG. 6 shows a relationship diagram of the offset value OV with respect to the thermosetting for each cooling set temperature.

  During the operation of the compressor 18 in the thermocycle control of the compressor 18 (when the thermo is on), the thermo setting (strong / medium / weak) set by the LCD panel 36. The lower the set temperature ST, the stronger the set temperature ST. When the set temperature ST is high (when the set temperature ST is high), the interior of the storage chamber 5 can be easily cooled to the set temperature ST at an early stage. As a result, the frequency of the compressor 18 is lowered and the evaporator 11 is discharged. As the refrigerant circulation amount decreases, the refrigeration capacity of the evaporator 11 decreases. Therefore, since the amount of heat exchange between the air in the storage chamber 5 and the evaporator 11 decreases, the temperature PT in the storage chamber 5 detected by the internal temperature sensor 31 and the evaporator 11 detected by the defrost sensor 28. The difference from the temperature ET increases. On the other hand, when the thermo setting is strong (when the set temperature ST is low), it takes some time until the inside of the storage chamber 5 is set to the set temperature ST, so the frequency of the compressor 18 is increased. Therefore, the refrigerant circulation amount to the evaporator 11 becomes large, the refrigeration capacity of the evaporator 11 increases, and the amount of heat exchange between the air in the storage chamber 5 and the evaporator 11 increases. The difference between the temperature PT in the storage chamber 5 detected by the defroster 28 and the temperature ET of the evaporator 11 detected by the defrost sensor 28 becomes small.

  Moreover, since the intrusion heat into the storage chamber 5 increases as the outside air temperature AT increases, the temperature PT in the storage chamber 5 is easily affected by the rise, and the evaporator 11 that exhibits the cooling action of the refrigerant is used. The temperature ET is not easily affected. Therefore, the higher the outside air temperature AT, the larger the difference between the temperature PT in the storage chamber 5 and the temperature ET of the evaporator 11 detected by the defrost sensor 28, and the smaller the outside air temperature AT, the smaller the difference.

  Such a tendency depends on the temperature PT in the storage chamber 5 detected by the internal temperature sensor 31 measured in the normal state with respect to the thermo setting for each outside air temperature as shown in FIG. 5 and the evaporation detected by the defrost sensor 28. This is a difference from the temperature ET of the vessel 11 (corresponding to the offset value OV changed in the backup control).

  For this reason, the memory 34 of the control device 9 stores a data table in which the offset value OV is increased as the outside air temperature AT is higher for each outside air temperature AT. Further, the data table stores an offset value OV that is set to be smaller as the thermo setting is weaker, that is, as the set temperature ST in the same cooling temperature range (refrigeration or freezing) is lower.

  In the present embodiment, the offset value OV is determined based on the outside air temperature AT detected by the outside air temperature sensor 48 and the data table constructed for each set thermo setting, but by parameterizing the thermo setting, You may obtain | require by calculating the offset value OV using the predetermined | prescribed relational expression which has the said tendency from the said thermo setting and external temperature AT.

  Further, in FIG. 6, the temperature PT in the storage chamber 5 detected by the internal temperature sensor 31 measured at the normal time with respect to the thermosetting for each cooling temperature range (refrigeration / freezing) and the defrosting sensor 28 are detected. The difference from the temperature ET of the evaporator 11 (corresponding to the offset value OV changed in the backup control) is shown.

  The evaporating temperature of the refrigerant in the evaporator 11 differs between the case where the set temperature ST in the storage chamber 5 (space to be cooled) is set as the refrigeration temperature range and the case where the set temperature ST is set as the refrigeration temperature range. That is, in the refrigeration temperature range, the evaporation temperature of the refrigerant in the evaporator 11 is low, and the influence of intrusion heat is large. Therefore, the temperature ET of the evaporator 11 detected by the defrost sensor 28 and the temperature PT detected by the internal temperature sensor 31. There is a tendency for the difference to increase.

  Therefore, the data table stored in the memory 34 of the control device 9 has a data table in which the set temperature ST is different between the refrigeration temperature range and the refrigeration temperature range. In the data table, the set temperature ST is the refrigeration temperature. In the region, the offset value OV tends to be larger than that in the refrigerated temperature region.

  Further, in the stable cooling state in which the inside of the storage chamber 5 is stably cooled, the temperature ET of the evaporator 11 detected by the defrost sensor 28 includes the outside air temperature AT, the thermosetting and the set temperature ST (freezing / refrigeration) as described above. The offset value OV read out in step (3) is used as the offset value OV to be changed, and the compressor 18 is controlled by substituting the temperature added with the offset value OV as the temperature PT in the storage chamber 5.

  On the other hand, in a state other than the stable cooling state such as during pull-down operation or immediately after the start of the compressor 18 in the thermocycle, the offset value OV is an offset that is switched in a direction larger than that in the stable cooling state. The value OV is adopted.

  That is, immediately after the start-up of the compressor 18 in the pull-down operation or in the thermocycle, the temperature ET of the evaporator 11 detected by the defrost sensor 28 is lower than the temperature PT in the storage chamber 5. For this reason, the offset value OV added to the temperature ET of the evaporator 11 that substitutes for the temperature PT in the storage chamber 5 is regarded as a temperature lower than the actual temperature PT unless the offset value OV is larger than the stable cooling state. 18 control is performed.

  Therefore, in the stable cooling state, the offset value OV read as described above is adopted as the offset value OV to be changed, and in a state other than the stable cooling state, an offset larger by a predetermined value than the read offset value OV. The offset value OV for changing the value OVh is adopted.

  At this time, whether or not the state is the stable cooling state or the other state depends on whether or not the temperature ET of the evaporator 11 detected by the defrost sensor 28 is higher than a predetermined offset switching temperature ETch. to decide. The offset switching temperature ETch is assumed to be a predetermined temperature (α) lower than the set temperature ST (ETch = ST−α). The predetermined temperature α is a constant that can be set to 0 and a negative value.

  Therefore, when the predetermined temperature α is set to 2 deg, the offset switching temperature ETch is the set temperature ST-2 deg. When the temperature ET detected by the defrost sensor 28 is lower than the offset switching temperature ETch (ET <ETch), it is determined that the cooling state is stable, and the offset value OV read as described above is changed as the offset value. Adopted as the value OV, when the temperature is equal to or higher than the offset switching temperature ETCH (ETch ≦ ET), it is determined that the state is other than the stable cooling state, and the offset value OVh larger than the read offset value OV by a predetermined value is set. This is adopted as the offset value OV to be changed.

  The offset switching temperature ETch is not limited to one, and a plurality of predetermined temperatures α may be set and a plurality of offset switching temperatures ETch may be provided. For example, in addition to the offset switching temperature ETch set to the set temperature ST-2 deg, the second offset switching temperature ETch2 set to the set temperature ST-(− 15 deg) is provided, and the defrosting sensor 28 is in a state other than the stable cooling state. When the detected temperature ET is lower than the second offset switching temperature ETch2 (ET <ETch2), the offset value OVh that is larger than the read offset value OV by a predetermined value is adopted as the offset value OV. When the temperature ET detected by the defrosting sensor 28 is equal to or higher than the second offset switching temperature ETch2 (ET ≧ ETch2), the offset value OVh2 larger than the offset value OVh by a predetermined value is adopted as the offset value OV. May be. Thereby, as the temperature ET detected by the defrost sensor 28 becomes higher than the set temperature ST, the offset values OVh, OVh2,... Larger than the read offset value OV may be adopted as the offset value OV. This makes it possible to achieve more accurate control.

(3) Backup Control Using Offset Value OV Hereinafter, backup control using the defrost sensor 28 when the internal temperature sensor 31 is abnormal will be described with reference to the graph of FIG. FIG. 7 shows changes in the temperature PT (ET + OV) after the offset value OV is changed, the temperature ET of the evaporator 11 detected by the defrost sensor 28, and the offset value OV in order from the top. Note that, here, the offset switching temperature ETch is set to a predetermined value α of 0 and is the same as the set temperature ST (ETch = ST).

  At the time of pull-down, since the temperature ET of the evaporator 11 detected by the defrost sensor 28 is higher than the set temperature ST, ET> ETch, and the control device 9 determines that the state is other than the stable cooling state. The offset value OV to be changed in this case is employed as an offset value for changing the offset value OVh that is higher than the offset value OV read based on the outside air temperature AT, the thermo setting, or the like.

  Therefore, the control device 9 controls the compressor 18 by substituting the temperature PT obtained by adding the offset value OVh to the temperature ET of the evaporator 11 detected by the defrosting sensor 28. When the temperature PT in the storage chamber 5 gradually decreases by the control of the compressor 18 and the temperature ET of the evaporator 11 detected by the defrost sensor 28 becomes lower than the set temperature ST, ET <ETch Therefore, the control device 9 determines that the cooling state is stable, and adopts the offset value OV read out based on the outside air temperature AT, the thermosetting, or the like as it is in this case. That is, when the pull-down is completed, it is determined that the state has shifted to the stable cooling state, and the offset value OV to be changed is decreased. Therefore, in the stable cooling state, the controller 9 controls the compressor 18 by substituting the temperature PT obtained by adding the offset value OV to the temperature ET of the evaporator 11 detected by the defrost sensor 28. In FIG. 7, the stable cooling state and the other states are partitioned by a one-dot chain line.

  When the temperature PT in the storage chamber 5 is gradually lowered by the control of the compressor 18 in the stable cooling state, and the substituted PT falls to the lower limit temperature LST lower than the set value ST by a predetermined temperature, the control device 9 stops the operation of the compressor 18 (thermo-off).

  Since the cooling operation is stopped by stopping the operation of the compressor 18, the temperature PT in the storage chamber 5 gradually increases. Then, after stopping the operation of the compressor 18 (thermo-off), the control device 9 determines whether or not a predetermined OFF time t1 has elapsed, and starts the compressor 18 when the OFF time t1 has elapsed ( Thermoon).

  The predetermined OFF time t1 is a short cycle prevention time set in order to prevent inconvenience due to restarting in a short time after the compressor 18 is stopped, and is set to 5 minutes, for example. The

  Thereby, when the internal temperature sensor 31 is abnormal, the temperature ET of the evaporator 11 detected by the defrost sensor 28 instead of the thermocycle control based on the temperature PT in the storage chamber 5 detected by the internal temperature sensor 31. The compressor 18 is stopped when the substitute temperature PT obtained by adding a predetermined offset value OV to the lower limit temperature LST, and the compressor 18 is stopped when a predetermined OFF time t1 has elapsed after the compressor 18 is stopped. The control to restart can be executed.

  In this case, the offset value OV added to the temperature ET of the evaporator 11 substituting the temperature PT is changed in a direction of increasing as the outside air temperature AT is higher, based on the outside air temperature AT detected by the outside air temperature sensor 48. Therefore, the offset value is considered (estimated) by taking into account (estimating) the difference from the temperature ET detected by the defrosting sensor 28 that is not easily affected by the increase in the outside air temperature AT despite the actual temperature PT in the storage chamber 5 being increased. OV can be changed.

  Further, in this embodiment, the control device 9 changes the offset value OV in the same cooling temperature region in such a direction that the offset temperature OV becomes smaller as the set temperature ST is lower, so The offset value OV can be changed in consideration of the fact that the temperature detected by the internal temperature sensor 31 and the temperature ET detected by the defrost sensor 28 are more approximate values.

  Furthermore, in the present embodiment, the control device 9 switches the offset value OV in a direction in which the other state becomes larger than the stable cooling state in which the inside of the storage chamber 5 is stably cooled, When the evaporator temperature ET detected by the defrosting sensor 28 is in a state other than the stable cooling state, for example, at the time of pull-down or immediately after the start of the compressor 18, it evaporates more than the temperature PT in the storage chamber 5 compared to the stable cooling state. The offset value OV can be changed in view of the fact that the temperature ET of the vessel is cooled in advance. Thereby, more accurate backup control according to the cooling state can be realized.

  Therefore, in order to obtain a substitute temperature PT, considering that the difference between the temperature ET of the evaporator 11 detected by the defrost sensor 28 and the temperature PT in the storage chamber 5 varies depending on various conditions. By changing the offset value OV added to the temperature ET of the evaporator 11, even if the internal temperature sensor 31 is abnormal, it is based on the temperature ET of the evaporator 11 and the outside air temperature AT detected by the defrost sensor 28. Thus, the compressor 18 can be stopped by the substituted temperature PT, and the disadvantage that the temperature in the storage chamber 5 falls below the lower limit temperature LST can be avoided. Therefore, it is possible to realize temperature control of the cooled space with high accuracy. Thereby, appropriate backup control can be realized until the internal temperature sensor 31 is repaired or replaced.

  Further, in the control of the compressor 18, when the compressor 18 is started, the compressor 18 is stopped and then the compressor 18 is started when a predetermined OFF time t1 has elapsed. The compressor 18 can be started without using the temperature PT.

  As described above, the temperature PT of the evaporator 11 is used as the substitute temperature PT. However, in the state where the compressor 18 is stopped, the temperature ET of the evaporator 11 is a cause of opening / closing of the door or the like. Therefore, it is difficult to follow the change in the temperature PT in the storage chamber 5 due to the structure, and because of the structure, the high-temperature refrigerant flows into the evaporator 11 when the compressor 18 is stopped, which is related to the temperature PT in the storage chamber 5. Inconvenience may occur that the temperature rises.

  On the other hand, in the present embodiment, the compressor 18 is frequently started and stopped by starting the compressor 18 when the predetermined OFF time t1 has elapsed without using the substitute temperature PT. Smooth cooling operation can be realized while preventing inconvenience.

(4) Extension control of OFF time t1 When the compressor 18 is started after the elapse of the OFF time t1 in the control of the compressor 18, for the same reason as the OFF time t1 being set, the compressor In order to prevent inconvenience due to a short time after starting 18, a predetermined ON time t <b> 2 and a short cycle prevention time for keeping the compressor 18 started are set. .

  Here, FIG. 8 shows a change in the substituted temperature PT when the OFF time t1 and the ON time t2 are set. The substituted PT gradually increases during the OFF time t1 after the compressor 18 is first stopped, and after the OFF time t1, the compressor 18 is used regardless of the PT value substituted by the control device 9. Start up.

  At this time, the compressor 18 is started for a predetermined ON time t2 after the compressor 18 is started regardless of the substituted PT value. Therefore, as shown in the figure, if the substituted PT is normal, even if the temperature falls to the lower limit temperature LST at which the compressor 18 is stopped, the compressor 18 cannot be stopped and is continuously operated. Thus, the substituted PT may be lower than the lower limit temperature LST.

  In this state, after the compressor 18 is started, the compressor 18 is operated until the ON time t2 elapses, and then the compressor 18 is stopped until the OFF time t1 elapses. May be lower than the set temperature ST. In the above control, even in this case, the control device 9 restarts the compressor 18 when the OFF time t1 elapses, so that the temperature PT in the storage chamber 5 drops excessively.

  Therefore, in this embodiment, the control device 9 determines whether or not the period after the substitute temperature PT falls below the set temperature ST continues for a certain time (t3, for example, 10 minutes) or longer, and continues for the time t3 or more. In this case, the next OFF time t1 is extended by a predetermined time. In this embodiment, the initially set OFF time t1 is 5 minutes, and when extending, a total of 7 minutes extended by 2 minutes is set as a new OFF time t1. The extended time is not limited to this.

  As a result, even if the ON time t2 for the compressor start / stop short cycle prevention control is set, the next OFF time t1 is lengthened to escape from the cycle that is overcooled. Is possible. Thereby, it becomes possible to realize temperature control of the cooled space with high accuracy.

  The extension control of the OFF time t1 is performed until the normal thermo-off control is executed in which the compressor 18 is stopped when the substituted PT falls to the lower limit temperature LST after the ON time t2 has elapsed. Thereby, the inconvenience that the inside of the storage chamber 5 is excessively cooled can be solved.

  Further, after the extension control of the OFF time t1, when the period in which the substitute temperature PT is lower than the set temperature ST continues for a certain time or longer, the control device 9 may further increase the OFF time t1. As a result, it is possible to escape from the cycle in which the cooling is excessively performed more efficiently, and it is possible to realize more accurate temperature control of the space to be cooled.

(5) Other Embodiments In the embodiment, the offset value OV used in the backup control is the outside air detected by the outside air temperature sensor 48 as described above from the data table stored in the memory 34 of the control device 9. The offset value OV read based on the temperature AT and the thermo setting set on the LCD panel 36 is adopted, but the present invention is not limited to this.

  That is, as another example, the control device 9 is configured on the condition that the temperature PT in the storage chamber 5 detected by the internal temperature sensor 31 is equal to or lower than the set temperature ST when the internal temperature sensor 31 is normal. A difference e between the temperature PT detected by the internal temperature sensor 31 and the temperature ET of the evaporator 11 detected by the defrost sensor 28 is calculated, and at that time, the difference for each outdoor temperature AT detected by the outdoor temperature sensor 48. A database is constructed by storing e as an offset value OV.

  The database divides the temperature of the outside air temperature AT into predetermined temperature zones (for example, 5 ° C. or lower, 5-20 ° C., 20-30 ° C., 30 ° C. or higher), and the temperatures PT detected by the internal temperature sensor 31 respectively. And the difference e between the temperature ET of the evaporator 11 detected by the defrost sensor 28 is stored. The difference e is an average value for each temperature zone of values obtained in a predetermined sampling cycle when the temperature PT in the storage chamber 5 detected by the internal temperature sensor 31 is equal to or lower than the set temperature ST, or The average value Ave in which the weight is placed on the latest value, for example, the average value (AVE + e) / 2) of the previous average value Ave and the latest value e is stored in the database.

  When the controller 9 detects an abnormality in the internal temperature sensor 31, the abnormality of the internal temperature sensor 31 is notified by turning on the alarm lamp (alarm means) 53 and the display unit of the control panel 35, and the outside air. The offset value OV corresponding to the outside air temperature AT detected by the temperature sensor 48 is read from the database, and the temperature obtained by adding the read offset value OV to the temperature ET of the evaporator 11 detected by the defrost sensor 28 is stored in the storage chamber 5. As a substitute for the temperature PT, similarly to the above embodiment, the compressor 18 is stopped when the temperature PT falls to the predetermined lower limit temperature LST, and then the compressor 18 is started after the predetermined OFF time t1 has elapsed. Execute machine control. In this case, the extension control of the OFF time t1 as described above is performed similarly.

  Thus, the evaporator detected by the defrost sensor 28 by changing (including rewriting) the offset value OV in consideration of the outside air temperature AT based on the database constructed when the internal temperature sensor 31 is normal. The temperature obtained by adding the offset value OV to the temperature ET of 11 can be substituted for the temperature PT in the storage chamber 5, and the compressor 18 can be controlled without any trouble.

  Therefore, it becomes possible to realize temperature control of the cooled space with high accuracy, and appropriate backup control can be realized until the repaired / replacement work of the cooled space temperature detecting means.

  In each of the above embodiments, the refrigeration apparatus 10 that uses carbon dioxide as the refrigerant has a so-called two-stage compression single-stage expansion intercooling cycle in which the refrigerant pressure (high-pressure) on the high-pressure side is equal to or higher than the critical pressure. By adopting it, the refrigerant circuit 7 becomes complicated, and the number of sensors (detection means) used for control increases. For this reason, an increase in the number of sensors increases the abnormality rate of the sensors. However, as described above, effective backup control can be realized against the abnormality of the internal temperature sensor 31, and thus the storage room 5 (cooled space). Insufficient cooling can be minimized.

R Commercial freezer (low temperature storage)
1 Insulation box 5 Storage room (cooled space)
7 Refrigerant circuit 8 Expansion valve 9 Control device (control means)
DESCRIPTION OF SYMBOLS 10 Refrigeration apparatus 11 Evaporator 12 Blower for cold air circulation 15 Defrost heater (defrosting means)
17 Machine room 18 Compressor (compression means)
18A Low stage side compression element 18B High stage side compression means 19 Gas cooler 28 Defrost sensor (Defrosting end temperature detection means)
29 Evaporator inlet side temperature sensor 31 Inside temperature sensor (cooled space temperature detection means)
32 timer (time limit means)
33 arithmetic processing unit 34 memory (storage means)
35 Control panel 36 LCD panel (setting means)
48 Outside temperature sensor (outside temperature detection means)
53 Alarm lamp (alarm means)

Claims (10)

In the refrigeration apparatus that cools the space to be cooled by the evaporator constituting the refrigerant circuit and melts and removes the frost on the evaporator by a predetermined defrosting means.
A cooled space temperature detecting means for detecting a temperature PT of the cooled space;
Defrosting end temperature detecting means provided in the evaporator so as to detect the temperature ET of the evaporator;
An outside air temperature detecting means for detecting the outside air temperature AT;
Control means for controlling the compression means and the defrosting means constituting the refrigerant circuit,
The control means controls the compression means so that the cooled space reaches a predetermined set temperature ST based on the temperature PT of the cooled space detected by the cooled space temperature detecting means, and the defrosting means At the time of defrosting the evaporator, the defrosting is completed at a predetermined defrosting end temperature DET of the evaporator detected by the defrosting end temperature detecting means,
When the cooled space temperature detecting means is abnormal, a temperature obtained by adding a predetermined offset value OV to the evaporator temperature ET detected by the defrosting end temperature detecting means is used as the temperature PT, and the outside air temperature A refrigeration apparatus that changes the offset value OV based on AT.   2. The refrigeration apparatus according to claim 1, wherein the control unit changes the offset value OV in a direction of increasing as the outside air temperature AT is higher.   3. The refrigeration apparatus according to claim 1, wherein the control unit changes the offset value OV in a direction of decreasing as the set temperature ST is lower.   2. The control unit according to claim 1, wherein the control unit switches the offset value OV in a direction in which the other state is larger than the stable cooling state in which the space to be cooled is stably cooled. 4. The refrigeration apparatus according to any one of 3. The control means calculates a difference e between the temperature PT of the cooled space detected by the cooled space temperature detecting means and the temperature ET of the evaporator detected by the defrosting end temperature detecting means at normal time, A database constructed by storing the difference e as the offset value OV for each outside air temperature AT;
When the cooled space temperature detecting means is abnormal, the offset value OV is changed by reading out the offset value OV corresponding to the outside air temperature AT detected by the outside air temperature detecting means from the database. The refrigeration apparatus according to claim 1. The control means starts the compression means at a predetermined upper limit temperature HST set above and below the set temperature based on the temperature PT of the cooled space detected by the cooled space temperature detecting means during normal operation. A thermocycle that stops at the lower limit temperature LST is executed,
When the temperature of the cooled space temperature detecting means is abnormal, the compressing means is stopped when the substitute temperature PT falls to the lower limit temperature LST, and then the compressing means is activated when a predetermined OFF time t1 has elapsed. 6. The refrigeration apparatus according to claim 1, wherein control is executed. The control means executes the compression means start / stop short cycle prevention control for prohibiting the compression means from stopping until a predetermined forced ON time t2 elapses after the compression means is activated.
The refrigeration apparatus according to claim 6, wherein the OFF time t1 is lengthened when a period in which the substitute temperature PT is lower than the set temperature ST continues for a certain time or longer.   2. The control means according to claim 1, wherein after the OFF time t <b> 1 is lengthened, the OFF time t <b> 1 is further lengthened when a period in which the substitute temperature PT is lower than the set temperature ST continues for a predetermined time or longer. 8. The refrigeration apparatus according to 7. At least one temperature detecting means for detecting a temperature that can be substituted for the temperature PT of the cooled space other than the defrosting end temperature detecting means;
When the difference between the temperature detected by the temperature detecting means and the temperature detected by the defrosting end temperature detecting means and the temperature detected by the cooled space temperature detecting means has increased to a predetermined value or more, The refrigeration apparatus according to any one of claims 1 to 8, wherein the refrigerated space temperature detection means is determined to be abnormal.   The refrigeration apparatus according to any one of claims 1 to 9, wherein the control means includes a warning means for notifying abnormality of the cooled space temperature detection means.

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