JP2012189287A - Cooler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance detection accuracy and to minimize the frequency of defrosting operation in detecting frost formed on an evaporator with an optical sensor.SOLUTION: A fin and tube heat exchanger is used as an evaporator 17 for cooling the inside of a fridge-freezer 1. The evaporator 17 is composed of an optical sensor 30 for detecting frost formation and an optical sensor 31 for detecting defrosting. The optical sensor 30 for detecting frost formation is composed of an optical sensor having a light-emitting part 30a facing a light-receiving part 30b. The path of light of the optical sensor 30 for detecting frost formation is set so as to pass a location distant from the surface of a tube 17b of the evaporator 17 by a thickness of the frost to be defrosted. The optical sensor 31 for detecting defrosting includes a reflection type optical sensor having a light-emitting part 31a and a light-receiving part 31b adjacent to each other. Light is emitted from the normal direction to a fin 17a of the evaporator 17.

Description

  The present invention relates to a refrigerator. In this specification, the term “refrigerator” refers to a general device that lowers the temperature of food or other articles that are to be cooled, and includes “refrigerator” “freezer” “freezer refrigerator” “cold storage” “show” The name as a product such as “case” or “vending machine” may be used.

  In the refrigerator, the heat of the internal space of the heat insulating housing (hereinafter referred to as “inside”) is taken away by the refrigeration cycle, and the heat is dissipated to the external space of the heat insulating housing (hereinafter referred to as “outside of the warehouse”). Cool the cooking cabinet. The refrigeration cycle consists of a compressor that compresses the refrigerant and circulates it in the refrigeration cycle, a condenser that dissipates the heat of the compressed refrigerant to the outside and condenses the refrigerant, a capillary tube that passes the condensed refrigerant, and a capillary tube The evaporator is configured to evaporate the refrigerant and take away the heat in the cabinet, and the refrigerant pipe connecting these elements.

  As an evaporator, a tube made of a metal having good heat conductivity such as aluminum, copper, or an alloy thereof is used to flow a refrigerant, and this tube is combined with a large number of fins made of a metal also having good heat conductivity. Fin and tube heat exchangers are often used. In order to make a long tube compact, the tube is usually formed in a meandering shape.

  Since the surface temperature of the evaporator is below the freezing point, moisture in the air in the cabinet is attached as frost. This phenomenon or adhering frost is hereinafter referred to as “frosting”. If the refrigerator continues the cooling operation, the amount of frost formation increases with time.

  When frost formation occurs, heat transfer between the internal air and the fins deteriorates, and the heat exchange efficiency of the evaporator decreases. Ventilation resistance when the air in the cabinet passes between the fins also increases, and the heat exchange efficiency is further deteriorated. Therefore, it is necessary to remove frost regularly. This operation is hereinafter referred to as “defrosting” and “defrosting operation”.

  In the defrosting operation generally performed, the operation of the compressor is stopped, the heater arranged near the evaporator is energized to heat the evaporator, and the frost is melted. If the defrosting operation is performed, the internal temperature also rises, so the timing must be set appropriately so that it does not become too frequent.

  In order to determine the timing of the defrosting operation, there is a method using a sensor that detects the amount of frost formation of the evaporator. Examples thereof can be seen in Patent Documents 1 and 2.

  The refrigerating and air-conditioning apparatus described in Patent Literature 1 includes frost detection means that includes a light emitting element composed of an LED and a light receiving element composed of an LED. A mechanism for applying light emitted from a light emitting element to frost is shown in FIGS. 4, 14, and 17 of the same document. In the configuration example of FIG. 4, light is applied to the frost at the tip of the fin, and the light that is reflected and returned corresponds to the light receiving element arranged alongside the light emitting element. In the configuration example of FIG. 14, the light emitting element and the light receiving element are arranged so as to sandwich the evaporator, and the light emitted from the light emitting element is irregularly reflected by frost attached to the fins and hits the light receiving element. In the configuration example of FIG. 17, the light emitting element and the light receiving element are arranged so as to sandwich the evaporator, and the optical axis is parallel to the surface of the fin. Frost is detected as frost grows and blocks the optical axis

  The refrigerator described in Patent Document 2 includes an optical frosting sensor that optically detects the amount of frost adhering to the front end surface of the fin of the cooler. The optical frost sensor is composed of an image sensor.

JP 2007-255811 A JP 2008-232605 A

  Both the refrigerating and air-conditioning apparatus described in Patent Document 1 and the refrigerator described in Patent Document 2 determine the frost formation of the evaporator by the frost adhered to the fins. Since the necessity for defrosting is determined only by frost formation on some fins, the frequency of defrosting operation may increase excessively. Moreover, in patent document 2, although it has the structure which can move a sensor position so that frost formation can be detected corresponding to the change of a frost location, it is realistic that a user or a maintenance inspector moves a sensor. May not be possible.

  The present invention has been made in view of the above points, and when detecting the frost formation of the evaporator with an optical sensor, the detection accuracy is improved and the frequency of the defrosting operation can be kept to the minimum necessary level. For the purpose. In addition, an object is to facilitate installation of the optical sensor at the optimum position.

  According to a preferred embodiment of the present invention, the refrigerator uses a fin-and-tube heat exchanger as an evaporator for cooling the interior, and an optical sensor for frost detection is combined with the evaporator, The optical sensor for detecting frost formation is constituted by an optical sensor in which a light emitting unit and a light receiving unit face each other, and the optical path of the optical sensor for detecting frost formation is defrosted from the surface of the tube of the evaporator. It is set to a shape that passes through a portion separated by the thickness of the frost that requires frosting.

  In the refrigerator having the above-described configuration, the optical sensor for frost detection is held by a mounting jig attached to the evaporator, and when the mounting jig is combined with the evaporator, the frost detection optical It is preferable that the optical path of the type sensor passes through a portion separated from the surface of the evaporator tube by the thickness of the frost that requires defrosting.

  In the refrigerator configured as described above, an optical sensor for detecting defrost is combined with the evaporator, and the optical sensor for detecting defrost is configured by a reflective optical sensor in which a light emitting unit and a light receiving unit are arranged in parallel. The defrosting detection optical sensor preferably emits light from the normal direction to the fins of the evaporator.

  In the refrigerator having the above configuration, the defrost detection optical sensor irradiates light to the fin near the center of the evaporator, and the evaporator contains the defrost detection optical sensor. The space to be formed is preferably formed by removing or excising a predetermined number of the fins.

  In the refrigerator having the above configuration, the evaporator has a substantially rectangular parallelepiped shape, and one side surface of the opposing two side surfaces having the maximum area faces the inner wall surface of the refrigerator, and air is supplied from a side surface other than the opposing two side surfaces having the maximum area. Inhalation is preferred.

  According to the present invention, when detecting the frost formation of the evaporator with the optical sensor for frost detection, a tube common to all the fins is selected as the detection target portion instead of setting a part of the fin as the detection target portion. Therefore, frost detection is not unstable due to variations in the amount of frost formation for each fin, and stable and accurate frost detection can be performed. Therefore, the frequency of the defrosting operation does not increase excessively. Further, the optical sensor for frost detection is held by a mounting jig attached to the evaporator, and when the mounting jig is combined with the evaporator, the optical path of the optical sensor for frost detection is the tube of the evaporator. Since it passes through a portion of the frost that needs to be defrosted from the surface, the frost detection optical sensor can be easily installed at the optimum position.

It is a vertical sectional view of the refrigerator-freezer which is an embodiment of the present invention. It is a perspective view explaining arrangement | positioning of the optical sensor with respect to an evaporator. It is a top view explaining arrangement | positioning of the optical sensor with respect to an evaporator. It is a schematic block diagram of the optical sensor for frost formation detection. It is a schematic block diagram of the optical sensor for a defrost detection. It is a perspective view explaining the situation where an optical sensor for frost formation detection is held on an attachment jig, and the attachment jig is attached to an evaporator. It is a perspective view which shows the condition where the optical sensor for frost formation detection was hold | maintained at the end plate, and the end plate was mounted | worn with the evaporator. It is a 1st flowchart explaining a defrost operation. It is a 2nd flowchart explaining a defrost operation.

  Hereinafter, an embodiment in which the present invention is applied to a domestic refrigerator-freezer will be described with reference to the drawings. A refrigerator-freezer 1 shown in FIG. 1 has a heat insulating casing 10 constituted by an outer box made of steel plate, an inner box made of synthetic resin, and a heat insulating material filled therebetween. A plurality of storage chambers are formed inside the heat insulating housing 10. The number of storage chambers is three in the illustrated example, and is an upper storage chamber 11U, a middle storage chamber 11M, and a lower storage chamber 11L in order from the top. The inside of the middle storage chamber 11M is further divided into two upper and lower stages by the partition shelf 12. The front side of each storage room is an opening, and a heat-insulating door closes them. The upper storage chamber 11U is provided with a door 13U, the middle storage chamber 11M is provided with an upper compartment door 13MU and a lower compartment door 13ML, and the lower storage chamber 11L is provided with a door 13L. The door 13L is integrated with a drawer-type container (not shown) inserted into the lower storage chamber 11L.

  The upper storage room 11U, the middle storage room 11M, and the lower storage room 11L are assigned roles as a freezing room, a refrigeration room, and a vegetable room, and each storage room is cooled to a temperature suitable for its own role. Each storage chamber is cooled by a refrigeration cycle disposed on the back side of the heat insulating housing 10. Among the components of the refrigeration cycle, what appears in FIG. 1 is a compressor 15 housed in a machine room 14 at the lower back of the heat insulating housing 10, an upper storage room 11U, a middle storage room 11M, and a lower stage. The evaporator 17 is disposed in the ventilation space 16 formed between the back surface of the storage chamber 11L and the heat insulating housing 10. In the refrigeration cycle, a condenser for radiating the heat of the compressed refrigerant to the outside of the cabinet to condense the refrigerant, a capillary tube for passing the condensed refrigerant, a refrigerant pipe, and the like are not shown.

  The ventilation space 16 is provided with a suction port and a blow-out port that lead to each storage chamber at appropriate positions. In the ventilation space 16, a blower 18 disposed above the evaporator 17 generates a circulating air flow in the cabinet. That is, when the blower 18 is operated, the air in the cabinet is sucked into the ventilation space 16 from a location below the evaporator 17. The sucked air passes through the evaporator 17 from bottom to top and is cooled in the process. The cooled air is blown out from an air outlet (not shown) provided in the upper compartment of the upper storage chamber 11U and the middle storage chamber 11M. The cooling air cools the storage chamber from which it has been blown to a predetermined temperature, and then goes to the lower storage chamber to cool the storage chamber to a predetermined temperature. Thereafter, the air is sucked into the ventilation space 16 again.

  Inside the ventilation space 16, a temperature sensor 19 is arranged at a position close to the top of the evaporator 17. Further, a defrosting heater 20 is disposed under the evaporator 17. The defrosting heater 20 is a glass tube heater. When the defrosting heater 20 is energized, a warm airflow rises from the heater 20 and the frosting of the evaporator 17 is melted by the airflow.

  A control chamber 21 is formed on the back surface of the heat insulating housing 10 at a location above the machine chamber 14. A control unit 22 that controls the entire refrigerator-freezer 1 is housed in the control room 21. The control unit 22 is configured by a circuit board on which electronic components and electrical components are mounted.

  The evaporator 17 is constituted by a fin-and-tube heat exchanger. As shown in FIG. 2, the evaporator 17 has a large number of vertical fins 17a made of a thin metal plate having good heat conduction so that a ventilation space is generated between them. The tubes 17b, which are arranged in parallel to each other and are similarly made of metal having good heat conduction, penetrate the fins 17a in the horizontal direction. Two tubes 17b are arranged in parallel and both have a meandering shape. A U-shaped bend portion 17b1 that gives a meandering shape to the tube 17b protrudes outward from the outermost fin 17a.

  The evaporator 17 has a substantially rectangular parallelepiped shape, and in the rectangular parallelepiped shape, the front and back surfaces have the largest area, the opposite two side surfaces, the top surface and the bottom surface have the next two opposite surfaces, and the left side surface and the right side surface have the smallest area. There are two opposing sides. The back surface, which is one of the two opposing side surfaces having the largest area, faces the vertical inner wall surface of the heat insulating housing 10, and air is sucked from the bottom surface.

  By setting the posture of the evaporator 17 as described above, the evaporator 17 can be installed in a narrow space in the front-rear direction, and can be easily mounted on the household refrigerator-freezer 1. Further, in Patent Documents 1 and 2, it is assumed that air is sucked from the side surface having the largest area. However, the air flow rate greatly varies depending on the location, and it is difficult to perform heat exchange uniformly in the entire evaporator 17. turn into. By adopting a configuration in which air is sucked from the side surfaces other than the two opposing side surfaces having the maximum area as in the present embodiment and flows in parallel with the maximum area side surface, heat can be uniformly exchanged throughout the evaporator 17. It becomes easy.

  When the compressor 15 is driven, the cooling operation of the refrigerator-freezer 1 is performed. The refrigerant, which is compressed by the compressor 15 and becomes a high-temperature and high-pressure gas, flows down while dissipating heat in a condenser (not shown) and becomes supercooled liquid. After passing through a dryer (not shown), the supercooled liquid is depressurized by a capillary tube (not shown), enters the evaporator 17 and evaporates. The evaporator 17 is cooled by the evaporation of the refrigerant. Thereafter, the refrigerant returns to the compressor 15.

  When the blower 18 is driven during the cooling operation, an airflow flowing from the bottom to the top in the ventilation space 16 is generated. The airflow is cooled in the process of passing through the evaporator 17. The cooled air is distributed to the upper storage chamber 11U, the middle storage chamber 11M, and the lower storage chamber 11L in accordance with the temperature required for each chamber and the load fluctuation of each chamber, thereby cooling the interior of the cabinet.

  When the door 13U, 13MU, 13ML, or 13L is opened during the cooling operation, the humidity inside the cabinet increases due to moisture brought in by the air flowing into the cabinet from the outside. Humidity in the cabinet also increases due to new storage items in the cabinet. When the inside humidity rises, frosting on the evaporator 17 starts. As long as the amount of frost formation is small, the defrosting operation is necessary when the gap between the fins 17a is blocked or the frost is accumulated on the surface of the tube 17b. That is, it is necessary to stop the compressor 15 and energize the defrosting heater 20.

  The start timing of the defrosting operation must be appropriate. Otherwise, the defrosting operation will be performed frequently, and the internal temperature will rise, and the power consumption will not be reduced. Therefore, an optical sensor is combined with the evaporator 17 so that the defrosting operation is started at an appropriate timing.

  What is combined with the evaporator 17 is an optical sensor 30 for detecting frost formation and an optical sensor 31 for detecting defrost. As shown in FIG. 4, the frost detection optical sensor 30 is a so-called transmissive optical sensor in which a light emitting unit 30a and a light receiving unit 30b are disposed facing each other. As shown in FIG. 5, the defrost detection optical sensor 31 is a so-called reflective optical sensor in which a light emitting portion 31a and a light receiving portion 31b are arranged in parallel.

  The optical sensor 30 for detecting frost formation outputs a value of the light intensity of the light received by the light receiving unit 30b or a value obtained by converting the light intensity into a voltage to the control unit 22. The controller 22 determines the presence or absence of frost from the output value of the optical sensor 30 for detecting frost formation.

  The defrost detection optical sensor 31 also outputs to the control unit 22 the value of the light intensity received by the light receiving unit 31b or the value obtained by converting the light intensity into a voltage. The control unit 22 determines the progress of defrosting or the completion of defrosting from the output value of the defrost detection optical sensor 31.

  The optical path of the optical sensor 30 for detecting frost formation is set so as to pass through a portion separated from the surface of the tube 17b of the evaporator 17 by a predetermined distance d1. The distance d1 is the thickness of frost that requires defrosting. When the thickness of frost formation reaches d1, the light intensity of the light received by the light receiving unit 30b is rapidly reduced. Accordingly, the control unit 22 determines that frost formation has occurred in the evaporator 17.

  Thus, when detecting the frost formation of the evaporator 17 with the optical sensor 30 for frost detection, the tube 17b which is common to all the fins 17a is detected as a detection target instead of setting a part of the fins 17a as a detection target location. Since the location is selected, the frost detection does not become unstable due to variations in the frost amount for each fin 17a, and stable and accurate frost detection can be performed. Therefore, the frequency of the defrosting operation does not increase excessively.

  The optical sensor 30 for detecting frost formation is attached to the evaporator 17 using an attachment jig 32 shown in FIG. The mounting jig 32 is made of synthetic resin or metal, and has a shape in which a plurality of pins hang from a flat base 32a. There are a total of five pins, two of which are located outside the outermost one of the fins 17 a of the evaporator 17 (hereinafter referred to as “outermost fin”). The remaining three are located inside the outermost fin 17a. Two pins positioned outside the outermost fin 17a are referred to as pins 33a, and three pins positioned inside the outermost fin 17a are referred to as pins 33b.

  The two pins 33a sandwich one of the two tubes 17b at the U-shaped bend portion 17b1. Three pins 33b sandwiching the outermost fin 17a between the pin 33a and the center one enter between the two tubes 17b, and the center one and the remaining two are two tubes. 17b is sandwiched. Such a sandwiching structure prevents the mounting jig 32 from being displaced relative to the evaporator 17.

  The light emitting unit 30a and the light receiving unit 30b of the optical sensor 30 for detecting frost formation are supported by one of the pins 33a via a bracket 34, respectively. As shown on the right side of FIG. 6, when the mounting jig 32 is settled at a predetermined position of the evaporator 17, the optical path between the light emitting part 30a and the light receiving part 30b is the U-shaped bend part 17b1 of the tube 17b. Passes through a portion separated from the surface by the thickness of frost that requires defrosting (ie, distance d1 in FIG. 4). For this reason, the optical sensor 30 for detecting frost formation can be easily installed at the optimum position.

  It is also possible to attach the frosting detection optical sensor to the evaporator 17 using the mounting jig 35 shown in FIG. The mounting jig 35 is a flat plate made of synthetic resin or metal, and is configured as an end plate that is overlaid on the outer surface of the outermost fin 17a. The attachment jig 35 is formed with a total of four through-holes 35a through which a total of four U-shaped bend portions 17b1 are passed. Two brackets 36 sandwiching one of the U-shaped bends 17b1 protruding from the through hole 35a protrude from the mounting jig 35, and the light emitting portion 30a and the light receiving portion 30b are supported by the bracket 36.

  If the attachment jig 35 is brought into close contact with the outer surface of the outermost fin 17a and the U-shaped bend portion 17b1 is passed through all the four through holes 35a, the displacement of the attachment jig 35 with respect to the evaporator 17 is prevented. . In such a state of FIG. 7, the optical path between the light emitting part 30a and the light receiving part 30b is separated from the surface of the U-shaped bend part 17b1 of the tube 17b by the thickness of frost that requires defrosting. Pass through only a point. For this reason, the optical sensor 30 for detecting frost formation can be easily installed at the optimum position.

  The optical sensor 30 for detecting frost formation can detect that the thickness of the frost has increased and defrosting is necessary, but during the defrosting operation, the defrosting operation is no longer necessary until the defrosting operation is no longer necessary. It cannot be detected that the thickness has decreased. Therefore, a defrost detection optical sensor 31 is provided separately from the frost detection optical sensor 30.

  The light emitting unit 31a of the defrosting detection optical sensor 31 irradiates light toward the fins 17a from a substantially normal direction. The irradiated light is reflected by the fin 17a itself or by frost adhering to the surface of the fin 17a and is incident on the light receiving unit 31b. With the difference in light intensity based on the difference in reflectance between the fin 17a and the frost, the control unit 22 is in a state where frost is left on the surface of the fin 17a or a state where the fin 17a is exposed as the defrosting proceeds Judgment is made.

  The defrost detection optical sensor 31 irradiates light to the fin 17 a near the center of the evaporator 17. This is because the defrosting progresses more toward the center of the evaporator 17 and the defrosting situation can be most reliably grasped by monitoring the location.

  The interval between the fins 17a is narrow, and it is impossible to place the defrost detection optical sensor 31 there. Therefore, as shown in FIG. 2, a predetermined number of fins 17 a of the evaporator 17 are removed to form a space 37, and the defrost detection optical sensor 31 is disposed there. Thereby, it becomes possible to irradiate light to the fin 17a used as a target from a normal line direction. Instead of forming the space 37 by removing the fins 17a, the space 37 may be formed by providing cut portions (notches) in a predetermined number of fins 17a.

  The control unit 22 starts the defrosting operation when any of the plurality of defrosting operation start conditions is satisfied, and ends the defrosting operation when any of the plurality of defrosting operation end conditions is satisfied. . Thereby, the start and end of the defrosting operation are performed with good timing, and an efficient defrosting operation is performed. The defrosting operation start condition and the defrosting operation end condition will be described with reference to the flowcharts of FIGS.

  First, a case where the defrosting operation is performed according to the flowchart of FIG. 8 will be described. In step # 101, the control unit 22 checks whether or not a frost detection signal is output from the frost detection optical sensor 30. “The frost detection optical sensor 30 has detected frost formation on the evaporator 17” is one of the defrosting operation start conditions (first defrosting operation start condition). If this condition is satisfied, the process proceeds to step # 102.

  In step # 102, the control unit 22 starts the defrosting operation. That is, the defrosting heater 20 is turned on, and the compressor 15 and the blower 18 are turned off. Then, the process proceeds to step # 103.

  In step # 103, the control unit 22 checks whether or not a defrost detection signal is output from the defrost detection optical sensor 31. “The defrost detection optical sensor 31 has detected the defrost of the evaporator 17” is one of the defrost operation end conditions (first defrost operation end condition). If this condition is satisfied, the process proceeds to step # 104.

  In step # 104, the control unit 22 ends the defrosting operation. That is, the defrosting heater 20 is turned off.

  Thereafter, the control unit 22 turns on the compressor 15 and the blower 18 and restarts the cooling operation.

  Next, a case where the defrosting operation is performed according to the flowchart of FIG. 9 will be described. In step # 111, the control unit 22 checks whether or not the accumulated operation time of the compressor 15 since the end of the previous defrosting operation has reached the predetermined time s1. “The accumulated operation time of the compressor 15 since the end of the previous defrost operation has reached the predetermined time s1” is one of the defrost operation start conditions (second defrost operation start condition). If this condition is satisfied, the process proceeds to step # 112.

  When the defrosting operation start condition is not satisfied in step # 111, the process proceeds to step # 115. In step # 115, the control unit 22 checks whether or not a frost detection signal is output from the frost detection optical sensor 30. When the frosting detection signal is output, the process proceeds to step # 116. If no frost detection signal is output, the process returns to step # 111.

  In step # 116, the control unit 22 checks whether or not the accumulated operation time of the compressor 15 since the end of the previous defrosting operation has reached the predetermined time s2. The predetermined time s2 is shorter than the predetermined time s1 in step # 111. “When the accumulated operation time of the compressor 15 since the end of the previous defrost operation reaches a predetermined time s2 shorter than the predetermined time s1, the frost detection optical sensor 30 detects the frost formation of the evaporator 17. "Is" one of the defrosting operation start conditions (third defrosting operation start condition). If this condition is satisfied, the process proceeds to step # 117, and if not satisfied, the process returns to step # 111.

  The reason why the process returns from step # 116 to step # 111 is that the phenomenon that the frost detection optical sensor 30 outputs a frost detection signal is caused by frost formation only in the frost detection optical sensor 30 or a foreign object. This is because it is considered that this is caused by adhering to the optical sensor 30 for detecting frost formation. Thus, even if a frost detection signal is output from the optical sensor 30 for frost detection, the defrost operation is not started until the predetermined time s2 is reached, thereby cooling by frequent defrost operation. Defects, and excessive rise in the internal temperature can be prevented.

  In Step # 117, the control unit 22 indicates that “the frosting detection optical sensor 30 has evaporated when the accumulated operation time of the compressor 15 since the end of the previous defrosting operation has reached a predetermined time s2 shorter than the predetermined time s1. It is checked whether or not the start of the defrosting operation based on the defrosting operation start condition that “the frosting of the device 17 has been detected” has been continued twice in the past and this time is the third time in succession. If yes, go to Step # 118, otherwise go to Step # 112.

  In step # 118, the control unit 22 checks whether or not the accumulated operation time of the compressor 15 since the end of the previous defrost operation has reached the predetermined time s1. If this condition is satisfied, the process proceeds to step # 112.

  Step # 118 is interposed after step # 117 even if the frost detection optical sensor 30 is malfunctioning or foreign matter adheres to the frost detection optical sensor 30. This is in order to avoid

  In step # 112, the control unit 22 starts the defrosting operation. That is, the defrosting heater 20 is turned on, and the compressor 15 and the blower 18 are turned off. Then, the process proceeds to step # 113.

  In step # 113, the control unit 22 checks whether or not the output signal of the temperature sensor 19 indicates “temperature ≧ T1”. The predetermined temperature T1 is a temperature detected by the temperature sensor 19 when defrosting is completed. “The temperature sensor 19 has detected a temperature equal to or higher than the predetermined temperature T1” is one of the defrosting operation end conditions (second defrosting operation end condition). If this condition is satisfied, the process proceeds to step # 114, and if not satisfied, the process proceeds to step # 119.

  In step # 114, the control unit 22 ends the defrosting operation. That is, the defrosting heater 20 is turned off.

  Thereafter, the control unit 22 turns on the compressor 15 and the blower 18 and restarts the cooling operation.

  When the process proceeds from step # 113 to step # 114, the control unit 22 turns off the defrosting heater 20 and then waits for a certain period of time until the water generated by melting of the frost completely falls. The blower 18 is turned on and the cooling operation is resumed.

  In step # 119, the control unit 22 checks whether or not a defrost detection signal is output from the defrost detection optical sensor 31. If this condition is satisfied, the process proceeds to step # 114, and if not satisfied, the process proceeds to step # 120.

  By proceeding from step # 113 to step # 119 and further proceeding to step # 114, even if the temperature sensor 19 detects a temperature lower than the predetermined temperature T1, the defrost detection optical sensor 31 detects defrost. In such a case, the defrosting operation ends. Thereby, although the frost formation is actually removed, it is possible to avoid an increase in the internal temperature due to continuing to turn on the defrosting heater 20 and to reduce power consumption loss.

  In Step # 120, the control unit 22 checks whether or not the defrosting operation time since the start of the current defrosting operation has reached the predetermined time s3. “The defrosting operation time since the start of the current defrosting operation has reached the predetermined time s3” is one of the defrosting operation end conditions (third defrosting operation end condition). If this condition is satisfied, the process proceeds to step # 114, and if not satisfied, the process returns to step # 113.

  From step # 113, the process proceeds to step # 120 through step # 119, and further proceeds to step # 114. Then, the temperature sensor 19 detects a temperature lower than the predetermined temperature T1, and the defrost detection optical sensor 31 removes the temperature. Even if no frost is detected, the defrosting operation ends when the defrosting operation time since the start of the current defrosting operation reaches the predetermined time s3. Thereby, the rise in the internal temperature by continuing to turn on the heater 20 for defrosting can be avoided, and the loss of power consumption can be reduced.

  “The detection temperature of the temperature sensor 19 is lower than the predetermined temperature T1, the defrosting operation time since the start of the current defrosting operation is shorter than the predetermined time s3, and the defrosting detection optical sensor 31 detects the defrosting. "What has been done" is one of the defrosting operation termination conditions (fourth defrosting operation termination conditions). If this condition is satisfied, the process proceeds to step # 114.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  The present invention is widely applicable to cooling devices.

DESCRIPTION OF SYMBOLS 1 Refrigeration refrigerator 10 Heat insulation housing | casing 15 Compressor 17 Evaporator 17a Fin 17b Tube 17b1 U-shaped bend part 22 Control part 30 Optical sensor for frost formation detection 30a Light emission part 30b Light reception part 31 Optical sensor for defrost detection 31a Light emission Part 31b Light receiving part 32, 35 Mounting jig 37 Space

Claims (5)

In a refrigerator using a fin-and-tube heat exchanger as an evaporator for cooling inside the cabinet,
The evaporator is combined with an optical sensor for detecting frost formation, and the optical sensor for detecting frost formation is constituted by an optical sensor in which a light emitting portion and a light receiving portion face each other, and the optical type for detecting frost formation. The optical path of a sensor is set to the shape which passes the location separated by the thickness of the frost which needs defrosting from the surface of the tube of the said evaporator, The refrigerator characterized by the above-mentioned.   The frost detection optical sensor is held by a mounting jig attached to the evaporator, and when the mounting jig is combined with the evaporator, the optical path of the frost detection optical sensor is the evaporation. 2. The refrigerator according to claim 1, wherein the cooler passes through a portion separated by a thickness of frost that requires defrosting from the surface of the tube of the vessel.   An optical sensor for defrost detection is combined with the evaporator, and the optical sensor for defrost detection is composed of a reflective optical sensor in which a light emitting unit and a light receiving unit are arranged in parallel, and the defrost detection optical sensor The refrigerator according to claim 1 or 2, wherein the type sensor irradiates light from the normal direction to the fins of the evaporator.   The defrost detection optical sensor irradiates light to the fin near the center of the evaporator, and the evaporator has a space for storing the defrost detection optical sensor in a predetermined number. The refrigerator according to claim 3, wherein the refrigerator is formed by removing or excising the fins.   The evaporator has a substantially rectangular parallelepiped shape, and one side surface of the opposing two side surfaces having the largest area faces the inner wall surface of the refrigerator, and air is sucked from a side surface other than the opposing two side surfaces having the largest area. The refrigerator according to any one of claims 1 to 4.

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