JP3172265B2 - Low temperature showcase - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-temperature showcase in which an evaporator and a blower are arranged in a duct and an air curtain is formed in an opening.

[0002]

2. Description of the Related Art Conventionally, in a low-temperature showcase of this kind, an air curtain is formed in an opening for the purpose of preventing outside air from entering through the opening because a heat insulating wall is opened forward. In addition, since the temperature of the heat exchanger also increases during the defrosting of the heat exchanger (evaporator), when the blower is operated in that state, the heat at the time of the defrosting is sent to the inside of the refrigerator, which is preferable. Absent. Then, for example, Japanese Patent Laid-Open No.
No. 8 (F25D21 / 06), in a low-temperature showcase, an inner and outer two-layer duct is formed in a heat insulating wall, and an inner-layer heat exchanger and an inner-layer blower are provided in the inner-layer duct, and an outer-layer duct is provided in the outer-layer duct. The outer layer heat exchanger and the outer layer blower are respectively arranged to form a double air curtain at the opening, and at the time of defrosting the inner layer heat exchanger exerting a cooling action,
The high-temperature and high-pressure refrigerant discharged from the compressor is passed through the inner layer heat exchanger and heated, and the condensed refrigerant is passed through the outer layer heat exchanger to exert a cooling function, and the inner layer blower is stopped. By opening the damper that divides the duct, the air before the heat exchange with the outer layer heat exchanger flows to the inner layer heat exchanger. According to such a configuration, since the inner-layer blower is stopped during the defrosting of the inner-layer heat exchanger, the heat at the time of defrosting is not sent out to the inside of the refrigerator, and ice burn to the drain receiver is not performed. Occurrence is also prevented.

[0003] For example, in Japanese Patent Application Laid-Open No. 4-113183, although there is no damper as described above, at the time of defrosting a similar inner layer heat exchanger, the inner layer blower is temporarily stopped and then reversely rotated. Air from the inner layer heat exchanger is prevented from entering the storage.

[0004]

However, in the former configuration, the amount of circulating air forming the air curtain is reduced by stopping the inner layer blower. The heat penetration increases, and the temperature inside the refrigerator increases. In the latter case, the outer layer blower is accelerated during defrosting of the inner layer heat exchanger to strengthen the air curtain, but in addition to the outer layer blower, the inner layer blower is slightly reversed. Because of this, it is necessary to reduce the size of the inner-layer blower itself or to reduce the number of installed units. Conversely, the air curtain of the inner-layer blower becomes weaker during the cooling operation, and as a result, the cooling capacity of the low-temperature showcase decreases. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and involves heat intrusion from an evaporator into a refrigerator during defrosting, and heat intrusion from outside air flowing into the refrigerator through an opening. It is an object of the present invention to provide a low-temperature showcase that can reduce both of them in a well-balanced manner and minimize a rise in the internal temperature during defrosting.

[0006]

According to the low temperature showcase of the present invention, a duct is formed in a heat insulating wall having an opening in the front, and an evaporator and a blower are arranged in the duct, and the duct is formed in the opening. An air curtain is formed. The defrosting means of the evaporator and the blower are operated at a normal speed when cooling by the evaporator, and the defrosting means is used by the defrosting means when defrosting the evaporator. And a control device that executes the deceleration of the blower in the first half and the second half of the defrosting operation of the evaporator, and operates the blower at a normal speed in the middle period of the defrosting. It is characterized by doing.

In the low-temperature showcase according to the second aspect of the present invention, a duct is formed in a heat insulating wall having an opening in the front, and an evaporator and a blower are arranged in the duct to form an air curtain in the opening. A defrosting means for the evaporator, and a control device for operating the blower at a normal speed during cooling by the evaporator, and performing defrosting of the evaporator by the defrosting means when defrosting the evaporator. The control device operates the blower at a normal speed in the first half and the second half of the defrosting of the evaporator, and operates the blower at a reduced speed in the middle of the defrosting. .

According to a third aspect of the present invention, there is provided a low-temperature showcase, wherein a second duct is formed outside the duct in addition to the configuration of each of the above-mentioned inventions, and a second blower is disposed in the second duct. The control device is characterized in that the second blower is operated to form an inner and outer two-layer air curtain at the opening.

In addition to the above, the control device operates the second blower at a normal speed during cooling by the evaporator, and increases the speed of the second blower during defrosting of the evaporator. It is characterized by driving.

[0010]

According to the low temperature showcase of the first aspect of the present invention,
During cooling by the evaporator, the blower is operated at normal speed, whereby an air curtain is formed at the opening. Similarly, at the time of defrosting of the evaporator, the defrosting of the evaporator is performed by the defrosting means. By operating the blower at a reduced speed in the first half of the defrosting time, the temperature of the evaporator due to the heating of the defrosting means is increased. Promotes ascent and accelerates frost melting. The blower is operated at a normal speed during the middle period of the defrosting when the temperature in the storage of the heat insulating wall is increased by the defrosting, and forms the same air curtain at the time of cooling to prevent the invasion of the outside air. Although the temperature of the evaporator rises in the latter half of the defrosting period, the amount of heat flowing into the refrigerator from the evaporator is reduced because the blower is operated at a reduced speed, and the air curtain of the opening is open during any deceleration operation. Are formed, although slightly weakened, and the invasion of outside air is suppressed.

According to the low-temperature showcase of the second aspect, the blower is operated at a normal speed during cooling by the evaporator, whereby an air curtain is formed at the opening. Similarly, when defrosting the evaporator, defrosting of the evaporator is performed by the defrosting means. Particularly, when the outside air temperature is high, by operating the blower at a normal speed at the initial stage of the defrosting, the outside air having a high temperature can be defrosted. Is passed through the evaporator to promote the melting of frost, and the air curtain is formed in a normal state to suppress the invasion of outside air. In the middle stage of the defrosting operation, the blower is operated at a reduced speed, so that the temperature of the evaporator is increased by heating the defrosting means. To prevent the invasion of outside air. In addition, the air curtain at the opening is formed although the air curtain is slightly weakened even during the deceleration operation, and the invasion of outside air is suppressed.

According to the low-temperature showcase of the third aspect of the present invention, in addition to the above, a double air curtain is formed at the opening, so that the invasion of outside air from the opening is more effectively prevented and the evaporator is removed. Since the outer air curtain is formed in the same manner as in the case of cooling in the case of frost, it is possible to suppress an increase in the internal temperature of the evaporator when the evaporator is defrosted due to intrusion of outside air.

According to the low-temperature showcase of the fourth aspect of the present invention, in addition to the above, the second blower is operated at an increased speed during defrosting, so that even if the inner air curtain is weakened during defrosting, The effect of preventing the outside air from entering the air curtain at the opening is maintained.

[0014]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal side view of a low-temperature showcase S of the present invention,
FIG. 2 is a refrigerant circuit diagram of the low-temperature showcase S, and FIG. 3 is an electric circuit diagram of the low-temperature showcase S. The low-temperature showcase S is an open showcase in which a main body is constituted by a heat insulating wall 42 formed with an opening 43 for storing and taking out goods in front thereof, and is provided at a predetermined interval inside the heat insulating wall 42. A first partitioning plate 44 is provided, and the first partitioning plate 44 is provided.
The inner and outer two-layer ducts 47 and 48 are formed by disposing the second partition plate 46 at a predetermined interval inside the inside. An inner layer evaporator 49 of a plate fin type and an inner layer fan 51 as an axial flow type blower composed of a DC motor or a two-output AC motor are arranged in the inner layer duct 47, and an outer layer fan as a second duct is provided. An outer layer fan 53 as a second blower similar to the same outer layer evaporator 52 is disposed in the duct 48.

The outer-layer evaporator 52 is disposed at a position higher than the inner-layer evaporator 49.
Numerals 7 and 48 communicate with an inner layer discharge port 54 and an outer layer discharge port 56 arranged side by side with the upper edge of the opening 43, respectively, and both communicate with a suction port 57 formed at the lower edge of the opening 43. Further, a plurality of shelves 59 are erected in a storage room 58 as a storage formed inside the second partition plate 46 in the heat insulating wall 42 and used for displaying food.

Next, in the refrigerant circuit of FIG. 2, a discharge side pipe 2 is connected to a refrigerant discharge side 1D of a compressor 1 constituted by a scroll compressor or a semi-hermetic compressor. It is connected to the refrigerant inlet side 3A. An outlet pipe 4 is connected to the refrigerant outlet 3B of the condenser 3, and the outlet pipe 4 is connected to a refrigerant inlet 5A of the receiver tank 5 via a check valve 39. A dryer 7, a sight glass 8, a valve 9, solenoid valves 10 and 11 are connected in series to an outlet pipe 6 connected to the refrigerant outlet side 5B of the receiver tank 5, and the solenoid valve 11 connects the expansion valve 12 to the outlet pipe 6. The evaporator is connected to the inner layer evaporator 49.

The outlet side of the inner layer evaporator 49 is connected to the accumulator 16 via the auxiliary accumulator 40 from the low pressure side pipe 15 via the solenoid valve 14. The solenoid valve 1 is provided in a bypass pipe 17 that bypasses the solenoid valve 11 and the expansion valve 12.
A pipe 19 branched from between the solenoid valve 11 and the expansion valve 12 is connected to the outer layer evaporator 52 via the solenoid valve 20 and the expansion valve 21. The outlet side of the outer layer evaporator 52 is connected to the low pressure side pipe 15, and the pipe 24 branched from between the inner layer evaporator 49 and the solenoid valve 14 is connected to the inlet side of the solenoid valve 20 via the check valve 25. Have been. Further, a suction side pipe 26 connected to the outlet side of the accumulator 16 is connected to a suction side 1S of the compressor 1.

Outlet piping 4 between the condenser 3 and the check valve 39
The defrosting pipe 30 branched from the compressor is connected to the outlet side of the solenoid valve 10 via the solenoid valve 31. Further, the pipe 32 branched from the discharge pipe 2 of the compressor 1 is connected to the solenoid valve 33 and the low pressure adjustment. It is connected to the low pressure side pipe 15 via a valve 34. Next, in the electric circuit of FIG. 3, the output of a temperature sensor 62 which is attached to the windward side of the inner layer discharge port 54 and detects the temperature of the discharged cool air, and the temperature of the inner layer evaporator 49 are attached to a general-purpose microcomputer 61 as a control device. The output of the defrost end temperature sensor 63 for detecting the temperature is input. The output of the microcomputer 61 includes the compressor 1,
Each solenoid valve 10, 11, 14, 18, 20, 31, and 33
A valve driving unit 64 for controlling the opening and closing of the fan is connected, and the inner fan 51 and the outer fan 53 are connected via rotation speed controllers 66 and 67 such as chopper circuits, respectively.

Next, the operation of the low-temperature showcase S will be described with reference to the operation explanatory diagram of FIG. FIG. 4 shows inner and outer layer fans 51 and 53 for each operation state of the low-temperature showcase S.
Shows the operating state of. During the cooling operation by the inner layer evaporator 49, the microcomputer 61 controls the solenoid valves 10, 1
1, 14 and 29 are opened, the other solenoid valves are closed and the compressor 1
To drive. The high-temperature and high-pressure gas refrigerant discharged from the compressor 1 radiates heat in the condenser 3 and condenses, and flows into the receiver tank 5 as a gas-liquid mixed refrigerant. Receiver tank 5
Inside, the refrigerant is separated into gas and liquid, and the liquid refrigerant accumulates downward, passes from the outlet side 5A, passes through the outlet side pipe 6 as shown by the solid line arrow in FIG. After that, it flows into the inner layer evaporator 49. The refrigerant flowing into the inner layer evaporator 49 evaporates there, passes through the electromagnetic valve 14, passes through the low-pressure side pipe 15, flows into the auxiliary accumulator 40, and then flows into the accumulator 16. Here, the unevaporated liquid refrigerant is separated, and only the gas refrigerant is sucked into the compressor 1 from the suction side pipe 26. The microcomputer 61 controls the operation of the compressor 1 based on the output of the temperature sensor 62.

The microcomputer 61 during such a cooling operation
Drives the inner fan 51 and the outer fan 53 at a normal speed. When the inner fan 51 is operated, the air sucked from the suction port 57 flows through the inner duct 47 into the inner evaporator 4.
9, where it is cooled by heat exchange with the inner layer evaporator 49 and then discharged from the inner layer discharge port 54. As a result, a cold air curtain CA as shown by a solid arrow in FIG. 1 is formed in the opening 43, and a part of the air curtain CA circulates in the storage room 58 due to the Coneard effect, whereby the inside of the storage room 58 is brought to a predetermined refrigeration temperature. Cooling.

On the other hand, by the operation of the outer layer fan 53, the air sucked from the suction port 57 is sent to the outer layer evaporator 52 through the outer layer duct 48. It rises in the duct 48 and is discharged from the outer layer discharge port 56. As a result, the opening 43 has an air curtain C as shown by a dashed arrow in FIG.
A protective air curtain GA is formed on the outside of A, and the effect of preventing outside air from entering through the opening 43 is obtained by reinforcing the air curtain CA.

The cooling operation is performed for a predetermined time (for example, 3 hours).
After the elapse, the microcomputer 61 sets the inner layer evaporator 4
9 is performed. However, before the defrosting operation is started, the solenoid valve 20 is further opened from the above state for a predetermined short period (for example, 30 seconds), and the outer layer evaporator 52 is also throttled by the expansion valve 21 as shown by a dashed arrow in FIG. The cooled refrigerant is introduced and evaporated. That is, the microcomputer 61 exerts a cooling action in both the inner layer evaporator 49 and the outer layer evaporator 52 before starting the defrosting operation, and discharges cool air from the inner and outer layer discharge ports 54 and 56 to move the inside of the storage chamber 58. Cool strongly.

After the cooling operation is completed, the microcomputer 61 opens the solenoid valves 31, 18, 20, and 33 and closes the other solenoid valves. As a result, the gas-liquid mixed refrigerant that has been condensed by removing the rough heat in the condenser 3 passes through the defrosting pipe 30 as shown by the dashed arrow in FIG. It flows into the inner layer evaporator 49 by bypassing the expansion valve 12. The inner-layer evaporator 49 is heated by the inflow of the gas-liquid mixed refrigerant having a relatively high temperature, and the inner-layer evaporator 4 is heated by the heat of the refrigerant (hereinafter, referred to as defrost heat).
The frost that has grown to 9 gradually melts. At the same time, the refrigerant condensed inside the inner layer evaporator 49 is supplied from the pipe 24 to the check valve 25.
After passing through the solenoid valve 20 and being throttled by the expansion valve 21,
It flows into the outer layer evaporator 52 and evaporates. Thus, during the defrosting of the inner layer evaporator 49, the air flowing through the outer layer duct 48 is cooled by the outer layer evaporator 52, and the storage chamber 58 can be cooled by discharging the air from the outer layer discharge port 56. The refrigerant evaporated in the outer layer evaporator 52 similarly returns from the auxiliary accumulator 40 to the compressor 1 via the accumulator 16. During the defrosting, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 is supplied to the solenoid valve 33 and the low-pressure pressure regulating valve 3.
4 and flows into the suction side pipe 15, thereby preventing the low pressure side pressure of the compressor 1 from dropping too much.

After the defrosting of the inner layer evaporator 49 is completed, for example, +
When the temperature rises to 8 ° C., the microcomputer 61
Detects the end of the defrosting of the inner layer evaporator 49 by the defrosting end temperature sensor 63, opens only the solenoid valve 20 for a predetermined period (for example, three minutes), and closes the other solenoid valves, thereby opening both the evaporators 49 and 52. Perform the refrigerant recovery operation in the inside. Since the residual water droplets fall from the inner layer evaporator 49 during the refrigerant recovery operation, the refrigerant recovery operation is a draining operation of the inner layer evaporator 49. When the refrigerant recovery operation (water removal operation) is completed, the microcomputer 61 returns to the above-described cooling operation again.

Here, during the defrosting operation and the refrigerant recovery operation (water draining operation), the microcomputer 61 operates the internal fan 51 at a reduced speed by the rotation speed controller 66. Although the temperature of the inner layer evaporator 49 is increased by the defrosting operation, the amount of the defrosting heat flowing into the storage chamber 58 from the inner layer evaporator 49 is reduced by operating the inner layer fan 51 at a reduced speed. In addition, air curtain CA
Is formed without disappearing, the effect of suppressing the invasion of the outside air is secured. Thereby, the inner layer evaporator 49
During the defrosting of the storage chamber 58 is suppressed.

On the other hand, the microcomputer 61 operates the outer layer fan 53 at a normal speed to form a similar protective air curtain GA to reinforce the air curtain CA. At this time, the outer layer fan 53 is connected to the rotation speed controller 6.
7, the speed-up operation may be performed. Thereby, the air volume of the protection air curtain GA is increased, and the protection effect is strengthened, thereby compensating for the effect of preventing the outside air from entering due to the weakening of the air curtain CA. As a result, the amount of heat that outside air brings into the storage chamber 58 during defrosting can be minimized.

FIG. 5 is an operation explanatory diagram for explaining another control state of the inner layer fan 51 by the microcomputer 61. The structure of the low-temperature showcase S and the operating states other than the inner-layer fan 51 are the same as those described above. In this case, the microcomputer 61 performs the deceleration operation of the inner layer fan 51 during the defrosting operation as described above, but the microcomputer 61 starts the refrigerant recovery operation (water draining operation) at the subsequent stage.
1 is returned to normal speed operation. In the refrigerant recovery operation (water draining operation), since the heating of the inner layer evaporator 49 has been completed, the amount of defrost heat flowing into the storage chamber 58 is small even if the operation speed of the inner layer fan 51 is returned to normal at this stage. Conversely, by increasing the air volume from the inner layer discharge port 54 at an early stage, the strength of the air curtain CA is restored to reduce the invasion of the outside air, so that the temperature rise in the storage room 58 can be suppressed. Become like

FIG. 6 is an operation explanatory diagram for explaining still another control state of the inner fan 51 by the microcomputer 61. The structure of the low-temperature showcase S and the operating states other than the inner-layer fan 51 are the same as those described above. In this case, the microcomputer 61 divides the defrosting operation into the first half and the second half, and operates the inner layer fan 51 at a normal speed for a predetermined period after the defrosting operation is started. Similarly, the inner fan 51 is decelerated, and the inner fan 51 is returned to the normal speed operation at the stage when the refrigerant recovery operation (water draining operation) is started.

In the first half of the defrosting operation immediately after the start of the defrosting operation, the temperature of the inner layer evaporator 49 is still low. The amount of inflowing defrost heat is small. In the latter stage of the defrosting operation in which the temperature of the inner layer evaporator 49 is rising, the amount of defrost heat flowing from the inner layer evaporator 49 into the storage chamber 58 is reduced by operating the inner layer fan 51 at a reduced speed as described above. In addition, the air curtain CA is formed without losing the air curtain CA although the air volume is small. Thus, FIG.
In this case, the period during which the air curtain CA is weakened is shortened.
By reducing the intrusion of outside air from the storage chamber 58, the temperature rise in the storage chamber 58 can be effectively suppressed.

Next, FIG. 7 is an operation explanatory diagram for explaining still another control state of the inner layer fan 51 by the microcomputer 61. The structure of the low-temperature showcase S and the operating states other than the inner-layer fan 51 are the same as those described above. In this case, the microcomputer 61 divides the defrosting operation into the first half, the middle half, and the second half. In the first half of the defrosting operation immediately after the defrosting operation, the microcomputer 61 performs the deceleration operation of the inner layer fan 51 as described above. Returns the inner fan 51 to the normal speed once, and in the later stage of the defrosting operation, decelerates the inner fan 51 again, and at the stage of entering the refrigerant recovery operation (water draining operation), the inner fan 51 is returned to the normal speed. Return to operation.

In the first half of the defrosting operation, the inner layer evaporator 49 is used.
Is low, and it takes time to rise to a temperature at which frost begins to melt, but by operating the inner fan 51 at a reduced speed in the first half, the temperature rise of the inner evaporator 49 due to the high-temperature refrigerant is reduced. The defrosting operation can be promptly terminated by accelerating the thawing of the frost. And
In the middle stage of the defrosting operation, in which the temperature of the storage room 58 starts to increase due to the defrosting operation, the inner layer fan 51 is operated at a normal speed, and the same air curtain CA is formed at the time of cooling to prevent outside air from entering through the opening 43. . In this middle period, the temperature of the inner layer evaporator 49 is also relatively low, so that the amount of defrost heat flowing into the storage chamber 58 is small even by the operation at the normal speed. On the other hand, since the temperature of the inner layer evaporator 49 also increases in the latter half of the defrosting operation, the amount of defrost heat flowing from the inner layer evaporator 49 into the storage chamber 58 is reduced by operating the inner layer fan 51 at a reduced speed. In the deceleration operation, the air curtain CA of the opening 43 is similarly formed, although slightly weakened, to suppress the invasion of outside air.

FIG. 8 is an operation explanatory diagram for explaining still another control state of the inner layer fan 51 by the microcomputer 61. The structure of the low-temperature showcase S and the operating states other than the inner-layer fan 51 are the same as those described above. In this case, the microcomputer 61 divides the defrosting operation into the first half, the middle half, and the second half, and in the first half of the defrosting operation immediately after the defrosting operation is started, the inner fan 51 is operated at the normal speed as it is, and the subsequent defrosting is performed. In the middle stage of the operation, the inner fan 51 is decelerated in the same manner as described above, and in the latter half of the defrosting operation, the inner fan 51 is returned to the normal speed again, and the operation directly proceeds to the refrigerant recovery operation (water draining operation).

In the first half of the defrosting operation immediately after the start of the defrosting operation, the temperature of the inner layer evaporator 49 is still low. The amount of inflowing defrost heat is small. In particular, in a situation where the outside air temperature is high, the high temperature outside air can be circulated through the inner layer evaporator 49 at a normal speed to promote the melting of frost. In the middle stage of the defrosting operation, the inner fan 51 is decelerated and operated, so that the inner layer evaporator 49 with the high temperature refrigerant is used.
The defrosting operation can be quickly terminated by accelerating the temperature rise of the frost. Then, in the latter half of the defrosting operation, the inner curtain 51 is operated at the normal speed to secure the air curtain CA as in the cooling operation. Thus, in the case of FIG.
Since the period during which A becomes weak becomes extremely short, especially in an environment where the outside air temperature is high, it is possible to more effectively suppress the rise in the temperature in the storage room 58 by making the intrusion of outside air from the opening 43 smaller. become.

Next, FIG. 9 shows another embodiment of the structure of the low-temperature showcase S. In the figure, the same reference numerals as those in FIG. In this case, the first
A window 69 located between the evaporators 49 and 52 is formed in the partition plate 44, and the window 69 is opened and closed by a damper 72 driven by a motor 71. The microcomputer 61 closes the window 69 by the motor 71 during the cooling operation and the refrigerant recovery operation (water draining operation) in each of the control states of FIGS.
During the defrosting operation, the window hole 69 is opened by the motor 71 to communicate the inner duct 47 below the inner evaporator 49 with the outer duct 48, and the inner duct 48 above the inner evaporator 49 is closed. .

As a result, the air in the inner duct 47 whose temperature has risen due to the defrosting heat from the inner evaporator 49 flows into the outer duct 48 and joins the air flowing there, and is cooled by the outer evaporator 52. Thereafter, since the liquid is discharged from the outer layer discharge port 56, the flow of defrost heat from the inner layer evaporator 49 into the storage chamber 58 can be further reduced. In such a structure, the air curtain CA from the inner layer discharge port 54 disappears during the defrosting operation, but the air curtain CA merges with the air curtain GA from the outer layer discharge port 56 and is blown out. Increase and
After the heat generated from the inner layer evaporator 49 is cooled by the outer layer evaporator 52, the heat is discharged into the storage chamber 58. In the various operating states shown in FIGS. The same effect as in the case of FIG.

FIG. 10 shows still another embodiment of the structure of the low-temperature showcase S, and FIG. 11 shows a refrigerant circuit diagram of the low-temperature showcase S in that case. In the drawings, the same reference numerals as those in FIGS. 1 and 2 denote the same components, and a description thereof will be omitted. In this case, the outer layer evaporator 52 has been eliminated, so that in the refrigerant circuit of FIG.
4. The check valve 25, the solenoid valve 20 and the expansion valve 21 are also eliminated, and a suction pressure adjusting valve 74 is connected to the outlet side of the auxiliary accumulator 40. The operation of each of the remaining solenoid valves is the same as described above. In this structure, since the outer evaporator 52 does not exist, cooling is not performed by the outer evaporator 52 during the defrosting of the inner evaporator 49. However, in the various operation states shown in FIGS. The same effect as in the case of FIGS. 1 and 2 described above is obtained with respect to the progress of defrosting and the intrusion of outside air.

In each of the embodiments described above, the low-temperature showcase having two layers of ducts is described. However, the present invention is not limited to this. Even a low-temperature showcase having only the inner layer duct described above is effective. Further, as the defrosting means, a description has been given of a means for flowing a relatively high-temperature refrigerant to the inner layer evaporator, but may be a means for flowing a high-temperature and high-pressure refrigerant just discharged from the compressor,
The present invention is effective even when heating is performed by an electric heater.

[0038]

As described above in detail, according to the first aspect of the present invention, the evaporator is heated by the defrost means by operating the blower at a reduced speed in the first half of the defrost period when the temperature of the evaporator does not rise. The temperature rise of the frost can be promoted, and the frost can be quickly melted and the defrost can be quickly terminated. In the middle stage of defrosting, when the temperature inside the heat insulating wall increases due to defrosting, the blower is operated at a normal speed to form an air curtain similar to that during cooling, preventing the invasion of outside air and the temperature of the evaporator. In the latter half of the defrosting period when the air blows, the blower is operated at a reduced speed, so that the amount of heat flowing into the refrigerator from the evaporator decreases, and the air curtain at the opening becomes weaker during any deceleration operation. Therefore, the intrusion of outside air is suppressed, and the rise in the internal temperature can be minimized as a whole.

According to the second aspect of the present invention, since the blower is operated at the normal speed in the initial stage of the defrosting when the temperature of the evaporator is still low, particularly when the outside air temperature is high, the high temperature outside air is supplied to the evaporator. Can be circulated to promote frost melting. In the middle stage of the defrosting operation, the blower is decelerated, so that the temperature of the evaporator is increased by the heating of the defrosting means, so that the defrosting can be completed quickly, and in the later stage of the defrosting, the speed returns to the normal speed again. As a result, an air curtain similar to that at the time of cooling is formed to prevent the invasion of outside air, so that in a situation where the outside air temperature is high, an increase in the internal temperature of the refrigerator can be minimized.

According to the third aspect of the present invention, in addition to the above, a double air curtain is formed in the opening, so that invasion of outside air from the opening can be more effectively prevented.
Even when the evaporator is defrosted, the outer air curtain is formed in the same manner as during cooling, so that it is possible to further suppress an increase in the internal temperature of the evaporator when the evaporator is defrosted due to outside air.

According to the fourth aspect of the present invention, in addition to the above, the second air blower is operated at an increased speed during the defrosting operation. The effect of preventing outside air intrusion is maintained, so that the rise in the internal temperature can be further suppressed.

[Brief description of the drawings]

FIG. 1 is a vertical side view of a low-temperature showcase showing an embodiment of the present invention.

FIG. 2 is a refrigerant circuit diagram of a low-temperature showcase.

FIG. 3 is an electric circuit diagram of a low-temperature showcase.

FIG. 4 is a diagram illustrating a first operation of the low-temperature showcase.

FIG. 5 is a diagram illustrating a second operation of the low-temperature showcase.

FIG. 6 is a diagram illustrating a third operation of the low-temperature showcase.

FIG. 7 is a diagram illustrating a fourth operation of the low-temperature showcase.

FIG. 8 is a diagram illustrating a fifth operation of the low-temperature showcase.

FIG. 9 is a longitudinal sectional view of the low-temperature showcase for explaining another structure of the low-temperature showcase.

FIG. 10 is a longitudinal sectional view of a low-temperature showcase for explaining another structure of the low-temperature showcase.

FIG. 11 is a refrigerant circuit diagram of the low-temperature showcase of FIG. 10;

[Explanation of symbols]

 S Low-temperature showcase 42 Insulation wall 47 Inner layer duct 48 Outer layer duct 49 Inner layer evaporator 51 Inner layer fan 52 Outer layer evaporator 53 Outer layer fan 61 Microcomputer

Claims (4)

(57) [Claims] 1. A low-temperature showcase in which a duct is formed in a heat insulating wall having an opening in the front, and an evaporator and a blower are arranged in the duct to form an air curtain in the opening. Defrosting means and, at the time of cooling by the evaporator, operate the blower at a normal speed,
A control device for performing defrosting of the evaporator by the defrosting means at the time of defrosting the evaporator, wherein the control device operates by decelerating the blower in the first half and the second half of the defrosting of the evaporator. A low-temperature showcase that operates the blower at the normal speed in the middle stage of the defrosting. 2. A low-temperature showcase in which a duct is formed in a heat insulating wall having an opening in the front, and an evaporator and a blower are arranged in the duct to form an air curtain in the opening. Defrosting means and, at the time of cooling by the evaporator, operate the blower at a normal speed,
A control device for performing defrosting of the evaporator by the defrosting means at the time of defrosting of the evaporator, the control device sets the blower to the normal speed in the first half and the second half of the defrosting of the evaporator. A low-temperature showcase, wherein the blower is operated at a reduced speed in the middle stage of the defrosting. 3. A second duct is formed outside the duct,
The second blower is arranged in the second duct, and the control device operates the second blower to form an inner and outer two-layer air curtain at the opening. The low temperature showcase described. 4. The control device operates the second blower at a normal speed during cooling by the evaporator, and operates the second blower at an increased speed when the evaporator is defrosted. The low-temperature showcase according to claim 3.