JPH06213555A - Defrosting device of cooling unit - Google Patents

Abstract

PURPOSE:To provide a defrosting device of a cooling unit wherein defrosting of a cooler and drain plate can be performed without overheating the cooler. CONSTITUTION:There are provided a cycle wherein a compressor 14, condenser 17, expansion valve 23, and cooler 21 are connected in series, a drain plate 25 for receiving drain generated in the cooler 21, a first defrosting means which sends high temperature, high pressure refrigerant delivered from the compressor 14 directly to the cooler 21 to heat it, and a second defrosting means which heats the drain plate 25 by means of an electric heater 26 provided in the drain plate 25. Further there are provided a temperature sensor 27 of the first defrosting means which is provided in the cooler 21 to sense the completion of defrosting, a temperature sensor 28 of the second defrosting means which is provided in the drain plate 25 to sense the completion of defrosting, and a plurality of return set temperatures from the sensor 27 and the sensor 28, and also a set element 31 which selects each return set temperature to set it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting device for a cooling unit used as a cooling device for, for example, a prefabricated storage.

[0002]

2. Description of the Related Art The cooling unit has a cycle in which a compressor, a switching valve, a condenser, an expansion valve and a cooler are sequentially connected. When the refrigerating cycle is operated to cool the storage or the like, it is inevitable that the cooler and the drain tray that receives the drain generated by the cooling by the cooler are frosted. Therefore, defrosting of the cooler and the drain dish is performed every predetermined time.

Conventionally, the defrosting of the cooling unit is
The cooler was heated by flowing hot refrigerant, and the drain tray was heated by an electric heater. In that case, defrosting the cooler with hot refrigerant has a higher heat exchange efficiency than defrosting the drain dish with a heater. Therefore, the defrost recovery temperature is set to a temperature at which the ice in the drain tray can be reliably melted, and defrosting between the cooler and the drain tray is performed.

However, if the defrosting recovery temperature is set to the defrosting temperature of the drain tray, the temperature of the cooler will rise too much when the defrosting of the drain tray is completed. For example, in a normal defrosting operation, the cooler rises to about 30 to 40 ° C on average, but a part of the cooler may be heated to 70 to 80 ° C.

FIG. 4 shows a general prefabricated storage 1 for freezing.
The cooler 2 is disposed above the storage chamber of the storage 1. A drain tray 3 having an electric heater 3a for defrosting is provided below the cooler 2, and a blower 4 for the cooler is arranged on one side of the cooler 2. By operating the blower 4, the cold air in the refrigerator is circulated in the direction of the arrow.

By the way, when the temperature of a part of the cooler 2 rises too much during defrosting as described above, the ice in the vicinity of the cooler 2 evaporates and the steam is cooled to the ceiling surface 1a of the storage 1. There was a case in which water drops D were attached.

Further, when hot refrigerant is flown through the cooler to defrost it, the switching valve is switched to allow the refrigerant discharged from the compressor to flow through the cooler without passing through the condenser. When such a defrosting operation is performed, if the outside air temperature is low and the condenser is cooled by the cooling action of the blower for the condenser, a considerable amount of liquid refrigerant will be sunk in the condenser. As a result, a sufficient amount of hot refrigerant cannot be supplied to the cooler during the defrosting operation, and it may take a considerable amount of time to complete the defrosting of the cooler.

[0008]

As described above, conventionally, the defrost return temperature for cooling is set in accordance with the drain dish that is not likely to be defrosted, so that the temperature of the cooler is increased more than necessary. There was an occasion. Further, in the defrosting operation, when the outside air temperature is low, the amount of the liquid refrigerant lying in the condenser increases, so that the amount of the hot refrigerant that defrosts the cooler may decrease.

A first object of the present invention is to provide a defrosting device for a cooling unit which can surely defrost the cooler and the drain tray without overheating the cooler. .

A second object is to provide a defrosting device for a cooling unit capable of preventing a large amount of liquid refrigerant from stagnation in the condenser even when the outside air temperature is low during defrosting operation. It is in.

A third object is that, when the normal defrosting operation is switched to the cooling operation, the high-temperature high-pressure refrigerant is prevented from leaking to the circuit for the defrosting operation from the switching valve that switches the flow of the refrigerant in accordance with the operation. Another object of the present invention is to provide a defrosting device for a cooling unit capable of preventing the defrosting.

[0012]

A first invention is a compressor,
A cycle in which a condenser, an expansion valve and a cooler are sequentially connected, and a drain tray for receiving the drain generated in the cooler,
A first defrosting means for flowing the high-temperature high-pressure refrigerant discharged from the compressor directly to the cooler to heat it, and an electric heater attached to the drain tray, and heating the drain tray by the electric heater. 2 defrosting means, a return sensor of the first defrosting means for detecting the end of defrosting provided in the cooler, and a second defrosting means for detecting the end of defrosting provided in the drain tray. Of the reset sensor, the reset sensor of the first defrosting means and the reset sensor of the second defrosting means, and the setting means for selecting and setting each of these reset setting temperatures. It is characterized by having.

A second aspect of the invention is a cycle in which a compressor, a condenser, an expansion valve and a cooler are sequentially connected, and a high temperature high pressure refrigerant discharged from the compressor is passed through the condenser and the expansion valve without being passed through the cooler. Defrosting means to flow to, the pressure detecting means in the condenser, a blower for the condenser for heat exchange between the condenser and the outside air, when performing defrosting by the defrosting means, the pressure detected by the detecting means And a control means for stopping the operation of the condenser blower until the detected pressure is lower than the set value when the detected pressure is lower than the set value.

A third aspect of the present invention receives a cycle in which a compressor, a condenser, an expansion valve and a cooler are sequentially connected, and a cooler arranged in an upper part of a storage chamber, a blower for the cooler and a drain generated in the cooler. A cooling unit composed of a drain tray, a first defrosting means for heating a high-temperature high-pressure refrigerant discharged from the compressor directly to a cooler, and an electric heater attached to the drain tray, A second defrosting means for heating the drain tray with this electric heater, a return sensor for the first defrosting means for detecting the end of the defrost provided in the cooler, and a drain tray are provided. Second to detect the end of defrost
And a setting means for setting the reset set temperature by the reset sensor of the second defrost means to be higher than the reset set temperature of the reset sensor of the first defrost means. And

A fourth aspect of the invention is a cycle in which a compressor, a condenser, an expansion valve and a cooler are sequentially connected, and a high temperature high pressure refrigerant discharged from the compressor is passed through a bypass pipe without passing through the condenser and the expansion valve. A switching valve that switches between a defrosting operation that flows to the cooler and a cooling operation that causes the high-temperature high-pressure refrigerant to flow to the cooler through the condenser and an expansion valve, and a negative pressure in the bypass pipe during the cooling operation, and at that pressure Urging means for urging the switching state of the switching valve.

[0016]

According to the first and third aspects of the invention, since the defrosting recovery temperatures of the cooler and the drain tray can be set to different temperatures, it is possible to defrost them without overheating the cooler. it can.

According to the second aspect of the present invention, the amount of liquid refrigerant lying in the condenser can be reduced even when the outside air temperature is low during defrost handling. According to the fourth aspect of the present invention, when the cooling operation is switched to, the bypass pipe is made to have a negative pressure, and the pressure is applied to the switching valve, so that the switching state is reliably maintained and the discharge from the compressor is performed. The high temperature and high pressure refrigerant thus generated is prevented from leaking from the switching valve to the bypass pipe.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a split-type cooling unit 11 such as a storage. The cooling unit 11 is divided into an outdoor unit 12 and an indoor unit 13, and the indoor unit 13 is an upper portion of the storage chamber of the storage 1 shown in FIG. It is located in.

The outdoor unit 12 is provided with a compressor 14 that forms a cycle. The discharge side of the compressor 14 is connected to the inlet side of the condenser 17 via one port of the muffler 15 and the four-way switching valve 16.

The outlet side of the condenser 17 is connected to one end of a liquid side refrigerant pipe 20 via a first opening / closing control valve 18 and a dryer 19. The other end of the liquid-side refrigerant pipe 20 is connected to the indoor unit 12. The indoor unit 12 is provided with a cooler 21. A second opening / closing control valve 22 and an expansion valve 23 are connected in parallel to the inlet side of the cooler 21, and the other end of the liquid side refrigerant pipe 20 is connected to these. The expansion valve 23 is a temperature expansion valve, and the temperature sensing portion 23a thereof detects the temperature on the outlet side of the cooler 21.

The outdoor unit 13 includes the cooler 2
1, an indoor blower 24 is arranged, and a drain tray 25 for receiving the drain dropped from the cooler 21 is provided. The drain tray 25 is heated by an electric heater 26 during defrosting.

The temperature of the cooler 21 is detected by a first temperature sensor 27, and the temperature of the drain tray 25 is a second temperature sensor.
Of the temperature sensor 28. The detection signals of these temperature sensors 27 and 28 are input to the control unit 29. An operation unit 31 is connected to the control unit 29. The operating section 31 can set the temperature T ₁₀ of the cooler 21 and the temperature T ₂₀ of the drain tray 25 during defrosting. The control unit 29 includes first comparison means for comparing the set temperatures T ₁₀ and T ₂₀ set by the operation unit 31 with the detected temperatures T ₁₁ and T ₂₁ detected by the sensors 27 and 28, respectively. ing.

When the detected temperature T _{11 of} the first temperature sensor 27 is T ₁₁ ≧ T ₁₀ with respect to the set temperature T ₁₀ , the defrosting of the cooler 21 is finished as described later. The detected temperature T _{21 of} the second temperature sensor 28 is the set temperature T _20.
On the other hand, when T ₂₁ ≧ T ₂₀ is satisfied, the defrosting of the drain tray 25 is completed as described later.

That is, the first temperature sensor 27 is a return sensor for detecting the end of defrosting of the cooler 21, and the second temperature sensor 28 is a return sensor for detecting the end of defrosting of the drain tray 25. ing.

One end of a gas side refrigerant pipe 31 is connected to the outlet side of the cooler 21. This gas side refrigerant pipe 3
The other end of 1 is connected to the compressor 14 on the suction side via an accumulator 32 and a suction regulator 33.

The other port of the four-way switching valve 16 and the outlet side of the condenser 17 are connected by a bypass pipe 34. The bypass tube 34 is provided with a high voltage switch 35a. The outlet side of the dryer 19 and the suction side of the compressor 14 are connected via a third opening / closing control valve 35 and a capillary tube 36 which is an expansion valve.

An outdoor blower 37, which is a blower for the condenser, is arranged so as to face the condenser 17. The outdoor blower 37 blows outside air to cool the condenser 17. The pressure of the refrigerant in the condenser 17, which fluctuates due to the cooling action of the blower 37, is detected by the pressure sensor 38. The detected pressure Pd detected by the pressure sensor 38 is compared with the set pressure Pf set in the control unit 29. That is,
The control unit 29 has a second comparing means for comparing the detected pressure Pd and the set pressure Pf.

When performing the defrosting operation between the cooler 21 and the drain tray 25, the defrosting operation is performed as will be described later only when the relation between the detected pressure Pd and the set pressure Pf is Pd ≥Pf. It has become.

The control unit 29 includes the outdoor blower 2
4, the indoor blower 37, the first to third opening / closing control valves 18,
Drive means for controlling the drive of each of the valves 22 and 35 and the four-way switching valve 16 is provided. A timer circuit 39 is connected to the control unit 29, and the defrosting operation is periodically performed according to the set time set in the timer circuit 39.

Next, the cooling unit 1 having the above structure.
The defrosting operation No. 1 will be described with reference to the flowchart of FIG. First, prior to the defrosting operation, the cooling unit 11 is subjected to the cooling operation shown in step 1 (S1). The flow of the refrigerant at that time is shown by a solid arrow in FIG.
That is, the hot refrigerant discharged from the compressor 14 of the outdoor unit 12 flows from the four-way switching valve 16 to the condenser 17 to be condensed and becomes a liquid refrigerant. The liquid refrigerant flows to the expansion valve 23 of the indoor unit 13 through the first opening / closing control valve 18 and the dryer 19. The liquid refrigerant is decompressed by the expansion valve 23 and evaporated, and exchanges heat with the indoor air blown by the indoor blower 24. That is, the room air is cooled.

The refrigerant in the gas-liquid mixed state that has exchanged heat with the cooler 21 is separated into gas and liquid by the accumulator 32, and only the gas is sucked into the compressor 14, and the above circulation is repeated.
In S2, the cooling operation time is counted. In S3, it is determined whether or not the count in S2 is the defrost cycle. That is, when the cooling operation is continued for a predetermined time and the defrosting cycle starts, frost is generated on the cooler 21 and the drain tray 25 thereof.

At the defrost cycle, the pressure sensor 3
Detected pressure P of the refrigerant in the condenser 17 detected by
d is compared with the set pressure Pf set in the control unit 29. When the outside air temperature is low during the cooling operation in S1, the refrigerant is excessively cooled in the condenser 17 by the outdoor blower 37, the amount of liquid refrigerant stagnation in the condenser 17 increases, and the pressure in the condenser 17 increases. descend.

Therefore, the relationship between the detected pressure Pd and the set pressure Pf compared by the control unit 29 is Pd ≤ Pf
Becomes In that case, the operation of the outdoor blower 37 is stopped as shown in S5, and the supercooling of the condenser 17 by the outdoor air is prevented. If the supercooling of the condenser 17 is prevented, the amount of refrigerant stagnation in the condenser 17 decreases, so that the pressure increases and the relationship between the detected pressure Pd and the set pressure Pf becomes Pd ≧ Pf.

When Pd ≧ Pf, the defrosting operation is started. In the defrosting operation, first, the first opening / closing valve 18 is closed in S6, and then the cooler 21 and the drain tray 25 are defrosted. For defrosting the cooler 21, first, as shown in S7, the four-way switching valve 16 is driven to connect the discharge side of the compressor 14 to the outlet side of the condenser 17 via the bypass pipe 34, and further to the expansion valve 23. The second opening / closing control valve 22 provided in parallel with the above is opened.

As a result, the hot refrigerant discharged from the compressor 14 circulates as indicated by the broken line arrow in FIG.
That is, the hot refrigerant discharged from the compressor 14 does not pass through the condenser 17, and the bypass pipe 34 causes the second on-off control valve 2 to pass through.
2 and flows into the cooler 21. Therefore, the cooler 21 is heated by the hot refrigerant and defrosted.

The temperature of the cooler 21 is detected by the first temperature sensor 27. The detected temperature T ₁₁ is the set temperature T set in the control unit 29 by the operation unit 31 in S9.
Compared with ₁₀ . Whether the detected temperature T ₁₁ is equal to the set temperature T _10, if rose more than that, it is considered the defrosting of condenser 21 step S10 is terminated, the defrosting operation of the cooler 21 is completed. That is, the four-way switching valve 16 and the second opening / closing control valve 22 that are driven to defrost the cooler 21
It can be returned to the state before defrosting.

Simultaneously with the defrosting operation of the cooler 21, the drain tray 25 is defrosted. Defrosting the drain plate 25 is S11.
As shown by (4), the electric heater 26 is energized by the drive signal from the control unit 29 to heat the drain tray 25. The temperature of the drain tray 25 is detected by the second temperature sensor 28. The temperature T ₂₁ detected by the temperature sensor 28 is controlled by the operation unit 31 by the control unit 29 as indicated by S12.
Is compared with the set temperature T ₂₀ set to. Detection temperature T ₂₁
A low but than the set temperature T _20, the electric heat - energization of the motor 26 is continued, or the detected temperature T ₂₁ is substantially equal to the set temperature T _20, when it comes to higher, the drain pan as shown in S13 The defrosting operation of No. 25 ends.

According to such a defrosting operation, the cooler 21
The set temperature T ₁₀ that is the defrost return temperature of the above and the set temperature T ₂₀ that is the defrost return temperature of the drain tray 25 can be set separately by the setting unit 31 connected to the control unit 29. That is, the size of the cooler 21 and the drain tray 2
The set temperature T ₁₀ of the cooler 21 and the set temperature T ₂₀ of the drain tray 25 can be set in accordance with the size of 5 or the degree of increase in temperature thereof by a predetermined mode.

Table 1 below shows three setting modes. Mode
The case 1 is the case of the normal cooling unit 11, in which case the defrosting recovery temperature of the cooler 21 and the drain tray 25 is set to 10
By providing a difference of about ° C, it is possible to surely defrost both of them in substantially the same time and without overheating the cooler 21.

Mode 2 is a case where the cooler 21 is a relatively large chilled high humidity cooler, and in that case, the cooler 2 is used.
Since the heat capacity of No. 1 becomes large, the defrost return temperature of both may be set to about the same 10 ° C. The mode 3 is the case of the refrigerating type cooling unit 11 with a large amount of invasion of outside air, and in that case, since frost is formed on the drain tray 25, the defrosting recovery temperature of the cooler 21 is 10 ° C. If the defrosting recovery temperature of the drain tray 25 is set to about 25 ° C., both of these can be defrosted well.

[0041]

[Table 1]

Prior to performing the defrosting operation, the refrigerant pressure in the condenser 17 is detected, and the outdoor blower 37 is stopped until the detected pressure Pa reaches the set pressure Pf, that is, the refrigerant in the condenser 17 is cooled. The defrosting operation was not started until the sleeping amount decreased. Therefore, a sufficient amount of hot refrigerant circulates through the cooler 21 during the defrosting operation, so that even if the outside air temperature is low, the defrosting of the cooler 21 can be performed reliably and in a short time. it can.

FIG. 3A shows the defrost cycle of the present invention, and FIG. 3B shows the conventional defrost cycle. In the defrosting cycle of the present invention, after the cooling operation shown by A, there is a stop time of the outdoor blower 37 shown by B ', then the defrosting operation shown by B1 and the next cooling operation shown by C.

On the other hand, in the conventional defrost cycle, although there is no time to stop the outdoor blower 37 as in the present invention, when the outside air temperature is low, the amount of refrigerant stagnation in the condenser 17 increases and cooling is performed. Since the amount of hot refrigerant circulating in the vessel 21 decreases, the defrosting time B2 becomes longer, and as a result, the time t2 between the defrosting ends becomes longer than the defrosting end time t1 of the present invention. .

5 and 6 show another embodiment of the present invention. The same parts as those in the above-described embodiment are designated by the same reference numerals and the description thereof will be omitted. That is, this embodiment is a four-way switching valve 1
6 and the outlet side of the condenser 17 to connect the bypass pipe 34
In addition, a check valve 41 is provided with the flow direction facing the condenser 17 side. The downstream side of the check valve 41 and the compressor 14
A capillary tube 42 is provided between the suction tube and the suction side.

The four-way switching valve 16 is U-shaped as shown in FIG.
A slider 51 having a V-shaped passage 51a is slidably housed in a valve chamber 52. In the valve chamber 52, a pressure receiving body 53 for sliding the slider 51 is provided integrally with the slider 51. A first pressure receiving portion 53a is formed at one end of the pressure receiving body 53, and a second pressure receiving portion 53b is formed at the other end.

In the valve chamber 52, the first of the pressure receiving body 53 is formed.
The first to fourth four ports D, C, E and S are formed between the pressure receiving portion 53a and the second pressure receiving portion 53b.
The first port D communicates with the discharge side of the compressor 14, and the second port C communicates with the inflow side of the condenser 17. The third port E communicates with the inflow side of the check valve 41, and the fourth port S is closed.

One end of the first suction passage 54a communicates with one end of the valve chamber 52 on the side of the first pressure receiving portion 53a, and the other end on the side of the second pressure receiving portion 53b has a second suction passage. The other end of 54b communicates. The other end of each suction path 54a, 54b is
Two ports L of the three ports of the drive solenoid valve 55 for driving the pressure receiving body 53 (four-way switching valve 16),
It communicates with M respectively. Remaining 1 of drive solenoid valve 55
The two ports N are connected to the suction side of the compressor 14 by a negative pressure pipe 55a.

The drive solenoid valve 55 has a housing 56, a valve body 57 slidably provided in the housing 56, and a coil portion 58 for driving the valve body 57. During the normal cooling operation, the coil portion 58 is not energized,
In this state, the first suction passage 54a communicates with the suction side of the compressor 14 via the ports L and N and the negative pressure pipe 55a.

As a result, the pressure of the first pressure receiving portion 53a of the pressure receiving body 53 becomes lower than that of the second pressure receiving portion 53b, so that the pressure receiving body 53 is urged together with the slider 51 in the direction indicated by the arrow X in FIG. It has been slid to the position indicated by the solid line. At that position, the third port E is moved by the slider 51.
Is closed and the first port D and the second port C communicate with each other, so that the four-way switching valve 16 connects the discharge side of the compressor 14 to the inflow side of the condenser 17. This is the state during normal cooling operation.

When the coil portion 58 of the drive solenoid valve 55 is energized, the second suction pipe line 54b communicates with the suction side of the compressor 14 via the drive solenoid valve 55 and the negative pressure pipe 55a. 51 is slid to the position shown by the chain line in FIG. 6, and the first port D and the third port E communicate with each other. That is, the discharge side of the compressor 14 is communicated with the inflow side of the cooler 21 via the check valve 41. This state can be switched to during defrosting operation.

In the cooling operation state in which the first port D communicates with the second port C and the refrigerant flows in the cycle shown in FIG. 5 as indicated by the solid line arrow, the check valve 41 and the four-way switching are performed. The bypass pipe 34 whose both ends are cut off from the flow of the refrigerant by the valve 16 has one end connected to a midway portion thereof and the other end connected to the compressor 1
The pressure is made negative through the capillary tube 42 which is communicated with the suction side of No. 4.

When the pressure in the bypass pipe 34 decreases, the pressure in the passage 51a of the slider 51 communicating with the bypass pipe 34 also decreases, so that the internal pressure of the slider 51 becomes lower than the external pressure. Since the slider 51 is strongly pressed against the inner surface of the valve chamber 52 of the four-way switching valve 16 due to the pressure difference between the inside and the outside, the third port E is reliably cut off from the internal space of the valve chamber 52 by the slider 51. Thereby,
Since it is possible to prevent the high-pressure refrigerant flowing from the first port D to the second port C from leaking to the cooler 21 through the third port E and the bypass pipe 34, the defrosting operation is performed. Even if the bypass pipe 34 is provided, it is possible to prevent the normal cooling operation efficiency from decreasing.

The present invention is not limited to the above-mentioned embodiments and can be variously modified. For example, the first opening / closing control valve is provided on the outlet side of the condenser in order to flow the hot refrigerant to the cooler without passing through the condenser during the defrosting operation, but instead of this, the refrigerant is transferred from the condenser to the cooler. A check valve may be provided on the outlet side of the condenser to prevent the flow in the opposite direction.

[0055]

As described above, according to the first invention described in claim 1 and the third invention described in claim 3, the defrost return temperatures of the cooler and the drain tray are set separately. I made it possible. Therefore, if the cooler is more likely to be heated than the drain tray, the defrost return temperature of the cooler is set lower than the defrost return temperature of the drain tray to heat the cooler too much. It is possible to reliably defrost both of them. That is, even if the defrosting conditions such as the size and the degree of temperature rise of the cooler and the drain tray are different, by setting the defrosting return temperature accordingly, it is possible to perform these defrosting favorably. Become.

According to a second aspect of the present invention, when the outside air temperature is low, the operation of the outdoor blower is stopped until the refrigerant pressure in the condenser rises to a predetermined pressure, and then the defrosting operation is performed. To do. Therefore, the amount of refrigerant stagnation in the condenser can be reduced, and the circulation amount of hot refrigerant to the cooler can be increased. Therefore, even when the outside air temperature is low, defrosting of the cooler by the hot refrigerant can be ensured. And, it can be performed in a short time.

According to the fourth aspect of the present invention, a negative pressure is applied to the switching valve through the bypass pipe during the normal cooling operation to maintain the switching state of the switching valve. Therefore, it is possible to prevent the high-temperature and high-pressure refrigerant discharged from the compressor from leaking to the bypass pipe for the defrosting operation through the switching valve, so that the leakage does not reduce the operating efficiency during the cooling operation.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a cycle showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a flowchart for the defrosting operation.

FIG. 3A is a graph showing the relationship between the refrigerant pressure of the condenser of the present invention and time, and FIG. 3B is a graph showing the relationship of the refrigerant pressure of the conventional condenser and time.

FIG. 4 is an explanatory view of a state where water droplets adhere to the storage when the cooler is overheated.

FIG. 5 is a configuration diagram of a cycle showing the overall configuration of another embodiment of the present invention.

FIG. 6 is a configuration diagram of the same four-way switching valve.

[Explanation of symbols]

14 ... Compressor, 16 ... Four-way switching valve, 17 ... Condenser, 21
... cooler, 22 ... second opening / closing control valve, 23 ... expansion valve, 2
5 ... Drain tray, 26 ... Electric heater, 27 ... 1st temperature sensor, 28 ... 2nd temperature sensor, 29 ... Control part, 31 ...
Setting part, 34 ... Bypass pipe, 37 ... Outdoor blower, 38 ...
Pressure sensor, 39 ... Timer circuit.

Claims (4)

[Claims] 1. A cycle in which a compressor, a condenser, an expansion valve and a cooler are sequentially connected, a drain tray for receiving drain generated in the cooler, and a direct cooler for cooling high-temperature high-pressure refrigerant discharged from the compressor. First defrosting means for flowing and heating to
An electric heater is attached to the drain tray, and second defrosting means for heating the drain tray by the electric heater and first defrosting means for detecting the completion of defrosting provided in the cooler. Return sensor, a return sensor of the second defrosting means for detecting the end of defrosting provided on the drain tray, a return sensor of the first defrosting means and a return sensor of the second defrosting means. A defrosting device for a cooling unit, comprising a plurality of preset temperatures, and a setting means for selecting and setting each of these reset preset temperatures. 2. A cycle in which a compressor, a condenser, an expansion valve, and a cooler are sequentially connected, and defrosting in which high-temperature high-pressure refrigerant discharged from the compressor is flowed to the cooler without passing through the condenser and the expansion valve. Means, a pressure detection means in the condenser, a blower for a condenser for heat exchange between the condenser and the outside air, and when performing defrosting by the defrosting means, the detected pressure by the detecting means is a set value. A defrosting device for a cooling unit, comprising: a control unit that stops the operation of the condenser blower until the detected pressure is lower than a set value by comparison. 3. A cycle in which a compressor, a condenser, an expansion valve, and a cooler are sequentially connected, and a cooler, a blower for the cooler, and a drain tray for receiving the drain generated in the cooler, which are arranged in the upper part of the storage chamber. A cooling unit that is configured, a first defrosting unit that heats high-temperature high-pressure refrigerant discharged from the compressor by directly flowing to a cooler, and an electric heater is attached to the drain tray. A second defrosting means for heating the drain tray by means of a heater, a return sensor for the first defrosting means for detecting the end of defrosting provided in the cooler, and a defrosting end provided for the drain tray. A reset sensor for the second defrosting means for detecting, and a setting means for setting the reset set temperature by the reset sensor of the second defrost means higher than the reset set temperature of the reset sensor of the first defrost means. Cooling uni characterized by Defroster. 4. A cycle in which a compressor, a condenser, an expansion valve and a cooler are sequentially connected, and high-temperature high-pressure refrigerant discharged from the compressor is passed through the bypass pipe to the cooler without passing through the condenser and the expansion valve. A switching valve that switches between a defrosting operation that flows and a cooling operation that causes the high-temperature high-pressure refrigerant to flow through the condenser and an expansion valve to the cooler; A defrosting device for a cooling unit, comprising: a biasing means for biasing the state.