JPH0278873A - Defrost operation controller for refrigerating device - Google Patents

Abstract

PURPOSE:To prevent the unnecessary temperature rise in a refrigerator and improve the using efficiency of electric power by a method wherein a means, supplying a drain pan heater with hot gas necessary for only the actual melting of frozen drain in a drain pan upon defrost operation by hot gas, is provided in the title device. CONSTITUTION:Upon defrost operation effected by a first switching and controlling means 21, the switching of a second three-way valve 13 is controlled by a second switching and controlling valve 24 so that hot gas flows to the side of a drain pan heater 11. Frozen drain in a drain pan 15 is molten and the clogging of drain may be prevented effectively. When ice in the drain pan 15 is molten, it is detected by a defrost detecting means 23. The second three- way valve 13 is controlled so as to be switched so that the hot gas flows to the side of a partial bypass passage 12 and not flows to the side of the drain pan heater 11 in a hot gas bypass passage 9. Accordingly, the drain pan 15, the fins of an evaporator 4, tube plates, a rear plate and the like are not heated unnecessary and a predetermined defrost operation may be effected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a defrost operation control device for a refrigeration system,
In particular, the present invention relates to an improvement in which defrost operation is performed by bypassing hot gas to the heater of the evaporator and its drain pan.

(Prior Art) Conventionally, as disclosed in JP-A No. 61-29652, for example, a main refrigerant circuit has a main refrigerant circuit in which a compressor, a condenser, a pressure reducing mechanism, and an evaporator equipped with a drain pan are sequentially connected. In addition, there is a hot gas bypass path that bypasses the refrigerant discharged from the compressor to the evaporator, a drain pan heater installed in the hot gas bypass path to heat the drain pan, and a hot gas bypass path that bypasses the refrigerant discharged from the compressor to the evaporator. In a refrigeration system equipped with a connection switching mechanism that switches to a gas bypass path, at the time of frosting, a defrost operation is performed in which the discharged refrigerant flows through a hot gas bypass path including a drain pan heater, thereby performing a predetermined defrost. A technique that prevents so-called drain clogging by melting frozen drain in a drain pan is known as a well-known technique.

(Problems to be Solved by the Invention) However, in the conventional device described above, when the outside temperature is low such as in winter, the defrosting time is longer than when the outside temperature is high.

Furthermore, when hot gas is passed through the drain pan heater, the amount of heat actually used to melt the frozen drain in the drain pan is several tens of percent of the amount of heat of the hot gas, and the remaining amount of heat is used for the drain pan, evaporator fins, tube sheet, etc. There is a problem in that the back plate is used to heat the back plate more than necessary, and as a result, for example, the temperature inside the refrigerator increases more than necessary, and power is wasted.

The present invention has been made in view of the above, and its purpose is to provide a means for communicating only the hot gas necessary for actually melting the frozen drain in the drain pan to the drain pan heater during a defrost operation using hot gas. By doing so, the purpose is to effectively prevent the temperature inside the refrigerator from increasing more than necessary and improve the efficiency of electric power usage.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention includes a compressor (1), a condenser (2), a pressure reducing mechanism (
3) and evaporator (4) with drain pan (15)
The main refrigerant circuit (6) is formed by sequentially connecting the above-mentioned compressor (
a hot gas bypass path (9) connecting the discharge pipe (53) of 1) and the evaporator (4) so that the discharged refrigerant can be bypassed;
A first connection switching mechanism (10) that switches the flow of discharged refrigerant between the main refrigerant circuit (6) and the hot gas bypass path (9).
), a drain pan heater (11) that is disposed in the hot gas bypass path (9) and heats the drain pan (15) with the discharged refrigerant, and a drain pan heater (11) that bypasses the drain pan heater (11) in the hot gas bypass path (9). A second connection switching mechanism (1) that switches the flow of the discharged refrigerant in the partial bypass path (12) and the hot gas bypass path (9) to the drain pan heater (11) side and the partial bypass path (12) side.
3) A refrigeration system is assumed.

As an operation control device for the refrigeration equipment, during frosting,
A first switching control means (21) that controls the first connection switching mechanism (10) so that the discharged refrigerant flows to the hot gas bypass path (9) side, and a defrost operation by the first switching control means (21). , ice-melting detection means (23) for detecting when the drain pan (15) is ice-thawing; and the ice-melting detection means (23).
When the defrost operation starts, the discharged refrigerant flows to the drain pan heater (11) and the drain pan (1
5), the second connection switching mechanism (13) is arranged so that the flow bypasses to the partial bypass path (12) after the ice melts.
A second switching control means (24) for switching control is provided.

A second solving means replaces the ice melting detection means (23) in the first solving means with a heater outlet temperature detection means (T h3) that detects the outlet temperature of the drain pan heater (11).
Receiving the output of the heater outlet temperature detection means (Th3),
It is constructed of a determining means (22) that determines that the ice is melted when the differential value as the amount of change in drain pan heater outlet temperature with respect to unit time becomes positive.

A third solving means replaces the ice melting detection means (23) in the first solving means with a heater inlet temperature detection means (T h2) that detects the inlet temperature of the drain pan heater (11).
A heater outlet temperature detection means (Th3) for detecting the outlet temperature of the drain pan heater (11), and both detection means (Th3) for detecting the outlet temperature of the drain pan heater (11).
2) A determination means (22) receives the output of (Th3) and determines that the ice has melted when the difference between the inlet temperature and the outlet temperature of the drain pan heater (11) reaches the maximum. .

A fourth solving means replaces the deicing detecting means (23) in the first solving means with a discharge pipe temperature detecting means (T h1) that detects the temperature of the discharge pipe (53) of the compressor (1). A heater outlet temperature detection means (Th3) for detecting the outlet temperature of the drain pan heater (11), and both detection means (Th1)
), (Th3) and determines that the ice is melted when the temperature difference between the discharge pipe temperature and the drain pan heater outlet temperature reaches the maximum.

A fifth solving means replaces the deicing detecting means (23) in the first solving means with drain pan temperature detecting means (T h4) arranged in the drain pan (15) and detecting the temperature of the drain pan (15); The drain pan temperature detection means (T
h4) and determines that the ice has melted when the drain pan temperature exceeds a predetermined value.

(Function) With the above configuration, in the invention of claim (1), during operation of the device, the first switching control means (21) switches the connection of the first connection switching mechanism (10) to the main refrigerant circuit (6) side. Operation is carried out in the switched state, and the refrigerant discharged from the compressor (1) flows only through the main refrigerant circuit (6), is condensed and liquefied in the condenser (2), and then is liquefied in the evaporator (4). The predetermined freezing is performed by evaporating and circulating.

When the surface of the evaporator (4) becomes frosted during operation of the device, the first switching control means (21) switches the connection of the first connection switching mechanism (10) to the hot gas bypass path (9). ) side, and a defrost operation is performed in which the discharged refrigerant is bypassed as hot gas to the hot gas bypass path (9).

゛ At that time, since hot gas flows toward the drain pan heater (11), the frozen drain in the drain pan (15) is melted, and drain clogging is effectively prevented. When the deicing detection means (23) detects that the drain bun (15) is deicing, the second switching control means (24) causes the hot gas in the hot gas bypass path (9) to pass through the partial bypass path (9). 12) side and not the drain pan heater (11) side, the fins, tube plate, and back of the drain pan (15) and evaporator (4) The board etc. will not be heated more than necessary.

In addition, since the hot gas bypasses the drain pan heater (11), pressure loss and heat loss due to passing through the drain pan heater (11) are eliminated, and high temperature hot gas is introduced into the evaporator (4) for defrosting. Driving time is reduced. Therefore, an unnecessarily high rise in the internal temperature of the refrigerator is effectively prevented, and power usage efficiency is improved.

In the invention of claim (2), in the invention of claim (1), when the ice melting detection means (23) detects the time of ice melting, the heater outlet temperature detection means (Th3) detects the temperature of the drain pan heater (11). The outlet temperature is detected and the determination means (2
2), it is detected that the drain pan (15) is thawed when the differential value of the heater outlet temperature becomes positive, so the ice in the drain pan (15) is thawed and the drain pan surface temperature and evaporator ( 4) The point in time when the fin surface temperature etc. significantly increases can be accurately detected. Therefore, the above claim (1)
), the effects of the invention will be significantly demonstrated.

In the invention of claim (3), the determination means (22) determines the heater inlet temperature detected by the heater inlet temperature detection means (Th2) and the heater outlet temperature detected by the heater outlet temperature detection means (Th3). Since it is determined that the ice has melted when the temperature difference between the heater outlet temperature and the This means that the same effects as the invention of claim (2) can be achieved.

In the invention of claim (4), the discriminating means (22) distinguishes between the discharge pipe temperature detected by the discharge pipe temperature detecting means (Th1) and the heater outlet temperature detected by the heater outlet temperature detecting means (Th3). Since it is determined that the ice has melted when the difference in temperature between the temperature and the temperature of , Therefore, the above claim (2
) can provide the same effect as the invention.

In the invention of claim (5), a drain pan temperature detection means (T
h4) is installed, and when the drain pan temperature becomes higher than a predetermined value, the determining means (22) determines that the ice has melted.
The time of thawing of the ice is detected, and therefore, the effect of the invention of claim (1) above is more significantly exhibited.

(Example) Hereinafter, an example of the present invention will be described based on the drawings from FIG. 2 onwards.

FIG. 2 shows the overall configuration of a container refrigerator according to an embodiment of the invention of claims (1) to (4), in which (1) is a compressor, (2) is a compressor, and (2) is a compressor;
) is a condenser for condensing and liquefying the refrigerant discharged from the compressor (1), and (3) is a decompressor for reducing the pressure of the liquid refrigerant condensed and liquefied in the condenser (2) to a predetermined low pressure state. a mechanism, an expansion valve (4), an evaporator equipped with a drain pan (15), and for evaporating the refrigerant reduced in pressure by the expansion valve (3); ~ (4) are connected by refrigerant piping (5) so that refrigerant can flow,
A main refrigerant circuit (6) is configured in which the cold heat imparted by the condenser (2) through heat exchange with outside air is released into the internal air in the evaporator (4).

In the main refrigerant circuit (6), the expansion valve (
A first electromagnetic on-off valve (7) for opening and closing the main refrigerant circuit (6) is interposed between the electromagnetic on-off valve (7) and the condenser (2). ) between the main refrigerant circuit (
6) is provided with a second electromagnetic on-off valve (8) that opens and closes the valve. By means of the first and second electromagnetic on-off valves (7) and (8), a certain amount of refrigerant is stored in the piping between them during pump down operation, which will be described later, and flows to the hot gas bypass path (9) during defrost operation. It is designed to keep the amount of refrigerant constant.

Furthermore, the discharge pipe (53) of the compressor (1) and the evaporator (
4) There is a discharge refrigerant (hereinafter referred to as hot gas) between
A hot gas bypass path (9) is provided to connect the main refrigerant circuit (6) in a bypass manner, and its discharge pipe (
53), a first three-way valve as a first connection switching mechanism that switches the hot gas flow to the main refrigerant circuit (6) side in the off state and to the hot gas bypass path (9) side in the on state. (10) is provided. In addition, the hot gas bypass path (9) is provided with a drain pan (15) of the evaporator (4).
) is provided with a drain pan heater (11) for heating the ice.When frosting, by passing hot gas through the drain pan heater (11), the ice is thawed in the evaporator (4) and falls into the drain pan (15). This system melts the unmelted ice in the water to prevent so-called drain clogging.

Here, the expansion valve (3), the electromagnetic on-off valve (7) and the first three-way valve (10) are a defrost operation control section (21) built into a controller (18) for controlling the operation of the entire device. When the evaporator (4) is frosted, the defrost operation control section (21) switches the first three-way valve (10) to the on state and turns on the compressor (
It functions as a first connection switching mechanism that controls the refrigerant discharged from 1) to flow as hot gas to the hot gas bypass path (9).

On the other hand, a partial bypass path (12) that bypasses the drain pan heater (11) is provided in the hot gas bypass path (9), and furthermore, at a branch point with the drain pan heater (11), A second three-way valve (13) is interposed as a second connection switching mechanism that switches the hot gas flow to the drain pan heater (11) in the on state and to the partial bypass path (12) in the off state.

Further, in accordance with the invention of claims (2) to (4), the device is provided with sensors, and (The) is a suction pipe sensor arranged in the suction pipe and detects the suction pipe temperature TO; (T
h1) is arranged in the discharge pipe (53) of the compressor (1),
A discharge pipe sensor (T h2) serves as a discharge pipe temperature detection means for detecting the discharge pipe temperature TI, and a drain pan heater (11
) is placed on the inlet side of the drain pan heater inlet &T2
A heater inlet sensor (Th3) is placed at the outlet of the drain pan heater (11), and a heater outlet sensor (Th3) is located at the outlet of the drain pan heater (11).
h3). Each of the above sensors (T ho) to (T h
3) and the second three-way valve (13) are connected to the controller (18) so that signals can be exchanged, and as described later, the second three-way valve (13) The connection state of the second three-way valve (13) can be switched.

In the figure, (16) is a receiver for storing the refrigerant condensed in the condenser (2), and (LPS) is a receiver that detects a drop in low pressure during pump-down operation and starts pump-down operation at a predetermined value. This is a low-pressure pressure switch that outputs a signal to terminate the process.

When operating the device, 1. Second electromagnetic on-off valve (7).

(8) is open and the first three-way valve (10) is off, the refrigerant discharged from the compressor (1) flows only through the main refrigerant circuit (6) and the condenser (2). After being condensed and liquefied, the liquid is circulated to be evaporated in an evaporator (4), thereby cooling the inside of the refrigerator to a set temperature.

At that time, if the surface of the evaporator (4) becomes frosted during operation of the device, the suction pipe sensor (Th
(for example, under the condition that the temperature TO≦-23°C), the defrost operation control section (21) in the controller (18) activates the first electromagnetic on-off valve (7).
is closed, the second electromagnetic on-off valve (8) remains open, and the refrigerant in the main refrigerant circuit (6) flows through the condenser (2) and receiver (1).
6) A so-called pump-down operation is performed in which the liquid is stored in a liquid reservoir formed by piping. Then, when the low pressure switch (LPS) is turned off and the pump down operation is completed, the first three-way valve (10) is turned on,
And the first solenoid on-off valve (7) opens and the second solenoid on-off valve (8)
The operation is performed with the pump closed, and the first one of the refrigerant stored in the pump-down operation is operated. Second electromagnetic on-off valve (7), (8)
A certain amount of ff1 (e.g. 300cc) stored in the pipe between
A defrost operation is performed in which the evaporator (4) is defrosted by bypassing the hot gas (refrigerant amount) to the hot gas bypass path (9) as hot gas.

Further, as a feature of the present invention, during the defrost operation by the defrost operation control section (21), the temperature sensor (
The controller (18) switches and controls the second three-way valve (13) in response to the signals Tho) to (Th3). The content of the control will be explained based on the flowchart of FIG. 3, taking the invention of claim (2) as an example.
When defrost operation is started in step S1, the second three-way valve (13) is turned on in step S2 to flow hot gas to the drain pan heater (11) side, and in step S3, the heater outlet sensor (T h3) is turned on. It is determined whether the change in outlet temperature T3 with respect to unit time, that is, the differential value dT3/dt with respect to time is positive or not, and if it is positive,
Proceeding to step S4, the second three-way valve (13) is turned off to bypass the hot gas to the partial bypass path (12). That is, the drain pan heater (11)
The hot gas is allowed to flow directly to the evaporator (4) without introducing hot gas.

Thereafter, in step S5, the suction pipe temperature TO rises to a higher temperature than 35° C., and then, in step S6, the defrost operation is ended.

In the above flow, in the invention of claim (2), step S3 includes a determining means (22) for determining whether or not the ice in the drain pan (15) has been completely thawed, and the invention of claim (1) Now, the heater outlet sensor (heater outlet temperature detection means') (Th3) and the discrimination means (22
) constitutes an ice-melting detection means (23) that detects when the drain pan (15) is ice-thawed. Also, step S
2 and S4, upon receiving the output of the deicing detection means (23) during the defrost operation, the discharged refrigerant flows to the drain pan heater (11) at the start of the defrost operation, and after the drain pan (15) has thawed, the discharged refrigerant flows through the partial bypass path. (12)
A second switching control means (24) for controlling the second three-way valve (second switching mechanism) (13) so that the flow bypasses the side.
) is configured.

Therefore, in the invention of claim (1), during the defrost operation by the defrost operation control section (first switching control means) (21), the second switching control means (24) directs hot gas to the drain pan heater (11) side. The second three-way valve (13) is controlled to switch so that the drain pan (15)
The frozen drain inside will melt, effectively preventing drain clogging. Then, when the deicing detection means (23) detects that the drain pan (15) is deicing, the hot gas flows to the partial bypass path (12) in the hot gas bypass path (9), and the drain pan heater ( Since the second three-way valve (13) is controlled so that the flow does not flow to the 11) side, the drain pan (15), fins, tube plate, back plate, etc. of the evaporator (4) are removed more than necessary, unlike conventional ones. A predetermined defrost operation is performed without heating. In addition, since the hot gas bypasses the drain pan heater (11), pressure loss and heat loss due to the drain pan heater (11) are eliminated, and high temperature hot gas can be introduced into the evaporator (4), which allows defrost operation. Time is reduced. Therefore, it is possible to effectively prevent the temperature inside the refrigerator from rising more than necessary and improve the efficiency of power usage.

In addition, in the invention of claim (2:J), a drain pan heater (
A heater outlet sensor (T h3) is installed on the outlet pipe of 11), and when the differential value dT3 /d t of the temperature T3 becomes positive, it is detected that the drain pan (15) is thawed. Therefore, it is possible to accurately detect the point in time when the inside of the drain pan (15) thaws and the temperature rises.

That is, as shown in FIG. 4, when hot gas continues to flow through the drain pan heater (11), the solid line shows the change in the heater outlet temperature T3 over time, and the broken line shows the change in the suction pipe temperature TO. If the change in the fin surface temperature Tf in 4) is represented by a dashed dotted line, and the change in the surface temperature Td of the drain pan (15) is represented by a dashed double dotted line, then dT3/dt
After the point where becomes positive (part ■ in the figure), the drain pan surface temperature Td and the fin surface temperature T of the evaporator (4)
In both cases, the temperature increases significantly. Therefore, at that point, the flow of hot gas is switched to the partial bypass path (12) side and does not flow to the drain pan heater (11) side, so that the effect of the invention of claim (1) above is significantly exhibited. be.

Next, in the invention of claim (3), in the flow shown in FIG. -T3) is the maximum, the other steps are the same. Similarly, in the invention of claim (4), the determination in step S3 by the determining means (22) in the flow of FIG.
1 and the heater outlet temperature T3 (Tl - T3) is replaced so as to determine whether or not the temperature difference (Tl - T3) is the maximum.

That is, in the inventions of claims (3) and (4), the fifth
As shown in the figure, the time t at which the change in heater outlet temperature T3 with respect to time in the invention of claim (2) is maximum.
A time point approximately corresponding to 1. /, the difference in temperature between the inlet temperature T2 and outlet temperature T3 of the drain pan (11) (T2-T3)
and the difference a between the discharge pipe temperature TI and the heater outlet temperature T3
(Tl - T3 > is the maximum, so the above claim (2)
) can produce the same effect as the invention of .

Also, in particular, as in the above embodiment, a so-called metering type in which a pump-down operation is performed prior to the defrost operation, and a certain amount of refrigerant from the refrigerant stored in the pump-down operation is introduced into the evaporator as hot gas. Even in hot gas defrosting, not all of the heat of a certain amount of hot gas is used to defrost the drain pan heater, and as a result,
Unnecessary heating of evaporator parts, drain pans, etc. may cause the temperature inside the refrigerator to rise, but in that case, the same action as above will effectively prevent the temperature inside the refrigerator from rising more than necessary. can do.

In addition, in the above embodiment, the heater outlet sensor (T h
3) was placed at the outlet of the drain pan heater (11), but the drain pan heater (11) and the partial bypass path (12)
It goes without saying that the hot gas bypass passage (9) may be disposed between the junction with the hot gas bypass passage (9) and the outlet of the hot gas bypass passage (9).

Next, the invention of claim (5) will be explained. Claim (5
), the heater inlet sensor (T h2) and the heater outlet sensor (T h3) are not necessary, and instead, the drain pan (15) is equipped with a drain pan as a drain pan temperature detection means for detecting the drain pan temperature T4. A sensor (Th4) is installed (portion shown by the broken line in Figure 2). The connection state of the second three-way valve (13) is controlled in accordance with the signal from the drain pan sensor (Th4). The contents will be explained based on the flowchart of FIG. 6. In step S7, when the second three-way valve (13) is turned on and defrost operation is started, in step S8, the drain pan sensor (Th4) detects It is determined whether or not the drain pan temperature T4 is higher than a predetermined temperature (0+α) obtained by adding a predetermined temperature α to the melting point of water 0°C, and determines whether T4>
(0+α), it is determined that there is no ice in the drain pan (15) and there is no risk of drain clogging, and step S
9, the second three-way valve (13) is turned off so that hot gas does not flow to the drain pan heater (11) side and the partial bypass path (
12) Control the flow to the side. Then step S
10, it is determined whether the drain pan temperature T4 is below zero,
If it is not below zero, in step Sl+, the suction pipe temperature TO
Defrost operation is performed in this state until TO becomes higher than 35°C, and when TO>35 ('C), the defrost operation is ended in step S12.

On the other hand, if T4≦0 is determined in step SIO, for example, if ice from the evaporator (4) falls into the drain pan (15)' and the drain pan temperature T4 falls below zero degrees, the 2. Switch the three-way valve (13) to the on state and introduce hot gas into the drain pan heater (11). Then, in step S14, the suction pipe temperature TO becomes 35
After repeating the above steps 88 to SI3 until To >35 ('C), the defrost operation is stopped.

In the above flow, step S8 includes a determining means (22) for determining whether or not the drain pan temperature T4 has become higher than a predetermined temperature (0+α), and the drain pan temperature detecting means (Th4) and the determining means ( 22
) constitutes ice melting detection means (23). Then, in step S9, the output of the ice melting detection means (23) is received, and after the drain pan (15) has melted, the second three-way valve ( 13), a second switching control means (24) is configured.

Therefore, in the invention of claim (5), the direct drain pan (1
A temperature sensor (T h4) is attached to the drain pan (T h4), and when the drain pan temperature T4 becomes higher than a predetermined value (0 + ) is detected, and the effect of the invention of claim (1) above can be more clearly exhibited.

(Effects of the Invention) As explained above, according to the invention of claim (1), when the evaporator is frosted, the discharged refrigerant is made to flow as hot gas into the hot gas bypass path including the drain pan heater of the evaporator. In the defrost operation control system of the refrigeration system, when the drain pan is thawed, the hot gas is bypassed from the drain pan heater, so that high-temperature gas is not heated to the evaporator without unnecessary heating of the drain pan or evaporator fins. By introducing hot gas, the defrosting operation time can be shortened, thereby effectively preventing an unnecessary rise in the temperature inside the refrigerator and improving the efficiency of electric power usage.

According to the invention of claim (2), as the means for detecting ice melting in the invention of claim '(1), the time when the differential value of the outlet temperature of the drain pan with respect to time becomes positive is determined as the time when the drain pan is melting. Therefore, it is possible to accurately detect the point in time when the temperature rise of the drain pan, the fins of the evaporator, etc. becomes large, and the effect of the invention of claim (1) can be more significantly exhibited. .

According to the invention of claim (3), as the means for detecting ice melting in the invention of claim (1), the time when the difference between the inlet temperature and the outlet temperature of the drain pan becomes maximum is determined as the time when the drain pan is thawed. The above claim (
The same effect as the invention 2) can be obtained.

According to the invention of claim (4), as the means for detecting ice melting in the invention of claim (1), the time when the temperature difference between the discharge pipe temperature and the outlet temperature of the drain pan reaches a maximum is determined as the time when the drain pan is melting. Since the determination is made as follows, it is possible to obtain the same effect as the invention of claim (2) above.

According to the invention of claim (5), since the time when the temperature of the drain pan becomes higher than a predetermined value is determined as the thawing state, the thawing state of the drain pan can be directly detected. The effect of the invention (1) can be significantly obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the invention according to claims (1) to (5). Fig. 2 and the following show embodiments of the present invention, Fig. 2 is a refrigerant system diagram showing its overall configuration, Fig. 3 is a flowchart showing the control contents of the invention of claims (1) and (2), and Fig. Figure 4 is a characteristic diagram showing changes in suction pipe temperature, drain pan heater outlet temperature, and temperature of each part over time in the invention of claim (2), and Figure 5 is a characteristic diagram showing changes in discharge pipe temperature, heater inlet temperature, and heater outlet temperature over time. The characteristic diagram showing the changes, and FIG. 6, is a flowchart showing the control contents of the invention of claim (5). (1)...Compressor, (2)...Condenser, (3)...
・Expansion valve (pressure reduction mechanism), (4)...Evaporator, (53)
...Discharge pipe, (6)...Main refrigerant circuit, (9)...
Hot gas bypass path, (10)...first three-way valve (first connection switching mechanism), (11)...drain pan temperature, (
12)...Partial bypass path, (13)...Second three-way valve (second connection switching mechanism), (21)...Defrost operation control section (first switching control means), (22)... - Discrimination means, (23)... Deicing detection means, (24)... Second
Switching control means, (Th1)...Discharge pipe sensor (Discharge pipe temperature detection means), (Th2)...Heater inlet sensor (Heater inlet temperature detection means), (Th3)...Heater outlet sensor (Heater outlet temperature detection means), (T h
4)...Discharge pipe sensor (discharge pipe temperature detection means). Figure 4 between B+S Figure 4

Claims (5)

[Claims] (1) A main refrigerant circuit (6) formed by sequentially connecting a compressor (1), a condenser (2), a pressure reducing mechanism (3), and an evaporator (4) equipped with a drain pan (15); A hot gas bypass path (9) connects the discharge pipe (5a) of (1) and the evaporator (4) so that the discharged refrigerant can be bypassed, and a hot gas bypass path that connects the flow of the discharged refrigerant to the main refrigerant circuit (6). a first connection switching mechanism (10) that switches to the road (9) side;
a drain pan heater (11) that is interposed in the hot gas bypass path (9) and heats the drain pan (15) with discharged refrigerant; and a partial bypass path that bypasses the drain pan heater (11) in the hot gas bypass path (9). (12) and a second connection switching mechanism (13) that switches the flow of the discharged refrigerant in the hot gas bypass path (9) between the drain pan heater (11) side and the partial bypass path (12) side. , a first switching control means (21) for controlling the first connection switching mechanism (10) so that the discharged refrigerant flows to the hot gas bypass path (9) during frosting;
), during defrost operation by the first switching control means (21), deicing detection means (23) for detecting when the drain pan (15) is thawed; , the second connection switching mechanism (13) is configured such that the discharged refrigerant flows to the drain pan heater (11) at the start of the defrost operation, and bypasses and flows to the partial bypass path (12) after the drain pan (15) is thawed. 1. A defrost operation control device for a refrigeration system, comprising: second switching control means (24) for switching control. (2) The ice melting detection means (23) receives the output of the heater outlet temperature detection means (Th3) that detects the outlet temperature of the drain pan heater (11) and the heater outlet temperature detection means (Th3), and the drain pan heater The refrigeration system according to claim 1, further comprising a determining means (22) that determines that the ice has melted when the differential value as the amount of change in the outlet temperature with respect to unit time becomes positive. defrost operation control device. (3) The deicing detection means (23) includes a heater inlet temperature detection means (Th2) that detects the inlet temperature of the drain pan heater (11), and a heater outlet temperature detection means that detects the outlet temperature of the drain pan heater (11). (Th3) and the outputs of both the above-mentioned detection means (Th2) and (Th3), and determines that the ice has melted when the difference in temperature between the inlet temperature and the outlet temperature of the drain pan heater (11) reaches the maximum. Means (22)
A defrost operation control device for a refrigeration system according to claim 1, characterized in that it is comprised of: (4) The deicing detection means (23) is a discharge pipe temperature detection means (T) that detects the temperature of the discharge pipe (5a) of the compressor (1).
h1), a heater outlet temperature detection means (Th3) that detects the outlet temperature of the drain pan heater (11), and receives the outputs of both the above detection means (Th1) and (Th3), and detects the discharge pipe temperature and the drain pan heater outlet temperature. 2. The defrost operation control device for a refrigeration system according to claim 1, further comprising a determining means (22) for determining that the ice is thawed when the temperature difference between the two reaches a maximum. (5) The deicing detection means (23) includes a drain pan (15).
), the drain pan temperature detection means (Th4) detects the temperature of the drain pan (15), receives the output of the drain pan temperature detection means (Th4), and detects the thawed state when the drain pan temperature exceeds a predetermined value. Discrimination means (
Claim (1) characterized in that it consists of
) A defrost operation control device for a refrigeration system.