JP3136644B2 - Off-cycle defrost equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an off-cycle defrost apparatus which uses a high-temperature refrigerant liquid in a refrigeration circuit as a defrost heat source so that the rise of defrost can be accelerated.

[0002]

2. Description of the Related Art In an air conditioner generally referred to as a cooling device in a broad sense including a refrigerator, when a temperature of an air conditioning target area such as a refrigerator is 2 ° C. or more, a compressor is stopped and a fan of an indoor unit is turned on. Off-cycle defrost, which is a method of operating and using the amount of heat held by air in the air conditioning target area as a defrost heat source, is often used, and a detector that switches to defrost operation at predetermined intervals or detects the amount of frost formation In most cases, automatic defrost operation is performed, such as by performing a defrost operation in response to a command from the user.

[0003]

When the interval for switching to the defrost operation is not properly set, or when the humidity of the refrigerated product is very high, or when the frost detector does not operate properly, for example, Severe frost formation is inevitable, but in the case of off-cycle defrost, since the frost is applied from the surface of the attached frost, the defrost time is significantly longer, the room temperature fluctuates greatly, and refrigerated Problems such as deterioration in quality occur.

[0004] It is an object of the present invention to provide an off-cycle defrost apparatus which can shorten the defrost time by utilizing a part of the refrigerant liquid having a high temperature as a heat source for frost in the early stage of the off-cycle defrost operation. It is in.

[0005]

According to the present invention, a compressor 1, a condenser 2, an expansion means 3, an evaporator 4, and an accumulator 5 are provided.
Is cyclically connected by refrigerant piping,
The evaporator 4 is provided in the refrigerator compartment 12 and exchanges heat with the indoor air circulated by the indoor fan 7 to cool the condenser 2 by the outdoor fan, thereby removing frost adhering to the evaporator 4 during the cooling operation. In the off-cycle defrost device in which the operation of the compressor 1 is stopped and the indoor fan 7 is removed while operating, the solenoid valve 8 connected in parallel to the expansion means 3 and closed during the cooling operation, and the discharge of the compressor 1 A high-pressure switch 11 is provided in a refrigerant pipe connecting the outlet and the condenser 2 and outputs a signal when the pressure is detected to be equal to or higher than a predetermined value. Means for opening the solenoid valve 8 when the detected pressure becomes equal to or higher than a predetermined value by a signal output from the pressure switch 11 and guiding the high-temperature refrigerant liquid from the condenser 2 to the evaporator 4 by bypassing the expansion means 3; Including It is an off cycle defrost and wherein the door.

[0006]

According to the present invention, when the off-cycle defrost is started, the outdoor fan 6 is stopped, so that heat dissipation is suppressed in the condenser 2 and the heat storage operation is performed. High-temperature refrigerant liquid stays in the condenser 2 and the pressure increases. When the pressure in the condenser 2 exceeds a predetermined value, a signal is output from the high pressure switch 11 and the solenoid valve 8 is opened. The high-temperature refrigerant liquid on the side of the condenser 2 bypasses the expansion means 3, passes through the solenoid valve 8, and is sent to the evaporator 4. Since the high-temperature refrigerant liquid heats the heat transfer tubes and the fins of the evaporator 4, the frost is melted from the heat transfer surface side to promote the frost, and the separation from the heat transfer tubes and the fins is fast. As a result, the defrost time is reduced.

Further, by operating the compressor 1 for a predetermined time, for example, several seconds after the solenoid valve 8 is opened, the movement of the high-temperature refrigerant liquid to the evaporator 4 side is made smooth and large. And the frosting action is increased, and the defrosting time is further reduced.

[0008]

FIG. 1 is a refrigeration circuit diagram of an air conditioner according to an embodiment of the present invention. The compressor 1, the condenser 2, the expansion means 3, for example, a temperature-sensitive automatic expansion valve (hereinafter abbreviated as expansion valve), the evaporator 4, and the accumulator 5 are cyclically connected by refrigerant pipes to form a well-known refrigeration system for cooling. A cycle is formed, and by operating the compressor 1, in the condenser 2, heat exchange of latent heat of condensation is performed between the outside air sent by the outdoor fan 6 and the high-temperature and high-pressure refrigerant gas. In the evaporator 4, heat exchange of latent heat of evaporation is performed between the room air circulated by the indoor fan 7 and the low-temperature low-pressure refrigerant gas, and the inside of the refrigerator compartment 12 is cooled to 2 to 10 ° C.

The degree of opening of the expansion valve 3 is automatically adjusted so that the degree of superheat at the coil outlet of the evaporator 4 becomes constant. To the expansion valve 3, an electromagnetic valve 8 is connected in parallel. . A high pressure switch 11 is connected to a high pressure gas pipe connecting the discharge port of the compressor 1 and the condenser 2.

FIG. 2 is a block diagram of a control circuit of the above-mentioned harmony apparatus, FIG. 3 is a time chart showing an operation state according to each embodiment of the present invention, and FIG. 4 shows an operation of the processing unit 9 shown in FIG. It is a flowchart explaining. The processing unit 9 includes a timer circuit 10 to switch the cooling operation to the off-cycle defrost operation based on a preset interval, to reach a preset defrost operation time, or to output a defrost end signal from a defrost detector (not shown). The off-cycle defrost operation is switched to the cooling operation in whichever is earlier, whichever comes first.

The mode of the off-cycle defrost operation is as described below.

When frost adheres to the coil of the evaporator 4 during the cooling operation to reach the limit amount, the process proceeds to step a1, and the cooling operation is switched to the defrost operation. In this state, which is indicated by time t2 in FIG. 3, the compressor 1 is kept operating, and the process immediately proceeds to the next step a2, where the outdoor fan 6 stops.

Since the heat radiation is suppressed in the condenser 2 by stopping the outdoor fan 6, the pressure and the temperature in the coil are increased, and the heat storage operation is performed.
When the high pressure reaches a predetermined value or more, step a3
The high pressure switch 11 outputs an off signal.

In accordance with the output of the OFF signal, the process proceeds to step a4, where the solenoid valve 8 is opened and closed, and the compressor 1 is stopped with a delay of 1 to 2 seconds. The high-temperature refrigerant liquid staying in the condenser 2 is pumped by the compressor 1 for 1-2 seconds, and by the presence of a pressure difference between the condenser 2 side and the evaporator 4 side. , Bypassing the expansion valve 3 and passing through the low-pressure liquid pipe into the coil of the evaporator 4.

When the coil of the evaporator 4 is heated by the high-temperature refrigerant liquid, the frost starts to melt quickly from the adhesion surface.

When the defrost operation is completed, for example, when a predetermined defrost operation time is reached, step a5
Then, the process proceeds to step a6, where the solenoid valve 8 is switched to the closed state, and the compressor 1 starts operating.

The high-temperature refrigerant liquid partially evaporates in the evaporator 4, but the liquid component is stored in the accumulator 5, so that there is no problem that the compressor 1 sucks the refrigerant liquid to perform liquid compression. However, when starting immediately after off-cycle defrosting, it is preferable to start while performing capacity control such as reducing the capacity by an unloading device or performing low-speed operation.

The operating sequence described above is shown in FIG. 3A. FIG. 3B shows the operation progress according to another embodiment of the present invention. The compressor 1 is stopped in response to a switching command to the off-cycle defrost operation, and the solenoid valve 8 is opened around the same time. The valve is operated, and the movement of the high-temperature refrigerant liquid to the evaporator 4 is performed by a pressure difference between high and low pressures. In this case, too, a considerable amount of refrigerant is required to reach pressure equilibrium. The liquid can flow smoothly, and the object of the present invention is sufficiently achieved.

[0019]

As described above, according to the present invention, during the off-cycle defrost, the high-temperature refrigerant liquid stored in the condenser 2 is bypassed to the expansion means 3 and guided to the evaporator 4, so that the evaporator 4 By temporarily heating the frost growing on the coils and fins of No. 4 from the adhering surface, the separation of the frost,
As a result, the defrosting time is shortened and the fluctuation range of the cooling temperature can be suppressed to a small value as compared with the case where the melting is performed by room air.

A high-temperature refrigerant liquid is used as a defrost heat source by a high-low pressure difference or by a pump action of the compressor 1 which operates for a predetermined time. Compared with the system, the increase in power consumption is far less, and an energy saving effect is also achieved.

[Brief description of the drawings]

FIG. 1 is a refrigeration circuit diagram of an air conditioner according to an embodiment of the present invention.

FIG. 2 is a control circuit block diagram of the air conditioner shown in FIG.

FIG. 3 is a time chart showing an operation state according to each embodiment of the present invention.

FIG. 4 is a flowchart illustrating an operation of each processing unit illustrated in FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Condenser 3 Expansion means 4 Evaporator 8 Solenoid valve

────────────────────────────────────────────────── (5) References JP-A-2-259379 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 47/02 F25D 21/00

Claims (1)

(57) [Claims] An indoor fan is formed by cyclically connecting a compressor, a condenser, an expansion means, an evaporator, and an accumulator by a refrigerant pipe. A refrigeration circuit that exchanges heat with the indoor air circulated by the refrigeration unit 7 and cools the condenser 2 with an outdoor fan causes frost adhering to the evaporator 4 during the cooling operation to stop the operation of the compressor 1 and stop the operation of the indoor fan 7. In the off-cycle defrost device which is removed during operation, the solenoid valve 8 connected in parallel with the expansion means 3 and closed during the cooling operation, and the pressure of the refrigerant pipe connecting the discharge port of the compressor 1 and the condenser 2 are reduced. A high-pressure switch 11 for detecting and outputting a signal indicating whether or not the detected pressure is equal to or higher than a predetermined value; and a signal output from the high-pressure pressure switch 11 for stopping the outdoor fan 6 at the start of off-cycle defrost. Means for opening the solenoid valve 8 when the detected pressure becomes equal to or higher than a predetermined value, and for guiding the high-temperature refrigerant liquid from the condenser 2 to the evaporator 4 by bypassing the expansion means 3. Defrost device.