JPH04340072A - Off-cycle defrosting device - Google Patents

Abstract

PURPOSE:To decrease defrosting time by using a part of high temperature refrigerant solution as a defrosting heat source during off-cycle defrosting. CONSTITUTION:A solenoid valve 8 is connected in parallel with an expansion means 3 in a refrigerating circuit. This solenoid valve 8 is opened during off- cycle defrosting, so that high temperature refrigerant solution from a condenser 2 side is guided to an evaporator 4. A compressor 1 stops with delay of one to two seconds after the solenoid valve 8 is opened and smoothly moves the high temperature refrigerant solution.

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 device that utilizes a high-temperature refrigerant liquid in a refrigeration circuit as a defrost heat source to speed up the start-up of defrost.

0002

[Prior Art] In an air conditioner, which is generally referred to as a cooling device in a broad sense that includes a refrigerator, the compressor is stopped and the fan of the indoor unit is turned on when the temperature of the area to be air conditioned, such as the refrigerator room, is 2°C or higher. Off-cycle defrost is often used, which uses the amount of heat held by the air in the air conditioned area as a defrost heat source, and switches to defrost operation at predetermined intervals, or uses a detector to detect the amount of frost. In most cases, automatic defrost operation is performed, such as defrost operation based on a command from the driver.

0003

[Problem to be solved by the invention] If the interval setting for switching to defrost operation is not appropriate, or the humidity of refrigerated items is extremely high, or if the frost detector does not operate properly, Although it is inevitable that severe frost will form, in the case of off-cycle defrost, since the frost that has adhered to the surface is melted from the surface, the defrost time is significantly longer, the room temperature fluctuates significantly, and the temperature of refrigerated items Problems such as quality deterioration occur.

[0004] An object of the present invention is to provide an off-cycle defrost device that can shorten defrost time by using a portion of the high-temperature refrigerant liquid as a heat source for defrosting at the beginning of off-cycle defrost operation. It is in.

[0005]

[Means for Solving the Problems] The present invention provides a solenoid valve 8 connected in parallel to an expansion means 3 in a refrigeration circuit, and a solenoid valve 8 connected in parallel to an expansion means 3 in a refrigeration circuit.
is opened during off-cycle defrosting to allow the high temperature refrigerant liquid from the condenser 2 side to bypass the expansion means 3 and flow into the evaporator 4.
This off-cycle defrosting device is characterized in that it includes a means for guiding the compressor 1 to the compressor 1 and stopping the compressor 1 after a predetermined time has elapsed since the electromagnetic valve 8 is opened.

[0006]

[Operation] According to the present invention, during off-cycle defrosting,
For example, in the initial stage, the high-temperature refrigerant liquid on the condenser 2 side can be sent to the evaporator 4 by simply opening the solenoid valve 8, and this high-temperature refrigerant liquid flows through the heat transfer tubes and fins of the evaporator 4. For heating, frost is melted from the heat transfer surface side, promoting frost melting and leaving the heat transfer tubes and fins faster, thereby shortening the defrost time.

Furthermore, by operating the compressor 1 for a predetermined period of time, for example, several seconds after the solenoid valve 8 opens, the high-temperature refrigerant liquid can be moved smoothly and in large quantities to the evaporator 4 side. This increases the frost melting effect and further shortens the defrost time.

[0008]

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

The opening degree of the expansion valve 3 is automatically adjusted so that the degree of superheating at the coil outlet of the evaporator 4 is a constant value.A solenoid valve 8 is connected in parallel to the expansion valve 3. . Further, a high-pressure switch 11 is branch-connected to a high-pressure gas pipe that connects the discharge port of the compressor 1 and the condenser 2 .

FIG. 2 is a control circuit block diagram of the above harmonizing device, FIG. 3 is a time chart showing the operating state of each embodiment of the present invention, and FIG. 4 is a diagram showing the operation of the processing section 9 shown in FIG. It is a flowchart explaining. The processing unit 9 includes a timer circuit 10, and switches the cooling operation to off-cycle defrost operation based on a preset interval, and when the preset defrost operation time is reached or a defrost end signal is sent from a defrost detector (not shown). The off-cycle defrost operation is switched to the cooling operation at the earliest of the following.

[0011] The mode of off-cycle defrost operation is as described below.

[0012] When frost adheres to the coil of the evaporator 4 during the cooling operation and reaches a limit amount, step a1 is reached and the cooling operation is switched to a defrost operation. In this state indicated by time t2 in FIG. 3, the compressor 1 remains in operation, and the process immediately moves to the next step a2, where the outdoor fan 6 is stopped.

By stopping the outdoor fan 6, heat radiation is suppressed in the condenser 2, so the pressure and temperature inside the coil rise, a heat storage operation is performed, and at time t3 in FIG.
When the high pressure reaches the predetermined value or higher, step a3
Then, the high pressure switch 11 outputs an off signal.

[0014] In response to the output of this off signal, the process moves 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 remaining in the condenser 2 is pumped by the compressor 1 for 1 to 2 seconds, and
Due to the existence of a pressure difference between the condenser 2 side and the evaporator 4 side, the liquid bypasses the expansion valve 3 and is fed into the coil of the evaporator 4 through the low-pressure liquid pipe.

[0015] As the coil of the evaporator 4 is heated with the high temperature refrigerant liquid, frost quickly begins to melt from the surface to which it is attached.

[0016] When the predetermined defrost operation time is reached and the defrost ends, step a5
Then, the process moves to step a6, where the solenoid valve 8 is switched to close and the compressor 1 starts operating.

Although a portion of the high-temperature refrigerant liquid evaporates in the evaporator 4, the liquid portion is stored in the accumulator 5, so problems such as the compressor 1 sucking the refrigerant liquid and compressing the liquid do not occur. However, when starting immediately after off-cycle defrost, it is preferable to start while controlling the capacity by lowering the capacity with an unloading device or operating at a low speed.

The operation progress described above is shown in FIG. 3A. FIG. 3B shows the operation progress according to another embodiment of the present invention, in which the compressor 1 is stopped in response to a command to switch to off-cycle defrost operation, and the solenoid valve 8 is opened immediately after this. The valve is activated, and the movement of the high-temperature refrigerant liquid to the evaporator 4 is carried out by the pressure difference between high and low pressures, and even in this case, a considerable amount of refrigerant is lost before the pressure is balanced. The liquid can be made to flow smoothly, and the object of the present invention is fully achieved.

[0019]

As described above, according to the present invention, the high-temperature refrigerant liquid stored in the condenser 2 is bypassed to the expansion means 3 and guided to the evaporator 4 during off-cycle defrosting. By temporarily heating the frost growing on the coils and fins of No. 4 from the adhesion surface, the frost can be removed.
As a result, the defrost time is shortened and the fluctuation range of the cooling temperature can be suppressed to a small extent as the melting is significantly accelerated compared to when using indoor air.

[0020] Also, hot gas defrosting is a method in which high-temperature refrigerant liquid is used as a defrost heat source by the pressure difference between high and low pressures or by the pumping action of the compressor 1 that operates for a predetermined period of time. Compared to conventional methods, the increase in power consumption is far less, and energy-saving effects can also be achieved.

[Brief explanation of the drawing]

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. 1;

FIG. 3 is a time chart showing operating conditions according to each embodiment of the present invention.

FIG. 4 is a flowchart illustrating the operation of each processing unit shown in FIG. 2;

[Explanation of symbols]

1 Compressor 2 Condenser 3. Expansion means 4 Evaporator 8 Solenoid valve

Claims (1)

[Claims] Claim 1: A solenoid valve 8 connected in parallel to the expansion means 3 in the refrigeration circuit, and a solenoid valve 8 opened during off-cycle defrost to cause the high temperature refrigerant liquid from the condenser 2 side to bypass the expansion means 3. The off-cycle defrosting device is characterized in that it includes means for guiding the compressor 1 to the evaporator 4 and for stopping the compressor 1 after a predetermined time has elapsed after the electromagnetic valve 8 opens.