JPH04324048A - Air conditioner - Google Patents

Abstract

PURPOSE:To maintain a cooling capacity and recover a heat exchange capacity of an indoor heat exchanger by detecting the formation of frost by means of a frost sensor in the indoor heat exchanger during cooling operation and halting the operation of a compressor during frost detection and continuing the operation of an indoor fan on the other hand. CONSTITUTION:When cooling operation is carried out during low open air temperature, the evaporation temperature of refrigerant in an indoor heat exchanger 6 is below the freezing temperature of moisture contained in the indoor air so that frost may be formed on the surface of heat exchange tubes 24 of the indoor heat exchanger 6 and the surface of fins. The frost formation proceeds to the middle stage of the indoor heat exchanger 6. When a temperature sensor 22 outputs an indoor temperature which has dropped to a defrosting setting temperature T1 and below, a control section 20 decides that there exists the danger of liquid compression and halts the operation of a compressor 9 and an outdoor fan 11, that is, the operation of outdoor equipment 2. Since the temperature of the indoor air is higher than the temperature of the indoor heat exchanger 6 at that time, the indoor heat exchanger 6 is defrosted by the indoor air supplied by an indoor fan 7 under continuous operation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner used to cool a predetermined area, such as a room, regardless of the season.

0002

[Prior Art] The demand for air conditioners is not limited to cooling in the summer, but has expanded to include room cooling in order to operate specific equipment such as computers within a constant temperature range. The room has a cooling load)
. In recent years, there have been cases in which the cooling operation of such rooms continues for 24 hours, regardless of the winter season when the outside temperature is low or day and night.

[0003] The air conditioners used for this type of cooling are similar to those used for summer cooling. For example, a computer room can be cooled using a separate type air conditioner (combining an indoor unit 1 installed indoors and an outdoor unit 2 installed outdoors) as shown in Fig. 7. is being carried out.

Specifically, the indoor unit 1 includes an indoor heat exchanger 6 (evaporator) in a main body 5 provided with an inlet 3 and an outlet 4; An accompanying indoor fan 7 (for example, a cross-flow fan) is provided to circulate indoor air through the indoor heat exchanger 6.

The outdoor unit 2 also includes a compressor 9, a compressor 9,
Outdoor heat exchanger 10 (condenser), this outdoor heat exchanger 1
An outdoor fan 11 and a capillary tube 12 (pressure reducing device) are provided to circulate outside air to the outdoor heat exchanger 10.
It is structured to allow outside air to pass through.

[0006]The indoor unit 1 and the outdoor unit 2 are connected to the refrigerant pipe 1.
3 to form a refrigeration cycle circuit 14. That is, an outdoor heat exchanger 10, a capillary tube 12, and an indoor heat exchanger 6 are sequentially connected to the discharge portion of the compressor 9 via a refrigerant pipe 13. Then, the cooling cycle of this refrigeration cycle circuit 14 (the high temperature and high pressure refrigerant gas from the compressor 9 is condensed in the outdoor heat exchanger 10, expanded to low temperature and low pressure in the capillary tube 12, and evaporated in the indoor heat exchanger 6). cycle), indoor, i.e. computer
The tarum is cooled by the heat of evaporation of the refrigerant.

By the way, according to the air conditioner for such applications, when operating in winter when the outside temperature is low, the condensing temperature decreases even if the room temperature is constant, as is clear from the characteristics shown in FIG. 6). As the condensation pressure decreases with this change in condensation temperature, the evaporation pressure also decreases, and the evaporation temperature of the indoor heat exchanger 6 decreases to below the condensation temperature in the indoor air. Therefore, when the evaporation temperature becomes low, moisture contained in the indoor air forms frost in the indoor heat exchanger 6.

However, this frost freezes over time and blocks the ventilation area between the fins of the indoor heat exchanger 6.
As shown in FIG. 9, as the amount of frost increases, a problem occurs in which the cooling capacity is reduced.

Moreover, frost formation not only reduces the cooling capacity but also causes damage to the compressor 9. That is, when frosting progresses until the entire ventilated area of the indoor heat exchanger 6 is frozen, no heat exchange is performed in the indoor heat exchanger 6, and the liquid refrigerant reaching the indoor heat exchanger 6 is Compressor 9 as is
is sucked in and causes liquid compression.

[0010] In order to improve this problem, conventional technology has been developed to prevent frost formation in the indoor heat exchanger 6 by controlling the rotation speed of the outdoor fan 7 to suppress the decrease in the condensing temperature. is proposed.

[0011]

[Problem to be Solved by the Invention] However, although this structure for controlling the rotation speed of the outdoor fan 7 can eliminate the trouble caused by frost formation, it requires a highly functional control system and is therefore expensive in terms of cost. There's a problem. Therefore, there is a high demand for technology that improves this point.

[0012] The present invention was made in view of these circumstances, and its purpose is to provide an air conditioner that can prevent troubles caused by frost formation through simple control. There is a particular thing.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the air conditioner of the present invention is capable of cooling operation by sequentially connecting an outdoor heat exchanger, a pressure reducing device, and an indoor heat exchanger to a compressor. a refrigeration cycle circuit provided in the indoor heat exchanger and activated during cooling operation of the refrigeration cycle circuit,
an indoor fan that circulates indoor air to the indoor heat exchanger;
a sensor provided in the indoor heat exchanger that detects frost formation on the indoor heat exchanger during cooling operation; and a sensor that stops the compressor upon detection of frost formation on the sensor and stops the operation of the indoor fan. The reason is that we have provided a means to continue the process.

[0014]

[Function] According to the air conditioner of the present invention, when the sensor detects that frost has formed on the indoor heat exchanger during cooling operation at low outside temperatures, the indoor fan continues to operate and compresses Machine operation stops.

Here, since the temperature of the indoor air (room temperature) is much higher than the temperature of the indoor heat exchanger, the indoor air blown by the above-mentioned indoor fan will remove the frost that has formed on the indoor heat exchanger. Thaw (defrost). During this defrosting,
Even if the compressor is not operating, the latent heat of the frost cools the room. Thereby, the heat exchange capacity of the indoor heat exchanger is restored while maintaining the cooling capacity.

[0016] Therefore, by simple control such as stopping the operation of the compressor and continuing operation of the indoor fan, it is possible to prevent troubles caused by frost formation, that is, a decrease in cooling capacity and damage to the compressor due to liquid compression. can.

[0017]

[Embodiment] Hereinafter, the present invention will be explained in the first embodiment shown in FIGS. 1 to 3.
This will be explained based on an example. In this example, the same components as those described in the "Prior Art" section are given the same reference numerals and their explanations are omitted, and in this section, different parts (essential parts of the invention) will be explained. Let me explain.

In this embodiment, a simple control system such as on/off control of the compressor 9 and continuous operation control of the indoor fan 7 is used to defrost the frost that has formed on the indoor heat exchanger 6 while ensuring the cooling capacity. They differ in some respects.

That is, 20 is a control section. Control unit 2
0 is composed of, for example, a microcomputer. A fan motor (not shown) of the indoor fan 7, a motor section (not shown) of the compressor 9, and a fan motor (not shown) of the outdoor fan 11 are connected to the control section 20. The control unit 20 operates the indoor fan 7, the compressor 9, and the outdoor fan 11 in accordance with the ON operation input from the operation unit 21 in the same way as in the past to maintain the indoor temperature at a predetermined temperature (cooling). driving).

Also connected to the control section 20 is a temperature sensor 22 provided in the indoor heat exchanger 6 and constituted by an element such as a thermistor. The temperature sensor 22 is provided on the outer peripheral portion of the heat exchange pipe 24, which corresponds to the middle between the inlet 6a and the outlet 6b of the indoor heat exchanger 6. By attaching the temperature sensor 22 at this position, it is possible to detect whether or not frost has formed up to the middle part of the indoor heat exchanger 6.

A storage section 25 is connected to the control section 20 . This storage unit 25 stores a defrosting set temperature T1 for starting defrosting operation and a defrosting return temperature T2 (T1 < T2) for returning from defrosting operation to cooling operation.

Further, the control unit 20 is configured to read the defrosting set temperature T1 from the storage unit 25 and compare it with the indoor heat exchanger temperature output from the temperature sensor 22 when the cooling operation is started. As a result of the comparison, if the indoor heat exchanger temperature is below the defrosting set temperature T1, it is determined that frost has formed on the indoor heat exchanger 6, which may cause excessive reduction in cooling capacity and liquid compression. Therefore, the compressor 9 and the outdoor fan 11 are set to stop operating during cooling operation. As a result, the cooling operation is switched to an operation in which only the indoor fan 11 operates, and the frost on the indoor heat exchanger 6 is melted by indoor air (indoor defrosting operation).

The control unit 20 is also set to compare the defrost return temperature T2 and the indoor heat exchanger temperature after the defrosting operation is started. As a result of the comparison, if the indoor heat exchanger temperature is equal to or higher than the defrosting return temperature T2, it is determined that defrosting has been completed, and the compressor 9 and outdoor fan 11, which had been stopped, are set to operate as specified. There is. This allows the defrosting operation to return to the cooling operation. Next, the operation of the air conditioner configured as described above will be explained based on the flowchart shown in FIG. 2 and the timing chart shown in FIG. 3.

[0024] The operation unit 21 is operated to turn on the cooling operation. In response to this ON signal, the control unit 20 turns on the compressor 9, the outdoor fan 11, and the indoor fan 7. Then, the refrigerant discharged from the compressor 9 is transferred to the outdoor heat exchanger 10 (condenser).
, the capillary tube 12, and the indoor heat exchanger 6 (evaporator) in order.

[0025] As a result, the room is cooled by the heat of evaporation of the refrigerant. That is, indoor air sucked in from the suction port 3 by the indoor fan 7 exchanges heat with the indoor heat exchanger 6 to become cold air, and this cold air is blown out from the air outlet 4 into the room.

When this cooling operation is performed at low outside temperatures (for example, in winter), the evaporation temperature of the refrigerant in the indoor heat exchanger 6 is lower than the condensation temperature of moisture in the indoor air, so the indoor heat exchange Frost forms on the surface of the heat exchange pipe 24 and the surface of the fins of the vessel 6. At this time, first, the air flow path between the fins on the upstream side (inlet 6a side) of the indoor heat exchanger 6 is blocked by frost formation. Then, it gradually advances from the upstream side (inlet 6a) to the downstream side (outlet 6 side) of the indoor heat exchanger 6 (because heat exchange is no longer performed due to the blockage of the air flow path).

When the frosting progresses to the middle stage of the indoor heat exchanger 6, the temperature sensor 22 detects the defrosting set temperature T1.
The indoor heat exchanger temperature that has decreased below is output. Then,
Based on the comparison result, the control unit 20 determines that there is a risk of excessive reduction in cooling capacity and further liquid compression, and turns off the operation of the compressor 9 and the outdoor fan 11, that is, the operation of the outdoor unit 2.
Stop.

At this time, since the temperature of the indoor air (room temperature) is much higher than the temperature of the indoor heat exchanger 6, the indoor air blown by the continuously operating indoor fan 7 causes the indoor heat exchanger 6 to The frost that has formed on various parts of the area will be melted. In other words, it is defrosted. During this indoor defrosting, the compressor 9 is not operating, but indoor cooling continues due to the latent heat of the frost. Thereby, the heat exchange capacity of the indoor heat exchanger 6 is recovered while maintaining the cooling capacity.

As a result of this defrosting, when the temperature sensor 22 outputs the indoor heat exchanger temperature that has exceeded the defrosting return temperature T2, the control section 20 determines that the defrosting has been completed based on the comparison result, and The machine 2 is restored, that is, the compressor 9 and the outdoor fan 11 are turned on (operated). As a result, the defrosting operation returns to the cooling operation, and the room is cooled again in the cooling cycle.

[0030] Therefore, by simple control such as stopping the operation of the compressor 9 and continuing operation of the indoor fan 11, it is possible to prevent troubles caused by frost formation, such as a decrease in cooling capacity due to frost formation or liquid compression. Can be done. Note that the present invention is not limited to the first embodiment described above, but may be implemented as a second embodiment shown in FIGS. 4 to 6.

In the second embodiment, in order to perform sufficient defrosting, a temperature sensor 30 for starting defrosting is provided at the same location as in the first embodiment, and a temperature sensor 31 for defrosting recovery is provided. is provided at the mouth constituting the inlet 6a of the indoor heat exchanger 6,
When the temperature of the intermediate part of the indoor heat exchanger 6 (indoor heat exchanger temperature) becomes below the defrosting set temperature T1, the cooling operation is switched to the indoor defrosting operation, and the mouth of the inlet 6a of the indoor heat exchanger 6 is switched. When the temperature (indoor heat exchanger temperature) becomes equal to or higher than the defrosting return temperature T2, the indoor defrosting operation is returned to the cooling operation. However, in the second embodiment, the same parts as in the above-described first embodiment are given the same reference numerals, and the explanation thereof will be omitted.

[0032] In the first embodiment and the second embodiment, the indoor defrosting operation is immediately returned to the cooling operation when the indoor heat exchanger temperature becomes equal to or higher than the defrosting return temperature T2, but the present invention is not limited to this. For example, the cooling operation may be resumed after a predetermined period of time has elapsed since the indoor heat exchanger temperature became equal to or higher than the defrosting return temperature T2. In this way, the indoor heat exchanger 6 can be reliably defrosted.

[0033]

[Effects of the Invention] As explained above, according to the present invention,
It is possible to defrost the frost that has adhered to the indoor heat exchanger while cooling the room using the latent heat of frost, and it is possible to restore the heat exchange capacity of the indoor heat exchanger while maintaining the cooling capacity.

[0034] Therefore, by simple control such as stopping the operation of the compressor and continuing operation of the indoor fan, it is possible to prevent troubles caused by frost formation, that is, a decrease in cooling capacity and damage to the compressor due to liquid compression. can

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an air conditioner according to a first embodiment of the present invention together with a control system.

FIG. 2 is a flowchart showing the defrosting process of the indoor heat exchanger during cooling operation at low outside temperatures in the same embodiment.

[Fig. 3] Timing chart showing the operating timing of the indoor fan and outdoor unit during cooling operation at low outside temperatures in the same embodiment.
to.

FIG. 4 is a diagram showing the configuration of an air conditioner according to a second embodiment of the invention together with a control system.

FIG. 5 is a flowchart showing the defrosting process of the indoor heat exchanger during cooling operation at low outside temperatures in the same embodiment.

[Fig. 6] Timing chart showing the operating timing of the indoor fan and outdoor unit during cooling operation at low outside temperatures in the same embodiment.
to.

FIG. 7 is a diagram showing the configuration of an air conditioner used for cooling a conventional computer room.

FIG. 8 is a diagram showing the relationship between condensation temperature and evaporation temperature with respect to changes in outside temperature.

FIG. 9 is a diagram showing the relationship between the cooling capacity and the progress of frost formation in the indoor heat exchanger.

[Explanation of symbols]

1... Indoor unit, 2... Outdoor unit, 6... Indoor heat exchanger, 7... Indoor fan, 9... Compressor, 10... Outdoor heat exchanger, 11...
Outdoor fan, 14... Refrigeration cycle circuit, 20... Control unit,
22...Temperature sensor.

Claims (1)

[Claims] [Claim 1] The compressor includes an outdoor heat exchanger, a pressure reduction device,
a refrigeration cycle circuit capable of cooling operation, which is formed by sequentially connecting indoor heat exchangers; an indoor fan for circulating air; a sensor provided on the indoor heat exchanger to detect frost formation on the indoor heat exchanger during cooling operation; and a sensor for stopping the compressor upon detection of frost formation by the sensor; An air conditioner comprising means for continuing operation of the indoor fan.