JPH0245736Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to an improvement in an air conditioner comprising a refrigeration cycle capable of cooling and heating operation using an electrically conductive expansion valve.

[Technical background of the invention and its problems]

Recently, air conditioners have been developed that use electric expansion valves to configure a refrigeration cycle capable of heating and cooling operation, allowing the refrigeration cycle to be controlled using a variety of signal media. has been done.

As shown in Fig. 1, the throttling operation is controlled by the controller e between the indoor heat exchanger c and the outdoor heat exchanger d of the refrigeration cycle b, which is equipped with a four-way valve a for switching between cooling and heating. The cooling and heating operations are controlled according to the temperature information inputted to the control unit e through the temperature sensor g.

By the way, in an air conditioner capable of cooling and heating, in order to remove frost generated on the outdoor heat exchanger d during the heating operation, a so-called defrosting operation is performed in place of the cooling operation during the heating operation.

When an electric expansion valve f is used for this defrosting operation, normally, as shown in Fig. 2, the electric expansion valve f remains almost the same during heating operation and defrosting operation. Control is adopted to allow the user to enter.

However, with this technique of switching from heating operation to defrosting operation at the same opening degree, even when defrosting operation is performed, as shown in Fig. 3, the indoor heat exchanger d
During heating operation, a large amount of liquid phase refrigerant exists inside the outdoor heat exchanger d, resulting in an extremely large heat capacity, and the liquid phase refrigerant largely covers the inner surface of the outdoor heat exchanger d, reducing the heat exchange performance for defrosting. There is an inconvenience in letting it happen. For this reason, the temperature rise for defrosting in the outdoor heat exchanger d is slow, and the defrosting time is unavoidably prolonged.

[Purpose of invention]

This invention was made in view of the above-mentioned circumstances, and its purpose is to provide an air conditioner that can shorten the defrosting time.

[Summary of the idea]

This invention uses the control unit to control the throttle opening of the electric expansion valve to be smaller than the throttle opening of the heating operation for a certain period of time during the heating operation immediately before starting the defrosting operation. The purpose is to start defrosting operation in a state where the amount of liquid phase refrigerant is reduced, thereby dramatically increasing heat exchange performance and shortening the defrosting time by increasing the temperature quickly.

[Example of idea]

This invention will be explained below based on embodiments shown in the drawings. FIG. 4 shows an embodiment of this invention, in which 1 is a compressor, 2 is a four-way valve, 3 is an outdoor heat exchanger, and 4 is an indoor heat exchanger. Each of these devices is sequentially connected through a refrigerant circulation path 5. Moreover, an electric expansion valve 6 is provided between the outdoor heat exchanger 3 and the indoor heat exchanger 4, and constitutes a refrigeration cycle 7 capable of air-conditioning/heating operation. Note that 7a indicates a cooling capillary reach tube provided in parallel to the electric expansion valve 6. On the other hand, in the figure, 8 indicates a control section that controls the electric expansion valve 6. and,
The output side of this control section 8 is connected to the electric expansion valve 6 via a signal line 9a, and the input side of the control section 8 is connected to a temperature sensor 10 provided on the outlet side of the pressure machine 1.
is connected to the temperature sensor 10 via the signal line 9b.
Based on the temperature of the refrigeration cycle that is input to the control unit 8 from the controller 8, the electric expansion valve 6 is controlled to be throttled as desired. Here, to explain the electric expansion valve 6, for example, as shown in FIG.
A valve body 13 is provided which communicates with the valve body 13 through the valve body 13, and a valve stem 15 supported by a diaphragm 14 so as to be openable and closable with respect to the valve port portion 12 is installed inside the valve body 13, and a ball is provided on the head side of the valve body 12. 16b, a driver 16c screwed together so as to be freely advanced and retractable, and a stepping motor 16 that moves the valve stem 15 forward and backward through the diaphragm 14 are installed in this order, and a signal is output from the control section 8. By doing so, the stepping rotation of the output shaft 16a of the stepping motor 16 causes the driver 16c and the ball 16b to advance and retreat by rotating the driver, thereby opening the valve port portion 12 to a required flow area through the diaphragm 14 and the valve stem 15. , and can be closed.

In addition, when switching from heating operation to defrosting operation, the control unit 8 controls the throttle opening of the electric expansion valve 6 for a certain period of time in the heating operation immediately before entering the defrosting operation. For example, the opening degree is set to be smaller than the minimum opening degree.

Next, the operation of the air conditioner configured as described above will be explained.

When performing heating, the four-way valve 2 is switched to the heating side and the compressor 1 is operated.
four-way valve 2, indoor heat exchanger 4, electric expansion valve 6,
A heating cycle is configured in which the refrigerant sequentially flows through the outdoor heat exchanger 3 as shown by the broken line, and heating is performed. Note that when performing cooling, if the four-way valve 2 is switched to the cooling side and the compressor 1 is operated, cooling will be performed according to the configuration of the cooling cycle shown by the solid line.

During this heating operation, frost builds up on the outdoor heat exchanger 3, and when a defrosting operation is performed to eliminate this frost, the four-way valve 2 switches to the cooling side as frost occurs, and the defrosting operation begins. It turns out.
When this defrosting operation is switched, conventionally the heating operation is switched to the defrosting operation while the throttle opening of the electric expansion valve 6 remains almost the same, and the cold phase refrigerant that exists in a large amount in the outdoor heat exchanger 3 is used. However, as shown in Figure 6, this design lowers the heat exchange performance during defrosting operation and requires a long time for defrosting.However, in this invention, as shown in Figure 6, the electric The expansion valve 6 is throttled (throttle opening is smaller) than the throttle opening when in the heating operation state according to a command from the control unit 8, and the heating operation is performed for a certain period of time, for example, at the minimum opening. After that, defrosting operation begins. Therefore, in the outdoor heat exchanger 3 immediately before starting the defrosting operation, as shown in FIG. 7, the liquid phase refrigerant present in the outdoor heat exchanger 3 is reduced, and the Temperature rises. In this way, with the refrigerant in the outdoor heat exchanger 3 being reduced, defrosting operation is started using the refrigerant with a discharge temperature higher than usual, and the efficiency of the outdoor heat exchanger 3 is reduced due to the rapid temperature rise. Good high heat exchange performance can be obtained. Therefore, the defrosting time can be shortened. According to the experiment, as shown in FIG. 8, the temperature change of the outdoor heat exchanger 3 after defrosting started was found to be higher than the temperature rise transition A caused by the conventional electric expansion valve 6 control. The temperature rise transition B caused by the control of throttling the electric expansion valve 6 immediately before starting the defrosting operation clearly showed a rapid temperature rise.

In addition, in the above-mentioned embodiment, this invention was applied to a refrigeration cycle equipped with an electrically operated expansion valve with an additional capillary tube for cooling, but a reversible electrically operated expansion valve that independently performs throttling operation during cooling and heating is also applicable. Needless to say, the present invention can also be applied to a refrigeration cycle equipped with a valve.

Furthermore, in the above-described embodiment, the electric tension valve is simply operated based on the temperature of the refrigeration cycle to control the heating and cooling cycle, but as shown in FIG. By providing a time constant circuit 22 composed of a resistor 20 and a capacitor 21, the responsiveness of the electric expansion valve 6 can be set arbitrarily by changing the capacitance of the resistor 20 and capacitor 21. It is possible to prevent periodic fluctuations in the refrigeration cycle state and avoid a decrease in refrigeration capacity.

[Effect of idea]

As explained above, according to this invention, the aperture opening of the electric expansion valve is controlled to be small for a certain period of time during the heating operation immediately before starting the defrosting operation. Defrosting operation begins with a refrigerant with a discharge temperature higher than usual in a purified state in which the existing liquid phase refrigerant is reduced, and the heat exchange performance as an outdoor heat exchanger during defrosting operation is dramatically improved. will be increased.

Therefore, it becomes possible to eliminate frost formation by quickly increasing the temperature, and the defrosting time can be shortened.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an air conditioner employing a conventional electric expansion valve, and Fig. 2 is a diagram showing the opening degree of the electric expansion valve when switching from heating operation to defrosting operation. Fig. 3 is a sectional view showing the presence of refrigerant in the outdoor heat exchanger before starting the defrosting operation, Fig. 4 is a configuration diagram showing an air conditioner according to an embodiment of this invention, and Fig. 5 Figure 6 is a cross-sectional view showing the structure of the electric expansion valve, Figure 6 is a line diagram showing the opening status of the electric expansion valve just before starting defrosting operation, and Figure 7 is the outdoor heat before defrosting operation. Figure 8 is a cross-sectional view showing the presence of refrigerant in the exchanger, Figure 8 is a diagram showing the temperature rise transition of the outdoor heat exchanger during defrosting operation in comparison with the conventional temperature rise transition, and Figure 9 is a diagram showing the temperature rise transition of the outdoor heat exchanger during defrosting operation. It is a block diagram which shows the air conditioner of another Example of this invention. 3...Outdoor heat exchanger, 4...Indoor heat exchanger, 6...Electric expansion valve, 8...Control unit, 10...
...temperature detector.

Claims (1)

[Scope of utility model registration request] A refrigeration cycle capable of air-conditioning and heating is configured by installing an electric expansion valve between an outdoor heat exchanger and an indoor heat exchanger, and the electric expansion valve is throttled during heating operation just before starting defrosting operation. An air conditioner characterized by comprising means for reducing the opening degree for a certain period of time compared to the opening degree for heating operation.