JPS63243648A - Heat pump air conditioner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Application The present invention relates to a heat pump type air conditioner that uses air as a heat source, and more specifically to a defrosting control device that melts frost that adheres to an outdoor heat exchanger when the outside air temperature is low. It is related to.

Conventional technology Most defrosting methods for outdoor heat exchangers in conventional air source heat pump air conditioners use a cooling cycle by switching a four-way valve.
It uses a reverse cycle defrosting system in which the outdoor heat exchanger is used as a condenser and the indoor heat exchanger is used as an evaporator, and the indoor fan was stopped at this time to prevent cold drafts. In this method, there is basically little refrigerant circulation and it is not possible to expect much increase in compressor input, so the defrosting time becomes longer and the indoor fan stops for several minutes during defrosting operation, resulting in a lack of heating sensation.
From the user's point of view, comfort is impaired, and even after the four-way valve is switched to return to heating operation after defrosting operation, it takes time for the temperature of the indoor heat exchanger to rise. It wasn't possible.

In recent years, in place of the reverse cycle defrosting system which has these drawbacks, the four-way valve is kept as it is in heating operation even during defrosting operation.
A hot gas bypass defrosting system allows part of the discharged gas from the compressor to flow through the indoor heat exchanger to maintain some heating capacity, while the rest of the discharged gas is guided to the inlet of the outdoor heat exchanger for defrosting. It has been proposed (for example, "Japan Refrigeration Association Lecture Proceedings", 5ss-tt, P53).

An example of the above-mentioned conventional heat pump type air conditioner will be described below with reference to the drawings.

FIG. 3 shows a refrigeration cycle diagram of a conventional heat pump type air conditioner. In the figure, 1 is a variable frequency compressor whose capacity can be controlled, 2 is a four-way valve, 3 is an indoor heat exchanger, and 4 is a variable frequency compressor with variable capacity control.
5 is an outdoor heat exchanger, 6 is a bypass circuit FLLr, and 7 is an on-off valve provided in the bypass circuit. During normal heating operation, the two-way valve 7 is closed to form a heating cycle, but when frost forms on the outdoor heat exchanger 5 when the outside air temperature is low, the heating capacity decreases and a defrosting operation becomes necessary. At the same time as the valve 7 is opened, the operating frequency of the compressor 1 is suddenly raised to the maximum operating frequency, and a portion of the high temperature discharged gas is guided to the outlet side of the outdoor heat exchanger 5 via the hot gas bypass circuit. At the same time, the remainder of the high-temperature discharged gas is passed through the four-way valve 2, the indoor heat exchanger 3, and the electromagnetic expansion valve 4 in the same way as during the heating operation, and the heating operation continues.
At the outlet side of the refrigerant, the refrigerant is joined with the refrigerant branched on the high pressure side. With the above configuration, the refrigerant defrosts the outdoor heat exchanger 5 and then returns to the variable frequency compressor 1 via the four-way valve 2 to complete the defrosting cycle.

Problems to be Solved by the Invention However, the above configuration has the following problems. FIG. 4 shows the operating frequency of the compressor 1 immediately before the defrosting operation, during the defrosting operation, and after the defrosting operation is completed. As shown in the figure, at the same time as the defrosting operation is started, the operating frequency of the compressor 1 increases at once from the operating frequency immediately before starting the defrosting operation to the maximum operating frequency. At the same time, the two-way valve 7 opens and a part of the high-temperature discharged gas is bypassed to the outlet side of the outdoor heat exchanger 5 through the hot gas bypass circuit, so the high-low pressure difference instantly disappears as shown in Figure 5. As a result, the refrigerant foams at low pressure and the compressor oil is discharged to the outside of the compressor 1 together with the refrigerant, causing the oil level to drop rapidly, but at the same time, the frequency of the compressor 1 also rises to its maximum frequency, causing the oil level to further decrease. This has the disadvantage that the life and reliability of the compressor are significantly reduced. Furthermore, when the frequency of the compressor 1 drops from the maximum frequency to the rated frequency (usually around 60 Hz) to hasten the end of the defrosting operation, the difference in high and low pressures decreases, so the refrigerant foams at a low pressure and is compressed as described above. The machine oil is discharged out of the compressor 1 along with the refrigerant, and the oil level drops rapidly, but at the same time, after the defrosting operation is finished, the operating frequency of the compressor 1 is raised again to around the maximum frequency, so the oil level decreases further. This had the disadvantage that the life and reliability of the compressor were significantly reduced.

In view of the above problems, the present invention aims to improve compressor reliability by ensuring a compressor oil level during defrosting of an air conditioner.

Means for Solving the Problems In order to solve the above problems, the heat pump type air conditioner of the present invention includes a compressor, a western valve, an indoor heat exchanger, a throttling device with variable throttling amount, an outdoor heat exchanger, etc. A refrigeration cycle is constructed by sequentially connecting the pipes in an annular manner through piping, with piping leading from the compressor to the indoor heat exchanger, which is at high pressure during heating operation, and piping from the outdoor heat exchanger, which is at low pressure during heating operation, to the compressor. A bypass circuit is formed to connect the piping leading to the pipe, and a single closing valve is provided in the bypass circuit, and when the defrosting operation of the outdoor heat exchanger starts, the throttling amount of the throttling device is made smaller than the throttling amount during the heating operation. Furthermore, the on-off valve is opened, the frequency of the compressor is increased stepwise during defrosting, and when the defrosting operation is completed, the compressor is stopped for a certain period of time and then the heating operation is started again.

Effect: With the above configuration, the present invention does not raise the compressor operating frequency all at once to the maximum frequency when defrosting operation starts, but increases it in stages, so it is possible to prevent sudden oil splashing immediately after defrosting starts, and to improve compression. The liquid level inside the aircraft can also be ensured. Furthermore, at the same time as the defrosting operation ends, the compressor operating frequency is not raised to near the maximum frequency, but the compressor is stopped for a certain period of time and then the heating operation is restarted, which prevents sudden oil splashing after the defrosting operation is completed. This can result in improved compressor life and reliability.

EXAMPLE Hereinafter, a heat pump type air conditioner according to an example of the present invention will be described with reference to the drawings. Since the refrigeration cycle is the same as the conventional example, it will be explained with reference to FIG. 3. In the figure, 1 is a compressor, 2 is a four-way valve, 3 is an indoor heat exchanger, and 4 is an electric expansion valve 5 whose valve opening can be varied by electromagnetic force.
6 is an outdoor heat exchanger, 6 is a bypass circuit, 7 is an on-off valve provided in the bypass circuit, and 8 is an indoor fan that blows the air that has exchanged heat with the indoor heat exchanger 3 into the room. 9 is a transistor motor that drives this indoor fan. This is a variable speed drive motor. Further, 10 is an indoor temperature detection element that detects the temperature of the indoor heat exchanger 5, 11 is an outdoor temperature detection element that detects the temperature of the outdoor heat exchanger 5, and 12 is the indoor temperature detection element 10. This is a control circuit that receives the temperature symbol of the outdoor temperature detection element 11 and controls the electric expansion valve 4, the on-off valve 7, and the drive motor 9. Then, the compressor 1, four-way valve 2, indoor heat exchanger 3, electric expansion valve 4, and outdoor heat exchanger 5 are sequentially connected in an annular manner, and the discharge side of the compressor 1 and the outdoor heat exchanger 5 are operated for heating. A bypass circuit 6 with an on-off valve 7 is provided in the middle of the bypass circuit.

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

During normal heating operation, the on-off valve is closed, and the refrigerant flows through the compressor 1, four-way valve 2, indoor heat exchanger 3, electric expansion valve 4, outdoor heat exchanger 5, and four-way valve 2. The refrigerant returns to the compressor 1 to form a heating cycle, and no refrigerant flows through the bypass circuit 6.

However, when the outside temperature is low, frost forms on the outdoor heat exchanger 5, and when the temperature signal of the outdoor temperature detection element 11 drops to the set value, the control circuit 12 issues a command to start defrosting, and the four-way valve 2 remains in the same state. Open the on-off valve 7 and turn the high temperature discharge gas on to point a.
', and part of the water is directly sent to the indoor heat exchanger 3.
The remaining part is guided to the outlet side of the outdoor heat exchanger 5, and the valve opening of the electric expansion valve 4 is slightly opened to make the throttle amount almost zero, and the rotation speed of the drive motor 9, that is, the rotation speed of the indoor fan 8, is reduced. Defrosting begins by lowering the air volume blown into the room compared to during heating operation.

FIG. 1 is a Mollier diagram showing a cycle during defrosting operation of an embodiment of the heat pump air conditioner shown in FIG.

Symbols '-e' shown in the figure correspond to those shown in FIG. That is, during defrosting operation, the high-temperature discharge gas that flows directly from point a' to the indoor heat exchanger 3 has a relatively low temperature (approximately 3
It condenses and radiates heat at a temperature of 0 to 40 degrees Celsius), moves to point b', rotates the indoor fan at low speed, and continues heating operation. The pressure is reduced by a slight restriction in the piping and the electric expansion valve 4 on the way, and the pressure reaches point C', which flows into the outdoor heat exchanger 5, and then the temperature reaches about 0, which is the melting temperature of frost.
'C condenses and radiates heat to defrost and reach point ♂. The enthalpy difference of the refrigerant used for defrosting at this time is ΔIdef=Ic'
-1d', and the state of the refrigerant flowing into the outdoor heat exchanger 5 is already two-phase as shown at point C'. By the way, the enthalpy difference of the refrigerant used for indoor heating is 1 m'-lb' if heat loss during the heating is ignored.

On the other hand, the remaining high-temperature discharged gas is led to the outlet side of the outdoor heat exchanger 5. After the maenthalpy change, it joins and mixes with the liquid-rich refrigerant that has flowed through the main circuit to form a point e', and the compressor 1 is inhaled. At this point e', although the refrigerant is in a two-phase state, the dryness x/e of the refrigerant is large and the liquid content is small, so liquid return and liquid compression can be reduced or substantially avoided.

Furthermore, since the refrigerant flowing into the outdoor heat exchanger 5 during defrosting operation is basically in a two-phase state, the refrigerant temperature, that is, the surface temperature of the outdoor heat exchanger 5, is also constant, and there is no unevenness in the surface temperature. Therefore, uniform defrosting can be achieved.

FIG. 2 shows the operating frequency of the compressor 1 immediately before the defrosting operation, during the defrosting operation, and after the defrosting operation is completed. As shown in the figure, simultaneously with the start of defrosting, the frequency of the compressor 1 is raised stepwise from the operating frequency immediately before the start of defrosting, rather than being raised all at once to the maximum operating frequency. As a result, the two-way valve 7 opens immediately after the start of defrosting, the high-low pressure difference disappears instantly, the refrigerant foams at low pressure, the compressor oil is discharged out of the compressor 1 together with the refrigerant, and the oil level drops rapidly, but at the same time Since the frequency of the compressor 1 does not increase all at once to the maximum frequency, but increases in stages, further reduction in the oil level can be prevented, and the reliability of the compressor can be significantly improved. In addition, Δ10 and Δf shown in Fig. 2 are as follows from the experimental results: Δ10≠20-30 seconds,
It is desirable that Δf≠5Hχ. Furthermore, the operating frequency of the compressor 1 is not raised to near the maximum frequency at the same time as the defrosting operation is completed, and the compressor 1 is stopped for a certain period of time and then the heating operation is performed again, so that oil suddenly jumps out after the defrosting operation is completed. This makes it possible to improve compressor life and reliability. Note that Δt shown in Figure 2 is at least 3 according to experimental results.
It is about 0 seconds. Furthermore, although the present invention has been described using an electric expansion valve 4 which uses electromagnetic force as a driving source and whose valve speed is variable as the best mode of the throttle device, it may be configured using a plurality of throttles such as capillaries, and can be changed as needed. Alternatively, a bimetal, a shape memory alloy, or the like may be used as means for roughly varying the valve opening degree.

Effects of the Invention As described above, the heat pump type air conditioner of the present invention has a compressor, a four-way valve, an indoor heat exchanger, and a first air conditioner with a variable throttle amount.
A refrigeration cycle is formed by sequentially connecting a throttling device, an outdoor heat exchanger, etc. with piping in a ring shape, and the piping from the compressor to the indoor heat exchanger, which is at high pressure during heating operation, and the piping from the indoor heat exchanger, which is at low pressure during heating operation, A bypass circuit is formed from the outdoor heat exchanger to a pipe leading to the compressor, and an on-off valve is provided in the bypass circuit, so that when the outdoor heat exchanger starts defrosting operation, the throttling amount of the throttling device is adjusted to the heating temperature. The amount of throttling is smaller than that during operation, the on-off valve is opened, and the compressor is stopped for a certain period of time at the end of defrosting operation and heating operation is resumed. A part of the high-temperature discharged gas is allowed to flow through the compressor to enable continued heating operation, reducing a large amount of liquid returning to the compressor and liquid compression, and ensuring the oil level in the compressor, resulting in highly reliable pumping over a long period of time. It has various advantages such as being able to perform frost operation.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram plotting the cycle during defrosting operation of a heat pump type air conditioner in an embodiment of the present invention on a Mollier diagram, and Fig. 2 is a frequency change during defrosting operation of the air conditioner. Figure 3 is a refrigeration cycle diagram, Figure 4 is an explanatory diagram showing
The figure is an explanatory diagram showing frequency changes during conventional defrosting operation.
The figure is an explanatory diagram showing changes in high and low pressure during defrosting operation. 1... Compressor, 2... Four-way valve, 3...
...Indoor heat exchanger, 4...Electric expansion valve, 5.
...Outdoor heat exchanger, 6...Bypass circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure L'jD' Figure 2 11, Z;

Claims (2)

[Claims] (1) A variable frequency compressor, a four-way valve, an indoor heat exchanger, a throttling device with different throttling amounts during heating operation and defrosting operation, an outdoor heat exchanger, etc. are sequentially connected in a circular manner with piping to form a refrigeration cycle. forming a bypass circuit connecting piping from the compressor to the indoor heat exchanger that becomes high pressure during heating operation and piping from the outdoor heat exchanger to the compressor that also becomes low pressure during heating operation, An on-off valve is provided in the bypass circuit, and when the outdoor heat exchanger starts defrosting operation, the throttling amount of the throttling device is made smaller than the throttling amount during heating operation,
The heat pump type air conditioner opens the on-off valve, lowers the air volume of the indoor fan compared to during heating operation, and changes the air volume of the indoor fan during defrosting operation. (2) A patent claim using a variable frequency compressor that increases the frequency of the variable frequency compressor in stages during defrosting operation, and when the defrosting operation ends, the compressor is stopped for a certain period of time and then heating operation is performed again. A heat pump air conditioner according to item 1.