JPH0373794B2 - - Google Patents

Description

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

Conventional technology The defrosting method of the outdoor heat exchanger of conventional air source heat pump air conditioners is mostly reversed in that the four-way valve is switched to create a cooling cycle, and the outdoor heat exchanger is used as a condenser and the indoor heat exchanger is used as an evaporator. The cyclic defrosting method was used, and the indoor fan was stopped at this time to prevent cold drafts.

With 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, so there is a lack of heating sensation and comfort. This is not satisfactory from the user's point of view, as it takes time for the temperature of the indoor heat exchanger to rise even after the four-way valve switches after defrosting operation and returns to heating operation. It wasn't something.

In recent years, in place of the reverse cycle defrosting method which has such drawbacks, the four-way valve is kept as it is in heating operation during defrosting operation, and part of the gas discharged from the compressor is passed to the indoor heat exchanger to A hot gas bypass defrosting method has been proposed that defrosts the remaining discharged gas by guiding it to the inlet of the outdoor heat exchanger while maintaining the heating capacity (for example, "Japan Refrigeration Association Lecture Proceedings",
S59−11, P.53).

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

FIG. 4 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, 4 is an electric expansion valve whose valve opening can be varied, 5 is an outdoor heat exchanger,
6 is a hot gas bypass circuit, and 7 is a two-way valve. The hot gas bypass circuit 6 connects the discharge side of the variable frequency compressor 1 to a pipe that becomes the inlet side during heating operation of the outdoor heat exchanger 5, and includes a two-way valve 7 in the middle.

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. The diverter valve 7 is opened to guide most of the high temperature discharged gas to the inlet side of the outdoor heat exchanger 5 via the hot gas bypass circuit 6. 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 electric expansion valve 4 in the same way as during heating operation, and a slight heating operation is continued, and the inlet side of the outdoor heat exchanger 5 is At a certain point c, most of the refrigerant branched off on the high pressure side is merged with the refrigerant. After this combined refrigerant defrosts the outdoor heat exchanger 5 with its own condensation heat, it returns to the variable frequency compressor 1 via the four-way valve 2 and completes the defrosting cycle.

Problems to be Solved by the Invention However, the above configuration has the following problems. FIG. 5 shows a Mollier diagram of the conventional heat pump type air conditioner shown in FIG. 4 during defrosting operation. Symbols a to e shown in the figure correspond to those shown in FIG.

That is, during defrosting operation, the refrigerant branched at point a on the compressor discharge side joins at point c on the inlet side of the outdoor heat exchanger 5, and this point c exists in a high-temperature superheated region.
Here, the refrigerant has an enthalpy of i _c . After condensation, that is, after defrosting, the refrigerant state changes to a point d with a high liquid content in the two-phase region, and reaches a point e after pressure loss.
Since this refrigerant having a dryness x _e with a high liquid content is directly sucked into the variable frequency compressor 1, a considerable amount of liquid compression is performed. This poses a major problem in terms of compressor reliability, considering the number of defrosting operations during the annual heat pump season. Furthermore, from the usage status of the refrigerant during defrosting (point c → point d), the sensible heat (superheat region) and latent heat (two-phase region) of the refrigerant are used, and as the frost melts, drain water begins to drip. In the later stages of defrosting, a temperature distribution occurs on the surface of the outdoor heat exchanger 5, so that convective heat is radiated from the high temperature portion of the surface of the outdoor heat exchanger 5 to the surrounding atmosphere, reducing the defrosting performance.

Further, FIG. 6 shows the change in the heating capacity of the conventional heat pump type air conditioner during defrosting operation, and FIG. 7 similarly shows the change in high pressure side pressure and low pressure side pressure during defrosting operation. In FIG. 7, A indicates the high pressure side pressure, and B indicates the low pressure side pressure. As is clear from the figure, as defrosting progresses, the ratio of the high pressure side pressure A and the low pressure side pressure B, that is, the compression ratio, decreases, and the low pressure side pressure B increases, so that the suction side of the frequency variable compressor 1 decreases. As the specific volume of the refrigerant decreases, the amount of refrigerant circulated within the refrigeration cycle increases, and therefore the heating capacity decreases significantly at the start of defrosting and then gradually increases.

As a result, when defrosting begins, the heating capacity decreases significantly and the temperature of the air blown into the room also drops, potentially causing discomfort to the occupants. It was getting too big, and the defrosting time was getting longer. In view of the above-mentioned problems, the present invention allows a portion of the high temperature discharged gas to flow through the indoor heat exchanger during defrosting operation to allow continued heating operation, thereby reducing a large amount of liquid returning to the compressor and liquid compression. Improves the temperature distribution on the surface of the outdoor heat exchanger to achieve uniform defrosting with a uniform temperature, lowers the air volume of the indoor fan at the start of defrosting operation than during heating operation, and reduces the air volume of the indoor fan during defrosting operation. To provide a heat pump type air conditioner which is highly reliable over a long period of time and has improved defrosting efficiency without causing discomfort to residents.

Means for Solving the Problems In order to solve the above problems, the heat pump air conditioner of the present invention includes a compressor, a four-way valve, an indoor heat exchanger, a throttling device with a variable throttling amount, and an outdoor heat exchanger. The pipes are connected by piping to form a refrigeration cycle, and include piping from the compressor to the indoor heat exchanger that is at high pressure during heating operation, and piping from the outdoor heat exchanger to the compressor that is also at low pressure during heating operation. forming a bypass circuit connecting said bypass circuit, providing an on-off valve in said bypass circuit, and providing heating capacity detection means capable of detecting a change in heating capacity during a defrosting operation for defrosting said outdoor heat exchanger; A flow path control means is provided that opens the on-off valve by setting the throttling amount of the throttling device to a predetermined value smaller than the throttling amount during heating operation at the start of operation, and also provides flow path control means near the indoor heat exchanger at the start of defrosting operation. The air volume of the indoor fan that blows heat-exchanged air into the room is lower than during heating operation,
Air volume control means is provided for changing the air volume of the indoor fan in accordance with the value detected by the heating capacity detection means during defrosting operation.

Effects With the above configuration, the present invention allows part of the high temperature discharged gas to flow to the indoor heat exchanger even during defrosting operation to continue the heating operation, and reduces the aperture of the first throttle device to discharge the high temperature discharged gas. Since the remainder of the gas is returned directly to the outdoor heat exchanger outlet, which is the compressor suction side, the refrigerant circulation is good, and while the compressor input is maintained, the dryness of the compressor suction refrigerant can be increased, even though it is two-phase. It can reduce backflow and liquid compression. In addition, the refrigerant flowing into the outdoor heat exchanger becomes two-phase, and the temperature on the surface of the outdoor heat exchanger rises uniformly and uniformly from the early and middle stages of defrosting, as well as from the latter stages of dripping water after melting to the drying stage. This prevents the temperature of a portion from rising rapidly before returning to heating operation, which reduces convective heat loss to the surroundings and improves defrosting efficiency. Furthermore, the air volume control means reduces the air volume of the indoor fan at the start of defrosting operation, and changes the air volume of this indoor fan during defrosting operation according to the heating capacity, so that residents do not feel uncomfortable during defrosting. Moreover, the defrosting efficiency can be further improved without unnecessary heating.

Embodiment A heat pump air conditioner according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a refrigeration cycle diagram of a heat pump air conditioner according to an embodiment of the present invention.

In the figure, 11 is a compressor, 12 is a four-way valve,
13 is an indoor heat exchanger, 14 is an electric expansion valve whose opening degree can be varied by electromagnetic force, 15 is an outdoor heat exchanger, 16
17 is a bypass circuit, 17 is an on-off valve provided in the bypass circuit, 18 is an indoor fan that blows air that has exchanged heat with the indoor heat exchanger 13 into the room, and 19 is a variable speed drive such as a transistor motor that drives this indoor fan. It's a motor. Further, 20 is an indoor temperature detection element for detecting the temperature of the indoor heat exchanger 13;
is an outdoor temperature detection element that detects the temperature of the outdoor heat exchanger 15, and 22 is this indoor temperature detection element 2.
0. This is a control circuit that receives a temperature signal from the outdoor temperature detection element 21 and controls the electric expansion valve 14, the on-off valve 17, and the drive motor 19. And a compressor 11, a four-way valve 12, an indoor heat exchanger 13, an electric expansion valve 14,
The outdoor heat exchangers 15 are sequentially connected in an annular manner, and the discharge side of the compressor 11 and the outlet side of the outdoor heat exchanger 15 during heating operation are connected, and a bypass circuit 16 equipped with an on-off valve 17 is provided in the middle. It was established.

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

During normal heating operation, the on-off valve 17 is closed, and the refrigerant flows through the compressor 11, the four-way valve 12, the indoor heat exchanger 13, the electric expansion valve 14, the outdoor heat exchanger 15, and the four-way valve 12. The refrigerant returns to the compressor 11 to form a heating cycle, and no refrigerant flows into the bypass circuit 16.

However, when the outside temperature is low, frost forms on the outdoor heat exchanger 15, and when the temperature signal of the outdoor temperature detection element 21 drops to the set value, the control circuit 22 issues a command to start defrosting, and the four-way valve 12 remains in the same state. Open/close valve 1
7 is opened and the high temperature discharged gas is branched at point a',
A part of it flows directly to the indoor heat exchanger 13, and the rest is guided to the outlet side of the outdoor heat exchanger 15.The electric expansion valve 14 is slightly opened fully to reduce the throttle amount to almost zero, and the drive motor Defrosting is started by lowering the rotation speed of the fan 19, that is, the rotation speed of the indoor fan 18, from that during heating operation to reduce the amount of air blown into the room.

FIG. 2 is a Mollier diagram showing a cycle during defrosting operation of one embodiment of the heat pump type air conditioner shown in FIG.

Symbols a' to e' shown in the figure correspond to those shown in FIG. In other words, the high temperature discharged gas that flows directly from point a' to the indoor heat exchanger 13 during defrosting operation is:
Since the valve opening degree of the electric expansion valve 14 is almost fully open, the heat is condensed and radiated at a relatively low temperature (approximately 30 to 40°C), and the temperature moves to point b', where the indoor fan is rotated at a low speed and heating operation can be continued. The pressure is reduced by the piping in the middle and a slight restriction of the electric expansion valve 14, and the temperature becomes point c', which is the temperature of the outdoor heat exchanger 1.
5, and further reaches approximately 0°C, which is the melting temperature of frost.
The condensed heat is radiated and defrosted at point d'. The enthalpy difference of the refrigerant used for defrosting at this time is Δi _def = i _c ′−i _d ′, and the state of the refrigerant flowing into the outdoor heat exchanger 15 is at point
As shown in c′, it has already become two-phase. By the way, the enthalpy difference of the refrigerant used for room heating is i _a ′−i _b ′ if we ignore the heat loss during the process.

On the other hand, the remaining high temperature discharge gas is transferred to the outdoor heat exchanger 15.
Since the refrigerant is guided to the outlet side of the refrigerant, after changing its enthalpy, it joins and mixes with the liquid-rich refrigerant that has flowed through the main circuit, reaches point e', and is sucked into the compressor 11.
This point e′ is the dryness of the refrigerant even though it is in a two-phase state.
Since xe′ is large and the liquid content is small, liquid return and liquid compression can be reduced or substantially avoided. Furthermore, since the refrigerant flowing into the outdoor heat exchanger 15 during defrosting operation is basically in a two-phase state, the refrigerant temperature, that is, the surface temperature of the outdoor heat exchanger 15, is also constant, and there is no unevenness in the surface temperature. Uniform defrosting can be achieved.

In addition, when the defrosting operation starts, opening the on-off valve 17 greatly reduces the high-pressure side pressure and rapidly reduces the heating capacity, but since the rotation speed of the indoor fan 18 is lower than during heating operation, the indoor heat It is possible to reduce the decrease in the temperature of the air blown into the room by exchanging heat with the exchanger 13, so that the occupants do not feel uncomfortable.
Furthermore, as defrosting progresses, the high-pressure side pressure gradually increases and the heating capacity increases, as shown in the conventional example, but the indoor temperature detection element 21
When the temperature signal rises to the set value, the control circuit 22
By lowering the rotation speed of the drive motor 19, that is, the rotation speed of the indoor fan 18, and suppressing the increase in heating capacity, the defrosting capacity of the outdoor heat exchanger 15 is increased, and therefore the defrosting efficiency can be further improved. becomes.

The solid line in FIG. 3 shows the change in the heating capacity during defrosting operation of the heat pump air conditioner in one embodiment of the present invention. Compared to the change in heating capacity during defrosting of the conventional heat pump air conditioner shown in FIG. 1, unnecessary heating is not performed near the end of defrosting.

Although the present invention has been described using an electric expansion valve 14 that uses electromagnetic force as a drive source to vary the valve opening degree as the best form of the throttle device, it is also possible to construct it using a plurality of throttles such as capillaries and switch as appropriate. Furthermore, a bimetal, a shape memory alloy, or the like may be used as means for varying the valve opening degree.
Further, although the increase in heating capacity is detected using the temperature of the indoor heat exchanger 13, the present invention is not limited to this, and any pressure, temperature, etc. to be detected may be used as long as an increase in heating capacity can be detected. The location and means thereof are arbitrary. The same applies to the determination of the time to start defrosting.

Effects of the Invention As described above, the heat pump air conditioner of the present invention configures a refrigeration cycle by connecting a compressor, a four-way valve, an indoor heat exchanger, a throttling device with variable throttling amount, and an outdoor heat exchanger through piping. and forming a bypass circuit that connects piping from the compressor to the indoor heat exchanger, which is at high pressure during heating operation, and piping from the outdoor heat exchanger to the compressor, which is also at low pressure during heating operation, and An on-off valve is provided in the bypass circuit, and a heating capacity detection means capable of detecting a change in heating capacity during a defrosting operation to defrost the outdoor heat exchanger is provided, and a heating capacity detection means is provided that can detect a change in the heating capacity during a defrosting operation to defrost the outdoor heat exchanger, and when the defrosting operation is started, the throttle of the throttle device is A flow path control means is provided to open the on-off valve by setting the flow rate to a predetermined value smaller than the throttling amount during heating operation, and is also provided near the indoor heat exchanger at the start of defrosting operation to direct the heat-exchanged air indoors. The device is equipped with an air volume control means that lowers the air volume of the indoor fan blowing out compared to during heating operation, and changes the air volume of the indoor fan in accordance with the value detected by the heating capacity detection means during defrosting operation. At times, part of the high-temperature discharged gas can be passed through the indoor heat exchanger to allow continued heating operation, reducing the amount of liquid returned to the compressor and liquid compression, and improving the temperature distribution on the surface of the outdoor heat exchanger. Achieving uniform defrosting with a uniform temperature, the air volume control means lowers the air volume of the indoor fan at the start of defrosting operation, and changes the air volume of the indoor fan according to the heating capacity during defrosting operation. It is highly reliable over a long period of time, and has various effects such as being able to improve defrosting efficiency without causing discomfort to residents.

[Brief explanation of drawings]

Fig. 1 is a refrigeration cycle diagram of a heat pump air conditioner according to an embodiment of the present invention, Fig. 2 is a diagram showing the cycle during defrosting operation of the heat pump air conditioner on a Mollier diagram, and Fig. 3 is a diagram showing the cycle during defrosting operation of the heat pump air conditioner. An explanatory diagram showing changes in heating capacity during defrosting operation of the heat pump air conditioner, Figure 4 is a refrigeration cycle diagram of a conventional heat pump air conditioner, and Figure 5 is a diagram of the conventional heat pump air conditioner shown in Figure 4. Figure 6 is an explanatory diagram showing the change in heating capacity during defrosting operation of a conventional heat pump air conditioner, and Figure 7 is a diagram showing the cycle during defrosting operation of a conventional heat pump air conditioner on a Mollier diagram. FIG. 2 is an explanatory diagram showing changes in high-pressure side pressure and low-pressure side pressure during defrosting operation of the heat pump air conditioner. 11...Compressor, 12...Four-way valve, 13...Indoor heat exchanger, 14...Electric expansion valve (throttle device),
15...Outdoor heat exchanger, 16...Bypass circuit,
17...Opening/closing valve, 18...Indoor fan, 19...
Drive motor (air volume control means), 20... Indoor temperature detection element (heating capacity detection means), 22... Control circuit (air volume, flow path control means).

Claims (1)

[Scope of Claims] 1. A refrigeration cycle is constructed by connecting a compressor, a four-way valve, an indoor heat exchanger, a throttling device with a variable throttling amount, and an outdoor heat exchanger through piping, and the above-mentioned compressor, which is at high pressure during heating operation, is constructed. A bypass circuit is formed that connects piping from the compressor to the indoor heat exchanger and piping from the outdoor heat exchanger to the compressor, which also has a low pressure during heating operation, and an on-off valve is provided in the bypass circuit, and the A heating capacity detection means capable of detecting a change in heating capacity during a defrosting operation to defrost an outdoor heat exchanger is provided, and the throttle amount of the throttle device is set at the start of the defrosting operation from the throttle amount during the heating operation. Similarly, at the start of defrosting operation, a flow path control means is provided to open the on-off valve to a small predetermined value, and the air volume of an indoor fan that is installed near the indoor heat exchanger and blows heat-exchanged air into the room is set during heating operation. The heat pump type air conditioner is provided with an air volume control means that changes the air volume of the indoor fan according to the value detected by the heating capacity detection means during defrosting operation. 2. The heat pump according to claim 1, wherein during defrosting operation, when the value detected by the heating capacity detection means exceeds a predetermined value, the air volume control means controls the air volume of the indoor fan to be lower than that at the start of the defrosting operation. type air conditioner.