CN104736944B - air conditioner - Google Patents

Abstract

In the air conditioner using R32 cold-producing medium, constructing the aperture control mode of a kind of expansion valve, this aperture control mode can stably control the temperature of the ejection cold-producing medium of compressor.Air conditioner (10) possesses refrigerant loop (11) and control portion (30), this refrigerant loop (11) connects and has compressor (12), outdoor heat converter (14), expansion valve (15) and indoor heat converter (16), in refrigerant loop (11), HFC32 is circulated as cold-producing medium, the aperture that this control portion (30) just carries out changing the aperture of expansion valve (15) ormal weight every the sample time t of regulation controls, and makes bleed pipe temperature Tp of compressor (12) become target bleed pipe temperature Tpa.Aperture at expansion valve (15) is less than the sample time t in the such region of setting, is more than or equal to the sample time t length in the such region of setting than the aperture at expansion valve (15).

Description

air conditioner

technical field

The invention relates to an air conditioner using R32 as a refrigerant, in particular to an opening degree control method of an expansion valve.

Background technique

Hitherto, as an air conditioner equipped with a refrigerant circuit that performs a vapor compression refrigeration cycle by circulating a refrigerant, there is known an air conditioner that controls the discharge cooling of the compressor by controlling the opening of the expansion valve. The temperature of the refrigerant, thereby indirectly adjusting the superheat of the refrigerant sucked into the compressor. For example, as disclosed in Patent Document 1, in this type of air conditioner, the opening degree of the expansion valve is feedback-controlled at a predetermined cycle.

In addition, in recent years, as shown in Patent Document 2, an air conditioner using R32 (HFC32) having a small global warming potential (GWP) as a refrigerant has attracted attention in order to reduce the influence on global warming.

prior art literature

patent documents

Patent Document 1: Japanese Publication of Utility Model Publication No. 3-34564

Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-122677

Contents of the invention

The technical problem to be solved by the invention

However, there is a problem that, in an air conditioner using R32 as a refrigerant, if the opening degree of the expansion valve is controlled at a fixed cycle as described above, the refrigerant circulation amount will decrease in the low-load region. It is difficult to stably control the temperature of the refrigerant discharged from the compressor.

Since R32 is a refrigerant with a high cooling capacity per unit volume among various refrigerants, it is possible to reduce the amount of refrigerant circulation required in the refrigerant circuit, and in the low-load area, the refrigerant circulation amount becomes less. Even if the opening degree of the expansion valve is changed in the low-load region, the temperature of the discharged refrigerant does not immediately reach the target temperature because the refrigerant circulation amount is very small. Therefore, in the next opening control, although the opening of the expansion valve has actually been controlled to an appropriate opening, the expansion valve will be further changed because there is still a temperature difference between the temperature of the injected refrigerant and the target temperature. valve opening. When such expansion valve opening control is continued, a so-called fluctuation phenomenon occurs, in which the temperature of the discharged refrigerant exceeds the target temperature and then falls below the target temperature, and this situation is repeated. As a result, it is difficult to stably control the temperature of the discharged refrigerant.

The present invention has been made in view of the above problems, and its purpose is to construct an opening degree control method of the expansion valve in an air conditioner using R32 as a refrigerant. In this opening degree control method, the compressor can be stably controlled. The temperature of the sprayed refrigerant.

Technical solutions to solve technical problems

The invention of the first aspect is aimed at an air conditioner, which includes a refrigerant circuit 11 and a control unit 30, and a compressor 12, an outdoor heat exchanger 14, an expansion valve 15, and an indoor heat exchanger are connected to the refrigerant circuit 11. The exchanger 16 and HFC32 circulate in the refrigerant circuit 11 as a refrigerant, so that the refrigerant circuit 11 performs a refrigeration cycle, and the control unit 30 changes the opening degree of the expansion valve 15 by a predetermined amount at a predetermined cycle. temperature control so that the temperature of the refrigerant discharged from the compressor (12) becomes the target temperature. The predetermined period in a region where the opening degree of the expansion valve 15 is smaller than a predetermined value is longer than the predetermined period in a region where the opening degree of the expansion valve 15 is equal to or larger than the predetermined value.

In the invention of the first aspect, in the region where the opening degree of the expansion valve 15 is small, that is, when the amount of refrigerant circulating in the refrigerant circuit 11 is small, the period of the opening degree control becomes longer, Therefore, the temperature of the discharged refrigerant reaches (approaches) the target temperature in the period from changing the opening degree of the expansion valve 15 to performing the next opening degree control. That is, the next opening degree control is performed after the temperature of the discharged refrigerant stabilizes.

The second aspect of the invention is directed to an air conditioner, which includes a refrigerant circuit 11 and a control unit 30, and a compressor 12, an outdoor heat exchanger 14, an expansion valve 15, and an indoor heat exchanger are connected to the refrigerant circuit 11. The exchanger 16 and HFC32 circulate in the refrigerant circuit 11 as a refrigerant, so that the refrigerant circuit 11 performs a refrigeration cycle, and the control unit 30 changes the opening degree of the expansion valve 15 by a predetermined amount at a predetermined cycle. temperature control so that the temperature of the refrigerant discharged from the compressor (12) becomes the target temperature. The predetermined amount in a region where the opening degree of the expansion valve 15 is smaller than a predetermined value is smaller than the predetermined amount in a region where the opening degree of the expansion valve 15 is equal to or larger than the predetermined value.

In the second aspect of the invention, since the change in the opening degree of the expansion valve 15 becomes small in the region where the opening degree of the expansion valve 15 is small, the change in the temperature of the discharged refrigerant caused by the opening degree control once amount becomes smaller. Accordingly, the temperature of the discharged refrigerant does not rise or fall greatly, and it is possible to suppress the occurrence of a state in which the temperature of the discharged refrigerant exceeds the target temperature and then falls below the target temperature.

The third aspect of the invention is based on the first aspect of the invention, and has the following characteristics: the predetermined amount in the region where the opening degree of the expansion valve 15 is smaller than the predetermined value is greater than that in the expansion valve 15. The predetermined amount is small in a region where the opening degree of the valve 15 is equal to or greater than the predetermined value.

In the third aspect of the invention, since the predetermined period becomes longer and the amount of change in the opening degree becomes smaller in the region where the opening degree of the expansion valve 15 is small, the temperature of the discharged refrigerant tends to decrease. The opening degree control is stabilized before the first opening degree control, and the amount of change in the temperature of the discharged refrigerant caused by the first opening degree control becomes small. Accordingly, it is possible to reliably avoid the occurrence of a state in which the temperature of the discharged refrigerant exceeds the target temperature and then falls below the target temperature.

The fourth aspect of the invention is based on the first or third aspect of the invention, and has the following characteristics: in the region where the opening degree of the expansion valve 15 is smaller than the predetermined value, the smaller the opening degree, the lower the opening degree of the expansion valve 15. The prescribed period is gradually longer.

In the fourth aspect of the invention, the smaller the opening of the expansion valve 15 is, the less the amount of refrigerant circulation in the refrigerant circuit 11 is, and the longer it takes for the temperature of the discharged refrigerant to reach the target temperature. However, since the predetermined period is gradually longer as the opening degree is smaller, the temperature of the discharged refrigerant can reliably reach the target temperature before the next opening degree control is performed.

The fifth aspect of the invention is based on any one of the first to fourth aspects of the invention, and has the following features: the expansion valve 15 is such an expansion valve, that is, when the opening degree is smaller than the specified value, it is compatible with The amount of change in the opening of the expansion valve 15 is smaller than the amount of change in the refrigerant flow rate in the expansion valve 15 .

In the fifth aspect of the invention, in the region where the opening degree of the expansion valve 15 is smaller than the specified value, the change range of the refrigerant flow rate is not as large as the change amount of the opening degree, so the refrigerant circulation amount in the refrigerant circuit 11 The change range is not large. Therefore, the time required for the temperature of the discharged refrigerant to reach the target temperature becomes longer. However, since the predetermined cycle becomes longer or the amount of change in the opening becomes smaller in the region where the opening is smaller than the predetermined value, it is possible to effectively avoid a state where the temperature of the discharged refrigerant exceeds the target temperature for a while and falls below the target temperature for a while. occur.

The effect of the invention

As described above, according to the present invention, the cycle of the opening degree control in the region where the opening degree of the expansion valve 15 is smaller than the predetermined value is achieved compared to the opening degree in the region where the opening degree of the expansion valve 15 is equal to or larger than the predetermined value. The cycle of the control is long, so even when the amount of refrigerant circulating in the refrigerant circuit 11 is small, it is possible to control the discharge during the period from changing the opening of the expansion valve 15 to the next opening control. The temperature of the refrigerant reaches (closes to) the target temperature. That is, the next opening degree control can be performed after the temperature of the discharged refrigerant stabilizes. Therefore, in the next opening degree control, the change amount of the opening degree can be appropriately set, and thus, the temperature of the discharged refrigerant can be avoided from exceeding the target temperature at one time and lowering the target temperature at another time. As a result, fluctuations in the temperature of the discharged refrigerant can be prevented, and the temperature of the discharged refrigerant can be stably controlled.

According to the second aspect of the invention, the amount of change in the opening degree of the expansion valve 15 in the region where the opening degree of the expansion valve 15 is smaller than the predetermined value is greater than that in the region where the opening degree of the expansion valve 15 is greater than or equal to the predetermined value. Since the amount of change is small, when the amount of refrigerant circulating in the refrigerant circuit 11 is small, the amount of change in the temperature of the discharged refrigerant caused by one opening degree control can be reduced. As a result, since the temperature of the discharged refrigerant does not rise or fall significantly, it is possible to avoid a state in which the temperature of the discharged refrigerant exceeds the target temperature and then falls below the target temperature. As a result, fluctuations in the temperature of the discharged refrigerant can be prevented, and the temperature of the discharged refrigerant can be stably controlled.

According to the third aspect of the invention, the cycle of the opening degree control in the region where the opening degree of the expansion valve 15 is smaller than the predetermined value is achieved than the opening degree control in the region where the opening degree of the expansion valve 15 is equal to or greater than the predetermined value The cycle is long, and the amount of change in the opening of the expansion valve 15 in the region where the opening of the expansion valve 15 is smaller than the specified value is greater than the amount of change in the opening of the expansion valve 15 in the region where the opening of the expansion valve 15 is greater than or equal to the specified value. Therefore, it is possible to reliably avoid the occurrence of a state in which the temperature of the discharged refrigerant exceeds the target temperature for a while and falls below the target temperature for a while. Accordingly, it is possible to reliably and stably control the temperature of the discharged refrigerant.

According to the invention of the fourth aspect, in the region where the opening degree of the expansion valve 15 is smaller than the predetermined value, the smaller the opening degree is, the longer the period of the opening degree control is stepwise. Before the control, the temperature of the discharged refrigerant is reliably brought to (closer to) the target temperature. Accordingly, it is possible to reliably and stably control the temperature of the discharged refrigerant.

According to the fifth aspect of the invention, in the region where the opening degree of the expansion valve 15 is smaller than the predetermined value, the change range of the refrigerant circulation amount in the refrigerant circuit 11 cannot be as large as the change amount of the opening degree. The time it takes for the temperature to reach the target temperature becomes longer. However, since the cycle of the opening degree control is lengthened or the amount of change in the opening degree is made small in accordance with the region where the opening degree of the expansion valve 15 is smaller than the predetermined value, it is possible to effectively prevent the temperature of the discharged refrigerant from exceeding the target temperature for a while. A state below the target temperature occurs. Therefore, fluctuations in the temperature of the discharged refrigerant can be effectively prevented.

Description of drawings

FIG. 1 is a piping diagram showing the structure of an air conditioner according to a first embodiment.

FIG. 2 is a flowchart showing an opening degree control method of the expansion valve according to the first embodiment.

FIG. 3 is a table showing the relationship between the opening area of the expansion valve and the sampling time.

FIG. 4 is a graph showing the relationship between the opening degree of the expansion valve and the refrigerant flow rate.

FIG. 5 is a flowchart showing an opening degree control method of the expansion valve according to the second embodiment.

FIG. 6 is a table showing the relationship between the opening area of the expansion valve and the opening change amount.

detailed description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following embodiments are essentially preferred examples, and are not intended to limit the scope of the present invention, its application objects or uses.

[First Embodiment]

A first embodiment of the present invention will be described. As shown in FIG. 1 , an air conditioner 10 according to the present embodiment includes a refrigerant circuit 11 and can switch between a cooling operation and a heating operation. A compressor 12, a four-way reversing valve 13, an outdoor heat exchanger 14, an expansion valve 15, and an indoor heat exchanger 16 are connected to the refrigerant circuit 11, and the refrigerant circuit 11 constitutes a closed circuit. The refrigerant circuit 11 is configured to fill the refrigerant circuit 11 with R32 (HFC32 (difluoromethane)) as a refrigerant, and to circulate the refrigerant to perform a vapor compression refrigeration cycle.

In the refrigerant circuit 11, the fourth valve port of the four-way reversing valve 13 is connected to the discharge pipe of the compressor 12, and the second valve port of the four-way reversing valve 13 is connected to the suction pipe of the compressor 12, The first valve port of the four-way reversing valve 13 is connected with the end of the outdoor heat exchanger 14 , and the third valve port of the four-way reversing valve 13 is connected with the end of the indoor heat exchanger 16 . The four-way reversing valve 13 is configured to be able to communicate between the first valve port and the fourth valve port, and the first state (the state shown by the solid line in FIG. Switching is made between a second state (a state indicated by a dotted line in FIG. 1 ) in which one valve port communicates with the second valve port and the third valve port communicates with the fourth valve port.

In the refrigerant circuit 11, when the four-way reversing valve 13 is switched to the first state, the refrigerant circulates under the refrigeration cycle in which the outdoor heat exchanger 14 works as a condenser and the indoor heat exchanger 16 works as an evaporator. In the refrigerant circuit 11, when the four-way reversing valve 13 is switched to the second state, the refrigerant circulates under the heating cycle in which the indoor heat exchanger 16 works as a condenser and the outdoor heat exchanger 14 works as an evaporator . That is, the four-way switching valve 13 constitutes a switching mechanism for switching the circulation direction of the refrigerant in the refrigerant circuit 11 .

The compressor 12 is a variable-displacement compressor 12 capable of adjusting the operating frequency through a DC-to-AC conversion circuit. The expansion valve 15 is configured such that its opening can be changed by a pulse motor. The outdoor heat exchanger 14 is configured so that the refrigerant exchanges heat with outdoor air, and the indoor heat exchanger 16 is configured so that the refrigerant exchanges heat with indoor air.

〈Sensor, control part〉

The air conditioner 10 is provided with a control unit 30 and various sensors, and the control unit 30 is used to control the operating frequency of the compressor 12 and the opening degree of the expansion valve 15 .

As shown in FIG. 1 , a discharge pipe temperature sensor 21 , an outdoor heat exchanger temperature sensor 22 , and an indoor heat exchanger temperature sensor 23 are provided in the refrigerant circuit 11 . The discharge pipe temperature sensor 21 detects the temperature of the discharge pipe of the compressor 12 (hereinafter referred to as the discharge pipe temperature Tp). The discharge pipe temperature Tp corresponds to the temperature of the refrigerant discharged from the compressor 12 . The outdoor heat exchanger temperature sensor 22 detects the temperature of the refrigerant in the outdoor heat exchanger 14 , and the indoor heat exchanger temperature sensor 23 detects the temperature of the refrigerant in the indoor heat exchanger 16 . During the cooling operation, the temperature detected by the outdoor heat exchanger temperature sensor 22 corresponds to the condensation temperature Tc of the refrigerant, and during the heating operation, the temperature detected by the outdoor heat exchanger temperature sensor 22 corresponds to the temperature of the refrigerant. Evaporation temperature Te. During the cooling operation, the temperature detected by the indoor heat exchanger temperature sensor 23 corresponds to the evaporation temperature Te of the refrigerant, and during the heating operation, the temperature detected by the indoor heat exchanger temperature sensor 23 corresponds to the condensation temperature of the refrigerant. temperature Tc.

During cooling operation and heating operation, the control unit 30 controls the opening of the expansion valve 15 at a predetermined cycle (hereinafter referred to as sampling time t) so that the discharge pipe temperature Tp of the compressor 12 becomes the target discharge pipe temperature Tp. Temperature Tpa. The control unit 30 is configured to change the sampling time t according to the current opening range of the expansion valve 15 . Details of the opening degree control will be described below.

-working condition-

The operation of the air conditioner 10 will be described.

During the cooling operation, in the refrigerant circuit 11, the four-way selector valve 13 is switched to the first state. During the cooling operation, the refrigerant discharged from the compressor 12 radiates heat to the outdoor air in the outdoor heat exchanger 27 and is condensed. The condensed refrigerant is decompressed (expanded) when passing through the expansion valve 15 . The depressurized refrigerant absorbs heat from the indoor air in the indoor heat exchanger 16 to evaporate, and the indoor air is cooled and supplied into the room. This cools the room. The refrigerant evaporated in the indoor heat exchanger 16 is compressed in the compressor 12 and discharged again.

During the heating operation, in the refrigerant circuit 11, the four-way selector valve 13 is switched to the second state. During the heating operation, the refrigerant discharged from the compressor 12 dissipates heat to the indoor air in the indoor heat exchanger 16 to condense, thereby heating the indoor air. This heats the room. The condensed refrigerant is decompressed (expanded) when passing through the expansion valve 15 . The depressurized refrigerant absorbs heat from the outdoor air in the outdoor heat exchanger 14 and evaporates. The evaporated refrigerant is compressed in the compressor 12 and then discharged again.

<Operation status of the control department>

During cooling operation and heating operation, the control unit 30 controls the opening of the expansion valve 15 every predetermined sampling time t (seconds) so that the discharge pipe temperature Tp of the compressor 12 becomes the target discharge pipe temperature Tpa. Specifically, the control unit 30 performs feedback control of the opening degree of the expansion valve 15 according to the flowchart shown in FIG. 2 .

In step ST1, it is judged whether or not a predetermined sampling time t has elapsed since the last drive of the expansion valve 15 (changing the opening degree of the expansion valve 15). If the predetermined sampling time t has elapsed, the process proceeds to step ST2.

In step ST2, the target discharge pipe temperature Tpa is set. In this embodiment, the target discharge pipe temperature Tpa is set to a value that is the degree of superheat of the refrigerant sucked by the compressor 12 (that is, the superheat of the refrigerant at the outlet of the heat exchangers 14 and 16 that work as evaporators). heat) becomes the specified value. That is, in the present embodiment, the degree of superheat of the sucked refrigerant is indirectly controlled by controlling the discharge pipe temperature Tp.

Specifically, in the control unit 30, the target discharge temperature is set based on the condensation temperature Tc which is the temperature detected by the outdoor heat exchanger temperature sensor 22 and the evaporation temperature Te which is the temperature detected by the indoor heat exchanger temperature sensor 23. Tube temperature Tpa. For example, the target discharge pipe temperature Tpa is obtained by the following calculation formula. In addition, α, β, and γ in the following are predetermined coefficients.

Target ejection pipe temperature Tpa=α×condensing temperature Tc-β×evaporating temperature Te+γ

After setting the target discharge pipe temperature Tpa as described above, the process proceeds to step ST3. In step ST3 , the current discharge pipe temperature Tp measured by the discharge pipe temperature sensor 21 is input to the control unit 30 .

In the next step ST4 , the opening degree change ΔP (number of pulses) of the expansion valve 15 required to bring the current input discharge pipe temperature Tp into (closer to) the target discharge pipe temperature Tpa is set. If the opening of the expansion valve 15 is increased, the amount of refrigerant circulating in the heat exchangers 14 and 16 working as evaporators will increase, so the degree of superheat of the outlet refrigerant will decrease. As a result, the discharge pipe temperature Tp will decrease. If the opening of the expansion valve 15 decreases, the amount of refrigerant circulating in the heat exchangers 14 and 16 that work as evaporators will decrease, so the degree of superheat of the outlet refrigerant will increase, and as a result, the temperature Tp of the discharge pipe will decrease. rise.

Specifically, the control unit 30 is provided in advance with a table (fuzzy table) for setting the opening degree change amount ΔP. In the fuzzy table, the amount of change in opening degree ΔP is determined from the deviation between the discharge pipe temperature Tp and the target discharge pipe temperature Tpa, and the amount of change in the discharge pipe temperature Tp per unit time. Therefore, the control unit 30 calculates the above-mentioned deviation, and calculates the above-mentioned amount of change per unit time from the discharge pipe temperature Tp at the time of the previous opening control and the current discharge pipe temperature Tp, and based on the calculated deviation and change amount to set the opening change amount ΔP.

After the opening change amount ΔP is set, in step ST5 , the control unit 30 drives the expansion valve 15 to increase or decrease the opening change amount ΔP of the expansion valve 15 .

In the next step ST6, a new sampling time t is set. That is, the sampling time t is maintained or changed. As shown in FIG. 3 , in the present embodiment, the sampling time t is set to a different value according to the opening range of the expansion valve 15 . In this embodiment, as shown in FIG. 4 , the range from the minimum opening to the maximum opening of the expansion valve 15 is divided into three opening areas (large opening area, middle opening area, and small opening area). . The large opening area is the range from the first specified value Px to the maximum opening, the medium opening area is the range from the second specified value Py to less than the first specified value Px, and the small opening area is from the minimum opening to less than The range of the second predetermined value Py.

Then, in step ST6, when the current opening P of the expansion valve 15 is in the large opening area, the sampling time t is set as "ta (seconds)", and when the current opening P of the expansion valve 15 is in the middle In the opening range, the sampling time t is set to "tb (seconds)", and when the current opening P of the expansion valve 15 is in the small opening range, the sampling time t is set to "tc (seconds)". Here, the above-mentioned current opening degree P of the expansion valve 15 refers to the opening degree of the expansion valve 15 after being driven in step ST5 (after the opening degree P is changed). The size relationship of ta, tb, and tc is ta<tb<tc.

As described above, in the opening degree control method of the expansion valve 15 of the present embodiment, the sampling time t in the region where the opening degree P of the expansion valve 15 is smaller than the first predetermined value Px is shorter than that in the region where the opening degree P of the expansion valve 15 is smaller than the first predetermined value Px. The sampling time t is long in the region where P is equal to or greater than the first predetermined value Px. Furthermore, in the present embodiment, in the region smaller than the first predetermined value Px, the sampling time t is gradually increased as the opening degree P of the expansion valve 15 becomes smaller. That is, in the present embodiment, the smaller the opening P of the expansion valve 15 is, the longer the sampling time t is set.

As shown in FIG. 4 , the expansion valve 15 of this embodiment has such a characteristic that when the opening P is smaller than the first predetermined value Px, the refrigerant flow rate in the expansion valve 15 relative to the amount of change in the opening P variation decreases. That is, in the expansion valve 15, even if the opening degree P is changed by the same opening degree change amount ΔP in the middle opening degree region and the small opening degree region, the change amount of the refrigerant flow rate is equally small. More specifically, in the opening degree control method of the expansion valve 15 in this embodiment, the opening degree at which the relationship between the opening degree P and the refrigerant flow rate changes in the expansion valve 15 is set as the first predetermined value Px.

Once a new sampling time t is set in step ST6, it returns to step ST1 for the next opening degree control. That is, in step ST1, it is judged whether or not the newly set sampling time t has elapsed since the expansion valve 15 was driven, and if the newly set sampling time t has elapsed, the process proceeds to and after step ST2 in the same manner. A step of.

In the region where the opening P of the expansion valve 15 is small (the middle opening region, the small opening region), the flow rate of the refrigerant in the expansion valve 15 decreases, and the amount of refrigerant circulating in the refrigerant circuit 11 decreases. In the present embodiment, since R32 is used as the refrigerant, the amount of refrigerant circulation becomes very small in the region where the opening P of the expansion valve 15 is small. In this opening range where the amount of refrigerant circulation is small, even if the opening P of the expansion valve 15 is changed, the discharge pipe temperature Tp also rises or falls very slowly, from the discharge pipe temperature Tp to the target discharge pipe temperature Tpa Quite time consuming. In this case, if the opening degree control is performed with the same sampling time t as the region where the opening degree P of the expansion valve 15 is large (large opening degree region), although the opening degree P of the expansion valve 15 is actually controlled When reaching an appropriate opening degree, the control unit 30 will still perform control to further change the opening degree P of the expansion valve 15 because there is still a temperature difference between the discharge pipe temperature Tp and the target discharge pipe temperature Tpa. That is, the next opening degree control is performed during the transition period in which the discharge pipe temperature Tp changes toward the target discharge pipe temperature Tpa. As a result, a fluctuating phenomenon occurs in which the discharge pipe temperature Tp exceeds the target discharge pipe temperature Tpa for a while and falls below the target discharge pipe temperature Tpa for a while, and this situation is repeated.

On the other hand, according to the opening degree control method of the expansion valve 15 in this embodiment, since the smaller the opening degree P of the expansion valve 15 is, the longer the sampling time t is, it is possible to change the opening degree P of the expansion valve 15 to make the injection The next opening degree control is performed after the outlet pipe temperature Tp reaches (approaches) the target outlet pipe temperature Tpa. That is, before the next opening degree control is performed, the discharge pipe temperature Tp can be brought to (close to) the target discharge pipe temperature Tpa and the discharge pipe temperature Tp can be stabilized.

-Effect of Embodiment-

As described above, according to the present embodiment, the sampling time t (period of opening control) of the opening degree control in the region where the opening degree P of the expansion valve 15 is smaller than the predetermined value (first predetermined value Px) is achieved. , is longer than the sampling time t (period of opening control) of the opening degree control in the region where the opening degree P of the expansion valve 15 is equal to or greater than a predetermined value (first predetermined value Px). Therefore, even when the amount of refrigerant circulating in the refrigerant circuit 11 is small, it is possible to bring the discharge pipe temperature Tp to 100°C during the period from changing the opening degree of the expansion valve 15 to performing the next opening degree control. (Close to) the target discharge pipe temperature Tpa. That is, the next opening degree control can be performed after the discharge pipe temperature Tp stabilizes. Therefore, in the next opening degree control, the deviation between the discharge pipe temperature Tp and the target discharge pipe temperature Tpa can be appropriately detected, and thus the opening degree change amount ΔP can be appropriately set. In this way, it is possible to avoid a state where the discharge pipe temperature Tp exceeds the target discharge pipe temperature Tpa for a while and falls below the target discharge pipe temperature Tpa for a while. As a result, the fluctuation phenomenon of the discharge pipe temperature Tp can be prevented, and the discharge pipe temperature Tp can be stably controlled.

In addition, in the present embodiment, it is possible to further increase the sampling time t in the opening range that is smaller than the second predetermined value Py that is smaller than the first predetermined value Px. That is, in the region where the opening P of the expansion valve 15 is smaller than the predetermined value (the first predetermined value Px), the sampling time t of the opening control is gradually increased as the opening P becomes smaller. Therefore, even if the refrigerant circulation amount is close to the minimum circulation amount, the discharge pipe temperature Tp can be reliably brought to (closer to) the target discharge pipe temperature Tpa before the next opening degree control is performed. Therefore, the discharge pipe temperature Tp can be controlled reliably and stably.

In the region where the opening degree P of the expansion valve 15 is smaller than a prescribed value (first prescribed value Px), based on the characteristics of the expansion valve 15, in the refrigerant circuit 11, the refrigerant circulation amount does not change as much as the opening degree change amount ΔP Large (refer to Figure 4). Therefore, the time required for the discharge pipe temperature Tp to reach (close to) the target discharge pipe temperature Tpa becomes longer in a region where the opening degree P of the expansion valve 15 is smaller than a predetermined value (first predetermined value Px). In the opening degree control method of this embodiment, since the sampling time t of the opening degree control is increased in accordance with the region smaller than the predetermined value (first predetermined value Px), it is possible to effectively prevent the discharge pipe temperature Tp from exceeding the target for a while. A state occurs in which the discharge pipe temperature Tpa is lower than the target discharge pipe temperature Tpa for a while. Therefore, the fluctuation phenomenon of the discharge pipe temperature Tp can be effectively prevented.

[Second Embodiment]

A second embodiment of the present invention will be described. This embodiment changes the opening degree control method of the expansion valve 15 in the air conditioner 10 of the first embodiment. That is to say, in the first embodiment, the sampling time t is made longer in the region where the opening P of the expansion valve 15 is smaller than the predetermined value, but in the present embodiment, the expansion valve 15 is In a region where the opening degree P is smaller than a predetermined value, the sampling time t is kept constant, and the opening degree change amount ΔP is reduced.

The control unit 30 in the present embodiment controls the opening degree of the expansion valve 15 according to the flowchart shown in FIG. 5 . The control operations in steps ST1 to ST3 are the same as those in the first embodiment.

In step ST4, similarly to the first embodiment, the opening degree change ΔP (number of pulses) of the expansion valve 15 required to bring the current discharge pipe temperature Tp to (closer to) the target discharge pipe temperature Tpa is calculated. ) to set. The control unit 30 is provided with a fuzzy table in advance, and in the fuzzy table, the opening degree is determined based on the deviation between the discharge pipe temperature Tp and the target discharge pipe temperature Tpa and the change amount per unit time of the discharge pipe temperature Tp. The amount of change ΔP.

As shown in FIG. 6 , in the fuzzy table of the present embodiment, the opening degree change amount ΔP is set to a different value according to the opening degree region of the expansion valve 15 . Similar to the first embodiment, the opening range of the expansion valve 15 is divided into three ranges: a large opening range, a medium opening range, and a small opening range. In step ST4, when the current opening P of the expansion valve 15 is in the large opening region, the opening change ΔP is set to “ΔPa (number of pulses)”, and when the current opening P of the expansion valve 15 is In the middle opening area, the opening change amount ΔP is set as "ΔPb (number of pulses)", and when the current opening P of the expansion valve 15 is in the small opening area, the opening change amount ΔP is set as " ΔPc (number of pulses)". The magnitude relationship of ΔPa, ΔPb, and ΔPc is ΔPa>ΔPb>ΔPc.

As described above, in the opening degree control method of the expansion valve 15 according to the present embodiment, the opening degree change ΔP in the region where the opening degree P of the expansion valve 15 is smaller than the first predetermined value Px is larger than that in the region where the opening degree P of the expansion valve 15 is smaller than the first predetermined value Px. The opening degree change amount ΔP is small in a region where the opening degree P is equal to or larger than the first predetermined value Px. Furthermore, in the present embodiment, in the region smaller than the first predetermined value Px, the opening degree change ΔP of the expansion valve 15 decreases stepwise as the opening degree P of the expansion valve 15 becomes smaller. That is, in the present embodiment, the smaller the opening P of the expansion valve 15 is, the smaller the opening change ΔP is set. Therefore, in the present embodiment, even if the deviation between the discharge pipe temperature Tp and the target discharge pipe temperature Tpa and the change amount per unit time of the discharge pipe temperature Tp are the same, as long as the opening P of the expansion valve 15 is larger The smaller the opening degree change ΔP is, the smaller it will be.

After the opening change amount ΔP is set in step ST4, the control unit 30 drives the expansion valve 15 to increase or decrease the opening change amount ΔP of the expansion valve 15 in step ST5. Once the expansion valve 15 is driven, it returns to step ST1 to perform the next opening degree control.

According to the opening degree control method of the expansion valve 15 in this embodiment, it is possible to make the opening degree change ΔP in the region where the opening degree P of the expansion valve 15 is smaller than the predetermined value (the first predetermined value Px) be greater than that in the region where the opening degree P is smaller than the predetermined value (first predetermined value Px). Since the opening degree change ΔP in the region where the opening degree P of the expansion valve 15 is equal to or greater than the predetermined value (the first predetermined value Px) is small, it is possible to reduce the amount of refrigerant circulating in the refrigerant circuit 11 when the amount of refrigerant circulating in the refrigerant circuit 11 is small. The amount of change in the discharge pipe temperature Tp caused by one opening degree control becomes small. As a result, since the discharge pipe temperature Tp does not rise or fall significantly, it is possible to avoid a state where the discharge pipe temperature Tp exceeds the target discharge pipe temperature Tpa and then falls below the target discharge pipe temperature Tpa. As a result, the fluctuation phenomenon of the discharge pipe temperature Tp can be prevented, and the discharge pipe temperature Tp can be stably controlled. Other effects are the same as those of the first embodiment.

[Other Embodiments]

In the present invention, each of the above-described embodiments can also be configured as follows.

For example, in the opening control method according to the first embodiment, the smaller the opening P of the expansion valve 15 is, the longer the sampling time t is, and as in the second embodiment, The smaller the opening P of the expansion valve 15 is, the smaller the opening change ΔP is. In this way, it is possible to reliably avoid the occurrence of a state in which the discharge pipe temperature Tp exceeds the target discharge pipe temperature Tpa for a while and falls below the target discharge pipe temperature Tpa for a while. Therefore, the discharge pipe temperature Tp can be controlled more stably.

In each of the above-described embodiments, the opening range of the expansion valve 15 is divided into three areas, but it may be divided into two areas, or may be divided into four or more areas. When dividing into two regions, it is preferable to omit the second predetermined value Py out of the first predetermined value Px and the second predetermined value Py in consideration of the characteristics of the expansion valve 15 (the relationship between the opening degree and the refrigerant flow rate).

The air conditioner 10 in each of the above-described embodiments may be an air conditioner capable of performing only one of the cooling operation and the heating operation.

Industrial applicability

As described above, the present invention is useful for an air conditioner provided with a refrigerant circuit in which R32 as a refrigerant circulates so that the refrigerant circuit performs a vapor compression refrigeration cycle.

Symbol Description

10 air conditioner

11 Refrigerant circuit

12 compressors

14 Outdoor heat exchanger

15 expansion valve

16 Indoor heat exchanger

30 Control Department

Claims (4)

1. An air conditioner, which is equipped with a refrigerant circuit (11) and a control unit (30), and is connected with a compressor (12), an outdoor heat exchanger (14), an expansion valve ( 15) and the indoor heat exchanger (16), HFC32 circulates in the refrigerant circuit (11) as a refrigerant, so that the refrigerant circuit (11) performs a refrigeration cycle, and the control unit (30) performs a cycle of The opening degree control of the expansion valve (15) is changed by a predetermined amount, so that the temperature of the refrigerant discharged from the compressor (12) becomes a target temperature, and it is characterized in that: The air conditioner further includes a detection unit (21) for detecting the temperature of the refrigerant discharged from the compressor (12), The control unit (30) sets the predetermined amount based on the temperature of the refrigerant discharged from the compressor (12) detected by the detection unit (21), and The predetermined cycle in the region where the opening degree of the expansion valve (15) is smaller than a predetermined value is longer than the predetermined period in the region where the opening degree of the expansion valve (15) is equal to or larger than the predetermined value. long period, A detection period in which the detection unit (21) detects the temperature of the refrigerant discharged from the compressor (12) is the same as the predetermined period. 2. The air conditioner according to claim 1, characterized in that: The predetermined amount in the region where the opening degree of the expansion valve (15) is smaller than the predetermined value is larger than the predetermined amount in the region where the opening degree of the expansion valve (15) is greater than or equal to the predetermined value. The specified amount is small. 3. The air conditioner according to claim 1 or 2, characterized in that: In a region where the opening degree of the expansion valve (15) is smaller than the predetermined value, the predetermined period becomes longer in stages as the opening degree becomes smaller. 4. The air conditioner according to claim 1, characterized in that: The expansion valve (15) is an expansion valve in which, when the opening degree is smaller than the predetermined value, the amount of change in the opening degree of the expansion valve (15) is The amount of change in the refrigerant flow rate is reduced.