JPH07294028A - Air conditioner - Google Patents

Abstract

PURPOSE:To provide the controls of the optimum discharge temperature of an air conditioner using HFC refrigerant and the temperature of an indoor heat exchanger. CONSTITUTION:An air conditioner uses HFC refrigerant and comprises a controller 14 which detects the temperature of an indoor heat exchanger 11 to decide at which of four or more stages of preset temperature zones an indoor heat exchanger temperature is and outputs a frequency control signal for increasing an output frequency at a predetermined speed in the lowest temperature zone, increasing the frequency at a low speed in an intermediate lower temperature zone, maintaining a present frequency in an intermediate upper temperature zone or decreasing the frequency at a predetermined speed in the highest temperature zone to an inverter 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved control of the temperature of an indoor heat exchanger of an air conditioner using HFC refrigerant and / or the discharge temperature of a compressor.

[0002]

2. Description of the Related Art Generally, an air conditioner using an HCFC refrigerant has a function of controlling the temperature of an indoor heat exchanger and the discharge temperature of a compressor to be below a predetermined value. The protection function has not been examined.

Since a compressor of an air conditioner using an HFC refrigerant has a lower lubrication performance than a compressor using an HCFC refrigerant, it is required to control the compressor with a small fluctuation in the rotation speed.
Therefore, an object of the present invention is to provide an air conditioner that uses an HFC refrigerant and that enables stable compressor rotation speed control without the discharge temperature and the indoor heat exchanger temperature exceeding the allowable temperature. To do.

[0004]

In order to achieve the above object, the present invention provides a temperature detector for detecting the temperature of an indoor heat exchanger, and a temperature in four stages in which the temperature of the indoor heat exchanger is preset. In addition to discriminating which is in the zone, the output frequency is increased at a predetermined speed in the lowest temperature zone,
Frequency control that increases the output frequency at a slow speed in the middle lower temperature zone, maintains the current frequency in the middle upper temperature zone, and decreases the output frequency at a predetermined speed in the highest temperature zone. And a controller for outputting a signal to the inverter.

Further, according to the present invention, the temperature detector for detecting the temperature of the gas discharged from the compressor and which of the four temperature zones the discharge temperature is preset in are discriminated and the lowest temperature is detected. In the zone, the output frequency is increased at a predetermined speed, in the middle lower temperature zone, the output frequency is increased at a slower speed, in the middle upper temperature zone, the current frequency is maintained, and at the highest temperature. The zone is provided with a control unit that outputs a frequency control signal that reduces the output frequency at a predetermined speed to the inverter.

Further, according to the present invention, the temperature detector for detecting the temperature of the indoor heat exchanger and whether the indoor heat exchanger temperature is in a preset four-step temperature zone are determined, and The output frequency increases at a predetermined speed in the low temperature zone, the output frequency increases at a slow speed in the middle lower temperature zone, the current frequency is maintained in the middle upper temperature zone, and the set temperature is set. In the above temperature zones, a frequency control signal that reduces the output frequency at a predetermined speed is output to the inverter, and when the indoor heat exchanger temperature falls from the highest temperature zone to the intermediate temperature zone, this is determined and the intermediate temperature is determined. And a control unit for increasing or decreasing the output frequency of the inverter based on the temperature zone in which the upper limit of the temperature zone is reset high.

Further, according to the present invention, the temperature detector for detecting the temperature of the gas discharged from the compressor and which of the four temperature zones the discharge temperature is preset in are determined, and the temperature is the lowest. In the temperature zone, the output frequency is increased at a predetermined speed, in the middle lower temperature zone, the output frequency is increased slowly, in the middle upper temperature zone, the current frequency is maintained, and in the temperature zone above the set temperature. Then, output a frequency control signal that reduces the output frequency at a predetermined speed to the inverter,
When the discharge temperature drops from the highest temperature zone to the middle temperature zone, it is determined and the controller that increases / decreases the output frequency of the inverter based on the temperature zone in which the upper limit of the middle temperature zone is set high again And is provided.

[0008]

According to the present invention as set forth in claim 1 or claim 2, when the indoor heat exchanger temperature and the discharge temperature approach the set temperature, the output frequency of the inverter gradually increases and the current frequency is maintained. As the frequency is not raised too much,
Fluctuations in frequency, indoor heat exchanger temperature, and discharge temperature are suppressed.

Further, according to the present invention as set forth in claim 3 or 4, after the operation is started, once the indoor heat exchanger temperature and the discharge temperature exceed the preset temperature and then fall below the preset temperature, Since the upper limit of the temperature zone in which the frequency is maintained is expanded, the frequency does not fluctuate and the temperature, the indoor heat exchanger temperature, and the discharge temperature are maintained at temperatures close to the set temperature.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an air conditioner according to the present invention will be described below with reference to the accompanying drawings. It should be noted that, in the examples, the one using R134a as the HFC refrigerant will be described.

FIG. 1 shows an air conditioner according to this embodiment. Reference numeral 1 indicates an outdoor unit and reference numeral 2 indicates an indoor unit. The outdoor unit 1 includes a compressor 4 that controls a rotation speed by changing a frequency with an inverter 3, an outdoor heat exchanger 5 that condenses or evaporates a high-temperature high-pressure refrigerant discharged from the compressor 4,
The outdoor fan 6 is provided. A four-way valve 7 is incorporated in a pipe that connects the compressor 4 and the outdoor heat exchanger 5, and the four-way valve 7 switches between cooling and heating operations. Further, an expansion valve 8 is incorporated in the middle of the pipe connecting the indoor heat exchanger 5 and the indoor unit 2. The indoor unit 2 includes an indoor heat exchanger 10 and an indoor fan 11.

Next, the control system of the air conditioner configured as described above will be described. In the air conditioner of this embodiment, a wireless remote control type control panel 12 is used.
You can switch between temperature setting, cooling, and heating operation. An indoor control unit 1 in which a microcomputer is incorporated in each of the outdoor unit 1 and the indoor unit 2
3. An outdoor control unit 14 is provided, and the indoor control unit 13 and the outdoor control unit 14 operate according to a preset program by using the operation signal from the control panel 12 as an input.

Here, the control panel 12 selects an operation switch (not shown), a temperature setter 15 for setting the indoor temperature and the target temperature of the indoor heat exchanger, and a cooling / heating operation mode. The temperature setting signal and the mode selection signal output from the temperature setting device 15 and the mode selection switch 16 are transmitted from the receiving unit 18 on the indoor unit 2 side to the indoor unit 2 via the control circuit 17. Control unit 1
Given to 3.

The outputs of the room temperature detector 19 and the heat exchanger temperature detector 20 are introduced into the indoor control section 13, and
These temperature data and control signals are transmitted to the outdoor control unit 14 via the signal line 22. Further, the output of the discharge temperature detector 21 that detects the discharge temperature Td of the compressor 4 is introduced into the outdoor control unit 14. Based on these inputs, the outdoor control unit 14 outputs control signals to the inverter 4, the outdoor fan motor 6a, and the four-way valve 7 in accordance with the processing procedure of the program shown in FIG.

Here, FIG. 2 is a graph showing the change over time in the discharge temperature Td of the compressor 4 or the indoor heat exchanger temperature Tc when the air conditioner is performing heating operation at maximum capacity. In this embodiment, the indoor heat exchanger temperature Tc is detected by the indoor heat exchanger temperature detector 20, and the outdoor control unit 14 determines that the indoor heat exchanger temperature Tc is four temperature zones A to D.
That is, Tc≤T3; A zone T3≤Tc≤T2; B zone T2≤Tc≤T1; C zone T1≤Tc; C zone It is determined whether the temperature belongs to one of the temperature zones (regions). The operation of changing the output frequency of the inverter 3 is executed according to the determination result. Numerically, T1 = 52 ° C., T2 = 48 ° C. and T3 = 45 ° C. are suitable.

The control in each temperature zone A to D is as follows.
Since the difference from the preset temperature T1 is large in the zone A having the lowest temperature, the inverter 3
The output frequency of is continuously increased at the normal rising speed.
In the B zone having a temperature zone higher than that of the A zone, the output frequency of the inverter 3 is increased at a speed slower than the frequency increasing speed of the temperature zone A. The temperature zones C and D are temperature zones defined by the maximum allowable set temperature T1. In the temperature zone C, the indoor heat exchanger temperature Tc rises too much and does not exceed the set temperature T1. In order to do so, the increase in frequency is prohibited and the current output frequency is maintained. Still, the indoor heat exchanger temperature T
Temperature zone D when c exceeds the set temperature T1
Then, the output frequency is lowered at a predetermined speed.

Next, the outdoor control unit 14 in the above control
The specific content of the operation will be described with reference to the flowchart of FIG. First, in step S1, the outdoor control unit 14
Reads the target frequency f and the indoor heat exchanger temperature Tc transmitted from the indoor control unit 13. Here, the target frequency f
Is data calculated by the indoor control unit 13 based on the difference between the set room temperature and the room temperature at the present time. Performing an operation of increasing or decreasing in the following steps with the target frequency f as the upper limit of the output frequency of the inverter 3 become.

Then, in step S2, the target frequency f is compared with the current output frequency F1 of the inverter 3. If the current output frequency F1 is equal to or lower than the target frequency f, the process proceeds to step S3, and after it is determined whether the current output frequency F1 is equal to the target frequency f, the indoor heat exchanger temperature Tc is respectively determined in step S4 and step S9. It is determined which temperature zone the temperature zone is in, and the process of setting the changing rate data of the output frequency is executed according to the temperature zone as follows. That is, when the indoor heat exchanger temperature Tc is the lowest temperature zone in the A zone (step S5), the output frequency of the inverter 3 is set to a normal rising speed, for example, 1 in 0.5 seconds.
In order to increase the frequency in Hz, the frequency output timer TM1 is set with normal data of the time interval of the frequency increase, and
+1 is added to the data of the output frequency F1.

When the indoor heat exchanger temperature Tc corresponds to the B zone (step S6), the output frequency of the inverter 3 is increased at a slower change rate than usual (for example, 1 Hz per 2 seconds). ), The slow data of the frequency rising time interval is set in the frequency output timer TM1, and +1 is added to the data of the output frequency F1. Similarly, in step S7 when the indoor heat exchanger temperature Tc is in the C zone, data for maintaining the current output frequency F1 is set, and in step S8 when the indoor heat exchanger temperature Tc is in the D zone, the output is performed. In order to decrease the frequency at a slow change rate (for example, 1 Hz in 2 seconds), the slow data of the frequency decrease time interval is set in the frequency output timer TM1 and the output frequency F1 data is subtracted by -1.

In subsequent steps S12 and S13, the frequency output timer TM1 is operated to determine whether the set time set in the above step has elapsed. If the set time has elapsed, the set output frequency F1 is set. Outputs the frequency command signal to the inverter 4.

Step S9 is a process when the current output frequency F1 is equal to the target frequency f. In this case, the indoor heat exchanger temperature Tc is still low A to C
When in the zone, the current frequency is maintained (step S10). On the other hand, when the indoor heat exchanger temperature Tc is in the D zone, the set temperature T1 remains unchanged at this frequency.
Since there is a possibility that the output frequency F1 will be greatly exceeded, the process proceeds to step S8, in which the slow data of the frequency decrease time interval is set in the frequency output timer TM1 so that the output frequency F1 decreases slowly, and the data of the output frequency F1 is set. −
Subtract one. If it is determined in step S2 that the target frequency F has decreased due to a change in room temperature and the current output frequency F1 exceeds the target frequency f, step S1
In this case, 1 lowers the output frequency F1 to the target frequency f at a normal change speed, so that the frequency output timer TM1 is set with normal data of the frequency decrease time interval and the output frequency F1 data is subtracted by -1. .

Next, FIG. 4 is a time chart showing changes in the indoor heat exchanger temperature Tc and the output frequency when the above control is executed. In the figure, regarding the change in the indoor heat exchanger temperature Tc, the solid line represents the average temperature change per unit time, and the broken line represents the actual indoor heat exchanger temperature Tc detected by the indoor heat exchanger temperature detector 20. Represents the fluctuation of. Therefore, the output frequency of the inverter 3 increases or decreases according to the change of the actual value of the indoor heat exchanger temperature Tc shown by the broken line. That is, since the indoor heat exchanger temperature Tc is in the A zone from the start of operation to the time t1, the output frequency rises at the normal speed. At the same time, the rotation speed of the compressor 4 increases, so that the indoor heat exchanger temperature Tc continues to increase. When the indoor heat exchanger temperature Tc enters the B zone (time t1 to t2), the output frequency increases at a slower and slower speed than before. Along with this, when the indoor heat exchanger temperature Tc slowly rises and reaches the C zone, this output frequency is maintained as it is (time t.
2-t3). After that, when the indoor heat exchanger temperature Tc reaches the D zone (time t3 to t4) even though the output frequency is maintained, the output frequency is gradually decreased, so that the indoor heat exchanger is gradually reduced. The temperature Tc changes from rising to falling. When the indoor heat exchanger temperature Tc falls to the C zone (time t4 to t5), the output frequency is maintained as it is. After that, the indoor heat exchanger temperature Tc is maintained near the set temperature T1 without much change while repeating a small change near the set temperature T1 at the boundary between the D zone and the C zone.

As described above, the output frequency of the inverter 3 is increased / decreased according to which of the four temperature zones A to D the detected indoor heat exchanger temperature Tc during heating is. Although the embodiment for controlling the temperature has been described, the discharge temperature detector 21 detects the discharge temperature Td of the compressor 4 instead of the indoor heat exchanger temperature Tc,
Similarly, the output frequency of the inverter 3 may be increased or decreased for each temperature zone to which the discharge temperature Td belongs.
In this case, the separation temperature of each zone is T1 = 95 ° C, T2
= 100 ° C., T3 = about 105 ° C. Then, since the indoor heat exchanger temperature Tc and the discharge temperature Td during heating increase / decrease in accordance with the increase / decrease in the rotation speed of the compressor 4, both of them behave in the same manner as the output frequency of the inverter 3 changes. Therefore, the same effect can be obtained from the viewpoint of controlling the fluctuation of the frequency to the minimum.

Next, another embodiment will be described with reference to FIGS.
Will be described with reference to. In the second embodiment, like the control of the first embodiment, each of the four temperature zones A to D is divided so that the indoor heat exchanger temperature Tc or the discharge temperature Td is maintained at the set temperature T1. As shown in FIG. 5 (a), the output frequency of the inverter 3 is increased or decreased, but the indoor heat exchanger temperature Tc or the discharge temperature Td changes from the temperature zone D where the output frequency is slowly decreased to the output frequency F1. When returning to the temperature zone C for maintaining the temperature zone C, the zone of the temperature zone C is expanded to a higher temperature side (see FIG. 5 (d)). Based on this, the output frequency of the inverter 3 is increased or decreased.

The discharge temperature Td will be described below with respect to the specific operation contents of the outdoor control unit 14 which executes the control in this embodiment.
The control will be described as an example in accordance with the flowchart of FIG.
First, in steps S20 to S32, in the process of the change of the discharge temperature Td accompanying the change of the output frequency,
This is a process for discriminating a change when the discharge temperature Td particularly drops from the D zone to the C zone as a variation between the other temperature zones A to D. In this case, the variable N takes a value of 0, 1, or 2, and when the discharge temperature Td is included in the temperature zone B, 0 is set in the variable N, and when the discharge temperature Td is included in the temperature zone C, the variable N is set. 2 is assigned to the variable N, and 1 is assigned to the variable N when included in the temperature zone D. From the value of the variable N, the discharge temperature T is changed from the D zone to the C zone.
It is determined that d has changed.

That is, first, in step S20, the fluctuation N
After initializing the value of 0 to 0, the target frequency f and the discharge temperature Td are read in step S21. Then, step S22
It is determined whether the variable N is 0 or not. When the variable N is 0, the process proceeds to step S23, the discharge temperature Td is compared with the set temperature T1 that demarcates the temperature zone C and the temperature zone D, and the discharge temperature Td is higher than the set temperature T1 in the D zone. In this case, the variable N is given a value of 1 in step S24. On the other hand, when the variable N has a value other than 0, the process proceeds to step S25 and it is determined whether or not the variable N is 1. As a result, when the variable N is 1, that is, when the discharge temperature Td has been in the D zone until then, step S26.
The discharge temperature Td and the set temperature T at the present time.
Compare with 1. As a result, the discharge temperature Td becomes the set temperature T1.
When the value falls below, the process proceeds to step S27, and the variable N is given a value of 2. Only when the value of the variable N is 2 at this time, the discharge temperature Td once changes from the D zone to the C
When you are in the zone, so step S
By determining whether the value of the variable N is 2 at 30,
It can be distinguished from other temperature fluctuations.

If the variable N is a value other than 2 according to the determination result in step S30, the process proceeds to step S31.
Select the pattern of the temperature zones A to D in FIG.
On the other hand, when the variable N is 2, the process proceeds to step S32,
The patterns of the temperature zones A'to D'in (b) are selected. The operation of steps S33 to S47 (FIGS. 6 and 7) is the same as the operation of the flowchart of FIG. 3 described above, and the discharge temperature Td is in any of the temperature zones A to D or the temperature zones A ′ to D ′. If yes, the output frequency of the inverter 3 is increased or decreased for each temperature zone. The A and A'zones increase the frequency at a normal rate of change, the B and B'zones increase the frequency more slowly than usual, the C and C'zones maintain the current frequency, and the D and The D'zone is a zone that decreases more slowly than usual. Note that step S
40 and the zone discrimination in step S35 are A and A'zone,
Since B and B'zones, C and C'zones, and D and D'zones have the same control contents, they are discriminated to be the same zones, and the process branches to the following steps.

Next, FIG. 8 is a time chart showing changes in the discharge temperature Td and the output frequency when the above control is executed. Regarding the change of the discharge temperature Td, the solid line represents the average temperature change per unit time, and the broken line represents the actual change of the discharge temperature Td.

First, a time t which is shortly after the start of operation.
Up to 1, the discharge temperature Td of the compressor 4 is low, and in the A zone at this stage, the output frequency of the inverter 3 increases at a normal speed. Following the increase in the output frequency, the discharge temperature Td rises with a change due to the response delay. From time t1 to t2 after the discharge temperature Td enters the B zone, the output frequency rises at a slower speed than before so that the discharge temperature Td does not rise too much. Discharge temperature T
d continues to rise as a whole, and the output frequency is maintained as it is at the time when it reaches the C zone (time t2 to t).
3). During this period, when the discharge temperature Td further rises and reaches the D zone, the output frequency is gradually lowered, so the discharge temperature Td turns from rising to falling.

After that, when the discharge temperature Td drops from the D zone to the C zone due to the decrease in the output frequency, this temperature fluctuation is caused by the steps S22 to S25, S26, S27 and S3 in the flowchart of FIG.
0 and S32, the C zone is discriminated and the upper limit of the C zone is higher, as shown in FIG.
Expanded to the zone. From this point onward (time t4), when the discharge temperature Td changes stably within the temperature range of the C'zone while repeating small fluctuations, the output frequency is maintained at a constant value.

The embodiment in which the output frequency is increased / decreased by the inverter 3 to control the discharge temperature Td according to which of the four temperature zones A to D the detected discharge temperature Td belongs to is as described above. However, the indoor heat exchanger temperature Tc is detected by using the indoor heat exchanger temperature detector 20 instead of the discharge temperature Td, and the inverter is similarly set for each temperature zone to which the indoor heat exchanger temperature Tc belongs. The output frequency of 3 may be increased or decreased.

In the first and second embodiments described above, the limit temperature is set further above the D zone, and when the limit temperature is exceeded despite the control of each A to D zone, Since there is a high possibility of failure of the refrigeration cycle equipment, the compressor may be stopped immediately.

In the embodiment of the present invention, the R134a HFC refrigerant is used as the compressor refrigerant, but other HFC refrigerant may be used instead of the R134a refrigerant.

As another HFC refrigerant, R is used as a single refrigerant.
22 Difluoromethane (R3
2), pentafluoroethane (R125), 1,1,
2,2-Tetrafluoroethane (R134), 1,1,
2-trifluoroethane (R143), 1,1,1-trifluoroethane (R143a), 1,1-difluoroethane (R152a), monofluorethane (R161)
Is mentioned.

The HFC refrigerant is not limited to a single refrigerant and may be a mixture of two or more HFC refrigerants. As an HFC mixed refrigerant, R125 / R1
43a / R134a mixed refrigerant, R32 / R134a mixed refrigerant, R32 / R125 mixed refrigerant, R32 / R1
A mixed refrigerant of 25 / R134a and a mixed refrigerant of R125 / R143a are considered.

[0036]

As is apparent from the above description, according to the present invention, in the air conditioner using the HFC refrigerant, the output of the inverter for each temperature zone is changed according to the variation of the indoor heat exchanger temperature and the discharge temperature. Since the operation to change the speed to increase / decrease the frequency is performed, the frequency of the indoor heat exchanger temperature and the discharge temperature is not increased or decreased too much due to the response delay, so that the frequency is stabilized and the indoor heat exchange is performed. It is possible to stabilize the temperature close to the set temperature by controlling the hunting of the container temperature and the discharge temperature.

Further, once the indoor heat exchanger temperature and the discharge temperature exceed the set temperature and then fall below the set temperature, the zone for maintaining the frequency is expanded upward, so that It is possible to suppress frequency fluctuations and perform stable temperature control.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of an embodiment of an air conditioner according to the present invention.

FIG. 2 is a diagram showing an example of temperature changes of the indoor heat exchanger temperature or the discharge temperature after the start of operation of the air conditioner and the divided temperature zones.

FIG. 3 is a flowchart describing the operation of the control unit according to the present invention as defined in claim 1 or 2.

FIG. 4 is a time chart showing a relationship between a change in the output frequency of the inverter according to the present invention and a change in the indoor heat exchanger temperature Tc.

FIG. 5 is an explanatory view showing an example of division of temperature zones in the present invention according to claim 3 or 4.

FIG. 6 is a flowchart describing the operation of the control unit according to the present invention as defined in claim 1 or 2.

FIG. 7 is a flowchart describing the operation of the control unit according to the present invention as defined in claim 1 or 2.

FIG. 8 is a time chart showing a relationship between a change in the number of output cycles of the inverter according to the present invention and a change in the indoor heat exchanger temperature Tc.

[Explanation of symbols]

 1 outdoor unit 2 indoor unit 3 inverter 4 compressor 5 outdoor heat exchanger 6 outdoor fan 7 four-way valve 10 indoor heat exchanger 11 indoor fan 12 control panel 13 indoor control unit 14 outdoor control unit 20 indoor heat exchanger temperature detector 21 Discharge temperature detector

Claims (4)

[Claims] 1. An air conditioner that uses an HFC refrigerant and controls the rotation speed of a compressor by changing the frequency by an inverter, and a temperature detector that detects the temperature of an indoor heat exchanger and the temperature of this indoor heat exchanger It is determined which of the four temperature zones is set in advance, the output frequency is increased at a predetermined speed in the lowest temperature zone, and the output frequency is increased at a slow speed in the middle lower temperature zone. Increased,
An air conditioner characterized by comprising a control unit for maintaining a current frequency in an intermediate upper temperature zone, and for outputting a frequency control signal to the inverter for decreasing the output frequency at a predetermined speed in the uppermost temperature zone. Machine. 2. An air conditioner that uses an HFC refrigerant and changes the frequency by an inverter to control the rotation speed of the compressor. A temperature detector that detects the temperature of the gas discharged from the compressor and the discharge temperature are preset. It is determined which of the four temperature zones is being used, the output frequency is increased at a predetermined speed in the lowest temperature zone, and the output frequency is increased at a slow speed in the intermediate lower temperature zone. , An air temperature control device that maintains a current frequency in an intermediate upper temperature zone and outputs a frequency control signal to the inverter that reduces the output frequency at a predetermined speed in the highest temperature zone. Harmony machine. 3. An air conditioner that uses an HFC refrigerant and controls the rotation speed of a compressor by changing the frequency by an inverter, and a temperature detector that detects the temperature of the indoor heat exchanger and the temperature of the indoor heat exchanger. It determines which of the four temperature zones is set in advance, increases the output frequency of the inverter at a predetermined speed in the lowest temperature zone, and outputs at a slow speed in the intermediate lower temperature zone. The frequency is increased, the current frequency is maintained in the upper middle temperature zone, and the frequency control signal that decreases the output frequency at a predetermined speed is output to the inverter in the uppermost temperature zone. When the temperature of the indoor heat exchanger falls in the temperature zone of, the output frequency of the inverter is determined based on the temperature zone in which the upper limit of the intermediate zone is set high again by discriminating this. An air conditioner characterized by comprising a control unit that reduced. 4. An air conditioner using HFC refrigerant and changing the frequency by an inverter to control the rotation speed of the compressor. A temperature detector for detecting the temperature of the gas discharged from the compressor and the discharge temperature are preset. It is determined which one of the four temperature zones is used, the output frequency of the inverter is increased at a predetermined speed in the lowest temperature zone, and the output frequency is increased at a slow speed in the intermediate lower temperature zone. The frequency control signal that increases and maintains the current frequency in the middle upper temperature zone and decreases the output frequency at a predetermined speed in the temperature zone above the set temperature is output to the inverter,
When the discharge temperature drops from the highest temperature zone to the middle temperature zone, it is determined and the controller that increases / decreases the output frequency of the inverter based on the temperature zone in which the upper limit of the middle temperature zone is set high again An air conditioner comprising: