JP3144884B2 - Air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner for controlling an ability to maintain a constant blowing temperature.

[0002]

2. Description of the Related Art As a conventional air conditioner for performing constant blow-off temperature control, there is one disclosed in Japanese Patent Application Laid-Open No. 2-122138.

[0003] Hereinafter, an air conditioner that performs the above-described conventional blow-out temperature constant control will be described with reference to the drawings. FIG.
Is a schematic configuration diagram showing a conventional air conditioner, 1 is a duct type indoor unit main body, and detects the temperature of air blown out by the indoor heat exchanger 2, the indoor blower 3, and the indoor blower 3 therein. And a blowout temperature detector 4 for detecting the temperature. Reference numeral 5 denotes an outdoor unit main body, in which a variable capacity compressor 6, an outdoor heat exchanger 7,
An outdoor blower 8 and a compressor controller 9 for controlling the performance of the compressor 6 are provided.

A duct 11 connects the indoor unit main body 1 to the room to be air-conditioned 10, and guides warm air or cold air to the room to be air-conditioned 10. A variable air volume unit 12 is provided in the middle of the duct 11 to control the room temperature of the room to be air-conditioned 10 by changing the air volume. Reference numeral 13 denotes a return duct,
The air is guided from 0 to the indoor unit main body 1. 14 is an intake duct,
An exhaust duct 15 includes an air supply duct 14 and an exhaust duct 15.
In any case, a fan 1 as a supply / exhaust device in the middle of the duct
4a, 15a, exhausts a part of the air in the return duct 13 and supplies outside air to the air-conditioned room 10
Is ventilating.

Reference numeral 16 denotes an air volume control device of the variable air volume unit 12, which is detected by a room temperature detector 18b and a set room temperature T0 set by a room temperature setter 18a provided in a room temperature controller 17 in the room 10 to be air-conditioned. The damper (not shown) and the motor (not shown) in the variable air volume unit 12 are controlled by the difference from the room temperature T1 to control the air volume passing through the duct 11. Reference numeral 19 denotes an operation switch for the variable air volume unit 12. When the operation switch 19 is turned off, the variable air volume unit 12 is operated.
The inside damper is closed to stop the passing airflow, and the air conditioning is stopped.

[0006] The operation of the air conditioner configured as described above, which performs the blow-off temperature constant control, during cooling will be described below with reference to FIG.

The operation switch 19 of the variable air volume unit 12
Is ON, the damper in the variable air volume unit 12 is opened, air conditioning is started, and the room temperature setting unit 18 in the room temperature controller 17 is opened.
The difference (step a) between the set room temperature T0 set at a and the room temperature T1 detected by the room temperature detector 18b (step a) is the cooling / heating T1.
When −T0> 0, the air volume control device 16 controls the variable air volume unit 12 so that the air volume in the duct 11 increases (step b). Conversely, when T1-T0 <0, the duct 11
Is controlled so as to reduce the amount of air inside (step c).

At this time, in order to secure the ventilation air volume of the room to be air-conditioned 10, the variable air volume unit 12 does not reduce the air volume passing through the duct 11 at least to a predetermined air volume.
As described above, although the amount of air passing through the duct 11 changes, the compressor controller 9 adjusts the capacity of the compressor 6 so that the blowout temperature detected by the blowout temperature detector 4 in the indoor unit main body 1 is always constant. Variable (step d).

As described above, air is always blown from the indoor unit main body 1 at a constant blowing temperature, and the air volume supplied to the air-conditioned room 10 is changed by the variable air volume unit 12 to air-condition the air-conditioned room 10. It is.

[0010]

However, in the above-mentioned conventional structure, even if the air-conditioning load of the room to be air-conditioned decreases, the supply air volume cannot be reduced below a certain air volume in order to secure the ventilation air volume. However, there is a disadvantage that the room to be air-conditioned is too cold, and when heated, it is too warm, that is, the performance of the air conditioner does not decrease.

According to the present invention, when the air-conditioning load of the room to be air-conditioned is reduced, the air-conditioned room is not cooled too much during cooling or overheated during heating to secure a ventilation air volume and maintain a comfortable indoor environment. Aim.

[0012]

In order to achieve the above object, an air conditioner according to the present invention comprises an outlet temperature detector for detecting the temperature of air blown from an indoor unit main body, and a return temperature detector for detecting a return air temperature. A compressor, a compressor controller for controlling the operation of the compressor, and a controller for controlling the compressor controller.

The control device causes the compressor controller to control the capacity of the compressor so that the blown air temperature detected by the blowout temperature detector becomes a preset set temperature, and the return temperature is set. When the temperature is lowered by a certain value during cooling or by a certain temperature during heating, the control is performed such that the set temperature of the blown air temperature is increased by a predetermined value during the cooling operation and decreased by a predetermined value during the heating operation.

In another air conditioner of the present invention, an air temperature detector for detecting the temperature of air blown from an indoor unit main body;
It has a return temperature detector for detecting the return air temperature, a compressor controller for controlling the operation of the compressor, and a control device for controlling the compressor controller.

The control device controls the compressor controller to control the capacity of the compressor so that the temperature of the blown air detected by the blower temperature detector becomes a preset temperature, and the temperature of the blown air is controlled. If the cooling temperature is lower than the set temperature by a certain temperature during cooling or a certain temperature during heating, the operation of the compressor is stopped (thermo OFF), and the operation of the compressor is stopped a predetermined number of times within a predetermined time, or When the return air temperature is lower than the set temperature by a certain value during cooling or by a certain temperature during heating, control is performed to raise the set temperature of the blow-off air temperature by a predetermined value during cooling operation and to lower it by a predetermined value during heating operation. are doing.

[0016]

In the air conditioner of the present invention, when the air-conditioning load of the room to be air-conditioned is reduced, the amount of air passing through the duct is reduced by the variable air volume unit, and the temperature of the air discharged from the air conditioner decreases during cooling and increases during heating. At this time, the controller controls the capacity of the compressor so as to keep the blown air temperature constant.
When the return air temperature is lower than the set temperature by a certain value during cooling or by a certain temperature during heating, the control device raises the set temperature of the air blown from the indoor unit body by a predetermined value during the cooling operation (by a predetermined value during the heating operation). In addition, the compressor controller controls the capacity of the compressor (reduces the capacity) so that the temperature of the air blown out from the indoor unit itself becomes the newly set temperature.
Is performed.

As a result, by detecting the return temperature, it is possible to detect a decrease in the load on the entire room to be conditioned, and the temperature of the air blown out from the indoor unit increases by a predetermined value during the cooling operation (decreases by a predetermined value during the heating operation). Even if the air conditioning load is the same, the variable air volume unit increases the air volume passing through the duct, and furthermore, the variable air volume unit can reduce the air volume to the minimum air volume (ventilation air volume), further reducing the compressor capacity. This prevents the supply of cold air during cooling and hot air during heating even though there is no load, and prevents a decrease in comfort due to excessive cooling and excessive heating.

According to another air conditioner of the present invention, when the air-conditioning load of the room to be air-conditioned is reduced, the air volume passing through the duct is reduced by the variable air volume unit, and the temperature of the air blown out of the air conditioner is reduced during cooling to reduce the heating. At this time, the controller controls the capacity of the compressor to keep the blown air temperature constant, and at the same time, the blown air temperature falls below the set temperature by a fixed temperature during cooling or by a certain temperature during heating. Then, the operation of the compressor is stopped (thermo-off), when the operation of the compressor has been stopped a predetermined number of times within a predetermined time, or when the return air temperature is lower than the set temperature by a certain temperature during cooling or during heating. When the temperature rises by a certain amount, the control device raises the set temperature of the air blown from the indoor unit main body by a predetermined value during the cooling operation (decreases the predetermined temperature during the heating operation), and increases the air blown from the indoor unit main body. Temperature to perform the capacity control of the compressor to the compressor controller to be newly set temperature (capacity reduction) of.

As a result, in response to a sudden decrease in the load caused by stopping the air supply at the variable air volume unit, the decrease in the air conditioning load can be detected by detecting the thermo-OFF based on the blown air temperature, and the return temperature can be detected by detecting the return temperature. A decrease in the load of the entire conditioned room can be detected. At this time, even if the temperature of the air blown out from the indoor unit increases by a predetermined value during the cooling operation (decreases by the predetermined value during the heating operation) and the air conditioning load of the conditioned room is the same, the variable air volume unit As a result, the air volume passing through the duct increases, and the variable air volume unit can further reduce the air volume to the minimum air volume (ventilation air volume). In addition, it is possible to prevent continuous supply of cold air during cooling and hot air during heating, thereby preventing a decrease in comfort due to excessive cooling and excessive heating.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the air conditioner according to the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an air conditioner of one embodiment of the present invention, FIG. 2 is a block diagram of the air conditioner of the embodiment,
FIG. 3 is a flowchart showing the operation of the air conditioner of the embodiment.

In FIG. 1, a duct type indoor unit main body 1 is shown.
Has an indoor heat exchanger 2, an indoor blower 3, an outlet temperature detector 4, and a return temperature detector 20 inside.
The outdoor unit main body 5 includes a compressor 6 having a variable capacity, an outdoor heat exchanger 7, an outdoor blower 8, and a compressor controller 21 inside.

In FIG. 2, reference numeral 22 denotes a control device for controlling the air conditioner according to the present embodiment, which is an outlet temperature setting device 23 for setting the outlet temperature (set outlet temperature t0) and an outlet temperature detector 4.
A blow-out temperature comparator 24 for comparing the blow-out temperature t1 detected at and the set blow-out temperature t0, a return temperature setting unit 25 for setting a return temperature (set return temperature t2),
Return temperature t detected by return temperature detector 20
Return temperature comparator 26 for comparing the set return temperature t2 with a set return temperature t2, and an operation mode detector 2 for detecting an operation mode
7 is built in.

The control device 22 changes the capacity of the compressor 6 via the compressor controller 21 according to the comparison result of the blow-out temperature comparator 24 and the operation mode detected by the operation mode detector 27, and also returns the return temperature comparator The set temperature of the outlet temperature setter 23 is changed according to the comparison result of 26.

Next, a specific example of this operation will be described with reference to the flowchart of FIG. 3 showing the operation during the cooling operation.

The operation switch 19 of the variable air volume unit 12
Is ON, the damper in the variable air volume unit 12 is opened, air conditioning is started, and the room temperature setting unit 18 in the room temperature controller 17 is opened.
When the difference between the set room temperature T0 set in a and the room temperature T1 detected by the room temperature detector 18b is T1-T0> 0, the air volume control device 16 is variable so that the air volume in the duct 11 increases. The air volume unit 12 is controlled (step 1).
Conversely, when T1−T0 <0, control is performed to reduce the air volume in the duct 11 (step 1).

At this time, in order to secure the ventilation air volume of the room to be air-conditioned 10, the variable air volume unit 12 does not reduce the air volume passing through the duct 11 at least below a preset air volume.
As described above, although the amount of air passing through the duct 11 changes, the compressor control is performed so that the outlet temperature t1 detected by the outlet temperature detector 4 in the indoor unit main body 1 always becomes the set temperature t0 of the outlet temperature setter 23. The compressor 20 varies the capacity of the compressor 6. (Step 2).

The control device 22 determines the return temperature t3
Is lower than the set return temperature t2 by a constant temperature A during cooling (t3−t2 ≦ −A) or a constant temperature B during heating (t3−t2 ≧ B), it is determined that the load of the entire air-conditioned room is reduced. The set temperature t0 of the outlet temperature setting device 23 from the indoor unit main body is increased by a predetermined value during cooling and decreased by a predetermined value during heating (step 3).

The controller 22 raises the set temperature t0 of the air blown from the indoor unit body 1 by a predetermined value during the cooling operation (decreases the predetermined value during the heating operation), and newly sets the temperature t1 of the air blown from the indoor unit body 1. The compressor controller 21 controls the capacity of the compressor 6 (decreases the capacity) so as to reach the temperature t0.

More specifically, when the return temperature t3 is lower than the set return temperature t2 by a constant temperature A during cooling, the constant blow temperature t0 is changed from 15 ° C. to 18 ° C. At this time, the maximum supply air volume to the air-conditioned room 10 is 50 m ³
/ Min, minimum supply airflow (ventilation required air amount) is 20 m ³ / min
Then, if the constant blowing temperature t0 remains at 15 ° C.,
The capacity can be reduced only to about 40%, and when the cooling load of the room to be air-conditioned 10 is 40% or less, which is the above-described problem, the room is overcooled.

As in the present embodiment, when the return temperature t3 falls below the set return temperature by the control device 22 by a certain value during cooling operation (or by a certain value during heating operation), the constant blowing temperature t0 is changed to 18 ° C. Assuming that the suction temperature of the indoor unit 1 is 26 ° C., 20 (26−18) / 5
Control from 0 (26-15) = 0.29 to about 29% can be performed while securing a minimum air flow of 20 m ³ / min.

In the case of heating, as in the case of cooling,
The heating capacity control range can be expanded while ensuring the minimum air volume.

As described above, when the return temperature t3 falls below the set return temperature t2 by the constant temperature A during cooling or the constant temperature B during heating, the controller 22 reduces the set temperature t0 of the blown air temperature during cooling. By increasing the predetermined value and decreasing the predetermined value during heating, it is possible to expand the capacity control range while securing the minimum ventilation air volume, and to prevent the room from being overcooled or overheated when the air-conditioning load of the room to be air-conditioned 10 is reduced. it can.

Hereinafter, another embodiment of the air conditioner according to the present invention will be described with reference to the drawings. The same components as those of the prior art will be denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 4 is a schematic configuration diagram of an air conditioner according to another embodiment of the present invention, FIG. 5 is a block diagram of the air conditioner of the embodiment, and FIG. 6 shows the operation of the air conditioner of the embodiment. It is a flowchart shown.

In FIG. 4, a duct type indoor unit main body 1 is shown.
Is provided with an indoor heat exchanger 2, an indoor blower 3, an outlet temperature detector 4, and a return temperature detector 30 inside.
The outdoor unit main body 5 includes a compressor 6 having a variable capacity, an outdoor heat exchanger 7, an outdoor blower 8, and a compressor controller 31 inside.

In FIG. 5, reference numeral 32 denotes a control device for controlling the air conditioner of the present embodiment, which is an outlet temperature setting device 33 for setting the outlet temperature (set outlet temperature t0), and an outlet temperature detector 4.
A blow-out temperature comparator 34 for comparing the blow-out temperature t1 detected at the above with the set blow-out temperature t0, and a return temperature setting unit 35 for setting a return temperature (set return temperature t2);
Return temperature t detected by return temperature detector 30
3 and a set return temperature t2, a return temperature comparator 36, and an operation mode detector 3 for detecting an operation mode
7 and a counter 38 for counting the number of stops X of the compressor 6.

The controller 32 changes the capacity of the compressor 6 via the compressor controller 31 in accordance with the comparison result of the blow-out temperature comparator 34 and the operation mode detected by the operation mode detector 37, and performs the compression by the counter 38. The set temperature of the blowout temperature setter 33 is changed according to the number of times of machine stoppage or the comparison result of the return temperature comparator 26.

Next, a specific example of this operation will be described with reference to the flowchart of FIG. 6 showing the operation during the cooling operation.

Operation switch 19 of the variable air volume unit 12
Is ON, if the difference between the set room temperature T0 set by the room temperature setting unit 18a in the room temperature controller 17 and the room temperature T1 detected by the room temperature detector 18b is T1-T0> 0,
The air volume control device 16 controls the variable air volume unit 12 so that the air volume in the duct 11 increases (step 4). Conversely, if T1-T0 <0, control is performed to reduce the air volume in the duct 11 (step 4).

At this time, in order to secure the ventilation air volume of the room to be air-conditioned 10, the variable air volume unit 12 does not reduce the air volume passing through the duct 11 at least below a preset air volume.
As described above, although the amount of air passing through the duct 11 changes, the compressor control is performed such that the outlet temperature t1 detected by the outlet temperature detector 4 in the indoor unit main body 1 always becomes the set temperature t0 of the outlet temperature setting device 33. The compressor 30 changes the capacity of the compressor 6 (step 5).

The control device 32 determines whether the blowing temperature t1 is lower than the set temperature t0 by a constant temperature C during cooling (t1-t).
0 ≦ −C) or whether the constant temperature D during heating rises (t1−t0 ≧
D) Then, the compressor controller 30 is controlled to stop the operation of the compressor 6 (step 7), and at the same time, the number of stop times X of the compressor 6 counted by the
However, when a predetermined number of times occur within a predetermined time, when the air supply is stopped by the variable air volume unit, a sudden decrease in the load is detected.
It is determined that the air-conditioning load has decreased, and the set temperature t0 of the outlet temperature setting device 33 is increased by a predetermined value during cooling and reduced by a predetermined value during heating (step 6).

Whether the return temperature t3 is lower than the set return temperature t2 by a constant temperature A during cooling (t3−t2 ≦
-A) or does the constant temperature B increase during heating (t3-t2 ≧ B)
Then, it is determined that the load on the entire room to be air-conditioned is reduced, and the set temperature t0 of the outlet temperature setting device 33 is increased by a predetermined value during cooling and is decreased by a predetermined value during heating (step 6).

The control device 32 raises the set temperature t0 of the air blown from the indoor unit main body 1 by a predetermined value during the cooling operation (decreases the predetermined value during the heating operation), and newly sets the temperature t1 of the air blown from the indoor unit main body 1. The compressor controller 31 controls the capacity of the compressor 6 (reduces the capacity) so that the temperature t0 is reached.

More specifically, when the operation of the compressor 6 is stopped a predetermined number of times X within a predetermined time, or when the return temperature t3 falls below the set return temperature t2 by a constant temperature A during cooling, a constant blow temperature t0 from 15 ° C to 18
Change to ° C. At this time, assuming that the maximum supply air volume to the air-conditioned room 10 is 50 m ³ / min and the minimum supply air volume (required ventilation air volume) is 20 m ³ / min, if the constant blow temperature t0 remains at 15 ° C., the capacity is about If the cooling load of the room to be air-conditioned 10, which is the above-mentioned problem, becomes 40% or less, the room can be overcooled.

As in the present embodiment, when the return temperature t3 is lower than the set return temperature by the control device 32 during the cooling operation (or increases during the heating operation), the constant blowing temperature t0 is changed to 18 ° C. Then, if the suction temperature of the indoor unit 1 is assumed to be 26 ° C., 20 (26−18) / 50
The control from (26-15) = 0.29 to about 29% can be performed while securing the minimum airflow of 20 m ³ / min.

In the case of heating, as in the case of cooling,
The heating capacity control range can be expanded while ensuring the minimum air volume.

As described above, when the operation of the compressor 6 is stopped a predetermined number of times X within the predetermined time by the control device 32, the sudden decrease in the load caused by the stoppage of the air supply by the variable air volume unit is as follows. Thermo OF by outlet air temperature
By detecting F, a decrease in the air conditioning load can be detected, and when the return temperature t3 falls below the set return temperature t2 by a constant temperature A during cooling or a constant temperature B during heating, the return temperature is detected to detect the air-conditioning target. A decrease in the load of the entire room can be detected. At this time, the capacity control range can be expanded while securing the minimum ventilation air volume by lowering the set temperature t0 of the blown air temperature during cooling, by a predetermined value, and during heating, by a predetermined value. In addition, when the air conditioning load of the room to be air-conditioned 10 is reduced, it is possible to prevent the room from being too cold or too warm.

Further, by detecting both a sudden decrease in load and a decrease in the load of the whole room to be air-conditioned, and changing the set temperature of the blown air temperature, the capacity control of the air conditioner in the room to be air-conditioned is performed. The range can be expanded while always ensuring the minimum airflow.

[0050]

As described above, in the air conditioner of the present invention, the return temperature t3 is set to the set return temperature t2 by the control device.
Thus, when the constant temperature A during cooling decreases or the constant temperature B during heating increases, the set temperature t0 of the blow-off air temperature is reduced during cooling,
Since the control for increasing the predetermined value and performing the control for lowering the predetermined value during heating is performed, even when the air-conditioning load of the room to be air-conditioned is low, sufficient capacity control can be performed while securing the ventilation air volume, and the room to be air-conditioned becomes too cold during cooling. In addition, it is possible to prevent overheating during heating and to maintain a comfortable indoor environment.

According to another air conditioner of the present invention, the controller stops the operation of the compressor a predetermined number of times X within a predetermined time.
If this occurs, the air conditioning load can be detected by detecting the thermo-OFF based on the blown air temperature, and the return temperature t3 can be detected as the set return temperature t2 in response to a sudden decrease in the load caused by stopping the air supply with the variable air volume unit.
If the constant temperature during cooling A decreases or the constant temperature during heating increases, the return temperature can be detected to detect a decrease in the load of the entire room to be conditioned. By increasing the predetermined value and decreasing the predetermined value during heating, the capacity control range can be expanded while securing the minimum ventilation air volume, and the room can be prevented from being overcooled or overheated when the air-conditioning load of the room to be air-conditioned decreases. .

Further, by detecting both a sudden decrease in load and a decrease in the load of the whole room to be air-conditioned, and changing the set temperature of the blown air temperature, the capacity control of the air conditioner in the room to be air-conditioned is performed. The range can be expanded while always ensuring the minimum air volume, and there is an effect that a comfortable indoor environment can be maintained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an air conditioner according to the present invention.

FIG. 2 is a block diagram of the air conditioner of the embodiment.

FIG. 3 is a flowchart showing an operation of the air conditioner of the embodiment during a cooling operation.

FIG. 4 is a schematic configuration diagram of another embodiment of the air conditioner according to the present invention.

FIG. 5 is a block diagram of the air conditioner of the embodiment.

FIG. 6 is a flowchart showing the operation of the air conditioner of the embodiment during a cooling operation.

FIG. 7 is a schematic configuration diagram of a conventional air conditioner.

FIG. 8 is a flowchart showing an operation of the conventional air conditioner during a cooling operation.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 indoor unit main body 2 indoor heat exchanger 3 indoor blower 4 outlet temperature detector 5 outdoor unit main body 6 compressor 7 outdoor heat exchanger 8 outdoor blower 10 air-conditioned room 11 duct 12 variable air volume unit 16 air volume control device 20, 30 Return temperature detector 21, 31 Compressor controller 22, 32 Controller

Claims (2)

(57) [Claims] 1. A duct-type indoor unit body provided in a duct communicating with a room to be air-conditioned and having an indoor-side heat exchanger and an indoor-side blower therein, and a variable-capacity compressor, an outdoor-side heat exchanger therein. An outdoor unit main body having an outdoor blower, a variable air volume unit provided in a duct downstream of the indoor unit main body to change an air flow rate through the duct, an operation mode of the air conditioner, and setting of a room temperature of the room to be air-conditioned. An air volume control device that controls the variable air volume unit so that the room temperature of the room to be air-conditioned matches the set room temperature in accordance with the room temperature, an air temperature detector that detects the temperature of air blown from the indoor unit main body, A return temperature detector for detecting a return air temperature sucked into the machine body, a compressor controller for controlling operation of the compressor, and a control device for controlling the compressor controller, the control device comprising: The compressor controller controls the performance of the compressor so that the blow-off air temperature detected by the blow-out temperature detector becomes a preset temperature, and returns the return temperature detected by the return temperature detector. If the air temperature is lower than the preset temperature by a certain value during the cooling operation or by a certain value during the heating operation, the set temperature of the blowing air temperature is increased by a predetermined value during the cooling operation,
An air conditioner characterized by lowering a predetermined value during heating operation. 2. A duct type indoor unit body provided in a duct communicating with a room to be air-conditioned and having an indoor side heat exchanger and an indoor side blower therein, and a variable capacity compressor, an outdoor side heat exchanger inside, An outdoor unit main body having an outdoor blower, a variable air volume unit provided in a duct downstream of the indoor unit main body to change an air flow rate through the duct, an operation mode of the air conditioner, and setting of a room temperature of the room to be air-conditioned. An air volume control device that controls the variable air volume unit so that the room temperature of the room to be air-conditioned matches the set room temperature in accordance with the room temperature, an air temperature detector that detects the temperature of air blown from the indoor unit main body, A return temperature detector for detecting a return air temperature sucked into the machine body, a compressor controller for controlling operation of the compressor, and a control device for controlling the compressor controller, the control device comprising: The compressor controller controls the performance of the compressor so that the blow-out air temperature detected by the blow-out temperature detector becomes a preset set temperature, and the blow-out air temperature becomes lower than the set temperature during cooling. When the temperature drops or the temperature rises during heating, the operation of the compressor is stopped, and when the operation of the compressor is stopped a predetermined number of times within a predetermined time, or when the return air temperature is lower than the set temperature and the cooling operation is constant. An air conditioner characterized in that when a temperature drops or a certain temperature rises during heating, the set temperature of the blow-out air temperature is increased by a predetermined value during a cooling operation and decreased by a predetermined value during a heating operation.