JPH11132605A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a decrease in heating capacity and heating efficiency by detecting each temperature of a refrigerant sucked into an outdoor heat exchanger and a compressor and controlling during heating an execution of a defrosting operation according to a detected temperature of the refrigerant of both the outdoor heat exchanger and the compressor. SOLUTION: To an outdoor control unit 40 are connected a four-way valve 2, a motor driven expansion valve 4, an outdoor fan motor 6M, a heat exchanger temperature sensor 11, a refrigerant temperature sensor 13, and an inverter circuit 41. A corrected temperature of a temperature detected by the heat exchanger temperature sensor 11 is obtained by correcting a a temperature detected by the refrigerant temperature sensor 13 and a correction factor. This corrected temperature is then used to judge defrosting conditions. When a prescribed defrosting condition is established, a heating cycle is changed to a defrosting cycle by the four-way valve 2, a high temperature refrigerant is supplied to an outdoor heat exchanger thereby to execute a defrosting operation. As a result, it is possible to grasp a frosting amount of the outdoor heat exchanger and execute defrosting at an optimum timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner having a function of defrosting an outdoor heat exchanger during heating.

[0002]

2. Description of the Related Art A heat pump refrigeration cycle for circulating a refrigerant by sequentially connecting a compressor, a four-way valve, an indoor heat exchanger, a decompressor, and an outdoor heat exchanger with a pipe is provided. 2. Description of the Related Art There is an air conditioner that performs a heating operation by making an outdoor heat exchanger function as an evaporator.

[0003] In this air conditioner, during heating, frost gradually adheres to the surface of the outdoor heat exchanger (evaporator), and as it is, the amount of heat exchange in the outdoor heat exchanger decreases, leading to a decrease in heating capacity. I will.

As a countermeasure, the temperature Te of the outdoor heat exchanger is detected, the amount of frost formed in the outdoor heat exchanger is determined from the detected temperature Te, and the flow of the refrigerant is reversed when the defrosting condition is satisfied. The refrigerant discharged from the compressor (high-temperature refrigerant) flows into the outdoor heat exchanger as it is, and a defrosting operation (reverse defrosting) for removing frost by the heat of the high-temperature refrigerant is performed.

[0005] As a means for determining the defrosting condition based on the detected temperature Te, there is a temperature drop detection method. This is because the minimum value Teo of the detected temperature Te is detected in a predetermined period Δt after a lapse of ta time from the start of the compressor or the end of the previous defrosting operation, and after the predetermined period Δt elapses, the minimum value Teo and the heat exchanger are determined. When the state where the difference ΔTe (= Teo−Te) from the temperature Te is equal to or more than the set value is continued for a predetermined time or longer, or when the detected temperature T
When the state where e is equal to or less than the predetermined value is continued for a predetermined time or more, the defrosting operation is started.

[0006]

When the refrigerant is accumulated in the outdoor heat exchanger when the operation is stopped (refrigerant stagnation), or when the piping of the refrigeration cycle is long, even if the compressor starts and heating starts, or Even when the defrosting operation (reverse defrosting) is completed and the operation returns to the heating, it may take time for the temperature Te of the outdoor heat exchanger to rise. In this case, the minimum value Teo detected after the start-up becomes an unnecessarily low value, and as a result, the defrosting condition is not easily satisfied, the amount of frost formed on the outdoor heat exchanger increases, and the heating capacity is adversely affected. I will.

[0007] Further, if there is a change in the set indoor temperature for adjusting the indoor temperature or a change in the speed of the indoor fan for adjusting the indoor air flow, the state of the refrigeration cycle greatly changes.
Under such a situation, a phenomenon occurs in which the temperature Te of the outdoor heat exchanger drops transiently even though the amount of frost formed in the outdoor heat exchanger is still small, and unnecessary defrosting operation starts, that is, so-called empty defrosting. Would. Since the defrosting operation (reverse defrosting) interrupts the heating operation, unnecessary execution of the defrosting operation causes a decrease in the heating efficiency.

[0008] The present invention has been made in view of the above circumstances,
The purpose is to accurately capture the amount of frost formed in the outdoor heat exchanger even when the temperature of the outdoor heat exchanger Te rises slowly at the time of starting heating or returning to heating, or even when the refrigeration cycle varies greatly. An object of the present invention is to provide an air conditioner that can perform defrosting at an optimal timing, thereby preventing a decrease in heating capacity and heating efficiency, and having excellent reliability.

[0009]

An air conditioner according to a first aspect of the present invention includes a refrigeration cycle for connecting a compressor, an indoor heat exchanger, a decompressor, and an outdoor heat exchanger to circulate a refrigerant. A first temperature sensor for detecting a temperature Te of the outdoor heat exchanger, and a refrigerant sucked into the compressor in an air conditioner capable of performing a heating operation in which a heat exchanger functions as a condenser and an outdoor heat exchanger functions as an evaporator. A second temperature sensor for detecting the temperature Ts of the outdoor heat exchanger, and controlling the execution of the defrosting operation on the outdoor heat exchanger according to the detected temperature Te of the first temperature sensor and the detected temperature Ts of the second temperature sensor during heating. Control means for performing
Is provided.

In the air conditioner of the second invention, the control means of the first invention corrects the detected temperature Te by using the detected temperature Ts and the correction coefficient K to obtain a corrected temperature TE, and starts the compressor or the previous time. A predetermined period Δta time after the end of the defrosting operation Δ
At t, the lowest value TEo of the correction temperature TE is detected, and tb time [>] from the start of the compressor or the end of the previous defrosting operation
(Ta + Δt)], when the difference ΔTE (= TEo−TE) between the minimum value TEo and the correction temperature TE is equal to or higher than the set value for a predetermined time or when the correction temperature TE is equal to or lower than the predetermined value for a predetermined time. When the above is continued, the defrosting operation is started.

In the air conditioner of the third invention, the control means of the first invention corrects the detected temperature Te using the detected temperature Ts and the correction coefficient K to obtain the corrected temperature TE, and also starts the compressor or determines whether the correction temperature TE has been reached. In the predetermined period Δt after the lapse of ta time from the end of the defrosting operation, the minimum value Teo of the detected temperature Te is detected, and the minimum value Teo is corrected by the detection temperature Ts and the correction coefficient K to obtain the minimum value TEo. Tb time from the start or the end of the previous defrosting operation [> (ta + Δ
t)], and then the difference ΔTE between the minimum value TEo and the correction temperature TE
The defrosting operation is started when the state where (= TEo-TE) is equal to or higher than the set value has been continued for a predetermined time or longer, or when the state where the correction temperature TE is equal to or lower than the predetermined value has been continued for a predetermined time or longer.

According to a fourth aspect of the present invention, there is provided an air conditioner, wherein the control means according to the second or third aspect of the present invention is arranged such that when the set indoor temperature for indoor temperature adjustment is changed, or when the indoor fan speed for indoor air volume adjustment is changed. Whenever there is a change, the lowest value TE
Update o.

An air conditioner according to a fifth aspect of the present invention includes a refrigeration cycle for connecting a compressor, an indoor heat exchanger, a decompressor, and an outdoor heat exchanger to circulate a refrigerant, wherein the indoor heat exchanger includes a condenser and an outdoor heat exchanger. In an air conditioner capable of performing a heating operation in which a heat exchanger functions as an evaporator, a first temperature sensor for detecting a temperature Te of the outdoor heat exchanger and a temperature Ts of a refrigerant sucked into the compressor are detected. At the time of heating with the second temperature sensor, the difference (= Te−Ts) between the detected temperature Te of the first temperature sensor and the detected temperature Ts of the second temperature sensor is determined as the degree of superheat SH, and this degree of superheat SH is determined in advance. Set target superheat degree S
First control means for controlling the flow rate of refrigerant to the outdoor heat exchanger such that the deviation ΔSH from Ho becomes zero, and the outdoor heat exchanger according to the detected temperature Te of the first temperature sensor and the deviation ΔSH during heating. Second control means for controlling the execution of the defrosting operation on the exchanger.

In an air conditioner according to a sixth aspect of the present invention, the second control means of the fifth aspect of the present invention corrects the detected temperature Te by using the deviation ΔSH and the correction coefficient K to obtain the corrected temperature TE, and starts the compressor or the previous time. In the predetermined period Δt after the end of the defrosting operation of the present embodiment, the minimum value TEo of the correction temperature TE is detected during the predetermined period Δt, and the start of the compressor or the end of the previous defrosting operation for tb time [>]
(Ta + Δt)], when the difference ΔTE (= TEo−TE) between the minimum value TEo and the correction temperature TE is equal to or higher than the set value for a predetermined time or when the correction temperature TE is equal to or lower than the predetermined value for a predetermined time. When the above is continued, the defrosting operation is started.

According to an air conditioner of a seventh aspect, the second control means of the fifth aspect corrects the detected temperature Te by using the deviation ΔSH and the correction coefficient K to obtain a correction temperature TE.
The minimum value Teo of the detected temperature Te is detected during a predetermined period Δt after the start of the compressor or the end of the previous defrosting operation after ta time, and the minimum value Teo is corrected by the deviation ΔSH and the correction coefficient K to set the minimum value TEo. Tb time [> (ta + Δ) from the start of the compressor or the end of the previous defrosting operation.
t)], and then the difference ΔTE between the minimum value TEo and the correction temperature TE
The defrosting operation is started when the state where (= TEo-TE) is equal to or higher than the set value has been continued for a predetermined time or longer, or when the state where the correction temperature TE is equal to or lower than the predetermined value has been continued for a predetermined time or longer.

An air conditioner according to an eighth aspect of the present invention is the air conditioner according to the sixth or seventh aspect, wherein the control means according to the sixth or seventh aspect of the present invention is adapted such that when the set indoor temperature for indoor temperature adjustment is changed, or when the indoor fan speed for indoor air volume adjustment is changed. Whenever there is a change, the lowest value TE
Update o.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(1) An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 2, the outdoor unit A and the indoor unit B are equipped with a heat pump refrigeration cycle.

Reference numeral 1 denotes a variable capacity compressor. An outdoor heat exchanger 3 is connected to a discharge port of the compressor 1 via a four-way valve 2 by piping. An indoor heat exchanger 5 is connected to the outdoor heat exchanger 3 via a motorized expansion valve 4 which is a decompressor, and the indoor heat exchanger 5 is connected to a suction port of the compressor 1 via a four-way valve 2. Connected.

An outdoor fan 6 is provided near the outdoor heat exchanger 3 and an indoor fan 7 is provided near the indoor heat exchanger 5. A heat exchanger temperature sensor (first temperature sensor) 11 for detecting the heat exchanger temperature Te is attached to the outdoor heat exchanger 3.
An indoor temperature sensor 12 for detecting an indoor temperature Ta is provided in a suction air passage of the indoor fan 7. A refrigerant temperature sensor (second temperature sensor) 1 for detecting a temperature Ts of the refrigerant sucked into the compressor 1 in a pipe between the four-way valve 2 and a suction port of the compressor 1.
3 is attached.

FIG. 1 shows the control circuit. The indoor control unit 20 of the indoor unit B is connected to the commercial AC power supply 30, and the outdoor control unit 40 of the outdoor unit A is connected to the indoor control unit 20 via the power line ACL and the serial signal line SL.

The indoor control unit 20 is connected to a light receiving unit 21, an indoor fan motor 7M, and an indoor temperature sensor 12. The light receiving unit 21 receives infrared light transmitted from a remote control device (hereinafter, simply referred to as a remote controller) 22.

The outdoor control unit 40 includes a four-way valve 2, an electric expansion valve 4, an outdoor fan motor 6M, a heat exchanger temperature sensor 11,
The refrigerant temperature sensor 13 and the inverter circuit 41 are connected. The inverter circuit 41 rectifies the voltage of the power supply line ACL, converts the rectified voltage into a voltage of a frequency (and level) according to a command from the outdoor control unit 40, and outputs the voltage. This output is supplied as drive power to the compressor motor 1M.

The indoor control unit 20 and the outdoor control unit 40
The air conditioner is controlled while performing data transfer synchronized with the power supply voltage through the serial signal line SL,
The following functional means [1] to [6] are provided.

[1] The refrigerant discharged from the compressor 1 flows in the direction of the solid arrows in FIG. 2 to form a cooling cycle, and the outdoor heat exchanger 3 functions as a condenser and the indoor heat exchanger 5 functions as an evaporator.
Means for performing a cooling operation.

[2] The refrigerant discharged from the compressor 1 flows in the direction of the dashed arrow in FIG. 2 by switching the four-way valve 2 to form a heating cycle, and the indoor heat exchanger 5 is used as a condenser, and the outdoor heat exchanger 3 is used as a heater. A means for performing a heating operation by functioning as an evaporator.

[3] The difference Δ between the detected temperature Ta of the indoor temperature sensor 12 and the set temperature Ts of the remote controller during cooling and heating.
Control means for determining T as the air conditioning load and controlling the output frequency (operating frequency of the compressor 1) F of the inverter circuit 41 in accordance with the difference ΔT.

[4] At the time of heating, the difference (= Te−Ts) between the detected temperature Te of the heat exchanger temperature sensor 11 and the detected temperature Ts of the refrigerant temperature sensor 13 is determined by the degree of superheat SH.
The opening degree of the electric expansion valve 4 is adjusted so that the deviation ΔSH between the superheat degree SH and a predetermined target superheat degree SHo becomes zero, and the refrigerant flow rate to the outdoor heat exchanger (evaporator) 3 is determined. Control means to control.

[5] At the time of heating, the heating cycle is switched to the defrost cycle by the four-way valve 2, and the outdoor heat exchanger (evaporator) 3
Defrosting operation means for executing a defrosting operation on the outdoor heat exchanger 3 by supplying a high-temperature refrigerant to the outdoor heat exchanger 3.

[6] During heating, the detected temperature Te of the heat exchanger temperature sensor 11 and the detected temperature Ts of the refrigerant temperature sensor 13
Control means for controlling execution of the defrosting operation by the defrosting operation means according to

Next, the operation of the above configuration will be described. At the time of heating, as shown in the flowchart of FIG. 3, a time count t is performed simultaneously with the activation of the compressor 1 (or the end of the previous defrosting operation) (step 101).

The detection temperature Te of the heat exchanger temperature sensor 11 (the temperature of the outdoor heat exchanger 5) is corrected by the detection temperature Ts of the refrigerant temperature sensor 13 (the suction refrigerant temperature of the compressor 1) Ts and the correction coefficient K, and the correction temperature TE is required (Step 10
2).

That is, the correction temperature TE is obtained by the following equation. The correction coefficient K is a value larger than “0” and smaller than “1”, for example, 0.1 to 0.5. TE = Te × K + Ts × (1−K) Then, the defrosting condition is determined using the correction temperature TE (step 103). FIG. 4 shows a specific example of this determination.

That is, when the time count t reaches the ta time (= 2 minutes), a predetermined period Δt (= 10 minutes) thereafter
At 40 seconds), the minimum value TEo of the correction temperature TE is detected. Then, the time count t is tb time (= 27 minutes 40
Seconds later, the difference ΔTE between the minimum value TEo and the correction temperature TE (=
TEo-TE is equal to or greater than the set value for a predetermined time (= 20).
Seconds) or more, the defrost condition is satisfied (step 10).
3 YES), the defrosting operation is started (step 104).
When the correction temperature TE is in the A zone (-2 ° C <TE ≦-
8 ° C), 3 ° C is selected, and when the correction temperature TE is in the B zone (−8 ° C <TE ≦ −20 ° C), 2.5 ° C is selected.

The correction temperature TE is a predetermined value (= −20 ° C.)
When the following state (C zone) is continued for a predetermined time (= 20 seconds) or more, the same defrosting condition is satisfied (YE in step 103).
S), the defrosting operation is started (step 104).

If the defrosting condition is not satisfied (step 10
3) (NO), the normal heating operation is continued (step 105).
). By the way, when the operating frequency F of the compressor 1 changes due to a change in the set indoor temperature for indoor temperature control, the opening degree of the electric expansion valve 4 changes, the heat exchanger temperature Te changes, and the suction refrigerant temperature Ts changes. 5 is shown in FIG.
SH (= Te−Ts) is the degree of superheat, SHo is the target degree of superheat,
ΔSH is the deviation between the superheat degree SH and the target superheat degree SHo, ΔT
e is the difference between the heat exchanger temperature Te and the correction temperature TE.

Although the heat exchanger temperature Te changes with a change in the operating frequency F (Hz), in order to accurately grasp the frost formation state of the outdoor heat exchanger 5, the actual heat exchanger temperature Te must be calculated. It is also preferable to use the correction temperature TE.

Further, the suction refrigerant temperature Ts changes with the change of the heat exchanger temperature Te, and there is a relationship corresponding to the correction coefficient K between the temperatures Te and Ts. Therefore,
The correction temperature TE can be obtained by using the suction refrigerant temperature Ts and the correction coefficient K.

The correction coefficient K is derived as follows. TE = Te + ΔTe ΔTe = f (ΔSH) = K × ΔSH K = − [ΔTe / ΔSH] The steady-state characteristics of the heat exchanger temperature Te and the superheat degree SH were obtained by experiments using the operating frequency F (Hz) as a parameter. FIG. From this steady characteristic, the value of the correction coefficient K can be calculated. The calculation result is shown in FIG. And
Correction temperature TE calculated using the calculated correction coefficient K
FIG. 8 shows the operation frequency F (Hz) as a parameter and in comparison with the heat exchanger temperature Te. Correction temperature T
E is indicated by a solid line, and the heat exchanger temperature Te is indicated by a broken line, so that a stable correction temperature TE can be obtained regardless of a decrease in the heat exchanger temperature Te. FIG. 9 shows temporal changes of the corrected temperature TE and the heat exchanger temperature Te together with other temperature values Ta, Tc (temperature of the indoor heat exchanger 3), Ts, and the operating frequency F.

In this manner, the heat exchanger temperature Te is corrected to obtain a corrected temperature TE without a transient drop, and the corrected temperature TE
The optimum minimum value which does not become unnecessarily low even in a situation where it takes a long time for the heat exchanger temperature Te to rise due to refrigerant stagnation or long piping due to the determination of the defrosting condition TEo can be obtained, so that the frost amount of the outdoor heat exchanger 5 can be accurately captured before the frost amount of the outdoor heat exchanger 5 increases, and defrosting can be performed at an optimal timing, thereby preventing a decrease in the heating capacity. Can be prevented.

Also, there is a change in the set indoor temperature for adjusting the indoor temperature, and accordingly, the operating frequency F of the compressor 1 is changed.
When the refrigerating cycle fluctuates greatly, for example, when the refrigeration cycle fluctuates more than 20 Hz or when there is a change in the indoor fan speed for indoor air flow control, the heat exchanger temperature Te is low even though the amount of frost on the outdoor heat exchanger 5 is still small. Although the phenomenon of transient drop occurs,
Without using the heat exchanger temperature Te, the defrosting condition is determined from the correction temperature TE without a transient decrease.
The defrosting amount can be accurately captured to perform defrosting at an optimal timing, and unnecessary defrosting operation, that is, so-called empty defrosting can be avoided to prevent a decrease in heating efficiency.

(2) First Modification In the above-described embodiment, the minimum value TEo is detected after the correction temperature TE is obtained, but the minimum value Te of the detected temperature Te is detected.
Alternatively, the minimum value TEo may be determined by correcting the minimum value Teo with the detected temperature Ts and the correction coefficient K. That is, the minimum value TEo is obtained by the following equation. TEo = Teo × K + Ts × (1−K) This minimum value TEo is set whenever the set indoor temperature for indoor temperature control is changed or the indoor fan speed is changed for indoor air flow control. Updated as required.

(3) Second Modification In the above embodiment, the suction refrigerant temperature Ts and the correction coefficient K
Is obtained from the above equation, the above-mentioned TE = Te + Δ
Based on Te, ΔTe = K × ΔSH, the correction temperature TE may be obtained using the deviation ΔSH between the superheat degree SH and the target superheat degree SHo and the correction coefficient K. That is, the correction temperature TE is obtained by the following equation.

TE = Te + ΔSH × K Then, after calculating this correction temperature TE, its minimum value TE
may be detected, the minimum value Teo of the detected temperature Te is detected, and the minimum value Teo is determined by the deviation ΔSH and the correction coefficient K.
Alternatively, the minimum value TEo may be obtained by performing the above correction. The minimum value TEo in this case is obtained by the following equation. TEo = Teo + ΔSH × K This minimum value TEo is obtained and updated each time there is a change in the set indoor temperature for indoor temperature control or when there is a change in the indoor fan speed for indoor air flow control. .

[0044]

As described above, according to the present invention, the temperature Te of the outdoor heat exchanger is detected, and the temperature Ts of the refrigerant sucked into the compressor is detected.
e and the detected temperature Ts, the execution of the defrosting operation on the outdoor heat exchanger is controlled. Therefore, even when the temperature of the outdoor heat exchanger Te rises slowly at the time of starting heating or returning to heating, the refrigeration cycle Even in the case of large fluctuations, it is possible to accurately capture the amount of frost formed in the outdoor heat exchanger and perform defrosting at the optimal timing, thereby providing excellent reliability that can prevent a decrease in heating capacity and heating efficiency. An air conditioner can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control circuit according to one embodiment of the present invention.

FIG. 2 is a configuration diagram of a refrigeration cycle of the embodiment.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

FIG. 4 is an exemplary view for explaining determination of a defrosting condition in the embodiment.

FIG. 5 is a diagram showing an example of changes in a heat exchanger temperature Te and a suction refrigerant temperature Ts in the embodiment.

FIG. 6 shows a heat exchanger temperature Te and a superheat degree S in the embodiment.
The figure which shows the steady-state characteristic with H using operating frequency F as a parameter.

FIG. 7 is a view showing a value of a correction coefficient K calculated from the steady-state characteristic of FIG. 6;

FIG. 8 is a diagram showing a correction temperature TE calculated using a correction coefficient K in the embodiment with the operating frequency F as a parameter and in comparison with the heat exchanger temperature Te.

FIG. 9 is a diagram showing temporal changes of a correction temperature TE and a heat exchanger temperature Te in the embodiment, together with other temperature values Ta, Tc, Ts, and an operation frequency F.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Compressor 2 ... Four-way valve 3 ... Outdoor heat exchanger 4 ... Electric expansion valve 5 ... Indoor heat exchanger 11 ... Heat exchanger temperature sensor (1st temperature sensor) 12 ... Indoor temperature sensor 13 ... Refrigerant temperature temperature sensor ( (Second temperature sensor) 20 indoor control unit 40 outdoor control unit

Claims (8)

[Claims] 1. A refrigeration cycle for connecting a compressor, an indoor heat exchanger, a decompressor, and an outdoor heat exchanger to circulate a refrigerant, wherein the indoor heat exchanger functions as a condenser and the outdoor heat exchanger functions as an evaporator. A first temperature sensor for detecting a temperature Te of the outdoor heat exchanger, and a second temperature sensor for detecting a temperature Ts of a refrigerant sucked into the compressor.
A temperature sensor; and control means for controlling execution of a defrosting operation on the outdoor heat exchanger in accordance with the detected temperature Te of the first temperature sensor and the detected temperature Ts of the second temperature sensor during heating. An air conditioner characterized by that: 2. The air conditioner according to claim 1, wherein the control unit corrects the detected temperature Te by using the detected temperature Ts and the correction coefficient K to obtain a corrected temperature TE, and starts the compressor or a previous time. The minimum value TEo of the correction temperature TE is detected during a predetermined period Δt after the end of the defrosting operation for a predetermined period Δt, and after the start of the compressor or the end of the previous defrosting operation tb time [> (ta + Δt)], the minimum value TEo is determined. Correction temperature T
The defrosting operation is started when the state where the difference ΔTE from E (= TEo−TE) is equal to or more than the set value has continued for a predetermined time or more, or the state where the correction temperature TE is equal to or less than the predetermined value has continued for a predetermined time or more An air conditioner characterized by the following. 3. The air conditioner according to claim 1, wherein the control means corrects the detected temperature Te by using the detected temperature Ts and the correction coefficient K to obtain a corrected temperature TE, and starts or starts the compressor at a previous time. From the end of the defrosting operation of
At a predetermined time period Δt after the time a, the minimum value Teo of the detection temperature Te is detected, and the minimum value Teo is corrected by the detection temperature Ts and the correction coefficient K to obtain the minimum value TEo. Tb time from the end of operation [>
(Ta + Δt)], when the difference ΔTE (= TEo−TE) between the minimum value TEo and the correction temperature TE is equal to or higher than the set value for a predetermined time or when the correction temperature TE is equal to or lower than the predetermined value for a predetermined time. An air conditioner characterized by starting a defrosting operation when continued. 4. The air conditioner according to claim 2, wherein the control unit is configured to change the indoor fan speed for adjusting the indoor air flow when there is a change in the set indoor temperature for adjusting the indoor temperature. An air conditioner characterized by updating the minimum value TEo each time there is a change. 5. A refrigeration cycle for connecting a compressor, an indoor heat exchanger, a decompressor and an outdoor heat exchanger to circulate a refrigerant, wherein the indoor heat exchanger functions as a condenser and the outdoor heat exchanger functions as an evaporator. A first temperature sensor for detecting a temperature Te of the outdoor heat exchanger, and a second temperature sensor for detecting a temperature Ts of a refrigerant sucked into the compressor.
A temperature sensor, a heating temperature detected by the first temperature sensor during heating, and the second temperature sensor.
The difference (= Te−Ts) from the temperature detected by the temperature sensor (= Te−Ts) is determined as the superheat degree SH, and the difference ΔSH between the superheat degree SH and the predetermined target superheat degree SHo is set to zero so that the outdoor heat exchanger becomes zero. A first control means for controlling the flow rate of the refrigerant, and a second control means for controlling execution of a defrosting operation on the outdoor heat exchanger in accordance with the detected temperature Te of the first temperature sensor and the deviation ΔSH during heating. An air conditioner, comprising: 6. The air conditioner according to claim 5, wherein the second control means corrects the detected temperature Te by using a deviation ΔSH and a correction coefficient K to obtain a correction temperature TE, and starts the compressor or a previous time. The minimum value TEo of the correction temperature TE is detected during a predetermined period Δt after a lapse of ta time from the end of the defrosting operation, and the time tb has elapsed since the compressor was started or the previous defrosting operation was completed.
After the time [> (ta + Δt)], the state where the difference ΔTE (= TEo−TE) between the minimum value TEo and the correction temperature TE is equal to or more than the set value for a predetermined time or more, or the state where the correction temperature TE is equal to or less than the predetermined value Characterized in that the defrosting operation is started when the operation is continued for a predetermined time or more. 7. The air conditioner according to claim 5, wherein the second control means corrects the detected temperature Te by using a deviation ΔSH and a correction coefficient K to obtain a correction temperature TE, and starts the compressor or T since the end of the previous defrost operation
In a predetermined period Δt after the time a, the minimum value Teo of the detected temperature Te is detected, and the minimum value Teo is corrected by the deviation ΔSH and the correction coefficient K to obtain the minimum value TEo, and the start of the compressor or the previous defrost operation Tb time from the end [> (t
a + Δt)], and the difference Δ between the minimum value TEo and the correction temperature TE
The defrosting operation is started when the state where TE (= TEo−TE) is equal to or higher than the set value has continued for a predetermined time or longer, or when the state where the correction temperature TE is equal to or lower than a predetermined value has continued for a predetermined time or longer. Air conditioner. 8. The air conditioner according to claim 6, wherein the second control means is configured to change a set indoor temperature for adjusting the indoor temperature or to adjust an indoor air flow. An air conditioner characterized by updating the minimum value TEo whenever the fan speed is changed.