CN110953662A

CN110953662A - Air conditioner

Info

Publication number: CN110953662A
Application number: CN201910496471.9A
Authority: CN
Inventors: 朱帅; 安部隼; 冈田觉
Original assignee: Toshiba Carrier Corp
Current assignee: Toshiba Carrier Corp
Priority date: 2018-09-26
Filing date: 2019-06-10
Publication date: 2020-04-03
Also published as: JP2020051666A; JP7148344B2

Abstract

The invention provides an air conditioner which can continue heating operation as far as possible and can defrost an outdoor heat exchanger with good efficiency. In the air conditioner of the embodiment, when defrosting of the outdoor heat exchanger is performed during the heating operation, the control device executes a continuous heating and defrosting operation in which defrosting is performed while the heating cycle is still in progress by controlling the opening degree of the electronic expansion valve to be open and operating the outdoor fan, instead of switching the circulation direction of the refrigerant flowing in the refrigerant pipe by the four-way valve, when the outside air temperature detected by the outdoor temperature sensor is higher than a predetermined temperature and the time from the last defrosting to the start of the present defrosting is equal to or longer than a predetermined time.

Description

Air conditioner

Technical Field

Embodiments of the present invention relate to an air conditioner.

Background

Conventionally, in an air conditioner, if frost is generated on an outdoor heat exchanger during a heating operation, defrosting is performed by switching the circulation direction of a refrigerant in a refrigeration cycle to a reverse cycle defrosting operation in the opposite direction. In the reverse cycle defrosting operation, the refrigeration cycle is a cycle for the cooling operation, and the indoor heat exchanger is used as the evaporator, so that defrosting can be performed in a short time, but warm air cannot be supplied to the indoor space.

In this regard, patent document 1 discloses a hot gas bypass defrosting operation in which a part of the high-temperature refrigerant discharged from the compressor is supplied to the outdoor heat exchanger through a bypass pipe, as a method different from the reverse cycle defrosting operation. In the hot-gas bypass defrosting operation, the outdoor heat exchanger can be defrosted while the refrigeration cycle is used as a cycle for heating operation.

[ patent document 1 ] Japanese patent application laid-open No. 11-257718

Disclosure of Invention

However, in the hot-gas bypass defrosting operation, since both the outdoor heat exchanger and the indoor heat exchanger serve as condensers, the refrigerant in the refrigeration cycle may not absorb heat, and the defrosting time may be prolonged. Therefore, an object of the present invention is to provide an air conditioner capable of continuing a heating operation as much as possible and efficiently defrosting an outdoor heat exchanger.

The air conditioner of the embodiment comprises: a refrigeration cycle in which a compressor, a four-way valve, an indoor heat exchanger, an electronic expansion valve, and an outdoor heat exchanger are connected in an annular manner by a refrigerant line; an outdoor fan for sending outside air to the outdoor heat exchanger; an outdoor temperature sensor for detecting an outdoor air temperature; and a controller that, when defrosting of the outdoor heat exchanger is performed during a heating operation, executes a heating-continuing defrosting operation in which the opening degree of the electronic expansion valve is opened and the outdoor fan is operated, without switching the circulation direction of the refrigerant flowing through the refrigerant pipe line by the four-way valve, and when the outside air temperature detected by the outdoor temperature sensor is higher than a predetermined temperature and the time from the last defrosting to the start of the present defrosting is equal to or longer than a predetermined time, the defrosting is continued while the heating cycle is still in progress by controlling the outdoor fan to be operated while the opening degree of the electronic expansion valve is opened.

Thus, an air conditioner can be obtained in which the heating operation is continued as much as possible and the outdoor heat exchanger is defrosted efficiently.

Drawings

Fig. 1 is a view schematically showing the structure of an air conditioner according to the present embodiment;

fig. 2 is a flowchart showing a flow of processing when defrosting of the outdoor heat exchanger is performed;

fig. 3 is a timing chart showing the control contents in the reverse cycle defrosting operation;

fig. 4 is a timing chart showing the control contents during the heating and defrosting operation.

In the figure, 1-air conditioner; 2-a compressor; 3-a four-way valve; 4-indoor heat exchanger; 4 a-indoor fan; 5-an electronic expansion valve; 6-outdoor heat exchanger; 6 a-outdoor fan; 7-refrigerant line; 8-refrigeration cycle; 10-a control device; 13-outdoor temperature sensor; 15-inhalation temperature sensor

Detailed Description

One embodiment is described below with reference to the drawings. As shown in fig. 1, the air conditioner 1 includes a heat pump type refrigeration cycle 8 in which a compressor 2, a four-way valve 3, an indoor heat exchanger 4, an electronic expansion valve 5, and an outdoor heat exchanger 6 are annularly connected by a refrigerant pipe 7.

An indoor unit 11 installed indoors houses an indoor heat exchanger 4 and an indoor fan 4a that sends indoor air to the heat exchanger 4. Although not shown in detail, the indoor fan 4a is, for example, a cross-flow fan, and generates an air flow in the indoor heat exchanger 4 by sucking indoor air from the suction port of the indoor unit 11, and generates an air flow in which the air that has been subjected to the heat exchange in the indoor heat exchanger 4 is blown out into the room from the discharge port of the indoor unit 11.

The outdoor unit 12 installed outdoors accommodates the compressor 2, the four-way valve 3, the electronic expansion valve 5, and the outdoor heat exchanger 6, and accommodates an outdoor fan 6a that sends outside air to the outdoor heat exchanger 6. Although not shown in detail, the outdoor fan 6a is, for example, an impeller fan, and generates an air flow for passing outside air from the back surface side of the outdoor unit 12 through the outdoor heat exchanger 6, and an air flow for blowing the outside air superheated and exchanged in the outdoor heat exchanger 6 out from a discharge port on the front surface of the outdoor unit 12.

The compressor 2 sucks gas refrigerant from the suction port 2a side, compresses the refrigerant, and discharges the compressed refrigerant from the discharge port 2b side, thereby increasing the pressure and temperature of the refrigerant to circulate the refrigerant in the refrigerant line 7. The compressor 2 is, for example, of a variable displacement type, and is configured so that the rotation speed, which is the operating frequency thereof, can be changed by a control device 10 (inverter control device) to be described later.

The four-way valve 3 switches the circulation direction of the refrigerant flowing through the refrigerant pipe 7 to a circulation direction corresponding to each operation at the time of heating operation, cooling operation, or reverse cycle defrosting operation performed during heating operation. Specifically, the four-way valve 3 is switched between the following states: in the heating operation, a heating cycle state in which the flow path of the refrigerant discharged from the discharge port 2b of the compressor 2 is connected to the indoor heat exchanger 4 and the flow path of the refrigerant sucked into the suction port 2a is connected to the outdoor heat exchanger 6, and in the cooling operation or the reverse cycle defrosting operation, a cooling cycle state in which the flow path of the refrigerant discharged from the discharge port 2b of the compressor 2 is connected to the outdoor heat exchanger 6 and the flow path of the refrigerant sucked into the suction port 2a is connected to the indoor heat exchanger 4. As a result, the refrigerant flows in the direction indicated by the solid arrow a in fig. 1 in the heating cycle state, and flows in the direction indicated by the broken arrow B in fig. 1 in the cooling cycle state.

In the indoor heat exchanger 4, heat radiation or heat absorption operation is performed in accordance with the flow direction of the refrigerant, and heat exchange with air passing through the heat exchanger 4 is promoted by the operation of the indoor fan 4 a. In the outdoor heat exchanger 6, heat radiation or heat absorption is performed in accordance with the flow direction of the refrigerant, and heat exchange with air passing through the heat exchanger 6 is promoted by the operation of the outdoor fan 6 a. The electronic expansion Valve 5 is an expansion device that appropriately adjusts the amount of refrigerant throttling by controlling the opening degree of the Valve between a minimum opening degree and a maximum opening degree, and is formed of, for example, a PMV (Pulse Motor Valve).

The air conditioner 1 includes an outdoor temperature sensor 13, an outdoor heat exchanger temperature sensor 14, and a suction temperature sensor 15 of the compressor 2 as temperature detection means. The temperature sensors 13 to 15 are composed of, for example, thermistors, and are disposed in the outdoor unit 12. The outdoor temperature sensor 13 is installed in a place where the outdoor unit 12 contacts the outside air, is usually installed on the air intake side of the outdoor heat exchanger 6, and detects the outdoor temperature, that is, the outside air temperature. The outdoor heat exchanger temperature sensor 14 is attached to a pipe line or the like of the outdoor heat exchanger 6, and detects the temperature of the outdoor heat exchanger 6. The suction temperature sensor 15 is provided on the refrigerant line 7 on the suction port 2a side of the compressor 2, and detects the temperature of the refrigerant sucked into the compressor 2.

The control device 10 of the air conditioner 1 is mainly configured by a microcomputer, for example, and includes storage means such as a ROM and a RAM, not shown. The storage unit stores therein an operation control program to be described later. The controller 10 is connected to the compressor 2, the four-way valve 3, the electronic expansion valve 5, the indoor fan 4a, the outdoor fan 6a, and the temperature sensors 13 to 15 (see the two-dot chain lines in fig. 1). The controller 10 controls the operations of the compressor 2, the four-way valve 3, the electronic expansion valve 5, and the outdoor fan 6a based on an input signal input from an operation unit such as a remote controller not shown, and detection signals input from the temperature sensors 13 to 15. Note that, although only the control device 10 is described in the outdoor unit 12 in the figure for simplicity of explanation, an indoor controller, not shown, is actually provided in the indoor unit 11, and necessary information is acquired by communication with the control device 10 of the outdoor unit 12. An input signal input from an operation unit such as a remote controller is input to the control device 10 via the indoor controller, and the operation/stop and the rotation speed of the indoor fan 4a are controlled by the indoor controller. As described above, the indoor controller corresponds to a control device that controls the operation of the air conditioner 1 together with the control device 10 that is an outdoor controller. The control device of the air conditioner 1 is a device provided at least in one of the outdoor unit 12 and the indoor unit 11. For convenience of explanation, the control device 10 is described as a device that also controls, for example, the indoor fan 4a, since it is assumed that the control device includes an indoor controller.

When the temperature of the outdoor heat exchanger 6 is 0 ℃ or lower and lower than the dew point temperature of the outside air during the heating operation, the moisture in the outside air is turned into frost and adheres to the outdoor heat exchanger 6. In this case, the reverse cycle defrosting operation is performed to suppress deterioration of heating performance due to the growth of frost. The reverse cycle defrosting operation performs defrosting of the outdoor heat exchanger 6 by switching the circulation direction of the refrigerant during the heating operation to the refrigeration cycle in the opposite direction by the four-way valve 3. The air conditioner 1 according to the present embodiment is configured to be able to perform a heating and defrosting continuation operation, which is different from the reverse cycle defrosting operation, and performs defrosting while the heating cycle is still being performed, instead of switching the refrigerant circulation direction by the four-way valve 3. That is, the present embodiment uses the reverse cycle defrosting operation and the continuous heating defrosting operation, respectively, as appropriate depending on the situation.

Fig. 2 shows a process flow of the operation control routine related to the heating and defrosting continuation operation. As shown in the drawing, the heating-continued defrosting operation and the reverse-cycle defrosting operation in the present embodiment are selectively performed. During the heating operation, the controller 10 monitors the outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature sensor 14, and determines whether defrosting is necessary based on the temperature change. When defrosting is necessary, the process of fig. 2 is started assuming that the defrosting start condition is established.

That is, first, during the heating operation, when the defrosting start condition is satisfied as the temperature of the outdoor heat exchanger 6 decreases, the controller 10 acquires the outside air temperature T detected by the outdoor temperature sensor 13_OUTJudging the outside air temperature T_OUTWhether or not it is higher than a predetermined temperature T0 (e.g., 0 ℃ C.) defined in advance(step S1). The value T0 of the predetermined temperature is stored in the storage unit in advance, and is not limited to 0 ℃, and can be changed as appropriate, but is set to a value higher than at least 0 ℃ in order to melt frost of the outdoor heat exchanger 6 with outside air during the continuous heating and defrosting operation. The defrosting start condition can be determined by using various known conditions in consideration of the temperature of the outdoor heat exchanger 6, the amount of temperature decrease and the rate of decrease in the temperature of the indoor and outdoor heat exchangers 6 for a predetermined time, and the outdoor air temperature detected by the outdoor temperature sensor 13.

Outside air temperature T_OUTWhen the temperature is higher than the predetermined temperature T0 (T)_OUTIf yes in step S1 > T0, the controller 10 determines whether or not the time M from the start of the previous defrosting to the start of the present defrosting is equal to or longer than a predetermined time tc (step S2). In other words, if the latest defrosting is performed by the reverse-cycle defrosting operation, the time at which the reverse-cycle defrosting operation is started is calculated (refer to the start time t of fig. 3 described later)_R1) Time M to the current time (the time when the present defrosting is started). Then, if the latest defrosting is performed by continuing the heating defrosting operation, the time at which the heating defrosting operation is continued from the start of the defrosting operation is calculated (see the start time t of fig. 4)_C1) The time M to the current time is compared with the calculated time Tc. In addition, since the time for the reverse cycle defrosting operation or the time for continuing the heating defrosting operation is not very long, the time M may be set to be the time (t) since the last defrosting end_R2Or t_C2) And the moment when the defrosting is started. The time M can be considered as a period from defrosting to defrosting, and the predetermined time tc can be set as a starting point (t) from which the timer is started_R1，t_C1，t_R2，t_C2) And the corresponding appropriate value tc.

When it is determined by the comparison that the reverse-cycle defrosting operation is not performed and the heating and defrosting operation is not continued for the predetermined time tc, that is, when the time M until the start of the present defrosting is equal to or longer than the predetermined time tc (M ≧ tc) (yes in step S2), the controller 10 starts the heating and defrosting operation (step S4, see fig. 4). In contrast, until the beginning of the textIf the time M before the sub-defrosting does not exceed the predetermined time tc (M < tc), that is, if the defrosting cycle is short (no in step S2), or if the outside air temperature T is higher than the predetermined time tc_OUTWhen the predetermined temperature T0 is not higher (no in step S1), the reverse cycle defrosting operation is started (step S3, see fig. 3). Next, the control contents after step S3 will be described in the order of the reverse cycle defrosting operation and the heating defrosting operation continuation with reference to fig. 3 and 4.

< 1. reverse cycle defrost operation >

FIG. 3 is a graph showing the operating frequency F of the compressor 2 and the rotational speed N of the outdoor fan 6a during the reverse cycle defrosting operation_OUTAnd the rotating speed N of the indoor fan 4a_INA timing chart of the opening X of the electronic expansion valve 5(PMV) and the switching state of the four-way valve 3.

When the control device 10 detects "defrosting detection" shown in fig. 3, that is, when it detects that defrosting is necessary and the defrosting start condition is satisfied, it sets the time t at which the defrosting start condition is satisfied_R1(strictly speaking, at the time when the determination of step S1 or S2 is "no"), the heating operation is interrupted. At this time, the outdoor fan 6a and the indoor fan 4a are stopped and their respective rotation speeds N are set_OUT、N_IN0 and temporarily stops the compressor 2 to make its operating frequency F0.

Next, the controller 10 switches the circulation direction of the refrigerant flowing through the refrigerant line 7 from the circulation direction in the heating cycle state (see solid arrow a in fig. 1) to the circulation direction in the cooling cycle state (see broken arrow B) by the four-way valve 3. This alleviates the high-low pressure difference of the refrigerant during the heating operation, and facilitates the start-up of the compressor 2. After this switching, the compressor 2 is started as shown in fig. 3, and the operation frequency F is gradually increased, thereby starting the reverse cycle defrosting operation. The opening X of the electronic expansion valve 5 is set at the time t when the defrosting start condition is satisfied, for example_R1Starting time t from the start of the reverse cycle defrosting operation_R1′The maximum opening degree is set so as to be beneficial to alleviating the high-low pressure difference of the refrigerant, and the starting time t is_R1′Thereafter, the opening degree is set to be slightly larger than the maximum opening degree.

Thus, defrosting is performed in reverse cycleDuring operation, until t_R1The outdoor heat exchanger 6 functioning as an evaporator immediately before (until the heating operation) at the time t when the defrosting operation is started_R1′And later on as a condenser. Therefore, even at the outside air temperature T_OUTFor example, 0 ℃ or lower, or when the present reverse cycle defrosting operation is performed within a short time (less than the predetermined time tc) from the previous defrosting operation due to insufficient previous defrosting, the frost adhering to the outdoor heat exchanger 6 can be melted in a short time by the heat radiation action of the outdoor heat exchanger 6.

During the reverse-cycle defrosting operation in step S3, the indoor heat exchanger 4 starts the reverse-cycle defrosting operation at time t_R1′And then functions as an evaporator to absorb heat. Therefore, during the reverse cycle defrosting operation, the indoor heat exchanger 4 cannot generate warm air, and cannot continue the heating operation. During the reverse cycle defrosting operation, the controller 10 determines whether or not the defrosting end condition is satisfied based on the temperature of the outdoor heat exchanger 6 detected by the outdoor heat exchanger temperature sensor 14. When the condition for defrosting completion is satisfied, the controller 10 sets the timing t to_R2The compressor 2 is stopped, and the reverse cycle defrosting operation is ended (step S6 in fig. 2). The condition for ending defrosting may be determined by combining not only the temperature of the outdoor heat exchanger 6 but also a temperature change thereof.

Then, the controller 10 switches the four-way valve 3 so that the circulation direction of the refrigerant flowing through the refrigerant pipe 7 is returned from the circulation direction in the refrigeration cycle state (see a broken-line arrow B in fig. 1) to the circulation direction in the heating cycle state (see a solid-line arrow a) (see fig. 3). The controller 10 controls the outdoor fan 6a and the indoor fan 4a in the stopped state to rotate at the number of rotations N before starting defrosting_OUT、N_INAnd (5) starting. Next, the controller 10 starts the compressor 2, gradually increases the operation frequency F to the operation frequency before the start of defrosting, and returns the opening degree X of the electronic expansion valve 5 to the opening degree before the start of defrosting, thereby returning to the normal heating operation (step S7 in fig. 2), and ends the processing.

In addition, electrons expandWhen the reverse cycle defrosting operation is finished, the opening X of the expansion valve 5 is set to t (t in fig. 3)_R2、t_R2′The period in between) is set to the maximum opening degree. Therefore, when the four-way valve 3 is switched at the time of starting or ending the reverse cycle defrosting operation, the difference between the pressure of the high-pressure refrigerant and the pressure of the low-pressure refrigerant can be reduced by the electronic expansion valve 5, and switching noise and vibration of the four-way valve 3 can be suppressed.

< 2. continuous heating and defrosting operation >

FIG. 4 is a graph showing the operating frequency F of the compressor and the rotational speed N of the outdoor fan 6a during the continuous heating and defrosting operation_OUTAnd the rotating speed N of the indoor fan 4a_INA timing chart of the opening X of the electronic expansion valve 5(PMV), the switching state of the four-way valve 3, and the refrigerant temperature Tc detected by the suction temperature sensor 15. The control device 10 sets the defrosting start condition to be satisfied at time t_C1(strictly speaking, at the time when the determination at S2 is yes) the heating and defrosting operation is continued.

In this case, as shown in fig. 4, the opening degree X of the electronic expansion valve 5 is controlled by the control device 10 to be larger than the opening degree immediately before the start of the present defrosting. That is, the opening X of the electronic expansion valve 5 is at the time t from the start of the heating and defrosting operation_C1To the end time t_C2Is set and maintained at a predetermined opening degree (e.g., maximum opening degree). By setting the opening X to the fully open state in this way, the difference between the pressure of the high-pressure refrigerant and the pressure of the low-pressure refrigerant in the refrigeration cycle 8 can be reduced as much as possible, and a refrigerant of a temperature and amount suitable for defrosting the outdoor heat exchanger 6 can be passed. Thus, by t from FIG. 4_C1The opening X of the electronic expansion valve 5 starts to be increased at this time, and the outdoor heat exchanger 6 can be brought to a temperature suitable for defrosting without switching the refrigerant circulation direction by the four-way valve 3.

The outdoor fan 6a is at the start time t from the continued heating defrosting operation_C1To the end time t_C2Until the controlled device 10 reaches a predetermined rotation speed N_OUT(e.g., maximum rotational speed) is drivingly controlled. The rotational speed N is shown in FIG. 4_OUTSet to be the same as the maximum rotational speed of the outdoor fan 6a during the heating operationIn the case of a value, from the start time t_C1The example is shown when the fan 6a is started to be driven at the maximum rotational speed during the heating operation. Thus, the rotational speed N_OUTThe rotation speed may be set to the same rotation speed as the rotation speed of the outdoor fan 6a during the normal heating operation, or may be set to a rotation speed higher than the rotation speed during the normal heating operation. Therefore, by rotating at a predetermined number of revolutions N_OUTBy operating the outdoor fan 6a, heat exchange with the outside air having a temperature higher than the predetermined temperature T0 passing through the outdoor heat exchanger 6 can be promoted, the amount of heat absorbed by the outdoor heat exchanger 6 can be increased, and defrosting of the heat exchanger 6 can be performed more efficiently.

The indoor fan 4a is at the start time t from the continued heating defrosting operation_C1To the end time t_C2Until the controlled device 10 reaches a predetermined rotation speed N_INIs drivingly controlled. The rotational speed N_INThe rotation speed of the indoor fan 4a is set to a value lower than that of the indoor fan during normal heating operation, for example, to suppress the amount of heat dissipated from the indoor heat exchanger 4. Therefore, by rotating at a predetermined number of revolutions N_INBy operating the indoor fan 4a, warm air can be supplied to the interior of the room while the amount of heat dissipated by the indoor heat exchanger 4 is suppressed, and a drop in the temperature of the refrigerant flowing into the outdoor heat exchanger 6 can be suppressed, thereby achieving a state suitable for defrosting the heat exchanger 6.

The compressor 2 is at the start time t from the continued heating defrosting operation_C1To the end time t_C2The control device 10 is driven and controlled at a predetermined operating frequency F. That is, as shown in fig. 4, as the heating and defrosting operation is continued, the operating frequency F of the compressor 2 is set low, and the low operating frequency is maintained until the end time t_C2. Thereby, the heating defrosting operation is continued from the start time t_C1Initially, the operating frequency F of the compressor 2 is set to provide a temperature and amount of refrigerant suitable for defrosting the outdoor heat exchanger 6.

In this way, during the continuous heating and defrosting operation, the temperature of the refrigerant flowing into the outdoor heat exchanger 6 can be controlled by controlling the opening X of the electronic expansion valve 5, controlling the operation of each of the indoor fan 4a and the outdoor fan 6a, or controlling the operating frequency F of the compressor 2The frost adhering to the outdoor heat exchanger 6 can be melted by raising the temperature of the outdoor heat exchanger 6. As shown in fig. 4, the refrigerant temperature Tc at the suction port 2a side of the compressor 2 is also at the start time t of the heating and defrosting operation to be continued_C1And gradually rises as the defrosting of the outdoor heat exchanger 6 proceeds.

At this time, the control device 10 determines that the time t for continuing the heating and defrosting operation reaches the upper limit t when it is determined that the refrigerant temperature Tc detected by the suction temperature sensor 15 is higher than the predetermined refrigerant temperature Tch or when it is determined that the time t for continuing the heating and defrosting operation reaches the upper limit t_MAX(also referred to as "upper limit time t_MAX") the heating and defrosting operation is continued. That is, the predetermined refrigerant temperature Tch is "defrosting completion determination temperature" shown in fig. 4, and the upper limit time t is_MAXThe values of the two (predetermined refrigerant temperature Tch and upper limit time t) are determined so that the expected defrosting time is exceeded and the predetermined determination time is determined so that the defrosting operation is not continued_MAX) Are stored in the storage unit in advance. The controller 10 monitors the refrigerant temperature Tc detected by the suction temperature sensor 15 at the suction port 2a side of the compressor 2 during the heating and defrosting continuation operation, and calculates the start time t of the heating and defrosting continuation operation_C1Time t from.

The control device 10 is configured to set the refrigerant temperature Tc to be equal to or lower than the predetermined refrigerant temperature Tch and to set the time t for continuing the heating and defrosting operation to be less than the upper limit time t_MAXIn the case of (1) (no in step 5 of fig. 2), the heating and defrosting operation is continued (S4). In contrast, when the refrigerant temperature Tc is higher than the prescribed refrigerant temperature Tch (Tc > Tch), or the time t during which the heating and defrosting operation is continued reaches the upper limit time t_MAXWhen (t is more than or equal to t)_MAX) At any one time t_C2When the defrosting end condition is satisfied (yes in step S5), the heating and defrosting operation is continued (step S6).

Then, the controller 10 returns from the heating and defrosting continuation operation to the normal heating operation (step S7), and ends the processing. In addition, the heating operation is returned to the normal operation by returning to the state before the defrosting start condition is establishedThe operating frequency F of the compressor 2 and the rotational speed N of the

fans

4a and 6a_IN、N_OUTAnd the opening degree X of the electronic expansion valve 5 (see fig. 4).

As described above, the air conditioner 1 of the present embodiment includes the refrigeration cycle 8, the outdoor fan 6a, the outdoor temperature sensor 13, and the controller 10, and when the controller 10 performs defrosting of the outdoor heat exchanger during the heating operation, the controller 10 detects the outside air temperature T detected by the outdoor temperature sensor 13_OUTWhen the temperature is higher than the predetermined temperature T0 and the time M from the previous defrosting to the start of the present defrosting is equal to or longer than the predetermined time tc, a heating-and-defrosting continuation operation is performed in which the defrosting is performed while the heating cycle is still being performed by controlling the opening X of the electronic expansion valve 5 to be opened and operating the outdoor fan 6a, instead of switching the circulation direction of the refrigerant flowing through the refrigerant pipe 7 by the four-way valve 3.

Accordingly, the temperature of the outdoor heat exchanger 6 can be raised by opening the opening X of the electronic expansion valve 5 while the heating operation is continued, or the heat exchange with the outside air having a temperature higher than the predetermined temperature T0 passing through the outdoor heat exchanger 6 can be promoted by the operation of the outdoor fan 6a, and the temperature can be maintained at the outside air temperature T_OUTThe defrosting operation is performed at an appropriate timing according to the frequency of defrosting, and the defrosting of the outdoor heat exchanger 6 can be performed efficiently. Further, since it is not necessary to stop the heating operation, it is not necessary to switch the four-way valve 3 and stop the compressor 2, and thus, it is possible to suppress load fluctuation, reduce noise and vibration, and perform defrosting without giving a feeling of discomfort to the user.

When defrosting of the outdoor heat exchanger 6 is performed during the heating operation, the controller 10 detects the outside air temperature T by the outdoor temperature sensor 13_OUTWhen the temperature is lower than a predetermined temperature T0 or when the time M from the previous defrosting to the start of the present defrosting is less than a predetermined time tc, a reverse cycle is executed in which the defrosting is performed by switching the refrigerant cycle direction to the refrigeration cycle in the opposite direction by the four-way valve 3And (5) defrosting operation.

Accordingly, at, for example, the outside air temperature T_OUTWhen the defrosting operation is relatively low (for example, 0 ℃ or lower), or when the previous defrosting operation is insufficient and the present defrosting operation is performed in a short time (less than the predetermined time tc) from the previous defrosting operation, the indoor heat exchanger 6 is used as an evaporator by the reverse cycle defrosting operation, and therefore, the defrosting operation can be reliably completed in a short time. Therefore, by selectively performing the relevant reverse-cycle defrosting operation and the continuous heating defrosting operation, defrosting that is effective in general and continues indoor heating as much as possible can be performed.

The control device 10 also operates the indoor fan 4a to control the operating frequency of the compressor 2 during the heating and defrosting operation. Accordingly, the heating operation can be continued and the defrosting of the outdoor heat exchanger 6 can be performed more efficiently in conjunction with the opening degree control of the electronic expansion valve 5 and the operation control of the outdoor fan 6 a.

When the refrigerant temperature Tc detected by the suction temperature sensor 15 is higher than a predetermined refrigerant temperature Tch, the controller 10 ends the heating and defrosting continuation operation. Accordingly, the defrosting can be completed by indicating the refrigerant temperature Tc associated with the defrosting, and wasteful defrosting operation can be eliminated.

The control device 10 specifies an upper limit t for the time t during which the heating and defrosting operation is continued in advance_MAXAt the execution time t, the upper limit t is reached_MAXIn the case of (3), the heating and defrosting operation is continued. Accordingly, even if the sensing function of the suction temperature sensor 15 is damaged due to some cause, for example, the heating and defrosting continuation operation can be terminated regardless of the refrigerant temperature Tc that is the detection result, and the heating and defrosting continuation operation can be extended without meaning.

The present invention is not limited to the embodiments and modifications described above and shown in the drawings, and can be modified and expanded as desired without departing from the spirit and scope thereof. For example, the opening degree X of the electronic expansion valve 5 during the continuous heating and defrosting operation shown in fig. 4 may be larger than the maximum opening degree X during the normal heating operation as long as the opening degree X is larger than the opening degree X during the normal heating operationThe large opening degree is small. Further, the rotational speed N of each

fan

4a, 6a during the heating defrosting operation is continued_IN、N_OUTIt is also possible to appropriately change, for example, the rotational speed N of the outdoor fan 6a_OUTThe rotation speed may be set to a rotation speed lower than the maximum rotation speed as long as heat exchange with the outside air is promoted. The operating frequency F of the compressor 2 may be set as appropriate to be suitable for defrosting.

Further, the reverse cycle defrosting operation and the heating and defrosting continuation operation are both targeted for the "last defrosting" for the time M (see step 2 in fig. 2) from the "last defrosting" to the start of the present defrosting, but at least either one of them may be targeted for the "last defrosting". That is, for example, instead of step S2, a step of determining whether or not the time M from the end of the previous heating and defrosting operation to the start of the present defrosting is equal to or longer than the predetermined time tc may be performed. Even if the "last defrosting" is only to be performed in the heating and defrosting continuation operation, the reverse cycle defrosting operation and the heating and defrosting continuation operation are performed depending on whether or not the subsequent time exceeds the predetermined time tc, and therefore the same effect as the above-described embodiment is obtained. Even when the time M from the last defrosting to the start of the present defrosting is the time from the start of the last defrosting to the start of the present defrosting or the time from the end of the last defrosting to the start of the present defrosting as described above, the predetermined time tc to be compared with the time can be appropriately set, thereby performing the expected defrosting operation. In addition, the conditions such as the defrosting start condition and the specific numerical values may be appropriately set within a range not exceeding the purpose. In addition, when the heating operation is stopped by the user operation, the count of the time of the defrosting interval is reset to zero. Then, for the first defrosting operation after the start of the heating operation, the time from the start of the heating operation to the start of the first defrosting is treated as time M, and this time M is compared with a predetermined time tc to determine whether to select the reverse cycle defrosting operation or the continuous heating defrosting operation as the defrosting operation.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example only, and are not intended to limit the scope of the invention. These new embodiments may be implemented in other various ways, and various omissions, substitutions, and changes may be made without departing from the spirit of the invention. These embodiments and modifications are included in the scope and spirit of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

Claims

1. An air conditioner is provided with:

a refrigeration cycle in which a compressor, a four-way valve, an indoor heat exchanger, an electronic expansion valve and an outdoor heat exchanger are connected in an annular manner by using a refrigerant pipeline,

an outdoor fan for sending outside air to the outdoor heat exchanger,

an outdoor temperature sensor for detecting the temperature of the outdoor air, an

And a controller that, when defrosting of the outdoor heat exchanger is performed during a heating operation, executes a heating-continued defrosting operation in which the defrosting is performed while the heating cycle is still in progress by controlling the opening degree of the electronic expansion valve to be open and operating the outdoor fan, without switching the circulation direction of the refrigerant flowing through the refrigerant pipe by the four-way valve, when the outside air temperature detected by the outdoor temperature sensor is higher than a predetermined temperature and the time from the last defrosting to the start of the present defrosting is equal to or longer than a predetermined time.

2. The air conditioner according to claim 1, wherein the controller performs a reverse cycle defrosting operation in which the refrigerant is circulated in a direction opposite to a direction in which the refrigerant is circulated by the four-way valve, when the outside air temperature detected by the outside temperature sensor is equal to or lower than a predetermined temperature or when the time is shorter than a predetermined time, during defrosting of the outdoor heat exchanger during the heating operation.

3. The air conditioner according to claim 1 or 2, comprising an indoor fan that sends indoor air to the indoor heat exchanger, wherein the controller further operates the indoor fan to control an operation frequency of the compressor during the heating and defrosting continuation operation.

4. The air conditioner according to any one of claims 1 to 3, comprising a suction temperature sensor for detecting a refrigerant temperature on a suction side of the compressor, wherein the control device ends the heating and defrosting continuation operation when the refrigerant temperature detected by the suction temperature sensor becomes higher than a predetermined refrigerant temperature.

5. The air conditioner according to claim 4, wherein the time for performing the heating and defrosting continuation operation is previously defined to have an upper limit, and the controller terminates the heating and defrosting continuation operation when the time for performing the heating and defrosting continuation operation reaches the upper limit.

6. The air conditioner according to any one of claims 1 to 3, wherein a time from a last defrosting to a start of a present defrosting is a time from a start of a last defrosting to a start of a present defrosting.

7. The air conditioner according to any one of claims 1 to 3, wherein a time from a last defrosting to a start of a present defrosting is a time from an end of the last defrosting to the start of the present defrosting.