GB2548526A - Indoor unit and air conditioning device using same - Google Patents

Abstract

This indoor unit comprises: an indoor-side heat exchanger which performs heat exchange between air and a refrigerant; an indoor fan which sends air to the indoor-side heat exchanger; and a control device which controls the operation of the indoor fan. The control device is equipped with: a current detection unit which detects the operating current of the indoor fan; an air volume calculation unit which calculates the volume of the air sent from the indoor fan on the basis of the operating current detected by the current detection unit; a storage unit which stores air blower characteristic information showing the relationship between the air volume and the static pressure of the indoor fan at each rotational speed; a rotational speed setting unit which sets the rotational speed of the indoor fan so that the air volume becomes a preset air volume, on the basis of the air volume calculated by the air volume calculation unit and the air blower characteristic information stored in the storage unit; and a rotation control unit which drives the indoor fan on the basis of the rotational speed set by the rotational speed setting unit.

Description

DESCRIPTION Title of Invention INDOOR UNITAND AIR-CONDITIONING APPARATUS INCLUDING THE SAME Technical Field [0001]

The present invention relates to an indoor unit that controls a static pressure supplied by an indoor fan such that the static pressure is kept constant and an air-conditioning apparatus including the indoor unit.

Background Art [0002]

Air-conditioning apparatuses known in the art include a heat pump air-conditioning apparatus including a refrigerant circuit. In the refrigerant circuit, for example, an outdoor unit including a compressor and an outdoor-unit-side heat exchanger and an indoor unit including an expansion valve, an indoor-unit-side heat exchanger, and an indoor fan are connected by refrigerant pipes. The refrigerant circuit is configured such that the outdoor unit, serving as a heat source side unit, and the indoor unit, serving as a load side unit, are connected by the refrigerant pipes through which refrigerant is circulated. In the indoor-unit-side heat exchanger in the refrigerant circuit, the refrigerant is evaporated by removing heat from air in an air-conditioning target space, serving as a heat exchange target, or is condensed by transferring heat to the air in the air-conditioning target space, serving as the heat exchange target. Consequently, the air-conditioning apparatus conditions the air in the air-conditioning target space.

[0003]

An indoor unit of an air-conditioning apparatus may be disposed in a constant temperature and humidity chamber in which temperature and humidity are precisely kept constant. For example, the indoor unit has a structure in which an indoor-unit-side heat exchanger and an indoor fan that blows air to the indoor-unit-side heat exchanger are accommodated in a casing. Indoor fan drive systems include a pulley drive system in which an indoor-unit-side fan is connected to a motor by pulleys and a belt. The air flow rate, which is a rate of air from or through an indoor fan, or the static pressure of air from the indoor fan, varies depending on the environment in which an indoor unit is installed. The air flow rate through the indoor fan has to be adjusted in accordance with the use environment. In the pulley drive system, the rotation speed of the indoor-unit-side fan is changed by changing the diameter of a pulley connected to the indoor-unit-side fan and the diameter of a pulley connected to the motor, thereby adjusting the air flow rate.

[0004]

During a continuous operation, the airflow rate through an indoor fan decreases due to, for example, an increase in filter pressure loss. To suppress a decrease in air flow rate, the rotation speed of the indoor fan may be increased. In the pulley drive system, however, the diameter of the pulley connected to the indoor-unit-side fan and the diameter of the pulley connected to the motor cannot be changed during operation.

[0005]

To keep an air flow rate on an air supply side constant, a recently developed humidity control device controls, based on a motor load on the air supply side, an air flow rate on an air discharge side such that the air flow rate on the air discharge side is kept constant (refer to Patent Literature 1, for example). Patent Literature 1 discloses, as a method of controlling the airflow rate through an air supply fan or an air discharge fan to keep the air flow rate constant, control of the rotation speed of a motor for the fan based on the relationship between the rotation speed and an operating current of the motor.

Citation List Patent Literature [0006]

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2010-139144 Summary of Invention Technical Problem [0007]

If an indoor unit is continuously operated and an airflow rate decreases due to, for example, an increase in filter pressure loss as described above, a predetermined air flow rate can be obtained by controlling the rotation speed of a motor for a fan based on the relationship between the rotation speed and an operating current of the motor in a manner similar to that in Patent Literature 1. In the case where the indoor unit is installed in, for example, a constant temperature and humidity chamber, however, precisely obtaining a predetermined static pressure is required as well as keeping a constant air flow rate as in Patent Literature 1.

[0008]

The present invention has been made to overcome the above-described problem and is intended to provide an indoor unit capable of precisely controlling an air flow rate and a static pressure and an air-conditioning apparatus including the indoor unit.

Solution to Problem [0009]

An embodiment of the present invention provides an indoor unit including an indoor-side heat exchanger configured to exchange heat between air and refrigerant; an indoor fan configured to blow the air to the indoor-side heat exchanger; and a controller configured to control operation of the indoor fan, the controller including a current detection unit configured to detect an operating current for the indoor fan, an air flow rate calculation unit configured to calculate an air flow rate being a flow rate of the air blown by the indoor fan based on the operating current detected by the current detection unit, a storage unit configured to store air-sending-device characteristic information indicating a relationship between the air flow rate and a static pressure for each rotation speed of the indoor fan, a rotation speed setting unit configured to set, based on the air flow rate calculated by the air flow rate calculation unit and the airsending-device characteristic information stored in the storage unit, a rotation speed of the indoor fan at which the air flow rate substantially agrees with a set air flow rate. and a rotation control unit configured to drive the indoor fan based on the rotation speed set by the rotation speed setting unit Advantageous Effects of Invention [0010]

In the indoor unit according to the embodiment of the present invention and an air-conditioning apparatus including the indoor unit, a rotation speed of the indoor fan at which the air flow rate agrees with the set air flow rate is set based on the air flow rate calculated by the airflow rate calculation unit and the air-sending-device characteristic information stored in the storage unit. If a change in air flow rate is caused by pressure loss, the rotation speed is adjusted to the set air flow rate and the preset static pressure based on the air-sending-device characteristic information. Thus, the airflow rate and the static pressure can be precisely controlled.

Brief Description of Drawings [0011] [Fig. 1] Fig. 1 is a refrigerant circuit diagram illustrating an air-conditioning apparatus including an indoor unit according to Embodiment 1 of the present invention.

[Fig. 2] Fig. 2 is a perspective view of an example of the indoor unit according to Embodiment 1 of the present invention.

[Fig. 3] Fig. 3 is a block diagram illustrating an exemplary controller and an exemplary remote control in the indoor unit in Fig. 1.

[Fig. 4] Fig. 4 is a graph illustrating an example of air-sending-device characteristic information (airflow rate-static pressure characteristic) stored in a storage unit in Fig. 3.

[Fig. 5] Fig. 5 is a graph illustrating exemplary setting of a rotation speed in the controller in Fig. 4.

[Fig. 6] Fig. 6 is a graph illustrating exemplary automatic airflow rate control in the controller in Fig. 3.

[Fig. 7] Fig. 7 is a flowchart illustrating an exemplary operation at initialization in the controller in Fig. 3.

[Fig. 8] Fig. 8 is a flowchart illustrating exemplary automatic air flow rate control in the controller in Fig. 3.

[Fig. 9] Fig. 9 is a flowchart illustrating exemplary automatic airflow rate control in Embodiment 2 of the present invention.

Description of Embodiments [0012]

Embodiment 1

The indoor unit of Embodiment 1 of the present invention will be described below with reference to the drawings. Fig. 1 is a refrigerant circuit diagram illustrating an air-conditioning apparatus including an indoor unit according to Embodiment 1 of the present invention. An air-conditioning apparatus 1 of Fig. 1 includes an outdoor unit 10, serving as a heat source side unit, and an indoor unit 20, serving as a use side unit. The outdoor unit 10 and the indoor unit 20 are connected by refrigerant pipes, thus forming a refrigerant circuit. The refrigerant circuit is filled with refrigerant. The air-conditioning apparatus 1 performs air-conditioning by circulating the refrigerant through the refrigerant pipes.

[0013]

The outdoor unit 10 includes a compressor 11, a flow switching device 12, an outdoor-side heat exchanger 13, and a subcooling heat exchanger 14. Operation valves 17a and 17b are provided to the refrigerant pipes connected to the indoor unit 20. The compressor 11 compresses the refrigerant to a high temperature, high pressure state. The flow switching device 12 is, for example, a four-way valve, and performs switching between connection states in a refrigeration cycle in accordance with operation state, such as a cooling operation or a heating operation. The outdoor-side heat exchanger 13 is, for example, a fin and tube heat exchanger including heat transfer tubes and many fins, and exchanges heat between the refrigerant and outdoor air. The outdoor-side heat exchanger 13 serves as a condenser in the cooling operation and serves as an evaporator in the heating operation.

[0014]

The subcooling heat exchanger 14 is, for example, a double-pipe heat exchanger, and subcools the refrigerant flowing from the outdoor-side heat exchanger 13 to the indoor unit 20 in the cooling operation. The refrigerant pipe between the subcooling heat exchanger 14 and the indoor unit 20 branches and is connected to an outdoor-side expansion valve 15. The refrigerant leaving the outdoor-side expansion valve 15 is connected to a suction side of the compressor 11 via the subcooling heat exchanger 14 and an accumulator 16. The accumulator 16, which stores the refrigerant, is connected to the suction side of the compressor 11 and the flow switching device 12.

[0015]

The indoor unit 20 includes an indoor-side heat exchanger 21, an indoor fan 22, and an indoor expansion device 23. The indoor-side heat exchanger 21 is, for example, a fin and tube heat exchanger including heat transfer tubes and many fins. The indoor-side heat exchanger 21 is connected at a first end to the flow switching device 12 in the outdoor unit 10 and is connected at a second end to the indoor expansion device 23. The indoor-side heat exchanger 21 serves as an evaporator in the cooling operation and serves as a condenser in the heating operation. The indoor fan 22, which delivers air to the indoor-side heat exchanger 21, is driven and rotated by, for example, inverter control. An air flow rate through the indoor fan 22 can be adjusted by changing the rotation speed of the indoor fan 22. The indoor expansion device 23 is, for example, an electronic expansion valve. Setting the opening degree of the indoor expansion device 23 adjusts the flow rate of the refrigerant through the expansion device. The indoor expansion device 23 serves as a pressure reducing valve or an expansion valve to reduce the pressure of the refrigerant and expand it.

[0016]

The indoor unit 20 further includes a controller 40 configured to control operation of the above-described indoor fan 22 and a remote control 30 connected to the controller 40 by wire or wirelessly such that the remote control 30 can transmit and receive information to and from the controller 40. The remote control 30 transmits information accepted from a user to the controller 40. The controller 40 controls operation of the indoor unit 20 based on the information transmitted from the remote control 30. The controller 40 transmits information indicating operational status of the indoor unit 20 to the remote control 30. The remote control 30 displays the operational status of the indoor unit 20 to inform the user of the status.

[0017]

The flow of the refrigerant in the cooling operation as operation example of the air-conditioning apparatus 1 will now be described with reference to Fig. 1. The refrigerant discharged from the compressor 11 flows through the flow switching device 12 into the outdoor-side heat exchanger 13, in which the refrigerant exchanges heat with the air. The refrigerant, subjected to heat exchange in the outdoor-side heat exchanger 13, is subcooled by the subcooling heat exchanger 14. After that, the refrigerant flows into the indoor unit 20. At this time, part of the refrigerant flows through the outdoor-side expansion valve 15 to the subcooling heat exchanger 14 and then flows into the accumulator 16. The refrigerant that has flowed into the indoor unit 20 is pressure-reduced by the indoor expansion device 23 and then flows into the indoor-side heat exchanger 21. In the indoor-side heat exchanger 21, the refrigerant exchanges heat with indoor air, thus cooling the indoor air. After that, the refrigerant flows out of the indoor-side heat exchanger 21 and flows through the flow switching device 12 in the outdoor unit into the accumulator 16, where the refrigerant is stored. The refrigerant stored in the accumulator 16 is again sucked into the compressor 11.

[0018]

Fig. 2 is a perspective view illustrating an example of the indoor unit 20 in Embodiment of the present invention. The indoor unit 20 has a structure in which the indoor-side heat exchanger 21 and the indoor fan 22 are accommodated in, for example, a rectangular casing 20A. The indoor fan 22 is disposed above the indoor-side heat exchanger 21. The controller 40 is disposed below the indoor-side heat exchanger 21. The indoor fan 22 includes a fan body 22a and a motor 22b. The fan body 22a is coupled directly to the motor 22b.

[0019]

The fan body 22a comprises, for example, a sirocco fan, and has an air outlet 22x provided to an upper surface of the casing 20A. The fan body 22a is driven and rotated by driving the motor 22b, thus producing an air flow from lower part of the indoor-side heat exchanger 21 to the air outlet 22x in the casing 20A. The air blown from the air outlet 22x is supplied directly or through a duct to an indoor load side. The operation of the indoor fan 22 is controlled by the controller 40.

[0020]

Fig. 3 is a block diagram illustrating an exemplary remote control and an exemplary controller in the indoor unit in Fig. 1. The remote control 30 in Fig. 3 includes an input unit 31 including buttons for accepting an input from a user, a display unit 32 that displays, for example, the operational status of the indoor unit, a remote-control control unit 33 that controls operation of the input unit 31 and operation of the display unit 32, and a remote-control communication unit 34 that transmits and receives information to and from the controller 40 in a wired or wireless manner. In the remote control 30, the input unit 31 and the display unit 32 may be included in a touch panel. In particular, with the input unit 31 of the remote control 30, the user inputs a set air flow rate Qs and a set static pressure Ps for the indoor unit 20. The remote-control communication unit 34 transmits the set air flow rate Qs and the set static pressure Ps, input through the input unit 31, to the controller 40.

[0021]

The controller 40 controls the operation of the indoor fan 22 based on an operating current I supplied to the indoor fan 22. The controller 40 includes a rotation control unit 41, a current detection unit 42, an air flow rate calculation unit 43, a rotation speed setting unit 44, and a storage unit 45. Furthermore, the controller 40 transmits and receives information to and from the remote-control communication unit 34 of the remote control 30 via a control communication unit 46. The rotation control unit 41 controls the operation of the indoor fan 22, for example, such that the indoor fan 22 is inverter-controlled. In this case, the rotation control unit 41 controls the indoor fan 22 to provide a rotation speed N set in the rotation speed setting unit 44.

[0022]

The current detection unit 42 detects the operating current I supplied to the motor 22b of the indoor fan 22. For example, a current sensor for detecting the operating current I to the motor 22b is disposed in a power supply circuit for supplying input power to the motor 22b. The current detection unit 42 obtains the operating current I detected by the current sensor. The current detection unit 42 detects the operating current I with a predetermined sampling period T. The sampling period T may be set in the current detection unit 42 or may be set through the remote control 30 by the user.

[0023]

The air flow rate calculation unit 43 calculates an air flow rate Q of air blown by the indoor fan 22 based on the operating current I detected by the current detection unit 42. Specifically, when the motor 22b is inverter-controlled as described above, the airflow rate Q and the operating current I have a predetermined relationship.

The air flow rate calculation unit 43 stores the relationship between the operating current I and the air flow rate Q associated with, for example, the model of the indoor fan 22, and calculates the air flow rate Q based on the operating current I. The relationship is as follows: an increase in filter pressure loss caused by, for example, filter clogging causes a reduction in airflow rate Q, resulting in a reduction in operating current I.

[0024]

The rotation speed setting unit 44 sets, based on the air flow rate Q calculated by the air flow rate calculation unit 43 and air-sending-device characteristic information stored in the storage unit 45, the rotation speed N of the indoor fan 22 at which the air flow rate Q substantially agrees with the set air flow rate Qs. In this case, the set air flow rate Qs and the set static pressure Ps are set in the remote control 30 at, for example, initialization of the indoor unit 20.

[0025]

Fig. 4 is a graph illustrating an example of the air-sending-device characteristic information (air flow rate-static pressure characteristic) stored in the storage unit in Fig. 3. In Fig. 4, the horizontal axis represents the flow rate of air blown by the indoor fan 22 and the vertical axis represents the static pressure. The storage unit 45 stores the air-sending-device characteristic information for each horsepower. In Fig. 4, the difference between a total static pressure and an internal resistance of the indoor unit 20 is the static pressure.

[0026]

Fig. 5 is a graph illustrating an example of setting of the rotation speed in the controller in Fig. 3. The rotation speed setting based on the set air flow rate Qs and the set static pressure Ps will now be described with reference to Fig. 5. For example, it is assumed that the remote control 30 transmits unit information indicating a set air flow rate Qs = 90 [m^/min] and a set static pressure Ps = 245 [Ps] to the control communication unit 46. The rotation speed setting unit 44 obtains an internal resistance = 115 [Pa] at an airflow rate = 90 [m^/min] based on the air-sending-device characteristic information. The rotation speed setting unit 44 adds the internal resistance to the set static pressure Ps to calculate a necessary total static pressure of 360 [Pa] = 115 [Pa] + 245 [Pa], and sets the rotation speed N of the indoor fan 22 to 700 [rpm] at which the total static pressure is 360 [Pa]. The rotation control unit 41 controls the indoor fan 22 such that the indoor fan 22 is rotated at a rotation speed N of 700 [rpm] calculated by the rotation speed setting unit 44.

[0027]

As described above, the rotation speed setting unit 44 obtains the set airflow rate Qs and the set static pressure Ps at initialization, and calculates an initial rotation speed Ns based on the air-sending-device characteristic information, the set airflow rate Qs, and the set static pressure Ps. In this case, the air flow rate calculation unit 43 has a function of calculating an initial operating current Is from the set air flow rate Qs. The control communication unit 46 transmits information indicating the initial rotation speed Ns and the initial operating current Is to the remote control 30. The display unit 32 of the remote control 30 displays the initial rotation speed Ns and the initial operating current Is.

[0028]

In this case, if the filter pressure loss is increased by, for example, filter clogging in the continuous operation of the indoor unit 20, the air flow rate Q decreases. If the rotation control unit 41 maintains the rotation at the initial rotation speed Ns set at initialization in spite of the decrease in air flow rate Q, the set static pressure Ps would not be obtained. For this reason, the controller 40 has a function of automatically controlling the air flow rate. Specifically, the rotation speed setting unit 44 sets the rotation speed N based on the air flow rate Q during automatic air flow rate control of the indoor unit 20.

[0029]

Fig. 6 is a graph illustrating an example of the automatic air flow rate control in the controller in Fig. 3. It is assumed that while the set air flow rate Qs is set to 90 [m^/min] as illustrated in Fig. 5, for example, filter pressure loss causes the internal resistance in the indoor unit 20 to increase from an initial internal resistance RO to an internal resistance R1. At this time, the air flow rate Q decreases from 90 [m^/min] to 85 [m^/min]. This means that, for example, for 10-horsepower cooling, a cooling capacity is reduced by 1.5 percent. In addition, a static pressure at a rotation speed N = 700 [rpm] and an air flow rate Q = 85 [m^/min] is greater than a static pressure at a rotation speed N = 700 [rpm] and an air flow rate Q = 90 [m^/min]. In such a state, the set static pressure Ps is not obtained and the capacity is reduced. To reduce a reduction in capacity, the rotation speed setting unit 44 sets a rotation speed N increased by an increase in internal resistance.

[0030]

Specifically, the rotation speed setting unit 44 calculates an increase in internal resistance based on the air-sending-device characteristic information, the rotation speed N, and the airflow rate Q, and obtains a rotation speed N including the calculated increase in internal resistance. In the above-described case of Fig. 6, the rotation speed setting unit 44 changes the rotation speed N of the indoor fan 22 from 700 [rpm] to 800 [rpm]. As described above, operation point can be grasped with respect to the air-sending-device characteristic information, so that the rotation speed N of the indoor fan 22 can be adjusted such that the set air flow rate Qs and the set static pressure Ps are obtained. Thus, the air flow rate and the static pressure can be precisely kept constant.

[0031]

The controller 40 has a function of transmitting information indicating the above-described adjusted rotation speed N, the operating current I, the static pressure, and the air flow rate Q to the remote control 30 via the control communication unit 46. The remote-control control unit 33 of the remote control 30 causes the display unit 32 to display the changed rotation speed N, the operating current I, the static pressure, and the airflow rate Q. Consequently, the user can grasp the operational status of the indoor unit 20 from the remote control 30.

[0032]

Furthermore, the rotation speed setting unit 44 has a function of determining whether the calculated rotation speed N is greater than a maximum presettable rotation speed Nmax. The maximum presettable rotation speed Nmax is a maximum rotation speed of the indoor fan 22 limited by the fan body 22a and the motor 22b. A rotation speed N greater than the maximum presettable rotation speed Nmax means that filter pressure loss causes the indoor unit 20 to fail to provide the preset air flow rate Qs. When the rotation speed N is greater than the maximum presettable rotation speed Nmax, the rotation speed setting unit 44 transmits information indicating a reduction in airflow rate to the remote control 30 via the control communication unit 46. In response to the information, the display unit 32 of the remote control 30 displays an alarm indicating a reduction in air flow rate.

[0033]

In addition, the rotation speed setting unit 44 has a function of adjusting the rotation speed N when the air flow rate Q calculated by the air flow rate calculation unit 43 is greater than a minimum threshold air flow rate Qmin. The minimum threshold air flow rate Qmin is set to a value less than the set air flow rate Qs. For example, the user inputs the minimum threshold airflow rate Qmin through the input unit 31 of the remote control 30. The minimum threshold air flow rate Qmin may be preset in the storage unit 45. In this case, the rotation speed setting unit 44 performs control such that the airflow rate Q is greater than the minimum threshold air flow rate Qmin and less than the set air flow rate Qs (Qmin < Q < Qs). In other words, the rotation speed setting unit 44 does not adjust the rotation speed N until the air flow rate Q is the minimum threshold air flow rate Qmin or less. This can reduce a likelihood that the rotation speed N to frequently change.

[0034]

Fig. 7 is a flowchart illustrating an exemplary operation at initialization in the controller in Fig. 3. The initialization in the controller 40 will now be described with reference to Figs. 1 to 7. First, unit information (horsepower, the set airflow rate Qs, and the set static pressure Ps) is input to the remote control 30 (step ST1). The unit information input to the remote control 30 is transmitted from the remote control 30 to the controller 40 (step ST2).

[0035]

After that, the rotation speed setting unit 44 of the controller 40 calculates the initial rotation speed Ns of the indoor fan 22 based on the air-sending-device characteristic information for each horsepower in the storage unit 45 and the set air flow rate Qs and the set static pressure Ps transmitted from the remote control 30 (refer to Figs. 4 and 5). In addition, the airflow rate calculation unit 43 calculates the initial operating current Is. The initial rotation speed Ns and the initial operating current Is are stored into the storage unit 45 and are also transmitted to the remote control 30 (step ST3). Upon completion of receiving the initial rotation speed Ns and the initial operating current Is, the remote control 30 causes the display unit 32 of the remote control 30 to display "Completion of Initial Value Setting" (step ST4). Thus, the initialization of the indoor fan 22 is completed.

[0036]

Then, a test operation of the indoor fan 22 is performed (step ST5). Operation of the indoor fan 22 is started at the initial rotation speed Ns. Whether the rotation speed N of the fan substantially agrees with the initial rotation speed Ns is determined (step ST6). If the rotation speed N of the fan is not the initial rotation speed Ns (NO in step ST6), an operating frequency of the motor 22b is adjusted such that the rotation speed N substantially agrees with the initial rotation speed Ns. If the rotation speed N is the initial rotation speed Ns (YES in step ST6), a timer begins to measure a predetermined continuous operation time period (e.g., 30 minutes) (step ST7).

The reason why the continuous operation time period is 30 minutes is that the time taken for the operating current I supplied to the motor 22b to stabilize is 30 minutes.

If the operation is stopped due to, for example, a power failure, the timer may be reset and the test operation may be performed again from the beginning.

[0037]

Then, the operating current I to the motor 22b after a lapse of the continuous operation time period is detected. Since the operating current I to the motor 22b fluctuates, the current detection unit 42 determines whether the operating current I in the test operation is within a predetermined range (e.g., 95% to 105%) of the initial operating current Is (step STS). If the operating current I in the test operation is out of the predetermined range of the initial operating current Is (NO in step STS), the static pressure is adjusted such that the operating current I in the test operation is within the predetermined range (step ST9). The static pressure adjustment is performed using a known technique, for example, adjusting the angle of a damper (not illustrated) or a shutter (not illustrated) in the air outlet 22x. For example, when the indoor fan 22 is connected to an air-conditioning target space by a duct, the internal resistance varies depending on the length of the duct. The static pressure may be adjusted accordingly depending on the use environment. If the operating current I in the test operation is within the predetermined range of the initial operating current Is (YES in step STS), the operation is stopped, or the test operation is terminated.

[0038]

Fig. 8 is a flowchart illustrating an example of the automatic air flow rate control in the controller in Fig. 3. First, the user inputs the sampling period T and the minimum threshold airflow rate Qmin through the input unit 31 of the remote control 30. The remote control 30 transmits information indicating the input sampling period T and the input minimum threshold airflow rate Qmin to the controller 40 (step ST11). The operation of the indoor fan 22 is started (step ST12).

[0039]

The timer begins to measure a time period from the start of the operation and the controller 40 determines whether the measured time period is greater than the sampling period T (step ST13). If the measured time period is less than or equal to the sampling period T (NO in step ST13), the timer is not reset and measuring the accumulated time period is continued. On the other hand, if the measured time period is greater than the sampling period T (YES in step ST13), the current detection unit 42 detects the operating current I and the airflow rate calculation unit 43 calculates the airflow rate Q based on the operating current I (step ST14).

[0040]

After that, the rotation speed setting unit 44 determines whether the air flow rate Q is less than the minimum threshold air flow rate Qmin (step ST 15). If the air flow rate Q is the minimum threshold airflow rate Qmin or greater (NO in step ST15), it is determined that it is unnecessary to adjust the rotation speed N, and the timer for the sampling period T is reset (step ST16) to again measure a time period (step ST13). On the other hand, if the airflow rate Q is less than the minimum threshold air flow rate Qmin (YES in step ST15), the rotation speed setting unit 44 calculates the rotation speed N of the indoor fan 22 at which the set air flow rate Os and the set airflow rate Qs are obtained (step ST17).

[0041]

Then, the rotation speed setting unit 44 determines whether the rotation speed N is greater than the maximum presettable rotation speed Nmax (step ST18). If the rotation speed N is the maximum presettable rotation speed Nmax or less (NO in step ST18), the rotation control unit 41 controls driving of the indoor fan 22 based on the rotation speed N calculated by the rotation speed setting unit 44. At this time, the timer for the sampling period T is reset (step ST 16) to again measure a time period.

On the other hand, if the rotation speed N is greater than the maximum presettable rotation speed Nmax (YES in step ST18), it is determined that, for example, clogging causes the indoor unit 20 to fail to provide an air flow rate greater than or equal to the minimum threshold airflow rate Qmin, the remote control 30 displays an alarm indicating a reduction in air flow rate (step ST 19). The automatic air flow rate control is terminated.

[0042]

According to Embodiment 1 described above, the rotation speed N of the indoor fan 22 at which the air flow rate Q substantially agrees with the set air flow rate Qs is set based on the air flow rate Q calculated by the airflow rate calculation unit 43 and the air-sending-device characteristic information stored in the storage unit 45. If a change in air flow rate is caused by pressure loss, the rotation speed N is adjusted based on the air-sending-device characteristic information such that the set airflow rate Qs and the set static pressure Ps are provided. Consequently, the air flow rate and the static pressure can be precisely controlled. In other words, such an automatic air flow rate control mode allows the air flow rate to be within a range requested by the user. Allowing the air flow rate to be within the range requested by the user eliminates or reduces a change in capacity. This leads to improvement in controllability in a use environment, in particular, for providing constant temperature and humidity conditions, for example.

[0043]

Embodiment 2

Fig. 9 is a flowchart of automatic air flow rate control in Embodiment 2 of the present invention. An exemplary automatic air flow rate control operation will be described with reference to Fig. 9. In the automatic air flow rate control of Fig. 9, the same steps as those in Fig. 8 are designated by the same reference numerals and a description of these steps is omitted. The difference between Embodiment 2 in Fig. 9 and Embodiment 1 is steps following the step in which the rotation speed N is greater than the maximum presettable rotation speed Nmax.

[0044]

Specifically, if the rotation speed N calculated by the rotation speed setting unit 44 is greater than the maximum presettable rotation speed Nmax (YES in step ST18), the rotation speed setting unit 44 sets the rotation speed N to the maximum presettable rotation speed Nmax (step ST20). While the indoor fan 22 is rotated at the maximum presettable rotation speed Nmax, the rotation speed setting unit 44 determines whether the airflow rate Q is less than the minimum threshold airflow rate Qmin (step ST21).

[0045]

If the air flow rate Q is the minimum threshold air flow rate Qmin or greater (NO in step ST21), the rotation control unit 41 controls the indoor fan 22 based on the rotation speed N = the maximum presettable rotation speed Nmax. At this time, the timer for the sampling period T is reset (step ST 16) to again measure a time period. On the other hand, if the air flow rate Q is less than the minimum threshold air flow rate Qmin, it is determined that the indoor unit fails to provide an airflow rate greater than or equal to the minimum threshold airflow rate Qmin. The remote control 30 displays an alarm indicating a reduction in air flow rate. The automatic air flow rate control is terminated.

[0046]

According to Embodiment 2 described above, the indoor unit 20 can continue the continuous operation for a longer time period without being stopped.

Specifically, if the indoor unit is used to provide constant temperature and humidity conditions, it will be operated 24 hours. It is necessary to minimize a likelihood that the indoor unit may be stopped. For this reason, if the rotation speed N is greater than the maximum presettable rotation speed Nmax, the operation may be continued as long as the indoor unit can provide an air flow rate Q greater than or equal to the minimum threshold airflow rate Qmin. Thus, the continuous operation time period can be further extended. In addition, since the remote control 30 displays an alarm when the airflow rate Q is less than the minimum threshold airflow rate Qmin, the user can periodically determine whether the filter is clogged. Furthermore, according to Embodiment 2, if a change in airflow rate is caused due to pressure loss, the rotation speed N is adjusted based on the air-sending-device characteristic information such that the set air flow rate Qs and the set static pressure Ps are provided, as in Embodiment 1. Thus, the air flow rate and the static pressure can be precisely controlled.

[0047]

Embodiment 1 of the present invention is not limited to Embodiment 1 described above. For example, in Embodiment 1 described above, the single indoor fan 22 and the single motor 22b are provided. If two indoor fans 22 and two motors 22b are arranged, similar control can be performed.

Reference Signs List [0048] 1 air-conditioning apparatus 10 outdoor unit 11 compressor 12 flow switching device 13 outdoor-side heat exchanger 14 subcooling heat exchanger 15 outdoor-side expansion valve 16 accumulator 17a, 17b operation valve 20 indoor unit 20A casing 21 indoor-side heat exchanger 22 indoor fan 22a fan body 22b motor 22x air outlet 23 indoor-side expansion device 30 remote control 31 input unit 32 display unit 33 remote-control control unit 34 remote-control communication unit 40 controller 41 rotation control unit 42 current detection unit 43 air flow rate calculation unit 44 rotation speed setting unit 45 storage unit 46 control communication unit I operating current Is initial operating current N rotation speed Nmax maximum presettable rotation speed Ns initial rotation speed Ps preset static pressure Q air flow rate Qmin minimum threshold air flow rate Qs preset air flow rate RO, R1 internal resistance T sampling period

Claims (1)

1. CLAIMS [Claim 1] An indoor unit comprising: an indoor-side heat exchanger configured to exchange heat between air and refrigerant; an indoor fan configured to blow the air to the indoor-side heat exchanger; and a controller configured to control operation of the indoor fan, the controller including a current detection unit configured to detect an operating current for the indoor fan, an airflow rate calculation unit configured to calculate an airflow rate being a flow rate of the air blown by the indoor fan based on the operating current detected by the current detection unit, a storage unit configured to store air-sending-device characteristic information indicating a relationship between the airflow rate and a static pressure for each rotation speed of the indoor fan, a rotation speed setting unit configured to set, based on the airflow rate calculated by the airflow rate calculation unit and the air-sending-device characteristic information stored in the storage unit, a rotation speed of the indoor fan at which the air flow rate substantially agrees with a set air flow rate, and a rotation control unit configured to drive the indoor fan based on the rotation speed set by the rotation speed setting unit. [Claim 2] The indoor unit of claim 1, wherein the storage unit is configured to store the air-sending-device characteristic information indicating a relationship between the airflow rate and a total static pressure for each rotation speed, and a relationship between the airflow rate and an internal resistance, and the rotation speed setting unit is configured to set the rotation speed of the indoor fan such that the total static pressure that depends on the rotation speed of the indoor fan is equal to a sum of the internal resistance and a set static pressure. [Claim 3] The indoor unit of claim 1 or 2, wherein the rotation speed setting unit is configured to determine whether the air flow rate is greater than a minimum threshold air flow rate, and set the rotation speed when determining that the air flow rate is less than the minimum threshold airflow rate. [Claim 4] The indoor unit of claim 2 or 3, further comprising: a remote control configured to transmit and receive information to and from the controller, wherein the remote control includes an input unit through which the set airflow rate is input, and the rotation speed setting unit is configured to obtain the set airflow rate and the set static pressure from the remote control. [Claim 5] The indoor unit of claim 4, wherein in a state where the set air flow rate and the set static pressure are obtained from the remote control, the rotation control unit performs a test operation and stores the set air flow rate, the set static pressure, and the operating current in the test operation into the storage unit. [Claim 6] The indoor unit of claim 4 or 5, wherein the rotation speed setting unit is configured to determine whether the rotation speed of the indoor fan is greater than a maximum presettable rotation speed, and output, when determining that the rotation speed of the indoor fan is greater than the maximum presettable rotation speed, information indicating a reduction in air flow rate to the remote control. [Claim 7] The indoor unit of any one of claims 1 to 5, wherein the rotation speed setting unit is configured to determine whether the rotation speed of the indoor fan is greater than a maximum presettable rotation speed, and set, when determining that the rotation speed of the indoor fan is greater than the maximum presettable rotation speed and the air flow rate is greater than a minimum threshold airflow rate, the rotation speed of the indoor fan to the maximum presettable rotation speed. [Claim 8] An air-conditioning apparatus comprising: the indoor unit of any one of claims 1 to 7; and an outdoor unit connected to the indoor unit by refrigerant pipes to constitute a refrigerant circuit together with the outdoor unit.