JP2013210124A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air conditioner which can perform energy saving operation after the operation condition which can perform effective energy saving operation is discerned.SOLUTION: A capacity ratio α of which a sum capacity of an indoor device in which the temperature difference in the room temperature for a preset temperature exceeds a predetermined temperature is divided by the sum capacity of the total indoor devices under operation is calculated, and when the capacity ratio α is less than a predetermined ratio and the frequency of a compressor 1 is less than the lower limit of the frequency range where a high compressor efficiency can obtain more than a predetermined level, if it is during the air conditioning period, while lowering target evaporation temperature instead of the target maintenance control, the control is performed which raises an upper limit of the frequency of the compressor 1, whereas if it is during the heating period, while raising target condensation temperature instead of target maintenance control, the control is performed which raises an upper limit of the frequency of the compressor 1.

Description

  The present invention relates to an air conditioner.

  Conventionally, there is a multi-type air conditioner in which a plurality of indoor units are connected to one outdoor unit to constitute a refrigeration cycle. In this type of air conditioner, the frequency of the compressor installed in the outdoor unit is based on the difference between the set temperature of each room in which each indoor unit is installed and the indoor temperature detected by each operating indoor unit. In addition, the opening degree of each electronic expansion valve installed in each indoor unit is controlled to control the room temperature in each room close to the set temperature (see, for example, Patent Document 1).

  Various specific methods for frequency control of the compressor and opening control of the electronic expansion valve of each indoor unit have been proposed. For example, determine the target evaporating temperature during cooling and the target condensing temperature during heating so that indoor units in a room with a large difference between the set temperature and room temperature can exhibit sufficient air conditioning capacity (cooling capacity or heating capacity). doing. Then, the frequency of the compressor is controlled so as to be the target evaporation temperature or the target condensation temperature, and each electronic expansion valve is controlled so that the degree of superheat (at the time of cooling) or the degree of supercooling (at the time of heating) becomes a target value. In general, the opening degree is individually controlled.

JP 2005-24153 A (page 4)

  By the way, in recent years, energy-saving control is required for air conditioners. However, in the conventional control in which the target evaporating temperature and the target condensing temperature are determined according to the indoor unit having a large temperature difference, if there is a variation in the temperature difference between the indoor units, for example, even one unit has a large temperature difference. In order to increase the air conditioning capacity in accordance with the indoor unit, control for lowering the target evaporation temperature or raising the target condensation temperature is performed. In the refrigeration cycle, the lower the target evaporation temperature and the higher the target condensing temperature, the lower the operating efficiency. Therefore, determine the target evaporating temperature and the target condensing temperature according to one indoor unit with a large temperature difference. Is not preferable from the viewpoint of energy saving.

  On the other hand, when there is a plurality of indoor units having a large temperature difference and the control for increasing the air conditioning capability is not performed in order to obtain a high energy saving effect, the indoor comfort is impaired. As described above, in an air conditioner having a plurality of indoor units, there is a problem that it is difficult to determine an operation state in which energy-saving operation can be effectively performed.

  The present invention has been made in view of these points, and an object of the present invention is to provide an air conditioner capable of performing an energy-saving operation after determining an operation state in which the energy-saving operation can be effectively performed.

  An air conditioner according to the present invention includes an outdoor unit having a compressor and an outdoor heat exchanger, a plurality of indoor units having a throttle device and an indoor heat exchanger, and capable of operating at least one of cooling and heating, During cooling, the target evaporation temperature is determined based on the temperature difference between the set temperature of each room where the indoor unit is installed and the room temperature detected by the indoor unit. During heating, the target condensation temperature is determined based on the temperature difference. And a control device that performs target maintenance control for controlling the frequency of the compressor so as to maintain the determined target evaporation temperature or target condensation temperature, and the control device has a differential temperature that is equal to or higher than a preset predetermined temperature. The volume ratio obtained by dividing the total capacity of the indoor units by the total capacity of all the indoor units in operation is calculated, and high compressor efficiency is obtained in which the volume ratio is less than the predetermined ratio and the frequency of the compressor is equal to or higher than the predetermined level. If the frequency range is less than the lower limit In the case of cooling, instead of the target maintenance control, control is performed to lower the target evaporation temperature and increase the upper limit value of the compressor frequency, and in the case of heating, the target condensation temperature is set instead of the target maintenance control. The control is performed to raise the upper limit value of the compressor frequency as well as raising the compressor frequency.

  According to the present invention, an energy-saving operation can be performed after ascertaining an operation situation in which an energy-saving operation can be effectively performed based on the capacity ratio and the compressor frequency.

It is a block diagram of the air conditioner which concerns on one embodiment of this invention. It is explanatory drawing of the determination method of target evaporation temperature according to temperature difference (DELTA) T. It is a figure which shows the temperature change of the room when controlling the frequency of a compressor. It is the figure which showed the compressor efficiency characteristic for every evaporation temperature. It is explanatory drawing of the determination method of the target condensation temperature according to temperature difference (DELTA) T. It is the figure which showed the compressor efficiency characteristic for every condensation temperature. It is a block diagram which shows the structure of the air conditioner which concerns on one embodiment of this invention. It is a flowchart which shows the control action of the air conditioner which concerns on one embodiment of this invention. It is a figure which shows the relationship between volume ratio (alpha) and a compressor frequency upper limit.

(Configuration of air conditioner)
FIG. 1 is a configuration diagram of an air conditioner according to an embodiment of the present invention.
The air conditioner includes an outdoor unit A and a plurality of indoor units B1, B2, and B3 (when each indoor unit is not distinguished, they are collectively referred to as B). Each indoor unit B is connected in parallel to the outdoor unit A, and is installed in a separate room to perform air conditioning of each room. Although an example in which three indoor units are installed is shown here, the number of indoor units installed is not limited to three. The outdoor unit A and the plurality of indoor units B constitute a refrigeration cycle, which will be described later, and perform indoor air conditioning by circulating refrigerant in the refrigeration cycle.

  First, the configuration of the outdoor unit A will be described. The outdoor unit A includes a compressor 1, an oil separator 2, a four-way valve 3, an outdoor heat exchanger 4, and an accumulator 7. The outdoor unit A also includes an oil return circuit 8 that returns the oil separated by the oil separator 2 to the suction side of the compressor 1 through the on-off valve 8a and the capillary tube 8b. The outdoor unit A further includes an outdoor fan 9 that blows air to the outdoor heat exchanger 4.

  The compressor 1 is a compressor capable of changing the frequency, compresses the sucked gas refrigerant, discharges it as a high-temperature and high-pressure gas refrigerant, and circulates the refrigerant in the refrigeration cycle.

  The oil separator 2 is for separating oil from the refrigerant discharged from the compressor 1.

  The four-way valve 3 switches the refrigerant flow path in the refrigeration cycle. Switching of the flow path of the four-way valve 3 is performed based on a drive signal output from an outdoor control device 100 described later, and a flow path for sending refrigerant discharged from the compressor 1 to the outdoor heat exchanger 4 or indoor heat. It switches to the flow path sent to the exchanger 6. Switching between the cooling operation and the heating operation is possible by switching the four-way valve 3. The air conditioner only needs to be capable of at least one of cooling and heating. Therefore, the four-way valve 3 is not necessarily an essential configuration and can be omitted.

  The outdoor heat exchanger 4 performs heat exchange between the inflowing refrigerant and the outside air from the outdoor blower 9. In FIG. 1, the case where heat is exchanged with the outside air by the outdoor fan 9 is described. However, a plate type or a double pipe type that exchanges heat with the water pipe may be used.

  The accumulator 7 is installed on the suction side of the compressor 1, separates the refrigerant flowing into the accumulator 7 into gas refrigerant and liquid refrigerant, stores excess liquid refrigerant, and stores the gas refrigerant in the compressor 1. The function to send to.

Next, the configuration of the indoor unit B will be described. Each indoor unit B1, B2, B3 has the same configuration.
The indoor unit B has the expansion device 5 and the indoor heat exchanger 6, and these are connected in series by refrigerant piping. The indoor unit B1 further includes an indoor blower 11 that sends room air to the indoor heat exchanger 6.

  The expansion device 5 expands and depressurizes the inflowing refrigerant, and is composed of an electric expansion valve whose opening degree can be adjusted.

  The indoor heat exchanger 6 performs heat exchange between the refrigerant flowing in and the indoor air from the indoor blower 11.

  The outdoor unit A and each indoor unit B are connected by an extension pipe, and a compressor 1, an oil separator 2, a four-way valve 3, an outdoor heat exchanger 4, an expansion device 5, an indoor heat exchanger 6 and an accumulator 7 are sequentially connected. Thus, a refrigeration cycle is configured. Note that the configuration of the refrigeration cycle is not limited to that shown in the drawing, and may be a configuration including at least the compressor 1, the outdoor heat exchanger 4, the expansion device 5, and the indoor heat exchanger 6.

(Sensors and control device)
Next, sensors and control devices provided in the air conditioner will be described.
The outdoor unit A includes a suction pressure sensor 21 that detects the suction pressure of the compressor 1 and a discharge pressure sensor 22 that detects the discharge pressure of the compressor 1.

  The outdoor unit A includes an outdoor control device 100 that controls the operation of each unit constituting the outdoor unit A, and communicates with an indoor control device 110 (described later) provided in each indoor unit B as a communication means. The communication line 120 is connected so that sensor information and control information can be transmitted and received. The outdoor control device 100 is composed of a microcomputer and includes a CPU, a RAM, a ROM, and the like, and a control program is stored in the ROM.

  The outdoor control device 100 can acquire the detected pressure detected by the suction pressure sensor 21 and the discharge pressure sensor 22, and the capacity of the indoor heat exchanger 6 and the indoor temperature detected by the indoor temperature detection sensor 33 described later can be obtained. Various information including the set temperature can be acquired from the indoor control device 110 of each indoor unit B via the communication line 120. The outdoor control device 100 controls the frequency of the compressor 1, the switching of the four-way valve 3, the rotational speed control of the outdoor blower 9, the open / close control of the on-off valve 8 a, etc. based on these various information and a preinstalled control program. The whole outdoor unit A is controlled.

  The indoor unit B is provided on the liquid side of the indoor heat exchanger 6 to detect the temperature of the refrigerant, and the liquid side temperature sensor 31 is provided on the gas side of the indoor heat exchanger 6 to detect the temperature of the refrigerant. And a temperature sensor 32. Moreover, the indoor temperature detection sensor 33 which detects the temperature (room temperature) of the indoor air which flows into the indoor unit B is provided.

  In addition, the indoor unit B includes an indoor control device 110 that controls the operation of each part constituting the indoor unit B. The indoor control device 110 is composed of a microcomputer and includes a CPU, a RAM, a ROM, and the like. Further, the indoor unit B is connected to a remote controller 12 for individually operating the indoor unit B so that a user can input a set temperature or the like.

  In the indoor unit B, a model is set according to the cooling / heating capacity (corresponding to the capacity of the indoor heat exchanger 6) that can be exhibited by a switch provided on a control board (not shown). The indoor control device 110 of the indoor unit B can grasp the capacity of its own indoor heat exchanger 6 (hereinafter referred to as the capacity of the indoor unit) by setting a switch on its control board (not shown). .

  The indoor control device 110 can capture the operating state (whether it is in cooling operation or heating operation), the temperature detected by the various sensors 31 to 33, and the set temperature set from the remote controller 12. Therefore, the opening degree control of the expansion device 5 and the rotational speed control of the indoor blower 11 are performed based on these pieces of information. The indoor control device 110 can transmit and receive sensor information and control information to and from the outdoor control device 100 of the outdoor unit A. That is, the indoor control device 110 and the outdoor control device 100 constitute a control device that controls the entire air conditioner.

  In the above configuration example, the configuration in which the cooperation processing is performed by performing data communication between the outdoor control device 100 and the indoor control device 110 is shown, but all the functions of the indoor control device 110 are provided to the outdoor control device 100. It is good also as the structure given.

(Cooling operation)
Next, the cooling operation of the air conditioner will be described based on FIG. When carrying out the cooling operation, the control device switches the flow path of the four-way valve 3 in advance so that the refrigerant discharged from the compressor 1 flows to the outdoor heat exchanger 4 (solid line side in FIG. 1). The high-temperature and high-pressure refrigerant compressed by the compressor 1 is discharged from the compressor 1 and then flows into the outdoor heat exchanger 4 through the four-way valve 3. The refrigerant that has flowed into the outdoor heat exchanger 4 is condensed by exchanging heat with the outside air sent by the outdoor blower 9 and becomes high-pressure liquid refrigerant and flows out of the outdoor heat exchanger 4. The liquid refrigerant that has flowed out of the outdoor heat exchanger 4 branches and flows into the expansion device 5 of each indoor unit B. The liquid refrigerant flowing into the expansion device 5 is expanded and depressurized to become a low-pressure refrigerant, and flows into the indoor heat exchanger 6 respectively. The refrigerant that has flowed into the indoor heat exchanger 6 evaporates by exchanging heat with the indoor air sent by the indoor blower 11 and flows out of the indoor heat exchanger 6. The refrigerant flowing out from each indoor heat exchanger 6 joins and then returns to the compressor 1 via the four-way valve 3 and the accumulator 7. The room is cooled by repeating the above operation.

(Heating operation)
The heating operation of the air conditioner will be described based on FIG. When the heating operation is performed, the control device switches the flow path of the four-way valve 3 in advance so that the refrigerant discharged from the compressor 1 flows to the indoor heat exchanger 6 (dotted line side in FIG. 1). The high-temperature and high-pressure refrigerant compressed by the compressor 1 is discharged from the compressor 1, then passes through the four-way valve 3, and then branches and flows into each indoor heat exchanger 6. The refrigerant that has flowed into the indoor heat exchanger 6 is condensed by exchanging heat with the indoor air sent by the indoor blower 11 and becomes high-pressure liquid refrigerant and flows out of the indoor heat exchanger 6. The refrigerant that has flowed out of the indoor heat exchanger 6 flows into the expansion device 5 and is expanded and depressurized by the expansion device 5 to become a low-pressure refrigerant. The low-pressure refrigerant that has flowed out of each expansion device 5 joins and flows into the outdoor heat exchanger 4. The refrigerant flowing into the outdoor heat exchanger 4 evaporates by exchanging heat with the outdoor air sent by the outdoor blower 9 and flows out of the outdoor heat exchanger 4. The refrigerant that has flowed out of the outdoor heat exchanger 4 returns to the compressor 1 via the four-way valve 3 and the accumulator 7. The room is heated by repeating the above operation.

(Capacity control during cooling)
Next, capacity control during cooling will be described.
During cooling, the frequency of the compressor 1 is controlled so that the evaporation temperature becomes the target evaporation temperature. Specifically, if the evaporation temperature is lower than the target evaporation temperature, the frequency of the compressor 1 is decreased to lower the cooling capacity. If the evaporation temperature is higher than the target evaporation temperature, the frequency of the compressor 1 is increased. Increase cooling capacity. For example, as shown in FIG. 2 below, the target evaporation temperature is changed according to a temperature difference ΔT (a temperature difference between the set temperature and the room temperature).

FIG. 2 is an explanatory diagram of a method for determining the target evaporation temperature according to the temperature difference ΔT. In FIG. 2, the horizontal axis represents the temperature difference ΔT, and the vertical axis represents the target evaporation temperature. The graph shown in FIG. 2 shows the target evaporation temperature at which sufficient cooling capacity can be exhibited when the temperature difference ΔT.
As shown in FIG. 2, the target evaporation temperature is lowered as the temperature difference ΔT increases. When the temperature difference ΔT is equal to or higher than the predetermined temperature T0, the minimum target evaporation temperature is set. As the temperature difference ΔT for determining the target evaporation temperature, the largest temperature difference ΔT of each indoor unit B is used as a representative.

  That is, the temperature difference ΔT of each room during cooling is detected, and the target evaporation temperature is determined based on FIG. 2 based on the largest temperature difference ΔT among the temperature differences ΔT. Therefore, the evaporation temperature at which sufficient cooling capacity is exhibited in the indoor unit B that has detected the temperature difference ΔT is determined as the target evaporation temperature. The outdoor unit A controls the frequency of the compressor 1 so that the evaporation temperature obtained by converting the suction pressure detected by the suction pressure sensor 21 becomes the target evaporation temperature determined as described above. The rotational speed of the outdoor blower 9 is controlled.

FIG. 3 is a diagram illustrating a temperature change in the room when the frequency of the compressor is controlled.
As shown in FIG. 3, when the frequency of the compressor 1 is low, the room temperature increases, and when the frequency is high, the room temperature decreases.

  Further, each indoor unit B performs control to adjust its expansion device 5 so that the degree of superheat of the outlet refrigerant of its own indoor heat exchanger 6 becomes constant at the target degree of superheat.

(Compressor efficiency during cooling)
FIG. 4 is a graph showing compressor efficiency characteristics for each evaporation temperature, with the horizontal axis representing the compressor frequency and the vertical axis representing the compressor efficiency. The compressor efficiency characteristics are determined by structural elements such as the internal structure of the compressor 1 and the number of windings of the motor. In FIG. 4, (1) is the compressor efficiency characteristic at the evaporation temperature Ta, (2) is the compressor efficiency characteristic at the evaporation temperature To (> Ta), and (3) is at the evaporation temperature Tb (> To). Shows the compressor efficiency characteristics.

  First, based on FIG. 4, the change of the compressor efficiency accompanying the increase / decrease in a compressor frequency is demonstrated. When operating at the point O (compressor frequency fo, evaporation temperature To) in FIG. 4, if the compressor frequency is increased, the evaporation temperature decreases. That is, the point A changes to the lower right to become a point A. Conversely, when the compressor frequency is decreased, the evaporation temperature rises. That is, a transition is made from the point O to the upper left to become a point B.

  Next, the frequency range in which high compressor efficiency can be obtained will be described with reference to FIG. As shown in FIG. 4, when the evaporation temperature is lowered, the compressor efficiency is generally lowered. However, there is a frequency range in which a high compressor efficiency of a predetermined level ε1 or more can be obtained even when the evaporation temperature is lowered. In the example of the compressor efficiency characteristic (1) having the lowest evaporation temperature in FIG. 4, the compressor efficiency characteristic (1) is generally lower in compressor efficiency than the other (2) and (3). When the compressor frequency is in the range of f1 to f2, high compressor efficiency of a predetermined level ε1 or higher can be achieved.

  Therefore, if the current frequency of the compressor 1 at the time of cooling is fo lower than f1, for example, even if the evaporation temperature is lowered from To to Ta, the frequency is fa and within a frequency range where high compressor efficiency can be obtained. Therefore, high compressor efficiency can be expected. Therefore, although the operation efficiency is deteriorated by lowering the target evaporation temperature, among them, the reduction in the operation efficiency is reduced by increasing the compressor frequency within the frequency range f1 to f2 in which high compressor efficiency is obtained. Can be reduced. The frequency ranges f1 to f2 are stored in advance in the control device of the air conditioner.

(Switching control according to volume ratio α during cooling)
Next, switching control according to the volume ratio α, which is characteristic control of the present embodiment, will be described. The volume ratio α is calculated by the following formula.
Volume ratio α = total capacity of indoor heat exchanger 6 of each indoor unit in which differential temperature ΔT is equal to or higher than a predetermined temperature (for example, 1 ° C.) / Total capacity of indoor heat exchanger 6 of all indoor units in operation Then, although the relationship by volume ratio was described, indoor unit operation capacity may be sufficient.

  When the volume ratio α is equal to or higher than a predetermined ratio (for example, 30%), in other words, when there are many indoor units with insufficient capacity, the target evaporation temperature is set with priority given to setting the room temperature to the set temperature rather than the energy-saving operation. The control is maintained, that is, the operation is performed at the target evaporation temperature at which the capacity is obtained in the indoor unit having the largest temperature difference ΔT. On the other hand, when the volume ratio α is less than the predetermined ratio, in other words, when there are few indoor units with insufficient capacity, it is checked whether the compressor efficiency can be increased by increasing the compressor frequency (specifically, If the current compressor frequency is less than the lower frequency limit f1) and the compressor efficiency can be increased, the target evaporation temperature is lowered by a predetermined temperature (for example, 1 ° C.), and the upper limit of the compressor frequency is predetermined. Increase the frequency (for example, 10 Hz). With this control, as described above, the operation efficiency is deteriorated by lowering the target evaporation temperature, but among them, the compressor frequency is increased within the frequency range f1 to f2 in which high compressor efficiency is obtained. Thus, the reduction in efficiency can be reduced.

(Capacity control during heating)
Next, capacity control during heating will be described.
During heating, the frequency of the compressor 1 is controlled so that the condensation temperature becomes the target condensation temperature. Specifically, if the condensation temperature is lower than the target condensation temperature, the frequency of the compressor 1 is increased to increase the heating capacity. If the condensation temperature is higher than the target condensation temperature, the frequency of the compressor 1 is decreased to perform cooling. Decrease ability. The target condensing temperature is changed according to, for example, a temperature difference ΔT (a temperature difference between the set temperature and the room temperature) as shown in FIG.

FIG. 5 is an explanatory diagram of a method for determining the target condensing temperature according to the temperature difference ΔT. In FIG. 5, the horizontal axis represents the temperature difference ΔT, and the vertical axis represents the target condensation temperature. The graph shown in FIG. 5 shows the target condensation temperature at which sufficient heating capacity can be exhibited when the temperature difference ΔT.
As shown in FIG. 5, the target condensation temperature is raised as the temperature difference ΔT increases. When the temperature difference ΔT is equal to or higher than the predetermined temperature T0, the maximum target condensing temperature is set. As the temperature difference ΔT for determining the target condensing temperature, the largest temperature difference ΔT of each indoor unit B is used as a representative.

  That is, the temperature difference ΔT of each room being heated is detected, and the target condensing temperature is determined based on the largest temperature difference among the temperature differences ΔT. The outdoor unit A controls the frequency of the compressor 1 so that the condensation temperature obtained by converting the discharge pressure detected by the discharge pressure sensor 22 becomes the target condensation temperature determined as described above. The rotational speed of the outdoor blower 9 is controlled.

  Each indoor unit B performs control to adjust its expansion device 5 so that the degree of subcooling of the outlet refrigerant of its own indoor heat exchanger 6 becomes constant to the target degree of subcooling.

(Compressor efficiency during heating)
FIG. 6 is a diagram showing compressor efficiency characteristics for each condensation temperature, with the horizontal axis representing the compressor frequency and the vertical axis representing the compressor efficiency. The compressor efficiency characteristics are determined by structural elements such as the internal structure of the compressor 1 and the number of windings of the motor. In FIG. 6, (1) is the compressor efficiency characteristic at the condensation temperature Ta, (2) is the compressor efficiency characteristic at the condensation temperature To (<Ta), and (3) is at the condensation temperature Tb (<To). Shows the compressor efficiency characteristics.

  First, based on FIG. 6, the change of the compressor efficiency accompanying the increase / decrease in a compressor frequency is demonstrated. When operating at the point O (compressor frequency fo, condensing temperature To) in FIG. 6, if the compressor frequency is increased, the condensing temperature rises. That is, the point A changes to the lower right to become a point A. Conversely, when the compressor frequency is decreased, the condensation temperature decreases. That is, a transition is made from the point O to the upper left to become a point B.

  Next, the frequency range in which high compressor efficiency can be obtained will be described with reference to FIG. As shown in FIG. 6, when the condensation temperature is raised, the compressor efficiency generally decreases. However, even if the condensation temperature is raised, there is a compressor frequency range in which a high compressor efficiency higher than a predetermined level ε1 can be obtained. To do. In the example of the compressor efficiency characteristic (1) having the highest condensation temperature in FIG. 6, although the compressor efficiency characteristic (1) is generally lower in the compressor efficiency than the other (2) and (3), When the compressor frequency is in the range of f1 to f2, high compressor efficiency of a predetermined level ε1 or higher can be achieved.

  Therefore, if the current frequency of the compressor 1 at the time of heating is fo lower than f1, for example, even if the condensation temperature is increased from To to Ta, the frequency is fa and within a frequency range where high compressor efficiency can be obtained. Therefore, high compressor efficiency can be expected. Therefore, although the operation efficiency is deteriorated by lowering the target condensation temperature, among them, the reduction of the operation efficiency is lowered by increasing the compressor frequency within the frequency range f1 to f2 in which high compressor efficiency is obtained. The width can be reduced.

(Switching control according to volume ratio α during heating)
Next, switching control according to the volume ratio α, which is characteristic control of the present embodiment, will be described. The volume ratio α is calculated by the following formula.
Volume ratio α = total capacity of indoor heat exchanger 6 of each indoor unit in which differential temperature ΔT is equal to or higher than a predetermined temperature (for example, 1 ° C.) / Total capacity of indoor heat exchanger 6 of all indoor units in operation In the heating, for example, a system is selected such that the compressor frequency (here, 50 Hz) is maximized when the volume ratio α is 40%. Here, the relationship by the volume ratio is described, but the indoor unit operation capacity may be used.

  When the volume ratio α is greater than or equal to a predetermined ratio (for example, 30%), in other words, when there are many indoor units with insufficient capacity, the target condensing temperature is maintained with priority given to setting the room temperature to a set temperature rather than energy-saving control. In other words, the indoor unit with the largest temperature difference ΔT is operated at the target condensation temperature at which the capacity is obtained. On the other hand, when the volume ratio α is less than the predetermined ratio, in other words, when there are few indoor units with insufficient capacity, it is checked whether the compressor efficiency can be increased by increasing the compressor frequency (specifically, If the current compressor frequency is less than the lower frequency limit f1) and the compressor efficiency can be increased, the target condensation temperature is increased by a predetermined temperature (for example, 1 ° C.), and the upper limit of the compressor frequency is predetermined. Increase the frequency (for example, 10 Hz). With this control, as described above, raising the target condensation temperature degrades the operating efficiency, but among them, by raising the compressor frequency within the frequency range f1 to f2 where high compressor efficiency is obtained. Thus, the reduction in efficiency can be reduced.

(Control block diagram)
FIG. 7 is a block diagram showing a configuration of an air conditioner according to an embodiment of the present invention. Hereinafter, the flow of the control device and measurement data provided in the air conditioner will be described with reference to FIG. 7 and FIG. 1 described above.

  The outdoor control device 100 includes an evaporation temperature / condensation temperature conversion unit 101, a differential temperature / volume ratio calculation unit 102, a target evaporation temperature / target condensation temperature calculation unit 103, and a compressor frequency determination unit 104 by a CPU and a control program. Are functionally configured. As described above, the present embodiment is characterized in that the target evaporation temperature is changed in consideration of the temperature difference ΔT of each room and the capacity of each indoor unit B, and the compressor frequency is determined. This characteristic control is realized by each processing unit.

  The evaporation temperature / condensation temperature conversion unit 101 converts the suction pressure detected by the suction pressure sensor 21 into an evaporation temperature, converts the discharge pressure detected by the discharge pressure sensor 22 into a condensation temperature, and sets the evaporation temperature and the condensation temperature. It passes to the target evaporation temperature / target condensation temperature calculation unit 103 and the compressor frequency determination unit 104.

  The differential temperature / volume ratio calculation unit 102 calculates the differential temperature ΔT based on the indoor temperature and the set temperature from each indoor control device 110, and the volume based on the capacity of each indoor unit from each indoor control device 110. The ratio α is calculated, and the calculated differential temperature ΔT and the volume ratio α are passed to the target evaporation temperature / target condensation temperature calculation unit 103. Here, the example in which each of the indoor control devices 110 communicates the indoor temperature and the set temperature to the outdoor unit A has been described. However, each of the indoor control devices 110 calculates the differential temperature ΔT to calculate the outdoor temperature of the outdoor unit A. You may transmit to the control apparatus 100.

  The target evaporation temperature / target condensation temperature calculation unit 103 determines the compressor frequency by calculating the target evaporation temperature based on the evaporation temperature, the differential temperature ΔT and the volume ratio α from the evaporation temperature / condensation temperature conversion unit 101 during cooling. To the unit 104. The target evaporation temperature / target condensation temperature calculation unit 103 calculates the compressor frequency by calculating the target condensation temperature based on the condensation temperature, the differential temperature ΔT and the volume ratio α from the evaporation temperature / condensation temperature conversion unit 101 during heating. Processing to be passed to the unit 104 is performed.

  During cooling, the compressor frequency determining unit 104 determines the frequency of the compressor 1 based on the target evaporation temperature from the target evaporation temperature / target condensation temperature calculation unit 103 and the evaporation temperature from the evaporation temperature / condensation temperature conversion unit 101. To decide. At the time of heating, the frequency of the compressor 1 is determined based on the target condensation temperature from the target evaporation temperature / target condensation temperature calculation unit 103 and the condensation temperature from the evaporation temperature / condensation temperature conversion unit 101.

(Control flow)
FIG. 8 is a flowchart showing the control operation of the air conditioner according to the embodiment of the present invention. Next, the control operation of the air conditioner will be described with reference to FIG. Here, all the indoor units B are in cooling operation, and in all the indoor units B, the temperature difference ΔT is 1 ° C. or less. It is assumed that ΔT increases and the temperature difference ΔT in the indoor unit B1 changes to 2 ° C. In addition, each temperature difference ΔT in the indoor units B2 and B3 is 0.5 ° C., and the volume ratio α is 20%. Then, it is assumed that the stable operation state (compressor frequency, evaporation temperature) before the operation state changes is in a state indicated by a point O in FIG. In the flowchart of FIG. 8, specific numerical values are used for the temperature difference ΔT, the predetermined ratio, and the like. However, this is merely an example, and these may be set as appropriate according to actual use conditions. .

  The air conditioner has started a cooling operation (S1), and determines whether a transient temperature change at the start of the operation is in progress (S2). Specifically, the time change of the differential temperature ΔT in each indoor unit B is checked, and if there is an indoor unit B whose time difference of the differential temperature ΔT is 0.5 ° C. or more, a transient temperature change at the start of operation. Judge that it is inside. On the other hand, when the time change of the temperature difference ΔT is less than 0.5 ° C. in any indoor unit B, it is determined that the temperature is not changing transiently at the start of operation. In step S2, it is only necessary to check whether the temperature change due to the indoor load is occurring instead of the transient temperature change at the start of operation. Here, the time change of the differential temperature ΔT is monitored. It may be configured to monitor whether a predetermined time has elapsed since the start of the operation.

  In this case, since there is no transitional temperature change, the process proceeds to “No” in step S2. Subsequently, among the indoor units B, there is an indoor unit having a differential temperature ΔT larger than 1 ° C. (predetermined temperature). Is checked (S3). This temperature may be determined by the load on the room and the air conditioning capacity, and may be other than 1 ° C. as described above. Here, since the temperature difference ΔT of the indoor unit B1 is changed from 2 ° C. to 2 ° C., the process proceeds to “Yes” in step S3, and then the volume ratio α is 30% (predetermined ratio). It is judged whether it is less than (S4).

Here, a method for determining the predetermined ratio of the volume ratio α used in step S4 will be described.
FIG. 9 is a diagram showing the relationship between the volume ratio α and the compressor frequency upper limit, in which the horizontal axis represents the volume ratio α and the vertical axis represents the compressor frequency upper limit. FIG. 9 shows each of cooling and heating.
As described above, the relationship between the compressor efficiency and the compressor frequency is determined by structural elements such as the internal structure of the compressor 1 and the number of turns of the motor (see FIG. 4). The compressor frequency when the compressor efficiency is the best is 50 Hz in FIG. 4, and in the cooling side characteristics of FIG. 9, 30%, which is the volume ratio α when the compressor frequency is 50 Hz, is a predetermined ratio. To decide. The predetermined ratio is less than 50%.

Returning to the description of the flow of FIG.
In step S4, it is determined whether the volume ratio α is less than 30%. When the volume ratio α is 30% or more, in other words, when there are many indoor units having a large temperature difference ΔT, the target evaporation temperature is maintained (S10). That is, as described with reference to FIG. 2 above, the control is performed such that the evaporation temperature at which sufficient cooling capacity can be exhibited in the indoor unit B1 having the largest temperature difference ΔT is determined as the target evaporation temperature and maintained at the determined target evaporation temperature (target Maintenance control). Therefore, when there are many indoor units having a large temperature difference ΔT and “NO” is determined in step S4, the energy-saving operation is not performed, and the control is given priority to setting the room temperature to the set temperature.

  Here, since the volume ratio α is 20%, the process proceeds to “Yes” in step S4, and then the lower limit value of the frequency range f1 to f2 (see FIG. 2) in which the current compressor frequency becomes high compressor efficiency. It is determined whether it is less than f1 (S5).

  Here, the operating state is a state indicated by a point O in FIG. 4, and the compressor frequency is smaller than the lower limit value f1 of the frequency range in which high compressor efficiency is achieved at fo. The temperature is lowered by 1 ° C. and the upper frequency limit is raised by 10 Hz (S6).

  In this step S6, the frequency upper limit after raising the frequency upper limit by 10 Hz is assumed to be less than 50 Hz. And control which raises a compressor frequency within the range of a frequency upper limit is performed so that it may become the target evaporation temperature determined by step S6 (S7). As described above, when “Yes” is determined in both the steps S4 and S5, the control in steps S6 and S7 is performed instead of the control in S10.

  Then, by performing control to increase the compressor frequency, the differential temperature ΔT of the indoor unit B1 (the indoor unit having the largest differential temperature ΔT) is lowered to 0.5 ° C. or less (S8), and the indoor temperature approaches the set temperature. Then, the target evaporation temperature is raised by 1 ° C., and the upper limit of the compressor frequency is restored (S9). Then, the target evaporation temperature is maintained, the process returns to step S1, and the same process is repeated.

  Here, the energy-saving effect by this control is demonstrated. According to the flow shown in FIG. 8, when the volume ratio α is less than 30% and the compressor frequency is less than f1, the control of S6 and S7 is performed. In this case, since the operation at a higher evaporation temperature can be performed as compared with the case of performing the control of S10, an energy saving effect can be obtained.

  As described above, according to this embodiment, when the capacity ratio α is less than the predetermined ratio and the compressor frequency is less than the lower limit value of the frequency range where high compressor efficiency can be obtained, energy-saving operation can be effectively performed. Since it is determined that the operation is in progress and the target evaporation temperature is lowered and the compressor frequency is raised, efficient operation is possible and energy-saving operation can be realized.

  Further, energy saving operation can be realized as a total by raising and lowering the target evaporation temperature.

  Although FIG. 8 shows the case of the cooling operation, in the case of the heating operation, the target condensation temperature is set to, for example, + 1 ° C. in step S6, the target evaporation temperature is set to, for example, −1 ° C. in step S9, and in step S10 The target condensing temperature may be maintained. Other steps are the same as in the cooling operation.

  In the description of the flow of FIG. 8, the case where there is one indoor unit B having a large temperature difference ΔT is described as an example, but the same applies to the case where there are a plurality of indoor units B having a large temperature difference ΔT.

  Further, in the flow of FIG. 8, the control is performed to change the target evaporation temperature and the upper limit value of the compressor frequency in step S6 and step S9, but the control may be performed to change the compressor frequency.

  Further, in the flow of FIG. 8, the temperature difference ΔT of the indoor unit B is determined in step S8. However, since there is a correlation between the difference temperature ΔT becoming smaller and the volume ratio becoming smaller, there is a difference. Instead of determining the temperature ΔT, it may be determined by a capacity ratio.

  DESCRIPTION OF SYMBOLS 1 Compressor, 2 Oil separator, 3 Four way valve, 4 Outdoor heat exchanger, 5 Throttling device, 6 Indoor heat exchanger, 7 Accumulator, 8 Oil return circuit, 8a On-off valve, 8b Capillary tube, 9 Outdoor blower, 11 Indoor fan, 12 Remote control, 21 Suction pressure sensor, 22 Discharge pressure sensor, 31 Liquid side temperature sensor, 32 Gas side temperature sensor, 33 Indoor temperature detection sensor, 100 Outdoor control device, 101 Evaporation temperature / condensation temperature conversion unit, 102 Difference Temperature / volume ratio calculation unit, 103 target evaporation temperature / target condensation temperature calculation unit, 104 compressor frequency determination unit, 110 indoor control device, 120 communication line, A outdoor unit, B (B1, B2, B3) indoor unit.

Claims (1)

An outdoor unit having a compressor and an outdoor heat exchanger;
A plurality of indoor units having an expansion device and an indoor heat exchanger and capable of operating at least one of cooling and heating;
During cooling, the target evaporation temperature is determined based on the temperature difference between the set temperature of each room where the indoor unit is installed and the room temperature detected by the indoor unit, and during heating, based on the temperature difference. A controller for determining a target condensation temperature and performing a target maintenance control for controlling a frequency of the compressor so as to maintain the determined target evaporation temperature or the target condensation temperature;
The controller is
A volume ratio obtained by dividing the total capacity of the indoor units in which the differential temperature is equal to or higher than a preset predetermined temperature by the total capacity of all the indoor units in operation is calculated, and the volume ratio is less than the predetermined ratio and the compressor If the frequency is less than the lower limit of the frequency range where high compressor efficiency above a predetermined level can be obtained,
Instead of the target maintenance control during cooling, the target evaporation temperature is lowered and the upper limit value of the compressor frequency is increased.
An air conditioner that performs control to raise the target condensation temperature and raise the upper limit of the frequency of the compressor instead of the target maintenance control during the heating.

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