JPH11173628A - Air conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a liquid refrigerant from being retained in an indoor unit and rapid change of diffusing temperature. SOLUTION: This air conditioner is equipped with an outdoor unit A which has a compressor 1, an outdoor heat exchanger 3 being a heat exchanger on heat source side, and an outdoor electric motor operated expansion valve 4 being a pressure reducing valve on heat source side, a plurality of indoor units B, C, and D which have indoor heat exchangers 7 being heat exchangers on utilization side and indoor electric motor operated expansion valves 6 being flow control valves, a refrigerant pipe 10 which connects the plural indoor units B, C, and D in parallel to the outdoor unit A, a gas pipe temperature detection means Th2 which detects the indoor gas pipe temperature of the indoor heat exchanger 7, a suction air temperature detection means Th1 which detects the indoor suction air temperature of the indoor heat exchanger 7, and an aperture control means 52A which controls the aperture of the said indoor electric motor operated expansion valve 6 so that the difference between the temperatures detected in thermostat off condition by the gas pipe temperature detection means Th2 and the suction air temperature detection means Th1 may come to a specified value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-type air conditioner in which a plurality of indoor units are connected in parallel to an outdoor unit, and more particularly to an operation control thereof.

[0002]

2. Description of the Related Art Conventionally, a plurality of outdoor units having a use side heat exchanger and a flow control valve are connected in parallel to an outdoor unit having a compressor, a heat source side heat exchanger and a heat source side pressure reducing valve. A multi-type air conditioner in which the opening of a flow control valve is adjusted according to the air conditioning load in each room is well known.

Japanese Patent No. 2522065 proposes an air conditioner in which a means for returning a refrigerant to a main refrigerant pipe when liquid refrigerant stays in a use side heat exchanger in an indoor unit in a thermo-off state is proposed. I have. FIG. 8 shows a refrigerant piping system diagram used in the method. This air conditioner has 1
For three outdoor units A, three indoor units B to
D is a multi-type air conditioner connected in parallel.

In FIG. 8, an outdoor unit A includes a compressor 1, a four-way switching valve 2 for switching as shown by a solid line in a cooling operation, and a dashed line in a heating operation, and as a condenser in a cooling operation. An outdoor heat exchanger 3 that is a heat source side heat exchanger that functions as an evaporator during heating; and an outdoor electric expansion valve 4 as a pressure reducing valve that adjusts a refrigerant flow rate during a cooling operation and reduces a refrigerant pressure during a heating operation. A receiver 5 for storing the liquid refrigerant, and an accumulator 8 for separating the liquid refrigerant in the suction refrigerant.

On the other hand, each of the indoor units B to D has the same structure. The indoor electric expansion valve as a flow control valve having a function of reducing the pressure of the refrigerant during the cooling operation and adjusting the flow rate of the refrigerant during the heating operation. 6, an indoor heat exchanger 7 serving as a use-side heat exchanger functioning as an evaporator during cooling operation and as a condenser during heating, and an indoor fan 7a attached to the indoor heat exchanger 7. .

[0006] The compressor 1, the outdoor heat exchanger 3, the outdoor electric expansion valve 4, the receiver 5, and the accumulator 8 of the outdoor unit A are connected by a main refrigerant pipe 9a of a refrigerant pipe 9 so that refrigerant can flow therethrough. The indoor electric expansion valves 6 and the indoor heat exchangers 7 of the indoor units B to D are connected to each other through a branch pipe 9b of the refrigerant pipe 9 so that the refrigerant can flow therethrough.
are connected in parallel to the main refrigerant pipe 9a. As described above, the refrigerant circuit 10 is configured such that heat (or cold heat) obtained by heat exchange with outdoor air is transferred to the indoor air by heat transfer. Note that reference numeral 11 in the figure denotes a shut-off valve interposed in the main refrigerant pipe 9a of the outdoor unit A, 1
Reference numeral 2 denotes a closing valve provided in the branch pipe 9b in each of the indoor units BD.

[0008] The air conditioner shown in FIG.
The high-pressure gas refrigerant discharged from the compressor 1 passes through the four-way switching valve 2, the main refrigerant pipe 9 a, the closing valve 11, and passes through each branch pipe 9.
b, flows into each indoor unit BD through each closing valve 12. The flow rate of the inflowing gas refrigerant is adjusted by the indoor electric expansion valve 6 and condensed by each indoor heat exchanger 7 to become a liquid refrigerant.
After passing through the closing valve 12, each branch pipe 9 b, merging with the main refrigerant pipe 9 a, passing through the receiver 5, the pressure is reduced by the outdoor electric expansion valve 4. The low-pressure refrigerant evaporates in the outdoor heat exchanger 3, passes through the four-way switching valve 2, and flows into the accumulator 8. The non-evaporated refrigerant is separated by the accumulator 8, and the gas refrigerant is sucked into the compressor 1.

According to the conventional air conditioner described above, in the heating operation, the following control is performed in order to prevent the refrigerant from accumulating in the indoor units B to D that have been thermo-off and the amount of refrigerant circulating in the refrigerant circuit being insufficient. Is going. That is,
The opening degree of the indoor electric expansion valve 6 is fixed to a predetermined low opening degree, and the indoor suction air temperature T1 detected by the suction air detection means Th1.
And the indoor liquid pipe temperature T detected by the liquid pipe temperature detecting means Th4.
When the temperature deviation (T4−T1) of No. 4 becomes equal to or less than a predetermined value,
It is determined that the liquid refrigerant is excessively accumulated in the outdoor unit, and the indoor electric expansion valve 6 is set to a predetermined opening degree or more (fully open) to collect the liquid refrigerant accumulated in the indoor unit. In addition,
The air volume of the indoor fan 7a at the time of the thermo-off is set to a slight wind so that the heating capacity is not excessive.

[0009]

It has been found that the air conditioner which performs the above control has the following problems.
That is, since the opening degree of the indoor electric expansion valve 6 at the time of heating thermo-off is fixed to a low opening degree, the liquid refrigerant gradually accumulates in the indoor unit. This gradually lowers the temperature of the air blown into the room. However, when the liquid refrigerant is recovered by fully opening the electric expansion valve 6, the blow-out temperature increases significantly. When the outlet temperature fluctuates rapidly,
The feeling of heating gets worse.

[0010] Therefore, an object of the present invention is to provide an air conditioner that can prevent liquid refrigerant from accumulating in an indoor unit and prevent a sudden change in the outlet temperature.

[0011]

The air conditioner of the present invention comprises an outdoor unit having a compressor, a heat source side heat exchanger and a heat source side pressure reducing valve, and a plurality of indoor units having a use side heat exchanger and a flow control valve. Unit, a refrigerant pipe for connecting a plurality of indoor units in parallel to the outdoor unit, gas pipe temperature detecting means for detecting the temperature of the indoor gas pipe of the use side heat exchanger, and suction air of the use side heat exchanger A suction air temperature detecting means for detecting a temperature, and an opening for controlling an opening degree of the flow control valve such that a difference between the temperatures respectively detected by the gas pipe temperature detecting means and the suction air temperature detecting means in the thermo-off state becomes a predetermined value. The problem has been solved by adopting a means including a degree control means.

According to the present invention, the temperature difference (T) between the gas pipe temperature T2 detected by the gas pipe temperature detecting means and the suction air temperature T1 detected by the suction air temperature detecting means is determined.
If (2-T1) is smaller than the predetermined value x, the temperature difference (T2-
The flow control valve is opened by a predetermined amount by the opening control means so that T1) matches the predetermined value x. Conversely, the temperature difference (T2-T
1) is larger than the predetermined value x, the temperature difference (T2-T
The flow control valve is closed by a predetermined amount by the opening control means so that 1) coincides with the predetermined value x.

As described above, according to the present invention, the temperature difference between the gas pipe temperature T2 and the suction air temperature T1 (T2
−T1) is controlled to be maintained at the predetermined value x, so that the amount of liquid refrigerant in the use-side heat exchanger can be kept constant, and the rapid movement of liquid refrigerant as in the related art is required. There is no sudden change in the outlet temperature, that is, the heating capacity. Further, in the present invention, if the predetermined value x is set to a small value, the opening degree of the flow control valve is reduced, and the refrigerant flow rate is reduced, so that the heating capacity is reduced. As a result, it is possible to prevent overheating during thermo-off. it can.

Further, in the air conditioner of the present invention, a compressor,
An outdoor unit having a heat source side heat exchanger and a heat source side pressure reducing valve, a plurality of indoor units having a use side heat exchanger and a flow control valve, and a refrigerant pipe for connecting the plurality of indoor units to the outdoor unit in parallel An outlet air temperature detecting means for detecting an outlet air temperature of the use side heat exchanger; an intake air temperature detecting means for detecting an inlet air temperature of the use side heat exchanger; and an outlet air temperature detecting means and a suction in a thermo-off state. The object is also solved by adopting means including an opening control means for controlling the opening of the flow control valve so that the difference between the temperatures detected by the air temperature detecting means becomes a predetermined value.

According to the present invention, the temperature difference (T3-T1) between the indoor air temperature T3 detected by the air temperature detecting means and the indoor air temperature T1 detected by the air temperature detecting means is obtained. If it is less than the predetermined value x, the opening degree control means opens the flow control valve by a predetermined amount so that the temperature difference (T3-T1) approaches the predetermined value x. Conversely, if the temperature difference (T3-T1) is larger than the predetermined value x, the opening control means closes the flow control valve by a predetermined amount so that the temperature difference (T3-T1) approaches the predetermined value x.

As described above, the temperature difference (T3-T1) between the indoor air temperature T3 and the suction air temperature T1 when the thermostat is turned off.
Is controlled so as to maintain the predetermined value x, the liquid refrigerant amount in the use side heat exchanger can be kept constant, and the liquid refrigerant does not suddenly move unlike the related art. There is no sudden change in the blowout temperature, that is, the heating capacity. Further, in the present invention, if the predetermined value x is set to a small value, the opening degree of the flow control valve is reduced, and the refrigerant flow rate is reduced, so that the heating capacity is reduced. As a result, it is possible to prevent overheating during thermo-off. it can.

Further, in the air conditioner of the present invention, an outdoor unit having a compressor, a heat source side heat exchanger and a heat source side pressure reducing valve, a plurality of indoor units having a use side heat exchanger and a flow control valve, and an outdoor unit A refrigerant pipe for connecting a plurality of indoor units in parallel to each other, a liquid pipe temperature detecting means for detecting a temperature of an indoor liquid pipe of the use side heat exchanger, and a suction for detecting a suction air temperature of the use side heat exchanger Air temperature detection means, and opening degree control means for controlling the opening degree of the flow control valve so that the difference between the temperatures respectively detected by the liquid pipe temperature detection means and the suction air temperature detection means in the thermo-off state becomes a predetermined value. The above problem has also been solved by adopting such means.

According to the present invention described above, the temperature difference (T4-T1) between the indoor liquid pipe temperature T4 detected by the liquid pipe temperature detecting means and the indoor suction air temperature T1 detected by the suction air temperature detecting means is obtained. If less than the predetermined value x, the temperature difference (T
The flow control valve is opened by a predetermined amount by the opening control means so that 4-T1) approaches the predetermined value x. Conversely, the temperature difference (T4-
If T1) is larger than the predetermined value x, the temperature difference (T4−T
The flow control valve is closed by a predetermined amount by the opening control means so that 1) approaches the predetermined value x.

As described above, in order to control the temperature difference (T4-T1) between the indoor liquid pipe temperature T4 and the suction air temperature T1 at the time of the thermo-off to the predetermined value x, the liquid refrigerant in the use side heat exchanger is controlled. Since the amount can be kept constant and there is no abrupt movement of the liquid refrigerant as in the prior art, there is no abrupt change in the blowing temperature, that is, the heating capacity. Further, in the present invention, if the predetermined value x is set to a small value, the opening degree of the flow control valve is reduced, and the refrigerant flow rate is reduced, so that the heating capacity is reduced. As a result, it is possible to prevent overheating during thermo-off. it can.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An air conditioner of the present invention will be described below based on an embodiment. (First Embodiment) FIG. 1 is a block diagram showing a basic configuration of an air conditioner according to a first embodiment of the present invention.

As shown in FIG. 1, the outdoor unit A is basically composed of a compressor 1, an outdoor heat exchanger 3 which is a heat source side heat exchanger, and a heat source side pressure reducing valve 4. In contrast, the indoor heat exchanger 7, which is a use side heat exchanger,
An indoor unit B having an indoor fan 7a attached to the indoor heat exchanger 7 and an indoor electric expansion valve 6 as a flow control valve
To D are connected in parallel. The connection is made by the main refrigerant pipe 9a in the outdoor unit A and by the indoor units B to
D is connected to each branch pipe 9b, and each branch pipe 9b is connected in parallel to the main refrigerant pipe 9a to form the refrigerant circuit 10.

The above air conditioner is provided with gas pipe temperature detecting means Th2 for detecting the temperature of the indoor gas pipe of the indoor heat exchanger 7.
The difference (T2) between the temperature information T2 and T1 from the suction air temperature detection means Th1 for detecting the suction air temperature of the indoor heat exchanger 7 and the gas pipe temperature detection means Th2 and the suction air temperature detection means Th1 during the heating operation. −T1), and when (T2−T1) is less than the predetermined value x, the indoor electric expansion valves 6 of the indoor units B to D are set so that the temperature difference (T2−T1) matches the predetermined value x. When the temperature difference (T2−T1) is larger than a predetermined value x, the indoor electric expansion valve 6 is closed by a predetermined amount so that the temperature difference (T2−T1) matches the predetermined value x. An operation control device including the means 52A is provided.

FIG. 2 is a refrigerant piping system diagram more concretely showing the air conditioner having the block diagram shown in FIG. 1, and the same parts as those in FIG. 1 are denoted by the same reference numerals. The outdoor unit A includes a compressor 1, a four-way switching valve 2 that switches as shown by the solid line in the drawing during the cooling operation, and a dotted line during the heating operation, and an outdoor heat exchanger 3 that is a heat source side heat exchanger. It comprises an outdoor electric expansion valve 4 as a pressure reducing valve, a receiver 5 for storing liquid refrigerant, and an accumulator 8 for separating liquid refrigerant in the suction refrigerant.

The compressor 1, the outdoor heat exchanger 3, the outdoor electric expansion valve 4, the receiver 5, and the accumulator 8 of the outdoor unit A are connected by a main refrigerant pipe 9a of a refrigerant pipe 9 so that refrigerant can flow therethrough. The indoor electric expansion valves 6 and the indoor heat exchangers 7 of the indoor units B to D are connected to each other through a branch pipe 9b of the refrigerant pipe 9 so that the refrigerant can flow therethrough.
are connected in parallel to the main refrigerant pipe 9a. As described above, the refrigerant circuit 10 is configured such that heat (or cold heat) obtained by heat exchange with outdoor air is transferred to the indoor air by heat transfer. Note that reference numeral 11 in the figure denotes a shut-off valve interposed in the main refrigerant pipe 9a of the outdoor unit A, 1
Reference numeral 2 denotes a closing valve provided in the branch pipe 9b in each of the indoor units BD.

Each of the indoor units B to D has a gas pipe temperature detecting means Th for detecting the temperature of the indoor gas pipe of the indoor heat exchanger 7.
2, suction air temperature detection means Th1 for detecting the suction air temperature of the indoor heat exchanger 7, and each gas pipe temperature detection means Th2 and each suction air temperature detection means Th1 are provided to the above-mentioned opening degree control means 52A. It is connected.

When a heating operation is performed by the above-described air conditioner, the refrigerant is discharged from the compressor 1, passes through the main refrigerant pipe 9a, branches off at each branch pipe 9b, and branches to each of the indoor units BD. Flow in. After being condensed in each indoor exchanger 7 and returned to the main refrigerant pipe 9a and decompressed by the outdoor electric expansion valve 4, it is evaporated in the outdoor heat exchanger 3 and sucked into the compressor 1.

In order to cope with the heating load in each room in which the indoor units B to D are installed, the heating load is set by the set temperature in each room and the suction air temperature T by the suction air temperature detecting means Th1.
1 is grasped, and if this difference is large, the heating load is large, so the opening degree of the indoor electric expansion valve 6 is large. Conversely, if this difference is small, the heating load is small, so the indoor electric expansion valve is small. 6 is controlled so as to reduce the opening degree, and the capacity of each of the indoor heat exchangers 7,... Is adjusted.

When the difference between the set temperature and the intake air temperature T1 is extremely small, the thermo-off state is set. In the indoor unit (for example, C) in the thermo-off state, the difference between T2 and T1 by the opening control means 52A based on the suction air temperature T1 by the suction air temperature detection means Th1 and the gas pipe temperature T2 by the gas pipe temperature detection means Th2. (T2-T1)
When (T2−T1) is less than the predetermined value x, the indoor electric expansion valve 6 of the indoor unit C is opened by a predetermined amount so that the temperature difference (T2−T1) matches the predetermined value x.
Conversely, when the temperature difference (T2-T1) is larger than the predetermined value x, the indoor electric expansion valve 6 is closed by a predetermined amount so that the temperature difference (T2-T1) matches the predetermined value x.

The above control will be described in the order of steps S1 to S7 in the flowchart shown in FIG. In step S1, it is determined whether or not the indoor unit is in a thermo-off state. If it is in the thermo-off state, the process proceeds to step S3. If it is not in the thermo-off state, the process proceeds to step S2. In step S2, the indoor electric expansion valve 6 is set to the full opening. In step S3, T
It is determined whether or not 2-T1 matches the predetermined value x. If they match, the process proceeds to step S4, and if they do not match, the process proceeds to step S5.

In step S4, control is performed to maintain the opening of the indoor electric expansion valve 6. In step S5, T2-T
It is determined whether or not 1 is less than a predetermined value x. If it is less than x, the process proceeds to step S6, and if it is more than the predetermined value x, the process proceeds to step S7. In step S6, the opening degree of the indoor electric expansion valve 6 is controlled to be opened by a predetermined amount so that T2-T1 matches the predetermined value x. In step S7, the opening degree of the indoor electric expansion valve 6 is controlled to be closed by a predetermined amount so that T2-T1 matches the predetermined value x.

Therefore, the amount of the liquid refrigerant in the indoor heat exchanger 7 of the indoor unit C can be kept constant, and there is no sudden change in the heating capacity. If the predetermined value x is set to a small value, the opening degree of the flow control valve becomes small, and the flow rate of the refrigerant becomes small. As a result, the heating capacity is reduced. As a result, it is possible to prevent excessive heating during thermo-off.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention.
It is a block diagram showing the basic composition of the air conditioner concerning an embodiment.

As shown in FIG. 4, the outdoor unit A basically comprises a compressor 1, an outdoor heat exchanger 3 as a heat source side heat exchanger, and an outdoor electric expansion valve 4 as a heat source side pressure reducing valve. And the indoor unit A,
An indoor fan 7a attached to the indoor heat exchanger 7 and indoor units BD having a flow control valve 6 are connected in parallel. The connection is made with the main refrigerant pipe 9 in the outdoor unit A.
a, the indoor units B to D are connected by the respective branch pipes 9b, and the respective branch pipes 9b are connected in parallel to the main refrigerant pipe 9a to form the refrigerant circuit 10.

This air conditioner is provided with a blown air temperature detecting means Th3 for detecting the temperature of the indoor blown air of the indoor heat exchanger 7.
And a difference (T3) between the temperature information T3 and T1 from the suction air temperature detecting means Th1 for detecting the suction air temperature of the indoor heat exchanger 7 and the blow-out air temperature detecting means Th3 and the suction air temperature detecting means Th1 during the heating operation. -T1), and when (T3-T1) is less than the predetermined value x, the indoor electric expansion valves 6 of the indoor units B to D are set so that the temperature difference (T3-T1) matches the predetermined value x. When the temperature difference (T3-T1) is larger than the predetermined value x, the indoor electric expansion valve 6 is closed by a predetermined amount so that the temperature difference (T3-T1) becomes equal to the predetermined value x. An operation control device including the means 52A is provided.

FIG. 5 is a refrigerant piping system diagram more concretely showing the air conditioner having the block diagram shown in FIG. 4, and the same parts as those in FIG. 4 are denoted by the same reference numerals. The outdoor unit A includes a compressor 1, a four-way switching valve 2 that switches as shown by the solid line in the drawing during the cooling operation, and a dotted line during the heating operation, and an outdoor heat exchanger 3 that is a heat source side heat exchanger. It comprises an outdoor electric expansion valve 4 as a pressure reducing valve, a receiver 5 for storing liquid refrigerant, and an accumulator 8 for separating liquid refrigerant in the suction refrigerant.

The compressor 1, the outdoor heat exchanger 3, the outdoor electric expansion valve 4, the receiver 5, and the accumulator 8 of the outdoor unit A are connected by a main refrigerant pipe 9a of a refrigerant pipe 9 so that refrigerant can flow therethrough. The indoor electric expansion valves 6 and the indoor heat exchangers 7 of the indoor units B to D are connected to each other through a branch pipe 9b of the refrigerant pipe 9 so that the refrigerant can flow therethrough.
are connected in parallel to the main refrigerant pipe 9a. As described above, the refrigerant circuit 10 is configured such that heat (or cold heat) obtained by heat exchange with outdoor air is transferred to the indoor air by heat transfer. Note that reference numeral 11 in the figure denotes a shut-off valve interposed in the main refrigerant pipe 9a of the outdoor unit A, 1
Reference numeral 2 denotes a closing valve provided in the branch pipe 9b in each of the indoor units BD.

Each of the indoor units B to D has an outlet air temperature detecting means Th3 for detecting the indoor air temperature of the indoor heat exchanger 7, and an inlet air temperature detecting means for detecting the indoor air temperature of the indoor heat exchanger 7. Means Th1 is provided, and each gas outlet air temperature detecting means Th3 and each suction air temperature detecting means Th are provided.
1 is connected to the opening control means 52B described above.

When a heating operation is performed by the above-described air conditioner, the refrigerant is discharged from the compressor 1, passes through the main refrigerant pipe 9a, branches off at each branch pipe 9b, and is branched to each of the indoor units BD. Flow in. After being condensed in each indoor exchanger 7 and returned to the main refrigerant pipe 9a and decompressed by the outdoor electric expansion valve 4, it is evaporated in the outdoor heat exchanger 3 and sucked into the compressor 1.

In order to cope with the heating load in each room in which the indoor units B to D are installed, the difference between the set temperature in each room and the room suction air temperature T1 by the suction air temperature detecting means Th1 is grasped. If this difference is large, the heating load is large, so the opening degree of the indoor electric expansion valve 6 is increased,
Conversely, if this difference is small, the heating load is small, so the opening degree of the indoor electric expansion valve 6 is controlled to be small, and the capacity of each indoor heat exchanger 7,... Is adjusted.

When the difference between the set temperature and the suction air temperature T1 is extremely small, the thermo-off state is set. In the indoor unit (for example, C) in the thermo-off state, the opening degree control means 52B uses T3 and T1 based on the indoor suction air temperature T1 by the suction air temperature detection means Th1 and the indoor discharge air temperature T3 by the gas pipe temperature detection means Th3. Difference (T3-
T1) is obtained, and when (T3-T1) is smaller than the predetermined value x, the indoor electric expansion valve 6 of the indoor unit C is opened by a predetermined amount so that the temperature difference (T3-T1) matches the predetermined value x. Conversely, when the temperature difference (T3-T1) is larger than the predetermined value x, the indoor electric expansion valve 6 is closed by a predetermined amount so that the temperature difference (T3-T1) matches the predetermined value x.

The above control will be described in the order of steps S1 to S7 in the flowchart shown in FIG. In step S1, it is determined whether or not the indoor unit is in a thermo-off state. If it is in the thermo-off state, the process proceeds to step S3. If it is not in the thermo-off state, the process proceeds to step S2. In step S2, the indoor electric expansion valve 6 is set to the full opening. In step S3, T
It is determined whether 3-T1 matches the predetermined value x, and if they match, the process proceeds to step S4, and if they do not match, the process proceeds to step S5.

In step S4, control is performed to maintain the opening of the indoor electric expansion valve 6. In step S5, T3-T
It is determined whether or not 1 is less than a predetermined value x. If it is less than x, the process proceeds to step S6, and if it is more than the predetermined value x, the process proceeds to step S7. In step S6, the opening degree of the indoor electric expansion valve 6 is controlled to be opened by a predetermined amount so that T3-T1 matches the predetermined value x. In step S7, the opening degree of the indoor electric expansion valve 6 is controlled to be closed by a predetermined amount so that T3-T1 matches the predetermined value x.

Therefore, the amount of liquid refrigerant in the indoor heat exchanger 7 of the indoor unit C can be kept constant, and there is no sudden change in the heating capacity. If the predetermined value x is set to a small value, the opening degree of the flow control valve becomes small, and the flow rate of the refrigerant becomes small. As a result, the heating capacity is reduced. As a result, it is possible to prevent excessive heating during thermo-off.

(Third Embodiment) FIG. 7 shows a third embodiment of the present invention.
It is a block diagram which shows the basic structure of the air conditioner concerning embodiment of this invention.

As shown in FIG. 7, the outdoor unit A basically includes a compressor 1, an outdoor heat exchanger 3 as a heat source side heat exchanger, and an outdoor electric expansion valve 4 as a heat source side pressure reducing valve. The outdoor unit A is provided with an indoor heat exchanger 7 as a use side heat exchanger, an indoor fan 7a attached to the indoor heat exchanger 7, and an indoor electric expansion valve 6 as a flow control valve. The indoor units BD are connected in parallel. The connection is made by the main refrigerant pipe 9a in the outdoor unit A.
Further, the indoor units B to D are respectively connected by the branch pipes 9b,
Each branch pipe 9b is connected in parallel to the main refrigerant pipe 9a to form a refrigerant circuit 10.

The air conditioner described above has a liquid pipe temperature detecting means Th4 for detecting the indoor liquid pipe temperature of the indoor heat exchanger 7, and a suction air temperature detecting means Th1 for detecting the suction air temperature of the indoor heat exchanger 7. The liquid pipe temperature detecting means Th4 during the heating operation.
And temperature information T4 from the suction air temperature detecting means Th1.
And T1 (T4−T1), and (T4
-T1) is less than the predetermined value x, the temperature difference (T4-T
The indoor electric expansion valves 6 of the indoor units B to D are opened by a predetermined amount so that 1) matches the predetermined value x, and conversely, the temperature difference (T4−T
1) is larger than the predetermined value x, the temperature difference (T4-T
The operation control device includes an opening control means 52C for closing the indoor electric expansion valve 6 by a predetermined amount so that 1) matches the predetermined value x.

FIG. 8 is a refrigerant piping system diagram more concretely showing the air conditioner having the block diagram shown in FIG. 7, and the same parts as those in FIG. 7 are denoted by the same reference numerals. The outdoor unit A includes a compressor 1, a four-way switching valve 2 that switches as shown by the solid line in the drawing during the cooling operation, and a dotted line during the heating operation, and an outdoor heat exchanger 3 that is a heat source side heat exchanger. It comprises an outdoor electric expansion valve 4 as a pressure reducing valve, a receiver 5 for storing liquid refrigerant, and an accumulator 8 for separating liquid refrigerant in the suction refrigerant.

The compressor 1, the outdoor heat exchanger 3, the outdoor electric expansion valve 4, the receiver 5, and the accumulator 8 of the outdoor unit A are connected by a main refrigerant pipe 9a of the refrigerant pipe 9 so that the refrigerant can flow therethrough. The indoor electric expansion valves 6 and the indoor heat exchangers 7 of the indoor units B to D are connected to each other through a branch pipe 9b of the refrigerant pipe 9 so that the refrigerant can flow therethrough.
are connected in parallel to the main refrigerant pipe 9a. As described above, the refrigerant circuit 10 is configured such that heat (or cold heat) obtained by heat exchange with outdoor air is transferred to the indoor air by heat transfer. Note that reference numeral 11 in the figure denotes a shut-off valve interposed in the main refrigerant pipe 9a of the outdoor unit A, 1
Reference numeral 2 denotes a closing valve provided in the branch pipe 9b in each of the indoor units BD.

Each of the indoor units BD has a liquid pipe temperature detecting means Th4 for detecting the temperature of the indoor liquid pipe of the indoor heat exchanger 7.
And a suction air temperature detecting means Th1 for detecting the indoor suction air temperature of the indoor heat exchanger 7, and each liquid pipe temperature detecting means Th4 and each suction air temperature detecting means Th1 are provided to the opening degree control means 52C. It is connected.

When a heating operation is performed by the air conditioner described above, the refrigerant is discharged from the compressor 1, passes through the main refrigerant pipe 9a, branches off at each branch pipe 9b, and is branched to each of the indoor units BD. Flow in. After being condensed in each indoor exchanger 7 and returned to the main refrigerant pipe 9a and decompressed by the outdoor electric expansion valve 4, it is evaporated in the outdoor heat exchanger 3 and sucked into the compressor 1.

In order to cope with the heating load in each room where the indoor units B to D are installed, the heating load is set to the set temperature in each room and the suction air temperature T by the suction air temperature detecting means Th1.
1 is grasped, and if this difference is large, the heating load is large, so the opening degree of the indoor electric expansion valve 6 is large. Conversely, if this difference is small, the heating load is small, so the indoor electric expansion valve is small. 6 is controlled so as to reduce the opening degree, and the capacity of each of the indoor heat exchangers 7,... Is adjusted.

When the difference between the set temperature and the suction air temperature T1 is extremely small, the thermo-off state is set. In the indoor unit (for example, C) in the thermo-off state, the difference between T4 and T1 is determined by the opening control means 52C based on the suction air temperature T1 by the suction air temperature detection means Th1 and the gas pipe temperature T4 by the liquid pipe temperature detection means Th4. (T4-T1) is obtained, and when (T4-T1) is less than the predetermined value x, the indoor electric expansion valve 6 of the indoor unit C is set so that the temperature difference (T4-T1) matches the predetermined value x. If the temperature difference (T4−T1) is larger than the predetermined value x,
The indoor electric expansion valve 6 is closed by a predetermined amount so that the temperature difference (T4T1) matches the predetermined value x.

The above control will be described in the order of steps S1 to S7 in the flowchart shown in FIG. In step S1, it is determined whether or not the indoor unit is in a thermo-off state. If it is in the thermo-off state, the process proceeds to step S3. If it is not in the thermo-off state, the process proceeds to step S2. In step S2, the indoor electric expansion valve 6 is set to the full opening. In step S3, T
It is determined whether 4-T1 matches the predetermined value x. If they match, the process proceeds to step S4, and if they do not match, the process proceeds to step S5.

In step S4, control is performed to maintain the opening of the indoor electric expansion valve 6. In step S5, T4-T
It is determined whether or not 1 is less than a predetermined value x. If it is less than x, the process proceeds to step S6, and if it is more than the predetermined value x, the process proceeds to step S7. In step S6, the opening degree of the indoor electric expansion valve 6 is controlled to be opened by a predetermined amount so that T4-T1 matches the predetermined value x. In step S7, the opening degree of the indoor electric expansion valve 6 is controlled to be closed by a predetermined amount so that T4-T1 matches the predetermined value x.

Therefore, the amount of liquid refrigerant in the indoor heat exchanger 7 of the indoor unit C can be kept constant, and there is no sudden change in the heating capacity. If the predetermined value x is set to a small value, the opening degree of the flow control valve becomes small, and the flow rate of the refrigerant becomes small. As a result, the heating capacity is reduced. As a result, it is possible to prevent excessive heating during thermo-off.

[0056]

As described above, in the present invention, in the thermo-off state, the flow control valve is controlled so that the indoor gas pipe temperature, the indoor blow-out air temperature, or the difference between the indoor liquid pipe temperature and the suction air temperature coincides with a predetermined value. Control the opening of the
The amount of liquid refrigerant in the use-side heat exchanger can be kept constant, and the heating capacity does not suddenly fluctuate. Further, in the present invention, if the predetermined value is set to a small value, the opening degree of the flow control valve is reduced, and the refrigerant flow rate is reduced, so that the heating capacity is reduced. As a result, it is possible to prevent overheating during thermo-off. .

[Brief description of the drawings]

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

FIG. 2 is a refrigerant piping system diagram of the air conditioner according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating valve control at the time of thermo-off of the air-conditioning apparatus according to the first embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of an air conditioner according to a second embodiment of the present invention.

FIG. 5 is a refrigerant piping system diagram of an air conditioner according to a second embodiment of the present invention.

FIG. 6 is a flowchart illustrating valve control at the time of thermo-off of the air-conditioning apparatus according to Embodiment 2 of the present invention.

FIG. 7 is a block diagram illustrating a configuration of an air conditioner according to a third embodiment of the present invention.

FIG. 8 is a refrigerant piping system diagram of an air conditioner according to a third embodiment of the present invention.

FIG. 9 is a flowchart showing valve control at the time of thermo-off of the air-conditioning apparatus according to Embodiment 3 of the present invention.

[Explanation of symbols]

 1 Compressor 3 Outdoor heat exchanger (heat source side heat exchanger) 4 Outdoor electric expansion valve (heat source side pressure reducing valve) 6 Indoor electric expansion valve (flow control valve) 7 Indoor heat exchanger (use side heat exchanger) 9a Main Refrigerant piping 9b Branch pipe 10 Refrigerant circuit Th1 Suction air temperature detecting means Th2 Gas pipe temperature detecting means Th3 Blowing air temperature detecting means Th4 Liquid pipe temperature detecting means 52A, 52B, 52C Opening degree controlling means

Claims (3)

[Claims] 1. An outdoor unit having a compressor, a heat source side heat exchanger and a heat source side pressure reducing valve, a plurality of indoor units having a use side heat exchanger and a flow control valve, and a plurality of indoor units with respect to the outdoor unit A refrigerant pipe for connecting in parallel, a gas pipe temperature detecting means for detecting the indoor gas pipe temperature of the use side heat exchanger, and a suction air temperature detecting means for detecting the indoor suction air temperature of the use side heat exchanger, Opening control means for controlling the opening of the flow control valve so that the difference between the temperatures detected by the gas pipe temperature detecting means and the suction air temperature detecting means in the thermo-off state becomes a predetermined value. Air conditioner. 2. An outdoor unit having a compressor, a heat source side heat exchanger and a heat source side pressure reducing valve, a plurality of indoor units having a use side heat exchanger and a flow control valve, and a plurality of indoor units for the outdoor unit. Refrigerant pipes that connect in parallel with each other, blow-out air temperature detecting means for detecting the indoor blow-out air temperature of the use side heat exchanger, and suction air temperature detecting means for detecting the indoor suction air temperature of the use side heat exchanger, Opening degree control means for controlling the opening degree of the flow rate control valve so that the difference between the temperatures detected by the blow-out air temperature detection means and the suction air temperature detection means in the thermo-off state is a predetermined value. Air conditioner. 3. An outdoor unit having a compressor, a heat source side heat exchanger and a heat source side pressure reducing valve, a plurality of indoor units having a use side heat exchanger and a flow control valve, and a plurality of indoor units for the outdoor unit. A refrigerant pipe for connecting in parallel, a liquid pipe temperature detecting means for detecting the indoor liquid pipe temperature of the use side heat exchanger, a suction air temperature detecting means for detecting the indoor suction air temperature of the use side heat exchanger, Opening control means for controlling the opening of the flow control valve so that the difference between the temperatures detected by the gas pipe temperature detecting means and the suction air temperature detecting means in the thermo-off state becomes a predetermined value. Air conditioner.