JP2007271215A - Outdoor unit, and air conditioner comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an outdoor unit capable of preventing rise of high pressure even when indoor units are connected by the smallest number of units with a smallest capacity, in a multi-room air conditioner where the plurality of indoor units are connected to one outdoor unit. <P>SOLUTION: This outdoor unit 2 of the air conditioner to which the plurality of indoor units 3 are connected, comprises a compressor 11, a container 20 and a control portion 4. The container 20 is disposed at a suction side of the compressor 11, and can increase and decrease a refrigerant storing amount. The control portion 4 controls a moist operation to store excess refrigerant in the container 20 when a capacity of a refrigerant circulating passage including the compressor 11 and the container 20 becomes below a prescribed amount in a heating operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to refrigerant capacity control in a multi-room air conditioner in which a plurality of indoor units are connected to one outdoor unit.

Conventionally, as a method for adjusting surplus refrigerant in an air conditioner, there is a method in which surplus refrigerant is stored in an outdoor heat exchanger during cooling operation, and in surplus refrigerant in an indoor heat exchanger during heating operation (see, for example, Patent Document 1). . In this method, the capacity of the outdoor heat exchanger is large during cooling operation, and therefore, there is little effect on performance and reliability even if excess refrigerant is stored in the outdoor heat exchanger, but the volume of the indoor heat exchanger is not affected during heating operation. Therefore, there is a problem that high pressure rises if excessive refrigerant is accumulated. Moreover, in order to adjust an excess refrigerant | coolant, a liquid receiver may be provided (for example, refer patent document 2). However, in the method of providing the liquid receiver, the number of parts increases, which causes a high cost. Therefore, a method of controlling the degree of supercooling in an area where liquid compression does not occur and the discharge pipe temperature does not rise abnormally (for example, Patent Document 3) is employed.
JP 2002-295915 A JP 2003-106610 A JP-A-7-198187

  However, in a multi-room type air conditioner in which a plurality of indoor units are connected to one outdoor unit, a compressor with a large capacity is used to ensure the capacity when the indoor units are connected with the maximum number and maximum capacity. It is installed and filled with refrigerant amount in anticipation of it. In this type of cooling system, when the indoor units are connected with the minimum number of units and the minimum capacity, the amount of refrigerant filled becomes excessive, so the excess refrigerant cannot be adjusted only by the supercooling degree control, and the high pressure rises. There is a risk of inviting.

  An object of the present invention is to provide an outdoor unit capable of preventing an increase in high pressure even when a plurality of indoor units are connected with a minimum number and capacity in a multi-room air conditioner in which a plurality of indoor units are connected to one outdoor unit. It is to provide.

An outdoor unit according to a first aspect of the present invention is an outdoor unit of an air conditioner to which a plurality of indoor units are connected, and includes a compressor, a container, and a control unit. A container is arrange | positioned at the suction side of a compressor and can increase / decrease a refrigerant | coolant storage amount. The controller performs wet operation control for storing excess refrigerant in the container when the capacity of the refrigerant circulation path including the compressor and the container falls below a predetermined amount during the heating operation.
In this outdoor unit, even when the total capacity of the connected indoor units is small and the capacity of the refrigerant circuit is below a predetermined amount, excess refrigerant is stored in the container by wet operation control, so the liquid on the high pressure side (indoor unit side) Refrigerant decreases. For this reason, an abnormal increase in the high-pressure side pressure is prevented.

The outdoor unit according to the second invention is the outdoor unit according to the first invention, and the wet operation control is performed when the number of connected indoor units is equal to or less than a predetermined number.
In this outdoor unit, when the number of connected indoor units is equal to or less than the predetermined number, the excess refrigerant is stored in the container by the damp operation control, so the liquid refrigerant on the high-pressure side decreases. For this reason, an abnormal increase in the high-pressure side pressure is prevented.

An outdoor unit according to a third aspect of the present invention is the outdoor unit according to the first aspect of the present invention, wherein the wet operation control includes lowering an upper limit value of the target discharge pipe temperature of the compressor set based on the operation state. .
Here, in order to lower the upper limit value of the target discharge pipe temperature of the compressor, the opening degree of the expansion valve provided on the outdoor unit side increases, and the refrigerant accumulates in the container. For this reason, an abnormal increase in the high-pressure side pressure is prevented. Furthermore, since it is not necessary to provide components such as a liquid receiver, the cost is low.

An outdoor unit according to a fourth aspect of the present invention is the outdoor unit according to the first aspect of the present invention, and the operating frequency of the compressor is adjusted based on the operating state. Wet operation control is performed when the capacity of the refrigerant circuit including the compressor and the container is less than a predetermined amount, and the operation frequency of the compressor is equal to or lower than the predetermined frequency.
Here, in general, when the high-pressure side pressure increases, the operation frequency decreases due to the peak cut control. When the high-pressure side pressure cannot be reduced by this peak cut control, that is, when the high-pressure side pressure cannot be reduced even when the operating frequency is lowered, the wet operation is started. For this reason, an abnormal increase in the high-pressure side pressure is prevented.

An outdoor unit according to a fifth aspect of the present invention is the outdoor unit according to the first aspect of the present invention, wherein the wet operation control is performed such that the capacity of the refrigerant circulation path including the compressor and the container is less than a predetermined amount, and the refrigerant condensing temperature is equal to or higher than the predetermined temperature. Done in the case of
Here, when the high-pressure side pressure increases, the condensation temperature increases. Therefore, when the condensation temperature rises to a predetermined temperature, it is determined that the high-pressure side pressure has risen, and the wet operation is started. For this reason, an abnormal increase in the high-pressure side pressure is prevented.

An outdoor unit according to a sixth aspect of the present invention is the outdoor unit according to the third aspect of the present invention, wherein the upper limit value of the target discharge pipe temperature is lowered to the discharge pipe temperature at which the minimum discharge overheating is ensured, and the wet operation control is performed.
Here, since the surplus refrigerant is stored in the container by simple control, an abnormal increase in the high-pressure side pressure is prevented. Furthermore, since it is not necessary to provide components such as a liquid receiver, the cost is low. And a compressor can be protected even if it performs wet operation.

An air conditioner according to a seventh aspect includes the outdoor unit according to any one of the first to sixth aspects, and a plurality of indoor units connected to the outdoor unit.
Even when the indoor units are connected with the minimum number and the minimum capacity, the surplus refrigerant can be adjusted, and an abnormal increase in the high-pressure side pressure can be prevented.

In the outdoor unit according to the first aspect of the present invention, even when the total capacity of the connected indoor units is small and the capacity of the refrigerant circuit is less than a predetermined amount, the excess refrigerant is stored in the container by the wet operation control. Decrease. For this reason, an abnormal increase in the high-pressure side pressure is prevented.
In the outdoor unit according to the second invention, when the number of indoor units connected is equal to or less than the predetermined number, the excess refrigerant is stored in the container by the wet operation control, so the liquid refrigerant on the high-pressure side decreases. For this reason, an abnormal increase in the high-pressure side pressure is prevented.

The outdoor unit according to the third aspect of the present invention is low in cost because it is not necessary to provide an extra component such as a liquid receiver in addition to preventing an abnormal increase in the high pressure side pressure.
In the outdoor unit according to the fourth aspect of the invention, when the operating frequency is reduced to a predetermined frequency, it is determined that the high-pressure side pressure is increasing, and the wet operation is started. For this reason, an abnormal increase in the high-pressure side pressure is prevented.

In the outdoor unit according to the fifth aspect of the invention, when the condensation temperature rises to a predetermined temperature, it is determined that the high-pressure side pressure is rising, and the damp operation is started. For this reason, an abnormal increase in the high-pressure side pressure is prevented.
The outdoor unit according to the sixth aspect of the present invention is low in cost because it is not necessary to provide a liquid receiver or the like in addition to preventing an abnormal increase in the high-pressure side pressure. And a compressor can be protected even if it performs wet operation.

  The air conditioner according to the seventh aspect of the invention can adjust the excess refrigerant even when the indoor units are connected with the minimum number and the minimum capacity, and can prevent an abnormal increase in the high-pressure side pressure.

<Configuration of air conditioner>
The refrigerant circuit of the air conditioning apparatus containing the outdoor unit which concerns on one Embodiment of this invention is shown in FIG. The air conditioner 1 is a multi-room type air conditioner, and has a configuration in which a plurality of indoor units 3 are connected in parallel to one outdoor unit 2. The refrigerant circuit 10 of the air conditioner 1 is mainly composed of a compressor 11, a four-way switching valve 12, an outdoor heat exchanger 13, an expansion valve 14, and an indoor heat exchanger 16, which are connected in order. It is a cycle. Here, the compressor 11 is a variable capacity inverter compressor that performs rotational speed control by an inverter. An accumulator (container) 20 that can increase or decrease the refrigerant storage amount is provided on the suction side of the compressor 11.

  The compressor 11, the four-way switching valve 12, the outdoor heat exchanger 13 and the expansion valve 14 are included in the outdoor unit 2, and the indoor heat exchanger 16 is included in the indoor unit 3. The four-way switching valve 12 and the indoor heat exchanger 16 are connected by a refrigerant communication pipe 17a, and the expansion valve 14 and the indoor heat exchanger 16 are connected by a refrigerant communication pipe 17b. The refrigerant communication pipes 17 a and 17 b are arranged between the outdoor unit 2 and the indoor unit 3. A gas side shut-off valve 18 and a liquid side shut-off valve 19 are provided at a terminal portion of the internal refrigerant circuit of the outdoor unit 2. The gas side closing valve 18 is arranged on the four-way switching valve 12 side, and the liquid side closing valve 19 is arranged on the expansion valve 14 side. A refrigerant communication pipe 17 a is connected to the gas side shut-off valve 18, and a refrigerant communication pipe 17 b is connected to the liquid side shut-off valve 19. These closing valves 18 and 19 are closed when the outdoor unit 2 and the indoor unit 3 are installed. Then, the closing valves 18 and 19 are opened after the outdoor unit 2 and the indoor unit 3 are installed on the site and the refrigerant communication pipe 17a and the refrigerant communication pipe 17b are connected to the closing valves 18 and 19, respectively.

  Moreover, the air conditioning apparatus 1 of this embodiment is provided with many temperature sensors consisting of thermistors. The outdoor temperature sensor 102 detects the ambient temperature where the outdoor unit 2 is installed, and the discharge pipe temperature sensor 111 is attached to the discharge pipe of the compressor 11 and detects the discharge pipe temperature To. During the heating operation, the evaporation temperature sensor 113 is attached to the outdoor heat exchanger 13 and detects the evaporation temperature Te, and the condensation temperature sensor 116 is attached to the indoor heat exchanger 16 and detects the condensation temperature Tc. The liquid pipe temperature sensor 117 is attached to the outlet side of the indoor heat exchanger 16 during heating operation, and detects the liquid pipe temperature Tl. Based on the detection values of these temperature sensors, the control unit 4 controls the operation of the air conditioner 1.

<Operation of air conditioner>
(Cooling operation)
Next, the operation of the air conditioner 1 will be described. During the cooling operation, the four-way switching valve 12 is maintained in the state indicated by the solid line in FIG. The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows into the outdoor heat exchanger 13 through the four-way switching valve 12, and exchanges heat with the outdoor air to condense and liquefy. The liquefied refrigerant is depressurized to a predetermined low pressure by the expansion valve 14 and further evaporated by exchanging heat with indoor air in the indoor heat exchanger 16. The indoor air cooled by the evaporation of the refrigerant is blown out into the room by an indoor fan (not shown) to cool the room. The refrigerant evaporated and vaporized in the indoor heat exchanger 16 returns to the outdoor unit 2 through the refrigerant communication pipe 17 a and is sucked into the compressor 11.

(Heating operation)
During the heating operation, the four-way switching valve 12 is maintained in a state indicated by a broken line in FIG. The high-temperature and high-pressure gas refrigerant discharged from the compressor 11 flows into the indoor heat exchanger 16 of each indoor unit 3 through the four-way switching valve 12, and exchanges heat with indoor air to condense and liquefy. The indoor air heated by the condensation of the refrigerant is blown out into the room by an indoor fan to heat the room. The refrigerant liquefied in the indoor heat exchanger 16 returns to the outdoor unit 2 through the refrigerant communication pipe 17b. The refrigerant that has returned to the outdoor unit 2 is decompressed to a predetermined low pressure by the expansion valve 14, and is further evaporated by exchanging heat with outdoor air in the outdoor heat exchanger 13. The refrigerant evaporated and evaporated in the outdoor heat exchanger 13 is sucked into the compressor 11 through the four-way switching valve 12.

<Normal control>
FIG. 2 is a control block diagram of an air conditioner including an outdoor unit according to an embodiment of the present invention. The control unit 4 includes a target discharge pipe temperature setting unit 41, an expansion valve solution degree control unit 42, and an inverter control unit 43. The target discharge pipe temperature setting unit 41 detects detected values Tc and Te of temperature sensors 113, 116, and 117. , Tl is set to the target discharge pipe temperature Tm. The expansion valve opening degree control unit 42 calculates the deviation between the target discharge pipe temperature Tm and the discharge pipe temperature To and adjusts the opening degree of the expansion valve 14 so that the target discharge pipe temperature Tm and the discharge pipe temperature To coincide. Do. The inverter control unit 43 sets the operating frequency of the compressor 11 in a timely manner, and causes the compressor 11 to optimally operate.

The target discharge pipe temperature Tm is calculated by the equation Tm = α × Tc−β × Te + γ, where γ is a supercooling degree correction term and is calculated based on the actual supercooling degree (Tl−Tc). . When the actual supercooling degree is smaller than the target supercooling degree, the supercooling degree correction term γ becomes positive and the target discharge pipe temperature Tm increases. Therefore, the liquid in the accumulator 20 is reduced and the degree of supercooling is added. When the actual supercooling degree is larger than the target supercooling degree (the supercooling degree is too high), γ becomes negative, the target discharge pipe temperature Tm decreases, the liquid in the accumulator 20 increases, and the supercooling occurs. The degree becomes smaller.
By the way, in the multi-room type air conditioner, in order to cope with a change in the shape of the indoor unit, an amount of refrigerant that can support the connection of the maximum number of large-capacity indoor units is selected. Therefore, when the heating operation is performed with the minimum connection of the small-capacity indoor unit, excess refrigerant is stored on the high-pressure side, so that the super-cooling is excessive and the high-pressure side pressure abnormally increases.

<Capacity control>
Therefore, in order to avoid an abnormal increase in the high-pressure side pressure, during heating operation, if the high pressure rises below a predetermined operating frequency, the discharge pipe temperature upper limit value is secured as the discharge superheat degree that becomes the wetness limit of the compressor 11. The value is changed to a possible value, and the wet operation is performed by adjusting the opening of the expansion valve 14. By performing this wetting operation, surplus refrigerant is accumulated in the accumulator 20 connected in front of the suction port of the compressor 11, and the liquid refrigerant on the condenser side (indoor unit side) is reduced to reduce the high pressure.

(Heating operation control logic)
FIG. 3 is a flowchart of the heating operation control. The capacity control is a part of the heating operation control. When the heating operation is started, it is determined whether or not the capacity control is performed. First, in S1, it is determined whether or not the capacity of the connected indoor unit is less than QL. In the case of Yes in S1, the process proceeds to S2, and it is determined whether or not the operating frequency of the compressor 11 is less than FL. If Yes in S2, the process proceeds to S3, and it is determined whether or not the condensation temperature is equal to or lower than TcH. In the case of Yes in S3, the wetness control operation is performed. In addition, normal control is performed when any of S1, S2, and S3 is No. Note that QL, FL, and TcH are obtained in advance by experiments and stored in the control unit 4.

(Wet operation control logic)
FIG. 4 is a flowchart of wet operation control. In S11, the target discharge temperature Tm is set to Tmh that can ensure the minimum discharge superheat degree. Next, the process proceeds to S12, and the discharge pipe temperatures To and Tmh are compared. In S13, the opening degree of the expansion valve 14 is set from the difference between To and Tmh. For example, if To ≧ Tmh, the opening degree of the expansion valve 14 is set to be increased, and if To <Tmh, the opening degree of the expansion valve 14 is set to be reduced. Then, the process proceeds to S14 and the expansion valve 14 is operated. After operating the expansion valve 14, the process returns to S1.

<Features>
(1)
The outdoor unit 2 is connected to a plurality of indoor units 3. The outdoor unit 2 includes a compressor 11 that can change the operating frequency, an accumulator 20, and a control unit 4. The accumulator 20 is connected to the suction side of the compressor 11 and can increase or decrease the refrigerant storage amount. When the capacity of the refrigerant circuit including the compressor 11 and the accumulator 20 falls below a predetermined amount during the heating operation, the control unit 4 performs wet operation control for accumulating excess refrigerant in the accumulator 20. For this reason, even when the number of connected indoor units 3 is the minimum (two or less), the excess refrigerant is accumulated in the accumulator 20 by the wet operation control, so the liquid refrigerant on the indoor heat exchanger 16 side is reduced, and the high pressure side pressure is reduced. Abnormal rise is prevented. Further, in the wet operation control, the upper limit value of the target discharge pipe temperature of the compressor 11 is lowered to the discharge pipe temperature at which the minimum discharge overheating is ensured, so that the opening degree of the expansion valve 14 is increased and the refrigerant is transferred to the accumulator 20. Accumulate. For this reason, it is not necessary to provide components, such as a liquid receiver, and it is low-cost.

(2)
In the outdoor unit 2, the wet operation control is performed when the capacity of the refrigerant circulation path including the compressor 11 and the accumulator 20 is less than a predetermined amount, and the operation frequency of the compressor is equal to or lower than the predetermined frequency. That is, it is determined that the high-pressure side pressure has increased when the operating frequency is reduced to a predetermined frequency, and an abnormal increase in the high-pressure side pressure is prevented by the wet operation. Further, the wet operation control is performed when the capacity of the refrigerant circuit including the compressor 11 and the accumulator 20 is less than a predetermined amount and the refrigerant condensing temperature is equal to or higher than the predetermined temperature. That is, when the condensation temperature rises to a predetermined temperature, it is determined that the high-pressure side pressure has risen, and an abnormal increase in the high-pressure side pressure is prevented by the wet operation.

(3)
The air conditioner 1 provided with the outdoor unit 2 is wet for storing excess refrigerant in the accumulator 20 when the capacity of the refrigerant circulation path including the compressor 11 and the accumulator 20 falls below a predetermined amount during heating operation. A control unit that performs operation control is provided. For this reason, it is possible to adjust the surplus refrigerant and to prevent an abnormal increase in the high-pressure side pressure.

  As described above, according to the present invention, the surplus refrigerant in the refrigeration circuit can be adjusted by simple means, so that it is useful for a multi-room air conditioner in which a plurality of indoor units are connected to one outdoor unit. is there.

The refrigerant circuit of the air conditioning apparatus containing the outdoor unit which concerns on one Embodiment of this invention. The control block diagram of the outdoor unit which concerns on the same embodiment. The flowchart of the heating operation control of the outdoor unit which concerns on the same embodiment. The flowchart of the wet operation control of the outdoor unit which concerns on the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air conditioning apparatus 2 Outdoor unit 3 Indoor unit 4 Control part 11 Compressor 20 Accumulator (container)

Claims (7)

An outdoor unit of an air conditioner (1) to which a plurality of indoor units (3) are connected,
A compressor (11);
A container (20) disposed on the suction side of the compressor (11) and capable of increasing or decreasing a refrigerant storage amount;
During the heating operation, when the capacity of the refrigerant circuit including the compressor (11) and the container (20) falls below a predetermined amount, wet operation control is performed to store excess refrigerant in the container (20). A control unit (4);
An outdoor unit (2) equipped with The wet operation control is performed when the number of connected indoor units (3) is a predetermined number or less.
The outdoor unit (2) according to claim 1. The wet operation control includes lowering an upper limit value of a target discharge pipe temperature of the compressor (11) set based on an operation state.
The outdoor unit (2) according to claim 1. The operating frequency of the compressor (11) is adjusted based on the operating state,
The wet operation control is performed when the capacity of the refrigerant circuit including the compressor (11) and the container (20) is less than a predetermined amount, and the operation frequency of the compressor (11) is equal to or lower than a predetermined frequency.
The outdoor unit (2) according to claim 1. The wet operation control is performed when the capacity of the refrigerant circuit including the compressor (11) and the container (20) is less than a predetermined amount, and the condensation temperature of the refrigerant is equal to or higher than a predetermined temperature.
The outdoor unit (2) according to claim 1. Wet operation control is performed by lowering the upper limit value of the target discharge pipe temperature to a discharge pipe temperature at which the minimum discharge overheating that can protect the compressor reliability is ensured,
The outdoor unit (2) according to claim 3. The outdoor unit (2) according to any one of claims 1 to 6, and a plurality of indoor units (3) connected to the outdoor unit (2).
Air conditioner (1).

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