JP2955424B2 - Air conditioner - Google Patents

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 comprising an outdoor unit and a plurality of indoor units.

[0002]

2. Description of the Related Art In a building having a large number of rooms, a multi-type air conditioner having a plurality of indoor units is used.

[0003] In this multi-type air conditioner, the refrigerant piping tends to be long, so that the lubricating oil of the compressor flowing out during the refrigeration cycle accumulates in the refrigeration cycle as it is, and the lubricating oil in the compressor runs short. May be. Insufficient lubricating oil in the compressor hinders lubrication of the sliding parts of the compressor, and in the worst case, causes damage to the compressor. Therefore, during operation, an oil recovery operation for increasing the operating frequency of the compressor is periodically performed, and the lubricating oil in the refrigeration cycle is forcibly recovered by the compressor.

When a plurality of compressors are mounted on the outdoor unit, the lubricating oil in each compressor concentrates on the compressor with the higher capacity, and the compressor with the lower capacity runs short of lubricating oil. That situation occurs.

[0005] Therefore, the case of each compressor is connected by an oil equalizing pipe, and the oil equalizing operation for giving a difference in the operating frequency of each compressor is periodically executed, whereby the pressure in the case is made different. Lubricating oil is made uniform through an oil equalizing pipe.

[0006]

In the oil recovery operation, the interval between the execution and the next execution is fixed, and the execution time itself is also fixed. Therefore, the lubricating oil cannot be reliably recovered depending on the installation condition, which may adversely affect the life of the compressor or damage the compressor. Conversely, the oil recovery operation may be performed uselessly even though the recovery is completed, in which case the appropriate air conditioning is interrupted and the comfort is impaired. on the other hand,
Also in the oil leveling operation, the interval from the execution to the next execution is fixed, and the execution time is fixed.

[0007] For this reason, there is a case where the lubricating oil amount of each compressor becomes unbalanced because an appropriate oil leveling cannot be performed, and there is the same concern as above. In addition, even if the oil leveling is completed, the oil leveling operation may be performed uselessly, and the comfort is impaired as described above. The present invention has been made in view of the above circumstances,

According to the air conditioner of the first aspect, the lubricating oil in the refrigeration cycle can be reliably recovered to the compressor, thereby improving the life of the compressor and preventing wasteful recovery and improving comfort. The purpose is to be able to secure.

[0009]

[0010]

According to a first aspect of the present invention, there is provided an air conditioner comprising: an outdoor unit having a plurality of compressors and an outdoor heat exchanger; a plurality of indoor units each having an indoor heat exchanger; Machine, an outdoor heat exchanger, a refrigeration cycle connected to each indoor heat exchanger, and means for controlling the number of operating and operating frequency of each of the compressors according to the air conditioning load,
An oil recovery operation means for alternately increasing the operating frequency of each compressor to collect the lubricating oil in each compressor, a means for periodically executing the oil recovery operation for each time interval Ta and a time ta, Means for detecting the low pressure side of the cycle;
Means for changing at least one of an execution time interval Ta, an execution time ta, and an operation frequency of the oil recovery operation according to the detected pressure and the number of operating compressors.

[0011]

[0012]

The air conditioner of the first aspect has a function of an oil recovery operation in which the operating frequency of each compressor is alternately increased to collect the lubricating oil in each compressor, and this oil recovery operation is performed at every time interval Ta. It is executed periodically at time ta. However, at least one of the execution time interval Ta, the execution time ta, and the operation frequency of the oil recovery operation is changed according to the low-pressure side pressure of the refrigeration cycle and the number of operating compressors.

[0013]

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. This first embodiment corresponds to the air conditioner of the first aspect. In FIG. 1, A is an outdoor unit, and a plurality of indoor units C ₁ , C ₂ , and C ₃ are connected to the outdoor unit A via a distribution unit B by piping. The outdoor unit A includes compressors 1 and 2. Each of the compressors 1 and 2 has two built-in compressors in one closed case.

That is, the compressor 1 has a variable capacity compressor 3 driven by an inverter and a fixed capacity compressor 4 driven by a commercial power supply. The compressor 2 includes a variable capacity compressor 5 driven by an inverter and a fixed capacity compressor 6 driven by a commercial power supply. Hereinafter, the compressors 1 and 2 will be referred to as compressor cases 1 and 2 for convenience of description. An outdoor heat exchanger 9 is connected to the discharge ports of the compressors 3, 4, 5, and 6 via a check valve 7 in the forward direction and further via a four-way valve 8, respectively. Outdoor heat exchanger 9
Is connected to a header H via a check valve 10 and a liquid receiver 11 for forming a cooling cycle. A heating expansion valve 12 is connected in parallel with the check valve 10.

In the header H, motorized flow control valves (pulse motor valves; hereinafter abbreviated as PMV) 21, 31,
The indoor heat exchangers 24, 34 and 44 are connected via a parallel circuit of a cooling valve 41, a cooling expansion valve 22, 32 and 42 and a heating cycle forming check valve 23, 33 and 43. The header H is connected to the indoor heat exchangers 24, 34, 44, and the header H is connected to the compressors 3, 4, 4 via the accumulator 13.
Connect to inlets 5 and 6. Thus, the outdoor unit A, the distribution unit B, and the indoor units C ₁ , C ₂ ,
In C _3, constitute a heat pump type refrigeration cycle.

That is, during the cooling operation, the refrigerant flows in the direction of the solid arrow in the drawing to form a cooling cycle, and in the heating operation, the switching operation of the four-way valve 8 causes the refrigerant to flow in the direction of the broken line in the drawing to form the heating cycle. I do.

The cooling expansion valves 22, 32, and 42 have temperature-sensitive cylinders 22a, 32a, and 42a, respectively, and these temperature-sensitive cylinders are connected to gas-side refrigerant pipes of the indoor heat exchangers 24, 34, and 44, respectively. Attach.

An oil equalizing pipe connection port is provided at each of the reference oil level positions of the compressor cases 1 and 2, and both connection ports are connected by an oil equalizing pipe 14. The oil equalizing pipe 14 is for flowing lubricating oil.

From the accumulator 13 to the compressors 3, 4,
The pressure sensor 15 is attached to the piping extending to the suction ports 5 and 6. The pressure sensor 15 detects the low pressure Ps of the refrigeration cycle. The control circuit is shown in FIG.

The outdoor unit A has an outdoor control section 50. The distribution control unit 60 of the distribution unit B is connected to the outdoor control unit 50, and the distribution control unit 60 is connected to the indoor unit C.
₁ , C ₂ and C ₃ are respectively connected to the indoor control units 70.

The outdoor controller 50 comprises a microcomputer and its peripheral circuits. In this outdoor control unit 50,
The four-way valve 8, the pressure sensor 15, the inverters 51 and 53, the switches 52 and 54, the timer 55, and the frequency detector 56 are connected.

The inverter circuits 51 and 53 rectify the voltage of the commercial AC power supply 57, convert the rectified voltage to a voltage of a predetermined frequency by switching according to a command from the outdoor control unit 50, and output the voltage. This output is supplied to compressor motor 3
M and 5M drive power. Switches 52 and 54 are, for example, relay contacts. Through these switches 52 and 54, the compressor motor 4M,
Connect 6M. The distribution control unit 60 comprises a microcomputer and its peripheral circuits. This distribution control unit 60
To the PMVs 21, 31, and 41.

The indoor controller 70 comprises a microcomputer and its peripheral circuits. In this indoor control unit 70,
A remote control type operation device (hereinafter, abbreviated as a remote control) 71 and an indoor temperature sensor 72 are connected.
The indoor control unit 70 includes the following functional units. (1) Distribution unit B transmits an operation start command, operation mode setting command, and operation stop command based on operation of remote controller 71
Means to send to. (2) Means for obtaining the difference between the detected temperature of the room temperature sensor 72 and the room temperature set by the remote controller 71 as an air conditioning load, and sending the air conditioning load data to the distribution unit B. Distribution control unit 6
0 has the following functional means. (1) Means for calculating the sum of the air conditioning loads of the indoor units C ₁ , C ₂ , C ₃ and transmitting the total air conditioning load data to the outdoor unit A. (2) Means for controlling the degree of opening of the PMVs 21, 31, 41 according to the air conditioning loads of the indoor units C ₁ , C ₂ , C ₃ . The outdoor control unit 50 includes the following functional units. (1) Means for controlling the number of operating compressors 3, 4, 5, 6 and the operating frequency F of compressors 3, 5 according to the total air conditioning load. (2) Oil recovery operating means for raising the operating frequency F of the compressors 3, 5 alternately to recover the lubricating oil to the compressors 3, 4, 5, and 6. (3) Means for periodically executing the oil recovery operation at time ta (minutes) at time intervals Ta (minutes) based on the count of the timer 55.

(4) Means for changing the execution interval Ta, execution time ta, and operation frequency F of the oil recovery operation according to the detected pressure Ps of the pressure sensor 15 and the number of compressors 3, 4, 5, and 6 operated. Next, the operation of the above configuration will be described.

During operation, as shown in FIG.
The number of operating vehicles and the operating frequencies of 4, 5, and 6 are switched to a plurality of patterns (A), (A), (C), and (D) according to the total of the air conditioning loads. That is, when the air conditioning load is small (L ₁ ≦ L
<L ₂ ), the pattern (A) is selected and the variable capacity operation of the compressor 3 is executed. When the air-conditioning load slightly increases (L ₂ ≦ L <
L ₃ ) and the pattern (a) are selected, and the capacity variable operation of each of the compressors 3 and 5 is executed. When the air-conditioning load further increases (L ₃ ≦ L <L ₄ ), the pattern (C) is selected, and the variable capacity operation of the compressors 3 and 5 and the fixed capacity operation of the compressor 4 are executed. When the air conditioning load increases (L ₄ ≦ L <
L ₅ ), the pattern (D) is selected, and the variable capacity operation of the compressors 3 and 5 and the fixed capacity operation of the compressors 4 and 6 are executed.

During operation, the timer 55 counts the time, and the operating frequency F of the compressors 3 and 5 is alternately increased to a predetermined value by the time ta at each time interval Ta to execute the oil recovery operation.

When the operating frequency F of the compressors 3, 5 increases,
The refrigerant discharge capacity of the compressors 3 and 5 is increased, and the lubricating oil in the refrigeration cycle is forcibly recovered by the compressors 3, 4, 5, and 6 at that pressure.

At the time of this periodic oil recovery operation, as shown in FIG. 4, the pressure sensor 15 detects the low pressure side pressure Ps,
Comparing the set value P ₁ and the low side pressure Ps. Furthermore, compared with the operation number N of the compressor 3, 4, 5, 6 and the set value N _1.

[0030] When the low-pressure side pressure Ps is higher than the set value P _1, as shown in FIG. 5, normal T ₁ as an execution interval Ta
Is set, and a normal t ₁ is set as the execution time ta, and F ₁ is set as the operation frequency F.

[0031] be decreased to equal to or less low-pressure side pressure Ps and the set value P _1, The greater the number of operating units N is below the set value N _1, likewise, to set the normal T ₁ as an execution interval Ta, execution Normal time t ₁ is set as the time ta, and F ₁ is set as the operating frequency F.

When the low-pressure side pressure Ps falls below or equal to the set value P ₁ and the number of operating vehicles N is smaller than the set value N ₁ , the execution interval Ta is shorter than normal by α as shown in FIG. T ₁ -α) and the execution time ta
Is set to (t ₁ + β) longer than usual by β, and the operating frequency F is set to F ₂ (> F ₁ ) higher than usual.

That is, when a large amount of lubricating oil is accumulated in the refrigeration cycle and the low pressure side pressure Ps is reduced, and when the operating number N is small and the discharged refrigerant pressure is not so high, the oil recovery is performed. Operation execution interval Ta
, And the execution time ta is extended, and the refrigerant pressure discharged from the compressors 3 and 5 is further increased.

As described above, by increasing the recovery capacity,
A large amount of lubricating oil accumulated in the refrigeration cycle can be reliably collected in the compressors 3, 4, 5, and 6. Therefore, it is possible to avoid adverse effects on the life of the compressors 3, 4, 5, and 6, and damage to the compressors 3, 4, 5, and 6.

Further, the increase in the recovery capacity is only required when the required pressure is based on the low pressure side pressure Ps and the number of operating units N.
It is possible to prevent adverse effects on air conditioning as much as possible and to secure sufficient comfort.

In the above embodiment, the execution interval Ta, the execution time ta, and the operating frequency F are changed, but the same effect can be obtained by changing at least one of them. . Next, a second embodiment of the present invention will be described. The second embodiment corresponds to the air conditioner of the second aspect. Here, (2), (3), and (4) among the various functional units of the outdoor control unit 50 are different as described below, and the other configuration is the same as that of the first embodiment. (2) Oil-equalizing operation means for causing the lubricating oils in the compressor cases 1 and 2 to flow mutually through the oil-equalizing pipe 14 by making the operating frequencies F of the compressors 3 and 4 different. (3) Means for periodically executing the oil equalizing operation at a time interval Tb (minute) based on the count of the timer 55 and for a time tb (minute). (4) The execution interval Tb and execution time tb of the oil leveling operation are determined by the detection pressure Ps of the pressure sensor 15 and the compressors 3, 4, 5,
6 means for changing according to the number of operating vehicles. The operation will be described.

First, in the operation of the pattern (A), only the compressor 3 on the compressor case 1 side is in the operating state, and as shown in FIG. The operation is not required and is not executed.

In the operation of the pattern (a), as shown in FIG. 8, an oil leveling operation in which the operating frequency F ₃ of the compressor 3 is alternately lowered and increased by tb / 2, and an operating frequency F ₅ of the compressor 5 is increased. Similarly, the oil leveling operation, which is alternately lowered and increased by tb / 2, is repeatedly executed at time intervals Tb. tb and Tb are
The timer 55 elapses.

In this case, the operating frequency F ₃ can be lowered or raised by
As shown by a downward arrow in FIG. 9, first, the lubricating oil of the compressor case 1 is moved to the compressor case 2 (upper side), and then the lubricating oil of the compressor case 2 is moved to the compressor case 1 (lower side). ). Down-up of the operating frequency F ₅ are the same as indicated by the upward arrow in FIG. 9, first moves the lubricating oil in the compressor casing 2 to the compressor casing 1 (lower side), then the lubricating oil in the compressor casing 1 Is moved to the compressor case 2 (upper side). This alternate movement of the lubricating oil makes the lubricating oil in the compressor cases 1 and 2 uniform.

In the operation of the pattern (c), the compressor 4 in the operation ON state is turned off for tb, and the compressor 6 in the operation OFF state is turned on during that time. This oil leveling operation is repeatedly executed at each time interval Tb.

In this case, the operation of the compressor 4 is turned off and the operation of the compressor 6 is turned on, as shown by the upward arrow in FIG. As a result, the lubricating oil in the compressor case 1 moves to the compressor case 2 (upper side). Then, as shown by the downward arrow in FIG. 9, from the state where the lubricating oil in the compressor case 2 is increased (upper side), the compressor 4 is turned on and the compressor 6 is turned off, so that the compressor case 2 is turned off. Lubricating oil moves to the compressor case 1 (lower side). Due to this alternating movement of lubricating oil,
Lubricating oil in the compressor cases 1 and 2 is made uniform.

In the operation of the pattern (d), as in the case of the pattern (a), as shown in FIG. 8, the operating frequency F ₃ of the compressor 3 is decreased by tb / 2 and increased, and then the operating frequency of the compressor 5 is increased. F ₅ also raised lowered by tb / 2ta and repeating this for each time interval Tb.

In the regular oil leveling operation, as shown in FIG. 10, the low pressure side pressure Ps is detected by the pressure sensor 15,
The low pressure side pressure Ps and the reference value P ₁ (for example, 3 kg / c
m ² ) And compare.

When the low-pressure side pressure Ps is substantially the same as the reference value P ₁ (Ps = P ₁ ), 30 minutes of the normal value is set as the execution interval Tb, and 90 seconds of the normal value is set as the execution time ta. Set. When the low-pressure side pressure Ps becomes lower than the reference value _{P 1 (Ps <P 1)} , set the 20-minute as the execution interval Tb, and sets a 120 seconds as the execution time ta.

That is, if the outside air temperature decreases during the heating operation, a large amount of lubricating oil accumulates in the refrigeration cycle and the return of the lubricating oil to the compressors 3, 4, 5, and 6 becomes poor. This is captured by a decrease in the low pressure side pressure Ps, and the execution interval Tb of the oil equalizing operation is shortened and the execution time tb is extended.

By increasing the frequency and the occupation time of the oil equalizing operation in this way, even if the lubricating oil returns to the compressors 3, 4, 5, 6 poorly, the lubricating oil amount tends to be unbalanced. In addition, the lubricating oil in the compressor cases 1 and 2 can be reliably made uniform. Therefore, the compressor 3,
The efficient operation of 4, 5, 6 can be continued, and the life of the compressors 3, 4, 5, 6 can be improved. Further, when the low-pressure side pressure Ps is higher than the reference value _{P 1 (Ps> P 1)} ,
40 minutes is set as the execution interval Tb, and the execution time ta
Is set to 60 seconds.

That is, in a situation where the lubricating oil can be easily made uniform, the execution interval Tb of the oil equalizing operation is extended, the execution time tb is shortened, and the frequency and the occupation time of the oil equalizing operation are reduced. In this way, by avoiding wasteful equalization of the lubricating oil, adverse effects on air conditioning can be prevented as much as possible, and sufficient comfort can be secured.

In the above embodiment, the execution interval Tb and the execution time tb are changed, but the same effect can be obtained by changing at least one of them. Further, in each embodiment, the case where the number of compressors is four has been described as an example, but the number of compressors can be appropriately set.

[0049]

As described above, according to the present invention,

The air conditioner according to the present invention has an oil recovery operation function for increasing the operating frequency of each compressor and recovering the lubricating oil in each compressor.
And at least one of the execution time interval Ta, the execution time ta, and the operation frequency of the oil recovery operation according to the low pressure side pressure of the refrigeration cycle and the number of operating compressors. As a result, the lubricating oil in the refrigeration cycle can be reliably collected in the compressor, thereby improving the life of the compressor and preventing wasteful collection to ensure comfort.

[0051]

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a refrigeration cycle according to first and second embodiments of the present invention.

FIG. 2 is a block diagram showing a configuration of a control circuit of each embodiment.

FIG. 3 is a diagram showing a format of the number of operating units and an operating frequency in each embodiment.

FIG. 4 is a flowchart for explaining control of an oil recovery operation in the first embodiment.

FIG. 5 is a time chart showing a control pattern of a normal oil recovery operation in the first embodiment.

FIG. 6 is a time chart showing a control pattern of an oil recovery operation when the low pressure side pressure drops in the first embodiment.

FIG. 7 is a diagram showing the amount of lubricating oil in the compressor cases 1 and 2 in the operation of the pattern (A) in the second embodiment.

FIG. 8 is a time chart showing a control pattern of the oil equalizing operation in the second embodiment.

9 is a diagram showing a change in the amount of lubricating oil in the compressor cases 1 and 2 in the oil equalizing operation in FIG.

FIG. 10 is a flowchart for explaining control of oil equalizing operation in the second embodiment.

[Explanation of symbols]

A: outdoor unit, B: distribution unit, C ₁ , C ₂ , C
₃ ... indoor unit, 1, 2 ... compressor case, 3, 5 ... variable capacity compressor, 4, 6 ... fixed capacity compressor, 14 ... oil equalizing pipe, 15 ... pressure sensor, 50 ... outdoor control unit, 55 ... timer , 56: frequency detection unit, 60: distribution control unit, 70: indoor control unit.

Claims (1)

(57) [Claims] 1. An outdoor unit having a plurality of compressors and an outdoor heat exchanger, a plurality of indoor units each having an indoor heat exchanger, the compressor, the outdoor heat exchanger, and the indoor heat exchanger. A connected refrigeration cycle, means for controlling the number of operating units and operating frequency of each of the compressors in accordance with the air conditioning load, and oil recovery for increasing the operating frequency of each of the compressors alternately to collect lubricating oil in each of the compressors Operating means, means for periodically performing the oil recovery operation at time intervals Ta at time intervals Ta, means for detecting the low-pressure side pressure of the refrigeration cycle, and the detected pressure and the number of operating compressors. Means for changing at least one of an execution time interval Ta, an execution time ta, and an operation frequency of the oil recovery operation in response to the request.