JPH01203680A - Air conditioner - Google Patents

Abstract

PURPOSE:To obtain an oil equalizing effect between each compressor without using an oil equalizer pipe of large bore by providing an oil equalizer pipe between both the compressors while operating both the compressors in almost the same operating frequency or with a difference of predetermined frequency while both the compressors are in simultaneous operation. CONSTITUTION:While two sets of compressors 1, 2 are in operation, oil equalizing operation is performed alternately repeating in every fixed period the first oil equalizing operation, which relatively on-off controls by every fixed time an operating frequency of the one compressor 1 of both the compressors 1, 2 as compared with an operating frequency of the compressor 2, during this time, holds its operating frequency to the fixed operating frequency, and the second oil equalizing operation which performs the first oil equalizing operation in a condition that both the compressors 1, 2 are replaced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement of a multi-type air conditioner including one outdoor unit and a plurality of indoor units.

(Prior Art) Generally, this type of air conditioner includes one equipped with a heat pump type refrigeration cycle as shown in FIG.

In FIG. 7, A is an outdoor unit, B is a branch unit, and C, D, and E are indoor units. The outdoor unit A is equipped with two variable capacity compressors 1 and 2.
are connected in parallel via check valves 3 and 4, respectively.

A parallel body of a compressor 1°2, a four-way valve 5, an outdoor heat exchanger 6, a heating expansion valve 7 and a cooling cycle forming check valve 8,
Liquid tank 9, electric flow rate adjustment valve 11, 21, 31
, a parallel body of cooling expansion valves 12, 22.32 and heating cycle forming check valves 13.23.33, indoor heat exchanger 14.
24.34, Gas side on-off valve (electromagnetic on-off valve) 15.25.
35, the accumulator 10, etc. are successively connected to form a heat pump type refrigeration cycle.

Note that each of the cooling expansion valves 12, 22, and 32 has a temperature-sensing tube 12a, 22a, and 32a, and these temperature-sensing tubes are attached to the gas side refrigerant pipes of the indoor heat exchangers 14, 24, and 34, respectively. There is.

That is, the indoor heat exchangers 14, 24, and 34 are configured in parallel, and during cooling operation, the refrigerant flows in the direction of the solid arrow in the figure to form a cooling cycle, and during heating operation, the four-way valve 5
The switching operation causes the refrigerant to flow in the direction of the dotted arrow in the figure to form a heating cycle.

In such an air conditioner, the required capacity of each indoor unit must be satisfied (in addition to controlling the number and capacity of the compressors 1.2 in operation, the flow rate control valves 11, 21, 31
The opening degree of each is controlled to adjust the flow rate of refrigerant to each indoor heat exchanger.

The expansion valves 12, 22, and 32 maintain the refrigerant superheat degree in each indoor heat exchanger constant regardless of changes in the refrigerant flow rate, thereby ensuring stable and efficient operation.

Therefore, for example, when the required capacity of each indoor unit increases during cooling operation, the capacity of the compressor 1 increases,
Furthermore, in addition to compressor 1, compressor 2 is also activated. If the required capacity of each indoor unit decreases from this state, the capacity of compressor 2 may decrease, or even the capacity of compressor 2 may decrease.
The operation of the compressor 1 is stopped and only the compressor 1 is operated.

However, in such an air conditioner, the amount of oil discharged from the compressor 1.2 and the amount of oil returned do not match completely;
As time passes, the amount of lubricating oil in one compressor increases,
The amount of lubricating oil in the other compressor decreases, creating an imbalance in the amount of oil between the two, making stable operation difficult.

Moreover, if the lubricating oil level drops below the limit oil level (operable level), the supply of lubricating oil to the lubricating parts will be cut off, and compressor 1.2 will be damaged. .

Therefore, in order to eliminate the imbalance in the amount of oil in each compressor 1 and 2, an oil equalizing pipe is used to communicate between each compressor 1 and 2, and the lubricating oil is moved from the side with more oil to the side with less oil. There is something I did.

However, since the capacity of each compressor 1.2 is not completely the same, the pressure loss of the suction pipe of the compressor with a relatively larger capacity is large, and the pressure inside the compressor case is conversely reduced. This tendency is remarkable when the capacity of each compressor 1.2 is different.

As a result, the refrigerant gas moves from the compressor on the side where the case internal pressure is high to the compressor on the side where the case internal pressure is low through the oil equalizing pipe, and the lubricating oil also moves in the same direction.

When the amount of oil returned in the compressor on the side where the case internal pressure is higher is greater than the oil discharge amount, the lubricating oil above the level of the oil equalizing pipe moves through the oil equalizing pipe to the compressor on the side where the case internal pressure is lower, and each compression The oil level inside the machine becomes equal at the oil equalization pipe position. Conversely, when the amount of returned oil is smaller than the amount of oil discharged, the oil level in the compressor on the side where the case internal pressure is higher decreases over time and eventually falls below the critical oil level. In this case, the lubricating oil in the compressor on the side with lower case internal pressure is
Movement of the side with higher pressure inside the case to the compressor is prevented.

Therefore, it is possible to equalize the oil level in each compressor 1, 2 and equalize the pressure inside the case of each compressor 1, 2 by increasing the diameter of the oil equalizing pipe. ing.

However, when a large-diameter oil equalizing pipe is used, vibrations generated in one compressor are easily transmitted to the other compressor via the oil equalizing pipe, and depending on the combination of operating frequency ranges of recompressors 1 and 2, resonance may occur. This causes problems such as compressor vibration and compressor noise, and there is also the risk of damage to the oil equalizing pipe.

(Problem to be Solved by the Invention) When the compressors 1 and 2 are communicated with each other by an oil equalizing pipe, due to the pressure difference in the case of each compressor 1.2, the compressor with the higher pressure in the case The lubricating oil in the case moves to the compressor with lower case internal pressure through the oil equalizing pipe, and each compressor 1.2
There is a problem that the oil level in the case of the compressors 1 and 2 becomes uneven, and the oil level in each compressor 1.2 is made uniform by using a large diameter oil equalizing pipe, and the pressure in the case of each compressor 1 and 2 is improved. If you try to equalize the pressure, the vibrations generated in one compressor will be transmitted to the other compressor through the oil equalizing pipe, resulting in poor quality.
Depending on the combination of operating frequency ranges of the recompressors 1 and 2, resonance etc. may occur, leading to problems such as compressor vibration and compressor noise, and there is also a risk of damage to the oil equalizing pipe.

This invention was made in view of the above circumstances,
The purpose of this is to achieve an oil equalizing effect between each compressor without using large diameter oil equalizing pipes, avoid compressor vibration and compressor noise, and ensure sufficient strength of the oil equalizing pipes. It is an object of the present invention to provide an air conditioner that can improve reliability and further improve oil equalization effect.

[Structure of the invention]

(Means for solving the problem) In addition to providing an oil equalizing pipe between each compressor, a first
and a second driving state in which the recompressor is driven with a predetermined frequency difference between the operating frequencies of the recompressor. The first recompressor is driven at substantially the same operating frequency, and then the operating frequency of one of the recompressors is raised or lowered by a fixed period of time relative to the other, and the operating frequency of the other is maintained at a constant operating frequency. A second oil equalizing operation means is provided for performing the first oil equalizing operation with the oil equalizing operation means and the recompressor replaced.

(Function) During simultaneous operation of the recompressors, a first driving state in which the recompressors are driven at substantially the same operating frequency and a second driving state in which the recompressors are driven with a predetermined frequency difference between the operating frequencies of the recompressors. By controlling the drive states in combination with the above two, the resolution of the overall capacity of the recompressor is increased, and during oil equalization operation, the recompressor is first driven at approximately the same operating frequency, and then the recompressor is driven at approximately the same operating frequency. By increasing or decreasing the operating frequency of one of the two for a fixed period of time relative to the other, and maintaining the operating frequency of the other at a constant operating frequency, the recompressor can be kept in the second operating state. Prevents oil equalization operation from starting,
Furthermore, the first oil equalizing operation and the second oil equalizing operation are repeated at regular intervals, and during the first and second oil equalizing operations, the operating frequency of the recompressor is relatively raised or lowered, and the recompressor compresses By efficiently distributing the lubricating oil inside the machine case through the oil equalizing pipe, we can achieve an oil equalizing effect between each compressor without using large diameter oil equalizing pipes, and also avoid compressor vibration and compressor noise. This is what I did.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 to 6. 1 to 6 that are the same as those in FIG. 7 are designated by the same reference numerals, and their explanations will be omitted.

As shown in FIG. 1, an oil separator 41 is provided on the refrigerant discharge side piping of the compressor 1, and an oil bypass pipe 42 is provided from the oil separator 41 to the refrigerant suction side piping of the compressor 1.

Further, an oil separator 43 is provided on the refrigerant discharge side piping of the compressor 2, and an oil bypass pipe 44 is provided from the oil separator 43 to the refrigerant suction side piping of the compressor 2.

Further, as shown in FIG. 2, the cases of the compressors 1.2 are communicated with each other through oil equalizing pipes 45. In this case, the compressors 1.2 are installed on the same plane. In addition, the optimal reference oil level and the minimum allowable limit oil level for the lubricating oil stored in the case of the compressor 1.2 are predetermined, and the position at approximately the same height as the reference oil level is determined in advance. Attach oil equalizing pipe 45 to.

On the other hand, FIG. 3 shows a control circuit for the refrigeration cycle. In FIG. 3, 50 is an outdoor control section attached to the outdoor unit A. This outdoor control section 50 is composed of a microcomputer and its peripheral circuits, and is connected to inverter circuits 51 and 52 externally. Inverter circuit 5
1.52 rectifies the voltage of the AC power supply 53, converts it into an AC voltage of a predetermined frequency by switching according to a command from the outdoor control unit 50, and drives the compressor motor IM.

There is also one that supplies each of the 2M as driving power.

Further, 60 is a multi-control unit attached to the branch unit B. This multi-control unit 60 consists of a microcomputer and its peripheral circuits, and externally includes flow rate regulating valves 11.
21.31 and on-off valves 15.25.35 are connected, respectively.

Furthermore, 70, 80.90 are indoor control units attached to the indoor units C9D and H, respectively.

These indoor control units 70, 80, and 90 consist of a microcomputer and its peripheral circuits, and are externally connected to the operation unit 7.
1,81.91 and indoor temperature sensor 72.82.92
are connected to each other.

Each indoor control unit 70, 80, 90 receives a frequency setting signal f1. f2. Multi-control unit 60 with f3 as required capacity
It is designed to be transferred to The multi-control unit 60 controls each indoor unit C, D,
The total required capacity of H is determined, and the corresponding frequency setting signal fo is transferred to the outdoor control section 50.

Next, the operation of the above configuration will be explained.

It is assumed that all indoor units are currently performing cooling operation.

At this time, the indoor control section 70 of the indoor unit C calculates the difference between the temperature detected by the indoor temperature sensor 72 and the set temperature determined by the operation operation section 71, and outputs a frequency setting signal f corresponding to the temperature difference. It is transferred to the multi-control unit 60 as the required cooling capacity. Similarly, the indoor control sections 8 of indoor units D and E
0.90 is also the frequency setting signal f2. f3 is transferred to the multi-control unit 60 as the required cooling capacity.

Furthermore, the multi-control unit 60 controls each indoor unit C and D based on the frequency setting fd number transferred.

Find the total required cooling capacity of E. Then, the frequency setting signal fo corresponding to the calculated sum is transferred to the outdoor control section 50. In this outdoor control section 50, the frequency setting signal f is transferred. The total required cooling capacity of each indoor unit c, D, and H is determined based on the total required cooling capacity, and compressor 1.2 is
Number of operating units and operating frequency (inverter circuit 51.5
2 output frequency) F is controlled. In this case, in the outdoor control unit 50, as the total required cooling capacity increases, the compression I
The operation is to shift from operating one compressor 1.1 to operating two compressors 1.2.

Furthermore, while the compressor 1 is operating, most of the lubricating oil contained in the discharged refrigerant is recovered by the oil separator 41 and returned to the compressor 1 through the oil bypass pipe 42. Similarly, during operation of the compressor 2, most of the lubricating oil contained in the discharged refrigerant is recovered by the oil separator 43 and returned to the compressor 2 through the oil bypass pipe 44. Note that the refrigerant that is not recovered goes through the refrigeration cycle and returns to the compressor 1.2.

On the other hand, in the multi-control unit 60, each indoor unit C1D, E
The refrigerant flow is adjusted according to the frequency setting signal from the regulating valve 11.2.
It controls the opening degree of 1.31, and each indoor unit C, D
, H flows into each indoor heat exchanger 14, 24°34. In addition, expansion valve 1
According to 2.22.32, each indoor heat exchanger 14, 24.3
The degree of superheating of the refrigerant in No. 4 is controlled to be constant.

In addition, in the outdoor control unit 50, while the two compressors 1 and 2 are in operation,
A first driving state in which the recompressors 1 and 2 are driven at substantially the same operating frequency, and a second driving state in which the recompressors 1 and 2 are driven with a predetermined frequency difference between the operating frequencies. In combination, the overall capacity of recompressor 1.2 is controlled. for example,
Now, the operating frequency Fa of one compressor 1 is Fa, ), and the operating frequency Fb of the other compressor 2 is FbO (FaO-Fb(
Assuming that each of the indoor units C and D is driven in the state of 1) (first drive state), each of the indoor units C and D is in this state.

When the total required capacity from the E side increases, first, the operating frequency Fa of the compressor 1 is increased to Fa□+ΔF, and the operating frequency Fb of the compressor 2 is maintained at Fbo while being driven ( second driving state). Next, after driving in this state for a predetermined time, the operating frequency Fb of the compressor 2 is increased to Fbo+ΔF, the operating frequency Fa of the compressor 1 is increased to FaO+ΔF, and the operating frequency Fb of the compressor 2 is increased to Fb,+ΔF.
Drive at F for a predetermined time (first drive state). Furthermore, the operating frequency Fa of the compressor 1 is similarly increased to Fa(1+2ΔF, and the operating frequency Fb of the compressor 2 is increased to Fbo
The operating frequency Fb of the compressor 2 is then set to Fbo+.
2ΔF, and the operating frequency Fa of compressor 1 becomes Fa□
+2ΔF, the operating frequency Fb of compressor 2 is FbO+2Δ
Drive at F for a predetermined time (first drive state). Then, while repeating the first drive state and the second drive state alternately in this way, the recompressor 1.2 is integrated until the state corresponds to the total required capacity from each indoor unit C, D, and E side. Control abilities.

Therefore, in this case, the operating frequency Fa of the recompressor 1.2 is changed when the overall capacity of the recompressor 1.2 is changed.

Compared to increasing and decreasing Fb at the same time, it is possible to improve the resolution of the total capacity of the recompressor 1゜2, so it is possible to increase or decrease Fb in detail in response to changes in the total required capacity from each indoor unit C, D, and E side. The overall capacity of the recompressors 1.2 can be controlled, and the operating efficiency and comfort of the recompressors 1, 2 can be improved.

In addition, in the outdoor control unit 50, while the two compressors 1 and 2 are in operation,
An oil equalization operation is performed to equalize the amount of lubricating oil in the compressor cases of the recompressors 1 and 2.

The oil equalizing operation of the compressor 1.2 will be explained with reference to FIGS. 4 to 6. Figure 4 shows how the operating frequency F'a of one compressor 1 changes during oil equalization operation (indicated by a solid line in the figure) and how the operating frequency Fb of the other compressor 2 changes (
(indicated by dotted lines in the same figure).

Now, the compressors 1 and 2 are driven in a normal operating state (a state in which the first driving state and the second driving state are alternately repeated), and the recompressor 1.2 is operating in the second driving state. Suppose that For example, as shown in FIG. 4, the operating frequency Fa of the compressor 1 is set to Fal, and the operating frequency Fb of the compressor 2 is set to Fbo (
Fa□#FbO.

Fal-FaO+ΔF>Fbo).

When a certain period of time T has elapsed in this state, a first oil equalization operation is performed.

During this first oil equalization operation, the operating frequency Fa of the compressor 1 is first lowered from Fal to Fao, and the recompressor 1.2 is operated at approximately the same operating frequency (the operating frequency Fa of the compressor 1 is reduced to Fao).
o, the compressor 2 is driven at the operating frequency Fb (Fbo) for a predetermined period of time. Thereafter, the operating frequency Fa of one compressor 1 is lowered by n steps. In this case, the operating frequency Fb of the other compressor 2 is maintained at Fbo.

Therefore, in this case, the operating frequency F a of the compressor 1
2 is lower than the operating frequency Fbo of the compressor 2,
Since the pressure Pa in the case of the compressor 1 becomes higher than the pressure Pb in the case of the compressor 2, the lubricating oil in the case of the compressor 1 on the high pressure side passes through the oil equalizing pipe 45 together with the refrigerant and gradually compresses it on the low pressure side. The oil flows into the case of the compressor 2, and as shown in FIG. 5, the oil level in the case of the compressor 1 gradually decreases, and the oil level in the case of the compressor 2 gradually rises. Note that the lower limit level of the oil level in the case of the compressor 1 in this case is up to the lower surface position of the oil equalizing pipe 45.

Moreover, when time t1 elapses with the operating frequency Fa of the compressor 1 being lowered to Fa2, the operating frequency Fa of the compressor 1 is increased by n steps from Fao at this point.

In this case, the operating frequency Fb of the compressor 2 is maintained at Fbo.

Therefore, in this case, the operating frequency Fa3 of the compressor 1 is higher than the operating frequency Fbo of the compressor 2, and the pressure Pa in the case of the compressor 1 is lower than the pressure Pb in the case of the compressor 2. Therefore, the lubricating oil in the case of the compressor 2 on the high pressure side gradually flows into the case of the compressor 1 on the low pressure side through the oil equalizing pipe 45 together with the refrigerant, and as shown in FIG. The oil level inside the case of the compressor 1 gradually decreases, and the oil level inside the case of the compressor 1 gradually rises.

Furthermore, after 12 hours have passed with the operating frequency Fa of the compressor 1 raised to Fa3, the first oil equalization operation is completed at this point, and the operating frequency Fa of the compressor 1 is returned to Fal to return to the normal operating state. Return to Therefore, in the normal operating range after the first oil equalization operation, the compressor 2
The oil level inside the case of the compressor 1 is maintained at a higher level than the curved surface inside the case. Then, after a certain period of time T has elapsed in this normal operating state, oil equalization operation is performed with the recompressors 1 and 2 replaced (second oil equalization operation).

During this second oil equalization operation, the operating frequency of the compressor 1 is 9 at the beginning.
Recompressor 1 by lowering F, a from Fal to F, a, 0
, 2 are approximately the same operating frequency (operating frequency Fa of compressor 1
is driven for a predetermined time at the operating frequency Fb of the compressor 2 (Fbo). Thereafter, the operating frequency Fb of the compressor 2 is lowered by n steps. In this case, the operating frequency Fa of the compressor 1 is maintained at FaO. Therefore, in this case, the operating frequency Fb2 of the compressor 2 is lower than the operating frequency Fa(,) of the compressor 1, and the pressure pb in the case of the compressor 2 is the pressure P
a, the lubricating oil in the case of the compressor 2 on the high pressure side gradually flows into the case of the compressor 1 on the low pressure side through the oil equalizing pipe 45 together with the refrigerant, and as shown in FIG. As the oil level in case 2 gradually decreases,
The oil level in the case of the compressor 1 gradually rises.

Moreover, when time t1 elapses with the operating frequency Fb of the compressor 2 being lowered to Fb2, the operating frequency Fb of the compressor 2 is increased by n steps from Fbo at this point.

In this case, the operating frequency Fa of the compressor 1 is maintained at Fao.

Therefore, in this case, the operating frequency Fb of the compressor 2 is higher than the operating frequency FaO of the compressor 1, and the pressure pb in the case of the compressor 2 is lower than the pressure Pa in the case of the compressor Ill. Therefore, the lubricating oil in the case of the compressor 1 on the high pressure side gradually flows into the case of the compressor 2 on the low pressure side through the oil equalizing pipe 45 together with the refrigerant, and as shown in FIG. The oil level in the case of the compressor 2 gradually decreases, and the oil level in the case of the compressor 2 gradually rises.

Furthermore, when time t2 elapses with the operating frequency Fb of the compressor 2 raised to Fb3, at this point the operating frequency Fb of the compressor 2 is Fbo, and the operating frequency Fa of the compressor 1 is Fbo.
Al, and return to normal operation. Therefore, this second
In the normal operating range after the end of the oil equalization operation, the oil level inside the case of the compressor 2 is maintained in a higher state than the curved surface inside the case of the compressor 1, as shown in FIG. Thereafter, the normal operation and the first oil equalizing operation or the second oil equalizing operation are alternately repeated at regular intervals.

Thus, in the case of the above configuration, the compressor is
During unit operation, the operating frequency Fa of one of the recompressors 1. A first oil equalizing operation in which Fb is maintained at a constant operating frequency Fbo and a second oil equalizing operation in which the first oil equalizing operation is performed with the recompressor 1.2 replaced are alternately repeated at regular intervals. Since the oil leveling operation is performed, the oil level state of the compressor 1.2 in the normal operating range after the first oil leveling operation and the compressor 1 in the normal operating range after the second oil leveling operation are different. , 2, the oil level can be alternately changed between high and low levels. Therefore, even during long-term operation, it is possible to prevent the oil level of compressors 1.2 from being extremely biased to one side, and it is possible to equalize the oil level of compressors 1.2. .

Therefore, stable operation is possible at all times, oil leakage and locking of the compressor 1.2 can be prevented, and damage to the compressor 1.2 can be prevented.

Furthermore, there is no need for a large-diameter oil equalizing pipe 45;
Since a small-diameter one can be used, sufficient strength can be ensured, compressor vibration and compressor noise can be suppressed, and it is also advantageous in terms of cost.

In addition, there is no need to install costly float type regulators, oil level sensors, etc. in the compressors 1 and 2 (because oil leveling effects can be obtained, the overall configuration can be simplified and costs can be reduced). can be achieved.

Furthermore, during oil equalization operation of the compressors 1 and 2, the frequency is lowered by n steps from the operating frequency FaO (or Fbo) during normal operation, and the operating frequency Fao (or Fbo) during normal operation is lowered by n steps.
Since the operation of increasing the frequency by n steps from the operating frequency Fao (or Fbo) during normal operation is performed alternately, the inverter circuit 51 (or 52) This inverter circuit 5
Even if the current release that reduces the output frequency of 1 (or 52) by a certain value operates and oil equalization operation when the frequency increases becomes impossible, the operating frequency Fa□ during normal operation
(or Fbo), it is possible to reliably perform oil equalization operation when the frequency is lowered by n steps than Fbo. Therefore, an oil equalizing effect can be obtained by performing oil equalizing operation at least once within one hour.

Further, both compressors 1 and 2 have an operating frequency Fa.

Even when Fb reaches the maximum value, oil equalization operation can be reliably performed when the frequency is lowered by n steps than the operating frequency Fao (or Fbo) during normal operation, so at least one Oil equalization effect can be obtained by performing oil equalization operation twice.

Furthermore, both compressors 1 and 2 have an operating frequency Fa.

Even when Fb reaches the minimum value, oil equalization operation can be reliably performed when the frequency is increased by n steps from the operating frequency Fao (or Fbo) during normal operation, so at least 1 Oil equalization effect can be obtained by performing oil equalization operation twice.

Also, during the simultaneous operation of the recompressor 1.2, the first
Since the driving state of the recompressors 1.2 and the second driving state of driving with a predetermined frequency difference ΔF between the operating frequencies of the recompressors 1.2 are controlled in combination, the recompressors 1. 2
The resolution of the overall capacity can be increased.

Furthermore, during the oil equalization operation, the recompressors 1 and 2 are operated at substantially the same operating frequency (Fa) before starting the oil equalization operation.

ζFbo) and then started the oil equalization operation of recompressors 1 and 2, so that recompressors 1 and 2
It is possible to prevent the oil equalization operation from starting while the engine is still in the driving state. Therefore, the oil equalization operation is started while the recompressor 1.2 remains in the second driving state, and the difference ΔF in the operating frequency of the recompressor 1.2 during the oil equalization operation becomes uneven. Recompressor 1.
Even if the oil equalizing operation is started while the oil pump 2 remains in the second driving state, a uniform oil equalizing effect can be obtained.

Note that this invention is not limited to the above embodiments. For example, in the above embodiment, the case where there are three indoor units has been described, but it is also possible to implement the case with more or two indoor units.

Furthermore, it goes without saying that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] According to the present invention, an oil equalizing pipe is provided between each compressor, and during simultaneous operation of the recompressors, the first driving state and the recompressor are driven at substantially the same operating frequency. A means for controlling the overall capacity of the recompressor by combining a second driving state in which the recompressor is driven with a predetermined frequency difference between the operating frequencies of the recompressor. the first recompressor, and then increases or decreases the operating frequency of one of the recompressors relative to the other in fixed time increments, and maintains the operating frequency of the other at a constant operating frequency; Since a second oil equalizing operation means is provided to perform the first oil equalizing operation when the compressor is replaced, it is possible to obtain an oil equalizing effect between each compressor without using a large diameter oil equalizing pipe. ,
Compressor vibration and compressor noise can be avoided, and reliability can be increased by ensuring sufficient strength of the oil equalizing pipe, and in addition, the oil equalizing effect can be further improved.

[Brief explanation of the drawing]

1 to 6 show an embodiment of the present invention,
Figure 1 is an overall schematic diagram showing the refrigeration cycle in the air conditioner, Figure 2 is a schematic diagram showing the relationship between each compressor and oil equalizing pipes, and Figure 3 is a schematic diagram showing the configuration of the refrigeration cycle control circuit. The configuration diagram, Figure 4 is a characteristic diagram showing how the operating frequency changes during oil equalization operation, and Figure 5 shows the oil change when the operating frequency of the first compressor is lower than the operating frequency of the second compressor. A schematic configuration diagram showing a state of surface change. FIG. 6 is a schematic configuration diagram showing a state of curved surface change when the operating frequency of the first compressor is higher than the operating frequency of the second compressor. FIG. 1 is an overall schematic configuration diagram showing a refrigeration cycle in an air conditioner. A...Outdoor unit, B...Branch unit, C, D
. E... Indoor unit, 1, 2... Variable capacity compressor,
45... Oil equalizing pipe, 50... Outdoor control section, 60...
Multi-control unit, 70, 80.90...Indoor control unit. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Time - Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In an air conditioner comprising an outdoor unit having two variable capacity compressors and a plurality of indoor units, the number of operating units and operating frequency of each compressor is controlled according to the required capacity of these indoor units. An oil equalizing pipe provided between the machines and a predetermined frequency difference between a first driving state in which both compressors are driven at substantially the same operating frequency and the operating frequencies of both compressors during simultaneous operation of both compressors. means for controlling the overall capacity of both compressors by combining a second driving state in which the two compressors are driven at substantially the same operating frequency; a first oil-equalizing operation means for raising and lowering the operating frequency of one of the compressors by a fixed amount of time relative to the other, and maintaining the operating frequency of the other compressor at a fixed operating frequency; and a second oil equalizing operation means that performs the first oil equalizing operation in a replaced state.