JPH01203678A - 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 performing oil equalizing operation which relatively up-down controls an operating frequency of both the compressors during their simultaneous operation. CONSTITUTION:An oil equalizer pipe 45 is provided between compressors 1, 2. Normal operation drives both the compressors by an almost equal operating frequency. The first oil equalizing operation relatively up-down controls by every fixed time an operating frequency of one of both the compressors as compared with the other frequency while holds an operating frequency of the other compressor to a fixed operating frequency. The second oil equalizing operation performs the first oil equalizing operation in a condition that both the compressors are replaced with each other. An oil equalizing operation means, which repeatedly performs in every fixed period the normal operation, first oil equalizing operation and the second oil equalizing operation during simultaneous operation of both the compressors 1, 2, is provided.

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 1.2.
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 a cooling expansion valve 12, 22.32 and a heating cycle forming check valve 13, 23.33, an 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.

The cooling expansion valves 12, 22.32 each have a temperature sensing tube 12a, 22a, 32a, and these temperature sensing tubes are connected to the gas side refrigerant piping of the indoor heat exchanger 14, 24.34, respectively. We are adding more.

That is, the indoor heat exchanger ``rA14.24.34'' is arranged in parallel, and during cooling operation, the refrigerant flows in the direction of the solid arrow shown in the figure to form a cooling cycle, and during heating operation, the switching operation of the four-way valve 5 causes the refrigerant to flow in the direction shown in the figure. A heating cycle is created by flowing refrigerant in the direction of the dotted arrow.

In such an air conditioner, in order to satisfy the required capacity of each indoor unit, the number and capacity of compressors 1.2 in operation are controlled, and the flow rate control valves 11, 21, 31 are controlled.
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 degree of superheating of the refrigerant 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. From this state, the required capacity of each indoor unit becomes small (as a result, the capacity of compressor 2 decreases, or even compressor 2
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 completely match, so
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.

Furthermore, if the lubricating oil level falls below the limit oil level (operable level), the supply of lubricating oil to the lubricating section is cut off, resulting in damage to the compressor 1.2.

Therefore, in order to eliminate the imbalance in the amount of oil in each compressor 1.2, we communicated each compressor 1.2 with an oil equalizing pipe and moved the lubricating part from the side with more oil amount to the one with less oil amount. There is something I did.

However, since the capacities of the compressors 1 and 2 are not completely the same, the pressure loss in the suction pipe of the compressor with relatively greater 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. The oil level in the compressor becomes equal at the oil equalizing pipe position. Conversely, when the amount of returned oil is less 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 level. In this case, the lubricating part in the compressor on the side where the case internal pressure is low is prevented from moving to the compressor on the side where the case internal pressure is high due to the difference in the case internal pressure of each compressor.

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 the operating frequency ranges of the side compressors 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 is The lubricating oil in the case moves to the compressor with lower 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 more likely to be transmitted to the other compressor via the oil equalizing pipe.
Depending on the combination of the operating frequency ranges of the side compressors 1 and 2, resonance etc. may occur, causing 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, thereby avoiding compressor vibration and compressor noise, and to maintain sufficient strength of the oil equalizing pipes. Our goal is to provide an air conditioner with excellent reliability that can ensure the following.

[Structure of the invention] (Means for solving the problem) In addition to providing an oil equalizing pipe between each compressor, normal operation and side compression are performed in which the side compressors are driven at substantially the same operating frequency during simultaneous operation of the side compressors. The first oil equalization operation involves increasing or decreasing 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 at a constant operating frequency. The oil equalizing operation means is provided for repeating the first oil equalizing operation and the second oil equalizing operation at regular intervals.

(Function) During simultaneous operation of the side compressor, normal operation, first oil equalization operation, and second oil equalization operation are repeated at regular intervals, and during the first and second oil equalization operation, the side compressor is operated. By relatively raising and lowering the frequency and efficiently distributing the lubricating oil in the compressor case of the side compressor through the oil equalizing pipe, it is possible to obtain an oil equalizing effect between each compressor without using a large diameter oil equalizing pipe. This is designed to avoid compressor vibration and compressor noise.

(Example) The same parts as in FIG. S are given the same reference numerals, and the explanation thereof 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, compressor 1.2 is installed in the same way. 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.

2M respectively as driving power.

Further, 60 is a multi-control unit 60 attached to the branch unit B. This multi-control unit 60 is made up of a microcomputer and its peripheral circuits, and has an external flow rate of J! J
Control valve 11, 21.31 and one-open/close valve 15.25.35
are connected to each other.

Furthermore, 70, 80.90 are indoor control units attached to the indoor units C2D and H, respectively.

These indoor control units 70, 80, and 90 consist of a microcomputer and its peripheral circuits, and an external 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 from the transferred frequency setting signal.
, H is calculated, and the corresponding frequency setting signal f is determined. 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 H
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, D) based on the transferred frequency setting signal.

Find the total required cooling capacity of E. Then, a frequency setting signal f corresponding to the calculated sum. is transferred to the outdoor control section 50. This outdoor control unit 50 calculates the total required cooling capacity of each indoor unit C, D, and H based on the frequency setting signal f that is transferred, and depending on the total, the compressor 1.
Number of operating units and operating frequency (inverter circuit 51.5
2 output frequency) F is controlled. In this case, the outdoor control unit 50 shifts from operating one compressor 1 to operating two compressors 1 and 2 as the total required cooling capacity increases.

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
Refrigerant flow regulating valve 11.2 according to the frequency setting signal from
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
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,
In a normal operation in which the recompressors 1 and 2 are driven at approximately the same operating frequency, one of the recompressors 1 and 2, for example, the operating frequency Fa of the compressor 1 is relatively compared to the operating frequency Fb of the compressor 2. A first oil equalizing operation is performed in which the operating frequency Fb of the compressor 2 is maintained at a constant operating frequency Fbo, and a first oil equalizing operation is performed with the recompressors 1 and 2 replaced. An oil equalizing operation is performed in which the second oil equalizing operation is repeated alternately at regular intervals.

The oil equalizing operation of the compressors 1 and 2 will be explained with reference to FIGS. 4 to 6. Figure 4 shows how the operating frequency Fa of one compressor 1 changes during oil equalization operation (indicated by a solid line in the figure).
and the state of change in the operating frequency Fb of the other compressor 2 (indicated by a dotted line in the figure), respectively.

Now, for example, the operating frequency Fa of compressors 1 and 2.

They are respectively driven in a normal operating state in which Fb is set to substantially the same state (Fao=pbo), and when a certain period of time T has elapsed in this normal operating state, a first oil equalizing operation is performed.

During this first oil equalization operation, first, 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 Fa1 of the compressor 1 is lower than the operating frequency Fbo of the compressor 2, and the pressure Pa in the case of the compressor 1 is higher than the pressure Pb in the case of the compressor 2. 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. 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.

Further, when [1 hour has elapsed with the operating frequency Fa of the compressor 1 being decreased to Fa, 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 Fa2 of compressor 1 is higher than the operating frequency Fbo of compressor 2, and the pressure Pa in the case of compressor 1 is lower than the pressure Pb in the case of 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 in the case of the compressor 1 gradually decreases, and the oil level in the case of the compressor 1 gradually rises.

Furthermore, when time t2 has elapsed with the operating frequency Fa of the compressor 1 raised to Fa2, the first oil equalization operation is completed at this point, and the operating frequency Fa of the compressor 1 is returned to FaO to return to the normal operating state. Return to Therefore, in the normal operation region (II) after the first oil equalization operation, the oil level in the case of compressor 1 rose compared to the oil level in the case of compressor 2, as shown in Figure 6. maintained in the state. Then, after a certain period of time T has elapsed in this normal operating state, a second oil equalizing operation is performed.

During this second oil equalization operation, first, 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 as Fa (. Therefore, in this case, the operating frequency Fa of the compressor 2 is Fb
l is lower than the operating frequency Fao of the compressor 1,
Since the pressure Pb inside the case of the compressor 2 becomes higher than the pressure Pa inside the case of the compressor 1, the lubricating oil inside the case of the compressor 2 on the high pressure side passes through the oil equalizing pipe 45 together with the refrigerant and gradually compresses the low pressure side. The oil flows into the case of the compressor 1, and as shown in FIG. 6, the oil level in the case of the compressor 2 gradually decreases, and the oil level in the case of the compressor 1 gradually rises.

Further, when time t1 has elapsed with the operating frequency Fb of the compressor 2 being lowered to Fbl, the operating frequency Fb of the compressor 2 is increased from Fbo by n steps of frequency 4 at this point. In this case, the operating frequency Fa of the compressor 1 is maintained at Fa□.

Therefore, in this case, the operating frequency Fb2 of compressor 2 is higher than the operating frequency Fao of compressor 1, and the pressure pb in the case of compressor 2 is lower than the pressure Pa in the case of compressor 1. 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 the operating frequency Fb of the compressor 2 is raised to Fb2 for a period of t2, the operating frequency Fb of the compressor 2 is returned to Fbo at this point, and the normal operating state is returned. Therefore, the normal operation area (1
), the oil level inside the case of the compressor 2 is maintained at a higher level than the curved surface inside the case of the compressor 1, as shown in FIG.

Thereafter, the normal operation and the first oil-leveling operation or the second oil-equalizing operation are alternately repeated at regular intervals.

Thus, in the case of the configuration described in "-", during the operation of the two compressors 1 and 2, during normal operation in which the recompressors 1 and 2 are driven at substantially the same operating frequency, and when the recompressors 1 and 2 are operated at approximately the same operating frequency, A first system that increases or decreases the operating frequency Fa of one compressor 1 relative to the operating frequency Fb of the compressor 2 by a certain period of time, and maintains the operating frequency Fb of the compressor 2 at a constant operating frequency Fb□ during that time. The first oil equalizing operation is repeated at regular intervals, and the first oil equalizing operation is performed with the recompressor 1.2 replaced. Compressor 1 in normal operation region (II) after completion of oil equalization operation
．． The height of the oil level can be alternately changed between the oil level state of the compressor 1.2 and the oil level state of the compressor 1.2 in the normal operation region (4') after the end of the second oil equalization operation.

Therefore, even during long-term operation, it is possible to prevent the oil level of the compressors 1 and 2 from being extremely biased to one side, and it is possible to equalize the oil level of the compressors 1 and 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 avoided, and it is also advantageous in terms of cost.

In addition, it is possible to obtain an oil equalization effect without installing a costly float type regulator, oil level sensor, etc. in the compressor 1.2, so the overall configuration can be simplified and the cost can be reduced. It is possible to reduce the

Furthermore, during oil equalization operation of compressor 1.2, the frequency is lowered by n steps than the operating frequency Fag (or Fb,) during normal operation, and the operating frequency Fa□ during normal operation.
(or Fbo), the frequency is increased by n steps.
When increasing the step frequency, an abnormality in the output current of the inverter circuit 51 (or 52) is determined, and a current release is activated to reduce the output frequency of the inverter circuit 51 (or 52) by a certain value, resulting in oil equalization operation when the frequency increases. Even if the operating frequency Fao becomes unavailable 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 its maximum value, oil equalization operation can be reliably performed when the frequency is lowered by n steps than the operating frequency Fa□ (or Fbo) during normal operation. The oil equalizing effect can be obtained by performing one oil equalizing operation.

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

Even if 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.

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.

[Effect of the invention] According to this invention, an oil equalizing pipe is provided between each compressor, and during simultaneous operation of both compressors, normal operation in which both compressors are driven at approximately the same operating frequency, and First oil equalization operation in which the operating frequency of one is increased or decreased by a fixed amount of time relative to the other and the other operating frequency is maintained at a constant operating frequency, and the first oil equalization operation is performed with both compressors replaced. Since we have provided an oil equalizing operation means that repeats the second oil equalizing operation at regular intervals, it is possible to obtain an oil equalizing effect between each compressor without using a large diameter oil equalizing pipe, and this allows the compression Machine vibration and compressor noise can be avoided, and sufficient strength of the oil equalizing pipe can be ensured, leading to improved reliability.

[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. FIG. 6 is a schematic configuration diagram showing the oil level change state when the operating frequency of the first compressor is higher than the operating frequency of the second compressor, and FIG. 7 is a schematic configuration diagram showing the oil level change state. FIG. 1 is an overall schematic configuration diagram showing a refrigeration cycle in a conventional 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

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. During simultaneous operation of the oil equalizing pipe provided between the machines and both compressors, normal operation in which both compressors are driven at approximately the same operating frequency, and the operating frequency of one of the compressors compared to the other. A first oil equalizing operation in which the operating frequency of the other compressor is maintained at a constant operating frequency by increasing and decreasing the operating frequency for a certain period of time, and a second oil equalizing operation in which the first oil equalizing operation is performed with both compressors replaced. An air conditioner characterized by comprising an oil equalizing operation means that repeats oil operation at regular intervals.