JPH01127864A - Air conditioner - Google Patents

Abstract

PURPOSE: To secure oil equalizing effect among compressors by reducing by a same value output frequency of another inverter circuit when output frequency by inverter protective means is reduced during oil equalizing operation where a predetermined difference is provided among the output frequencies of the inverter circuits upon operation of two compressors. CONSTITUTION: In an oil equalizing operation mode, operation frequency of a compressor 1 is raised from a predetermined value while operation frequency of a compressor 2 is lowered from a predetermined value to provide a predetermined difference between the operation frequencies. When the operation frequency of the compressor 1 is higher than that of the compressor 2, case pressure of the compressor 1 is lower than that of the compressor 2, and freezer oil of the compressor 2 facilitated to flow to the compressor 1 through an oil equalizing pipe 40. Herein, an outdoor control section 50 monitors output current through the inverter circuits 51, 52 with current detectors 55, 56, and reduces the operation frequency of the compressor 1 when there is produced output current failure of the inverter circuit 51 during the oil equalizing operation for inverter protection while likewise reducing also the operation frequency of the compressor 2. Hereby, oil equalizing effect is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a multi-type air conditioner consisting of an 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. Outdoor unit A has two variable capacity compressors 1.2, and the compressors 1.2
are connected in parallel via check valves 3 and 4, respectively.

And compression! 11゜2, four-way valve 5, outdoor heat exchanger 6,
Parallel body of heating expansion valve 7 and cooling cycle forming check valve 8, liquid tank 9, electric flow rate adjustment valve 11, 21, 3
1. Parallel body of cooling expansion valve 12.22.32 and heating cycle forming check valve 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.

In addition, each of the cooling expansion valves 12, 22, and 32 is temperature sensitive!
112a, 22a, and 32a, and these temperature sensing tubes are respectively attached to the gas side refrigerant pipes of the in-mold heat exchangers 14, 24, and 34.

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 broken line arrow in the figure to form a heating cycle.

Such an air conditioner is equipped with two inverter circuits that supply driving power to the compressor 111°2.
In order to satisfy the required capacity of each indoor unit, the output frequency of each inverter circuit is controlled (controlling the number and capacity of compressors 1 and 2), and the flow rate control valve 11.
1.31 is controlled to adjust the amount of refrigerant 8i 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 the compression I11, the compressor 2 is also activated. If the required capacity of each indoor unit decreases from this state, the capacity of the compressor 2 may decrease, or even the compression [
The operation of compressor 2 is stopped and only compressor 1 is operated.

Furthermore, means for detecting an abnormality in the output current of each inverter circuit is provided, and when the abnormality is detected, the output frequency of the corresponding inverter circuit is reduced by a certain value to protect the inverter.

(Problems to be Solved by the Invention) In such an air conditioner, there may be an imbalance in the amount of refrigerating machine oil in each compressor, making stable operation difficult.

Therefore, an oil equalization operation was performed periodically to create a certain difference in the capacity of each compressor, thereby eliminating the imbalance in the amount of refrigerating machine oil. There is something.

However, if the above-mentioned inverter protection intervenes during such oil equalization operation, it becomes impossible to ensure a certain difference in the capacity of each compressor, and the oil equalization effect is impaired.

This invention was made in view of the above circumstances,
The main objective thereof is to provide an air conditioner that can reliably perform oil equalization operation without being affected by interruptions of inverter protection means, thereby enabling stable operation at all times.

[Structure of the Invention] (Means for Solving the Problems) An outdoor unit having two compressors, a plurality of indoor units, two inverter circuits that drive each of the compressors, and an inverter circuit that drives each of the compressors. means for controlling the output frequency according to the required capacity of each of the indoor units; means for detecting an abnormality in the output current of each of the inverter circuits; and inverter protection for reducing the output frequency of the corresponding inverter circuit by a certain value upon detection of the abnormality. means, an oil equalizing pipe provided between each of the compressors, an oil equalizing operation means for providing a certain difference in the output frequency of each of the inverter circuits when two of the compressors are in operation; , means for reducing the output frequency of another inverter circuit by the same value when the output frequency is reduced by the inverter protection means.

(Function) When two compressors are operated, by creating a certain difference in the output frequency of each inverter circuit, the refrigerating machine oil of each compressor efficiently flows through the oil equalizing pipe, and the oil equalizing effect between each compressor is improved. can get. At this time, if the inverter protection means operates to reduce the output frequency, the output frequencies of the other inverter circuits are reduced by the same value to ensure a constant difference in the output frequencies.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. In the drawings, parts 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 FIGS. 1 and 2, the bottoms of the cases of the compressors 1 and 2 are connected through oil equalizing pipes 45.

The control circuit is shown in FIG.

The outdoor unit A includes an outdoor control section 50. This outdoor control section 50 is made up of a microcomputer and its peripheral circuits, and has external inverter circuits 51 and 52.
, and a timer circuit 53 are connected. The inverter circuits 51 and 52 rectify the voltage of the AC power supply 54, convert it into an AC voltage of a predetermined frequency by switching according to a command from the outdoor control unit 50, and convert it into an AC voltage of a predetermined frequency.

2M respectively as driving power.

Then, Wl is applied to the output lines of the inverter circuits 51 and 52.
Current detectors 55.56 are provided, and the current detectors 55.5
6 is supplied to the outdoor control unit 50.

Branching unit B includes a multi-control unit 60. This multi-control unit 60 consists of a microcomputer and its peripheral circuits, and externally includes flow rate regulating valves 11, 21, and 3.
1 and an on-off valve 15.25°35.

Indoor units C, D, and E have indoor control units 70°80.9
It is equipped with 0. These indoor control units consist of a microcomputer and its peripheral circuits, and are externally connected to an operating unit 71.81.91 and an indoor temperature sensor 72.82.9.
2 are connected to each other.

Then, each indoor control unit receives frequency setting signals f1°f2. f
3 is transferred to the multi-control unit 60 as the required capacity. The multi-control unit 60 calculates the total required capacity of each indoor unit from the transferred frequency setting signal, and sends the corresponding frequency setting signal t'o to the outdoor control unit 5.
It is configured to transfer to 0.

Next, the operation of the above configuration will be explained with reference to FIGS. 4, 5, and 6.

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 unit 71, and transmits the frequency setting signal f corresponding to the temperature difference to the multi-control unit 60 as the required cooling capacity. do. Similarly, the indoor control sections 80 and 90 of the indoor units D and H also transfer the frequency setting signals f2 and r to the multi-control section 60 as the required cooling capacity.

The multi-control unit 60 calculates the total required cooling capacity of each indoor unit based on the transferred frequency setting signal. Then, the frequency setting signal @fa corresponding to the calculated sum is transferred to the outdoor control unit 50.

The outdoor control unit 50 receives the transmitted frequency setting signal 1.
The total required cooling capacity of each indoor unit is determined based on the total required cooling capacity, and the number of operating compressors 1.2 and the operating frequency (output frequency of the inverter circuit 51.52) F are calculated according to the total.
control.

In this case, the outdoor control l1llil150 shifts from operation of one unit of compression t111 to operation of two units of compression 111.2 as the total required cooling capacity increases.

When these two units are in operation, the outdoor control unit 50 sets the operating frequency of the compressor 1゜2 to a command frequency (based on the total required cooling capacity).
Set to Fs. Then, the oil equalization operation mode is executed periodically.

In this oil equalization operation mode, compression! ! 11 is increased by a predetermined value, for example, 5 Hz, and Fl (=Fs+5-)
At the same time, the operating frequency of the compressor 2 is lowered by a predetermined value, for example, by 5, to F 2 (-F s -5Hz), and a certain difference (10Hz>) is created between the two operating frequencies.Then, the timer circuit 53 starts a time count. Started TI 17 times.

In this way, when the operating frequency of the compressor 1 becomes higher than the operating frequency of the compressor 1f12, the case pressure of the compressor 1 becomes lower than the case pressure of the compressor 2, and the frozen Akebono oil of the compressor 12 is compressed through the oil equalizing pipe 40. It becomes easier to distribute to machine 1.

When the time count T1 reaches the set time Ta, compression n
The operating frequency of 1.2 is the command frequency 1! Set to iFs, end oil equalization operation, and return to normal operation (see Figure 5).
.

By the way, the outdoor control unit 50 monitors the output currents of the inverter circuits 51 and 52 using current detectors 55 and 56, and determines that the output current is abnormal when the output current exceeds a predetermined value.

When it is determined that the output current of the inverter circuit 51 is abnormal, the output frequency of the inverter circuit 51 (operating frequency of the compressor 1) is reduced by a fixed value, for example, 10 cycles, and current release is performed.

When it is determined that the output current of the inverter circuit 52 is abnormal, the output frequency of the inverter circuit 52 (compression 11!2
(operating frequency) by the same constant value of 10Hz,
Perform current release. In other words, inverter protection is performed.

However, if an abnormality in the output current of the inverter circuit 51 occurs during the oil equalization operation, the operating frequency of the compressor 1 is changed to F1(
= F s + 5 Hz > to be reduced by 10H1 to protect the inverter, but at that time compressor 2
The same applies to the operating frequency F 2 (-F s -5Hz) of 10)! z (see Figure 6). Then, the timer circuit 53 starts a time count T2.

In this way, even if the inverter protection means operates and the output frequency is reduced during oil-equalizing operation, by reducing the output frequencies of other inverter circuits by the same value, the output frequency required for oil-equalizing operation can be kept constant. The difference (10)1z) can be ensured, that is, the case pressure of compression *i and the compression l3
It is possible to ensure a sufficient difference between the case pressure of 12 and the oil equalization effect can be reliably obtained.

Time count T while protecting inverter! is the set time Ta
When the timing reaches the oil equalization operation end timing, the operating frequency of the compressor 2 is increased by 10-10 to make it the same as the operating frequency of the compressor 1. Then, when the time count T2 reaches the set time Tb, the operating frequency of the compression 111.2 is set to the command frequency FS, the inverter protection is canceled, and normal operation is resumed.

Up to this point, we have described oil equalization operation in which the operating frequency of compressor 1 is increased by 5 Hz and the operating frequency of compressor 2 is lowered by 5 Hz. There is also an oil equalization operation that lowers the operating frequency of f11 by 5, and these are performed alternately. Then, the operating frequency of compressor 2 is increased by 5-5 to increase the operating frequency of compressor 1 to 5 Hz.
In the oil equalization operation, when the output current of the inverter circuit 52 is abnormal, the output frequency of the inverter circuit 52 (operating frequency at a pressure of $111 m2) is set to a constant value, for example, 10
Hz is reduced to protect the inverter, but at this time the output frequency of the inverter circuit 51 (the operating frequency of the compressor 1)
Similarly, 10) 1z will be reduced.

Further, when a one unit operation command is issued, the operation shifts to one unit of the compressor 1.

On the other hand, the multi-control unit 60 controls the opening degrees of the refrigerant flow rate adjustment valves 11, 21, and 31 according to the frequency setting signal from each indoor unit, so that the R adjustment corresponding to the required cooling capacity of each indoor unit is performed. A large amount of refrigerant flows into each indoor heat exchanger. Furthermore, the degree of superheating of the refrigerant in each indoor heat exchanger is controlled to be constant by the expansion valves 12, 22, and 32.

In this way, when the inverter protection means operates to reduce the output frequency during oil-equalizing operation, the output frequencies of other inverter circuits are reduced by the same value, and the constant difference in output frequency required for oil-equalizing operation is reduced. Since this is ensured, the oil equalization operation can be reliably executed without being affected by the interruption of the inverter protection means. Therefore, it is possible to prevent oil from rising in the compressor 1.2, and efficient and stable operation is possible at all times.

In the above actual flow example, the case where there are three indoor units has been explained, but it is possible to implement the case with more than three or two indoor units as well.

In addition, the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without changing the gist.

[Effects of the Invention] As described above, according to the present invention, an outdoor unit having two compressors, a plurality of indoor units, two inverter circuits for driving each of the compressors, and means for controlling the output frequency of the inverter circuit according to the required capacity of each of the indoor units; means for detecting an output current abnormality of each of the inverter circuits; and upon detecting the abnormality, reducing the output frequency of the corresponding inverter circuit by a certain value. an oil equalizing pipe provided between each of the compressors, an oil equalizing operation means that provides a certain difference in the output frequency of each of the inverter circuits when two of the compressors are operated; During oil operation, when the output frequency is reduced by the inverter protection means, the output frequency of other inverter circuits is reduced by the same value, so the oil can be equalized without being affected by the interruption of the inverter protection means. The air conditioner can be operated reliably, thereby providing an air conditioner that can always operate stably.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a refrigeration cycle in one embodiment of the present invention, FIG. 2 is a perspective view showing each compressor and oil equalizing pipe in the same embodiment, and FIG. 3 is a configuration of a control circuit in the same embodiment. FIG. 4 is a flowchart for explaining the operation of the embodiment, FIGS. 5 and 6 are time charts for explaining the operation of the embodiment, and FIG. 7 is a flowchart for explaining the operation of the embodiment.
The figure is a diagram showing the configuration of a refrigeration cycle in a conventional air conditioner. A...Outdoor unit, B...Branch unit, C, D
. E... Indoor unit, 1, 2... Variable capacity compressor,
40... Oil equalizing pipe, 50... Outdoor control section, 51.52
...Inverter direct circuit, 55.56...Current detector,
60...Multi control unit, 70.80.90...Indoor control unit. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 4

Claims (1)

[Claims] An outdoor unit having two compressors, a plurality of indoor units, two inverter circuits that drive each of the compressors, and the output frequency of these inverter circuits is controlled according to the required capacity of each of the indoor units. means for detecting an output current abnormality of each of the inverter circuits; inverter protection means for reducing the output frequency of the corresponding inverter circuit by a certain value upon detection of the abnormality; and an oil equalizing pipe provided between each of the compressors. , an oil equalizing operation means for providing a certain difference in the output frequency of each of the inverter circuits when two of the compressors are operated, and an output frequency is reduced by the inverter protection means during the oil equalizing operation. An air conditioner comprising means for reducing the output frequency of the inverter circuit by the same value.