JPH0610562B2 - Heat pump type air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat pump type cooling and heating apparatus in which a plurality of compressors are used to form a single refrigerant cycle.

[Conventional technology]

The heat pump type air conditioner has a refrigerating cycle capacity according to the indoor cooling load or heating load.
One with multiple compressors connected to a single refrigerant circuit,
There is one that performs variable frequency control of a compressor by an inverter device or the like. These devices enable highly efficient operation by controlling the number of operating compressors or controlling the power supply frequency, that is, by controlling the capacity of the compressor.
The number of stoppages is reduced, the refrigeration cycle loss is reduced by turning the compressor on and off, and the comfort on the indoor side is improved. Therefore, a device for controlling the capacity of such a compressor is becoming popular.

Further, a so-called multi-cooling and heating device in which a plurality of indoor units are connected to one outdoor unit also has an installation space, installation workability,
It is widely used because of its excellent price. In this multi air conditioner, since the heating and cooling load changes over a wide range due to changes in the number of operating indoor units, normally two compressors are used in a single refrigeration cycle, and one compressor is powered by a commercial frequency power source. In many cases, the capacity of the compressor is controlled by driving the other compressor with a power source whose variable frequency is controlled by an inverter.

FIG. 4 is a refrigerant circuit diagram of such a conventional heat pump type cooling and heating device. In the figure, reference numerals 1a and 1b denote two compressors for compressing and circulating the refrigerant, and one compressor 1a has an inverter device (frequency variable device) (not shown)
Driven at a frequency in the range of 100Hz, the other compressor 1
b is driven at a commercial frequency of 50 Hz (60 Hz). 2 is an oil separator that separates refrigerant and oil (refrigerator oil) from the gas discharged from the compressors 1a and 1b. 3 is a four-way switching valve that switches the refrigerant flow between cooling and heating. 4 is an outdoor heat exchanger. 5 is a throttle device including an expansion valve, 6a and 6b are two indoor units arranged in parallel, 7 is an accumulator, 8a and 8b are refrigerant pipes connected to the oil separator 2, and 9 is inside the oil separator 2. An oil recovery pipe for returning the separated oil to the suction side of the compressors 1a, 1b,
Reference numerals 10a and 10b are capillaries connected to the oil recovery pipe 9. The capillaries 10a and 10b are provided in parallel with each other, and the oil is evenly returned to both the compressors 1a and 1b.
In addition, the bypass of the discharged refrigerant to the compressor intake side is reduced to prevent the deterioration of the capacity during normal operation. Reference numerals 11a and 11b are suction pipes connecting the respective capillaries 10a and 10b and the compressors 1a and 1b, and 12 is opened when the suction pressure of the gas refrigerant is lower than a predetermined pressure or the discharge pressure is higher than a predetermined pressure. Solenoid valve that protects the compressors 1a and 1b by
It is also used for capacity control, and the refrigerant discharged from the solenoid valve 12 returns to the accumulator 7 through the pipe 13. Reference numeral 14 is a gas pipe connecting the accumulator 7 and the suction pipes 11a, 11b, 15a, 15b are ball valves at the refrigerant inlet / outlet portion of the outdoor unit having the compressors 1a, 1b, 16a,
Reference numeral 16b is an extension pipe between the indoor and outdoor units.

In the cooling and heating device having the two compressors 1a and 1b as described above, the oil is returned to the compression side without being taken out to the indoor and outdoor heat exchangers, and a predetermined amount of oil is constantly supplied to the compressors 1a and 1b. Therefore, the function of the oil separator 2 is an important point. Further, when the extension pipes 16a and 16b are long pipes extending to several tens of meters, or when the number of connected indoor units is a large number of 5 or 6 or more, the amount of oil taken out increases. From the viewpoint of protecting the compressor, the oil separation efficiency of the oil separator 2 and the means for returning the separated oil to the compressor are important points. In the example of FIG. 4, in order to return the oil separated by the oil separator 2 to both the compressors 1a and 1b evenly,
When the compressor 1b is stopped, all the collected oil is sucked into the suction pipe 1
It returns to the compressor 1a through 1a.

Further, there is also known one having an oil recovery circuit as shown in FIG. That is, the capillary tube 1 is attached to the oil recovery pipe 9.
7 is connected, and the oil separated by the oil separator 2 is returned to the pipe 13 on the inlet side of the accumulator 7 through this capillary 17, and the suction pipe 1
The oil is returned together with the refrigerant to the compressors 1a and 1b through 1a and 11b.

[Problems to be solved by the invention]

As described above, in the conventional cooling and heating apparatus having the two compressors and forming the heat pump circuit by the single refrigerant cycle, the oil separated by the oil separator is always returned to the suction side. When operating two compressors, the amount of oil discharged from each compressor changes relative to the change in the operating frequency of one compressor, and depending on the operating conditions, the residual oil amount shifts to either compressor, There has been a problem that the amount of oil is insufficient, the life of the compressor is shortened, and in the case where it is remarkable, it burns out. That is, for example, 2 of the same capacity
When two compressors are used, the oil discharge amount is almost proportional to the operating frequency, so the oil carry-out amount of one compressor is constant, but the operating frequency of the other compressor changes, so the other When the operating frequency of the compressor is higher than that of one compressor, the residual oil amount of the other compressor is reduced, and when the operating frequency is opposite, the residual oil amount of the other compressor is reduced and The compressor oil level is high, which causes similar problems even when the compressors have different capacities.

The present invention has been made in order to solve such a problem, and provides a heat pump type cooling and heating device in which the amount of oil in each compressor is made uniform, the life of the compressor is extended, and the reliability is improved. To do.

[Means for solving problems]

The heat pump type cooling and heating device of the present invention includes a recovery pipe for returning the oil separated by the oil separator to the suction side of the compressor above and below the lower end of the oil separator for separating the refrigerant and the oil from the discharge gas of the compressor. , And the recovery pipe connected to the lower end of the compressor is connected in series with an on-off valve and a capillary tube. Also, a capillary tube is installed in the upper recovery pipe, and the amount of oil in each compressor becomes uniform. The control unit controls the on-off valve according to each operation time, and the control unit stops the compressor with a low operating frequency when opening the on-off valve to make the oil amount of each compressor uniform. It was made to let.

[Operation] In the heat pump type air conditioner of the present invention, oil recovery pipes are connected to the lower end of the oil separator and above the oil separator, and the recovery pipe connected to the lower end is provided with an on-off valve and a series circuit of capillaries. A capillary tube is also provided in the upper recovery pipe. Then, the control unit controls the on-off valve according to the operating condition, and equalizes the oil amount of each compressor.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a refrigerant circuit diagram of a heat pump type cooling and heating apparatus according to the present invention, and the same reference numerals as those in FIGS. 4 and 5 of the related art indicate the same constituent elements. One compressor 1a is variable-frequency controlled, and the other compressor 1b is driven at a commercial frequency. Oil separator 2 for separating refrigerant and oil from the discharge gas of these compressors 1a, 1b
At the lower end and above the oil recovery pipe 9,
18 is connected, and an opening / closing valve 19 is provided in the lower recovery pipe 9. Capillary tubes 17 and 20 are connected to the other side of each of the recovery pipes 9 and 18, and the ends thereof communicate with the accumulator 7 via a pipe 13. The on-off valve 19 is controlled by the control unit 21 so that the oil amounts of the compressors 1a and 1b become uniform.

FIG. 2 is a configuration diagram showing the details of the oil separator 2. The tip of the refrigerant pipe 8a through which the gas discharged from the compressors 1a and 1b passes reaches the center of the oil separator 2, and an oil separation filter 22 is arranged above it, and the tip of the refrigerant pipe 8b is arranged above it. positioned. The upper oil recovery pipe 18 is attached to the compressor 1
It is determined from the amount (A) of the oil 23 discharged from a and 1b and the operation time interval of the opening / closing valve 19. Further, as shown in FIG. 3, the suction pipes 11a and 11b in the accumulator 7 are provided with a small hole 24 for sucking oil in the lower part thereof.

Next, the operation will be described.

The flow of the refrigerating cycle at the time of cooling and heating is well known, and therefore omitted. However, the compressors 1a and 1b in FIG. 1 are rolling piston compressors, and since the inside of the compressor shell is on the high pressure side, the oil is inside the shell. Is separated from the discharge gas at and is stored under the shell. Therefore, refrigerant and oil do not flow into the stopped compressor while one compressor is in operation, and the compressor is the same as a device that constitutes a refrigeration cycle with one normal compressor. In operation, if a predetermined oil level is maintained in the compressor shell, the oil discharged from the compressor is separated by the oil separator 2 and returns to the compressor, so there is no particular problem. .
The on-off valve 19 is closed during operation of this compressor, so that the oil separated in the oil separator 2 accumulates in the lower part of the oil separator 2 and reaches the level of the upper oil recovery pipe 18. Then, a considerable amount of oil discharged from the compressor returns to the low pressure side of the compressor through the capillary tube 20. That is, when the on-off valve 19 is closed as described above, oil is stored in the oil separator 2 up to the level of the oil recovery pipe 18.

When the two compressors are in operation, the operating frequency of the compressor 1a is constantly changing as described above, so that the oil levels in both compressors are relatively constantly changing. This oil level change is performed by collecting the oil discharge amount data for the compressor operating frequency in advance and storing the data of the change pattern of the mutual compressor operating frequency in the memory during actual operation. You can know the relative change over time. For example, if the operating frequency of the compressor 1a is the compressor 1b
When the operation at a higher frequency than the operating frequency continues for a predetermined time, the oil level of the compressor 1a decreases, but the on-off valve 19 is closed in the oil separator 2, so that the oil level reaches the level of the upper recovery pipe 18. Is accumulated. Therefore,
By opening the on-off valve 19, this oil is returned to the compressor 1a having a low oil level, and the oil level is leveled. At this time, the compressor 1b is temporarily stopped and the compressor 1
When the independent operation of a is performed and the opening / closing valve 19 is opened at the same time,
The oil in the oil separator 2 enters the accumulator 7 through the pipe 13, and the entire amount of the oil in the oil separator 2 returns to the compressor 1a from the small hole 24 of the suction pipe 11a.

Further, since the oil accumulated in the oil separator 2 before the opening of the opening / closing valve 19 is the discharge oil from the compressors 1a and 1b, by returning this oil to the compressor 1a by the above-mentioned control, both compressions are performed. The oil level inside the machine is the compressor 1a
Will be higher. Then, the operation of the compressor 1b is stopped,
The opening / closing valve 19 is opened for a predetermined time and then closed, and the compressor 1b is started to start a normal cooling or heating operation. By performing such a driving operation every predetermined time, the oil level of both compressors can be maintained above a predetermined level.

When the operation in the state where the operating frequency of the compressor 1b is higher than that of the compressor 1a continues for a predetermined time or longer, the operation of the compressor 1a is stopped and the opening / closing valve 19 contrary to the above operation.
Is opened, and the oil in the oil separator 2 is returned to the compressor 1b.

In addition, when two compressors are in operation, a frequency change in which the operating frequency of the compressor 1a becomes relatively higher or lower than the operating frequency of the compressor 1b occurs within a predetermined time for performing the oil-equalizing operation operation. In this case, a change in the oil level due to a change in the relative operating frequency is calculated from the data in the memory described above, and when the difference in the oil level reaches a predetermined amount, the same oil leveling operation as described above is performed.

Further, during the overload operation in which the load on the compressor becomes excessive during the cooling and heating operations, the on-off valve 19 is opened regardless of the operation of one compressor or two compressors, and a part of the discharged refrigerant is on the low pressure side. Operation to measure the reduction of the load by returning to. That is, the solenoid valve 12 dedicated to overload reduction was provided in the past, but in the present embodiment, the opening / closing valve 19 for oil recovery operation also serves as the solenoid valve for overload reduction.

Here, as described above, the discharged refrigerant gas is discharged into the oil separator 2 from the central portion of the oil separator 2 through the refrigerant pipe 8a, the discharged gas is passed through the filter 22, and then the oil separator is discharged from the refrigerant pipe 8b. The oil that has been discharged to the outside of the filter 2 and separated by the filter 23 drops and collects in the lower part of the oil separator 2. Then, when this oil accumulates to the level of the upper oil recovery pipe 18,
Oil is returned from the oil recovery pipe 18 to the suction side of the compressor. Further, when the on-off valve 19 is opened, the entire amount of oil in the oil separator 2 is returned to the compressor suction side.

In this way, the on-off valve 19 is opened and closed according to the operating state of the compressors 1a and 1b to control the amount of oil returning to each compressor, so that the oil does not deviate to one of the compressors. Therefore, burnout of the compressor is prevented, the life of the compressor is extended, and the reliability is improved. Further, the on-off valve can be used also without providing a new solenoid valve for reducing the load.

The oil recovery pipe 18 is intended to return only the oil, and the oil discharge amount may be several% of the refrigerant discharge amount. Therefore, the resistance of the capillary tube 20 of this recovery circuit is the capillary tube 17 of one recovery circuit. Relatively larger than the resistance of. That is, since the oil recovery pipe 9 has a function of returning the oil once in a short time and a function of opening the open / close valve 19 at the time of overload and returning the discharged refrigerant to the low pressure side, the resistance of the capillary tube 17 is relatively large. It is made smaller.

〔The invention's effect〕

As described above, according to the present invention, the oil recovery pipes are connected to the lower end of the oil separator and above the oil separator, respectively, and the lower oil recovery pipe is provided with a series circuit of an on-off valve and a capillary tube. A capillary tube is also installed in the recovery pipe of
Since the on-off valve is controlled according to the operating state of the compressor, the amount of oil in each compressor is equalized, burnout of the compressor can be prevented, the life can be extended, and reliability is improved. The effect of doing is obtained.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram showing an embodiment of the present invention, FIG. 2 is a configuration diagram showing details of the oil separator of FIG. 1, and FIG.
1 is a sectional view showing a main part of the suction pipe of FIG. 1, FIG. 4 is a refrigerant circuit diagram of a conventional heat pump type cooling and heating device, and FIG. 5 is a refrigerant circuit diagram showing another conventional example. 1a, 1b ...... Compressor 2 ...... Oil separator 7 ...... Accumulator 9, 18 ...... Oil recovery pipe 11a, 11b ...... Intake pipe 19 ...... Open / close valve 21 ...... Control part 23 ...... Oil In the figure, the same The reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A heat pump type having a plurality of compressors, each of which compresses and circulates a refrigerant and whose variable frequency is controlled, and those compressors are connected in parallel to form one refrigeration cycle. In a cooling and heating device, a recovery pipe for returning the separated oil to the suction side of the compressor is connected to the lower end of the oil separator that separates the refrigerant and the oil from the discharge gas of the compressor, and above the lower end of the oil separator. An on-off valve and a capillary tube are installed in series in the recovery pipe connected to the, and a capillary tube is also installed in the upper recovery pipe, and the amount of oil in each compressor is adjusted according to the operating time of each. And a control unit for controlling the opening / closing valve, and the control unit stops the compressor having a low operating frequency when the opening / closing valve is opened to make the oil amount of each compressor uniform. Flop-type air conditioner. 2. The heat pump type cooling and heating apparatus according to claim 1, wherein the control section opens the on-off valve to return the refrigerant to the suction side of the compressor when overloaded.