WO2018124083A1

WO2018124083A1 - Oil equalization control device, refrigerant circuit system, and oil equalization control method

Info

Publication number: WO2018124083A1
Application number: PCT/JP2017/046672
Authority: WO
Inventors: 隆博加藤; 達弘安田; 正幸瀧川
Original assignee: 三菱重工サーマルシステムズ株式会社
Priority date: 2016-12-28
Filing date: 2017-12-26
Publication date: 2018-07-05
Also published as: EP3537061A4; CN110114622A; EP3537061A1; JP2018109452A

Abstract

An oil equalization control device, provided with: a sensor information acquisition unit for acquiring, in a refrigerant circuit provided with a plurality of compressors, a state quantity relating to the amount of refrigerating machine oil in a compressor, for each of the plurality of compressors; a control sequence determination unit for determining the control sequence for the compressors in oil equalization control in accordance with the amounts of the refrigerating machine oil in the compressors based on the state quantities; and an oil equalization control unit for varying the rotation speed of at least one of the plurality of compressors and performing oil equalization control on the basis of the order determined by the control sequence determination unit.

Description

Oil equalization control device, refrigerant circuit system, and oil equalization control method

The present invention relates to an oil equalization control device, a refrigerant circuit system, and an oil equalization control method.
Priority is claimed on Japanese Patent Application No. 2016-256135, filed Dec. 28, 2016, the content of which is incorporated herein by reference.

In an air conditioner including a plurality of compressors in one outdoor unit, or in an air conditioning system including a plurality of outdoor units, the low pressure portion of each compressor is piped (even A configuration in which oil pipes are connected may be adopted. Furthermore, oil equalization control may be performed to eliminate an imbalance in the amount of refrigeration oil of each compressor. In a typical oil equalizing control, for example, for a plurality of compressors operating at the same rotational speed, a pressure difference between the compressor and another by increasing the rotational speed of a part of the compressors. And move the refrigerator oil through the oil equalizing pipe from high pressure to low pressure.

As a related technology, Patent Document 1 discloses that the liquid level position of refrigeration oil in each compressor is detected by a liquid level sensor or the like, and the rotational speed of the compressor is controlled to reduce the difference in liquid level position. A technology for eliminating the uneven distribution of refrigeration oil is described.

JP 2005-241070 A

By the way, in the above-mentioned general oil equalization control, order is allocated beforehand for every compressor, and control which raises a rotational speed in this order is performed in many cases. Considering the original purpose of oil equalization control, it is desirable to recover refrigeration oil in order from a compressor with a smaller amount of refrigeration oil. In that case, it is necessary to reduce the pressure of the compressor by increasing the rotational speed of the compressor with a small amount of refrigeration oil, and to draw the refrigeration oil from another relatively high pressure compressor. However, in the above-described general oil equalization control, the rotational speed is increased in the order of a predetermined number without considering the amount of refrigeration oil of each compressor, for example, it is stored in the first compressor. If the amount of existing refrigeration oil is originally large, the amount of refrigeration oil may be further increased, resulting in further worsening the imbalance.

The present invention provides an oil equalization control device, a refrigerant circuit system, and an oil equalization control method that can solve the above-mentioned problems.

According to a first aspect of the present invention, in a refrigerant circuit including a plurality of compressors connected in parallel with each other, the oil equalization control device relates to the amount of refrigeration oil in the compressor for each of the plurality of compressors. A control information determining unit for acquiring a state quantity, a control order determining unit for determining a control order of the compressor in oil equalization control according to an amount of refrigeration oil in the compressor based on the state quantity, and the control order determination The oil equalizing control unit performs oil leveling control by changing the rotational speed of at least one of the plurality of compressors based on the order determined by the unit.

According to the second aspect of the present invention, the control order determination unit determines the control order as the order in which the amounts of refrigeration oil are arranged in ascending order, and the oil equalizing control unit determines the control order as follows: The rotational speed of the compressor after changing the order is changed so that the pressure of the compressor after changing the order becomes relatively low.

According to the third aspect of the present invention, the sensor information acquisition unit acquires, for each of the plurality of compressors, a measurement value of the pressure on the low pressure side, and the control order determination unit relatively The order of the compressors to lower the pressure is set in order from the one with the highest measurement value of the pressure.

According to the fourth aspect of the present invention, the sensor information acquisition unit acquires the measurement value of the temperature below the dome for each of the plurality of compressors, and the control order determination unit relatively increases the pressure The order of the compressors to be reduced is set in order from the lower one of the measured temperature values.

According to the fifth aspect of the present invention, the oil equalizing control section increases the rotational speed for each of the plurality of compressors in the order of the control for a predetermined time.

According to a sixth aspect of the present invention, the refrigerant circuit system includes: a plurality of compressors connected in parallel to each other; an oil equalizing pipe connecting the plurality of compressors to each other; And an oil control device.

According to a seventh aspect of the present invention, an oil equalizing control method is provided in a refrigerant circuit in which the oil equalizing control device includes a plurality of compressors connected in parallel with one another, wherein each of the plurality of compressors Based on the steps of acquiring a state quantity related to the amount of refrigeration oil, determining the control order of the compressor in oil equalization control according to the amount of refrigeration oil in the compressor based on the state amount, and based on the control order The oil equalizing control is performed by changing the rotational speed of at least one of the plurality of compressors.

According to the oil equalizing control device, the refrigerant circuit system, and the oil equalizing control method described above, it is possible to eliminate the imbalance of the refrigerator oil among the plurality of compressors and to improve the reliability of the system.

It is a 1st schematic which shows an example of the refrigerant circuit system in one Embodiment of this invention. It is a schematic block diagram of a control device in one embodiment of the present invention. It is a figure explaining the control order of the compressor in one embodiment of the present invention. It is a figure explaining an example of rotation speed control of a compressor in one embodiment of the present invention. It is a flow chart which shows an example of oil equivalent control in one embodiment of the present invention. It is a 2nd schematic diagram showing an example of the refrigerant circuit system in one embodiment of the present invention.

Embodiment
Hereinafter, a refrigerant circuit system according to an embodiment of the present invention will be described with reference to FIGS. 1 to 6.
It is a 1st schematic which shows an example of the refrigerant circuit system in one Embodiment of this invention.
The refrigerant circuit system 100 is, for example, a refrigerant circuit system used for an air conditioner. As shown in FIG. 1, the refrigerant circuit system 100 includes

compressors

1A and 1B,

oil separators

2A and 2B,

discharge pipes

3A and 3B,

oil return pipes

4A and 4B,

solenoid valves

5A and 5B,

suction pipes

6A and 6B, and the like. An oil pipe 7, a four-way valve 8, an accumulator 9, an outdoor heat exchanger 10, a receiver 11, an expansion valve 12, an indoor heat exchanger 13, a liquid pipe 14,

gas pipes

15, 16 and 17, and a control device 20 are included. . The refrigerant circuit system 100 shown in FIG. 1 schematically shows a basic configuration, and may further include other components.

The

compressors

1A and 1B compress the refrigerant and supply the compressed high-pressure refrigerant to the refrigerant circuit. The

compressors

1A and 1B are connected in parallel to each other, and are controlled to operate with equal displacement during normal operation. For example, when the

compressors

1A and 1B are the same model, the

compressors

1A and 1B are operated at the same rotational speed.
The

oil separators

2A and 2B are provided on the discharge side of the

compressors

1A and 1B, respectively, and are devices for separating the refrigerator oil from the refrigerant mixed with the refrigerator oil fed through the

discharge pipes

3A and 3B. The

oil separators

2A and 2B have, for example, a cylindrical shape in which the upper and lower sides are closed, and store the separated refrigeration oil.
One end of each of the

oil return pipes

4A and 4B is connected to the lower portion of the container of each of the

oil separators

2A and 2B. The opposite ends of the

oil return pipes

4A, 4B are connected to the

compressors

1A, 1B, respectively. The oil return pipe 4A is provided with a solenoid valve 5A. By adjusting the opening degree of the solenoid valve 5A, the amount of refrigeration oil returned from the oil separator 2A to the compressor 1A can be adjusted. Similarly, the oil return pipe 4B is provided with a solenoid valve 5B, and by adjusting the opening degree of the solenoid valve 5B, it is possible to adjust the amount of refrigeration oil returned from the oil separator 2B to the compressor 1B.
The oil equalizing pipe 7 communicates the

compressors

1A and 1B, and averages refrigerator oil stored in the two compressors.

The four-way valve 8 switches the flow direction of the refrigerant between the heating operation and the cooling operation. For example, in the heating operation, the high pressure refrigerant discharged by the

compressors

1A and 1B is guided to the gas pipe 15 by the four-way valve 8, and the indoor heat exchanger 13 (condenser) dissipates the heat of the refrigerant into the room . The refrigerant liquefied by passing through the indoor heat exchanger 13 is reduced in pressure by the expansion valve 12, passes through the liquid pipe 14, and is supplied to the outdoor heat exchanger 10 (evaporator). The receiver 11 provided in the liquid pipe 14 stores the liquefied liquid refrigerant. The refrigerant vaporized in the outdoor heat exchanger 10 passes through the gas pipe 17, reaches the four-way valve 8, passes through the gas pipe 16, and is supplied to the accumulator 9. The accumulator 9 is a pressure vessel provided on the upstream side of the

compressors

1A and 1B. The accumulator 9 performs gas-liquid separation of the refrigerant supplied to the

compressors

1A and 1B. The refrigerant gas separated by the accumulator 9 passes through the

suction pipes

6A, 6B and is sucked into the

compressors

1A, 1B, respectively.

During the cooling operation, the refrigerant circulates in the opposite direction to that during the heating operation. That is, the high-pressure refrigerant discharged by the

compressors

1A and 1B is guided to the gas pipe 17 by the four-way valve 8, and the outdoor heat exchanger 10 (condenser), the liquid pipe 14, the expansion valve 12, the indoor heat exchanger It is supplied to 13 (evaporator). The refrigerant that has exchanged heat with the air in the room by the indoor heat exchanger 13 passes through the gas pipe 15, is led to the gas pipe 16 by the four-way valve 8, and passes through the accumulator 9 to the

compressors

1A and 1B. It is inhaled.

The refrigerant discharged from the

compressors

1A and 1B includes refrigerator oil. Most of the refrigeration oil discharged by the

compressors

1A, 1B is captured by the

oil separators

2A, 2B and returned to the

compressors

1A, 1B via the

oil return pipes

4A, 4B. The other refrigeration oil circulates the refrigeration cycle formed as described above and flows into the accumulator 9. Part of the refrigeration oil flowing into the accumulator 9 is returned to the

compressors

1A and 1B together with the vaporized refrigerant, and the remainder is stored in the accumulator 9.

If the amount of refrigeration oil recovered to the

compressors

1A and 1B is insufficient, problems such as burn-in occur in the

compressors

1A and 1B. Therefore, for example, the control device 20 freezes an appropriate amount of refrigeration oil every fixed operation time. Execute oil return control to recover the machine oil. Although various methods exist for oil return control, in the refrigerant circuit system 100, for example, control is performed to recover refrigeration oil to the accumulator 9. Thereafter, the control device 20 performs control to gradually return the refrigeration oil collected by the accumulator 9 to the

compressors

1A and 1B over time. At this time, as a result of performing control of returning refrigeration oil from the accumulator 9 to the

compressors

1A and 1B, the control device 20 performs oil equalization control so that imbalance does not occur in refrigeration oil stored in the

compressors

1A and 1B. .

A pressure sensor PA is provided on the suction side of the compressor 1A, and a pressure sensor PB is provided on the suction side of the compressor 1B. A temperature sensor TA is provided below the dome of the compressor 1A, and a temperature sensor TB is provided below the dome of the compressor 1B. Further, a liquid level detection sensor LA for detecting the height of the oil level of the refrigerating machine oil is provided inside the compressor 1A, and a liquid level detection sensor LB is similarly provided inside the compressor 1B. These sensors do not have to be all provided. For example, only the pressure sensors PA and PB may be provided, or only the temperature sensors TA and TB may be provided.
The control device 20 of the refrigerant circuit system 100 measures the pressure on the suction side (low pressure side) of the

compressors

1A and 1B measured by the pressure sensors PA and PB, or the domes of the

compressors

1A and 1B measured by the temperature sensors TA and TB. Based on the lower temperature or the height of the oil level measured by the liquid level detection sensors LA and LB, the oil leveling control is performed so that the compressor oil returns to the compressor preferentially from the compressor lacking the refrigerator oil in order Do. The control device 20 will be described in detail with reference to FIG.

FIG. 2 is a schematic block diagram of an oil equalization control device in an embodiment of the present invention.
The control device 20 is, for example, a computer device such as a microcomputer. The control device 20 is connected to pressure sensors PA, PB, temperature sensors TA, TB, liquid level detection sensors LA, LB, and

compressors

1A, 1B. As shown in FIG. 2, the control device 20 includes a sensor information acquisition unit 21, a control order determination unit 22, an oil equalization control unit 23, and a storage unit 24. The control device 20 performs various controls of the refrigerant circuit system 100 in addition to the oil equalization control, but in the present specification, the description of functions relating to other controls is omitted.

The sensor information acquisition unit 21 acquires, for each of the

compressors

1A and 1B, a state quantity relating to the amount of refrigeration oil in the compressor. For example, the sensor information acquisition unit 21 acquires the pressure of the refrigerant on the suction side of the

compressors

1A and 1B measured by the pressure sensors PA and PB. The sensor information acquisition unit 21 acquires the temperature below the dome of the

compressors

1A and 1B measured by the temperature sensors TA and TB. The sensor information acquisition unit 21 acquires the liquid level heights of the

compressors

1A and 1B measured by the liquid level detection sensors LA and LB.

The control order determination unit 22 determines the control order of the compressor in oil equalization control according to the amount of refrigeration oil in the

compressors

1A and 1B based on the state quantities acquired by the sensor information acquisition unit 21. Specifically, the control order determination unit 22 determines to increase the rotational speed in order from the compressor in which the amount of refrigeration oil is small. Hereinafter, the order of increasing the rotational speed of the compressor will be referred to as the control order. For example, with respect to the compressors 1A and the like, the control order determination unit 22 arranges the pressure on the suction side in order from the highest pressure, and sets this as the control order. For example, the control order determination unit 22 arranges in order from the one where the temperature below the dome is low, and sets this as the control order. For example, the control order determination unit 22 arranges the oil levels of the refrigeration oil in order from the lower one and sets this as the control order.

The oil equalization control unit 23 performs oil equalization control by changing the rotational speed of at least one of the plurality of compressors 1A and the like based on the control order determined by the control order determination unit 22. More specifically, the oil equalizing control unit 23, in order of control, sets the rotational speed of the compressor for a predetermined time so that the pressure of the compressor in the order becomes relatively low compared to the remaining compressors. Raise it.

The storage unit 24 stores various information such as various measurement values acquired by the sensor information acquisition unit 21 and control parameters such as the rotational speed of the compressor after the increase. The storage unit 24 stores a program for realizing the function of the control device 20.
The control order determination unit 22 and the oil equalization control unit 23 are functions implemented by a CPU (Central Processing Unit) included in the control device 20 reading and executing a program from the storage unit 24.

Next, oil equalization control of the present embodiment will be described using FIG. 3.
FIG. 3 is a diagram for explaining the control order of the compressor in the embodiment of the present invention.
FIG. 3 shows the control order of the suction side pressure of the compressor, the temperature below the dome, the position of the oil surface of the refrigerator oil, the amount of the refrigerator oil, and the rotational speed of the compressor. In the refrigerant circuit system 100 illustrated in FIG. 1, although the number of compressors is two, three compressions are shown in the table of FIG. 3 in order to more clearly explain the oil equalization control feature of the present embodiment. The above relationship in the case of a system in which machines 1 to 3 are connected in parallel to one another is illustrated.
In the case of the example shown in FIG. 3, the suction side pressure of the compressor 1, the temperature below the dome, and the position of the oil level of the refrigerator oil are respectively medium pressure, medium temperature, and medium among three compressors. Indicates that the oil level of the. Similarly, compressor 2 shows the highest pressure, lowest temperature, lowest oil level, among three, and compressor 3 has the lowest pressure, highest temperature, highest oil level among three. Show that.
The higher the suction side pressure, the lower the amount of refrigeration oil stored by the compressor. Thus, for example, the pressure "high" of the compressor 2 indicates that the amount of refrigerator oil of the compressor 2 is the smallest among the three.
The refrigeration oil in the compressor has the property of absorbing heat generated by the motor of the compressor, so the temperature below the dome increases as the amount of refrigeration oil increases, and the temperature below the dome decreases as the amount of refrigeration oil decreases. Therefore, for example, the temperature “low” of the compressor 2 indicates that the amount of the refrigerator oil of the compressor 2 is the smallest among the three.
The value of "oil level" indicates that the amount of refrigerator oil in the compressor is high if it is high and low if it is low. For example, the oil level "low" of the compressor indicates that the amount of refrigerating machine oil of the compressor 2 is the smallest among the three.

From the above, in the case of the compressors 1 to 3 illustrated in FIG. 3, the amount of refrigeration oil of the compressor 2 is the smallest, and then the amount of refrigeration oil of the compressor 1 is the smallest, and the amount of refrigeration oil of the compressor 3 Will be the most common. The control order determination unit 22 determines the compressor as described above based on the state quantities (pressure, temperature, oil level height) related to the amount of refrigeration oil in the compressors 1 to 3 acquired by the sensor information acquisition unit 21. The amount of refrigeration oil in 1 to 3 is determined, and it is decided to increase the rotational speed in order from the compressor with the smaller amount of refrigeration oil. That is, in the case of the above example, the control order determination unit 22 first increases the rotational speed of the compressor 2 with the least amount of refrigeration oil, and then the compressor 1 with the least amount of refrigeration oil and finally compression with the most amount of refrigeration oil It is decided to increase the rotational speed of the machine 3. Then, based on the order determined by the control order determination unit 22, the oil equalizing control unit 23 first increases the rotational speed of the compressor 2 for a predetermined time. As a result, the pressure of the compressor 2 decreases, and the refrigerator oil moves from the

other compressors

1 and 3 having a high pressure to the compressor 2 via the oil equalizing pipe 7. When the predetermined time has elapsed, the oil equalizing control unit 23 returns the rotational speed of the compressor 2 to the original speed, and then increases the rotational speed of the compressor 1 for a predetermined time. When the predetermined time further elapses, the oil equalizing control unit 23 returns the rotational speed of the compressor 1 to the original speed, and finally raises the rotational speed of the compressor 3 for a predetermined time. As described above, in the present embodiment, oil equalization control is performed in which the rotational speed is increased for a predetermined time in order from the compressor with the smaller amount of refrigeration oil. As a result, the imbalance of refrigeration oil among the plurality of compressors 1 to 3 can be eliminated, the shutdown of the compressors 1 to 3 due to the shortage of refrigeration oil or the like can be prevented, and the reliability of the system can be improved.

Next, oil equalization control in the refrigerant circuit system 100 illustrated in FIG. 1 will be described using FIG. 4.
FIG. 4 is a diagram for explaining rotational speed control of a compressor according to an embodiment of the present invention.
FIG. 4 shows an example of oil equalization control according to the present embodiment that is performed at two different times during operation of the refrigerant circuit system 100.
FIG. 4A and FIG. 4B show correspondence tables of the state quantities of the

compressors

1A and 1B and the speed-up order at two time points (start timings 1 and 2). FIG. 4C shows the transition of the rotational speed of the compressor 1A. FIG. 4 (d) shows the transition of the rotational speed of the compressor 1B.
Referring to the state quantities of the

compressors

1A and 1B at the start timing 1 of oil equalization control shown in FIG. 4A, the pressure of the compressor 1A is "high", the pressure of the compressor 1B is "low", etc. There is. That is, at the start timing 1, the amount of refrigeration oil of the compressor 1A is smaller than that of the compressor 1B. In this case, the control order determination unit 22 determines to increase the rotational speed by a predetermined time in the order of the compressor 1A and the compressor 1B. Based on this determination, the oil equalizing control unit 23 first operates the compressor 1A by increasing the rotational speed to a predetermined rotational speed for a predetermined time H1. On the other hand, the rotational speed of the compressor 1B may be unchanged as it is, or the rotational speed may be reduced to a predetermined rotational speed for a predetermined time H1 as illustrated in FIG. By reducing the rotational speed of the compressor 1B, the pressure difference between the

compressors

1A and 1B can be further increased. Thus, for example, the degree of increase in the rotational speed of the compressor 1A can be suppressed, and the operation stop of the compressor 1A due to the operation of the protection control can be prevented. Next, when the predetermined time H1 has elapsed, the oil equalizing control unit 23 replaces the

compressors

1A and 1B, increases the rotational speed to a predetermined value for the predetermined time H1, and operates the compressor 1B for the predetermined time H1. The rotational speed is reduced to a predetermined value to operate the compressor 1A. When the operation to increase the rotational speed of the

compressors

1A and 1B is performed one time each, the oil equalizing control unit 23 restores the rotational speeds of the

compressors

1A and 1B and ends the oil equalization control. After that, for a while, the control device 20 normally operates the

compressors

1A and 1B at the rotational speed according to the load.

Then, when the normal operation continues for a predetermined time, the control device 20 executes the oil return control, and thereafter performs control for returning the refrigerator oil from the accumulator 9 to the

compressors

1A and 1B after the predetermined time has elapsed. At the same time, the control device 20 starts oil equalization control (start timing 2).
FIG. 4B shows state quantities of the

compressors

1A and 1B at the start timing 2 acquired by the sensor information acquisition unit 21. At the start timing 2, unlike the start timing 1, the refrigeration oil of the compressor 1A is larger than the refrigeration oil of the compressor 1B. The control order determination unit 22 determines to perform control to increase the rotational speed in the order of the compressor 1B and the compressor 1A as the control order of the compressor 1A and the compressor 1B in oil equalization control. Then, the oil equalizing control unit 23 first operates to increase the rotational speed of the compressor 2 to a predetermined value for a predetermined time H1 and reduces the rotational speed to a predetermined value for a predetermined time H1 for one compressor 1A. Let me drive. If these operations are continued for a predetermined time H1, then the oil equalizing control unit 23 switches the

compressors

1A and 1B, raises the rotational speed to a predetermined value for a predetermined time H1, and operates the compressor 1A. The compressor 1B is operated with the rotational speed reduced to a predetermined value for a time H1. When these operations are continued for a predetermined time H1, the oil equalizing control unit 23 restores the rotational speeds of the

compressors

1A and 1B, and ends the second oil equalizing control.

In the conventional oil equalization control, the rotational speed is often increased according to a predetermined order without considering the amount of refrigeration oil in the compressor. In such a case, for example, control to distribute the refrigeration oil to the compressor having a relatively large amount of refrigeration oil is executed first, and an imbalance may occur, or the protection function is activated in that state to equalize. In the case where the oil control ends halfway, the imbalance of the refrigerator oil may be further aggravated by the execution of the oil equalization control. On the other hand, in the present embodiment, according to the amount of refrigeration oil of each compressor at the start of oil equalization control, the rotational speed is set to return the refrigeration oil to the compressor in order from the one with the smallest amount of refrigeration oil. Control to raise. Since the control is performed in the direction in which the refrigeration oil becomes uniform, the imbalance does not increase during oil equalization control, and even if the oil equalization control is not completed due to the activation of the protective function, etc. It does not become worse than before the start of control.

FIG. 5 is a flowchart showing an example of oil equalization control according to an embodiment of the present invention.
The flow of oil equalization processing will be described using the refrigerant circuit system 100 of FIG. 1 as an example, with reference to FIG. 5. As a premise, for example, it is assumed that the oil return operation is performed, a predetermined time has elapsed, and the oil buildup control start timing has come.
First, the sensor information acquisition unit 21 acquires sensor information on all the compressors (1A, 1B) (step S11). Specifically, the sensor information acquisition unit 21 acquires measurement values of the pressure on the suction side of the

compressors

1A and 1B by the pressure sensors PA and PB. The sensor information acquisition part 21 acquires the measured value of the temperature under the domes of the

compressors

1A and 1B by the temperature sensors TA and TB. The sensor information acquisition part 21 acquires the measured value of the height of the oil level of

compressors

1A, 1B by liquid level detection sensor LA, LB. The sensor information acquisition unit 21 outputs the acquired various measurement values to the control order determination unit 22.

Next, based on the measurement values acquired by the sensor information acquisition unit 21, the control order determination unit 22 determines the control order of all the

compressors

1A and 1B in ascending order of the amount of refrigeration oil in the compressors (step S12). ). For example, when the control order determination unit 22 determines the control order based on the measurement values of the pressure sensors PA and PB, the control order determination unit 22 determines that the measurement value of the pressure sensor PA <the measurement value of the pressure sensor PB. The order of the compressor 1B and the compressor 1A is set in ascending order of the amount of. The control order determination unit 22 determines to increase the rotational speed in the order of the compressor 1B and the compressor 1A. When the measured value of the pressure sensor PA> the measured value of the pressure sensor PB, the control order determination unit 22 sets the control order of the compressor 1A and the compressor 1B in ascending order of the amount of refrigeration oil, and the compressor 1A, the compressor It is decided to increase the rotational speed in the order of 1B.

For example, when the control order determination unit 22 determines the control order based on the measurement values of the temperature sensors TA and TB, if the measurement order determination unit 22 determines that the measurement value of the temperature sensor TA <the measurement value of the temperature sensor TB, the refrigerator oil The control order of the compressor 1A and the compressor 1B is set in the ascending order of the amount of d, and it is decided to increase the rotational speed in the order of the compressor 1A and the compressor 1B. For example, when the control order determination unit 22 determines the control order based on the measurement values of the liquid level detection sensors LA and LB, if the measurement value of the liquid level detection sensor LA <the measurement value of the liquid level detection sensor LB, the control order is determined. The section 22 sets the control order such as the compressor 1A and the compressor 1B in ascending order of the amount of refrigerating machine oil, and decides to increase the rotational speed of the compressor in the order of the compressor 1A and the compressor 1B.
The refrigerant circuit system 100 illustrated in FIG. 1 includes three types of sensors such as the pressure sensor PA, the temperature sensor TA, and the liquid level detection sensor LA, etc. It is sufficient if at least one type of sensor is provided. The control order determination unit 22 determines the control order of all the

compressors

1A and 1B based on the measurement values measured by at least one type of measurement values among the measurement values measured by the various sensors. The control order determination unit 22 outputs the determined control order to the oil equalization control unit 23.

Next, the oil equalizing control unit 23 increases the rotational speed of the compressor in the control order determined by the control order determination unit 22 (step S13). For example, when the control order is the order of the compressor 1A and the compressor 1B, the oil equalizing control unit 23 increases the rotational speed of the compressor 1A for a predetermined time, and then returns the rotational speed to the original rotational speed. At this time, while increasing the rotational speed of the compressor 1A, the oil equalizing control unit 23 may perform control to reduce the rotational speed of the compressor 1B for a predetermined time, and then return it to the original state. Information on the rotational speed after rising and the rotational speed after decreasing is recorded in the storage unit 24. The oil equalizing control unit 23 controls the rotational speeds of the

compressors

1A and 1B based on the information.
When the rotational speed of the compressor 1A is returned to the original rotational speed, the oil equalizing control unit 23 increases the rotational speed of the compressor 1B for a predetermined time, and then performs control to restore the original rotational speed. At this time, while increasing the rotational speed of the compressor 1B, the oil equalizing control unit 23 may perform control to reduce the rotational speed of the compressor 1A by a predetermined time, and then return it to the original state. Above, 1 time oil equalization control is complete | finished. The control of increasing the rotational speed of all the compressors may be repeated not only once but a plurality of times in the control order determined by the control order determination unit 22 in one oil equalization control.

Next, also when the start timing of oil equalization control is reached, the control device 20 controls the rotational speed of the

compressors

1A and 1B in the same procedure. By performing control according to the actual state of the amount of refrigerating machine oil stored in the

compressors

1A and 1B at the start of oil equalization control in this way, the risk of the amount of refrigerating machine oil becoming unbalanced due to oil equalization control Can be reduced. A state in which refrigerator oil is distributed equally to all the

compressors

1A and 1B by performing control to increase the rotational speed of all the

compressors

1A and 1B in a control order determined by the control order determination unit 22 Can.

Next, another configuration example of the refrigerant circuit provided with a plurality of compressors will be described.
FIG. 6 is a second schematic diagram showing an example of a refrigerant circuit system in an embodiment of the present invention.
The refrigerant circuit system 100 ′ includes two

outdoor units

30A and 30B. The outdoor unit 30A includes a compressor 1A, an oil separator 2A, a discharge pipe 3A, an oil return pipe 4A, a suction pipe 6A, a four-way valve 8A, an accumulator 9A, an outdoor heat exchanger 10A, and the like. The outdoor unit 30B includes a compressor 1B, an oil separator 2B, a discharge pipe 3B, an oil return pipe 4B, a suction pipe 6B, a four-way valve 8B, an accumulator 9B, an outdoor heat exchanger 10B and the like. The

compressors

1A and 1B of the outdoor unit 30A and the outdoor unit 30B are connected by an oil equalizing pipe 7, respectively. The

outdoor units

30A and 30B, the expansion valve 12, and the indoor heat exchanger 13 are connected by a liquid pipe 14 and a gas pipe 15. A pressure sensor PA is provided on the suction side of the compressor 1A, a temperature sensor TA is provided below the dome, and a liquid level detection sensor LA is provided inside the compressor 1A. The same applies to the compressor 1B. These sensors do not need to be all provided, and only one kind of sensor of the same type may be provided in the outdoor unit 30A and the outdoor unit 30B. The refrigerant circuit system 100 ′ shown in FIG. 6 schematically shows a basic configuration, and may further include other components. For example, two or more indoor units 40 including the expansion valve 12 and the indoor heat exchanger 13 may be provided.

Also in the refrigerant circuit system 100 ', the

compressors

1A and 1B are connected in parallel, and are operated at the same rotational speed during normal operation. The control device 20 executes the oil return operation every predetermined time, and thereafter executes oil equalization control after the predetermined time has elapsed. It is possible to apply the oil equalization control of the present embodiment to the refrigerant circuit system 100 'including the plurality of

outdoor units

30A and 30B as described above.

The oil pressure control will be described by taking the refrigerant circuit system 100 'as an example. For example, the sensor information acquisition unit 21 acquires measurement values of the pressure sensor PA of the outdoor unit 30A and the pressure sensor PB of the outdoor unit 30B (step S11). The control order determination unit 22 acquires those measurement values and determines the control order (step S12). For example, in the case where the measurement value of pressure sensor PA> the measurement value of pressure sensor PB, control order determination unit 22 first determines compressor rotation speed of compressor 1A of outdoor unit 30A and then compressor 1B of outdoor unit 30B. Decide to raise it. Next, the oil equalizing control unit 23 first increases the rotational speed of the compressor 1A for a predetermined time in the control order determined by the control order determination unit 22, and then returns the rotational speed to the original rotational speed. Next, the oil equalizing control unit 23 increases the rotational speed of the compressor 1B for a predetermined time, and then performs control to restore the original rotational speed (step S13). Thereby, the imbalance of the quantity of refrigeration oil of compressor 1A of outdoor unit 30A and compressor 1B of outdoor unit 30B is canceled.

In addition, without departing from the spirit of the present invention, it is possible to replace components in the above-described embodiment with known components as appropriate. The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the number of compressors connected in parallel with each other in the configuration of FIG. 1 may be three or more. For example, in the configuration of FIG. 6, the number of outdoor units 30A and the like may be three or more. In the control of the rotational speed of the compressor at the time of oil equalization control, control may be performed to reduce the rotational speed of the compressor in descending order of the amount of refrigeration oil in the compressor.

100, 100 '

refrigerant circuit system

1A,

1B compressor

2A,

2B oil separator

3A,

3B discharge pipe

4A, 4B

oil return pipe

5A,

5B solenoid valve

6A, 6B suction pipe 7

oil equalization pipe

8, 8A, 8B four-

way valve

9, 9A,

9B Accumulator

10, 10A, 10B Outdoor heat exchanger 11, 11A, 11B Receiver 12, 12A, 12B Expansion valve 13 Indoor heat exchanger 14

Liquid pipe

15, 16, 16A, 16B, 17, 17A, 17B Gas pipe 20 Control device 21 Sensor information acquisition unit 22 Control order determination unit 23 Oil equalization control unit 24 Storage unit PA, PB Pressure sensor TA, TB Temperature sensor LA, LB Liquid level detection sensor

Claims

In a refrigerant circuit comprising a plurality of compressors connected in parallel with one another:
A sensor information acquisition unit configured to acquire a state quantity related to the amount of refrigeration oil in the compressor for each of the plurality of compressors;
A control order determination unit configured to determine a control order of the compressor in oil equalization control according to the amount of refrigeration oil in the compressor based on the state quantity;
An oil equalizing control unit that performs oil equalizing control by changing the rotational speed of at least one of the plurality of compressors based on the order determined by the control order determining unit;
Oil equalizing control device comprising:
The control order determination unit determines the control order as the order in which the amount of refrigeration oil is smaller in order.
The oil equalizing control unit changes the rotational speed of the compressor having the order so that the pressure of the compressor having the order becomes relatively low in the control order.
The oil equalization control device according to claim 1.
The sensor information acquisition unit acquires, for each of the plurality of compressors, a measurement value of pressure on the low pressure side thereof;
The control order determination unit sets the order of the compressors for which the pressure is relatively reduced, in order from the one with the highest measurement value of the pressure.
The oil equalization control device according to claim 2.
The sensor information acquisition unit acquires a measurement value of the temperature below the dome for each of the plurality of compressors,
The control order determination unit sets the order of the compressors for which the pressure is relatively reduced, in order from the one where the measured value of the temperature is low.
The oil equalization control device according to claim 2.
The oil equalizing control device according to any one of claims 1 to 4, wherein the oil equalizing control unit increases the rotational speed for each of the plurality of compressors in the order of the control by a predetermined time.
A plurality of compressors connected in parallel with one another,
An oil equalizing pipe connecting the plurality of compressors to each other;
The oil equalizing control device according to any one of claims 1 to 5,
Refrigerant circuit system provided with
The oil pressure control system
Obtaining a state quantity related to the amount of refrigeration oil in the compressor for each of the plurality of compressors in a refrigerant circuit including a plurality of compressors connected in parallel with each other;
Determining the control order of the compressor in oil equalization control according to the amount of refrigeration oil in the compressor based on the state quantity;
The oil equalizing control is performed by changing the rotational speed of at least one of the plurality of compressors based on the control order.
Oil equalization control method.