JP6750388B2 - Refrigeration equipment - Google Patents

Description

The present invention relates to a refrigeration system.

BACKGROUND ART Conventionally, there is known a refrigeration system having a plurality of compressors in a heat source unit and improving the reliability of the compressors by allowing an intermediate pressure refrigerant to flow into each compressor via an injection pipe. For example, in the refrigeration system disclosed in Patent Document 1 (JP 2010-54186 A), the opening degree of the injection valve connected to the injection pipe is adjusted based on the temperature of the refrigerant discharged from each compressor. As a result, the flow rate of the intermediate-pressure refrigerant flowing into each compressor is adjusted.

In the conventional refrigeration system as disclosed in Patent Document 1, each injection valve is generally connected to a common upstream common pipe. In such a conventional refrigeration system, when the opening of one of the injection valves (target injection valve) is changed, the intermediate pressure passing through the other common injection valve (non-target injection valve) through the upstream common pipe. The flow rate of the refrigerant and the injection amount into the compressor corresponding to the asymmetrical injection valve may vary.

As a result, the temperature of the refrigerant discharged from the compressor may change, and the opening degree of the asymmetrical injection valve may change. Thereafter, as the opening degree of the non-target injection valve changes, the flow rate of the intermediate-pressure refrigerant passing through the target injection valve via the upstream common pipe and the injection amount into the compressor corresponding to the target injection valve may change. Therefore, a hunting phenomenon in which the temperature of the refrigerant discharged from the compressor changes and the opening degree of the target injection valve changes again may occur.

When such a hunting phenomenon occurs, in each compressor, the state of the intermediate pressure refrigerant flowing in becomes unstable, and the refrigerant in the compression chamber becomes an overheated operation state in which it becomes an overheated state, or becomes a wet operation state in which it becomes an excessively wet state. However, it is also assumed that the reliability will decrease.

Then, the subject of this invention is providing the refrigeration apparatus which suppresses the reliability fall of a compressor.

A refrigeration system according to a first aspect of the present invention includes a plurality of compressors, a plurality of injection pipes, a plurality of injection valves, an upstream common pipe, and a controller. The plurality of compressors are arranged in parallel with each other. The compressor draws in low-pressure refrigerant, compresses it, and discharges it as high-pressure refrigerant. The injection pipe corresponds to either compressor. The injection pipe is connected to the corresponding compressor. The injection pipe allows the intermediate pressure refrigerant to flow into the corresponding compressor. The injection valve corresponds to either injection pipe. One end of the injection valve is connected to the corresponding injection pipe. The injection valve regulates the flow rate of the intermediate pressure refrigerant in the corresponding injection pipe. The upstream common pipe is connected to the other end of each injection valve. The intermediate-pressure refrigerant flowing into each injection valve flows through the upstream common pipe. The controller controls the operation of each injection valve according to the situation. The controller executes the hunting suppression control when changing the opening of the target injection valve. The target injection valve is any of the injection valves. In the hunting suppression control, the opening of the non-target injection valve is changed to the hunting suppression opening. The non-target injection valve is an injection valve other than the target injection valve. The hunting suppression opening is an opening that suppresses a change in the state of the refrigerant due to a change in the opening of the target injection valve in the compressor corresponding to the non-target injection valve.

In the refrigeration system according to the first aspect of the present invention, the controller executes the hunting suppression control when the opening degree of the target injection valve (any of the injection valves) is changed, and in the hunting suppression control, the non-target injection valve (another injection valve). Valve) is changed to a hunting suppression opening (an opening that suppresses a change in the state of the refrigerant caused by a change in the opening of the target injection valve in the compressor corresponding to the non-target injection valve). As a result, when the opening degree of the target injection valve is changed, the opening degree of the non-target injection valve is changed to the hunting suppression opening degree. As a result, when the opening degree of the target injection valve is changed, the state change of the refrigerant due to the opening degree change of the target injection valve is suppressed in the compressor corresponding to the non-target injection valve. Therefore, the temperature change of the refrigerant discharged from the compressor corresponding to the non-target injection valve is suppressed due to the change in the opening degree of the target injection valve. In this connection, after changing the opening of a specific injection valve, the opening of another injection valve is changed, and then the opening of the specific injection valve is changed again. A hunting phenomenon in which changes are alternately repeated is suppressed. Therefore, in each of the compressors, it is possible to prevent the inflowing intermediate pressure refrigerant from becoming unstable and becoming a wet operation state or an overheat operation state. Therefore, deterioration of reliability of the compressor is suppressed.

A refrigeration apparatus according to a second aspect of the present invention is the refrigeration apparatus according to the first aspect, wherein the controller includes a hunting suppression opening degree determination unit. The hunting suppression opening degree determination unit determines the hunting suppression opening degree to be an opening degree that suppresses the fluctuation of the flow rate of the intermediate-pressure refrigerant passing through the non-target injection valve due to the change in the opening degree of the target injection valve.

Thereby, when the opening degree of the target injection valve is changed, the opening degree of the non-target injection valve changes due to the flow rate of the intermediate-pressure refrigerant passing through the non-target injection valve due to the opening degree change of the target injection valve. It is changed to an opening degree that suppresses this. As a result, when the opening degree of the target injection valve is changed, the flow rate of the intermediate pressure refrigerant passing through the non-target injection valve via the upstream common pipe, and the injection amount of the compressor corresponding to the non-target injection valve Fluctuation is suppressed. Therefore, the hunting phenomenon in which the opening degree of each injection valve is alternately repeated after the opening degree of the specific injection valve is changed is suppressed. Therefore, in each of the compressors, it is possible to prevent the inflowing intermediate pressure refrigerant from becoming unstable and becoming a wet operation state or an overheat operation state. Therefore, deterioration of reliability of the compressor is suppressed.

A refrigeration apparatus according to a third aspect of the present invention is the refrigeration apparatus according to the second aspect, wherein the controller further includes a pre-change refrigerant flow rate storage unit, a prediction unit, and a difference value calculation unit. The pre-change refrigerant flow rate storage unit stores the pre-change refrigerant flow rate. The pre-change refrigerant flow rate is the flow rate of the intermediate-pressure refrigerant that passes through the non-target injection valve before the opening degree of the target injection valve is changed. The predicting unit predicts the changed refrigerant flow rate based on the increase/decrease in the opening degree of the target injection valve. The changed refrigerant flow rate is the flow rate of the intermediate pressure refrigerant that passes through the asymmetrical injection valve. The difference value calculation unit calculates a difference value between the pre-change refrigerant flow rate and the post-change refrigerant flow rate. The hunting suppression opening degree determination unit determines the hunting suppression opening degree to be an opening degree having a difference value of 0 or a value close to 0.

Accordingly, the hunting suppression opening degree is determined based on the difference value between the pre-change refrigerant flow rate and the post-change refrigerant flow rate. As a result, the hunting suppression opening is accurately determined to an appropriate opening, and after changing the non-target injection valve to the hunting suppression opening, the target injection valve opening is changed in the compressor corresponding to the non-target injection valve. The resulting change in the state of the refrigerant is suppressed with high accuracy. Therefore, in each compressor, the state of the inflowing intermediate-pressure refrigerant becomes unstable, and the wet operation state or the overheat operation state is suppressed with high accuracy. Therefore, the reduction in reliability of the compressor is further suppressed.

A refrigeration system according to a fourth aspect of the present invention is the refrigeration system according to the second or third aspect, wherein the controller further includes a characteristic information storage unit. The characteristic information storage unit stores the injection valve characteristic information. The injection valve characteristic information is information that defines the correlation between the opening degree of each injection valve and the flow rate of the intermediate-pressure refrigerant that passes through. The hunting suppression opening determination unit determines the hunting suppression opening based on the injection valve characteristic information.

As a result, the hunting suppression opening degree is determined based on the previously derived characteristics of the asymmetrical injection valve. As a result, the hunting suppression opening degree is determined to be an opening degree with which the fluctuation of the flow rate of the intermediate-pressure refrigerant passing through the non-target injection valve due to the change in the opening degree of the target injection valve is highly accurately suppressed. Therefore, after the non-target injection valve is changed to the hunting suppression opening degree, the change in the refrigerant state due to the change in the opening degree of the target injection valve in the compressor corresponding to the non-target injection valve is highly accurately suppressed. That is, in each compressor, the inflowing intermediate-pressure refrigerant becomes unstable, and the wet operation state or the overheat operation state is highly accurately suppressed. Therefore, the reduction in reliability of the compressor is further suppressed.

A refrigeration apparatus according to a fifth aspect of the present invention is the refrigeration apparatus according to any of the first to fourth aspects, wherein the controller executes discharge refrigerant temperature control. The discharge refrigerant temperature control is control for changing the opening degree of each injection valve to the optimum opening degree. The optimum opening is the opening of each injection valve at which the temperature of the high-pressure refrigerant discharged from each corresponding compressor becomes a target value. The controller executes the hunting suppression control along with the discharge refrigerant temperature control.

As a result, the discharge pipe temperature of each compressor is controlled to the target value. As a result, in each of the compressors, it is possible to prevent the refrigerant from entering an overheat operation state where the pressure becomes excessively high or a wet operation state where the refrigerant becomes excessively wet. In addition, the hunting phenomenon that accompanies the discharge refrigerant temperature control is suppressed. Therefore, the deterioration of the reliability of the compressor is further suppressed.

In the refrigeration apparatus according to the first aspect of the present invention, when the opening degree of the target injection valve is changed, the state change of the refrigerant due to the opening degree change of the target injection valve in the compressor corresponding to the non-target injection valve is changed. Suppressed. Therefore, the temperature change of the refrigerant discharged from the compressor corresponding to the non-target injection valve is suppressed due to the change in the opening degree of the target injection valve. In this connection, after changing the opening of a specific injection valve, the opening of another injection valve is changed, and then the opening of the specific injection valve is changed again. A hunting phenomenon in which changes are alternately repeated is suppressed. Therefore, in each of the compressors, it is possible to prevent the inflowing intermediate pressure refrigerant from becoming unstable and becoming a wet operation state or an overheat operation state. Therefore, deterioration of reliability of the compressor is suppressed.

In the refrigerating apparatus according to the second aspect of the present invention, the deterioration of reliability of the compressor is suppressed.

In the refrigerating apparatus according to the third aspect, the fourth aspect, or the fifth aspect of the present invention, deterioration in reliability of the compressor is further suppressed.

1 is a schematic configuration diagram of a refrigerating apparatus according to an embodiment of the present invention. FIG. 3 is a block diagram schematically showing a schematic configuration of a controller and each unit connected to the controller. The flowchart shown about an example of the flow of the process which concerns on discharge refrigerant temperature control and hunting suppression control by a controller.

Hereinafter, a refrigeration apparatus 100 according to an embodiment of the present invention will be described with reference to the drawings. The following embodiments are specific examples of the present invention and do not limit the technical scope of the present invention, and can be appropriately modified within the scope of the invention.

(1) Refrigeration system 100
FIG. 1 is a schematic configuration diagram of a refrigeration apparatus 100 according to an embodiment of the present invention. The refrigerating apparatus 100 is an apparatus that cools a user-side space such as a refrigerating warehouse or a showcase of a store by a vapor compression refrigeration cycle. The refrigeration system 100 mainly includes a heat source unit 10, a plurality (here, two) of use units 30 (30a, 30b), and a controller 50 that controls the operation of the refrigeration system 100.

In the refrigeration system 100, one heat source unit 10 and each utilization unit 30 are connected via the gas refrigerant communication pipe G1 and the liquid refrigerant communication pipe L1 to form the refrigerant circuit RC. In the refrigeration system 100, a refrigeration cycle is performed in which the refrigerant enclosed in the refrigerant circuit RC is compressed, cooled or condensed, decompressed, heated or evaporated, and then compressed again. The refrigerant circuit RC is filled with an HFC refrigerant such as R32 or R410A. The refrigerant circuit RC may be filled with a refrigerant other than the HFC refrigerant, such as ammonia or CO ₂ .

(1-1) Heat source unit 10
(1-1-1) Circuit Elements Arranged in Heat Source Unit 10 The heat source unit 10 is connected to the utilization unit 30 via the gas refrigerant communication pipe G1 and the liquid refrigerant communication pipe L1, and is a part of the refrigerant circuit RC. Is composed of. The heat source unit 10 mainly includes a plurality of (here, three) compressors 11 (first compressor 11a, second compressor 11b, third compressor 11c) as circuit elements that constitute the refrigerant circuit RC, and a heat source. The side heat exchanger 12, the receiver 13, the subcooling heat exchanger 14, the first expansion valve 15, the second expansion valve 16, and the same number of injection valves 17 (here, three) as the compressor 11 (here, three). It has a 1-injection valve 17a, a second injection valve 17b, a third injection valve 17c), a gas side closing valve SV1 and a liquid side closing valve SV2.

Each compressor 11 sucks the low-pressure refrigerant in the refrigeration cycle, compresses it, and discharges it as a high-pressure refrigerant. The compressor 11 is, for example, a scroll type compressor, and has a closed structure in which a compression element (not shown) is rotationally driven by a compressor motor (not shown) in a casing. In the present embodiment, the first compressor 11a is a “variable displacement compressor” with a variable operating capacity in which the rotation speed of the compressor motor is appropriately controlled by an inverter during operation. The second compressor 11b and the third compressor 11c are "constant-capacity compressors" in which the rotational speed of the compressor motor during operation is constant and the operating capacity is constant. The first compressor 11a, the second compressor 11b, and the third compressor 11c are arranged in parallel with each other.

The heat source side heat exchanger 12 is a heat exchanger that functions as a radiator or condenser of high-pressure refrigerant in the refrigeration cycle. The heat source side heat exchanger 12 includes a heat transfer tube (not shown) through which the refrigerant flows, and is configured such that the refrigerant in the heat transfer tube and the airflow generated by the heat source side fan 19 (described later) exchange heat. Has been done.

The receiver 13 is a container that temporarily stores the refrigerant flowing out from the heat source side heat exchanger 12. Inside the receiver 13, a refrigerant storage space having a capacity corresponding to the amount of refrigerant enclosed in the refrigerant circuit RC is formed.

The subcooling heat exchanger 14 is, for example, a double tube heat exchanger. The supercooling heat exchanger 14 is formed with two refrigerant flow passages (a first flow passage 141 and a second flow passage 142). The first flow channel 141 is a flow channel through which the refrigerant flowing out from the receiver 13 passes. The second flow path 142 is a flow path through which the intermediate pressure refrigerant, which has been decompressed by the second expansion valve 16 after passing through the first flow path 141, passes. The subcooling heat exchanger 14 is configured such that the refrigerant in the first flow path 141 and the refrigerant in the second flow path 142 exchange heat.

The first expansion valve 15 is an electric expansion valve whose opening degree can be controlled, and decompresses the refrigerant passing therethrough according to the opening degree. The first expansion valve 15 decompresses the high-pressure liquid refrigerant that has passed through the first flow passage 141 of the subcooling heat exchanger 14 into a low-pressure gas-liquid two-phase refrigerant.

The second expansion valve 16 is an electric expansion valve whose opening degree can be controlled. The second expansion valve 16 reduces the pressure of the refrigerant passing therethrough or increases or decreases the flow rate of the refrigerant passing therethrough according to the opening degree. The second expansion valve 16 passes through the first flow path 141 of the supercooling heat exchanger 14 to reduce the pressure of the high-pressure liquid refrigerant to a medium-pressure gas-liquid two-phase refrigerant/liquid refrigerant (intermediate-pressure refrigerant). The second expansion valve 16 is arranged on the upstream side of the refrigerant flow of the upstream common pipe (the twelfth pipe P12 described later) flowing on the upstream side of the injection valve 17, and adjusts the flow rate of the intermediate-pressure refrigerant flowing through the upstream common pipe. Functions as a "flow control valve".

Each injection valve 17 is an electric expansion valve whose opening degree can be controlled. Each injection valve 17 reduces the pressure of the refrigerant passing therethrough or increases or decreases the flow rate of the refrigerant passing therethrough according to the opening degree. Each of the injection valves 17 has one end connected to an injection pipe (a fourth pipe P4 described later) of the corresponding compressor 11 and adjusts the flow rate of the intermediate-pressure refrigerant passing therethrough. Here, the first injection valve 17a corresponds to the first compressor 11a and the fourth pipe P4a (described later). The second injection valve 17b corresponds to the second compressor 11b and the fourth pipe P4b (described later). The third injection valve 17c corresponds to the third compressor 11c and the fourth pipe P4c (described later).

The gas side closing valve SV1 is a manual valve connected to one end of the gas refrigerant communication pipe G1. The liquid side closing valve SV2 is a manual valve connected to one end of the liquid refrigerant communication pipe L1.

(1-1-2) Refrigerant Pipes Arranged in Heat Source Unit 10 The heat source unit 10 has a plurality of refrigerant pipes (specifically, the same number as the first pipes P1 and the number of compressors 11) that connect each circuit element. (Three) second pipe P2 (P2a, P2b, P2c), third pipe P3 (P3a, P3b, P3c) and fourth pipe P4 (P4a, P4b, P4c), and fifth pipe P5-twelfth pipe P12).

The first pipe P1 individually connects one end of the gas side stop valve SV1 and one end of each second pipe P2 (suction pipe). The first pipe P1 functions as a “low pressure side refrigerant pipe” in which the refrigerant flowing through the suction pipe of each compressor 11 (that is, the low pressure refrigerant flowing into each compressor 11) flows collectively.

Each second pipe P2 corresponds to one of the compressors 11, is connected to the suction port of the corresponding compressor 11, and functions as a “suction pipe” through which the low-pressure refrigerant flowing into the corresponding compressor 11 flows. The second pipe P2a corresponds to the first compressor 11a, the second pipe P2b corresponds to the second compressor 11b, and the second pipe P2c corresponds to the third compressor 11c.

Each third pipe P3 corresponds to one of the compressors 11, is connected to the discharge port of the corresponding compressor 11, and functions as a discharge pipe through which the high-pressure refrigerant discharged from the corresponding compressor 11 flows. The third pipe P3a corresponds to the first compressor 11a, the third pipe P3b corresponds to the second compressor 11b, and the third pipe P3c corresponds to the third compressor 11c.

Each of the fourth pipes P4 corresponds to one of the compressors 11, is connected to the injection port of the corresponding compressor 11, and functions as an “injection pipe” that allows the intermediate pressure refrigerant to flow into the compression chamber of the corresponding compressor 11. To do. The fourth pipe P4a corresponds to the first compressor 11a, the fourth pipe P4b corresponds to the second compressor 11b, and the fourth pipe P4c corresponds to the third compressor 11c.

The fifth pipe P5 individually connects one end of each third pipe P3 and the gas side of the heat source side heat exchanger 12. The fifth pipe P5 functions as a “high pressure side refrigerant pipe” in which the refrigerant flowing through the discharge pipe of each compressor 11 (that is, the high pressure refrigerant discharged from each compressor 11) flows together.

The sixth pipe P6 connects the liquid side of the heat source side heat exchanger 12 and the refrigerant inlet port of the receiver 13. The seventh pipe P7 connects the refrigerant outlet port of the receiver 13 and one end of the first flow path 141 of the supercooling heat exchanger 14. The eighth pipe P8 connects the other end of the first flow path 141 of the subcooling heat exchanger 14 and one end of the first expansion valve 15. The ninth pipe P9 connects one end of the first expansion valve 15 and one end of the liquid side closing valve SV2. The tenth pipe P10 extends from between one end and the other end of the eighth pipe P8 and is connected to one end of the second expansion valve 16. The eleventh pipe P11 connects the other end of the second expansion valve 16 and one end of the second flow path 142 of the supercooling heat exchanger 14.

The twelfth pipe P12 individually connects the other end of the second flow path 142 of the subcooling heat exchanger 14 and the other end of each injection valve 17. More specifically, the twelfth pipe P12 has one end connected to the second flow path 142 and the other end branched into three, which are individually connected to the respective injection valves 17. The twelfth pipe P12 is connected to the other end of each injection valve 17, and functions as an “upstream common pipe” in which the intermediate-pressure refrigerant flowing into each injection valve 17 flows collectively.

In the refrigerant circuit RC, the tenth pipe P10, the second expansion valve 16, the eleventh pipe P11, the second flow path 142 of the supercooling heat exchanger 14, the twelfth pipe P12, each injection valve 17, and each first pipe. The injection line J1 is constituted by the four pipes P4. The injection line J1 is a refrigerant flow path for branching a part of the refrigerant flowing through the eighth pipe P8 and causing the refrigerant to flow (inject) into each compressor 11.

(1-1-3) Other Devices Arranged in Heat Source Unit 10 The heat source unit 10 flows into the heat source unit 10 from the outside of the heat source unit 10, passes through the heat source side heat exchanger 12, and then to the outside of the heat source unit 10. It has a heat source side fan 19 for generating an outflowing air flow. The heat source side fan 19 is a blower for supplying the heat source side heat exchanger 12 with air as a cooling source of the refrigerant flowing through the heat source side heat exchanger 12. The heat source side fan 19 is, for example, a propeller fan or a sirocco fan, and is rotationally driven by a heat source side fan motor (not shown).

The heat source unit 10 includes a low pressure side pressure sensor 21, a high pressure side pressure sensor 22, an intermediate pressure sensor 23, and a plurality of discharge temperature sensors 25 (first discharge temperature sensor 25a, second discharge temperature sensor 25b, third discharge temperature). It has various sensors such as the sensor 25c).

The low-pressure side pressure sensor 21 is arranged in the first pipe P1 (low-pressure side refrigerant pipe) located on the refrigerant flow upstream side of the suction pipes (P2a, P2b, P2c) of each compressor 11. The low pressure side pressure sensor 21 detects the low pressure side pressure LP that is the pressure of the refrigerant (that is, the low pressure refrigerant on the suction side of each compressor 11) passing through the first pipe P1.

The high-pressure side pressure sensor 22 is arranged in the fifth pipe P5 located on the refrigerant flow downstream side of the discharge pipes (P3a, P3b, P3c) of each compressor 11. The high pressure side pressure sensor 22 detects the high pressure side pressure HP which is the pressure of the refrigerant (that is, the high pressure refrigerant on the discharge side of each compressor 11) passing through the fifth pipe P5.

The intermediate pressure sensor 23 is arranged in the twelfth pipe P12 (upstream common pipe) located on the refrigerant flow upstream side of the injection pipes (P4a, P4b, P4c) of each compressor 11. The intermediate pressure sensor 23 detects the intermediate pressure MP which is the pressure of the refrigerant passing through the twelfth pipe P12 (that is, the intermediate pressure refrigerant flowing into each injection valve 17).

The discharge temperature sensor 25 is arranged in the discharge pipe (P3a, P3b, or P3c) connected to the corresponding compressor 11, and detects the temperature of the high-pressure refrigerant discharged from the corresponding compressor 11 (discharge refrigerant temperature HT). To do. The first discharge temperature sensor 25a corresponds to the first compressor 11a, the second discharge temperature sensor 25b corresponds to the second compressor 11b, and the third discharge temperature sensor 25c corresponds to the third compressor 11c.

(1-2) Usage unit 30
The utilization unit 30 is connected to the heat source unit 10 via the gas refrigerant communication pipe G1 and the liquid refrigerant communication pipe L1, and constitutes a part of the refrigerant circuit RC. In the present embodiment, two utilization units 30 (30a and 30b) are connected to one heat source unit 10. The usage units 30 are arranged in parallel with each other.

Each usage unit 30 has a usage-side expansion valve 31 and a usage-side heat exchanger 32. The use-side expansion valve 31 reduces the pressure of the refrigerant passing therethrough or increases or decreases the flow rate of the refrigerant passing therethrough according to the opening degree. The usage-side heat exchanger 32 is a heat exchanger that functions as an evaporator for low-pressure refrigerant in the refrigeration cycle and cools the air in the refrigerator. The usage-side heat exchanger 32 includes a heat transfer tube (not shown) through which the refrigerant flows, and is configured such that the refrigerant in the heat transfer tube and the airflow generated by the usage-side fan 35 (described later) exchange heat. Has been done.

In addition, the usage unit 30 generates a flow of air that flows into the usage unit 30 from outside the usage unit 30, passes through the usage side heat exchanger 32, and then flows out to the outside of the usage unit 30 (use side space). 35. The usage-side fan 35 is a fan for supplying the usage-side heat exchanger 32 with air as a heat source for the refrigerant flowing through the usage-side heat exchanger 32. The usage-side fan 35 is, for example, a centrifugal fan or a sirocco fan, and is rotationally driven by a usage-side fan motor (not shown).

(1-3) Controller 50
The controller 50 is a control unit that controls the operation state of the refrigeration system 100 by controlling the operation of each actuator included in the refrigeration system 100. The controller 50 is mounted on a board arranged in the heat source unit 10 and/or the utilization unit 30 (not shown). The controller 50 has a microcomputer including a CPU and a memory. The controller 50 is electrically connected to each actuator included in the refrigeration system 100, and inputs and outputs signals. In addition, the controller 50 is electrically connected to various sensors included in the refrigeration system 100, and receives a signal corresponding to the detection result as appropriate. Details of the controller 50 will be described later.

(2) Flow of Refrigerant in Refrigerant Circuit RC During Cooling Operation Hereinafter, the flow of refrigerant in the refrigerant circuit RC during operation will be described. In the refrigeration system 100, during operation, the capacity of the first compressor 11a (variable capacity compressor) is controlled according to the cooling load required by the utilization unit 30, and the second compressor 11b and the third compressor 11c (capacity). The constant compressor is operated at the rated speed. Specifically, with respect to the low-pressure side pressure LP, the high-pressure side pressure HP, and/or the intermediate pressure MP, respective target values are set according to the cooling load required by the utilization unit 30, and the set target values are set. The number of driven compressors 11 and the operating capacity of the first compressor 11a are controlled so as to be realized. As a result, the refrigerant with which the refrigerant circuit RC is filled mainly contains one of the operating compressor 11, heat source side heat exchanger 12, receiver 13, supercooling heat exchanger 14 (first flow path 141), and A cooling operation (refrigeration cycle operation) in which the 1-expansion valve 15, the usage-side expansion valve 31, and the usage-side heat exchanger 32 circulate in this order is performed.

During the cooling operation, the refrigerant is drawn through the suction pipe (P2a, P2b, or P2c) into the compressor 11 that is being driven, compressed, and then discharged as high-pressure refrigerant. Here, the low pressure in the refrigeration cycle is the low pressure side pressure LP detected by the low pressure side pressure sensor 21, the high pressure is the high pressure side pressure HP detected by the high pressure side pressure sensor 22, and the intermediate pressure is measured by the intermediate pressure sensor 23. It is the detected intermediate pressure MP.

The gas refrigerant discharged from each compressor 11 flows through the corresponding discharge pipes (P3a, P3b, P3c) and merges with the refrigerant discharged from the other compressors 11 in the fifth pipe P5 to generate heat on the heat source side. It flows into the gas side end of the exchanger 12. In each of the operating compressors 11, the intermediate-pressure refrigerant is injected into the compression chamber through the injection pipe (fourth pipe P4), and the temperature of the discharged high-pressure refrigerant is controlled to a target value. ..

The gas refrigerant flowing into the gas-side end of the heat-source-side heat exchanger 12 exchanges heat with the air supplied by the heat-source-side fan 19 in the heat-source-side heat exchanger 12 to radiate heat and condense, thereby producing a high-pressure liquid refrigerant. / Becomes a gas-liquid two-phase refrigerant and flows out from the liquid side end of the heat source side heat exchanger 12. The refrigerant flowing out from the liquid side end of the heat source side heat exchanger 12 flows into the refrigerant inlet port of the receiver 13 via the sixth pipe P6. The refrigerant flowing into the receiver 13 is temporarily stored in the receiver 13 as a saturated liquid refrigerant, and then flows out from the refrigerant outlet of the receiver 13.

The liquid refrigerant flowing out from the outlet of the receiver 13 flows into the first flow path 141 of the supercooling heat exchanger 14 via the seventh pipe P7. The liquid refrigerant flowing into the first flow passage 141 of the subcooling heat exchanger 14 is further cooled by exchanging heat with the refrigerant flowing through the second flow passage 142 in the supercooling heat exchanger 14, and is in the supercooled state. It becomes a refrigerant and flows out from the subcooling heat exchanger 14.

The supercooled liquid refrigerant flowing out from the subcooling heat exchanger 14 flows through the eighth pipe P8. The refrigerant flowing through the eighth pipe P8 branches into two. One of the two branched refrigerants in the eighth pipe P8 flows into the first expansion valve 15. The refrigerant flowing into the first expansion valve 15 is decompressed according to the opening degree of the first expansion valve 15 to become a low-pressure gas-liquid two-phase refrigerant. The gas-liquid two-phase refrigerant that has passed through the first expansion valve 15 passes through the liquid side stop valve SV2 via the ninth pipe P9 and flows out from the heat source unit 10.

On the other hand, the other of the two branched refrigerants in the eighth pipe P8 flows into the injection line J1. The refrigerant flowing into the injection line J1 flows into the second expansion valve 16 via the tenth pipe P10. The refrigerant flowing into the second expansion valve 16 is decompressed according to the opening degree of the second expansion valve 16 to become an intermediate pressure liquid refrigerant/gas-liquid two-phase refrigerant. The refrigerant that has passed through the second expansion valve 16 flows into the second flow path 142 of the supercooling heat exchanger 14 via the eleventh pipe P11. The flow rate of the refrigerant flowing through the injection line J1 mainly fluctuates based on the opening degree of the second expansion valve 16, the opening degree of each injection valve 17, the frequency of the compressor 11 being driven, and the like.

The liquid refrigerant flowing into the second flow path 142 of the supercooling heat exchanger 14 is heated by exchanging heat with the refrigerant flowing through the first flow path 141 in the subcooling heat exchanger 14, and is heated to the intermediate pressure gas-liquid two. It becomes a phase refrigerant/gas refrigerant and flows out from the subcooling heat exchanger 14. The intermediate-pressure gas-liquid two-phase refrigerant/gas refrigerant flowing out from the subcooling heat exchanger 14 flows through the twelfth pipe P12. The flow rate of the refrigerant flowing through the second flow path 142 of the subcooling heat exchanger 14 and the twelfth pipe P12 increases or decreases according to the opening degree of the second expansion valve 16.

The refrigerant flowing through the twelfth pipe P12 branches into three and flows into each injection valve 17. The refrigerant flowing into each injection valve 17 is decompressed/flow-rate-adjusted according to the opening degree of the injection valve 17, and injected into the compression chamber of the compressor 11 via the injection pipe (fourth pipe P4).

Here, the injection is performed for the purpose of controlling the temperature of the refrigerant discharged from the compressor 11 to a target value. That is, when the compressed high-pressure refrigerant in the operating compressor 11 is in an overheated operation state in which the high-pressure refrigerant is excessively superheated, the reliability of the compressor 11 decreases. In order to suppress such a situation, an intermediate pressure refrigerant having an optimal flow rate (optimal injection amount) is injected into the compressor 11 depending on the situation. The optimum injection amount is appropriately adjusted according to the detection value of each discharge temperature sensor 25 (that is, the discharge refrigerant temperature HT).

The low-pressure two-phase refrigerant flowing out of the heat source unit 10 flows into each usage unit 30 via the liquid refrigerant communication pipe L1. The refrigerant that has flowed into the usage unit 30 flows into the usage-side expansion valve 31, is decompressed/flow-rate-controlled according to the opening degree of the usage-side expansion valve 31, and flows into the liquid-side end of the usage-side heat exchanger 32.

The refrigerant flowing into the liquid side end of the usage-side heat exchanger 32 exchanges heat with the air supplied by the usage-side fan 35 in the usage-side heat exchanger 32, evaporates, and is used as a low-pressure gas refrigerant. It flows out from the gas side end of the side heat exchanger 32.

The gas refrigerant flowing out from the gas side end of the usage side heat exchanger 32 flows into the heat source unit 10 via the gas refrigerant communication pipe G1 and the gas side closing valve SV1. The refrigerant flowing into the heat source unit 10 flows through the first pipe P1 and is sucked into the compressor 11 which is being driven again.

(3) Details of Controller 50 FIG. 2 is a block diagram schematically showing a schematic configuration of the controller 50 and each unit connected to the controller 50.

The controller 50 includes respective actuators included in the heat source unit 10 (specifically, the compressor 11 (compressor motor), the first expansion valve 15, the injection valve 17, and the heat source side fan 19 (heat source side fan motor), It is electrically connected to various sensors (low-pressure side pressure sensor 21, high-pressure side pressure sensor 22, intermediate pressure sensor 23, respective discharge temperature sensors 25, etc.) The controller 50 also uses each usage unit 30 (30a and 30a). 30b) is electrically connected to the actuators (specifically, the use-side fan 35 (use-side fan motor) and the use-side expansion valve 31).

The controller 50 mainly has a storage unit 51, an input control unit 52, a drive signal output unit 53, an actuator control unit 54, and an INJ valve control unit 55. Each of these units in the controller 50 is realized by organically functioning each element (CPU, various memories, communication modules, various interfaces, various electric components, etc.) that constitutes the controller 50.

(3-1) Storage unit 51 (pre-change refrigerant flow rate storage unit, characteristic information storage unit)
The storage unit 51 is composed of various memories such as a ROM, a RAM, and/or a flash memory, and includes a plurality of storage areas. For example, the storage unit 51 includes a program storage area 511 for storing a control program that defines processing in each unit of the controller 50.

Further, the storage unit 51 includes a characteristic information storage area 512. The characteristic information storage area 512 is a storage area for individually storing characteristic information of each valve (specifically, the second expansion valve 16 and each injection valve 17 etc.) included in the refrigeration system 100. Here, the characteristic information is information that defines a correlation between the valve opening degree and the flow rate of the passing refrigerant, and is derived in advance.

In addition, the storage unit 51 includes a sensor value storage area 513. The sensor value storage area 513 is a detection value of each sensor included in the refrigeration system 100 (specifically, the low pressure side pressure sensor 21, the high pressure side pressure sensor 22, the intermediate pressure sensor 23, each discharge temperature sensor 25, and the like). This is a storage area for individually storing the low-pressure side pressure LP, the intermediate pressure MP, the high-pressure side pressure HP, the discharge refrigerant temperature HT, and the like.

The storage unit 51 also includes an INJ amount storage area 514. The INJ amount storage area 514 individually stores information for specifying the flow rate of intermediate pressure refrigerant (hereinafter, referred to as “injection amount IJ1”) flowing into each compressor 11 through the injection pipe (P4) per predetermined time. This is a storage area for In other words, the injection amount IJ1 is the flow rate of the intermediate pressure refrigerant passing through the corresponding injection valve 17 per predetermined time.

The storage unit 51 also includes a changed INJ amount storage area 515. The INJ difference value storage area 516 stores the flow rate of the intermediate pressure refrigerant flowing into each compressor 11 through the injection pipe (P4) per predetermined time after the opening degree of the injection valve 17 is changed according to the discharge refrigerant temperature control described later. This is a storage area for individually storing information that specifies a predicted value (hereinafter, referred to as “changed injection amount IJ2”).

The storage unit 51 also includes an INJ difference value storage area 516. The INJ difference value storage area 516 identifies a difference value DV that is a difference value between each changed injection amount IJ2 and the corresponding injection amount IJ1 (that is, the injection amount IJ1 before the opening change of the target injection valve 17). A storage area for individually storing information to be stored.

In addition, the storage unit 51 is provided for determining the state of the opening degree of each valve (specifically, the first expansion valve 15, the second expansion valve 16, the injection valve 17 and the like) included in the refrigeration system 100. Multiple flags are provided. For example, the storage unit 51 is provided with a first flag FL1, a second flag FL2, a third flag FL3, and a fourth flag FL4. Each flag includes a predetermined number of bits and is set according to the state of the opening degree of the corresponding valve (for example, the number of pulses). That is, by referring to the state of each flag, the opening state (current opening) of each valve can be determined in real time. In the present embodiment, the first flag FL1 corresponds to the first injection valve 17a, the second flag FL2 corresponds to the second injection valve 17b, the third flag FL3 corresponds to the third injection valve 17c, and the fourth flag. FL4 corresponds to the second expansion valve 16.

Further, the storage unit 51 is provided with a command determination flag (not shown) and the like capable of determining various commands input by the user (for example, the set temperature of each usage unit 30).

(3-2) Input control unit 52
The input control unit 52 acquires a signal output from each of the other units to the controller 50 and stores the signal in the storage unit 51. For example, the input control unit 52 receives signals corresponding to detection results output from various sensors (21-23, 25, etc.), adds predetermined identification data, and stores the signals in the sensor value storage area 513 individually.

(3-3) Drive signal output unit 53
The drive signal output unit 53 outputs a predetermined drive signal (drive voltage) to each actuator (11a-11c, 15, 16, 17a-17c, 19, 35, 36, etc.). The drive signal output unit 53 includes a plurality of inverters (not shown), and outputs a drive signal to the first compressor 11a, the heat source side fan 19, and each usage side fan 35 via the corresponding inverters. ..

(3-4) Actuator control unit 54
The actuator control unit 54 controls the operation of each actuator included in the refrigeration system 100 (the heat source unit 10 and the utilization unit 30) according to the situation according to the control program. For example, the actuator control unit 54 determines the rotation speed of the compressor 11, the rotation speeds of the heat source side fan 19 and the respective use side fans 35, and the opening degree of the first expansion valve 15 according to the set temperature, the detection values of various sensors, and the like. , The opening degree of the second expansion valve 16 and the opening degree of each usage-side expansion valve 31, depending on the type of command, the magnitude of the cooling load, the detection value of each sensor (21, 22, 23, 25), etc. Control in real time.

(3-5) INJ valve control unit 55
The INJ valve control unit 55 controls the operation of each injection valve 17 according to the situation in accordance with the control program. The INJ valve control unit 55 controls the opening degree of each injection valve 17 (17a, 17b, 17c) to an optimum opening degree at which the temperature of the high-pressure refrigerant discharged from each compressor 11 becomes a target value during operation. A discharge refrigerant temperature control unit 56 that executes temperature control is included. The INJ valve control unit 55 also includes a hunting suppression control unit 57 that executes hunting suppression control for suppressing a hunting phenomenon that is caused by a change in the opening degree of the injection valve 17 associated with the discharge refrigerant temperature control.

(3-5-1) Discharge refrigerant temperature control unit 56
In the discharge refrigerant temperature control, the discharge refrigerant temperature control unit 56 appropriately refers to the discharge refrigerant temperature HT of each compressor 11 stored in the sensor value storage area 513 so that each discharge refrigerant temperature HT matches the target value. Then, the optimum injection amount for each compressor 11 is calculated individually. In particular, in the discharge refrigerant temperature control, when there is the compressor 11 whose discharge refrigerant temperature HT matches the target value, the discharge refrigerant temperature control unit 56 first sets the injection amount IJ1 of the compressor 11 as the optimum injection amount. The calculated injection amount IJ1 of the other compressor 11 is calculated based on the calculated optimum injection amount.

For example, the discharge refrigerant temperature HT of the second compressor 11b (constant capacity compressor) matches the target value, and the discharge of the first compressor 11a (variable capacity compressor) and the third compressor 11c (constant capacity compressor) When the refrigerant temperature HT does not match the target value, the discharge refrigerant temperature control unit 56 first determines that the discharge refrigerant temperature HT of the second compressor 11b matches the target value, and then the second compressor 11b. Regarding the above, the current injection amount IJ1 is calculated as the optimum injection amount. Regarding the current injection amount IJ1 of the second compressor 11b, a difference value obtained by dividing the low-pressure side pressure LP from the intermediate pressure MP stored in the sensor value storage area 513 (hereinafter referred to as “pressure difference DP”). And the corresponding current opening degree of the second injection valve 17b.

Next, regarding the optimum injection amount of the first compressor 11a, which is a “variable capacity compressor”, the optimum injection amount of the second compressor 11b, the rotation speed of the first compressor 11a, and the second compressor 11b. It is calculated using the following calculation formula (A) based on the rotation speed ratio.
Optimal injection amount of the first compressor 11a=(optimal injection amount of the second compressor 11b+revolution of the first compressor 11a)/revolution of the second compressor 11b (A)
Then, similar to the second compressor 11b, the optimum injection amount of the third compressor 11c, which is a “constant capacity compressor”, is calculated as the same flow rate as the optimum injection amount of the second compressor 11b.

In addition, for example, regarding the processing when the discharge refrigerant temperature HT of the third compressor 11c matches the target value and the discharge refrigerant temperature HT of the first compressor 11a and the second compressor 11b does not match the target value, In the example, the second compressor 11b is replaced with the third compressor 11c, and the third compressor 11c is replaced with the second compressor 11b.

In the discharge refrigerant temperature control, regarding the target value of the discharge refrigerant temperature HT of each compressor 11 and the method of calculating the optimum injection amount, the type of the input command, the size of the cooling load, and the rotation speed of the compressor 11 are described. Accordingly, a predetermined calculation formula is individually defined in the control program, or a predetermined table is stored in the program storage area 511, and the calculation formula and/or the table is used.

The discharge refrigerant temperature control unit 56 individually determines the opening degree of each injection valve 17 based on the calculated optimum injection amount of each compressor 11. At this time, the discharged refrigerant temperature control unit 56 stores the characteristic information (injection valve characteristic information defining the correlation between the opening degree and the flow rate of the passing refrigerant) of each injection valve 17 stored in the characteristic information storage area 512. With reference to the characteristic information, the opening degree (optimal opening degree) that matches the optimum injection amount is individually determined for each injection valve 17.

After that, the discharge refrigerant temperature control unit 56 causes the drive signal output unit 53 to output a drive signal (pulse signal) required for each injection valve 17 from the current opening to the optimum opening. Further, the discharge refrigerant temperature control unit 56 sets a predetermined flag (FL1, FL2, FL3) of the storage unit 51 based on the current opening degree of each injection valve 17.

(3-5-2) Hunting suppression control unit 57
The hunting suppression control unit 57 is configured to execute the hunting suppression control based on the following viewpoints. That is, when the optimum opening degree of one of the injection valves 17 (hereinafter, referred to as “target injection valve 17”) is changed in accordance with the discharge refrigerant temperature control, the intermediate pressure MP may change, but the intermediate pressure MP may change. When occurs, the optimum opening degree of the other injection valve 17 (hereinafter, referred to as "asymmetrical injection valve 17") can be changed. Then, when the optimum opening of the non-target injection valve 17 is changed, the intermediate pressure MP may change again, but when the change of the intermediate pressure MP occurs, the optimum opening of the target injection valve 17 may be changed again. .. As described above, a hunting phenomenon in which the opening degree of each injection valve 17 is alternately repeated may occur due to the control of the discharged refrigerant temperature. When such a hunting phenomenon occurs, the state of the intermediate pressure refrigerant flowing into each compressor 11 becomes unstable, and the refrigerant in the compression chamber becomes excessively overheated, or the wet operation state becomes excessively wet. Therefore, the reliability may be reduced. The hunting suppression control unit 57 is configured to execute hunting suppression control in order to suppress the hunting phenomenon.

The hunting suppression control unit 57 includes a post-change INJ amount prediction unit 571 (prediction unit), a difference value calculation unit 572, and a hunting suppression opening degree determination unit 573 in relation to the hunting suppression control.

The post-change INJ amount prediction unit 571 changes the opening degree when any of the opening degrees of the injection valves 17 in the respective flags (FL1, FL2, FL3) included in the storage section 51 is changed in accordance with the discharge refrigerant temperature control. Based on the changed opening (change of the opening) of the changed injection valve 17 (that is, the target injection valve 17), each injection amount IJ1 stored in the storage unit 51, the rotation speed of the compressor 11, and the like. , A predicted value for the fluctuating intermediate pressure MP (hereinafter, referred to as “changed intermediate pressure MP′”) is calculated. Then, based on the opening degree of the injection valve 17 whose opening degree has not been changed (that is, the asymmetrical injection valve 17) and the pressure difference DP (the difference value obtained by dividing the low pressure side pressure LP from the changed intermediate pressure MP′) The predicted flow rate of the intermediate-pressure refrigerant (changed injection amount IJ2) passing through each non-target injection valve 17 is individually calculated per hour. That is, the post-change INJ amount prediction unit 571 predicts the post-change injection amount IJ2 based on the increase/decrease in the opening degree of the target injection valve 17 and the like. The changed INJ amount prediction unit 571 individually stores the calculated changed injection amount IJ2 in the changed INJ amount storage area 515 of the storage unit 51.

When the changed injection amount IJ2 is newly stored in the changed INJ amount storage area 515, the difference value calculation unit 572 causes the changed injection amount IJ2 and the corresponding injection amount IJ1 in the INJ amount storage area 514 (that is, A difference value DV between the post-change injection amount IJ2 and the pre-change injection amount IJ1) is calculated. The difference value calculation unit 572 stores the calculated difference value DV in the INJ difference value storage area 516 of the storage unit 51.

The hunting suppression opening degree determination unit 573 relates to the opening degree of the asymmetrical injection valve 17, that is, an opening degree that cancels the difference value DV, that is, an opening degree at which the difference value DV becomes 0 or a value close to 0 (hereinafter, “hunting suppression degree”). "Opening degree"). More specifically, the hunting suppression opening degree determination unit 573 determines the opening degree that increases or decreases according to the difference value DV from the current opening degree of the non-target injection valve 17 corresponding to the changed injection amount IJ2. To decide. As a result, the hunting suppression opening is determined such that the differential pressure across the non-target injection valve 17 is the same before and after the target injection valve 17 is changed to the optimum opening. That is, the hunting suppression opening is an opening that suppresses a change in the state of the refrigerant due to a change in the opening of the target injection valve 17 in the compressor 11 corresponding to the target injection valve 17.

It should be noted that the "opening degree at which the differential pressure across the non-target injection valve 17 is the same" here means that the non-target injection valve 17 before and after the target injection valve 17 is changed to the optimum opening degree. It includes not only the opening at which the front-to-back differential pressure is completely the same, but also the opening at which it is substantially the same. That is, even when the differential pressure across the non-target injection valve 17 before and after the target injection valve 17 is changed to the optimum opening degree is different, if the error is a slight difference, "the target injection valve 17 is optimal. The differential pressure across the asymmetrical injection valve 17 before and after the opening is changed is the same."

Note that the hunting suppression opening determination unit 573 is configured to inject the characteristic information of the asymmetrical injection valve 17 stored in the characteristic information storage area 512 (injection regarding the correlation between the opening and the flow rate of the refrigerant passing per predetermined time). The hunting suppression opening is determined based on the valve information). Therefore, the hunting suppression opening degree is determined with high accuracy to an opening degree that suppresses a change in the state of the refrigerant due to a change in the opening degree of the target injection valve 17 in the compressor 11 corresponding to the non-target injection valve 17. It is like this.

After that, the hunting suppression opening degree determination unit 573 causes the drive signal output unit 53 to output a drive signal (pulse signal) necessary for the hunting suppression opening degree determined from the current opening degree with respect to the corresponding non-target injection valve 17, and A predetermined flag (FL1, FL2, FL3) in the storage unit 51 is set.

(4) Process Flow of Controller 50 An example of the flow of discharge refrigerant temperature control and hunting suppression control by the controller 50 will be described below with reference to FIG. FIG. 3 is a flow chart showing an example of the flow of processing relating to discharge refrigerant temperature control and hunting suppression control by the controller 50. In FIG. 3, particularly, the processing relating to the discharge refrigerant temperature control is shown in steps S102 to S105, and the processing relating to the hunting suppression control is shown in steps S106 to S110. Note that the processing flow shown in FIG. 3 is an example, and can be changed as appropriate. For example, the order of steps may be changed within a consistent range, and some steps may be executed in parallel with other steps. Further, the controller 50 executes the process related to the discharge refrigerant temperature control and the hunting suppression control in parallel with the process related to other controls.

During operation, the controller 50 executes the processes related to the discharge refrigerant temperature control and the hunting suppression control in the flow as shown in steps S101 to S110 shown in FIG.

In step S101, the controller 50 individually determines the injection amount IJ1 of each compressor 11 based on the current opening degree of each injection valve 17 and the pressure difference DP (a difference value obtained by dividing the low-pressure side pressure LP from the intermediate pressure MP). Calculate to. Then, it progresses to step S102.

In step S102, the controller 50 returns to step S101 when the discharge refrigerant temperature HT of each compressor 11 matches the target value (that is, YES). On the other hand, if the discharge refrigerant temperature HT of each compressor 11 does not match the target value (that is, NO), the process proceeds to step S103.

In step S103, the controller 50 calculates the optimum injection amount for each compressor 11 whose discharge refrigerant temperature HT deviates from the target value so that the discharge refrigerant temperature HT matches the target value. Then, it progresses to step S104.

In step S104, the controller 50, regarding the injection valve 17 (target injection valve 17) corresponding to the compressor 11 related to the calculated optimum injection amount, the opening degree (optimal opening degree) that matches the optimum injection amount based on the characteristic information. To decide. Then, it progresses to step S105.

In step S105, the controller 50 outputs a drive signal (pulse signal) required for the target injection valve 17 from the current opening to the optimum opening to control each injection valve 17 to the optimum opening. Then, it progresses to step S106.

In step S106, the controller 50 changes the opening degree of the target injection valve 17 to the optimum opening degree by controlling the discharge refrigerant temperature. The post-change intermediate pressure MP′ (predicted value of the intermediate pressure MP) is calculated based on each injection amount IJ1 stored in 51, the rotation speed of the compressor 11, and the like. Then, it progresses to step S107.

In step S107, the controller 50 determines, for each non-target injection valve 17, the opening degree of the non-target injection valve 17 and the pressure difference DP (a difference value obtained by dividing the low-pressure side pressure LP from the changed intermediate pressure MP′). Based on this, the changed injection amount IJ2 (predicted flow rate of the intermediate pressure refrigerant passing through each non-target injection valve 17 per predetermined time) is individually calculated. Then, it progresses to step S108.

In step S108, the controller 50 calculates a difference value DV (a difference value between each changed injection amount IJ2 and the corresponding injection amount IJ1). Then, it progresses to step S109.

In step S109, the controller 50 individually determines the hunting suppression opening degree for each asymmetrical injection valve 17 based on each calculated difference value DV. More specifically, the controller 50 determines, for each asymmetrical injection valve 17, the opening that increases or decreases from the current opening according to the difference value DV as the hunting suppression opening. At this time, the controller 50 determines the hunting suppression opening degree based on the characteristic information of the asymmetrical injection valve 17 (injection valve characteristic information regarding the correlation between the opening degree and the flow rate of the passing refrigerant). Then, it progresses to step S110.

In step S110, the controller 50 individually outputs, to each non-target injection valve 17, a drive signal (pulse signal) required for the hunting suppression opening determined from the current opening to hunt each non-target injection valve 17. Control the opening degree. Then, it returns to step S101.

(5) Features of the refrigeration system 100 (5-1)
In the refrigeration system 100 according to the above-described embodiment, the reliability of the compressor 11 is prevented from decreasing.

That is, by adjusting the opening degree of the injection valve connected to the injection pipe connected to each compressor, based on the temperature of the refrigerant discharged from each compressor, of the intermediate pressure refrigerant to flow into each compressor. In a conventional refrigeration system that adjusts the flow rate, each injection valve is generally connected to a common upstream common pipe. In such a conventional refrigeration system, when the opening of one of the injection valves (target injection valve) is changed, the intermediate pressure passing through the other common injection valve (non-target injection valve) through the upstream common pipe. The flow rate of the refrigerant and the injection amount into the compressor corresponding to the asymmetrical injection valve may vary.

As a result, the temperature of the refrigerant discharged from the compressor may change, and the opening degree of the asymmetrical injection valve may change. Thereafter, as the opening degree of the non-target injection valve changes, the flow rate of the intermediate-pressure refrigerant passing through the target injection valve via the upstream common pipe and the injection amount into the compressor corresponding to the target injection valve may change. Therefore, a hunting phenomenon may occur in which the temperature of the refrigerant discharged from the compressor is changed and the opening degree of the target injection valve is changed again.

When such a hunting phenomenon occurs, in each compressor, the state of the intermediate pressure refrigerant flowing in becomes unstable, and the refrigerant in the compression chamber becomes an overheated operation state in which it becomes an overheated state, or becomes a wet operation state in which it becomes an excessively wet state. However, it is also assumed that the reliability will decrease.

In this respect, in the refrigeration system 100 of the above-described embodiment, the controller 50 executes the hunting suppression control when the opening degree of the target injection valve 17 (any of the injection valves 17) is changed, and in the hunting suppression control, the non-target injection valve 17 is used. Opening of (another injection valve 17) is a hunting suppression opening (opening for suppressing a change in the state of the refrigerant due to a change in the opening of the target injection valve 17 in the compressor 11 corresponding to the non-target injection valve 17) Change to. Thereby, when the opening degree of the target injection valve 17 is changed, the opening degree of the non-target injection valve 17 is changed to the hunting suppression opening degree.

As a result, when the opening degree of the target injection valve 17 is changed, the state change of the refrigerant due to the opening degree change of the target injection valve 17 in the compressor 11 corresponding to the non-target injection valve 17 is suppressed. It has become. Therefore, the temperature change of the refrigerant discharged from the compressor 11 corresponding to the non-target injection valve 17 is suppressed due to the change in the opening degree of the target injection valve 17. In connection with this, after changing the opening of the specific injection valve 17, the opening of the other injection valve 17 is changed, and then the opening of the specific injection valve 17 is changed again. The hunting phenomenon in which the opening degree 17 is alternately repeated is suppressed.

Therefore, in each compressor 11, it is suppressed that the inflowing intermediate-pressure refrigerant becomes unstable and becomes the wet operation state or the overheat operation state. Therefore, the decrease in reliability of the compressor 11 is suppressed.

(5-2)
In the refrigeration system 100 according to the above embodiment, the controller 50 includes the hunting suppression opening degree determination unit 573. The hunting suppression opening determination unit 573 sets the hunting suppression opening to an opening that suppresses fluctuations in the flow rate of the intermediate-pressure refrigerant passing through the non-target injection valve 17 due to the change in the opening of the target injection valve 17. I have decided.

Accordingly, when the opening degree of the target injection valve 17 is changed, the opening degree of the non-target injection valve 17 is determined by the flow rate of the intermediate-pressure refrigerant passing through the non-target injection valve 17 due to the opening degree change of the target injection valve 17. Then, the opening is changed so as to suppress the fluctuation. As a result, when the opening degree of the target injection valve 17 is changed, the flow rate of the intermediate pressure refrigerant passing through the non-target injection valve 17 via the upstream common pipe (P12) and the compression corresponding to the non-target injection valve 17 Fluctuations in the amount of injection into the machine 11 are suppressed. Therefore, after the opening degree of the specific injection valve 17 is changed, the hunting phenomenon in which the opening degree change of each injection valve 17 is alternately repeated is suppressed. Therefore, in each compressor 11, it is suppressed that the inflowing intermediate-pressure refrigerant becomes unstable and becomes the wet operation state or the overheat operation state. Therefore, the decrease in reliability of the compressor 11 is suppressed.

(5-3)
In the refrigeration system 100 according to the above-described embodiment, the controller 50 is based on the storage unit 51 (INJ amount storage area 514) that stores the injection amount IJ1 (refrigerant flow rate before change) and the increase/decrease in the opening degree of the target injection valve 17. It includes a post-change INJ amount prediction unit 571 that predicts the post-change injection amount IJ2 (post-change refrigerant flow rate), and a difference value calculation unit 572 that calculates a difference value DV between the injection amount IJ1 and the post-change injection amount IJ2. .. The hunting suppression opening determination unit 573 determines the hunting suppression opening to be an opening at which the difference value DV becomes 0 or a value close to 0.

Thus, the hunting suppression opening is determined based on the difference value DV between the injection amount IJ1 and the changed injection amount IJ2. As a result, the hunting suppression opening is accurately determined to an appropriate opening, and after changing the non-target injection valve 17 to the hunting suppression opening, the target injection valve 17 in the compressor 11 corresponding to the non-target injection valve 17 is changed. The change in the state of the refrigerant due to the change in the opening degree is highly accurately suppressed. Therefore, in each of the compressors 11, it is highly accurately suppressed that the state of the inflowing intermediate pressure refrigerant becomes unstable and becomes the wet operation state or the overheat operation state. Therefore, the decrease in reliability of the compressor 11 is suppressed with high accuracy.

(5-4)
In the refrigeration system 100 according to the above-described embodiment, the controller 50 includes the storage unit 51, and in the storage unit 51 (characteristic information storage area 512), the correlation between the opening degree of each injection valve 17 and the flow rate of the intermediate pressure refrigerant passing therethrough is shown. The defined characteristic information (injection valve characteristic information) is stored. The hunting suppression opening determination unit 573 determines the hunting suppression opening based on the characteristic information.

As a result, the hunting suppression opening degree is determined based on the characteristics of the non-target injection valve 17 that are derived in advance. As a result, the hunting suppression opening is determined to be an opening that highly accurately suppresses the fluctuation of the flow rate of the intermediate-pressure refrigerant passing through the non-target injection valve 17 due to the change in the opening of the target injection valve 17. It is like this. Therefore, after the non-target injection valve 17 is changed to the hunting suppression opening degree, the state change of the refrigerant due to the change in the opening degree of the target injection valve 17 in the compressor 11 corresponding to the non-target injection valve 17 is highly accurately suppressed. Has been done. That is, in each of the compressors 11, the state of the inflowing intermediate-pressure refrigerant becomes unstable, and the wet operation state or the overheat operation state is highly accurately suppressed. Therefore, the deterioration of the reliability of the compressor 11 is suppressed with high accuracy.

(5-5)
In the refrigeration system 100 according to the above embodiment, the controller 50 sets the opening degree of each injection valve 17 to the optimum opening degree (the temperature of the high-pressure refrigerant discharged from each corresponding compressor 11 becomes a target value, each injection valve 17). The discharge refrigerant temperature control for changing to the opening degree) is executed, and the hunting suppression control is executed along with the discharge refrigerant temperature control.

As a result, the discharge pipe temperature of each compressor 11 is controlled to the target value. As a result, in each compressor 11, the state of the refrigerant is suppressed from being in an overheat operation state in which the pressure is excessively high or in a wet operation state in which the refrigerant is excessively wet. In addition, the hunting phenomenon due to the discharge refrigerant temperature control is suppressed. Therefore, the decrease in reliability of the compressor 11 is particularly suppressed.

(6) Modifications The above-described embodiment can be modified as appropriate as shown in the following modifications. Note that each modification may be applied in combination with another modification as long as no contradiction occurs.

(6-1) Modification A
In the above embodiment, the controller 50 is configured to execute the hunting suppression control along with the discharge refrigerant temperature control. However, the conditions can be changed as appropriate. For example, the controller 50 may be configured to execute the hunting suppression control when the opening degree of any of the injection valves 17 is changed by another control that is different from the discharge refrigerant temperature control.

(6-2) Modification B
The calculation method of the optimum injection amount, the optimum opening amount, the injection amount IJ1, the changed injection amount IJ2, and/or the hunting suppression opening amount in the above embodiment is merely an example, and is different from the method described in the above embodiment. The method may be appropriately adopted.

(6-3) Modification C
The circuit configuration of the refrigerant circuit RC and the devices arranged in the refrigeration system 100 in the above-described embodiment can be appropriately changed, and some circuit elements and devices can be appropriately omitted. For example, the receiver 13 arranged in the heat source unit 10 and the use side expansion valve 31 arranged in each of the usage units 30 are not always necessary and can be omitted as appropriate. Further, the use-side expansion valve 31 may be a temperature-sensitive expansion valve, a pressure reducing mechanism such as a capillary tube, instead of the electric expansion valve.

Further, in the refrigerant circuit RC, other circuit elements or devices may be included instead of/in addition to the circuit elements or devices. For example, in the refrigerant circuit RC, a four-way switching valve may be newly arranged to allow defrost operation or heating operation in which the refrigerant flows between the heat source unit 10 and the usage unit 30 in a cycle reverse to that in the cooling operation. Good. In this case, the four-way switching valve is connected to each pipe configured by dividing the first pipe P1 into upstream and downstream and each pipe configured by dividing the fifth pipe P5 into upstream and downstream, and the reverse The heat source side heat exchanger 12 may be controlled to function as a refrigerant evaporator and the use side heat exchanger 32 may be controlled to function as a refrigerant radiator or condenser during a cycle.

(6-4) Modification D
In the above-described embodiment, the present invention is applied to the refrigerating apparatus 100 that cools the inside of a refrigerated warehouse or a store showcase. However, the present invention is not limited to this, and the present invention can be applied to other refrigeration systems. For example, the present invention may be applied to a refrigeration system that cools a shipping container. Further, for example, the present invention can be applied to an air conditioning system (air conditioner) that realizes air conditioning by cooling the inside of a building, a water heater, a heat pump chiller, and the like.

(6-5) Modification E
In the above-mentioned embodiment, it has one heat source unit 10 and three utilization units 30. However, the number of heat source units 10 arranged in the refrigeration system 100 is not particularly limited, and may be two or more. Moreover, the number of the utilization units 30 included in the refrigeration apparatus 100 is not particularly limited, and may be one or three or more.

(6-6) Modification F
In the above-described embodiment, among the plurality of compressors 11 arranged in the heat source unit 10, the variable capacity compressor is one of the first compressors 11a, and the constant capacity compressor is the second compressor 11b and the third compressor 11b. There were two compressors 11c. However, the distribution of the variable capacity compressors and the fixed capacity compressors can be appropriately changed according to design specifications. For example, two or three variable capacity compressors may be used. Further, for example, all the compressors 11 may be variable capacity compressors. Further, for example, all the compressors 11 may be constant capacity compressors.

Further, in the above embodiment, three compressors 11 are arranged in total, but the number of compressors 11 can be appropriately changed according to the design specifications. For example, the number of compressors 11 may be two, or four or more. In this case, the allocation of the variable capacity compressor and the fixed capacity compressor may be appropriately selected.

(6-7) Modification G
In the above embodiment, the arrangement position of the controller 50 is not particularly limited. The controller 50 does not necessarily need to be installed in the same space as the heat source unit 10 and/or the utilization unit 30, but is installed in a remote place connected to the heat source unit 10 and/or the utilization unit 30 via a communication network. May be. In addition, each element (CPU, memory, various electric parts, etc.) configuring the controller 50 does not necessarily have to be installed in the same position, and each element arranged in a dispersive different space is connected via a communication network. By doing so, the controller 50 may be configured.

INDUSTRIAL APPLICABILITY The present invention can be used for refrigeration equipment.

10: Heat source unit 11: Compressor 11a-11c: 1st compressor-3rd compressor 12: Heat source side heat exchanger 13: Receiver 14: Supercooling heat exchanger 15: 1st expansion valve 16: 2nd expansion valve 17: Injection valve (target injection valve, non-target injection valve)
17a-17c: 1st injection valve-3rd injection valve 19: Heat source side fan 21: Low pressure side pressure sensor 22: High pressure side pressure sensor 23: Intermediate pressure sensor 25: Discharge temperature sensor 25a-25c: 1st discharge temperature sensor- Third discharge temperature sensor 30: Utilization unit 50: Controller 51: Storage unit (pre-change refrigerant flow rate storage unit, characteristic information storage unit)
52: Input control unit 53: Drive signal output unit 54: Actuator control unit 55: INJ valve control unit 56: Discharge refrigerant temperature control unit 57: Hunting suppression control unit 100: Refrigeration device 141: First flow path 142: Second flow Path 571: changed INJ amount prediction unit (prediction unit)
572: Difference value calculation part 573: Hunting suppression opening degree determination part DV: Difference value FL1-FL4: 1st flag-4th flag G1: Gas refrigerant connection piping IJ1: Injection amount (refrigerant flow rate before change)
IJ2: injection amount after change (refrigerant flow rate after change)
J1: injection line L1: liquid refrigerant communication pipe MP': post-change intermediate pressure P1: first pipe P2 (P2a, P2b, P2c): second pipe (suction pipe)
P3 (P3a, P3b, P3c): Third pipe (discharge pipe)
P4 (P4a, P4b, P4c): Fourth pipe (injection pipe)
P5-P11: 5th piping-11th piping P12: 12th piping (upstream common piping)
RC: Refrigerant circuit SV1: Gas side closing valve SV2: Liquid side closing valve

JP, 2010-54186, A

Claims (5)

A plurality of compressors (11) arranged in parallel with each other, which suck in low-pressure refrigerant, compress it, and discharge it as high-pressure refrigerant;
A plurality of injection pipes (P4) corresponding to any of the compressors, which are connected to the corresponding compressors and allow an intermediate pressure refrigerant to flow thereinto;
A plurality of injection valves (17) corresponding to any of the injection pipes, one end of which is connected to the corresponding injection pipe, and which adjusts the flow rate of the intermediate-pressure refrigerant;
An upstream common pipe (P12) connected to the other end of each injection valve, through which the intermediate-pressure refrigerant flowing into each injection valve flows,
A controller (50) for controlling the operation of each of the injection valves according to the situation;
Equipped with
The controller is
Performing hunting suppression control at the time of changing the opening of the target injection valve that is any of the injection valves,
In the hunting suppression control, the opening degree of the non-target injection valve which is the injection valve other than the target injection valve, due to the opening degree change of the target injection valve in the compressor corresponding to the non-target injection valve. Change to a hunting suppression opening that suppresses changes in the state of the refrigerant,
Refrigeration system (100). The controller determines the hunting suppression opening to an opening that suppresses fluctuation of the flow rate of the intermediate-pressure refrigerant passing through the non-target injection valve due to a change in the opening of the target injection valve. Including a suppression opening determination unit (573),
The refrigeration system (100) according to claim 1. The controller is
A pre-change refrigerant flow rate storage unit (51) that stores a pre-change refrigerant flow rate (IJ1) that is a flow rate of the intermediate-pressure refrigerant that passes through the non-target injection valve before changing the opening degree of the target injection valve;
A prediction unit (571) for predicting a changed refrigerant flow rate (IJ2) which is a flow rate of the intermediate-pressure refrigerant passing through the non-target injection valve, based on an increase/decrease in the opening degree of the target injection valve;
A difference value calculation unit (572) for calculating a difference value between the pre-change refrigerant flow rate and the post-change refrigerant flow rate,
Further including,
The hunting suppression opening degree determination unit determines the hunting suppression opening degree to be an opening degree at which the difference value is 0 or a value close to 0.
The refrigeration system (100) according to claim 2. The controller further includes a characteristic information storage unit (51) that stores injection valve characteristic information that defines a correlation between the opening degree of each of the injection valves and the flow rate of the intermediate-pressure refrigerant passing therethrough,
The hunting suppression opening determination unit determines the hunting suppression opening based on the injection valve characteristic information,
The refrigeration system (100) according to claim 2 or 3. The controller is
The opening of each of the injection valves, the temperature of the high-pressure refrigerant discharged from each of the corresponding compressor to perform a discharge refrigerant temperature control to change to an optimal opening of a target value,
The hunting suppression control is executed along with the discharge refrigerant temperature control,
The refrigeration system (100) according to any one of claims 1 to 4.

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