Control device, compression system and control method

Abstract

To provide a control device, a compression system and a control method capable of reducing an execution frequency of oil return operation.SOLUTION: A control device comprises a control unit that, when turning on or off a solenoid valve provided in a circuit that returns oil discharged from a compressor together with a refrigerant to the inside of the compressor according to an amount of oil inside the compressor, turns on the solenoid valve when the amount of oil is equal to or less than a first threshold, and turns off the solenoid valve when the amount of oil is equal to or larger than a second threshold that is larger than the first threshold and a time that has elapsed since the solenoid valve was turned on exceeds a minimum on time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control device, a compression system, and a control method. [Background technology]

[0002] In the air conditioner described in Patent Document 1, multiple predetermined oil return conditions are set, and when any of the oil return conditions is met, oil return operation is initiated to recover lubricating oil that has leaked into the refrigerant circuit and ensure a predetermined amount of oil in the compressor. Furthermore, in this air conditioner, the oil return operation ends when a predetermined termination condition is met. Furthermore, in this air conditioner, if the oil return operation is performed when a high outdoor temperature is set as the oil return condition, the oil return operation is prohibited for a certain period of time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-149659 Summary of the Invention [Problem to be solved by the invention]

[0004] However, among the multiple types of oil return conditions described in Patent Document 1, there are some that do not have restrictions on the frequency of start and end, which poses a problem that, depending on the operating conditions, for example, the start and end of the oil return operation may be repeated frequently.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a control device, a compression system, and a control method that can reduce the frequency of oil return operation. [Means for solving the problem]

[0006] In order to solve the above problem, the control device of the present disclosure includes a control unit that, when turning on or off a solenoid valve provided in a circuit that returns oil discharged from a compressor together with refrigerant to the inside of the compressor depending on the amount of oil inside the compressor, turns on the solenoid valve when the amount of oil is equal to or less than a first threshold, and turns off the solenoid valve when the amount of oil is equal to or greater than a second threshold that is greater than the first threshold and the elapsed time since the solenoid valve was turned on exceeds a minimum on time.

[0007] The compression system according to the present disclosure includes a compressor that compresses a refrigerant and discharges it together with oil stored therein; a tank that stores the oil separated from the refrigerant; and a control unit that, when turning on or off a solenoid valve provided in a circuit that returns the oil from the tank to the inside of the compressor depending on the amount of oil inside the compressor, turns on the solenoid valve when the amount of oil is equal to or less than a first threshold, and turns off the solenoid valve when the amount of oil is equal to or greater than a second threshold that is greater than the first threshold and the elapsed time since the solenoid valve was turned on exceeds a minimum on time.

[0008] The control method disclosed herein turns on or off a solenoid valve provided in a circuit that returns oil discharged from a compressor together with a refrigerant to the inside of the compressor depending on the amount of oil inside the compressor. When the amount of oil is equal to or less than a first threshold, the solenoid valve is turned on, and when the amount of oil is equal to or greater than a second threshold that is greater than the first threshold and the elapsed time since the solenoid valve was turned on exceeds a minimum on time. [Effects of the Invention]

[0009] According to the control device, compression system, and control method of the present disclosure, it is possible to reduce the frequency of performing the oil return operation. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example configuration of a compression system according to an embodiment of the present disclosure. [Figure 2] 10 is a flowchart illustrating an example of operation of the compression system according to an embodiment of the present disclosure. [Figure 3] 4 is a timing chart illustrating an example of operation of a compression system according to an embodiment of the present disclosure. [Figure 4] 10 is a flowchart illustrating an example of operation of the compression system according to an embodiment of the present disclosure. [Figure 5] FIG. 1 is a schematic block diagram illustrating the configuration of a computer according to at least one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] A control device, a compression system, and a control method according to an embodiment of the present disclosure will be described below with reference to FIGS. 1 to 4. FIG. 1 is a diagram illustrating an example configuration of a compression system according to an embodiment of the present disclosure. FIG. 2 is a flowchart illustrating an example operation of a compression system according to an embodiment of the present disclosure. FIG. 3 is a timing chart illustrating an example operation of a compression system according to an embodiment of the present disclosure. FIG. 4 is a flowchart illustrating an example operation of a compression system according to an embodiment of the present disclosure. Note that the same or corresponding components in each drawing are designated by the same reference numerals, and descriptions thereof will be omitted as appropriate.

[0012] (Compression system configuration) The compression system 1 shown in Fig. 1 is a compression system installed in, for example, a large-capacity CO2 refrigerator, and includes a high-stage compressor 11, a low-stage compressor 21, a control panel 3, a separator 4, an oil tank 5, a constant oil return circuit 61, a capillary circuit for adjusting the oil return amount 63, a constant oil return circuit 71, a capillary circuit for adjusting the oil return amount 73, and peripheral devices thereof. In this embodiment, the refrigerant is carbon dioxide. However, the embodiment of the present disclosure is not limited to this.

[0013] High-stage compressor 11 is a compressor that compresses a refrigerant, and is connected to oil pod 12, which stores oil (also called lubricating oil, refrigeration oil, etc.) that is filled inside high-stage compressor 11, by pipe 13. The oil level in oil pod 12 matches the oil level in high-stage compressor 11. The oil level in oil pod 12 is detected by oil level sensor 14. Refrigerant compressed in low-stage compressor 21 is introduced into high-stage compressor 11 via an intercooler, accumulator, capillary, strainer, etc., which are not shown.

[0014] Low-stage compressor 21 is a compressor that compresses a refrigerant, and is connected to oil pod 22, which stores oil filled inside low-stage compressor 21, by pipe 23. The oil level in oil pod 22 matches the oil level in low-stage compressor 21. The oil level in oil pod 22 is measured by oil level sensor 24. Refrigerant is introduced into low-stage compressor 21 via an accumulator or the like (not shown).

[0015] Oil is discharged from the high-stage compressor 11 along with the refrigerant. The oil discharged together with the refrigerant is separated by the separator 4, and the separated oil is stored in the oil tank 5. The oil stored in the oil tank 5 is returned to the high-stage compressor 11 and the low-stage compressor 21 via the constant oil return circuit 61 and the constant oil return circuit 71. The amount of oil discharged from the high-stage compressor 11 and the low-stage compressor 21 varies depending on the startup of the high-stage compressor 11 and the low-stage compressor 21 and load fluctuations. For example, if the constant oil return circuit 61 and the constant oil return circuit 71 are unable to return all the oil, the amount of returned oil is adjusted by controlling the opening and closing of the solenoid valve 64 or the solenoid valve 74 provided in the oil return amount adjustment capillary circuit 63 or the solenoid valve 74 provided in the oil return amount adjustment capillary circuit 73. In this embodiment, the operation of turning on the solenoid valve 64 or the solenoid valve 74 corresponds to the oil return operation.

[0016] The separator 4 and the oil tank 5 are connected by a pressure equalizing pipe 41. The constant oil return circuit 61 is equipped with a capillary 62. The constant oil return circuit 71 is equipped with a capillary 72. The capillary circuit 63 for adjusting the oil return amount is equipped with a solenoid valve 64 and a capillary 65. The capillary circuit 73 for adjusting the oil return amount is equipped with a solenoid valve 74 and a capillary 75. The solenoid valve 64 is controlled to open and close by the control panel 3. The solenoid valve 74 is controlled to open and close by the control panel 3. A detection signal indicating the oil level detected by the oil level sensor 14 is output to the control panel 3. A detection signal indicating the oil level detected by the oil level sensor 24 is output to the control panel 3.

[0017] On the other hand, the control panel 3 controls each part of the compression system 1 (or a chiller including the compression system 1). The control panel 3 is one example of a configuration of a control device according to the present disclosure. In this embodiment, the control panel 3 includes a solenoid valve control unit 31, a solenoid valve control unit 32, a time update unit 33, and a time update unit 34.

[0018] The solenoid valve control unit 31 controls the opening and closing (controls the solenoid valve 64 to be turned on or off) based on the detection signal of the oil level sensor 14. The detection signal of the oil level sensor 14 is, for example, a signal indicating the height of the oil level. The height of the oil level can be converted into the amount of oil based on the internal structure of the high-stage compressor 11. Therefore, the solenoid valve control unit 31 may turn the solenoid valve 64 on or off depending on the amount of oil inside the high-stage compressor 11, or may turn it on or off depending on the oil level. For example, the solenoid valve control unit 31 turns on the solenoid valve 64 when the amount of oil is equal to or less than a first threshold corresponding to a low oil level. Furthermore, the solenoid valve control unit 31 turns off the solenoid valve 64 when, for example, the amount of oil is equal to or greater than a second threshold corresponding to a full oil level that is greater than the first threshold corresponding to a low oil level, and the elapsed time since the solenoid valve 64 was turned on exceeds a minimum on-time. Here, the minimum on-time is a value determined based on the upper limit number of on-off cycles (endurance number) of the solenoid valve 64 and the future operating time of the solenoid valve 64. The future operating time may be the normal replacement time or product life (or usable period) of the solenoid valve 64, or the product life of the high-stage compressor 11. The minimum on-time is determined so that the value obtained by dividing the future operating time by the minimum on-time does not exceed the upper limit number of on-off cycles (endurance number) of the solenoid valve 64.

[0019] Furthermore, the time update unit 33 updates the minimum on-time in the solenoid valve control unit 31 when a predetermined update condition is satisfied. The update condition can be, for example, the time elapsed since the time of factory shipment or the last update of the minimum on-time, or the operating time of the high-stage compressor 11 since the last update of the minimum on-time has reached a predetermined time. The time update unit 33 updates the minimum on-time so that, at the time the update condition is satisfied, the value obtained by dividing the future operating time by the minimum on-time does not exceed the upper limit number of on-off cycles (endurance number) of the solenoid valve 64.

[0020] Similarly to the solenoid valve control unit 31, the solenoid valve control unit 32 controls the opening and closing (controls the solenoid valve 74 to turn on or off) based on the detection signal of the oil level sensor 24. Similarly to the time update unit 33, the time update unit 34 updates the minimum on-time in the solenoid valve control unit 32 when a predetermined update condition is satisfied.

[0021] (Example of compression system operation) 2 to 4, an example of the operation of the solenoid valve control unit 31 and the time update unit 33 in the compression system 1 will be described. Note that the operation of the solenoid valve control unit 32 and the time update unit 34 is the same as the operation of the solenoid valve control unit 31 and the time update unit 33.

[0022] The process shown in FIG. 2 is repeatedly executed at a predetermined cycle after the control panel 3 is started. When the process shown in FIG. 2 is started, the solenoid valve control unit 31 determines whether the solenoid valve 64 is off (closed state) (S11). If the solenoid valve 64 is off (S11: YES), the solenoid valve control unit 31 determines whether the oil level has remained below the drought level for a predetermined period of time or more (S12). This continuing for a predetermined period of time or more ensures that the oil level is stable at or below the drought level. If the oil level has remained below the drought level for a predetermined period of time or more (S12: YES), the solenoid valve control unit 31 turns on (opens) the solenoid valve 64 (S13) and ends the process shown in FIG. 2. If the oil level has not remained below the drought level for a predetermined period of time or more (S12: NO), the solenoid valve control unit 31 ends the process shown in FIG. 2.

[0023] On the other hand, if the solenoid valve 64 is on (S11: NO), the solenoid valve control unit 31 determines whether the state in which the oil level is equal to or higher than the full oil level has continued for a predetermined time or longer (S14). If the state in which the oil level is equal to or higher than the full oil level has continued for a predetermined time or longer (S14: YES), the solenoid valve control unit 31 determines whether the on-time of the solenoid valve 64 (the time elapsed since it was turned on) is equal to or longer than the minimum on-time (S15). If the on-time of the solenoid valve 64 is equal to or longer than the minimum on-time (S15: YES), the solenoid valve control unit 31 turns off (closes) the solenoid valve 64 (S16) and ends the processing shown in FIG. 2. If the state in which the oil level is equal to or higher than the full oil level has not continued for a predetermined time or longer (S14: NO), or if the on-time of the solenoid valve 64 is not equal to or longer than the minimum on-time (S15: NO), the solenoid valve control unit 31 ends the processing shown in FIG. 2.

[0024] Figure 3 shows an example of the oil amount and solenoid valve operation. In the example shown in Figure 3, the oil amount reaches a low oil level at time t1, and the solenoid valve 64 turns on at time t2 after a predetermined time has elapsed. Then, at time t3, the oil amount reaches a full oil level. However, at time t3, the minimum on-time has not yet elapsed since time t2. At time t4, the minimum on-time has elapsed, and the solenoid valve 64 turns off.

[0025] At time t5, the oil level becomes low, and at time t6, the solenoid valve 64 is turned on. At time t7, the minimum on time has elapsed, but the oil level has not yet reached the full oil level. At time t8, the oil level reaches the full oil level, and at time t9, after a predetermined time has elapsed, the solenoid valve 64 is turned off.

[0026] As shown in Figure 3, the oil level reaches the full oil level at time t3, but solenoid valve 64 is not turned off at this point, and the oil level continues to increase. Increasing the oil level beyond the full oil level reduces the compression efficiency of high-stage compressor 11. However, because the frequency of on / off operation of solenoid valve 64 can be reduced, the replacement life of solenoid valve 64 can be maintained at a predetermined value.

[0027] Next, an example of the operation of the time update unit 33 will be described with reference to Fig. 4. The process shown in Fig. 4 is repeatedly executed at a predetermined cycle after the control panel 3 is started. When the process shown in Fig. 4 starts, the time update unit 33 determines whether or not predetermined update conditions are satisfied (S21). If the update conditions are satisfied, the time update unit 33 calculates the minimum on-time based on, for example, the operating time of the compressor, the estimated remaining operating time, the number of times the solenoid valve is opened and closed, and the upper limit of the number of times the solenoid valve is opened and closed, updates the set value of the minimum on-time (S22), and ends the process shown in Fig. 4.

[0028] (Actions and Effects) According to this embodiment, when turning on or off a solenoid valve provided in a circuit that returns oil discharged from the compressor together with refrigerant to the compressor according to the amount of oil inside the compressor, the solenoid valve control unit turns on the solenoid valve when the amount of oil is equal to or less than a first threshold, and turns off the solenoid valve when the amount of oil is equal to or greater than a second threshold that is greater than the first threshold and the elapsed time since the solenoid valve was turned on exceeds the minimum on time. This configuration makes it possible to reduce the frequency of the oil return operation (the on and off operation of solenoid valves 64 and 74, which are oil return valves).

[0029] (Other embodiments) The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

[0030] <Computer Configuration> FIG. 5 is a schematic block diagram illustrating the configuration of a computer according to at least one embodiment. The computer 90 includes a processor 91 , a main memory 92 , a storage 93 , and an interface 94 . The control panel 3 described above is implemented in a computer 90. The operations of the above-described processing units are stored in the form of a program in a storage 93. A processor 91 reads the program from the storage 93, loads it into a main memory 92, and executes the above-described processing in accordance with the program. The processor 91 also allocates storage areas in the main memory 92 corresponding to the above-described storage units in accordance with the program.

[0031] The program may be for realizing some of the functions to be performed by the computer 90. For example, the program may be combined with other programs already stored in storage or other programs implemented in other devices to perform the functions. In other embodiments, the computer may include a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device) in addition to or instead of the above configuration. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor may be realized by the integrated circuit.

[0032] Examples of storage 93 include a hard disk drive (HDD), a solid state drive (SSD), a magnetic disk, a magneto-optical disk, a compact disc read-only memory (CD-ROM), a digital versatile disc read-only memory (DVD-ROM), and a semiconductor memory. Storage 93 may be an internal medium directly connected to the bus of computer 90, or an external medium connected to computer 90 via interface 94 or a communication line. Furthermore, when this program is distributed to computer 90 via a communication line, computer 90 that receives the program may load the program into main memory 92 and execute the above-described processing. In at least one embodiment, storage 93 is a non-transitory tangible storage medium.

[0033] <Additional Notes> The control device (control panel 3) described in each embodiment can be understood, for example, as follows.

[0034] (1) A control device (control panel 3) according to a first embodiment includes control units (solenoid valve control units 31 and 32) that, when turning on or off solenoid valves 64 and 74 provided in circuits (oil return amount adjustment capillary circuits 63 and 73) that return oil discharged together with refrigerant from compressors (high-stage compressor 11 and low-stage compressor 21) to the inside of the compressors, turn on the solenoid valves when the amount of oil is equal to or less than a first threshold, and turn off the solenoid valves when the amount of oil is equal to or greater than a second threshold that is greater than the first threshold and the elapsed time since the solenoid valves were turned on exceeds a minimum on time. According to this embodiment and the following embodiments, the frequency of oil return operation (on and off operation of solenoid valves 64 and 74, which are oil return valves) can be reduced.

[0035] (2) A control device (control panel 3) according to a second aspect is the control device (control panel 3) of (1), in which the minimum on-time is a value determined based on the upper limit number of on-off cycles of the solenoid valve and the future operating time of the solenoid valve. According to this aspect, for example, it is possible to reliably reduce the frequency of maintenance of the control valve.

[0036] (3) A control device (control panel 3) according to a third aspect is the control device (control panel 3) of (1) or (2), in which the minimum on-time is updated when a predetermined update condition is satisfied. According to this aspect, it is possible to appropriately achieve both a reduction in frequency and suppression of a decrease in compressor efficiency.

[0037] (4) A compression system according to a fourth aspect includes compressors (high-stage compressor 11 and low-stage compressor 21) that compress a refrigerant and discharge it together with oil stored therein, a tank (oil tank 5) that stores the oil separated from the refrigerant, and a control unit (solenoid valve control units 31 and 32) that turns on or off solenoid valves 64 and 74 provided in circuits (capillary circuits 63 and 73 for adjusting return oil amount) that return the oil from the tank to the compressor according to the amount of oil inside the compressor when the amount of oil is equal to or less than a first threshold, and turns off the solenoid valve when the amount of oil is equal to or greater than a second threshold that is greater than the first threshold and the elapsed time since the solenoid valve was turned on exceeds a minimum on time.

[0038] (5) A fifth aspect of the control method involves turning on or off a solenoid valve provided in a circuit that returns oil discharged from a compressor together with a refrigerant to the inside of the compressor depending on the amount of oil inside the compressor. When the amount of oil is equal to or less than a first threshold, the solenoid valve is turned on, and when the amount of oil is equal to or greater than a second threshold that is greater than the first threshold and the time that has elapsed since the solenoid valve was turned on exceeds a minimum on time. [Explanation of symbols]

[0039] 1...Compression system 11...High-stage compressor 12...Oil pod 21...Low stage compressor 22...Oil pod 14, 24...Oil level sensor 3...Control panel 31...Solenoid valve control section 32...Solenoid valve control section 33…Time update section 34…Time update section

Claims

1. A solenoid valve is provided in a circuit that returns oil discharged from the compressor together with the refrigerant to the inside of the compressor. When performing opening or closing control according to the amount of oil inside the compressor, When the amount of oil becomes equal to or less than a first threshold value, the solenoid valve is controlled to be open; When the amount of oil is equal to or greater than a second threshold value that is greater than the first threshold value and the elapsed time since the solenoid valve was opened exceeds a minimum on-time, the solenoid valve is closed. Control unit Control device provided.

2. The minimum on-time is a value determined based on the upper limit number of cycles of the open control and the close control of the solenoid valve and the future operation time of the solenoid valve. The control device according to claim 1 .

3. The minimum on-time is updated when a predetermined update condition is met. The control device according to claim 1 or 2.

4. a compressor that compresses a refrigerant and discharges it together with oil stored therein; a tank for storing the oil separated from the refrigerant; a control unit that, when controlling to open or close a solenoid valve provided in a circuit that returns the oil from the tank to the inside of the compressor in accordance with the amount of oil inside the compressor, controls to open the solenoid valve when the amount of oil is equal to or less than a first threshold, and controls to close the solenoid valve when the amount of oil is equal to or greater than a second threshold that is greater than the first threshold and the elapsed time since the solenoid valve was controlled to open exceeds a minimum on time; A compression system comprising:

5. When controlling the opening or closing of a solenoid valve provided in a circuit that returns oil discharged together with a refrigerant from a compressor to the inside of the compressor in accordance with the amount of oil inside the compressor, When the amount of oil becomes equal to or less than a first threshold value, the solenoid valve is controlled to be open; When the amount of oil is equal to or greater than a second threshold value that is greater than the first threshold value and the elapsed time since the solenoid valve was opened exceeds a minimum on-time, the solenoid valve is closed. Control method.

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