Refrigerant recovery control method, device and medium for multi-split air conditioning system

Abstract

The application provides a refrigerant recovery control method, device and medium for a multi-connected air conditioning system, which comprises the following steps: a refrigerant recovery mode entering step: when a refrigerant recovery instruction is received, all outdoor units are controlled to enter a refrigerant recovery mode; a detection step: the total number of outdoor units is detected; a first refrigerant recovery step: a first stop valve corresponding to the end side of one outdoor unit is closed, and the position of the first stop valve is associated with refrigerant recovery to indoor units or outdoor units; a first refrigerant recovery termination step: after a fault signal is detected, the cumulative fault number of the outdoor unit group is recorded, and a second stop valve is closed; a comparison step: the cumulative fault number is compared with the total number; and a control step: if the cumulative fault number is less than the total number, the outdoor units without the fault signal are controlled to continue running and return to the first refrigerant recovery step. According to the application, the refrigerant can be recovered in batches by only one technician, the convenience of refrigerant recovery is improved, and repeated start and stop of the machine are avoided.

Description

Technical Field

[0001] This invention relates to the field of air conditioning, specifically to a refrigerant recovery control method, device, and medium for a multi-split air conditioning system. Background Technology

[0002] Existing multi-split air conditioning systems consist of multiple outdoor unit modules connected in parallel, installed and put into use after installation. When refrigerant needs to be recovered to the outdoor units, after the system enters refrigerant recovery mode, multiple technicians must simultaneously close the high-pressure shut-off valves of all outdoor units. The compressor's suction then draws the refrigerant from the piping and indoor units back to the outdoor units. After recovery is complete, the technicians simultaneously close the low-pressure shut-off valves of all outdoor units to finish the refrigerant recovery. This existing recovery method requires multiple technicians to simultaneously operate and close the shut-off valves, resulting in low convenience and high maintenance costs.

[0003] Furthermore, in existing technologies, a fault will be reported after the refrigerant recovery of a single outdoor or indoor unit is completed, causing the entire multi-split air conditioning system to shut down. When the refrigerant is not fully recovered, it is necessary to repeatedly start and stop the system to continue recovering the refrigerant until all the refrigerant is recovered. This increases the workload of technicians, makes the refrigerant recovery work cumbersome, and greatly reduces the efficiency of refrigerant recovery. Summary of the Invention

[0004] To address the above problems, this invention provides a refrigerant recovery control method, device, and medium for multi-split air conditioning systems. By closing a set of first and second shut-off valves each time, the refrigerant is recovered to the indoor or outdoor unit in multiple stages. Only one technician is needed to complete the refrigerant recovery, improving the convenience of refrigerant recovery, reducing manpower, and helping to save maintenance costs. Furthermore, the outdoor unit reports a fault to indicate that the refrigerant recovery of a single indoor or outdoor unit is complete, and the overall refrigerant recovery progress is judged by accumulating the number of faults. This not only improves the convenience of refrigerant recovery but also helps to monitor the refrigerant recovery status in real time, improving the safety and stability of refrigerant recovery.

[0005] This invention provides a refrigerant recovery control method for a multi-split air conditioning system. The multi-split air conditioning system includes: indoor units and outdoor units connected in parallel. The indoor units include multiple indoor units, and the outdoor units include multiple outdoor units. Each outdoor unit has a first shut-off valve and a second shut-off valve connected in series at both ends. The refrigerant recovery control method includes: a refrigerant recovery mode entry step: upon receiving a refrigerant recovery command, controlling all outdoor units to enter refrigerant recovery mode; a detection step: detecting the total number of outdoor units in the multi-split air conditioning system; a first refrigerant recovery step: closing the first shut-off valve corresponding to the end of one of the multiple outdoor units, the position of the first shut-off valve being associated with refrigerant recovery to an indoor unit or an outdoor unit; a first refrigerant recovery termination step: after detecting a fault signal from an outdoor unit with the first shut-off valve closed, recording the cumulative number of faults of the outdoor unit, and closing the second shut-off valve; a comparison step: comparing the cumulative number of faults with the total number of units; and a control step: if the cumulative number of faults is less than the total number of units, controlling the outdoor units that have not reported faults to continue operating and returning to the first refrigerant recovery step.

[0006] According to this technical solution, compared with existing technologies, during refrigerant recovery, multiple technicians are no longer needed to simultaneously close all high-pressure and low-pressure shut-off valves. Only one technician needs to close the high-pressure and low-pressure shut-off valves separately at different times to achieve phased refrigerant recovery from a multi-split air conditioning system. This reduces the labor required for refrigerant recovery and the operational difficulty, improving the convenience of refrigerant recovery and helping to reduce maintenance costs. Furthermore, outdoor units that do not report faults can directly proceed to the next round of refrigerant recovery without shutting down, avoiding repeated start-ups and shutdowns, improving the simplicity of the control method, saving manpower, and increasing refrigerant recovery efficiency.

[0007] In the optional technical solution of the present invention, in the first refrigerant recovery step, if the refrigerant is recovered to the outdoor unit, the first shut-off valve is a high-pressure shut-off valve, which is connected between the outdoor heat exchanger of the outdoor unit and the indoor unit; if the refrigerant is recovered to the indoor unit, the first shut-off valve is a low-pressure shut-off valve, which is connected between the compressor of the outdoor unit and the indoor unit.

[0008] According to this technical solution, when recovering refrigerant to the outdoor unit, the high-pressure shut-off valve is closed first, which cuts off the flow of refrigerant to the indoor unit, resulting in residual refrigerant in the indoor unit. At the same time, the compressor's suction can recover the refrigerant from the indoor unit to the outdoor unit. After the refrigerant is recovered to the outdoor unit, the low-pressure shut-off valve is closed to prevent refrigerant leakage into the outdoor unit and improve the recovery effect. When recovering refrigerant to the indoor unit, the low-pressure shut-off valve is closed first, and the refrigerant from the compressor outlet flows into the indoor unit through the outdoor unit, realizing the recovery of refrigerant to the indoor unit, while preventing the refrigerant from the indoor unit outlet from returning to the compressor.

[0009] In the optional technical solution of the present invention, in the control step, if the cumulative number of faults is not less than the total number of units, the multi-split air conditioning system is controlled to exit the refrigerant recovery mode.

[0010] According to the technical solution, when the cumulative number of faults is greater than or equal to the total number of units, it indicates that all outdoor units have reported faults, meaning that all refrigerant in the indoor units and pipes has been recovered to all outdoor units, thus completing the refrigerant recovery. At this point, the refrigerant recovery mode is exited to facilitate subsequent operations.

[0011] In the optional technical solution of the present invention, in the refrigerant recovery mode, the multi-split air conditioning system is forced to operate in cooling mode.

[0012] In an optional technical solution of the present invention, the control step further includes controlling the outdoor unit that reports a fault signal to stop.

[0013] According to this technical solution, controlling the outdoor unit that reports a fault signal to shut down helps ensure the safety and stability of the multi-split air conditioning system, while also saving unnecessary energy consumption.

[0014] In an optional technical solution of the present invention, in the first refrigerant recovery termination step, each time an outdoor unit that has closed the first shut-off valve reports a fault signal, the cumulative number of faults increases by one.

[0015] According to this technical solution, the progress of refrigerant recovery to the outdoor or indoor unit can be determined by accumulating the number of failures. That is, the closer the accumulated number of failures is to the total number of outdoor units, the closer the refrigerant recovery is to completion. Judging the refrigerant recovery progress by accumulating the number of failures improves the ease of judging the refrigerant recovery progress.

[0016] The present invention also provides a refrigerant recovery control device for a multi-split air conditioning system, which performs the above-described refrigerant recovery control method for a multi-split air conditioning system.

[0017] In an optional technical solution of the present invention, the refrigerant recovery control device includes: a detection module for detecting the total number of outdoor units in a multi-split air conditioning system; a recording and updating module for recording and updating the number of faults of the outdoor units in refrigerant recovery mode; a comparison module for comparing the cumulative number of faults of the outdoor units with the total number of units; and a control module configured to: control all outdoor units to enter refrigerant recovery mode when a refrigerant recovery command is received; and control the outdoor units that have not reported faults to continue operating in refrigerant recovery mode if the cumulative number of faults is less than the total number of units.

[0018] In another aspect, the present invention provides a computer-readable storage medium storing a computer program that, when executed, implements the refrigerant recovery control method for the multi-split air conditioning system described above. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the refrigerant recovery system of the multi-split air conditioning system to the outdoor unit in an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the refrigerant recovery system of the multi-split air conditioning system in an embodiment of the present invention.

[0021] Figure 3 This is a schematic diagram of the refrigerant recovery control method for a multi-split air conditioning system according to an embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram of the refrigerant recovery control method for a multi-split air conditioning system according to an embodiment of the present invention.

[0023] Figure 5 This is a schematic diagram of the modular structure of the refrigerant recovery control device for a multi-split air conditioning system in an embodiment of the present invention.

[0024] Figure label:

[0025] Indoor unit 1; Indoor unit 11; Outdoor unit 2; Outdoor unit 21; Compressor 211; Outdoor heat exchanger 212; First shut-off valve 31; Second shut-off valve 32; Detection module 41; Recording and updating module 42; Comparison module 43; Control module 44. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 , Figure 2 and Figure 3 As shown, this invention provides a refrigerant recovery control method for a multi-split air conditioning system. The multi-split air conditioning system includes: indoor unit 1 and outdoor unit 2 connected in parallel. Indoor unit 1 includes multiple indoor units 11, and outdoor unit 2 includes multiple outdoor units 21. Each outdoor unit 21 has a first shut-off valve 31 and a second shut-off valve 32 connected in series at both ends. The refrigerant recovery control method includes:

[0028] Refrigerant recovery mode entry steps: Upon receiving a refrigerant recovery command, control all outdoor units 21 to enter refrigerant recovery mode;

[0029] Testing steps: Detect the total number n of outdoor units 21 in the multi-split air conditioning system;

[0030] First refrigerant recovery step: Close the first shut-off valve 31 corresponding to the end side of one of the multiple outdoor units 21. The position of the first shut-off valve 31 is associated with the refrigerant recovery to the indoor unit 11 or the outdoor unit 21.

[0031] First refrigerant recovery termination step: After detecting that the outdoor unit 21, which has closed the first shut-off valve 31, reports a fault shutdown signal, record the cumulative number of faults e of the outdoor unit 21 (the initial value of e is 0), and close the second shut-off valve 32.

[0032] Comparison steps: Compare the cumulative number of failures e with the total number of units n;

[0033] Control steps: If the cumulative number of faults e is less than the total number of units n, control the outdoor unit 21 that has not reported a fault to continue running (i.e., without stopping) and return to the first refrigerant recovery step.

[0034] Specifically, the outdoor unit 21 includes a compressor 211 and an outdoor heat exchanger 212 connected in series with the compressor 211. The compressor 211, the outdoor heat exchanger 212, and the indoor unit 11 form a refrigerant circuit. Each outdoor unit 21 has a first shut-off valve 31 and a second shut-off valve 32 connected in series at both ends, including the following situations: the first shut-off valve 31 (high-pressure shut-off valve) is connected between the indoor unit 11 and the outdoor heat exchanger 212, and the second shut-off valve 32 (low-pressure shut-off valve) is connected between the indoor unit 11 and the compressor 211; or the second shut-off valve 32 (high-pressure shut-off valve) is connected between the indoor unit 11 and the outdoor heat exchanger 212, and the first shut-off valve 31 (low-pressure shut-off valve) is connected between the indoor unit 11 and the compressor 211. The position of the first shut-off valve 31 is related to whether the refrigerant is recovered to the indoor unit 11 or the outdoor unit 21. Specifically, when the refrigerant is recovered to the indoor unit 11, the low-pressure shut-off valve is closed first, followed by the high-pressure shut-off valve; when the refrigerant is recovered to the indoor unit, the high-pressure shut-off valve is closed first, followed by the low-pressure shut-off valve. The valve that closes first is the first shut-off valve 31, and the valve that closes last is the second shut-off valve 32.

[0035] like Figure 1 , Figure 4 As shown, the control principle of this implementation method is as follows: In refrigerant recovery mode, all outdoor units 21 are forced to operate in cooling mode. Figure 1(The middle arrow indicates the refrigerant flow direction in cooling mode.) The refrigerant returns to the compressor 211 via the compressor 211, outdoor heat exchanger 212, and indoor unit 11. When refrigerant is recovered to outdoor unit 21, the first shut-off valve 31 (high-pressure shut-off valve) corresponding to one outdoor unit 21 is closed, the connection between indoor unit 11 and outdoor heat exchanger 212 is interrupted, and the refrigerant in outdoor heat exchanger 212 cannot enter indoor unit 11. Under the suction action of compressor 211, the refrigerant in indoor unit 11 returns to compressor 211 and is discharged to outdoor heat exchanger 212. When the amount of refrigerant in outdoor heat exchanger 212 reaches the recovery limit (the maximum amount of refrigerant that outdoor heat exchanger 212 can recover), the refrigerant cannot continue to flow, and outdoor unit 21 reports a fault shutdown signal, thus completing the refrigerant recovery of one outdoor unit 21. The second shut-off valve 32 (low-pressure shut-off valve) is closed to prevent the refrigerant recovered to outdoor unit 21 from flowing out. When the number of faults of outdoor unit 21 is less than the total number of units n, the above steps are repeated to recover the refrigerant for the next outdoor unit 21 until the refrigerant is recovered to all outdoor units 21.

[0036] like Figure 2 , Figure 4 As shown, when refrigerant is recovered to indoor unit 11, the first shut-off valve 31 (low-pressure shut-off valve) is closed, interrupting the connection between indoor unit 11 and compressor 211. Refrigerant from the outlet of indoor unit 11 cannot enter compressor 211 and remains in indoor unit 11. Refrigerant from the outlet of compressor 211 enters indoor unit 11 via outdoor heat exchanger 212, thus achieving refrigerant recovery to indoor unit 11. When the amount of refrigerant discharged from outdoor unit 21 reaches the refrigerant recovery limit of indoor unit 11 (the maximum refrigerant recovery amount that indoor unit 11 can achieve), the refrigerant cannot continue to flow, and outdoor unit 21 reports a fault shutdown signal, thus completing the refrigerant purging of one outdoor unit 21 or the refrigerant recovery of one indoor unit 11. The second shut-off valve 32 (high-pressure shut-off valve) is then closed. The above steps are repeated to recover refrigerant for the next indoor unit 11 until all refrigerant is recovered to all indoor units 11. Because the amount of refrigerant in a multi-split air conditioning system is large, the capacity of one indoor unit 11 or outdoor unit 21 is not enough to recover all the refrigerant, so multiple indoor units 11 or multiple outdoor units 21 are needed to perform multiple refrigerant recovery operations.

[0037] Compared to existing technologies, this new refrigerant recovery method eliminates the need for multiple technicians to simultaneously close all high-pressure and low-pressure shut-off valves. Instead, a single technician can repeatedly close these valves at different times to achieve phased refrigerant recovery in multi-split air conditioning systems. This reduces the manpower required for refrigerant recovery and simplifies the operation, improving convenience and reducing maintenance costs. Furthermore, outdoor units 21 that do not report a fault can continue refrigerant recovery without shutting down, transferring the refrigerant to the next outdoor unit 21. This avoids the frequent start-up and shutdown cycles caused by outdoor unit 21 shutting down (compressor shutdown) after each fault report, simplifying the control method, saving manpower, and extending the lifespan of compressor 211.

[0038] In this embodiment, the indoor unit 11 and the outdoor unit 21 are connected in parallel and interconnected. Therefore, the number of indoor units 11 and the number of outdoor units 21 may be the same or different. This embodiment does not limit this.

[0039] In a preferred embodiment of the present invention, in the first refrigerant recovery step, if the refrigerant is recovered to the outdoor unit 21, the first shut-off valve 31 is a high-pressure shut-off valve, which is connected between the outdoor heat exchanger 212 of the outdoor unit 21 and the indoor unit 11; if the refrigerant is recovered to the indoor unit 11, the first shut-off valve 31 is a low-pressure shut-off valve, which is connected between the compressor 211 of the outdoor unit 21 and the indoor unit 11.

[0040] In the above manner, when the refrigerant is recovered to the outdoor unit 21, the high-pressure shut-off valve is closed first, which cuts off the flow of refrigerant to the indoor unit 11, resulting in refrigerant residue in the indoor unit 11. At the same time, the refrigerant on the indoor unit 11 side can be recovered to the outdoor unit 21 by the suction of the compressor 211. After the refrigerant is recovered to the outdoor unit 21, the low-pressure shut-off valve is closed, which can prevent the refrigerant entering the outdoor unit 21 from leaking and improve the recovery effect. When the refrigerant is recovered to the indoor unit 11, the low-pressure shut-off valve is closed first, and the refrigerant at the outlet of the compressor 211 flows into the indoor unit 11 through the outdoor unit 21, realizing the recovery of refrigerant to the indoor unit 11, while preventing the refrigerant at the outlet of the indoor unit 11 from returning to the compressor 211.

[0041] In a preferred embodiment of the present invention, during the control step, if the cumulative number of faults e is not less than the total number of units n, the multi-split air conditioning system is controlled to exit the refrigerant recovery mode. When the cumulative number of faults e is greater than or equal to the total number of units n, it indicates that all outdoor units 21 have reported faults, meaning that all refrigerant in the indoor units 11 and pipelines has been recovered to all outdoor units 21, thus completing the refrigerant recovery. At this point, the refrigerant recovery mode is exited for easier subsequent operations.

[0042] In a preferred embodiment of the present invention, the multi-split air conditioning system is forced to operate in cooling mode during refrigerant recovery. Refrigerant recovery in cooling mode improves the refrigerant recovery rate, while refrigerant recovery in heating mode may result in incomplete recovery of the refrigeration oil.

[0043] In a preferred embodiment of the present invention, the control step further includes controlling the outdoor unit 21 that reported the fault shutdown signal to stop. Controlling the outdoor unit 21 that reported the fault shutdown signal to stop, that is, stopping the operation of the compressor 211 of the outdoor unit 21, helps to ensure the safety and stability of the multi-split air conditioning system, while saving unnecessary energy consumption.

[0044] In a preferred embodiment of the present invention, during the first refrigerant recovery termination step, each time an outdoor unit 21 with the first shut-off valve 31 closed reports a fault shutdown signal, the cumulative fault count e increases by one. By accumulating the number of faults in the outdoor unit 21, the progress of refrigerant recovery to the outdoor unit 21 or indoor unit 11 can be determined. That is, the closer the cumulative fault count e is to the total number of outdoor units 21 n, the closer the refrigerant recovery is to completion. Judging the refrigerant recovery progress by accumulating the number of faults e improves the ease of judging the refrigerant recovery progress.

[0045] In some implementations, refrigerant recovery modes can be set, including a first refrigerant recovery mode and a second refrigerant recovery mode. The first refrigerant recovery mode refers to refrigerant recovery to the outdoor unit 21, and the second refrigerant recovery mode refers to refrigerant recovery to the indoor unit 11. By selecting the desired refrigerant recovery mode, the closing sequence of the high-pressure shut-off valve and the low-pressure shut-off valve can be adjusted accordingly to meet different refrigerant recovery needs. In some implementations, the closing of the first shut-off valve 31 and the second shut-off valve 32 is not limited to manual closing; it can also be electrically controlled. Electric control of valves is a common application and will not be elaborated further here.

[0046] The present invention also provides a refrigerant recovery control device for a multi-split air conditioning system, which performs the above-described refrigerant recovery control method for a multi-split air conditioning system.

[0047] In a preferred embodiment of the present invention, such as Figure 5 As shown, the refrigerant recovery control device includes: a detection module 41, which detects the total number n of outdoor units 21 in the multi-split air conditioning system; a recording and updating module 42, which records and updates the number of faults of outdoor units 21 in refrigerant recovery mode; a comparison module 43, which compares the cumulative number of faults e of outdoor units 21 with the total number n; and a control module 44, configured to: control all outdoor units 21 to enter refrigerant recovery mode when a refrigerant recovery command is received; and if the cumulative number of faults e is less than the total number n, control the outdoor units 21 that have not reported faults to continue operating in refrigerant recovery mode.

[0048] Specifically, the control module 44 can be an integrated circuit chip with signal processing capabilities. The control module 44 can be a general-purpose processor, including a Central Processing Unit (CPU), or a microcontroller, microcontroller unit (MCU), complex programmable logic device (CPLD), field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), embedded ARM, etc. The detection module 41, recording and updating module 42, and comparison module 43 can all be integrated into or partially integrated into the control module 44. The control module 44 can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this invention. The detection module 41 is used to execute the above-mentioned detection steps. The recording and updating module 42 can also record and update the cumulative number of faults e by superimposing and calculating the cumulative number of faults e. The comparison module 43 is used to execute the above-mentioned comparison steps, and the control module 44 executes the above-mentioned control steps.

[0049] In another aspect, the present invention provides a computer-readable storage medium storing a computer program that, when executed, implements the refrigerant recovery control method for the multi-split air conditioning system described above.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A refrigerant recovery control method for a multi-split air conditioning system, characterized in that, The multi-split air conditioning system includes: indoor units and outdoor units connected in parallel, wherein the indoor units include multiple indoor units, and the outdoor units include multiple outdoor units, with a first shut-off valve and a second shut-off valve connected in series at both ends of each outdoor unit; the refrigerant recovery control method includes: Refrigerant recovery mode entry steps: Upon receiving a refrigerant recovery command, control all outdoor units to enter refrigerant recovery mode; in the refrigerant recovery mode, the multi-split air conditioning system is forced to operate in cooling mode; Testing steps: Detect the total number of outdoor units in the multi-split air conditioning system; First refrigerant recovery step: Close the first shut-off valve corresponding to the end side of one of the multiple outdoor units. The position of the first shut-off valve is associated with refrigerant recovery to the indoor unit or the outdoor unit. If the refrigerant is recovered to the outdoor unit, the first shut-off valve is a high-pressure shut-off valve, which is connected between the outdoor heat exchanger of the outdoor unit and the indoor unit. If the refrigerant is recovered to the indoor unit, the first shut-off valve is a low-pressure shut-off valve, which is connected between the compressor of the outdoor unit and the indoor unit. First refrigerant recovery termination step: After detecting a fault signal from the outdoor unit that has closed the first shut-off valve, record the cumulative number of faults of the outdoor unit and close the second shut-off valve; Comparison step: Compare the cumulative number of failures with the total number of units; Control steps: If the cumulative number of faults is less than the total number of units, control the outdoor units that have not reported faults to continue operating and return to the first refrigerant recovery step; if the cumulative number of faults is not less than the total number of units, control the multi-split air conditioning system to exit the refrigerant recovery mode.

2. The refrigerant recovery control method for a multi-split air conditioning system according to claim 1, characterized in that, The control steps also include stopping the outdoor unit that reports a fault signal.

3. The refrigerant recovery control method for a multi-split air conditioning system according to claim 2, characterized in that, In the first refrigerant recovery termination step, each time the outdoor unit that has closed the first shut-off valve reports a fault signal, the cumulative number of faults increases by one.

4. A refrigerant recovery control device for a multi-split air conditioning system, characterized in that, The refrigerant recovery control method for a multi-split air conditioning system according to any one of claims 1 to 3.

5. The refrigerant recovery control device for a multi-split air conditioning system according to claim 4, characterized in that, The refrigerant recovery control device includes: The detection module detects the total number of outdoor units in the multi-split air conditioning system. The recording and updating module is used to record and update the number of failures of the outdoor unit in the refrigerant recovery mode; The comparison module compares the cumulative number of failures with the total number of units. The control module is configured to: upon receiving a refrigerant recovery command, control all outdoor units to enter the refrigerant recovery mode; and If the cumulative number of faults is less than the total number of units, the outdoor units that have not reported faults will continue to operate in refrigerant recovery mode.

6. A computer-readable storage medium, characterized in that, The system contains a computer program that, when executed, implements the refrigerant recovery control method for a multi-split air conditioning system as described in any one of claims 1 to 3.

Images