Air supply system, control method for air supply system, and control program for air supply system

Abstract

To provide an air supply system and a control method for the air supply system that can maintain the dryness state of dried compressed air.SOLUTION: An air supply system (10) comprises: an air drying circuit (11) that is provided between a compressor (4) for sending compressed air and an air tank (30) for storing dried compressed air, and that comprises a filter (17) containing a drying agent for capturing moisture; and an ECU (80) that controls the air drying circuit (11). During a supply operation in which the compressor (4) is driven and the compressed air is sent to the filter (17) and supplied to the air tank (30), the ECU (80) uses a moisture content to assess a dryness state of the dried compressed air stored in the air tank (30), and determines whether to perform a regeneration operation in which the dried compressed air is caused to pass through the filter (17) in a reverse direction and drain-off that passes through the filter (17) is discharged from a drain discharge port (27).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to an air supply system, a control method for the air supply system, and a control program for the air supply system.

Background Art

[0002] In vehicles such as trucks, buses, and construction machines, a pneumatic system including a brake system and a suspension system is controlled using compressed air sent from a compressor. This compressed air contains liquid impurities such as moisture contained in the atmosphere and oil for lubricating the inside of the compressor. When compressed air containing a large amount of moisture and oil enters the pneumatic system, it may cause rusting and swelling of rubber members, etc., and may cause malfunction. For this reason, a compressed air dryer for removing impurities such as moisture and oil in the compressed air is provided downstream of the compressor.

[0003] The compressed air dryer includes a desiccant and various valves. The compressed air dryer performs a load operation (dehumidification operation) to remove moisture and the like from the compressed air. The compressed dry air generated by the dehumidification operation is stored in a storage section. Further, the cleaning function of the compressed air dryer decreases according to the amount of compressed dry air passing through. For this reason, the compressed air dryer performs an unload operation (regeneration operation) to remove the oil and moisture adsorbed on the desiccant from the desiccant and discharge the removed oil and moisture as drain (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the compressed air drying device switches between a dehumidifying operation and a regeneration operation based on the pressure in the storage section. When the consumption of the compressed dry air stored in the storage section continues, the dehumidifying operation continues without switching to the regeneration operation, and there is a risk that the moisture content of the compressed dry air stored in the storage section will increase. Therefore, it is required to maintain the dry state of the compressed dry air.

[0006] An object of the present disclosure is to provide an air supply system capable of maintaining the dry state of compressed dry air and a control method for the air supply system.

Means for Solving the Problems

[0007] The air supply system for solving the above problems includes an air drying circuit having a filter containing a desiccant for capturing moisture provided between a compressor for delivering compressed air and an air tank for storing compressed dry air, and a control device for controlling the air drying circuit. When the compressor is driven and the compressed air is sent to the filter and supplied to the air tank during the supply operation, the control device determines the dry state of the compressed dry air stored in the air tank from the moisture content, and determines whether to execute a regeneration operation of passing the compressed dry air in the reverse direction through the filter and discharging the fluid that has passed through the filter from the discharge port.

[0008] The control method for the air supply system for solving the above problems is a control method for an air supply system including an air drying circuit having a filter containing a desiccant for capturing moisture provided between a compressor for delivering compressed air and an air tank for storing compressed dry air, and a control device for controlling the air drying circuit. When the compressor is driven and the compressed air is sent to the filter and supplied to the air tank during the supply operation, the control device determines the dry state of the compressed dry air stored in the air tank from the moisture content, and determines whether to execute a regeneration operation of passing the compressed dry air in the reverse direction through the filter and discharging the fluid that has passed through the filter from the discharge port.

[0009] The control program of the air supply system for solving the above problems is provided between a compressor that delivers compressed air and an air tank that stores compressed and dried air, and is a control program of an air supply system including an air drying circuit having a filter containing a desiccant for capturing moisture, and a control device that controls the air drying circuit. The control device is configured to function as a drying state determination unit that determines the drying state of the compressed and dried air stored in the air tank from the moisture content during a supply operation in which the compressor is driven, the compressed air is delivered to the filter, and supplied to the air tank, and a regeneration operation execution determination unit that determines whether or not to execute a regeneration operation of passing the compressed and dried air in the reverse direction through the filter and discharging the fluid that has passed through the filter from a discharge port based on the drying state of the compressed and dried air.

[0010] According to the above configuration, during the supply operation, the drying state of the compressed and dried air is determined from the moisture content, and it is determined whether or not to execute the regeneration operation. For this reason, when the supply operation is executed and the regeneration of the desiccant is insufficient, the regeneration operation is executed. Therefore, the drying state of the compressed and dried air can be maintained.

[0011] Regarding the above air supply system, the control device may be configured to acquire the pressure information of the air tank and the air discharge amount of the compressor, calculate the consumption amount of the compressed and dried air stored in the air tank based on the pressure change of the air tank, and calculate the moisture content of the compressed and dried air using the consumption amount of the compressed and dried air and the air discharge amount.

[0012] When consuming compressed and dried air by braking or regeneration operation while supplying compressed and dried air to the air tank, it is difficult to calculate the moisture content of the compressed and dried air in the air tank. Therefore, according to the above configuration, by calculating the consumption amount of the compressed and dried air from the pressure change of the air tank and the air discharge amount of the compressor, and calculating the moisture content contained in the consumed compressed and dried air, it is possible to accurately estimate the moisture content of the air tank after the compressed and dried air has been consumed by braking or regeneration operation.

[0013] Regarding the above air supply system, the control device may be configured to execute the regeneration operation when the pressure of the compressed dry air reaches the cut-out pressure for performing the regeneration operation and the dry state of the compressed dry air does not satisfy a predetermined condition.

[0014] When the supply and consumption of the compressed dry air are performed and the pressure of the compressed dry air does not reach the cut-out pressure and the supply of the compressed dry air continues, the drying ability by the filter decreases. Therefore, according to the above configuration, when the pressure of the compressed dry air does not reach the cut-out pressure and the dry state of the compressed dry air does not satisfy a predetermined condition, the desiccant is regenerated by executing the regeneration operation, and the dry state of the compressed dry air can be maintained.

[0015] Regarding the above air supply system, the control device may be configured to execute a purge operation of passing the compressed dry air in the air drying circuit in the reverse direction through the filter and discharging the fluid that has passed through the filter from the discharge port when the pressure of the compressed dry air reaches the cut-out pressure and the dry state of the compressed dry air satisfies a predetermined condition.

[0016] According to the above configuration, when the dry state of the compressed dry air satisfies a predetermined condition, instead of the regeneration operation of passing the compressed dry air in the air tank in the reverse direction through the filter, a purge operation of passing the compressed dry air in the air drying circuit in the reverse direction through the filter is performed. For this reason, consumption of the compressed dry air in the air tank can be suppressed.

[0017] Regarding the above air supply system, it may include a discharge valve that communicates a branch path connected to the air drying circuit and the discharge port, and a regeneration control valve that switches between a forward flow from the filter toward the air tank and a reverse flow from the air tank toward the filter, and the control device may be configured to control the discharge valve and the regeneration control valve.

[0018] According to the above configuration, by controlling the discharge valve and the regeneration control valve with the control device, the supply operation and the regeneration operation can be performed.

Effect of the Invention

[0019] According to the present disclosure, the dry state of the compressed dry air can be maintained.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0021] (First Embodiment) Referring to FIGS. 1 to 8, a first embodiment of the air supply system will be described. The air supply system is mounted on vehicles such as trucks, buses, and construction machines. The compressed and dried air supplied by the air supply system is used for pneumatic devices such as a brake system mounted on the vehicle.

[0022] <Air supply system 10> The air supply system 10 will be described with reference to FIG. 1. The air supply system 10 includes a compressor 4, an air drying circuit 11, and an ECU (Electronic Control Unit) 80 as a control device.

[0023] The ECU 80 is connected to the air drying circuit 11 via a plurality of wirings E61 to E67. The ECU 80 includes an arithmetic unit, a communication interface unit, a volatile memory unit, and a non-volatile memory unit. The arithmetic unit is a computer processor and is configured to control the air drying circuit 11 according to an air supply program stored in the non-volatile memory unit (storage medium). The arithmetic unit may implement at least a part of the processing it executes by a circuit such as an ASIC. The air supply program may be executed by one computer processor or by a plurality of computer processors. Further, the ECU 80 includes a storage unit 80A that stores the result of the operation of the air drying circuit 11. The storage unit 80A is a non-volatile memory unit or a volatile memory unit and may be the same as or different from the storage unit in which the control program is stored.

[0024] The ECU 80 is connected to other ECUs (not shown) mounted on the vehicle, such as an engine ECU and a brake ECU, via a vehicle network such as a CAN (Controller Area Network). The ECU 80 acquires information indicating the vehicle state from those ECUs. The information indicating the vehicle state includes, for example, off information of the ignition switch, vehicle speed, engine drive information, and the like.

[0025] The state of the compressor 4 is switched between an operating state (loaded operation) in which air is compressed and delivered based on a command value from the ECU 80, and a non-operating state (idle operation) in which air is not compressed. The compressor 4 operates with power transmitted from a rotational drive source such as an engine.

[0026] The air drying circuit 11 is a so-called air dryer. The air drying circuit 11 is connected to the ECU 80 and removes moisture and the like contained in the compressed air sent from the compressor 4 during loaded operation. The air drying circuit 11 sends the compressed air after drying (hereinafter, compressed and dried air) to the supply circuit 12. The compressed and dried air supplied to the supply circuit 12 is stored in the air tank 30.

[0027] The compressed and dried air stored in the air tank 30 is supplied to pneumatic devices such as a brake system mounted on the vehicle. For example, when the frequency of brake operation is high, such as when the vehicle is traveling on a downhill road or in an urban area, the consumption of the compressed and dried air stored in the air tank 30 increases. Conversely, when the frequency of brake operation is low, the consumption of the compressed and dried air stored in the air tank 30 decreases.

[0028] The air drying circuit 11 has a maintenance port P12. The maintenance port P12 is a port for supplying air to the air drying circuit 11 through it during maintenance.

[0029] <Air drying circuit 11> The air drying circuit 11 includes a filter 17 inside the case 11A (see Fig. 2A) and the like. The filter 17 is provided in the middle of the air supply passage 18 connecting the compressor 4 and the supply circuit 12. Note that the filter 17 contains a desiccant. Further, the filter 17 may include an oil trapping portion for trapping oil separately from the desiccant. The oil trapping portion may be any material that can trap oil while allowing air to pass through, such as a foam like urethane foam, a metal material having a large number of ventilation holes, or a glass fiber filter.

[0030] Filter 17 removes moisture contained in the compressed air by passing the compressed air sent from the compressor 4 through a desiccant, thereby drying the compressed air. Further, the desiccant or the oil removal section captures the oil contained in the compressed air to purify the compressed air. The compressed air that has passed through the filter 17 is supplied to the supply circuit 12 via a downstream check valve 19 that serves as a check valve allowing only the downstream air flow with respect to the filter 17. That is, when the filter 17 side is the upstream and the supply circuit 12 side is the downstream, the downstream check valve 19 allows only the air flow from the upstream to the downstream. Since the downstream check valve 19 has a predetermined valve opening pressure (sealing pressure), when the compressed air flows, the upstream pressure is higher than the downstream pressure by the valve opening pressure.

[0031] Also, a bypass flow path 20 as a bypass circuit bypassing the downstream check valve 19 is provided in parallel with the downstream check valve 19 downstream of the filter 17. A regeneration control valve 21 is provided in the bypass flow path 20.

[0032] The regeneration control valve 21 is an electromagnetic valve controlled by the ECU 80. The ECU 80 switches the operation of the regeneration control valve 21 by controlling the on / off (driving / non-driving) of the power supply of the regeneration control valve 21 via the wiring E64. The regeneration control valve 21 closes to seal the bypass flow path 20 when the power supply is off, and opens to communicate the bypass flow path 20 when the power supply is on. The ECU 80 operates the regeneration control valve 21 when, for example, receiving the value of the air pressure in the air tank 30 and the value of the air pressure exceeds a predetermined range.

[0033] An orifice 22 is provided between the regeneration control valve 21 and the filter 17 in the bypass passage 20. When the regeneration control valve 21 is energized, the compressed dry air on the supply circuit 12 side is sent to the filter 17 through the bypass passage 20 in a state where the flow rate is regulated by the orifice 22. The compressed dry air sent to the filter 17 flows backward through the filter 17 from downstream to upstream and passes through the filter 17. Such a process is an operation to regenerate the filter 17, which is called the regeneration operation of the dryer. At this time, since the compressed dry air sent to the filter 17 is the dried and purified air that has passed through the air supply passage 18, the filter 17, etc. and is supplied to the supply circuit 12, the moisture and oil captured by the filter 17, etc. can be removed from the filter 17. In normal control, when the pressure in the air tank 30 reaches the upper limit value (cut-out pressure), the ECU 80 opens the regeneration control valve 21. On the other hand, when the pressure in the air tank 30 reaches the lower limit value (cut-in pressure), the opened regeneration control valve 21 is closed.

[0034] A branch passage 16 branches from a portion between the compressor 4 and the filter 17. A drain discharge valve 25 is provided in the branch passage 16, and a drain outlet 27 is connected to the end of the branch passage 16.

[0035] The drain, which is a fluid containing the moisture and oil removed from the filter 17, is sent to the drain discharge valve 25 together with the compressed air. The drain discharge valve 25 is a pneumatically driven valve driven by air pressure and is provided in the branch passage 16 between the filter 17 and the drain outlet 27. The drain discharge valve 25 is a 2-port 2-position valve that changes its position between a closed position and an open position. When the drain discharge valve 25 is in the open position, the drain is sent to the drain outlet 27. The drain discharged from the drain outlet 27 may be recovered by an oil separator (not shown). Note that the drain corresponds to the fluid that has passed through the filter 17 in the reverse direction.

[0036] The drain discharge valve 25 is controlled by a governor 26A. The governor 26A is a solenoid valve controlled by an ECU 80. The ECU 80 switches the operation of the governor 26A by controlling the on / off (drive / non-drive) of the power supply of the governor 26A via a wiring E63. When the power supply of the governor 26A is turned on, the governor 26A opens the drain discharge valve 25 by inputting a pneumatic signal to the drain discharge valve 25. Also, when the power supply of the governor 26A is turned off, the governor 26A closes the drain discharge valve 25 by releasing it to the atmospheric pressure without inputting a pneumatic signal to the drain discharge valve 25.

[0037] The drain discharge valve 25 is maintained in a closed valve position when no pneumatic signal is input from the governor 26A, and switches to an open valve position when a pneumatic signal is input from the governor 26A. Also, when the pressure at the input port connected to the compressor 4 in the drain discharge valve 25 exceeds the upper limit value, the drain discharge valve 25 is forcibly switched to the open valve position.

[0038] An upstream check valve 15 is provided between the compressor 4 and the filter 17 and also between the compressor 4 and the branch passage 16. The upstream check valve 15 allows only the flow of air from upstream to downstream when the compressor 4 side is the upstream and the filter 17 side is the downstream. Since the upstream check valve 15 has a predetermined opening pressure (sealing pressure), when compressed air flows, the upstream pressure becomes higher than the downstream pressure by the opening pressure. A lead valve at the outlet of the compressor 4 is provided upstream of the upstream check valve 15. A branch passage 16 and a filter 17 are provided downstream of the upstream check valve 15.

[0039] <Compressor 4> The compressor 4 is controlled by an unload control valve 26B. The unload control valve 26B is a solenoid valve controlled by an ECU 80. The ECU 80 switches the operation of the unload control valve 26B by controlling the energization and de-energization (driving / non-driving) of the power supply of the unload control valve 26B via a wiring E62. When the power supply of the unload control valve 26B is cut off, it switches to the open position, and the flow path between the unload control valve 26B and the compressor 4 is opened to the atmosphere. Also, when the power supply of the unload control valve 26B is turned on, it switches to the supply position, and sends an air pressure signal consisting of compressed air to the compressor 4.

[0040] When an air pressure signal is input from the unload control valve 26B, the state of the compressor 4 switches to the non-operating state (idle operation). For example, when the pressure in the supply circuit 12 reaches the cut-out pressure, the supply of compressed dry air is unnecessary. When the pressure on the supply circuit 12 side reaches the cut-out pressure and the ECU 80 turns on the power supply of the unload control valve 26B (drives the unload control valve 26B), the unload control valve 26B switches to the supply position. Thereby, an air pressure signal is supplied from the unload control valve 26B to the compressor 4, and the state of the compressor 4 switches to the non-operating state.

[0041] <Sensor> A pressure sensor 50 is provided between the compressor 4 and the upstream check valve 15. The pressure sensor 50 is connected to the air supply passage 18, measures the air pressure in the air supply passage 18, and transmits the measured result to the ECU 80 via a wiring E61.

[0042] A humidity sensor 51 and a temperature sensor 52 are provided between the downstream check valve 19 and the supply circuit 12. The humidity sensor 51 measures the humidity of the compressed and dried air downstream of the filter 17 and outputs the measured result to the ECU 80 via the wiring E65. The temperature sensor 52 measures the temperature of the compressed and dried air downstream of the filter 17 and outputs the measured result to the ECU 80 via the wiring E66. The ECU 80 determines the dry state of the compressed and dried air based on the humidity and temperature of the compressed and dried air input from the humidity sensor 51 and the temperature sensor 52. That is, the humidity and temperature of the compressed and dried air are indicators indicating the dry state of the compressed and dried air.

[0043] A pressure sensor 53 is provided between the downstream check valve 19 and the supply circuit 12. The pressure sensor 53 is provided so as to be able to detect, for example, the air pressure in the air tank 30 in which the compressed and dried air is stored, and is connected to the ECU 80 via the wiring E67. The pressure between the downstream check valve 19 and the supply circuit 12 is the same as the pressure in the air tank 30, and the detection result of the pressure sensor 53 can be used as the pressure in the air tank 30. Note that the pressure sensor 53 may be provided in the supply circuit 12 or in the air tank 30.

[0044] The ECU 80 acquires the pressure information of the air tank 30 and the air discharge amount of the compressor 4, and calculates the air consumption amount of the compressed and dried air stored in the air tank 30 based on the pressure change of the air tank 30. Then, the ECU 80 calculates the moisture content of the compressed and dried air using the air consumption amount and the air discharge amount of the compressed and dried air.

[0045] Specifically, the ECU 80 acquires the air pressure in the air tank 30 from the pressure sensor 53 as pressure information. Further, the ECU 80 calculates the air discharge amount from the rotation speed of the compressor 4. The ECU 80 calculates the air consumption amount of the compressed and dried air stored in the air tank 30 based on the atmospheric pressure standard according to the formula (1). The pressure reduction value can be obtained from the difference between the previous value and the current value detected by the pressure sensor 53.

[0046] Air consumption = (Decompression value [kPa] / Atmospheric pressure [kPa]) × Tank capacity [L] + Air discharge amount (previous value) [L]…(1) The moisture content in the consumed air contained in the consumed air is calculated according to Formula (2). Note that the tank moisture content is the absolute value of the moisture content contained in the air tank 30, which is calculated from the compressed air temperature and compressed air humidity in the air tank 30 at the end of regeneration.

[0047] Moisture content in consumed air [g] = Tank moisture content [g] × Air consumption between cycles [L] × (Atmospheric pressure [kPa] / (Cut-out pressure [kPa] + Atmospheric pressure [kPa])) ÷ Tank capacity [L]…(2) Note that the air consumption can be directly calculated from the pressure change (decompression value) when there is no air discharge amount. Also, when there is an air discharge amount, the air consumption is calculated from the pressure change (decompression value) and the air discharge amount.

[0048] <Operation description of air drying circuit 11> As shown in FIGS. 2A to 2F, the air drying circuit 11 has a plurality of operation modes including at least the first operation mode to the eighth operation mode.

[0049] (First operation mode) As shown in FIG. 2A, the first operation mode is a mode for performing a "supply" operation for normal dehumidification (load). In this first operation mode, the regeneration control valve 21, the governor 26A, and the unload control valve 26B are each closed (described as "CLOSE" in the figure). At this time, no power is supplied to the regeneration control valve 21, the governor 26A, and the unload control valve 26B. Also, the governor 26A and the unload control valve 26B each open the ports of the compressor 4 and the drain discharge valve 25 connected downstream thereof to the atmosphere. In the first operation mode, when compressed air is being supplied from the compressor 4 (described as "ON" in the figure), moisture and the like are removed by the filter 17, and compressed air is supplied to the supply circuit 12.

[0050] (Second operation mode) As shown in FIG. 2B, the second operation mode is a mode in which the compressed dry air in the air drying circuit 11 is passed through the filter 17 to perform a "purge" operation to purify the filter 17. In this second operation mode, the regeneration control valve 21 is closed, and the governor 26A and the unload control valve 26B are each opened (described as "OPEN" in the figure). At this time, power is supplied to the governor 26A and the unload control valve 26B, and the ports of the compressor 4 and the drain discharge valve 25 connected to their downstream are each connected upstream (to the supply circuit 12 side). As a result, the compressor 4 is switched to the non-operating state (described as "OFF" in the figure), and the drain discharge valve 25 is opened. As a result, the compressed dry air between the downstream check valve 19 and the filter 17 flows through the filter 17 in a direction opposite to the air flow in the first operation mode (supply) (reverse flow), and the moisture and the like captured by the filter 17 are discharged as drain from the drain outlet 27. Also, the air pressure in the filter 17 and the air supply passage 18 is released to the atmospheric pressure.

[0051] (Third operation mode) As shown in FIG. 2C, the third operation mode is a mode in which a "playback" operation of playing back the filter 17 is performed. In this third operation mode, the playback control valve 21, the governor 26A, and the unload control valve 26B are each opened. At this time, in addition to the governor 26A and the unload control valve 26B, power is also supplied to the playback control valve 21. In the third operation mode, the compressor 4 is set to a non-operating state, and the compressed dry air stored in the supply circuit 12 or the air tank 30 is caused to flow backward through the filter 17 and discharged from the drain outlet 27. As a result, moisture and the like captured by the filter 17 are removed. Both the second operation mode and the third operation mode are modes for purifying the filter 17, but the third operation mode is different from the second operation mode in that at least the playback control valve 21 is opened. Thereby, in the third operation mode, the compressed dry air in the air tank 30 can be passed through the filter 17 via the supply circuit 12 and the bypass passage 20. Therefore, the effect of purifying the filter 17 is higher than that of the second operation mode. Also, even in the third operation mode, the air pressure in the filter 17 and the air supply passage 18 is released to the atmospheric pressure.

[0052] (Fourth operation mode) As shown in Fig. 2D, the fourth operation mode is a mode that performs an "oil cut" operation of discharging the compressed air supplied from the compressor 4 while operating the compressor 4. When the compressor 4 is in a non-operating state, oil may accumulate in the compression chamber of the compressor 4. When the state of the compressor 4 is switched to the operating state with oil accumulated in the compression chamber, the amount of oil contained in the compressed air sent from the compression chamber may increase. The oil cut operation is executed for the purpose of discharging this excessive oil compressed air through the drain discharge valve 25 in order to reduce the load on the filter 17. In this fourth operation mode, the regeneration control valve 21 and the unload control valve 26B are each closed, and the governor 26A is closed after being opened for a certain period. In the fourth operation mode, when the compressor 4 is in the operating state, the compressed air supplied by the compressor 4 is discharged from the drain outlet 27 for a certain period. Therefore, it is possible to suppress an increase in the amount of moisture captured and the amount of oil captured by the filter 17 immediately after the compressor 4 is switched from the non-operating state to the operating state. When the engine speed increases in the operating state and when the amount of oil from the compressor 4 increases during high load of the engine, etc., the oil cut operation can also be performed.

[0053] (Fifth operation mode) As shown in Fig. 2E, the fifth operation mode is a mode that performs a "purge-less supply stop" operation of stopping the compressor 4 without purge. In this fifth operation mode, the regeneration control valve 21 and the governor 26A are each closed, and the unload control valve 26B is opened. In the fifth operation mode, when the compressor 4 is in a non-operating state, the air pressure is maintained by not discharging the compressed air or compressed dry air remaining in the desiccant of the air supply passage 18 or the filter 17 from the drain outlet 27.

[0054] (Sixth operation mode) As shown in FIG. 2F, the sixth operation mode is a mode for performing a "compressor assist" operation that performs a pressurization process. In this sixth operation mode, the regeneration control valve 21 and the unload control valve 26B are each opened, and the governor 26A is closed. In the sixth operation mode, when the compressor 4 is in a non-operating state, the compressed air in the supply circuit 12 is supplied (reversed) to the desiccant in the air supply passage 18 and the filter 17, so that the pressure in the air supply passage 18 and the filter 17 is made higher than the atmospheric pressure, and the back pressure (air pressure) of the upstream check valve 15 is maintained at a pressure higher than the atmospheric pressure. Therefore, the generation of negative pressure in the cylinder can be suppressed, and the operation load of the compressor 4 during idling can be reduced. Specifically, when the compressor 4 is idling, the drain discharge valve 25 is sealed, and the air pressure in the desiccant of the filter 17 and in the air supply passage 18 is maintained at a pressure higher than the atmospheric pressure by the compressed air supplied by the compressor 4.

[0055] (Seventh operation mode) As shown in FIG. 2A, the seventh operation mode is a mode for performing a "regeneration supply" operation that performs dehumidification (loading) during regeneration when the engine is in a no-load state and the compressor 4 is driven. In this seventh operation mode, similar to the first operation mode, the regeneration control valve 21, the governor 26A, and the unload control valve 26B are each closed (described as "CLOSE" in the figure).

[0056] (Eighth operation mode) As shown in FIG. 2C, the eighth operation mode is a mode for performing a "forced regeneration" operation that forcibly regenerates the filter 17. In this eighth operation mode, similar to the third operation mode, the regeneration control valve 21, the governor 26A, and the unload control valve 26B are each opened.

[0057] (Transition of operation mode) As shown in FIG. 3, the eight operation modes of the air drying circuit 11 are changed based on each determination by the ECU 80.

[0058] Referring to FIGS. 4 to 8, the transition from each operation mode will be described. The ECU 80 performs a supply process of supplying the compressed air output by the compressor 4 to the supply circuit 12. The supply process is started according to conditions such as when the engine is driven, for example. In the supply process, the air drying circuit 11 is in the supply (first operation) mode M1.

[0059] As shown in FIG. 4, in the supply (first operation) mode M1, the ECU 80 determines whether the pressure in the supply circuit 12 is higher than the cut-out pressure (step S11). That is, the ECU 80 acquires the pressure of the air tank 30 detected by the pressure sensor 53 and determines whether the pressure has reached the cut-out pressure.

[0060] Then, when the ECU 80 determines that the pressure in the supply circuit 12 has reached the cut-out pressure (step S11: YES), it determines whether the moisture content in the air tank 30 is high (step S12). That is, since it is necessary to regenerate the desiccant of the filter 17 when the moisture content in the air tank 30 is equal to or more than a predetermined value, the ECU 80 determines the moisture content in the air tank 30.

[0061] Then, when the ECU 80 determines that the moisture content in the air tank 30 is equal to or more than the predetermined value (step S12: YES), it shifts to the regeneration (third operation) mode M3 in which the compressed dry air stored in the air tank 30 is passed through the filter 17 to regenerate the desiccant of the filter 17.

[0062] Further, when the ECU 80 determines that the moisture content in the air tank 30 is less than the predetermined value (step S12: NO), it passes the compressed dry air between the downstream check valve 19 and the filter 17 through the filter 17, and shifts to the purge (second operation) mode M2 in which the moisture and the like captured by the filter 17 are discharged as drain from the drain outlet 27.

[0063] On the other hand, when the ECU 80 determines that the pressure in the supply circuit 12 has not reached the cut-out pressure (step S11: NO), it determines whether the transition condition to the oil cut (fourth operation) mode M4 is satisfied (step S13). That is, the ECU 80 determines whether all of the following conditions are satisfied as the transition condition to the oil cut (fourth operation) mode M4: the elapse of a predetermined time, the number of times of oil cut being less than the specified number, and the operating rate of the compressor 4 being low. Then, when the ECU 80 determines that the transition condition to the oil cut (fourth operation) mode M4 is not satisfied (step S13: NO), it returns the process to step S11.

[0064] On the other hand, when the ECU 80 determines that the transition condition to the oil cut (fourth operation) mode M4 is satisfied (step S13: YES), it shifts to the oil cut (fourth operation) mode M4 in which compressed air supplied from the compressor 4 is discharged while operating the compressor 4.

[0065] After shifting to the oil cut (fourth operation) mode M4, the ECU 80 determines whether a predetermined time has elapsed (step S14). That is, the ECU 80 performs the oil cut (fourth operation) mode M4 for a predetermined time. Then, when the ECU 80 determines that the predetermined time has elapsed (step S14: YES), it shifts to the supply (first operation) mode M1.

[0066] As shown in FIG. 5, in the purge (second operation) mode M2 and the regeneration (third operation) mode M3, the ECU 80 determines whether a predetermined time has elapsed (step S21). That is, the ECU 80 performs the purge (second operation) mode M2 and the regeneration (third operation) mode M3 for a predetermined time.

[0067] Then, when the ECU 80 determines that the predetermined time has not elapsed (step S21: NO), it determines whether the pressure in the supply circuit 12 is lower than the cut-in pressure (step S24). That is, the ECU 80 acquires the pressure of the air tank 30 detected by the pressure sensor 53 and determines whether the pressure has reached the cut-in pressure.

[0068] When the ECU 80 determines that the pressure in the supply circuit 12 has reached the cut-in pressure (step S24: YES), since there is not enough compressed dry air, it shifts to the supply (first operation) mode M1. On the other hand, when the ECU 80 determines that the pressure in the supply circuit 12 has not reached the cut-in pressure (step S24: NO), it returns the process to step S21.

[0069] On the other hand, when the ECU 80 determines that a predetermined time has elapsed (step S21: YES), it determines whether or not the compressor assist (sixth operation) process is enabled (step S22).

[0070] When the ECU 80 determines that the compressor assist (sixth operation) process is disabled (step S22: NO), it shifts to the purge-less supply stop (fifth operation) mode M5 in which the compressor 4 is stopped without purge.

[0071] Also, when the ECU 80 determines that the compressor assist (sixth operation) process is enabled (step S22: YES), it shifts to the compressor assist (sixth operation) mode M6 in which the pressure application process is performed.

[0072] After shifting to the compressor assist (sixth operation) mode M6, the ECU 80 determines whether or not a predetermined time has elapsed (step S23). That is, the ECU 80 performs the compressor assist (sixth operation) mode M6 for a predetermined time. Then, when the ECU 80 determines that a predetermined time has elapsed (step S23: YES), it shifts to the purge-less supply stop (fifth operation) mode M5.

[0073] As shown in FIG. 6, in the purge-less supply stop (fifth operation) mode M5, the ECU 80 determines whether or not the pressure in the supply circuit 12 is lower than the cut-in pressure (step S31). That is, the ECU 80 acquires the pressure of the air tank 30 detected by the pressure sensor 53 and determines whether or not the pressure has reached the cut-in pressure.

[0074] When the ECU 80 determines that the pressure in the supply circuit 12 has reached the cut-in pressure (step S31: YES), since there is insufficient compressed dry air, it shifts to the supply (first operation) mode M1.

[0075] On the other hand, when the ECU 80 determines that the pressure in the supply circuit 12 has not reached the cut-in pressure (step S31: NO), it determines whether the shift condition to the regeneration supply (seventh operation) mode M7 is satisfied (step S32). That is, the ECU 80 determines whether all of the following conditions for shifting to the regeneration supply (seventh operation) mode M7 are satisfied: the vehicle is in motion, there is no fuel consumption, and the pressure in the supply circuit 12 is less than the threshold value. And when the ECU 80 determines that the shift condition to the regeneration supply (seventh operation) mode M7 is not satisfied (step S32: NO), it returns the process to step S31.

[0076] On the other hand, when the ECU 80 determines that the shift condition to the regeneration supply (seventh operation) mode M7 is satisfied (step S32: YES), it shifts to the regeneration supply (seventh operation) mode M7 in which dehumidification (loading) is performed during regeneration.

[0077] As shown in FIG. 7, in the regeneration supply (seventh operation) mode M7, the ECU 80 determines whether the shift condition to the purge-less supply stop (fifth operation) mode M5 is satisfied (step S41). That is, the ECU 80 determines whether at least one of the following conditions for shifting to the purge-less supply stop (fifth operation) mode M5 is satisfied: the pressure in the supply circuit 12 is higher than the cut-out pressure, a predetermined time has elapsed, and the fuel consumption of the engine is high. And when the ECU 80 determines that the shift condition to the purge-less supply stop (fifth operation) mode M5 is satisfied (step S41: YES), it shifts to the purge-less supply stop (fifth operation) mode M5.

[0078] On the other hand, when the ECU 80 determines that the condition for shifting to the purge-less supply stop (fifth operation) mode M5 is not satisfied (step S41: NO), it determines whether the pressure in the supply circuit 12 is lower than the cut-in pressure (step S42). That is, the ECU 80 acquires the pressure of the air tank 30 detected by the pressure sensor 53 and determines whether the pressure has reached the cut-in pressure.

[0079] Then, when the ECU 80 determines that the pressure in the supply circuit 12 has reached the cut-in pressure (step S42: YES), since there is not enough compressed dry air, it shifts to the supply (first operation) mode M1.

[0080] On the other hand, when the ECU 80 determines that the pressure in the supply circuit 12 has not reached the cut-in pressure (step S42: NO), it determines whether the condition for shifting to the forced regeneration (eighth operation) mode M8 is satisfied (step S43). That is, the ECU 80 determines whether both of the following conditions for shifting to the forced regeneration (eighth operation) mode M8 are satisfied: the pressure in the supply circuit 12 is higher than the threshold value, and the moisture content in the air tank 30 is high. In the regeneration supply (seventh operation) mode M7, the ECU 80 determines the dry state of the compressed dry air based on the moisture content of the tank air in the air tank 30. That is, the moisture content of the tank air in the air tank 30 is an index indicating the dry state of the compressed dry air. The ECU 80 determines that the moisture content in the air tank 30 is high if the moisture content of the tank air is equal to or more than a predetermined value, and determines that the moisture content in the air tank 30 is low if the moisture content of the tank air is less than the predetermined value. Then, when the ECU 80 determines that the condition for shifting to the forced regeneration (eighth operation) mode M8 is not satisfied (step S43: NO), it returns the process to step S42.

[0081] On the other hand, when the ECU 80 determines that the condition for shifting to the forced regeneration (eighth operation) mode M8 is satisfied (step S43: YES), it shifts to the forced regeneration (eighth operation) mode M8 in which the filter 17 is forcibly regenerated. When it is determined that the moisture content is high and other conditions are satisfied, the ECU 80 executes the forced regeneration (eighth operation) mode M8 in which the compressed dry air flows in the reverse direction.

[0082] As shown in FIG. 8, in the forced reproduction (eighth operation) mode M8, the ECU 80 determines whether or not a predetermined time has elapsed (step S51). That is, the ECU 80 performs the forced reproduction (eighth operation) mode M8 for a predetermined time.

[0083] Then, when the ECU 80 determines that the predetermined time has not elapsed (step S51: NO), it determines whether or not the pressure of the supply circuit 12 is lower than the cut-in pressure (step S55). That is, the ECU 80 acquires the pressure of the air tank 30 detected by the pressure sensor 53 and determines whether or not the pressure has reached the cut-in pressure.

[0084] Then, when the ECU 80 determines that the pressure of the supply circuit 12 has reached the cut-in pressure (step S55: YES), since there is not enough compressed dry air, it shifts to the supply (first operation) mode M1. On the other hand, when the ECU 80 determines that the pressure of the supply circuit 12 has not reached the cut-in pressure (step S55: NO), it returns the process to step S51.

[0085] On the other hand, when the ECU 80 determines that the predetermined time has elapsed (step S51: YES), it determines whether or not the operation rate of the compressor 4 is high (step S52). That is, the ECU 80 determines whether or not the load during driving of the compressor 4 is high based on the operation rate of the compressor 4.

[0086] Then, when the ECU 80 determines that the operation rate of the compressor 4 is high (step S52: YES), since compressor assist (sixth operation) is not required, it shifts to the supply (first operation) mode M1.

[0087] On the other hand, when the ECU 80 determines that the operation rate of the compressor 4 is low (step S52: NO), in order to perform compressor assist (sixth operation), it determines whether or not the compressor assist (sixth operation) process is enabled (step S53).

[0088] When the ECU 80 determines that the compressor assist (sixth operation) process is disabled (step S53: NO), it shifts to the purge-less supply stop (fifth operation) mode M5. Also, when the ECU 80 determines that the compressor assist (sixth operation) process is enabled (step S53: YES), it shifts to the compressor assist (sixth operation) mode M6.

[0089] After shifting to the compressor assist (sixth operation) mode M6, the ECU 80 determines whether or not a predetermined time has elapsed (step S54). That is, the ECU 80 performs the compressor assist (sixth operation) mode M6 for a predetermined time. Then, when the ECU 80 determines that the predetermined time has elapsed (step S54: YES), it shifts to the purge-less supply stop (fifth operation) mode M5.

[0090] Next, the effects of the first embodiment will be described. (1) At the time of supply (first operation), it is determined whether to execute regeneration (third operation) by determining the dry state of the compressed dry air from the moisture content. For this reason, regeneration (third operation) is executed when supply (first operation) is performed and the regeneration of the desiccant is insufficient. Therefore, the dry state of the compressed dry air can be maintained.

[0091] (2) By calculating the consumption amount of the compressed dry air from the pressure change of the air tank 30 and the air discharge amount of the compressor 4, and calculating the moisture content contained in the consumed compressed dry air, the moisture content of the air tank 30 after the compressed dry air is consumed by braking or the regeneration operation can be accurately estimated.

[0092] (3) When the pressure of the compressed dry air does not reach the cut-out pressure and the dry state of the compressed dry air does not satisfy a predetermined condition such as a predetermined value, that is, when an index indicating the dry state of the compressed dry air is not within a predetermined range, the desiccant is regenerated by executing regeneration (third operation), and the dry state of the compressed dry air can be maintained.

[0093] When the dry state of the compressed dry air satisfies a predetermined condition, instead of performing regeneration (the third operation) in which the compressed dry air in the air tank 30 passes through the filter 17 in the reverse direction, purging (the second operation) is performed in which the compressed dry air in the air supply passage 18 passes through the filter 17 in the reverse direction. For this reason, consumption of the compressed dry air in the air tank 30 can be suppressed.

[0094] (5) By the ECU 80 controlling the drain discharge valve 25 and the regeneration control valve 21, supply (the first operation) and regeneration (the third operation) can be performed. (Second Embodiment) Hereinafter, with reference to FIG. 9, a second embodiment of the air supply system will be described. The air supply system of this embodiment is different from the first embodiment in that the dry state of the compressed dry air in the air tank 30 is determined using the tank air moisture saturation as the moisture content. Hereinafter, the description will focus on the differences from the first embodiment.

[0095] Conventionally, the air supply system switches between the dehumidifying operation and the regeneration operation based on the pressure in the storage unit regardless of the dry state of the compressed air. Depending on the atmospheric temperature situation, ultimately the dry state of the compressed air in the storage unit becomes excessive, and as a result, the consumption of the compressed air required to promote and maintain the dry state increases, and there is a possibility that the operation of the compressor increases. Therefore, it is required to maintain the dry state of the compressed dry air to the extent necessary according to the atmospheric situation without becoming excessive.

[0096] As shown in FIG. 9, the ECU 80 calculates the target dew point by subtracting the dew point depression from the outside air temperature as a reference according to Equation (11). For example, the dew point depression may be basically set to 17°C, made larger in spring and autumn when the daily temperature difference is large, and made smaller in summer and winter when the daily temperature difference is small.

[0097] Target dew point [°C] = outside air temperature [°C] - dew point depression [°C] ··· (11) At this time, by making it possible to set the dew point drop degree according to the outside air temperature, it becomes possible to change the target moisture content by dehumidification. Therefore, for example, the moisture content of the compressed dry air in the air tank 30 according to the outside air temperature can be freely set, an optimal dehumidification effect can be obtained, and the consumption amount of the compressed dry air consumed during the regeneration implementation throughout the year can be reduced.

[0098] The ECU 80 calculates the "tank air containable moisture amount" by converting the "target dew point" according to Equation (12). Tank air containable moisture amount [g] = (target dew point [g / m 3 × tank capacity [L]) / unit conversion coefficient (L / m 3 ) ··· (12) The ECU 80 calculates the "tank air contained moisture reference amount", which is the moisture amount of the air tank 30, from the compressed dry air flowing backward into the filter 17 during the regeneration of the filter 17 according to Equation (13).

[0099] Tank air contained moisture reference amount [g] = { (regenerated air temperature [g / m 3 × regenerated air humidity [%RH]) / unit conversion coefficient (%)} × tank capacity [L] / unit conversion coefficient (L / m 3 ) ··· (13) The ECU 80 calculates the "supply air contained moisture amount" considering the ventilation amount of the dry air flowing into the filter 17 during the supply of the dry air according to Equation (14) from the inter-cycle supply air amount, the saturated water vapor amount at the supply air temperature, and the supply air humidity.

[0100] Supply air contained moisture amount [g] = { (saturated water vapor amount [g / m 3 × supply air humidity [%RH]) / unit conversion coefficient (%)} × { inter-cycle supply air amount [L] / unit conversion coefficient (L / m 3 )} × { atmospheric pressure [kPa] / (cut-out pressure [kPaG] + atmospheric pressure [kPa])} ··· (14) The ECU 80 calculates the "consumed air contained moisture amount" from the pressure reduction value of the air tank 30 and the inter-cycle consumed air amount considering the moisture discharge during the consumption of the compressed dry air according to Equation (15).

[0101] Consumed air moisture content [g] = Tank moisture content [g] × Amount of consumed air between cycles × {Atmospheric pressure [kPa] / (Cut-out pressure [kPaG] + Atmospheric pressure [kPa])} ÷ Tank capacity [L] ··· (15) The ECU 80 calculates the "change in tank air moisture content", which is the difference between the "supplied air moisture content" and the "consumed air moisture content", according to Equation (16).

[0102] Change in tank air moisture content [g] = Supplied air moisture content [g] - Consumed air moisture content [g] ··· (16) The ECU 80 calculates the "tank air moisture content", which is the moisture content of the air tank 30 at the time when the supply of dry air ends, from the "change in tank air moisture content" according to Equation (17).

[0103] Tank air moisture content [g] = Tank air moisture reference content [g] + Change in tank air moisture content [g] ··· (17) Furthermore, the ECU 80 calculates the "tank air moisture saturation", which is an index indicating the margin with respect to the moisture content that can be contained in the compressed dry air in the air tank 30, using the above "tank air moisture content that can be contained" and "tank air moisture content" according to Equation (18) in order to obtain the dehumidification effect of the compressed dry air in the air tank 30.

[0104] Tank air moisture saturation [-] = Tank air moisture content [g] / Tank air moisture content that can be contained [g] ··· (18) The ECU 80 performs control using the "tank air moisture saturation" calculated as described above for the determination of whether the "moisture content" in the first embodiment is high or low. In this case, the value of the "predetermined value" is changed according to the "tank air moisture saturation". For example, when the "tank air moisture saturation" exceeds the threshold value at the time when the supply of dry air ends, the ECU 80 performs regeneration of the filter 17 assuming that the compressed dry air is not in a dry state. That is, the tank air moisture saturation is an index indicating the dry state of the compressed dry air.

[0105] Next, the effects of the second embodiment will be described. In addition to the effects (1) to (5) of the first embodiment, the second embodiment has the following effects. (6) Since the moisture amount is determined based on the saturation degree of the air in the tank with moisture, an optimal dehumidifying effect can be obtained, and the consumption amount of compressed dry air consumed during the regeneration of the filter 17 throughout the year can be reduced.

[0106] (Other embodiments) Each of the above embodiments can be implemented with the following modifications. Each of the above embodiments and the following modification examples can be implemented in combination with each other within a range where there is no technical contradiction.

[0107] · In the first embodiment described above, the dry state of the compressed dry air was determined based on the moisture amount of the consumed air. However, the dry state of the compressed dry air may be determined by estimating the moisture content of the air in the tank from the humidity and temperature of the compressed dry air in the air tank 30.

[0108] · In the second embodiment described above, the target dew point was calculated using the dew point drop degree when the outside air temperature was used as a reference. However, the target dew point may be calculated using the dew point drop degree when the ambient temperature of the air tank 30 is used as a reference. Also, the target dew point may be set according to the date. In this way, the moisture amount of the compressed dry air in the air tank 30 corresponding to the change of seasons can be freely set, an optimal dehumidifying effect can be obtained, and the consumption amount of compressed dry air during the regeneration of the filter 17 throughout the year can be reduced.

[0109] · In each of the above embodiments, the purge (second operation) mode M2, regeneration (third operation) mode M3, oil cut (fourth operation) mode M4, compressor assist (sixth operation) mode M6, regeneration supply (seventh operation) mode M7, and forced regeneration (eighth operation) mode M8 are performed for a predetermined time. However, the predetermined time in each mode may be set arbitrarily.

[0110] · In step S13 of each of the above embodiments, the transition condition to the oil cut (fourth operation) mode M4 was that all of the number of times of oil cut being less than the specified number of times and the operating rate of the compressor 4 being low were satisfied. Instead, the ECU 80 may shift to the oil cut (fourth operation) mode M4 when at least one of them is satisfied. That is, in step S13, the ECU 80 determines whether at least one of the elapse of a predetermined time, the number of times of oil cut being less than the specified number of times, and the operating rate of the compressor 4 being low is satisfied as the transition condition to the oil cut (fourth operation) mode M4.

[0111] · In step S32 of each of the above embodiments, the transition condition to the regeneration supply (seventh operation) mode M7 was that all of the vehicle being in motion, no fuel consumption, and the pressure of the supply circuit 12 being less than the threshold value were satisfied. Instead, the ECU 80 may shift to the regeneration supply (seventh operation) mode M7 when at least one of them is satisfied. That is, in step S32, the ECU 80 determines whether at least one of the vehicle being in motion, no fuel consumption, and the pressure of the supply circuit 12 being less than the threshold value is satisfied as the transition condition to the regeneration supply (seventh operation) mode M7.

[0112] · In step S43 of each of the above embodiments, the transition condition to the forced regeneration (eighth operation) mode M8 was that both the pressure of the supply circuit 12 being higher than the threshold value and the moisture content of the air tank 30 being high were satisfied. Instead, the ECU 80 may shift to the forced regeneration (eighth operation) mode M8 when at least the moisture content of the air tank 30 being high is satisfied. That is, in step S43, the ECU 80 determines whether the moisture content of the air tank 30 being high is satisfied as the transition condition to the forced regeneration (eighth operation) mode M8.

[0113] · In each of the above embodiments, the filter 17 includes an oil component capturing portion, but the oil component capturing portion may be omitted from the filter 17. · In each of the above embodiments, the air drying circuit is not limited to the one having the above configuration. The air drying circuit only needs to be configured to be capable of executing a supply (first operation) mode M1, a purge (second operation) mode M2, and a regeneration (third operation) mode M3. Therefore, the air drying circuit does not necessarily have to have an oil cut (fourth operation) mode M4, a purge-less supply stop (fifth operation) mode M5, a compressor assist (sixth operation) mode M6, a regeneration supply (seventh operation) mode M7, or a forced regeneration (eighth operation) mode M8 as essential operations.

[0114] · In each of the above embodiments, the purge (second operation) mode M2 may be omitted. · In each of the above embodiments, the air supply system 10 has been described as being mounted on vehicles such as trucks, buses, and construction machines. As another aspect, the air supply system may be mounted on other vehicles such as passenger cars and railway vehicles.

[0115] · The ECU 80 is not limited to performing software processing for all the processes it executes. For example, the ECU 80 may include a dedicated hardware circuit (e.g., an application-specific integrated circuit: ASIC) that performs hardware processing for at least a part of the processes it executes. That is, the ECU 80 can be configured as a circuitry including 1) one or more processors that operate according to a computer program (software), 2) one or more dedicated hardware circuits that execute at least a part of various processes, or 3) a combination thereof. The processor includes a CPU and memories such as a RAM and a ROM, and the memories store program codes or instructions configured to cause the CPU to execute processes. The memories, i.e., computer-readable media, include any available media that can be accessed by a general-purpose or dedicated computer.

Description of Reference Numerals

[0116] 4... Compressor, 10... Air supply system, 11... Air drying circuit, 12... Supply circuit, 15... Upstream check valve, 16... Branch passage, 17... Filter, 18... Air supply passage, 19... Downstream check valve, 20... Bypass flow path, 21... Regeneration control valve, 22... Orifice, 25... Drain discharge valve, 26A... Governor, 26B... Unload control valve, 27... Drain outlet as the discharge port, 30... Air tank, 50... Pressure sensor, 51... Humidity sensor, 52... Temperature sensor, 53... Pressure sensor, 80... ECU, 80A... Memory unit, E61~E67... Wiring.

Claims

1. An air drying circuit provided between a compressor that sends out compressed air and an air tank that stores compressed and dried air, and having a filter containing a desiccant for capturing moisture, and a control device for controlling the air drying circuit, comprising: when the compressor is driven and the compressed air is sent to the filter and supplied to the air tank during a supply operation, the control device determines the dry state of the compressed and dried air stored in the air tank from the moisture content, and is configured to determine whether to execute a regeneration operation of passing the compressed and dried air in a reverse direction through the filter and discharging the fluid that has passed through the filter from a discharge port based on the dry state of the compressed and dried air. An air supply system.

2. The control device acquires pressure information of the air tank and an air discharge amount of the compressor, calculates a consumption amount of the compressed and dried air stored in the air tank based on a pressure change of the air tank, and is configured to calculate a moisture content of the compressed and dried air using the consumption amount of the compressed and dried air and the air discharge amount. The air supply system according to claim 1.

3. The control device is configured to execute the regeneration operation when the pressure of the compressed and dried air reaches a cut-out pressure at which the regeneration operation is performed and the dry state of the compressed and dried air does not satisfy a predetermined condition. The air supply system according to claim 1 or 2.

4. When the pressure of the compressed and dried air reaches the cut-out pressure and the dry state of the compressed and dried air satisfies a predetermined value, the control device passes the compressed and dried air in the air drying circuit in the reverse direction through the filter and discharges the fluid that has passed through the filter from the discharge port, and is configured to execute a purge operation. The air supply system according to claim 3.

5. a discharge valve that communicates a branch path connected to the air drying circuit and the discharge port, and a regeneration control valve that switches between a forward flow from the filter toward the air tank and a reverse flow from the air tank toward the filter, wherein the control device is configured to control the discharge valve and the regeneration control valve. The air supply system according to any one of claims 1 to 4.

6. An air drying circuit provided between a compressor that delivers compressed air and an air tank that stores compressed and dried air, and having a filter containing a desiccant for capturing moisture, A control method for an air supply system including a control device that controls the air drying circuit, the control method comprising: The control device, During a supply operation in which the compressor is driven and the compressed air is delivered to the filter and supplied to the air tank, determining the dry state of the compressed and dried air stored in the air tank from the moisture content, Based on the dry state of the compressed and dried air, determining whether to perform a regeneration operation in which the compressed and dried air is passed through the filter in the reverse direction and the fluid that has passed through the filter is discharged from the discharge port, A control method for an air supply system.

7. An air supply system control program including an air drying circuit provided between a compressor that delivers compressed air and an air tank that stores compressed and dried air, and having a filter containing a desiccant for capturing moisture, and a control device that controls the air drying circuit, the control program causing the control device to During a supply operation in which the compressor is driven and the compressed air is delivered to the filter and supplied to the air tank, function as a dry state determination unit that determines the dry state of the compressed and dried air stored in the air tank from the moisture content, and Based on the dry state of the compressed and dried air, function as a regeneration operation execution determination unit that determines whether to perform a regeneration operation in which the compressed and dried air is passed through the filter in the reverse direction and the fluid that has passed through the filter is discharged from the discharge port, An air supply system control program.

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