AIR SUPPLY SYSTEM, CONTROL METHOD FOR AIR SUPPLY SYSTEM, AND CONTROL PROGRAM FOR AIR SUPPLY SYSTEM

Abstract

An air supply system (10) capable of maintaining a dry state of compressed dry air and a control method for the air supply system are provided. The air supply system (10) includes an air drying circuit (11) provided between a compressor (4) that delivers compressed air and an air tank (30) that stores the compressed dry air and having a filter (17) containing a desiccant that captures moisture, and an ECU (80) that controls the air drying circuit (11). During a supply operation in which the compressor (4) is driven to deliver compressed air to the filter (17) and supply it to the air tank (30), the ECU (80) determines the dryness state of the compressed dry air stored in the air tank (30) from the moisture content, and determines whether to perform a regeneration operation in which the compressed dry air passes through the filter (17) in the reverse direction and drains the drain that has passed through the filter (17) from a drain outlet (27).

Description

[Technical field]

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

[0002] In vehicles such as trucks, buses, and construction machines, pneumatic systems, including brake systems and suspension systems, are controlled using compressed air sent from a compressor. This compressed air contains liquid impurities such as moisture contained in the atmosphere and oil that lubricates the inside of the compressor. If compressed air containing a lot of moisture and oil enters a pneumatic system, it may cause rust and swelling of rubber components, which may lead to malfunctions. For this reason, a compressed air dryer is provided downstream of the compressor to remove impurities such as moisture and oil from the compressed air.

[0003] The compressed air dryer is equipped with 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. 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 to the desiccant from the desiccant and release the removed oil and moisture as drain (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-201323 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the compressed air drying device switches between the dehumidification operation and the regeneration operation based on the pressure in the storage section. When the compressed dry air stored in the storage section continues to be consumed, the dehumidification operation continues without switching to the regeneration operation, which may increase the moisture content of the compressed dry air stored in the storage section. 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 and a control method for an air supply system that can maintain the dry state of compressed dry air. [Means for solving the problem]

[0007] An air supply system that solves the above problem includes an air drying circuit having a filter containing a desiccant that captures moisture, which is disposed between a compressor that sends out compressed air and an air tank that stores compressed, dry air, and a control device that controls the air drying circuit. During a supply operation in which the compressor is driven and the compressed air is sent to the filter and supplied to the air tank, the control device determines the dryness state of the compressed, dry air stored in the air tank from the moisture content, and decides whether or not to perform a regeneration operation in which the compressed, dry air is passed through the filter in the reverse direction and the fluid that has passed through the filter is discharged from an outlet.

[0008] A control method for an air supply system that solves the above problem is a control method for an air supply system that includes an air drying circuit having a filter containing a desiccant that captures moisture, which is arranged between a compressor that sends out compressed air and an air tank that stores compressed, dry air, and a control device that controls the air drying circuit, wherein, during a supply operation in which the compressor is driven and the compressed air is sent to the filter and supplied to the air tank, the control device determines the dryness state of the compressed, dry air stored in the air tank from the moisture content, and decides whether to perform a regeneration operation in which the compressed, dry air is passed through the filter in the reverse direction and the fluid that has passed through the filter is discharged from an outlet.

[0009] A control program for an air supply system that solves the above problem is a control program for an air supply system that includes an air drying circuit that is arranged between a compressor that sends out compressed air and an air tank that stores compressed dry air and has a filter containing a desiccant that captures moisture, and a control device that controls the air drying circuit, and causes the control device to function as a dryness state determination unit that determines the dryness state of the compressed dry air stored in the air tank from the moisture content during a supply operation in which the compressor is driven and the compressed air is sent to the filter and supplied to the air tank, and a regeneration operation execution determination unit that determines whether to execute a regeneration operation in which the compressed dry air is passed through the filter in the reverse direction and the fluid that has passed through the filter is discharged from an outlet, based on the dryness state of the compressed dry air.

[0010] According to the above configuration, during the supply operation, the dryness state of the compressed dry air is judged from the moisture content to determine whether or not to perform the regeneration operation. Therefore, when the supply operation is performed and regeneration of the desiccant is insufficient, the regeneration operation is performed. Thus, the dryness state of the compressed dry air can be maintained.

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

[0012] When compressed dry air is supplied to the air tank and consumed through braking or regeneration, it is difficult to calculate the moisture content of the compressed dry air in the air tank. Therefore, according to the above configuration, the consumption amount of compressed dry air is calculated from the pressure change in the air tank and the air discharge amount of the compressor, and the moisture content contained in the consumed compressed dry air is calculated, so that the moisture content in the air tank after the compressed dry air is consumed through braking or regeneration can be accurately estimated.

[0013] For the above air supply system, the control device may be configured to perform the regeneration operation when the pressure of the compressed dry air reaches a cutout pressure for performing the regeneration operation and the dryness state of the compressed dry air does not satisfy a specified condition.

[0014] When compressed dry air is supplied and consumed and the pressure of the compressed dry air does not reach the cutout pressure and the supply of the compressed dry air continues, the drying ability of the filter decreases. Therefore, according to the above configuration, when the pressure of the compressed dry air does not reach the cutout pressure and the dry state of the compressed dry air does not satisfy the predetermined condition, the regeneration operation is performed to regenerate the desiccant and maintain the dry state of the compressed dry air.

[0015] For the above air supply system, the control device may be configured to perform a purging operation in which, when the pressure of the compressed dry air reaches the cutout pressure and the dryness state of the compressed dry air satisfies a predetermined condition, the compressed dry air of the air drying circuit is passed through the filter in the reverse direction and the fluid that has passed through the filter is discharged from the outlet.

[0016] According to the above configuration, when the dryness state of the compressed dry air satisfies a predetermined condition, a purge operation is performed in which the compressed dry air in the air drying circuit is passed through the filter in the reverse direction, rather than a regeneration operation in which the compressed dry air in the air tank is passed through the filter in the reverse direction, thereby suppressing consumption of the compressed dry air in the air tank.

[0017] The above air supply system may include an exhaust valve that connects a branch path connected to the air drying circuit with the exhaust port, and a regeneration control valve that switches between a forward flow from the filter to the air tank and a reverse flow from the air tank to the filter, and the control device may be configured to control the exhaust valve and the regeneration control valve.

[0018] According to the above configuration, the control device controls the discharge valve and the regeneration control valve, so that 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] 1 is a diagram showing a schematic configuration of an air supply system according to a first embodiment; [Diagram 2] FIG. 2A is a diagram showing the first and seventh operation modes of the air drying circuit of the embodiment of FIG. 1; FIG. 2B is a diagram showing the second operation mode of the air drying circuit of the embodiment of FIG. 1; FIG. 2C is a diagram showing the third and eighth operation modes of the air drying circuit of the embodiment of FIG. 1; and FIGS. 2D to 2F are diagrams showing the fourth to sixth operation modes of the air drying circuit of the embodiment of FIG. 1, respectively. [Diagram 3] 2 is a transition diagram showing transition of the operation of the air drying circuit of the embodiment of FIG. 1. [Figure 4] 2 is a flow chart illustrating the transition from a first mode of operation of the air drying circuit of the embodiment of FIG. 1; [Diagram 5] 4 is a flow chart illustrating transitions from the second and third modes of operation of the air drying circuit of the embodiment of FIG. 1; [Figure 6] 4 is a flow chart illustrating the transition from the fifth operational mode of the air drying circuit of the embodiment of FIG. 1; [Figure 7] 4 is a flow chart illustrating the transition from the seventh operational mode of the air drying circuit of the embodiment of FIG. 1; [Figure 8] 4 is a flow chart illustrating the transition from the eighth operational mode of the air drying circuit of the embodiment of FIG. 1; [Figure 9] FIG. 11 is a schematic diagram showing a process for calculating tank air moisture saturation in a second embodiment of the air supply system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] (First embodiment) A first embodiment of an air supply system will be described with reference to Fig. 1 to Fig. 8. The air supply system is mounted on vehicles such as trucks, buses, construction machines, etc. Compressed, dry air supplied by the air supply system is used for pneumatic equipment such as a brake system mounted on the vehicle.

[0022] <Air Supply System 10> An 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 a calculation unit, a communication interface unit, a volatile storage unit, and a nonvolatile storage unit. The calculation unit is a computer processor, and is configured to control the air drying circuit 11 according to an air supply program stored in the nonvolatile storage unit (storage medium). The calculation unit may realize at least a part of the processing executed by itself by a circuit such as an ASIC. The air supply program may be executed by one computer processor or may be executed by a plurality of computer processors. The ECU 80 also includes a storage unit 80A that stores the results of the operation of the air drying circuit 11. The storage unit 80A is a nonvolatile storage unit or a volatile storage 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 an in-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, ignition switch off information, vehicle speed, engine drive information, and the like.

[0025] The state of the compressor 4 is switched between an operating state (load operation) in which air is compressed and sent out, and a non-operating state (idle operation) in which air is not compressed, based on a command value from the ECU 80. The compressor 4 is operated by power transmitted from a rotary 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 load operation. The air drying circuit 11 sends out the compressed air after being dried (hereinafter, compressed dry air) to the supply circuit 12. The compressed dry air supplied to the supply circuit 12 is stored in the air tank 30.

[0027] The compressed dry air stored in the air tank 30 is supplied to pneumatic equipment such as a brake system mounted on the vehicle. For example, when the brakes are applied frequently, such as when the vehicle is traveling downhill or in an urban area, the amount of compressed dry air stored in the air tank 30 is increased. Conversely, when the brakes are applied infrequently, the amount of compressed dry air stored in the air tank 30 is reduced.

[0028] The air drying circuit 11 has a maintenance port P12. The maintenance port P12 is a port through which air is supplied to the air drying circuit 11 during maintenance.

[0029] <Air drying circuit 11> The air drying circuit 11 includes a filter 17 inside the case 11A (see FIG. 2A ). The filter 17 is provided in the air supply passage 18 that connects the compressor 4 and the supply circuit 12. The filter 17 includes a desiccant. The filter 17 may include an oil capture section that captures oil, in addition to the desiccant. The oil capture section may be any material that can capture oil while allowing air to pass through, such as a foam such as urethane foam, a metal material with multiple air holes, or a glass fiber filter.

[0030] The filter 17 removes moisture contained in the compressed air from the compressed air by passing the compressed air sent from the compressor 4 through a desiccant, thereby drying the compressed air. The desiccant or oil trap captures 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, which serves as a check valve that allows only downstream air flow relative to the filter 17. In other words, the downstream check valve 19 allows only air flow from upstream to downstream, with the filter 17 side being the upstream and the supply circuit 12 side being the downstream. The downstream check valve 19 has a predetermined valve opening pressure (sealing pressure), so that when compressed air flows, the upstream pressure is higher than the downstream pressure by the valve opening pressure.

[0031] Further, downstream of the filter 17, a bypass passage 20 serving as a detour around the downstream check valve 19 is provided in parallel to the downstream check valve 19. The bypass passage 20 is provided with a regeneration control valve 21.

[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 (drive / non-drive) of the power supply to the regeneration control valve 21 via a wire E64. The regeneration control valve 21 closes to block 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, for example, receives the value of the air pressure in the air tank 30 and operates the regeneration control valve 21 when the air pressure value exceeds a predetermined range.

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

[0034] A branch passage 16 branches off 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 discharge port 27 is connected to an end of the branch passage 16.

[0035] Drain, which is a fluid containing water and oil removed from the filter 17, is sent to the drain discharge valve 25 together with compressed air. The drain discharge valve 25 is an air-pressure-driven valve that is driven by air pressure, and is provided in the branch passage 16 between the filter 17 and a drain discharge port 27. The drain discharge valve 25 is a two-port two-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 discharge port 27. The drain discharged from the drain discharge port 27 may be collected by an oil separator (not shown). 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 the ECU 80. The ECU 80 switches the operation of the governor 26A by controlling the on / off (drive / non-drive) of the power supply to the governor 26A via a wiring E63. When the power supply is turned on, the governor 26A inputs an air pressure signal to the drain discharge valve 25 to open the drain discharge valve 25. When the power supply is turned off, the governor 26A closes the drain discharge valve 25 by opening the drain discharge valve 25 to atmospheric pressure without inputting an air pressure signal to the drain discharge valve 25.

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

[0038] An upstream check valve 15 is provided between the compressor 4 and the filter 17, and between the compressor 4 and the branch passage 16. When the compressor 4 side is the upstream and the filter 17 side is the downstream, the upstream check valve 15 only allows air to flow from upstream to downstream. Since the upstream check valve 15 has a predetermined valve opening pressure (sealing pressure), when compressed air flows, the upstream pressure is higher than the downstream pressure by the valve opening pressure. A reed 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 the unloading control valve 26B. The unloading control valve 26B is a solenoid valve controlled by the ECU 80. The ECU 80 switches the operation of the unloading control valve 26B by controlling the on / off (drive / non-drive) of the power supply to the unloading control valve 26B via the wiring E62. When the power supply is turned off, the unloading control valve 26B switches to the open position and opens the flow path between the unloading control valve 26B and the compressor 4 to the atmosphere. When the power supply is turned on, the unloading control valve 26B 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 unloading control valve 26B, the state of the compressor 4 is switched to a non-operating state (idle operation). For example, when the pressure in the supply circuit 12 reaches the cutout pressure, the supply of compressed dry air is not necessary. When the pressure on the supply circuit 12 side reaches the cutout pressure and the ECU 80 turns on the power of the unloading control valve 26B (drives the unloading control valve 26B), the unloading control valve 26B is switched to the supply position. As a result, an air pressure signal is supplied from the unloading control valve 26B to the compressor 4, and the state of the compressor 4 is switched to a 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 measurement 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 dry air downstream of the filter 17 and outputs the measurement result to the ECU 80 via a wiring E65. The temperature sensor 52 measures the temperature of the compressed dry air downstream of the filter 17 and outputs the measurement result to the ECU 80 via a wiring E66. The ECU 80 determines the dryness state of the compressed dry air based on the humidity and temperature of the compressed dry air input from the humidity sensor 51 and the temperature sensor 52. That is, the humidity and temperature of the compressed dry air are indexes that indicate the dryness state of the compressed dry 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 to be able to detect, for example, the air pressure in the air tank 30 in which compressed dry air is stored, and is connected to the ECU 80 via a 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. The pressure sensor 53 may be provided in the supply circuit 12 or in the air tank 30.

[0044] The ECU 80 acquires pressure information of the air tank 30 and the air discharge rate of the compressor 4, and calculates the air consumption rate of the compressed dry 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 dry air using the air consumption rate and the air discharge rate of the compressed dry air.

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

[0046] Air consumption = (reduced pressure [kPa] / atmospheric pressure [kPa]) x tank capacity [L] + air discharge amount (previous value) [L]…(1) The moisture content of the consumed air is calculated according to formula (2). The moisture content of the tank is the absolute value of the moisture content in the air tank 30, calculated from the compressed air temperature and compressed air humidity in the air tank 30 at the end of regeneration.

[0047] Moisture content of consumed air [g] = Moisture content of tank [g] × Air consumption during cycle [L] × (Atmospheric pressure [kPa] / (Cutout pressure [kPa] + Atmospheric pressure [kPa])) ÷ Tank capacity [L]…(2) The air consumption can be calculated directly from the pressure change (reduced pressure value) when there is no air discharge, and is calculated from the pressure change (reduced pressure value) and the air discharge when there is an air discharge.

[0048] <Operation of the 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 a first operation mode to an 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 performing normal dehumidification (loading). In this first operation mode, the regeneration control valve 21, the governor 26A, and the unloading control valve 26B are each closed (indicated as "CLOSE" in the figure). At this time, power is not supplied to the regeneration control valve 21, the governor 26A, and the unloading control valve 26B. In addition, the governor 26A and the unloading control valve 26B open the port of the compressor 4 and the port of the drain discharge valve 25 connected downstream thereof to the atmosphere, respectively. In the first operation mode, when compressed air is supplied from the compressor 4 (indicated as "ON" in the figure), moisture and the like are removed by the filter 17, and the compressed air is supplied to the supply circuit 12.

[0050] (Second operating mode) As shown in FIG. 2B, the second operation mode is a mode in which a "purge" operation is performed in which the compressed dry air in the air drying circuit 11 is passed through the filter 17 to purify the filter 17. In this second operation mode, the regeneration control valve 21 is closed, and the governor 26A and the unloading control valve 26B are opened (indicated as "OPEN" in the figure). At this time, the governor 26A and the unloading control valve 26B are each supplied with power, and the port of the compressor 4 and the port of the drain discharge valve 25 connected downstream of them are each connected upstream (to the supply circuit 12). This switches the compressor 4 to a non-operating state (indicated 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 (backflows) through the filter 17 in the opposite direction to the air flow in the first operation mode (supply), and moisture and the like captured by the filter 17 are discharged from the drain discharge port 27 as drain. Additionally, the air pressure in the filter 17 and the air supply passage 18 is released to atmospheric pressure.

[0051] (Third operation mode) As shown in FIG. 2C, the third operation mode is a mode in which a "regeneration" operation is performed to regenerate the filter 17. In this third operation mode, the regeneration control valve 21, the governor 26A, and the unloading control valve 26B are each opened. At this time, power is supplied to the regeneration control valve 21 as well as the governor 26A and the unloading control valve 26B. In the third operation mode, the compressor 4 is put into a non-operating state, and the compressed dry air stored in the supply circuit 12 or the air tank 30 is caused to flow back to the filter 17 and discharged from the drain outlet 27. This removes moisture and the like captured in the filter 17. Although the second operation mode and the third operation mode are both modes in which the filter 17 is purified, the third operation mode differs from the second operation mode in that at least the regeneration control valve 21 is opened. As a result, 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 flow path 20. Therefore, the effect of cleaning the filter 17 is higher than in the second operation mode. Also in the third operation mode, the air pressure in the filter 17 and the air supply passage 18 is released to atmospheric pressure.

[0052] (4th operation mode) As shown in FIG. 2D, the fourth operation mode is a mode in which an "oil cut" operation is performed to discharge the compressed air supplied from the compressor 4 while the compressor 4 is operating. When the compressor 4 is not operating, oil may accumulate in the compression chamber of the compressor 4. When the compressor 4 is switched to an 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 performed for the purpose of discharging the compressed air containing an excess of oil 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 closed, and the governor 26A is closed after being opened for a certain period of time. In the fourth operation mode, when the compressor 4 is operating, the compressed air supplied by the compressor 4 is discharged from the drain discharge port 27 for a certain period of time. Therefore, it is possible to suppress an increase in the amount of water and oil trapped in the filter 17 immediately after the compressor 4 is switched from a non-operating state to an operating state. When the engine speed increases in an operating state or when the amount of oil from the compressor 4 increases due to high engine load, etc., an oil cut operation can also be performed.

[0053] (5th operation mode) 2E, the fifth operation mode is a "purgeless supply stop" operation mode in which the compressor 4 is stopped without purging. In this fifth operation mode, the regeneration control valve 21 and the governor 26A are closed, and the unload control valve 26B is opened. In the fifth operation mode, when the compressor 4 is not in operation, the compressed air or compressed dry air remaining in the air supply passage 18 or the desiccant in the filter 17 is not discharged from the drain outlet 27, thereby maintaining the air pressure.

[0054] (6th operation mode) As shown in FIG. 2F, the sixth operation mode is a mode in which a "compressor assist" operation for performing a pressurization process is performed. In this sixth operation mode, the regeneration control valve 21 and the unload control valve 26B are opened, and the governor 26A is closed. In the sixth operation mode, when the compressor 4 is not in operation, the compressed air of the supply circuit 12 is supplied (backflowed) into the air supply passage 18 and the desiccant of the filter 17, thereby making the pressure of the air supply passage 18 and the filter 17 higher than atmospheric pressure, and maintaining the back pressure (air pressure) of the upstream check valve 15 at a pressure higher than atmospheric pressure. Thus, the generation of negative pressure in the cylinder can be suppressed, and the operating 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 compressed air supplied by the compressor 4 maintains the air pressure in the desiccant of the filter 17 and in the air supply passage 18 at a pressure higher than atmospheric pressure.

[0055] (7th operating mode) 2A, the seventh operation mode is a "regenerative supply" operation mode in which dehumidification (loading) is performed during regeneration in which the compressor 4 is driven when the engine is in an unloaded state. In this seventh operation mode, similarly to the first operation mode, the regeneration control valve 21, the governor 26A, and the unload control valve 26B are each closed (indicated as "CLOSE" in the figure).

[0056] (8th operation mode) 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, similarly to the third operation mode, the regeneration control valve 21, the governor 26A, and the unload control valve 26B are each opened.

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

[0058] The transitions from each operation mode will be described with reference to FIGS. 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 a condition, for example, when the engine is driven. In the supply process, the air drying circuit 11 is in a supply (first operation) mode M1.

[0059] 4, in the supply (first operation) mode M1, the ECU 80 determines whether or not the pressure in the supply circuit 12 is higher than the cutout pressure (step S11). That is, the ECU 80 obtains the pressure in the air tank 30 detected by the pressure sensor 53, and determines whether or not the pressure has reached the cutout pressure.

[0060] When the ECU 80 determines that the pressure in the supply circuit 12 has reached the cutout pressure (step S11: YES), it determines whether the amount of moisture in the air tank 30 is large (step S12). That is, when the amount of moisture in the air tank 30 is equal to or greater than a predetermined value, the ECU 80 determines the amount of moisture in the air tank 30 because it is necessary to regenerate the desiccant in the filter 17.

[0061] Then, when the ECU 80 determines that the amount of moisture in the air tank 30 is equal to or greater than a predetermined value (step S12: YES), it transitions to a 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 in the filter 17.

[0062] In addition, when the ECU 80 determines that the amount of moisture in the air tank 30 is less than a predetermined value (step S12: NO), it transitions to a purge (second operation) mode M2 ​​in which the compressed dry air between the downstream check valve 19 and the filter 17 passes through the filter 17, and the moisture and other substances 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 cutout pressure (step S11: NO), it determines whether or not the conditions for transitioning to the oil cut (fourth operation) mode M4 are satisfied (step S13). That is, the ECU 80 determines whether or not all of the following conditions for transitioning to the oil cut (fourth operation) mode M4 are satisfied: a predetermined time has elapsed, the number of times that oil cut has been performed is less than a specified number of times, and the operating rate of the compressor 4 is low. Then, when the ECU 80 determines that the conditions for transitioning to the oil cut (fourth operation) mode M4 are not satisfied (step S13: NO), it returns the process to step S11.

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

[0065] After transitioning 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), the ECU 80 transitions to the supply (first operation) mode M1.

[0066] 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] If the ECU 80 determines that the predetermined time has not elapsed (step S21: NO), the ECU 80 determines whether the pressure in the supply circuit 12 is lower than the cut-in pressure (step S24). That is, the ECU 80 obtains the pressure in 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), the compressed dry air is insufficient, and the mode transitions 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), the process returns to step S21.

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

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

[0071] Furthermore, when the ECU 80 determines that the compressor assist (sixth operation) processing is enabled (step S22: YES), the ECU 80 transitions to a compressor assist (sixth operation) mode M6 in which a pressurization processing is performed.

[0072] After transitioning to the compressor assist (sixth operation) mode M6, the ECU 80 determines whether 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 the predetermined time has elapsed (step S23: YES), the ECU 80 transitions to the purge-less supply stop (fifth operation) mode M5.

[0073] 6, in the purge-less supply stop (fifth operation) mode M5, the ECU 80 determines whether the pressure in the supply circuit 12 is lower than the cut-in pressure (step S31). That is, the ECU 80 acquires the pressure in the air tank 30 detected by the pressure sensor 53, and determines whether 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), the compressed dry air is insufficient, and therefore the ECU 80 transitions 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 or not the conditions for transitioning to the regenerative supply (seventh operation) mode M7 are satisfied (step S32). That is, the ECU 80 determines whether or not all of the following conditions for transitioning to the regenerative supply (seventh operation) mode M7 are satisfied: the vehicle is traveling, no fuel is being consumed, and the pressure in the supply circuit 12 is less than a threshold value. Then, when the ECU 80 determines that the conditions for transitioning to the regenerative supply (seventh operation) mode M7 are not satisfied (step S32: NO), it returns the process to step S31.

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

[0077] 7, in the regenerative supply (seventh operation) mode M7, the ECU 80 determines whether or not a condition for transitioning to the purge-less supply stop (fifth operation) mode M5 is satisfied (step S41). That is, the ECU 80 determines whether or not at least one of the following conditions for transitioning to the purge-less supply stop (fifth operation) mode M5 is satisfied: the pressure in the supply circuit 12 is higher than the cutout pressure, a predetermined time has elapsed, and the fuel consumption of the engine is high. Then, when the ECU 80 determines that the condition for transitioning to the purge-less supply stop (fifth operation) mode M5 is satisfied (step S41: YES), the ECU 80 transitions to the purge-less supply stop (fifth operation) mode M5.

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

[0079] When the ECU 80 determines that the pressure in the supply circuit 12 has reached the cut-in pressure (step S42: YES), the compressed dry air is insufficient, and therefore the ECU 80 transitions 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 or not the condition for transitioning to the forced regeneration (eighth operation) mode M8 is satisfied (step S43). That is, the ECU 80 determines whether or not both of the conditions for transitioning to the forced regeneration (eighth operation) mode M8, that is, the pressure in the supply circuit 12 is higher than the threshold and the amount of moisture in the air tank 30 is large, are satisfied as the conditions for transitioning to the forced regeneration (eighth operation) mode M8. In the regenerative supply (seventh operation) mode M7, the ECU 80 determines the dryness 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 dryness state of the compressed dry air. If the moisture content of the tank air is equal to or greater than a predetermined value, the ECU 80 determines that the moisture content of the air tank 30 is large, and if the moisture content of the tank air is less than the predetermined value, the ECU 80 determines that the moisture content of the air tank 30 is small. If the ECU 80 determines that the condition for transition to the forced regeneration (eighth operation) mode M8 is not met (step S43: NO), the ECU 80 returns the process to step S42.

[0081] On the other hand, when the ECU 80 determines that the condition for transitioning to the forced regeneration (eighth operation) mode M8 is satisfied (step S43: YES), the ECU 80 transitions to the forced regeneration (eighth operation) mode M8 which forcibly regenerates the filter 17. 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 compressed dry air flows in the reverse direction.

[0082] 8, in the forced regeneration (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 regeneration (eighth operation) mode M8 for a predetermined time.

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

[0084] When the ECU 80 determines that the pressure in the supply circuit 12 has reached the cut-in pressure (step S55: YES), the compressed dry air is insufficient, and the mode transitions 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 S55: NO), the process returns to step S51.

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

[0086] If the ECU 80 determines that the operating rate of the compressor 4 is high (step S52: YES), the compressor assist (sixth operation) is not necessary, and therefore the ECU 80 transitions to the supply (first operation) mode M1.

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

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

[0089] After transitioning to the compressor assist (sixth operation) mode M6, the ECU 80 determines whether 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), the ECU 80 transitions to the purge-less supply stop (fifth operation) mode M5.

[0090] Next, the effects of the first embodiment will be described. (1) During supply (first operation), the dryness state of the compressed dry air is judged from the moisture content to determine whether or not to perform regeneration (third operation). Therefore, when supply (first operation) is performed and regeneration of the desiccant is insufficient, regeneration (third operation) is performed. This makes it possible to maintain the dryness of the compressed dry air.

[0091] (2) By calculating the consumption of compressed dry air from the pressure change in the air tank 30 and the air discharge volume of the compressor 4, and then calculating the amount of moisture contained in the consumed compressed dry air, it is possible to accurately estimate the amount of moisture in the air tank 30 after the compressed dry air has been consumed by braking or regeneration operations.

[0092] (3) When the pressure of the compressed dry air does not reach the cutout pressure and the dryness state of the compressed dry air does not satisfy specified conditions such as a specified value, i.e., when the indicator indicating the dryness state of the compressed dry air is not within a specified range, the desiccant is regenerated by performing regeneration (third operation) to maintain the dryness of the compressed dry air.

[0093] (4) When the dryness state of the compressed dry air satisfies a predetermined condition, purging (second operation) is performed by passing the compressed dry air in the air supply passage 18 through the filter 17 in the opposite direction, rather than regeneration (third operation) by passing the compressed dry air in the air tank 30 through the filter 17 in the opposite direction. This makes it possible to suppress consumption of the compressed dry air in the air tank 30.

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

[0095] Conventionally, air supply systems switch between dehumidification and regeneration based on the pressure in the storage unit, regardless of the dryness of the compressed air. Depending on the atmospheric temperature conditions, the compressed air in the storage unit may eventually become excessively dry, resulting in an increase in the consumption of compressed air required to promote and maintain the dryness, and increased compressor operation. Therefore, there is a need to maintain the dryness of the compressed dry air to the necessary level according to the atmospheric conditions without becoming excessive.

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

[0097] Target dew point [℃] = Outside temperature [℃] - Dew point depression [℃] (11) At this time, by making it possible to set the degree of dew point depression according to the outside air temperature, it becomes possible to change the target moisture content due to dehumidification. Therefore, for example, it becomes possible to freely set the moisture content of the compressed dry air in the air tank 30 according to the outside air temperature, thereby obtaining an optimal dehumidification effect and reducing the consumption of compressed dry air during regeneration throughout the year.

[0098] The ECU 80 calculates the "capacity of moisture contained in the tank air" by converting the "target dew point" according to equation (12). Tank air moisture content [g] = (target dew point [g / m 3 ] × tank capacity [L]) / unit conversion factor (L / m 3 ) · · · (12) The ECU 80 calculates the "tank air moisture reference amount", which is the amount of moisture in the air tank 30, from the compressed dry air that flows back into the filter 17 during regeneration of the filter 17, in accordance with equation (13).

[0099] Tank air moisture content standard amount [g] = {(regeneration air temperature [g / m 3 ] × Regeneration air humidity [%RH]) / Unit conversion factor (%)} × Tank capacity [L] / Unit conversion factor (L / m 3 ) · · · (13) According to equation (14), ECU 80 calculates the "moisture content of the supply air", taking into account the air flow rate of dry air flowing into filter 17 when dry air is supplied, from the amount of supply air during the cycle, the amount of saturated water vapor at the supply air temperature, and the supply air humidity.

[0100] Moisture content of supply air [g] = {(saturated water vapor content [g / m 3 ] × supply air humidity [%RH]) / unit conversion factor (%)} × {cycle supply air volume [L] / unit conversion factor (L / m 3 )}×{atmospheric pressure [kPa] / (cutout pressure [kPaG]+atmospheric pressure [kPa])}···(14) The ECU 80 calculates the "moisture content of consumed air" from the reduced pressure value of the air tank 30, taking into account the moisture discharged when the compressed dry air is consumed, and the amount of air consumed during the cycle, according to equation (15).

[0101] Moisture content of consumed air [g] = Moisture content of tank [g] × Air consumption during cycle × {Atmospheric pressure [kPa] / (Cutout pressure [kPaG] + Atmospheric pressure [kPa])} ÷ Tank capacity [L] (15) The ECU 80 calculates the "amount of change in moisture content in tank air" which is the difference between the "amount of moisture content in supplied air" and the "amount of moisture content in consumed air" according to equation (16).

[0102] Change in moisture content of tank air [g] = moisture content of supply air [g] - moisture content of consumed air [g] (16) The ECU 80 calculates the "tank air moisture content", which is the amount of moisture in the air tank 30 at the time when the supply of dry air is terminated, from the "tank air content change amount" in accordance with equation (17).

[0103] Tank air moisture content [g] = tank air moisture reference content [g] + tank air moisture change [g] (17) Furthermore, in order to obtain a dehumidifying effect for the compressed dry air in the air tank 30, the ECU 80 calculates the "tank air moisture saturation" as an index showing the margin for the amount of moisture that can be contained in the compressed dry air in the air tank 30, using the above-mentioned "tank air maximum moisture content" and "tank air maximum moisture content" according to equation (18).

[0104] Tank air moisture saturation [-] = tank air moisture content [g] / tank air moisture capacity [g] (18) The ECU 80 performs control by using the "tank air moisture saturation" calculated as described above to determine whether the "moisture content" in the first embodiment is high or low. In this case, the "predetermined value" is changed according to the "tank air moisture saturation." For example, if the "tank air moisture saturation" exceeds a threshold value at the time when the supply of dry air is terminated, the ECU 80 determines that the compressed dry air is not in a dry state and performs regeneration of the filter 17. In other words, the tank air moisture saturation is an index that indicates the dry state of the compressed dry air.

[0105] Next, a description will be given of the effects of the second embodiment. In addition to the effects (1) to (5) of the first embodiment, the second embodiment has the following effects. (6) The amount of moisture is determined based on the tank air moisture saturation level, so that an optimal dehumidification effect can be obtained and the amount of compressed dry air consumed during regeneration of the filter 17 throughout the year can be reduced.

[0106] (Other embodiments) The above-described embodiments may be modified as follows: The above-described embodiments and the following modifications may be combined with each other to the extent that no technical contradiction occurs.

[0107] In the first embodiment, the dryness of the compressed dry air is determined based on the moisture content of the consumed air. However, the dryness of the compressed dry air may be determined by estimating the moisture content of the tank air from the humidity and temperature of the compressed dry air in the air tank 30.

[0108] In the second embodiment, the target dew point is calculated using the dew point depression degree based on the outside air temperature, but the target dew point may be calculated using the dew point depression degree based on the ambient temperature of the air tank 30. The target dew point may also be set according to the date. In this way, the moisture content of the compressed dry air in the air tank 30 can be freely set according to seasonal changes, an optimal dehumidification effect can be obtained, and the consumption of compressed dry air during regeneration of the filter 17 can be reduced throughout the year.

[0109] In each of the above embodiments, the purge (second operation) mode M2, the regeneration (third operation) mode M3, the oil cut (fourth operation) mode M4, the compressor assist (sixth operation) mode M6, the regenerative supply (seventh operation) mode M7, and the 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 in each of the above embodiments, the conditions for transitioning to the oil cut (fourth operation) mode M4 are that all of the following conditions are met: the number of times that oil cut is performed is less than a specified number of times; and the operation rate of the compressor 4 is low. Alternatively, the ECU 80 may transition to the oil cut (fourth operation) mode M4 when at least one of these conditions is met. That is, in step S13, the ECU 80 determines whether or not at least one of the following conditions for transitioning to the oil cut (fourth operation) mode M4 is met: the elapse of a predetermined time, the number of times that oil cut is performed is less than a specified number of times, and the operation rate of the compressor 4 is low.

[0111] In step S32 in each of the above embodiments, the conditions for transitioning to the regenerative supply (seventh operation) mode M7 are that the vehicle is running, that there is no fuel consumption, and that the pressure in the supply circuit 12 is less than the threshold. Alternatively, the ECU 80 may transition to the regenerative supply (seventh operation) mode M7 when at least one of these conditions is satisfied. That is, in step S32, the ECU 80 determines whether or not at least one of the conditions for transitioning to the regenerative supply (seventh operation) mode M7 is satisfied: that the vehicle is running, that there is no fuel consumption, and that the pressure in the supply circuit 12 is less than the threshold.

[0112] In step S43 in each of the above embodiments, the condition for transitioning to the forced regeneration (eighth operation) mode M8 is that both the pressure in the supply circuit 12 is higher than the threshold value and the amount of moisture in the air tank 30 is large. Alternatively, the ECU 80 may transition to the forced regeneration (eighth operation) mode M8 when at least the amount of moisture in the air tank 30 is large. That is, in step S43, the ECU 80 determines whether the condition for transitioning to the forced regeneration (eighth operation) mode M8 is that the amount of moisture in the air tank 30 is large.

[0113] In each of the above embodiments, the filter 17 includes an oil trapping portion. However, the oil trapping portion may be omitted from the filter 17. In each of the above embodiments, the air drying circuit is not limited to the above configuration. Essentially, the air drying circuit may be configured to execute the supply (first operation) mode M1, the purge (second operation) mode M2, and the regeneration (third operation) mode M3. Therefore, the air drying circuit does not necessarily require the oil cut (fourth operation) mode M4, the purge-less supply stop (fifth operation) mode M5, the compressor assist (sixth operation) mode M6, the regenerative supply (seventh operation) mode M7, and the forced regeneration (eighth operation) mode M8.

[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 a vehicle such as a truck, a bus, a construction machine, etc. In other embodiments, the air supply system may be mounted on other vehicles such as a passenger car, a railroad car, etc.

[0115] The ECU 80 is not limited to a circuit that performs software processing for all of the processes it executes. For example, the ECU 80 may be equipped with 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 may be configured as a circuit 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 the various processes; or 3) a combination thereof. The processor includes a CPU and memory such as RAM and ROM, and the memory stores program code or instructions configured to cause the CPU to execute the processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[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 discharge port as discharge port, 30...air tank, 50...pressure sensor, 51...humidity sensor, 52...temperature sensor, 53...pressure sensor, 80...ECU, 80A...memory unit, E61 to E67...wiring.

Claims

1. an air drying circuit provided between a compressor that delivers compressed air and an air tank that stores compressed dry air, the air drying circuit having a filter containing a desiccant that captures moisture; A control device for controlling the air drying circuit, the control device, during a supply operation in which the compressor is driven to send the compressed air to the filter and then supplied to the air tank, determines a dryness state of the compressed dry air stored in the air tank from a tank air moisture saturation level that indicates a margin for the amount of moisture that can be contained in the compressed dry air in the air tank, the tank air moisture saturation level being calculated using a tank air moisture content, which is the amount of moisture that can be contained in the compressed dry air in the air tank, and a tank air moisture content, which is the amount of moisture contained in the compressed dry air in the air tank; and determining whether to execute a regeneration operation in which the compressed dry air is passed through the filter in a reverse direction to discharge the fluid that has passed through the filter from an outlet based on the dryness state of the compressed dry air. Air supply system.

2. The control device is configured to execute the regeneration operation when the pressure of the compressed dry air reaches a cutout pressure for performing the regeneration operation and the dryness state of the compressed dry air does not satisfy a predetermined condition.

2. The air supply system of claim 1.

3. the control device is configured to execute a purging operation in which the compressed dry air of the air drying circuit passes through the filter in the reverse direction and the fluid that has passed through the filter is discharged from the outlet when the pressure of the compressed dry air reaches the cutout pressure and the dryness state of the compressed dry air satisfies a predetermined value.

3. An air supply system according to claim 2.

4. a discharge valve communicating a branch passage connected to the air drying circuit with the discharge port; a regeneration control valve for switching between a forward flow from the filter to the air tank and a reverse flow from the air tank to the filter, The control device is configured to control the exhaust valve and the regeneration control valve. An air supply system according to any one of claims 1 to 3.

5. an air drying circuit provided between a compressor that delivers compressed air and an air tank that stores compressed dry air, the air drying circuit having a filter containing a desiccant that captures moisture; A control device for controlling the air drying circuit, comprising: The control device, During a supply operation in which the compressor is driven to send the compressed air to the filter and supply it to the air tank, the dryness state of the compressed dry air stored in the air tank is determined from a tank air moisture saturation level, which indicates a margin for the amount of moisture that can be contained in the compressed dry air of the air tank, and is calculated using a tank air moisture content, which is the amount of moisture that can be contained in the compressed dry air of the air tank, and a tank air moisture content, which is the amount of moisture contained in the compressed dry air of the air tank; determining whether to perform a regeneration operation in which the compressed dry air is passed through the filter in a reverse direction to discharge the fluid that has passed through the filter from an outlet based on the dryness state of the compressed dry air; A method for controlling an air supply system.

6. A control program for an air supply system including an air drying circuit, the air drying circuit being provided between a compressor that delivers compressed air and an air tank that stores compressed dry air, and having a filter that contains a desiccant that captures moisture, and a control device that controls the air drying circuit, the control device comprising: a dryness state determination unit that determines a dryness state of the compressed dry air stored in the air tank from a tank air moisture saturation level that indicates a margin for a moisture amount that can be contained in the compressed dry air of the air tank, the moisture saturation level being calculated using a tank air moisture content that is a moisture amount that can be contained in the compressed dry air of the air tank and a tank air moisture content that is a moisture amount contained in the compressed dry air of the air tank, during a supply operation in which the compressor is driven to send the compressed air to the filter and supply it to the air tank; and a regeneration operation execution determination unit that determines whether or not to execute a regeneration operation in which the compressed dry air is passed through the filter in a reverse direction and the fluid that has passed through the filter is discharged from an outlet based on the dryness state of the compressed dry air; Air supply system control program.

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