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

Abstract

The invention provides an air supply system, a control method of the air supply system, and a control program of the air supply system. An air supply system is provided with: an air drying circuit provided between a compressor for delivering compressed air and an air tank, the air drying circuit having a filter for capturing moisture; and an ECU that controls the air drying circuit so as to perform: a dehumidification operation in which compressed air sent out from the compressor passes through the filter in the forward direction and is supplied to the gas tank, and a filter purification operation in which the compressed air passes through the filter in the forward direction and is supplied to the gas tank; and a filter purification operation in which the compressed dry air passes through the filter (17) in the reverse direction and the fluid that has passed through the filter is discharged from the liquid discharge port, and the ECU acquires operation information indicating the operation state of the compressor and changes the execution frequency of the filter purification operation on the basis of the acquired operation information of the compressor.

Description

[0001] This application is a divisional application of a Chinese invention patent application filed on February 25, 2020, with application number 2020800301125 (PCT / JP2020 / 007467), and invention name “Air supply system, control method of air supply system, and control program of air supply system”. Technical Field

[0002] The present disclosure relates to an air supply system, a control method of the air supply system, and a control program of the air supply system. Background Art

[0003] In vehicles such as trucks, buses, and construction machinery, compressed air delivered from a compressor is used to control air pressure systems including brake systems and suspension systems. The compressed air contains moisture contained in the atmosphere and liquid impurities such as oil used to lubricate the compressor. If compressed air containing a large amount of moisture and oil enters the air pressure system, it may cause rust and swelling of rubber components, which may cause malfunctions. Therefore, a compressed air drying device is provided downstream of the compressor to remove impurities such as moisture and oil in the compressed air.

[0004] The compressed air drying device is equipped with various valves and a filter containing a desiccant. The compressed air drying device performs a dehumidification operation of removing moisture and the like from the compressed air by passing the compressed air through the filter. The compressed dry air generated by the dehumidification operation is stored in an air tank. In addition, the purification function of the compressed air drying device decreases according to the amount of compressed dry air passing through. Therefore, the compressed air drying device performs a regeneration operation of removing oil and moisture adsorbed on the desiccant from the desiccant and discharging the removed oil and moisture as drainage (for example, refer to Patent Document 1).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-201323 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] Some compressed air drying devices perform a discharge action for purposes other than dehumidification, such as the above-mentioned regeneration action: the discharge action consumes compressed air sent from a compressor driven by a rotary drive source such as an engine or compressed dry air stored in a storage unit. Such a discharge action will more or less increase the load on the rotary drive source. On the other hand, in recent years, it has been required to improve the fuel consumption rate of vehicles. Therefore, the following improvement is required: suppressing the consumption of compressed air or compressed dry air and maintaining the dehumidification function of the compressed air drying device.

[0010] An object of the present disclosure is to suppress air consumption by an air drying circuit for purposes other than dehumidification and to maintain the dehumidification function of the air drying circuit well.

[0011] Solutions for solving problems

[0012] An air supply system that solves the above-mentioned problem comprises: an air drying circuit, which is arranged between a compressor that sends out compressed air and a storage section that stores compressed dry air, and the air drying circuit has a filter that captures moisture; and a control device, which controls the air drying circuit, wherein the control device: controls the air drying circuit to perform a dehumidification action, which is an action of causing the compressed air sent out from the compressor to pass through the filter in a forward direction to supply the compressed air to the storage section; controls the air drying circuit to perform a filter purification action, which is an action of causing the compressed dry air to pass through the filter in a reverse direction to discharge the fluid that has passed through the filter from a discharge port; obtains working information indicating the working state of the compressor, and changes the execution frequency of the filter purification action based on the obtained working information of the compressor.

[0013] A control method for an air supply system that solves the above-mentioned problem, the air supply system comprising: an air drying circuit, which is arranged between a compressor that sends out compressed air and a storage section that stores compressed dry air, the air drying circuit having a filter that captures moisture; and a control device, which controls the air drying circuit, in which the control device performs the following steps: controlling the air drying circuit to perform a dehumidification action, the dehumidification action is an action of causing the compressed air sent out from the compressor to pass through the filter in a forward direction to supply the compressed air to the storage section; controlling the air drying circuit to perform a filter purification action, the filter purification action is an action of causing the compressed dry air to pass through the filter in a reverse direction to discharge the fluid that has passed through the filter from a discharge port; acquiring working information indicating the working status of the compressor; and changing the execution frequency of the filter purification action based on the acquired working information of the compressor.

[0014] A control program for an air supply system that solves the above-mentioned problem, the air supply system comprising: an air drying circuit, which is arranged between a compressor that sends out compressed air and a storage section that stores compressed dry air, the air drying circuit having a filter that captures moisture; and a control device, which controls the air drying circuit, the control program causing the control device to function as the following sections: a dehumidification action execution section, which controls the air drying circuit to execute a dehumidification action, the dehumidification action being an action of causing the compressed air sent out from the compressor to pass through the filter in a forward direction to supply the compressed air to the storage section; a filter purification action execution section, which controls the air drying circuit to execute a filter purification action, the filter purification action being an action of causing the compressed dry air to pass through the filter in a reverse direction to discharge the fluid that has passed through the filter from a discharge port; an acquisition section, which acquires operating information indicating the operating status of the compressor; and a change section, which changes the execution frequency of the filter purification action based on the acquired operating information of the compressor.

[0015] When the continuous or discontinuous working time of the compressor within a fixed period is long, the amount of air passing through the filter during this period increases, so the amount of moisture captured by the filter will inevitably increase. In addition, if the working time of the compressor becomes longer, the temperature of the compressed air rises, and the amount of moisture contained in each unit volume of compressed air also tends to increase. According to the above structure, the control device changes the frequency of the filter purification action based on the working information of the compressor. That is, the control device can reduce the frequency of the filter purification action when it is determined based on the working state of the compressor that it is necessary to give priority to supplying compressed dry air from the storage unit to devices other than the air drying circuit. In addition, the control device can increase the frequency of the filter purification action when it is determined based on the working state of the compressor that the filter purification is necessary.

[0016] For the above-mentioned air supply system, the control device can be constructed as follows: when it is determined based on the working information that the working state of the compressor is the second working state, the execution frequency of the filter purification action is made higher than the execution frequency of the filter purification action in the first working state, wherein the amount of air delivered from the compressor within a fixed period in the second working state can be larger than the amount of air delivered from the compressor within the fixed period in the first working state.

[0017] When the working state of the compressor is the second working state, the amount of air passing through the filter increases, and as a result, it is estimated that the amount of moisture captured by the filter also increases. In addition, when the working state of the compressor is the second working state, the temperature of the compressed air sent from the compressor becomes higher, so there is a tendency for the amount of moisture contained in the compressed air to increase. According to the above structure, when the working state of the compressor is the second working state, the moisture captured by the filter can be discharged at a high frequency by increasing the frequency of the discharge action. Therefore, the dehumidification performance of the filter can be well maintained.

[0018] For the above-mentioned air supply system, the control device can be configured as follows: when it is determined that the working state of the compressor is a third working state, the filter purification action is not performed, wherein the amount of air delivered from the compressor within a fixed period in the third working state can be larger than the amount of air delivered from the compressor within the fixed period in the second working state.

[0019] According to the above configuration, the filter cleaning operation is not performed when the compressor is in the third operating state. Therefore, when the amount of compressed dry air consumed by a device other than the air drying circuit is high, the operation mode is not switched to the filter cleaning operation, so that the compressed dry air can continue to be supplied to the device.

[0020] For the above-mentioned air supply system, the air drying circuit may include: a connecting passage connecting the compressor and the filter; a supply passage for passing the compressed dry air that has passed the filter; and a discharge valve connected to a branch passage branching from the connecting passage, the discharge valve performing a discharge action of discharging the fluid that has passed the filter by connecting the branch passage with a discharge port, the control device may control the air drying circuit to perform a purge action as the filter purification action, the purge action being an action of opening the discharge valve to allow the compressed dry air in the air drying circuit to pass through the filter in the reverse direction, and the control device may be configured to change the frequency of the purge action based on the working information of the compressor.

[0021] According to the above configuration, the frequency of the purge operation can be changed based on the operating state of the compressor.

[0022] For the above-mentioned air supply system, the control device can be configured to: obtain the moisture content of the compressed dry air supplied to the storage section, and when the moisture content is above a threshold value, determine to perform the purging action, and when the working state of the compressor is the second working state, set the threshold value lower than when the working state of the compressor is not the second working state.

[0023] According to the above configuration, the threshold value of the moisture content is changed based on the operating state of the compressor, so even when the compressor delivers highly humid compressed air and the filter captures a large amount of moisture so that the compressed dry air passing through the filter is in a significantly low humidity state, the purging action is likely to occur. Therefore, the frequency of the purging action can be appropriately adjusted.

[0024] For the above-mentioned air supply system, the control device can be constructed as follows: when it is determined based on the working information that the working state of the compressor is the second working state, the execution frequency of the filter purification action is lower than the execution frequency of the filter purification action in the first working state, wherein the amount of air delivered from the compressor in the second working state can be larger than the amount of air delivered from the compressor in the first working state.

[0025] According to the above configuration, when the compressor is in the second operating state, the frequency of the discharge operation is reduced so that a sufficient amount of compressed dry air can be stored in the storage unit, thereby preferentially supplying the compressed dry air to devices other than the air drying circuit.

[0026] For the above-mentioned air supply system, the air drying circuit may include: a connecting passage connecting the compressor and the filter; a supply passage for passing the compressed dry air that has passed through the filter; and a discharge valve connected to a branch passage branching from the connecting passage, the discharge valve performing a discharge action of discharging the fluid that has passed through the filter by connecting the branch passage with a discharge port, the control device may control the air drying circuit to perform a regeneration action as the filter purification action, the regeneration action being an action of opening the discharge valve to allow the compressed dry air in the storage section to pass through the filter in the reverse direction, and the control device may be configured to change the frequency of the regeneration action based on the working information of the compressor.

[0027] According to the above configuration, when the operating state of the compressor is the second operating state, the frequency of the regeneration operation is changed, so that, for example, the compressed dry air can be preferentially supplied to devices other than the air drying circuit.

[0028] An air supply system that solves the above-mentioned problem comprises: an air drying circuit, which is arranged between a compressor that sends out compressed air and a storage section that stores compressed dry air, and the air drying circuit has a filter that captures moisture; and a control device, which controls the air drying circuit, wherein the control device can be configured to: control the air drying circuit to perform a dehumidification action, which is an action of causing the compressed air sent from the compressor to pass through the filter in a forward direction to supply the compressed air to the storage section; control the air drying circuit to perform an oil discharge action, which is an action of causing the compressed air sent from the compressor to be discharged from a discharge port without passing through the filter; obtain working information indicating the working state of the compressor, and change the execution frequency of the oil discharge action based on the obtained working information of the compressor.

[0029] A control method for an air supply system that solves the above-mentioned problem, the air supply system comprising: an air drying circuit, which is arranged between a compressor that sends out compressed air and a storage section that stores compressed dry air, the air drying circuit having a filter that captures moisture; and a control device, which controls the air drying circuit, in which the control device performs the following steps: controlling the air drying circuit to perform a dehumidification action, the dehumidification action is an action of causing the compressed air sent from the compressor to pass through the filter in a forward direction to supply the compressed air to the storage section; controlling the air drying circuit to perform an oil discharge action, the oil discharge action is an action of causing the compressed air sent from the compressor to be discharged from a discharge port without passing through the filter; acquiring working information indicating the working status of the compressor; and changing the frequency of the oil discharge action based on the acquired working information of the compressor.

[0030] A control program for an air supply system that solves the above-mentioned problem, the air supply system comprising: an air drying circuit, which is arranged between a compressor that sends out compressed air and a storage section that stores compressed dry air, the air drying circuit having a filter that captures moisture; and a control device, which controls the air drying circuit, the control program causing the control device to function as the following sections: a dehumidification action execution section, which controls the air drying circuit to execute a dehumidification action, the dehumidification action being an action of causing the compressed air sent from the compressor to pass through the filter in a forward direction to supply the compressed air to the storage section; a discharge action execution section, which controls the air drying circuit to execute an oil discharge action, the oil discharge action being an action of causing the compressed air sent from the compressor to be discharged from a discharge port without passing through the filter; an acquisition section, which acquires working information indicating the working state of the compressor; and a change section, which changes the execution frequency of the oil discharge action based on the acquired working information of the compressor.

[0031] When the continuous or discontinuous operation time of the compressor within a fixed period is long, the amount of air passing through the filter during this period increases, and therefore the amount of oil captured by the filter will inevitably increase. In addition, if the operating time of the compressor becomes longer, the temperature of the compressed air rises, and the oil contained in each unit volume of compressed air also tends to increase. According to the above structure, the control device changes the frequency of the oil discharge action based on the operating information of the compressor. That is, the control device can reduce the frequency of the oil discharge action when it is determined based on the operating state of the compressor that it is necessary to give priority to supplying compressed dry air from the storage unit to devices other than the air drying circuit. In addition, when it is determined based on the operating state of the compressor that an oil discharge action is required, the control device can discharge compressed air containing a large amount of oil without passing through the filter, thereby reducing the load on the filter.

[0032] For the above-mentioned air supply system, the control device can be constructed as follows: when it is determined based on the working information that the working state of the compressor is a second working state, the execution frequency of the oil discharge action is made higher than the execution frequency of the oil discharge action in the first working state, wherein the amount of air delivered from the compressor within a fixed period in the second working state can be larger than the amount of air delivered from the compressor within the fixed period in the first working state.

[0033] When the working state of the compressor is the second working state, the amount of air passing through the filter increases, and as a result, it is estimated that the amount of oil captured by the filter also increases. In addition, when the working state of the compressor is the second working state, the temperature of the compressed air sent from the compressor becomes higher, so there is a tendency for the amount of oil contained in the compressed air to increase. According to the above structure, when the working state of the compressor is the second working state, the oil captured by the filter can be discharged at a high frequency by increasing the frequency of the discharge action. Therefore, the performance of the filter can be well maintained.

[0034] For the above-mentioned air supply system, the control device can be constructed as follows: when it is determined that the working state of the compressor is the third working state, the oil discharge action is not performed, wherein the amount of air delivered from the compressor within a fixed period in the third working state can be larger than the amount of air delivered from the compressor within the fixed period in the second working state.

[0035] According to the above configuration, when the compressor is in the third operating state, the filter cleaning operation is not performed. Therefore, when the consumption of compressed dry air is high, the operation mode is not switched to the discharge operation, so that the compressed dry air can be continuously supplied.

[0036] For the above-mentioned air supply system, the control device may be configured to obtain the working time and non-working time of the compressor as the working state of the compressor, and calculate the working rate of the compressor based on the obtained working time and non-working time.

[0037] The operating time of the compressor affects the temperature of the compressed air. Therefore, by determining the operating state of the compressor based on the operating time, the timing of performing an action other than the dehumidification action can be accurately determined.

[0038] Effects of the Invention

[0039] According to the present disclosure, it is possible to suppress the air drying circuit from consuming air for purposes other than dehumidification, and to maintain the dehumidification function of the air drying circuit well. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a structural diagram showing a schematic structure of one embodiment of an air supply system.

[0041] Figure 2A to Figure 2F It is shown separately Figure 1 FIG. 1 is a diagram showing first to sixth operation modes of an air drying circuit according to an embodiment of the present invention.

[0042] Figure 3 yes Figure 1A schematic diagram of the start threshold information of an implementation method.

[0043] Figure 4 It is shown Figure 1 A flowchart of an example of a process of supplying compressed air in an embodiment of the present invention.

[0044] Figure 5 It is shown Figure 1 A flowchart of an example of a process for updating a start threshold value in an implementation manner of FIG.

[0045] Figure 6 It is shown Figure 1 A flowchart of an example of a process of a purification step in an embodiment of the present invention.

[0046] Figure 7 It is shown Figure 1 A flowchart of an example of a process of degreasing action in an embodiment of the present invention. DETAILED DESCRIPTION

[0047] Reference Figure 1 to Figure 7 , to illustrate an embodiment of the air supply system. The air supply system is mounted on vehicles such as trucks, buses, and construction machinery. The compressed dry air generated by the air supply system is used, for example, in air pressure systems such as brake systems (brake devices) or suspension systems (suspension devices).

[0048] <Air supply system 10>

[0049] Reference Figure 1 The air supply system 10 will be described. 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.

[0050] ECU 80 is connected to the air drying circuit 11 via a plurality of wirings E61 to E67. ECU 80 includes a computing unit, a communication interface unit, a volatile storage unit, and a non-volatile storage unit. The computing unit is a computer processor, and the computing unit is configured to control the air drying circuit 11 according to an air supply program stored in a non-volatile storage unit (storage medium). The computing unit may also implement at least a portion of the processing performed by itself through a circuit such as an ASIC. The air supply program may be executed by one computer processor or by multiple computer processors. In addition, ECU 80 includes a storage unit 80A, and the storage unit 80A stores information for determining the execution frequency of each action of the air drying circuit 11. The storage unit 80A is a non-volatile storage unit or a volatile storage unit, and may be the same as or different from the storage unit storing the above-mentioned control program.

[0051] The ECU 80 is connected to other ECUs (not shown) mounted on the vehicle, such as the engine ECU and the brake ECU, via an on-vehicle network such as a CAN (Controller Area Network). The ECU 80 obtains information indicating the vehicle status from these ECUs. The information indicating the vehicle status includes, for example, information indicating whether the ignition switch is turned off, the vehicle speed, and engine driving information.

[0052] The state of the compressor 4 is switched between an operating state (load operation) in which air is compressed and supplied and a non-operating state (idle operation) in which air is not compressed based on a command from the ECU 80. The compressor 4 is operated by power transmitted from a rotational drive source such as an engine.

[0053] 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 from the compressed air delivered by the compressor 4 in load operation. The air drying circuit 11 supplies the dried compressed air (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.

[0054] The compressed dry air stored in the air tank 30 is supplied to the air pressure system such as the brake system mounted on the vehicle. For example, when the frequency of brake operation is high, such as when the vehicle is traveling downhill or in an urban area, the consumption of the compressed dry air stored in the air tank 30 increases. On the contrary, when the frequency of brake operation is low, the consumption of the compressed dry air stored in the air tank 30 decreases.

[0055] 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 during maintenance.

[0056] In the housing 11A of the air drying circuit 11 (see Figure 2A ) is provided with a filter 17 inside. The filter 17 is provided in the middle of the air supply passage 18 connecting the compressor 4 and the supply circuit 12. The filter 17 includes a desiccant. In addition to the desiccant, the filter 17 also includes an oil-capturing portion for capturing oil. The oil-capturing portion can be any one as long as it can capture oil while allowing air to pass through, such as a foam such as polyurethane foam, a metal material having a plurality of vents, a glass fiber filter, etc.

[0057] The filter 17 allows the compressed air sent from the compressor 4 to pass through a desiccant, thereby removing the moisture contained in the compressed air to dry the compressed air. In addition, the oil capture unit 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 the downstream one-way valve 19. When the filter 17 side is set to the upstream and the supply circuit 12 side is set to the downstream, the downstream one-way valve 19 only allows air to flow from the upstream to the downstream. In addition, the downstream one-way valve 19 has a specified valve opening pressure (closing pressure), so when the compressed air flows, the pressure upstream is higher than the pressure downstream by the valve opening pressure.

[0058] In addition, a bypass flow path 20 is provided downstream of the filter 17 in parallel with the downstream check valve 19 as a bypass path for bypassing the downstream check valve 19. The bypass flow path 20 is provided with a regeneration control valve 21.

[0059] The regeneration control valve 21 is a solenoid valve controlled by the ECU 80. The ECU 80 controls the power supply of the regeneration control valve 21 to be turned on / off (driven / non-driven) via the wiring E64, thereby switching the operation of the regeneration control valve 21. The regeneration control valve 21 is closed when the power supply is turned off to block the bypass flow path 20, and is opened when the power supply is turned on to connect the bypass flow path 20. The ECU 80 receives the value of the air pressure in the gas tank 30, for example, and operates the regeneration control valve 21 when the value of the air pressure exceeds a predetermined range.

[0060] An orifice 22 is provided between the regeneration control valve 21 and the filter 17 in the bypass flow path 20. When the regeneration control valve 21 is energized, the compressed dry air on the supply circuit 12 side is delivered to the filter 17 via the bypass flow path 20 in a state where the flow rate is limited by the orifice 22. The compressed dry air delivered to the filter 17 flows back in the filter 17 from downstream to upstream and passes through the filter 17. Such a process is an action to regenerate the filter 17, which is called a regeneration action of the air drying circuit 11. At this time, the compressed dry air delivered to the filter 17 is the dried and purified air supplied to the supply circuit 12 from the air supply passage 18 through the filter 17, etc., so that the moisture and oil captured by the filter 17 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 the upper limit value (cut-out pressure). On the other hand, when the pressure in the gas tank 30 reaches the lower limit value (cut-in pressure), the regeneration control valve 21 that has been opened is closed.

[0061] A branch passage 16 branches off from a portion between the compressor 4 and the filter 17. The branch passage 16 is provided with a waste liquid discharge valve 25, and a waste liquid discharge port 27 is connected to the terminal end of the branch passage 16.

[0062] The drain liquid, which is a fluid containing water and oil removed from the filter 17, is transported to the drain liquid discharge valve 25 together with the compressed air. The drain liquid discharge valve 25 is an air pressure driven valve driven by air pressure, and the drain liquid discharge valve 25 is arranged between the filter 17 and the drain liquid discharge port 27 in the branch passage 16. The drain liquid discharge valve 25 is a two-position two-way valve that changes its position between a closed valve position and an open valve position. When the drain liquid discharge valve 25 is in the open valve position, the drain liquid is transported to the drain liquid discharge port 27. The drain liquid discharged from the drain liquid discharge port 27 can also be recovered by an oil separator not shown. In addition, the drain liquid is equivalent to the fluid that has passed through the filter 17 in the reverse direction.

[0063] The drain valve 25 is controlled by the regulator 26A. The regulator 26A is a solenoid valve controlled by the ECU 80. The ECU 80 controls the power supply of the regulator 26A to be turned on / off (driven / non-driven) via the wiring E63, thereby switching the operation of the regulator 26A. When the power is turned on, the regulator 26A is switched to an input position in which an air pressure signal is input to the drain valve 25, thereby opening the drain valve 25. In addition, when the power is turned off, the regulator 26A is switched to an open position in which an air pressure signal is not input to the drain valve 25 and the port of the drain valve 25 is opened to the atmospheric pressure, thereby closing the drain valve 25.

[0064] The drain valve 25 is maintained in the closed position blocking the branch passage 16 when no air pressure signal is input from the regulator 26A, and is switched to the open position connecting the branch passage 16 when the air pressure signal is input from the regulator 26A. In addition, when the pressure of the input port of the drain valve 25 connected to the compressor 4 exceeds the upper limit value, the drain valve 25 is forcibly switched to the open position.

[0065] 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 set to the upstream and the filter 17 side is set to the downstream, the upstream check valve 15 only allows air to flow from the upstream to the downstream. The upstream check valve 15 has a specified valve opening pressure (closing pressure), so when the compressed air flows, the pressure upstream is higher than the pressure downstream by the valve opening pressure. In addition, 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.

[0066] 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 controls the power on / off (driving / non-driving) of the unloading control valve 26B via the wiring E62, thereby switching the action of the unloading control valve 26B. When the power is cut off, the unloading control valve 26B is switched to the open position to open the flow path between the unloading control valve 26B and the compressor 4 to the atmosphere. In addition, when the power is turned on, the unloading control valve 26B is switched to the supply position to send an air pressure signal composed of compressed air to the compressor 4.

[0067] 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 (idling). For example, when the pressure in the gas tank 30 reaches the cut-out pressure, it is not necessary to supply compressed dry air. When the pressure on the supply circuit 12 side reaches the cut-out 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 switches 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.

[0068] 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 to measure the air pressure of the air supply passage 18 and transmits the measured result to the ECU 80 via the wiring E61.

[0069] 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 can detect absolute humidity or relative humidity. The humidity sensor 51 and the temperature sensor 52 measure the humidity and the temperature of the compressed air downstream of the filter 17, respectively, and output the measured results to the ECU 80 via the wirings E65 and E66. The ECU 80 determines the humidification state of the compressed dry air based on the humidity and the temperature input from the humidity sensor 51 and the temperature sensor 52.

[0070] Furthermore, a pressure sensor 53 is provided between the downstream check valve 19 and the supply circuit 12. The pressure sensor 53 is provided in a manner capable of detecting the air pressure in the gas tank 30, and outputs the detected pressure value 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 of the gas tank 30, and the detection result of the pressure sensor 53 can be used as the pressure in the gas tank 30. In addition, the pressure sensor 53 can be provided in the supply circuit 12, and can also be provided in the gas tank 30.

[0071] <Description of Operation of Air Drying Circuit 11>

[0072] like Figure 2A to Figure 2F As shown, the air drying circuit 11 has a plurality of operation modes including at least a first operation mode to a sixth operation mode.

[0073] (First action mode)

[0074] like Figure 2A As shown, the first action mode is a mode for performing a normal dehumidification action (load operation). In the first action mode, the regeneration control valve 21 and the unloading control valve 26B are closed (recorded as "CLOSE" in the figure), and the regulator 26A is set to an open position (recorded as "CLOSE" in the figure) in which an air pressure signal is not input to the drain valve 25. At this time, no power is supplied to the regeneration control valve 21, the regulator 26A, and the unloading control valve 26B. In addition, the regulator 26A and the unloading control valve 26B open the ports of the compressor 4 connected to their downstream and the ports of the drain valve 25 to the atmosphere. In the first action mode, when compressed air is supplied from the compressor 4 (recorded as "ON" in the figure), the compressed air is supplied to the supply circuit 12 after the moisture and the like are removed by the filter 17.

[0075] (Second action mode)

[0076] like Figure 2B As shown in FIG. 1 , the second operation mode is a mode for performing a purge operation of passing the compressed dry air in the air drying circuit 11 through the filter 17 to purify the filter 17. In the second mode, the regeneration control valve 21 is closed, the unloading control valve 26B is set to the supply position (represented as "OPEN" in the figure), and the regulator 26A is set to the input position (represented as "OPEN" in the figure). At this time, power is supplied to the regulator 26A and the unloading control valve 26B, respectively, and the port of the compressor 4 connected to the downstream thereof and the port of the drain discharge valve 25 are connected to the upstream (supply circuit 12 side) respectively. As a result, the compressor 4 is switched to the non-operating state (represented 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 the opposite direction to the air flow in the first operation mode (dehumidification mode) (counterflow), and the moisture captured by the filter 17 is discharged from the drain discharge port 27 as drain. In addition, the air pressure of the filter 17 and the air supply passage 18 is released to the atmospheric pressure.

[0077] (Third Action Mode)

[0078] like Figure 2CAs shown in FIG. 1 , the third operation mode is a mode for performing a regeneration operation to regenerate the filter 17. In the third operation mode, the regeneration control valve 21 is opened, the regulator 26A is set to the input position, and the unloading control valve 26B is set to the supply position (respectively described as "OPEN" in the figure). At this time, in addition to supplying power to the regulator 26A and the unloading control valve 26B, power is also supplied to the regeneration 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 gas tank 30 is reversed through the filter 17 and discharged from the drain outlet 27. Thus, the moisture captured by the filter 17 is removed. The second operation mode and the third operation mode are both modes for purifying the filter 17, but the third operation mode is different from the second operation mode at least in that the regeneration control valve 21 is opened. Therefore, in the third operation mode, the compressed dry air in the gas tank 30 can pass through the filter 17 via the supply circuit 12 and the bypass flow path 20. Therefore, the effect of purifying the filter 17 is higher than that in the second operation mode. Furthermore, in the third operation mode, the air pressure of the filter 17 and the air supply passage 18 is also released to the atmospheric pressure.

[0079] (Fourth Action Mode)

[0080] like Figure 2D As shown in FIG. 1 , the fourth operation mode is a mode for performing an oil removal operation. In the fourth operation mode, the air with excessive oil content delivered from the compressor 4 is discharged from the drain outlet 27 without passing through the filter 17 while the compressor 4 is operated. When the compressor 4 is in a non-operating state, oil may accumulate in the compression chamber of the compressor 4. If the state of the compressor 4 is switched to the operating state while oil accumulates in the compression chamber, the amount of oil contained in the compressed air delivered from the compression chamber increases. If oil adheres to the desiccant, the dehumidification performance of the desiccant decreases. Therefore, an oil removal operation for discharging the compressed air with excessive oil content is performed. In the fourth operation mode, the regeneration control valve 21 is closed, the unloading control valve 26B is set to an open position (represented as "CLOSE" in the figure), and the regulator 26A is set to an open position (represented as "CLOSE" in the figure) after driving for a fixed period of time. As a result, even if compressed air containing a large amount of oil content is delivered from the compressor 4, the compressed air can be discharged from the drain outlet 27 without passing through the filter 17. Therefore, it is possible to suppress the dehumidification performance of the filter 17 from decreasing immediately after the compressor 4 switches from the non-operating state to the operating state. The deoiling operation can also be performed when the oil content from the compressor 4 increases when the engine speed increases or the engine load is high in the operating state.

[0081] (Fifth Action Mode)

[0082] like Figure 2EAs shown in the figure, the fifth operation mode is a mode for performing a compressor stop operation without purging. In the fifth operation mode, the regeneration control valve 21 is closed, the regulator 26A is set to the open position (represented as "CLOSE" in the figure), and the unloading control valve 26B is set to the supply position (represented as "OPEN" in the figure). In the fifth operation mode, when the compressor 4 is in a non-operating state, the compressed air or compressed dry air remaining in the air supply passage 18 or the desiccant of the filter 17 is not discharged from the drain outlet 27, thereby maintaining the air pressure.

[0083] (Sixth Action Mode)

[0084] like Figure 2F As shown in the figure, the sixth action mode is a mode for performing auxiliary action for pressurization treatment. In the sixth action mode, the regeneration control valve 21 is opened, the unloading control valve 26B is set to the supply position (recorded as "OPEN" in the figure), and the regulator 26A is set to the open position (recorded as "CLOSE" in the figure). In the sixth action mode, when the compressor 4 is in a non-operating state, the compressed air of the supply circuit 12 is supplied (backflow) to the desiccant of the air supply passage 18 and the filter 17, thereby making the pressure of the air supply passage 18 and the filter 17 higher than the atmospheric pressure, so that the back pressure (air pressure) of the upstream check valve 15 is maintained at a pressure higher than the atmospheric pressure.

[0085] <Setting the execution conditions of the action mode>

[0086] Next, refer to Figure 3 and Figure 4 , to explain the execution conditions of the purging action (second action mode), the regeneration action (third action mode) and the degreasing action (fourth action mode). The purging action and the degreasing action maintain the dehumidification performance of the filter 17 well. On the other hand, the purging action and the degreasing action consume the compressed dry air in the air drying circuit 11 or the compressed air sent from the compressor 4, thereby increasing the operating load of the compressor 4. The compressor 4 generates compressed air by the rotational force transmitted from the rotational drive source such as the engine. Therefore, the increase in the operating load of the compressor 4 increases the load of the rotational drive source, further leading to an increase in the energy consumption of the vehicle such as fuel.

[0087] On the other hand, the regeneration operation is performed for the purpose of maintaining the purification performance of the filter 17 well, like the purging operation and the degreasing operation, but it is different from the purging operation and the degreasing operation in that it consumes the compressed dry air in the air tank 30. As a result of consuming the compressed dry air, not only the operating load of the compressor 4 is increased, but also there is a tendency that the compressed dry air in the air tank 30 is insufficient. That is, when the regeneration operation is performed in a driving condition where a large amount of compressed dry air in the air tank 30 is consumed, such as a driving condition where the frequency of brake operation is high, in addition to the compressed dry air consumed by the air pressure system such as the brake system, the compressed dry air is also consumed by the regeneration operation, so the consumption of the compressed dry air in the air tank 30 increases.

[0088] Therefore, by setting the execution conditions of the regeneration operation, the purge operation, and the degreasing operation, the execution frequency of these operations is optimized, thereby optimizing the consumption of compressed air or compressed dry air.

[0089] First, the execution conditions of the purging action are described. Preferably, the purging action is performed when the amount of moisture captured and retained by the filter 17 increases. When the amount of moisture captured by the filter 17 increases so that the captured moisture amount is greater than the moisture capture capacity of the filter 17, the humidity state of the compressed dry air passing through the filter 17 will inevitably become a high humidity state. Therefore, whether the purging action needs to be performed is determined based on the comparison between the index representing the humidity state of the compressed dry air and its threshold value. In the present embodiment, the moisture amount contained in the compressed dry air supplied to the gas tank 30 within a fixed period (hereinafter referred to as the contained moisture amount) is used as an index representing the humidity state of the compressed dry air. The contained moisture amount of the compressed dry air can be estimated, for example, based on the air delivery amount (discharge amount) from the compressor 4, the humidity detected by the humidity sensor 51 during the regeneration action, and the like.

[0090] On the other hand, it is impossible to estimate whether the amount of moisture captured by the filter 17 is gradually increasing or rapidly increasing based on the wetness state of the compressed dry air after passing through the filter 17. The speed of increase in the amount of captured moisture captured by the filter 17 depends on the amount and wetness state of the compressed air sent from the compressor 4. The amount of compressed air increases with the increase in the operating rate of the compressor 4. In addition, when the temperature of the compressed air rises, the amount of saturated water vapor (saturated water vapor pressure) in the compressed air increases, and thus the amount of water vapor contained in the compressed air tends to increase. The temperature of the compressed air rises due to the compression of the air by the compressor 4, etc., and therefore becomes higher with the increase in the operating rate of the compressor 4. Therefore, in the present embodiment, the execution frequency of the purge action is appropriated by setting a threshold value of the amount of moisture used to start the purge action in accordance with the operating rate R of the compressor 4.

[0091] As Figure 3 shown, the ECU 80 stores the start threshold information 100 in the storage unit 80A. The start threshold information 100 includes the range 101 of the operating rate R of the compressor 4, the level 102 associated with each range 101 of the operating rate R, the cut-out pressure 103, the moisture content threshold 104, and the temperature threshold 105. The level 102 indicates the state mode of the air drying circuit 11 and is set according to the range of the operating rate R of the compressor 4. In addition, although the start threshold information 100 associates each range with a threshold, the start threshold information 100 only needs to be information capable of determining the start threshold according to the operating rate R of the compressor 4, and its form is not limited. For example, the start threshold information 100 may be a map, and the start threshold information 100 associates the axis corresponding to the operating rate R with the axis corresponding to the cut-out pressure, the axis corresponding to the moisture content threshold, and the axis corresponding to the temperature threshold, respectively, and sets the start threshold for each operation.

[0092] In the start threshold information 100, the higher the operating rate R of the compressor 4, the lower the moisture content threshold Mth of the moisture content containing the reference for starting the purge operation is set. Thus, when the operating rate R of the compressor 4 is high, the purge operation is likely to occur, and therefore the execution frequency of the purge operation can be increased under fixed conditions. However, when the operating rate R of the compressor is equal to or higher than a specified value, the purge operation is prohibited, and a value for prohibition is set for the moisture content threshold Mth. Specifically, when the operating rate R is "less than 10%", the moisture content threshold Mth1 is set as the threshold of the moisture content. When the operating rate R is "10% or more and less than 30%", the moisture content threshold Mth2 (<Mth1) is set. And when the operating rate R is "30% or more and less than 50%", the moisture content threshold Mth3 (<threshold Mth2) is set. That is, when the operating rate R is "less than 50%", in ascending order of the operating rate R, the moisture content threshold Mth1 (high) as a high value, the moisture content threshold Mth2 (medium) as a medium value, and the moisture content threshold Mth3 (low) as a low value are set. In addition, when the operating rate R is "50% or more", the purge operation is prohibited.

[0093] On the other hand, when the working rate R is equal to or higher than a specified value (e.g., 50%), it is estimated that the vehicle is in a driving condition where the consumption of compressed dry air is large. During the period ha of the operation mode transition, compressed dry air cannot be supplied from the air drying circuit 11 to the air tank 30. Therefore, in such a situation, when switching the operation mode of the air drying circuit 11 from the dehumidifying operation (the first operation mode) to the purging operation (the second operation mode), the storage amount of the compressed dry air in the air tank 30 may be insufficient. Therefore, when the working rate R is equal to or higher than the specified value, compressed dry air is preferentially supplied to the air pressure system without performing the purging operation.

[0094] Next, the execution conditions of the oil removal operation will be described. Immediately after the air drying circuit 11 is switched from the non-operating state to the operating state, sometimes the compressed air sent out from the compressor 4 contains a large amount of oil, and this oil may adhere to the filter 17 through the flow path (charge line) between the compressor 4 and the filter 17 in the air supply passage 18. If the state where the oil adheres to the filter 17 is maintained, the moisture capture amount of the desiccant decreases, and the desiccant deteriorates earlier. Therefore, preferably, the oil removal operation is performed immediately after the switch from the non-operating state to the operating state to reduce the load applied to the filter 17. Since the amount of oil contained in the compressed air is also large when the temperature of the compressed air is high, it is determined whether the oil removal operation needs to be performed based on the comparison between the temperature detected by the temperature sensor 52 and its threshold value. In addition, since the amount of oil increases as the working rate of the compressor 4 becomes higher, the execution frequency of the oil removal operation is made appropriate by setting the temperature threshold value of the compressed dry air corresponding to the working rate R of the compressor 4.

[0095] As Figure 3 shown, in the start threshold information 100, the higher the working rate R of the compressor 4, the lower the temperature threshold Tth is set. However, when the working rate R of the compressor is equal to or higher than a specified value, the oil removal operation is prohibited, and a value for prohibiting the setting of the temperature threshold Tth is set. Specifically, when the working rate R is "less than 10%", the temperature threshold Tth1 is set, and when the working rate R is "10% or more and less than 30%", the temperature threshold Tth2 (<Tth1) is set. And when the working rate R is "30% or more and less than 50%", the temperature threshold Tth3 (<threshold Tth2) is set. That is, when the working rate R is "less than 50%", in the order of the working rate R from low to high, the temperature threshold Tth1 (high) as a high value, the temperature threshold Tth2 (medium) as a medium value, and the temperature threshold Tth3 (low) as a low value are set. In addition, when the working rate R is "50% or more", the oil removal operation is prohibited.

[0096] The reason why the temperature threshold value Tth is lowered as the operating rate R increases is explained. First, when the operating rate R of the compressor 4 increases, the amount of air sent from the compressor 4 increases, so the amount of air passing through the filter 17 also increases, and it is estimated that the amount of oil captured by the filter 17 tends to increase accordingly. Second, the increase in the temperature of the compressed air is the main reason for the increase in the amount of oil contained in the compressed air. Therefore, according to the operating rate R, the temperature threshold value Tth for starting the deoiling action is changed to make the execution frequency of the deoiling action appropriate, thereby reducing the load on the filter 17. When the operating rate R of the compressor 4 is high, the execution frequency of the deoiling action is increased to reduce the amount of oil retained by the filter 17. On the other hand, when the execution frequency of the operation of the compressor 4 is low, the execution frequency of the deoiling action is reduced to reduce the amount of compressed air consumed by the deoiling action. In addition, the reason for prohibiting the deoiling action when the operating rate R is above the specified value is the same as that of the purging action.

[0097] Next, the starting threshold of the regeneration operation is described. The regeneration operation is performed on the premise that the pressure in the gas tank 30 is above the cut-out pressure Po, which is the threshold of the pressure in the gas tank 30. In addition, the regeneration operation is started when the pressure in the gas tank 30 is above the cut-out pressure Po and the moisture content in the gas tank 30 is above the threshold of the moisture content in the gas tank 30. Therefore, the cut-out pressure Po is changed according to the operating rate R of the compressor 4, thereby making the execution frequency of the regeneration operation appropriate.

[0098] like Figure 3 As shown in the start threshold information 100, the higher the operating rate R of the compressor 4 is, the higher the cut-out pressure Po is set. Specifically, when the operating rate R is "less than 50%", the cut-out pressure Po1 (low) is set as a relatively low value, and when the operating rate R is "more than 50%", the cut-out pressure Po2 (high) is set as a relatively high value (Po2>Po1). In addition, Figure 3 In the start threshold information 100 shown, the cut-out pressure is set to two stages, but it may be set to three or more stages.

[0099] The reason why the cut-out pressure Po is increased as the operating rate R increases is described below. For example, when the operating rate R is low, such as in the case of "less than 50%", it is estimated that the consumption of compressed dry air by the air pressure system such as the brake system is low. In such a situation, the cut-out pressure Po is set to a relatively low value to relatively increase the execution frequency of the regeneration action, thereby increasing the frequency of purification of the filter 17. On the other hand, when the operating rate R is high, such as in the case of "more than 50%", it is estimated that the consumption of compressed dry air by the air pressure system such as the brake system is high. In such a situation, the cut-out pressure is set to a relatively high value to relatively reduce the execution frequency of the regeneration action, thereby giving priority to supplying compressed dry air to the air pressure system.

[0100] (Control of air drying circuit 11)

[0101] Next, refer to Figures 4 to 7 , to illustrate the process of ECU 80 controlling the air drying circuit 11.

[0102] like Figure 4 As shown, the ECU 80 performs an air supply process (step S1) of supplying the compressed air output by the compressor 4 to the supply circuit 12. The air supply process is started, for example, under a predetermined condition such as the engine being driven. Alternatively, the air supply process may be started when the pressure of the air tank 30 reaches a predetermined pressure such as a cut-in pressure as a lower limit value. In the air supply process, the air drying circuit 11 is in the first operation mode.

[0103] When the air supply process starts, the ECU 80 determines whether to stop the air supply (step S2). Specifically, the ECU 80 obtains the pressure in the gas tank 30 detected by the pressure sensor 53 to determine whether the pressure reaches the cut-out pressure. When the ECU 80 determines that the pressure in the gas tank 30 has not reached the cut-out pressure (step S2: "No"), the process returns to the air supply process (step S1).

[0104] When the ECU 80 determines that the pressure in the gas tank 30 has reached the cut-out pressure (step S2: YES), it ends the air supply process, puts the compressor 4 into an inoperative state, and executes a purge process such as performing a regeneration operation (step S3).

[0105] When the purification process (step S3) is completed, ECU 80 performs an air non-supply process (step S4). In the air non-supply process, when the compressor 4 is in a non-operating state, the air pressure is adjusted in such a way that the back pressure of the upstream one-way valve 15 is maintained high. For example, in the air non-supply process, at least one of the second action mode, the fifth action mode, and the sixth action mode is executed once or multiple times to adjust the air pressure. When the adjustment of the air pressure is completed, ECU 80 determines whether to end the air supply based on the vehicle state (step S5). For example, the end of the air supply is determined based on the vehicle state such as the engine stopping of the vehicle.

[0106] If it is determined that the air supply is not completed (step S5: No), the ECU 80 returns the process to step S1 and executes the process following the air supply step (step S1). On the other hand, if it is determined that the air supply is completed (step S5: Yes), the air supply is stopped.

[0107] In addition, the ECU 80 defines the period from the end of the regeneration action to the start of the next regeneration action as one cycle. Moreover, at the start of one cycle, the level of the state mode of the air drying circuit 11 is determined based on the operating rate R of the compressor 4, and the various start thresholds such as the cut-out pressure, the moisture content threshold, and the temperature threshold are set according to the level.

[0108] Reference Figure 5 The setting of the start threshold is described below. ECU 80 determines whether to update the start threshold (step S100). For example, ECU 80 determines whether a new cycle has started. When ECU 80 determines that a new cycle has not started and there is no need to update the start threshold (step S100: "No"), it ends the process. In addition, the update of the start threshold may also be performed at other timings. For example, the update of the start threshold may be performed in each period shorter than the average time of one cycle described above, at the end of one cycle, or at a timing between the start and end of one cycle.

[0109] When it is determined that the update start threshold is reached (step S100: "Yes"), ECU 80 obtains the compressor operating state (operating information) (step S101). In the present embodiment, the compressor operating state is the operating time (load time) and non-operating time (unloading time) of the compressor 4 in one cycle. ECU 80 defines the dehumidification action (first action mode) as load operation, and defines the purging action (second action mode), regeneration action (third action mode), degreasing action (fourth action mode), compressor stop action without purging (fifth action mode) and compressor auxiliary action (sixth action mode) as unloading operation. Moreover, the time for performing the load operation is stored as the load time T1, and the time for performing the unloading operation is stored as the unloading time T2 in the storage unit 80A of ECU 80, and they are updated at a specified timing.

[0110] Next, ECU 80 calculates the operating rate of compressor 4 based on the operating state of compressor 4 (step S102). The operating rate is calculated as the ratio of load time T1 to the sum of load time T1 and unload time T2 as shown in the following equation (1).

[0111] Working rate R = (load time T1) / (load time T1 + unloading time T2) ... (1)

[0112] Next, the ECU 80 determines the level of the air drying circuit 11 based on the operating rate of the compressor 4 using the start threshold information 100 (step S103). For example, when the operating rate of the compressor 4 is "less than 10%", "1" is set as the level.

[0113] When setting the level, the ECU 80 uses the start threshold information 100 to set the start threshold for the cut-out pressure, moisture threshold, and temperature threshold corresponding to the level (step S104). When the level is "1", the "cut-out pressure Po1" is set as the cut-out pressure, the "moisture threshold Mth1" is set as the moisture threshold, and the "temperature threshold Tth1" is set as the temperature threshold. These start thresholds are maintained until the next cycle and are updated when the next cycle starts.

[0114] (Purification process)

[0115] Reference Figure 6 The details of the purification process (step S3) are described below. As described above, the purification process starts when the pressure of the gas tank 30 is equal to or higher than the cut-out pressure. In addition, the cut-out pressure is updated based on the operating rate of the compressor 4. That is, even if the operating rate of the compressor 4 is high, when the pressure in the gas tank 30 reaches the cut-out pressure set relatively high, the purification process is performed provided that sufficient compressed dry air is stored in the gas tank 30.

[0116] ECU 80 determines whether it is necessary to perform the regeneration operation of filter 17 (step S30). The conditions for determining whether it is necessary are not particularly limited, but it may be, for example, that ECU 80 estimates the moisture content of the compressed dry air on the supply circuit 12 side using at least one of the humidity and temperature on the supply circuit 12 side, and determines that regeneration is necessary when the moisture content tends to increase. It may also be, for example, that ECU 80 estimates the moisture content of the compressed dry air in the gas tank 30 (hereinafter, the moisture content in the tank) using the humidity detected by the humidity sensor 51, and determines that regeneration is necessary when the moisture content is above a threshold. In addition, the moisture content in the tank is updated at each prescribed period such as each cycle. As an example, the moisture content Mtk in the tank can be calculated using the temperature Tmp detected by the temperature sensor 52, the saturated water vapor pressure at the temperature Tmp, the humidity Hmd detected by the humidity sensor 51, and the capacity of the gas tank 30.

[0117] For example, when the amount of water in the tank Mtk is greater than the threshold value and the ECU 80 determines that the regeneration action is necessary (step S30: Yes), the air drying circuit 11 is switched to the third action mode to perform the regeneration action (step S31). The regeneration action ends when the pressure of the gas tank 30 reaches the cut-in pressure or when the end condition is satisfied, such as a fixed time. When the regeneration action ends, the purification process (step S3) ends, and the process proceeds to the next step.

[0118] On the other hand, when the ECU 80 determines in step S30 that the filter 17 does not need to be regenerated (step S30: No), it determines whether the moisture content of the compressed dry air is greater than the moisture content threshold value Mth (step S32). In addition, the moisture content threshold value Mth used at this time is updated based on the operating state of the compressor 4.

[0119] When the ECU 80 determines that the amount of water contained is greater than the water content threshold value Mth (step S32: "Yes"), the air drying circuit 11 is switched to the second operation mode to perform a purging operation (step S33). When the operating rate of the compressor 4 is low, the water content threshold value Mth is set relatively high, so the execution frequency of the purging operation becomes low according to the condition that the pressure in the gas tank 30 reaches the cut-out pressure. In addition, when the operating rate of the compressor 4 is high, the water content threshold value Mth is set low, so the execution frequency of the purging operation becomes high according to the condition that the pressure in the gas tank 30 reaches the cut-out pressure. In addition, when the operating rate R of the compressor 4 is greater than the specified value, the water content threshold value Mth set to be prohibited is used, so the purging operation is not performed.

[0120] On the other hand, when the ECU 80 determines that the moisture content is less than the moisture content threshold value Mth (step S32: No), it switches the air drying circuit 11 to the fifth operation mode to stop the compressor (step S34).

[0121] (Control of degreasing action)

[0122] Next, refer to Figure 7 , the control of the ECU 80 to cause the air drying circuit 11 to execute the degreasing operation will be described. The degreasing operation is executed as a process different from the purge process (step S3).

[0123] It is assumed that the ECU 80 stores the time elapsed from the time point when the last degreasing operation was completed in the storage unit 80A, etc. In addition, the ECU 80 stores the number of times the degreasing operation is performed in the storage unit 80A, etc., and updates the number in one cycle or in a fixed period other than this. The number of executions may be reset at a predetermined timing when the fixed period ends, the ignition switch of the vehicle is turned off, maintenance is performed, etc.

[0124] The ECU 80 obtains the elapsed time from the time point when the last degreasing operation was completed from the storage unit 80A, etc., and compares the elapsed time with a preset fixed time to determine whether the fixed time has elapsed from the last degreasing operation (step S110). If it is determined that the fixed time has not elapsed from the last degreasing operation (step S110: No), the process ends.

[0125] When the ECU 80 determines that a fixed time has passed since the last degreasing operation (step S110: Yes), it determines whether the number of executions of the degreasing operation is less than the predetermined executable number (step S111). When the ECU 80 determines that the number of executions of the degreasing operation exceeds the executable number (step S111: No), it ends the process. On the other hand, when the ECU 80 determines that the number of executions of the degreasing operation is less than the executable number (step S111: Yes), it acquires the temperature detected by the temperature sensor 52 (step S112).

[0126] ECU 80 determines whether the acquired temperature is above the temperature threshold value Tth (step S113). The temperature threshold value Tth used here is set according to the operating rate of the compressor 4. When ECU 80 determines that the acquired temperature is above the temperature threshold value Tth (step S113: "Yes"), it switches the air drying circuit 11 to the fourth operation mode to perform the degreasing action (step S114). When the operating rate of the compressor 4 is low, the temperature threshold value Tth is set high, so the execution frequency of the degreasing action becomes low. In addition, when the operating rate of the compressor 4 is high, the temperature threshold value Tth is set low, so the execution frequency of the degreasing action becomes high. In addition, when the operating rate R of the compressor 4 is above the specified value, the temperature threshold value Tth set to be prohibited is used, so the degreasing action is not performed.

[0127] On the other hand, when the ECU 80 determines that the acquired temperature is lower than the temperature threshold value Tth (step S113 : No), the processing ends.

[0128] As described above, according to the above embodiment, the following effects are obtained.

[0129] (1) The ECU 80 of the air drying circuit 11 acquires operating information indicating the operating state of the compressor 4, and changes the execution frequency of the purging action, the degreasing action, and the regeneration action based on the acquired operating information of the compressor 4. That is, when it is determined based on the operating state of the compressor that it is necessary to give priority to supplying compressed dry air to the air pressure system mounted on the vehicle, the execution frequency of these actions can be reduced. In addition, when it is determined that the filter 17 needs to be purified while the amount of compressed dry air supplied to the air pressure system is ensured, the ECU 80 can increase the execution frequency of these actions to purify the filter 17.

[0130] (2) When the pressure in the gas tank 30 reaches the cut-out pressure, that is, when the gas tank 30 is sufficiently filled with compressed dry air, and when the operating rate of the compressor 4 is high, the frequency of executing the purge operation is increased. On the other hand, when the operating rate of the compressor 4 is low, the frequency of executing the purge operation is reduced. That is, when the amount of air passing through the filter 17 increases within a fixed period due to the high operating rate of the compressor 4, and the temperature of the compressed air delivered from the compressor 4 increases, the frequency of purifying the filter 17 can be increased. On the other hand, when the amount of air passing through the filter 17 decreases due to the low operating rate of the compressor 4, and the temperature of the compressed air delivered from the compressor 4 decreases, the consumption of compressed dry air can be suppressed.

[0131] (3) Whether or not the purging action needs to be performed is determined based on whether the moisture content of the compressed dry air is above the moisture content threshold value Mth. In addition, when it is determined that the operating rate of the compressor 4 is low, the moisture content threshold value Mth is set high, and when it is determined that the operating rate of the compressor 4 is high, the moisture content threshold value Mth is set low. Therefore, it is possible to perform the purging action by considering not only the wetness state of the compressed dry air after passing through the filter 17, but also the wetness state of the compressed air before passing through the filter 17. That is, even when compressed air in a high humidity state is delivered from the compressor 4, and the compressed dry air passing through the filter 17 is in a significantly low humidity state because the filter 17 captures a large amount of moisture, the purging action is likely to occur. Therefore, the execution frequency of the purging action can be appropriated.

[0132] (4) In the start threshold information 100, a prohibition value is set for the threshold for the purge operation and the threshold for the degreasing operation corresponding to the case where the operating rate of the compressor 4 is higher than a predetermined value. Therefore, the operation mode is not switched when the consumption of the compressed dry air by the air pressure system is large, so that the compressed dry air can be stably supplied from the air drying circuit 11 to the air tank 30 continuously.

[0133] (5) When the operating rate of the compressor 4 is high, the cut-out pressure is set high. In this way, by setting the cut-out pressure high, a sufficient amount of compressed dry air is stored in the air tank 30, so that the filter cleaning operation including the purging operation and the regeneration operation can be performed. Therefore, the compressed dry air can be preferentially supplied to the air pressure system mounted on the vehicle.

[0134] (6) Whether the degreasing operation needs to be performed is determined based on whether the temperature of the compressed dry air is equal to or higher than the temperature threshold value Tth. In addition, when it is determined that the operating rate of the compressor 4 is low, the temperature threshold value Tth is set high, and when it is determined that the operating rate of the compressor 4 is high, the temperature threshold value Tth is set low. Therefore, when the temperature of the compressed dry air becomes low due to the low operating rate of the compressor 4, the execution frequency of the degreasing operation can be reduced, and when the temperature of the compressed dry air becomes high due to the high operating rate of the compressor 4, the execution frequency of the degreasing operation can be increased.

[0135] (7) The operating rate based on the load time and the unload time is used as the operating information of the compressor 4. The load time and the unload time affect the temperature of the compressed air generated by the compressor 4. Therefore, the operating state of the compressor 4 is determined based on these, thereby accurately determining the timing of the purging action, the degreasing action, and the regeneration action.

[0136] The above-mentioned embodiment can be modified and implemented as follows. The present embodiment and the following modified examples can be combined and implemented within the scope of no technical contradiction.

[0137] In the above embodiment, the condition for starting the purge operation is that the moisture content of the compressed dry air supplied to the gas tank 30 is equal to or greater than the moisture content threshold value, on the premise that the pressure in the gas tank 30 is equal to or greater than the cut-out pressure. However, the moisture content may be replaced by any index indicating the moisture state of the compressed dry air or the gas tank 30. The index may be, for example, the moisture content per unit volume of the compressed dry air, the humidity detected by the humidity sensor 51 during the dehumidification operation, or the moisture content in the gas tank 30. In addition, it may be determined whether the purge operation needs to be performed based only on the moisture state of the compressed dry air or the gas tank 30, regardless of whether the pressure in the gas tank 30 is equal to or greater than the cut-out pressure.

[0138] In the above embodiment, the condition for starting the regeneration operation is that the moisture content in the gas tank 30 is greater than the threshold value, provided that the pressure in the gas tank 30 is greater than the cut-out pressure. However, an arbitrary index indicating the wet state of the compressed dry air or the gas tank 30 may be used instead of the moisture content in the gas tank 30. Examples of the index may be the moisture content per unit volume of the compressed dry air, the humidity detected by the humidity sensor 51 during the dehumidification operation, or the moisture content of the compressed dry air supplied to the gas tank 30.

[0139] In the above embodiment, the conditions for starting the degreasing operation are set as the elapsed time from the last degreasing operation being a fixed time or longer, the number of executions being less than the executable number, and the temperature of the compressed dry air being less than the temperature threshold, but it may be one or both of them. In addition, the pressure in the gas tank 30 being greater than the cut-out pressure may be added to the conditions for starting the degreasing operation. In this case, the degreasing operation is not performed unless a sufficient amount of compressed dry air is stored in the gas tank 30, so that the compressed dry air can be supplied to the air pressure system with priority by suppressing the consumption of the compressed air sent from the compressor 4.

[0140] In the above embodiment, when the operating rate of the compressor 4 is low (e.g., less than 10%), the temperature threshold is set high to reduce the execution frequency of the degreasing action, and when the operating rate of the compressor 4 is high (e.g., 30% or more and less than 50%), the temperature threshold is set low to increase the execution frequency of the degreasing action. In addition, for actions other than the degreasing action and the following purging action, the execution frequency of the action may be increased when the operating rate of the compressor 4 is low, and the execution frequency of the action may be reduced when the operating rate is high. For the purging action, when the operating rate of the compressor 4 is low (e.g., less than 10%), the moisture content threshold is set high to reduce the execution frequency of the purging action, and when the operating rate of the compressor 4 is high (e.g., 30% or more and less than 50%), the moisture content threshold is set low to increase the execution frequency of the purging action. For example, even in the case of the regeneration operation, if the prescribed conditions such as reducing the consumption of the compressed dry air in the air tank 30 are satisfied, the execution frequency of the regeneration operation may be reduced when the operating rate of the compressor 4 is low, and the execution frequency of the regeneration operation may be increased when the operating rate is high. Alternatively, even in the case of an operation other than the purging operation, the degreasing operation, and the regeneration operation, as long as it is an operation other than the dehumidification operation and the air is discharged from the drain outlet 27, the execution frequency of the operation may be reduced when the operating rate of the compressor 4 is low, and the execution frequency of the operation may be increased when the operating rate is high.

[0141] In the above-mentioned embodiment, when the operating rate of the compressor 4 is above a prescribed value, a prohibition value is set as a threshold value, thereby prohibiting the purging action and the degreasing action. In addition to this method, a threshold value may be set for all operating rates (0% to 100%) of the compressor 4. Even in this case, the higher the operating rate of the compressor 4, the lower the threshold value. Alternatively, for example, when the operating rate of the compressor 4 is less than a prescribed value such as 50%, the higher the operating rate of the compressor 4, the lower the threshold value, and when the operating rate of the compressor 4 is above a prescribed value, the higher the operating rate of the compressor 4, the higher the threshold value.

[0142] In the above embodiment, when the operating rate of the compressor 4 is above the prescribed value, a prohibition value is set as a threshold value, thereby prohibiting the purging action and the degreasing action. In addition to this mode, when the operating rate of the compressor 4 is above the prescribed value, only the purging action may be prohibited, or only the degreasing action may be prohibited. In addition, when the operating rate of the compressor 4 is above the prescribed value, both the purging action and the regeneration action, both the degreasing action and the regeneration action, or all of the purging action, the degreasing action, and the regeneration action may be prohibited.

[0143] In the above-mentioned embodiment, the conditions for the regeneration action, the conditions for the purge action, and the conditions for the degreasing action are set, and each action is performed according to these conditions, but each action may be performed according to one or two of these conditions. If at least one of the three action modes is performed according to the conditions of the above-mentioned embodiment, it is possible to suppress the consumption of air other than the dehumidification action and maintain the dehumidification performance of the air drying circuit 11. For example, it is also possible to perform the purge action under other conditions. Alternatively, it is also possible to omit the purge action from the action mode of the air drying circuit 11. Alternatively, it is also possible to perform the degreasing action under other conditions. Alternatively, it is also possible to omit the degreasing action from the action mode of the air drying circuit 11. Alternatively, it is also possible to perform the regeneration action under other conditions. Alternatively, it is also possible to omit the regeneration action from the action mode of the air drying circuit 11.

[0144] In the above embodiment, the filter 17 includes the oil-capturing portion, but the oil-capturing portion may be omitted from the filter 17 .

[0145] The air drying circuit is not limited to the above-mentioned structure. In short, the air drying circuit may be configured as long as it can perform the dehumidification operation and the regeneration operation. Therefore, the air drying circuit does not necessarily require the second operation mode and the fourth to sixth operation modes.

[0146] In the above embodiment, the air supply system 10 is described as a system installed in a vehicle such as a truck, a bus, or a construction machine. In other embodiments, the air supply system 10 may be installed in another mobile body such as a car or a railway vehicle.

[0147] ECU 80 is not limited to software processing of all the processes executed by itself. For example, ECU 80 may also have a dedicated hardware circuit (such as an application-specific integrated circuit: ASIC), which performs hardware processing on at least a part of the processes executed by ECU 80 itself. That is, ECU 80 can be constructed to include the following circuits: 1) one or more processors that act 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 a memory such as RAM and ROM, and the memory stores program codes or instructions that are configured to enable the CPU to execute processes. The memory, i.e., a computer-readable medium, includes all available media that can be accessed by a general-purpose or special-purpose computer.

[0148] Description of Reference Numerals

[0149] 4: compressor; 10: air supply system; 11: air drying circuit; 12: supply circuit; 15: upstream non-return valve; 16: branch passage; 17: filter; 18: air supply passage; 19: downstream non-return valve; 20: bypass flow path; 21: regeneration control valve; 22: throttle hole; 25: drain valve; 26A: regulator; 26B: unloading control valve; 27: drain outlet as a discharge port; 30: gas tank as a storage part; 50: pressure sensor; 51: humidity sensor; 52: temperature sensor; 53: pressure sensor; 80: ECU; 80A: storage part; E61~E67: wiring.

Claims

1. An air supply system comprising: an air drying circuit provided between a compressor for delivering compressed air and a storage unit for storing the compressed dry air, the air drying circuit having a filter for capturing moisture; and a control device, which controls the air drying circuit, in, The control device is composed of: controlling the air drying circuit to perform a dehumidification operation, wherein the compressed air sent from the compressor passes through the filter in a forward direction to supply the compressed air to the storage portion, controlling the air drying circuit to perform a filter cleaning action, wherein the compressed dry air is passed through the filter in a reverse direction to discharge the fluid that has passed through the filter from a discharge port, acquiring operating information indicating the operating status of the compressor, The frequency of executing the filter cleaning operation is changed based on the acquired operating information of the compressor.

2. The air supply system according to claim 1, characterized in that: The control device is configured to, when it is determined based on the working information that the working state of the compressor is a second working state, make the execution frequency of the filter purification action higher than the execution frequency of the filter purification action in the first working state, wherein the amount of air delivered from the compressor within a fixed period in the second working state is greater than the amount of air delivered from the compressor within the fixed period in the first working state.

3. The air supply system according to claim 2, characterized in that: The control device is configured to not perform the filter purification action when it is determined that the operating state of the compressor is a third operating state, wherein the amount of air delivered from the compressor within a fixed period in the third operating state is greater than the amount of air delivered from the compressor within the fixed period in the second operating state.

4. The air supply system according to claim 2 or 3, characterized in that: The air drying circuit comprises: a connecting passage connecting the compressor with the filter; a supply passage through which the compressed dry air that has passed through the filter passes; and a discharge valve connected to a branch path branched from the connection path, the discharge valve performing a discharge operation of discharging the fluid having passed through the filter by connecting the branch path to a discharge port, The control device controls the air drying circuit to perform a purge action as the filter cleaning action, wherein the purge action is an action of opening the discharge valve to allow the compressed dry air in the air drying circuit to pass through the filter in the reverse direction. The control device is configured to change the frequency of the purge operation based on the operation information of the compressor.

5. The air supply system according to claim 4, characterized in that The control device is composed of: acquiring the moisture content of the compressed dry air supplied to the storage unit, When the water content is equal to or greater than a threshold value, it is determined that the purge operation is to be performed. When the operating state of the compressor is the second operating state, the threshold value is set lower than when the operating state of the compressor is not the second operating state.

6. The air supply system according to claim 1, characterized in that: The control device is configured to, when it is determined based on the working information that the working state of the compressor is a second working state, make the execution frequency of the filter purification action lower than the execution frequency of the filter purification action in the first working state, wherein the amount of air delivered from the compressor in the second working state is greater than the amount of air delivered from the compressor in the first working state.

7. The air supply system according to claim 6, characterized in that The air drying circuit comprises: a connecting passage connecting the compressor with the filter; a supply passage through which the compressed dry air that has passed through the filter passes; and a discharge valve connected to a branch path branched from the connection path, the discharge valve performing a discharge operation of discharging the fluid having passed through the filter by connecting the branch path to a discharge port, The control device controls the air drying circuit to perform a regeneration action as the filter cleaning action, the regeneration action being an action of opening the discharge valve to allow the compressed dry air in the storage unit to pass through the filter in the reverse direction, The control device is configured to change the frequency of the regeneration operation based on the operation information of the compressor.

8. An air supply system comprising: an air drying circuit provided between a compressor for delivering compressed air and a storage unit for storing the compressed dry air, the air drying circuit having a filter for capturing moisture; and a control device, which controls the air drying circuit, in, The control device is composed of: controlling the air drying circuit to perform a dehumidification operation, wherein the compressed air sent from the compressor passes through the filter in a forward direction to supply the compressed air to the storage portion, controlling the air drying circuit to perform an oil discharge operation, wherein the compressed air delivered from the compressor is discharged from a discharge port without passing through the filter, acquiring operating information indicating the operating status of the compressor, The frequency of executing the oil discharge operation is changed based on the acquired operation information of the compressor.

9. The air supply system according to claim 8, characterized in that The control device is configured to, when it is determined based on the working information that the working state of the compressor is a second working state, make the execution frequency of the oil discharge action higher than the execution frequency of the oil discharge action in the first working state, wherein the amount of air delivered from the compressor within a fixed period in the second working state is greater than the amount of air delivered from the compressor within the fixed period in the first working state.

10. The air supply system according to claim 9, characterized in that The control device is configured to not perform the oil discharge action when it is determined that the operating state of the compressor is a third operating state, wherein the amount of air delivered from the compressor within a fixed period in the third operating state is greater than the amount of air delivered from the compressor within the fixed period in the second operating state.

11. The air supply system according to any one of claims 1 to 10, characterized in that: The control device is composed of: Acquire the working time and non-working time of the compressor as the working state of the compressor, The operating rate of the compressor is calculated based on the acquired operating time and the non-operating time.

12. A control method for an air supply system, the air supply system comprising: an air drying circuit provided between a compressor for delivering compressed air and a storage unit for storing compressed dry air, the air drying circuit having a filter for capturing moisture; and a control device for controlling the air drying circuit, In the control method of the air supply system, The control device performs the following steps: controlling the air drying circuit to perform a dehumidification operation, wherein the compressed air sent from the compressor passes through the filter in a forward direction to supply the compressed air to the storage portion; controlling the air drying circuit to perform a filter cleaning action, wherein the compressed dry air is passed through the filter in a reverse direction to discharge the fluid that has passed through the filter from a discharge port; Acquiring operating information indicating an operating status of the compressor; as well as The frequency of executing the filter cleaning operation is changed based on the acquired operating information of the compressor.

13. A control method for an air supply system, the air supply system comprising: an air drying circuit provided between a compressor for delivering compressed air and a storage unit for storing compressed dry air, the air drying circuit having a filter for capturing moisture; and a control device for controlling the air drying circuit, In the control method of the air supply system, The control device performs the following steps: controlling the air drying circuit to perform a dehumidification operation, wherein the compressed air sent from the compressor passes through the filter in a forward direction to supply the compressed air to the storage portion; controlling the air drying circuit to perform an oil discharge action, wherein the compressed air delivered from the compressor is discharged from a discharge port without passing through the filter; Acquiring operating information indicating an operating status of the compressor; as well as The frequency of executing the oil discharge operation is changed based on the acquired operation information of the compressor.

14. A control program for an air supply system, the air supply system comprising: an air drying circuit provided between a compressor for delivering compressed air and a storage unit for storing compressed dry air, the air drying circuit having a filter for capturing moisture; and a control device for controlling the air drying circuit, The control program causes the control device to function as the following units: a dehumidification operation execution unit that controls the air drying circuit to execute a dehumidification operation, wherein the dehumidification operation causes the compressed air sent from the compressor to pass through the filter in a forward direction to supply the compressed air to the storage unit; a filter cleaning action execution unit that controls the air drying circuit to execute a filter cleaning action, wherein the filter cleaning action is an action of passing the compressed dry air through the filter in a reverse direction to discharge the fluid that has passed through the filter from a discharge port; an acquisition unit configured to acquire operation information indicating an operation state of the compressor; as well as A changing unit changes the frequency of executing the filter cleaning operation based on the acquired operating information of the compressor.

15. A control program for an air supply system, the air supply system comprising: an air drying circuit provided between a compressor for delivering compressed air and a storage unit for storing compressed dry air, the air drying circuit having a filter for capturing moisture; and a control device for controlling the air drying circuit, The control program causes the control device to function as the following units: a dehumidification operation execution unit that controls the air drying circuit to execute a dehumidification operation, wherein the dehumidification operation causes the compressed air sent from the compressor to pass through the filter in a forward direction to supply the compressed air to the storage unit; a discharge action execution unit that controls the air drying circuit to execute an oil discharge action, wherein the compressed air sent from the compressor is discharged from a discharge port without passing through the filter; an acquisition unit configured to acquire operation information indicating an operation state of the compressor; as well as A changing unit changes the execution frequency of the oil discharge operation based on the acquired operation information of the compressor.

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