Air supply system and control method for an air supply system

Abstract

Provided is an air supply system. The air supply system includes: a compressor having a load operation mode and an idle operation mode; a desiccant configured to remove moisture from compressed air delivered by the compressor; a first electromagnetic valve configured to selectively switch the compressor between the load operation mode and the idle operation mode; a drain discharge valve connected to a branch passage branched from a connection passage, the drain discharge valve being configured to open the branch passage in response to a second electromagnetic valve being driven and being configured to close the branch passage in response to the second electromagnetic valve not being driven; and a control device configured to control the first electromagnetic valve and the second electromagnetic valve.

Description

[0001] This application is a divisional application of the application filed on June 6, 2019, with application number 201980052434.7 and entitled "Air Supply System". Technical Field

[0002] This disclosure relates to an air supply system for supplying compressed air to a device. Background Technology

[0003] In vehicles such as trucks, buses, and construction machinery, compressed air supplied from a compressor is used to control air pressure systems such as brakes and suspensions. This compressed air contains liquid impurities such as moisture from the atmosphere and oil used to lubricate the compressor. When compressed air containing a lot of moisture and oil enters the air pressure system, it can cause rust, swelling of rubber components, and other malfunctions. Therefore, a compressed air drying device is installed downstream of the compressor to remove moisture, oil, and other impurities from the compressed air.

[0004] The compressed air drying device performs loading operation (dehumidification operation) for removing oily moisture and unloading operation (regeneration operation) for removing oily moisture adsorbed on the desiccant and discharging the oily moisture as drainage. Furthermore, to prevent drainage from being sprayed onto the road surface, the drainage discharged from the air dryer is sent to an oil separator. In the oil separator, air containing oily moisture is separated into oil and clean air by colliding with a collision material (see, for example, Patent Document 1).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-234632 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] Since the purification and regeneration processes consume a certain amount of compressed air, even the purification and regeneration processes necessary to discharge clean air increase the operating load on the compressor. Therefore, the increased operating load on the compressor, which generates compressed air by transmitting rotational force from a rotary drive source such as an engine, increases the load on the rotary drive source, thereby increasing the consumption of energy such as fuel.

[0010] The purpose of this disclosure is to provide an air supply system that can reduce the load on the compressor.

[0011] To continuously supply clean air to an air dryer whose cleaning function is reduced in accordance with the amount of compressed air supplied, a regeneration or purification process is required to restore the air dryer's cleaning function by reversing the flow of compressed air. For example, a purification process is performed each time unloading occurs, and a regeneration process is performed based on the number of unloading cycles and the elapsed time. Such purification and regeneration processes consume compressed air, thus increasing the engine load to some extent. However, in recent years, due to the requirement to improve vehicle combustion efficiency, purification and regeneration processes are no longer performed mechanically, but rather with appropriate execution conditions. This allows for improvements that can suppress compressed air consumption and maintain the air dryer's function.

[0012] The purpose of this disclosure is to provide an air supply system capable of suppressing the consumption of compressed air.

[0013] Solution for solving the problem

[0014] According to one aspect of this disclosure, an air supply system comprises: a compressor having a load operation mode in which the compressor delivers compressed air and an idle operation mode in which the compressor does not deliver compressed air; a desiccant configured to remove moisture from the compressed air delivered by the compressor; a connection passage connecting the compressor to the desiccant, the connection passage being for allowing the flow of compressed air; a first solenoid valve configured to selectively switch the compressor between the load operation mode and the idle operation mode, configured to switch to the idle operation mode in response to the first solenoid valve being actuated, and configured to switch to the load operation mode in response to the first solenoid valve not being actuated; a drain valve connected to a branch passage branching from the connection passage, the drain valve configured to open the branch passage in response to the second solenoid valve being actuated, and configured to close the branch passage in response to the second solenoid valve not being actuated; and a control device configured to switch between actuating and deactuating the first solenoid valve, and switching between actuating and deactuating the second solenoid valve. Attached Figure Description

[0015] Figure 1 This is a structural diagram showing the outline structure of a first embodiment of the air supply system.

[0016] Figure 2(a) is a diagram showing the first operating mode of the air dryer in the first embodiment; (b) is a diagram showing the second operating mode of the air dryer in the first embodiment; (c) is a diagram showing the third operating mode of the air dryer in the first embodiment; (d) is a diagram showing the fourth operating mode of the air dryer in the first embodiment; (e) is a diagram showing the fifth operating mode of the air dryer in the first embodiment; and (f) is a diagram showing the sixth operating mode of the air dryer in the first embodiment.

[0017] Figure 3 This is a flowchart illustrating an example of the process of supplying compressed air in the first embodiment.

[0018] Figure 4 This is a flowchart illustrating an example of the air dryer and regeneration process in the first embodiment.

[0019] Figure 5 This is a flowchart illustrating an example of the process of running the compressor idle in the first embodiment.

[0020] Figure 6 This is a flowchart illustrating an example of the process of adjusting the pressure of the connection path in the first embodiment.

[0021] Figure 7 This is a flowchart illustrating an example of the process of adjusting the pressure of the connection passage in a second embodiment of the air supply system.

[0022] Figure 8 This is a flowchart illustrating an example of the process of adjusting the pressure of the connection passage in a third embodiment of the air supply system.

[0023] Figure 9 This is a flowchart illustrating an example of the process of adjusting the pressure of the connection passage in a fourth embodiment of the air supply system.

[0024] Figure 10 This is a flowchart illustrating an example of the pressure adjustment process for the connection passage in the fifth embodiment of the air supply system.

[0025] Figure 11 This is a flowchart illustrating an example of the degreasing process in the fifth embodiment.

[0026] Figure 12 This is a flowchart illustrating an example of a humidity-based regeneration process in a sixth embodiment of an air supply system.

[0027] Figure 13This is a flowchart illustrating an example of the process of supplying compressed air in the seventh embodiment.

[0028] Figure 14 This is a flowchart illustrating an example of the air drying and regeneration process in the seventh embodiment.

[0029] Figure 15 This is a flowchart illustrating an example of the process of running the compressor idle in the seventh embodiment.

[0030] Figure 16 This is a flowchart illustrating an example of the process for adjusting the pressure of the connection path in the seventh embodiment. Detailed Implementation

[0031] (First Implementation)

[0032] Reference Figures 1-6 This describes a first implementation of an air supply system. The air supply system is installed in vehicles such as trucks, buses, and construction machinery.

[0033] <Structure of Air Supply System 10>

[0034] Reference Figure 1 The structure of the air supply system 10 is described below. The air supply system 10 includes a compressor 4, an air drying circuit 11, and an ECU 80 as a control device. The control device or its constituent elements can be configured to include 1) one or more processors that operate according to a computer program (software), 2) one or more dedicated hardware circuits such as an application-specific integrated circuit (ASIC) that performs at least a portion of various processes, or 3) a circuit combining these. The processor includes a CPU and memories such as RAM and ROM, which store program code or instructions configured to cause the CPU to perform processes. Memory, i.e., computer-readable media, includes all media accessible to general-purpose or special-purpose computers.

[0035] The air supply system 10 connects multiple wirings E61 to E66 to the ECU 80. The ECU 80 has an arithmetic unit, a volatile memory unit, and a non-volatile memory unit, and provides instruction values ​​to the air drying circuit 11 according to the program stored in the non-volatile memory unit.

[0036] Based on the command values ​​from ECU 80, compressor 4 selectively switches between an operating state (load operation mode) that supplies compressed air and a non-operating state (idle operation mode) that does not compress air. That is, compressor 4 has a load operation mode in which compressor 4 supplies compressed air and an idle operation mode in which compressor 4 does not supply compressed air.

[0037] Air drying circuit 11 is a so-called air dryer. Air drying circuit 11 is connected to ECU 80 and dries the compressed air supplied from compressor 4 under load. Air drying circuit 11 delivers the dried compressed air to supply circuit 12.

[0038] The supply circuit 12 stores the compressed air supplied from the air drying circuit 11 into an air tank (not shown) mounted on the vehicle, and supplies it to various loads (not shown).

[0039] The air drying circuit 11 has a maintenance port P12. The maintenance port P12 is used to supply air to the air drying circuit 11 during maintenance.

[0040] <Structure of Air Drying Circuit 11>

[0041] Air drying circuit 11 is internal 11A (refer to) Figure 2 (a)~ Figure 2 (f) includes a filter 17. In the first embodiment, the filter 17 is disposed midway in the air supply passage 18 that connects the compressor 4 to the supply circuit 12. Furthermore, the filter 17 functions as a desiccant. Additionally, the air supply passage 18 functions as a connection passage.

[0042] Filter 17 dries the air by removing moisture from it by passing it through a desiccant, and cleans it by removing oil from it using a filtration section. Air passing through filter 17 is supplied to supply circuit 12 via downstream check valve 19, which acts as a check valve and only allows air to flow downstream from filter 17. In other words, downstream check valve 19 only allows air to flow from the upstream side of filter 17 to the downstream side of supply circuit 12. Furthermore, because downstream check valve 19 has a predetermined opening pressure (closing pressure), the upstream pressure is higher than the downstream pressure by a pressure corresponding to the opening pressure when compressed air flows.

[0043] Furthermore, downstream of filter 17, a bypass passage, namely bypass flow path 20, is provided in parallel with downstream check valve 19, bypassing downstream check valve 19. A regeneration control valve 21 is provided in bypass flow path 20. That is, regeneration control valve 21 is located midway in the passage connected in parallel with the passage where downstream check valve 19 is provided.

[0044] The regeneration control valve 21 is a solenoid valve that switches its operation based on the power supply switching (driven / undriven) from the ECU 80 via wiring E64. When the power is off, the regeneration control valve 21 closes, sealing the bypass flow path 20; when the power is on, it opens, opening the bypass flow path 20. The ECU 80, for example, receives the air pressure value in the air tank and activates the regeneration control valve 21 when the air pressure value exceeds a specified range.

[0045] A throttling orifice 22 is provided between the regeneration control valve 21 on the bypass flow path 20 and the filter 17. When the regeneration control valve 21 is energized, compressed air from the supply circuit 12 side is delivered to the filter 17 via the bypass flow path 20 with its flow rate restricted by the throttling orifice 22. The air delivered to the filter 17 flows counter-currently from the downstream side to the upstream side of the filter 17. This process regenerates the filter 17 and is called the dryer regeneration process. The compressed air delivered to the filter 17 at this time is dried and cleaned air supplied to the supply circuit 12 after passing through the filter 17 from the air supply passage 18, thus removing the moisture and oil trapped in the filter 17. Therefore, the regeneration control valve 21 is opened for a specified period by the ECU 80. The specified period is set based on theory, experiment, or experience to allow the filter 17 to regenerate.

[0046] A branch passage 16 connected to a drain valve 25 is provided between the compressor 4 and the filter 17. That is, the branch passage 16 branches off from the air supply passage 18. A drain outlet 27 is provided at the end of the branch passage 16.

[0047] The drainage containing moisture and oil removed from filter 17 is conveyed along with compressed air to drain valve 25. Drain valve 25 is an air-pressure driven valve, located between filter 17 and drain outlet 27 on a branch passage 16 of the air supply passage 18. Drain valve 25 is a two-port, two-position valve that changes position between a closed position and an open position. In the open position, drain valve 25 delivers drainage to drain outlet 27. The drainage discharged from drain outlet 27 can be recovered by an oil separator (not shown).

[0048] The drain valve 25 is controlled by a speed controller 26A. The speed controller 26A is a solenoid valve, operated by the ECU 80 via wiring E63 to switch the power supply on / off (driven / undriven). When the power is on, the speed controller 26A opens the drain valve 25 by inputting an air pressure signal. Conversely, when the power is off, the speed controller 26A closes the drain valve 25 by setting the pressure to atmospheric pressure. Furthermore, the speed controller 26A acts as a second solenoid valve.

[0049] The drain valve 25 is kept in the closed position when no air pressure signal is input from the speed controller 26A, and changes to the open position when an air pressure signal is input from the speed controller 26A. In addition, if the input port of the drain valve 25 on the compressor 4 side exceeds the upper limit and becomes high pressure, the drain valve 25 is forcibly switched to the open position.

[0050] 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 designated as upstream and the filter 17 side as downstream, the upstream check valve 15 only allows air to flow from upstream to downstream. Because the upstream check valve 15 has a specified opening pressure (closing pressure), the pressure upstream is higher than the pressure downstream by a pressure corresponding to the opening pressure when compressed air flows. Furthermore, a reed valve for the compressor 4 outlet is provided upstream of the upstream check valve 15, and the branch passage 16 and the filter 17 are provided downstream of the upstream check valve 15.

[0051] <Compressor 4>

[0052] The compressor 4 is controlled by the unloading control valve 26B. The unloading control valve 26B is a solenoid valve that operates in response to power-on / off (drive / non-drive) operations from the ECU 80 via wiring E62. When the power is off, the unloading control valve 26B is in the open position, opening the flow path between it and the compressor 4 to the atmosphere. Conversely, when the power is on, the unloading control valve 26B is in the supply position, supplying the compressor 4 with an air pressure signal generated by compressed air. The unloading control valve 26B and the speed controller 26A are controlled independently. Furthermore, the unloading control valve 26B functions as a first solenoid valve.

[0053] When the compressor 4 receives an air pressure signal from the unloading control valve 26B, it enters a non-operating state (idling). For example, when the pressure in the supply circuit 12 reaches the upper limit pressure, no dry compressed air supply is required. The pressure in the supply circuit 12 is measured by a pressure sensor (not shown) and input to the ECU 80. When the ECU 80 turns on (drives) the power based on the pressure sensor's measurement, the unloading control valve 26B is in the supply position. Thus, an air pressure signal is supplied to the compressor 4 from the unloading control valve 26B.

[0054] <Sensor>

[0055] A pressure sensor 50 is installed between the compressor 4 and the upstream check valve 15. The pressure sensor 50 measures the air pressure in the connected air supply passage 18 and transmits the measured result to the ECU 80 via wiring E61.

[0056] A humidity sensor 51 and a temperature sensor 52 are provided between the downstream one-way valve 19 and the supply circuit 12. The humidity sensor 51 and temperature sensor 52 each measure the humidity and temperature of the compressed air downstream of the filter 17, and output the measured results to the ECU 80 via wiring E65 and E66. The ECU 80 calculates the dew point based on the humidity and temperature of the input compressed air. A humidity measurement unit can be constructed using the humidity sensor 51, temperature sensor 52, and ECU 80. For example, assuming the humidity of the compressed air output from the compressor 4 is approximately 100%, the amount of water removed by the filter 17 can be calculated based on the difference between 100% and the measured humidity, and the amount of saturated water vapor at the temperature.

[0057] <Operating Instructions for Air Drying Circuit 11>

[0058] like Figure 2 (a)~ Figure 2 As shown in (f), the air drying circuit 11 has six operating modes, from the first operating mode to the sixth operating mode.

[0059] like Figure 2As shown in (a), the first operating mode is the mode for performing normal loading operations for supply processing, which is the mode in which the regeneration control valve 21, speed controller 26A, and unloading control valve 26B are closed. That is, the regeneration control valve 21, speed controller 26A, and unloading control valve 26B are each "CLOSE". At this time, the regeneration control valve 21, speed controller 26A, and unloading control valve 26B do not receive power supply. In addition, the speed controller 26A and unloading control valve 26B open the port of the compressor 4 connected downstream of them and the port of the drain valve 25 to the atmosphere, respectively. In the first operating mode, when compressed air is supplied from the compressor 4, moisture and oil are removed by a desiccant, and compressed air is supplied to the supply circuit 12. That is, the compressor 4 is "ON".

[0060] like Figure 2 As shown in (b), the second operating mode is the mode in which the compressor stops operating for purification treatment (with purification treatment), which is the mode in which the regeneration control valve 21 is closed and the speed controller 26A and the unloading control valve 26B are opened respectively. That is, the regeneration control valve 21 is "CLOSE", and the speed controller 26A and the unloading control valve 26B are each "OPEN". At this time, the speed controller 26A and the unloading control valve 26B are each supplied with power, and the ports of the compressor 4 and the drain valve 25 downstream of them are respectively connected to the upstream side (supply circuit 12). In the second operating mode, when the compressor 4 is not in operation, the compressed air in the desiccant of the filter 17 or the air supply passage 18, together with moisture, oil, etc., is discharged from the drain outlet 27, so that the air pressure in the desiccant of the filter 17 or the air supply passage 18 is atmospheric pressure. That is, the compressor 4 is "OFF".

[0061] like Figure 2 As shown in (c), the third operating mode is the mode for performing the regeneration operation, which involves opening the regeneration control valve 21, the speed controller 26A, and the unloading control valve 26B respectively. At this time, power is also supplied to the regeneration control valve 21. In the third operating mode, the compressor 4 is deactivated, and the compressed air supplied to the circuit 12 is reversed to the filter 17 (in the desiccant) and discharged from the drain outlet 27, thereby removing moisture from the desiccant in the filter 17.

[0062] like Figure 2As shown in (d), the fourth operating mode is the oil removal mode, which involves closing the regeneration control valve 21 and the unloading control valve 26B respectively, and closing the governor 26A after a certain period of valve opening. In the fourth operating mode, when the compressor 4 is in the working state, the compressed air supplied by the compressor 4 is discharged from the drain outlet 27 for a certain period of time. For example, immediately after switching from the non-working state to the working state, the compressed air containing a relatively large amount of oil is discharged from the drain outlet 27, which can reduce the deterioration of the filter 17. The oil removal operation can also be performed when the engine speed increases or the engine load is high during the working state, or when the oil from the compressor 4 increases.

[0063] like Figure 2 As shown in (e), the fifth operating mode is a mode in which the compressor stops (without purification treatment), which involves closing the regeneration control valve 21 and the speed controller 26A respectively and opening the unloading control valve 26B. In the fifth operating mode, when the compressor 4 is not in operation, the compressed air remaining in the desiccant in the air supply passage 18 or the filter 17 is not discharged from the drain outlet 27, thereby maintaining the air pressure.

[0064] like Figure 2 As shown in (f), the sixth operating mode is an auxiliary operation for pressurization, which involves opening the regeneration control valve 21 and the unloading control valve 26B respectively and closing the speed controller 26A. In the sixth operating mode, when the compressor 4 is not in operation, the compressed air from the supply circuit 12 is supplied (reverse flow) to the air supply passage 18 or the desiccant in the filter 17 to a pressure higher than atmospheric pressure, maintaining the back pressure (air pressure) of the upstream check valve 15 at a pressure higher than atmospheric pressure.

[0065] <Compressor Auxiliary Actions>

[0066] Reference Figures 3-6 This is to explain the auxiliary operation of the compressor.

[0067] When the piston of compressor 4 descends during no-load operation, a negative pressure is generated in the cylinder corresponding to the increase in volume, which increases the operating load. Therefore, compressor assistance is used to mitigate the increase in operating load caused by the negative pressure. Specifically, in compressor assistance, when the piston of compressor 4 descends during no-load operation, the reed valve at the outlet of compressor 4 is closed by maintaining a pressure higher than atmospheric pressure in the desiccant of filter 17 or in the air supply passage 18, thereby maintaining to some extent the pressure generated when the piston rises in the cylinder, thus suppressing the generation of negative pressure in the cylinder. As a result, the operating load of compressor 4 during no-load operation can be reduced. Specifically, when compressor 4 is running no-load, the drain valve 25 is closed, and the compressed air supplied by compressor 4 maintains the air pressure in the desiccant of filter 17 or in the air supply passage 18 at a pressure higher than atmospheric pressure.

[0068] When the air supply system 10 starts supplying compressed air, it performs an air supply process that supplies compressed air output from the compressor 4 to the supply circuit 12. Figure 3 (Step S10). In the air supply process, the air drying circuit 11 is in the first operating mode, removing moisture and oil from the compressed air supplied from the compressor 4 before outputting it to the supply circuit 12. Furthermore, in the air supply process, the process ends when the air pressure in the supply circuit 12, for example, the air pressure in the air tank, exceeds the upper limit value.

[0069] During the air supply process ( Figure 3 When the air supply operation ends in step S10, the air supply system 10 puts the compressor 4 into a non-operating state and performs the dryer regeneration process. Figure 3 Step S11). In the dryer regeneration process, a dryer regeneration process is performed to regenerate the filter 17.

[0070] like Figure 4 As shown, during the dryer regeneration process, ECU 80 performs a humidity measurement step. Figure 4 (Step S20). In the humidity measurement process, the humidity of the compressed air is measured based on the humidity measured by the humidity sensor 51 and the temperature measured by the temperature sensor 52.

[0071] Next, ECU 80 determines whether "purification" of filter 17 is required. Figure 4 (Step S21). The ECU 80 determines that "purification" is required when the humidity of the compressed air is above the first humidity threshold, and determines that "purification" is not required when the humidity of the compressed air is below the first humidity threshold. In addition, whether "purification" is required can also be determined based on "airflow to the filter" and "oil flow to the filter".

[0072] Then, in cases where it is determined that "purification" is required ( Figure 4 Step S21: "Yes"), ECU 80 sets the air drying circuit 11 to the second operating mode, stopping the compressor (with purification process). Figure 4 After step S22), determine whether "regeneration treatment" of filter 17 is required. Figure 4 (Step S24). The ECU 80 determines that "regeneration processing" is required when the humidity of the compressed air is above the second humidity threshold, and determines that "regeneration processing" is not required when the humidity of the compressed air is below the second humidity threshold.

[0073] In cases where it is determined that "regeneration processing" is required ( Figure 4 Step S24: "Yes"), ECU 80 sets the air drying circuit 11 to the third operating mode to perform regeneration operation. Figure 4 Step S25). Then, when the regeneration process is complete, ECU80 ends the dryer regeneration process ( Figure 3 Step S11) allows the process to proceed to the next step.

[0074] On the other hand, in cases where it is determined that "regeneration processing" is not required ( Figure 4 Step S24: "No"), ECU80 ends the dryer regeneration process ( Figure 3 Step S11) allows the process to proceed to the next step.

[0075] On the other hand, in cases where it is determined that "purification" is not necessary ( Figure 4 Step S21: "No"), ECU 80 sets the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 4 Step S23). By performing a compressor stop operation (without purification), the desiccant in filter 17 or the air supply passage 18 is not opened to the atmosphere after compressor 4 stops, thus maintaining the back pressure of the upstream check valve 15 at a level higher than atmospheric pressure. Therefore, compressor assistance can be performed. This also enables the dryer regeneration process ( Figure 3 Step S11) ends, and processing proceeds to the next step.

[0076] Next, as Figure 3 As shown, the air supply system 10 performs an air non-supply process ( Figure 3 (Step S12). In the air-off process, the ECU 80 performs air-off processing during compressor shutdown to maintain a high back pressure on the upstream check valve 15.

[0077] A detailed explanation is provided, such as... Figure 5As shown, in non-supply air processing, the ECU 80 determines whether the air pressure in the desiccant of filter 17 or in the air supply passage 18 is high. Figure 5 (Step S30). The ECU 80 compares the measured value of the pressure sensor 50 with the high pressure threshold. If the value is above the high pressure threshold, the air pressure is determined to be high; if the value is below the high pressure threshold, the air pressure is determined to be low.

[0078] In cases where the air pressure is high in the desiccant in filter 17 or in the air supply passage 18 ( Figure 5 Step S30: "Yes"), ECU 80 sets the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 5 Step S32). On the other hand, if the air pressure in the desiccant determined to be in filter 17 or in the air supply passage 18 is low ( Figure 5 Step S30: "No"), ECU 80 performs auxiliary actions ( Figure 5 Step S31). In the auxiliary operation, the air drying circuit 11 is set to the sixth operating mode, and the air pressure in the desiccant of the filter 17 or in the air supply passage 18 is increased. Then, the air drying circuit 11 is set to the fifth operating mode, and the compressor stops (no purification treatment). Figure 5 (Step S32). Therefore, the back pressure of the upstream check valve 15 is maintained at a level higher than atmospheric pressure, enabling compressor assistance.

[0079] Next, ECU 80 performs a pressure adjustment process. Figure 5 (Step S33). In the pressure adjustment process, ECU 80 performs pressure adjustment.

[0080] like Figure 6 As shown, during the pressure adjustment process, the ECU 80 determines whether the air pressure in the desiccant of the filter 17 or in the air supply passage 18 is low. Figure 6 (Step S40). If the measured value of the pressure sensor 50 is below the low-pressure threshold, the ECU 80 determines that the air pressure is low; if the measured value of the pressure sensor 50 is above the low-pressure threshold, the ECU 80 determines that the air pressure is not low. Furthermore, in the first embodiment, an upstream one-way valve 15 is provided downstream of the pressure sensor 50, thus stabilizing the value of the pressure sensor 50 and reducing the frequency of auxiliary and purification actions.

[0081] In cases where the air pressure is determined to be low ( Figure 6 Step S40: "Yes"), ECU 80 sets the air drying circuit 11 to the sixth operating mode to perform auxiliary operations ( Figure 6Step S41), then, the air drying circuit 11 is set to the fifth operating mode, and the compressor stops (no purification treatment). Figure 6 Step S42). On the other hand, if it is determined that the air pressure is not low ( Figure 6 Step S40: "No"), ECU 80 sets the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 6 Step S42).

[0082] Additionally, ECU 80 determines whether the air pressure is high ( Figure 6 (Step S43). If the measured value of the pressure sensor 50 is above the high pressure threshold, the ECU 80 determines that the air pressure is high; if the measured value of the pressure sensor 50 is below the high pressure threshold, the ECU 80 determines that the air pressure is not high.

[0083] In cases where high air pressure is determined ( Figure 6 Step S43: "Yes"), ECU 80 sets the air drying circuit 11 to the second operating mode, stopping the compressor (with purification process). Figure 6 Step S44), and set the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 6 Step S45). On the other hand, in the case where the air pressure is determined to be low ( Figure 6 Step S43: "No"), ECU 80 sets the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 6 Step S45). Therefore, the back pressure of the upstream check valve 15 is maintained higher than atmospheric pressure, enabling compressor assistance. In other words, the air pressure has a relationship of "atmospheric pressure < low pressure threshold < high pressure threshold". Next, the ECU 80 performs air pressure determination processing ( Figure 6 Step S46). In the air pressure determination process, if the measured value of the pressure sensor 50 is less than the high pressure threshold and greater than the low pressure threshold, the air pressure is determined to be "appropriate". If it is greater than the high pressure threshold or less than the low pressure threshold, the air pressure is determined to be "inappropriate".

[0084] Then, as Figure 5 As shown, when the pressure adjustment process is completed, the pressure adjustment step ( Figure 5 Step S33) ends, proceed to the next step.

[0085] Next, determine whether to terminate the air non-supply process. Figure 5(Step S34). When it is necessary to operate the compressor 4 under load, the ECU 80 determines to terminate the air non-supply process; on the other hand, when it is not necessary to operate the compressor 4 under load, it determines not to terminate the air non-supply process.

[0086] That is, in cases where it is determined that the non-supply air processing should not be terminated ( Figure 5 Step S34: "No"), ECU 80 continues with the pressure adjustment process ( Figure 5 Step S33). On the other hand, in the case where it is determined that the air non-supply process will be terminated ( Figure 5 Step S34: "Yes"), end the air non-supply process ( Figure 3 (Step S13) Proceed to the next step.

[0087] Then, as Figure 3 As shown, determine whether to stop the air supply. Figure 3 Step S13). Regarding air supply, the process is determined to end based on factors such as the vehicle's engine stopping, or not to end based on factors such as the vehicle's engine continuing to rotate.

[0088] In cases where it is determined that the air supply will not be stopped ( Figure 3 Step S13: "No"), ECU 80 returns the process to step S10, executing the air supply procedure ( Figure 3 The processing after step S10). On the other hand, in the case where it is determined that the air supply will be terminated ( Figure 3 Step S13: “Yes”, which stops the air supply.

[0089] As explained above, the following effects can be obtained according to the first embodiment.

[0090] (1) When the solenoid valve that enables the compressor 4 to run idle (unload) is the same as the solenoid valve that switches the drain valve 25, the air pressure in the air supply passage 18 or the desiccant becomes atmospheric pressure while the compressor 4 is running idle. Therefore, the compressor 4 cannot draw in air from the reed valve that closes when the piston descends during idle operation, and the cylinder becomes under negative pressure, increasing the operating load. According to the above structure, the compressor 4 is switched between load operation and idle operation by the unloading control valve 26B, and the drain valve 25 is switched between closed and open by the speed controller 26A. That is, the unloading control valve 26B and the speed controller 26A are controlled separately. Therefore, when the compressor 4 is running idle, the drain valve 25 can be closed in advance. For example, if the drain valve 25 is closed in advance, the air pressure in the air supply passage 18 or the air pressure in the desiccant of the filter 17 can be maintained to a certain extent at a pressure higher than atmospheric pressure by the air pressure supplied by the compressor 4. Therefore, the pressure inside the cylinder of compressor 4 is maintained at a high pressure by the rise of the piston, thus suppressing the negative pressure generated inside the cylinder when the piston falls. As a result, the load on compressor 4 can be reduced.

[0091] (2) During at least a portion of the period when the compressor 4 is running idle, the air pressure in the air supply passage 18 connected to the reed valve of the compressor 4 or the air pressure in the desiccant of the filter 17 is maintained at a high level because the branch passage 16 is closed. In particular, when the compressor 4 switches from load operation to idle operation, the decrease in air pressure in the air supply passage 18 or the desiccant of the filter 17 is also suppressed by maintaining the drain valve 25 closed in advance.

[0092] (3) In the air supply passage 18, the air pressure between the reed valve on the outlet side of the compressor 4 and the upstream check valve 15 can be maintained by the closing pressure of the upstream check valve 15.

[0093] (4) When the branch passage 16 is closed by the drain valve 25, the regeneration control valve 21 is opened to supply compressed air downstream of the downstream check valve 19, thereby increasing the air pressure in the air supply passage 18 or the desiccant in the filter 17.

[0094] (5) Referring to the measurement results of the pressure sensor 50, the opening / closing of the regeneration control valve 21 is controlled according to the air pressure in the air supply passage 18 or the desiccant in the filter 17, thereby adjusting the air pressure in the air supply passage 18 or the desiccant in the filter 17 to a pressure higher than atmospheric pressure.

[0095] (6) The pressure sensor 50 can measure the air pressure in the air supply passage 18 connected to the reed valve on the outlet side of the compressor 4 or in the desiccant of the filter 17, and adjust the opening / closing of the regeneration control valve 21 by means of the measured residual pressure.

[0096] (7) When the unloading control valve 26B is driven (unloading), it can perform unpurified treatment, purified treatment, regeneration treatment and pressurization treatment in a timely manner.

[0097] (8) It can maintain the air pressure in the air supply passage 18 or the desiccant in the filter 17 at a specified value higher than atmospheric pressure. In addition, if the value of the pressure sensor 50 is observed for feedback processing, the air pressure can be maintained at the specified value with higher accuracy.

[0098] (9) It is possible to set the air pressure in the air supply passage 18, which is reduced to atmospheric pressure during the regeneration process, or in the desiccant of the filter 17, to a pressure higher than atmospheric pressure.

[0099] (Second Implementation)

[0100] Reference Figure 7 A second embodiment of the air supply system is described. The difference between the second and first embodiments is that the upstream check valve 15 is not provided in the air supply passage 18. In other words, the second embodiment has the features of the first embodiment. Figure 1 The structure does not include an upstream check valve 15.

[0101] In the second embodiment, by performing compressor auxiliary operation, the ECU 80 functions as in the first embodiment. Figure 5 Perform the pressure adjustment process as shown. Figure 5 (Step S33). Furthermore, in the pressure adjustment process, ECU 80 performs pressure adjustment processing.

[0102] like Figure 7 As shown, during the pressure adjustment process, the ECU 80 determines whether the air pressure in the desiccant of the filter 17 or the air pressure in the air supply passage 18 is low. Figure 7 (Step S50). Furthermore, in the second embodiment, a pressure sensor 50 is provided between the compressor 4 and the filter 17, but no upstream check valve is provided. Therefore, the value of the pressure sensor 50 may be somewhat unstable compared to the structure of the first embodiment, but pressure adjustment can be better performed by relatively increasing the number of auxiliary and purification actions.

[0103] In cases where the air pressure is determined to be low ( Figure 7 Step S50: "Yes"), ECU 80 performs auxiliary actions ( Figure 7Step S51). On the other hand, if it is determined that the air pressure is not low ( Figure 7 If step S50: "No"), or if the auxiliary action in step S51 ends, the ECU 80 performs a compressor stop operation (without purification treatment). Figure 7 Step S52).

[0104] Next, the ECU 80 determines whether the air pressure is high ( Figure 7 Step S53).

[0105] In cases where high air pressure is determined ( Figure 7 Step S53: "Yes"), ECU 80 performs compressor stop operation (with purification treatment) Figure 7 Step S54). On the other hand, in the case where the air pressure is determined to be low ( Figure 7 Step S53: "No"), or if the purification action in step S54 is completed, then ECU 80 performs a compressor stop action (no purification treatment). Figure 7 Step S55). As a result, the air pressure in the desiccant of the filter 17, located upstream of the downstream check valve 19, or in the air supply passage 18, is maintained above atmospheric pressure, enabling compressor assistance. Additionally, the ECU 80 performs the following air pressure determination process ( Figure 7 Step S56): If the air pressure is less than the high pressure threshold and above the low pressure threshold, it is determined that the air pressure is "appropriate"; otherwise, it is determined that the air pressure is "inappropriate".

[0106] As explained above, according to the second embodiment, in addition to the effects (1), (2), (4), (5), (7) to (9) described in the first embodiment, the following effects can also be obtained.

[0107] (10) Even without the upstream check valve 15, the drain valve 25 is closed in advance when the compressor 4 is running dry to maintain the air pressure in the desiccant of the filter 17 or the air pressure in the air supply passage 18 at a pressure higher than atmospheric pressure to a certain extent. As a result, the load on the compressor 4 can be reduced.

[0108] (Third Implementation)

[0109] Reference Figure 8 This describes a third embodiment of the air supply system. The difference between the third and first embodiments is that the pressure sensor 50 is not installed in the air supply passage 18. In other words, the third embodiment has the features of the first embodiment. Figure 1 The structure does not include a pressure sensor 50.

[0110] In the third embodiment, by performing a compressor auxiliary operation, the ECU 80 functions as in the first embodiment. Figure 5 Perform the pressure adjustment process as shown. Figure 5 (Step S33). Furthermore, in the pressure adjustment process, ECU 80 performs pressure adjustment processing.

[0111] like Figure 8 As shown, ECU 80 determines whether to perform auxiliary operations during pressure adjustment processing. Figure 8 (Step S60). In the third embodiment, since the upstream check valve 15 is provided, the ECU 80 determines that no assistance is needed if the compressor stops after it stops (without purification treatment) or if the previous action was an auxiliary action. Conversely, the ECU 80 determines that assistance is needed if the previous action was a compressor stop (with purification treatment) or a regeneration action.

[0112] In cases where assistance is deemed necessary ( Figure 8 Step S60: "Yes"), ECU 80 performs auxiliary actions ( Figure 8 Step S61). On the other hand, in cases where it is determined that no assistance is needed ( Figure 8 If step S60: "No") or the auxiliary action in step S61 ends, ECU 80 determines whether to end the auxiliary action. Figure 8 (Step S62). For example, when the conditions for causing compressor 4 to operate under load are met, it is determined that the auxiliary operation will end.

[0113] In cases where the assist is not terminated ( Figure 8 If step S62: "No"), ECU 80 returns to step S60 to continue the action corresponding to the determination of whether assistance is needed. On the other hand, if the determination is to end assistance ( Figure 8 Step S62: "Yes"), ECU 80 stops the compressor (without purification treatment) Figure 8 (Step S63). Then, return to the pressure adjustment process to proceed to the next step of the pressure adjustment process.

[0114] As explained above, according to the third embodiment, in addition to the effects (1) to (4) and (6) to (9) described in the first embodiment, the following effects can also be obtained.

[0115] (11) Even without a pressure sensor 50, the drain valve 25 is closed before the compressor 4 is running dry, so that the air pressure in the air supply passage 18 or the desiccant in the filter 17 is maintained to a certain extent higher than atmospheric pressure by the closing pressure of the upstream check valve 15. Thus, the load on the compressor 4 can be reduced.

[0116] (Fourth Implementation)

[0117] Reference Figure 9 A fourth embodiment of the air supply system is described. The fourth embodiment differs from the first embodiment in that it does not include a pressure sensor 50 and an upstream check valve 15 in the air supply passage 18. In other words, the fourth embodiment has the features of the first embodiment... Figure 1 The structure does not include a pressure sensor 50 and an upstream check valve 15.

[0118] In the fourth embodiment, by performing a compressor auxiliary operation, the ECU 80 functions as in the first embodiment. Figure 5 Perform the pressure adjustment process as shown. Figure 5 (Step S33). Furthermore, in the pressure adjustment process, the ECU 80 performs pressure adjustment processing. Additionally, in the fourth embodiment, since no upstream check valve is provided, the air pressure may become somewhat unstable compared to the structure of the first embodiment. Furthermore, since no pressure sensor is provided, feedback control based on air pressure is not possible. Therefore, control for pressure adjustment processing is performed based on predetermined conditions.

[0119] like Figure 9 As shown, ECU 80 determines whether to perform auxiliary operations during pressure adjustment processing. Figure 9 (Step S70). In the fourth embodiment, since the pressure sensor 50 and the upstream check valve 15 are not provided, the ECU 80 determines that no assistance is needed if the compressor stops after it stops (without purification treatment) or if the previous action was an auxiliary action. Conversely, the ECU 80 determines that assistance is needed if the compressor stops (with purification treatment) or if a regeneration action is performed.

[0120] In cases where assistance is deemed necessary ( Figure 9 Step S70: "Yes"), ECU 80 performs auxiliary actions ( Figure 9 Step S71). On the other hand, in cases where it is determined that no assistance is needed ( Figure 9 If step S70: "No") or the auxiliary action in step S71 ends, ECU 80 determines whether to end the auxiliary action. Figure 9(Step S72). For example, when the conditions for causing compressor 4 to operate under load are met, it is determined that the auxiliary operation will end.

[0121] In cases where the assist is not terminated ( Figure 9 If step S72: "No"), ECU 80 returns the processing to step S70 and performs the action corresponding to the determination of whether assistance is needed. On the other hand, if the determination is to end assistance ( Figure 9 Step S72: "Yes"), ECU 80 stops the compressor (without purification treatment) Figure 9 (Step S73). Then, return to the pressure adjustment process to proceed to the next step of the pressure adjustment process.

[0122] As explained above, according to the fourth embodiment, in addition to the effects (1), (2), (4), (7) to (9) described in the first embodiment, the following effects can also be obtained.

[0123] (12) Even without the pressure sensor 50 and the upstream check valve 15, the drain valve 25 is closed in advance when the compressor 4 is running dry, so as to maintain the air pressure in the air supply passage 18 or the desiccant in the filter 17 at a pressure higher than atmospheric pressure to a certain extent. As a result, the load on the compressor 4 can be reduced.

[0124] (Fifth Implementation)

[0125] Reference Figure 10 and Figure 11 A fifth embodiment of the air supply system will be described. The difference between the fifth and first embodiments is that degreasing is performed during normal load operation. Here, an example of performing degreasing at the start of load operation will be described.

[0126] like Figure 10 As shown, when the air supply system 10 starts supplying air, it first performs an oil removal process. Figure 10 In step S83), degreasing is performed.

[0127] like Figure 11 As shown, during the degreasing process, ECU 80 determines whether degreasing should be performed. Figure 11 Step S90). In cases where degreasing is deemed necessary ( Figure 11 Step S90: "Yes"), ECU 80 sets the air drying circuit 11 to the fourth operating mode (see... Figure 2 (d)) to perform degreasing action ( Figure 11 Step S91). On the other hand, if it is determined that degreasing is not required ( Figure 11If step S90: "No") or if the oil removal action in step S91 is completed, the ECU 80 ends the oil removal process. Figure 10 Step S83).

[0128] Next, the same procedure as when supplying air is started in the first embodiment is performed. That is, the air supply system 10 sequentially performs the air supply procedure of supplying compressed air output from the compressor 4 to the supply circuit 12. Figure 10 Step S80), dryer regeneration process ( Figure 10 Step S81) and air non-supply process ( Figure 10 Step S82).

[0129] Then, ECU 80 determines whether to terminate the air supply. Figure 10 Step S84).

[0130] In cases where it is determined that the air supply will not be stopped ( Figure 10 If step S84: "No"), ECU 80 returns the process to step S83 and continues the air supply process. On the other hand, if it is determined that the air supply process is to be terminated ( Figure 10 Step S84: “Yes”, which stops the air supply.

[0131] As explained above, according to the fifth embodiment, in addition to the effects (1) to (12) described in the first to fourth embodiments, the following effects can also be obtained.

[0132] (13) Discharging compressed air containing a relatively large amount of oil from the drain outlet 27 can reduce the deterioration of the filter 17 caused by oil and moisture. For example, it is preferable to do this immediately after the compressor 4 switches from a non-operating state to an operating state.

[0133] (Sixth Implementation Method)

[0134] Reference Figure 12 A sixth embodiment of the air supply system is described. The difference between the sixth and first embodiments is that forced regeneration is performed during the operation of the compressor 4 under load. In the sixth embodiment, the humidity of the compressed air is measured while the compressor 4 is operating under load, and forced regeneration is performed based on the measured humidity.

[0135] like Figure 12 As shown, when air supply begins, ECU 80 performs an air supply operation, supplying compressed air from compressor 4 to supply circuit 12. Figure 12 Step S100). Additionally, the ECU 80 performs a humidity measurement process to measure the humidity of the compressed air supplied by the opposing supply circuit 12. Figure 12 Step S101).

[0136] Then, ECU 80 determines whether a "regeneration process" is required. Figure 12 Step S102).

[0137] In cases where it is determined that "regeneration processing" is required ( Figure 12 Step S102: "Yes"), ECU 80 sets the air drying circuit 11 to the third operating mode (see... Figure 2 (c)) Forced to perform regeneration action ( Figure 12 Step S103). On the other hand, if it is determined that "regeneration processing" is not required ( Figure 12 In step S102: "No"), ECU 80 keeps compressor 4 running under load (first operating mode) and determines whether to terminate the air supply. Figure 12 Step S104).

[0138] In cases where it is determined that the air supply will not be stopped ( Figure 12 Step S104: "No"), ECU 80 returns processing to... Figure 12 In step S100, the air supply process continues. On the other hand, if it is determined that the air supply process is to be terminated ( Figure 12 Step S104: “Yes”, which stops the air supply.

[0139] As explained above, according to the sixth embodiment, in addition to the effects (1) to (13) described in the first embodiment, the following effects can also be obtained.

[0140] (14) Regeneration can be performed even in the air supply, thus suppressing the deterioration of filter 17.

[0141] (Seventh Implementation)

[0142] Reference Figures 13-16 The seventh embodiment of the air supply system is described. The difference between the seventh embodiment and the first embodiment is that the compressed air usage is appropriately adjusted instead of the compressor auxiliary operation.

[0143] <Action to Appropriate Compressed Air Usage>

[0144] Reference Figures 13-16 This explains the action to ensure the appropriate amount of compressed air is used.

[0145] Since the regeneration and purification operations used to restore the dehumidification performance of filter 17 consume a certain amount of compressed air, the operating load of compressor 4 increases in order to supply the consumed compressed air. To explain in detail, the increase in the operating load of compressor 4, which generates compressed air through rotational force transmitted from a rotary drive source such as an engine, increases the load on the rotary drive source, thereby increasing the consumption of energy such as fuel. Therefore, by setting the execution conditions of the regeneration and purification operations, the frequency of regeneration and purification operations can be appropriately optimized, thereby optimizing the amount of compressed air used and reducing the load on compressor 4.

[0146] Furthermore, when the regeneration and purification operations are not performed, and the compressor 4 is running idle, the drain valve 25 is closed, which allows the compressed air supplied by the compressor 4 to maintain the air pressure in the desiccant of the filter 17 or in the air supply passage 18 at a pressure higher than atmospheric pressure. This achieves an effect comparable to compressor assistance, reducing the operating load of the compressor 4 during idle operation.

[0147] like Figure 13 As shown, when the air supply system 10 starts supplying compressed air, it performs an air supply process that supplies compressed air output from the compressor 4 to the supply circuit 12. Figure 13 (Step S110). In the air supply process, the air drying circuit 11 is in the first operating mode, removing moisture and oil from the compressed air supplied by the compressor 4 and then outputting it to the supply circuit 12. Furthermore, the air supply process ends when the air pressure in the supply circuit 12, such as the air pressure in the air tank, exceeds the upper limit.

[0148] During the air supply process ( Figure 13 When the air supply operation ends in step S110, the air supply system 10 puts the compressor 4 into a non-operating state and performs the dryer regeneration process. Figure 13 Step S111). In the dryer regeneration process, a dryer regeneration process is performed to regenerate the filter 17.

[0149] like Figure 14 As shown, during the dryer regeneration process, ECU 80 performs a humidity measurement step. Figure 14 (Step S120). In the humidity measurement process, the ECU 80 measures the humidity of the compressed air based on the humidity measured by the humidity sensor 51 and the temperature measured by the temperature sensor 52. The humidity sensor 51 is equivalent to the humidity measurement unit.

[0150] Next, ECU 80 determines whether the humidity level is "medium" or higher. Figure 14(Step S121). When the humidity of the compressed air is above the low humidity threshold, the ECU 80 determines that the humidity is "medium" or above, and when the humidity of the compressed air is below the low humidity threshold, it determines that the humidity is not "medium" or above.

[0151] Then, under the condition that the humidity is determined to be "medium" or above ( Figure 14 Step S121: "Yes"), ECU 80 sets the air drying circuit 11 to the second operating mode, stopping the compressor (with purification process). Figure 14 After step S122), determine whether the humidity is "high" or above. Figure 14 (Step S124). When the humidity of the compressed air is above the high humidity threshold, the ECU 80 determines that the humidity is "high" or above, and when the humidity of the compressed air is below the high humidity threshold, it determines that the humidity is not "high" or above.

[0152] In cases where the humidity is determined to be "high" or above ( Figure 14 Step S124: "Yes"), ECU 80 sets the air drying circuit 11 to the third operating mode to perform regeneration operation. Figure 14 Step S125). Then, when the regeneration process is complete, ECU 80 ends the dryer regeneration process ( Figure 13 Step S111) allows the process to proceed to the next step.

[0153] On the other hand, in cases where the humidity is determined to be less than "high" ( Figure 14 Step S124: "No"), ECU 80 ends the dryer regeneration process ( Figure 13 Step S111) allows the process to proceed to the next step.

[0154] On the other hand, in cases where the humidity is determined to be less than "moderate" ( Figure 14 Step S121: "No"), ECU 80 sets the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 14 Step S123). By performing a compressor stop operation (without purification treatment), the desiccant in filter 17 or the air supply passage 18 is not opened to the atmosphere after compressor 4 stops, thus the effect of compressor assistance can be expected. This is also the dryer regeneration process ( Figure 13 Step S111) ends, and processing proceeds to the next step.

[0155] Therefore, when compressor 4 is running idle, if the humidity of the compressed air supplied by compressor 4 is high and the desiccant absorbs a large amount of moisture, the oil-containing moisture is discharged along with the air from the desiccant in the air supply passage 18 or filter 17 connected to the drain valve, thus maintaining air cleanliness (steps S122, S25). At this time, if the humidity is "high" or higher, a regeneration operation is performed using compressed air flowing in reverse from the supply circuit 12 (step S125); if the humidity is "medium" or higher, a purification operation is performed using the compressed air remaining in the air drying circuit 11 (step S122). Conversely, if the humidity of the compressed air supplied by compressor 4 is low, the desiccant absorbs a small amount of moisture, and consequently, the amount of oil discharged from compressor 4 along with the compressed air is small, air is not discharged from the desiccant in the air supply passage 18 or filter 17, thus suppressing compressed air consumption (step S123).

[0156] Next, as Figure 13 As shown, the air supply system 10 performs an air non-supply process ( Figure 13 (Step S112). In the air-off process, the ECU80 performs air-off processing during compressor shutdown to maintain a high back pressure on the upstream check valve 15.

[0157] A detailed explanation is provided, such as... Figure 15 As shown, during air supply non-supply processing, ECU 80 performs non-supply operation ( Figure 15 Step S130). During non-supply operation, ECU 80 performs a pressure adjustment process based on the measurement value of pressure sensor 50. Figure 16 In the pressure adjustment process, ECU 80 performs pressure adjustment. For example, in the pressure adjustment process, the air pressure in the desiccant of filter 17 or in the air supply passage 18 is adjusted as needed.

[0158] like Figure 16 As shown, during the pressure adjustment process, the ECU 80 determines whether the air pressure in the desiccant of the filter 17 or in the air supply passage 18 is low. Figure 16 (Step S140). If the measured value of the pressure sensor 50 is below the low-pressure threshold, the ECU 80 determines that the air pressure is low; if the measured value of the pressure sensor 50 is above the low-pressure threshold, it determines that the air pressure is not low. Furthermore, in the seventh embodiment, an upstream one-way valve 15 is provided downstream of the pressure sensor 50, so the value of the pressure sensor 50 is stable, and the number of auxiliary actions and purification actions can be reduced.

[0159] In cases where the air pressure is determined to be low ( Figure 16Step S140: "Yes"), ECU 80 sets the air drying circuit 11 to the sixth operating mode to perform auxiliary operations ( Figure 16 Step S141), then, the air drying circuit 11 is set to the fifth operating mode, and the compressor stops (no purification treatment). Figure 16 Step S142). On the other hand, in the case where it is determined that the air pressure is not low ( Figure 16 Step S140: "No"), ECU 80 sets the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 16 Step S142).

[0160] Additionally, ECU 80 determines whether the air pressure is high ( Figure 16 (Step S143). If the measured value of the pressure sensor 50 is above the high pressure threshold, the ECU 80 determines that the air pressure is high; if the measured value of the pressure sensor 50 is below the high pressure threshold, the ECU determines that the air pressure is not high.

[0161] In cases where high air pressure is determined ( Figure 16 Step S143: "Yes"), ECU 80 sets the air drying circuit 11 to the second operating mode, stopping the compressor (with purification process). Figure 16 Step S144), and set the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 16 Step S145). On the other hand, in the case where the air pressure is determined to be low ( Figure 16 Step S143: "No"), ECU 80 sets the air drying circuit 11 to the fifth operating mode, stopping the compressor (no purification process). Figure 16 Step S145). Therefore, the back pressure of the upstream check valve 15 is maintained higher than atmospheric pressure, enabling compressor assistance. In other words, the air pressure has a relationship of "atmospheric pressure < low pressure threshold < high pressure threshold". Next, the ECU 80 performs air pressure determination processing ( Figure 16 Step S146). In the air pressure determination process, if the measured value of the pressure sensor 50 is less than the high pressure threshold and greater than the low pressure threshold, the air pressure is determined to be "appropriate". If it is greater than the high pressure threshold or less than the low pressure threshold, the air pressure is determined to be "inappropriate".

[0162] Then, as Figure 15 As shown, when the pressure adjustment process ends, the non-supply operation ( Figure 15 Step S130) ends, proceed to the next step.

[0163] Next, determine whether to terminate the air non-supply process. Figure 15 (Step S131). When it is necessary to operate the compressor 4 under load, the ECU 80 determines to terminate the air non-supply process; on the other hand, when it is not necessary to operate the compressor 4 under load, it determines not to terminate the air non-supply process.

[0164] That is, in cases where it is determined that the non-supply air processing should not be terminated ( Figure 15 Step S131: "No"), ECU 80 continues to perform non-supply operation ( Figure 15 Step S130). On the other hand, in the case where it is determined that the air non-supply process will be terminated ( Figure 15 Step S131: "Yes"), end the air non-supply process ( Figure 13 (Step S113) Proceed to the next step.

[0165] Then, as Figure 13 As shown, determine whether to stop the air supply. Figure 13 Step S113). Regarding air supply, for example, it is determined to end based on the vehicle's engine stopping, or it is determined not to end based on the vehicle's engine continuing to rotate.

[0166] In cases where it is determined that the air supply will not be stopped ( Figure 13 Step S113: "No"), ECU 80 returns the process to step S110 and executes the air supply procedure. Figure 13 The processing after step S110). On the other hand, in the case where it is determined that the air supply will be terminated ( Figure 13 Step S113: “Yes”, which stops the air supply.

[0167] As explained above, the following effects can be obtained according to the seventh embodiment.

[0168] (15) When the solenoid valve that switches the compressor 4 to idle (unload) is the same as the solenoid valve that switches the drain valve 25, air in the connection passage or in the desiccant is released into the atmosphere in accordance with the idling of the compressor 4. Therefore, a portion of the compressed air supplied by the compressor 4 is discharged in an unused state, thus consuming compressed air. According to the above structure, the compressor 4 is switched between load operation and idling by the unloading control valve 26B, and the drain valve 25 is switched between closed and open by the speed controller 26A based on the humidity measured by the humidity measuring unit. Therefore, when the compressor 4 is idling, the drain valve 25 can be closed in advance. For example, if the drain valve 25 is closed in advance when the air is already dry, the air pressure in the air supply passage 18 or the air pressure in the desiccant of the dryer filter 17 can be maintained at a pressure higher than atmospheric pressure by the air pressure supplied by the compressor 4. As a result, the consumption of compressed air can be suppressed.

[0169] (16) When the compressor 4 is running idle, if the humidity of the supplied compressed air is high, the desiccant in the filter 17 absorbs more moisture. Therefore, the oily moisture is discharged along with the air from the air supply passage 18 connected to the drain valve 25 or from the desiccant in the filter 17, thereby maintaining air cleanliness. Conversely, if the humidity of the supplied compressed air is low, the desiccant in the filter 17 absorbs less moisture. Therefore, the air pressure in the air supply passage 18 or from the desiccant in the filter 17 is maintained, thereby suppressing the consumption of compressed air.

[0170] (17) By opening the regeneration control valve 21, the dried compressed air can be reversed from the air tank, for example, so the desiccant of the filter 17 can be regenerated using the reversed dried air.

[0171] (18) Because it is possible to control the opening of the regeneration control valve for a specified period, it is possible to perform regeneration processing for a specified period.

[0172] (19) Through pressure regulation, even after regeneration, it is possible to maintain a high air pressure in the air supply passage 18 or in the desiccant of the filter 17. For example, compressor assistance can be performed.

[0173] (Other implementation methods)

[0174] Furthermore, the above-described embodiments can also be implemented in the following ways.

[0175] The above embodiments can be combined without creating contradictions. For example, at least one of the fifth and sixth embodiments can be combined with the first to fourth embodiments respectively. At least one of the fifth and sixth embodiments can be combined with the seventh embodiment.

[0176] In the first embodiment described above, the pressure sensor 50 is shown to be installed upstream of the upstream check valve 15. However, it is not limited to this; the pressure sensor may also be installed downstream of the upstream check valve. This allows for direct detection of the air pressure in the branch passage.

[0177] • In the above embodiments, the filter 17 is configured to have a desiccant and a filter section, but it may also have a configuration that has only one of the desiccant and the filter section.

[0178] • In the above embodiments, the case in which a filter 17 is provided is illustrated, but it is not limited to this. Alternatively, an oil mist separator may be provided upstream of the filter 17.

[0179] The oil mist separator includes a filter that separates oil from compressed air through collision, capturing oil contained in the compressed air delivered from compressor 4. The filter can be made of compressed metal or a porous material such as sponge. By incorporating this oil mist separator, the cleanliness of the compressed air can be further improved.

[0180] Alternatively, after the ECU 80 performs regeneration processing on the air drying circuit 11 in the third operating mode, without driving the speed controller 26A via the fifth or second operating mode to close the drain valve 25, it can be set to the sixth operating mode to perform compressor assistance. Thus, even after regeneration processing, a high air pressure in the connection passage or in the desiccant can be quickly maintained. This enables what is known as compressor assistance.

[0181] In the above embodiments, a humidity measuring unit is illustrated by comprising a humidity sensor 51, a temperature sensor 52, and an ECU 80. However, this is not a limitation; the humidity measuring unit may be composed of a device including a sensor, as long as humidity can be measured. For example, it may not be a component that uses an ECU for calculation.

[0182] In the embodiments described above, the air supply system 10 was described as being installed in vehicles such as trucks, buses, and construction machinery. Alternatively, the air supply system may also be installed in other vehicles such as cars and railway vehicles.

Claims

1. An air supply system, comprising: The compressor is capable of switching between load operation that delivers compressed air and idling operation that does not deliver the compressed air. A desiccant, used to remove moisture from the compressed air delivered by the compressor; A connection passage that connects the compressor and the desiccant in a manner in which compressed air can flow; A valve used to switch the compressor between operating under load and operating without load; A drain valve, which is connected to a branch passage of the connecting passage, is used to close or open the branch passage; A downstream check valve that allows flow of air from the desiccant to the side opposite to the compressor; and A regeneration control valve is positioned midway through the passage connected in parallel with the downstream check valve. When the compressor is in operation, an oil removal action is performed to close the regeneration control valve and close the drain valve after a specified opening period.

2. An air supply system, comprising: The compressor is capable of switching between load operation that delivers compressed air and idling operation that does not deliver the compressed air. A desiccant, used to remove moisture from the compressed air delivered by the compressor; A connection passage that connects the compressor and the desiccant in a manner in which compressed air can flow; A first solenoid valve is used to switch the compressor between load operation and no-load operation. The compressor is switched to no-load operation when the first solenoid valve is driven, and the compressor is switched to load operation when the first solenoid valve is not driven. A drain valve, connected to a branch passage of the connecting passage, closes or opens the branch passage in response to the actuation or non-actuation of the second solenoid valve. A control device capable of switching between driving and not driving the first solenoid valve, and switching between driving and not driving the second solenoid valve. A downstream check valve that allows flow of air from the desiccant to the side opposite to the compressor; and A regeneration control valve is positioned midway through the passage connected in parallel with the downstream check valve. When the compressor is in working condition without driving the first solenoid valve, the control device performs an oil removal action to close the regeneration control valve and close the second solenoid valve after a specified opening period.

3. The air supply system according to claim 2, wherein, The control device performs the oil removal action immediately after the compressor switches from a non-working state to a working state.

4. The air supply system according to claim 2 or 3, wherein, After performing the degreasing action, the control device performs an air supply action, supplying the compressed air output from the compressor to the desiccant. When neither the first nor the second solenoid valve is activated, the connection destination will be open to the atmosphere. The drain valve opens the branch passage to the atmosphere without actuating the second solenoid valve.

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