Integrated air supply unit

Abstract

To provide a method for designing a more efficient reciprocating piston compressor.SOLUTION: The method for designing a more efficient reciprocating piston compressor comprising the steps of: providing an air compressor 166 having a first compression stage adapted for compressing gas from a low pressure to an intermediate pressure and including a first piston 220 connected to reciprocate in a first cylinder, a second compression stage adapted for compressing gas from the intermediate pressure to a higher pressure and including a second piston 230 connected to reciprocate in a second cylinder, and a motor connected to reciprocate said first piston in said first cylinder over a stroke and said second piston in said second cylinder over a stroke; and establishing a sufficiently fewer number of strokes over which the gas to be pressured starting from the atmosphere pressure.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an air supply unit of an air suspension system for an automobile, and more particularly to an integrated air supply unit.

Background Art

[0002] An automotive compressor unit is generally disposed, for example, in a region below the luggage compartment of a vehicle, and supplies compressed air to, for example, a level control system of an air suspension system of the vehicle. The air suspension can adjust the rigidity and damping of the vehicle suspension in real time according to the movement of the vehicle and the road surface condition so that the suspension system is in the best shock absorption state and the vehicle can provide good comfort to the user in various road conditions. As a core component of the air suspension system, the air supply unit compresses air and injects it into the air spring, which provides power to realize the function of adjusting the rigidity and damping of the air suspension.

[0003] In the air supply equipment used in the air suspension system of an automobile, it is generally known that a single-stage compression method (by pressure stage) is commonly applied as a compressor solution. This compressor has a large output gas volume, but due to the low output gas pressure, the adjustment sensitivity of the air suspension system for automobiles becomes low.

[0004] Therefore, there is a need for a better and more efficient compressed air control device with high-pressure air output.

Summary of the Invention

[0005] In one aspect, one embodiment discloses a compressed air control device for a compressed air source of an automobile. The compressed air control device may include a housing. The housing may include an air inlet having an opening located on the outer surface of the housing. The housing may include an electric motor and an air dryer. The air dryer may form a first functional unit together with the electric motor.

[0006] Optionally, in any embodiment, the compressed air control device may further include a crankcase.

[0007] Optionally, in any embodiment, the crankcase may further include an air compressor.

[0008] Optionally, in any embodiment, the compressed air control device may further include a second functional unit, and the second functional unit includes a plurality of valve assemblies and an electronic control device.

[0009] Optionally, in any embodiment, the second functional unit may be removably attached to the crankcase.

[0010] Optionally, in any embodiment, the first functional unit is attached to the crankcase away from the air inlet opening.

[0011] Optionally, in any embodiment, the plurality of valve assemblies includes a plurality of pneumatic valves.

[0012] Optionally, in any embodiment, the air compressor may be driven by an electric motor 。

[0013] Optionally, in any embodiment, the air compressor is embodied as a two-piston compressor.

[0014] Optionally, in any embodiment, the two-piston compressor is centrally attached via a crankpin.

[0015] Optionally, in any embodiment, the electronic control device includes an electronic connector.

[0016] Optionally, in any embodiment, the compressed air control device is assembled to a vehicle.

[0017] In yet another aspect, one embodiment discloses a method for designing a more efficient reciprocating piston compressor. The method includes a first compression stage including a first piston adapted to compress gas from a low pressure to a medium pressure and connected to reciprocate within a first cylinder, a second compression stage including a second piston adapted to compress gas from a medium pressure to a high pressure and connected to reciprocate within a second cylinder, providing a pneumatic compressor having a motor connected to reciprocate the first piston within the first cylinder over a stroke and to reciprocate the second piston within the second cylinder over a stroke, and establishing a sufficiently small number of strokes through which the gas being compressed passes starting from atmospheric pressure.

[0018] Optionally, in any aspect, the method further includes pumping gas from a pressurized container to the first compression stage.

[0019] Optionally, in any aspect, the step may further include mixing air with the gas pumped from the pressurized container.

[0020] Optionally, in any aspect, the step may further include pumping gas from a pressurized container to the second compression stage.

[0021] Optionally, in any aspect, the step may further include diverting a portion of the gas pumped from the pressure container to the atmosphere if the pressure is higher than a set pressure.

[0022] Optionally, in any aspect, the step may further include diverting a portion of the pressurized gas after the first compression stage to the atmosphere.

[0023] Optionally, in any aspect, the step may further include drying the pressurized gas after the second compression stage.

[0024] Optionally, in any aspect, the step may further include monitoring the pressure of the pressurized gas by using a pressure sensor.

[0025] Optionally, in any aspect, the step may further include transferring the dried pressurized gas to a pressure vessel for storage.

[0026] Optionally, in any aspect, the step may further include transferring the dried pressurized gas to an air spring of a vehicle suspension system.

[0027] Optionally, in any aspect, the step may further include adjusting the dried pressurized gas by a solenoid valve before transferring it to the air spring.

[0028] In yet another aspect, one embodiment discloses a compressed air control device comprising a housing and a crankcase. The housing includes an air inlet having an opening located on the outer surface of the housing. The crankcase comprises an air compressor. A first functional unit may be attached and connected to the crankcase away from the air inlet opening.

[0029] In yet another aspect, one embodiment discloses a compressed air control device comprising a crankcase, a housing, and a second functional unit. The crankcase comprises an air compressor. The housing has an electric motor and forms a first functional unit. The housing is attached to the crankcase. The second functional unit may comprise a valve assembly and an electronic control device. The second functional unit may be removably attached and connected to the crankcase.

[0030] In yet another aspect, a method for designing a more efficient reciprocating piston compressor includes: a) providing a first compression stage including a first piston adapted to compress gas from a low pressure to an intermediate pressure and connected to reciprocate within a first cylinder, a second compression stage including a second piston adapted to compress gas from the intermediate pressure to a high pressure and connected to reciprocate within a second cylinder, and an electric motor connected to reciprocate the first piston over a stroke within the first cylinder and to reciprocate the second piston over a stroke within the second cylinder; and b) pumping gas from a pressurized container to the first compression stage in order to increase the output air pressure from the second compression stage.

[0031] In yet another aspect, a method for designing a more efficient reciprocating piston compressor includes: a) providing a first compression stage including a first piston adapted to compress gas from a low pressure to an intermediate pressure and connected to reciprocate within a first cylinder, a second compression stage including a second piston adapted to compress gas from the intermediate pressure to a high pressure and connected to reciprocate within a second cylinder, and an electric motor connected to reciprocate the first piston over a stroke within the first cylinder and to reciprocate the second piston over a stroke within the second cylinder; and b) pumping gas from a pressurized container to the second compression stage in order to increase the output air pressure from the second compression stage.

[0032] To more clearly illustrate the technical solutions in the embodiments or exemplary technologies of the present disclosure, the drawings used in the description of the embodiments or exemplary embodiments are briefly described below. Obviously, the drawings in the following description are only specific embodiments of the present disclosure, and other drawings can be obtained according to the structures shown in the drawings without any creative work for those skilled in the art.

Brief Description of the Drawings

[0033]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0034] The implementation, functional features and advantages of the present disclosure will be further described with reference to the accompanying drawings.

[0035] Definitions The present invention is not limited to the specific methodologies, protocols, and reagents described herein because they can change. Further, the terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the present invention. As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0036] Unless otherwise defined, all technical and scientific terms and any acronyms used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Any methods and materials similar or equivalent to those described herein can be used in the practice of the invention, but the preferred methods, apparatus, and materials are described herein. The technical means, creative features, objectives, and effects of this patent application may be easy to understand. The following embodiments further illustrate this patent application. However, the following embodiments are merely preferred embodiments of the utility patent application and do not represent all of them. Based on the examples in the implementation method, other examples obtained by those of ordinary skill in the art without creative work shall be considered within the protection scope of the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified. The materials used in the following examples can be obtained from commercial sources unless otherwise specified.

[0037] Embodiment Embodiments of the present invention relate to a compressed air control device for an automotive compressed air source and a method for designing a more efficient reciprocating piston compressor.

[0038] Referring initially to FIGS. 1 and 2, a compressed air control device 100 for an automotive compressed air source includes a housing 120. The housing 120 may have an electric motor 130 and a gas dryer 150. The housing 120 may include an air inlet 192 having an opening 194 located on an outer surface 122 of the housing 120. The air dryer 150, together with the electric motor 130, forms a first functional unit 110. The housing 120 serves to protect the motor 130 and the gas dryer 150 from external damage and may prevent the ingress of dust into the motor 130 and the gas dryer 150. In one embodiment, the motor may be an electric motor. An electric motor is an electromechanical device that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the magnetic field and current in the motor's wire winding to generate a force in the form of torque applied to the motor's shaft.

[0039] The electric motor may be powered by a direct current (DC) source such as a battery or a rectifier, or by an alternating current (AC) source such as a power grid, an inverter or a generator.

[0040] Electric motors can be classified according to considerations such as power supply type, structure, application, and type of motion output. They can be powered by AC or DC, can be brushed or brushless, single-phase, two-phase or three-phase, and can have axial or radial flux, and can be air-cooled or liquid-cooled.

[0041] The compressed air control device 100 further includes a crankcase 160, and the crankcase includes an air compressor 166 (also shown in FIG. 3) inside the crankcase 160. The first functional unit 110 is attached to and connected to the crankcase 160 away from the air inlet opening 194. In one embodiment, the crankcase 160 is a housing surrounding the air compressor 166.

[0042] Further in FIG. 1, the compressed air control device 100 may further include a second functional unit 140. The second functional unit 140 may include a valve assembly 190 and an electronic control device 180. The valve assembly 190 may include a plurality of pneumatic valves 198 (details are described in FIGS. 3-9). In one embodiment, the second functional unit 140 may be removably attached to the crankcase 160.

[0043] In one embodiment, the electronic control device 180 may include an electronic connector such as a solenoid valve 390 (shown in FIG. 4), for example.

[0044] As shown in FIG. 3, the air compressor 166 may be, for example, a three-cylinder star-type compressor. The air compressor 166 can be driven via the electric motor 130. In one embodiment, the air compressor 166 is embodied as a two-piston compressor, and the pistons are attached to the center of the crankpin 280. As a result, small torque fluctuations and small starting torque are similarly generated as a result of the quiet compressor operation.

[0045] As a result of being attached to the crankpin 280, the motor mounting device also has less load, and as a result, it is possible to make the dimensions of the motor mounting device smaller. The smaller the compressor volume of the cylinders of the two-piston compressor, the less heat can be dissipated in a simpler way. These advantages also result in a longer service life and improved starting time as a result of the longer-lasting performance of the integrated air supply unit.

[0046] The first piston head 290 is connected to the first stage link mechanism or piston 220. The second piston head 240 may be connected to the second stage link mechanism or piston 230. The first stage link mechanism or piston 220 may have a diameter larger than the diameter of the second stage link mechanism or piston 230. The cylinder corresponding to the first stage link mechanism or piston 220 is larger than the cylinder corresponding to the second link mechanism or piston 230. Air is supplied from the environment to the air compressor 166 through the air inlet 192 through the opening 194 in the outer surface 122 of the housing 110. Therefore, it is possible to connect the concept of a multi-stage compressor. The inlet valve 210 connected to the cylinder of the first stage compression is a one-way valve. The air outlet valve 260 connected to the cylinder of the first stage compression may also be a one-way valve or a check valve. The compressed air conduit 270 may be connected from the air outlet valve 260 to the air inlet valve 250 for the second stage compression.

[0047] As shown in FIG. 4, the atmosphere 310 can be guided to the air inlet valve 210 via the electric motor 130 to the first-stage air compressor 340. After the first-stage air compressor 340, the pressurized air may be guided to the air outlet valve 260. The compressed air is further guided to the air inlet valve 320 to the second-stage air compressor 342 for the second compression. Further compressed air is guided to the air outlet valve 330 and may be guided to either the air dryer 150 or the air outlet valve 350. The air outlet valve 250 may be an air pressure valve. The dried compressed air from the air dryer 150 can be guided to either the air outlet valve 360 or the air outlet valve 390 to the air springs 392, 294, 396, 398 and the compressed air container 380. The air outlets 360 and 390 may be solenoid valves such as solenoid valves. The pressure sensor 370 can be used to monitor the pressure of the compressed air after the air dryer 150. The air outlet valve 360 may be connected to the atmosphere 310. The compressed air container 380 may also be connected to the air outlet solenoid valve 390. The air outlet valve 250 may be an air pressure valve. The dried compressed air from the air dryer 150 can be guided to either the air outlet valve 360 or the air outlet valve 390 to the air springs 392, 294, 396, 398 and the compressed air container 380. The air outlets 360 and 390 may be solenoid valves such as solenoid valves. The pressure sensor 370 can be used to monitor the pressure of the compressed air after the air dryer 150. The air outlet valve 360 may be connected to the atmosphere 310. The compressed air container 380 may also be connected to the air outlet solenoid valve 390.

[0048] FIG. 5 emphasizes the air expansion air pressure circuit diagram by the arrows. The method may further include the step of pressurizing or pumping the dried pressurized gas to the pressurized container 380 for storage, as shown by the arrows. Further, the air flows from the atmosphere 310 to the air springs 392, 394, 396, and 398 as described above.

[0049] As shown in FIG. 6, the air is discharged to the atmosphere through the gas container 380 and the air springs 392, 394, 396, and 398 via the air outlet 360 or 350.

[0050] As shown in FIG. 7, in another embodiment, an exemplary method for designing a more efficient reciprocating piston compressor includes: a) a first compression stage 340 including a first piston adapted to compress a gas, such as the ambient gas 310, for example from a low pressure to a medium pressure, and connected to reciprocate within a first cylinder; a second compression stage including a second piston adapted to compress the gas from the medium pressure to a high pressure and connected to reciprocate within a second cylinder; and a motor connected to reciprocate the first piston within the first cylinder over a stroke and to reciprocate the second piston within the second cylinder over a stroke to provide a pneumatic compressor 166 (shown in FIG. 3); and b) starting from atmospheric pressure, establishing a sufficiently small number of strokes through which the gas to be pressurized passes.

[0051] Furthermore, as shown in FIG. 7, the method may further include pumping gas from a pressurized container 380 to the second compression stage 342 through an air inlet valve 320 to boost the air press process such that high pressure gas is present from the second stage compression 342.

[0052] As shown in FIG. 8, the method may further include pumping gas from a pressurized container 380 to the first compression stage 340 through an air inlet valve 210 to boost the air press process such that high pressure gas is present from the first stage compression 340. Since these are valves (not shown) passing through an electric motor 210 which are one-way or check valves, the gas from the pressurized container 380 will not escape to the atmosphere. Instead, the gas pumped from the pressurized container 380 may be mixed with the atmosphere and will be guided to the air inlet valve 210.

[0053] As shown in FIG. 9, the method may further include diverting a portion of the gas pumped from the pressure vessel 380 to the atmosphere through the solenoid valve 820 when the pressure is at or higher than the set pressure or a predetermined pressure. In another embodiment, the method may further include diverting a portion of the pressurized gas, for example, before proceeding to the first compression stage 340 and instead diverting it to the atmosphere through the air inlet valve 210 and the solenoid valve 820.

[0054] Further in FIG. 9, the method further includes transferring to a suspension system or an air spring of a vehicle. Additionally, the method may further include adjusting the dried pressurized gas by a solenoid valve, such as a solenoid valve, before transferring it to the air spring.

[0055] The main components of the air supply for an air suspension system including an air compressor, valves, and a control device are usually separately housed in separate vehicles as far as vibration technology is concerned. The components are connected by dedicated air pressure and electric wires that do not save much space, which leads to high application costs and high costs.

[0056] When supplying air to an air suspension system for an automobile, the concept of a single-stage compressor with a linear piston is usually used as the compressor. Such a compressor mostly has a crankcase embodied from synthetic material or die-cast aluminum driven by an electric motor, a cylinder with a cylinder head embodied from die-cast aluminum, and an air dryer embodied from synthetic material. Further, one or more valves, such as an inlet valve or an outlet valve, are attached to the cylinder head. The motor control of the electric motor is generally controlled by a mechanical relay and is not installed in the compressor, which in turn results in additional lines. Embodiments of the present invention will overcome the drawbacks of the prior art.

[0057] The housing of the electronic control device is preferably manufactured from a synthetic material and includes, in particular, the electronic connection to the vehicle electrical system. This is advantageously plugged in a sealed manner into the crankcase in order to provide protection against the influence of the environment.

[0058] The electronic connectors on the control device are used for all necessary signal lines and also for the entire power supply, as a result of which the assembly costs and application costs are clearly reduced.

[0059] The motor control of the electric motor is here integrated into the air supply section and is carried out by semiconductor switches. Furthermore, the control device can also perform the normal tasks of an air suspension system, such as level control and shock absorption control.

[0060] The internal electronic connections to the other components of the control device are preferably made by means of plug connections or press-in connections, as a result of which they are not affected by interference. The solenoid valve coil is connected to the electronic end stage of the control device using short connection contacts, as a result of which any possible interference is reduced. This improves electromagnetic compatibility. The short connection results in the voltage drop across the line being minimized and the power output of the solenoid valve increasing. As a result, a short insensitive regulating circuit is used, as a result of which, in addition to push-and-hold control, it is also possible to control the current control, for example to generate a lamp profile. The solenoid valve can be used with a higher, more reliable operating push current, as a result of which the structural volume of the solenoid valve can be reduced.

[0061] The diagnostic function for motor control can be reliably generated by the integrated air supply, and for example, operating data such as "compressor operation: yes / no" can be stored and evaluated. Due to the fact that normal electric wires are omitted otherwise, the entire diagnostic behavior and fail-safe behavior are improved. The influence of interference can be eliminated by the direct connection between the compressor, the solenoid valve block, and the control device. As a result, all connections and functions within the air supply unit can be monitored.

[0062] The integrated air supply unit is preferably used in an air suspension system for motor vehicles having the concept of closed air supply. In the case of this air suspension system, the components include a pneumatic compressor having an electric motor, an air dryer, a pneumatic valve and a pneumatic connector, as well as an electronic control unit.

[0063] This air suspension system is provided with an electronically controllable switching valve device having four 2 / 2-way control valves.

[0064] In the switching valve device, valves that can be switched independently of each other are installed such that the pressure difference is always in one direction and the higher pressure closes the valve. Due to the fact that the elastic force does not need to keep the sealing sheet closed against the pressure, an elastic element with a smaller elastic force can be installed, which in turn allows for smaller valves and coils.

[0065] Various operating states of the air suspension system are achieved by the switching valve device.

[0066] When the air suspension system operates in closed air supply, it is filled from the pressure storage device without using the compressor. All four switching valves are opened and the air suspension system is quickly filled by the large available cross-section. Similarly, the air suspension system is quickly emptied into the pressure storage device by all four open switching valves.

[0067] According to a further preferred embodiment, the switching valve device comprises four pilot-controlled 2 / 2-way control valves.

[0068] These valves have the advantage of being able to switch large pneumatic power because the power depends on pressure and volumetric current. The valves behave differently according to the flow-through direction or the pressure difference. Therefore, the opening holding pressure, the closing holding pressure, and the opening cross-sectional area can be designed as required. By using these valves, the overall usefulness is improved. Furthermore, the installation volume can be significantly reduced compared to known embodiments.

[0069] Those skilled in the art will understand that numerous modifications and / or changes can be made to the present invention without departing from the widely described scope of the present invention, as shown in the specific embodiments. Therefore, this embodiment should be considered illustrative in all respects and not restrictive.

[0070] The above has shown and described the basic principles, main features, and advantages of this patent application. Those skilled in the art should understand that this patent application is not limited by the above-described embodiments. The above-described embodiments and explanations are merely preferred examples of this patent application and are not intended to limit this patent application without departing from it. This utility patent application has various modifications and improvements on the premise of its spirit and scope, and these modifications and improvements are within the scope of the claimed utility patent application. The scope of protection claimed by the utility patent application is defined by the appended claims and their equivalents.

Claims

1. A method for designing a more efficient reciprocating piston compressor, comprising: a) providing a first compression stage including a first piston adapted to compress gas from a low pressure to an intermediate pressure and connected to reciprocate within a first cylinder, a second compression stage including a second piston adapted to compress gas from the intermediate pressure to a high pressure and connected to reciprocate within a second cylinder, and an electric motor connected to reciprocate the first piston over a stroke within the first cylinder and to reciprocate the second piston over a stroke within the second cylinder; b) setting the number of strokes during which the gas is pressurized starting from atmospheric pressure to be sufficiently small. A method comprising the above steps.

2. The method according to claim 1, further comprising the step of pumping gas from a pressurized container to the first compression stage.

3. The method according to claim 2, further comprising the step of mixing air with the gas pumped from the pressurized container.

4. The method according to claim 1, further comprising the step of pumping gas from the pressurized container to the second compression stage.

5. The method according to claim 1, further comprising the step of diverting a portion of the gas pumped from the pressurized container to the atmosphere when the pressure is higher than a set pressure.

6. The method according to claim 1, further comprising the step of diverting a portion of the pressurized gas to the atmosphere before the first compression stage.

7. The method according to claim 1, further comprising the step of drying the pressurized gas after the second compression stage.

8. The method according to claim 1, further comprising the step of monitoring the pressure of the pressurized gas using a pressure sensor.

9. The method according to claim 7, further comprising the step of transferring the dried pressurized gas to a pressurized container for storage.

10. The method according to claim 7, further comprising the step of transferring the dried pressurized gas to an air spring of a vehicle suspension system.

11. The method according to claim 10, further comprising the step of adjusting the dried pressurized gas by means of a solenoid valve before transferring it to the air spring.

12. A method for designing a more efficient reciprocating piston compressor, comprising: a) a first compression stage including a first piston adapted to compress gas from low pressure to intermediate pressure and connected to reciprocate within a first cylinder, and a second compression stage including a second piston adapted to compress gas from intermediate pressure to high pressure and connected to reciprocate within a second cylinder, and an electric motor connected to reciprocate the first piston over a stroke within the first cylinder and to reciprocate the second piston over a stroke within the second cylinder; b) providing a pneumatic compressor having an electric motor connected to reciprocate the first piston over a stroke within the first cylinder and to reciprocate the second piston over a stroke within the second cylinder; c) pumping gas from a pressurized container to the first compression stage to increase the output air pressure from the second compression stage; d) mixing the atmosphere with the gas pumped from the pressurized container; e) bypassing a portion of the gas pumped from the pressurized container to the atmosphere when the pressure is higher than a set pressure; f) bypassing a portion of the pressurized gas to the atmosphere before the first compression stage; g) drying the pressurized gas after the second compression stage; h) transferring the dried pressurized gas to an air spring of a vehicle suspension system. A method for designing a more efficient reciprocating piston compressor, the method comprising: a) providing a pneumatic compressor having a first compression stage including a first piston adapted to compress gas from low pressure to intermediate pressure and connected to reciprocate within a first cylinder, and a second compression stage including a second piston adapted to compress gas from intermediate pressure to high pressure and connected to reciprocate within a second cylinder, and an electric motor connected to reciprocate the first piston over a stroke within the first cylinder and to reciprocate the second piston over a stroke within the second cylinder; b) pumping gas from a pressurized container to the second compression stage to increase the output air pressure from the second compression stage. A method according to claim 18, further comprising drying the pressurized gas after the second compression stage. A method according to claim 13, further comprising mixing the atmosphere with the gas pumped from the pressurized container. A method according to claim 14, further comprising bypassing a portion of the gas pumped from the pressurized container to the atmosphere when the pressure is higher than a set pressure. A method according to claim 15, further comprising bypassing a portion of the pressurized gas to the atmosphere before the first compression stage. A method according to claim 16, further comprising drying the pressurized gas after the second compression stage. A method according to claim 17, further comprising transferring the dried pressurized gas to an air spring of a vehicle suspension system. A method for designing a more efficient reciprocating piston compressor, the method comprising: a) providing a pneumatic compressor having a first compression stage including a first piston adapted to compress gas from low pressure to intermediate pressure and connected to reciprocate within a first cylinder, and a second compression stage including a second piston adapted to compress gas from intermediate pressure to high pressure and connected to reciprocate within a second cylinder, and an electric motor connected to reciprocate the first piston over a stroke within the first cylinder and to reciprocate the second piston over a stroke within the second cylinder; b) pumping gas from a pressurized container to the second compression stage to increase the output air pressure from the second compression stage. A method according to claim 19, further comprising drying the pressurized gas after the second compression stage.

20. The method according to claim 18, further comprising the step of adjusting the pressurized gas dried by the solenoid valve before transferring it to the air spring.

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