Compressed air supply system, pneumatic system, vehicle and method for operating a pneumatic system, in particular an air suspension system of a vehicle

Abstract

Compressed air supply system (10) for operating a pneumatic system (90) in the form of a switchable open or closed compressed air supply system with a pneumatic system (90) connected via a switching valve arrangement (80), wherein the compressed air supply system (10) comprises: - an air supply (0) for supplying supply air to a compressor (50), which has a first compression volume (51) and a second compression volume (52) each for compressing the supply air to compressed air, - a compressed air supply (1) for providing the compressed air from the compressor (50), wherein the compressor (50) is designed as a two-cylindrical compressor with the first compression volume (51) and with the second compression volume (52), characterized in that - on the suction side of the compressor (50) both the first and the second compression volume (51, 52) are connected to the air supply (0), wherein the first and the second compression volume (51, 52) are connected to the air supply (0) in parallel such that the first and the second compression volume (51, 52) can draw in supply air together via the air supply (0) in both a first operating mode (MOD1) and a second operating mode (MOD2), and - on the pressure side of the compressor (50) for the provision of compressed air in the first operating mode (MOD1) the first and the second compression volume (51, 52) are switchably connected to the compressed air supply (1) and in parallel, and in the second operating mode (MOD2) only the first compression volume (51) is switchably connected to the compressed air supply (1), wherein In the first operating mode (MOD1), the first and second compression volumes (51, 52) can deliver compressed air to the compressed air supply (1) in a phase-shifted manner, and In the second operating mode (MOD2), the first compression volume (51) can supply compressed air to the compressed air supply (1), wherein in the second operating mode (MOD2), the second compression volume (52) can be switched off by means of a return valve (21) such that the second compression volume (52) cannot supply compressed air to the compressed air supply (1) in the second operating mode (MOD2), wherein - the return valve (21) can be pneumatically controlled by means of a control pressure line (45) to the return valve (21), which is designed to supply control pressure for pneumatic control of the return valve (21).

Description

[0001] The invention relates to a compressed air supply system for operating a pneumatic system according to the preamble of claim 1. The invention further relates to a pneumatic system and a vehicle with the compressed air supply system.

[0002] The invention also relates to a method for operating a compressed air supply system according to the preamble of claim 17.

[0003] A compressed air supply system is used in all types of vehicles, particularly for supplying compressed air to a vehicle's air suspension system. An air suspension system can also include a leveling system that can be used to adjust the distance between the vehicle axle and the vehicle body.

[0004] An air spring system can be implemented, for example, as a closed level control system as disclosed in EP 1 243 447 B1.

[0005] In principle, a compressed air supply system can also be implemented as an open compressed air supply system, i.e., with a vent connection. A closed or open compressed air supply system is typically used to operate a pneumatic system, such as the aforementioned air suspension system and / or level control system of a vehicle. Such a pneumatic system, designed as an air suspension system and / or level control system, is thus connected to the compressed air supply system to form a pneumatic system.

[0006] An air suspension system and / or level control system usually comprises a number of air bellows pneumatically connected to a common line (gallery), which can raise the vehicle body as they become increasingly inflated and lower it accordingly as they become less inflated. As the distance between the vehicle axle and the vehicle body or ground clearance increases, even larger uneven surfaces can be overcome without coming into contact with the vehicle body. Such systems are preferably used in off-road vehicles and sport utility vehicles (SUVs). Especially with SUVs and very powerful engines, it is desirable to have a comparatively low ground clearance for high speeds on the road on the one hand, and a comparatively high ground clearance for off-road use on the other.It is also desirable to implement a change in ground clearance as quickly as possible, which increases the demands on speed, flexibility, and reliability of a compressed air supply system. This applies particularly to compressed air supply systems designed to deliver comparatively large air volumes at comparatively high pressures when required, and which therefore feature a compressor with a first and second compression volume.

[0007] For example, DE 10 2008 034 240 A1 discloses a level control system for vehicles by the applicant, by which a vehicle body is cushioned relative to at least one vehicle axle and which has a two- or multi-stage compressor and is implemented as a closed level control system. The compressor has a first compression volume with a first intake chamber and a first compression chamber, with a pressure medium line connecting the first intake chamber of the compressor to the atmosphere. Furthermore, the compressor has a second compression volume with a second intake chamber and a second compression chamber, with the first compression chamber and the second intake chamber communicating with each other.It is possible to use a valve to ensure that the first compression volume of the compressor practically delivers in a circle, and to transfer the pressure medium sucked in and compressed in the first compression chamber via an outlet valve and the aforementioned switched-through valve into a pressure medium line in order to save the power of the first compression volume or to reduce it in a predetermined manner. From the aforementioned pressure medium line, the pressure medium is then transferred either into the first intake chamber or into the atmosphere. Such a system is thus capable of reducing or saving a first compression volume, so that only the second compression volume contributes to the compression of the pressure medium. However, such a level control system can still be improved in terms of its flexibility.

[0008] EP 2 222 488 B1, in contrast, shows a comparatively simply constructed closed level control system with a compressor, wherein, in a first operating mode, compression takes place in both a first compression volume and a second compression volume, and compressed air is fed into consumers of the level control system, so that a particularly large amount of air can be transferred into the level control system. For this purpose, a second compression volume can be added to the first compression volume via a 3 / 2-way valve; a suction chamber line of a first compression volume and an outlet line of a second compression volume are connected to the 3 / 2-way valve. In this way, in a first operating mode, compressed air can be transferred exclusively from a first compression volume to the outlet line.In another operating mode, the aforementioned suction chamber line can also be blocked and the aforementioned outlet line can be switched through, so that the second compression volume is connected to the first compression volume. The 3 / 2-way valve is electrically controlled for this purpose. In the latter case, in which both compression volumes are involved in delivering compressed air, the compressor delivers the maximum available compressed air. The connection of the second compression volume to the first compression volume is preferably used when the pressure in the suction chamber is low. Such a level control system can also be further improved in terms of its flexibility.

[0009] DE 103 21 771 A1 describes a method for limiting the power of a compressor which compresses an air flow to a predetermined pressure in at least two compression stages, wherein the compressed air flow is matched to the power capacity of an electric drive, characterized in that when the predetermined power limit of a compressor capable of higher power is reached, the pressure of at least one of the compression stages which is upstream of the last compression stage is adjusted to the pressure of its respective upstream compression stage.

[0010] The object of the invention is to provide an improved solution for a compressed air supply system. In particular, flexible operation should be enabled while maintaining a high volume and pressure output of the compressed air supply system. In particular, this should be realized for a pneumatic system comprising the aforementioned compressed air supply system and a pneumatic system, in particular in the form of a level control system and / or air suspension system of a vehicle. Preferably, the compressed air supply system and / or the pneumatic system and the pneumatic system should place a reduced load on a vehicle's electrical system. In particular, a compressed air supply system and / or a pneumatic system as well as a pneumatic system of the aforementioned type should be operable optionally as an open or closed system.Furthermore, it is an object of the invention to provide a vehicle having similar advantages and a method for operating a compressed air supply system and / or pneumatic system, in particular a pneumatic system.

[0011] The problem concerning the compressed air supply system is solved with a compressed air supply system of claim 1.

[0012] The invention relates to a compressed air supply system, in particular a switchable open or closed compressed air supply system, for operating a pneumatic system, preferably a pneumatic system connected via a switching valve arrangement, in particular a pneumatic system in the form of an air suspension system and / or level control system of a vehicle. The compressed air supply system comprises: an air supply for supplying supply air to a compressor, which has a first compression volume and a second compression volume, each for compressing the supply air into compressed air; a compressed air supply for providing the compressed air from the compressor, wherein the compressor is designed as a two-cylinder compressor with the first compression volume and the second compression volume.

[0013] According to the invention, it is provided that on the suction side of the compressor both the first and the second compression volume are connected to the air supply, wherein the first and the second compression volume are connected to the air supply in parallel such that the first and the second compression volume can jointly receive supply air via the air supply both in a first operating mode and in a second operating mode.

[0014] According to the concept of the invention, it is provided that on the pressure side of the compressor for providing the compressed air in the first operating mode (open operation), the first and the second compression volume are switchable and connected in parallel to the compressed air supply.

[0015] According to the concept of the invention, it is provided that in the second operating mode (closed operation) only the first compression volume is switchably connected to the compressed air supply.

[0016] In the first operating mode, the first and second compression volumes can deliver compressed air to the compressed air supply with a phase shift; thus connected in parallel and clocked. In the second operating mode, the first compression volume—in particular only the first compression volume—can deliver compressed air to the compressed air supply, wherein in the second operating mode, the second compression volume can be switched off by means of a return valve such that the second compression volume cannot deliver compressed air to the compressed air supply in the second operating mode. The return valve is pneumatically controllable by means of a control pressure line to the return valve, which is designed to carry control pressure for pneumatically controlling the return valve.

[0017] The compressed air supply system is in particular a switchable open or closed compressed air supply system for operating a pneumatic system, preferably a pneumatic system connected via a switching valve arrangement, in particular a pneumatic system in the form of an air suspension system and / or level control system of a vehicle.

[0018] The invention also relates to a pneumatic system comprising the aforementioned compressed air supply system and a pneumatic system, in particular in the form of an air spring system and / or a level control system of claim 14. The invention also relates to a vehicle of claim 15.

[0019] The object relating to the method is achieved according to the invention with a method for operating a compressed air supply system and / or pneumatic system according to claim 17.

[0020] The invention is based on a method for operating a pneumatic system, preferably a pneumatic system connected via a switching valve arrangement, in particular a pneumatic system in the form of an air spring system and / or level control system of a vehicle, wherein the compressed air supply system, in particular a switchably open or closed compressed air supply system, comprises: - an air supply to a compressor having a first compression volume and a second compression volume, each for compressing the supply air to compressed air, - a compressed air supply for providing the compressed air from the compressor, wherein the compressor is designed as a two-cylinder compressor with the first compression volume and with the second compression volume.

[0021] According to the invention, it is provided that on the suction side of the compressor, both the first and the second compression volume are connected to the air supply, wherein the first and the second compression volume are connected to the air supply in parallel such that the first and the second compression volume can jointly receive supply air via the air supply both in a first operating mode and in a second operating mode, which in this respect can be operated in particular in parallel and in a clocked manner, and - on the pressure side of the compressor for providing the compressed air in the first operating mode, in the first operating mode, the first and the second compression volume are switchably connected to the compressed air supply and in parallel, and in the second operating mode, only the first compression volume is switchably connected to the compressed air supply, the method comprising the steps: - delivering compressed air in the first operating mode, wherein the first and second compression volumes deliver compressed air to the compressed air supply in a phase-shifted manner, and - Dispensing compressed air in the second operating mode, wherein the second compression volume can be switched off by means of a return valve such that the second compression volume cannot deliver compressed air to the compressed air supply in the second operating mode, wherein the return valve is pneumatically controlled by means of a control pressure line to the return valve for pneumatically controlling the return valve.

[0022] In particular, the first operating mode (open operation) of the compressed air supply system is assigned a first switching state of the return valve, preferably for pneumatically separating the line of the return valve in order to prevent a flow of compressed air, and the second operating mode (closed operation) of the compressed air supply system is assigned a second switching state of the return valve, preferably for pneumatically connecting the line of the return valve in order to enable a flow of compressed air.

[0023] It is preferably provided that in the second operating mode only the first compression volume can deliver compressed air to the compressed air supply, in particular only the first compression volume can operate in compression mode.

[0024] Taking the aforementioned aspects into account, the invention is based on a compressed air supply system of the type mentioned at the outset, which essentially comprises: an air supply and a compressed air supply, wherein the compressor is designed as a two-cylinder compressor with a first compression volume and a second compression volume. In principle -- presented in simplified terms -- in a first operating mode, the first and second compression volumes should be able to deliver compressed air, and in a second operating mode, only the first compression volume should be able to deliver compressed air. The invention has further recognized that it is advantageous if the compressor is capable of operating with both compression volumes in parallel; thus, in contrast to the sequential switching of a first and second compression volume provided for in the prior art.

[0025] In this respect, the concept of the invention is such that on the suction side of the compressor, both the first and the second compression volume are connected to the air supply, wherein the first and the second compression volume are connected to the air supply in parallel such that the first and the second compression volume can jointly receive supply air via the air supply both in a first operating mode and in a second operating mode, but on the pressure side of the compressor, in order to provide the compressed air in the first operating mode, the first and the second compression volume are switchably connected to the compressed air supply and in parallel, and in the second operating mode only the first compression volume is switchably connected to the compressed air supply.

[0026] According to the invention, it is provided that in the first operating mode, the first and the second compression volume can deliver compressed air to the compressed air supply (1) in a phase-shifted manner, and in the second operating mode, the first compression volume can deliver compressed air to the compressed air supply, wherein in the second operating mode, the second compression volume can be switched off by means of a return valve in such a way that the second compression volume cannot deliver compressed air to the compressed air supply in the second operating mode.

[0027] The first operating mode is also referred to below as "open operation," and the second operating mode as "closed operation." The return valve is pneumatically controlled via a control pressure line to the return valve, which is designed to supply control pressure for pneumatically controlling the return valve.

[0028] The concept of the invention has the advantage of enabling joint compressed air generation from the first and second compression volumes, which are connected in parallel to the compressed air connection. This increases the flexibility and speed of available compressed air generation.

[0029] Furthermore, the concept of the invention provides the basis for a more advantageous design of the compressed air supply system. Thus, within the scope of an advantageous option for regenerating the air dryer, i.e., while venting the pneumatic system, or in the manner mentioned in the first and / or second operating mode, compressed air can also be delivered to the vent connection or only to the vent connection.

[0030] Furthermore, the concept of the invention offers the possibility of designing the first and second compression volumes similarly, which has numerous advantages when implementing the compressor. In particular, the return valve arrangement is designed such that in the second operating mode, only the first compression volume can deliver compressed air to the compressed air connection. With a similar design of the first and second compression volumes, it is particularly advantageous to expand the concept such that in the second operating mode, only the second compression volume is capable of delivering compressed air to the compressed air connection and / or the vent connection. Advantageously, within the scope of a further development, the return valve arrangement can be used to select as required which of the first compression volume or the second compression volume is capable of delivering compressed air to the compressed air connection.

[0031] For this reason, the invention explicitly conceives less of a switching valve arrangement as in the prior art for connecting a second compression volume or disconnecting a first compression volume, but rather a return valve arrangement with a return valve preferably connected between the pressure side and the suction side of the compressor. According to the invention, in the second operating mode, the second compression volume is switched off by means of a return valve, wherein the return valve is pneumatically controlled, and the control pressure in a control pressure line is guided to the return valve for pneumatic control.

[0032] The invention recognizes that this results in the aforementioned synergies and is also capable of implementing at least one return valve, preferably at least a first and a second return valve, in the return valve arrangement without significant additional effort. The concept of the invention nevertheless makes it possible to provide different switching states for both a gallery of a pneumatic system and a compressed air reservoir of the pneumatic system.

[0033] Advantageous further developments of the invention can be found in the subclaims, which implement the concept of the invention within the scope of the task with further advantages.

[0034] Preferably, at least via the return valve, the first and / or second compression volume is switchably connected to the compressed air supply on the pressure side of the compressor, and / or the first and / or second compression volume is switchably connected to the air supply on the suction side of the compressor. A main pneumatic line comprising an air dryer and a compressed air connection to a switching valve arrangement can be connected to the compressed air supply. The compressed air supply with the main pneumatic line can be connected between a first part and a second part of a connecting line, wherein the connecting line is connected between the first and second compression volumes.

[0035] Within the scope of a particularly preferred development, the return valve arrangement comprises a return valve connected between the pressure side and the suction side of the compressor and / or a second isolating valve connected on the pressure side between the first and the second compression volume. The development has recognized that the implementation of the return valve arrangement with the return valve and the isolating valve increases the flexibility of operation of the return valve arrangement and, at the same time, offers a comparatively simple implementation compared to a comparatively complex switching valve, in particular a 3 / 2-way valve, of the prior art. In particular, this enables advantageous operation in the first operating mode, in which the first and the second compression volume are connected in parallel and can jointly deliver compressed air to the compressed air connection.

[0036] Advantageously, the return valve connected between the pressure side and the suction side of the compressor, a 2 / 2-way valve, and / or a check valve connected on the pressure side between the first and second compression volumes are a non-return valve. Both options can be implemented individually, alternatively, or in combination for the return valve arrangement. The aforementioned option of a return valve in the form of a 2 / 2-way valve is a comparatively simple option; other options for implementing a return valve also exist.

[0037] Furthermore, a return valve arrangement preferably comprises at least the return valve and / or a separating valve. The first and / or second compression volumes are preferably connected on the pressure side to the compressed air supply via the return valve arrangement in a line.

[0038] Specifically, the following arrangements of a separating valve and / or a corresponding control pressure line have proven advantageous. In particular, a second and / or further separating valve can be arranged on the outlet side of the outlet valve of the first or second compression volume. The second and / or further separating valve can be arranged in the discharge line of the first or second compression volume.

[0039] The first and / or further isolating valve can be arranged in the supply line of the first or second compression volume. For example, in a first preferred variant, the first and / or further isolating valve can be arranged in the supply line upstream of the inlet valve of the first or second compression volume in the flow direction.

[0040] For example, in a second preferred variant, the first and / or further separating valve can be arranged in the supply line in the flow direction of the inlet valve of the first or second compression volume after the inlet valve.

[0041] Preferably, the first and / or second isolating valve is a check valve opening in the direction of the compressed air supply.

[0042] Implementing the first, second, and / or further isolation valves as check valves is a comparatively simple option; there are also other options for implementing the second isolation valve, e.g., as a 2 / 2-way valve. In particular, the first and / or second isolation valve is a 2 / 2-way valve of a recirculation valve arrangement.

[0043] A synergistic combination of a 2 / 2-way valve and a check valve has the advantage that it is not only simple to implement, but also pneumatically controllable. This has the advantage that the need for electrical control of the return valve arrangement by the vehicle's electrical system is largely eliminated. Preferably, the inlet valve of the first or second compression volume is integrated into the first and / or second isolation valve, or the first and / or second isolation valve acts on the inlet valve of the first or second compression volume in such a way that the inlet valve remains closed when the first and / or second isolation valve is pressurized.

[0044] Thus, in a further development, it is particularly advantageous that the return valve connected between the pressure side and the suction side of the compressor is pneumatically controllable. It is particularly advantageous that the return valve can be controlled with a suction-side control pressure. This can be provided relatively easily from a compressed air reservoir or a gallery of the pneumatic system. Preferably, it is provided that a line to the second compression volume - the control pressure line to a bypass line of the line, and / or - the control pressure line to a supply line of the line, and / or - the control pressure line is connected to a discharge line of the line.

[0045] In particular, an adjustable threshold pressure can be provided for the return valve or further return valve and / or for the first or further isolation valve. The threshold pressure can advantageously be adjusted via the valve spring of the return valve or the valve spring of the isolation valve.

[0046] Preferably, the return valve is only transferred from a first switching state to a second switching state when the pressure in the control line exceeds a threshold value. The first switching state is assigned, in particular, to the first operating mode. The second switching state is assigned, in particular, to the second operating mode. The threshold value of the return valve is preferably adjustable in a range from 2 bar to 8 bar above atmospheric pressure.

[0047] The first, second, or further return valve in the form of a 2 / 2-way valve can be implemented relatively easily as a 2 / 2-way valve that opens against a valve spring force. Additionally or alternatively, the isolation valve in the form of a check valve can be implemented relatively easily as a check valve that opens automatically against a valve spring force, so that electrical control of the second isolation valve can also be omitted.

[0048] The compressed air supply system is advantageously further developed by a vent connection, wherein the first and / or second compression volumes are connected to the vent connection on the pressure side of the compressor. A further isolating valve of the return valve arrangement is assigned to the vent connection, wherein the further isolating valve switchably pneumatically separates a vent line from the vent connection, preferably without actuation. The further isolating valve is preferably designed as a 2 / 2-way valve.

[0049] The recirculation valve arrangement can be particularly advantageously adjusted so that it separates pneumatically in the uncontrolled state. Preferably, in the first operating mode, the first and / or second recirculation valve—preferably the 2 / 2-way valve—connected between the pressure side and the suction side of the compressor pneumatically separates the pressure side and the suction side of the compressor, in particular pneumatically separates it when uncontrolled. This means that, in particular in the case of a pneumatically controlled first and / or fourth recirculation valve, preferably the 2 / 2-way valve, this pneumatically separates the pressure side and the suction side in the event that no pressure is applied to the first and / or fourth recirculation valve, in particular on the suction side.

[0050] In the second operating mode, it is preferably provided that the first and / or fourth return valve, which is connected between the pressure side and the suction side of the compressor, preferably in a controlled manner, pneumatically connects the pressure side and the suction side of the compressor. In particular, it is provided that, in the event of a pressure applied on the suction side (in particular used as a control pressure), once a threshold pressure is reached, the first and / or fourth return valve opens automatically, i.e., pneumatically controlled, against the spring force of the valve spring. Thus, while the pressure side and suction side of the compressor are pneumatically separated in the pneumatically uncontrolled state of the first and / or fourth return valve (pneumatically open state of the first return valve), both compression volumes of the compressor are able to draw in air from the environment from the air supply in parallel and together and to convey compressed air to the compressed air connection in a similarly joint and parallel manner.

[0051] In the second operating mode, however, only the second compression volume can deliver compressed air to the compressed air connection. For this purpose, a second return valve connected on the pressure side between the first and second compression volumes can keep a check valve that automatically opens from the second compression volume toward the first compression volume closed. The compressed air generated by the first compression volume is thus instead pumped into the main pneumatic line, against the blocking direction of the check valve.

[0052] With regard to the pneumatic system, it has proven advantageous to connect a switching valve assembly to the compressed air connection, which is designed to selectively supply compressed air to a first or second compressed air reservoir of a pneumatic system. A first compressed air reservoir can be, in particular, a bellows, and a second compressed air reservoir can be, in particular, a pressure accumulator of a vehicle's air suspension system.

[0053] It has proven advantageous for the switching valve arrangement to have a first pair of isolation valves and / or a second pair of isolation valves. A bellows and / or a pressure accumulator of a vehicle's air suspension system can optionally be pressurized with compressed air, and the switching valve arrangement comprises: a pair of bellows valves, in particular a first pair of 2 / 2-way valves, assigned to the first compressed air reservoir and / or a pair of accumulator valves, in particular a second pair of 2 / 2-way valves, assigned to the second compressed air reservoir.

[0054] In this respect, a first pair of isolation valves can be assigned to a gallery with one or more bellows of an air suspension system, and / or a second pair of isolation valves can be assigned to a pressure accumulator of the pneumatic system. The first and / or second pair of isolation valves is preferably formed as a first and / or second pair of 2 / 2-way valves.

[0055] Preferably, the switching valve arrangement can alternatively also have a first 3 / 2-way valve which is assigned to the compressed air reservoir and / or a second 3 / 2-way valve which is assigned to the second compressed air reservoir.

[0056] In a particularly preferred embodiment, all or some of the above-mentioned valves of the return valve arrangement are pneumatically controlled, in particular opening automatically against a valve spring force.

[0057] Alternatively or additionally, one, some or all of the valves of the switching valve arrangement can also be implemented as electrically controlled valves (e.g. solenoid valves) with electrical control.

[0058] In a particularly preferred embodiment, all or some of the valves of the aforementioned switching valve arrangement are preferably pneumatically controlled, i.e., they open automatically against the pressure of a valve spring force. Alternatively or additionally, one, some, or all of the valves of the switching valve arrangement can also be implemented as electrically controlled valves, i.e., in particular, with electrical control.

[0059] The compressor preferably has a first check valve as an inlet valve of a first compression volume and a second check valve as an inlet valve of a second compression volume.

[0060] The compressor further preferably has a first check valve as the outlet valve of the first compression volume and a second check valve as the outlet valve of the second compression volume.

[0061] Furthermore, the compressed air supply system preferably has a first check valve at the air supply and a second check valve at the compressed air connection. In particular, the second check valve at the compressed air connection can be arranged parallel to a throttle, which is advantageous for the regeneration of the air dryer.

[0062] These and other preferred developments and embodiments of the invention are the subject of the dependent claims and drawings and specify both the compressed air supply system and the method with regard to particularly advantageous embodiments, preferably with respect to an air suspension system of a vehicle. However, as explained in the context of the general aspect of the invention, the concept of the invention is not limited to the development relating to an air suspension system and / or level control system of a vehicle.

[0063] In particular, such embodiments of the invention are described below with reference to the drawings. These are not necessarily intended to represent the embodiments to scale; rather, where useful for explanation, the drawings are schematic and / or slightly distorted. With regard to additions to the teachings immediately apparent from the drawings, reference is made to the relevant prior art. It should be noted that various modifications and changes to the form and detail of an embodiment can be made without deviating from the general idea of ​​the invention. The features of the invention disclosed in the description, in the figures of the drawings and in the claims can be essential for the further development of the invention, both individually and in any combination.In addition, all combinations of at least two of the features disclosed in the description, the figures and / or the claims fall within the scope of the invention.

[0064] The general concept of the invention is not limited to the exact form or detail of the preferred embodiment illustrated and described below, nor is it limited to an object that would be limited compared to the object claimed in the claims. In the case of specified dimensioning ranges, values ​​within the stated limits are also intended to be disclosed as limit values ​​and can be used and claimed as desired. Identical or similar parts, or parts with identical or similar functions, are provided with the same reference numerals where appropriate for the sake of simplicity.

[0065] Further advantages, features, and details of the invention will become apparent from the following description of the preferred embodiments and from the following drawings. The drawing shows in detail: Fig. 1 a particularly preferred embodiment of a pneumatic system with a compressed air supply system, wherein a pneumatically controllable return valve with a control pressure line is provided on a bypass line, and with a pneumatic system in the form of an air suspension system and level control system of a vehicle, wherein the pneumatic system is implemented as an optionally open system of the compressed air supply system and pneumatic system in a first operating mode of the return valve or a closed system of the compressed air supply system and pneumatic system in a second operating mode of the return valve and the pneumatic system additionally has a vent connection that can be switched via an isolating valve designed as a check valve; Fig. 2A shows a further embodiment of a pneumatic system with a compressed air supply system, wherein the return valve is arranged in the supply line of the second compression volume - this in combination with a check valve as an inlet valve; Fig. 2B one to Fig. 2A slightly modified embodiment of a pneumatic system with a compressed air supply system, wherein the inlet valve of the second compression volume is integrated as a check valve in the return valve, Fig. 3 a particularly preferred embodiment of a pneumatic system with a compressed air supply system similar to the Fig. 1, wherein a pneumatically controllable return valve with a control pressure line is provided on a bypass line for a second compression volume and an electrically controllable further return valve with a control pressure line is provided on a bypass line for a first compression volume; Fig. 4 the design of the pneumatic system of the Fig. 1 in a switching state of a return valve arrangement with the return valve and the isolating valve designed as a check valve for the first operating mode (open operating mode), in which the pressure and suction sides are pneumatically separated by means of the return valve, i.e. the return valve separates pneumatically in an uncontrolled manner, such that the first and the second compression volume can deliver compressed air to the compressed air supply in a phase-shifted manner; Fig. 5 the embodiment of a pneumatic system of Fig. 1 in a switching state of a return valve arrangement with the return valve and the isolating valve designed as a check valve for the second operating mode (closed operation), in which the return valve pneumatically connects the pressure and suction sides, i.e. pneumatically connects in a pneumatically controlled state, so that only the first compression volume delivers compressed air to the compressed air supply; Fig. 6 a first embodiment of a switching valve arrangement for connecting a pneumatic system of the Fig. 1, wherein the switching valve arrangement is formed in the manner described with a first pair of 2 / 2-way valves and a second pair of 2 / 2-way valves; Fig. 7 an alternative embodiment of a switching valve arrangement for a pneumatic system of the aforementioned Fig. 1, wherein the switching valve arrangement comprises a first 3 / 2-way valve and a second 3 / 2-way valve; Fig. 8 a schematic representation of a vehicle with a pneumatic system of Fig. 1, wherein a vehicle control unit (ECU) is configured to specify a first and second operating mode for the pneumatic system, and wherein the return valve arrangement is pneumatically controlled and the switching valve arrangement is electrically controlled.

[0066] Fig. 1 shows a particularly preferred embodiment of a pneumatic system 100 with a compressed air supply system 10 and a pneumatic system 90, wherein the pneumatic system 90 is designed in the form of an air spring system 90', which also serves as a level control system. For this purpose, the pneumatic system 90 has a plurality of branch lines 98 pneumatically connected to a gallery 95, to each of which a bellows 91 of an air spring is connected. An electrically controlled 2 / 2-way valve 93 is connected upstream of each bellows 91 for pneumatically releasing or pneumatically disconnecting the branch line 98. The 2 / 2-way valve 93 is designed as a solenoid valve for this purpose. Also connected to the gallery 95 is a pressure sensor 94, by means of which the pressure p in the gallery 95 can be measured. The pneumatic system 90 also includes a compressed air reservoir 92, which is connected to another branch line 99.

[0067] The aforementioned compressed air supply system 10 serves to operate the pneumatic system 90 and to supply it with compressed air or to discharge the compressed air from the pneumatic system 90, specifically from the bellows 91 and / or the compressed air reservoir 92; the pneumatic system 100 comprising the compressed air supply system 10 and the pneumatic system 90 also enables the transfer of compressed air between the bellows 91 and / or the compressed air reservoir 92.

[0068] The compressed air supply system 10 provides compressed and dried air as compressed air at a compressed air connection 2. The air is sucked in via an air supply 0, namely via an air filter 0.1 and a check valve 0.2 via a supply line 0.3 to the air supply 0, compressed in a compressor 50, and made available at the compressed air supply 1. In the present case, the compressor 50 is a compressor with a first compression volume 51 and a second compression volume 52, each for compressing the supply air into compressed air. A compressed air supply 1 is designed to provide the compressed air from the compressor, wherein the compressor is designed as a two-cylinder compressor with the first compression volume 51 and the second compression volume 52 operable in parallel in a clocked manner.On the suction side of the compressor 50, both the first and the second compression volumes 51, 52 are connected to the air supply 0, wherein the first and the second compression volumes 51, 52 are connected to the air supply 0 in parallel such that the first and the second compression volumes 51, 52 can jointly receive supply air via the air supply 0 in both a first operating mode and a second operating mode. On the pressure side of the compressor 50, for providing the compressed air in the first operating mode, the first and the second compression volumes 51, 52 are switchable and connected in parallel to the compressed air supply 1. For the sake of clarity, the first and the second compression volumes 51, 52 are additionally designated "1" and "2" throughout the drawing.

[0069] The compressed air generated in this way is then passed through an air dryer 61 in the main pneumatic line 60 for drying and then made available at the compressed air connection 2, namely by passing the compressed air through the air dryer and then through an automatically opening check valve 62 of the main pneumatic line 60 to the compressed air connection 2.

[0070] Conversely, when venting a bellows 91 or the compressed air reservoir 92 with the check valve 62 closed, the compressed air to be vented is fed via the regeneration throttle 63, in turn, via the air dryer 61 to the compressed air supply 1—while regenerating the air dryer and removing moisture from it—to a vent connection 3. The compressed air can finally be vented to the environment via the vent line 70 through a silencer 71; for this purpose, an isolating valve 23 can be electrically controlled as a vent valve, namely here as a 2 / 2-way valve, and pneumatically connect the vent connection 3 to the silencer 71 in the vent line 70.

[0071] For this purpose, the compressed air supply 1 and the vent connection 3 are connected to the main pneumatic line 60 and the vent line 70, respectively, on a connecting line 40 of the compressor 50. The above-mentioned supply line 0.3 is also connected to the connecting line 40 via the air supply 0.

[0072] Within the scope of the concept of the invention, the embodiment of the compressed air supply system 10 has particularly noteworthy features, which are explained below.

[0073] On the one hand, as explained above, the compressor 50 is connected to the connecting line 40 as a compressor with a first compression volume 51 and, in parallel, with a second compression volume 52 via the connecting line 40 to the air supply 0. The first and second compression volumes 51, 52 are connected in parallel to the air supply 0 in such a way that these first and second compression volumes 51, 52, as explained above, can draw in air together and overall essentially simultaneously, albeit out of phase, i.e. in a clocked manner, via the air supply 0. In the present case, the compressor is therefore a compressor (TWIN compressor) with the first compression volume 51 and the second compression volume 52, whereby reference is made below to the compression volumes.In this respect, the description of the following embodiments also marginally applies to compressors whose first and second compression volumes are designed as first and second compressor stages; however, according to the concept of the invention, the present embodiment is not a two-stage compressor but rather a two-cylinder compressor, as referred to here.

[0074] The compressor 50 is driven in the present case by a motor M and crankshaft and connecting rod connections, which are not designated in more detail and are only symbolically represented, so that this mechanism moves the pistons, which are only symbolically represented here, back and forth in the first and second compression volumes 51, 52; this leads to the compression of the air sucked in via the first and second check inlet valves 41, 42 on the connecting line 40 in the first and second compression volumes 51, 52. The compressed air can in the present case -- following the inventive concept -- be passed on from the first and / or second compression volumes 51, 52 and via a first and / or second check outlet valve 43, 44 and the connecting line 40 to the compressed air supply 1.

[0075] According to the concept of the invention, the first and second compression volumes 51, 52 are connected in parallel to the connecting line 40 and the compressed air supply and then via the main pneumatic line 60 to the compressed air connection 2, so that compressed air can be delivered jointly and overall essentially simultaneously, although out of phase, ie in this respect clocked, to the compressed air supply 1 and the compressed air connection 2.

[0076] For this purpose, the compressed air supply system 10, following the concept of the invention, has a return valve arrangement 20, which in this case comprises three valves. The return valve 21 of the return valve arrangement 20 is connected in a bypass line 30 between the pressure side DS and the suction side SS of the compressor 50; in this respect, the return valve 21 could also be referred to as a bypass valve - ultimately, it serves to relieve the pressure of the second compression volume 52 even when it is compressing, as explained below. The control pressure line 45 to the return valve is also connected to the bypass line 30 for transmitting a control pressure p to the pneumatic piston 46 of the return valve 21. In addition, an isolating valve 22 is connected in the outlet line or the connecting line 40, referred to here as such, on the pressure side between the first and second compression volumes 51, 52.Another isolating valve 23, already explained above, is arranged in the vent line 70 as a vent valve.

[0077] Thus, the return valve arrangement 20 in the present case comprises a return valve 21, referred to here as such, in the form of a pneumatically controlled 2 / 2-way valve, wherein a control line 45 for branching off a control pressure is provided to the pneumatic piston 46 for controlling the return valve 21, which is designed here as a pneumatically controlled 2 / 2-way valve, and then the pneumatically controlled 2 / 2-way valve opens against the force of a valve spring 21F.

[0078] The optional isolation valve 22 can be designed in the form of a self-opening check valve RV, which opens against the force of a valve spring 22F - namely when a threshold pressure is applied in the connecting line 40.

[0079] The further optional isolating valve 23 of the return valve arrangement 20, which serves as a vent valve, is connected in the vent line 70 and, when a corresponding electrical control signal is applied to the solenoid, opens the vent line 70 against the spring force of the valve spring 23F.

[0080] Furthermore, the pneumatic system 100 comprises a pneumatic system 90 in the form of an air spring and level control system and a switching valve arrangement 80, which is designed to selectively supply compressed air to a first or second compressed air reservoir—here, the bellows 91 and / or the compressed air accumulator 92—of the pneumatic system 90 or to vent it. The isolating valve arrangement 80 has a venting switching valve 81, which pneumatically connects the corresponding filling line 85 between the compressed air connection 2 and the isolating valve arrangement 80 to vent the gallery 95. The switching valve arrangement 80 also has a second switching valve 82 as a venting valve, which is designed to vent the gallery 95 to the connecting line 40 via a venting line 87. The first switching valve 81 separates the corresponding filling line 85, while the further pneumatic vent line 87 is opened via the second switching valve 82, ieis pneumatically connected.

[0081] In a similar manner, the compressed air reservoir 92 can be filled via a third switching valve 83 in a corresponding further filling line 86 and vented via a corresponding fourth switching valve 84 in a further vent line 87.

[0082] The Fig. 1 is therefore essentially a closed pneumatic system in the form of a closed air spring and level control system. The pneumatic system 100 has a particularly preferred addition of an optional isolating valve 23 acting as a vent valve, namely the aforementioned return valve arrangement 20 with the return valve 21 and the optional further isolating valve 22 in the form of a pneumatically controllable 2 / 2-way valve or a self-opening check valve RV - all with corresponding valve springs 21F, 22F and 23F, respectively, and thus opening against a spring force. As can be seen from the description of Fig. 4 and Fig. 5 -- the compressed air supply system 10 is a switchable open or closed compressed air supply system 10.

[0083] Fig. 2A shows a further embodiment of a pneumatic system with a compressed air supply system, wherein the first return valve 21 is arranged in the supply line 30.1 of the second compression volume 51, 52—in combination with a check valve, which in this case is implemented separately from the return valve 21 and is referred to as an inlet valve 42. Such a return valve 21 can also be arranged additionally or alternatively (not shown) on the output side of the outlet valve 44 of the second compression volume 52 as a further or alternative return valve.

[0084] Fig. 2B shows a Fig. 2A shows a modified embodiment of a pneumatic system with a compressed air supply system, wherein the inlet valve 42 of the second compression volume is integrated into the return valve 21 as a check valve. Additionally or alternatively (not shown), another such return valve can also be arranged on the outlet side of the outlet valve 44 of the second compression volume 52, wherein the outlet valve 44 of the second compression volume 52 is integrated into the other such return valve. According to the embodiment of a pneumatic system of Fig. 2A and Fig. 2B, the return valve 21 is not integrated in a bypass line 30 to the second compression volume 52 but in a supply line 30.1, 30.2 of the second compression volume 52 ( Fig. 2A) or in a discharge line (not shown). In this case, the return valve 21 could also be described as a modified inlet or outlet valve—ultimately, it also serves to relieve pressure on the second compression volume 52 even when it is compressed, as will become clear below.

[0085] Fig. 3 shows a particularly preferred embodiment of a pneumatic system with a compressed air supply system similar to the Fig. 1, wherein a pneumatically controllable first return valve 21 and the control pressure line are connected to a bypass line 30 and an electrically controllable second return valve 24 and the control pressure line are connected to a bypass line 30'. According to the embodiment of the Fig. 3, for such a separating valve arrangement 20, in addition to the return valve 21 and the first and second separating valves 22, 23, a further return valve 24 can also be provided, which also has an adjustable threshold pressure; preferably a threshold pressure that can be adjusted pneumatically, electronically, and / or by means of a valve spring. In this respect, within the scope of a further development, the return valve arrangement can have a second or even further return valve 24—namely, to relieve the first compression volume and / or possibly further compression volumes as needed via a bypass line, analogous to the functioning of the first return valve 21.

[0086] In particular, according to the further embodiment of the Fig. 3 -- a second return valve 24 connected between the pressure side and the suction side of the compressor 50, --namely according to the further embodiment of the Fig. 3--preferably a second return valve 24 connected in a second bypass line 30' of the line, preferably a second return valve 24 connected between the pressure side and the suction side of the compressor 50 as an electrically or pneumatically controllable valve, designed to pneumatically control the control pressure, preferably via a control pressure line to the second return valve 24 as shown in Fig. 3 is shown.

[0087] In a first operating mode, in particular in a first switching state of the return valve, it could then --according to the further embodiment of the Fig. 3-- the first and / or second return valve 21, 24 connected between the pressure side and the suction side of the compressor 50, preferably uncontrolled, pneumatically separates the pressure side and the suction side of the compressor 50.

[0088] In the second operating mode, in particular in a second switching state of the return valve, the first and / or second return valve 21, 24 connected between the pressure side and the suction side of the compressor 50 can, preferably in a controlled manner, pneumatically connect the pressure side and the suction side of the compressor (50), in particular the first and / or second return valve 21, 24 can have an adjustable threshold pressure, preferably a threshold pressure that can be adjusted by means of a valve spring.

[0089] Fig. 4 and Fig. 5 now show preferred operating modes of the compressed air supply system for operating the pneumatic system, i.e., for operating the pneumatic system 100, with the lines supplied with compressed air being shown in bold. The pneumatic system 100 comprises --as in Fig. 4 and Fig. 5 shows the compressed air supply system 10 and the pneumatic system 90 as well as the switching valve arrangement 80 connected between them at the compressed air supply connection 2.

[0090] Using the example of filling the compressed air reservoir 92, Fig. 4 shows a first operating mode (open operation), in which the first return valve 21 in the bypass line 30 pneumatically separates the bypass line 30, i.e., prevents a flow of compressed air, namely in the non-pneumatically controlled state; i.e., no pressure p is applied to the control line 45, which therefore also does not apply to the control piston 46.

[0091] As already indicated above, the air sucked in via the air supply 0 is sucked in on the suction side of the compressor via the first and second compression volumes 51, 52 connected in parallel, in particular in a cyclic manner, via the air supply 0. The air flow shown in bold indicates the joint and parallel operation of the first and second compression volumes 51, 52, wherein in the first operating mode shown here (open operation of the compressed air supply system 10), the first and second compression volumes 51, 52 also jointly deliver compressed air to the compressed air supply 1 and the compressed air connection 2.

[0092] The compressed air is thus guided through the connecting line 40, while the motor M drives the twin compressor 50 (TWIN compressor). As already explained above, the compressed air is fed via the first and second output isolation valves 43, 44, each in the form of a check valve, to the air supply 1 and then to the main pneumatic line 60, dried in the air dryer 61, and passed through the throttle 63 to the compressed air supply 2. The compressed air reaches the compressed air reservoir 92 via the filling line 86 and the open third switching valve 83. For this first operating mode, only the inlet check valve 0.2, from the intake filter 0.1 to the air supply 0, is open. The compressed air flows from the compressed air supply 1 via the dryer 63 and the compressed air supply 2, and finally via the third switching line 86 to the compressed air reservoir 92.

[0093] Similarly, when the third switching valve 83 is closed and the filling line 86 is thus closed, the first switching valve 81 can open so that the compressed air from the compressed air supply 2 can be guided via the further filling line 85 from the compressed air supply connection 2 to the gallery 95.

[0094] With the corresponding function, the second and third switching valve 82, 84 are available for venting, which is exemplified by Fig. 5 is shown. Fig. 5 explains the second operating mode, the venting of a bellows 91, in this case two bellows 91. The corresponding isolating valves 93 arranged upstream of the bellows 91 are opened as a 2 / 2-way valve, and the compressed air can be discharged to the connecting line 40 via the second switching valve 82 and the vent line 87.

[0095] When the second switching valve 82 is open, a bellows pressure from one of the bellows 91 is applied via the vent line 87 and the connecting line 40 to the control line 45, and thus as control pressure p on the control piston 46 of the return valve 21. The bellows pressure thus serves as control pressure p for the pneumatic actuation of the return valve 21, which, as shown in Fig. 5 into the pneumatically connecting position and pneumatically connects the bypass line 30, ie makes a compressed air flow possible.

[0096] While in Fig. 4 shown first operating mode (open operation) the high-volume conveying of compressed air is in the foreground, since the first and the second compression volume 51, 52 are operated in parallel and phase-shifted - that is to say insofar as together but clocked - sucks in air and also conveys compressed air - is in the case of the in Fig. In the second operating mode shown in Figure 5, the return valve 21 connected between the pressure side and the suction side DS, SS of the compressor 50 is pneumatically connected in the bypass line 30 (closed operation of the compressed air supply system 10).

[0097] The movement of the piston in the second compression volume 52 does indeed draw in air from the air supply 0 and move it within the second compression volume 52. However, with a low pressure buildup and with the return valve 21 open, the compressed air thus generated can no longer cause the isolating valve 22 to open. Rather, the isolating valve 22, in the form of a check valve, is held closed by the spring 22F.

[0098] The compressed air only from the first compression volume 51 thus reaches the compressed air supply 1 via the first check output valve 43 and from there exclusively into the pneumatic main line 60 and the air dryer 61. In contrast, the piston operation of the second compression volume 52 is open, so that when the piston is operated, only air from the first check input valve 42 reaches the compressed air reservoir 92 via the second first check output valve 44 and the bypass line 30, finally into the pneumatically connecting filling line 86.

[0099] According to the concept of the invention, in the first operating mode, the return valve 21 is not pneumatically actuated and separates the bypass line 30, while the automatically opening check valve, as the second isolating valve 22, is open against the spring force of the valve spring 22F. In the second operating mode, only the first compression volume 51 is open and delivers compressed air to the compressed air supply 1 and the compressed air connection 2. The second compression volume 52, as explained above, is forced to convey in a circuit without compressed air passing through the compressed air supply 1; or at most from the first check inlet valve 42 via the second first check outlet valve 44 and the bypass line 30, finally again via the first compression volume 51 into the pneumatically connecting filling line 86 to the compressed air reservoir 92. The first --open-- operating mode (with supply air supplied via the inlet check valve 0.2, from the intake filter 0.1 for air supply 0) thus enables the joint conveyance of compressed air from the first and second compression volumes 51, 52, while the second --closed-- operating mode allows the conveyance of compressed air only from the first compression volume 51, while the second compression volume is "switched off" as a result of the conveyance of the second compression volume "in a circle" via the bypass line 30.

[0100] The same effect is achieved by the return valve 21 in the supply line 30.1 of the second compression volume 52 according to Fig. 2A and Fig. 2B. When this opens, --thus allowing a flow of compressed air-- the corresponding compression volume is no longer compressed -- in the Fig. 2A and Fig. 2B, this is the second compression volume 52 designated with “2”. The second --closed- operating mode also allows here only the conveyance of compressed air from the first compression volume 51, while the second compression volume 52 is “switched off” as a result of the conveyance of the second compression volume “back and forth” via the supply line 30.1.

[0101] In a similar way, another operating mode similar to the first operating mode (open operation as in Fig. 4) The first switching valve 81 must be open and the third switching valve 83 must be closed. In this case, compressed air can be pumped from the compressed air supply 2 into the bellows 91 when the second, third, and fourth switching valves 82, 84, 83 are closed, i.e., the corresponding switching line is pneumatically isolated.

[0102] Accordingly, for the second operating mode (closed operation, Fig. 5) the first and fourth switching valves 81, 84 are open. In this case, the compressed air reservoir 92 can be used to deliver a control pressure p via the control line 45 to the control piston 46 of the return valve, while the bellows 91 are opened and filled via the first switching valve 81 and the gallery 95. In particular, the return valve 21 is only opened when the pressure p in the control line 45 exceeds a threshold value p S from a first switching state, namely assigned to the first operating mode MOD1, to a second switching state, namely assigned to the second operating mode MOD2. The threshold value p S of the return valve 21 is adjustable in a range from 2 bar to 8 bar above atmospheric pressure.

[0103] Fig. 6 shows again in detail the connection via a separating valve arrangement 80 for the pneumatic system 90 according to Fig. 1 and for the operating mode of the Fig. 4 and Fig. 5, for which reason reference is made to the above description with reference to the same reference numerals.

[0104] Fig. 7 shows an alternative embodiment in which the pair of 2 / 2-way valves 81, 82 and 83, 84 are replaced by a 3 / 2-way valve 88 and 89, respectively. The arrangement of the gallery 95 and the storage branch line 99 is the same.

[0105] Fig.8 shows a vehicle 1000 in the form of an SUV with a vehicle control unit (ECU) operable in a first operating mode MOD1 and a second operating mode MOD2. A corresponding switching arrangement is transmitted via a switch S to the pneumatic system 100 comprising the compressed air supply system 10, the switching valve arrangement 80, and the pneumatic system 90—the air suspension and level control system of the vehicle 1000. The operating modes MOD1 and MOD2 can be transmitted via the data lines shown here as an electrical signal to the electrically controllable valves of the compressed air supply system 10, the switching valve arrangement 80, and the pneumatic system 90. In the manner described above, however, the return valve 21 and the second isolation valve 22 of the return valve arrangement 20 can operate reliably as pneumatically controlled valves 21, 22 without electrical actuation.This leads to a not inconsiderable reduction in the load on the vehicle’s electrical system 1000.

Claims

[1] Compressed air supply system (10) for operating a pneumatic system (90) in the form of a switchably open or closed compressed air supply system with a pneumatic system (90) connected via a switching valve arrangement (80), the compressed air supply system (10) comprising: - an air supply (0) for supplying supply air to a compressor (50) which has a first compression volume (51) and a second compression volume (52) each for compressing the supply air to compressed air, - a compressed air supply (1) for providing the compressed air from the compressor (50), wherein the compressor (50) is designed as a two-cylinder compressor with the first compression volume (51) and with the second compression volume (52), characterized by , that - on the suction side of the compressor (50), both the first and the second compression volume (51, 52) are connected to the air supply (0), wherein the first and the second compression volume (51, 52) are connected in parallel to the air supply (0) such that the first and the second compression volume (51, 52) can jointly receive supply air via the air supply (0) both in a first operating mode (MOD1) and in a second operating mode (MOD2), and - on the pressure side of the compressor (50) for providing the compressed air in the first operating mode (MOD1), the first and the second compression volume (51, 52) are switchably connected to the compressed air supply (1) and in parallel, and in the second operating mode (MOD2) only the first compression volume (51) is switchably connected to the compressed air supply (1), wherein in the first operating mode (MOD1), the first and second compression volumes (51, 52) can deliver compressed air to the compressed air supply (1) in a phase-shifted manner, and in the second operating mode (MOD2) the first compression volume (51) can deliver compressed air to the compressed air supply (1), wherein in the second operating mode (MOD2) the second compression volume (52) can be switched off by means of a return valve (21) such that the second compression volume (52) in the second operating mode (MOD2) cannot deliver compressed air to the compressed air supply (1), wherein - the return valve (21) is pneumatically controllable by means of a control pressure line (45) to the return valve (21), which is designed to carry control pressure for pneumatically controlling the return valve (21). [2] Compressed air supply system according to claim 1, characterized bythat in the second operating mode (MOD2) only the first compression volume (51) can deliver compressed air to the compressed air supply (1). [3] Compressed air supply system according to claim 1, characterized by that in the first operating mode (MOD1) the first compression volume (51) and the second compression volume (52) can deliver compressed air to the compressed air supply (1). [4] Compressed air supply system according to one of claims 1 to 3, characterized by , that - the control pressure line (45) to a bypass line (30) to the second compression volume (52), and / or - the control pressure line (45) to a supply line (30.1) to the second compression volume (52), and / or - the control pressure line (45) is connected to a discharge line (30.2) from the second compression volume (52). [5] Compressed air supply system according to claim 4, characterized bythat a separating valve (22) is arranged on the output side of an outlet valve (43, 44) of the first or second compression volume (51, 52). [6] Compressed air supply system according to claim 5, characterized by that the return valve (21) and / or the isolating valve (22) has a check valve (RV) opening in the direction of the compressed air supply (1). [7] Compressed air supply system according to claim 1, characterized by that the return valve (21) is arranged in the supply line (30.1) of the second compression volume (52). [8] Compressed air supply system according to claim 7, characterized by that the return valve (21) is arranged in the supply line (30.1, 30.2) upstream of the inlet valve (41, 42), namely in the flow direction of the inlet valve (41, 42) of the first or second compression volume (51, 52) upstream of the inlet valve (41, 42). [9] Compressed air supply system according to claim 7, characterized bythat the return valve (21) is arranged in the supply line (30.1, 30.2) after the inlet valve (41, 42) in the flow direction of the inlet valve (41, 42) of the first or second compression volume (51, 52) after the inlet valve (41, 42). [10] Compressed air supply system according to one of claims 8 or 9, characterized by that the inlet valve (42) of the second compression volume (52) is integrated in the return valve (21) or the return valve (21) acts on the inlet valve (42) of the second compression volume (52) in such a way that the inlet valve (42) remains closed when the return valve (21) is pressurized. [11] Compressed air supply system according to one of claims 1 to 10, characterized by that the return valve (21) is a 2 / 2-way valve, wherein a return valve arrangement (20) comprises the return valve (21) and the isolating valve (22). [12] Compressed air supply system according to one of claims 1 to 11, characterized by that the return valve (21) is only transferred from a first switching state, which is assigned to the first operating mode (MOD1), to a second switching state, which is assigned to the second operating mode (MOD2), when the pressure (p) in the control line (45) is above a threshold value (ps). [13] Compressed air supply system according to claim 12, characterized by that the threshold value (ps) of the feedback valve (21) is adjustable. [14] Pneumatic system (100) with a compressed air supply system (10) according to one of claims 1 to 13 and a switching valve arrangement (80) and a pneumatic system (90) and which has a gallery (95), comprising: - a branch line (98, 99) pneumatically connected to the gallery (95) with a bellows (91) and / or - a compressed air reservoir (92), and - a separating valve arranged upstream of the bellows (91) and / or the compressed air reservoir (92), in particular wherein the upstream separating valve (93) is electrically controllable. [15] Vehicle (1000) with a pneumatic system according to claim 14 and an electronic vehicle control unit (ECU), which electronic vehicle control unit (ECU) is free from electronic control of at least the recirculation valve (21) connected between the pressure side and the suction side of the compressor (50). [16] Vehicle (1000) according to claim 15, characterized by that the vehicle (1000) is a passenger car (1001). [17] Method for operating a compressed air supply system (10) with a pneumatic system (90) connected via a switching valve arrangement (80), wherein the compressed air supply system (10) is designed as a switchably open or closed compressed air supply system (10) and has the following: - an air supply (0) to a compressor (50) which has a first compression volume (51) and a second compression volume (52) each for compressing the supply air to compressed air, - a compressed air supply (1) for providing the compressed air from the compressor, wherein the compressor is designed as a two-cylinder compressor with the first compression volume (51) and with the second compression volume (52), characterized by , that - on the suction side of the compressor (50), both the first and the second compression volume (51, 52) are connected to the air supply (0), wherein the first and the second compression volume (51, 52) are connected in parallel to the air supply (0) such that the first and the second compression volume (51, 52) can jointly receive supply air via the air supply (0) both in a first operating mode (MOD1) and in a second operating mode (MOD2), and - on the pressure side of the compressor (50) for providing the compressed air in the first operating mode (MOD1), the first and second compression volumes (51, 52) are switchably connected to the compressed air supply (1) and in parallel, and in the second operating mode (MOD2) only the first compression volume (51) is switchably connected to the compressed air supply (1), the method comprising the steps: - delivering compressed air in the first operating mode (MOD1), wherein the first and second compression volumes (51, 52) deliver compressed air to the compressed air supply (1) in a phase-shifted manner, and - Delivering compressed air in the second operating mode (MOD2), wherein the second compression volume (52) can be switched off by means of a return valve (21) such that the second compression volume (52) cannot deliver compressed air to the compressed air supply (1) in the second operating mode (MOD2), wherein the return valve (21) is pneumatically controlled by means of a control pressure line (45) to the return valve (21) for pneumatically controlling the return valve (21). [18] Method according to claim 17, characterized by that the return valve (21) is pneumatically controlled with a suction-side pressure as control pressure (p) of a control pressure line (45). [19] Method according to claim 18, characterized by , that - the control pressure line (45) to a bypass line (30) to the second compression volume (52), and / or - the control pressure line (45) to a supply line (30.1) to the second compression volume (52), and / or - the control pressure line (45) is connected to a discharge line (30.2) to the second compression volume (52). [20] Method according to claim 17, 18 or 19, characterized by that the return valve (21) is above a threshold value (p S ) is transferred from a first switching state, namely the first operating mode MOD1, to a second switching state, namely the second operating mode MOD2. [21] Method according to claim 20, characterized by that the threshold value (ps) of the return valve (21) is set, in particular in a range of 2 bar to 8 bar above atmospheric pressure.

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