Compressed air supply system of a vehicle

Abstract

The invention addresses the problem of presenting a compressed air supply system (2.1) of a motor vehicle with a compressor designed as a spiral compressor in which the exhaust air of the compressed air consumers can be used to save drive energy of the electric motor and / or to increase the feed pressure of the compressor. Furthermore, with a cost-effective construction of the compressed air supply system, a mechanical overloading of the compressor is to be avoided. To this end a compressor (4.1) designed as a one-stage spiral compressor is provided, which is drivingly connected to an electric motor (6). The compressor (4.1) has a suction inlet (8), a feed outlet (10) and at least one further inlet (12, 14) or outlet (12', 14') for conducting air. In addition, a suction line (16) provided with a suction valve (20) is connected to the suction inlet (8) of the compressor. A feed line (22) is also provided, which is connected to the feed outlet (10) of the compressor and which is guided via a feed valve (24) or a non-return valve (25) to a storage container (26) or to the inlet of at least one compressed air consumer (35). A return line (30) is also provided, which is connected to an inlet (8; 12, 14) of the compressor and, via a boost valve (32), to a collection container (34) or to the outlet of at least one compressed air consumer (35). Finally, a pressure sensor (28, 36) is arranged in each of the storage container (26) and collection container (34) for determining the air pressure there.

Description

[0001] Compressed air supply system of a vehicle

[0002] The invention relates to a compressed air supply system for a vehicle, comprising a compressor designed as a single-stage scroll compressor, which is connected to an electric motor for driving purposes. The compressor has a suction inlet, a discharge outlet, and at least one further inlet or outlet for passing air.

[0003] In electric vehicles and hybrid vehicles operating in electric mode, which have a compressed air supply system and compressed air consumers, the operating noise of a compressor required to generate compressed air, especially a piston compressor, and the venting noise when releasing compressed air into the environment are clearly audible and are perceived as unpleasant and disturbing by both vehicle occupants and passersby. Therefore, vehicle manufacturers strive to use compressors with lower operating noise in their vehicles' compressed air supply systems and to avoid the release of compressed air into the environment by compressed air consumers.By using already cleaned, dried and charged, i.e. pressurised, exhaust air from compressed air consumers, for example to charge a storage tank or to regenerate an air dryer, energy can also be saved and a compressor with a lower rated power can be used.

[0004] Due to their smooth running, i.e. low vibrations and oscillations, as well as their low operating noise, scroll compressors are the preferred compressors for the compressed air systems of electric and hybrid vehicles. However, at high drive speeds and in so-called boost operation, in which a higher delivery pressure and higher delivery rate are achieved by supplying charged, i.e. pressurized, compressed air on the inlet side, excessively high air mass flow or pressures can lead to mechanical overload and subsequent damage to a scroll compressor. A scroll compressor has at least one spiral stator blade fixed to the housing and one movable spiral displacer blade, the walls of which define several crescent-shaped pressure chambers.While the stator blade is attached to an inner end wall of the compressor housing, the displacer blade is arranged on a displacer disk, which is rotatably mounted on an eccentric pin of a drive shaft. When the drive shaft rotates, i.e. is driven by a drive motor, the displacer disk and displacer blade perform an orbital movement around the stator blade in accordance with the circumferential displacement of the eccentric pin. A guide device ensures that the circumferential alignment of the displacer disk is maintained and the pressure chambers are displaced circumferentially in the direction of rotation of the drive shaft and radially from outside to inside, reducing their volume. To achieve relatively good sealing of the pressure chambers and thus a high efficiency of the scroll compressor, the displacer blade can approach the stator blade in places to within a few tenths of a millimeter, but without touching it.This requires precise manufacturing of the spiral blades, which is why scroll compressors are comparatively expensive and are therefore often only used as single-stage compressors in compressed air systems.

[0005] A typical scroll compressor is known, for example, from DE 34 07 939 C1. In this scroll compressor, a guide device, which ensures a largely rotation-free orbital movement of the displacement disc, is formed by a rocker crank arranged on the outer circumference of the displacement disc tangentially in extension of the displacement blade. The rocker crank is pivotally mounted at both ends, radially on the outside of the compressor housing and radially on the inside of the displacement disc. When the drive shaft rotates, the rocker crank is alternately deflected radially outward or inward around its outer bearing, which causes a periodic pivoting of the displacement disc in the circumferential direction.

[0006] Compressed air supply systems for vehicles are already known, particularly for supplying air suspension systems with compressed air. In these systems, cleaned and dried compressed air from the air springs can be used to charge a reservoir and / or regenerate an air dryer. For example, DE 100 55 108 A1 discloses a compressed air supply system for a vehicle for supplying an air suspension system. Compressed air from the vehicle's air springs can be used either to regenerate an air dryer arranged in a delivery line or, in boost mode of the scroll compressor, to charge a reservoir. Likewise, the air springs can be ventilated with compressed air from the reservoir in boost mode of the scroll compressor.

[0007] DE 11 2019 004 801 B4 describes a compressed air supply system for a vehicle with a scroll compressor for supplying an air suspension system. In boost mode, the air springs can be ventilated with compressed air from a reservoir, the reservoir can be charged with compressed air from the air springs, and an air dryer arranged in a delivery line can be regenerated with compressed air from the air springs. This compressed air supply system also makes it possible to direct compressed air from the air springs and / or the reservoir to the single inlet of the scroll compressor.

[0008] EP 0 777 052 ​​B1 discloses a scroll compressor for a vehicle air conditioning system, comprising a fixed scroll having a central outlet opening and two bypass openings arranged radially spaced from the outlet opening and forming a pair, and comprising a scroll that can be orbited around the fixed scroll and that engages with the fixed scroll, such that a gas is enclosed between the fixed scroll and the orbitable scroll. The scroll compressor is arranged in a gas-tight housing having an inlet and an outlet that connect the scroll compressor to a vehicle air conditioning system. The inlet admits gas into a low-pressure chamber formed on an intake side and discharges gas compressed in the scroll compressor from a high-pressure chamber formed on an outlet side to the air conditioning system.In addition, a rotatable hollow cylindrical rotary vane valve is arranged, with a valve wall having two slots formed as a pair therein, which can be controlled to the pair of bypass openings in order to prematurely blow off the gas trapped in the scroll compressor and thereby change the displacement of the compressor.

[0009] EP 1 656 503 B1 shows and describes a scroll compressor arrangement for a vacuum system, comprising a scroll compressor, a turbomolecular pump, and two interconnected vacuum chambers. The scroll compressor has two nested scrolls, one of which is fixed to the housing, and the other scroll is connected to an eccentric section of a drive shaft and arranged to orbit the stationary scroll. A first inlet and a second inlet are formed on two radially spaced-apart outer sections of the scroll compressor, and an outlet is formed on a central section radially inward and spaced from the inlets.

[0010] The invention is based on the object of presenting a compressed air supply system for a vehicle with a compressor designed as a scroll compressor, in which the exhaust air from the compressed air consumers can be used as needed to save drive energy for the electric motor and / or to increase the discharge pressure and the compressor's discharge capacity. Furthermore, a cost-effective design of the compressed air supply system should prevent mechanical overloading of the compressor and the electric motor during boost operation.

[0011] This object is achieved by means of a compressed air supply system of a vehicle having the features of claim 1. Advantageous developments of the compressed air supply system are defined in the dependent claims.

[0012] Accordingly, the object is achieved by a compressed air supply system with a compressor designed as a single-stage scroll compressor, which is drive-effectively connected to an electric motor. The compressor has a suction inlet, a delivery outlet and at least one further inlet or outlet for the passage of air. A suction line provided with a suction valve is connected to the suction inlet of the compressor. In addition, there is a delivery line which is connected to the delivery outlet of the compressor and is led via a delivery valve or check valve to a storage tank or to the inlet of at least one compressed air consumer. In addition, there is a return line which is connected to an inlet of the compressor and is led via a boost valve to a collection tank or to the outlet of at least one compressed air consumer.Finally, a pressure sensor is located in each of the storage tank and the collection tank to determine the air pressure there. Although the compressed air supply system can also be operated with a non-controllable electric motor, an electric motor with a variable speed is preferred. If the compressed air supply system has a non-controllable electric motor instead of a controllable electric motor, only those operating modes of the compressed air supply system can be used in which the electric motor operates at its nominal speed.

[0013] By driving the compressor with the variable-speed electric motor, the compressor's drive speed can be adjusted to the desired discharge pressure and, in boost mode, to the compressed air pressure in the return line. The additional compressor inlet can be a low-pressure inlet or a medium-pressure inlet, which is located in the end wall of a compressor housing, closely adjacent to a pressure chamber in which a corresponding air pressure is established during compressor operation, and to which the return line for supplying compressed air in boost mode can be connected.

[0014] The additional outlet of the compressor can be an appropriately arranged low-pressure outlet or a medium-pressure outlet to which a relief line for discharging compressed air can be connected in order to avoid mechanical overload of the compressor.

[0015] The pressure sensors located on the storage tank and the collection tank are used to measure the air pressures there. The pressure sensors are connected to a control unit via sensor lines. Knowledge of the measured air pressure values ​​is necessary for the control software in the control unit to activate or deactivate operating modes of the compressed air supply system using the switching valves of the compressed air supply system.

[0016] Below, advantageous embodiments of the compressed air supply system incorporating the features of the invention are presented. These variants of the compressed air supply system are designed such that they can be operated in different operating modes, which are also described and provided as examples. The air pressure limit values ​​specified for this purpose and the specific information regarding the boost pressures in the respective return lines are given only as examples and depend on the design of the respective compressor used, in particular on the maximum air pressure that can be generated on the compressor's output side.

[0017] According to a first embodiment of the compressed air supply system, the compressor has a medium-pressure inlet to which the return line is connected, and the suction valve and the boost valve are designed as 2 / 2-way switching valves that are closed in the unactuated idle state. Instead of these 2 / 2-way switching valves that are closed in the unactuated idle state, the suction valve and the boost valve could be designed as 2 / 2-way switching valves that are open in the unactuated idle state, which are initially closed under the control of a control unit when the vehicle ignition is switched on.

[0018] The suction valve and the boost valve can be configured either as 2 / 2-way solenoid valves or as pressure-controlled 2 / 2-way solenoid valves, with the latter each being assigned a 2 / 2-way solenoid valve as a pilot valve. The solenoid valves are connected to the aforementioned control unit via control lines. By opening the suction valve, the boost valve, or both valves, it is possible to specifically control whether only ambient air is drawn in during the compressor's suction operation, or only compressed air from the return line during the compressor's boost operation, or whether air from both air sources is drawn in.

[0019] In this first embodiment of the compressed air supply system, it is provided that the compressor can be operated in five operating modes (Mode 1 to Mode 5) during its compression work, depending on the boost pressure PL in the return line. In a first operating mode (Mode 1), in which the air is sucked in only from the environment at any boost pressure PL in the return line and with the suction valve open and the boost valve closed at a high drive speed (nM > nM_nom), in a second operating mode (Mode 2), in which the air is sucked in only from the return line at a boost pressure PL in the return line of 50% to 60% of the maximum pressure of the compressor and with the boost valve open at a high drive speed (nM > nM_nom), in a third operating mode (Mode 3),in which the air is sucked in from both the environment and the return line at a boost pressure PL in the return line of 51% to 60% of the maximum pressure of the compressor and with the suction valve and boost valve open at a low drive speed (nM < nM_nom), whereby in a fourth operating mode (Mode 4), in which the air is sucked in only from the return line at a boost pressure PL in the return line of 61% to 80% of the maximum pressure of the compressor and with the suction valve and boost valve closed at the nominal drive speed (nivi = nM_nom), and whereby in a fifth operating mode (Mode 5), in which the air is sucked in only from the return line at a boost pressure PL in the return line of 90% to 100% of the maximum pressure of the compressor and with the suction valve and boost valve open at a low speed (nivi < nM_nom), is sucked in.,

[0020] In this first embodiment and its second operating mode (Mode 2), the value range can be expanded so that in this second operating mode, the air is only drawn from the return line at a boost pressure in the return line of 0% to 60% of the compressor's maximum pressure and with the boost valve open at a high drive speed (nivi > nivi_ _nom). This expansion of the value range, starting at 0% up to the respective specified maximum value, can also be used with similar operating settings of the compressed air supply system, without further explanation here.

[0021] In a second embodiment of the compressed air supply system, which can be regarded as a further development of the first embodiment, it is provided that the compressor has a low-pressure inlet and a medium-pressure inlet, that the return line is branched on the output side into a first line branch with a first boost valve and into a second line branch with a second boost valve, that the first line branch is connected to the low-pressure inlet and the second line branch is connected to the medium-pressure inlet of the compressor, and that the suction valve and the two boost valves are designed as 2 / 2-way switching valves that are closed in the unactuated idle state.

[0022] The suction valve and the two boost valves can be configured either as 2 / 2-way solenoid valves or as pressure-controlled 2 / 2-way solenoid valves, with each of the latter being assigned a 2 / 2-way solenoid valve as a pilot valve. By opening the suction valve and the boost valves, either individually or in combination, it is possible to specifically control whether only ambient air is drawn in during the compressor's suction mode, or only compressed air from the return line during the compressor's boost mode, or whether air from both air sources is drawn in.

[0023] In this second embodiment of the compressed air supply system, the compressor can be operated in seven operating modes (Mode 1 to Mode 7) during its compression work, depending on the boost pressure in the return line. In a first operating mode (Mode 1), in which the air is sucked in only from the environment at any boost pressure PL in the return line and with the suction valve open and the boost valves closed at a high drive speed (nM > nM_nom), in a second operating mode (Mode 2), in which the air is sucked in only from the return line at a boost pressure PL in the return line of 10% to 20% of the maximum pressure of the compressor with the suction valve closed, the first boost valve open and the second boost valve closed at a high drive speed (nM > nM_nom), in a third operating mode (Mode 3),in which the air is sucked in only from the return line at a boost pressure PL in the return line of 21% to 40% of the maximum pressure of the compressor with the suction valve closed, the first boost valve open and the second boost valve closed at the nominal drive speed (nM = nM_nom), wherein in a fourth operating mode (Mode 4), in which the air is sucked in only from the return line at a boost pressure PL in the return line of 41% to 50% of the maximum pressure of the compressor with the suction valve closed, the first boost valve open and the second boost valve closed at a low drive speed (nM < nM_nom), wherein in a fifth operating mode (Mode 5), in which the air is sucked in only from the return line at a boost pressure PL in the return line of 51% to 60% of the maximum pressure of the compressor with the suction valve closed, the first boost valve closed and the second boost valve open Boost valve with high drive speed (nM > nM_nom) is only sucked from the return line,In a sixth operating mode (Mode 6), in which the air is drawn only from the return line at a boost pressure PL in the return line of 61% to 80% of the maximum pressure of the compressor with the suction valve closed, the first boost valve closed, and the second boost valve open at the nominal drive speed (nM = nM_nom), and in a seventh operating mode (Mode 7), in which the air is drawn only from the return line at a boost pressure (PL) in the return line of 90% to 100% of the maximum pressure of the compressor with the suction valve closed, the first boost valve closed, and the second boost valve open at a low drive speed (nM < nM_nom). The number of operating modes in this second embodiment of the compressed air supply system can be expanded beyond the seven operating modes described. The gradation can be even more detailed,for example, by creating more than two inputs in the compressor.

[0024] According to a third embodiment of the compressed air supply system, it is provided that the return line is connected to the suction line behind the suction valve as seen in the suction direction towards the compressor, and that this suction valve is designed as a first check valve blocking against the suction direction and that the boost valve arranged in the return line is designed as a 2 / 2-way switching valve closed in the unactuated idle state.

[0025] Accordingly, when the boost valve is closed during the compressor's suction operation, only air is drawn in from the ambient air. When the boost valve is open, the opening pressure of the first check valve and the boost pressure in the return line determine which air source the air is drawn in from. At equal pressures, the air is drawn in from both air sources in a mixed suction and boost operation. If the boost pressure in the return line is greater than the opening pressure of the first check valve, the compressed air is drawn in pure boost operation only from the return line.

[0026] In this third embodiment of the compressed air supply system, the compressor is designed primarily for boost operation at a comparatively low boost pressure of, for example, less than 5 x 10 5 Pa in the return line. This allows for the use of a comparatively smaller and therefore more cost-effective compressor.

[0027] In the third embodiment of the compressed air supply system, the compressor can be operated in four operating modes (Mode 1 to Mode 4) during its compression work, depending on the boost pressure in the return line, namely in a first operating mode (Mode 1), in which the air is only sucked in from the environment at any boost pressure PL in the return line with the boost valve closed and at a high drive speed (nM > nM_nom), in a second operating mode (Mode 2), in which the air is at least largely sucked in from the return line at a boost pressure PL in the return line of 10% to 20% of the maximum pressure of the compressor and the boost valve open and at a high drive speed (HM > nM_nom), in a third operating mode (Mode 3),in which the air is at least largely sucked in from the return line at a boost pressure PL in the return line of 21% to 40% of the maximum pressure of the compressor and an open boost valve at the nominal drive speed (riM = nM_nom), and in a fourth operating mode (Mode 4), in which the air is at least largely sucked in from the return line at a boost pressure PL in the return line of 41% to 50% of the maximum pressure of the compressor and an open boost valve at a low drive speed (rnvi < nM_nom).

[0028] According to a further development of this third embodiment, the return line, viewed in the suction direction toward the compressor, is connected behind the boost valve not to the suction line or the suction inlet of the compressor, but rather to its medium-pressure inlet via a bypass line. This would be useful if the expected boost pressure in the return line is comparatively low, but greater than the opening pressure of the suction valve, which serves as the first check valve.

[0029] In a fourth embodiment of the compressed air supply system, which represents a further development of the third embodiment, it is provided that a second check valve which blocks against the conveying direction is arranged in the conveying line between the conveying outlet of the compressor and an optional conveying valve, that the compressor has a medium-pressure outlet, that a first relief line is present which is connected to the medium-pressure outlet of the compressor and between the second check valve and the conveying valve to the conveying line, and that a third check valve which blocks in the direction of the medium-pressure outlet of the compressor is arranged in the first relief line.

[0030] Compressed air then flows into the delivery line via the relief line when a pressure determined by the opening pressure of the third check valve located in the relief line is exceeded in the pressure chamber to which the compressor's medium-pressure outlet is located. The two check valves prevent backflow of compressed air from the delivery line into the delivery outlet or the medium-pressure outlet. In this fourth embodiment of the compressed air supply system, the compressor can be operated in five operating modes (Mode 1 to Mode 5) during its compression work, depending on the boost pressure in the return line and the intended delivery pressure: a first operating mode (Mode 1),in which the air is only sucked in from the environment at any boost pressure PL in the return line and any discharge pressure PF with the boost valve closed and high drive speed (HM > nivi_nom), in a second operating mode (Mode 2), in which the air is only sucked in from the return line at a boost pressure PL in the return line of 10% to 40% of the maximum pressure of the compressor and a discharge pressure PF of less than 80% of the maximum pressure of the compressor with the boost valve open and high drive speed (rnvi > nM_nom), in a third operating mode (Mode 3), in which the air is only sucked in from the environment at a boost pressure PL in the return line of 41% to 70% of the maximum pressure of the compressor and a discharge pressure PF of less than 80% of the maximum pressure of the compressor with the boost valve open and the nominal drive speed (rnvi = HM. _nom). return line is sucked in, in a fourth operating mode (Mode 4),in which the air is only sucked from the return line at a boost pressure PL in the return line of 71% to 100% of the maximum pressure of the compressor and a discharge pressure PF of less than 80% of the maximum pressure of the compressor with the boost valve open and low drive speed (HM < nivi_nom), and in a fifth operating mode (Mode 5), in which the air is only sucked from the environment at a boost pressure PF in the return line of 10% to 100% of the maximum pressure of the compressor and a discharge pressure PF of more than 80% of the maximum pressure of the compressor at low speed (HM < nM_nom) with the boost valve closed.

[0031] According to a fifth embodiment of the compressed air supply system, which represents a further development of the fourth embodiment, it is provided that an air filter is arranged in the intake direction of the air upstream of the intake valve designed as a first check valve, that the compressor additionally has a low-pressure outlet to which a second relief line is connected, that the second relief line is connected with its other end via the first check valve to the suction line, that a first relief valve is arranged in the first relief line and a second relief valve is arranged in the second relief line, and that the two relief valves are designed as 2 / 2-way switching valves that are closed in the unactuated idle state.The two relief valves can be configured either as 2 / 2-way solenoid valves or as pressure-controlled 2 / 2-way solenoid valves, with each of the latter being assigned a 2 / 2-way solenoid valve as a pilot valve. By opening one or both of the two relief valves, it is possible to control, as required, whether, during the compressor's delivery operation, compressed air is directed via the first relief line into the suction line or the environment, or via the second relief line into the delivery line, or via both relief lines into the suction line or into the environment and the delivery line.

[0032] In this fifth embodiment of the compressed air supply system, the compressor can be operated in four operating modes (Mode 1 to Mode 4) during its compression work, depending on the boost pressure in the return line. Namely, the compressor can be operated in four operating modes (Mode 1 to Mode 4) during its compression work, depending on the boost pressure PL in the return line. In a first operating mode (Mode 1), in which the air is sucked in only from the environment at any boost pressure PL in the return line with the boost valve closed and the relief valves closed at the nominal drive speed (HM = nM_nom), in a second operating mode (Mode 2), in which the air is sucked in largely from the return line at a boost pressure PL in the return line of 10% to 20% of the maximum pressure of the compressor with the boost valve open and the relief valves closed at the nominal drive speed,wherein in a third operating mode (Mode 3), in which the air is sucked only from the return line at a boost pressure PL in the return line of 21% to 50% of the maximum pressure of the compressor with the boost valve and relief valves open and nominal drive speed, and wherein in a fourth operating mode (Mode 4), in which the air is sucked only from the return line at a boost pressure PL in the return line of 51% to 100% of the maximum pressure of the compressor with the boost valve and relief valves open and low drive speed (HM < nM_nom).

[0033] Since the relief valves are open in the last two operating modes (Mode 3 and Mode 4), overload protection for the compressor is implemented. Furthermore, in the third to fifth embodiments of the compressed air supply system described above, an air filter can be arranged upstream of the first check valve in the air intake direction. This prevents unwanted backflow of compressed air through the air filter into the surrounding atmosphere, particularly during boost operation.

[0034] Finally, it is pointed out that a compressed air supply system having the features of the invention can have a combination of the features of the various embodiments.

[0035] The invention is explained in more detail below with reference to five exemplary embodiments shown in the accompanying drawing.

[0036] Fig. 1 shows a first embodiment of a compressed air supply system of a vehicle according to the invention in a schematic representation,

[0037] Fig. 1a shows the compressor of the compressed air supply system according to Fig. 1, designed as a scroll compressor, in a cross-sectional view,

[0038] Fig. 1b possible operating modes of the compressed air supply system according to Fig. 1 in the form of a table,

[0039] Fig. 2 shows a second embodiment of a compressed air supply system according to the invention in a schematic representation,

[0040] Fig. 2a shows the compressor of the compressed air supply system according to Fig. 2, designed as a scroll compressor, in a cross-sectional view,

[0041] Fig. 2b possible operating modes of the compressed air supply system according to Fig. 2 in the form of a table,

[0042] Fig. 3 shows a third embodiment of a compressed air supply system according to the invention in a schematic representation,

[0043] Fig. 3a shows the compressor of the compressed air supply system according to Fig. 3, designed as a scroll compressor, in a cross-sectional view,

[0044] Fig. 3b possible operating modes of the compressed air supply system according to Fig. 3 in the form of a table,

[0045] Fig. 4 shows a fourth embodiment of a compressed air supply system according to the invention in a schematic representation, Fig. 4a shows the compressor designed as a scroll compressor of the compressed air supply system according to Fig. 4 in a cross-sectional view,

[0046] Fig. 4b possible operating modes of the compressed air supply system according to Fig. 4 in the form of a table,

[0047] Fig. 5 shows a fifth embodiment of a compressed air supply system according to the invention in a schematic representation,

[0048] Fig. 5a shows the compressor of the compressed air supply system according to Fig. 5, designed as a scroll compressor, in a cross-sectional view, and

[0049] Fig. 5b possible operating modes of the compressed air supply system according to Fig. 5 in the form of a table.

[0050] The first embodiment of a compressed air supply system 2.1 according to the invention, shown in Fig. 1, comprises a compressor 4.1, a suction line 16, a delivery line 22, and a return line 30. The compressor 4.1 is designed as a single-stage scroll compressor, which is driven by a variable-speed electric motor 6 and has a suction inlet 8, a delivery outlet 10, and a medium-pressure inlet 14.

[0051] In the suction line 16, which is connected to the suction inlet 8 of the compressor 4.1, an air filter 18 and a suction valve 20 are arranged in the suction direction. The suction valve 20 is designed as a 2 / 2-way solenoid valve that is closed in the de-energized, idle state. All solenoid valves of the compressed air supply system 2.1 can be switched by means of a control unit (not shown). When the compressor 4.1 is running and the suction valve 20 is open, air is drawn in from the environment via the suction line 16, with dust and dirt particles being retained by the air filter 18.

[0052] A delivery valve 24 is arranged in the delivery line 22, which is connected to the delivery outlet 10 of the compressor 4.1 and leads to a storage tank 26. At least one compressed air consumer 35 is connected to the storage tank 26 on the outlet side via a first 2 / 2-way solenoid valve 62 on the consumer side. This first 2 / 2-way solenoid valve 62 on the consumer side is open in the non-actuated state, as shown. The delivery valve 24 is designed here as a 2 / 2-way solenoid valve that is closed in the de-energized, idle state. Alternatively, a check valve 25 is arranged in the delivery line 22 and closes in the direction of the compressor 6, which is shown with a dashed line. When the compressor 4.1 is driven and the delivery valve 24 is open, compressed air is supplied from the compressor 4 via the delivery line 22.1 into the storage tank 26, wherein the delivery pressure PF can be determined by means of a first pressure sensor 28 connected to the storage tank 26.

[0053] A boost valve 32 is arranged in a return line 30, which leads from a collecting tank 34 to the medium-pressure inlet 14 of the compressor 4.1. The compressed air consumers 35 are connected on the output side to the collecting tank 34 via a second 2 / 2-way solenoid valve 64 on the consumer side. This second 2 / 2-way solenoid valve 64 on the consumer side is, as shown, closed in the unactuated state and open in the actuated state, so that in the open state, compressed air can flow from the at least one consumer 35 to the collecting tank 34. The boost valve 32 is designed here as a 2 / 2-way solenoid valve that is closed in the de-energized, idle state.

[0054] In boost mode, charged, i.e. pressurized, compressed air is conveyed from the collecting tank 34 into the compressor 4.1 via the return line 30 when the compressor 4.1 is driven and the boost valve 32 is open. The boost pressure PL in the return line 30 can be determined by means of a second pressure sensor 36 connected to the collecting tank 34. The boost mode of the compressor 4.1 can be used either to increase the discharge pressure PF present at the discharge outlet 10 of the compressor 4.1 or to reduce the drive speed or drive power of the electric motor 6.

[0055] The schematic cross-sectional view of Fig. 1a shows an exemplary embodiment of the compressor 4.1 designed as a scroll compressor. The scroll compressor 4.1 has a hollow cylindrical housing 38 with an end wall 40 and a spiral stator blade 42 immovably arranged thereon, as well as a spiral displacer blade 44 arranged on a displacement disk (not visible here). The stator blade 42 and the displacement blade 44 engage axially and delimit a plurality of crescent-shaped pressure chambers 46a, 46b, 46c, 46d, 46e, 46f between them. The displacement disk (not visible) is rotatably mounted on an eccentric pin of a drive shaft (not shown).When the drive shaft is rotating, i.e. driven by a drive motor 6, the displacement disc with the displacement blade 44 performs an orbital movement in accordance with the circumferential displacement of the eccentric pin, wherein a guide device (not shown) maintains the circumferential alignment of the displacement disc and the pressure chambers 46a - 46f are displaced circumferentially in the direction of rotation 48 of the drive shaft and radially from the outside to the inside, reducing their volume.

[0056] The suction inlet 8 of the scroll compressor 4.1 is arranged in the end wall 40 of the housing 38, radially outwardly adjacent to the largest pressure chamber 46a. The discharge outlet 10 of the scroll compressor 4.1 is arranged in the end wall 40 of the housing 38, radially inwardly adjacent to the smallest pressure chamber 46f. The aforementioned medium-pressure inlet 14 of the scroll compressor 4.1 is arranged in the end wall 40 of the housing 38, radially centrally adjacent to a pressure chamber 46d, in which a medium-high pressure is established when the displacement disk is driven.

[0057] According to the information in the table in Fig. 1b, the compressor 4.1 can be operated in five operating modes (Mode 1 to Mode 5) during its compression work, depending on the boost pressure PL in the return line 30. In the table in Fig. 1b, the de-energized, i.e., closed, state of the suction valve 20 and the boost valve 32 is indicated by a circle symbol, and the energized, i.e., open, state of these valves 20, 32 is indicated by a cross. The delivery valve 24 is always energized, or open, during delivery operation of the compressor 4, which is why its switching state is not shown in the table in Fig. 1b.

[0058] In a first operating mode (Mode 1), the air is drawn in only from the ambient air at any boost pressure PL in the return line 30 and with the intake valve 20 open, as well as with the boost valve 32 closed at a high drive speed (nM > nM_nom). In a second operating mode (Mode 2), the air is drawn in at a boost pressure PL of 5 x 10 5 Pa up to 6 x 10 5 Pa in the return line 30 and open boost valve 32 at high drive speed (nw > nM_nom) only from the return line 30. In a third operating mode (Mode 3), the air is sucked in at a boost pressure PL of 5 x 10 5 Pa up to 6 x 10 5 Pa in the return line 30 and open suction valve 20 and open boost valve 32 at low drive speed (nM < nM_nom) from both the environment and from the return line 30. In a fourth operating mode (Mode 4), the air is sucked in at a boost pressure PL of 6 x 10 5 Pa up to 8 x 10 5Pa in the return line 30 with the boost valve 32 open at the rated drive speed or nominal speed (rnvi = nwi_nom) is only sucked from the return line 30. And in a fifth operating mode (Mode 5), the air is sucked at a boost pressure PL of 9 x 10 5 Pa up to 10 x 10 5 Pa in the return line 30 and with the boost valve 32 open at low speed (nivi < nivi_nom) only sucked from the return line 30.

[0059] The five operating modes shown in Fig. 1b and just explained serve only as an example of the maximum permissible speed of the electric motor in each case, in order, on the one hand, to avoid overloading the electric motor and the compressor, and on the other hand, to still achieve the maximum possible delivery rate. Therefore, for example, the first operating mode (Mode 1) and the second operating mode (Mode 2) can also be operated at a low or nominal speed of the electric motor 6 instead of at a high motor speed. This also applies to the other subsequent embodiments and operating modes according to Figures 2b, 3b, 4b, 5b. The speeds nM (low, nominal, high) of the electric motor 6 mentioned in these embodiments represent the maximum possible motor speed for the respective operating mode, synonymous with the maximum permissible motor power, which should be undercut but not exceeded.For example, in an operating mode with an engine speed set to “nominal”, this speed may be undercut as required, but may not be exceeded.

[0060] The second embodiment of a compressed air supply system 2.2 of a vehicle according to the invention, shown in Fig. 2, differs from the first embodiment according to Fig. 1 in that the compressor 4.2 now additionally has a low-pressure inlet 12, and that the return line 30 is branched on the output side into a first line branch 30a with a first boost valve 32a and into a second line branch 30b with a second boost valve 32b. The first line branch 30a of the return line 30 is connected to the low-pressure inlet 12 of the compressor 4.2, and the second line branch 30b of the return line 30 is connected to the medium-pressure inlet 14 of the compressor 4.2. Both boost valves 32a, 32b are designed as 2 / 2-way solenoid valves that are closed in the de-energized, idle state. The connection to the compressed air consumers 35 is made here and in the following embodiments as shown in Fig.1 shown via the consumer-side 2 / 2-way solenoid valves 62, 64.

[0061] The schematic cross-sectional view of Fig. 2a shows that the low-pressure inlet 12 of the compressor 4.2 is arranged in the end wall 40 of the housing 38 radially further inward and axially adjacent to a pressure chamber 46c in which a low air pressure is established when the displacement disk is driven.

[0062] By structurally expanding this compressor 4.2 with the low-pressure inlet 12 and branching the return line 30 into two line branches 30a, 30b, more variants are now available for controlling boost operation of the compressor 4.2. Therefore, the compressor 4.2 can now be operated in seven operating modes (Mode 1 to Mode 7) during its compression work, depending on the boost pressure PL in the return line 30, as shown in the table in Fig. 2b. In the table, the de-energized, i.e., closed, state of the suction valve 20 and the closed state of the two boost valves 32a, 32 are each represented by a circle symbol, and the energized, i.e., open, state of these valves 20, 32a, 32b is each represented by a cross.

[0063] In a first operating mode (Mode 1), the air is sucked in only from the environment at any boost pressure PL in the return line 30 and with the intake valve 20 open at a high drive speed (HM > nivi_ _nom). In a second operating mode (Mode 2), the air is sucked in at a boost pressure PL of 1 x 10 5 Pa up to 2 x 10 5 Pa in the return line 30 and the first boost valve 32a is open at high drive speed (HM > nM_nom) only from the return line 30. In a third operating mode (Mode 3), the air is sucked in at a boost pressure PL of 2x 10 5 Pa up to 4 x 1Q 5 Pa in the return line 30 and the first boost valve 32a is open at the nominal drive speed (nM = nM_nom) only from the return line 30. In a fourth operating mode (Mode 4), the air is sucked in at a boost pressure PL of

[0064] 4 x 10 5 Pa up to 5 x 10 5Pa in the return line 30 and the first boost valve 32a is open at a low drive speed (nM < nM_nom) only from the return line 30. In a fifth operating mode (Mode 5), the air is sucked in at a boost pressure PL of

[0065] 5 x 10 5 Pa up to 6 x 10 5 Pa in the return line 30 and the second boost valve 32b is open at a high drive speed (nM > nM_nom) only from the return line 30. In a sixth operating mode (Mode 6), the air is sucked in at a boost pressure PL of 6 x 10 5 Pa up to 8 x 10 5 Pa in the return line 30 and the second boost valve 32b is open, with the nominal drive speed (HM = nivi_nom) only from the return line 30. And in a seventh operating mode (Mode 7), the air is sucked in at a boost pressure PL of 9 10 5 Pa up to 10 x 10 5Pa in the return line 30 and the second boost valve 32b opened with a low drive speed (FIM < riM_nom) is also only sucked in from the return line 30.

[0066] A third embodiment of a compressed air supply system 2.3 of a vehicle according to the invention, shown in Fig. 3, differs from the first embodiment according to Fig. 1 in that the return line 30 is connected to the suction line 16 or to the suction inlet 8 behind the suction valve 20' in the suction direction, and that the suction valve 20' is designed as a check valve blocking against the suction direction.

[0067] As Figures 3 and 3a show, the scroll compressor 4.3 in this embodiment also has the suction inlet 8, the discharge outlet 10 and the medium pressure inlet 14.

[0068] According to the information in the table in Fig. 3b, the compressor 4.3 can be operated in four modes (Mode 1 to Mode 4) during its compression work, depending on the boost pressure PL in the return line 30. In the table, the de-energized, i.e., closed, state of the boost valve 32 is represented by a circle symbol, as before, and the energized, i.e., open, state is represented by a cross.

[0069] In a first operating mode (Mode 1), the air is drawn in only from the ambient air at any boost pressure PL in the return line 30 at high drive speed (HM > nivi_nom). In a second operating mode (Mode 2), the air is drawn in at a boost pressure PL of 1 x 1O 5 Pa up to 2 x 10 5 Pa in the return line 30 and open boost valve 32 at high drive speed (riM > nM_nom). In a third operating mode (Mode 3), the air is drawn in at a boost pressure PL of 2 x 10 5 Pa to

[0070] 4 x 1Q 5 Pa in the return line 30 and the boost valve 32 is open at the nominal drive speed (HM = nM_nom) only from the return line 30. And in a fourth operating mode (Mode 4), the air is sucked in at a boost pressure PL of 4 x 10 5 Pa to

[0071] 5 x 10 5Pa in the return line 30 and open boost valve 32 at low drive speed (HM < nM_nom) is only sucked from the return line 30. According to a further development of this third embodiment shown in Fig. 3, the return line 30 is not connected to the suction line 16 or to the suction inlet 8 of the compressor 4.3, but via a medium-pressure return line 31 shown with a dotted line to its medium-pressure inlet 14. This variant can be used if the expected boost pressure in the return line 30 is comparatively low, but greater than the opening pressure of the suction valve 20' designed as the first check valve.

[0072] The fourth embodiment of a compressed air supply system 2.4 of a vehicle according to the invention, shown in Fig. 4, differs from the third embodiment according to Fig. 3 in that a second check valve 50, which blocks against the conveying direction, is arranged in the conveying line 22 between the conveying outlet 10 of the compressor 4.4 and the conveying valve 24, that the compressor 4.4 has a medium-pressure outlet 14', and that a first relief line 52 is present, which is connected to the medium-pressure outlet 14' of the compressor 4.4 and to the conveying line 22 between the second check valve 50 and the conveying valve 24. In addition, a third check valve 54, which blocks in the direction of the medium-pressure outlet 14', is arranged in the first relief line 52. The arrangement of the conveying valve 24 is merely optional.

[0073] In this arrangement, compressed air flows into the delivery line 22 via the first relief line 52 when the pressure at the medium pressure outlet 14' of the compressor 4.4 exceeds the opening pressure of the third check valve 54, whereby a mechanical overload of the compressor 4 can be automatically avoided.

[0074] The schematic cross-sectional view of Fig. 4a shows that the medium-pressure outlet 14' of the compressor 4.4 is arranged in the end wall 40 of the housing 38 radially centrally and axially adjacent to a pressure chamber 46d in which a medium-high air pressure is established when the displacement disk is driven.

[0075] According to the information in the table in Fig. 4b, this compressor 4.4 can be operated in five operating modes (Mode 1 to Mode 5) during its compression work, depending on the boost pressure PL in the return line 30 and the intended discharge pressure PF. In the table, the de-energized, i.e., closed, state of the boost valve 32 is indicated by a circle symbol, as before, and the energized, i.e., open, state of the boost valve 32 is indicated by a cross.

[0076] In a first operating mode (Mode 1), the air is drawn in only from the ambient air at any boost pressure PL in the return line 30 and any discharge pressure PF at high drive speed (nM > HM. _nom). In a second operating mode (Mode 2), the air is drawn in at a boost pressure PL of 1 x 10 5 Pa up to 4 x 10 5 Pa in the return line 30 and a discharge pressure PF of less than 8 x 1O 5Pa with the boost valve 32 open and the drive speed high (nM > nM_nom) the air is largely drawn in from the return line 30. In a third operating mode (Mode 3), the air is drawn in at a boost pressure PL of 4 x 10 5 Pa up to 7 x 10 5 Pa in the return line 30 and a discharge pressure PF of less than 8 x 10 5 Pa with the boost valve 32 open and the nominal drive speed (nM = nM_nom) only from the return line 30. In a fourth operating mode (Mode 4), the air is drawn in at a boost pressure PL of 7 x 1O 5 Pa up to 10 x 10 5 Pa in the return line 30 and a discharge pressure PF of less than 8 x 10 5 Pa with the boost valve 32 open and the drive speed low (nM < nM_nom) only from the return line 30. In a fifth operating mode (Mode 5), the air is drawn in at a boost pressure PL of 1 x 5 Pa up to 10 x 10 5 Pa in the return line 30 and a discharge pressure PF of more than 8 x 10 5Pa at low speed (nM < nM_nom) only sucked from the environment.

[0077] The fifth embodiment of a compressed air supply system 2.5 of a vehicle according to the invention, shown in Fig. 5, differs from the fourth embodiment according to Fig. 4 in that the compressor 4.5 additionally has a low-pressure outlet 12', that a second relief line 56 is present, which is connected to the low-pressure outlet 12' of the compressor 4.5 and to the suction line 16 between the air filter 18 and the suction valve 20' designed as the first check valve, and that a relief valve 58, 60 is arranged in each of the two relief lines 52, 56, each of which is designed as a 2 / 2-way solenoid valve that is closed in the de-energized, idle state. In this compressed air supply system 2.5, too, the arrangement of the delivery valve 24 is only optional.

[0078] By expanding compressor 4.5 with the low-pressure outlet 12' and the second relief line 56, as well as by arranging a relief valve 58, 60 in each of the two relief lines 52, 56, an additional flow path is available for relieving the pressure on compressor 4.5. Furthermore, the relief can be actively controlled by the compressed air flowing out via the additional outlets 12', 14' of compressor 4.5 by actuating the two relief valves 58, 60.

[0079] The schematic cross-sectional view of Fig. 5a shows that the low-pressure outlet 12' of the scroll compressor 4 is arranged in the end wall 40 of the housing 38 radially centrally and axially adjacent to a pressure chamber 46d in which a low pressure is established when the displacement disk is driven.

[0080] According to the information in the table in Fig. 5b, the compressor 4.5 can be operated in four operating modes (Mode 1 to Mode 4) during its compression work, depending on the boost pressure PL in the return line 30. In the table, the de-energized, i.e., closed, state of the boost valve 32 and the two relief valves 58, 60 is indicated by a circle symbol, and the energized, i.e., open, state of these valves 32; 58; 60 is indicated by a cross.

[0081] In a first operating mode (Mode 1), the air is drawn in only from the environment at any boost pressure PL in the return line 30 at the nominal drive speed (rnvi = nM_nom). In a second operating mode (Mode 2), the air is drawn in at a boost pressure PL of 1 x io 5 Pa to 2 x io 5Pa in the return line 30 with the boost valve 32 open and the nominal drive speed riM largely sucked in from the return line 30. In a third operating mode (Mode 3), the air is sucked in at a boost pressure PL of 2 x 1O 5 Pa up to 5 x 1Q 5 Pa in the return line 30 with the boost valve 32 and the relief valves 58, 60 open and the nominal drive speed riM only from the return line 30. And in a fourth operating mode (Mode 4), the air is sucked in at a boost pressure PL of 5 x 10 5 Pa up to 10 x 10 5 Pa in the return line 30 with the boost valve 32 open and the relief valves 58, 60 open and the drive speed low (nM < nM_nom) is also only sucked from the return line 30. Since the relief valves 58, 60 are open in the last two operating modes (modes 3 and 4), overload protection of the compressor 4 is implemented here.

[0082] In the embodiments shown in Figures 3, 4, and 5, electromagnetic switching valves can also be used instead of the check valves shown there. As can be seen from the explanation of Figures 1b, 2b, 3b, 4b, and 5b, the controlled variable for the respective operating modes is the current power of the electric motor 6 to protect it from overload. Therefore, if the currently set power of the electric motor 6 is too high, an operating mode with a lower power requirement for the electric motor 6 can be selected, and the compressed air supply system can be operated accordingly.

[0083] A further compressed air supply system according to the invention can be formed by a combination of those features which are shown in the embodiments according to Figures 1 to 5b and have just been described.

[0084] List of reference symbols (part of the description)

[0085] 2.1 Compressed air supply system (first embodiment)

[0086] 2.2 Compressed air supply system (second embodiment)

[0087] 2.3 Compressed air supply system (third embodiment)

[0088] 2.4 Compressed air supply system (fourth embodiment)

[0089] 2.5 Compressed air supply system (fifth embodiment)

[0090] 4.1 Compressor, scroll compressor (first embodiment)

[0091] 4.2 Compressor, scroll compressor (second embodiment)

[0092] 4.3 Compressor, scroll compressor (third embodiment)

[0093] 4.4 Compressor, scroll compressor (fourth embodiment)

[0094] 4.5 Compressor, scroll compressor (fifth embodiment)

[0095] 6 Electric motor

[0096] 8 Suction inlet

[0097] 10 conveyor outlet

[0098] 12 Low pressure inlet

[0099] 12' low pressure outlet

[0100] 14 Medium pressure inlet

[0101] 14' medium pressure outlet

[0102] 16 Suction line

[0103] 18 air filters

[0104] 20 Suction valve, 2 / 2-way solenoid valve

[0105] 20' suction valve (first check valve)

[0106] 22 conveyor line

[0107] 24 Delivery valve, 2 / 2-way solenoid valve

[0108] 25 Alternative check valve instead of delivery valve 24

[0109] 26 storage containers

[0110] 28 Pressure sensor in the reservoir

[0111] 30 Return line

[0112] 30a First branch of the return line

[0113] 30b Second branch of the return line

[0114] 31 Medium pressure return line

[0115] 32 Boost valve, 2 / 2-way solenoid valve

[0116] 32a First boost valve, 2 / 2-way solenoid valve 32b Second boost valve, 2 / 2-way solenoid valve

[0117] 34 collection containers

[0118] 35 compressed air consumers

[0119] 36 Pressure sensor in the collection tank

[0120] 38 housings

[0121] 40 front wall

[0122] 42 stator blades

[0123] 44 Displacement blade

[0124] 46a - 46f Pressure rooms

[0125] 48 Direction of rotation

[0126] 50 Second check valve

[0127] 52 First relief line

[0128] 54 Third check valve

[0129] 56 Second relief line

[0130] 58 First relief valve, 2 / 2-way solenoid valve

[0131] 60 Second relief valve, 2 / 2-way solenoid valve

[0132] 62 Consumer-side first 2 / 2-way solenoid valve

[0133] 64 Consumer-side second 2 / 2-way solenoid valve nM Motor speed, drive speed riM_nom Nominal drive speed

[0134] PF discharge pressure

[0135] PL boost pressure

Claims

Patent claims 1. Compressed air supply system (2.1, 2.2, 2.3, 2.4, 2.5) of a vehicle, with a compressor (4.1, 4.2, 4.3, 4.4, 4.5) designed as a single-stage scroll compressor, wherein the compressor is drive-effectively connected to an electric motor (6), wherein the compressor has a suction inlet (8), a delivery outlet (10) and at least one further inlet (12, 14) or outlet (12', 14') for passing air, wherein a suction line (16) provided with a suction valve (20, 20') is connected to the suction inlet (8) of the compressor, wherein a delivery line (22) is provided, which is connected to the delivery outlet (10) of the compressor and via a delivery valve (24) or check valve (25) to a storage container (26) or to the inlet of at least one compressed air consumer (35) and with a return line (30) which is connected to an inlet (8;12, 14) of the compressor and is led via a boost valve (32, 32a, 32b) to a collecting tank (34) or to the outlet of at least one compressed air consumer (35), and in which a pressure sensor (28, 36) is arranged in each of the storage tank (26) and the collecting tank (34) for determining the air pressure there.

2. Compressed air supply system (2.1, 2.2, 2.3, 2.4, 2.5) according to claim 1, characterized in that it has a variable-speed electric motor (6).

3. Compressed air supply system (2.1, 2.2, 2.3, 2.4, 2.5) according to claim 1 or 2, characterized in that the compressor (4.1) has a medium-pressure inlet (14), that the return line (30) is connected to the medium-pressure inlet (14) of the compressor (4), and that the suction valve (20) and the boost valve (32) are designed as 2 / 2-way switching valves which are closed in the unactuated rest state.

4. Compressed air supply system (2.1) according to one of the preceding claims, characterized in that the compressor (4.1) can be operated in its compression work depending on the boost pressure (pQ) in the return line (30) in five operating modes (Mode 1 to Mode 5), wherein in a first operating mode (Mode 1), in which the air is supplied at any boost pressure (PL) in the return line (30) and open suction valve (20) as well as with closed Boost valve (32) at high drive speed (AM > nivi_nom) is sucked in only from the environment, wherein in a second operating mode (Mode 2), in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line of 50% to 60% of the maximum pressure of the compressor 6 and an open boost valve (32) at high drive speed (AM > nM_nom), wherein in a third operating mode (Mode 3), in which the air is sucked in both from the environment and from the return line (30) at a boost pressure (PL) in the return line (30) of 50% to 60% of the maximum pressure of the compressor and an open suction valve (20) and boost valve (32) at low drive speed (AM < nM_nom), wherein in a fourth operating mode (Mode 4),in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line (30) of 61% to 80% of the maximum pressure of the compressor and with the suction valve (20) closed and the boost valve (32) open at the nominal drive speed (AM = nM_nom), and in a fifth operating mode (Mode 5), in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line (30) of 91% to 100% of the maximum pressure of the compressor and with the suction valve (20) closed and the boost valve (32) open at low speed (AM < nivi_nom).

5. Compressed air supply system (2.2) according to one of the claims, characterized in that the compressor (4.2) has a low-pressure inlet (12) and a medium-pressure inlet (14), that the return line (30) is branched on the output side into a first line branch (30a) with a first boost valve (32a) and into a second line branch (30b) with a second boost valve (32b), that the first line branch (30a) is connected to the low-pressure inlet (12) and the second line branch (30b) is connected to the medium-pressure inlet (14) of the compressor (4.2), and that the suction valve (20) and the two boost valves (32a, 32b) are designed as 2 / 2-way switching valves which are closed in the unactuated idle state.

6. Compressed air supply system (2.2) according to claim 5, characterized in that the compressor (4.2) can be operated in seven operating modes (Mode 1 to Mode 7) during its compression work depending on the boost pressure (PL) in the return line (30), wherein in a first operating mode (Mode 1), in which the air is sucked in only from the environment at any boost pressure (PL) in the return line (30) and open suction valve (20) as well as closed boost valves (32a, 32b) with high drive speed (HM > nwi_nom), wherein in a second operating mode (Mode 2), in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line (30) of 10% to 20% of the maximum pressure of the compressor with closed suction valve (20), open first boost valve (32a) and closed second boost valve (32b) with high drive speed (nivi > nM_nom), wherein in a third operating mode (Mode 3), in which the air is sucked in at a boost pressure (PL) in the return line (30) of 21% to 40% of Maximum pressure of the compressor with the suction valve closed (20),open first boost valve (32a) and closed second boost valve (32b) with the nominal drive speed (nivi = nivi_nom) only from the return line (30), wherein in a fourth operating mode (Mode 4), in which the air is sucked in at a boost pressure (PL) in the return line (30) of 41% to 50% of the maximum pressure of the compressor with the suction valve (20) closed, open first boost valve (32a) and closed second boost valve (32b) with a low drive speed (HM < nwi_nom) only from the return line (30), wherein in a fifth operating mode (Mode 5), in which the air is sucked in at a boost pressure (PL) in the return line (30) of 51% to 60% of the maximum pressure of the compressor with the suction valve (20) closed, closed first boost valve (32a) and open second boost valve (32b) with high drive speed (HM > nM_nom) is sucked only from the return line (30), whereby in a sixth operating mode (Mode 6),in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line (30) of 61% to 80% of the maximum pressure of the compressor with the suction valve (20) closed, the first boost valve (32a) closed and the second boost valve (32b) open at the nominal drive speed (nM = nM_nom), and in a seventh operating mode (Mode 7), in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line (30) of 91% to 100% of the maximum pressure of the compressor with the suction valve (20) closed, the first boost valve (32a) closed and the second boost valve (32b) open at a low drive speed (nM < nM_nom).

7. Compressed air supply system (2.3) according to one of the claims, characterized in that the return line (30) is connected to the suction line (16) behind the suction valve (20') as seen in the suction direction towards the compressor (4.3), and that the suction valve (20') is designed as a first check valve blocking against the suction direction and the boost valve (32) arranged in the return line (30) is designed as a 2 / 2-way switching valve closed in the unactuated rest state.

8. Compressed air supply system (2.3) according to claim 7, characterized in that the compressor (4.3) can be operated in four operating modes (Mode 1 to Mode 4) during its compression work depending on the boost pressure (PL) in the return line (30), wherein in a first operating mode (Mode 1), in which the air is sucked in only from the environment at any boost pressure (PL) in the return line (30) with the boost valve (32) closed at a high drive speed (HM > nM_nom), wherein in a second operating mode (Mode 2), in which the air is sucked in at least largely from the return line (30) at a boost pressure (PL) in the return line (30) of 10% to 20% of the maximum pressure of the compressor and the boost valve (32) open at a high drive speed (HM > nM_nom), in a third operating mode (Mode 3),in which the air is at least largely sucked in from the return line (30) at a boost pressure (PL) in the return line (30) of 21% to 40% of the maximum pressure of the compressor and an open boost valve (32) at the nominal drive speed (nM = nM_nom), and in a fourth operating mode (Mode 4), in which the air is at least largely sucked in from the return line (30) at a boost pressure (PL) in the return line (30) of 41% to 50% of the maximum pressure of the compressor and an open boost valve (32) at a low drive speed (nM < nM_nom).

9. Compressed air supply system (2.4) according to one of the claims, characterized in that a second check valve (50) blocking against the conveying direction is arranged in the conveying line (22) between the conveying outlet (10) of the compressor (4.4) and an optional conveying valve (24), that the compressor (4.4) has a medium-pressure outlet (14'), that a first relief line (52) is present, which is connected to the medium-pressure outlet (14') of the compressor (4.4) and between the second check valve (50) and the delivery valve (24) is connected to the delivery line (22), and that in the first relief line (52) a third check valve (54) is arranged which blocks in the direction of the medium pressure outlet (14') of the compressor (4.4).

10. Compressed air supply system (2.4) according to claim 9, characterized in that the compressor (4.4) can be operated in its compression work depending on the boost pressure (PL) in the return line (30) and the intended delivery pressure (PF) in five operating modes (Mode 1 to Mode 5), wherein in a first operating mode (Mode 1), in which the air is sucked in only from the environment at any boost pressure (PL) in the return line (30) and any delivery pressure (PF) with the boost valve (32) closed at a high drive speed (HM > nwi_nom), wherein in a second operating mode (Mode 2), in which the air is sucked in at a boost pressure (PL) in the return line (30) of 10% to 40% of the maximum pressure of the compressor and a delivery pressure (PF) of less than 80% of the maximum pressure of the compressor with the boost valve (32) open and at a high drive speed (HM > nM_nom) is only sucked from the return line (30), whereby in a third operating mode (Mode 3),in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line (30) of 41% to 70% of the maximum pressure of the compressor and a delivery pressure (PF) of less than 80% of the maximum pressure of the compressor with the boost valve (32) open and the nominal drive speed (ni i = nM_nom), wherein in a fourth operating mode (Mode 4), in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line (30) of 71% to 100% of the maximum pressure of the compressor and a delivery pressure (PF) of less than 80% of the maximum pressure of the compressor with the boost valve (32) open and a low drive speed (HM < nw_nom), and wherein in a fifth operating mode (Mode 5),in which the air is only sucked in from the environment at a boost pressure (PF) in the return line (30) of 10% to 100% of the maximum pressure of the compressor and a discharge pressure (PF) of more than 80% of the maximum pressure of the compressor at low speed (nM < nM_nom) with the boost valve (32) closed.

11. Compressed air supply system (2.5) according to one of the claims, characterized in that the compressor (4.5) additionally has a low-pressure outlet (12') to which a second relief line (56) is connected, that the second relief line (56) is connected with its other end to the suction line (16) via the first check valve (20'), that a first relief valve (58) is arranged in the first relief line (52) and a second relief valve (60) is arranged in the second relief line (56), and that the two relief valves (58, 60) are designed as 2 / 2-way switching valves which are closed in the unactuated rest state.

12. Compressed air supply system (2.5) according to claim 11, characterized in that the compressor (4.5) can be operated in four operating modes (Mode 1 to Mode 4) during its compression work depending on the boost pressure (PL) in the return line (30), wherein in a first operating mode (Mode 1), in which the air is sucked in only from the environment at any boost pressure (PL) in the return line (30) with the boost valve (32) closed and with the relief valves (58; 60) closed at the nominal drive speed (rnvi = HM. _nom), wherein in a second operating mode (Mode 2), in which the air is sucked in at a boost pressure (PL) in the return line (30) of 10% to 20% of the maximum pressure of the compressor with the boost valve (32) open and with the relief valves (58;60) is sucked in largely from the return line (30) at nominal drive speed, wherein in a third operating mode (Mode 3), in which the air is sucked in only from the return line (30) at a boost pressure (PL) in the return line (30) of 21% to 50% of the maximum pressure of the compressor with the boost valve (32) and the relief valves (58; 60) open and at nominal drive speed, and wherein in a fourth operating mode (Mode 4), in which the air is sucked in only from the return line at a boost pressure (PL) in the return line (30) of 51% to 100% of the maximum pressure of the compressor with the boost valve (32) and the relief valves (58; 60) open and at low drive speed (nM < nM_nom); 13. Compressed air supply system (2.3, 2.4, 2.5) according to one of the preceding claims, characterized in that an air filter (18) is arranged in the intake direction of the air in front of the first check valve (20'), 14. Compressed air supply system according to several of the preceding claims, characterized in that it comprises a combination of the features.

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