Operating strategy for limiting power consumption of brushless motor of electrically driven passenger vehicle air spring compressor by mode switching

Abstract

The invention relates to a compressed air supply system (30), in particular for a motor vehicle, having at least the following components: one or more compressed air consumers (34), a compressed air line, an electrically controllable valve, a compressed air control unit (56) for actuating the electrically controllable valve, a compressor or compressor (12) having an electric motor (14) as a drive, and a pressure accumulator (36). The one or more compressed air consumers (32) are or can be pneumatically connected to the compressor or compressor (12) and / or the pressure accumulator (36) via a compressed air line and an electrically controllable valve, such that the compressed air supply system (30) can be operated either in an open operating mode or in a closed operating mode. According to the invention, the compressed air control unit (56) has a current signal input for a current signal which represents a motor current (IB) consumed or to be consumed by an electric motor (14) driving the compressor or compressor (12). The compressed air control unit (56) is designed to actuate the electrically controllable valve according to an open operating mode of the compressed air supply system (30) when a current signal (SIB) is applied to the current signal input (92), said current signal representing an average motor current (IB) whose magnitude is equal to or greater than a predetermined maximum value (Imax) of the motor current.

Description

TECHNICAL FIELD

[0001] The present application relates to a compressed air supply for a vehicle. The present application also relates to a method for operating such a compressed air supply. BACKGROUND

[0002] In a motor vehicle, a compressed air supply can supply, for example, air spring devices as compressed air consumers and / or pneumatic brake devices as compressed air consumers with compressed air. In order to be able to provide such compressed air consumers with compressed air having a sufficiently high pressure, a compressor is required for compressed air generation. Such a compressor is typically driven by an electric motor, which consumes a motor current during operation. In the present description, compressor and compressor are used synonymously and both refer to a unit which compresses air, i.e. which compresses air.

[0003] In addition to a compressed air consumer or a plurality of compressed air consumers, a compressor and its drive, a main component of a compressed air supply is an electrically controllable valve which can be controlled, i.e. opened or closed, for example, by a compressed air control. In this way, it is possible to purposefully deliver compressed air to the individual compressed air consumers of the compressed air supply or to also discharge compressed air. Depending on which compressed air consumer needs to be supplied with compressed air in the respective operating situation, the compression work to be performed by the compressor can be very different. As will be explained in more detail below, the torque to be delivered by the drive of the compressor or compressor is related to which pressure the compressed air needs to have for the respective operating situation. When the compressor or compressor is driven by an electric motor, the current consumption of the electric motor is related to the torque to be delivered, i.e. the operating load of the drive, in the case of a supply voltage typically provided by the on-board network of the vehicle.

[0004] Preferably, the compressor and the associated drive, in particular the associated electric motor, are combined into a structural unit, which is referred to hereinafter as a compressor module. The compressor module is used, for example, in a compressed air supply for a motor vehicle.

[0005] As electric motor for driving a compressor or a gas compressor a brushless direct current motor (BLDC motor) is preferably used. A brushless direct current motor as so-called internal rotor typically has a rotor with electromagnetic coils, i.e. with windings, with permanent magnets and a motor control. The motor control is configured as electronic commutator such that the motor control controls the current delivery to the windings (in the following also referred to as coils) via power switches such that the coils are periodically supplied with current in turn such that a rotating magnetic field is obtained which via magnetic forces causes the rotor with permanent magnets to rotate synchronously. Such a brushless direct current motor with permanent magnets is therefore also referred to as PMSM motor, wherein PMSM means permanent magnet synchronous motor. The abbreviation PMSM is typically used herein for sinus commutated brushless electric motors, whereas the abbreviation BLDC (brushless direct current) is generally used for square wave commutated brushless electric motors. In case of square wave commutation the energization of the (e.g. three or n times three) coils is digitally switched, i.e. either zero current or full current is applied to the respective coil or phase of the coils. In case of sinus commutation each coil of the motor is energized with a sinus curve shifted by 120° such that a constantly rotating magnetic field with constant strength is obtained.

[0006] For the speed regulation of a known brushless electric motor the electric motor has means for rotor angle detection with electronic sensors, e.g. Hall sensors, for detecting the rotor positioning. Thus, also the phase angle between the applied rotating field and the mechanical rotation of the rotor can be detected and the phase angle of the rotating field can be adjusted accordingly. Thus, a BLDC motor behaves similar to a mechanically commutated direct current motor. However, a brushless direct current motor is more efficient, less wearing and can be better speed regulated than an electric motor with brush commutator.

[0007] In a compressor module for compressed air generation in a compressed air supply installation, for example for a motor vehicle, a compressor for generating compressed air and its electric motor used as a drive form a structural unit. In order to achieve an efficient and environmentally friendly operation, the design and operation of the electric motor, for example a brushless DC electric motor, is a particular challenge. This challenge consists, inter alia, in the fact that the compressor module should be able to provide sufficient compressed air in the respective compressed air supply installation at all times in a variety of different possible operating situations, and also in rare operating situations. This means that the compressor module must provide sufficient compressed air for the compressed air supply installation even in unfavorable conditions which only rarely occur, the worst-case operating situation. For this purpose, the drive, i.e. for example a brushless DC electric motor, must also be designed accordingly. In the case of a given supply voltage for the electric motor, a higher mechanical load, i.e. a higher mechanical output power, necessarily leads to a greater current consumption of the electric motor. However, in order to protect the on-board network of the motor vehicle, the maximum current consumption of the DC electric motor must be limited.

[0008] A BLDC motor is known from WO 2020 / 225024 A1 which is used to drive a compressor to run at a constant rotational speed and in order to avoid an over-dimensioning of the motor specification, the rotational speed needs to be reduced depending on the load conditions (operating voltage and load (torque)). SUMMARY

[0009] It is the task of the present application to ensure a reliable and environmentally friendly operation of the compressor module in the simplest possible way.

[0010] In order to solve this task, according to the application a compressed air supply installation, in particular for a motor vehicle, is specified which has at least the following components: - one or more compressed air consumers, - a compressed air line, - an electrically controllable valve, - a compressed air control for actuating the electrically controllable valve, - a compressor or a compressor wheel with an electric motor as a drive, and - a pressure accumulator.

[0011] The one or more compressed air consumers are pneumatically or pneumatically connectable via the compressed air line and the electrically controllable valve to the compressor or compressor wheel and / or to the pressure accumulator, so that the compressed air supply installation can be operated either in an open operating mode or in a closed operating mode.

[0012] In the closed mode of operation, compressed air is delivered from the pressure accumulator to one or more compressed air consumers or from the compressed air consumers to the pressure accumulator by means of the compressor or the air compressor, respectively. For this purpose, the electrically controllable valve and the compressor or the air compressor are actuated by the compressed air control unit in accordance with the closed mode of operation. In the open mode of operation, compressed air is delivered from the environment to one or more compressed air consumers or to the pressure accumulator by means of the compressor or the air compressor. For this purpose, the electrically controllable valve is actuated by the compressed air control unit in accordance with the open mode of operation.

[0013] According to the application, the compressed air control unit has a current signal signal input for a current signal which represents the motor current consumed or to be consumed by the electric motor driving the compressor or the air compressor. The compressed air control unit is designed to actuate the electrically controllable valve in accordance with the open mode of operation of the compressed air supply facility when a current signal is applied at the current signal signal input which represents an average motor current whose magnitude is equal to or greater than a predefined maximum value of the motor current. As a criterion for switching the mode of operation, it is preferable not to take into account the instantaneous value of the motor current but rather an average motor current which represents a short-time average value of the motor current, in order thus to have made it impossible for the switching of the mode of operation to be triggered by short instantaneous current peaks or periodic fluctuations of the instantaneous value of the motor current. The value of the average motor current can be formed by the motor control unit, for example, by the motor control unit measuring the three-phase current and then calculating the average current consumption of the electric motor therefrom.

[0014] The application makes it possible for the electric motor to be designed in accordance with the standard as a constant-speed motor. According to the application, the necessary drive power of the compressor or the air compressor is reduced by switching from the closed mode of operation to the open mode of operation when the permissible current consumption is exceeded. For this purpose, the current, time-averaged or low-pass filtered current consumption of the electric motor for driving the compressor or the air compressor is ascertained, and when a defined limit value is exceeded, the closed operation of the compressed air supply facility is terminated and regulated in the open mode of operation until the end.

[0015] The mode switching on the basis of the average motor current has the advantage here that it is not necessary to reserve device-specific tolerances, different pressure ranges and further values influencing the current in the form of worst-case assumptions, but rather to maximize the performance of the compressor in all operating ranges.

[0016] Furthermore, the application also makes it possible to maintain the rotational speed of the compressor and the drive constant, since the rotational speed is not reduced when the maximum permissible motor current I max is exceeded, but rather the load is reduced by means of the mode switching.

[0017] Advantageous refinements of the application are evident from the dependent claims and are explained in detail in terms of the objects and in terms of further advantages, which achieve the above-mentioned concept in an advantageous and expedient manner.

[0018] Preferably, the current signal input is connected to at least one current sensor, which is designed to detect the motor current I consumed by the electric motor driving the compressor or the blower B and outputs a signal representing the motor current to the compressed air control. The current sensor can be taken from the current sensors of the motor control, which are usually provided for each phase. The formation of the average motor current can already be achieved by the motor control on the compressor module or by the compressed air control. For example, the motor control can derive the average motor current from the three measured phase currents. Alternatively, it is also possible to provide an additional current sensor.

[0019] In a preferred embodiment, the compressed air consumer is an air spring arrangement of a vehicle, which has one or more air bellows.

[0020] Preferably, the compressor or the blower and the electric motor are combined in the form of a compressor module into a structural unit and are thus optimally coordinated with one another on the one hand and are integrated as a unit into the compressed air supply facility on the other hand.

[0021] The electric motor is preferably a speed-regulated BLDC motor, to which at least one target rotational speed is predetermined in operation.

[0022] Especially with regard to the discharge of air from the compressed air consumer, for example when lowering a vehicle with the aid of an air spring arrangement, it is advantageous if the compressed air control is designed to determine the average motor current to be consumed by the electric motor predictively on the basis of the air pressure in the compressed air supply facility and the request to the compressed air consumer, in particular a "lowering" request. When the predictively determined average motor current reaches or exceeds a defined maximum value for the motor current at the predetermined rotational speed, the motor rotational speed is set in a first step such that the permissible current is prevented from being reached or exceeded. Especially from an acoustic point of view, it is advantageous here that the entire lowering process is thus carried out without additional rotational speed adjustments. If the setting of the rotational speed in the first step results in a too low value, the start of the lowering process in open operation is carried out as a second step. It is advantageous here that a switch from closed operation to open operation is avoided during the current lowering process, since such a switch requires the activation of further valves. With this method, a perceptible delay in the lowering process is reliably avoided.

[0023] In the case of a "boost" request, i.e. when compressed air is to be delivered to a compressed air consumer, the switchover from the closed mode of operation to the open mode of operation can be effected simply by closing (activating) the pressure boost valve.

[0024] Preferably, the compressed air supply facility has a pressure sensor which is arranged and configured such that it detects the air pressure prevailing in the compressed air supply facility during operation and outputs a pressure signal representing the air pressure to the compressed air control. On the basis of the pressure signal and the request signal, the compressed air control can determine the required motor current predictively and compare it with the predetermined maximum motor current I max in order to cause a speed adjustment or a mode switchover if necessary.

[0025] Preferably, the compressed air supply facility has a reservoir valve which is arranged pneumatically between the pressure accumulator and the pneumatic main pressure line.

[0026] It is likewise advantageous if the compressed air supply facility has a pressure boost valve which is arranged pneumatically between the pressure accumulator and the pressure boost and return line.

[0027] A further aspect relates to the method of claim 10. The method serves to operate a compressed air supply facility, in particular a compressed air supply facility for a motor vehicle, which has: - one or more compressed air consumers, - a compressed air line, - an electrically controllable valve, - a compressed air control for actuating the electrically controllable valve, - a compressor or air compressor having an electric motor as a drive, and - a pressure accumulator.

[0028] The one or more compressed air consumers are pneumatically or pneumatically connectable via the compressed air line and the electrically controllable valve to the compressor or air compressor and / or to the pressure accumulator, such that the compressed air supply facility can be operated either in an open mode of operation or in a closed mode of operation.

[0029] According to the method, an electric current signal representing the motor current consumed or to be consumed by the electric motor driving the compressor or air compressor is delivered to the compressed air control during operation. When an average motor current I max whose magnitude is equal to or greater than the predetermined maximum value I BThe compressed air supply facility has a pressure accumulator, a compressor, a pressure accumulator valve, a return flow valve, a reserve valve, and a discharge valve. The pressure accumulator valve is pneumatically connected to the pressure accumulator. The return flow valve is pneumatically connected to the compressor. The reserve valve is pneumatically connected to the pressure accumulator. The discharge valve is pneumatically connected to the compressor. The compressed air control unit is designed to switch the compressed air supply facility from the closed operating mode to the open operating mode and to control the electrically controllable valves in accordance with the open operating mode of the compressed air supply facility when the average motor current is greater than a predetermined or learned motor current threshold value. The average motor current is a value averaged over a time period of a few tenths of a second and / or low-pass filtered. By forming the average motor current I B

[0030] Preferably, the switch from the closed operating mode to the open operating mode is effected by deactivating the pressure booster valve when compressed air is delivered to the pressure consumer. To this end, the compressed air supply facility has a pressure booster valve, which is pneumatically connected to the pressure accumulator.

[0031] According to an advantageous first variant, the switch from the closed operating mode to the open operating mode is effected by switching off the compressor, closing (deactivating) the return flow valve and the reserve valve, and opening (activating) the discharge valve when compressed air should be discharged from the pressure consumer. To this end, the compressed air supply facility has a discharge valve, a return flow valve, and a reserve valve, which is pneumatically connected to the pressure accumulator.

[0032] Since the average motor current is proportional to the drive torque (torque demand) required by the compressor, respectively, it is possible to select the open operating mode or the closed operating mode by means of predictive control even without taking into account the motor current itself, but only on the basis of influencing parameters that affect the torque demand of the compressor at a given rotational speed and their foreseeable temporal development (e.g. the growing back pressure as the pressure accumulator fills up). This approach (i.e. the predictive selection of the open or closed operating mode and the corresponding control of the compressed air supply facility) is an independent inventive concept, which can be implemented both in combination with the mode switching based on the motor current described herein and independently of the motor current. The method variants outlined below can therefore also be implemented independently of the method outlined above.

[0033] According to an advantageous first variant, the compressed air control unit activates the closed operating mode when the pressure in the pressure accumulator is below a predetermined or learned accumulator pressure limit value, or activates the open operating mode when the pressure in the pressure accumulator is above a predetermined or learned accumulator pressure limit value, for the case that compressed air should be discharged from the pressure consumer. To this end, the compressed air supply facility has a pressure sensor at the compressed air accumulator, and a discharge valve, a return flow valve, and a reserve valve, which is pneumatically connected to the pressure accumulator.

[0034] ​According to an advantageous first variant, the compressed air control activates the open run mode in the event that compressed air is discharged from the pressure consumer, by previously calculating or estimating the desired storage pressure on the basis of existing information about the storage pressure in the pressure accumulator and the volume of the pressure accumulator, the pressure in the compressed air consumer or one or more components of the compressed air consumer and its volume and height state, and activating the open run mode when the calculated or estimated storage pressure exceeds a predetermined storage pressure limit value. The compressor is then kept switched off, the return valve and the reservoir valve are kept closed (deactivated) and the discharge valve is opened (activated). Thus, the compressor is not switched on, the return valve and the reservoir valve are kept in the closed position and only the discharge valve and the respective pressure consumer valve are opened.

[0035] Preferably, the compressed air control sets the storage pressure limit value adaptively on the basis of a correlation between back pressure and current consumption learned in the operation of the compressor module. BRIEF DESCRIPTION OF DRAWINGS

[0036] Embodiments of the application are now described by way of example with reference to the accompanying drawings. The drawings are not necessarily to scale, and the embodiments can be implemented in a form other than as illustrated and described in the figures. Reference is made herein to related art in addition to what is explicitly described, in order to fully understand the teachings of the present application. It is noted that various modifications and alterations of the embodiments can be made in view of the teachings herein without departing from the overall spirit and scope of the present application. The features disclosed in the specification, drawings and / or claims can both separately and in any combination thereof be material for realising the application in its various forms. Furthermore, the features disclosed in the specification, drawings and / or claims can constitute all possible combinations of the features disclosed in the specification, drawings and / or claims. The general idea of the present application is not limited to the precise forms and details of the preferred embodiments shown and described herein below, or to the subject matter claimed in the claims as compared to the subject matter protected. In the case of stated dimensional ranges, the values within the stated boundaries are also disclosed and can be used and claimed as boundaries. Further advantages, features and details of the present application are derived from the following description of the preferred embodiments and the enclosed drawings. In the drawings:

[0037] Figure 1 a wiring diagram is shown for a compressed air supply installation and an example of a compressed air consumer in the form of an air spring of a vehicle;

[0038] Figure 2 a valve symbol is shown as depicted in Figure 1 for explaining its mode of operation;

[0039] Figure 3A compressor module with a compressor, an electric motor and a motor control unit is shown;

[0040] Figure 4 A diagram for illustrating the working mode of a brushless electric motor is shown;

[0041] Figure 5 A diagram for illustrating the current consumption of an electric motor rising in case of a back pressure rising is shown;

[0042] Figure 6 A symbolic illustration of a compressor and a brushless electric motor with a motor control unit for driving the compressor; and

[0043] Figure 7 A diagram for illustrating the effect of a switching from a closed operating mode (a) to an open operating mode (b) according to the present application on the current consumption of an electric motor driving a compressor. Figure 7 a) to an open operating mode (b). Figure 7 DETAILED DESCRIPTION

[0044] Figure 1 The compressed air supply facility 30 shown in Fig. 1 is used, for example, for supplying compressed air to an air spring facility 32 of a vehicle having a plurality of air springs 34. Instead of the air spring facility 32, other compressed air consumers, for example a compressed air brake facility, can also be pneumatically connected to the compressed air supply facility 30.

[0045] The term "compressed air consumer" is used here both for the entire air spring facility 32 or the compressed air brake facility and for a single spring bellows 34 of the air spring facility 32 or a compressed air brake of the compressed air brake facility and thus for any form of compressed air consumer.

[0046] The main components of the compressed air supply facility 30 are the compressor 12 and its drive 14, the compressed air line 22 and the electrically controllable valves 44, 46, 48, 50, 52 and 54, which can be controlled by the compressed air control unit 56, i.e. for example opened or closed. In this way, compressed air can be delivered to the individual compressed air consumers 34 or can also be discharged. Depending on which compressed air consumer 34 is to be supplied with compressed air in the respective operating situation, the compression work to be done by the compressor 12 can be very different. The compressed air control unit 56 is an electronic control unit, which can output electrical signals to the individual electrically controllable valves for activation and thus control the compressed air supply facility 30. The compressed air control unit 56 is connected to or contains a memory 90 for operating a predetermined program. Furthermore, the compressed air control unit 56 has different signal inputs, for example for a request signal S Anf ​a signal input 90 for a signal S representing the motor current I B a signal S IB a signal input 92 for a signal S representing the air pressure P present in the main pressure line 42 of the compressed air supply 30 Anl a signal S P Anl a signal input 94 for a signal S representing the air pressure P present in the pressure accumulator 36 of the compressed air supply 30 Anl a signal S PR a signal input 96 for a signal S representing the air pressure P present at the pressure consumer 34 Abn a signal S PAbn a signal input 98. Instead of the compressor 12, it is also possible to provide a certain type of air blower.

[0047] In order to achieve an efficiency increase and a sustained availability, so-called "closed air spring systems" are used in passenger vehicle air spring systems. These closed air spring systems can be air spring systems which operate with a compressed air supply 30 as depicted in Figure 1 Fig. 1, since the compressed air supply 30 has components such as the pressure accumulator 36 which enable a closed mode of operation in addition to an open mode of operation. In contrast to an "open system" or open mode of operation, in the closed mode of operation the air mass in the air spring is not reduced by discharging excess air into the environment, but rather by pumping this air into the pressure accumulator 36 using the compressor 12. The compressor 12 required for this is preferably designed for two-stage air charging and is driven by a BLDC motor 14. The closed mode of operation achieved by cyclical pumping takes place via the second stage 12.2, in the open mode of operation the compressor 12 works two-staged by means of pre-air charging by the first stage 12.1 and final air charging by the second stage 12.2.

[0048] In order to be able to implement the closed mode of operation, in the embodiment shown the compressed air supply 30 has, in addition to the pressure accumulator 36, a return valve 48, a reserve valve 52, a separation valve 44 and a pressure boost valve 54.

[0049] The return valve 48 is arranged pneumatically between the compressed air consumer 32 and the compressor 12, such that when the return valve 48 is activated, i.e. opened, compressed air can flow from the compressed air consumer 32 through the return valve into the pressure boost and return line 76 leading to the compressor 12.

[0050] The reserve valve 52 is arranged pneumatically between the pressure accumulator and the pneumatic main pressure line 40, such that when the reserve valve 52 is activated, i.e. opened, compressed air can flow from the pressure accumulator 36 through the reserve valve into the pneumatic main pressure line 40.

[0051] The pressure boost valve 54 is arranged pneumatically between the pressure reservoir 36 and the pressure boost and return line 76, such that when the pressure boost valve 54 is activated, i.e. opened, compressed air can flow from the pressure reservoir 36 through the pressure boost valve into the pressure boost and return line 76 leading to the compressor 12. Thus, the compressor 12 can re-compress the compressed air taken from the pressure reservoir 36 in closed operation before it delivers the compressed air to the compressed air consumer 32.

[0052] The separation valve 44 is arranged pneumatically between the main pressure line 40 and the air spring arrangement 32, such that when the separation valve 32 is activated, i.e. opened, compressed air can flow from the main pressure line 40 through the separation valve into the air spring arrangement 32.

[0053] Due to the required compressor power or rather the derived delivery power, the required torque for driving the compressor 12 in closed operation mode is significantly different from the torque required in open operation mode.

[0054] As already mentioned above, Figure 1 The compressed air supply arrangement 30 as shown in Fig. 1 can be operated in open operation mode or in closed operation mode. In open operation mode, external air is sucked in and compressed from the environment (see dotted short line arrows in Fig. 1), whereas in closed operation mode, air is taken from the pressure vessel 36, also referred to as reserve here, and compressed (see dotted long line arrows in Fig. 1). Figure 1 Figure 1

[0055] If the current consumption of the drive of the compressor, i.e. the current consumption of the electric motor 14, which is proportional to the required torque, is below about 25 A in open operation, the current consumption can rise to 50 A or even more in closed operation. Thus, the closed operation mode is the operating mode with the highest torque or current demand. Both operating modes should be equipped in a vehicle at the same time.

[0056] Next, it is first described how compressed air is delivered to the compressed air consumer 34, i.e. for example to the spring bellows 24 of the air spring arrangement 32 of a vehicle. This is necessary, for example, when the vehicle should be lifted unilaterally or bilaterally. In order to achieve such a lifting, compressed air has to be delivered to the bellows 34.

[0057] Open mode of operation

[0058] In the air spring arrangement, both lifting and lowering can be carried out in closed operation mode.

[0059] ​​In a first open mode of operation, for example for raising the air spring installation 12, for the supply of compressed air to the compressed air consumer 32, compressed air is conducted from the compressor 12 via the pneumatic main pressure line 40 to the compressed air consumer 32, i.e. the air spring installation 32. Within the air spring installation 32, the compressed air is distributed by means of the respective pressure consumer valves 46, in the embodiment shown air bag valves 46 for the spring air bags 34 of the air spring installation 32.

[0060] In the embodiment shown, the compressor 12 is embodied in two stages and has a first stage 12.1 and a second stage 12.2. Thus, in the open mode of operation, the outside air is first pre-compressed in both stages by means of the first compressor stage 12.1 and then re-compressed by means of the second compressor stage 12.2.

[0061] In the open mode of operation, the compressed air provided by the compressor 12 can be delivered to the pressure accumulator 36 instead of to the compressed air consumer, in order thus to create the prerequisites for the closed mode of operation.

[0062] Thus, for the supply of compressed air in the open mode of operation, a compressor such as the compressor 12 and a pneumatic main pressure line 40 are required, which delivers the compressed air provided by the compressor 12 to the compressed air consumer 32. Further components, such as the air dryer 38 or the separating or partitioning valve 44, are optional.

[0063] In a second open mode of operation, for example when lowering the air spring installation 12, the discharge valve is opened. The opening of the discharge valve 50 causes the pneumatically controlled two-position three-way valve 70 to move into the working position in which the air is released. After the discharge valve 50 is opened, the pressure of the air to be released serves as control pressure, which acts on the control piston 74 of the pneumatically controlled two-position three-way valve 70 and moves the two-position three-way valve 70 into the working position against the force of its return spring 72. The throttling 80.1 and 80.2 and the two check or non-return valves 42.1 and 42.2 can reasonably limit the control pressure for actuating the pneumatically controlled two-position three-way valve 70.

[0064] Closed mode of operation

[0065] In air spring installations, both raising and lowering can be carried out in the closed mode of operation. In general, this means that, in a first closed mode of operation, the compressed air consumer can be supplied with compressed air, while, in a second closed mode of operation, which is also referred to as a backflow mode, air can be discharged.

[0066] For the closed mode of operation, additionally a pressure accumulator 36, for example embodied as a compressed air container, a reservoir valve 52, optionally a pressure boost valve 54 and also optionally a separation valve 44, also optionally a return valve 48 and corresponding compressed air lines are required. For the closed mode of operation, the components not required for the open mode of operation, i.e. the pressure accumulator 36, the reservoir valve 52, the optional pressure boost valve 54 and the return valve 48, are shown in Figure 1

[0067] In a first closed mode of operation, for example for lifting the air spring installation, air is pumped from the pressure accumulator 36 into the air spring installation 32 and thus into its spring bellows 34 by means of the compressor 12 and its second compressor stage 12.2. For this purpose, the compressor 12, the pressure boost valve 54 and the separation valve 44 are activated and the bellows valve 46 is opened. In this way, lifting of the vehicle by means of the air spring installation 32 in the closed mode of operation of the compressed air supply installation 30 ("boosting") can be achieved. Since the air in the pressure container 36 already has a higher static pressure than the outside air in the environment, in the closed mode of operation, the air is only re-compressed by means of the second stage 12.2 of the compressor 12, while the first stage 12.1 of the compressor 12 is not active in a pneumatic sense in this case.

[0068] As in the open mode of operation, in the closed mode of operation, the compressed air is also delivered via the air dryer 38 into the pneumatic main pressure line 40 and is guided through the non-return valve or check valve 42.2 and thus is provided for delivery to the compressed air consumers 32.

[0069] In a second closed mode of operation, for example when lowering the air spring installation, air is pumped from the bellows 34 into the pressure accumulator 36. At this point, the compressor 12 is activated and the return valve 48 and the reservoir valve 52 are opened, i.e. activated. The air is then pumped from the bellows 36 through the return valve 48 and by means of the second stage 12.2 of the compressor 12 through the reservoir valve 52 into the pressure accumulator 36.

[0070] Distribution of compressed air within a compressed air consumer

[0071] The delivery of compressed air to one or more compressed air consumers 32 or to the pressure accumulator 36 and the distribution of compressed air within the compressed air consumers 32, in the present example between the air springs 34 of the air spring installation 32, takes place by means of electrically actuated two-position two-way valves 46, as Figure 2 ​The two-position two-way valve 60 as depicted in a is in its first (rest) position, in which it functions as a one-way valve or check valve, by means of a return spring 62. In its second (activated or working) position, the two-position two-way valve 46 is open. The electrically controllable two-position two-way valve 46 is connected to an electronic compressed air control 56, which can be identical to the electronic control unit for controlling the compressor module 10, and which can control a control magnet 64 of the two-position two-way valve 46. The two-position two-way valve 46 of the compressed air consumer 32 (in the present example an air spring installation 32) is connected to Figure 2 The two-position two-way valve 60 as depicted in a corresponds.

[0072] Air bleed

[0073] Irrespective of whether the compressed air supply 30 is operated in open or closed operating mode, it can be necessary to bleed one or more components of the compressed air consumer 32, for example the spring bellows 34. In the case of a vehicle with air spring installation, one or more bellows 36 of the air spring installation need to be bled when the vehicle should be lowered unilaterally or bilaterally.

[0074] In open or closed operating mode, the compressed air consumer 32 can also be bled, for example when the vehicle is lowered using the air spring installation. These variants of the bleeding of the compressed air consumer 32 will be explained in detail in the following. In both cases, it is a matter of bleeding the compressed air consumer 32, i.e. not of bleeding the compressed air supply 30 as a whole. Bleeding the compressed air supply 30 would necessarily be in open operation, in which air is delivered from the compressed air supply 30 to the environment.

[0075] Air bleed in open mode of operation

[0076] For bleeding in open operating mode, the compressed air supply 30 in the example shown is designed as an indirectly bled compressed air supply.

[0077] To this end, a discharge valve 50, a pneumatically controlled two-position three-way valve 70, a throttle 80.1 and 80.2 and a further check valve or one-way valve 42.1 are provided, see Figure 1 The respective frame 84 around the components for indirect bleeding in a.

[0078] In open operating mode, the compressed air supply 30 and one or more compressed air consumers 32 can be bled via the open discharge valve 50, which is likewise configured as an electrically controllable two-position two-way valve. Opening the discharge valve 50 leads to a flow of compressed air from the compressed air supply 30 via the discharge valve 50, the two-position three-way valve 70, the throttle 80.1 and 80.2 and the one-way valve 42.1 to the environment. Figure 2The pneumatically controlled two-position three-way valve 70 is moved into the working position in b. This working position is the position in which the air is bled off. After opening the discharge valve 50, the pressure of the air to be bled off acts as control pressure on the control piston 74, which moves the two-position three-way valve 70 into the working position against the force of its return spring 72. The throttles 80.1 and 80.2 and the two check or non-return valves 42.1 and 42.2 cause a reasonable restriction of the control pressure for actuating the pneumatically controlled two-position three-way valve 70.

[0079] Air bleed in closed mode of operation

[0080] In the closed mode of operation, components of the compressed air consumer 32 are bled off into the pressure vessel 36.

[0081] In the closed mode of operation, air is pumped from the air bellows 34 into the pressure accumulator 36 by means of the compressor 12 and its second compressor stage 12.2. For this purpose, the compressor 12 is activated and the return valve 48 and the reservoir valve 52 are opened. Thus, for example, a lowering of the air spring installation 32 can be carried out in the closed mode of operation. In this case, the first stage 12.1 of the compressor 12 is not active pneumatically.

[0082] Summary of open / closed mode of operation

[0083] The open mode of operation exists when - the compressor 12 conveys air directly from the environment to the compressed air consumer 34, for example the air bellows 34 of the air spring installation 32; then the compressor 12 is activated, the partition valve 44 is activated, the air bellows valve 46 is activated => request "raise"; - the compressor 12 charges the compressed air accumulator 36 from the environment; then the compressor 12 is activated, the reservoir valve 52 is activated => request "fill accumulator"; - air is bled off from the compressed air consumer 34, in the example: the air bellows 34 of the air spring installation 32, into the atmosphere (air bellows valve activated, partition valve activated, discharge valve activated) => request "lowering" into the atmosphere;

[0084] The closed mode of operation exists when - air is pumped from the air bellows 34 into the pressure accumulator 36; then the compressor 12 is activated, the return valve 48 is activated, the reservoir valve 52 is activated => request "lowering" in the closed mode of operation ("return flow"). In this case, the first stage 12.1 of the compressor 12 is not active pneumatically. - pumping air from the pressure accumulator 36 into the air bag 34; thus, the compressor 12 is activated, the pressure boost valve 54 is activated, the partition valve 44 is activated, the air bag valve 46 is activated => request for "lifting" ("pressure boost") in closed operating mode. In this case, the first stage 12.1 of the compressor 12 is not active in a pneumatic respect.

[0085] Compressor module

[0086] In Figure 3 , the compressor module 10 is set up for use in a compressed air supply installation 30, as it is exemplarily shown in Figure 1 in combination with a wiring diagram. The compressor module 10 is a structural unit consisting of the compressor 12, the electric motor 14 and the motor control (16, see Figure 6 ; not shown in Figure 1 ; typically connected directly via flanges on the electric motor 14) and further components (e.g. air dryer 18 and air distributor 20 etc.).

[0087] Figure 4 The stator and the rotor of the brushless DC motor are roughly shown. The roughly drawn brushless DC motor 14 is a so-called internal rotor, typically having a stator 14.1 equipped with electromagnetic coils (i.e. with coils), a rotor 14.2 equipped with permanent magnets and an electronic motor control 16 (see Figure 6 ). The motor control 16 is configured as an electronic commutator such that the motor control 16 controls the current delivery to the coils 14.3 of 14.1 via power switches and the connections A, B and C such that the coils 14.3 are periodically supplied with current in rotation, resulting in a rotating magnetic field which via magnetic forces causes a synchronous rotation of the rotor 14.2 equipped with permanent magnets.

[0088] For implementing the well-known speed regulation of the brushless electric motor 14, the electric motor has means for rotor angle detection, e.g. Hall sensors 14.4 for detecting the rotor positioning. Thus, the phase angle between the applied rotating field and the mechanical rotation of the rotor 14.2 can also be detected and the phase angle of the rotating field can be adjusted accordingly. Thus, the BLDC motor 14 exhibits similar characteristics as a mechanically commutated DC motor. However, as a brushless DC motor, it is more efficient, less prone to wear and better regulatable in terms of speed than an electric motor 14 with a brush commutator.

[0089] For generating the rotating field via the connections A, B and C by periodically energizing the coils 14.3, the motor control 16 is provided which functions as an electronic commutator; see Figure 6 .

[0090] The speed of the electric motor 14 is also regulated in a known manner via the motor control 16. For this purpose, the motor control 16 is assigned a target rotational speed. For the purpose of specifying the target rotational speed, an electronic control unit 100 is provided, which is supplied by the motor control 16 with a value for the average motor current or is connected to a current sensor 58, 102, which detects the respective motor current consumed by the electric motor 14 in operation.

[0091] The current consumption of the electric motor 14 can be calculated from the measured phase current by the motor control 16 or can be measured directly by means of the current sensor 58 or 102. In the first case, three current sensors 102 are required, which are necessary for operational safety in any case. In the second case, an additional current sensor 58 is required in the supply branch (see Figure 1 ). Variants without the use of a separate current sensor 58 are therefore preferred.

[0092] Compared to a non-regulated DC motor, a regulated brushless DC motor offers the advantage that its rotational speed can be adjusted steplessly without additional expenditure in terms of design. The commutation of a brushless DC motor takes place electronically, whereas a DC motor with a brush collector system is commutated mechanically.

[0093] For acoustic reasons, a constant rotational speed is required for air spring systems over the entire set load range (voltage, back pressure and charge pressure, temperature, geodetic height), which supports the use of a regulated DC motor.

[0094] The disadvantage of specifying the rotational speed is that, when n = constant is required, the motor current increases with increasing torque, which can exceed a defined maximum limit value of, for example, 35 A in individual cases. In order to comply with the maximum permissible current consumption, the compressor must be designed in such a way that this current consumption is not exceeded in the set application case under the worst-case operating conditions. Scenarios of this kind are, for example, the case of a loaded vehicle getting stuck in rough terrain.

[0095] It is proposed that the motor is now designed in accordance with the standard for constant rotational speed and, when the permissible current consumption, which is usually 35 A, is exceeded, the required drive power of the compressor is reduced. For this purpose, the current consumption of the compressor is ascertained, and when the defined limit value is exceeded, the closed operation of the compressor is terminated and regulated in open operation mode until the end.

[0096] The mode switching based on the average motor current has the advantage that no device-specific tolerances, different pressure ranges and additional values influencing the current consumption of the electric motor, i.e. the motor current, have to be reserved in the form of worst-case assumptions, but are detected device-specifically and maximize the performance of the compressor in all operating ranges.

[0097] Generally, the pneumatic power of the compressor for the air spring system is designed according to the most common operating point. For example, a volume flow of 130 l / min is required at a charging pressure of 11 bar and a back pressure of 11 bar. A maximum current consumption of 35 A, however, is applicable for all working areas (operating pressure and ambient pressure, voltage).

[0098] In order not to design the electric motor too large, the compressor is designed with a current consumption of approximately 30 A in the mentioned operating points (considering device-specific tolerances, effects of the service life, slightly higher operating loads). It is shown, in particular in the charging operation, that the required drive power or the required current increases significantly above 35 A with the rising back pressure (current ~ torque).

[0099] In the example shown in Figure 5 , the current increases by more than 2 A per bar of back pressure. The solution is to design the compressor module 10 in such a way that it does not exceed the current in the defined, rarely occurring worst-case operating points. This has the disadvantage, however, that the compressor module 10 exhibits a correspondingly reduced, not set performance in the frequent operating ranges. In this case, the required delivery power of 130 l / min, for example, at a pre-pressure of 11 bar and a back pressure of 11 bar, cannot be achieved. This problem is exacerbated by device-specific tolerances and effects of the service life. In order to avoid high currents, the rotational speed of the BLDC motor can be reduced. However, since the rotational speed is proportional to the current, this can result in a necessary rotational speed reduction that is too large. For example, if the current consumption should be reduced from 60 A to 35 A, the rotational speed must be reduced to 58%, for example, from 2850 min -1 to 1700 min -1 below. This significant rotational speed reduction can result in undesirable effects in terms of air-borne and structure-borne sound.

[0100] One approach is to operate the BLDC motor at a constant rotational speed and to reduce this rotational speed under certain load conditions (operating voltage and load) to avoid over-dimensioning the DC motor. The maximum current of, for example, 35 A is not exceeded in the case of a correct design and correct consideration of all influencing factors of the current, such as component tolerances, operating temperatures, in the form of worst-case assumptions. However, it is a prerequisite that all factors influencing the current, such as component tolerances, operating temperatures, have to be considered in the form of worst-case assumptions and that the resulting switch to a lower rotational speed with the resulting performance reduction is acceptable.

[0101] Therefore, the goal is not to design the compressor module according to the rarest worst case, but instead to design it according to the most common operating conditions combined with a current limitation for ensuring a predetermined current boundary in combination with the maximum compressor power in the scenario.

[0102] The requirement of a constant compressor rotational speed leads to an increase of the current consumption with increasing compressor drive torque, which is proportional to the required motor torque: Formula: where: = compressor drive torque (constant at constant pressure) = compressor rotational speed (kept constant according to conventional control strategy in BLDC) = efficiency = supply voltage (predetermined between 9 V and 16 V according to requirements) = motor current (typically limited to 35 A)

[0103] Measurements show that the motor current consumption of a charged compressor used in a passenger vehicle air spring system can increase by more than 2 A per bar increase in back pressure. Therefore, in the case of a design according to I = 30 A with a rated charge pressure of 11 bar and a back pressure of 11 bar, only a back pressure of up to 13.5 bar is allowed (which no longer covers the entire required operating range, for example, up to 18 bar). The following factors can lead to further reductions: - device differences due to manufacturing - break-in effects - wear - environmental conditions - self-heating

[0104] For switching from the closed mode to the open mode in accordance with the application in the event of a predetermined maximum motor current being reached or exceeded, the current consumption for the drive motor 14 of the compressor 12 is continuously known. As soon as the current consumption, i.e. the motor current, exceeds a predetermined limit value for a certain time, the torque requirement of the compressor is reduced by switching to the open mode of operation. In the example shown, the motor current reaches the current limit value of 35 A at a back pressure of about 11 bar in the case of a fully loaded operation. If the compressed air supply 30 continues to be operated in the closed mode, the electric motor 14 for driving the compressor 12 would consume a motor current of 48 A. By contrast, by switching to the open mode of operation, the current consumption of the electric motor 14 would be reduced to about 19 A, but of course the volume flow is also reduced accordingly. This is shown in Figure 7

[0105] The compressor module 10 is advantageously designed in such a way that it can perform most of the usage conditions without mode switching. Only the worst-case operating conditions, such as maximum load plus maximum altitude state or a large amount of axle interleaving, lead to a corresponding switching into the open mode of operation.

[0106] Furthermore, in the case of the application of the application, the basic design of the compressor 12 and the associated electric motor 14, i.e. the compressor module 10, should not be based on the worst-case tolerance conditions, etc., but should also be designed here similarly to the rated value.

[0107] Advantages are also obtained in the case of a temporarily too small rated width on the compressor pressure side, for example when only one air bag 34 is being supplied, and a too high back pressure is built up due to a too large volume flow, which again leads to a too high motor current.

[0108] The application of the switching from the closed mode of operation to the open mode of operation in accordance with the application is not limited to a compressor driven by a BLDC direct-current motor, although this is preferred, but can also be extended to compressors with other direct-current motors.

[0109] In the example, the switching from the closed mode of operation to the open mode of operation takes place as follows.

[0110] The switching from the boost by means of the boost valve 54, i.e. from the closed mode of operation, to the boost in the open mode of operation takes place very simply by switching off, i.e. deactivating and thus closing, the boost valve 54.

[0111] In the case of the backflow reduction action, i.e. in the case of the bleeding, for example to lower the vehicle, the switching to the open mode of operation is somewhat more complex, since the compressor 12 has to be switched off, the backflow valve 48 and the reservoir valve 52 have to be closed and the discharge valve 50 has to be opened. Therefore, a predictive regulation is advantageous here, as described below. ​

[0112] For the anticipatory regulation, not only the motor current is known, but also the pressure P on the pressure side of the compressor 12 or in the pressure accumulator 36. For this purpose, at least one P-U converter is provided as a pressure sensor 78. This P-U converter can be provided, for example, on the main pressure line 40 or on the pressure accumulator 36, or both and also elsewhere, depending on which pressures, for example, need to be detected for the anticipatory control.

[0113] The motor current I is predicted B,prä The accuracy, in turn, of the decision whether to carry out a descent, for example, in open or closed mode of operation, can be improved by increasing the prediction complexity via the following cases 1 to 3.

[0114] Since the motor current is proportional to the drive torque required by the compressor, respectively, the torque demand, it is possible, even without taking the motor current itself into account at all, but only on the basis of influencing parameters that influence the torque demand of the compressor at a given rotational speed and the foreseeable temporal development thereof, for example, the back pressure that grows as the pressure accumulator fills, to select the open or closed mode of operation by means of anticipatory control. This way, i.e., the anticipatory selection of open or closed mode of operation and the corresponding actuation of the compressed air supply, is an independent inventive concept that can be realized both in combination with the mode switching based on the motor current described herein and independently of the motor current.

[0115] In the simplest case 1, the compressed air control activates either the closed mode of operation or the open mode of operation depending on the current accumulator pressure, i.e., the air pressure in the pressure accumulator, in response to a "descent" request. If the current accumulator pressure is too close to the maximum permissible accumulator pressure limit value to be able to save enough air mass in the pressure accumulator to be able to discharge enough air from the air consumer, i.e., to descend the vehicle to a sufficient extent, for example, the open mode of operation is selected from the outset in order to avoid switching the mode of operation during the descent. For this purpose, the compressed air control is configured, inter alia, as a pressure estimator.

[0116] In the second case, the compressed air control is configured to calculate (air mass manager) or estimate (air mass estimator) the upcoming, i.e., to be expected, accumulator pressure in advance on the basis of existing information about the accumulator pressure and accumulator volume, air bag pressure, air bag geometry, and height status, and the requested regulation, for example, lifting or descent. If the calculated or estimated accumulator pressure exceeds a predetermined or learned accumulator pressure limit value, the lowering process is carried out from the outset by air bag venting to the atmosphere, i.e., in open mode of operation. No switching will take place during the descent.

[0117] In an advantageous third embodiment, the compressed-air control is configured to set the pressure limit value in case 2 or case 1 adaptively depending on a correlation between back pressure and current consumption learned in the operation of the compressor module 10. Here, unavoidable device tolerances are compensated as follows, i.e. the switching takes place in a self-calibrating form, which is specific to the compressor.

[0118] List of reference signs (part of the description)

[0119] 10 compressor module

[0120] 12 compressor

[0121] 12.1 first compressor stage

[0122] 12.2 second compressor stage

[0123] 14 electric motor

[0124] 14.1 stator

[0125] 14.2. rotor

[0126] 14.3 winding

[0127] 14.4. Hall sensor

[0128] 16 electronic motor control (motor electronics)

[0129] 18 air dryer

[0130] 20 air distributor

[0131] 22 compressed-air line (general)

[0132] 30 compressed-air supply

[0133] 32 air spring arrangement

[0134] 34 air bag of air spring

[0135] 36 pressure accumulator

[0136] 38 air dryer

[0137] 40 main pressure line (special compressed-air line)

[0138] 42 non-return valve

[0139] 44 separation valve (electrically controlled)

[0140] 46 pressure sensor valve (air bag valve, electrically controlled)

[0141] 48 return valve (electrically controlled)

[0142] 50 discharge valve (exhaust valve, electrically controlled)

[0143] 52 reservoir valve (electrically controlled)

[0144] 54 pressure build-up valve (electrically controlled)

[0145] 56 compressed air control

[0146] 58 current sensor

[0147] 60 two-position two-way valve (electrically controlled)

[0148] 62 return spring

[0149] 64 control magnet

[0150] 70 two-position three-way valve for indirect discharge (pneumatically controlled)

[0151] 72 return spring

[0152] 74 control piston

[0153] 76 pressure build-up and return line

[0154] 78 pressure sensor; P-U converter

[0155] 80 throttle

[0156] 82 components for closed operation

[0157] 84 components for indirect discharge

[0158] 90 memory for operating a predetermined program

[0159] 92 current signal input

[0160] 94 pressure signal input for signals representing the pressure in the pressure reservoir 36

[0161] 96 pressure signal input for signals representing the pressure of the compressed air in the main pressure line of the compressed air supply facility

[0162] 98 pressure signal input for signals representing the pressure of the compressed air in the compressed air consumer

[0163] 100 electronic control unit

[0164] P Abn pressure of the compressed air at the compressed air consumer

[0165] SPAbn signal representative of the pressure of the compressed air at the compressed air consumer

[0166] P Anl pressure of the compressed air in the main pressure line of the compressed air supply installation

[0167] S PAnl signal representative of the pressure of the compressed air in the main pressure line of the compressed air supply installation

[0168] P R pressure of the compressed air in the pressure accumulator

[0169] P R grenz accumulator pressure limit value, limit value for the pressure of the compressed air in the pressure accumulator

[0170] P R gesch estimated pressure of the compressed air in the pressure accumulator

[0171] S PR signal representative of the pressure of the compressed air in the pressure accumulator

[0172] n soll target rotational speed (operating specification)

[0173] I B signal representative of the motor current

[0174] S IB motor current

[0175] S Anf request signal

[0176] V volume of the compressed air consumer, in particular of the air spring

[0177] h height state of the compressed air consumer, in particular of the air spring

Claims

1. Compressed-air supply (30), in particular for a motor vehicle, having - one or more compressed-air consumers (32; 34), - a compressed-air line (40), - electrically controllable valves (44, 46, 48, 50, 52, 54), - a compressed-air control (56) for actuating the electrically controllable valves (44, 46, 48, 50, 52, 54), - a compressor (12) having an electric motor (14) as drive, and - a pressure accumulator (36), the one or more compressed-air consumers (32; 34) being pneumatically connected or connectable to the compressor (12) and / or to the pressure accumulator (36) via the compressed-air line (22) and the electrically controllable valves (44, 46, 48, 50, 52, 54), such that the compressed-air supply (30) can be operated either in an open operating mode or in a closed operating mode, the compressed-air consumer (32) being an air spring device (32) having one or more air bellows (34), the compressor (12) and the electric motor (14) combining to form a structural unit (10), the compressed-air supply (30) having a reservoir valve (52) which is arranged pneumatically between the pressure accumulator (36) and a pneumatic main pressure line (40), the compressed-air supply (30) having a pressure boost valve (54) which is arranged pneumatically between the pressure accumulator (36) and a pressure boost and return line (76).

10. Method for operating a compressed-air supply (30), in particular for a motor vehicle, having - one or more compressed-air consumers (32; 34), - a compressed-air line (40), - electrically controllable valves (44, 46, 48, 50, 52, 54), - a compressed-air control (56) for actuating the electrically controllable valves (44, 46, 48, 50, 52, 54), - a compressor (12) having an electric motor (14) as drive, and - a pressure accumulator (36), the one or more compressed-air consumers (32; 34) being pneumatically connected or connectable to the compressor (12) and / or to the pressure accumulator (36) via the compressed-air line (40) and the electrically controllable valves (44, 46, 48, 50, 52, 54), such that the compressed-air supply (30) can be operated either in an open operating mode or in a closed operating mode, characterized in that a switch from the closed operating mode to the open operating mode is effected by deactivating the pressure boost valve (54) when compressed air is delivered to the pressure consumer (32). ​ ​ ​ ​ ​ wherein ​ 14） characterized in that the compressed-air control (56) has a current signal signal input (90) for a current signal (S I ) which represents a motor current (I B ) consumed or to be consumed by an electric motor (14) driving the compressor (12), wherein the compressed-air control (56) is configured to actuate the electrically controllable valve (44, 46, 48, 50, 52, 54) in an open operating mode of the compressed-air supply (30) when a current signal (S max ) representing an average motor current (I B ) whose magnitude is equal to or greater than a predetermined maximum value (I IB ) of the motor current is applied at the current signal signal input (92).

2. Compressed air supply installation (30) according to claim 1, characterized in that The current signal input (92) is connected to at least one current sensor (58, 102) which is configured to detect a motor current (I B ) consumed by an electric motor (14) driving the compressor (12) and to output a signal (S IB ) representing the motor current to the compressed air control (56).

3. Compressed air supply installation (30) according to claim 1 or 2, characterized in that ​ 4. Compressed air supply installation (30) according to at least one of claims 1 to 3, characterized in that ​ 5. Compressed air supply installation (30) according to at least one of claims 1 to 4, characterized in that The electric motor (14) is a speed-regulated BLDC motor, and at least one target rotational speed (n soll ) is predetermined.

6. Compressed air supply installation (30) according to at least one of claims 1 to 5, characterized in that The compressed air control (56) is configured to predictively determine a motor current (I B prä ) to be consumed by the electric motor (14) on the basis of an air pressure (P Anl ) in the compressed air supply (30) and a request (S Anf ) to the compressed air consumer (32; 34), in particular a "fall" request (S Anf下降 ), and to cause a switchover into the open mode if the predictively determined motor current (I B prä ) reaches or exceeds a predetermined maximum value (I B max ) for the motor current.

7. Compressed air supply installation (30) according to claim 6, characterized in that The compressed air supply (30) has a pressure sensor (78) which is arranged and configured in such a way that it detects the air pressure (P Anl ) present in the compressed air supply (30) in operation and outputs a pressure signal (S PAnl ) representing the air pressure to the compressed air control (56).

8. Compressed air supply installation (30) according to at least one of claims 1 to 7, characterized in that ​ 9. Compressed air supply installation (30) according to at least one of claims 1 to 7, characterized in that ​ ​ ​ ​ ​ ​ ​ ​ wherein ​ ​ - in operation delivering to the compressed air control (56) a current signal (S B ) representative of a motor current (I IB ) consumed or to be consumed by the electric motor (14) driving the compressor (12), and - when a current signal (S B max ) representing an average motor current (I B ) whose magnitude is equal to or greater than a predetermined maximum value (I IB ) of the motor current is applied at the current signal input (92), the compressed air control (56) switches the compressed air supply (30) from the closed mode of operation to the open mode of operation and actuates the electrically controllable valves (44, 46, 48, 50, 52, 54) in accordance with the open mode of operation of the compressed air supply (30).

11. The method according to claim 10 for operating a compressed air supply installation (30) having a pressure boost valve (54) pneumatically connected to the pressure accumulator (36), wherein ​ 12. The method according to claim 10 or 11 for operating a compressed air supply installation (30) having a discharge valve (50), a return flow valve (48) and a reservoir valve (52) which is pneumatically connected to the pressure accumulator (36), wherein When compressed air is discharged from the pressure consumer (32), the switch from the closed mode of operation to the open mode of operation is effected by switching off the compressor (12), closing (deactivating) the return valve (48) and the reservoir valve (52) and opening (activating) the discharge valve (50).

13. The method according to claim 10 or 11 for operating a compressed air supply installation (30) having a pressure sensor (78) at the compressed air reservoir (36) and a discharge valve (50), a return flow valve (48) and a reserve valve (52) which is pneumatically connected to the pressure reservoir, wherein, When the current storage pressure in the pressure accumulator (36) is lower than a storage pressure limit value (P R grenz ) in the case that compressed air is discharged from the pressure consumer (32), the compressed air control (56) activates a closed operating mode, or when the current storage pressure (P R ) in the pressure accumulator (36) is equal to or greater than a storage pressure limit value (P R grenz ), the compressed air control activates an open operating mode.

14. The method according to claim 10 or 11 for operating a compressed air supply installation (30) having a pressure sensor (78) at the compressed air reservoir (36) and a discharge valve (50), a return valve (48) and a reserve valve (52) which is pneumatically connected to the pressure reservoir (36), wherein, In the case that compressed air is to be discharged from the pressure consumer (32), the compressed air control (56) is configured to calculate or estimate the desired storage pressure (P R ) in advance on the basis of existing information about the storage pressure in the pressure accumulator (36) and the volume of the pressure accumulator (36), the pressure (P Abn ) in the compressed air consumer (32; 34) or one or more components (34) of the compressed air consumer and its volume (V) and height state (h), and, in the case that the calculated or estimated storage pressure (P R gesch ) exceeds a predetermined storage pressure limit value (P R grenz ), to activate the open operating mode by switching off the compressor (12), closing (deactivating) the return valve (48) and the reservoir valve (52) and opening (activating) the discharge valve (50).

15. The method of any one of claims 12 to 14, wherein, The compressed air control section (56) sets the memory pressure limit value (P R grenz ) adaptively based on a correlation between the back pressure (P Anl ) learned during operation of the compressor module (10) and the current consumption (I B ).

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